HomeMy WebLinkAbout3.1 ! ITEM 3.1
TOWN OF LOS ALTOS HILLS December 3, 2015
Staff Report to the Planning Commission
SUBJECT: REVIEW AND CONSIDERATION OF AN INITIAL STUDY AND
ADOPTION OF A MITIGATED NEGATIVE DECLARATION FOR
THE MATADERO CREEK RESTORATION AND BANK
STABILIZATION PROJECT, PAGE MILL ROAD; FILE#426-15-MISC
FROM: Richard Chiu, City Engineer/Public Works Director i •d
Suzanne Avila, Planning Director Sk
RECOMMENDATION: That the Planning Commission:
Review and recommend that the City Council approve the Initial Study and adopt the
Mitigated Negative Declaration for stabilization and restoration of 330 feet of Matadero
Creek to reduce erosion and undercutting of the creek channel.
BACKGROUND
The proposed project is part of the Town's Capital Improvement Program adopted by the
City Council as part of the 2015-16 budget.
DISCUSSION:
The proposed project involves'the removal of a portion of the outfall apron below the
Page Mill Road box culvert, removal of 13 willow and walnut trees, grading the new
channel, creation of a rock rip-rap chute and reinforced drop-pool habitat feature,
downstream reinforcement of the creek banks, and replanting with willows, walnuts and
native grasses to provide shade for the creek. The project will control the undercutting
which if left in place could cause erosion upstream and eventually undermine the Page
Mill Road box culvert. Appropriate signage with one way traffic control will be utilized
during construction.
CEQA REVIEW
In conformance with CEQA requirements, an Initial Study/Mitigated Negative
Declaration have been prepared.for the project (Attachment 1). Copies of the Mitigated
Negative Declaration were forwarded to State Clearinghouse and a Notice of Intent to
adopt a Mitigated Negative Declaration was published in the Town Crier on October 21,
2015. In addition, the Mitigated Negative Declaration was posted on the Town's website
on October 23, 2015. The notice was also submitted to the Santa Clara County Clerks
Office for a 30 day public review period which began on October 21, 2015 and ended on
November 20, 2015.
Based on the Initial Study, staff concluded that the proposed project, as mitigated, will
not have a significant effect on the environment. Specific mitigation measures intended
to minimize any potential environmental impacts are described in the Initial Study.
PUBLIC COMMENTS
As of this date, the Town has received two comment letters regarding the project. The
City of Palo Alto advised that the City has no comments.
The Open Space Committee commented that "While the project appears to solve the
problem immediately downstream of the bridge, there is a concern that the portion of the
creek immediately upstream of the bridge needs to be attended to at the same time. In
particular, merely cutting down the cattails instead of eradicating them, will lead to
annual problem recurrence with ever more vigorous regrowth as more and more
sedimentation is arrested by the plant matter leading to eventual flooding of Page Mill
Road in a storm event, as the bridge becomes even further occluded. "
Response:
Permits for the Matadero Creek Restoration and Bank Stabilization Project do not include
in-channel work upstream of the bridge. The Town has communicated the Open Space
District's interests to the Santa Clara Valley Water District (SCVWD), and that agency
has stated that the District will be removing some of the excess sediments to improve
flows under the bridge. This work would be carried out under separate permits held by
SCVWD. The SCVWD's approach to managing the cattails within the wetland above the
bridge has not been described.
ATTACHMENTS
1. Initial Study and Negative Declaration
2
Draft Initial Study
for the
Matadero Creek Restoration
and Bank Stabilization Project
LOS ALTOS HILLS, SANTA CLARA COUNTY, CALIFORNIA
Prepared For:
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TABLE OF CONTENTS
1.0 INTRODUCTION AND PURPOSE 1
2.0 PROJECT INFORMATION 1
2.1 PROJECT TITLE 1
2.2 LEAD AGENCY NAME AND ADDRESS 1
2.3 CONTACT PERSON AND PHONE NUMBER 1
2.4 PROJECT LOCATION 1
2.5 GENERAL PLAN DESIGNATION AND ZONING DISTRICT 3
2.6 SURROUNDING LAND USES AND SETTING 3
3.0 PROJECT DESCRIPTION 9
3.1 PURPOSE AND NEED 9
3.2 PROJECT DESCRIPTION 9
3.3 PROJECT-RELATED APPROVALS, AGREEMENTS,AND PERMITS 15
3.4 PROJECT-RELATED APPROVALS, AGREEMENTS, AND PERMITS 16
4.0 ENVIRONMENTAL FACTORS POTENTIALLY AFFECTED 17
4.1 AESTHETICS 19
4.2 AGRICULTURE AND FORESTRY RESOURCES 20
4.3 AIR QUALITY 22
4.4 BIOLOGICAL RESOURCES 25
4.5 CULTURAL RESOURCES 38
4.6 GEOLOGY AND SOILS 40
4.7 GREENHOUSE GAS EMISSIONS 43
4.8 HAZARDS AND HAZARDOUS MATERIALS 44
4.9 HYDROLOGY AND WATER QUALITY 46
4.10 LAND USE AND PLANNING 50
4.11 MINERAL RESOURCES 52
4.12 NOISE 53
4.13 POPULATION AND HOUSING 58
4.14 PUBLIC SERVICES 59
4.15 RECREATION 60
4.16 TRANSPORTATION/TRAFFIC 61
4.17 UTILITIES AND SERVICE SYSTEMS 63
4.18 MANDATORY FINDINGS OF SIGNIFICANCE 65
5.0 REFERENCES 67
CHECKLIST INFORMATION SOURCES 67
SETTING REFERENCES 69
LIST OF FIGURES
Figure 1. Project Location 2
Figure 2. Aerial Overview of Project Area 5
Figure 3. Views of the Project Area 6
Figure 4. Views of the Project Area 7
Figure 5. Site Plan 10
Figure 6. Site Plan — Creek Channel Sections 11
Figure 7. Site Plan — Impacts Map 12
Figure 8. Site Plan — Restoration Plan 13
LIST OF TABLES
Table 1. Summary of Biological Communities in the Project Area 4
Table 2. Summary of Impacts to Wetlands and Waters 36
Table 3. Summary of Impacts to Mixed Riparian Woodland 36
Table 4. Construction Equipment Noise Generation 55
LIST OF APPENDICES
Appendix A. Biological Resources Report
Appendix B. Water Surface Profile Study and Design Recommendations
ii
1.0 INTRODUCTION AND PURPOSE
This Initial Study of environmental impacts is being prepared to conform to the requirements of
the California Environmental Quality Act (CEQA), the CEQA Guidelines (California Code of
Regulations 15000 et. seq.), and the regulations and policies of the Town of Los Altos Hills
(Town). This Initial Study evaluates the potential environmental impacts which might
reasonably be anticipated to result from implementation of the Matadero Creek Restoration and
Bank Stabilization Project(proposed project)
The Town of Los Altos Hills is the Lead Agency under CEQA and had this Initial Study prepared
to address the impacts of implementing the proposed project. The purpose of the project is to
provide creek bank and bed stabilization for Matadero Creek, reduce erosion and restore the
riparian habitat within the stream corridor near a portion of Page Mill Road for Town of Los Altos
Hills residents.
2.0 PROJECT INFORMATION
2.1 Project Title
Matadero Creek Restoration and Bank Stabilization Project
2.2 Lead Agency Name and Address
Town of Los Altos Hills
26379 Fremont Road
Los Altos Hills, CA 94022
2.3 Contact Person and Phone Number
Richard Chiu, Jr., PE,
Director of Public Works
rchiu@losaltoshills.ca.gov
650-947-2516
2.4 Project Location
The Matadero Creek Restoration and Bank Stabilization (project) would stabilize and restore a
portion of Matadero Creek on the northwest side of Page Mill Road in the Town of Los Altos
Hills, in Santa Clara County, California. A project location map is provided as Figure 1. The
project area is immediately downstream of a concrete box culvert which traverses under Page
Mill Road, approximately one-quarter mile west of Interstate 280. The project area is
approximately one acre, and includes about 350 linear feet of stream channel paralleling the
north side of Page Mill Road between Arastradero Road and Berry Hill Court.
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 1 October 2015
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2.5 General Plan Designation and Zoning District
General Plan Land Use Diagram: Open Space Conservation Area
Zoning District: Residential-Agricultural (R-A)
2.6 Surrounding Land Uses and Setting
The project area is surrounded by low density residential. Additional land uses in the vicinity
include a ride-share parking lot and Interstate 280 to the north. Open space preserve trails run
along the Page Mill Road corridor. The surrounding area is categorized as residential in both
the zoning code and General Plan.
Project Biological Setting
The project area is located in a residential area along Page Mill Road and includes a 350-foot-
long stretch of Matadero Creek on either side of Page Mill Road. The Matadero Creek
watershed above the project area is approximately 2.7 square miles (WRECO 2013) and
produces a peak discharge of 790 cubic feet per second (CFS). The watershed includes
portions of Stanford University property southwest of Interstate 280 and extends northeastward
through the City of Palo Alto where it drains through Matadero Creek to San Francisco Bay.
The biological setting is an important aspect of the project because the health of the riparian
habitat is dependent on the stability of Matadero Creek. Figure 2 shows an aerial image of the
project area with the biological communities overlaid on it.
Page Mill Road is an improved two-lane road and occupies approximately 0.08 acre of the
project area. A small area of disturbed, semi-landscaped land occurs along the southeast side
of Page Mill Road and is dominated by non-native and invasive plant species that are regularly
mowed. Photos of the project area northeast of Page Mill Road are included in Figure 3, Views
1 and 2.
Matadero Creek is a perennial, USGS blue-line stream located within mixed-riparian woodland.
Upstream (southwest) of Page Mill Road (and the project area), the creek has a relatively
shallow gradient and contains a large area of cattail (Typha sp.) wetlands adjacent to the road
(Figure 3, View 3). Downstream (northeast) of Page Mill Road, the creek's gentle gradient
(Figure 3, View 4) quickly gives way to a steeper channel. A dense riparian canopy is
dominated by arroyo willow (Salix lasiolepis) and Northern Californian black walnut (Juglans
hindsii). The creek is armored by sackcrete walls within the immediate vicinity of Page Mill
Road (Figure 4, View 5). Downstream, where the concrete armoring ends, a nick-point has
developed, creating a deep pool (Figure 4, View 6) and a deeply incised channel with
substantial erosion, undercutting, and bank slumping directly below Page Mill Road (Figure 4,
Views 7 and 8). Downstream, the wetlands are dominated by watercress (Nasturtium officinale)
and creeping bentgrass (Agrostis aff. gigantea).1
Mixed riparian woodland within the project area can be classified as Central Coast Arroyo
Willow Riparian Forest (Sawyer et al. 2009). No special-status plant species were identified
within the project area, and it was determined that the fragmented, disturbed nature of habitat
Perennial wetlands present in the project area meet the U.S. Army Core of Engineers (Corps) definition of
wetlands and are subject to Corps jurisdiction as Waters of the U.S. under Section 404 of the (Clean Water Act)
CWA. Perennial wetlands within the project area are also subject to jurisdiction by the Regional Water Quality
Control Board(RWQCB) under Section 401 of the CWA. Because these wetlands occur within the streambed of
Matadero Creek, they are also subject to jurisdiction by the California Fish and Wildlife (CDFW) under Section
1600 of the CFGC.
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 3 October 2015
within the project area, especially the dominance of non-native and invasive plant species,
greatly reduces the potential for special-status plant species to occur there. As such, it was
determined that no special-status plant species are likely to occur within the project area and no
further surveys are recommended.
In the project area, approximately 0.19 acre of mixed riparian woodland occurs along Matadero
Creek up- and downstream of Page Mill Road. Dominant tree species include arroyo willow and
Northern California black walnut;2 valley oak (Quercus lobata) and coast live oak (Quercus
agrifolia) are also present at lower densities. Downstream of Page Mill Road, the riparian
canopy cover density is generally greater than 80 percent. The understory is dominated by non-
native annual grasses and other native and non-native species such as fringed willowherb
(Epilobium ciliatum), Himalayan blackberry (Rubus armeniacus), California blackberry (Rubus
ursinus), upright snowberry (Symphoricarpos a/bus var. laevigatus), and poison oak
(Toxicodendron diversilobum). Many of the species found within the riparian woodland are
listed as having "moderate" to "high" potential for invasiveness by the California Invasive Plant
Council (Cal-IPC 2014). The understory also contained a large number of naturalized
horticultural (i.e., landscape) species.
A summary of the biological communities in the project area is provided in Table 1.
Table 1. Summary of Biological Communities in the Project Area
Community Type Extent Project Feature
Developed Land 0.08 acre Page Mill Road and adjacent shoulders
Perennial Wetlands 0.01 acre Wetlands upstream and downstream of Page Mill Road
Matadero Creek 333 linear Perennial Stream, box culvert, sackcrete, nick-point,
feet incised...
Mixed Riparian Woodland 0.19 acre Surrounding woodland vegetation
Special-Status Wildlife Species
A San Francisco dusky-footed woodrat (Neotoma fuscipes annectens) nest structure was
observed in the project area during preliminary surveys. Five birds, including Allen's
hummingbird (Selasphorus sasin), oak titmouse (Baeolophus inornatus), white-tailed kite
(Elanus /eucurus), (Brewster's) yellow warbler [Setophaga (Dendroica) petechia brewsteri], and
San Francisco (saltmarsh) yellowthroat (Geothlypis trichas sinuosa), were determined to have a
moderate to high potential to occur in the project area. California red-legged frog (Rana
draytonii) and western (Pacific) pond turtle (Emys marmorata) also have a moderate potential
for occurrence in the project area. Pre-construction surveys will be required to determine
whether any of these species are living or nesting within the project area.
2 Northern California black walnut (Juglans hindsii), has a California Rare Plant Rank of 18.1 (California Native
Plant Society [CNPS] 2014) indicating that it is rare, threatened, or endangered in California and elsewhere.
However, this ranking is intended for those individuals found within naturally occurring stands and within the
natural range of the species. Northern California black walnut individuals observed at the site are not within any
known natural community, according to the CNPS(2014) and Sawyer et al. (2009), and thus are not considered
to be special-status. However, these trees are protected as riparian woodland by the CDFW and may also be
protected by the City's tree protection ordinance.
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 4 October 2015
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Figure 3. Views of the Project Area - Matadero Creek Restoration and Bank Stabilization Project
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ENVIRONMENTAL CONSULTANTS
Matadero Creek Restoration and Bank Stabilization Project Los Altos Hills, Santa Clara County
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Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 8 October 2015
3.0 PROJECT DESCRIPTION
3.1 Purpose and Need
A three-foot vertical headcut has formed downstream of a box culvert overcrossing in Matadero
Creek adjacent to Page Mill Road. The downstream culvert outfall apron is currently reinforced
with sackcrete material in the channel. However, at the transition between the sackcrete
material and the downstream soft bottom channel, the three-foot vertical drop has eroded into
the downstream channel bottom and is causing undercutting and slumping further down the
channel where Matadero Creek parallels Page Mill Road.
In the winter of 2009 -2010, high flows in Matadero Creek caused a bank failure that threatened
the west bound lane of Page Mill Road. A temporary concrete railing (K-rail) has been installed
along the road edge because of the abrupt drop off, down 12 feet to the creek below. In
October 2012, emergency repairs were made to protect the roadway and included the
construction of a cast-in-drilled-hole (CIDH) pile wall that was constructed to avoid encroaching
into jurisdictional areas of Matadero Creek. Now, a more long-term solution is sought by the
Town of Los Altos Hills.
The project has the following goals:
• Reduce ongoing erosion and restore geomorphic equilibrium to Matadero Creek.
• Contain the 100-year flood event and provide naturalized pools in the creek channel.
• Prevent further undercutting and strengthen embankment of Page Mill Road above
ordinary high water mark.
• Maximize use of biotechnical methods to stabilize and shade the creek.
• Restore the native riparian vegetation around the improved creek channel.
3.2 Project Description
The project consists of removal of a portion of sackcrete material in the culvert outfall apron and
creation of a longer rock rip-rap chute structure which would eliminate the three-foot drop,
reinforce the drop pool, and dissipate the creek's energy before it parallels Page Mill Road. The
restoration and stabilization has been designed to improve the creek transition between the
sackcreted portion of the channel and the soft bottom channel downstream, and to reduce
erosional processes in the reach. Plans and Sectional views are provided in Figures 5-8.
The rock chute has been designed according to National Resource Conservation Service
standards and minimizes disruption to the existing drainage system, leaves the majority of the
scour pool that has developed as a habitat feature, and removes portions of upstream
sackcrete. Because of the creek curvature downstream of the transition area, improved banks
stabilization would be provided along the southerly bank that parallels Page Mill Road. Bank
stabilization below the approximate 10-year water surface elevation would be composed of rock
rip-rap planted with willow species (Salix spp.).
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 9 October 2015
I
I
LARi OF GRADING // �
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9 / BIOTECHNICAL ROCK
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PLAN VIEW
Figure 5. Site Plan
,03 1v-
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Matadero Creek Restoration and Bank Stabilization Project
ENVIRONMENTAL CONSULTANTS
P. Los Altos Hills, Santa Clara County
a 1
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2 ROCK CHUTE GRADE CONTROL STRUCTURE
SECTION C-C'
Figure 6. Site Plan - Creek Channel Sections
• wra
,....,0
ns Matadero Creek Restoration and Bank Stabilization Project ENVIRONMENTAL CONSULTANTS
Los Altos Hills, Santa Clara County
•
i /
I / I
/
LIMITS OF TEMPORARY IMPACT /""""
(1,3139 SOFT.)
. .:. ,. --ALTERNA7IWE
/ 36-DIAMETER ) CONSTRICTON
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/ I
17 DIAMETER
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.,. TREES TO SE
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/ DUMPS
..."' CONSTRUCTION
LIMITS OF GRADING
LIMITS OF PERMANENT IMPACT / .• ' �1�pyyET81
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\ ', ALL LOCATIONS ARE APPROXIMATE
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Figure 7. Site Plan - Impacts Map
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._a17 Matadero Creek Restoration and Bank Stabilization Project ENVIRONMENTAL CONSULTANTS
Los Altos Hills, Santa Clara County
I ►
EXPLANATION I //1
ALL LOCATIONS ART APPROXIMATE
• WILLOW IS.VQSPP i IRON ON-SITE STOCK(POLL
• WALNUT I.IIJGL S S SPP 111 OALLONI
• EXISTING TREE TO SE PRESERVED
I TEMPORARY CONTRIETION AREAS TO RE REV'EGETATED \ /
W11 H MOVESEED MIX OK tOtAL
AL _ A' CROSS SECTION LOCATION -- /
•
I7-WACTED TREES • • ,/
]-WALNUT IO (SALLANSSPP.I
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REPLACEMENTTREES lout/TYP{P., •. • .
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PLAN VIEW
Figure 8. Site Plan - Restoration Plan
< ,-.4114P'0 Owra
,a,
Matadero Creek Restoration and Bank Stabilization Project ENVIRONMENTAL CONSULTANTS
Los Altos Hills, Santa Clara County
Lastly, an existing secant wall on Page Mill Road would be replaced as a solider pile wall with
concrete lagging approximately above the 10-year water surface elevation of Matadero Creek.
The improved wall would reduce further creek intervention in the reach for creek for
maintenance activities. The project would also include removal of 13 trees including six large
willows (Salix spp.) and seven large walnut trees (Juglans spp), minor brush removal and
replacement with 16 walnuts and 43 willows planted with Coyote Brush (Baccharis spp.) that
has become established in this reach of creek.
Primary Components of the Project
1. Clear and grub within the construction boundary, mulch materials and store in staging
area.
2. Remove sackcrete in the culvert outfall, regrade the channel and streambanks
3. Build a rock rip-rap chute structure to stabilize the creek, minimize erosion and restore a
functioning pool and equilibrium to the creek.
4. Install a soldier pile wall along Page Mill Road and backfill with aggregate to minimize
future undercutting and maintenance.
5. Provide biotechnical bank stabilization and native plantings to recreate a fully functioning
stream in naturalized setting adjacent to Page Mill Road.
6. Provide long-term maintenance by the Town of Los Altos Hills.
Construction Strategies
The project would take about two months to construct. Pending permitting clearances,
construction is planned for July-August 2016, when stream flows, and school traffic on Page Mill
Road will be low. Willow planting and revegetation work would be done in early fall 2016.
Staging and Preconstruction: Construction equipment could be staged to the southwest of the
project on the shoulder of Page Mill Road. A mid-summer start would require certification of
presence or absence of sensitive bird species and identification and protection or relocation of
the resident San Francisco dusky-footed woodrat that lives in the middle of the site. Vegetation
to be saved would be clearly identified and protected. The construction boundary would be
clearly delineated, and willow stakes (3- 4' tall x 1 — 2" in diameter) would be salvaged from
existing willow stands and kept wet. The creek would be dewatered using cofferdams. Any fish
in the creek would be moved to similar pools in nearby reaches of Matadero Creek.
The project would be built in three steps:
1. A small construction entrance near the top of the proposed grade control structure would
provide access for equipment and materials in-channel work. Excavation equipment
would reform the proposed channel and lay back the bank grades. Approximately 200
cubic yards of earth would be moved, and less than 50 cubic yards of excess soil,
sackcrete and embankment materials would be off-hauled to a landfill. A non-woven
filter fabric would be placed in areas where rock rip-rap is proposed prior the backfilling
with approximately 200 cubic yards rock. Large rock would be placed first, and 6"
diameter tubes would be spaced among the fill area to allow access to the soil for final
installation of willow stakes. Smaller rock would fill the voids. Page Mill Road would not
be closed for this work, except for occasional equipment crossings.
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 14 October 2015
.
•i 2. The soldier pile wall would then be constructed on the Page Mill. Road bank. Solider
Piles would be placed: in drilled holes filled with concrete adjacent to the creek.
Concrete lagging would be placed within the soldier piles to form a wall. The area in
between the soldier pile wall and the existing secant wall at the Page Mill Road edge of
pavement would be filled with aggregate base material. Geotechnical tie backs may
also be installed using auger equipment if deemed necessary. During this portion of the
construction,.one-lane of Page Mill Road would be closed. Prior to reintroducing stream
flows into the creek, the contractor would verify that all deleterious construction materials
would be removed from the creek, that finish grading was complete, and that all irrigation
(if needed), erosion control seeding, fabric and wattles were in place.
3. After water is re-introduced to the creek, willow poles'would be planted to minimize the
impact of the rock veneer grade control structure along the channeland banks of the
creek• . Other plant materials would be installed as specified.
•
•
• Construction Equipment
•
Construction of the coffer damwouldrequire use of a large water-filled, rubber bladder, or other
similar impervious barrier, to block stream flows near the box culvert that passes under Page
Mill Road. Water would be captured in'a pipe and directed around the project area. When
dewatering the channel, biologists would be on-site to rescue stranded fish and move them to
more suitable pools nearby. ' __ •
'
Construction equipment used for excavating the stream channel would include a small, rubber
tired combination loader/backhoe, a track mounted excavator, an all-terrain bobcat, and
standard dump trucks. The stream channel work-area would be narrow,with only designated
pull-outs for equipment to pass. The narrow work area would require placement of rock and
finishing of lower sections first before backing out to finish upper sections. Hand work would
also be required for recontouring bank slopes.
Large truck mounted augur drills would drill holes for the soldier piles from Page Mill Road. The
road would remain open, though only one lane would be available with fiaggers directing one-
way traffic around theconstruction site..,Concrete would be poured into the holes from trucks
parked directly above. Piles and lagging would be placed using boom trucks or truckmounted •
cranes. Tiebacks would be installed 'as backfill from dump trucks would be' layered in and
compacted behind the wall. A drainage system, directing sheet flows from Page Mill Road away
from the project area would be'installed. Subgrade would be placed, compacted and finished
graded. Any paving damaged during construction would be replaced. Compactors, graders
and rollers would be the equipment needed to finish the road.
Restoration would include finish grading the recontoured banks, seeding native species (either
by hand or with a hydroseeder), installation of all erosion control features (salvaged mulch or
straw, jute netting, straw wattles and minor drainage) and driving the willow stakes: into the
designated spaces among the rock armoured channel. Follow up monitoring and maintenance
would be directed by the Town of Los Altos Hills. :
3.3 Project—Related Approvals, Agreements, and Permits
•
The Town of Los Altos Hills sought recommendations for rebuilding Matadero Creek which were
summarized in a memo from Wreco Engineering (Wreco 2013). Alternatives addressed in that
memo include:
• Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 15 ' • October 2015
A. Environmentally Sensitive.Long-term Solutions — Removal of concrete channel bottom in
and around the box culvert under Page Mill Road, filling the downstream scour hole, and
filling the downstream channel bottom to eliminate the fish barrier and reduce height of
embankments needing stabilization:and restoration back to original condition. Other fish
barriers exist downstream (1-280 crossing, among others), eliminating the potential
immediate benefits to fish barrier removal. Some concerns remain about raising the
creek bed elevation, the effects on 100 year water surface elevations and.potential
flooding of the.roadway. Variations of environmentally sensitive alternatives include:
a. Vegetated Rip Rap
b. Root Wads, Rock Slope Protection, and Willows
c. Log Cribwall
d. Gabion Basket, Hilfiker, or Terra Mesh Walls
B. Structural Alternatives
a. Concrete Retaining Wall- Requires too much excavation
b. Keystone Block Wall with Geogrid
c. Soldier Pile with Lagging
The selected alternative combines components of the Environmentally Sensitive (vegetated rip-
rap) with Structural Alternatives (Soldier Pile with Lagging) to address the failing channel
conditions.
3.4 Project—Related Approvals, Agreements, and Permits
The information contained in this Initial Study will be used by the Town of Los Altos Hills (the
CEQA Lead Agency) as it considers whether or not to approve the proposed project. If the
project is approved, the Initial Study would be used by the Town and responsible and trustee
agencies in conjunction with various approvals and permits. These actions include, but may not
be limited to, the following approvals by the agencies indicated:
Town of Los Altos Hills
• Clearing and Grading Permit
California Department of Transportation
• Encroachment Permit '
Army Corps of Engineers
• Clean Water Act Section 404 Nationwide or Individual Permit
California-Department of Fish and Wildlife
• Application for Section 1602 Lake and Streambed Alteration Agreement
Regional Water Quality Control Board
• Clean Water Act Section 401 Water Quality Certification
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 16 October 2015
4.0. ENVIRONMENTAL FACTORS POTENTIALLY AFFECTED
The environmental factors checked below would be potentially affected by this project, involving
at least one impact that is potentially significant unless mitigation is incorporated, as indicated
by the checklist on the following pages.
X Aesthetics Land Use/Planning
Agriculture and Forestry Mineral Resources
Resources
X Air Quality X Noise
X Biological Resources Population'and Housing.
X Cultural Resources X Public Services
X Geology and Soils Recreation.
Greenhouse Gas Emissions X Transportation/Traffic
X Hazards and Hazardous Utilities
Materials
X Hydrology and Water Quality X Mandatory Findings of
Significance'
Determination
On the basis of this initial evaluation:
I find that the project COULD NOT have a significant effecton the environment and a
NEGATIVE DECLARATION will be prepared. .
XII find that although the project could have a significant effect on the environment, there will
not be a significant effect in this case because revisions in the project have been made by or
agreed to by the project proponent. A MITIGATED NEGATIVE DECLARATION will be
prepared.
nI find that the project MAY have a significant effect on the environment, and an
ENVIRONMENTAL IMPACT REPORT is required.
' I find that the project MAY have a "Potentially significant impact" or "potentially significant
unless mitigated" impact on the environment, but at least one effect 1) has been adequately
analyzed in an earlier document pursuant to applicable legal standards, and 2) has been
addressed by mitigation measures based on the earlier analysis as described on attached
sheets. An ENVIRONMENTAL IMPACT REPORT is required, but it must analyzeonly the
effects that remain to be addressed. '
I find that although the project could have a significant effect on the environment, because all '"
potentially significant effects (a) have been analyzed adequately in 'an earlier EIR or
NEGATIVE DECLARATION pursuant to applicable standards, and (b) have been avoided or
mitigated pursuant to that earlier EIR or NEGATIVE DECLARATION, including revisions or
mitigation measures that are imposed upon the proposed project, nothing further is required.
Signature Date
Suzanne Avila, Director of Planning and Building Department '
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 17 October 2015
Initial Study Checklist
This section describes the existing environmental conditions in and near the project area and
evaluates environmental impacts associated with the proposed project. The environmental
checklist, as recommended in the CEQA Guidelines (Appendix G), was used to identify
environmental impacts that could occur if the proposed project is implemented. The right-hand
column in the checklist lists the source(s) for the answer to each question. .The cited sources
are identified at the end of this section.
Each of the environmental categories was fully evaluated, and one of the following four
determinations was made for each checklist question:.
"No Impact" :means that no impact to the- resource would occur as a result of
implementing the project.
"Less than Significant Impact" means that implementation of the project would not
result in a substantial and/or adverse change to the resource, and no, mitigation
measures are required.
"Less than Significant with Mitigation Incorporated" means that the incorporation of
one or more mitigation measures is necessary to reduce the impact from potentially
significant to less than significant.
"Potentially Significant Impact" means thatthere is either substantial evidence that a
project-related effect may be significant, or, due to a lack of existing information,
could have the potential to be significant. .
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 18 October 2015
{
4.1 Aesthetics
Less than -
Potentially Significant Less than
No
Significant with Significant Impact Source
Impact Mitigation Impact
AESTHETICS—Would the project: Incorporated
a) Have a substantial adverse effect on a ❑ ❑ ❑ ® 2
scenic vista?
b) Substantially damage scenic resources, ❑ ❑ ❑
including, but not limited to, trees, rock 1
outcroppings, and historic buildings within
a state scenic highway?
c) Substantially degrade theexistingvisual ❑ ® , ❑ , ❑
character or quality of the site and its 1,2
surroundings?
d) Create a new source of substantial light or ❑ ❑ ❑ .
glare which would adversely affect day or
nighttime views in the area?
Environmental Setting
The project area is located on and adjacent to the Page Mill Road, along a portion of Matadero
Creek within the Town of Los Altos Hills. The project area is located immediately downstream
of a concrete box culvert which traverses under Page Mill Road, approximately one-quarter mile
west of Interstate 280. The project area 'is approximately one acre and includes about 350
linear feet of stream channel paralleling the north side of Page Mill Road between Arastradero
Road and Berry Hill. Court. 'The project area is' surrounded by low density residential
development.
Views of the project area are generally limited to the surrounding residences, motorists, and
pedestrians along adjacent trails. Publically available views are confined to views from a trail
that runs parallel to Page Mill Road. Vegetation and topography prevent the project area from
being viewed outside of the immediate vicinity.
The project area is not located along any designated or eligible scenic highways and is not
visible from Interstate-280 (1-280), which is the nearest designated scenic highway located more
than 0.25 miles north of the Project Area(California Department of Transportation 2012).
Discussion of Impacts
a) -No Impact. For the purposes of this analysis, a scenic vista is defined as a vantage
point with a broad and expansive view of a significant landscape feature (e.g. a
- mountain, range, the Bay, . lake, or coastline) or of a significant historical or
architectural feature (e.g. views of a historic tower). No scenic vistas exist in or near
the project area. Therefore, the project would have no impact on these resources.
b) No Impact. A significant impact may occur if scenic resources within a state scenic
highway would be damaged or removed by a project. The project area is not located
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 19 October 2015
within an officially designated state scenic highway.3
c) Less than Significant Impact with Mitigation Incorporated. A significant impact
may occur if a project were to introduce incompatible visual elements on the project
area or visual' elements that would be incompatible with the character of the project
area or the area surrounding the site. The proposed project would not introduce an
incompatible visual element to the site or:surrounding area. The project does not
propose construction of any new buildings or changes to the project area other than
bank stabilization improvements. The majority of viewers of the project area are
limited to motorists traveling on Page Mill Road. These motorists would have fleeting
views of the proposed project and potentially a lower expectation of an aesthetically
pleasing view, particularly given their perceived focus on the road ahead, as well as
the general lack of scenic vistas or points of interest to attract patrons to in the
immediateproject vicinity. Additional views of the project area are available along a
public trail that runs parallel to the east of the project area. During the construction
phase of the project, elements such as construction vehicles, construction materials,
and other temporary construction elements would be located on the project area.
