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HomeMy WebLinkAbout4.1 TOWN OF LOS ALTOS HILLS September 7, 1995 Staff Report to the Planning Commission RE: REQUEST FOR CERTIFICATION OF FINAL SUPPLEMENTAL EIR, AND APPROVAL OF GENERAL PLAN AMENDMENT, PRE-ZONING, AND TENTATIVE SUBDIVISION MAP; LANDS OF VIDOVICH, 11920 STONEBROOK DRIVE. (254-93-TM and 257-93-EIR) FROM: Curtis Williams, Planning Directp... _ Debbie Pollart and Mike Porto, Contract Town Planners RECOMMENDATION That the Planning Commission: Recommend the following actions to the city Council: 1. certify the Final Supplemental EIR; 2. approve the General Plan Amendment (map and text changes); 3. approve pre-zoning to R-A (Residential Agricultural) zoning district; 4. approve the Tentative Subdivision Map with attached conditions; 5. adopt the attached Mitigation' Monitoring Program; 6. adopt Statements of Overriding Considerations (not attached); and 7. adopt Findings and Facts to support the above actions (not attached). Staff recommends the Commission utilize the following procedure for tonight's hearing: 1. ask questions of staff; 2. open the public hearing (hear,applicant first); 3. close the public hearing; 4. discuss items outlined in the staff report or otherwise of concern; 5. modify, add, or delete conditions of approval; and 6. move to either recommend approval of all actions or to deny all actions. If the Commission is able to recommend approval at this meeting, staff will return with revised conditions of approval, if so,directed, and with the necessary findings and statements of overriding considerations to support the Commission's action. BACKGROUND The current project application was deemed complete in November of 1994. Project modifications made after the date of submittal, such as the retaining wall, have been incorporated into staff's review. The, project has been subjected to CEQA requirements (preparation and circulation of a Supplemental EIR), reviewed by Town staff, the Town's technical consultants (William Cotton and Associates and Lands of Vidovich ' , September 7,1995 Page 2 Wilsey & Ham), and Tow committees (Quarry Hills Council sub-committee, Pathways committee, Enviro mental Design Committee), in addition to the public. Previous proposals for resi.ential development of the Neary Quarry area were submitted to the'County and/or Town, beginning in 1987. The following summary chronology is intended to pr.vide further background'for the Commission: February 1i987 Th: Town prepares the Quarry Hills Project Initial Study and Environmental Assessment for an 80-lot subdivision on 58-acre site. July 1988 Ap licant modifies the project, after which the Draft EIR for the Quarry Hills Residential Subdivision is prepared and circulated for public review. September 1988 San a Clara County completes an Expanded Initial Study and Negative Declaration for the Neary Quarry Rec amation Plan, adopts the Negative Declaration and approves the Reclamation Plan for Neary Quarry. April 1989 The Town certifies the Final EIR for the Quarry Hills Resiential Subdivision. The project is denied. September 1992 San a _Clara County circulates the Draft EIR for the Vid vich General Plan Amendment, which proposes a 25-1 t subdivision on 78 acres. That EIR was not certified and to date no action has taken place on the pending Gen ral Plan Amendment and proposed project. November 1994 Ap licant submits to the Town a tentative subdivision map for a modified project (23 lots) on 78 acres. March 1995 The Town circulates the Draft Supplemental EIR for the Quarry Hills Subdivision. April 1995 The Planning Commission conducts two public hearings to accept comments regarding the Draft EIR. June - Aug. 1995 Final Supplemental EIR (Response to Comments) for Quarry Hills Subdivision prepared by EIR consultants and • Tow staff, after receipt of additional information from appl'cant. Lands of Vidovich September 7,1995 Page 3 PROJECT DESCRIPTION/REQUEST The applicant requests approval of a proposed Tentative Subdivision Map by the Town of Los Altos Hills, allowing for the development of 23 residential lots on the 78-acre site, which is located in the Montebello Ridge area within the Town of Los Altos Hills' Sphere of Influence. The applicant proposes modifications to the adopted Neary Quarry Reclamation Plan and Lake Management Plan in conjunction with this proposal. This request will also entail expansion of the Town's Urban Service Area, pre-zoning and annexation of the project site to the Town of Los Altos Hills, and adoption of!minor text and map amendments to the Los Altos Hills' General Plan. Approval of the Tentative Subdivision Map as proposed by the applicant would allow construction of 23 residences on lots ranging in size from oneto eight acres in two distinct portions of the project site: the "Quarry Area" and the "Hillside Area." As part of the approved Reclamation Plan, a lake was created in the area excavated during the former quarrying on the site. The 23 residences would surround the north and west sides of the existing lake. Development of the project site would result in private residential lots (1-23) which cover approximately 70 percent of the subdivision area. Site coverage by street rights-of-way account for approximately four percent of the subdivision area. The remaining 26+ percent of the area would consist of the reclamation lake and surrounding open space. Access to the proposed subdivision would be provided from the north from the existing Stonebrook Drive, which would be extended into the site to connect to the three proposed streets (Streets A, B, and IC). Secondary access to the site, which would be used only in emergency situations, would be from.Magdalena Avenue to Stonebrook Drive, connecting to "C" Street in the subdivision. Sanitary sewer service would be provided by the Town of Los Altos Hills via a connection to Town-owned sewer lines, assuming that the project is annexed to the Town. In order to provide sanitary sewer service to the proposed residences, a gravity system would extend off-site from a point in the northeastern corner of the site (near Lot 11), and would generally follow the course of the existing alignment of Hale Creek for a distance of approximately 1,000 feet to connect with the sewer system in the Dawson Drive Subdivision (Tract No. 6462). The proposed alignment would extend through the Juan Prado Mea Preserve, a dedicated Town open space area. Available alternatives to the proposed sanitary sewer system could consist of either: 1) a pump with a force main up Stonebrook Drive to Prospect Avenue; or 2) the use of on-site septic systems. Storm drainage is conveyed through the site in several ways. A by-pass channel is proposed along the rear of lots 1 through 10 to carry flows from off-site to Hale Creek Lands of Vidovich September 7, 1995 Page 4 in the Preserve. On-site stor flows would be channeled to "roadside ditches" and conveyed in an open channel o the lake between lots 13 and 14. Off-site flows from Prospect Avenue and Stoneb ook Drive are proposed to be collected at the site boundary, conveyed in a pipe etween lots 7 and 8 (through a well site not owned by the applicant) and deposited in the open channel between lots 13 and 14. In the event the lake should exceed apacity, an outlet channel is proposed adjacent to Lot 11 to carry the overflow to H le Creek and the Preserve. Water service to the site would be provided either by he Purissima Water District or the California Water Service Company. Public trail easements from t e project site to the adjacent MidPeninsula Regional Open Space Distinct lands are proposed to extend through Lots 18, 19, 20, and 21. Public trail easements would also extend along the edge; of Lots 18 and 23 to provide trail access from the streets. These public trail easements would be approximately 10 feet in width and would generally follow existing unpaved paths that were once traveled by the former quarry t ucks. The applicant's request compri es several separate approvals by the Town: 1. Supplemental Environ ental Impact Report (SEIR) - The Planning Commission will need t determine if the Final SEIR (composed of the Draft SEIR and the Reppo se to Comments) is adequate and to make a recommendation to thecity Council as to the certification of the Final SEIR and its compliance with CEQA. The Commission must review and consider the Final SEIR before re ommendations to approve or deny the project can be made. Should the Planning Commission recommend certification of the Final SEIR, the attached Mitigation Monitoring and Reporting Program (MMRP) must also be adopted, and Fndings and Facts supporting the certification (not attached) must also be in icated. CEQA requires that for e ch significant avoidable j impact identified in the EIR, the Planning Commissi n must indicate what I measure(s) is proposed to mitigate the impact. .CE A further requires a written plan that describes each mitigation measure in t e EIR, and outlines who is responsible for seeing that the action is carrieout and at what stage in the development process mitigation must occur. he proposed mitigation measures are derived from the EIR and are contained in the Mitigation Monitoring and Reporting Program (MMRP). i For each significant unavoidable impact identified in the EIR, CEQA requires that, if the Project is approved, a "statement of overriding considerations" be made. The Commission and Council must first determine why mitigation is "infeasible", and then,must balance the benefits of a proposed project against Lands of Vidovich • September 7,1995 Page 5 its unavoidable environmental risks in determining whether to approve a project. If the Commission recommends approval of the project, it must find that the benefits outweigh the unavoidable significant impacts. If this is the case, staff will develop Statements of Overriding Considerations to be recommended for adoption at a subsequent meeting. Specific issues outlined in the SEIR are analyzed in the DISCUSSION section of this staff report. 2. General Plan Amendment - The proposed General Plan amendment (GPA) includes minor text and map changes in order to make the Town's General Plan internally consistent regarding the Neary Quarry. These changes are included as an attachment to the staff report. 3. Pre-Zoning - The proposed project includes the annexation of the 78-acre site to the Town of Los Altos Hills. The site is presently in an unincorporated area of Santa Clara County. Upon its annexation, the site is proposed to be zoned by the Town as R-A (Residential-Agriculture). Specific issues of the proposed pre-zoning are analyzed in the DISCUSSION section of this staff report. 4. Tentative Subdivision Map - The tentative subdivision map and supporting materials indicate the proposed lot and roadway layout, and geologic, engineering and improvement details for the subdivision. After a tentative map has been approved, even more detailed engineering materials will be submitted with a final subdivision map which must be approved by the City Council prior to any development o'n the site. A number of detailed conditions of approval have been recommended for the proposed tentative map. Many of these are noted in the .DISCUSSION section relevant to issues of concern, and al, complete set of conditions is included as an attachment to the staff report. Additionally, mitigation measures recommended in the EIR have been incorporated into a Mitigation Monitoring and Reporting Program which is also included as an attachment to the.staff report. The project also would require expansion of the Urban Service Area (USA) prior to annexation, in order to include the, 78-acre project site within the service area for the Town of Los Altos Hills. These proceedings come under the authority of the Santa Clara County Local Agency Formation Commission (LAFCO) and are pending action regarding project approval, particularly certification of the Final EIR. Lands of Vidovich September 7, 1995 Page 6 DISCUSSION This section h1as been ar anged to discuss each approval separately: the Environmental Impact Repot (EIR), General Plan Amendment (GPA), Pre-zoning, and Tentative Subdivision ap. Required findings and conditions of approval (COA) for each element of th- proposed project are disicussed within this section. A. Envir.nmen .1 Im. . Re• •rt EIR The Final Supplemental EIR FSEIR) consists of the following elements: 1. Draft Supplemental EIR or the Quarry Hills Subdivision, March 1995 (with reference to the Final EI' for the Quarry Hills Residential Subdivision, April 1989). 2. Response to Comments and Draft Mitigation Monitoring and Reporting Program, August 1995. Public hearings were held be ore the Planning Commission on April 12 and April 26, 1995, to accept commen s on the Draft Supplemental EIR. Following these hearings and subsequent to r-ceiving additional inforration from the applicant, the Response to Comments docu ent has been prepared. The public hearing on the EI was closed on April 26th and the final documents are now before the Commission. The Planning Commission must determine whether to recommend to the City Council certification of the EIR, i.e., that the documents fulfill all of the requirements of CEQA. The City Council will have to make two findings in order to certify the EIR: 1. The Final EIR has been completed in compliance with CEQA. 2. The Final EIR reflect- the independent judgment of the Town and the information contained i the Final EIR was reviewed and considered prior to action being taken on t e project. These findings encompass b th the public notice and processing requirements of CEQA as well as an acknowle o gment that the EIR adequately addresses the potential impacts of the proposed •roject and evaluates rieasonable alternatives and mitigation measures. The proposed project may not be approved until these two findings can be made. Lands of Vidovich September 7,1995 Page 7 EIR Issues The following potential environmental impacts were analyzed and discussed in the Draft SEIR: • Land Use. • Transportation.and Circulation • Geology, Soils,.and Seismicity • Hydrology and Water Quality • Vegetation and Wildlife • Utilities and Urban Services • Visual and Aesthetic Quality j • Air Quality • Noise • Cultural Resources • Hazardous Materials • Public Safety Issues The Draft SEIR identified potentially significant impacts for each of the topics listed above. The attached EIR Summary of Impacts outlines expected impacts and proposed mitigation measures for each topic. All potentially significant impacts would be mitigated to a level of insignificance based on the proposed mitigation measures except for the following impacts which were found to be significant and unavoidable: • Land Use - loss of State-designated mineral resource of significance (project-specific) • Loss of Open Space (cumulative) • Transportation and Circulation- access to Lots 19-21. Because of the existence of significant unavoidable impacts, the Commission and City Council must adopt Statements of Oyierriding Considerations if the Tentative Map is approved as proposed. If the Commission and Council delete proposed mitigation measures for other impacts, a Statement of Overriding Consideration may have to be made for each of those impacts as well. Statements of Overriding Considerations will be prepared prior to the Commission's final action: Similarly, findings of fact will not be presented until the Commission has provided further direction regarding its recommendations to the Council. For a summary of all potentially significant impacts and recommended mitigation measures, refer to the Mitigation Monitoring and Reporting Program (MMRP) included as an attachment to this staff report. All mitigation measures included in the MMRP will become conditions of approval for the proposed project if it is approved. B. General Plan Amendment The Planning Commission must make a recommendation to the City Council with respect to the requested amendment to the General Plan. The recommendation may be for approval, approval with modifications, or denial. 1 1 Lands of Vidovich September 7,1995 l Page 8 The applicant requests text nd map amendments to the Town of Los Altos Hills' General Plan and Land Use ap. These amendments would designate the site as residential and would delete references to the existence of an active quarry on the project site. Proposed text changes include amendments to the Land Use Element, Open Space Element, Recreation Element, and Conservation Element, which all refer to the Nearly Quarry as flan active quarry site and/or the site's designation and future use as open space pre•erve. The map designation would change from Open Space Preserve (OSP) to Resid-ntial Very Low to Low Density (R(V-L)). The proposed text and map C anges, as well as related findings, are included as an attachment to the staff report. 