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HomeMy WebLinkAboutItem 3.13.! Town of Los Altos Hills August 12, 2004 Staff Report to the Planning Commission RE: CONDITIONAL EXCEPTION TO ROAD DESIGN STANDARDS FOR MAXIMUM CUT AND FILL ALLOWED; LANDS OF HORTON; CHAPARRAL WAY SUBDIVISION; FILE# 77-04-MISC. FROM: _ Angelica Herrera Olivera, Assistant Planner APPROVED BY: Carl Cahill, Planning Director RECOMMENDATION That the Planning Commission: 1. Recommend for City Council approval the proposed roadway retaining wall design and conditional exception, which includes approximately 15 feet of cut and 9 feet of fill, subject to the attached conditions of approval and findings. BACKGROUND The City Council approved a Tentative Map for a four -lot subdivision on Chaparral Way on July 18, 2002, subject to conditions in Attachment 3. A 20 -foot wide road, within the existing 40 - wide Chaparral Way right-of-way, provides access to the site from Moody Road. The proposed entry cul-de-sac off of Chaparral Way contains a 24 -foot roadway within a 60 -foot private easement, which provides direct access to Lot 1. A 35 -foot wide private easement provides access to Lots 2, 3 and 4 off the western side of the cul-de-sac. The steep terrain along the roadways leading from Moody to the end of the cul-de-sac, along with required drainage facilities along and above the retraining walls necessitate taller retaining walls than the originally proposed 4 -foot tall retaining walls on the preliminary grading plan for the Tentative Map. The applicant is requesting a conditional exception to the road design standards for the Town, which limits the maximum cut and fill to 10 feet and 8 feet respectively. The proposed roadway retaining wall design requires up to 15 feet of cut and 9 feet of fill. However, the actual heights of the proposed roadway retaining walls vary from 4 feet to 101/2 feet tall. Pursuant to Section 9-1.703 of the Subdivisions Ordinance, a 10 -foot maximum cut and 8 -foot maximum fill is permitted in designing public and private roads. Pursuant to Section 9-1.1501 of the Subdivisions Ordinance, the Planning Commission may recommend for Council approval conditional exceptions from the provisions of this chapter when, in the opinion of the Planning Commission, undue hardship may result from the strict compliance with the provisions of this chapter, and an exception would not be contrary to the public interest. A recommendation for Council approval of a conditional exception requires that the Planning Commission approve certain findings. Staff has prepared the necessary findings for the Commission's review in Attachment 2. CLapaual Way Subdivision Planning Commission August 12,2004 Page 2 of 7 Roadway Retaining Wall Design The color -coded Sheet 1 of the Retaining Wall Site Plan illustrates the range in retaining wall heights proposed for the required roadways leading from Moody Road and Chaparral Way. The areas where the proposed cut and fill exceeds the maximum allowed pursuant to the Subdivisions Ordinance have also been labeled on Sheet 1. A majority of the retaining walls along the proposed roadway will exceed 4 feet in height. Approximately 2,595 lineal feet of retaining wall length will exceed 4 feet in height—approximately 64 percent of the total amount of retaining walls. Staff is recommending in condition of approval #1 that the proposed retaining walls shown along the driveway for Lot 1 (on west side of cul-de-sac), which include a 10'/z tall retaining wall, be reviewed at the time of site development with a new residence. Sheet S0.0 shows the typical retaining wall section along the roadway. The majority of the proposed retaining walls are terraced, up to three walls, in order to reduce the overall height of the retaining walls and to provide area for landscape screening. In addition, the walls are sloped back at a six degree angle to provide a more natural looking appearance. Three different types of roadway retaining walls were originally proposed: tie -back walls, pier and grade beam walls, and geogrid walls. However, the Town Geologist voiced several concerns regarding the proposed geogrid retaining walls, including a greater anticipated impact on existing trees. The current proposal involves only tie -back walls and pier and grade beam walls. Landscaping and Materials The Initial Study for the 4 -lot subdivision indicated that a total of 36 oak trees would have to be removed on the access road and Chaparral Way. An oak tree replacement plan is required as part of the Tentative Map project as mitigation. Oak trees that need to be removed shall be replaced at a 1:1 ratio as part of a landscape replacement plan submitted to the Planning Department for approval prior to recording the Final Map. The applicant is proposing to mitigate the extensive length of retaining walls by using a stone- like, earth tone colored, Allan -block veneer. Attachment 4 includes two separate views of the proposed roadway retaining wall design. Staff is recommending in condition of approval #2 (see Attachment 1) that the proposed color scheme for the Allan -block veneer be a darker hue of the same colors to blend in with the proposed and existing vegetation. A recommendation is also proposed for the color of the roadways and all proposed concrete surfaces to