These temporary elements would be removed upon completion of the construction
phase. Once the culvert and outfall modifications are in place, and restoration is
completed views would be similar to existing conditions. Tree removal would occur
as part of the project. However, implementation of.Mitigation Measures BIO-5 and 6
would require revegetation of altered areas. Therefore, the proposed project would
not significantly impact the visual character or quality of the site or surroundings and
no further analysis is required.
d) No Impact. Construction of the proposed project would not create a significant
source of light or glare during daytime. The long-term operation of the project would
not result in the addition of new sources of light and glare. Upon completion of•
construction the light and glare conditions at the project area would be nearly
identical to existing conditions. The proposed project would not create a new source
of substantial light or glare which adversely affect day or nighttime views in the area.
4.2 Agriculture and Forestry Resources
Less than:
Potentially Significant Less than
o
AGRICULTURE AND FORESTRY Significant with Significant Impact Source
Impact Mitigation Impact
RESOURCES—Would the project: . Incorporated .
a) Convert Prime Farmland, Unique ❑ ❑ . ❑
Farmland, or Farmland of Statewide
Importance (Farmland), as shown on the
maps prepared pursuant to the Farmland 4
Mapping and Monitoring Program of the. .
California Resources Agency, to non- . . .
agricultural use?
b) Conflict with existing zoning for agricultural ❑ ❑ ❑ // . 1,3,4
use, Or a Williamson Act contract?
3 Ca/trans Scenic Highway Program website. Accessed at http://www.dot.ca.gov/hq/LandArch/scenic/cahisys.htm,
November 29, 2010. .
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills . 20 . . October 2015
Less than
Potentially Significant Less than No
AGRICULTURE AND FORESTRY Significant. with Significant Impact Source
Impact Mitigation Impact
RESOURCES—Would the project: Incorporated
c) Conflict with existing zoning for, or cause ❑ ❑ ❑ El
rezoning of, forest land (as defined in
Public Resources Code section 12220(g)),
timberland (as defined by Public • 1,3,4
Resources Code section 4526), or
timberland zoned Timberland Production
(as defined by Government Code section
51104(g))?
d) Result in the loss of forest land or ❑ . ❑ ❑ A
conversion of forest land to non-forest 1
use?
e) Involve other changes in the existing ❑ ❑ ❑ ® 1
environment, which, due to their location
or nature, could result in conversion of
Farmland, to non-agricultural use or
conversion of forest land to non-forest
use??
Environmental Setting
The project area does not contain any farmland or forestry land and is not designated for
agricultural or forestry uses or Prime, 'Statewide, or Locally Important Farmland (California
Department of Conservation 2010). The proposed project is located in a semi-developed area
and follows existing roads, easements, and rights-of-way. Surrounding land is developed with
low density residential'and open space uses.
Discussion of Impacts
a-e) No Impact. According to the 2010 Farmland Mapping and Monitoring Program from
the State Department of Conservation, the project area is located in an area that is
designated as Urban, Built-Up Land and Other Land and the proposed project would,
therefore, have no impact on agricultural uses. The project area is:also not zoned for
agricultural use or under a Williamson Act contract. The proposed project involves
the construction and maintenance of storm drain facilities and infrastructure within an
already developed area that does not include any farmland. Therefore, the proposed
project would not result in the,conversion of forest land or farmland to a non-forest
use or a non-agricultural use, and would thus have no impact on forestry• or
agricultural resources.
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 21 October 2015
4.3 Air Quality
AIR QUALITY—Where available, the Less than
significance criteria established by the applicable Potentially Significant Less than
air quality management or air pollution control Significant with Significant Im act Source
district may be relied upon to make the following Impact Mitigation Impact p
determinations. Would the project: Incorporated
a) Conflict with or obstruct implementation of ❑ ❑ ❑ 1,2,10
the applicable air quality plan?.
b) Violate any air quality standard or 1,2,10
contribute to an existing or projected air
quality violation? . .
c) Result in a cumulatively considerable net ❑ ® ❑ ❑ 1,2,10
increase of any criteria pollutant for which
the project region is non-attainment under
an applicable federal or state ambient air
quality standard (including releasing
emissions which exceed quantitative
thresholds for ozone precursors)?
d) Expose sensitive receptors to substantial ❑ ►� ❑ ❑ 1,2,10
pollutant concentrations?
e) Create objectionable odors affecting a ❑ ❑ ® ❑ . 1,2,10
substantial number of people?
Environmental Setting
The proposed project is located in in Santa Clara County, adjacent to San Mateo County; both
counties are part of the San Francisco Bay Area Air Basin (SFBAAB). Air quality in this area is
determined by such natural factors as topography, meteorology, and climate, in addition to the
presence'of existing air pollution sources and ambient conditions. The potential, for high
pollutant concentrations developing at a given location depends upon the quantity of pollutants
emitted into the atmosphere in the surrounding area, orupwind, and the ability of the ,__
atmosphere to disperse the contaminated air. In the peninsula, air pollution potential is higher in.
the southeastern portion (including Los Altos Hills)'than in other parts; this is the area most
protected from the high winds and fog of the marine layer. Pollutant transport from upwind sites
is common. In the southeastern portion of the peninsula, air pollutant emissions are relatively
high due to motor vehicle traffic as well as stationary sources. Sources of air pollutants in the
nearby vicinity of the project area include vehicle emissions and other residential activities
(cooking, 'wood burning, and/or charcoal grilling; emissions associated with lawn and garden
maintenance; emissions associated with application of paints and coatings; etc.) The primary
sensitive receptors in,the vicinity are residents, which may include children, elderly people, or
people with respiratory illnesses.
Both the U.S. EPA and California have developed several ambient air quality standards (AAQS)
which have become increasingly stringent over the last several decades. Although emissions
and air pollution concentrations have decreased considerably, the SFBAAB is still classified as
"nonattainment" with respect to 'standards for ozone which is formed in the atmosphere by
chemical reactions between reactive organic gases (ROG) and oxides of nitrogen (NO,3 rather
than being emitted directly—and particulate matter (PM). Santa Clara County, in which the
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills '22 ' October 2015
project is proposed, is classified as a non-attainment basin for ozone thresholds but achieves an.
attainment level for carbon monoxide emissions.
For the proposed project, the only sources of emissions are those:associated with construction;
i.e., the proposed:project does not involve the construction of:a new air emissions source or of
developments which would attract motor vehicles, with their associated air emissions. New
construction equipment has been subject to increasingly stringent emissions requirements at
the Federal level (e.g., 40 CFR 89 and 1039), designated "Tier 1", "Tier 2", "Tier 3", etc.; older
construction equipment is subject to potential retrofit requirements required by the State of
California(13 CCR 2449, 13 CCR 2450-2466, and 17,CCR 93116).
There are multiple definitions of what emissions level would be considered "significant". If a •
large ("major") stationary source of air pollution were proposing to locate at the project area,
Federal New Source Review (NSR) regulations define "significant" emissions as being :100 tons
per year (TPY) of CO or 40 TPY:of ROG or NO..4 .For temporary activities at the project area.
such as'construction, if the project required Federal support or approvals; General Conformity
regulations would require a quantitative, formal determination of General Conformity with State
Implementation Plans (SIPs) if emissions Of NOR, ROG, or CO were in excess of 100:tons per
year(referred to as Federal de Minimis levels).5
In 2010, BAAQMD adopted quantitative thresholds:of significance for construction activities and
identified Best Management Practices for controlling PM associatedwith fugitive dust. The
quantitative thresholds were 82 lb/day for exhaust PM10 and 54:lb/day for exhaust PM2.5, NOR,
'and ROG (these thresholds correspond to 15 TPY and 10 TPY, respectively, if construction
were to last for 365 days). However, BAAQMD 'is no longer recommending that [those]
Thresholds be used as a generally applicable measure of a project's significant air quality
impacts.6 In the -previous version of the BAAQMD CEQA .Guidelines,' determination of
significance is based only upon whether or not Best Management Practices for controlling
fugitive dust (which are very similar to those identified in 2010) are implemented.-
Discussion of Impacts
a, b) Less than Significant with Mitigation Incorporated. Construction activities would
result in short-term increases in emissions:from the use of heavy equipment a ui ment that
generates dust; exhaust, and tire-wear emissions; soil disturbance; materials used in
construction; and construction traffic. Project construction would produce fugitive
dust (PM10 and PM2.5) during:`ground disturbance: and would generate carbon
monoxide, ozone precursors, and other emissions from vehicle and equipment
operation. Best .management practices• (BMPs) recommended by BAAQMD and
identified below in Mitigation Measure AIR-1 would be implemented during
construction to minimize fugitive dust. Construction emissions would be temporary,
lasting approximately two months, and would not have long-term effects on air
quality in the Bay Area.' Because of the small area of disturbance, temporary nature
of the emissions, and implementation' of .construction measures, impacts on air
4 40 CFR 51.165(a)(1)(x)(A);51.166(b)(23)(i);52.21(b)(23)..
Separately, Federal regulations,for General Conformity identify "routine :maintenance and repair activities,
including repair and'maintenance of administrative sites, roads, trails, and facilities"as "actions which would
result in...an increase in emissions that is clearly de minimis"[40 CFR 93.153(c)(2)(iv)]
6 . BAAQMD, "Updated CEQA Guidelines", available from http://www.baagmd.gov/Divisions/Planning-and-
Research/CEQA-GUIDELINES/Updated-CEQA-Guidelines.aspx.
7 BAAQMD, `BAAQMD CEQA Guidelines", December 1999,pp. 13-15.
Matadero Creek Restoration and Bank.Stabilization Project Draft Initial Study
Town of LosAltosHills 23 October 2015
quality would be less. than significant and .would comply with the Bay Area 2010.
Clean Air Plan.
Mitigation Measure AIR-1: Construction Emissions
• All exposed surfaces (e.g., parking areas, staging areas, soil piles, graded areas)
will be watered two times per day.
• All haul trucks transporting soil, sand, or other loose material off-site will be
covered. .
• All visible mud or dirt track-out onto adjacent public roads will be removed using
wet power vacuum street sweepers at least once per day. The use of dry power
sweeping is prohibited.
• All roadways and sidewalks to be paved will be completed as soon as possible.
• Idling times will be minimized either by shutting equipment off when not in use or
reducing the maximum idling time to five minutes (as required by the California
airborne toxics control measure Title 13, Section 2485 of California Code of
Regulations). . .
• Clear signage will be provided for construction workers at all access points.
• All construction equipment will be maintained and properly tuned in accordance
with manufacturer's specifications,: and all equipment will be checked by a
certified visible emissions evaluator.
• A publicly visible sign with the telephone number and person to contact at the
lead agency regarding any dust complaints will be posted in or near the project.
area. The contact person will respond to complaints and take corrective action
within 48 hours. The Air District's phone number will also be visible to ensure
compliance with applicable regulations. .
c) Less than Significant with Mitigation Incorporated. As discussed under items a)
b), the project would result in minor construction-related emissions. It would not
result in a. cumulatively considerable net increase of any criteria pollutant. The
project would cause short-term air quality impacts as a result of construction
activities; however, it would not result .in long-term' or cumulatively considerable
increases in air quality pollutant emissions for which the Bay Area is currently in non-
attainment (ozone and particulate matter). Implementation of the BMPs included in
Mitigation Measure Air-1 would ensure that the temporary increase in air pollutant
emissions associated with construction activities would result in less than significant
contributions to cumulative pollutant levels in the region.
d) .Less than Significant with Mitigation Incorporated. The primary sensitive
receptors in the vicinity are residents and, employees and customers of commercial
development, which may include children, elderly people, or people with respiratory
illnesses. Sensitive receptors located in close proximity to several locations along
the construction area could be exposed to temporary air pollutants from construction
activities,, such as fugitive dust, ozone precursors,. and carbon monoxide. The
duration of 'construction activities would be limited. Basic construction measures
recommended by BAAQMD, listed in Mitigation Measure Air-1, would be•
implemented during construction to minimize air pollutants. New construction
equipment has been subject to increasingly stringent emissions requirements at the
Federal level (e.g., 40 CFR 89 and 1039), designated"Tier 1", "Tier 2", "Tier 3", etc.;
older constructionequipment is subject to potential retrofit requirements required by
the State of California (13 CCR 2449, 13 CCR 2450-2466, and 17 CCR 93116). As
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Town of Los Altos Hills 24 ` October 2015
a result, sensitive receptors in the vicinity of the project would not be exposed to.
substantial pollutant concentrations, and impacts would be less than significant.
e) Less Than Significant Impact: Construction activities would involve the use of
gasoline or diesel-powered equipment that emits exhaust fumes. These activities
would take place intermittently throughout the workday, and the associated odors are
expected to dissipate within the immediate vicinity of the work area. Persons near
the construction work area may find these odors objectionable. However, the
proposed project would not include uses that have been identified by BAAQMD as
potential sources of objectionable odors, such as restaurants, manufacturing plants,
landfills, and agricultural and industrial operations. The infrequency of the
emissions, rapid dissipation of the exhaust and other odors into the air, and short-
term nature of the construction activities would result in less than significant odor
impacts.
4.4 Biological Resources
Less than
Potentially Significant Less than
No
Significant with Significant Source
BIOLOGICAL RESOURCES—Would the Impact Mitigation ImpactImpact
p
project: Incorporated
a) Have a substantial adverse effect, either ❑ ►1 ❑ ❑ 1,7,8
directly or through habitat modifications, on
any species identified as a candidate,
sensitive, or special-status species in local
or regional plans, policies, or regulations,:o r
by the.California Department of Fish and
Wildlife or U.S. Fish and Wildlife Service?
b) Have a substantial adverse effect on any ❑ ®. . ❑ ❑ 1,7,8
riparian habitat or other sensitive natural
community identified in local or regional
plans, policies, or regulations or by the
California Department of Fish and Wildlife
or U.S. Fish and Wildlife Service?
c) Have a substantial adverse effect on ❑ ® ❑• ❑ 1,7,8
federally protected wetlands as defined by
Section 404 of the Clean Water Act
(including, but not limited to, marsh, vernal
pool, coastal, etc.)through direct removal,
filling, hydrological interruption, or other
means?
d) Interfere substantially with the movement of ❑ ❑ // ❑ 1,7,8
any native resident or migratory fish or
wildlife species or with established native
resident or migratory wildlife corridors, or
impede the use-o f native wildlife nursery
sites?
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Town of Los Altos Hills 25 October 2015
Less than
Potentially Significant Less than
o
BIOLOGICAL RESOURCES—Would the Significant with Significant Impact Source
Impact Mitigation Impact
project: Incorporated
e) Conflict with any local policies or ❑'_ ® ❑ ❑ 1,7,8
ordinances protecting biological resources, :
such as a tree preservation policy or
ordinance?
f) Conflict with the provisions of an adopted ❑ ❑, ❑ ® 1,7,8
Habitat Conservation Plan, Natural
Community Conservation Plan, or other
approved local, regional, or state habitat
conservation plan?
The following analysis of biological resources is based on the Biological Resources Assessment
(BRA) prepared by WRA, Inc. (Appendix A).
Regulatory Setting
Sensitive Biological Communities
Sensitive biological communities include habitats that.fulfill special functions or have special
values, such as wetlands, streams, and riparian habitat. These habitats are regulated under
federal regulations (such as the Clean Water Act [CWA]), state. regulations (such as the Porter-
Cologne Act, the California Department of Fish and Wildlife (CDFW) Streambed Alteration
Program, and CEQA), or local ordinances or policies (such as City or County Tree Ordinances,
Special Habitat Management Areas, applicable Local Coastal Programs [LCP], and General
Plan Elements).
Waters of the United States
The U.S. Army Corps of Engineers (Corps) regulates "Waters of the United States" under
Section 404 of the CWA. Waters of the United States are defined in the Code of Federal
Regulations as waters susceptible to use in commerce, including interstate waters and
•wetlands, all other waters (intrastate waterbodies, including wetlands), and their tributaries (33
CFR 328.3). Potential wetland areas are identified by the presence of(1) hydrophilic vegetation
(or hydrophytes), (2) hydric soils, and (3) wetland hydrology. Areas thatare inundated at a
sufficient depth and for a sufficient duration to exclude growth of hydrophilic vegetation are
subject to CWA Section 404 jurisdiction as "non-wetland waters" (also referred toas "other
waters") and are often characterized by an ordinary high watermark (OHWM). Non-wetland
waters, for example, generally include lakes, rivers, and streams. The placement of fill material
into Waters of the United States generally requires an individual or nationwide permit from the
Corps under Section 404 of the CWA.
Waters of the State
The term "Waters of the State" is defined by the Porter-Cologne Act as "any surface water or
groundwater, including saline waters, within the boundaries of the state." The Regional Water
Quality Control Board (RWQCB) protects all waters in its regulatory scope and has special
responsibility for wetlands, riparian areas, and headwaters. These waterbodies have high
resource value, are vulnerable to filling, and are not systematically protected by other programs.
The RWQCB jurisdiction includes "isolated" wetlands and waters that may not be regulated by
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Town of Los Altos Hills 26 October 2015
the Corps under the CWA.- Waters of the State are regulated by the RWQCB under the State
Water Quality Certification Program,.which regulates discharges of fill and dredged material
under Section 401 of the CWA and under the Porter-Cologne Water Quality Control Act.
Projects that require a Corps permit, or that fall under other federal jurisdiction, and that have
the potential to impact Waters of the State, are required to comply with the terms of the Water
Quality Certification. If a proposed project does not require a federal permit, but does involve
dredge or fill activities that may result in a discharge to Waters of the State, the RWQCB has the
option to regulate the dredge and fill activities under its state authority in the form of Waste
Discharge Requirements.
Streams, Lakes, and Riparian Habitat
Streams and lakes, as habitat for fish and: wildlife species, are subject to jurisdiction by the
CDFW under Section 1600-1616 of the California Fish and Game Code (CFGC). Alterations to
or work within or adjacent to streambeds or lakes generally require an application for a Section
1602 Lake and Streambed Alteration Agreement. The term "stream", which includes creeks and
rivers, is defined in the California Code of Regulations as "a body of water that flows at least
periodically or intermittently through a bed or channel having.banks and supports fish or other
aquatic life [including] watercourses having a surface or subsurface flow that supports or has
supported riparian vegetation" (14 CCR 1.72). In :addition, the term "stream" can include
ephemeral streams, dry washes, watercourses with subsurface flows, canals, aqueducts,
irrigation ditches, and other means of water conveyance if theysupport aquatic life, riparian
vegetation, or stream-dependent terrestrialwildlife (CDFG 1994). "Riparian" is defined as "on,
or pertaining to, the banks of a stream" (CDFG 1994). "Riparian vegetation" is defined as
vegetation which occurs in and/or adjacent to a stream and is dependent on, and occurs
because of, the stream itself" (CDFG 1994). Removal of riparian vegetation also requires an
application for a Section 1602 Lake and Streambed Alteration Agreement from the CDFW.
Other Sensitive Biological Communities
Other sensitive biological communities not discussed above include habitats that fulfill special
functions or have special values. Natural communities considered sensitive are those identified
in local or regional plans, policies, regulations, or by the CDFW. The CDFW ranks sensitive
communities keeps records of their occurrences in its California Natural Diversity Database
(CNDDB; CDFW 2014). Sensitive plant communities are also identified in other reports
prepared by the CDFW (CDFG 2003, 2007, 2009). California Natural Diversity Database
vegetation alliances are ranked 1 through 5 based on NatureServe's (2014) methodology, with
those alliances ranked globally (G) or statewide (S) as 1 through 3 considered sensitive.
Impacts to sensitive natural communities identified in local or regional .plans, policies, or
regulations, or those identified by the CDFW or the U.S. Fish and Wildlife Service (USFWS),
must be considered and evaluated under CEQA (CCR Title 14, Div. 6, Chap. 3, Appendix G).
Specific habitats may also _ be identified as sensitive in city or county general plans or
ordinances.
Special-Status Species
Special-status species include those plants and wildlife species that have been formally listed,
are proposed as endangered or threatened, or are candidates for such listing under the federal
Endangered Species Act (ESA) or California Endangered Species Act (CESA). These acts
afford protection to both listed and proposed species. In addition, CDFW Species of Special
Concern, which are species that face extirpation in California if current population and habitat
trends continue, USFWS Birds of Conservation Concern, and CDFW special-status
invertebrates are all considered special-status species. Although CDFW Species of Special
Concern generally have no special legal status, they are given special consideration under
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Town of Los Altos Hills 27 October 2015
CEQA. In addition to regulations for special-status species, most birds in the United States,
including non-status species, are protected by the Migratory Bird Treaty Act of 1918. Under this
legislation, destroying, active nests, eggs, and young is illegal. Plant species on California
Native Plant Society (CNPS) Inventory of Rare and Endangered Plants (CNPS 2014) with
California Rare Plant Ranks (Rank) of 1 through 4 are also considered special-status plant
species and. must be considered under the CEQA.
Relevant Local Policies, Ordinances, and Regulations
Town of Los Altos Hills Tree Protection Ordinance
Chapter 2 of the Los Altos Hills Municipal Code requires a permit for the alteration or removal of
any street tree, shrub, or plant in any street, park, or public place in the Town. Permits are also
required for certain activities, such as excavation or placement ofconcrete, with a distance of 10
feet from the center of the trunk of any street tree. Permits are also required by the Town for
the removal of Heritage Oaks, which are defined as any tree of the genus Quercus that has a
trunk or multiple trunks measuring 36 inches in circumference (approximately 12 inches in
diameter) at a point 4 feet above the root crown (LAHMC 5-8.02(2)). Trees deemed by the
Town to be Heritage Trees cannot be removed or damaged except with approval of the Town
following a:public hearing.
Biological Communities in the Project Area
WRA, Inc. biologists conducted a site assessment on October 21, 2014. See Appendix A,
Figure 2, for a map of biological communities and for lists of observed or documented species
within or near the project area. Non-sensitive biological communities in the project area include
developed land and disturbed/landscaped areas (e.g., roadside shoulder'or adjacent mown
areas). Three sensitive biological communities occur in the project area: perennial wetland,
perennial stream (Matadero Creek), and mixed riparian woodland.
The developed and disturbed/landscaped portions of the project area include a two-lane paved
road and adjacent mowed areas lacking substantial tree cover.
Approximately 0.03 acre of perennial freshwater wetlands occur in vegetated .portions of
Matadero Creek northwest and southeast of Page Mill Road. These wetlands are dominated by
cattail (Typha sp.) upstream (southeast) of Page Mill Road and by watercress (Nasturtium
officinale) and creeping bentgrass (Agrostis:aff. gigantea) downstream (northwest) of Page Mill
Road. The perennial wetlands in the project area fit the description of Holland's coastal and
valley freshwater marsh (1986) and contain elements of Sawyer's Typha sp. Alliance (cattail
marshes) and Agrostis gigantea Semi-Natural Herbaceous Stands (bent grass meadows)
(Sawyer et al. 2009).
An approximately 333-foot-long stretch of Matadero Creek (approximately 0.04 acre, excluding
areas mapped as in-stream perennial wetlands) occurs within the project area. Matadero Creek
is a perennial USGS blue-line stream and was flowing during the site visit conducted for this
assessment. The creek was mapped based on the location of the OHWM, as evidenced by
scouring and sediment/drift deposits along the streambed. The creek is daylighted within the
project area. , Upstream (southeast) of Page Mill Road, the creek has a, relativelyshallow
gradient and contains a large area of cattail wetland adjacent to the' road. Downstream
(northwest) of Page Mill Road, the creek has a steeper gradient and is covered by a dense
riparian canopy dominated by arroyo willow (Salix lasiolepis) and northern California black
walnut (Juglans hindsii). The creek is armored by concrete sack walls within the immediate
vicinity of Page Mill Road. Downstream (northwest) of Page Mill Road, where the concrete
armoring ends, a nick-point has developed, resulting in a steeply incised channel with
substantial erosion, undercutting, and bank slumping.
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Town of Los Altos Hills 28 October 2015
In the project area, approximately 0.54 acre of mixed riparian woodland occurs along Matadero
Creek up- and downstream of Page Mill Road. Dominant tree species include arroyo willow and
northern California black walnut; valley oak (Quercus lobata) and coast live oak (Quercus
agrifolia) are also present at lower density. Downstream (northwest) of Page Mill Road, the
riparian canopy cover density is generally greater than 80 percent. The understory is dominated
by non-native annual grassesand other native and non-native species such as fringed
willowherb (Epilobium ciliatum), Himalayan blackberry (Rubus armeniacus), California
blackberry (Rubus'.ursinus), upright snowberry (Symphoricarpos a/bus var. laevigatus), and
poison oak (Toxicodendron diversilobum). Many of the species found within the.riparian
woodland are listed as having."moderate" to "high" potential for invasiveness by the Cal-IPC
(2014). The understory also contains a large number of naturalized horticultural species.
Upstream (southeast) of Page Mill Road, the riparian canopy is less dense and is dominated by
a similar suite of tree species, but with relatively higher cover ofvalley oak and coast live oak.
The understory upstream of Page Mill Road was dominated by non-native annual grasses and
other weedy vegetation that was mowed or otherwise maintained at 3.to 4 inches in height.
Mixed riparian woodland within' the project area can be classified as Central Coast.Arroyo
Willow Riparian Forest with elements of.Central Coast Live Oak Riparian Forest (Holland 1986).
The mixed riparian woodland fits the description of Sawyer's Salix lasiolepis Shrubland Alliance
(arroyo willow thickets) (Sawyer et al. 2009).
' Special-Status Species in the Project Area
Plants
Forty-seven special-status plant species have been documented from within the vicinity of the
project area (Appendix A, Figure 1). Many of these species occur in habitats that are not
present in the project area, such as coastal habitats, broadleaved or coniferous upland forests,
chaparral, valley and foothill grasslands, vernal pools, or serpentine soils. Special-status
species that occur in habitats not present in the project area were determined to have no
potential to occur in the project area. For special-status species known to occur in riparian
woodland (e.g., western leatherwood, Dirca occidentalis, CNPS 16.2 or Loma Prieta hoita,
Hoita strobilina, CNPS 16.1) or perennial wetlands (e.g., Hoover's button-celery, Eryngium
aristulatum var. hooveri, CNPS 1B.1, alkali milk-vetch, Astragalus tener var. tener, CNPS 1 B.2,
or legenere, Legenere limosa, CNPS 1 B.1), the project area may contain elements of suitable
habitat. However, no special-status plant species were identified within the project area during
the site visit (with the exception of northern California black walnut, see discussion below), and
it was determined that the fragmented, disturbed nature of habitat within. the project area,
including the high cover of non-native, invasive species, greatly reduces the potential for
special-status plant species to occur there. As such, it was determined that no special-status
plant species are likely to occur within the project area and no additional plant surveys are
recommended.
Northern California black walnut has a California Rare Plant Rank of 16.1 (CNPS 2014)
indicating that it is rare, threatened, or endangered in California and elsewhere. However, this
ranking is intended for those individuals found within naturally occurring stands and within the
natural range of the species. ,Stands of this species from areas that previously contained walnut
orchards or naturalized individuals that occur as a result of dispersal by wildlife or humans, as
well as planted landscape specimens, are not regarded as a natural community or as special-
status plants. Northern California black walnut individuals observed during the site visit are not
within any known natural community, according to the CNPS (2014) or Sawyer et al. (2009),
and thus are not considered to be special-status. As a native tree, northern California black
walnut grows only in central California, being limited to a few isolated stands very much
restricted in area and in nearly every case present near historical Native American village sites.
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Town of Los Altos Hills 29 October 2015
or camping grounds (Jepson 1923, CNPS 2014). The.Juglans hindsii and Hybrids Special and
Semi-Natural Woodland Stands (Hind's walnut and related stands) identified by Sawyer et al.
(2009) occurs in native groves near the town of Walnut Creek in Contra Costa County and on
the banks of the Sacramento River in Sacramento County. Although the walnut trees within the
project area are not considered special-status, they are protected as riparian woodland by the
CDFW and may also be protected by the Town's tree protection ordinance.
Wildlife
Of the 61 special-status wildlife species with potential to occurwithin the vicinity of the project
area, 51 species were determined to occur in habitats not present in the project area or in
habitats that may be presentin the project area but which are of poor quality and unsuitable for
the species (Appendix A). The nest structure of one special-status wildlife species, dusky
footed woodrat (Neotoma fuscipes annectens; CDFW Species of Special Concern) was
observed within the project area during the site assessment. Additionally, eight special-status
wildlife species were determined to have a moderate to high potential to occur within the project
area. Species that.were observed within the project area or determined to have the potential to
occur there are discussed in detail below. One federal-listed species for which the project area
provides ostensibly suitable habitat but which is unlikely to occur there is also discussed.
Species with the Potential to Occur
San Francisco dusky-footed woodrat (Neotoma fuscipes annectens). CDFW Species of
Special Concern. High Potential. This subspecies of the dusky-footed woodrat occurs in the
Coast Ranges between San Francisco Bay and the Salinas River (Matocq 2003). Occupied
habitats are variable and include forest, woodland, riparian areas, and chaparral. Woodrats
feed on woody plants, but will also consume fungi, grasses, flowers, and acorns. Foraging
occurs on the ground and in bushes and trees. This species constructs robust
structures/houses made of sticks and twigs in areas with moderate cover and a well-developed
understory containing woody debris. Breeding takes place from December to September.
Individuals are mostly nocturnal and are active year-round.
Riparian woodland within the project area provides suitable habitat for the San Francisco dusky-
footed woodrat, and one woodrat nest structure was observed within the project area during the
site assessment. Woodrats are presumably present in the project area year-round.
White-tailed kite (Elanus leucurus). CDFW Fully Protected Species. Moderate Potential.
White-tailed kite is resident in open to semi-open habitats throughout the lower elevations of
California, including grasslands, savannahs, woodlands, agricultural areas, and wetlands.
Vegetative structure and prey availability are more important habitat elements than associations
with specific plants or vegetative communities (Dunk 1995). Nests are constructed mostly of , -
twigs and are placed in trees, often at the edges of habitats. Nest trees are highly variable in
size, structure, and immediate surroundings, ranging from shrubs to trees greater than 150 feet
tall (Dunk 1995). This species preys upon a variety of small mammals, as well as other
vertebrates and invertebrates.
White-tailed kite may nest within or adjacent to the project area, most likely in large riparian
trees; however, use of other trees, including those directly adjacent to development, is also
possible.
Allen's hummingbird (Selasphorus sasin). USFWS Bird of Conservation Concern. High
Potential. Allen's hummingbird, common in many portions of its range, is a summer resident
along the majority of California's coast and a year-round resident in portions.of coastal southern
California and the Channel Islands. Breeding occurs in association with the coastal fog belt,
and typical habitats used include coastal scrub, riparian, woodland and forest edges, and
1 ,
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 30 • October 2015
eucalyptus and cypress grove_s (Mitchell 2000). Thespecies feeds on flower nectar and forages
for insects and spiders.
Riparian woodland within the project area provides suitable habitat for this species, including for
nesting.