1 I C. Pre-Zoning 1 The project site currently 1 es within the jurisdiction of Santa Clara County. Concurrent with approval of the Tentative Map (but prior to annexation), the applicant requests pre-zon ng of the project site to the R-A (Residential- Agricultural) zoning district. The pre-zoning simply indicates what the project site is intended to be designate. once annexation occurs. Subsequent to project approval, but concurrent w th finalization of the Subdivision Map action, the applicant requests annexation of the project site to the Town of Los Altos Hills. A recommended condition of pproval would require the applicant to consent to annexation of the site not late than 30 days after approval of the tentative map, and anticipates that annexation ould be completed prior to final map approval and commencement of any devel pment activities. Annexation requests are ty ically considered by the Local Agency Formation Commission (LAFCO), which is generally concerned that development is occurring in a logical manner and that public services and utilities can be provided to the project site without economi ally burdening the Town and service providers. In this case, howevr, if the property owner consents to annexation and if the property lies within the Town's Sphere of Influence (it does) and Urban Service Area (it does not), the Town may conduct a nexation proceedings without LAFCO review. The Town has initiated LAF 0 proceedings for expansion of the Urban Service Area (USA), as prerequisite t annexation of the property. The USA application is on file and is being processed by LAFCO at this time, but awaits finalization of the EIR before action. D. Tentative Subdivision Ma • The tentative subdivision ap application was submitted to the Town in November of 1994 and since that time has undergone extensive review by Town planning and engineering st ff, Town geotechnical and engineering consultants, and Town committees. Duni g the course of this review, changes or modifications Lands of Vidovich • September 7,1995 Page 9 to the project have been suggested.. Recommended changes are incorporated into the proposed Conditions of Approval (COA) for Planning Commission consideration. Prior to approval of the tentative map, the conditions may be accepted by the Commission and Council as written, may be modified or deleted, or additional conditions may be imposed. Findings Before a tentative subdivision map can be approved, the Town must find that the proposed subdivision, together with the provisions for its design and improvement, is consistent with the General Plan. In addition, the Town should make a "housing balance finding" as required by Government Code Section 66412.3 and a finding relating to future passive or natural heating or cooling opportunities as required by Section 66473.1. If the Town makes any of the following findings with respect to the project, it shall deny the tentative map: • The proposed map or the design or improvement of the proposed subdivision are inconsistent with the General Plan. • . The site is not physically suited, for the proposed. type or density of development. If the site is not suited for the proposed density or population or structures, the legislative body may approve the map with conditions that will reduce the density. • The design of proposed improvements are likely to cause substantial environmental damage, or substantially and avoidably injure fish, wildlife or their habitats, or cause serious public health problems. The map may be approved if an environmental impact report was prepared and appropriate findings are made that specific economic, social or other considerations make infeasible the mitigation measures 'or project alternatives identified in the EIR. • The design,or types of improvements of the subdivision will conflict with public easements for access through or use of, property within the proposed subdivision. The Town may approve the map if alternative public easements will be provided. • Discharge of waste from the proposed subdivision would violate existing requirements prescribed by a regional water quality control board. Also, the Town shall disapprove a map for the applicant's failure to meet or perform any of the requirements or conditions imposed by the Map Act or local ordinance pursuant thereto.. In approving or disapproving a map, the Town shall Lands of Vidovich September 7,1995 ' Page 10 apply only those ordinanc s, policies or standards in effect at the time the application was deemed com Tete (November 1994), with certain exceptions. Tentative Map Issues The Tentative Subdivision lap before the Planning Commission represents "the project" as submitted. Staff nd the Town's technical consultants (civil engineers Wilsey & Ham and geotechnical consultants William ;Cotton and Associates) have reviewed the map extensivey. The items discussed 1 below represent key issues which need to be resolved pri r to action on the tentative map. These items should be addressed to the satisfac-ion of the Planning Commission by accepting the applicant's proposal, by imposing relevant conditions of approval, or by recommending project modifications. The format for the following -ections includes a discussion of each key issue (staff's comments/concerns about what the applicant has proposed), staff's recommendation Ii egarding th.t issue, and relevant conditions of approval. 1. Emergent Access The Town's General Plan desi:nates Stonebrook Drive as a "through" roadway, but it is currently a private street on the Magdalena end. ' Emergency vehicle access is necessary, howevller, to provid- a second means to get to and from the site should a medical' emergency or natur:1 disaster occur, as there would otherwise be 23 residences with access limi ed to one cul-de-sac street. The connection of Stonebrook Avenue from Magdalena Road in the southeast (unincorporated Santa Clara County) to the subdivison is proposed as the emergency access route. The current roadway width of thi. segment of Stonebrook Avenue is only 15-18 feet, whereas the Los Altos Fire Dpartment requires a 20 foot width, allowing for two fire engines to pass each oth r. Widening of the roadway over approximately a 1,000 foot distance would res It in alteration of someexisting mature vegetation (including two large oak .tres) along the roadway, some of which provides screening from adjacent prope ties to the Quarry. This portion of roadway also runs close to the top of a nearly vertical cut at the southerly quarry wall. . The a licant is not presently proposing measures to widen the road or to mitigate potenLtiial instability of this area, although the applicant's geotechnical consultant, Alan Kropp Associates (AKA)1 has recommended remedial grading of that area, which w.uld also require extensive loss of vegetation on the north side of the road. In the ourse of staff review, William Cotton and Associates (WCA) concluded that correcti e grading is appropriate adjacent to this roadway to provide adequate protection of the roadway for emergency access. WCA determined that future landsliding, poss bly triggered by seismic conditions or significant rainfall, may interrupt use of t is roadway, and concluded that there is a "moderate" • Lands of Vidovich September 7,1995 Page 11 level of risk that future seismic activity could render this roadway impassable unless corrective measures are implemented. A further complication arises in that the roadway is apparently a private road, and lies within the jurisdiction of Santa Clara County. The applicant could, however, widen the road on his side of the street, and could offer to dedicate additional right- of-way to the County to accommodate widening and slope stability improvements. If the Town determines not to require widening or not to require corrective grading, the resultant impacts identified in the EIR would then be considered significant and a Statement of Overiding Considerations would be required to be adopted by the Town for each impact (circulation and slop stability). Recommendation: Require the dedication of additional right-of-way, that the emergency access! road pavement be widened to 20 feet, except for areas where mature trees exist (road may be narrowed to accommodate trees), and that corrective grading measures be implemented to assure stability of the roadway. Conditions of Approval • The Final Map shall include an offer to dedicate sufficient right-of-way (a minimum of 10 feet and, if necessary, slope easements) to Santa Clara County on the north side of Stonebrook Avenue on the applicant's property to accommodate widening of this segment of roadway (approximately 1,000 linear feet) to a minimum 20 foot width, and to perform corrective grading work (as recommended by.Alan Kropp Associates) and required drainage and other improvements in the right-of-way. The area shown for dedication shallbe to the satisfaction of the City Engineer and County authorities. • Prior to approval of the.Final Map improvement plans shall be submitted, for approval by the City Engineer and the Town's Geotechnical consultant, detailing the corrective grading work outlined by the applicant's geotechnical consultant for the southern Quarry rim adjacent .to Stonebrook Avenue. Improvement plans shall also include revegetation of the graded area, including trees for screening, to the satisfaction of the Planning Director. Grading improvements, and revegetation shall be completed prior to final mapapproval, unless an improvement agreement and related bonding is approved by the City Council. • • Prior to approval of the Final Map, improvement plans shall be submitted, for approval by the City Engineer, indicating the widening of the Stonebrook Avenue pavement to a width of 20 feet. Where such widening would damage heritage oak.trees, the pavement width shall be narrowed to avoid Lands of Vidovich September 7, 1995 Page 12 substantial impact to he trees. Improvements shall be constructed prior to final map approval, unless an improvement agreement and related bonding is approved by the City Council. 2. Abandonment of Portion of Stonebrook Drive (Lots 1-4) The proposed method of a cess to the subdivision is from Stonebrook Drive southerly of its intersection ith Prospect Avenue. "A" Street would become the primary access into the subdi ision with cul-de-sacs "B" and "C" serving the lots. Presently there is a 40 foot ri;ht-of-way from Stonebrook Drive that provides access to off-site parcels northerly :nd westerly of Lots 1-4. The applicant intends to abandon his half (20 foot wi•th) as part of the subdivision. Staff believes that the right-of-way is private, and that easements would need to be abandoned by the property owner's that hold rights to the existing right-of-way. While those properties are intended to be served by new streets "A" and "C", abandonment of those easements needs to occ r prior to approval of the Final Map, or the right-of- way should remain availabl•, and the lot sizes reduced accordingly. Also, new easements may need to be -stablished from the proposed subdivision to allow continued access. Recommendation: Req ire that abandonment of easements be finalized and any needed new easements be conveyed prior to approval of t e Final Map. or that the existing right-of-way remain available. Conditions of Approval • Prior to approval of the Final Map, the applicant shall finalize the abandonment of access -asements for right-of-way to the rear of Lots 1-4, and shall provide addition.l easements as necessary to accommodate continued access to off-site prop-rties. Alternatively, the applicant may retain the existing right-of-way a d shall indicate on the' revised Tentative and Final maps redueed lot sizes f•r those Lots 1-4. 3. Access to the Lake and inside Lots Lots 18, 22 and 23 are constr;ined by access limitations, but access appears to be feasible for these lots. Lots 19 21, however, present unique design issues that cannot be mitigated without significant redesign. The primary 'concern is with regard to the steepness of the driveways) and associated cut and fill. The proposed street/driveway grades to the•e lots is excessive (up to 19%), would heavily impact existing trees, and would creat- a serious hazard for stopping at the intersection with Street "C", especially in we I weather. Attempting to flatten the grade of the Lands of Vidovich September 7,1995 Page 13 driveways serving these lots would require significant grading and retaining walls, contrary to the Town's development standards and policies. Wilsey & Ham recommend a maximum driveway slope of 6% for a distance of 40 feet where the driveway approaches "C" Street. This can only be accomplished for these lots if "C" Street is moved northeasterly, constraining Lot 17. Lot 17 also contains the most appropriate access to the, Lake for vehicles and boats, and is a likely candidate for trail access parking. Lots 20 and 21 also have significant development constraints due to tree cover and open space concerns (see discussion of building site feasibility). The realignment of "C" street (eliminating Lot,17) and the elimination of lots--20 and 21 would allow for a single driveway to lot 19, with a safer transition from "C" street. If the Town determines to allow access to Lots 19-21 with steep grades or excessive cuts and fills, a Statement of Overriding Considerations will be required, as the EIR identifies this concern as a significant unavoidable impact. Recommendation: Direct the applicant to move that portion of "C" Street from its intersection with "B" street easterly to provide the recommended flat area for adequate vehicular transition to the hillside area for Lot 19. The effective result will eliminate the ability to develop Lot 17 for residential uses but will provide a safe lake access and maintenance facility staging- area. Lots 20 and 21 should be eliminated, to eliminate the safety concerns and environmental 'impacts regarding a roadway or joint driveway to those properties. Conditions of Approval ; _ • Prior to Final Map approval, the applicant shall submit a revised Tentative Map indicating the elimination of Lots 17, 20 and 21. Street "C" shall be realigned to provide direct access_ to the.lake along the route of the existing roadway and to provide adequate transition for the driveway to Lot 19. Lot 17 shall be combined with Parcel A and used for lake access and maintenance, and for recreational and parking uses to serve the subdivision residents and for public trail access. The revisions shall be reflected on the Final Map. • The revised Tentative Map shall also demonstrate that the driveway grade for Lot 19, as it approaches Street C, will not exceed a maximum of 6% for at least 40 feet from the street, and that driveway grades are reduced to the maximum extent practicable, to the satisfaction of the City Engineer. Lands of Vidovich September 7,1995 Page 14 4. Stability of Quarry Wal The quarry wall adjacent to .tonebrook Avenue along the southerly boundary of the property is of concern du- to its steepness and potential instability. Protective measures are necessary to a.sure the stability of the street above, to preclude pedestrians, animals and au omobiles from falling down this steep cut, and to protect persons below from slides and rockfalls. The applicant's geotechnical consultant has recommended emedial grading work on this slope, and the EIR and Quarry Reclamation Plan r:commended landscape plantings on the wall for stabilization. Fencing at the top of the wall would also enhance safety for those traveling along the roadway. his remedial repair, if required, should be completed in conjunction with the wi.ening of Stonebrook Drive. Again, if the Town determines not to require the remedial grading, 'a Statement of Overriding Considerations will be requires. A separate section of this report discusses the issue of access to the lake. 1 Recommendation: Require corrective grading, landscaping, and fencing to provide enhanced stability for i the emergency access route and to mprove safety for those using the road above and the quarry 'rea below. Conditions of Approval • Prior to approval of th- Final Map, improvement plans shall be submitted, for approval by the Citi Engineer and the Town's Geotechnical consultant, detailing the corrective trading work regarding the quarry wall, as outlined by the applicnt's geotec nical consultant. Improvement plans shall also include revegetation of the graded area, including trees for screening, to the satisfaction of the P anning Director. Grading improvements and revegetation shall be ompleted prior to Final Map approval, unless an improvement agreeme t and related bonding is approved by the City Council. • Prior to approval of th Final Map, the applicant shall fence the top of the quarry wall from the e d of Street "C" to Magdalena Avenue and along the rear of those lots alon the east end of the subdivision boundary, where feasible. The weight, type and location of this fence shall be subject to review and approval of the Town Planner and City Engineer. • Prior to approval of t e Final Map, the applicant shall submit with the • improvement plans, det ils of proposed stabilization plantings of the quarry wall, as recommended b a licensed Landscape Architect, and to be reviewed and approved by the Panning Director, the Town's arborist or landscape architect, and the Tow 's geotechnical consultant. The plantings shall be . I Lands of Vidovich September 7,1995 Page 15 installed prior to Final Map approval, unless an improvement agreement and related bonding is approved by the City Council. 5. Debris Basin The Environmental Impact Report and the Town's consultants have identified the potential for debris flows to 'originate within the subject property and travel downslope, adversely impacting existing off-site residences. Lot 21, as proposed on the Tentative Map, is constrained.by debris flow hazards. A significant portion, of the proposed relocated building envelope is still situated within the debris flow/colluvial fan deposits (Qc) mapped by Harlan Tait Associates. Specific site grading measures, resulting in elevation of the building pad as recommended by the applicant's geotechnical consultant, are an integral part of the safe development of this lot. Potential future debris flows originating within swales #1, #4 and #5 (i.e., locations as defined in the Harlan Tait Associates.Report of May 10, 1991) were identified as having a moderate to high potential for adversely impacting existing residential parcels adjacent to the subject subdivision': Mitigation measures to address hazards from swales #4 and #5, previously detailed by Alan Kropp Associates, include construction of a debris flow.retention basin within 'the subdivision property (i.e., in the northwestern portion of Lot 21). According to William Cotton and Associates, the conceptual debris basin design proposed in the northwestern portion of Lot 21 appears adequate. However, the crest height of the proposed berm (shown at. 15 feet above the existing grade) could probably be reduced to less than 10 feet considering that it is located considerably downslope, and at a much wider point. in the swale than a previously proposed berm (also designed with a 15-foot crest height). The EIR and the applicant's and Town's consultants also recommended that the potential for debris flows be disclosed to affected property owners, including the MidPeninsula Open Space District. Recommendation: Require the installation of a debris basin along the northwestern boundary of the Lot 21, and that the applicant disclose the debris flow hazard to all potentially affected property owners. Conditions of Approval • Prior to approval of the Final Map, improvement plans shall be submitted detailing plans for construction of a debris basin at the northwestern boundary of Lot 21. . The plans should minimize the height of the berm for. Lands of Vidovich September 7,1995 Page 16 the basin and shall include plans for landscaping the fill and other disturbed areas. Plans must be eviewed and approved by the Planning Director, City Engineer, and the To n's geotechnical consultant. The debris basin and related landscaping m st be installed prior to Final Map approval, unless an improvement agreem nt and related bonding is approved by the City Council. • Not later than 30 days fter approval of the Tentative Map, the applicant shall notify in writing theid-Peninsula Regional Open Space District and all private property own rs potentially impacted by debris flow hazards, as identified by the appli ant's geotechnical consultants. The form and content of the notification sha i1 be approved by the Planning Director and the City Attorney. • Prior to approval of he Final Map, the applicant shall submit a revised Tentative Map, depicting building envelopes and debris flow building exclusion zones on 11 of the hillside lots (18-23), consistent with the recommendations of the applicant's and the Town's geotechnical consultants. The building exclusio I zones shall also be reflected on the Final Map. No residential constructio shall be allowed within the building exclusion zone unless a detailed lot-s ecific geotechnical investigation is performed, to the satisfaction of the T wn's geotechnical consultant, to demonstrate the feasibility lof constructi n with appropriate mitigation measures. • Prior to approval of t e Final Map, an appropriate final pad elevation and proposed site grading lan for Lot 21 shall be prepared and accepted by the applicant's geotechnica consultant, and reviewed and approved by the City Engineer and Town ge technical consultant. • Prior to Final Map a proval, Study Plan #4, delineating final building envelopes and driveway alignments, as identified by the applicant's geotechnical consultat, shall be modified with the above changes and submitted for approva by the City Engineer and the Town's geotechnical consultant. The geo chnical consultant shall certify in writing that the recommendations of the plan are reflected in' the proposed improvement plans. 