reduce the potential visibility of the improvements from other surrounding hillside properties. The proposed landscaping selection, size, and placement are shown on Sheets 1, 2 and 3. Extensive landscaping is proposed both along the bottom as well as overhanging the tops of the retaining walls. As stated on the plans, the plants have been selected for their native or "naturalized" characteristics, drought and deer resistance, and compatibility with the weather and soils of the region. All planting areas shall be irrigated with a fully automatic drip irrigation system. Attachment 5 illustrates a colored version of Sheet 4 of the plans, which demonstrates the view of the terraced retaining walls from Moody Road immediately after landscaping and a view of the walls a few yeas later. Chaparral Way Subdivision Planning Commission August 12,2004 Page 3 of 7 Geotechnical Review The Town Geologist has reviewed the proposed roadway retaining wall design and has provided conditions, which have been incorporated in Attachment 1. The main issues centered on the structural feasibility of the proposed retaining wall design and the overall impacts to the site regarding grading and vegetation removal. Engineering Review The Engineering Department reviewed the proposed roadway retaining wall design for the maximum heights of cut and fill only. The final detailed grading and drainage plan for the street improvements for the Tentative Map shall be submitted to the Town once the retaining wall design has been approved. Possible Alternatives While alternatives to the proposed roadway design are possible, the net effect would be similar— substantial oak tree removal and excessive grading. The overall steepness of the site limits the possible alternate locations for the roadway. Situating the roadway further to the east would cut further into the hillside, requiring taller retaining walls and the additional removal of vegetation. Siting the roadway further to the west would create the same situation on the hillside east of the natural drainage Swale. The width of the roadway is another way in which the proposed roadway retaining wall design could be altered. The July 18, 2003 conditions of approval for the 4 -lot subdivision require a 24 - foot roadway. A lesser width could reduce the required cut and fill, retaining wall heights and perhaps be cause for fewer oak trees to be removed. However, the steepness of the winding cul- de-sac necessitates the 24 -foot width for fire truck access. Findings for a Conditional Exception In making its findings, the Planning Commission shall consider the existing land use of the area, the nature of the proposed use of the land, and the probable effect on traffic conditions. The nature of the proposed use of the land calls for a 4 -lot subdivision. Any worsening of the traffic condition along Chaparral Way during the construction of the entry cul-de-sac will be mitigated once the existing road is widened to a 20 -foot wide paved roadway. The strict application of the provisions of this chapter would deprive the applicant of the reasonable use of the subject property. There are special circumstances and conditions affecting the property that seem to warrant a conditional exception: 1) The majority of the site has 40 percent slopes or greater; 2) There is a large drainage swale located in the center of the site which drains to Chaparral Way and Moody Road, 3) One relatively small landslide deposit and two debris slides are located west of the main drainage Swale; and 4) The hillside site includes extensive oak woodland and grassland habitat. By granting the conditional exception to the applicant, no other landowner shall be deprived of the reasonable use of their individual land or subjected to undue burdens or hardships or be Chapamd Way Subdivision Planning Commission August 12, 2004 Page 4 of deprived of any material use or enjoyment of their individual property. The aesthetic improvements, retaining wall replacement and widening along Chaparral Way will enhance the access for the property owner to the east of the entry cul-de-sac (Lands of Mak) as well as for the property owners located further west along Chaparral Way. SUMMARY The proposed roadway retaining walls have been designed to be aesthetically pleasing and natural looking through the use of earth tone colored stone and extensive landscaping. Based on the findings discussed earlier, the steep terrain and natural conditions of the property provide special circumstances that merit a Conditional Exception to the allowable cut and fill for the design of the proposed roadways. Staff is available to answer any questions that the Commission or the public may have. Staff determined the project to be categorically exempt from CEQA pursuant to Article 11, Section 15162, "Subsequent EIRs and Negative Declarations" which allows project revisions that do not involve new significant environmental effects or a substantial increase in the severity of previously identified significant effects. ATTACHMENTS 1. Recommended Conditions of Approval, (2 pages); 2. Findings for the Conditional Exception, (I page); 3. Conditions of Approval for the 4 -lot subdivision, dated July 18, 2002, (4 pages); 4. Photos of proposed Allan -block veneer retaining walls, (2 pages); S. Colored Perspective of