Nuttall's woodpecker (Picoides nuttallii). USFWS Bird of Conservation Concern. High
Potential:.. Nuttall's woodpecker, common in much. of its range, is a -year-round resident
throughout most of California, west of the Sierra Nevada Range. Typical habitat is oak or mixed
' woodland, including riparian areas (Lowther 2000). Nesting occurs in tree cavities, principally
those of.oaks and larger riparian trees. This species forages on a .variety of arboreal .
invertebrates.
Nuttall's woodpecker occurs regularly in and near developed areas of the San Francisco Bay
area where suitable habitat is present. Thisspecies may occur within the project area's riparian
woodland.
Oak titmouse (Baeolophus inornatus). .USFWS Bird of Conservation Concern. High
Potential. This relatively common species is resident throughout much of California including
most of the coastal slope, the Central Valley and the western Sierra Nevada foothills. Primary
habitat is woodland dominated by oaks; local populations have adapted to woodlands of pines
and/or junipers in some areas (Cicero 2000). The species nests in tree cavities, usually natural
cavities or those excavated by woodpeckers; birds may partially excavate their own cavities.
The species forages for seeds and arboreal invertebrates. .
As with Nuttall's woodpecker, this species is relatively common throughout much of the San
Francisco Bay area and may occur among riparian trees and oaks within the project area.
(Brewster's) Yellow warbler (Setophaga petechia brewsteri). CDFW Species of Special
Concern, USFWS Bird of Conservation Concern. Moderate Potential. Yellow warbler is a
neotropical migrant bird that'is widespread in North America. The Brewster's (brewster,)
subspecies is a summer resident and represents the vast majority of yellow warblers that breed
in California. In California, west of the Central Valley, typical yellow warbler breeding habitat
consists of dense riparian vegetation along watercourses, including wet meadows, with willow
growth being particularly favored (Shuford and Gardali 2008). Insects compose most of the
diet.
Riparian woodland within the project area provides suitable nesting habitat for yellow warbler.
San Francisco (saltmarsh) 'common yellowthroat (Geothlypis trichas sinuosa). CDFW.
Species of Special Concern, USFWS Bird of Conservation Concern: Moderate Potential.
This subspecies of the common yellowthroat is endemic to the greater Sap Francisco Bay. area
and is present year-round in and near marshes (salt, brackish, and fresh), riparian thickets, and
coastal swales. Yellowthroats require thick, continuous vegetative cover, preferring wetland
vegetation and adjacent transitional areas (Shuford and Gardali 2008). Nesting occurs in dense
vegetation, usuallyonor near the ground. Arthropods (insects, spiders) compose most of the
diet.
Riparian woodland and emergent marsh vegetation (cattails) within the project area provide ..
suitable habitat for this species, including for.nesting.
Western pond turtle (Actinemys marmorata). CDFW Species of Special Concern.
Moderate Potential;. Western pond turtle is the only native freshwater turtle in California,
occurring in suitable aquatic habitats throughout California, west of the Sierra-Cascade crest
and Transverse Ranges (Jennings and Hayes 1994). Occupied habitats are both annual and
perennial water bodies and include coastal lagoons, lakes, ponds, marshes, rivers, and streams
Matadero Creek Restoration and Bank.Stabilization Project Draft Initial Study
Town of Los Altos Hills ' ' ' 31 October 2015
from sea level to 5,500 feet in elevation. Manmade habitats such as stock and wastewater
storage ponds, percolation ponds, canals, and reservoirs are also used.. This species requires
low-flowing or stagnant freshwater with basking structures, including rocks, logs, vegetation
mats, mud banks, and sand. Whereas pond turtles require suitable aquatic habitat for most of
the year, features that become seasonally unsuitable are also used. To escape periods of high
water flow, high salinity, or prolonged dry conditions, pond turtles may move upstream and/or •
take refuge in vegetated, upland habitat for up to four months (Rathbun et al. 2002). Nesting
occurs from late April through July; nesting habitat consists of open, dry, unshaded upland
areas with friable soils near suitable aquatic habitat, where females excavate nests and lay
eggs (Rathbun et al. 1992).
Within"the project area, Matadero Creek provides suitable aquatic habitat for western pond
turtle, provided that water is present. Thus, turtles may occur only seasonally and/or dependent
upon annual precipitation levels, rendering the habitat of limited quality overall. Nesting within
the project area is unlikely due to the highly-incised and steep banks along.the creek.
California red-legged frog (Rana draytonii), Federal Threatened, CDFW Species of
Special Concern, Moderate Potential. California red-legged :frog (CRLF) is the only native
"pond frog"found throughout much of California and was listed as Threatened by the USFWS in
1996. Suitable CRLF breeding habitat is characterized by deep (approximately two feet), still or
slow-moving water associated with emergent marshand/or overhanging riparian- vegetation
(USFWS 2010). Such habitats must hold water for a minimum of 20 weeks, and include ponds
(ephemeral and perennial), streams/creeks (ephemeral and perennial), seasonal wetlands,
springs, . seeps, man-made features (e.g., stock ponds, roadside ditches), marshes, and
lagoons. Dependent upon local conditions, CRLF may complete its entire life cycle in a
particular habitat patch (e.g., a perennial pond suitable for all life stages), or utilize multiple
habitat types. In aquatic habitats that dry-down seasonally, CRLF often undergo aestivation (a
period of inactivity) during the dry months, over-summering in small mammal burrows, moist leaf
litter, incised stream channels, or large cracks in the bottom,of dried: ponds (Jennings and
Hayes 1995). Adult and sub-adult_(newly metamorphosed) CRLF may disperse from breeding
habitats to nearby riparian and/or aestivation habitats in the summer. Conversely, during the
rainy season, CRLF may disperse from estivation sites to suitable breeding habitat. During
such dispersals, frogs can travel over one mile through upland areas (Bulger et al. 2003); such
upland dispersal habitats are variable and typically include riparian corridors, grasslands, and
oak savannas.
The majority of creeks in developed areas of the. San Francisco Bay.Area do not typically
provide suitable breeding habitat for. the CRLF due to unsuitable hydrology, the presence of
aquatic and/or terrestrial predators, and/or other factors. However, CRLF breeding has recently
been documented approximately 1.2 miles north of the project area within Deer Creek, a
tributary to Matadero Creek (CDFW 2014). There are also additional recent occurrences
(including. breeding occurrences) within five miles to the west (TRA Environmental Sciences
2011 [no additional documentation provided], CDFW 2014). Within the project area, Matadero
Creek is narrow and highly incised, and therefore the stream current during typical winters is
expected to be strong, with limited to non-existent still, deeper water suitable for CRLF
breeding.. However, given the occurrences in the general 'vicinity, and because riparian
corridors are often used by dispersing/migrating CRLF, this species was determined to have
moderate potential to occur in the project area. The potential.for CRLF to occur is greatest
during breeding migrations and dispersal events, particularly during the rainy season.
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Town of Los Altos Hills 32 October 2015
•
•
i I
Federal-Listed Species Unlikely to Occur
Steelhead-(Oncorhynchus mykiss irideus) - Central California Coast DPS. Federal Threatened.
• Unlikely. Steelheadis the native rainbow:trout of coastal California that spends part of its life
cycle in freshwater and part in the ocean. The Central California Coast Distinct Population
Segment (DPS) includes all. naturally spawned populations (and their progeny) in California
streams from the Russian River to Aptos Creek and the drainages of San Francisco and San •
Pablo Bays eastward to the Napa River (inclusive); the Sacramento-San Joaquin River Basin is
excluded.
Steelhead typically migrates,tomarine waters after spending two years in freshwater, though
they may stay there for up to seven years. Individuals then reside in marine waters for two or
three years prior to,returning to their natal stream to spawn as 4- or 5-year-olds.. Steelhead
adults typically spawn between December'and June. In California, females typically spawn two
times before they die. Successful reproduction requires abundant riffle.areas (shallows with.
gravel .or:cobble substrate) .for:spawning, and deeper pools with sufficient riparian cover for
rearing. High-quality.spawning ,habitat occurs in perennial streams with cool to cold water
temperatures, high dissolved oxygen levels, and fast-flowing water.
A technical report by Leidy (2005) summarizes known distribution information for steelhead in
Santa Clara County streams. Although Matadero. Creek is believed to have historically
supported a steelhead population, the creek was surveyed for steelhead in 1981 and 1997 and
none were found in either year. Additionally, when operated, the tide gates at the mouth of the
creek can prohibit passage by anadromous fishes. For these reasons, Leidy (2005) concluded.
that steelhead is absent from Matadero Creek.
Discussion of Impacts
a) Less than Significant with Mitigation Incorporated. The project area has
potential to support nine special-status wildlife species: San Francisco dusky-footed
woodrat, white-tailed kite, Allen's hummingbird, Nutall's woodpecker, oak titmouse,'
San Francisco common yellowthroat, ' yellow warbler western pond 'turtle and
California red-legged frog. If any of these special-status wildlife species•are present
in the project area, impacts to these species are possible during construction and
would potentially be significant. Implementation of Mitigation Measures BIO-1
through BIO-4 would reduce potentially significant impacts,to a less-than-significant
level. Because no special-status plants are likely to occur in the project area, no
impacts to special-status plants are anticipated and no mitigation measures are.
required. •
Mitigation Measure BIO-1: San Francisco Dusky-footed Woodrat
•
Prior to vegetation removal and/or ground disturbance within the project area, a pre-
construction survey-for woodrat structures would be conducted by a qualified
• biologist. Any woodrat structures found during the survey would be flagged and
subsequently avoided to the fullest extent feasible..
If avoidance is not possible, then structures to be impacted would be dismantled by,
hand under the supervision of a qualified,biologist.
If woodrat young are encountered during the dismantling process:the material would
be placed back on the house, and a work exclusion buffer of at least 10 feet would
,be implemented around the structure. The structure would remain undisturbed for at.
least two weeks to allow the young to mature and leave the nest of their own accord.
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Town of Los.Altos Hills 33 October 2015
After the avoidance period, the nest dismantling process may begin again. Nest
material would be.moved to adjacent vegetated areas that will not be disturbed.
Mitigation Measure BIO-2: Nesting Birds
To the fullest extent feasible, initial ground disturbance and/or vegetation removal
would occur during the non-breeding season (September 1 to January 31).
Preconstruction nesting bird surveys are typically not required during this period.
(Note, however, that some birds have the potential to nest year-round; ifnests are
observed during project activities, a biologist would be consulted, and the nest
avoided as described below.) .
If initial ground disturbance and/or vegetation removal occurs during the breeding
season (February 1 through August 31), a qualified biologist would conduct a
breeding bird survey no more than 14 days prior to ground disturbance to determine
whether any birds are nesting within or adjacent to project impact areas.
If active nests are found within project impact areas or close enough to these areas
to affect breeding success, the biologist would establish an appropriate work
exclusion zone around each nest. Exclusion zone sizes vary dependent upon bird
species, nest location, and existing visual buffers and ambient sound levels. A buffer
radius may be as small as 25 feet for common species and 100 feet or more for
special-status species and raptors. Once all young have become independent of the
nest (or the nest otherwise becomes inactive), work may recommence within the
exclusion zone.
If initial ground disturbance is delayed or there is a break in project activities of
greater than 14 days within the bird nesting season, then a follow-up nesting bird
survey would be performed to ensure no nests have been established in the interim
period.
Mitigation Measure BIO-3: Western Pond Turtle
A pre-construction survey for western pond turtles shall be conducted by a qualified
biologist within 48 hours of the initiation of work activities in or near the streambed. If
western pond turtles are present, they would be captured and relocated to suitable
habitat outside of the project area by a qualified, biologist. The biologist would
require specific approval from the CDFW to conduct such activities.
Mitigation Measure BIO-4: California Red:legged Frog
Pre-construction CRLF surveys would be performed within 48 hours of the initiation
of work activities, including exclusion fence installation and initial work activities.
Biological sensitivity training would be conducted for project construction personnel
focused on CRLF identification and the project-specific avoidance and minimization
measures to be implemented. Installation of a wildlife exclusion fence (or sections of
fencing) would be done to prevent CRLF (dispersing or otherwise) from entering
project work areas during: construction. Such fencing would be maintained
throughout project activities. All pits or trenches would be covered at the end of each
work day, or wildlife escape ramps would be installed. Daily inspections of the work
area would be conducted by trained project personnel to ensure no CRLF are
present.
b) . Less than Significant with Mitigation Incorporated. The project area contains
three sensitive biological communities: perennial wetland, perennial stream, and
mixed riparian woodland. Wetlands and waters in the project area are subject to
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Town of Los Altos Hills 34 October 2015
Corps jurisdiction :as. Waters of the U.S. under CWA Section 404, RWQCB ,
jurisdiction under.CWA Section 401, and CDFW jurisdiction under Section 1600 of
the CFGC. Mixed riparian woodland in the project area is also potentially subject to
RWQCB and CDFW jurisdiction:
The proposed project would temporarily impact perennial wetland, perennial stream,
and mixed riparian woodland. Existing conditions are a negligible sized wetland
dominated by non-native species. Wetland functionsfrom the existing conditions
provide little to no value for wildlife in terms of typical wetland functions (e.g., water
quality). Temporary impacts would be the result of grading activities, installation of a
grade control structure and revetment; :installation of a soldier pile wall, and
construction access and staging. The project would help to restore the natural
hydrology, of the stream by repairing a 3-foot headcut that would otherwise move
upstream and undermine more of the structure of the riparian canopy and eventually
the roadway. The project is designed to address erosion and bank slumping in the'.
stream, thus project.. activities will restore natural .hydrological, processes in the
stream and improve upon pre-disturbance conditions, as the project would restore
natural functions to the stream, which would also result in the"development of
instream wetland habitat at suitable locations. .
Construction activities would also require the removal of riparian trees (Table 3);
however, all riparian trees will be replanted at project completion, and therefore, the
impact to mixed riparian woodland habitat is also .considered temporary. The
concept for riparian plantings was developed by analyzing the. existing conditions
with the project area, the extent of proposed impacts to riparian trees, anticipated
natural dieback of planted trees,and the particular constraints and opportunities at
the site. Over time, plantings would return the mixed riparian woodland habitat to
near pre-disturbance conditions.
The extent of potentially significant temporary impacts to sensitive habitat is provided
in Table 2 and Table 3. Implementation of Mitigation Measure BIO-5 would reduce
potentially significant impacts to a less-than-significant.level.
i -
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Town of Los Altos Hills 35 . October 2015
Table 2. Summary of Impacts to Wetlands and Waters
Temporary Impacts
Jurisdictional Feature
(acres)
Impacts to Corps Jurisdiction
Perennial Wetland <0.01 acre
Non-wetland Waters (up to Ordinary High Water Mark) 0.02 acre(333 linear feet)
Total Area of Impacts to Corps Jurisdiction <0.03 acre
Impacts to RWQCB and.CDFW Jurisdiction
Perennial Wetland <0.01 acre
Non-wetland Waters (up to Top of Bank) 0.05 acre(333 linear feet)
Total Area of Impacts to RWQCB and CDFW Jurisdiction <0.06 acre
Table 3. Summary of Impacts to Mixed Riparian Woodland
Tree Species Number of Trees to be Removed
Northern California black walnut 7
Arroyo willow 6
Total 13
Mitigation Measure BIQ-5: Sensitive Habitat
Impacts to federally protected wetlands and non-wetland waters in the project area
will require a Corps CWA Section 404 Nationwide or Individual Permit and a
RWQCB CWA Section 401 Water Quality Certification. Impacts to areas subject to
CDFW jurisdiction will require application for a CFGC Section 1600 Lake and
Streambed Alteration Agreement from the CDFW. Prior to issuance of construction
and grading permits the applicant shall obtain a Corps Section 404 Nationwide
Permit, RWQCB Section 401 Water Quality Certification, and CDFW 1602 Lake and
Streambed Alteration Agreement. Best management practices to be implemented
during construction include, but are not limited to the following activities:
• Work in the creek belowthelevel of top-of-bank (TOB) shall be restricted to
June 1 through October 31 to correspond with the dry period. No equipment
shall be operated in areas of flowing or standing water and no fueling,
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Town of Los Altos Hills 36 October 2015
cleaning, ormaintenance of vehicles:or equipment shalltake place within any
areas where an accidental discharge into the creek may occur;
• Burlap bags filled with drain rock will-be installed around storm drains to route
sediment and other debris away from the drains;
• Earthmoving or other dust-producing activities will be suspended during
periods of high winds;
• All exposed or disturbed soil surfaces will be watered or covered to control
dust as necessary;
• Stockpiles of soil or other materials that.can be blown by the wind will be
watered or covered;
• All trucks hauling soil, sand, and other loose materials'will.be covered and all,
trucks will be required to maintain at least-two feet of freeboard;
• . All.paved access roads, parking areas, staging.areas, and,residential streets
adjacent to the construction sites will be swept daily with water sweepers;
• The use of suitable erosion control materials, including straw wattles, erosion
control blankets, etc., will be employed to reduce potential erosion associated
with excavation and grading;
• No debris will be allowed to enter into or be placed where it may be washed
by rainfall or runoff into the stream and all such debris:will be picked-up daily
and:properly disposed at an appropriate site; .
•` Equipment access to the creek will be restricted to as few locations as
possible and will be sited to avoid impacts to wetland and riparian vegetation
to the greatest extent feasible;-
• Prior to the start of construction, or the introduction of machinery into the
aquatic portion of the project site, a qualified biologist shall inspect the area to
determine if invasive species are present. All equipment that may have come
in contact with invasive plants or the seeds of these plants will be carefully
cleaned before arriving on the'site and shall be carefully cleaned before
removal from the site;
• Disturbance or removal of vegetation will not exceed the minimum necessary
to complete construction; and
• The work area will be delineated where necessary with orange construction
- fencing (or similar) to minimize impacts to habitat beyond the work limit.
c) Less than Significant with Mitigation Incorporated. The project area contains
federally-protected wetlands subject to the jurisdiction of the Corps pursuant to
Section 404 of the CWA. The extent of potentially significant impacts to federally
protected-wetlands is provided above in Table 2. The 435 square feet of perennial
wetland has little to no ecological value and its loss will be compensated by the
increase in stream area,'as well as the increase in stream function. Therefore, there
'will be no loss of Waters of the U.S. and no loss in functional value. Once the
natural hydrology and stream .morphology are returned, instream wetlands may
develop in suitable locations. In addition, implementation of Mitigation Measure BIO-
5 (above), including obtaining authorization from the Corps :via a Section 404
.Nationwide Permit, would further reduce less than significant impacts to federally-
protected wetlands.
d) Less than Significant Impact. No migratory corridors or nursery sites are
anticipated to be affected by the project. Because project activities have been
limited by design to the dry season, no impediments to fish passage are anticipated
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Town of Los Altos Hills 37 October 2015
as a result of projectactivities and any impacts to potential migratory corridors or.
nursery sites would be less than significant
e) Less than Significant with Mitigation Incorporated. The Town of Los Altos Hills
Tree Protection Ordinance requires a permit for the removal of any protected trees.
Any tree located within a public right-of-way is considered protected under the
ordinance. The proposed project includes the removal of 13 trees that would be
consideredprotected under this ordinance (Figure 7). Implementation of Mitigation
Measure BIO-6 would ensure that the project would not conflict with any local
policies or ordinances protecting biological resources and impacts would be less
than significant.
Mitigation Measure BIO-6: Tree Removal .
Prior to issuance of construction permits the applicant shall obtain a tree removal
permit. Additional avoidance and minimization measures recommended in these
permits shall be followed. This ratio shallbe two to one or as defined in the tree
removal permit, the stricter standard shall be followed.
f) No Impact. No state, regional, or federal habitat conservation plans or Natural
Community Conservation Plans have been adopted for the project area.
4.5 Cultural Resources
Less than
Significant
CULTURAL RESOURCES—Would the Potentially with Less than
Significant Mitigation Significant No
project: Impact Incorporated Impact Impact Source
a) Cause a substantial adverse change in the ❑ ❑ ® . ❑ 1,2
significance of a historical resource as
identified in Section 15064.5? -
b) Cause a substantial adverse change in the ❑ ® 0 ❑ 1,2 .
significance of an archaeological resource
pursuant to Section 15064.5?
c) Directly or indirectly destroy a unique ❑ ® ❑ ❑ 1,2
paleontological resource or site or unique
geologic feature? -
d) Disturb any human remains, including ❑ ❑ ❑ 1,2
those interred outside of formal
cemeteries?
Environmental Setting .
Discussion of Impacts
a) Less than Significant Impact. No historic properties/cultural resources listed,
determined, or potentially eligible for inclusion on the NRHP (36 CFR Part 800.4)
and/or California Register of Historic Resources (CRHR) (California Public
Resources Code Section 5024.1) were identified within or immediately adjacent to
the proposed project's APE. The Town's General Plan was consulted to identify
potential cultural resources. Impacts would be less than significant and not
mitigation is required.
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Town of Los Altos Hills 38 October 2015
b, c, d) Less than Significant with Mitigation Incorporated
Exposures of undisturbed native soil :are. very unlikely due to the infrastructure
improvements within the streambed and adjacent to the culvert outfall. Thereviewof
the various reports, maps, and other resources suggest a very low to low sensitivity
for prehistoric and/or historic era resources, as well as paleontological resources,
within or immediately adjacent to the culvert outfall. However, the limited potential
still exists for project grading to impact unknown archaeological - and/or
paleontological resources atthe site. These potentially significant impacts can be
mitigated to less-than-significant levels via implementation of Mitigation Measure
CULT-1.
Mitigation Measure CULT-1:Accidental Discovery :
In the event of post-review discoveries of archaeological or paleontological resources
the following recommendations apply: . .
• If any archaeological or paleontological deposits are encountered, all soil-
disturbingwork shall be ,halted at the location.of any discovery until a:qualified
archaeologist or paleontologist evaluates the significance of the find(s) and
prepares a recommendation for further action. If the cultural materials are
determined to be significant, a qualified cultural resourcesprofessional shall
develop an appropriate treatment plan in consultation with the Town tomitigate
the discovery. The plan could include avoidance and preservation measures to
preserve the materials in place; scientific collection and analysis; preparation of a
professional report in accordance with current professional standards; and,
professional museum curation of collected cultural materials and .resource
documentation. :
• The treatment of human remains and of associated or unassociated funerary
objects discovered during any soil-disturbing activity within the project shall
comply with applicable State laws. Pursuant to Section 7050.5 of the Health and
Safety Code, and PRC Section 5097.94, in the event of the discovery of human
remains during construction, there shall be no further excavation or disturbance
of the site or any nearby area reasonably suspected to overlie adjacent remains:
The Santa Clara County Coroner shall be immediately notified and shall make a
determination as to whether the remains are Native American.
• In the-event of the coroner's determination that the human remains are Native
American, notification of the Native American Heritage Commission (NAHC), is
required who shall appoint a Most Likely Descendant- (MLD) (PRC Section
5097.98). The archaeological consultant, project sponsor, and MLD shall make
all reasonable efforts to develop an agreement for the treatment, with appropriate
dignity, of human remains and associated or unassociated funerary objects
(CEQA Guidelines Section 15064.5(d)). The agreement. should take into
consideration the appropriate excavation, removal, recordation, analysis,
custodianship, curation,: and final disposition 'of the human remains and ,
associated or unassociated funerary. objects. California Public Resources Code
allows 48 hours to reach agreement on these matters. If the. MLD and the other
parties do not agree on the reburial method, the project will follow PRC Section
5097.98(b) which states' that "the landowner or his' or her authorized
representative shall reinter the human remains and items associated with Native
American burials:with appropriate dignity on the property in a:location not subject
to further subsurface disturbance."
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Town of Los Altos Hills 39 October 2015
4.6 Geology and Soils .
Less than
Significant
Potentially with Less than
Significant. Mitigation Significant No
GEOLOGY AND SOILS—Wouldthe project: Impact Incorporated Impact Impact Source
a) Expose people or structures to potential
substantial adverse effects, including the
risk of loss, injury, or death involving:
i) Rupture of a known earthquake fault, ❑ ❑ ❑ ® 1,2,9
as delineated on the most recent
Alquist-Priolo Earthquake Fault Zoning
Map issued by the State Geologist for
the area or based on other substantial
evidence of a known fault?
ii) Strong seismic ground shaking? ❑ ® ❑ 1,2,9
iii) Seismic-related ground failure, ❑ ❑ ❑ 1,2,9 -
including liquefaction?
iv) Landslides? ❑ ❑ ❑ �i 1,2,9
b) Result in substantial soil erosion or the ❑ ® ❑ ❑ 1,2,9
loss of topsoil?
c) Be located on a geologic unit or soil that is ❑ ❑ ® ❑ ', - 1,2,9
unstable, or that would become unstable
as.a result of the project, and potentially .
result in on-or off-site landslide, lateral
spreading, subsidence, liquefaction, or
collapse?
d) Be located on expansive soil, as defined in ❑ ❑ ❑ 1,2,9
Table 18-1-B of the Uniform Building
Code, creating substantial risks to life or
property?
e) Have soils incapable of adequately ❑ ❑ ❑ ® 1
supporting the use of septic tanks or
alternative wastewater disposal systems
where sewers are not available for the
disposal of wastewater?
Environmental Setting
On-Site Geologic Conditions
Soils • .
The Soil Survey of Santa Clara County (1991) indicates that the Study Area is underlain by two
soil series, Cropley clay, 2 to 9 percent slopes and Zeppelin-Mccoy complex, 15 to 30 percent
slopes.. Cropley clay consists of well drained alluvium derived from calcerous shale or residuum
derived from calcerous shale. The Zeppelin-Mccoy complex is composed of approximately 45
percent Zeppelin and similar soils, 40 percent Mccoy and similar soils, and 15 percent minor
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Town of Los Altos Hills 40 October 2015
•
components. Zeppelin and Mccoy soils are residuum.derived from weathered sandstone and
are well drained.
Seismicity
The San Francisco Bay area is one of the most seismically active areas in the country. While
seismologists cannot predict earthquake events, the U.S. Geological Survey's Working Group
on California Earthquake Probabilities (2003) estimates there is a 62 percent chance of at least
one magnitude 6.7 earthquake occurring in the Bay Area region between 2003 and 2032. As
seen with damage in San Francisco and Oakland due to the 1989 Loma Prieta earthquake that
was centered about 50 miles south, significant damage can occur at considerable distances.
Higher levels of shaking and damage would be expected for earthquakes occurring at closer
distances. The faults considered capable of generating significant earthquakes in the area are
generally associated with the well-defined areas of crustal movement, which trend
northwesterly. Faults considered:active by the State of.California and located closest to the site
include: San Andreas (3.0miles, southwest of the site), and Hayward (15.7 miles, northeast of
the site). The project area is not located within a State-designated Alquist-Priolo Earthquake
fault rupture zone.8
Liquefaction and Lateral Spreading
Soil liquefaction is a condition where saturated granular soils near the ground surface undergo a
substantial loss of strength during seismic events. Loose, water-saturated soils are transformed
from a solid to a liquid state during ground shaking. Liquefaction can result in significant
deformations and ground rupture or sand boils. Soils most susceptible to liquefaction are loose,
uniformly graded, saturated, fine-grained sands that lie close to the ground surface. Lateral
spreading is a type of ground failure related to liquefaction. It consists of the horizontal
displacement of flat-lying alluvial material toward an open area, such as a steep bank of a
stream channel. According to the Association of Bay Area Governments (ABAG), the project
area is located in a very high liquefaction hazard zone.9
Landslide
The project area is illustrated as flatland and an area with few landslides by ABAG and would
not be susceptible to earthquake-induced landslides or rainfall-induced landslides.10
Discussion of Impacts
a-i, iv) No Impact. No faults cross through the project area, and surface-rupture associated
with a fault is not anticipated in the Town. The potential for landslides from seismic
activity is considered low in the project .area based on the geologic units, flat
topography, and ABAG's hazard mapping. Seismic-related ground failure is not
anticipated in the project area, and the project would not expose people to these
hazards. .
a-ii, iii) Less than Significant Impact. Seismic activity associated with nearby faults could
cause ground shaking in the project area and could. create a risk for construction
workers, if an earthquake happens during construction. Occasional ground shaking
8 California Geological Survey Alquist-Priolo Earthquake Fault Zone Maps. Available at:
http://www.quake.ca.gov/gmaps/ap/ap maps.htm. Accessed:December 30, 2012.
9 ABAG Geographic Information Systems:Hazard Maps. Available at:
http://g1s3.abag.ca.gov/Website/lig scenario maps/viewer.htm. Accessed July 9, 2015.
1° ABAG Geographic Information Systems:Hazard Maps. Available at:
http://gis.abag.ca.gov/website/LandslideDebrisFlow/index.html. Accessed July 9, 2015.
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Town of Los Altos Hills 41 October 2015
is common in the Bay Area, and construction workers would take the necessary
precautions to maintain worker safety in the event of an earthquake. Liquefaction
associated with ground shaking if possible given ABAG's hazard map. However, the
construction phase of the proposed project is temporary. The project is being
designed to stabilize the project area and would provide an increased ability for the
site to cope with ground shaking and liquefaction. In addition, design of project
components would adhere to California Building Code requirements specific to the
area to .minimize the potential for damage from earthquake activity in the future.
Impacts associated with seismic ground shaking and liquefaction would be less than
significant.
b) Less than Significant with Mitigation Incorporated. The project proposes to
stabilize a portion of Matadero Creek. Excavation equipment-would reform the
proposed channel and lay back the bank grades. Approximately 200 cubic yards of
earth would be moved, and less than 50 cubic yards of excess,soil, sackcrete and
embankment materials would be off-hauled to a landfill. A non-woven filter fabric
would be placed in areas where rock rip-rap is proposed prior the backfilling with
approximately 200 cubic yards rock. Large rock would be placed first, and 6-inch
diameter tubes would be spaced among the fill area to allow access to the soil for
final installation of willow stakes. Smaller rock would fill the voids. Construction
measures included in Mitigation Measure HYDRO-1 would be implemented to
minimize the potential for erosion and indirect effects associated with soil erosion
(i.e., water quality impacts, fugitive dust). Impacts on soil would be less than
significant.
Mitigation Measure GEO-1: Soil Erosion
BMPs listed in Mitigation Measure HYDRO-1 shall be implemented to minimize the
potential for erosion and indirect effects associated with soil erosion (i.e., water
quality impacts, fugitive dust).
c, d) Less than Significant Impact. The potential for geologic and soil hazards from
unstable or expansive soils in the project area is considered medium to high based
on the geologic units and soil types. However, occasional :ground shaking is
common in the Bay Area, and construction workers would take the necessary
precautions to maintain worker safety in the event of an earthquake. Liquefaction
associated with ground shaking is also possible given ABAG's hazard map.
However, the construction phase of the proposed project is temporary and operation
of the proposed project would be an improvement over existing,conditions, as the
proposed project addresses the specific characteristics of the surrounding soils and
geologic conditions and would be designed to stabilize the failing bank and outfall
system. The proposed project is therefore not expected to be- affected by such
hazards, and construction workers would not be further exposed to these hazards
during construction.
e) No Impact. The project does not involve construction of septic tanks or wastewater
disposal systems.
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Town of Los Altos Hills 42 October 2015
4.7 Greenhouse Gas Emissions
Less than
GREENHOUSE GAS EMISSIONS—
Potentially Significant with Less than
Significant Mitigation Significant No
Wouldthe project: Impact Incorporated Impact Impact Source
a) Generate greenhouse gas ❑ ❑ ® ❑
emissions, either directly or
indirectly, that may have a
significant impact on the
environment?
b) Conflict with any applicable plan, ❑ ❑ ® ❑
policy, or regulation of an agency
adopted for the purpose of reducing
the emissions of greenhouse
gases?