6. Other Geotechnical Issues Lots 1 through 17 are generally considered feasiblefor development given the existing slopes and the mitig tion measures suggested by the EIR and the Town's consultants. However, sig ificant differential fill ;thickness beneath proposed building sites may result i the need for special;' (non-standard) residential foundation design due to var'ous on-going site grading activities which were not fully inspected or approved y the applicant's geotechnical consultant. William i 1 1 Lands of Vidovich September 7,1995 Page 17 Cotton and Associates (August .8, 1995 letter attached) has recommended that preliminary foundation recommendations be provided prior to Final Map approval. Progress Report #5, prepared by the applicant's geotechnical consultant to document site grading, contains a list of 11 site reclamation/grading operations that were not within their scope of inspection services. ;It is important that all portions of the property are presented for public or private use in a safe condition, and therefore William Cotton and Associates .has recommended that the geotechnical consultant identify any necessary corrective grading required prior to Final Map approval. Recommendation: Require that the applicant's geotechnical consultant provide preliminary foundation recommendations and identify any necessary corrective grading prior to Final Map approval. Conditions of Approval • Prior to approval of the Final Map, the applicant's geotechnical consultant shall submit preliminary foundation recommendations to define the general type of residential foundation deemed appropriate for each proposed lot. The potential need for any unusually deep or rigid foundation systems shall be addressed. The range of differential'fill thickness across proposed building envelopes shall be quantified as part of this evaluation. Any requirements for fill settlement monitoring prior to construction shall be addressed. The report recommendations shall be prepared to the satisfaction of the City Engineer and the Town's geotechnical consultant. Any recommendations for unusual foundation design shall be included in the CC&R's for the subdivision. • Prior to approval of the Final Map,I the applicant's geotechnical consultant shall identify the extent of necessary corrective grading;activities resultant from ongoing grading on.the site. ; The report shall be prepared to the satisfaction of the City Engineer and the Town's geotechnical consultant, and any corrective grading must be included on the improvement plans. • Prior to approval of the Final Map,'the applicant's geotechnical consultant shall review all proposed improvement plans and shall certify in writing that such plans are consistent with all geotechnical recommendations. The geotechnical consultant's.review shall include, at a minimum, all proposed grading and drainage, and all geotechnical mitigation measures. 7. Drainage . The applicant proposes to convey drainage from the subdivision to the lake and to Hale Creek. On-site drainage would be transported_ primarily through a series of "roadside ditches" to a channel outlet to the lake between Lots 13 and 14. Off-site Lands of Vidovich September 7, 1995 Page 18 drainage from areas to the w-st would be conveyed to a drainage pipe and ditch at street "C" to street "B" and t en to the outlet channellbetween Lots 13 and 14. Off- site drainage from the area to the north, which presently flows to Hale Creek, would be transported in a by-pass c annel along the rear of Lots 5 through 10 to Hale Creek. Drainage from Prospect Av:nue would be conveyed via a pipe from Stonebrook Drive between Lots 7 and 8, t rough an existing well site, again to the outlet channel between Lots 13 and 14. Fi ally, an outlet channel would be provided adjacent to Lots 10, 11 and 12 to carry o erflow to Hale Creek Juan Prado Mesa Preserve in the event that the lake level exceeds its capacity. Small sections of storm drain are also proposed to carry wate under the intersection of Streets C and B and under Stonebrook Drive at various •oints. While the lake will act in a •eneficial manner as a flood protection facility for the surrounding area, staffand the Town's consultants are concerned about several elements of the drainage system. First, there is significant potential for erosion and siltation in the roadway ditc es (and possibly flooding) if they must carry drainage from off-site, pa iiticularly from the area to the west. Wilsey & Ham have suggested that the roadside ditches be used to handle only "local drainage" and not as a method to channel large amo nts of off-site flows through the site to the lake. The off-site drainage through Lot 23 should be conveyed to the Lake via a storm drain pipe to an outlet at the weste n corner of the lake, not in the roadside ditches. The pipe should be sized to accom odate drainage from a 100-year storm. The by-pass channel must c ntinue to provide flows to Hale Creek, and as such should be lined (with clay o other impervious material) to prevent seepage into Lots 5-10. The by-pass chap el and the lake overflow channel should both be sized to accommodate drainage from a 100-year storm. The pipe from Prospect Avenue via Stonebrook Drive, betwee Lots 7 and 8, would be located through a well site, which is not own' ed by the a•plicant. This drainage (facility could be realigned to avoid the well site, and shoul• accommodate a 25-year storm flow. In addition, staff suggests that the proposed op-n channel between Lots '13 and 14 be placed in a pipe underground to avoid draina•e impacts on those lots, and that a drainage easement be dedicated behind Lots 1-4 �o accommodate drainage from upsiope lots, if needed upon development. Most of the open drainage c annels and enclosed pipes carrying off-site drainage must accommodate 100-year torm flows, except that some of the short sections of pipe carrying only localized o -site drainage may be designed to carry 25-year storm flows, and the pipe from the rospect Avenue drainage may be designed for the 25- year event, as larger events wi 1 not drain toward the lake. These design parameters • can be verified by the City En,ineer at the time improvement plans are submitted. 1 In addition, the subdivision i subject to the provisions of the Santa Clara County NPDES (non-poi t source pollution) general permit, requiring submittal of a Notice Lands of Vidovich September 7,1995 Page 19 of Intent and Stormwater Pollution Prevention Program to the State and to the Town, prior to construction. Recommendation: Require that the;, drainage system be revised as per the above suggestions, and that the City Engineer verify the capacity of drainage facilities in the review of improvement plans. Conditions of Approval • Prior to approval of the Final Map, a revised Tentative Map shall be submitted which: 1) conveys drainage in an underground pipe, rather than an open channel, from Lot 23 to the western corner of the lake; 2). conveys drainage in an underground pipe, rather than an open channel, between. Lots 13 and 14; 3) relocates the drainage pipe between Lots 7 and 8 to avoid the private well site, to the satisfaction of the City Engineer; and 4) provides a drainage easement to the rear of lots 1-4. All drainage easements shall be a minimum of 20 feet in width. The changes shall be reflected on the Final Map, with appropriate dedication of;easements. • Prior to approval of the Final Map, improvement plans shall be submitted,. detailing the construction plans for all drainage facilities, and demonstrating that all facilities can accommodate 100-year storm flows, with the exception of short sections of channels or pipes carrying only localized on-site drainage, and the Prospect Avenue drainage pipe, which may be designed to handle 25- year flows. The design of the by-pass channel shall include an impervious lining (concrete is not an acceptable material), and the plans shall demonstrate that adequatemeasures to control erosion and siltation on the proposed roadside ditches will be incorporated. Plans shall be reviewed and approved by the City Engineer. Drainage improvements must be installed prior to Final Map approval, or an improvement agreement and related bonding must be approved by the City Council. 8. Lake Water Quality, Access and Maintenance The lake is proposed as a private facility which will be a receptor for drainage from off-site including, insome cases, from public roadways. Water from off-site, primarily from existing Prospect Avenue] and Stonebrook Drive to the north and from the area northwesterly of Lots 1 and 23 will drain to and through the site. These flows have the potential for depositing pollutants into the privately-owned lake. The City Attorney has requested that a hold-harmless agreement be developed to assure that no liability is attributed to the public for potential adverse impacts to the lake. Lands of Vidovich . September 7, 1995 Page 20 I A 1988 Lake Management Plan, updated in 1994, propoIsed a number of measures to protect lake water quality re ative to sedimentation and erosion controls, debris, excessive plant growth (algae , and insect vectors (mosquitoes and midge fly larva). The EIR elaborated on sever 1 of these as proposed mitigation measures. These controls should be incorpor ted into construction practices and CC&R's for the subdivision residents. Another measure to protect lake water quality could include the incorporation of oil and g ease traps into the storm drain system, although such controls have little benefit in filtering nutrients and chemicals from fertilizers and pesticides. The Lake Management Plan al.o suggested that, for aesthetic reasons, the lake could be filled by the applicant (or .ubsequently by the homeowners) when it reached a low point. While this may ssmetimes be a realistic possibility, staff does not feel that filling of the lake should o ccur during drought periods when water rationing is in effect. The Lake Manage ent Plan indicated that !filling was not necessary for health and safety purposes. Staff is also concerned regardi g the provision of access to the lake for maintenance and emergency purposes. The only roadway adjacent to the lake itself is the cul-de- sac at the end of "C Street. he slope from "C" Street down to the lake edge is, however, too steep to accom odate motorized vehicles. There is an existing road down to the water surface thr ugh Lot 17, which could be utilized to provide access for emergency personnel and aintenance vehicles. It would be logical to utilize this existing access point for the maintenance and safety of the lake, but would eliminate Lot 17 ads a building ite. 1 As mentioned previously, there is a potential for sloughing or rocksliding from the steep quarry walls above the 1 ke to the banks below. As the lake could become an attractive nuisance for childre , hikers, etc., staff feels that access to the lake should be limited to emergency and aintenance purposes only. Maintenance of the lake, as a private facility; will fall under the auspices of the subdivision's Homeowners A sociation. Maintenance will include periodic clean- up of debris and vegetation, i sect control, aesthetic improvements, and occasional application of chemicals or pesticides. The feasibility of the Homeowners Association to fund and impl merit the required level'of maintenance for the lake needs to be documented in a manner to provide assurance that the lake will not become a health or safety hazad to the community. I. Recommendation: Requ re that the lake be privately owned and maintained, • and hat a hold-harmless agreement be executed regarding the own's liability for off-site water quality impacts on the ake; that the measures outlined in the Lake Man gement Plan and the hold-harmless agreement be incorporated into the subdivision's CC&R's; that access to the I ke be provided through Lot 17 , eliminating that lot as a uilding site; that fencing and signing of the lake be Lands of Vidovich September 7,1995 Page 21 provided to preclude access, other than for emergencies and maintenance purposes; and that lake maintenance responsibilities be clearly assigned to the Homeowners Association, including a mechanism for funding • maintenance activities. Conditions of Approval • Prior to approval of the. Final .Map, a hold-harmless agreement shall be recorded, applicable to all future owners of property in the subdivision, releasing the Town of Los Altos Hills from any, liability associated with water quality impacts potentially caused by drainage from public facilities. The agreement shall be prepared by the City Attorney, and shall be signed by the applicant and notarized prior to recordation. • Prior to the approval of the Final Map, the applicant shall prepare CC&R's outlining the responsibility of property owners in implementing the recommendations of the 1994 Lake Management Plan and the EIR mitigation measures, and acknowledging the hold-harmless agreement noted above. The CC&R's shall also prohibit boats,on the lake, other than for emergency or maintenance purposes. The applicant shall also prepare a maintenance agreement, detailing the responsibilities of the Homeowners Association, including a funding mechanism, for the maintenance of the lake, as per the 1994 Lake Management Plan. The CC&R's and maintenance agreement shall be submitted for review and approval by the City Engineer, Planning Director, and City Attorney, prior.to recordation. • Prior to approval of the Final Map, a revised Tentative Map shall be submitted relocating street "C" as necessary and providing for an easement for access to the lake for emergency purposes only through the combined Lot 17 and Parcel A. The realignment and easement shall be:reflected on the Final Map. • Prior to approval of the Final Map,'" improvement plans shall be submitted which outline details of the access road to the lake, and fencing, gates and signage around the lake, prohibiting access for all but emergency and maintenance purposes, other than along the rear of Lots 12 through 16. Drainage plans should incorporate debris grates and, if determined feasible by the City Engineer, grease traps into inlet or outlet structures. Plans shall be submitted for the review and approval of the Planning Director and the City Engineer. Improvements must be installed prior to Final Map approval, or an improvement agreement and related bonding must be approved by the City Council. . Lands of Vidovich September 7, 1995 Page 22 9. Hale Creek Staff, other public agencies, and the public has expressed concern that existing flows to Hale Creek be maintains to protect the riparian vegetation along the creek, especially through the Juan Prado Mesa Preserve. j The EIR requires protective measures to assure that no adverse drainage or sewer construction impacts are caused by the project, and th.t restoration of the riparian environment of the creek, per the Quarry Reclamation P an, be a condition of subdivision approval. The project proposes to maint:in flows to the creek byFusin a lined by-pass channel P P ; g Y-P to the rear of Lots 5-10, and •.taff other erosion control mechanisms should prevent erosion of the creek. Recommendation: Req ire that the by-pass' channel be lined with an imp•rvious material, that, appropriate erosion and sedi entation controls be incorporated into the drainage outl•t to the creek, and that 1 the required elements of the Rec ►mation Plan be implemented. Conditions of Approval • Prior to approval of the Final Map, improvement plans shall be submitted for the review and appr•val of the City Engineer, outlining the details of construction of the by-1•ass channel, which shall include verification of the capacity of the channe and it lining with an impervious material, such as clay, which does no create an artificial appearance. Erosion and sedimentation control sl all be provided at the channel outlet to Hale Creek. The plans hall also in.lude details of sewer lin construction in the vicinity of the creek, and prot-ctive measures outlined;in the EIR. Improvements shall be constructed prior to Final Map approval, unless an improvement agreement and related bonding is approved by the City Council. • Prior to approval of th Final Map, a Hale Creek restoration plan shall be submitted, in accordan e with the Quarry Reclamation Plan, for review and approval by the Planni g Director and the City Engineer. The plan shall be implemented prior t Final Map approval, unless an improvement agreement and related b ndingis approved by the City Council. 10. Maintenance of Draina e and Geotechnical Facilities The EIR and staff recommend tions will require long-term maintenance of drainage and geotechnical improvem nts to assure their effectiveness in minimizing environmental impacts. In articular, the project includes the lake and related access, the debris basin, corrective grading of steeply sloped areas, and a subsurface Lands of Vidovich September 7,1995 Page 23 interceptor for seepage on lots 5-10. All of these.facilities will require on-going maintenance by the Homeowners Association, or will become problems for the residents, and possibly for the public. As such, it is necessary that appropriate maintenance agreements be developed and enforced to assure continued maintenance of these private facilities. Recommendation: Require that maintenance agreements be developed and incorporated into the subdivision CC&R's to assure long- term maintenance of private drainage and geotechnical facilities. Conditions of Approval • Prior to approval of the Final Map, maintenance agreements shall be submitted and shall be incorporated into the CC&R's providing for the long- term maintenance of, at a minimum: the lake area and access to the lake, the debris basin, areas of corrective grading and revegetation, and the subsurface interceptor for seepage on lots 5-.10. The agreements shall provide mechanisms for sharing the costs of maintenance as well. The agreements and.CC&R's shall be submitted for review and approval by the Planning Director, City Engineer, and City Attorney, prior to recordation. 11. Building Site Feasibility Several of the proposed building sites are highly constrained by potential debris flows, subsurface seepage, steep topography, limited access, and/or extensive tree cover, and would result in a significant cumulative loss of open space. In particular: • Lots .21 and 23 are subject to potential debris flows, and the EIR: and the Town's geotechnical consultant have recommended mitigation measures to restrict building sites on those lots. • Access to Lots 19-21, as discussed previously, is unsafe as proposed and would likely involve extensive impacts on trees and grading. • Building sites for Lots 18-23, and particularly for Lots 20 and 21, would be located on steep slopes in highly visiblelocations, and would require substantial tree removal. The EIR recommends one-story homes on those. lots, siting below ridgelines, and a number of tree protection measures. • The location of Lot 17 would preclude appropriate vehicular access to the lake for emergency and maintenance purposes. Lands of Vidovich September 7, 1995 Page 24 1 • Lots 5-10 are potentially subject to subsurface seepage, which would affect the long-term viability of structures located there. The applicant's geotechnical consultant has provid d a preliminary design for a subsurface drainage system to resolve this p oblem. • The EIR suggests mitig tion measures to include:building setbacks from Hale Creek, and location of r sidences on Lots 6-8 to the area south of the by-pass channel. • The EIR identifies the umulative loss of open space from the development of this project, particula ly the hillsides, as an uniavoidable significant impact of the development. Reduced intensity of development on the hillside would not entirely miti ate this impact, but would enhance the open space element of the project. The following two provisions f the Town's Subdivision Code (Section 9-1.604) are relevant in evaluating the feasi ility of lot design: "(e) All subdivisions shall result in the creation of lots with adequate building sites wh.ch are capable of being developed or built upon while retaining the bas.c natural qualities of the lot. No subdivision shall create lots which are impractical for improvement or use due to the steepness of the t rrain, the location of watercourses, periodic flooding, earth movement, ize, shape, or other physical conditions. (g) On any lot inten ed for residential occupancy it shall be possible to provide safe ve icular access via a private or common driveway, conforming to the City standards, from a public or private road." Staff suggests that Lots 20 a d 21 should be deleted due to inadequate access, extensive impacts on trees, an. cumulative impacts on open space; and that Lot 17 should be eliminated to allow r-alignment of street "C" for adequate access to Lot 19 and to accommodate access to t e lake and parking for trail access. 