Retaining Walls with Landscaping (I page); 6. Cotton, Shires & Associates, Inc. letter, dated July 23, 2004, (3 pages); 7. Site development plans, (6 pages). cc: Jack and Nancy Horton Mark Helton, Giuliani & Kull, Inc. 26030 Altamont Road 4880 Stevens Creek Blvd., Ste 205 Los Altos Hills, CA 94022 San Jose, CA 95129 Chnpamal Way Subdivision Plamdng Commission August 12, 2004 Page 5 of 7 ATTACHMENT 1 RECOMMENDED CONDITIONS OF APPROVAL FOR A CONDITIONAL EXCEPTION TO ROAD DESIGN STANDARDS REGARDING MAXIMUM CUT AND FILL TO ALLOW UP TO 15 FEET OF CUT AND 9 FEET OF FILL LANDS OF HORTON; CHAPARRAL WAY SUBDIVISION FILE# 77 -04 -MSC A. PLANNING DEPARTMENT: 1. All proposed retaining walls associated with the driveway on Lot 1 (on west side of cul-de-sac), shall be reviewed at the time of site development with a new residence. 2. The proposed color scheme for the Allen -block veneer on all proposed retaining walls shall be comprised of a dark earth tone color to blend in with the proposed and existing vegetation. The color of all proposed roadways and concrete surfaces shall be stained a dark earth tone color to reduce the visibility of the improvements from other surrounding hillside properties prior to final inspection. 3. All landscape screening and irrigation shall be installed as shown on the plans to screen all retaining walls prior to final inspection. 4. No other modifications to the approved plans are allowed except as otherwise first reviewed and approved by the Planning Director or the Planning Commission, depending on the scope of the changes. 5. The applicant is responsible for acquiring all required permits from the Building Department prior to commencement of work. 6. As recommended by Cotton, Shires & Associates in their report dated July 23, 2004, the applicant shall comply with the following: a. Geotechnical Plan Review —The applicant's geotechnical consultant should review and approve, all geotechnical aspects of the project building and grading plans and supporting wall design calculations (i.e., site preparation and grading, site drainage improvements and design parameters for retaining walls and pavement to ensure that their recommendations have been properly incorporated. The results of the plan review should be summarized be the geotechnical consultant in a letter and submitted to the Town Engineer for review prior to issuance of building permits. b. Geotechnical Field Inspection — The geotechnical consultant should inspect, test (as needed), and approve all geotechnical aspect of the project construction. Cl parral Way Subdivision Plmudng Commission August 12, 2009 Page 6 of 7 The inspections should include, but not necessarily be limited to: site preparation and grading, site surface and subsurface drainage improvements, and excavations for foundations and retaining walls prior to the placement of steel and concrete. The consultant should also inspect the testing of wall tiebacks. The results of these inspections and the as -built conditions of the project shall be described be the geotechnical consultant in a letter and submitted to the Town Engineer for review prior to final (as built) inspection. Upon completion of the construction, a final inspection shall be required to be set with the Planning and Engineering Departments at least two weeks prior to final building inspection approval. NOTE: The Conditional Exception is valid for one year from the approval date (until August 12, 2005). All required building permits must be obtained within that year. Clupa l Way Subdivision Planting Commission August 12,20N Page 7 of 7 ATTACHMENT 2 FINDINGS OF APPROVAL FOR A CONDITIONAL EXCEPTION TO ROAD DESIGN STANDARDS REGARDING MAXP" CUT AND FILL TO ALLOW UP TO 15 FEET OF CUT AND 9 FEET OF FILL LANDS OF HORTON; CHAPARRAL WAY SUBDIVISION FILE# 77-04-1v1ISC (a) There are special circumstances or conditions affecting such property so that the strict application of the provisions of this chapter would deprive the applicant of the reasonable use of this land. The strict application of the provisions of this chapter would deprive the applicant of the reasonable use of the subject property. There are special circumstances and conditions affecting the property that seem to warrant a conditional exception: 1) The majority of the site has 40 percent slopes or greater; 2) There is a large drainage Swale located in the center of the site which drains to Chaparral Way and Moody Road, 3) One relatively small landslide deposit and two debris slides are located west of the main drainage swale; and 4) The hillside site includes extensive oak woodland and grassland habitat. The proposed 15 feet of cut and 9 feet of fill necessary for the proposed roadway retaining wall design are a result of the cumulative conditions of the subject property. (b) By granting the conditional exception applied for, any other landowner shall not be deprived of the reasonable use of his land nor be subjected to undue burdens or hardships or be deprived of any material use or enjoyment of his property. By granting the conditional exception to the applicant, no other landowner shall be deprived of the reasonable use of their individual land or subjected to undue burdens or hardships or be deprived of any material use or enjoyment of their individual property. The aesthetic improvements, retaining wall replacement and widening along Chaparral Way will enhance the access for the property owner to the east of the entry cul-de-sac (Lands of Mak) as well as for the property owners located further west along Chaparral Way. Any worsening of the traffic condition along Chaparral Way during the construction of the entry cul-de-sac will be mitigated once the existing road is widened to a 20 -foot wide paved roadway. 