Environmental Setting
Unlike emissions of criteriaand toxic air pollutants, which have local or regional impacts,
emissions of greenhouse gases (GHGs) that contribute to global warming or global climate
change have a broader, global impact. Global warming is a process whereby GHGs
accumulating in the atmosphere contribute to an.increase in the temperature of the earth's
atmosphere. The principal GHGs contributing to global warming are carbon dioxide (CO2),
methane (CH4), nitrous oxide (N20), and fluorinated compounds. These gases allow visible and
ultraviolet light from the sun to pass through the atmosphere, but they prevent heat from
escaping back out into space. Among the potential implications of global warming are the
myriad of global climate changes currently being observed, including rising sea levels, changing
precipitation patterns, and adverse impacts to water supply, water quality, agriculture, forestry,
and habitats. In addition, global warming increases electricity demand for cooling, decreases
the availability of water for farming and hydroelectric power, and affects regional air quality and
public health. Like most criteria and toxic air pollutants, much of the GHG production comes
from motor vehicles. GHG emissions can be reduced to some degree by improved coordination
of land use and transportation planning on the city, county, and subregional level, and other
measures to reduce automobile use.
In 2010, BAAQMD adopted quantitative thresholds of significance for construction activities, but
only identified GHG thresholds of significance for operational emissions; the District identified no
GHG thresholds for construction-related activities.
Discussion of Impacts
a) Less than Significant Impact. GHG emissions from the proposed project would be
produced from construction-related equipment emissions. The proposed project
would not result in the generation of emissions after construction is complete. Given
the nature of the proposed project and short duration of construction, GHG
emissions resulting from construction activities would be minor. While the proposed
project would have a small incremental contribution to GHG emissions within the
context of the Town and region, the individualimpact is considered less than
significant.
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Town of Los Altos Hills 43 • October 2015
b) Less than Significant Impact. The project would not generate significant emissions
of GHG and, therefore, would not conflict with any applicable plans, policies, or
regulations adopted for the purpose of reducing GHG emissions.
4.8 Hazards and Hazardous Materials
Less than
Significant
HAZARDS AND HAZARDOUS MATERIALS= Significant
with ; Less than
Significant Mitigation Significant No
Would the project: Impact Incorporated Impact Impact Source
a) Create a significant hazard to the public or 1,9
the environment through the routine
transport, use, or disposal of hazardous
materials?
b) Create a significant hazard to the public or ❑ ❑ ►1 ❑ 1,9
the environment through reasonably
foreseeable upset and accident conditions
involving the release of hazardous
materials into the environment?
c) Emit hazardous emissions or handle ❑ ❑ ❑ 1,9
hazardous or acutely hazardous materials,
substances, or waste within one-quarter
mile of an existing or proposed school?
d) Be located on a site which is included on a 0 ❑ ❑ // 1,9
list of hazardous materials sites compiled
pursuant to Government Code Section
65962.5 and, as a result, would it create a
significant hazard to the public or the
environment?
e) For a project located within an airport land ❑ ❑ ❑ ® 1,2
use plan or, where such a plan has not
been adopted, within two miles of a public
airport or public use airport, would the
project result in a safety hazard for people
residing or working in the Project Area?
f) For a project within the vicinity of a private ❑ ❑ ❑ 1,9
airstrip, would the project result in a safety
hazard for people residing or working in the
Project Area?
g) Impair implementation of or physically ❑ ❑ ❑ 1,9
interfere with an adopted emergency
response plan or emergency evacuation
plan?
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Town of Los Altos Hills 44 October 2015
Less than
Significant
HAZARDS AND HAZARDOUS MATERIALS.—.
Potentially with Less than
Significant Mitigation Significant No
Would the project: Impact Incorporated Impact Impact Source
h) Expose people or structures to a significant ❑. ❑ ❑ 1,9
risk of loss, injury or death involving .
wildland fires, including where wildlands
are adjacent to urbanized areas or where
residences are intermixed with wildlands?
Environmental Setting
A material is considered hazardous if it appears on a list of hazardous materials prepared by a
federal, state, or local agency or if it has characteristics defined as hazardous by such an
agency. A hazardous material is defined in Title 22 of the California Code of Regulations as
follows:
A substance or combination of substances which, because of its quantity, concentration, or
physical, chemical or infectious characteristics, may either (1) cause, or significantly
contribute to, an increase in or an increase in serious irreversible, or incapacitating
reversible, illness; or (2) pose a substantial present or potential hazard to human health or
environment when improperly treated, stored, transported or disposed of or otherwise
managed. (California Code of Regulations, Title 22, Section 66261.10)
Chemical and physical properties cause a substance to be considered hazardous. Such
properties includetoxicity, ignitability, corrosivity, and reactivity (as defined in California Code of
Regulations, Title 22, Sections 66261.20-66261.24). The accidental release of hazardous
materials into the environment could potentially contaminate soils, surface water, and
groundwater supplies. Under Government Code Section 65962.5, the California Department of
Toxic Substances Control (DTSC) maintains a list of hazardous substance sites. This list,
referred to as the "Cortese List," includes CALSITE hazardous material sites, sites with leaking
underground storage tanks, and landfills with evidence of groundwater contamination.
No hazardous substance sites from the Cortese List have been identified within the project area.
No hazardous material sites monitored, by DTSC on the agency's Envirostor database have
been reported within one-quarter of a mile of the project area (Department of Toxic Substances
Control, 20.11). .
Discussion of Impacts
a, b) Less than Significant Impact. Small amounts of hazardous materials would be
used during construction activities for equipment maintenance (e.g., fuel and
solvents), re-paving roads, and bank stabilization. Use of hazardous materials would
be limited to the construction phase and would comply with applicable local, state,
and federal standards associated with the handling and storage of hazardous
materials.. Hazardous materialswould not be stored or used, such as for equipment
maintenance, where they could affect nearby land uses or water quality. Standard
construction measures included in the project description will be implemented to
contain any accidental spills of oil and other hazardous materials, and the contractor
will be required to ensure that adequate materials are on hand to clean up any
accidental spill that may occur. With implementation of these standard measures
included in the project description, impacts associated with the use or accidental spill
of hazardous materials would be less than significant.
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Town of Los Altos Hills 45 October 2015
c) No Impact. The project area is not within 0.25-mile of an existing or proposed
private school. Therefore, no impact would occur.
d) No Impact. The proposed project area is not included on the list of hazardous
materials sites complied pursuant to Government Code Section 65962.5; therefore,
no impact would occur under this criterion.
e, f) No Impact. The project area is not located near a public or private airport. The
nearest airport is the Palo Alto Airport of Santa Clara County located approximately
5.5 miles of the project area.
g) Less than Significant Impact with Mitigation Incorporated. Construction
activities would require temporary lane closures and detours around the work area.
Emergency access to or evacuation from surrounding areas would not be restricted
during construction because of the availability of detours, but minor delays may be
experienced for access to or evacuation from the land uses adjacent to the work
area. Detours will be readily available at all times to allow emergency vehicles
access around the work area. With implementation of Mitigation Measures
TRAFFIC-1 and traffic control measures included in the project description, impacts
would be less than significant.
h) Less Than Significant Impact. According to the Association of Bay Area
Governments (ABAG) Wildland Urban Interface (WUI) Fire Threat map, portions of
the project area are located within and adjacent to an area subject to a moderate
threat of wildland fires. However, the project involves the short-term construction to
stabilize a portion of Matadero Creek. The long-term operation of the project would.
not increase the risk of wildfire near an urban area. Impacts would be less'than
significant.
4.9 Hydrology and Water Quality
Less than
Significant
HYDROLOGY AND WATER QUALITY—Would Potentially with Less than
Significant Mitigation Significant No
the project: Impact Incorporated Impact Impact Source
a) Violate any water quality standards or: ❑ ® ❑ ❑ 1,2,11
waste discharge requirements? .
b) Substantially deplete groundwater supplies ❑ ❑ ❑ ® 1
or interfere substantially with groundwater
recharge such that there would be a net
deficit in aquifer volume or a lowering of the
local groundwater table level (e.g., the
production rate of pre-existing nearby wells
would drop toa level which would not. .
support existing land uses or planned uses
for which permits have been granted)?
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Town of Los Altos Hills 46 October 2015
Less than
Significant
HYDROLOGY AND WATER QUALITY—Would Potentially with Less than
Significant Mitigation . Significant No
the project: Impact IncorporatedImpact Impact Source
c) Substantially alter the existing drainage ❑ ❑ 1,11
pattern of the site or area, including through
the alteration of the course of a stream or .
river, in a manner which would result in
substantial erosion or siltation on-or off-
site?
d) Substantially alter the existing drainage ❑ ❑ ® n . 1,11
pattern of the site or area, including through
the alteration of the course of a stream or
river, or substantially increase the rate or
amount of surface runoff in a manner which
would result in flooding on-or off-site?
e) Create or contribute runoff water that would ❑ ❑ ® ❑ 1,11
exceed the capacity of existing or planned
storm water drainage systems or provide
substantial additional sources of polluted
runoff?
f) Otherwise substantially degrade water ❑ ❑ ❑ ® 1
quality? .
g) Place housing within a 100-year flood ❑ ❑ ❑ 1,2
hazard area as mapped on a federal Flood
Hazard Boundary or Flood Insurance Rate
Map or other flood hazard delineation map?
h) Place within a 100-year flood hazard area ❑ ❑ ❑ ® 1,6
structures which would impede or redirect
flood flows?
i) Expose people or structures to a significant ❑ ❑ ❑ ® 1
risk of loss, injury or death.involving
flooding, including flooding as a result of
the failure of a levee or dam?
j) Inundation of seiche, tsunami, or mudflow? ❑ ❑ ❑ ® 1
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Town of Los Altos Hills 47 October 2015
Environmental Setting
The dominant source of hydrology in the Study Area is Matadero Creek, a perennial creek that
flows south to north, crossing below Page Mill Road and continuing adjacent to thetwo-lane
roadway. An approximately 333-foot-long stretch of Matadero Creek (approximately 0.04 acre,
-excluding areas mapped as in-stream perennial wetlands) occurs within the Study Area.
Matadero Creek is a perennial USGS blue-line stream. The creek is daylighted within the Study
Area. Upstream (southeast) of Page Mill Road, the creek has a relatively shallow gradient and
contains a large area of cattail wetland adjacent to the road. Downstream (northwest) of Page
Mill Road, the creek has a steeper gradient and is covered by a dense riparian canopy
dominated by arroyo willow (Salix lasiolepis) and Northern Californian black walnut (Juglans
hindsii). The creek is armored by concrete sack walls within the immediate.vicinity of Page Mill
Road. Downstream (northwest) of Page Mill Road, where the concrete armoring ends, a nick-
point has developed, resulting in a steeply incised channel with substantial erosion,
undercutting, and bank slumping.
According to the Federal Emergency Management Agency (.FEMA) Federal Insurance Rate
Maps (FIRM), the project area is located in flood zone AE. Zone AE is defined as an area within
the 100-year flood zone where a base flood elevation has been determined. The project area is
not subject to seiches and the project area is not located within a mapped Dam Failure
Inundation Area.
Discussion of Impacts
a) Less than Significant with Mitigation Incorporated.
Water quality standards can refer to drinking water standards or surface water
standards. Further, there are separate surface water standards for discharges from
wastewater treatment plants and for discharges of storrnwater. These are discussed
in turn below.
Drinking Water Standards
No Impact. Drinking water standards areimplemented by the state Department of
Public Health, and apply to local water distribution systems for domestic water
supply. There are no plans to install a domestic water distribution as part of the
project. -
Wastewater Treatment Standard :
No Impact. Waste Discharge: Requirements refers to standards applied to local
wastewater treatment facilities by the Regional Water Quality Control Board for
quantities and quality of wastewater discharge. There are no plans to install a
• centralized wastewater treatment facility for the project, so no discharge
requirements would apply. When construction workers are scheduled to be on-site
for extended periods, sanitary needs will be provided by portable chemical toilets that
will be serviced by an outside contractor as.needed.
Stormwater Standards
Less than Significant with Mitigation Incorporated. Soil. particles and other,
• materials could be carried in storm water runoff which could degrade water quality in
Matadero Creek. After implementation of BMPs described under Mitigation Measure
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 48 October 2015
HYDRO-1, potentially significant water quality impacts during construction would be
reduced to a less-than-significant level. The project would also reduce storm water
overflows, which would improve and protect water quality in the creek channel, the
storm drain system and receiving water bodies over the long term. Long-term water
quality impacts would be less than significant.
Mitigation Measure HYDRO-1: Water Quality Standards
Implementation of the following best management practices will reduce construction-
related water quality impacts to a less than significant level:
a. Burlap bags filled with drain rock will be installed around storm drains to route
sediment and other debris away from the drains.
b. Earthmoving or other dust-producingactivities will be suspended during
periods ofhigh,winds.
c. All exposed or disturbed soil surfaces will be watered .to control dust as
necessary. .
d. Stockpiles of soil or other materials that can'be blown by the wind will be
watered or covered.
e. All trucks hauling soil,.sand, and other loose materials will be covered:and all
trucks will be required to maintain at least two feet of freeboard. .
. ' f. All paved access roads, parking areas, staging areas, and residential streets .
- adjacent to the construction sites will be swept-daily(with water sweepers).
g. Vegetation in disturbed areas will be replanted as quickly as possible.
b) No Impact. The project would not 'require use of groundwater supplies or affect
groundwater recharge in the area. .
c, d, e, h) Less Than Significant. The:proposed project would notsubstantially alter the
existing drainage pattern of the .area. The proposed project is a bank stabilization
project that entails excavating sediments to mimic a natural creek habitat feature in
hydraulic function and provide adequate creek channel stabilization to Page Mill
• Road. The proposed alterations to the Matadero Creek channel geometry
downstream of the road crossing would not impact flood conditions at the Page Mill
Road culvert nor are water surface elevations raised as a resultof the project in the
1_. reach where the project is proposed. The'proposed project would alleviate flooding
and would not contribute substantial erosion or siltation or increase the rate or
amount of surface runoff in a manner which would result in increased flooding on- or
off-site. The restoration and stabilization will improve the creek transition between
the sackcreted portion.of the channel and the soft bottom,channel downstream and
reduce erosional processes in the reach. Therefore, the project would have a less
_; , than significant impact with respect to alteration of drainage patterns and rates.
1' f) No Impact. The project would not have other water quality impacts beyond those
discussed under item (a) above. .
• g, i,j) No Impact. The project would not involve placement of housing or other structures
in a flood 'zone and would not expose people.or structures to risks from flooding or.
inundation by seiche, tsunami, or mudflow.
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Town of Los Altos Hills 49 October2015
4.10 Land Use and Planning .
Less than.
Significant
LAND USE AND PLANNING—Would the
Potentiallyignifnt with Less than
Significant. Mitigation Significant No
project: . . Impact: Incorporated Impact Impact Source
a) Physically divide an established ❑ ❑ ❑ ®. 1
community?
b) Conflict with any applicable land use plan, ❑ ❑ ® : ❑ 2,3
policy, or regulation of an agency with
jurisdiction over the project(including, but '
not limited to the general plan, specific
plan, local coastal program; or zoning
ordinance) adopted for the purpose of
avoiding or mitigating an environmental
effect?
c) Conflict with any applicable habitat ❑.. ❑ ❑ ® 1
conservation plan'or natural communities
conservation plan?
Environmental Setting . .
The Town is unique in that it consists mainly of low-density single-family residential
development, with a minimum lot size of at least one acre. There are no commercial or
industrial uses within the Town's limits. The only non-residential uses within the Town are open-
space, parks and recreation facilities, off-road paths, and public and private institutions'such as
schools, religious facilities and governmental buildings.
Regulatory Setting
Town of Los Altos Hills General Plan
Land Use
Policy 1.1 Uses of land shall be consistent with the semi-rural atmosphere of the
community, minimize disturbance to natural terrain, minimize removal of the
natural vegetation, and create the maximum compatibility of development with
the natural environment through site design and landscaping.
Circulation '
Goal 2
Los Altos•Hills enjoys its quiet rural roadways. The Town wishes to preserve their current
character, and desires to maintain their level of service without increasing their capacity.
Policy 2.2 - Collectors, neighborhood connectors and local roads shall not be
designed or improved to an extent that would encourage through traffic.
Policy 2.8 - Roadway maintenance should not interfere with pathways or
drainage.
Goal 9 •
The roadways of Los Altos Hills are scenic and semi-rural. The design and maintenance of the
roadways should preserve these qualities. .
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Town of Los Altos Hills 50 October 2015
Policy 9.2 - The Town shall discourage the widening of any surface roads except
where critical for safety purposes.
Policy 9.6 - The Town shallrequest open space easements where necessary to
ensure the preservation of steep slopes, heritage oak trees and creek:areas.
Policy 9.7 - All roadway cut and fill scars shall be reduced to. a minimum for any
road improvement.
Program 9.2 — Preserve mature street trees, wherefeasible, when pathways or
other improvements are added to streets.
Goal C-7
Accommodate drainage and utilities in a manner that maintains the rural character of its
roadways.
Policy 11.1 .-. Drainage design shall be generally compatible with semi-rural
roadways, developed to complement existing drainage patterns, and consistent
with "Guidelines and Standards for Land Use Near Streams" adopted by the
Town in 2007..
Policy 11.6 - Open Space easements should be used to preserve natural
waterways and avoid excessive drainage structures.
•
Conservation
Policy_1.2 Work with the Santa Clara Valley Water District and other relevant regional
agencies to enhance riparian corridors and provide adequate flood control by use
of low impact restoration strategies.
Policy 1.3 Preserve the integrity of riparian corridors as unique and environmentally
sensitive resources.
Policy 2.1 Minimize disturbance of the natural terrain and vegetation.
Policy 2.2 Preserve and protect native and naturalized plants, with special attention to
preservation of unique, rare or endangered species and plant communities such
asoak woodlands.
Policy 2.7 Avoid'the development of environmentally sensitive areas that are rich in wildlife
or of a fragile ecological nature, such as areas of rare or endangered species of .
plants, or riparian areas. '
Policy 5.1 Keep or restore major drainage courses in their natural condition insofar as
possible because of their importance in supplying.major vegetation, land forms
and wildlife habitat, and storm drainage.
Policy 5.5 Reduce non-point source pollution in urban runoff.
Policy 6.1 Encourage soil stabilization measures that = mitigate soil erosion and
sedimentation. '
Policy 6.3 Minimize the removal of vegetation and require replanting to maintain soil
stability, prevent erosion, and retain the aesthetic quality of the community.
Safety
Policy 2.1 Reduce the potential effects of seismic and other geologic hazards, including
slope instability.
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Town of Los Altos Hills 51 • October 2015
Policy 2.2 Locate development so as to avoid geologic hazards, including slope instability,
to the maximum extent feasible.
Policy 2.4 In the event that significant structures are required in geologically hazardous
areas, all reasonable measures shall be taken to minimize the amount of risk
involved.
Policy 3.1 Leave natural channels and flood plains in a natural state, unencumbered by
development to the maximum extent feasible. Exceptions shall be made only in
situations where it is essential to protect established property values or for public
safety.
Discussion of Impacts
a) No Impact. The project involves stabilization of a portion of Matadero Creak. The
project would not physically divide an established community.
b) Less than Significant Impact. A proposed project would have a significant impact
if it were to conflict with any applicable land use 'plan, policy, or regulation of an
agency with jurisdiction over the project (including, but not limited to the general plan,
specific plan, local coastal program, or zoning ordinance) adopted:for the purpose of
avoiding or mitigating an environmental effect. The proposed project is subject to
several local policies, plans, and regulations, as described above. The primary
objective of the proposed project is to restore an existing creek channel bridge and
stabilize Matadero Creek. These actions would not conflict with the Town of Los
Altos Hills General Plan or other applicable plans or policies. Impacts would be less
than significant.
c) No Impact. No habitat conservation plans or natural community conservation plans
have been adopted for the Town of Los Altos Hills.
4.11 Mineral Resources
Less than
MINERAL RESOURCES—Would the Potentially Significant with Less.than
Significant Mitigation Significant No
project: Impact ' Incorporated Impact Impact Source
a) Result in the loss of availability of a ❑ ❑' ❑ // 2
known mineral resource that would '
be of value to the region and the
residents of the state?
b) Result in the loss of availability of a ❑ ❑ ❑ ® 2
locally important mineral resource
recovery site delineated on a local
general plan, specific plan, or other
land use plan?
Environmental Setting :
The Town of Los Altos Hills does not contain any lands designated for mineral production or
known for mineral deposits. _ Mineral resources that have been found and extracted in the
Town's planning area are primarily construction aggregate deposits. Neary Quarry, which
supplied base rock for the construction of Moffett Field and crushed rock for Highways 101 and
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Town of Los Altos Hills 52 October 2015
280, is no longer in operation. In, 1996 the Town approved the subdivision of Neary Quarry,
which has since been developed with single-family homes.
Discussion of Impacts
a, b) No Impact. The project area is not in or adjacent to any important mineral resource
areas.
4.12 Noise
Less than
Significant
Potentially with Less than
Significant Mitigation' Significant No.
NOISE—Would the project result in: Impact Incorporated Impact Impact Source
a) Exposure of persons to or generation of ❑ ® ❑' ❑ 1,2
noiselevels in excess of standards
• established in the local general plan or
noise ordinance, or applicable standards of .
other agencies? . .
b) Exposure of persons to or generation of ❑ ® ❑ ❑ I
excessive groundborne vibration or
groundborne noise levels? .
c) A;substantial permanent increase in •
❑ ❑ ❑
ambient noise levels in the project vicinity .
above levels existing without the project?
d) A substantial temporary or periodic ❑ ® ❑ . ❑
increase in ambient noise levels in the
project vicinity above levels existing without
the project? .
e) For a project located within an airport land ❑ ❑ �/ ❑
use plan or, where such a plan has not
been adopted, within two miles of a public
airport of public use airport,would the;
project expose people residing or working
in the Project Area to excessive noise
levels?
f) For a project within the vicinity of a private ❑ ❑ ❑ ZI
airstrip, would the project expose people
residing or working in the Project Area to
excessive noise levels? .
Environmental Setting
Although construction noise usually lasts only a limited period of time, it can severely restrict the
enjoyment of residential properties. Due .to the topography of the community, noise from
construction activities such as grading and the operation of other heavy equipment often carries
for great distances. The Town's Municipal Code limits the hours _and, days of •outside
construction activities to 8:00 a.m. to 5:30 p.m. Monday through Friday, with no use of heavy
• equipment on Saturday and no construction allowed on Sundays or public holidays. All
•
•
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Town of Los Altos Hills 53 October 2015
construction equipment operating within the Town should be encouraged to be equipped with
the most up-to-date muffling devices generally available. Noise in the project area and vicinity
is primarily from residences and vehicular traffic along Page Mill Road. The nearest sensitive
noise receptors are the residents along Amherst Court, Page Mill.Road and Berry Hill Lane.
Discussion of Impacts
a, c, d) Less than Significant Impact with Mitigation Incorporated. Sound is technically
described in terms of amplitude (loudness) and frequency (pitch). The standard unit
of sound'.amplitude measurement is the decibel (dB). The decibel scale is a
logarithmic scale that describes the physical intensity of the pressure vibrations that
make up any sound. The pitch of the sound is related to the frequency of the
pressure vibration. Since the human ear is not equally sensitive to a given sound
level at all frequencies, a special frequency-dependent rating scale has been devised
to relate noise to human sensitivity. The A-weighted decibel scale (dBA) provides
this compensation by discriminating against frequencies in a manner approximating
the sensitivity of the human ear.
Noise, on the other hand, is typically defined as unwanted sound. A typical noise
environment consists of a base of steady"background" noise that is the sum of many
distant and indistinguishable noise sources. Superimposed on this background
noise isthesound from individual local sources. These can vary from an occasional
aircraft or train passing by to virtually continuous noise from, for example, traffic on a
major highway.
Several rating scales have been developed to analyze the adverse effect of
community noise on people. Since environmental noise fluctuates over time, these
scales consider that the effect of noise upon people is largely dependent upon the
total acoustical energy content of the noise, as well as the time of day when the
noise occurs. Those that are applicable to this analysis are as follows:
• Leq = A Leq, or equivalent energy noise level, is the average acoustic energy
content of noise for a stated period of time. Thus, the Leq of a time-varying noise
and that of a steady noise are the same if they deliver the same acoustic energy
to the ear during exposure. For evaluating community impacts, this rating scale
does not vary, regardless of whether the noise occurs during the day or the night.
• Lmax—The maximum instantaneous noise level experienced during a given period
of time.
• Lmin.— The minimum instantaneous noise level experienced during a given period
of time. —
• CNEL—The Community Noise Equivalent Level is a 24-hour average Leq with a 5
dBA "weighting" during the hours. of 7:00 P.M. to 10:00 P.M. and a. 10 dBA
"weighting" added to noise during the hours of 10:00 P.M. to 7:00 A.M. to account
for noise sensitivity in the evening and nighttime, respectively. The logarithmic
effect of these additions is that a 60 dBA 24 hour Leq would result in a
measurement of 66.7 dBA CNEL.
Noise environments and consequences of human activities are usually well
represented by median noise levels during the day, night, or over a 24-hour period.
For residential uses, environmental noise levels are generally considered low when
the CNEL is below 60 dBA, moderate in the 60-70 dBA range, and high above 70
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Town of Los Altos Hills 54 October 2015
dBA.11 Noise levels greater than 85 dBA can cause temporary or permanent hearing
loss. Examples of low daytime levels are isolated, natural settings with noise levels
as low as 20 dBA and quiet suburban residential streets with noise levels around 40
dBA. Noise levels above 45 dBA at night can disrupt sleep. Examples of moderate
level noise environments are urban residential or semi-commercial areas (typically
55-60 dBA) and -commercial locations (typically 60 dBA). 'People may consider .
louder environments adverse, but most will accept the higher levels associated with
more noisy urban residential or residential-commercial areas (60-75 dBA) or dense
urban or industrial areas (65-80 dBA).
It is widely accepted that in the community noise environment the average healthy
ear can barely perceive CNEL noise level changes of 3 dBA. CNEL changes from 3
to 5 dBA may be noticed bysome individuals who are extremely sensitive to
changes in noise. A 5 dBA CNEL increase is readily noticeable, while the human ear
perceives a 10 dBA CNEL increase as a doubling of sound.
Noise levels from a particular source generally decline as distance to the receptor
increases. Other factors, such as the weather and reflecting or barriers, also help
intensify or reduce the noise level at any given location. A commonly used rule of
thumb for roadway noise is that for every doubling of distance from the source, the
noise level is reduced by about 3 dBA at acoustically "hard" locations (i.e., the area
between the noise source and the receptor is nearly complete asphalt, concrete,
hard-packed soil, or other solid materials) and 4.5 dBA.at acoustically"soft" locations
(i.e., the area between the source and receptor is normal earth or has vegetation;
including grass). Noise from stationary or point sources is reduced by about 6 to 7.5
dBA for every doubling of ,distance at acoustically hard and soft locations,
respectively. Noise levels are also generally reduced by 1 dBA for each 1,000 feet of
distance due to air absorption. Noise levels may also be reduced by intervening
structures — generally, a single row of buildings between the receptor and the noise
source reduces the noise level by about 5'dBA, while,a solid'wall or berm reduces
noise levels by 5 to 10 dBA. The normal noise attenuation within residential
structures with open windows is about 17 dBA, while the noise attenuation with
closed windows is about 25 dBA.12
Table 4 lists the Federal Transit Administrations typical construction equipment noise
levels at 50 feet.
Table 4. Construction Equipment Noise Generation
Equipment Typical Noise Level (dBA) 50 ft from Source
Air Compressor 81
Backhoe 80 '
Ballast Equalizer 82
11 Office of Planning and Research, State of California General Plan Guidelines, October 2003(in coordination with
the California Department of Health Services). '
12 National Cooperative Highway Research Program Report 117, Highway Noise: A Design Guide for Highway
Engineers, 1971.
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Town of Los Altos Hills 55 October 2015
Equipment Typical Noise Level (dBA) 50 ft from Source
Ballast Tamper 83
Compactor 82 •
Concrete Mixer 85
Concrete Pump 82
Concrete Vibrator 76
Crane, Derrick 88
Crane, Mobile 83
Dozer 85
Generator 81
Grader 85
Impact Wrench 85
Jack Hammer 88
Loader 85
Paver 89
Pile-driver(Impact) 101
Pile-driver(Sonic) 96
Pneumatic Tool 85
Pump 76
Roller 74
Saw 76
Scarifier 83
Scraper 89
Shovel 82
Spike Driver 77
Truck 88
Source:Federal Transit Administration. Transit Noise and Vibration Impact Assessment,
2006
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Town of Los Altos Hills 56 October 2015
, : Construction activities would generate temporary noise from equipment use and
pipeline installation, the most common noise generated would be from mobile diesel
equipment such as excavators,. dozers, trucks, front end loaders and compactors.
All construction work would be limited to.8:00 A.M. to 5:30 P.M: on weekdays unless
otherwise approved in writing by the Director of Public Works.
Table 4.illustrates typical noise levels from construction equipment at a.reference
distance of 50 feet. Noise levels from construction equipment attenuate ata rate of
six dBA per doubling :of distance. Therefore, the noise levels ata distance of 100
feet would be 6 dBA less than those shown in Table 4. Construction equipment
would generate maximum noise levels of approximately 89 decibels (dB) at 50 feet.
Construction noise levels may periodically exceed;noise standards. The temporary
noise from construction would not cause a substantial increase in ambient noise or.
expose sensitive receptors to unacceptable noise levels for long periods of time.
Impacts associated with construction noise would cause a significant, temporary
. . increase in noise levels. Incorporation of Mitigation Measure NOISE-1 would reduce
potentially significant noise impacts to a less-than-significant level.
Long-term operational noise impacts would be less thansignificant.because noise'
levels at the project area would be similar to existing.conditions.
Mitigation Measure NOISE-1: Construction Noise .
The Town shall incorporate the following practices into the construction documents
to be implemented by the project contractor:
•
• Construction hours shall be limited to 8 A.M. to 5:30 P.M. as stated in the Town
of Los Altos Hills Municipal Code. No heavy equipment'.use is allowed on
Saturdays and no construction is allowed on Sundays or holidays.
• Notify residences, and noise-sensitive land uses adjacent to.construction sites of
the construction -schedule in writing. Designate a "construction liaison" that is
responsible for responding to any local complaints about construction.noise. The
liaison shall determine the cause of the noise complaints (for example starting
too early, or a bad muffler) and institute reasonable measures to correct the
problem. Conspicuously post a .telephone number for the liaison at the
construction site.
• Coordinate construction activities so that they cause the least interference with
daytime activities in the community as practical.
• Minimize backing movements of equipment.
• Verify that equipment engines are fitted with appropriate mufflers that are in good
: operating condition.
• Prohibit unnecessary idling of internal combustion engines.
b) Less than Significant Impact. Construction activities can generate groundborne
vibration that is feelable (causes annoyance) and in extreme cases, causes physical
'damage to nearby buildings. Generally, groundborne-,vibration is feelable at much
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Town of Los Altos Hills 57 October 2015
lower levels than would be necessary to cause physical damage. Ground-borne
vibration is typically associated with blasting operations, the use of pile drivers, and
large-scale. demolition activities, none of which are anticipated for the construction
and operation of the proposed project. As such, no excessive ground-borne
vibrations would be generated by the proposed project and these impacts would be
less than significant..
e, f) No Impact. The project area is not near a public or private airport or airstrip. The
project would not expose people,to noise from airport activities.
4.13 Population and Housing
Less than
Significant
POPULATION AND HOUSING—Would the Sotnntially with Less than
Significant Mitigation Significant No
project: Impact Incorporated Impact Impact " Source
a) Induce substantial population growth in an ❑ ❑ ® ❑ 1
area, either directly(for example, by
proposing new homes and businesses)or
indirectly(for example, through extension
of roads or other infrastructure)?
b) Displace substantial numbers of existing ❑ ❑ ❑ // 1
housing, necessitating the construction of
replacement housing elsewhere?
c) Displace substantial numbers of people 1
necessitating the construction of
replacement housing elsewhere?