1 Recommendation: Requ re the applicant to revise the Tentative Map to elimi ate Lots 17, 20, and 21;; Lot 17 should be combined with arcel A (the lake parcel) to be used for lake access, trailhead parking, and/or rcreation; Lots 20 and 21 shoul, be combined into a common area open space lot; require implementation of subsurface seepage control for Lots -10; and impose all of the restrictions outlined in the E R regarding building setbacks, heights, etc. 1 1 Lands of Vidovich September 7,1995 Page 25 Conditions of Approval • Prior to approval of the Final Map, a revised Tentative Map shall be submitted which eliminates Lots 17, 20 and 21 as building sites. Lot 17 shall be combined with Parcel A and utilized for lake. access, trailhead parking, and recreation. Lots 20 and 21 shall be combined into a common area open space lot (Parcel B). • Prior to approval of the Final Map, a final design shall be submitted by the applicant's geotechnical consultant for the subdrain system for Lots 5-10. The plan shall be incorporated into the subdivision improvement plans for review and approval by the City Engineer and the Town's geotechnical consultant. The subsurface drain shall be constructed prior to Final Map approval, unless an improvement agreement and related bonding are approved by the City Council. • Prior to approval of the Final Map, CC&R's shall be prepared which include all mitigation measures identified in the EIR related to building setbacks, heights, locations, and design and colors. The CC&R's shall be submitted for review and approval of the Planning Director and City Attorney prior to recordation. 12. Conservation Easements The Town's codes and policies encourage the provision of conservation easements where necessary to protect significant environmental features, such as steep slopes, extensive tree cover, areas_ of geologic hazard, and stream corridors. The upper hillside areas of this subdivision, including the upper portions of lots 18 and 19 and all of lots'20 and 21, exhibit steep slopes, extensive trees, and susceptibility to debris flows, and staff suggests they should be protected. Rather than establishing conservation easements, however, it would be preferable to tie these upper hillside areas together as a common open space lot (Parcel B), comprised of virtually all of proposed Lots 20 and 21, and the upper portions of Lots 18 and 19 (those lots may be reconfigured somewhat). This approach, rather than conservation easements, may also benefit the applicant as any liability for impacts from debris flows or rockslides, etc. would be attributed to the Homeowners Association rather than a single property owner. Recommendation: Require that areas ; on the upper hillsides be combined into a common area open space lot (Parcel B), comprised of all of Lots 20 and 21, and, the upper hillsides of.Lots 18 and 19. , 1 Lands of Vidovich , September 7,1995 Page 26 Conditions of Approval • Prior to approval of the Final Map, a revised Tentative Map shall be submitted, delineating a common open space lot (Parcel B) comprised of the upper hillside areas of l ots 18 and 19, and all of Lots 20 and 21. The revised layout shall be reflecte. on the Final Map, including stipulation of restrictions applicable to the operspace lot, such that orily trails and minimal brush . clearing would be permitted. These restrictions shall also be noted in the subdivision CC&R's. 13. Traffic on Stonebrook rive Members of the public have expressed concern regarding the increased level of traffic on Stonebrook Drive d e to the subdivision, both from construction vehicles, as well as the long term inc ease on Stonebrook and El Monte Road. The EIR addressed this issue and concluded that the increased traffic level would not have a significant impact on the streets in the area or on the affected intersections. The filling of the Quarry wish dirt severely damaged Stonebrook Drive between Prospect Avenue and the s bdivision entrance. Subdivision construction will further damage the street, ich provides the main'entrance to the subdivision. Staff suggests that it would be appropriate to require the applicant to reconstruct this portion of Stonebrook Drive. Another section of this report nd the EIR addressed construction period impacts. Recommendation: Require the street improvements as depicted on the prop' sed plan, including dedication of 60 feet of right-of- way for Stonebrook Drive adjacent to Lots 5-7, as well as the upgraded emergency access to Magdalena Avenue; and require that Stonebrook Drive be reconstructed bet een Prospect Avenue and the subdivision entrance. 1 Conditions of Approval • The Final � Map shall dedicate street right-of-way for Stonebrook Drive • • - adjacent to.Lots 5-7, suc that the right-of-way width is no less than 60 feet, to the satisfaction of the C'ty Engineer. • Prior to acceptance of the subdivision improvements, the applicant shall reconstruct Stonebroo . Drive from Prospect Avenue to the subdivision entrance, with a mini urn pavement width of 24 feet, along with any necessary drainage imp tovements, to the satisfaction of the City Engineer. Lands of Vidovich September 7,1995 Page 27 14. Public vs. Private Streets The applicant has requested that the proposed streets be private streets. However, the Town's Subdivision Code and road policy require that all new subdivisions be installed as public streets. Recommendation: Require that all road rights-of-way within the project be dedicated to public use and that all rights-of-way dedicated to the Town be a minimum width of 60 feet. Conditions of Approval • The Final Map shall include dedication of all road rights-of-way to public use; all internal roadways shall be dedicated to the Town of Los Altos Hills, and dedication as required for Stonebrook Avenue in the unincorporated area shall be offered to Santa Clara County. All rights-of-way dedicated to the Town shall be a minimum width of 60 feet. 15. Construction-related Impacts Concerns , regarding construction-related impacts have involved traffic on Stonebrook Drive and air and noise impacts affecting neighbors from construction of roads, sewers, and houses. The EIR has included a number of mitigation measures (#81-87) to address these concerns, including dust control, site clean-up and sweeping, vehicle speed, equipment maintenance, and limited hours of operation. Additionally, the Town has standard conditions of approvalrequiring repair to damaged roads, on-site construction practices, and hours of operation. Recommendation: Require that the EIR mitigation measures be implemented and that the Town's standard conditions of approval be incorporated into project review and approval for subsequent homebuilding. Conditions of Approval • Prior to approval of the Final Map, a Grading and Construction Operation Plan shall be submitted for review and approval by the City Engineer and Planning Director. The plan shall address truck traffic issues regarding dust, noise, and vehicular and pedestrian traffic safety; storage of construction • materials; placement of sanitary facilities; parking for construction vehicles; and parking for construction personnel. A debris box shall be placed on site for collection of construction debris. , Lands of Vidovich September 7, 1995 Page 28 • Prior to approval of he Final Map, the applicant shall provide the City Engineer with photog aphs of the existing conditions of Stonebrook Drive from El Monte Road to the property boundary, and of all pathways adjacent to the site. The applica t shall agree, as part of an improvement agreement, to inform the Town of ar_y damage and shall repair any damage caused by the construction of the project to pathways, private driveways, and/or public and private roadways prior to acceptance of subdivision improvements. 16. Pathways/Trails and T ailhead Parking The proposed project would enerate about 60-70 new residents in the Town of Los Altos Hills, creating further demand for recreation land access to the Town and regional trail systems. The id-Peninsula Regional Open Space District (MROSD), Town staff, avid the Path ays Committee have indicated concern over the pathways/trails proposed y the applicant for the subdivisions, including connections to adjacent MROD lands. Several issues have been raised: • The trails adjacent to Lot 18 and Lot 23 are too steep and are redundant with the existing road/tra 1 shown topographically on Lot 19 or along the panhandle to Lots 19-2 , if Lots 20 and 21 are eliminated. • The MROSD has reque ted that a parking area be provided as a staging area for access to the region 1 trail system. The District suggested space be provided for at least 4 cars, up o a maximum of 8 parking spaces. Lot 17 has been identified as an appr priate location for such parking, and, as indicated previously, could also be used for lake access and community recreational facilities to serve the subdivision. • The MROSD favored p acing a conservation easement over the upper hillside areas of Lots 18-22, exe uted in favor of both the Town and the MROSD, and allowing trail access th ough that area. • Regarding the existing rail on the McCullough property and its connection to the Juan Prado Mesa reserve (JPMP), an expanded easement is needed (20 feet) over the .northeas -rn corner of Lot 11, to facilitate this important native path connection. • Staff believes that then should not be a public trail around the lake, due to safety and liability concerns. There is no needed connection through the Lake to other trails. The ap.licant proposes lake trail access (private) only along those lots (11-16) which back up onto the lake. • The Pathways Committ•e recommended that access to Lot 11, currently 60 feet wide, be narrowed so as to prevent further subdivision of that lot and to accommodate a trail connection from the subdivision to JPMP. Staff suggests, Lands of Vidovich September 7,1995 Page 29 however, that the wider right-of-way is appropriate in the event of future subdivision, and that a trail, if desired, can readily be accommodated within the 60-foot right-of-way. • If the right-of-way behind Lots 1-4 is abandoned, a trail could be located within that area, but would result in some loss of privacy to Lots 1-4, and is redundant with the trail along the subdivision streets. Recommendation: Require the following modifications to the map regarding trails, most of which were prepared by the Pathways Committee Chairman and the MidPeninsula Regional Open Space District. Conditions of Approval • Prior to approval of the Final Map, a revised Tentative Map shall be submitted, eliminating the trails adjacent to Lots 18 and 23. Additional access to the Mid-Peninsula Regional Open Space District property along the southerly boundary of the site shall be provided from "C" Street along either the existing access point at Lot 19 or approximately where the joint driveway to Lots 20 and 21 is proposed (assuming these lots are eliminated). Existing roads and trails could be designated easements within the recommended common open space lot (Parcel B). The plan shall be submitted for the review and approval of the Planning Director and the Pathways Committee. • The revised Tentative Map shall also show a small parking area (for a maximum capacity of 6 cars) to be located on proposed Lot 17 (suggested to be combined with Parcel A), in conjunction with the realignment of "C" Street and the conversion of Lot.17 to recreation and lake access uses. This parking would be intended to provide traillead access, as well as to support users of the recreational amenities on-site. The revised Tentative Map shall be accompanied by a site plan for Lot 17, which delineates parking, lake access, and maintenance and/or recreational facilities, for review and approval by the Planning Director and City Engineer. • The revised Tentative. Map shall also indicate a trail easement and connection from the end. of "B" Street adjacent to Lot 10 and the outlet channel to the Juan Prado Mesa Preserve, and a 20 foot easement for the native path connection from the McCullough subdivision to JPMP. • The Final Map shall reflect all pathway easements as shown on the revised Tentative Map. • Prior to approval of the Final Map, improvement plans,shall be submitted detailing proposed trail construction. Plans shall include a Class IIB pathway 1 , Lands of Vidovich 1 _ ,, September 7, 1995 Page 30 along the frontages of Lots 1 through 10 (streets "C" and "B"), along Street "A", along the Street " " cul-de-sac and the Stonebrook Avenue emergency access route from Stre t "C" to the subdivision boundary, and along the pathway easement fr m Lot 10 to Juan Prado Mesa Preserve. Trail connections to the Mid eninsula Open Space property and shall be native paths. Plans shall be ubmitted for review and approval by the Planning Director, City Engineer, and Pathways Committee. Construction of all trail improvements, including parking on Lot 17, must occur prior to Final Map approval, or an improvement agreement with related bonding must be approved b;y the City Council. 1 • Prior to approval of the Final Map, CC&R's shag be submitted which include prohibition of pedestrian access to the lake, for review and approval by the Planning Director and City Attorney. Exceptions shall be limited to emergency access and for maintenance purposes, land for those residential lots which abut the lake. mprovement plans for the subdivision shall include fencing and signage for estricting access to the lake. The CC&R's shall also acknowledge all trail easements and restrict encroachments of structures or vegetation into such easements. 17. Sewer Service The applicant proposes to provide sewer service to the subdivision by connection to the existing sewer located within the Juan Prado Mesa Preserve. Area residents are concerned that construction a d future maintenance work for the proposed sewer would be required from Dawson Drive and/or could have a detrimental impact on the Preserve. It appears that, through the trail system proposed by staff and the Pathways Committee, sewer onstruction and maintenance could be limited to access from the Quarry Hills property. The EIR suggests extensive mitigation measures, as outlined in the T•wn's 1990 Staff Report for the Sewer Line Extension, which indicates an alignment above Hale Creek and measures to protect existing vegetation and prevent erosio . The proposed sewer line wo Id be a gravity system, the most efficient way to provide service. Alternativ-s considered included pumping sewage up to Stonebrook Drive to connect to an existing line in Prospect Avenue, or to utilize on- site septic systems. The pum Bing method is undesirable because of the problems and costs associated with a lift .tation, and on-site sewage systems are precluded by the Quarry Reclamation Plan. Another issue associated with the sewer line is that .it is to be located on Town property (Juan Prado Mesa Preserve), requiring an encroachment permit from the Town. Generally, when use f public property is proposed, the applicant would compensate the Town. In his instance, the Towin may choose to require ' Lands of Vidovich • September 7,1995 Page 31 • improvements to Juan Prado Mesa Preserve or the surrounding area in lieu of payment. Recommendation: Require that sewer construction and maintenance be limited to access from the Quarry Hills Subdivision and follow all of the recommendations of the EIR and the 1990 Staff Report; and requirethe applicant to apply for an encroachment permit, providing consideration for the permit in the form of enhancement of the Preserve. Conditions of Approval • Prior to approval of the Final Map, improvement plans shall be submitted for construction of the sewer line, and shall reflect all of the conditions outlined in the EIR and in the 1990 Staff Report for the Quarry Hills Sewer Line Extension, including abiding by the recommendations of a licensed arborist, where the line is to be constructed within the driplines of oak trees. Plans shall be reviewed and approved by the City Engineer and the Planning Director, as well as by the City of Los Altos. Access shall be limited,to be taken from the Quarry Hills Subdivision only, and the maintenance service road shall be of a natural material consistent with the rural nature of the Preserve. Sewer improvements shall be constructed prior to Final Map approval, unless an improvement agreement and related bonding are approved by the City Council. • The Final Map shall include a note stipulating that access to the sewer line serving this subdivision from Dawson Drive is precluded. • Prior to Final Map approval, the applicant shall obtain from the Town an encroachment permit for construction of the sewer line through the Juan Prado Mesa Preserve. In consideration of the permit, the applicant shall implement fire protection enhancements- within the Preserve, to the satisfaction of the City Engineer. Enhancements, such as clearing dead brush, wood and branches, shall be made simultaneous with the sewer line installation. 