3 C IyD1:f1ONS FOR'Cl IL' FOUR LOTATTACHMENT SUBDIVISION OF A 16.13 ACRE PARCEL FILE 118-0 1 - fM-GD-ND (Revised by City Council .lily 18, 2002) LANDS OF MORTON, North of Moody Road on Chaparral Way GEOTECI INICAUEART'1I W ORK 1. Prepare a modified grading plan addressing inlennediate cut slope benches recommended by the Project Geotechnical Consultant including locations of lined interceptor ditches and heights of cut for the Town Geotechnical Consultant and staff review. 2. Subdivision improvement plans, including design details fur all roadway and driveway retaining walls shall be prepared for review by the Town Planner, the Town Engineer and the Town Geotechnical Consultant prior to issuance of permits for subdivision improvements. 3. Prior to issuance of permits for construction of residences on individual lots, plans detailing proposed development layouts, drainage and grading shall be evaluated by the Town Engineer and the Town Geotechnical Consultant_ LAND AND EASEMENT DEDICATION 4_ The applicant shall grant public utility easements to all utility companies for utility constrrmtion and maintenance, including hot not limited to: Pacific Bell, Pacific Gas and Electric Company, cable television, and the Purissima Bills Water District, to the satisfaction of the City Engineer_ 5. 'File applicant shall grant public utility easements to tre Town of Los Altos Ifills for utility constniction and maintenance to file satisfaction of the City Engineer_ 6. The proposed entry cul de sac will provide a 24 foot road within a 60 foot private easement as shown on the Tentative Map. The road shall be located to the satisfaction of the Town Engineer J 7_ All easement and right -of way dedications shall be created as part of the Final Map to the satisfaction of tie Town Engineer. Lands of Homes Conditions of approval July 29, 2002 Page 3 IMPROVEMENTS A grading and drainage plan which includes an erosion control plan shall be submitted for review and approval by the Town Engineer as part of the subdivision improvement plans. This plan shall conform to all standards adopted by the Town of Los Altos Hills and shall comply with all appropriate requirements of the Town's NPDES Permit relative to grading and sediment erosion control including but not limited to: a) restricting grading during the moratorium bola November 1 to April I except with prior written approval from the Town Engineer, b) protecting all finished graded Slopes from erosion using such techniques as hillside benching, erosion control matting and/or hydroseeding, c) protecting downstream stone drainage inlets from sedimentation, d) appropriate use of silt fencing to retain sediment on the project site, e) any other suitable measures outlined in the ABAG Manual of Standards. 3. The site drainage shall be designed as surface flow whenever possible to avoid concentration of runoff. The proposed drainage shall be designed to maintain the existing flow patterns. The applicant shall design and construct all subdivision drainage improvements as deemed necessary by the Town Engineer_ Stone drainage design shall be for the 25 yem storm and shall include analysis of the existing downstream drainage channels and pipes that will receive drainage Gom the subdivision to determine if they have adequate capacity to safely accommodate the additional (lows_ All required drainage improvements shall be constnlcted or bonded Rhr prior to recordation of the Final Map. 10_ Improvement plans Cor the subdivision shall be submitted for review and approval by the Town Engineer prior to commencement of inhpfovenhent work. These plans shall confunn to all standards adopted by the Town of Los Altos Hills. I1_ All lots within the subdivision shall be connected to the public water system to the satisfaction of the Town Engineer and the I'missima Ilills Water District. Services shall be installed to the property lines or be bonded for prior to recordation of the Final Nlap. Any necessary fees shall be paid prior to the recordation of the Final Map_ 12_ All existing and proposed public utilities that serve the property and those within the property shall be placed underground, in a'ecoldance with the Subdivision Ordinance, Sec. 9-1.1105. Plans for the location of all such utilities are to be included in the improvement plans for the subdivision. Improvements shall be installed or bonded for prior to recordation of the Final Map. 13. The proposed sanitary sewer system both public portion and private portion shall be designed and COnstrneled to the satisfaction of the Town Engineer or bonded Cor prior to recordation of the Final Map_ Any necessary fees shall be paid prior to recordation of tile Final Map. Lands of Horton Co ldilions of approval July 29, 2002 Page 4 14. All street improvements shall be constructed to the satisfaction of the Town Engineer or bonded for piiorto recordation OF (lie Final Map. PLANNING AND ZONING 15_ Any, and all, wells on the property shall be shown on the Improvement Plans, shall be properly registered with the Santa Clara Valley Water District, and shall be either maintained or abandoned in accordance with District standards. 