Environmental Setting
The project area is located in a developed low density residential neighborhood community of
Los Altos Hills. The project area is surrounded by low density residential. Additional land uses
in the vicinity include a ride-share parking lot and Interstate 280 to the north. Open space
preserve trails run along the Page Pill Road corridor. The surrounding area is categorized as
residential in both the zoning code and General Plan.
Discussion of Impacts
a, b, c) No Impact. The proposed stabilization project would not induce population growth.
Upon completion of the project, the project area would serve the same function as
existing conditions. The proposed project would be within existing easements and
rights-of-way and would not displace people or housing and would not result in the
addition of new housing or businesses.
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4.14 Public Services
Less than• .
Significant
Potentially with Less than
Significant- Mitigation Significant No
PUBLIC SERVICES—Would the project: Impact. Incorporated Impact Impact Source
a) Result in substantial adverse physical
impacts associated with the provision of
new or physically altered governmental
facilities, need for new or physically altered
governmental facilities, the construction of
which could cause significant
environmental impacts, in order to maintain
acceptable service ratios, response times,
or other performance objectives for any of
the public services:
Fire protection? ❑ ® ❑ ❑
Police protection? ❑ ® ❑ ❑
Schools? ❑ ❑ ❑ ./
Parks? ❑ ❑ ❑ ®
Other public facilities? ❑ ❑• ❑ 1Z11
Environmental Setting
Fire Protection
Fire Protection, suppression and safety services are provided by the Los Altos Hills County Fire
District. The District contracts with the Santa Clara County Fire Department for services. Fire
prevention programs provided by the District include free brush chipping and removal, brush
and yard waste drop-off days, and site visits for property fire fuel evaluations.
Police Protection
The Town of Los Altos Hills contracts with the Santa Clara County Sheriff's.Department for law
enforcement and public safety services. Residents of Los Altos Hills participate in the direct
election of the Sheriff. Specific services provided to the Town are negotiated and approved by
the Town Council:
Schools
Residents of Los Altos Hills are served by more than one public school district. Students from
the southern part:of Town attend schools in the Los Altos School District (K-8) and Mountain
View-Los Altos Union High School District (9-12), and those in the northern section attend Palo
Alto Unified School District (K-12) schools. These districts are governed by publicly-elected
boards. Residents from Los Altos Hills may also enroll in the Bullis Charter School (K-8), where
preference is given to LASD residents. The Gardner Bullis Elementary School, an LAH K-6
neighborhood school re-opened in 2008 and is available to all residents of Los Altos Hills.
Parks .
The nearest public park to the project area is Purissima Park.
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Other public facilities
The Town.is part of the Santa Clara County Library system and is most closely served by two
libraries located in Los Altos. The Los Altos Main Library is one of the most heavily used in
California. A seven-member Library Commission consists of two members from Los Altos Hills
and five from the Town of Los Altos Hills.
El Camino_Hospital is a non-profit community hospital. The hospital is located on Grant Road in
Mountain View, and serves Los Altos Hills residents as well as those living in surrounding
communities. El Camino Hospital is governed by a five member Board of Directors whose
members are publicly-elected. As a group, these representatives overseethe assets of the El
Camino Hospital District including El Camino Hospital, El Camino Hospital Foundation and Mid-
Peninsula Homecare and Hospice.
Discussion of Impact
a) Less than Significant with Mitigation Incorporated. Given the proposed project
would not permanently increase the existing residential or employment population in
the Town, the project would not result in a long-term increase in the demand for
public services or require construction of new governmental facilities. The purpose
of the project is to improve the stabilize MataderoCreek. Therefore, no impacts
related to schools, parks or other public facilities would occur. However, there is the
potential for construction activities to slow emergency response times.
Implementation of Mitigation Measure TRAFFIC-1 would reduce' potentially
significant impacts related to any potential Fire Protection and- Sheriff Department
delays to a less-than-significant level.
4.15 Recreation
Less than
Significant
Potentially with Less than
Significant Mitigation Significant No
RECREATION—Would the project: Impact Incorporated Impact Impact Source
a) Increase the use of existing neighborhood ❑ ❑ ❑ . ® 1
and regional parks or other recreational
facilities such that substantial physical
deterioration of the facility would occur or
be accelerated?
b) Include recreational facilities or require the ❑ ❑ . ' ❑ �• 1
construction or expansion of recreational
facilities which might have an adverse
physical effect on the environment?
Environmental Setting
No public parks or recreational facilities are located in the project area. The nearest public
recreation facility is Purissima Park located one mile to the east.
Discussion of Impacts
a-b) No Impact. The project would not involve any additional housing or businesses that
could increase residents and/or employees in the project area. The project would
not affect recreational facilities or increase the use of nearby recreational facilities.
The project would not require the construction or expansion of recreational facilities
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- , which might have .anadverse physical effect on the environment. Therefore, no.
impact would occur.
4.16 Transportation/Traffic
Less than
Significant
TRANSPORTATION/TRAFFIC—Would the Potentially wiLess than
Significant Mitigation Significant No
project: Impact Incorporated Impact Impact. Source
a) Conflict with an applicable plan, ordinance ❑ ® ❑ : ❑ I
or policy establishing measures of
effectiveness for;the performance of the
circulation system, taking into account all
modes of transportation including mass
transit and non-motorized travel and
relevant components of the circulation
system, including but not limited to .
intersections, streets, highways and
freeways, pedestrian and bicycle paths,
and mass transit?
•
b) Conflict with an applicable congestion ❑ ❑ ® ❑
management program, including, but not
limited to level of service standards and
travel demand measures, or other
standards established by the county
congestion management agency for
designated roads or highways?
c) Result in a change in air traffic patterns, ❑ ❑ ❑ ® I
including either an increase in traffic levels
or a change in location that results in
substantial safety risks?
d) Substantially increase hazards to a design: ❑ ❑ ❑ e/ .
feature(e.g., sharp curves or dangerous
intersections)or incompatible uses (e.g.,
farm equipment)?
•
e) Result in inadequate emergency access? ❑ ❑ ® ❑ .
f) Conflict with adopted policies, plans, or ❑ ❑ ❑ . // I
programs supporting alternative .
transportation (e.g., bus turnouts, bicycle
racks)?
Discussion of Impacts
a) Less than Significant with Mitigation Incorporated. The Town general plan
states that "Levels of service (LOS) for all roadways in Los Altos Hills shall be
consistent with the Town Goal and no less than LOS B, except for LOS C at arterials
and expressways". Temporary construction traffic would consist of equipment and
material transport periodically during the construction phase and a few additional
employee.vehicles daily during the construction phase. The temporary construction-
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Town of Los Altos Hills 61 October 2015
related traffic would is not expected to reduce the;levels of service for the roads.
Large vehicles transporting equipment and:materials to the project area could cause
slight delays for travelers adjacent to the project's access points as the construction
vehicles stop to unload. Mitigation Measure TRAFFIC-1 includes control measures
to alert travelers to potential delays and ensure that construction-related impacts are
less than significant.
Mitigation Measure TRAFFIC—I: Traffic Safety
• Use traffic cones, signs, lighted barricades, lights, and flagmen as described
and specified in the Manual of Uniform Traffic Control Devices, current
edition, California Supplement, Part 6 Temporary Traffic Control to provide for
public safety and convenience during construction, if necessary.
• Restore pavement, curbs, gutters, and sidewalks, as necessary, to pre-
disturbance conditions or better.
With these measures and the temporary nature; of construction-relatedtraffic,
impacts on traffic would be less than significant.
b) Less than Significant Impact. A significant impact may occur if the adopted
California Department of Transportation (Caltrans) and Santa Clara County
Congestion Management Agency (CMA) thresholds,for a significant.project impact
would be exceeded. To address the increasing public concern that traffic congestion
is impacting the quality of life and economic vitality of the State of California, the
Congestion Management Program (CMP) was enacted by Proposition 111. The
CMP designated a transportation network including all State highways and some
arterials within the County to be monitored by local jurisdictions. If the Level of
Service (LOS) standard deteriorates on the CMP network, then local jurisdictions
must,prepare a deficiency plan to be in conformance with the CMP program.
As discussed above, the proposed project would not permanently increase traffic on
local roads or highways to a level that would affect: intersection LOS. The project
would maintain at least one lane of traffic in one direction atall times. The proposed
project would not result in long-term traffic increases or impacts.
c) No Impact. This question would apply to the proposed project only if it were an,
aviation-related use. The project area does not contain any aviation-related uses,
and the proposed project would not include the development of any aviation-related
uses. Therefore,-the proposed project would not affect air traffic:patterns and would
have no effect on air traffic levels or safety
d) No Impact. A significant impact may occur if a project were to include a new
roadway design, introduce a new land use or permanent project features into an area
with specific transportation requirements and characteristics that have not been
previously :experienced in that area, or if project access or other features were
designed in such a way as to create hazardous conditions. The project would not
involve new road construction or activitiesthat could increase hazards due to a
design feature or incompatible uses. Adequate sight distance would be available for
motorists to access and depart the project area.
e) Less than Significant Impact. Significant delays. for emergency access to the
residences adjacent to the work area are not expected. The proposed project would
be staged off of local roads and within existing rights-of-way. The Town or its
construction contractors will coordinate with law enforcement and emergencyservice
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Town of Los Altos Hills 62 October 2015
providers prior to thestart of construction to ensure minimal disruption to service
during construction. Impacts relating to emergency access would be less than
significant.
f) No Impact. There are no adopted alternative transportation policies, plans, or
programs in the proposed project area. There would be no impact
4.17 Utilities and Service Systems
Less than
Significant
UTILITIES AND SERVICE SYSTEMS—Would
Potentiallyignfn . with Less than
Significant Mitigation Significant No
the project: Impact Incorporated Impact Impact Source
a) Exceed wastewater treatment requirements 0 ❑ ❑. IZI
of the applicable Regional Water Quality :
Control Board?
b) Require or result in the construction of new ❑ ❑ ❑
water or wastewater treatment facilities or
expansion of existing facilities, the
construction of which could cause
significant environmental effects?
c) Require or result in the construction of new ❑ ❑ ❑ 1,11
storm water drainage facilities or expansion
of existing facilities, the construction of
which could cause significant
environmental effects? '
d) Have sufficient water supplies available to ❑ ❑ ❑
serve the project from existing entitlements
and resources, or are new or expanded .
entitlements needed?
e) Result in a determination by the ❑ ❑ ❑ ® 1
wastewater treatment provider which
serves or may serve the project that it has-
adequate capacity to serve the project's
projected demand in addition to the
provider's existingcommitments?
f) Be served by a landfill with sufficient ❑ ❑ ® . ❑
permitted capacity to accommodate the '
project's solid waste disposal needs?
g) Comply with federal, state, and local ❑ ❑
statutes and regulations related to solid '
waste?
Environmental Setting
The project area is located adjacent to a developed area of the Town. Electrical and other utility
lines are also located along the roads, either underground or aboveground. The various utility
and service agencies that serve the project area are described,below.
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Town of Los Altos Hills 63 October 2015
Water Service
Water is supplied to approximately two-thirds of the Town residents by the Purissima Hills Water
District. The District is governed by a publicly-elected board. The remaining one-third of
residents are served by California Water Service Company, an investor owned utility company.
Currently, the project area is not connected to the Town's water system.
Sanitary Sewer Services/Wastewater Treatment
Wastewater is conveyed to the Palo Alto Regional Water Pollution Control Plant for treatment
and disposal. The Regional Water Quality Control Plant is owned and operated by the City of
Palo Alto for the communities of Los Altos, Los Altos Hills, Mountain View, Palo Alto, Stanford
University and the East Palo Alto Sanitary District. The Plant is an advanced treatment facility
that uses gravity settling, biological treatment with microorganisms and dual media filtration to
remove unwanted organic materials and toxins from the approximately 22 million gallons a day
of wastewater generated by the.service area's 220,000 residents.13 The Plant's treated effluent
meets'all of the stringent requirements for discharge to the sensitive South San Francisco Bay
Storm Drainage
Bank failure has occurred in the portion of Matadero Creek which is located immediately
downstream of a concrete box culvert, which traverses Page Mill Road, approximately 1/4 mile
south of Interstate 280 in the Town of Los Altos Hills. The box culvert contains a downstream
outfall apron comprising of sackcrete material. At the transition between the sackcrete material
and the downstream soft bottom channel, a 3-foot vertical headcut and scour pool has formed.
Downstream of the box culvert downcutting of the creek is occurring in the channel downstream
of the'culvert, likely in response to larger hydromodification issues in the watershed. The
downcutting has progressed upstream to the point of the approximate location of the culvert and
appears to have been arrested by the sackcrete apron at the outfall of the culvert.
Solid Waste
Garbage, recyclable materials and compostables collected in the Town of Los Altos. Hills are
brought to the GreenWaste Material Recovery Facility (MRF) in San Jose for processing.
Recyclable materials are sorted on the single-stream recyclables processing line at the MRF
where:they are separated by material type, baled and shipped to market for use as a recycled
product. All yard trimmings and organics are removed from the garbage andsent to: Z-Best
Composting Facility in Gilroy where they are screened for further processing: the woody debris
is chipped and used as a co-generation fuel and the lightweight yard trimmings and organics are
composted and used as a high-quality soil amendment. The non-recyclable and non-
compostable residuals remaining after processing are transported to a landfill for disposal.
Discussion of Impacts
a, d, e) : No Impact. The project would not generate wastewater or require a new water
supply. It would not impact wastewater treatment or capacity. No new water supply
or distribution facilities would be constructed or needed as part of the project. If
water supply is needed for dust control, it would be trucked into the site. Therefore,
no impacts to wastewater or water supply are anticipated.
b) No Impact. The project involves the stabilization of Matadero creek and would
involve temporary construction impacts related to debris removal and berm
construction. The proposed project would not require or result in the construction of
13 http://www.cityofpaloalto.org/gov/depts/pwd/rwgcp.asp
Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
Town of Los Altos Hills 64 October 2015
new water or wastewater treatment facilities or expansion of existing facilities, the
construction of which could cause significant environmental effects.
c) Less than Significant Impact. The project would.restore and stabilize the area
surrounding the project area by constructing a rip-rap chute structure which would
restore equilibrium conditions in the creek channel in regard to erosive processes.
The project would not require the construction of additional new storm water
facilities. As discussed in other sections of this report, all potentially significant
impacts related to the construction of the improvements can be reduced to less-than-
significantlevels via the implementation of feasible mitigation measures;
f, g) Less than Significant Impact. The ,project may generate a small quantity of solid
waste during construction, but all generated waste would be properly disposed or
recycled in an approved landfill or disposal facility with capacity to receive the.waste.
Any materials used during construction would be properly disposed of in accordance .
with federal, state, and local regulations. Impacts on solid waste facilities would be
less than.significant. .
4.18 Mandatory Findings of Significance .
Less.than:
Significant
Potentially with Less than
Significant Mitigation Significant No
MANDATORY FINDINGS OF SIGNIFICANCE Impact Incorporated Impact Impact . Source
a) Does the project have the potential to ❑ ® ❑ ❑. .
degrade the quality of the environment,
substantially reduce the habitat of a fish or .
wildlife species, cause a fish or wildlife .
population to drop below self-sustaining .
levels, threaten to eliminate a plant or .
animal community, reduce the number or
restrict the range of a rare or endangered •
plant or animal or eliminate important
examples of the major periods of California
history or prehistory?
b) Does the project have impacts that are ❑ ® ❑ : ❑
individually limited, but cumulatively
considerable? ("Cumulatively
considerable" means that the incremental
effects of a project are considerable when
viewed in connection with the effects of
past projects, the effects of other current
projects, and the effects of probable future
projects)?
c) Does the project have environmental . ❑ ® ❑ ❑
effects that will cause substantial adverse
effects on human beings, either directly or
indirectly?
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Town of Los Altos Hills 65 October 2015
Discussion
a) Less than Significant with Mitigation Incorporated. The incorporation of the
mitigation measures included in Section IV (Biological Resources) would reduce
potential impacts to a less-than-significant level. The project area does:not contain
any resource listed in, or determined to be eligible by, the State Historical Resource _
Commission and does not contain a resource included in a local register of historic
resources or identified as significant in a historical resource survey. Additionally, the
project area does not contain any object, building, structure, site, area, place, record,
or manuscript that a lead agency determined to be historically significant or.
significant in the architectural, engineering, scientific, economic, agricultural,
educational, social, political, military, or cultural annals of California. However,
cultural resources could potentially be uncovered during construction. Mitigation-
measures included in Section V (Cultural Resources) would reduce potential impacts
to a less-than-significant level.
b) Less than Significant with Mitigation Incorporated. Cumulatively considerable
means that the incremental effects of an individual project are considerable when
viewed in connection with the effects of past projects, the effects of other current
projects, and the effects of probable future projects. The analysis within this Initial
Study demonstrates that the project would not have any individually limited, but
cumulatively considerable impacts. As presented in the analysis in Air. Quality,
Biological Resources, Cultural Resources, Hazards and Hazardous Materials, Noise,
Public Services, and Transportation/Traffic sections, any potentially significant
impacts would be less than significant after mitigation. Due to the limited scope of
direct physical impacts to the environment associated with construction, the project's
impacts are project-specific in nature. Compliance with the conditions of approval
issued for the proposed development wouldfurther assure that project-level impacts
would not be cumulatively considerable. Consequently, the project along with other
cumulativeprojects will create a less than significant cumulative impact with respect
to all environmental issues.
c) Less than Significant with Mitigation Incorporated. The project, particularly
during the construction phase, could result in a variety of:temporary impacts to
human beings. The project's construction phase would result in potentially
significant impacts related to Air Quality, Biological Resources, Cultural Resources,
Hazards and Hazardous Materials, Noise, Public Services, and Transportation/Traffic
sections; however, all impacts can be mitigated to less-than-significant levels via the
mitigation measures included in this Initial Study.
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Town of LosAltosHills 66 October 2015
5.0 REFERENCES
Checklist Information Sources
1. Professional judgment and expertise of the environmental/technical specialists
evaluating the project, based on a review of. existing conditions and project details,
including standard construction measures
2. Town of Los Altos Hills General Plan
3. Town of Los Altos Hills Land Use Map
4. California Department of Conservation, 2010
5. California Department of Transportation, 2012
6. Federal Emergency Management Agency, 2011
7. WRA, Inc., Biological Resources Assessment, 2012
8. Department of Toxic Substances. Control, 2011, and State Water Resources Control
Board, 2011
9. ABAG Hazards Mapping, 2014
10. Bay Area Air Quality Management District, 2010
11. ENGEO, 2015
12. .Los;Altos Hills Municipal Code -
•
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Town of Los Altos Hills 67 October 2015
Report Preparers
Town of Los Altos Hills
Richard Chiu, Director of Public Works
ENGEO Inc.
Jonathan Buck, Project Manager
WRA, Inc.
Geoff Smick, Principal
Geoff Reilly, Senior Associate Environmental Planner.
Matt Richmond, Senior Associate Plant Ecologist
Paul Curfman, Associate Environmental Planner
Jonathan Hidalgo, Environmental Planner . .
•
•
r-_
•
r_
' _I
Matadero Creek Restoration and Bank.Stabilization Project Draft Initial Study
Town of Los Altos Hills 68 October 2015
Setting References
Bulger, J.B., S.J. Norman, and 'R.B., Seymour. 2003. Terrestrial.Activity and Conservation of
Adult California Red-legged Frogs (Rana aurora draytonii) in Coastal Forests and
Grasslands. Biological Conservation 110 (2003). 85-95.
[Cal-IPC] 'California Invasive Plant Council. 2014, Invasive Plant Inventory. Accessed
December 2014 online: http://www.cal-ipc.orq/ip/inventory/.
[Caltrans] California Department of Transportation. . 2012. Scenic highways: San Mateo
County. Available at: <http://www.dot.ca.gov/hq/LandArch/scenic highways/smateo.htm>.
Last updated 9/7/11. Accessed May 2015
[CDC] .California Department of Conservation. 2008. Farmland Mapping and Monitoring
Program: San Mateo County Important Farmland 2010. Available at:
<ftp://ftp.consrv.ca.gov/pub/dlrp/FMMP/pdf/2010/smtl0.pdf>. Accessed May 2015.
[CDFG] California Department of Fish and Game. 2009. List of California.Vegetation Alliances.
I Biogeographic Data Branch: Vegetation Classification and Mapping Program, Sacramento,
CA.
[CDFG] California Department of Fish and Game. 2007. List of California Vegetation Alliances.
Biogeographic Data Branch. Vegetation Classification and Mapping Program, Sacramento,
CA.
[CDFG] California Department of Fish and Game. 2003. List of California Terrestrial.Natural
Communities Recognized by the California Natural Diversity Database Wildlife and Habitat
Data Analysis Branch. Vegetation Classification and Mapping Program, Sacramento, CA.
[CDFG] California Department of Fish and Game. 1994. A Field Guide to Lake and Streambed
Alteration Agreements, Sections 1600-1607, California Fish and Game.Code. Environmental
Services Division, Sacramento, CA
[CDFW] California Department of Fish and Wildlife. 2014. California Natural Diversity
Database, Commercial Edition. CDFW Wildlife and Habitat Data Analysis Branch,
Sacramento, CA. Accessed: October 2014.
[CNPS] California Native Plant Society. 2014. Rare and Endangered Plant 'Inventory.
Sacramento, California. Online at: http://www.cnps.org/inventory. Accessed October 2014.
Cicero, C.'.2000. Oak Titmouse (Baeolophus inornatus), The Birds of North America Online (A.
Poole, Ed.). Ithaca: Cornell Lab• of Ornithology; Retrieved from the Birds of North America
Online: http://bna.birds.cornell.edu/bna/species/485a
Dunk, J.R. 1995. White-tailed Kite (Elanus leucurus), The Birds of North America Online (A.
Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America
Online: http://bna.birds.cornell.edu/bna/species/178
[DTSC] Department of Toxic Substances Control: 2011. EnviroStor database: San Mateo.
Available at: <http://www.envirostor.dtsc.ca.gov/public/>.' Accessed May 2015.
Matadero Creek Restoration and Bank.Stabilization Project Draft Initial Study
1 Town of Los Altos Hills 69 October 2015
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ENEGO.2015. Water Surface Profile Study and Design Recommendations
Holland, R.F. 1986. Preliminary Description of the Terrestrial Natural Communities of California.
California Department of Fish and Game, Sacramento, CA:
Jennings, M.R. and M.P. Hayes.. 1994. Amphibian and Reptile Species.of Special Concern in
California. Final report submitted to the California Department of Fish.and' Game, Inland
Fisheries Division, Rancho Cordova,_.California. Contract No: 8023. November. Jepson,
W.L. 1923. Trees of California. University of California, Berkeley, CA. 109 pp .
Leidy, R.A., G.S. Becker, B.N. Harvey. 2005. Historical distribution and current status of
steelhead/rainbow,trout (Oncorhynchus mykiss) in streams:of the San Francisco. Estuary,
California. Center.for Ecosystem Management and Restoration, Oakland, California.
Lowther, P.E. 2000. Nuttall's Woodpecker(Picoides nuttallii), Th'e Birds of North America Online
(A. Poole, Ed.). :Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North
America Online: http://bna.birds.cornell:edu/bna/species/555 : '
Matocq, M. 2003. Dusky-footed Woodrats (Neotoma fuscipes) at Hastings: A Research
Tradition. Hastings Natural History Reservation. Available online:
http://www.hastinqsreserve.orqNVoodrats/DFwoodrats.html .
Mitchell, Donald E. 2000. Allen's Hummingbird (Selasphorus sasin), The Birds of North America
Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North
America Online: http://bna.birds.cornell.edu/bna/species/501;
NatureServe. 2014. NatureServe Conservation Status. Available online at:
httn://www.natureserve.orq/explorer/ranking. - ,
[NRCS] Natural Resources Conservation Service. 2012. Web Soil Survey for San Mateo Area.
Available at: <http://websoilsurvey.nres.usda.gov/app/HomePage.htm>.. Accessed May :
2015. ` t
Rathbun, G. B., N: J. Scott, Jr., and T. G. Murphey. 2002. Terrestrial habitat use by Pacific pond
Turtles in a Mediterranean climate. The Southwestern Naturalist 47: 225-235.
Rathbun, G. B., N. Seipel and D: C. Holland. 1992. Nesting behavior and movements of western
pond turtles, Clemmys marmorata. The Southwestern Naturalist 37: 319-324.
Sawyer, J.O., T. Keeler-Wolf, and J.M. Evens. 2009. A Manual of California Vegetation,
2ndEdition. California Native Plant Society in collaboration, with California Department of
Fish and Game. Sacramento, CA.
Shuford, W.D. and Gardali, T., eds. 2008. California Bird Species of Special Concern: A ranked
Assessment of species, subspecies, anddistinct populations ofbirds of immediate conservation
concern-in California. Studies of Western Birds 1. Western Field Ornithologists, Camarillo,
California, and California Department of Fish and Game, Sacramento.
Matadero Creek Restoration and Bank'.Stabilization Project . ,Draft Initial Study
Town of Los Altos Hills 70 October 2015
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TRA Environmental Sciences, Inc. 2011. 1260 Westridge Drive Shorenstein Subdivision and
Planned Unit Development Project, Portola Valley, CA: Initial Study,and Mitigated Negative
Declaration. Prepared for Town of Portola Valley by TRA Environmental Sciences; Menlo
Park, CA. 128.pp.,
[Town] ' Town of Los Altos Hills. . 2007. General Plan. Website:
http://www.losaltoshills.ca.gov/documents-forms/browse/general-plan. Accessed May 2015.
[USGS] U.S. Geological Survey. 1998. Geology of Palo Alto 30 X 60 Minute Quadrangles,
California: A Digital Database. Available at: http://pubs.usgs.gov/of/1998/of98-348/
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Matadero Creek Restoration and Bank Stabilization Project Draft Initial Study
• Town of Los•Altos Hills 72 October 2015 •
APPENDIX A. BIOLOGICAL RESOURCES REPORT.
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BiologicalResource Assessment of the
Matadero Creek Study Area
LOS;ALTOS HILLS, SANTA CLARA COUNTY, CALIFORNIA
Prepared For: ' , etnr.
Town of Los Altos Hills ;,z '3- ', --': r,
•
> Cyt..• 'r" W -" —'
Town Hall Offices
26379 Fremont Road .
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Los Altos Hills, CA 94022k `• }ti
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Contact: Richard Chiu, Jr., PE
rchiu@losaltoshills°ca.gov •- • ,` ;4
= " yrs • 1�� s
Prepared By:
Pre
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WRA,'Inc.
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2169-G East Francisco Boulevard
San Rafael, California 94901.
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ENVIRONMENTAL CONSULTANTS
2169-G East Francisco Blvd.,;San Rafael, CA 94901 (415):454-8868 tel (415) 454-0129 fax info@wra-ca.com www.wra-ca.com
TABLE OF CONTENTS
EXECUTIVE SUMMARY 1
1.0 REGULATORY BACKGROUND 1
1.1 Sensitive Biological Communities 1
1.1.1 Waters of the United States 1
1.1.2 Waters of the State 1
1.1.3 Streams,,Lakes, and Riparian Habitat 1
1.1.4 Other Sensitive Biological Communities 2
, 1.2 Special-Status Species 2
1.3 Relevant Local Policies, Ordinances, Regulations 3
2.0 METHODS 3
2.1 Biological Communities 3
2.1.1 Non-sensitive Biological Communities 3
2.1.2 Sensitive Biological Communities 3
2.2 Special-Status Species 4
2.2.1 Literature Review 4
2.2.2 Site Assessment 5
2.3 Town of Los Altos Hills Tree Protection Ordinance 5
3.0 RESULTS 6
3.1 Biological Communities 6
3.1.1 Non-Sensitive Biological Communities 6
3.1.2 Sensitive Biological Communities 7
3.2 Special-Status Species 8
3.2.1 Plants 8
3.2.2 Wildlife 9
3.3 Protected Trees 12
3.4 Hydrology 13
3.5 Soils 13
4.0 SUMMARY AND RECOMMENDATIONS 13
4.1 Biological Communities 13
4.2 Special-Status Plant Species 14
4.3 Special-Status Wildlife Species 14
REFERENCES 17
� i
LIST OF APPENDICES
Appendix A. Figures
Figure 1. Project Location Map
Figure 2. Biological Communities
Appendix B. Plant and Wildlife Species Observed in the Study Area
Appendix C. Special-Status Wildlife Species
Appendix D. Study Area Photographs
EXECUTIVE SUMMARY
This report provides an assessment of potential natural community and special-status species
issues at the site of the proposed bank repairs to Matadero Creek along Page Mill Road in the
Town of Los Altos Hills, Santa Clara. County (Study Area; Figure 1, Appendix A). . The Study
Area extends along approximately 400 feet of Page Mill Road and includes a portion of
Matadero Creek, between Berry Hill Court and Arastradero Road, approximately one-quarter of
a mile southwest of Interstate 280 (1-280).
On October 21, 2014, WRA, Inc. (WRA) conducted a biological resources assessment within
the Study Area to identify potential biological constraints at the site, such as wetlands or riparian
habitats, and to determine the potential for sensitive plant and wildlife species to occur in the
Study Area. This information will support applications for regulatory agency permits and a
California Environmental Quality Act (CEQA) review for the proposed work. This report
describes the information available at the time of study and is based on site conditions that were
observed on the date of the site visit.
1.0 REGULATORY BACKGROUND
The following laws and regulations were applied to field investigations and assessment of
potential bank stabilization activities in the Study Area.
1.1 Sensitive Biological Communities
Sensitive biological communities include habitats that fulfill special functions or have special
values, such as wetlands, streams, or riparian habitat. These habitats are protected under
federal regulations such as the Clean Water Act (CWA); state regulations such as the Porter-
Cologne Act, the California Department of Fish and Wildlife (CDFW; formerly the California
Department of Fish and Game [CDFG]) Streambed Alteration Program, and the CEQA; or local
ordinances or policies such as city tree ordinances, Special Habitat Management Areas, and
General Plan Elements.
1.1.1 Waters of the United States
The U.S. Army Corps of Engineers (Corps) regulates "Waters of the United States" under
Section 404 of the CWA. Waters of the United States (herein referred to as "wetlands and non-
wetland waters") were assessed during the biological resources assessment and are discussed
in more detail a separate report prepared by WRA (WRA 2014).
1.1.2 Waters of the State
The Regional Water Quality Control Board (RWQCB) regulates "Waters of the State" under
Section 401 of the CWA and under the Porter-Cologne Water Quality Control Act. Waters of the
State (herein referred to as "wetlands and non-wetland waters") were assessed during ,the
biological resources assessment and are discussed in more detail in a separate report prepared
by WRA (WRA 2014). -
1.1.3 Streams, Lakes, and Riparian Habitat
Streams and lakes (included herein as "non-wetland waters"), as habitat for fish and wildlife
species, are subject to jurisdiction by the CDFW under Sections 1600-1616 of California Fish
1
and Game. Code (CFGC). Alterations to or work within or adjacent to streambeds or lakes.
generally:require a Section 1602 Lake and Streambed Alteration Agreement. The term
"stream", which includes creeks and rivers, is defined in the California Code of Regulations
(CCR) as "a body of water that flows at :least periodically or ,intermittently through :a bed or
channel having banks and supports fish or other aquatic life...[including] watercourses having a
surface or subsurface flow that.supports or has supported riparian vegetation" (14 CCR 1.72):
In addition, the term "stream" can include ephemeral streams, ;dry washes, watercourses with
subsurface flows,.canals, aqueducts, irrigation ditches, and other means of water conveyance if
they support aquaticlife, riparian vegetation, or stream-dependent terrestrial wildlife. (CDFG
1994): "Riparian" is defined as "on, or pertaining to, the banks of a. stream." Riparian
vegetation is defined as "vegetation which occurs in and/or; adjacent to a 'stream and is :
dependent on, and occurs because of, the:stream itself' (CDFG 1994). Removal of riparian
vegetation also requires a Section 1602 Lake and Streambed;Alteration Agreement from the
CDFW.