18. Water Service The applicant has obtained "will-serve" letters from both Purissima Water District and the California Water Service Company, but has not yet selected a water service provider. Both companies apparently,can accommodate the subdivision without major facility improvements. Required easements and improvements can be provided at the time of Final Map approval. Lands of Vidovich September 7,1995 Page 32 Recommendation: Req ire any required easements and improvements to be refl:cted on the Final Map and improvement plans for the subdivision. Conditions of Approval • The revised Tentative ap shall reflect which water company is to serve the subdivision, and shall be accompanied by an updated "will-serve" letter, outlining the company' requirements for easements and improvements. • The Final Map shall re ect any easements required by the water purveyor. • Prior to approval of th- Final Map, improvement plans shall be submitted, with details of any req ired water system improvements, to be reviewed and approved by the City Engineer and the water purveyor. Water system improvements shall be constructed prior to Final Map approval, unless an improvement agreeme, t with related bonding is approved by the City Council. I. CONCLUSION I The attached Conditions of Approval, Mitigation Monitoring and Reporting Program, and Final EIR ar- provided to support ; approval of the proposed subdivision. Witt relevant poi icy determinations, action may be taken to certify the EIR, adopt the General Plan • mendment, pre-zone the project site, and approve the Tentative Subdivision Map. Staff recommends that the Commission not take action on any one element of he application until it is ready to act on all elements. Action on all of these element would provide the Town with development control over critical areas immediatel adjacent to the Town limits. If the Commission recommen s approval, findings to support the EIR, General Plan Amendment, Pre-zoning and Tentative Map should' be cited. Additionally, the adoption of Statements of 0 erriding Considerations 'regarding mining and open space losses (and others if n cessary) should be recommended. And lastly, the Findings of Fact, Conditions of Approval, and Mitigation Monitoring and Reporting Program should be 'ncorporated into the approval package. Based upon direction from the Commissi n, detailed findings and revised conditions will be prepared for final Commissio action. If the Commission recommen s denial, the EIR should not be certified and findings . for denial of the subdivision should be stated. • . • 'Lands of Vidovich September 7,1995 . Page 33 ATTACHMENTS: 1. Conditions of Approval 2. Mitigation Monitoring and Reporting Program 3. General Plan Amendment Revisions and Findings • 4. EIR Summary of Impacts 5. August 8, 1995 Letter from William Cotton & Associates 6. Application 7. Correspondence _ cc: John Vidovich Jim Sisk De Anza Properties • Attachment 1 RECOMMENDED CONDITIONS OF APPROVAL Tentative Map (#254-93-TM).for Quarry Hills Subdivision Lands of Vidovich In addition to the conditions listed below, all mitigation measures adopted as part of the Mitigation Monitoring and Reporting Program shall also be incorporated into the Conditions of Approval. All of the following conditions must be satisfied prior to approval of the Final Map, or,in the case of improvements, a subdivision improvement agreement and required bonding may be approved by the City Council prior to Final Map approval, allowing the improvements to be deferred as per the agreement: General 1. The applicant/owner must, not later than 30 days. after approval of the Tentative Map by the City Council,provide written consent to include the property in the Town's Urban Service Area and to annexation of the property to the Town of Los Altos Hills. The consent shall.be submitted to the Town and to the Santa Clara County Local Agency Formation. Commission (LAFCO). 2. The applicant/owner shall finalize the abandonment of access easements for right-of-way to the rear of Lots 1-4 with all affected property owners, and shall provide additional easements and improvements as necessary to accommodate continued access to,off-site properties. Alternatively, the applicant may retain the existing access easement and shall indicate on the revised Tentative and Final maps reduced lot sizes for those Lots 1-4. 3. The applicant shall obtain from the Town an encroachment permit for construction of the sewer line through the Juan Prado Mesa Preserve. In consideration for the permit, the applicant shall implement fire protection enhancements within the Preserve,to the satisfaction of the City Engineer. Enhancements, such as clearing dead brush, wood and branches, shall be made simultaneous with the sewer line installation. All deadwood and prunings shall be removed from the Preserve at the applicant's expense. 4. Upon City Council approval,of the Tentative Map, no further construction activities shall take place within the subdivision boundaries without submittal of plans to the Town.of Los Altos Hills and approval by the City Engineer. Conditions of A proval: Quarry Hills Page 2 Revised Tentative Map and Final Map 5. The applicant shall submit a revised Tentative Map indicating the following changes: a) elimination of Lots 17,20 and 21 as building sites; b) realignment. f Street "C" from its intersection with Street "B" easterly to prof ide adequate transition for the driveway to Lot 19; c) Lot 17 shall be combined with Parcel "A" and used for lake access and maintenance,trailhead parking,and recreation; - d) Lots 20 and 21 shall be combined into'a common open space lot (Parcel "B"), a so encompassing the upper hillside areas of Lots 18 and 19,to be r.stricted from all development other than trails; e) demonstration that the driveway grade for Lot 19, as it approaches Street "C", w#1 not exceed a maximum of 6% for at least 40 feet from the street, and that driveway grades are reduced to the maximum ex ent practicable, to the, satisfaction of the City Engineer; f) building envei ope and debris flow building exclusion zones on hillside lots ( 8-23), consistent with the recommendations of the geotechnical consultants; g) a drainage pipe to convey off-site flow from Lot 23 to the western corner of the l9ke; h) a drainage pipe to convey flow between Lots 13 and 14 to the lake; i) relocation of the drainage pipe between Lots 7 and 8 to avoid the private well site; j) a drainage easement along the rear of Lots 1-4; k) elimination of the trails adjacent to Lots 18 and 23; 1) provision of a minimum 10 foot wide trail easement from Street " to the upper hillside trail connecting to MPROSD lands, either through Lot 19 or in the approximate j location of the proposed driveway to Lpts 20 and 21, or otherwise along existing roads and tails within the recommended common area open space lot (Parcel 13”); m) provision of a inimum 10 foot wide trail easement from the end of Street "B" a•jacent to Lot 10 and the outlet channel to the Juan Prado Mesa Pr-serve; n) widening of t e 10 foot wide trail easement at the northeastern corner of lot 11 to 20 feet wide; and o) accurate delineation of the subdivision !property boundary, to be clearly shown .s a bold line around the subdivision. The revised Tentative Map shall be submitted for review and approval by the Planning Director and the City Engineer. Conditions of Approval: Quarry Hills Page 3 6. The revised Tentative Map shall be accompanied by a site plan for Lot 17 (ascombined with Parcel "A"), which delineates a minimum of 6 parking spaces, lake access, and maintenance and/or recreational facilities. 7. The revised Tentative Map shall reflect which water company is to serve the subdivision, and shall be accompanied by an updated. "will-serve" letter, outlining the company's requirements for easements and improvements. 8. The Final Map shall reflect all of the above revisions to the Tentative,Map, including applicable easements as required. All drainage easements shall - be a minimum;of 20 feet in width. • 9. The Final Map shall reflect any buildingexclusion zones for hillside lots (18-23), and shall stipulate the restrictions of those zones. 10. The Final Map shall stipulate the restricted use of the common area open space lot (Parcel "B") over the.upper hillside areas, such,that those areas are limited to trail use and minimal.brush clearing for fire protection purposes, and that Parcel "A" is not to be used as a residential building site. • 11. The Final Map shall include a note or other method of stipulating that access to the. sewer line serving this subdivision from,Dawson Drive is .. precluded. 12. The Final Map shall reflect any easements required by the water purveyor. 13. The Final Map shall:contain a note prohibiting vehicular access toany lots in the subdivision from.Stonebrook Drive or Street "A". The restriction shall also be included in the CC&R's for the subdivision. 14. ' The Final Map shall indicate street names:acceptable to the Town and to the Los Altos Fire Department. Land and Easement Dedications 1 15. The Final'Map shall include an,.irrevocable offer to.dedicate sufficient right-of-way (a minimum of 10. feet and,if necessary, slope easements) on the north side of Stonebrook Avenue on the applicant's property to accommodate widening of this segment of roadway (approximately 1,000 • linear feet) to a minimum 20 foot pavement width, and to perform corrective grading work (as recommended by Alan Kropp Associates) and required drainage and other improvements in the right-of-way. The right-of-way shall be dedicated to lithe satisfaction of the City Engineer and County authorities. Conditions of Ap roval: Quarry ills Page 4 16. The Fi i al Map shat 1 include dedication of street right-of-way for Stonebrook Drive adj:cent to Lots 5-7, such that the right-of-way width is no less titan 60 feet,to the satisfaction of the City Engineer. 17. The Fin 1 Map shall i dude dedication of allroad rights-of-way to public use; all internal roa ways shall be dedicated to the Town of Los Altos Hills, .nd dedicati.n as required for Stonebrook Avenue. in the unincorporated area -hall be offered to Santa Clara County. All rights-of- way dedicated to the I own shall be a minimum width of 60 feet. 18. A minimum 20 foot ide emergency access easement shall be dedicated from Str1eet "B" thro gh Lot 17 to the lake, to the satisfaction of the City , Engineer. The easem:nt shall be dedicated on the.Final Map. 19. 10 footiATide pathwa easements shall be granted to the Town for public use, as hown on-the revised Tentative Map, except that the easement in the nort eastern corn,-r ofLot 11 (connecting the McCullough subdivision to Juan Prado Mesa'Preserve) shall be 20 feet wide. The subdivision CC&R's shall includ: language restricting improvements or vegetation from i fringing on these easements. The dedications shall be ' accompl'shed as part of the Final Map. 20. The Fin 1 Map shall 1.rovide for-any requested,easements to all.utility companies, including out not limited to: Pacific Bell,Pacific Gas &Electric Company and cable t:levision. 21. The applicant shall gr:nt public utility easements and public utility access easeme is to the To n of Los. Altos Hills where needed within the subdivi ion for utilit construction and maintenance to the satisfaction.of the Cit Engineer. This will provide access for installation and maintennce of the p blic water and sewer system. The dedications shall be acco plished as .art of the Final Map to the satisfaction of the City • Enginee 22. The Final Map shall ;irovide an access easement in favor of Ridgewater. Associates and Silver (A.P.N. 336-26-005 and 336-26-006) from Street "B" betweenLots 7 and 8 for purposes of access to the existing.parcels, to the 1 satisfact on of the Ci',y Engineer..This easement shall be recorded by a separate document a d signed by the affected property owners prior to ,approval of:the Final Map. • • 1 4 Conditions of Approval: Quarry Hills Page 5 Improvements 23. Improvement plans shall'be submitted, for approval by the City:Engineer, providing.details.of the widening of the Stonebrook Avenue pavement, from Street "C" to Magdalena Road, to a width of 20 feet.. Where:such widening would damage heritageoak trees, the pavement width shall be narrowed to avoid substantial impact to the trees. Plans shall also include a gate above Street "C", accessible only by emergency vehicles. 24. Improvement plans:shallbe submitted, for approval by the City Engineer and the Town's geotechnical consultant, detailingthe,corrective grading work outlined bythe applicant's geotechnical consultant regarding the southern Quarry wall, :adjacent tb Stonebrook Avenue.- Improvement plans shall also include revegetation of the graded area,including trees for screening,to the satisfaction;of the Planning Director. , 25. The improvement plans shall include fencing at the top of the rquarry wall from the end of Street "C" to Magdalena Avenue- and along the, rear of those lots along the east endof the subdivision boundary, where feasible. The.weight, type and location of this fenceshall be subject to review and approval of the Planning Director and City Engineer. . 26. The applicant shall submit with. the improvement plans details of proposed stabilization plantings of the quarry wall, as recommended by a licensed Landscape. Architect, to be reviewed and approvedby the Planning Director,_the Town's arborist or landscapearchitect, and the Town's geotechnical consultant. . - 27. Improvement plans shall:be submitted detailing plans for construction of a debris basin at the northwestern,boundary of Lot:21. The plans should minimize the height.of the berm for the basin and shall include plans for landscaping thefill and.other disturbed areas. Plans must be;reviewed and approved by the Planning Director, City Engineer, and the Town's geotechnical consultant, ,. 28. Improvement plans shall be submitted, detailing the construction plans for all drainage facilities, :and demonstrating that all :.facilities can accommodate 100-year,storm flows, with the exception ofshort sections of channels or pipes carrying only localized on-site drainage, and the Prospect Avenue drainage pipe, which may be designed to handle 25-year • flows.. The design of the by-pass channel"shall include an impervious lining .(concrete is not an acceptable material);.and the plans shall demonstrate that adequate measures to control erosion and siltation on the proposed-"roadside.ditches,,will be incorporated. Drainage plans should incorporate debris grates and, if determined feasible by the City Conditions of A proval: Quar Hills • Page 6 Engineier, grease tr:ps into inlet or outlet structures. Plans shall be submitted for the re .iew and approval of the City Engineer. 29. ; 'Impro'ement'plans .hall be submitted which outlineconstruction details of theccess'road-t• the lake; and fencing, gates and signage around the • lake;'prohibiting ac -ss for all but emergency-0d maintenance purposes, :.other than along the rear-of Lots 12 through 16.' Plans shall be submitted for the review an. approval of the Planning Director and the City Engineer. 30.' Impro ement"plan- shall provide erosion and sedimentation control: measures at the cha n �a el outlet to'Hale Creek, n'd'shall include a Hale Creek restoration pl:n, in accordance with the Quarry Reclamation Plan, for review and apprival by the Planning Director and the City Engineer. 31: Improyement pla s shall �be submitted detailing proposed trail construction. Plans .hall include a Class IIB pathway along the frontages of Lots 1 through 1 i (streets "C and "B"), along Street "A", along the Street 'C" cul-de-sa i. and the Stonebrook Avenue emergency access route from Street "C" to :the subdivision boundary, and. along the pathway easement from Lot' 10..to Juan Prado Mesa Preserve. Trail connections to the Mi Peninsula 0 en Space property shall be native'paths. Plans shall be sub itted for re iew and approval by the Planning Director, City Engine r, and Path ays Committee. 32. : Impro IIement plans hall be submitted for construction of on-site and off- site sever-lines, and shall reflect all of the conditions outlined in the EiR and in the 1990 Staf Report for the Quarry Fills Sewer Line Extension, includipg complian e with the recommendations of a licensed arborist, where the line is to b constructed within the dripli ies of oak trees. Plans • shall b t reviewed a d approved by the City 'Engineer,and the Planning ; - Directo�, as:well as •b the City of Los Altos. ' Access shall be limited to be takenrom the Qu.,rry Hills'Subdivision only, and the maintenance service road shall be of a natural material consistent with the rural nature of the reserve, to he satisfaction of the Planning Director and City Engineer. 33. Improvement plans •hall be submitted with details of any required water 'system improvemen's,.to be reviewed and appFroved by the City Engineer ' ' and the-water puree or. t 34. A project grading pl.n which includes an approved drainage and erosion control plan to min mize the impacts from erosion and sedimentation shall be submitted ith the improvement plans, to be reviewed and approved by the'Cit 'Engineer prior to issuance of grading permits. This . plan shall conform o all standards adopted by the Town of Los Altos Conditions of Approval: Quarry Hills Page 7 Hills and shall comply,with all appropriate requirements of the Town's NPDES permit relative-to grading and; erosion/sediment control encompassed in a Stormwater Pollution Prevention Plan submitted to the Town and to the Regional Water Quality Board including,but not limited to: a) restricting grading during the-grading moratorium from November 1. to April 1; b) protecting all finished graded slopes from;erosion using such techniques as hillslope benching, erosion control matting, and hydroseeding; c) protecting downstream storm drainage inlets from sedimentation; d) use of silt fencing to retain'sediment.on the project site; and e) any other suitable measures outlined in the Association of Bay Area Governments (ABAG) Manual of Standards. 35. Prior to beginning any grading,or construction operations, all significant trees shall be fenced at the dripline. The fencing shall be of material and structure to clearly delineate the dripline. Town,staff must inspect the. fencing and the trees:to be fenced prior to commencement of grading or construction; The fence must remain in place throughout the course of construction. No storage of equipment, vehicles or debris shall be allowed within the driplines of these trees. 1 36. A Grading and Construction Operation Plan for all subdivision improvements shall be submitted for review and approval by the City Engineer and Planning Director.. The plan shall address truck traffic issues regarding dust, noise, and vehicular and pedestrian traffic safety; storage of construction materials; placement of sanitary facilities; parking for construction vehicles; and parking for construction,personnel. One or more debris boxes- shall be placed on site for collection.of construction debris. 37. Prior to acceptance of the subdivision improvements, the applicant shall reconstruct.Stonebrook Drive from Prospect Avenue to the subdivision entrance, with a minimum:pavement width of 24 feet, along with any necessary drainage improvements,to the satisfaction of the City Engineer. 38. The applicant shall provide the City Engineer with photographs of the existingcondition of Stonebrook Drive from: El Monte =Road to the property boundary, and of all pathways adjacent to or on the site.. The applicant shall agree, as part of an improvement agreement, to inform the Town of any damage and shall repair any damage caused by the construction of the project to.pathways, private driveways, and/or public and private roadways prior to acceptance of the subdivision improvements. 39. The applicant shall be required,to apply, for and receive any Creek Alteration Permits:required by t11e California State:Department of- Fish Conditions of Aproyal: Quarry ills Page 8 and Game or by t e US. Army Corps of Engineers for proposed improvements;prior o issuance of construction-or encroachment permits. 40. ' . Improvement plans or fife protection, includpng the installation of fire hydran�s or other i provements as. required, by the Los Altos Fire Department, shall be submitted for the review and approval of the City Enginee and the Fire Department. 41. All.utili 'es located w thin the subdivision shall be installed underground, in accordance with S bdivision Ordinance,Sec.19-1.1105. Cable television, gas, el4tric, and tel.phone services installed to the property lines are ' included in this requ. ement. Plans for location of all such utilities are to be included in the im o rovement plans for the subdivision. 