1.1.4 Other Sensitive Biological Communities
Other sensitive biological communities not discussed above include habitats that fulfillspecial
functions or have special values. Natural communities considered sensitive are those identified
in local or regional plans, policies, regulations, or: by the CDFW. The CDFW ranks sensitive
communities as "threatened" or "very threatened" and keeps records of their occurrences in its
California.Natural Diversity Database (CNDDB; CDFW 2014). Sensitive plant communities are
also identified in other reports prepared by the CDFW (2003, 2007, 2009). California Natural
Diversity Database vegetation alliances are ranked 1 through 5based on NatureServe's (2014)
methodology, with those alliances ranked globally (G) or, statewide (S) as 1 through 3,
considered sensitive. Impacts to sensitive natural communities identified in local or regional
plans, policies, or regulations or those identified by the CDFW or the U.S. Fish and Wildlife.
Service (USFWS) must be considered and evaluated under th;e CEQA.(CCR Title 14, Div. 6,
Chap. 3, Appendix G). Specific habitats may also be identified as sensitive in city or county
general plans or ordinances.
1.2 Special-Status Species
Special-status species include those plants:and wildlife speciesthat have been formally listed,
: are proposed as endangered or threatened, or are candidates-for such listing under the federal.
Endangered Species Act (ESA) or California Endangered Species Act,(CESA). These acts
afford protection to both listed and proposed species. In addition, CDFW.Species of Special
Concern, which are species that face extirpation in California if current population and habitat .
trends continue,. USFWS Birds of Conservation Concern; and CDFW special-status
invertebrates are all considered special-status species. Although CDFW Species of Special
Concern generally have no special legal status, they are givenspecial consideration under the
CEQA: In addition to regulations for special-status species, most birds in the[United States,
including non-status species, are protected by the Migratory Bird Treaty Act of 1918. Under this
:legislation, destroying active nests, eggs, .and young is illegal: . Plant species on California
Native Plant Society (CNPS)inventory of Rare and Endangered Plants (Inventory, CNPS 2014)
with California Rare Plant Ranks (Rank) of 1 through 4 are alsol considered special-status plant
species and must be considered under the CEQA.
1
1.3 Relevant Local Policies, Ordinances, Regulations
Town of Los Altos Hills Tree Protection Ordinance
Chapter 2 of the Los Altos Hills Municipal Code requires a permit for the alteration or removal of
any street tree, shrub, or plant in any street, park or public place" in the Town. Permits are also
required for certain activities, such as excavation or placement of concrete, with a distance of 10
feet from the center of the trunk of any street tree. Permits are also required by the Town for
the removal of Heritage Oaks, which are defined as any tree of the genus Quercus, including,
but not limited to, Valley Oak (Quercus lobata), California Live Oak (Quercus agrifolia), Black
Oak (Quercus kelloggii), and Blue Oak (Quercus douglasih), that has a trunk or multiple trunks
measuring 36 inches in circumference (approximately°12 inches in diameter) at a point 4 feet
above the root crown. Trees deemed by the Town to be Heritage Trees cannot be removed or
damaged except with approval of the City Council following a public hearing.
2.0 METHODS
On October 21, 2014, the Study Area was traversed on foot to determine (1) plant communities
present within the Study Area, (2) whether existing conditions provide suitable habitat for any.
special-status plant or wildlife species, and (3) whether sensitive habitats are present. All plant
and wildlife species encountered were recorded and are summarized in Appendix B. In
addition, the location of anyareas potentially subject to regulatory jurisdiction by the Corps, the •
RWQCB, or the CDFW was documented.
2.1 Biological Communities
Prior to the site visit, the Soil Survey of Santa Clara County, [U.S. Department of Agriculture
(USDA) 1991], the United States Geologic Survey (USGS) 7.5-minute quadrangle map,for Palo
Alto (USGS 2012) and publically available aerial imagery of the Study Area were examined to
determine whether any unique soil types that could support sensitive plant communities and/or
aquatic features were present in the Study.Area. Biological communities present in the Study
Area were classified based on existing plant community descriptions\provided in the Preliminary
Descriptions of the Terrestrial Natural Communities of California (Holland 1986). However, in
some cases it is necessary to identify variants of community types or to describe non-vegetated
areas that are not described in the literature. Biological communities were classified as
sensitive or non-sensitive as"defined by the CEQA and other applicable laws and regulations.
2.1.1 Non-sensitive Biological Communities
Non-sensitive biological communities are those communities that are not afforded special
protection under the CEQA, or other state, federal, or local laws, regulations, or ordinances.
These communities may, however, provide suitable habitat for some special-status plant or
wildlife species.
2.1.2 Sensitive Biological Communities
Sensitive biological communities are defined as those communities that are given special
protection under the CEQA or other applicable federal, state, or local laws, regulations, or
ordinances. Special methods used to identify sensitive biological communities are discussed
below.
3
Wetlands and Non-Wetland Waters
The Study Area was surveyed to determine whether any wetlands and non-wetland waters
potentially subject to jurisdiction by the Corps, the RWQCB; or the CDFW were present.
Specific methods used to identify wetlands and non-wetland waters are described in a separate
report prepared by WRA (WRA 2014).
Other Sensitive Biological Communities
The Study Area was evaluated for the presence of other sensitive biological communities,
including riparian areas and sensitive plant communities recognized by the CDFW. Prior to the
site visit, aerial photographs and local soil maps were reviewed to assess the potential for
sensitive biological communities to occur in the Study Area. During the site assessment, all
plant communities were identified to the level necessary to determine their sensitivity following
Holland (1986) and Sawyer et al. (2009).
2.2 Special-Status Species
2.2.1 Literature Review
The potential occurrence of special-status species in the Study Area was evaluated by first
determining which special-status species occur in the vicinitY, of the Study Area through a
literature and database search. Database searches for known occurrences of; special-status ,
species focused on the Palo Alto, Mountain View, Cupertino, and Mindego Hill 7.5-minute
USGS quadrangles. The following sources were reviewed to determine which special-status
plant and wildlife species have been documented from within the vicinity of the Study Area:
• California Department of Fish and Wildlife (CDFVV) Natural Diversity Database (CNDDB)
records (CDFW 2014)
• • U.S. Fish and Wildlife Service (USFWS) Santa Clara County species list (USFWS 2014)
• California Bird Species of Special Concern: A Ranked Assessment of Species,
Subspecies, and Distinct Populations of Birds of Immediate Conservation Concern in
California (Shuford and Gardali 2008)
• • California Native Plant Society (CNPS) Inventory of Rare;and Endangered Plants (CNPS
2014)
4
1i
2.2.2 Site Assessment
A site visit wasmade to the Study Area to search for suitable habitats for special-status species.
Habitat conditions observed were used to evaluate the potential for the presence of special-
status species based on these searches and the professional expertise of the investigating
biologists. The potential for each special-status species to,occur in the Study Area was then,
evaluated accordingto the following criteria:
• No Potential. Habitat on and adjacent to the site is clearly unsuitable for the
species requirements (foraging, breeding, cover, substrate, elevation, hydrology,
plant community, site history, disturbance regime). Species determined to have
no potential to be found on the site are not discussed in this report.
• Unlikely. Few of the habitat components meeting the species requirements are
present, and/or the majority of habitat on and adjacent to the site is unsuitable or
of very poor quality. The species is not likely to be found on the site.
• Moderate Potential. Some of the habitat components meeting the species
requirements are present, and/or only some of the habitat on or adjacent to the
site is unsuitable. The species has a.moderate probability of being found on the
site.
• High Potential. All of the habitat components meeting the species requirements
are present and/or most of the habitat on or adjacent to the site is highly suitable.
The species has a high probability of being found on the site.
• Present. Species is observed on the site or has been recorded (i.e., CNDDB,
other reports) on the site recently.
The site assessment is intended to identify the presence or absence of suitable habitat for each
special-status species known to occur in the vicinity to determine its potential to occur in the
Study Area. The site visit does not constitute a protocol-level survey and is,not intended to
determine the actual presence or absence of a species; however, if a special-status species
was observed during the site visit, its presence was recorded and is discussed below. In cases
where little information is. known about species occurrences andhabitat requirements, the
species evaluation was based on best professional judgment of WRA biologists with experience
working with the species and habitats. For some species; a site assessment visit at the level
conducted for this report may not be sufficient to determine presence or absence of a species to
the specifications of-regulatory agencies. In these cases, a species may be assumed to be
present or further protocol-level special-status species surveys may be necessary.
2.3 Town of Los.Altos Hills Tree.Protection Ordinance
During the site assessment, the presence of trees potentially subject to the Town,of Los Altos
Tree Protection Ordinance was noted and is discussed below.
5
i
3.0 RESULTS.
The Study Area runs along approximately'400 feet of Page Mill,Road and includes a portion of
Matadero Creek, between Berry Hill Court and Arastradero Road, approximately:one-quarter of
a mile southwest of 1-280 in the Town of Los Altos Hills, Santa Clara County. The Study Area
consists of disturbed roadside areas and the riparian corridor along Matadero Creek set within a
residential community. Biological communities identified in the Study Area are shown on Figure
2, Appendix A. Appendix B lists the plant and wildlife species observed in the Study Area
during the site assessment. Photographs of the Study Area are included as Appendix D. The
following sections discuss the results of the site assessment.
3.1 Biological Communities
Biological communities observed in the Study Area are summarized in Table 1 ;and shown on ,
Figure 2, Appendix A. Non-sensitive biological communities in the Study Area include
developed, land and areas of'disturbed vegetation and/or landscaping. Sensitive biological •7
communities in the Study Area include perennial wetland, Matadero Creek, and Mixed Riparian , •
Woodland. These communities are described in more detail below. •
•
Table 1. Summary of Biological Communities in the Study Area.l
Community Type Acres / Linear Feet
Developed Land 0.22,acre
Disturbed/Landscaped 0.17 acre
Perennial Wetlands 0.03 lacre
Matadero Creek 333 linear feet
Mixed Riparian Woodland 0.54;acre
3.1.1 Non-Sensitive Biological Communities
DevelopedLand
The Study Area is set within a developed residential area along a two-lane, paved road.
Developed land within the Study Area is limited to Page. Mill Road which occupies I--
approximately 0.22 acres of the Study Area.
Disturbed/Landscaped
•
Approximately 0.17 acre of disturbed and/or landscaped areas were observed in the Study Area
along the southeast side of Page Mill Road. These areas are regularly maintained through
mowing and similar activities and are dominated by non-native and invasive plant species such I I
as ripgut brome (Bromus diandrus), wild oat (Avena sp.), Italian thistle (Carduus
pycnocephalus), and bull thistle (Cirsium vulgare). Many of the species foynd within the
disturbed'and/or landscaped portions of the Study Area are listed as having "moderate" to "high"
potential for invasiveness by the California Invasive Plant Council (Cal-IPC 2014). ' Disturbed •
and/or landscaped portions of the Study Area lacked substantial Itree cover, and the herbaceous
vegetation had been mowed or otherwise maintained at three to four inches tall.
•
•
6
•
3.1.2 Sensitive Biological Communities
Perennial Wetlands
Approximately 0.03 acre of perennial freshwater wetlands occur in vegetated areas of Matadero
Creek northwest and southeast of Page Mill Road. These wetlands are dominated by cattail
(Typha sp.) upstream (southeast) of Page Mill Road and ;by watercress (Nasturtium officinale)
and creeping bentgrass (Agrostis aff. gigantea) downstream (northwest) of Page Mill Road. The
perennial wetlands in the Study Area fit the description of Holland's coastal and valley
freshwater marsh (1986) and contain elements'of Sawyer's Typha sp. Alliance (cattail marshes)
and Agrostis gigantea Semi-Natural Herbaceous Stands (bent grass meadows) (Sawyer et al.
2009).
Perennial wetlands present in the Study Area meet the Corps definition of wetlands and are
subject to Corps jurisdiction as Waters of the U.S. under Section 404 of the CWA. Perennial
wetlands within the Study Area are also subject to jurisdiction by the RWQCB under Section
401 of the CWA. Because these wetlands occur within the streambed of Matadero Creek, they
are also subject to jurisdiction by the CDFW under Section 1600 of the CFGC. Perennial
wetlands are discussed in more detail in the wetland delineation report prepared by WRA (WRA
2014).
Matadero Creek
An approximately 333-foot-long stretch of Matadero Creek (approximately 0.04 acre, excluding
areas mapped as in-stream perennial wetlands) occurs within the Study Area. Matadero Creek
is a perennial, USGS blue-line stream and was flowing during the site visit conducted for this
assessment. The creek was mapped based on the location of the Ordinary High Water Mark
(OHWM), as evidenced by scouring and sediment/drift deposits along the streambed. The
creek is daylighted within the Study Area. Upstream (southeast) of Page Mill Road, the creek
has a relatively shallow gradient and contains a large area of cattail wetland adjacent to the
road. Downstream (northwest) of Page Mill Road, the creek has a steeper gradient and is
covered by a dense riparian canopy dominated by arroyo willow (Salix lasiolepis) and Northern
Californian black walnut (Juglans hindsii). The creek is armored by concrete sack walls within
the immediate vicinity of Page Mill Road. Downstream (northwest) of Page Mill Road, where
the concrete armoring ends, a, nick-point has developed, resulting in a steeply incised channel
with substantial erosion, undercutting, and bank slumping. Non-vegetated biological
communities, including perennial creeks, are not described by Holland (1986) or Sawyer et al.
(2009).
Mixed Riparian Woodland
Mixed riparian woodlands occur within or adjacent to waterways that are typically dominated by
deciduous trees. In the Study Area, approximately 0.54 acre of mixed riparian woodland occurs
along Matadero Creek up- and downstream of Page Mill Road. Dominant tree species include
arroyo willow and Northern California.black walnut; valley oak (Quercus lobata) and coast live
{ oak (Quercus agrifolia) are also present at lower,density. Downstream (northwest) of Page Mill
Road, the riparian canopy cover density is generally greater than.80 percent. The understory is
dominated by non-native annual grasses and other native and non-native species such as
fringed willowherb (Epilobium ciliatum), Himalayan blackberry (Rubus armeniacus), California
blackberry (Rubus ursinus), upright snowberrym horicar os albus var. laevi atus
ri) pg (S , and
p p g )
poison'oak '(Toxicodendron diversilobum). Many of the species found within the riparian
woodland are listed as having "moderate" to "high" potential for invasiveness by the Cal-IPC
(2014). The understory also contained a large number of naturalized horticultural species.
Upstream (southeast) of Page Mill Road, the riparian canopy is less dense and is dominated by
a similar suite of tree species, but with relatively higher cover of valley oak and,coast live oak.,
The understory upstream of Page Mill Road was dominated by,non-native annual grasses and
other weedy vegetation that was mowed or otherwise maintained at 3 to 4 inches in height.
Mixed riparian woodland within the Study Area can be classified'las Central Coast Arroyo Willow
Riparian Forest with elements of Central Coast Live Oak Riparian Forest (Holland 1986). The
mixed riparian woodland fits the description of Sawyer's Salix lasiolepis Shrubland Alliance
(arroyo willow thickets) (Sawyer et al. 2009).
3.2 Special-Status Species
3.2.1 Plants
Forty seven special-status plant species have been documented from within the vicinity of the r-
Study Area. Many of these species occur in habitats that are I not present in the Study Area,
such as coastal habitats, broadleaved or coniferous upland forests, chaparral, valley and foothill
grasslands, vernal pools, or serpentine soils. Special-status species that occur in habitats not
present in the Study Area were determined to have no potential,to occur in the Study Area and
are not discussed further. For special-status species'known to occur in riparian woodland (e.g.,
western leatherwood, Dirca 'occidentalis, CNPS 16.2 or Loma Prieta hoita, Hoita strobilina, r-
CNPS 16.1) or perennial wetlands (e.g., Hoover's button-celery, Eryngium aristulatum var.
hooveri, CNPS 1 B.1, alkali milk-vetch, Astragalus tener var. tener, CNPS 1 B.2, or legenere,
Legenere limosa, CNPS 1 B.1), the Study Area may contain elements of suitable habitat.
However, no special-status plant species were identified within the Study Area during the site
visit (with.the exception of Northern California black walnut, see explanation below), and it was
determined that the fragmented, disturbed nature of habitat within the Study Area, including the
high cover of non-native species, greatly reduces the potential for these species to occur there.
As such, it was determined that no special-status plant species are likely to occur within the
Study Area and no further surveys are recommended.
Northern California black walnut has 'a California Rare Plant Rank of 113.1 ! (CNPS 2014)
indicating that it is rare, threatened, or endangered in California and elsewhere.' However, this
ranking is intended for those individuals found within naturally occurring stands,and within the
natural range of the species. Stands of this species from areas that previously contained walnut
orchards or naturalized individuals that occur as a result of dispersal by wildlife or humans, as
well as planted landscape specimens, are not regarded as a natural community or as special-
status plants. Northern California black walnut individuals observed during the site visit are not
within any known natural community, according to the CNPS (2014), and' thus are not
considered to be special-status. As a native tree, Northern California black walnut grows only in
central California, being limited to a few isolated stands very much.restricted in area and in
every case present near old Native American village sites or camping grounds (Jepson 1923, _
CNPS 2014). The Juglans hindsii and Hybrids Special and Semi-Natural Woodland Stands
(Hind's walnut and related stands) identified by Sawyer et al. ;(2009) occurs in native groves
near the town of Walnut Creek in Contra Costa County and on the banks of the Sacramento
River in Sacramento County, and in non-native groves near Napa County. Although the walnut
trees within the Study Area are not special-status, they are protected as riparian woodland by -
the CDFW and may also be protected by the City's tree protection ordinance.
8
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i '.
3.2.2 Wildlife
Based on the database review and the experience of the consulting biologist, it was determined
that 61 special-status wildlife species either have been documented or have the potential to
occur within the vicinity of the Study Area (Appendix C). Of these species, 51 were determined
to occur in habitats not present in the Study Area such as tidal wetlands, shoreline areas,
coniferous forest, open grassland, or in habitats that may be present in the Study Area but are
unsuitable for the species or are of very poor quality. These species were determined to have
limited to no potential to occur within the Study Area and are not discussed further. The nest
structure of one special-status wildlife species, dusky footed woodrat (Neotoma fuscipes
annectens) was observed within the Study Area during the site assessment. Additionally, eight
special-status wildlife species..were determined to have a moderate to high potential to occur
within the Study Area. Species that were observed within the Study Area or determined to have
the potential to occur there are discussed in detail below. One federal listed species for which
the Study Area provides ostensibly suitable habitat but is unlikely to occur there is also
discussed.
Observed Species
San Francisco dusky-footed woodrat (Neotoma fuscipes annectens). CDFW Species of
Special Concern. Present. This subspecies of the dusky-footed woodrat occurs in the Coast
Ranges between San Francisco Bay and the Salinas River (Matocq 2003).' Occupied habitats
are variable and include forest, woodland, riparian areas, and chaparral. Woodrats feed on
woody plants, but will also consume fungi, grasses, flowers, and acorns. Foraging occurs on
the ground and in bushes and trees. This species constructs robust structures/houses made of
sticks and twigs in areas with 'moderate cover and a well-developed understory containing
woody debris. Breeding takes place from December to September. Individuals are mostly
nocturnal and are active year round.
Riparian woodland within the Study Area provides suitable habitat for the San Francisco dusky-
footed woodrat, and one woodrat nest structure was observed within the Study Area during the
site assessment. Woodrats are presumably present in the Study Area year-round.
Species with the Potential to Occur
White-tailed kite (Elanus leucurus). CDFW Fully Protected Species. Moderate Potential.
The white-tailed kite is resident in open to semi-open habitats throughout the lower elevations of
California, including grasslands, savannahs, woodlands, agricultural areas and wetlands.
Vegetative structure and prey availability seem to be more important habitat elements than
associations with specific plants or vegetative communities (Dunk 1995). Nests are constructed
mostly of twigs and placed in trees, often at habitat edges. Nest trees are highly variable in
size, structure, and immediate surroundings, ranging from shrubs to trees greater than 150 feet
tall (Dunk 1995). This,species preys upon a variety of small mammals, as well as other
vertebrates and invertebrates.
White-tailed kites may nest within or adjacent to the Study Area, most likely in large riparian
trees; however, use of other trees, including those directly adjacent to development, is also
possible.
Allen's hummingbird(Selasphorus sasin). USFWS Bird of Conservation Concern. High
Potential.' Allen's hummingbird, common in many portions of its range, is a summer resident
j 9
along the majority of California's coast and a year-round resident in portions of coastal southern
California and the Channel Islands. Breeding occurs in association with the coastal fog belt,
and typical habitats used include coastal scrub, riparian, woodland and forest edges, and
eucalyptus and cypress groves(Mitchell 2000). The species feeds on flower nectar and forages
for insects and spiders. -
Riparian woodland within the Study Area provides suitable habitat for this species, including for
nesting.
Nuttall's woodpecker (Picoides nuttallii). USFWS Bird of Conservation Concern. High
Potential. Nuttall's woodpecker, common in much of its range, is a year-round resident
throughout most of California, west of the Sierra Nevada Range: Typical habitat is oak or mixed
woodland, including riparian areas (Lowther 2000). Nesting occurs in tree cavities, principally
those of oaks and larger riparian trees. This species forages on a variety of arboreal
invertebrates. -
Nuttall's woodpeckers occur regularly in and near developed areas of the San;Francisco Bay
area where suitable habitat is present. This species may occur;within the Study,Area's riparian
woodland and adjacent trees.
Oak titmouse (Baeolophus inornatus). USFWS Bird of Conservation Concern. High
Potential. This relatively common species is resident throughout much of California including ,
most of the coastal slope, the Central Valley and the western Sierra Nevada foothills. Primary
habitat is woodland dominated by oaks; local populations have adapted to woodlands of pines
and/or junipers in some areas (Cicero 2000). The species nests in tree cavities, usually natural
cavities or those excavated by woodpeckers; birds may partially excavate their own cavities.
The species forages for seeds and arboreal invertebrates.
As with Nuttall's woodpecker, this species is relatively common throughout much of the San
Francisco Bay area and may occur among riparian trees and oaks within the Study Area.
(Brewster's) Yellow warbler (Setophaga petechia brewsteri). CDFW Species of Special
Concern, USFWS Bird of Conservation Concern. Moderate Potential. The yellow warbler
is a neotropical migrant bird that is widespread in North America. The Brewster's (brewsteri)
subspecies is a summer resident and represents the vast majority of yellow warblers that breed
in California_. In California, west of the Central Valley, typical yellow warbler breeding habitat
consists of dense riparian vegetation along watercourses, including wet meadows, with willow
growth being particularly favored (Shuford and Gardali 2008). Insects compose most of the
diet.
Riparian woodland within the Study Area provides suitable yellow warbler nesting habitat.
San Francisco (saltmarsh) common yellowthroat (Geothlypis trichas sinuosa). CDFW
Species of Special Concern, USFWS Bird of Conservation Concern. Moderate Potential.
This subspecies of the common yellowthroat is endemic to the greater San Francisco Bay area
and is present year-round in and near marshes (salt, brackish, and fresh), riparian thickets, and
coastal swales. Yellowthroats require thick, continuous vegetative cover, preferring wetland
vegetation and adjacent transitional areas (Shuford and Gardali;2008). Nesting occurs in dense
vegetation, usually on or near the ground. Arthropods (insects, spiders) compose most of the
diet.
10
i '
w; Riparian woodland andemergent marsh vegetation (cattails) within the Study Area provide
suitable habitat for this species, including for nesting.
Western pond turtle (Actinemys marmorata). CDFW Species of Special Concern.
Moderate Potential. The western pond turtle is the only native freshwater turtle in California,
occurring in suitable aquatic habitats throughout California, west of the Sierra-Cascade crest
and Transverse Ranges.(Jennings and Hayes 1994). Occupied habitats are both annual and
- perennial water bodies and include coastal lagoons, lakes, ponds, marshes, rivers, and streams
from sea level to 5,500 feet in elevation. Manmade habitats such as stock and wastewater
storage ponds, percolation ponds, canals, and reservoirs are also used. This species requires
low-flowing or stagnant freshwater with basking structures, including rocks, logs, vegetation
,mats, mud banks, and sand. Whereas pond turtles require suitable.aquatic habitat for most of
the year, features that become seasonally unsuitable are also used. To escape periods of high
water flow, high salinity, or prolonged dry conditions, pond turtles may move upstream and/or
take refuge in vegetated, upland habitat for up to four months (Rathbun et al. 2002). Nesting
occurs from late April through July; nesting habitat consists of open, dry, unshaded upland
areas with friable soils near suitable aquatic habitat, where females excavate nests and lay
eggs (Rathbun et al. 1992).
Within the Study Area, Matadero Creek provides suitable aquatic habitat for western pond turtle,
provided that it is inundated. Thus, turtles may occur only seasonally and/or dependent upon
annual precipitation levels, rendering the habitat of limited quality overall. Nesting within the
Study Area is unlikely due to the highly-incised and steep banks along the creek.
California red-legged frog (Rana draytoni►). Federal Threatened, CDFW Species of Special
Concern. Moderate Potential. The California red-legged frog (CRLF) is the only native "pond
frog" found throughout much of California and was listed as Threatened by the USFWS in 1996.
Suitable CRLF breeding habitat is characterized by deep (approximately two feet), still or slow-
moving water associated with emergent marsh and/or overhanging riparian vegetation (USFWS
2010). Such habitats must hold, water for a minimum of 20 weeks, and include ponds
(ephemeral and perennial), streams/creeks (ephemeral and perennial), seasonal wetlands,
springs, seeps, man-made features(e.g. stock ponds, roadside ditches), marshes, and lagoons.
Dependent upon local conditions, CRLF may complete its entire life cycle in a particular habitat
patch (e.g., a perennial pond suitable for all life stages), or utilize multiple habitat types. In
aquatic habitats that dry down seasonally, CRLF often undergo aestivation (a period of
inactivity) during the dry months, over-summering in small mammal burrows, moist leaf litter,
incised stream channels, or large cracks in the bottom of dried ponds (Jennings and Hayes
1995). Adult and sub-adult (newly metamorphosed) CRLF may disperse from breeding habitats
to nearby riparian and/or aestivation habitats .in the summer. Conversely, during the rainy
season, CRLF may disperse .from estivation sites to suitable breeding habitat. During such
dispersals, frogs can travel over one mile through upland areas (Bulger et al. 2003); such
upland dispersal habitats are variable and typically include riparian corridors, grasslands, and
oak savannas.
The majority of creeks in developed areas of the San Francisco Bay Area do not typically
provide suitable breeding habitat for the CRLF due to unsuitable hydrology, the presence of
aquatic and/or terrestrial predators, and/or other factors. However, CRLF breeding has recently
been documented approximately 1.2 miles north of the Study Area within Deer Creek, a
tributary to Matadero Creek (CDFW 2014). . There are also additional recent occurrences
(including breeding) within five miles to the west (TRA Environmental Sciences 2011 [no
11
L.
additional;documentation provided], CDFW 2014). Within the Study Area, Matadero Creek is
narrow and highly incised, and therefore the stream current during typical winters is expected to
be strong, with limited to non-existent still, deeper water suitable for CRLF breeding. However,
given the occurrences in the general vicinity, and because riparian corridors are often used by
dispersing/migrating CRLF, this species has moderate potential to occur in the Study Area. The
potential for CRLF occurrence is during breeding migrations and dispersal events, particularly
during the rainy season.
Federal-Listed species unlikely to occur
Steelhead (Oncorhynchus mykiss irideus) - Central California Coast PPS. Federal
Threatened. Unlikely. ' The steelhead is essentially the native rainbow trout of coastal
California that spends part of its life cycle in freshwater and part in the ocean. The Central
California Coast DPS includes all naturally-spawned populations (and their progeny) in
California streams from the Russian River to Aptos Creek, and the drainages of:San Francisco
and San Pablo Bays eastward to the Napa River (inclusive); thelSacramento-San Joaquin River
Basin is excluded.
Steelhead typically migrate to marine waters after spending two years in freshwater, though
they may,stay there for up to seven years. Individuals then reside in marine waters for two or
three years prior to returning to their natal stream to spawn as 4-or 5-year-olds. Steelhead
adults typically spawn between December and June. In California, females typically spawn two
times before they die. Successful reproduction requires abundant riffle areas (shallows with
gravel or cobble substrate) for spawning, and deeper pools with sufficient riparian cover for
rearing. High-quality spawning habitat occurs in perennial streams with cool: to cold water
temperatures, high dissolved oxygen levels, and fast-flowing water.
A technical report by Leidy (2005) summarizes known distribution information for steelhead in
Santa Clara County streams. Although Matadero Creek is believed to have historically
supported a steelhead population, the creek was surveyed for steelhead in 1981 and 1997 and
none were found in either year. Additionally, when operated, the tidal gates at the mouth of the
creek can prohibit passage by anadromous fishes. For these reasons, Leidy (2005) concludes
that steelhead is currently absent from Matadero Creek.
3.3 Protected Trees
The Study Area contains several heritage oak trees which are protected by the City of Los Altos
Hills. All trees located within the Town of Los Altos Hills public right of way are likely protected
under the Los Altos Hills Tree Protection Ordinance.
•
12 •
• ;
I I
3.4 Hydrology
The dominant source of hydrology in the Study Area is Matadero Creek, a perennial creek that
flows south to north, crossing below Page Mill Road and continuing adjacent to the two-lane
roadway. Within the Study Area, Matadero Creek becomes heavily incised starting at a nick-
point located downstream (northwest) from where the creek crosses under Page Mill Road. The
erosion originating at the nick-point has undercut the banks within the Study Area and caused
them to slump into the creekbed.
3.5 Soils
The Soil Survey of Santa Clara County (1991) indicates,that the.Study Area is underlain by two
soil series, Cropley clay, 2 to 9 percent slopes and Zeppelin-Mccoy complex, 15 to 30 percent
slopes. Cropley clay consists of well drained alluvium derived from calcerous shale or residuum
derived from calcerous shale. The Zeppelin-Mccoy complex is composed of approximately 45
percent Zeppelin and similar soils, 40 percent Mccoy and similar soils, and 15 percent minor
components. Zeppelin and Mccoy soils are residuum derived from weathered sandstone and
are well drained.
4.0 SUMMARY AND RECOMMENDATIONS
4.1 Biological Communities
Three sensitive biological communities were identified in the Study Area: perennial wetlands,
Matadero Creek, and mixed riparian woodland. These communities occur within or along
Matadero Creek, northwest and southeast of Page Mill Road. A jurisdictional .wetland
delineation was conducted during the site visit, the details of which are outlined in a separate
wetland delineation report which will. be submitted to the Corps for verification (WRA 2014).
The proposed project has the potential to impact jurisdictional waters and will likely require
permits from the Corps (Section 404 Nationwide Permit), the RWQCB (Section. 401
Certification), and the CDFW (Section 1602 Streambed Alteration Agreement). The OHWM of
Matadero Creek represents the landward limit of Corps jurisdiction within the Study Area, and
project work below the OHWM of Matadero Creek will require a permit from,the Corps. Top of
bank or the outer edge of the riparian canopy, whichever extends further, represents the limit of
RWQCB and CDFW jurisdiction within the Study Area. Work within top of bank or within the
riparian.canopy will require permits from the RWQCB and CDFW for any impacts to these
habitats.
Depending on the extent of impacts to the stream or wetland habitats, permit conditions may
require compensatory mitigation for any impacts to wetlands, non-wetland waters, and/or
riparian habitat. In addition, mitigation may be required for impacts to trees protected under the
City tree ordinance.
To reduce potential temporary impacts to sensitive biological communities in the Study Area,
best management practices should be employed to reduce impacts associated with any
potential repair work. Work should be conducted during the dry season, if possible. 'Vegetation
removal should be minimized to the greatest extent feasible. .Areas in which vegetation is
1 removed should be replanted or seeded with native plants appropriate for the site. Erosion
Control measures, such as the use of silt fencing or straw wattles, should be implemented in
areas of ground disturbance or vegetation removal.
13
4.2 Special-Status Plant Species
The Study Area lacks the potential to ;support any of-the 47 special-status; plant species
documented from the vicinity of the Study Area. Most of these species were determined to have
little to no potential-to occur because they are found in habitats which are not.present in the
Study Area or 'are associated with habitats that occur in the Study Area, but the highly
fragmented and disturbed nature of the habitats in the Study Area greatly reduces their potential
to occur. Although Northern California black walnut is considered a special-status plant when it
occurs in natural stands, the specimens observed within the Study Area do not'occur within a
natural stand and are not considered special-status. No other special-status plant species were
observed in the Study Area and no additional actions concerning special-status plant species
are recommended.
4.3 Special-Status Wildlife Species
One special-status wildlife species was determined to be present within the Study Area and
seven additional special-status wildlife species were determined to have a moderate to high
potential to occur within the Study Area. Only one of these species, CRLF, is listed under the
federal Endangered Species Act or the California Endangered Species Act. Recommendations
for special-status wildlife species are discussed below. ,
Nesting Birds
Six of the special-status wildlife species that were determined. to have the potential to occur
within the Study Area are birds. In addition to these species, a wide variety of other bird species
with baseline legal protection under the federal Migratory Bird Treaty Act and the'California Fish.
and Game Code have the potential to nest within the Study Area. Substrates within the Study
Area thatmay be used for nesting are highly variable and include trees, shrubbery, emergent
wetland vegetation, and the bridge on Page Mill Road.
To avoid adverse impacts to nesting birds due to project activities within the Study Area, the
following measures are recommended:
• To the fullest extent feasible, initial ground disturbance and/or vegetation removal
f should occur during the non-breeding.season (September 1 to January 31). Pre-
construction nesting bird surveys are typically not required during this period.
(Note, however, that some birds have the potential to nest year-round; if nests
are observed during project activities, a biologist should be consulted, and the
nest avoided as described below.)
• If initial ground disturbance and/or vegetation removal occurs during the breeding
season (February 1 through August 31), a qualified biologist should conduct a
breeding bird survey no more than 14 days prior toground disturbance to ,!_
determine whether any birds are nesting within or adjacent to project; impact
areas.
• If active nests are found within project impact areas o r close enough to these
areas to affect breeding success, the biologist should establish an appropriate
work exclusion zone around each nest. Exclusion zone sizes vary dependent
upon bird species, nest location, and existing visual buffers and ambient sound
14
ii
levels. A buffer radius may be as small as 25 feet for common species and 100
feet or more for special-status species and raptors. Once all young have
become independent of the nest (or the nest otherwise becomes inactive), work
may recommence within the exclusion zone.
• If initial ground disturbance is delayed or there is a break in project activities of
greater than 14 days within the bird nesting season, then a follow-up nesting bird
survey should be performed to ensure no nests have been established in the
,
interim period.
San Francisco Dusky-Footed Woodrat
To avoid adverse impacts to woodrats due to project activities within the Study Area, the
following measures are recommended:
• Prior to vegetation removal and/or ground disturbance within the Study Area, a
pre-construction survey for woodrat structures should be conducted by a
qualified biologist. Anywoodrat structures found during thesurvey should be
flagged and subsequently avoided to the fullest extent feasible.
• If avoidance is not possible, then structures to be impacted should be dismantled
by hand under the supervision of a qualified biologist.
• If woodrat young are encountered during the dismantling process, the material
should be placed back on the house, and a work exclusion buffer of at least 10
feet should be implemented around the structure. The structure should remain
undisturbed for at least two weeks to allow the young to mature and leave the
nest of their own accord. After the avoidance period, the nest dismantling
process may,begin again. Nest material should be moved to adjacent vegetated
areas that will not be disturbed.
Western Pond Turtle
To avoid adverse impacts to western pond turtle due to project activities within the Study Area,
the following measures are recommended:
• A pre-construction survey for pond turtles should be conducted by a qualified
biologist within 48 hours of the initiation of work activities in or near the
streambed.
• If turtles are present, they should be captured and relocated to suitable habitat
outside of the Study Area by a qualified biologist. The biologist would require
specific approval from the CDFW to conduct such activities.
California Red-Legged Frog
Aquatic habitat within the Study Area appears unlikely to support CRLF breeding. However,
CRLF may occur as dispersing juveniles or adults during migration or breeding season.
Therefore the following recommendations are suggested to reduce the potential for impacting
CRLF during project construction activities.
15
The following CRLF avoidance and minimization measures are suggested to avoid impacts to
this species:
• Pre-construction surveys should be performed within 481hours of the initiation of
work activities, including exclusion fence installation (if required, see below) and
initial work activities.
• Biological sensitivity training should be conducted for project construction
personnel focused on CRLF identification and the project-specific avoidance and
minimization measures to be implemented.
• Installation of a wildlife exclusion fence (or sections of fencing) should be done to
to prevent CRLF (dispersing or otherwise) from entering project work areas
during construction. Such fencing should be maintained throughout,project
activities.
• All pits' or trenches should be covered at the end of each work day, or wildlife
escape ramps should be installed.
• Daily inspections of the work area should be conducted by trained project
personnel to ensure no CRLF are present.
4.4 Protected Trees
If removal of protected trees is proposed, or trenching or other;ground disturbing activities will
occur within 10 feet of the trunk of a protected tree, tree removal permits may be required
pursuant to the Town of Los Altos Hills Tree Protection Ordinance. In some caes, removal of
protected trees may require tree replacement according to the guidelines in the ordinance.
Trees forming a riparian canopy over Matadero Creek area are also subject to jurisdiction by the
RWQCB and the CDFW. Both agencies may require compensatory mitigation for the removal
of riparian trees.
16 _
�,�� REFERENCES
Bulger, J.B., S.J. Norman, and R.B. Seymour. 2003. Terrestrial Activity and Conservation of
Adult California Red-legged Frogs (Rana aurora draytonii) in Coastal Forests and
Grasslands. Biological Conservation.110 (2003) 85-95.
[Cal-IPC] California Invasive Plant Council. 2014. Invasive Plant Inventory. Accessed December
2014 online: http://www.cal-ipc.org/ip/inventory/.
[CDFW] California Department of Fish and Wildlife. 2014. California Natural Diversity
Database, Commercial Edition. CDFW Wildlife and Habitat Data Analysis Branch,
Sacramento, CA. Accessed: October 2014.
California Department of Fish and Game (CDFG). 2009. List of California Vegetation Alliances.
Biogeographic Data Branch. Vegetation Classification and Mapping Program,
Sacramento, CA
California Department of Fish and Game (CDFG). 2007. List of California Vegetation Alliances.
Biogeographic Data Branch. Vegetation Classification and Mapping Program,
Sacramento, CA.
California Department of Fish and Game (CDFG). 2003. List of California Terrestrial Natural
Communities 'Recognized by the California Natural Diversity Database. Wildlife and
Habitat Data Analysis Branch. Vegetation Classification and Mapping Program,
Sacramento, CA.
Cicero, C. 2000. Oak Titmouse (Baeolophus inornatus), The Birds of North America Online (A.
Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North
America Online: http://bna.birds.cornell.edu/bna/species/485a
[CNPS] California Native Plant Society. 2014. Rare and Endangered Plant Inventory.
Sacramento, California. Online at: http://www.cnps.org%inventory. Accessed October
2014.
Dunk, J.R. 1995. White-tailed Kite (Elanus leucurus), The Birds of North America Online (A.
Poole, 'Ed.).. Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North
America Online: http://bna.birds.cornell.edu/bna/species/178
Holland, R.F. 1986. Preliminary Description of the Terrestrial Natural Communities of California.
California Department of Fish and Game, Sacramento, CA
Jennings, M.R. and M.P. Hayes. 1994. Amphibian and Reptile Species of Special Concern in
California. Final report submitted to the California Department of Fish and Game, Inland
Fisheries Division, Rancho Cordova, California. Contract No. 8023. November.
Jepson, W.L. 1923. Trees of California. University of California, Berkeley, CA. 109 pp.
Leidy, R.A., G.S. Becker, B.N. Harvey. 2005. Historical distribution and current status of
steelhead/rainbow trout (Oncorhynchus mykiss) in streams of the San Francisco
Estuary, California. Center for Ecosystem Management and Restoration, Oakland,
California.
17
Los Altos Hills Municipal Code. Title 12. Chapter 2. Accessed online December 2014:
http://qcode.us/codes/losaltoshills/.
Lowther, P.E. 2000. Nuttall's Woodpecker (Picoides nuttallii), The Birds of North America Online
(A: Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the ;Birds of North
America Online:http://bna.birds.cornell.edu/bna/species/555
Matocq, M. 2003. Dusky-footed Woodrats (Neotoma fuscipes) at Hastings: A Research
Tradition. Hastings Natural History Reservation. Available online:
http://www.hastingsreServe.org/Woodrats/DFwoodrats.htrn1
Mitchell, Donald E. 2000. Allen's Hummingbird.(Selasphorus sasin), The.Birds ofNorth America
Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of
North America Online: http://bna.birds.cornell.edu/bna/species/501
NatureServe. 2014. NatureServe Conservation Status. Available online at:
http://www.natureserve.org/explorer/ranking.
Rathbun, G. B., N. J. Scott, Jr., and T. G. Murphey. 2002. Terrestrial habitat use by Pacific pond
turtles in a Mediterranean climate. The Southwestern Naturalist 47.: 225-235.
Rathbun, G. B., N. Seipel and D. C. Holland. 1992. Nesting behavior and movements of western
pond turtles, Clemmys marmorata. The Southwestern Naturalist 37: 319-324.
Sawyer, J.O., T. Keeler-Wolf, and J.M. Evens. 2009. A Manual of California Vegetation, 2nd
Edition. California Native Plant Society in collaboration with California Department of
Fish and Game. Sacramento, CA.
Shuford, W.D. and Gardali, T., eds. '2008. California Bird Species of Special Concern: A ranked
assessment .of species, subspecies, and distinct populations of birds of immediate i
conservation concern in California. Studies of Western Birds 1. Western Field
Ornithologists, Camarillo, California, and California. Department of Fish and Game,
Sacramento. '
TRA Environmental.Sciences, Inc. 2011. 1260 Westridge Drive Shorenstein Subdivision and
Planned Unit Development Project, Portola Valley,. CA: Initial Study and Mitigated
Negative Declaration. Prepared for Town of Portola Walley by TRA ;Environmental
Sciences, Menlo Park, CA. 128 pp.
U.S. Department of Agriculture (USDA), Soil Conservation Service. 1991. Soil Survey of Santa
Clara County, California. In cooperation with the University of California Agricultural
Experiment Station.
U.S. Geologic Survey (USGS). 2012. Palo Alto 7.5-minute Quadrangle Map. '
[USFWS] United States Fish and Wildlife Service. 2014. Species List. Sacramento Fish and
Wildlife Service. Online at:
http://www.fws.gov/sacramento/es_species/Lists/es_species_lists-form.cfm. Accessed
October 2014.
18
[USFWS]. 2010. Endangered and Threatened Wildlife and Plants; Revised Designation of
Critical Habitat for the California Red-Legged Frog; Final Rule. Federal Register 75(51):
12816-12959. March 17.
WRA. 2014. U.S. Army Corps of Engineers Section 404 Jurisdictional Delineation of the
Matadero Creek Study Area, Los Altos Hills, Santa Clara County, Prepared for the Town
of Los Altos Hills. December 2014.
1
19
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Appendix A. Figures
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t
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t - y•r '•• ENVIRONMENTAL CONSULTANTS
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' Matadero Creek
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41 Santa Clara County,
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A
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Non-Sensitive Communities f'> . •- '' ir;
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Appendix A, Figure 1 . Project Location Map N w ra
i 03
w.....60_ E
I ENVIRONMENTAL CONSULTANTS
S
Matadero Creek 0 0.75 1.5
14
Santa Clara Count California MapMap ByDaaNumwaltvember
County, Miles Base ESRISourceSWorld Topo
Path L:\Acad 2000 Files\24000\24070\GIS\ArcMap\Figure 1 Loc Map mxd
This page intentionally blank.
Appendix B. Plant and Wildlife Species Observed in the Study Area
Appendix B. Plant and Wildlife Species Observed in the Study Area
SCIENTIFIC NAME COMMON NAME FAMILY ORIGIN
Plants
Aesculus californica California buckeye Sapindaceae native
Agrostis aff.gigantea creeping bentgrass Poaceae non-native
Artemisia douglasiana mugwort Asteraceae native
Avena sp. oat Poaceae non-native
Baccharis glutinosa marsh baccharis Asteraceae native
Baccharis pilularis coyote brush Asteraceae native
Bromus aff. carinatus California brome Poaceae native
Bromus diandrus ripgut brome Poaceae non-native
Carduus pycnocephalus Italian thistle Asteraceae non-native
Cirsium vulgare bull thistle Asteraceae non-native
Cornus sericea ssp.sericea redosier dogwood Cornaceae native
Cyperus eragrostis tall flatsedge Cyperaceae native
Epilobium ciliatum fringed willowherb Onagraceae native
Helenium puberulum rosilla Asteraceae native
Juglans hindsii Northern California black walnut Juglandaceae non-native*
Marah oregana coast manroot Cucurbitaceae native
Maytenus boaria mayten Celastraceae non-native
Melissa officinalis common balm Lamiaceae non-native
Nasturtium officinale watercress Brassicaceae native
Piptatherum miliaceum smilo grass Poaceae non-native
Platanus racemosa California sycamore Platanaceae native
Prunus sp. ornamental cherry Rosaceae non-native
Quercus lobata valley oak Fagaceae native
Rubus armeniacus Himalayan blackberry Rosaceae non-native
Rubus ursinus California blackberry Rosaceae native
Rumex pulcher fiddle dock Polygonaceae non-native
Salix lasiolepis arroyo willow Salicaceae native
Solanum americanum American black nightshade Solanaceae native
Symphoricarpos albus var.laevigatus upright snowberry Caprifoliaceae native
Torilis arvensis hedge parsley Apiaceae non-native
Toxicodendron diversilobum poison oak Anacardiaceae native
Typha sp. cattail Typhaceae native
Mammals
Odocoileus hemionus Mule deer Cervidae
Birds
Aphelocoma californica western scrub jay Corvidae
Baeolophus inornatus oak titmouse Paridae
Calypte anna Anna's hummingbird Trochilidae
Junco hyemalis dark-eyed junco Emberizidae
Corvus brachyrhynchos American crow Corvidae
Melanerpes formicivorus acorn woodpecker Picidae
Picoides nuttallii Nuttall's woodpecker Picidae
Sayornis nigricans black phoebe Tyrannidae
-
Poecile rufescens chestnut-backed chickadee Paridae
-
Melozone crissalis California towhee Emberizidae
Turdus migritorius American robin Turdidae
-
Zonotrichia atricapilla golden-crowned sparrow Emberizidae
*As a native tree Northern California black walnut grows only in central California,being limited to a few isolated stations very much restricted in area and
in every case present old Native American village sites or camping grounds(Jepson 1923,CNPS 2014).
Appendix C. Special-Status Wildlife Species
This page intentionally blank.
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
Mammals
pallid bat SSC, Habitat varied; occurs in deserts, Unlikely. The Study Area No further actions are
Antrozous pallidus WBWG grasslands, shrublands, woodlands, and does not contain rocky recommended.
High forests. Most common in open, forages outcrops or caves.
along river channels. Roost sites include
old buildings, rocky outcrops and caves
within sandstone outcroppings. Roosts
must protect bats from high temperatures.
Very sensitive to disturbance of roosting
sites.
Townsend's big- SC, SSC, Occurs in a wide variety of habitats from Unlikely. The Study Area No further actions are
eared bat WBWG deserts to mid-elevation mixed coniferous- does not contain caves or recommended.
Corynorhinus High deciduous forest. Females form maternity cave-like substrates.
townsendii colonies in buildings, caves and mines;
males roost singly or in small groups.
Foraging occurs in open forests, where
moths are gleaned from vegetation.
salt-marsh SSC Seldom observed; endemic to salt-marshes No Potential. The Study Area No further actions are
wandering shrew of the south arm of San Francisco Bay. contains no tidal wetland and recommended.
Sorex vagrans Typically in medium to high marsh where thus provides no habitat for
halicoetes abundant driftwood is scattered among this species.
pickleweed.
B- 1
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* POTENTIAL FOR
HABITAT OCCURRENCE RECOMMENDATIONS
salt marsh harvest FE, SE, Found only in the saline emergent wetlands No Potential. The Study Area No further actions are
mouse CFP, RP of the San Francisco Bay estuary and its contains no tidal wetland and recommended.
Reithrodontomys tributaries. Dense pickleweed is the thus provides no habitat for
raviventris primary habitat. Also requires higher- this species.
elevation areas for tidal flood escape.
Builds loosely organized nests within or
under cover; does not burrow.
San Francisco SSC Occurs in forest habitats of moderate Present. Riparian woodland Prior to ground disturbance
dusky-footed canopy, and moderate to dense within the Study Area and/or vegetation removal, a
woodrat understory. Also found in chaparral and provides suitable habitat for pre-construction survey should
Neotoma fuscipes riparian habitats. Builds and resides in this species, and one woodrat be conducted. Any woodrat
annectens robust structures made of sticks and twigs structure was observed there structures identified should be
that are placed on the ground or in the tree during the site visit. avoided, or dissembled by a
canopy. Feeds mainly on woody plants. qualified biologist if avoidance is
not feasible.
American badger SSC Occurs in drier open stages of most scrub, No Potential. Developed No further actions are
Taxidea taxus forest, and herbaceous habitats where areas surrounding the Study recommended.
friable soils and prey populations (primarily Area preclude the presence of
burrowing mammals) are present. this species.
Birds
Barrow's goldeneye SSC Winter visitor; does not nest in the vicinity Unlikely. Aquatic habitat No further actions are
Bucephala islandica of San Francisco Bay. Breeds in high within Matadero Creek is too recommended.
central and northern Sierra Nevada small in area to provide any
mountains. Wintering habitat is generally typical wintering habitat.
quiet, secluded waters.
B- 2
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
harlequin duck SSC Winter visitor; does not nest in the vicinity No Potential. Matadero No further actions are
Histrionicus of San Francisco Bay. Breeds in the Sierra Creek is far too restricted in recommended.
histrionicus Nevada along streams and rivers. area to provide any suitable
Wintering habitat is generally deep wintering habitat for this
expanses of coastal or estuarine water. species.
common loon SSC Winter visitor; does not nest in the vicinity No Potential. Matadero No further actions are
Gavia immer San Francisco Bay. Aquatic, generally Creek is far too restricted in recommended.
found in large, deep water bodies with area to provide any suitable
abundant fish. wintering habitat for this
species.
American white SSC Generally a winter visitor to the region No Potential. Matadero No further actions are
pelican (though present nearly year-round). Nests Creek is far too restricted in recommended.
Pelecanus colonially on large interior lakes; does not area to provide any suitable
erythrorhynchos nest in the vicinity of San Francisco Bay. wintering habitat for this
species.
California brown FD, SD, Generally a winter visitor to the region, No Potential. This species is No further actions are
pelican CFP though present nearly year-round. Nests restricted to marine and recommended.
Pelecanus colonially on offshore islands; nearest estuarine waters.
occidentalis rookeries are on the Channel Islands. San
californicus Francisco Bay provides important foraging
and loafing habitat.
golden eagle CFP Year-round resident in rolling foothill and Unlikely. The Study Area is No further actions are
Aquila chrysaetos mountain areas, sage-juniper flats, and small and surrounded by recommended.
desert. Cliff-walled canyons provide development. May
nesting habitat in most parts of range. occasionally fly over the area.
B- 3
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
ferruginous hawk BCC Winter visitor; does not nest in the vicinity No Potential. The Study Area No further actions are
Buteo regalis San Francisco Bay. Occurs in open is small and surrounded by recommended.
habitats, including grasslands, low foothills development and provides no
surrounding valleys, and agricultural areas. habitat for this species.
northern harrier SSC Resident and winter visitor. Found in open Unlikely. The Study Area is No further actions are
Circus cyaneus habitats such as marshes, grasslands and small and surrounded by recommended.
agricultural areas. Tends to nest near water development. May
in dense, tall vegetation. occasionally fly over the area.
white-tailed kite CFP Resident in a variety of coastal and valley Moderate Potential. A breeding bird survey should
Elanus leucurus lowlands, including grasslands, marshes, Although this species requires be conducted if ground
woodland and agricultural areas. Preys on open areas for foraging, disturbance and/or vegetation
small mammals and other small nesting may occur adjacent to removal occurs from February 1
vertebrates, and insects. Nests in trees and or even within developed to August 31; active nests
larger shrubs, often in relatively isolated areas. should be avoided.
stands.
bald eagle FD, SE, Generally a winter visitor; breeding in the Unlikely. The Study Area is No further actions are
Haliaeetus CFP vicinity of San Francisco Bay is very small and surrounded by recommended.
leucocephalus limited. Requires large bodies of water, or development, and provides no
free-flowing rivers with abundant fish typical habitat. May
adjacent snags or other perches. Nests in occasionally fly over the area.
large, old-growth, or dominant live tree with
open branchwork.
prairie falcon BCC Resident and winter visitor. Inhabits dry, No Potential. The Study Area No further actions are
Falco mexicanus open terrain. Breeding sites are located on is small and surrounded by recommended.
cliffs; forages widely. Prey upon a variety of development and provides no
vertebrates, mostly mammals and birds. habitat for this species.
B-4
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS .000
American peregrine FD, SD, Largely resident. Requires protected cliffs, Unlikely. The Study Area is No further actions are
falcon CFP ledges or manmade structures for nesting. small, developed and recommended.
Falco peregrinus Often associated with coasts, bays, provides no typical habitat for
anatum marshes and other open expanses of this species. May occasionally
water. Preys primarily upon waterbirds; fly over the area.
forages widely.
California black rail ST, BCC, Extremely secretive resident of open No Potential. The Study Area No further actions are
Laterallus CFP emergent marshes in the San Francisco contains no tidal or brackish recommended.
jamaicensis Bay estuary and portions of the Central wetland and provides no
coturniculus Valley. Occurs in salt, brackish and habitat for this species.
freshwater marshes. Nests in dense
stands of emergent vegetation. In the San
Francisco Bay estuary, generally rare south
of Marin County.
California clapper rail FE, SE, Resident in salt marshes of the San No Potential. The Study Area No further actions are
Rallus longirostris CFP Francisco Bay Estuary, with largest contains no tidal or brackish recommended.
obsoletus populations in south San Francisco Bay. wetland and provides no
Requires mud flats for foraging and dense habitat for this species.
marsh vegetation on higher ground for
nesting.
marbled murrelet FT, SE Occurs in coastal marine habitats for much No Potential. The Study Area No further actions are
does not contain coniferous
Brach ram hus of the year. Breeds in old-growth conifer recommended.
Y p stands (e.g. redwood, Douglas fir) forest and provides no habitat
marmoratus for this species.
containing platform-like branches near the
coast. Forages for marine fishes and
invertebrates.
B- 5
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
1
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
western snowy FT, SSC, Federal listing applies only to the Pacific No Potential. The Study Area No further actions are
plover BCC, RP coastal population. Found on sandy contains no beaches or salt recommended.
Charadrius beaches, dry salt ponds, mudflats and ponds and provides no habitat
alexandrinus nivosus adjacent levees, and shores of large alkali for this species.
lakes. Requires sandy, gravelly or friable
soils for nesting.
black oystercatcher BCC Resident on rocky shores of marine No Potential. The Study Area No further actions are
habitats along almost the entire California contains no rocky shores or recommended.
Haematopus coast and adjacent islands. Breeds on beaches and provides no
bachmani undisturbed, rocky, open shores and cliffs. habitat for this species.
long-billed curlew SSC Winter visitor to large coastal estuaries, No Potential. The Study Area No further actions are
Numenius upland herbaceous areas, and agricultural does not contain suitable recommended.
americanus lands. Within California, nests only in the shorelines, mudflats or
northeastern portion of the state in wet grassland.
meadow habitat.
Caspian tern BCC Summer resident. Nests colonially on Unlikely. Matadero Creek is No further actions are
Sterna caspia islands in bodies of open water, including too small in area and recommended.
San Francisco Bay. Forages for fish over secluded to provide habitat for
open water. this species; may occasionally
fly over the area.
black skimmer SSC, BCC Found primarily in southern California; No Potential. The Study Area No further actions are
Rynchops niger south San Francisco Bay has a small is surrounded by development recommended.
resident population. Nests colonially on and too far inland to provide
gravel bars, low islets, and sandy beaches. any habitat for this species.
Forages over open waters for small fishes.
B- 6
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
California least tern FE, SE, Summer resident. Breeds along the No Potential. Matadero Creek No further actions are
Sterna antillarum CFP California coast from San Francisco Bay is too small in area and recommended.
browni south. Nests colonially on barren or secluded to provide habitat for
sparsely vegetated, flat substrates near this species.
water. Forages for small fishes. San
Francisco Bay colonies usually located on
dry/abandoned salt ponds and along
estuarine shores.
Allen's hummingbird BCC Summer resident along the California High Potential. Riparian A breeding bird survey should
Selasphorus Basin coast. Breeds in a wide variety of habitats woodland within the Study be conducted if ground
that provide nectar-producing flowers, Area provides suitable nesting disturbance and/or vegetation
including parks and gardens. Migration habitat for this species. removal occurs from February 1
generally limited to the coastal zone. to August 31; active nests
should be avoided.
short-eared owl SSC Resident and winter visitor, found in open, No Potential. The Study Area No further actions are
Asio flammeus treeless areas with elevated perches and is small and surrounded by recommended.
dense vegetation. Tall grasses and/or development, with no open
emergent vegetation are needed for grasslands or marshes.
nesting and daytime seclusion.
long-eared owl SSC Largely resident. Nests in a variety of Unlikely. The Study Area is No further actions are
Asio otus woodland habitats, including oak and small and surrounded by recommended.
riparian. Requires adjacent open land for development, and unlikely to
foraging, and the presence of be used for nesting by this
old nests of other birds for nesting. species.
B- 7
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
western burrowing SSC, BCC Largely resident in the region. Found in Unlikely. The Study Area is No further actions are
owl grasslands and other open habitats with a surrounded by development, recommended.
Athene cunicularia sparse to absent shrub/tree canopy. Nests with no open grassland or
hypugea and roosts in old mammal burrows, other typical habitat for this
typically those of ground squirrels. Preys species.
upon insects, and also small mammals,
reptiles and birds.
Vaux's swift SSC Summer resident, primarily in forested Unlikely. The Study Area is No further actions are
Chaetura vauxi areas. Nests in tree cavities, favoring those small and surrounded by recommended.
with a large vertical extent. Also uses development, lacking the
chimneys and other manmade substrates. extensive coniferous forest
habitat favored by this
species.
black swift SSC, BCC Summer resident. Breeds in small colonies No Potential. The Study Area No further actions are
Cypseloides niger on cliffs behind or adjacent to waterfalls in contains no cliffs or waterfalls, recommended.
deep canyons and sea-bluffs above surf. and provides no suitable
Forages widely. habitat for this species.
Nuttall's woodpecker BCC Year-round resident in lowland woodlands High Potential. Riparian A breeding bird survey should
Picoides nuttallii throughout much of California west of the trees within the Study Area be conducted if ground
Sierra Nevada. Typical habitat is provide suitable habitat for disturbance and/or vegetation
dominated by oaks; also occurs in riparian this species. removal occurs from February 1
woodland. Nests in tree cavities. Relatively to August 31; active nests
common. should be avoided.
B- 8
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
olive-sided flycatcher SSC, BCC Summer resident. Breeds most often in Unlikely. The Study Area is No further actions are
Contopus cooperi montane coniferous forests; nests are surrounded by development, recommended.
typically in tall trees, often near open areas. lacking the extensive forest
Also breeds in coastal forest and habitat favored by this
woodlands. species.
loggerhead shrike SSC Resident in open habitats with scattered Unlikely. The Study Area is No further actions are
Lanius ludovicianus shrubs, trees, posts, and utility lines from surrounded by development, recommended.
which to forage for large insects. Nests are with no open grassland,
well concealed in densely-foliaged shrubs scrubland or other typical
or trees. habitat for this species.
purple martin SSC Summer resident. Breeds in woodlands Unlikely. The Study Area No further actions are
Progne subis and other relatively open habitat. Nests in surrounded by development, recommended.
cavities, usually in tall, isolated trees or with no extensive woodland or
man-made structures. open forest habitat favored by
this species.
bank swallow ST Summer resident; breeds in riparian and No Potential. The Study Area No further actions are
Riparia riparia other lowland habitats in western is surrounded by development recommended.
California. Nests colonially in burrows and provides no suitable
excavated on vertical faces with fine- breeding habitat for this
textured or sandy soils, including coastal species; no recent breeding
cliffs. records are known from the
vicinity.
B- 9
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
_ I
oak titmouse BCC Year-round resident in woodland and High Potential. Riparian A breeding bird survey should
Baeolophus savannah habitats where oaks are present, trees within the Study Area be conducted if ground
inornatus as well as riparian areas. Nests in tree provide suitable habitat for disturbance and/or vegetation
cavities. Relatively common. this species. removal occurs from February 1
to August 31; active nests
should be avoided.
•
(Brewster's) yellow SSC Summer resident, breeding in riparian Moderate Potential. Riparian A breeding bird survey should
warbler vegetation along water courses, usually in trees and other vegetation be conducted if ground
Setophaga willows with cottonwoods, aspens, along Matadero Creek may disturbance and/or vegetation
(Dendroica)petechia sycamores, and/or alders present. Also be used for nesting. removal occurs from February 1
brewsteri nests in suitable montane shrubbery. to August 31; active nests
should be avoided.
San Francisco BCC, SSC Endemic resident of the San Francisco Bay Moderate Potential. The A breeding bird survey should
(saltmarsh) region, in various marsh habitats Study Area contains be conducted if ground
yellowthroat (freshwater to salt). Requires thick, emergent(cattails) and dense disturbance and/or vegetation
Geothlypis trichas continuous cover down to water surface for riparian vegetation that removal occurs from February 1
sinuosa foraging, and tall grasses, tule patches, or provides suitable habitat for to August 31; active nests
willow for nesting. this species. should be avoided.
grasshopper sparrow SSC Summer resident, nesting in dense No Potential. The Study Area No further actions are
Ammodramus grasslands on rolling hills, lowland plains, is surrounded by development recommended.
savannarum in valleys and on hillsides. Generally and does not contain open
secretive. grassland, thus providing no
habitat for this species.
B- 10
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
Alameda song SSC, BCC Endemic resident subspecies of salt- No Potential. The Study Area No further actions are
sparrow marshes bordering the south arm of San does not contain tidal marsh recommended.
Melospiza melodic Francisco Bay. Favors pickleweed habitat, and provides no habitat for
pusillula and typically nests in gumplant and other this subspecies.
shrubs.