42. All subdivision improvements shall be constructed and installed prior to Final Map approval, or may be deferred per an improvement agreement and required bondin:; if approved by the City Council prior to Final Map approv1. CC&R's and aintenance A 1 reements 43. The applicant shall' prepare Conditions, Covenants, & 'Restrictions (C&R'S) for the sub,i ivision, setting forth, at a minimum, the following limitations on the sub ect properties: a) all of the reco mended"restrictions contained in the 1994 Lake Management P an and the related EIR mil gation measures; b) prohibition of boats on the lake, other than for emergency or it aintenance p rposes; c) - prohibition o' pedestrian access to the lake, other than for emergency ac•ess and for maintenances purposes, and for those residential lots hich abut the lake; d) prohibition of ehicular access to lots from Stonebrook Drive or S reet "A"; e) a 1 mitigation easures identified in "the EIR'related to building s tbacks, heights,locations, and design and colors; f) . fie safety re uirements for non-combustible roof coverings, interior fire sp inklers, and maintenance of brush clearances from structures; g) restriction on residential construction within any building e clusion zone ; , h) r strictions on ses allowed within Parcel "B" (common open space lo ) and on Par el "A" (lake and parking), as well as maintenance rsponsibilities such as for weed/brush abatement; i) ajknowledge •ent of all 'trail easements, and limitations on encroachments of improvements or vegetation into the easements; • ' Conditions of Approval: Quarry Hills Page 9 j) any special restrictions on foundation design, as identified by the applicant's geotechnical consultant; - k) maintenance responsibilities of the Homeowners Association and/or individual property owners regarding lake maintenance, access to the lake, common,.,area, or, open space, lots, areas of corrective,grading, the debris basin on Lot:21, and thesubsurface interceptor on;Lots 5-10; and 1) acknowledgement of hold harmless provisions.releasing the Town from any liability associated with water quality impacts potentially caused by drainage from public facilities., The CC&R's shall be.binding on all present and future property owners in the subdivision, and, shall prohibit modification of the,above provisions without the approval of the Town of Los Altos Hills.- The CC&R's shall be submitted- for review and approval by the City Engineer, Planning Director, and City Attorney,prior to recordation. 44. A hold harmless agreement shall be submitted,. applicable to all present and future owners of property in the subdivision, releasing the Town of Los Altos Hills from any liability associated with water quality impacts potentially caused by drainage from public facilities.,.,The agreement shall be prepared by the City:Attorney, and shall be signed by the applicant and notarized prior to recordation. Provisions of.the agreement shall also be incorporated into the CC&R's for,the subdivision. . 45. Maintenance agreements shall be submitted providing for the long-term maintenance of, at a minimum: the lake area and access to the lake, the debris basin, areas of corrective grading.and revegetation, and the subsurface interceptor for seepage on lots 5-10. , The agreements shall provide mechanisms for sharing the costs of maintenance-as well. The agreements shall be submitted for review and approval by the Planning Director, City Engineer,.and City Attorney, prior to recordation. Geotechnical 46. Not later than thirty;(30) days after the approval of the-Tentative Map, the applicant shall notify...in writing the,Mid-Peninsula Regional Open. Space Districtand all private property owners potentially impacted by debris flow hazards, as identified by the applicant's geotechnical consultant. The form,and content of the notification shall be approved by the Planning- Director and the City Attorney. , 47. An appropriate final pad elevation and pro_posed site grading plan for Lot 21 shall be prepared., and accepted- by the applicant's geotechnical consultant, and reviewed and approved,by,.the City Engineer and Town geotechnical consultant. i Conditions of A proval: Quarry ills Page 10 48. Study lan #4, del neating final 'buildiing envelopes and driveway alignm nts; as identi ied by the applicant's geotechnical consultant, shall be ,mo ified with:t, e.changes identified bye the Town's geotechnical ^consultant, and sub itted for approval by the-City Engineer and the `Towns geotechnical onsultant. The project geotechnical consultant shall I ' certify in writing tha the recommendations of the plan are reflected in the proposed improvem.nt plans. ' 49. The aplicant's ge•technical .consultant shall submit": preliminary founds ion recomm-ndations to define the general type of residential founda ion deemed .ppropriate for each proposed lot. The potential need for any unusually d:ep or rigid foundation'systems shall be addressed. - The range of differen ial fill thickness across proposed building envelopes shall be quantified .s part of this evaluation. Any requirements for fill settlement monitorin: prior to construction shay be addressed. The report recom endations sh.11 be prepared to the satisfaction of the City Engineer ; , and the Town's geot&chnical consultant. 50.- The ap licaht's ge•technical consultant shall' identify the extent of necessa y corrective t rading activities resultant from ongoing grading on ' the site. ' The repo t shall be prepared to _the satisfaction of the City Engineer and the -T•wn's geotechnical consultant, arid any corrective gradin must be incl ,ded on the improvement plans. 51. The applicant's , gee technical consultant shall review all proposed improv ment plans- and shall certify in writing that such plans are consistent with all „eotechnical recommendations. The geotechnical consultant's review s, all:include, ata minimum; all proposed grading and drainag improveme, ts, and all geotechnical mitigation measures., , 52. A final design sha 1 be submitted by the- applican't's geotechnical consultnt for the s bdrain system for Lots 5-10. The plan shall be ' incorporated into th- subdivision improvement plans for review and approval by the Cit Engineer and the Town's geotechnical consultant. ` .The results of the p an review'shall be summarized in a letter by the project geotechnical onsultant and submitted to the City Engineer for ' review and approval .rior to final approval of the improvement plans. 53. The geotechnical con-ultant shall inspect, test (as needed); and approve all geotechnical aspects •f the project construction. The inspections should include,but not nece-sarily be limited to: excavations, grading, and trench excavation and coin'action. The results of these inspections shall be described by the'geo echnical consultant in a letter and submitted to the City En ineer for revi-w prior to final project'approval. f ' , w - •' s Conditions of Approval: Quarry Hills Page 11 Planning and Zoning 54. All existing non-conforming structures (i.e., caretaker house) shall be removed from the site prior to approval of the Final Map, unless accommodations for demolition are included in a subdivision improvement agreement approved by the City Council. 55. Payment of Park and Recreation fees and all other applicable fees shall be required prior to recordation of the Final Map. 56. All subdivision conditions of approval and subdivision improvements shall be constructed, approved by the City Engineer, and accepted by the City Council prior to acceptance of applications for any site development permits or building permits for residences. 57. Upon discovering or unearthing any possible burial site asevidenced by human skeletal remains or artifacts, the person making such discovery shall immediately notify the County of Santa Clara Coroner and no further disturbance of the site may be made except as authorized by the County Coordinator of Indian Affairs. This shall be accomplished to the satisfaction of the County Coroners Office and the Planning Director, as may be necessary during the construction of the subdivision improvements. • Attachment 3 GENERAL PLAN AMENDMENT The applicant is requesting text and map amendments to the Town of Los Altos Hills General Plan. These amendments would designate the site as residential, from Open Space Preserve (OSP) to Residential Very Low (R-VL) and would _ delete references to the existence of an active quarry on the project site. A proposed map revision is attached. - Specifically, the requested text amendments are as follows (deletions are shown, in strjLTikeout): Land Use Element-Page 22,#127 The Neary Quarry presents significant problems to this area in terms of trucking, noise, dust and aesthetics. The quarry is shown as an open space preserve, an indication that it most likely will only be suitable as open space. Plans would need to be developed to enhance the site. Open Space Element Page-52, Item f (Neary Quarry) This site, within.the Town's sphere of influence, is designated as an open space preserve based on its function of "managed" production of natural the quarrying operation; however, since the quarry is a pre existing use, few controls arc levied by the County on the operation. It is anticipated that, when the quarrying operation ceases to exist, the site will be unsuitable for other than open space uses. Implementation The Town should.encourage the.County to establish and dust from trucks which have a negative impact on the surrounding residential areas. In addition, the County, the Town, and the property for other uses. Recreation Element - page 58, last paragraph, item 1, Open Space Preserve this site will ever be suitable for any use other than open space. Quarry Hills General Plan Amendment Page 2 1 I. i Conservation Element- Page 86,#616,item 4 1 Studies should be undertaken of the posciblc'future uses of the Neary General Plan Provisions One provision of the general plan is most relevant to this requested change, and provides criteria against which the requested amendment should be judged, as follows: Open Space Element - Pa e 45, #306, item 3 states, "In the context of the local physical situation, the ex raction of rock, sand, gravel and mineral resources is incompatible with goal for maintaining a quality environment and should be prohibited. Recommended Findings anAction The primary reason the arean question has been designated in the General Plan as "open space reserve" is ecause at the time the plan was last updated (mid- 1970s) the site was being utili ed as an active quarry operation. In 1988 the Neary Quarry Reclamation Plan was approved by Santa Clara County, with estimation that the quarry could be ope ated until 1998 at current (1988) excavation levels. With quarry operations no 1 nger taking place and reclamation in process, the major reason folr the "open s ace preserve" and "quarry" designations no longer exists. In December of 1993, the Cit Council adopted an appendix to the Conservation Element which supported tl1e conversion of the quarry area to residential use (attached). In light of the information contained in that appendix, the Planning Commission and City Coun4l may determine that.the'proposed amendment of the general plan amendment is in.the Town's best interests. 1 ,I „ .. ; ! ; 1 •••• 4. • %)P11-IT'LL.-lavi'cut?,'-.''' • -1 7 a 1 ‘,, - vi7..,•,:;;,00). ,- . 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P blic Resources Code Section2710 et seq (SMARA) r and the State ining and G logy Board Policy. California Code of Regulations, . Ir:;7 Chapter 8,Titl 14 Sections 675-3676. rw The State Mining and Geolo y Board has designated an area adjacent to the " Town of Los Altos Hills as a area of significant mineral resources. The State designation is known as "Se tor Z-Construction Aggregate Resource Area - Greenstone deiosit located i the Los Altos Hills southwest of the City of Los Altos in northwestern Santa lara County". See Special Report 146,Part II and ' SMARA Designation Report No. 7. li This area is in •wo ownershi s: Area 1 is approximately 282 acres and is owned by the Mid Perunsula Regio al Open Space District. Area 2 is approximately 78 acres and is owned by John idovich et al and contains the area formerly known — as the Neary Quarry. 0 stn` As of November, 1993,both reas are in the unincorporated area of the County of Santa Clara and in the spher of interest of the Town of Los Altos hills. Area 1 is part off Rancho San ntonio Open.Space Preselrve owned by the Mid /: Peninsula Regional Open Sp ce District. The Town of Los Altos Hills will not seek to include this area in it urban service area nor will it annex this area into t. its corporate limits since this roperty does not need municipal services. The use of this area as publicly owner open space is incompatib'lle-with mining of the mineral deposits on this pro erty. Since the Town of Los Altos Hills will not ^.._ annex Area 1, the County of anta Clara is the lead agency for purposes of SMARA. Area 2 is located west of Inte state 280 between El Monte and Magdalena. The area is bounded on the Aerth northwest and south by Stonebrook Drive. It is 11 = contiguous to the Town of L s Altos Hills. Quarryoperations began in 1 34 to provide fill and crushed stone to construct .. Moffet Field. T e quarry wa operated by John Sondgroth and Sons from 1934 i5; until 1940 and ndgroth Bro hers operated it until 1962. George Neary then rn operated the quarry until 197 when Patton Brothers Construction took over. A : _ t ;Reclamation Plan was appro ed by the Board of Supervisors of the County of i,t 1+ Santa Clara in April, 1989. The Plan was based upon the future site conditions i a `= following an additional 10 years of operations. The Plan contemplates an Vegq, 3` t riT T A io 1w Tm T n nTVTI TZTTPT1 TT 1' 31 RRSPnNSPS TO COMMENTS . i • _ - , . li ..1 I • ' 0 , . IR / additional 475,000 cubic yards of minerals would'be removed prior to _____ I completion of quarrying. The Neary-Vidovich Quarry Reclamation Plan Annual Monitoring Report- � County of Santa Clara File No: 2674-12-70-85P received by the County December 18, 1991 states on page 2, "There have not been any (mining) operations at the Quarry since May 31, 1989. The owner has determined that (mining) operations at the Quarry will not be resumed." R The Town of Los Altos Hills supports the decision of the owner to cease mining operations. It plans to include the area within itsl urban service area and annex . 11110 P the property into the Town following its approval of a tentative subdivision map for residential development. No quarry operations are allowed within the Town -- :1 of Los Altos Hills. i A residential subdivision of Area 2 would result in the permanent removal of mineral I* resources frompotential production. Public Resources Code significant Section 2762 requires that,prior to permitting a use in an area containing important mineral'resources, the Town must prepare a statement specifying its reasons for permitting the proposed use: .. ill From 1934 to May 31, 1989, the Neary Quarry has used as its only haul route Stonebrook Drive to El Monte and Interstate 280; Stonebrook is a city street;it is steep and winding. La Loma Drive, Prospect and a number of cul-de-sacs also use Stonebrook to exit their homes. The General Plan of the Town requires a minimum lot size of one acre. These ,_ large lots have resulted in low density residential development with very high 11 value. This type of development is occurring ini the area using the Stonebrook haul route. For example, the McCullouch Subdivision of 32 lots has access only on Stonebrook. This subdivision, along with others on Prospect, approved since to the traffic on Stonebrook. There would be the quarry was closed, have added no way to mitigate the conflict between increased residential traffic and the resumption of quarry hauling. The Town therefore finds that residential development of the quarry overrides the loss to the region of the remaining v quarry material. In order to comply with California Code of Regulations Section 3,576 (c) 3,the -- Town will record on property titles in the affected mineral resource areas, a notice identifying the mineral deposit. The notice will be recorded when the property is annexed to the Town. . • ( •. • • OUARRY HILLS SUBDIVISION 32 RESPONSE*, ' ''� i+ ; { . • a W1 Attachment 4 A 1 EIR SUMMARY QUARRY HILLS SUBDIVISION .;-,...-g;,),,,,:4,,,,,,.,at. I 'T_ ; ! �s ; ti I'V^xis SUMMARY DESCRIPTION OF THE PROPOSED PROJECT off- ' .. 1'I- b 4 .,, ,. y r • The primary component of the proposed project is the approval of a Tentative Map to allow for the ; .`f development of a 23-lot residential subdivision on a 78-acre site which is located in the Montebello-?•4 4;!:.- Ridge area in the Town of Los Altos Hills' Sphere of Influence. The development of the 23 ':'+..:kt': residential lotsis a modification of a 1988 proposal by the same applicant to construct a 43-lot' '.~;,r? =`° • f_.: subdivision on essentially the same site. [Note: A substantial portion of the original site in the 1988: `.:' -A" :: development proposal has since been sold to he Midpeninsula Regional Open Space District : I • (MROSD) for public open space purposes.] In addition to the Tentative Map, which would be called :: ' the Quarry Hills Subdivision, the project proposes a modification to the'adopted Neary Quarry '.;;, : .. :.., Reclamation Plan,expansion of the Los Altos Hills Urban Service Area, annexation of the site to the - ; - ITown of Los Altos Hills, zoning, and text amendments to the Town of Los Altos Hills General Plan. The project site is located in an unincorporated portion of Santa Clara County, adjacent to the ' _ southern boundary of the Town of Los Altos Hills, west of Interstate 280.: The 78-acre site is in an area known as the Montebello Ridge, and is the site of the former Neary Quarry. The project site, which is sometimes referred to as the Vidovich property, is bordered to the south by MROSD lands. SUMMARY OF ENVIRONMENTAL IMPACTS AND MITIGATION The following discussion, and Table S-1, summarize the primary impacts of the proposed Quarry Hills Subdivision Project. The reader is referred to the main body of this Supplemental EIR for Idetailed discussions of the environmental setting,'impacts, and mitigation measures. I A. LAND USE ' Impacts The proposed subdivision would be .compatible with the surrounding residential and II open space uses, and is generally consistent with the Town's plans and policies for the project site and its relation to the surrounding area. However, the project would result in one significant, unavoidable land use impact: the placement of a residential development upon the former quarry,which is a State-designated mineral resource of significance. (Significant Unavoidable Impact) i , Mitigation No mitigation is available since any development of the project site would render the quarry inaccessible. B. TRANSPORTATION AND TRAFFIC IImpacts . The 220 trips per day which would be generated by the project would not result in any significant impacts to nearby intersections or to the surrounding roadway network ;;; -, , ! 1�•nKfi;}1 `�� (Nonsignificant Impact) ,Yfr 4 -,t1,4t As y�4j 41,-4.-..t, . ..CIN, QUARRY HILLS SUBDIVISION vi MARCH 1993 DRAFT',S 1'F, �' , I , 4 � t t�ll l,l,�y1t tYi'.�yY I>.� Ci!t vs `. C9; `' y,?S — om -n �-T t_ .,_._—,....�++__ .,_ •._ 4yry.N.. ' 40 ,,..k ;.