Bryant's savannah SSC Resident subspecies, associated with the No Potential. The Study Area No further actions are
sparrow coastal fog belt. Occupies upper tidally- does not contain tidal marsh recommended.
Passerculus influenced areas, often found where tidal or adjacent grassland
sandwichensis wetland communities merge into grassland. habitats.
alaudinus Nests in vegetation on or near the ground,
including along roads, levees, and canals.
tricolored blackbird SSC Resident, though disperses somewhat Unlikely. Emergent wetland No further actions are
Agelaius tricolor when not breeding. Typically nests over or areas within the Study Area recommended.
near freshwater in dense cattails, tules, or are relatively small and
thickets of willow, blackberry, wild rose or unlikely to be used for nesting
other tall herbs. Highly colonial; breeding by this species.
aggregations tend to be large.
yellow-headed SSC Migrant and local summer resident. Nests Unlikely. Emergent wetland No further actions are
blackbird colonially in freshwater emergent wetlands areas within the Study Area recommended.
Xanthocephalus with dense vegetation and deep water, are relatively small and
xanthocephalus often along borders of lakes or larger unlikely to be used for nesting
ponds. by this species.
B- 11
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR
OCCURRENCE RECOMMENDATIONS
Reptiles and Amphibians
California tiger FT, ST, Inhabits annual grasslands, spending most Unlikely. Although this No further actions are
salamander SSC of the year underground in mammal species has been recommended.
Ambystoma burrows. Breeding occurs in vernal pools documented within five miles
californiense and other seasonal aquatic features. In the of the Study Area (CDFW
immediate vicinity of San Francisco Bay, 2014), the Study Area is
has a very limited distribution. separated from the nearest
occurrences by the Interstate
280 freeway. On a very local
scale, the Study Area is
surrounded by development
and does not contain vernal
pools or analogous seasonal
water features suitable for
breeding.
B- 12
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
California red-legged FT, SSC Associated with quiet perennial to Moderate Potential. Recent Consultation (informal or formal)
frog intermittent ponds, stream pools, marshes breeding has been with the USFWS may be
Rana draytonii and wetlands. Prefers shorelines with documented within Deer necessary. At a minimum, pre-
extensive emergent and/or overhanging Creek (a tributary of Matadero construction surveys should be
riparian vegetation. Documented to Creek) approximately 1.2 conducted prior to any work
disperse through upland habitats during miles north of the Study Area within or adjacent to the creek.
and after rains. (CDFW 2014). There are also If this species is found,
additional occurrences additional avoidance measures
(including breeding) within and biological monitoring during
five miles to the west (TRA work activities will likely be
Environmental Sciences required.
2011, CDFW 2014). Within
the Study Area, the creek is
unlikely to provide any
breeding habitat, but may be
used for dispersal and other
movements.
foothill yellow-legged SSC Found in or adjacent to rocky streams in a Unlikely. Urban creeks do not No further actions are
frog variety of habitats. Favors an open canopy typically provide suitable recommended.
and sunlit areas. Feed on both aquatic and habitat for this species, and
terrestrial invertebrates. there are no documented
occurrences in the watershed
that contains the Study Area
(CDFW 2014).
B- 13
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* POTENTIAL FOR
HABITAT OCCURRENCE RECOMMENDATIONS
San Francisco garter FE, SE, Found in the vicinity of freshwater marshes, No Potential. The Study Area No further actions are
snake CFP, RP ponds and slow-moving streams in San is outside of this subspecies' recommended.
Thamnophis sirtalis Mateo County and extreme northern Santa known range, which is
tetrataenia Cruz County. Prefers dense cover and restricted to San Mateo
water depths of at least one foot. Upland County and a very limited
areas near water are also very important. portion of Santa Cruz County.
Adults prey chiefly on large frogs.
western (Pacific) SSC Occurs in perennial ponds, lakes, rivers Moderate Potential. Pre-construction surveys should
pond turtle and streams with suitable basking habitat Although habitat within be conducted prior to any work
Emys marmorata (mud banks, mats of floating vegetation, Matadero Creek is of limited within or adjacent to the creek.
partially submerged logs) and submerged quality (particularly for If turtles are found, additional
shelter. Nests are excavated in unshaded breeding), this species may avoidance measures will likely
areas with friable soil and vegetative cover. occur there. be necessary.
Fishes
green sturgeon FT, SSC Anadromous. Spawns in the Sacramento No Potential. Matedero Creek No further actions are
Acipenser (NMFS) and Klamath River systems. Lingering provides no suitable habitat for recommended.
medirostris transients may be found throughout the this species and is outside of
San Francisco Bay estuary, particularly its range.
juveniles.
tidewater goby FE, SSC Brackish water habitats along the California No Potential. Matedero No further actions are
Eucyclogobius coast from Agua Hedionda Lagoon, San Creek provides no suitable recommended.
newberryi Diego County to the mouth of the Smith habitat for this species and is
River. Found in shallow lagoons and lower outside of its range.
stream reaches, they need fairly still but not
stagnant water and high oxygen levels.
B- 14
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
coho salmon - FE, SE Anadromous, spending most of life cycle in No Potential. This species No further actions are
Central CA Coast (NMFS) the ocean. Federal listing includes does not occur within the recommended.
ESU populations between Punta Gorda and San watershed that contains
Oncorhynchus Lorenzo River. State listing includes Matadero Creek.
kisutch populations south of San Francisco Bay
only. Occurs inland and in coastal marine
waters. Requires beds of loose, silt-free,
coarse gravel for spawning. Also needs
cover, cool water and sufficient dissolved
oxygen.
steelhead - Central FT Anadromous, spending most of life cycle in Unlikely. As per Leidy et al. No further actions are
CA Coast DPS (NMFS) the ocean. This ESU occurs from the (2005), Matadero Creek does recommended.
Oncorhynchus Russian River south to Soquel Creek and not contain a steelhead
mykiss Pajaro River, including the San Francisco population, and tidal gates at
and San Pablo Bay Basins. Adults migrate the mouth of the creek provide
upstream to spawn in cool, clear, well- at least a partial barrier to
oxygenated streams. Juveniles remain in anadromous fishes.
fresh water for one or more years before
migrating downstream to the ocean.
B- 15
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
steelhead -Central FT Anadromous, spending most of life cycle in No Potential. The Study Area No further actions are
Valley ESU (NMFS) the ocean. The Central Valley ESU is outside of this population's recommended.
Oncorhynchus includes all naturally spawned populations range.
mykiss irideus (and their progeny) in the Sacramento and
San Joaquin Rivers and their tributaries,
excluding San Francisco and San Pablo
bays and their tributaries. Preferred
spawning habitat for steelhead is in cool to
cold perennial streams with high dissolved
oxygen levels and fast flowing water.
chinook salmon— FE, SE, Anadromous, spending most of life cycle in Unlikely. No spawning occurs No further actions are
Sacramento River RP the ocean. Spawns in the Sacramento in streams which drain into recommended.
Winter-run ESU River but not in tributary streams. Requires South San Francisco Bay.
Oncorhynchus (NMFS) clean, cold water over gravel beds. Adults
tshawytscha migrate upstream to spawn in cool, clear,
well-oxygenated streams. Juveniles
typically migrate to the ocean soon after
emergence from the gravel.
longfin smelt ST, SSC, Anadromous. Found in open waters of No Potential. The Study Area No further actions are
Spirinchus RP estuaries, mostly in the middle or bottom of provides no suitable habitat recommended.
thaleichthys water column. Prefer salinities of 15 to 30 for this species and is outside
ppt, but can be found in completely of its range.
freshwater to almost pure seawater.
B- 16
Appendix C. Evaluation of Special Status Plant and Wildlife Species Documented in the Vicinity of the Study Area. List compiled from
the California Department of Fish and Wildlife (CDFW) Natural Diversity Database (CDFW 2014W), U.S. Fish and Wildlife Service (USFWS)
Species Lists, and California Native Plant Society (CNPS) Electronic Inventory search of the Palo Alto, Mountain View, Cupertino, and Mindego
Hill USGS 7.5 minute quadrangles and a review of other CDFG lists and publications (Jennings and Hayes 1994, Zeiner et al. 1990).
SPECIES STATUS* HABITAT POTENTIAL FOR OCCURRENCE RECOMMENDATIONS
Invertebrates
Bay checkerspot FT, RP, Restricted to native grasslands on outcrops No Potential. The Study Area No further actions are
butterfly SSI of serpentine soil in the vicinity of San provides no suitable habitat recommended.
Euphydryas editha Francisco Bay. Plantago erecta is the and is outside of this
bayensis primary host plant. Known extant subspecies' known range.
populations are all within Santa Clara
County.
Myrtle's silverspot FE, RP, Restricted to the foggy, coastal dunes/hills No Potential. The Study Area No further actions are
butterfly SSI of the Point Reyes peninsula; extirpated
Speyeria zerene p provides no suitable habitat recommended.
myrt/eae from coastal San Mateo County. Host for this species, and it has
plant thought to be Viola adunca. been extirpated in San Mateo
County.
monarch butterfly SSI (winter Winter roost sites located in wind-protected Unlikely. Tree rows within the No further actions are
Danaus plexippus roosts tree groves, with nectar and water sources Study Area do not provide recommended.
monitored nearby; sites are generally on or close to any typical roost habitat for
by CDFW) the coast. this species. Individual
monarchs may occur
regularly, particularly during
migration.
* Key to status codes:
FE Federal Endangered
FT Federal Threatened
FC Federal Candidate
FD Federal De-listed
FPD Federal Proposed for De-listing
NMFS Species under the Jurisdiction of the National Marine Fisheries Service
B- 17
BCC USFWS Birds of Conservation Concern
RP Sensitive species included in a USFWS Recovery Plan or Draft Recovery Plan
SE State Endangered
ST State Threatened
SR State Rare
CSC CDFW Species of Special Concern
CFP CDFW Fully Protected Animal
SSI CDFW Special Status Invertebrate
WBWG Western Bat Working Group High Priority species
List 1A CNPS List 1A: Plants presumed extinct in California
List 1B CNPS List 1 B: Plants rare, threatened or endangered in California and elsewhere
List 2 CNPS List 2: Plants rare, threatened, or endangered in California, but more common elsewhere
List 3 CNPS List 3: Plants about which CNPS needs more information (a review list)
B- 18
Appendix D. Study Area Photographs
This page intentionally blank.
Appendix D. Study Area Photographs
, i 4.
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Top: Perennial Wetland northwest of Page
Mill Road (facing southeast). (0) wra
Bottom: Perennial Wetland northwest of
Page Mill Road (facing northwest). ENVIRONMENTAL CONSULTANTS
Photographs taken: October 21, 2014
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Top: Upland bank northwest of Page Mill 0 \4/ rci
Road (facing northwest).
Bottom: View of Page Mill Road facing
southwest from upland bank. ENVIRONMENTAL CONSULTANTS
Photographs taken: October 21, 2014
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Top: Matadero Creek northwest of Page Mill ® wra
Road where erosion and scouring has incised
the channel.
Bottom: Northwest side of Page Mill Road ENVIRONMENTAL CONSULTANTS
facing west along the eroding bank.
Photographs taken: October 21, 2014
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Top: Matadero Creek northwest of Page Mill 0 wra
Road.
Bottom: Matadero Creek northwest of Page
MITI Road. ENVIRONMENTAL CONSULTANTS
Photographs taken: October 21, 2014
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Top: Perennial wetland southeast of Page
Mill Road (facing northwest). 0 wra
Bottom: Edge of perennial wetland southeast
of Page Mill Road (facing southeast). ENVIRONMENTAL CONSULTANTS
Photographs taken: October 21, 2014
'its P , w ;- IN , , Y,
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Top: Page Mill Road (facing northwest).
Bottom: Page Mill Road (facing northeast). wra
ENVIRONMENTAL CONSULTANTS
Photographs taken: October 21, 2014
APPENDIX B. WATER SURFACE PROFILE STUDY AND DESIGN
RECOMMENDATIONS
This page intentionally blank.
GEOTECHNICAL
EtveEc) ENVIRONMENTAL
WATER RESOURCES
CONSTRUCTION SERVICES
Expect Excellence
Project No.
11359.000.000
February 27, 2015
Mr. Richard Chiu
Public Works Director
Town of Los Altos Hills
26379 W. Fremont Road
Los Altos Hills, CA 94022
Subject: Matadero Creek Bank Stabilization Adjacent to Page Mill Road
Los Altos Hills, California
WATER SURFACE PROFILE STUDY AND DESIGN RECOMMENDATIONS
Dear Mr. Chiu
ENGEO is pleased to present this basis of design report for the creek bank stabilization
recommendations intended for the Matadero Creek improvements near Page Mill Road in the
Town of Los Altos Hills.
PURPOSE
Bank failure has occurred in the portion of Matadero Creek which is located immediately
downstream of a concrete box culvert, which traverses Page Mill Road approximately 1/4 mile
south of Interstate 280 in the Town of Los Altos Hills. The box culvert contains a downstream
outfall apron comprising sackcrete material. At the transition between the sackcrete material and
the downstream soft bottom channel, a 3-foot vertical headcut and scour pool has formed.
Downstream of the box culvert, Matadero Creek runs parallel with the Page Mill Road alignment
in the study reach near several improvements associated with the roadway.
The Project has the following goals:
• Remove sackcrete in the culvert outfall apron as necessary and create a rock rip-rap chute
structure which would restore equilibrium conditions in the creek channel in regard to
erosive processes.
• Provide biotechnical bank stabilization along the curvature of the creek downstream of the
rock chute structure, adjacent to Page Mill Road.
• Install a permanent soldier pile retaining wall system along Page Mill Road in order to
reduce future maintenance needs in the area where creek improvements are proposed.
• Include a long-term operations and maintenance manual component for the project for use by
the Town of Los Altos Hills after the project is complete.
2010 Crow Canyon Place,Suite 250• San Ramon,CA 94583•(925)866-9000•Fax(888)279-2698
www.engeo.com
Town of Los Altos Hills 11359.000.000
Matadero Creek Bank Stabilization Adjacent to Page Mill Road February 27,2015
WATER SURFACE PROFILE STUDY AND DESIGN RECOMMENDATIONS Page 2
HYDRAULIC MODELING
The results of the fluvial hydraulic analysis of this,portion of the creek were calculated using the
Hydrologic Engineering Center River Analysis System (HEC-RAS) 4.0 Beta computer program
published by the United States Army Corps of Engineers (USACE). HEC-RAS performs
one-dimensional hydraulic analyses for natural channels and is intended for calculating water
surface profiles and velocities in steady, gradually varied flow conditions. The basic HEC-RAS
computational procedure is based on the solution of the one-dimensional energy equation.
Energy losses consist of friction losses based on Manning's equation. The development of the
HEC-RAS model specific to this study is described in detail below.
A HEC-RAS model provided to us by WRECO was used as the basis for our model, which was
then revised with the proposed cross-sections located downstream of the culvert. Survey data
provided by Ruggeri-Jensen-Azar and dated 2012 were used to determine the existing condition
cross-sections which were input into the model. Then, based on design recommendations, a
proposed condition model was conducted.
1. Channel Geometry
In order to model the channel geometry, survey data was provided by RJA. Cross-sections were
drawn perpendicular to the direction of flow downstream of the culvert; locations of the cross-
sections are shown on Figure 1. Proposed condition channel geometry is based on the rock chute
and step pool calculations. The design recommendations below and Figure 1 provide more detail
on proposed cross-sections.
2. Input of Channel Flow Rate
Flow rates previously input into the WRECO model were used as the basis for channel flow
rates. According to the model, the 100-year recurrence interval flow rate is 790 cubic feet per
second(cfs). This flow rate was used to model peak water surface elevations through the channel
in the HEC-RAS model.
3. Input of Hydraulic Coefficients
The value of the Manning's roughness coefficient (n) establishes frictional resistance in the
channel and is thus related to the modeling of channel velocity and water surface profile by the
HEC-RAS program. The roughness coefficients previously input into the WRECO model were
used for this analysis. This value is based on recommended minimum, maximum and normal
values developed for a variety of vegetative and morphological conditions similar to those found
in the channel and banks of the study creek. The following table summarizes the coefficients
used in the modeling.
TABLE 1
Manning's 'n' value I)cscripiiun
0.035 (main channel) Clean, straight,full,no rifts or deep pools,
with some stones and weeds
U.06 (channel banks) Natural channels,poor condition
Town of Los Altos Hills 11359.000.000
Matadero Creek Bank Stabilization Adjacent to Page Mill Road February 27,2015
WATER SURFACE PROFILE STUDY AND DESIGN RECOMMENDATIONS Page 3
4. Flow Regime
Based on the preliminary results of the modeling, a subcritical flow was encountered in the creek
channel within the study reach. Therefore, the final results of the study are based on a subcritical
flow regime analysis.
5. Boundary Condition
A normal depth boundary condition was entered at the upstream and downstream ends of the
study reach using a bed slope of 0.0064 ft/ft,based on information in the WRECO model.
RESULTS OF HEC-RAS MODELING
The following table summarizes the water surface elevation for each station located within and
downstream of the rock chute structure:
TABLE 2
Results of H draulic Anal sis
100-YEAR WATER SURFACE ELEVATION STUDY
Station Q(cfs) Existing Water Surface Proposed Water Surface
Elevation(ft) Elevation (ft)
6.8 790 245.50 244.41
6.7 790 241.53 240.47
6.6 790 241.22 240.78
6.5 790 241.98 240.73
6.4 790 241.86 239.57
6 790 240.56 239.85
5 790 239.57 239.57
4 790 238.43 238.43
3 790 237.72 237.72
790 236.39 236.39
790 236.16 236.16
Based on the results of the modeling above, the proposed alterations to the Matadero Creek
channel geometry presented in this report downstream of the road crossing do not impact flood
conditions at the Page Mill Road culvert nor are water surface elevations raised as a result of the
project in the reach where the project is proposed.
DESIGN RECOMMENDATIONS
A rock step-pool structure will be incorporated to flatten the creek flowline gradient through the
culvert project limit. The design is based on a concept from Dave Rosgen of Wildland
Town of Los Altos Hills 11359.000.000
Matadero Creek Bank Stabilization Adjacent to Page Mill Road February 27,2015
WATER SURFACE PROFILE STUDY AND DESIGN RECOMMENDATIONS Page 4
Hydrology and is intended to create a structure that not only mimics a natural creek habitat
feature in hydraulic function, but also reduces the amount of rock required to provide adequate
stabilization. The step-pool design is comprised of vortex rock weir structure that is installed so
that high flows are directed towards a scour pool in the center of the channel during peak flow
events downstream of the crest of the structure. Under normal creek operating conditions, the
scour pool functions as a habitat pond.
Calculations were performed in accordance with the procedure outline by Thomas (2000). The
rock pool will have a length of approximately 27 feet and a scour depth of approximate 7.3 feet
as shown on Figure 1.
RIP-RAP SIZING
Revetment was sized using an empirical method developed by the U.S. Bureau of Reclamation,
described in Reference 4. This method was developed for estimating riprap size to be used
downstream of a stilling basin. The procedure was developed using eleven prototype installations
with velocities varying from about 1 foot per second to about 18 feet per second. This method
calculates the median size of stable rock with the following equation:
D50 = 0.0122 x 1/2.06
Where:
D50 is the stone size in feet.
V.is average velocity in cross section, ft/s
The results of this analysis demonstrate that a 500-pound rock revetment will provide
appropriate protection at this location if installed at a minimum thickness of 3.5 feet. ENGEO
should observe the construction of the step pool to verify that void spaces are sufficiently filled
in with smaller rock so that water is generally contained in the step pools. As indicated on the
improvement plans, we recommend the contractor fill in void spaces of the 1/4-ton rock with
75 lb. and 25 lb rock. Caltrans specification rip-rap so that void spaces greater than 4 inches in
the channel bed are eliminated.
DISCUSSION
The restoration and stabilization will improve the creek transition between the sackcreted portion
of the channel and the soft bottom channel downstream and reduce erosional processes in the
reach. The rock chute was designed according to National Resource Conservation Service
standards to reduce disruption to the existing drainage system to the maximum extent
practicable, leaving the majority of the scour pool that has developed as a habitat feature and
remove portions of upstream sackcrete. Also, because of the creek curvature downstream of the
transition area, improved bank stabilization will be provided along the southerly bank of the
creek parallel with Page Mill Road. Bank stabilization approximately below the 100-year water
surface elevation will be composed of rock rip-rap planted with willow species (Salix spp.).
Lastly, an existing secant wall on Page Mill Road will be replaced as a soldier pile wall with
concrete lagging approximately above the 100-year water surface elevation of Matadero Creek.
Town of Los Altos Hills 11359.000.000
Matadero Creek Bank Stabilization Adjacent to Page Mill Road February 27,2015
WATER SURFACE PROFILE STUDY AND DESIGN RECOMMENDATIONS Page 5
The improved wall will reduce further creek intervention in the reach for creek maintenance
activities.
Additionally, the Project will include minor vegetation removal and replanting. This will involve
removal and replacement of several small thickets of willows (Salix spp.) and Coyote Brush
(Baccharis spp.)that have established in the reach of creek.
IMPACTS
The following impacts are expected for the project:
1. Amount of Sackcrete removed: 70 square feet/8 cubic yards
2. Amount of Rock Rip-Rap added: 87 lineal feet plus 1648 square feet/ 183 cubic yards
3. Amount of earthwork required: 200 cubic yards
We are pleased to be of service to you on this study. If requested, we would be pleased to
continue to consult with you and your design team as project planning progresses.
QROf ESSiO4,4
Very truly yours, 4,9T_,v;s1AAN's
1- ce No. 67302
I ✓� * Exp.9/30/2016
Hilary /7athan D. Buck, PE9l CIV 0.. cs
hm/jdb/pcg/jf tor cA‘-.
Attachments: List of Selected References
Figures 1 and 2—HEC-RAS Work Maps
Appendix A—HEC-RAS Output
Appendix B—Project Site Plan
Appendix C—Monitoring Manual
ENGEO
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SELECTED REFERENCES
1. Thomas, D.B.; Abt, S.R.; Mussetter, R.A.; Harvey, M.D.; A Design Procedure for Sizing
Step-Pool Structures; 2000.
2. United States Army Corps of Engineers; HEC-RAS Version 4.0 Beta, Hydraulic Reference
Manual;Davis, California; 2003.
3. United States Army Corps of Engineers; Flood Control Engineering Manual, Hydraulic
Design of Flood Control Channels,EM-1110-2-1601, June 30, 1994.
4. United States Bureau of Reclamation; USBR EM-25, Peterka, 1958.
5. WRECO; Recommendations for Rebuilding the Matadero Creek Bank Adjacent to Page Mill
Road Memorandum,June 4,2013.
6. Ruggeri Jensen Azar(RJA); Survey data provided December 2014.
11359.000.000
February 27, 2015
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/ 6.7 241.53 240.47
Xp 6.6 241.22 240.78
6.5 241.98 240.73
6.4 241.86 .',239.57
., 2 .D 6.0 240.56 239.85
A5.0 239.57 239.57
,4.0 238.43 238.43
3.0 237.72 237.72
N 2.0 236.39 236.39
1.0 236.16 236.16
0 FEET 10 BASE MAP SOURCE:
0 METIERS 5 C IGEO PRE DEVELOPMENT HEC-RAS WORK MAP Esot1C000211359.000.000 FIGURE NO
MATADERO CREEK RESTORATION SCALE AS SHOWN 1
-Drped Ex°BB°ace- TOWN OF LOS ALTOS.CALIFORNIA 015000.01 PC I�»I PCG 1
.. ,, ORIGINAL FIGURE PRINTED IN COLOR
co 0111 O 2015 0Y ENGEO INCORPORATED.TNM DOCUMENT MAY NOT BE REPRODUCED IN WRENS 0R IN PART BY ANY YEARS 1011A100EYER.NOR AIRY IT RE 0201E0 OR EXCERPTED WITHOUT THE EXPRESS WRn100 CONSENT Or EN000 IN
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r Sface
K0 2 Station Surface Watearioo(0)'A. Elevation(0)
2411
N 8.0 247127 245.98
X iaa'i1 L 24.9'WD 6.8 245.50 244.41
6.7 241.53 240.47
420p.55
6.6 241.22 240.78 -
6.5 241.98 240.73
x 6.4 241.86 239.57
1 ., z •e 6.0 240.56 ' 239.85
5.0 239.57 239.57
4.0 238.43 238.43
3.0 237.72 237.72
N
2.0 236.39 236.39
1.0 236.16 236.16
0FEET 10 BASE MAP SOURCE:
0 1111583 5 \ n^^^ POST-DEVELOPMENT HEC-RAS WORK MAP P°T°11359.000.000 FIcun1No
Ll��llll'!ILL.. t I.J MATADERO CREEK RESIORAT1ON 5000E AS SHOWN 2
-Expect Excellence- TOWN OF LOS ALTOS,CALIFORNIA DRAWNIIY:PC ®®UR PCG
.... .. - -.ORIGINAL FIGURE PRINTED IN COLOR
FAIGEO
Expect Excellence-
APPENDIX A
HEC-RAS OUTPUT
Existing Proposed
River I Q i W.S. Vel W.S.
Sta I Total 1 Elev Chnl Elev Vel Chnl
{ (cfs) (ft) (ft/s) ' (ft) (ft/s)
6.8 . 790 245.5 10.79 244.41 10.38
6.7. 790 241.53. 12.56' .240.47. 6.9
66 790 241.22 12.54 240.78. 4.26
6.5 790. 241.98 . 5.99 240.73 4:39
6.4: 790 241.86> '6.45 239.57 9.29
6• 790 240:56 10.75. 239.85 7.41
5 790 239.57 7.89 239.57 7:89
4 : 790 238.43 10.25 238.43 10.25
3' 790 237.72 10.85 237.72 10.85
2 , 790 236.39 8.58. 236.39 8:58
1 790 236:16 7.77 236.16 7.77
11359.000.000
February 27, 2015
ENGEO _,.
Expect Excellence—
APPENDIX B
Project Site Plan
11359.000.000
February 27, 2015
iri ,-;,..../7,/
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PLAN VIEW .aR...�� � wia. ��• ♦4.. ��. Vt• �.
- ' v ROCK CHUTE GRADE CONTROL STRUCTURE
..I- .. .. SECTION CO-.. .. ..
I
1 ENG EO v._w.,w...� .:. 7
ENGEO•
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•
•
•
•
APPENDIX C:
Monitoring Manual
•
•
•
•
•
11359.000.000
..February 27, 2015
L-
E
—Expect Excellence—
PROCEDURES FOR GENERAL CREEK MAINTENANCE
II-1 Procedures. The following procedures are applicable to the identified maintenance
__ elements. The Creek Maintenance Consultant (CMC) provides guidance for the
maintenance process, and promotes management practices:with standards and guidelines.
The CMC is responsible for providing .effective and efficient use of staff and.
- subcontractors. Procedures for the following maintenance items are presented in the
following sections of this chapter:
• Monitoring and repair of creek structures (Section II-2)
• Stabilization and/or repair of eroded areas or failures of the creek banks(Section II-3)
• Monitoring and repair of creek structures (Section I1-4)
• Annual Reports (Section II-5)
I1-2 Monitoring/Maintenance of Creek Channel and.Banks. Creek channel and banks should
be monitored for obstructing vegetation, trash and sediment. Maintenance should include
1 only minor removal of debris obstructing proper flow characteristics as determined by
the Town, with appropriate consultation and permitting from the resource agencies. Only
portions of vegetation that are obstructing channel flow should be trimmed or removed
as necessary to allow creek function for conveying storm runoff. Woody debris should
be removed from the channel such that it does not obstruct flow and present a flooding
hazard. Tree root masses and woody debris within the channel and banks should be
allowed to remain; however, trash and other undesirable-debris obstructing flow should
be removed from the creek areas as needed, or at least once per year throughout the
maintenance period.
An annual stream reconnaissance should be conducted'to observe and document:
a. Evidence of excessive bank erosion.
b. Evidence of excessive sedimentation/aggradation on the channel bed, floodplain, or
near culvert entrances and exits.
c: The effects of major floods, including noting high water mark elevations.
The monitoring consultant will observe any incision or_aggradation and evaluate whether
it is.deemed"excessive" and in need of remedial actions.
t 'r
11359.000.000
February 27, 2015
GLL)
—Expect Excellence—
Longitudinal Profile. The longitudinal profile of the creek system should remain fairly
consistent,.without excessive scour,: erosion or deposition. Fresh scarps, nick points,
drops or sediment bars should be noted during the monitoring. The creek corridor should
be functioning as intended as an open-channel system. The meandering pattern should be.
allowed to remain, and the creek may alter its low-flow path from season to season. If
sediment accumulation is noted, it should be estimated by depth and location. Significant
erosion of bed or banks should be noted.
II-3 Stabilization and/or repair of eroded areas or failures of the creek banks. Monitoring of
the channels should involve visual.observation on an annual basis and after significant
storm events. The banks should be observed for obvious signs of vertical and horizontal
displacements, seepage or erosion caused by high creek levels. Any excessive slope ,
displacement, seepage or erosion should be reported and addressed by maintenance as
necessary. The Maintenance Entity or CMC will retain a geotechnical engineer and/or
erosion control specialist as needed,to determine appropriate remedial action necessary
tocorrect the problem.
The following guidelines are applied to all grading accomplished for construction of
stabilization measures:
• .Both an Engineering Geologist and a Geotechnical Engineer should be consulted on
significant bank repairs.
• Soil removal/placement should be limited to the minimum needed for erosion/flood
protection as determined by an Erosion Control specialist.
• No material should be placed in any special aquatic site, including wetlands,without
agency approval.
• No material should be placed 'in any location, or in any manner, so as to impair
surface water flow into or out of any wetland area without proper resource agency
permitting.
• No material should be placed in a manner that could allow it to be eroded by normal
or expected high flows.
i
11359.000.000 .
February 27, 2015
ENGEO
—Expect Excellence—
MONITORING ANI) MAINTENANCE TASKS
Area Monitoring Task Performance Standard Remedial Actions
Monitor evidence of "
Channel channel bed incision,' The longitudinal profile of Any significant deviation
Performance " which includes the creek system should from the existing channel
and documenting any remain fairly consistent, slope should be reported
Longitudinal knickpoints/headcuts and without excessive scour, and addressed by
Profile : the initiation and/or erosion or_deposition maintenance asnecessary.
growth of gullies
• Any excessive slope
4displacement, seepage or
The banks should be erosion should be reported
observed for obvious Significant displacement, and addressed by
! Bank signs of vertical and seepage or erosion should not maintenance as.necessary.
Performance horizontal displacements, occur along the channel Both an Engineering
seepage or erosion caused banks. Geologist and a
by high creek levels. Geotechnical Engineer
should be consulted on
significant bank repairs.
Any excessive deposition
or erosion in the creek
channel causing channel
The-channel width:depth width:depth ratio to change
Monitor evidence of . ratio is to be monitored for by more that 10%should
Sediment excessive deposition in changes that could affect the be reported and addressed
channel including active
Movement creek function or the by maintenance as
channel depth to width structural integrity of the necessary. Both an
• ratios. drop structures. Engineering Geologist and
a Geotechnical Engineer
should be consulted on
significant channel repairs.
I -
Portions of vegetation that
are,obstructing channel
Vegetation Creek channel and banks No vegetation should flow should be trimmed or
Performance should be monitored for obstruct flow in the creek removed as necessary to
obstructing vegetation. areas. - allow creek function for
conveying storm runoff.
Creek channel and banks Trash and other
Debris should be monitored for No trash or debris should undesirable debris'-.
Accumulation obstructing trash or obstruct flow in the creek obstructing flow should be
areas. removed from the creek
debris.
areas. -
LJ
11359.000.000 .
February 27, 2015