{„ TABLE S - • • 4;4 0 i'4 � :.,t m i e Ki 4a nCK d , a a o rota SUMMARY OF IMPACTS' a j Significant Impact which can be 1 • ' • Mitigated.: ... to a Significant Impact Nonsignificant Nonsignificant Unavoidable Category Impact, Level Impact LAND USE , Loss of Mineral Resource ✓ Compatibility with Surrounding Uses i I TRANSPORT II TION AND TRAFFIC Generation of Traffic ✓ Emergen y Access ;_. ✓ Access to Lots 19-21 ✓ GEOLOGY Erosion ✓ N. Quarry Wall Stability. / • General Slope Stability j . ✓ Onsite & Offsite Debris Flows ✓ ii Seismic Hazards . HYDROLOGY & WATER QUALITY Flooding ✓ Water QuiLlity ✓ VEGETATION'I & WILDLIFE Loss of Inderal Habitat ✓ ' Loss of Sage Scrub Habitat it Loss of Riparian Habitat . .. .. ✓ Impacts to Endangered Species - ✓ Loss of Qak Woodland } abitat ✓. Im acts to NestingRaptors' ✓ Impacts to Heritage Tree j ✓ VISUAL & AESTHETIC Light & Glare Impacts ✓ ,`,. . Alteration of Existing Views. !� • . • • QUARRY HILLS SUBDIVISION • vii I MARCH 1995 DRAFT SEIR i • • TABLE S - 1 continued) J OF IMPACTS •:....'..,...•:;:.',.-.,....:.- -.7t...,;.;:-.•:.,:t.., .' SUMMARY ..,......,.,,..-....i,,,..,....,,,,,,, Significant:: f 9ignificantC r�° r4 1} r �� 0 } s ,,•:, Ip -;,;,,-;:,,,-,::,:p.-:,,,. .....:.,---;,;;.,• is • which can be . : .Mitigated: - _rF,L ,, to a Significant :;i'-,-. ..: Impact . • Nonsignificant: Nonsignificant Unavoidable ` Category ; Impact Level . Impact UTILITIES & URBAN SERVICES of Impacts on Schools Impacts on Police & Tire . ✓ ✓ Impacts on Sanitary Sewers Impacts on Water Service. ✓. • Impacts on Parks. Impacts on Solid Waste / 1 AIR QUALITY Short-Term Construction. Long-Term ✓ • NOISE ✓ Short-Term Construction: 1 Long-Term ✓ CULTURAL RESOURCES .1I Archaeological Resources HAZARDOUS MATERIALS , Existing Contamination PUBLIC SAFETY ILake-Related Hazards ; CUMULATIVE %,I Loss of Open Space - - Traffic . ✓ Geologic I IIHydrologic/WaterQuality ✓ Vegetation & Wildlife I IIUrban Services/Utilities Iti , - .• ' -. . . " .. _ • MARCH 1995 DRAFT SIIIR , • • � '. . QUARRY HILLS SUBDMSION'„ , , vi ..,.i'.•,:,-,L•:„4,,, _. . ^;a. ril.+; t .} �;. s•r?.�• i i � . �. ';''•,..•;,••.;•••.•.,,,':,,„ t.7 °p° CCA <l[b v ,,'.. i1 , : ,. ,i,t ::! . n,., h: . V )�,'"AY V . , The proposed emergency/secondary access'to i the site is not adequate since existing 4 , ,;. = *,,' Stonebrook Avenue is narrow and the portion of Stonebrook within the project site _ • t�2;�.' ', '�i, 4 y �E y n would not be paved. '(Significant Impact) F PP ",Rs �x'y `"','frits.}, c ''s ' • ``' ° ^ `µ ` here is inadequate/unsafe access to proposed Lots 19-21 which violates Town standards. (Sig 'ficant Unavoidable Impact). .r;. Mitigation In order for the project to have adequate emergency/secondary access, Stonebrook - i Avenue.should e upgraded to an asphalt-paved; surface street of at least 20 feet in pved width, ex ending from Street C within!the project boundaries to Magdalena Avenue; this mitigation will have significant visual and vegetation impacts since it 1. will remove exiting trees along Stonebrook Avenue, west of Magdalena Avenue. These impacts, in turn, can be mitigated through the replanting of trees at the ratios spjecified in the Enz. (Nonsignificant Impact with Mitigation) Mitigation meas res for the inadequate driveways to Lots 1.9-21 consist of: 1) Redesigning the ommon/shared segment of the driveway as a public street having a paved width of 2 feet, with a cul-de-sac or other similar design feature at the end wiich would allo for fire department vehicles to turn around. Maximum grades for various segments of this public street are listed on page 46. 2) Driveways for individual lots s all be redesigned having no grades in excess of 15%. 3) The driveway for Lo 21 shall be widened or include pullouts to provide a means for vehicles to pass ach other. i Important Note: The mitigation described in;the previous paragraph for access to Lots 19-21 will itself require substantial additional'grading and the likely widespread use of retaining 4aiis. This will, in turn, result in substantial additional grading and visual impacts, oyer and above that for the project as it is•presently proposed. In other words,while it may be feasible to design a solution to this access problem from ani engineering and geologic perspective, the resultant visual impact would likely be both significant and unavoidable, and would be contrary to various sections of the • Town's Zoning and Site Development Code. (Significant Unavoidable Impact) II C. GEOLOGY Impacts Since the project site is located in a region with the potential for major seismic activity,and since the project site contains steep slopes and a former quarry with steep wails, 'the proposed 23-lot residential subdivision would result in a number of potentially significant geologic impacts. These potentially significant geologic impacts include hazards, both onsite and offsite, associated with seismic activity, I landslides/debris flows, stability of the steep quarry walls,general slope stability, and erosion. In addition, studies undertaken during!the preparation of this EIR revealed existing hazards to a number of adjacent offsite properties due to the potential for de ris flows to o cur, originating upslope on Midpeninsula Regional Open Space V s; see page Di trict land53 for details. (Significant Impact) 111 Mitigation .. The project's geot hnical engineers, with substantial review input from the Town's #.'r- ,.: . geologist, have de eloped an extensive list of measures to be included in the project ` _:;'' which will reduce geologic hazards, both onsite',and offsite, to a nonsignificant level. •...t.,.'' QUARRY HILLS SUBDIVISION ix MARCH 1995 DRAFT SEIR 1 P I These measures are listed on pages 558-63 in the text. (Nonsignificant Impact with , Mitigation) ;.,„q,,,,,--,�tw;.;:i-ii:: D.::.:.:, HYDROLOGY AND WATER QUALITY ',4 , } Impacts.', The project would not result in any significant flooding impacts, either onsite or „`k„ offsite. However, runoff from the project would contain various pollutants (e.g., oil ..::::;:i:::`•:.. & grease, heavy metals,pesticides &herbicides,etc.) which would degradethe water .. ;,; ; quality of Hale Creek and Quarry Hills Lake. Potential impacts to the water quality '-=. ofthe lake include algal blooms, proliferation of weeds, and mosquitos. Impacts to ",.',,:•�;.= . ;: the lake and creek due to_ erosion andt sedimentation were also identified as potentially :.:!....,',••••: significant. (Significant Impact) Mitigation The project will be required to develop a Storinwater Pollution Prevention Plan which . will contain measures to avoid/minimize water quality, impacts for both the construction and post-construction periods. The project's Lake Management Plan includes measures to avoid impacts to Quarry Hills Lake. The list of water quality mitigation. measures is found in the text of this document on pages 69-70. (Nonsignificant Impact with Mitigation) , 1 E. - VEGETATION AND WILDLIFE 1 Impacts, The impacts of the project include tie loss of oak woodland habitat,potential impacts to nesting raptors,.and impacts to.Heritage Oaks. The loss of oak woodland habitat would be greatest for the lots in the site's "Hillside. Area".. The current reclamation grading and project's proposed offsite sewer line. extension have already and will result in potential impacts to oaks woodland habitat. In addition, recommended remedial grading associated with upper quarry wall stability and the widening of Stonebrook.Avenue as an emergency/secondary access will remove a substantial number of trees along the north side of that street. (Significant Impact) Mitigation Pages 82-84 of the text lists the manyimitigation measures, all of which are included in the project, to minimize/avoid vegetation & wildlife impacts. These measures include the designing of the lots in the "Hillside Area" to minimize the loss of oak woodland habitat and replacement of impacted oak trees at a 5:1 ratio. Mitigation will also include the replacement of trees lost.as;part of the ongoing implementation of the Reclamation Plan. Measures to protect trees during construction are included in the project, as are pre-construction surveys for raptor nests. (Nonsignificant Impact with Mitigation) 1 F. UTILITIES AND URBAN SERVICES Impacts The proposed offsite extension of a sanitary sewer line to the Dawson Subdivision will result in potential impacts to the Hale Creek corridor, as well as impacts to the property at 11665 Dawson Drive. In addition, students from the project could exceed :'_. the capacity of the Los Altos School District. (Significant Impact) ,1k ; rPr , .:, W.�t` yid; 1f.-., 1 4 MARCH 1995 DRAFT S-+ f 1�s�t a •,& ,,ti��i '1.QUARRY HILLS SUBDIVISION ix , 1a `: , ;.ie of n/ �r?v�':F.Y l•T . .. ' •.' 1;',1110 1 , 1 f.3f 4._-..e r� d C` I� fF;04^r0),;" ', ,' :;k}'` '� kr c„',r ,)Mitigation ,,: As recommended in a 1990 Town of Los Altos Hills staff report, the construction of u i ;tfri` �, : the sewer line extension will be required to include a number of measures to minimize --J.:-44...1-44,.1, It r Impacts to the Dale Creek corridor, as well as to;the affected residence in the Dawson "�:j,;,(.>:'.•.. Subdivision. Impacts to the school district will be mitigated through the payment of a school impact fee, as mandated by State law. (Nonsignificant Impact with Mitigation) I • 1 G. VISUAL AND AESTHETIC IMPACTS ' ' ' -1 i. Impacts . The proposed p oject'would.result in signif cant visual and aesthetic impacts with I regard to light and glare, as well as alterations of existing views. The proposed frsidences will I e visible from a number of the adjacent residential areas, as well as I om portions .oi the adjacent public open space lands. The impact would be the greatest On the Hillside Lots '(i.e., Lots 18-23). This adverse impact would be siomewhat offset by the fact that the quarry would be replaced with a lake and low- I ensity residential development. In addition, the removal of trees along Stonebrook venue associated with remedial grading and the upgrading of that roadway will create a visual impact for the residences along Stonebrook. (Significant Impact) { F ! Mitigation Mitigation measures included in the project include the placement of residences below to ridgeline, retention of oak woodland habitat where feasible, preservation of prominent knolls,use of native landscaping,use of low-intensity exterior lighting, and tile-use of buildi ig materials & colors which'are compatible with the surroundings. The project wil also be required to comply with the Town's Zoning and Site i Development Or .nances. Recommended mitigation not included in the project would be to limit the h ight of houses on the Hillside lots to 1-story. It is also possible to a�oid the visual impacts associated with development in the"Hillside Area" (i.e.,Lots 18-23) by appro"l ing a modified version of the.proposed project such that lots in the "Hillside Area" are eliminated. [See discussion'of the Reduced Scale Alternative" on':page xiv.] (Nonsignificant Impact with Mitigation) L. H. AIR QUALITY • Impacts lib long-term significant air quality impacts will 'occur. However, short-term, construction-rela d impacts could be significant. Construction impacts would take tlie form of the li elihood of substantial generation of dust during various earthmoving activities. '(Si ficant Impact) ' , . a:Mitigation ::, The contractor w 11 be required to undertake various measures during construction to • av+oid/minimize a generation of airborne particulates. Measures will include the ;" :;-. ,,, ..,. .'. wateringand c venin of ex osed areas, �and sweeping of adjacent streets. g P t;7 f,,,r '(Nonsignificant pact with Mitigation) ! ,ti,, a;. ;-•.-''' :'_ ‘'• I, QUARRY:HILLS SUBDMSION xi MARCH 1995 DRAFT SEIR n'`: i A I. NOISE I • Impacts No long-term significant noise impacts will occur. However,short-term,construction- _. :` • related impacts could be significant. Construction impacts would take the form of ` .'.`;;= elevated noise levels during various construction activities. (Significant Impact) '' -l'''.1-,3;:-.1: ':.,, Mitigation:s The contractor will be required to undertake various measures during construction to;".`-'•:-:,,c. avoid/minimize excessive noise. Measures will include the use of equipment with • .. `: f - functioning mufflers and the limiting of construction to the hours of 7 AM to 7 PM, : n Mondays through Fridays. (Nonsignificant Impact with Mitigation) •'.'''''''',-7':: i I J. CULTURAL RESOURCES Impacts - Construction of Lots 1, 2, 22, and 23 of the proposed subdivision would be in a sensitive area. There is a possibility that this construction could disturb subsurface archaeological resources. (Significant Impact) IMitigation After vegetation is removed on Lots 1, 2, 22, and 23,the area would be inspected by a qualified.archaeologist. A written report detailing the findings of this inspection would be prepared and would identify appropriate mitigation measures. (Nonsignificant Impact with Mitigation) K. HAZARDOUS MATERIALS . , • Impacts The project site.is known to contain soils• contaminated with petroleum-related compounds from activities associated with the former quarrying. Although • remediation of this contamination is underway, the project could potentially expose Ifuture residents.to this contamination.• (Significant Impact) Mitigation Existing remediation will continue. If any further contamination is found, the extent I of the contamination will be determined and a remediation plan will be implemented. (Nonsignificant Impact with Mitigation) L. PUBLIC SAFETY ISSUES Impacts - The steep shoreline of the quarry lake would result in a potential safety hazard, particularly to children. (Significant Impact) Mitigation The southern shoreline would be fenced off to discourage-humans and wildlife from entering. The quarry benches would be planted with trees and shrubs to act as a deterrent to climbing these slopes; An emergency access road to the lake is also i recommended. (Nonsignificant Impact with Mitigation) ,' (I+fel riµSQ . . i y*•yyt^ 'j QUARRY HILLS SUBDIVISION ;diMARCH 1995 DRAFT SBIRJ yY``r0:-:-• .,,,.'' ' )0',,Ii.4.13,M2Ri:s;'f'.;,.v.",:ev,c,,.,;2 ktif a 40;:W.i'V'' . 'c"'N'i'll'' ''Zi': .. ;:41.10 N:Jcd il 040 :7 M. , t CUMULATIVE IMPACTS ,_; "NqUif n1pacts'" `Y' The ro used r ect, when combined with other existin and recentl -a roved '``:" ;Q. z,, P P P J g Y PP a;J .4 ` development;would result in a significant loss of open space in the area. (Significant i.,= Unavoidable,Impact) ' ' t ''' , -: ` ' - Nod significant cumulative traffic impacts were found to occur. (Nonsignificant Impact) Each project is required'to mitigate its own significant geologic impacts. Therefore, no significant cumulative' impacts will!occur. (Nonsignificant Impact) Ea h project is required to mitigate its own significant impacts on vegetation and I wildlife. ThereforlIe, no significant cumulative vegetation and wildlife impacts will li occur. (Nonsigniecant Impact) II • Eacfh project is required to mitigate its own significant hydrologic and water quality impacts. Therefore, no significant•cumulative hydrologic and water quality impacts 111 wiloccur. -(Nonsignificant Impact) f The combined effe t of all of the projects in the area would be to adversely effect the Lo Altos Schou District, since that district is operating close to capacity. 11 (Significant Impa t) .' 1 Mitigation While each projec contains measures to reduce'the cumulative loss of open space, taken together this impact cannot be reduced to a nonsignificant level. The loss of natural open space is an inevitable byproduct of any development in an area whereII thei1e are substantial open space resources. Specific mitigation recommended for this project is to improve access to the adjacent Midpeninsula Regional Open Space District lands by c II instructing trails and by providing offstreet parking near trailheads. De 'ls for this mi 'gation are found on page 115. (Significant Unavoidable Impact), The cumulative impact on the Los Altos School District will be mitigated through the10 payment of a scho 1 impact fee. (Nonsignificant Impact with Mitigation) I 11 - SUMMARY OF ALTERNATIVES EVALUATED lei A. NO PROJECT ALTERNATIVE o'ect Alt rnative is defined as no action which, in this case, would mean that the proposed The No Pr ,. 23-lot residential subdivision would not be constructed on the 78-acre project site. Under the No Project Alternative J the implementation of the previously-approved Neary Quarry Reclamation Plan and Lake Mana ement Plan woul continue. Under this alternative, the former quarry operations . :::4�, a g , could be'resumed on the 78-acre s to for another five to 15 years, or until such time as•the existing'fA .tt,0 5r' t 17 IZ Cyt \ ir' �'J 1� `. `'; a it s x s, t' • t•<1: QUARRY HILLS SUBDIVISION xiii MARCH 1995 DRAFT SEIR • :'''. I resources are exhausted). This alternative would be consistent with the site's designation by the State - I as a significant mineral resource zone. The- site would remain within an unincorporated,area of Santa Clara County. It is also possible under the No Project,Alternative that the applicant could construct five.residences, one on each of the five parcels on the 78-acre site, as allowed under County policies. =Fi� '.i:: The No Project Alternative assuming no .resumption of quarry activities and no residential : '°' r:`;'' construction would avoid all of the potentially significant impacts of the proposed 23-10:4V,;','.:': .• I subdivision. These impacts include the loss of the quarry as a mineral resource, various geologic;_' impacts, loss of oak woodland habitat, the impacts associated with the offsite extension of a sanitary ; sewer line, short-term noise and air quality impacts on surrounding properties, and visual/aesthetic '_ :.' _._• impacts. Ii If the applicant chose to develop one residence on each of the five.parcels on.the 78-acre project site, • I the impacts of such development would, be similar to those of the proposed project, but at a substantially reduced intensity. This reduced intensity could very well avoid someof the identified significant impacts of the proposed project, depending on:the size and locations of the five residences. I. For example, development of only five residences would likely not create a.significant visual impact or, at a minimum, the visual impact would be reduced when compared to that of the proposed project. I I The primary adverse effects of the No Project Alternative would be those which would occur if the former quarrying operations on the site were to'resume. Those impacts include the following: land use incompatibility with surrounding residences and MROSD lands, truck traffic, noise, generation of substantial dust, loss.of vegetation, and substantial visual/aesthetic impacts. Of course, if the former quarrying operations did not resume, these impacts would:not occur and the No Project Alternative would be,'on balance, environmentally superior to the proposed project. I, B. REDUCED SCALE ALTERNATIVE ,' The Reduced Scale Alternative was defined as development of a 17-lot residential subdivision on the site, as compared to the 23 lots of the proposed project. This alternative's 17 lots would be located I in the site's "Quarry Area", and would be roughly as shown for Lots 147 on the site plan for the proposed project: The Reduced Scale Alternative-would eliminate the six."Hillside Area" lots (i.e., Lots 18-23) that are in the proposed project. IThe environmental impacts of the Reduced Scale Alternative would be the same as those for the proposed project; except that the degree of each impact would be less. For example,when compared to theproposedproject, the Reduced Scale Alternative would generate fewer vehicle trips, less stormwater water runoff,require fewer urban servces,,impact less vegetation,generate fewer students to the school system, have less of•a visual/aesthetic impact on surrounding areas, and would retain Imore open space on the site,thereby.lessening they cumulative loss of open space. Two of the biggest differences between the proposed project and the Reduced Scale Alternative are in the. areas of geology and traffic. Specifically, the Reduced Scale Alternative would avoid the various geologic I impacts associated with constructing residences in the site's "Hillside Area". These impacts include potential debris flows,erosion, and slope stability issues. With regard to traffic,this alternative would , 1 'Resumption of quarrying would require the applicant to obtain a new Use Permit from,Santa Clara County. The quarrying is allowed under the existing site zoning,as well as the County's General Plan Land r;{ ;y; ._ IUse Designation for the site (Hillsides). Lit 1}. ',1' . •:. frry t t bY ,11 f 4A, • • •z' nitii�.,. i,02 : cti4 QUARRY HILLS SUBDIVISION xiv MARCH 1995 DRAFTER fI , , A . :r ; t '1'. • NI • , t . q i }wy4.\ �}, 1 NI' Llif :' 4' avoid the significant and unavoi able access-related impacts to Lots 19-21 of the proposed project. p4::. f# ', j�' �,� y1�.a 4'la. .. � ,tq�, Fy � l it I; `In addition, this alternative would eliminate the visual and aesthetic impacts associated with a i.74 t�� ` ,' constructing residences on elevated areas, although it should be noted that the proposed project would' ,,4� , Fti vi�,_' , not construct an) homes above he ridgelines. I • ; ' Of the various r sidential devel pment alternatives (including the proposed project), this Reduced z - Scale Alternative is the enviro entally-superior alternative. :� 1. C. ALTE ATIVE LA USE: PUBLIC OPEN SPACE Under this alterative, the Nea Iry Quarry Reclamation Plan would be completed and the 78-acre, project site would be maintained as dedicated public open space. This alternative resembles the I existing site conditions except rOr-- the use of the site as public open space. This open space alternative would avoid all of th potentially significant impacts of the proposed 23-lot subdivision, as summarized on the previousages. It' is important to note! however, that this alternative would r not meet the basic objective of the'proposed project, which isl to develop estate residential lots. 1 D. ALTERNATIVE LOC TIONS The Town of Los Altos Hills Planning Staff has indicated that there are a number of sites in the If Town which are presently vac i. and which, theoretically, could support a.residential project such as the one proposed by the appli ant: These sites are the following: 1) the 65-acre Packard.property; 2) the 41-acre Fenwick property and 3) the 44-acre Bellucci property. 1 Of these three properties, the Bellucci property is most similar to the Neary Quarry site in that portions of both sites contain step hillsides. The other two properties are generally characterized by less-steep, rolling hills. The de elopment of the proposed 23 lot subdivision on any of these three properties would result in impa is similar to.those at the Neary Quarry site, in terms of traffic generation, noise impacts; air qu `ty impacts, open space impacts, impacts on vegetation, demands on utilities and ur 1 an services, ani stormwater runoff impacts. However,unlike the proposed project, the development of a subdivisio on any-of these alternative sites would not result in the loss of a State-designated mineral resourc of significance. I Differences in impacts at each or these three sites would primarily be in the area of geology since every site has its own geologic and topographic characteristics.' Whatever those geologic impacts would be, typically they can be fnitigated, assuming that construction on active fault zones and on steep hillsides is avoided. No a sessment was completed on the three alternative sites with regard to the potential foir encountering chaeological resources and/or onsite contamination. Therefore, it _ is not known whether there woul be any cultural resources or hazardous materials impacts at those -_ alternative sites. i _ s, ,.ZP!. QUARRY HILLS SUB •DIVISION xv MARCH 1995 DRAFT SEW F I W illlaril Cotton 330 Village Lane i Fkir Los Gatos, California 95030 Attachment 5 and Associates (408) 354-5542 August 8, 1995 L1017P .. RECEIVED, AUG - 9 1995 - TOWN OF LOS'ALTOS HILLS TO : Mr.Curtis Williams Planning Director TOWN OF LOS ALTOS HILLS .I. 26379 Fremont'Road' , ' Los Altos Hills, California 94022' SUBJECT : Supplemental Geologic lid Geotechnical Review • • i RE : Vidovich/Quarry Hills Subdivision - We have completed a supplemental geologic and geotechnical review of the Tentative Map application using: - • Letter from De Anza Properties to Town of Los AltOs Hills, dated • July 26, 1995; •• • Seepage on Lots 5-10 (letter) prepared by Engeotech, dated July 24, . 1995; • Portion of Reclamation Drainage Plan'Illustrating Proposed Subdrains (1 sheet,.50-scale) prepared;by Kirkeby Engineering, dated July 24, 1995; _ I • Progress Report #5 - Quarry Hills Reclamation Project, prepared by Alan Kropp Associates (AKA) dated)December 27, 1994; i - • •- Second Response to Reviewer Comments (report) prepared,by Alan Kropp and Associates, dated September 13, 1994; • Tentative Map - Lot Design and Development Plan (1 sheet, 100- . scale) preparer not,indicated, dated'October 18, 1993; and • Study Plan #4 (1 sheet, 40-scale) prepared by''S&A Engineering, dated September 24, 1993. . • cM(IMMFFRING GEOLOGY • ENVIRONMENTAL EARTH SCIENCES • FOUNDATION ENGINEERING 4 I . Mr. Curtis Williams i August 8, 1995 Page 2 I L1017P 1 DISCUSSION The applicant proposes to subdivide the subject property into 23 lots for residential development. In o r review report of July 27, 1995, we outlined three geotechnical issues to be addres ed prior to Tentative Map approval. In addition, we listed six geotechnical issues to b. satisfactorily addressed prior to Final Map approval. • 01,C_ U Ilk ,LIII • ►i A: ,LIP . 1 : 1111 • ► ' I Proposed site development is constrained by the following geotechnical factors: • Adverse seepage wi in proposed building envelope (Lots 5 through 10); • Potenl ial for debris flows to originate within tll e subject property that may travel do nslope and adversely impact existing off-site residences; • Potential instabilit of the southwestern quarry rim that may disru t the propose Stonebrook Avenue emergency access route; • tential instabilityf the southeastern quarry rim that may impact Po p the adjacent neighb rs'back yards; • Potential debris flo hazards on three proposed'lots resulting in the need to carefully define safe building envelopes; • Significant differential fill thickness beneath proposed building sites that may result in t e need for special (non-standard) residential foundation design; a d. • Various ongoing s to grading activities not 'fully inspected or approved by the ap licant's geotechnical consultant. The first two issues listed above have been adequately addressed by conceptual design information submitted b the applicant and his consultants. Adverse seepage across Lots 5 th rlough 10 can be mitigated by subdrairi systems, but the group responsible for maintenance of he proposed subdrains should be clearly designated during the subdivision process. Final design plans for the subdrain system should be reviewed and approved by the T wn Engineer and Town Geotechnical Consultant. The conceptual debris basin design p oposed in the northwestern portion of Lot 21 appears generally adequate. However, t e crest height of the proposed berm (currently 15 feet above existing grade) could pro ably be reduced to less than 10 feet considering that it is located considerably downslo e, and at a much wider point in the swale than the previously proposed berm (i.e., a so designed with a 15-foot crest height). Final design of the berm should)include drain ge measures to properly convey surface water flow. Regarding the proposed Stonebrook Avenue emergency access route, we understand that the applicant is ilkot proposing measures to mitigate potential instability of this area. The project geo echnical consultant has previously concluded that corrective grading is appropri ,te adjacent to this roadway to provide adequate William Cotton and Associates Mr. Curtis Williams August 8, 1995 Page 3 L1017P protection of the roadway for emergency access. We concur with the,consultant that future landsliding, possibly:triggered:by seismic conditions or significant rainfall, may interrupt use of this roadway. In our opinion, there is a moderate level of risk-that future landsliding could render this roadway impassable until corrective measures are implemented. The riskof not implementing measures to mitigate potential instability. along StonebrOok Avenue should be considered by the Town during evaluation of the Tentative Map. The remaining items 1 through 6 may have significance to visual'or economic aspects of the project. We recommend that the Town Planning Commission and Council be made aware of these geotechnical.issues during the Tentative Map evaluation process, and that these issues be resolved no later than prior to Final Map approval: 1. Potential Southeastern Quarry Rim Instability - The project geotechnical consultant has previously identified the potential for failure and retreat of the quarry rim that may encroach into the back yards of adjacent neighbors to the southeast. While a significant hazard to any existing homes is not anticipated, the consultant has indicated that corrective grading and/or wall construction along this portion of the quarry rim !could reduce the potential for encroachment of instability into adjacent back, yard, areas., The Town Attorney should address whether the Town may incur any liability for not requiring stabilization of these slopes as part of the subdivision process. 2. Preliminary Foundation Recommendations - Preliminary recommendations should be prepared by the Project Geotechnical Consultant to define the general type of residential foundation deemed appropriate for each proposed lot. The potential need for any unusually deep or rigid foundation systems should be addressed. The range of differential fill thickness across proposed building envelopes should be quantified as part of this evaluation. Any requirements for fill settlement monitoring prior to construction should be addressed. It is important that .the geotechnical consultant, who has inspected! most of the reclamation and subdivision grading, define appropriate types_of foundations for individual lots. Preliminary foundation recommendations should be prepared prior to approval of the Final Map. . 3. On Site Debris Flow Hazard I Mitigation - As discussed and recommended in our review report of October 14, 1994,the building envelope.on Lot 23 should be revised in orderto make it consistent with Alan Kropp Associates (AKA) recommendations. The revised building envelope, along,with a debris flow building exclusion zone/conservation easement (i.e., zoneincluding the Qc fan across Lot 23 previously mapped by Harlan Tait Associates), should be • indicated;on the Final Map. No residential construction should be allowed within the building exclusion zone/conservation easement unless detailed lot-specific geotechnical investigation is'performed to demonstrate•the feasibility of construction with appropriate mitigation measures. • William Cotton and Associates I. =- Mr. Curtis Williams August 8, 1995 Page 4 L1017P Lot 21 is also constr ined by debris flow hazards. As noted in our Qctober 1994 revie report, a significant portion of the proposed, , relocated building envelope is still situated within the debris flow/colluvial fan deposits (Qc) mapped by Harlan Tait Associates (HTA). Specific site grading measures, resulting in elevation of the building pad as recommended by AKA, are an integral part of the afe development of this lot. An appropriate final pad elevation and proposed site grading plan should be prepared and accep ed by AKA prior to Final Map approval. The Town may request such information, if deemed necessary for aesthetic evaluation, prior to Tentative Map approval. The referenced Stud Plan #4, with the modifications stated above, is to become part f the Final Map application. It should be understood that sp cific final building envelopes and driveway alignments are to be defined by the modified Study Plan#4. 4. Quarry Wall Landsliding - AKA has indicated that the benched quarry walls have a -sigh potential for ongoing shallow landsliding. The consultant has concluded that corrective grading of these slopes (i.e., removing existing benches, landslide deposits and loose debris) to forrki a smooth slope would significantly reduce the potential for future shallow failLres. While these slopes do not present an apparent hazard to proposed residential building sites, hikers and possible boaters may be at risk unless appropriate measures are taken. We understad that no private boats will,be allowed on the lake. However, nec ssary fencing or other appropriate measures shoul be designed, 'n conjunction with final development plans for the project, to prec ude pedestrian access onto or beneath the benched quarry wall . 5. Geotechnically Un ocumented Site Grading - The referenced Progress Report #5J prepared by AKA regarding site grading operations, contains list of 11 site reclamation/grading operations that were not within their scope of inspection services. It' is important that all portions of the property are ultimately presented for public or privat use in a safe condition. consequently, the extent of necessary corrective grading activities should be defined by the Project Geot chnical Consultant to the satisfaction of the Town Engineer and Town Geotechnical Consultant prior to Final Map approval. 6. Supplemental Subdivision-Level Improvement Plans - Supplemental plans should be prepared to illustrate all proposed subdivision level improvements. A detailed site drainage plan . should be included illustrating all existing/proposed final water inlet and outlet facilities for the reservoir. Items such as proposed • street i.avement sections, fire hydrant locations, and final design details for surface drainage facilities and seepage mitigation should be prepared as deemed necessary by the Town Engineer. If crushed rock (other than Class 2 Permeable material) is utilized in subdrain construction, then this drain rock should be entirely enclosed by filter fabric. Final design of the debris flow basin in Lot 21, includ4g surface drainage measures and adequate berm height, William Cotton and Associates -4. r ; Mr. Curtis Williams August 8, 1995 Page 5 L1017P should be submitted. Supplemental subdivision-level improvement plans should be reviewed and approved by the Town Engineer and Town Geotechnical Consultant prior to acceptance of the Final Map. Respectfully submitted, WILLIAM COTTON AND ASSOCIATES, INC. TOWN GEOTECHNICAL CONSULTANT W)-e7 /1 ,,e07&(L- — William R.Cotton Principal Engineering Geologist CEG 882 Patrick O. Shires Principal Geotechnical Engineer GE 770 Ted Sayre Senior Engineering Geologist WRC:POS:TS:rb William Cotton and Associates • Attachment 6 NOV ®� 1 I . TOWN OF LOS .N.07 11 4- 17171-411".."--7..111)4444&` MIS IIILMONT 110A0. LOS ALTOS HILLS. CALIFORNIA MI 8i p ' •• ' r (41gMI•Ti.1 n • •.' Al O \ 111 ... �ilt • California �4` + d • Joao*" SUBDIVISION APPLICATION For Official Use Receipt:. .By , Date Fee TOWN OF LOS ALTOS HILLS, CALIFORNIA Deposit , Applic.�A The undersigned hereby files a Preliminary/Tentative, Subdivision Map and. supporting information in accordance with the provisions of the Subdivision Chapter of the Municipal Code and any amendments thereto: 1 . APPLICANT: -Name(Print or Type). jot! k) Street Address 20 W. ' YLEMQ1.)T .. Li,a - , CitycLuoto CE Telephone: Business408 -13?) 44Home Applicant is: Owner Authorized Agent of Owner iciik)( If agen1tl , complete item2below) - • 2. OWNER : Name(print or type ) . `1 i O\ E t 7 LL - Street Address - $MIME - ,. City Telephone: Business Home 3. DESCRIPTION OF PROPERTY: Street -Adddr.e ss . l l 9 ZU •_S1-0Nal IL Subdivision Name Q(A 0 12 IL Y C7t •L—L S , Lot No. - Assessor' s Parcel Number 336.,- 10 ) 33�-33-1t J 33c2-34- rS, 1(,, l'7 (Please check above descripti on carefully with Planning Commission Secretar in case of any doubt to insure accuracy) 4. Maps, Statements and Materials required by Subdivision Ordinance submitt as a part of application (List all items submitted ) . -pcu1G,LUaS TD(2_1\1SLOP ) 2) POU (4 ) c._o P 1 ac o S L o ' CCAS 5 I Ft CJ>T(O h) M A P CO to t (r ) C o p` 01= 02-6 Fl L � b1�IL3 ,� rzl� c . b • .,•:,:. (•: • ., .1' . .. . ... . . . . . . . . . . . . . . Subdivision Application . . . Page 2 . A " - • ' ' , 0 . ,• ' . • ' . •. • ,• • . . . • . 4 . Maps, Statements and Materials (cone. ) r; co kya 0 ) c)0 P / • o o L1 2. -corz-1-, nk ,f_ p (, 0.1e(Os- .-2-7 o P. co (D*- N st-r\1 C___ALL:cjA t_2s-T-71 :bh. 5 .. . _. . . . . . ‘ • . .. - . - . . . • • . . . . . .. . • • .. ... ..• - ... .. . • . . • _ • . . . - I , the undersigned , do hereby certify that the facts and information contained in this application are accurate and complete to the best of my. knowledge . declare under penal y of perjury that the foregoing in true and correct . • Executed . at E;(-ALL \NAL- = .. - .. . • , • . ' . California on ' — 17--:-L. 43 . . - . . . - . ........ - (date) . . . . , Signature of owner (s); Nr_e_c_c)\--.. • . . • _ • OR • • . ' • - .. . • - • Signature' ofApplicant/Agent; (requires fetter of authorization from owner) - . . , .. . . - . . • . . . , . . . . • • . . . . . - • . • ..- ,- '. '. . . . . - • • • . • • . . . . . . , . . _. ' . .• 3/87 . . • . . • .. • ' . • , . . • . . . 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' ' • • •I ..• . . :. , , -.....":;• '143q ' ,,.,./'."•4•:•4•"‘•:i•;•.&pa.) . • ' . . - . . . . .. ••••••• .• • ... , • ' .`' • - •• .• .• . . . " '.••• l' •• : • 1 •.:•• .,::••••''... ^-.•.. • .• , . c i S•':',7•J'ti..,_P-:44,.'Itc11•,:ki17,4,1'.;k44741°.•Visilli4.1..44-A^ * i,� ftp . • %Wil VD Ramos- r 6 ... CITY OF LOS ALTO One North San Antonio Road) Los Altos,California 94022-3088 Tel: (415) 948-1491 Fax: (415) 941-7419 August 21, 1995 City Council and 'harming Commission Town of Los Alto Hills VIA FAX & MAIL 26379 Fremont Ro d Los Altos Hills, A 94022 SUBJECT: Responses to Comments on the Draft Supplemental Environmental Impact Report (DSlIR) for the proposed Quarry Hills Subdivision Dear Honorable M yor, Councilmembers and Commissioners: Thank you for pro1iding us with your responses to.our May 1, 1995 comments on the DSEIR for the proposed Quarry Hills Subdivision. The responses to our, comments are generally adequate with the understanding that the construction control measures listed at the bottom of page 68 and the permanent control measures listed at tfhe top of page 69 are typical of those which are included in an SWPPP for a project of this ty/e. . . Although no mention of it is made in the DSEIR, it would be expected that the Mitigation Monitoring Progra I for the Final EIR would identify the agency or agencies responsible for review and approv of the SWPPP and the annualupdates of the erosion control plan, as well as for enforcement of:the SWPPP during construction. Thank you very m ch for your consideration and please feel free to contact me at 948-2790, x211 if your have y questions. l Sincerely,ooloveyJ . i1/( Janj es D. Mackenzie, AICP Senior Planner cc: City Manag-r Planning Director Fire Department RESPONSIVE-INNOVATIVE-CONCERNED