16_ Payment of storm drainage fees, Park and Recreation dedication fees, Pathway in-lieu fees, Roadway in-lieu fees and all other applicable fees shall be required prior to recordation of the Final Map. The Park and Recreation dedication fees shall be provided fu accordance with section 211403 and section 9. 1. 1404 based on appraised value of each approved lot. 17. All subdivision conditions of approval and subdivision improvements shall be constructed and approved by the 'Town Lngineer prior to issuance of any site development permits. I8. The applicant shall inform the Town of any damage and shall repair any damage caused by construction of the subdivision improvements to pathways, private driveways and public and private roadways prior to final acceptance off lie subdivision by the Town. The applicant shall provide (he Town with photographs of the existing conditions of the roadways and pathways prior to recordation of the Final Map. 12 A grading and construction plan shall be submitted by the subdivider for review and approval by the 'Town Engineer and Planning Director prior to issuance of a grading permit for subdivision improvements. The grading and construction operation plan shall address truck traffic Issues regarding dust, noise and vehicular and pedestrian safety on Chaparral Road, Moody Road and surrounding roadways, storage of construction materials; placement of sanitary facilities, parking for construction vehicles; and parking for construction personnel. A debris box shall be placed onsite for collection of construction debris. Arrangements shall be made with the Los Altos Garbage Co. for the debris box as they have a franchise with the Town. P 20. Prior to beginning any grading oconstruction operations, all signi r ficant trees shall be fenced at the dripline; and shall be of material and slnreture to clearly delineate that dripline. Town staff must inspect the fencing and trees to be tented prior to starting grading or construction. 'file fence must remain in place throughout the course of construction. No storage of equipment, vehicles or debris shall be allowed within the driplines. Lands of Horton Conditions of approval July 29, 211112 Page 5 21. Upon discovering or unearthing any possible burial site as evidenced 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. 'Phis shall be accomplished to the satisfaction of the County Coroner's OtT'me and the Planning Director, as may be necessary during the construction ol'subdivision improvements. FIRE DISTRICT REQUIREMENT S 22. "fhe requirements of' the Santa Clara County hire Department dated February 6, 2001 shalt be adhered to except as modified by the FireDepartmentreview and approval of the applicant's (ire hock access plan. m ® \\« \ � .� . /y\33 ATTACHMENT Cq July 23, 2004 L0431H TO: Angelica Herrera Olivera Assistant Planner TOWN OF LAS ALTOS HILLS 26379 Fremont Road Los Altos Hills, California 94022 SUBJECT: Supplemental Geotechnical Review RE: Horton/Blue Oak Ridge Subdivision Chaparral Way At your request, we have completed a supplemental geotechnical review of permit applications for the construction of a new roadway and associated retaining walls using: • Retaining Wall Elevations, Sections and Details (Sheets S1.2, S2.1 and S3.5) prepared by Adamo & Associates, dated July 23,2004; • Blue Oak Ridge Subdivision- Roadway retaining walls (8 sheets) prepared by Adamos & associates, dated July 14,2004; and • Retaining Wall Structural Calculations prepared by Adamo & Associates, dated July 14, 2004. In addition, we have reviewed pertinent technical documents from the proposed project subdivision file. DISCUSSION We understand that the applicant is seeking Town approval of plans for the construction of a roadway, and associated retaining walls into the subject property. In our previous project review memorandum (dated July 1, 2004), we relayed a discussion regarding project retaining wall design issues with Tom Adamo (Project Structural Engineer), who had assisted in preparation of earlier project roadway wall design plans. Mr. Adamo indicated that the originally designed geogrid reinforced retaining walls along the roadway alignment would be replaced with tieback walls and/or pier and grade beam walls. We understand that the basic appearance of these replacement walls will be the same as the other tie -back walls and pier and grade beam walls previously Angelica Herrera Olivera Page 2 July 23, 2004 IA431H proposed for use along the roadway. The referenced revised roadway retaining wall plans illustrated the design and proposed distribution of the above two types of walls. Based on our review of the referenced documents, the revised roadway plans resolve our previously indicated geotechnical concerns with project retaining wall design. Consequently, we do not have remaining concerns with geotechnical aspects of proposed project design. We did note one apparent drafting error in the table on Plan Sheet SI.2 where the values provided for 125 percent and 150 percent test loads are reversed. It would be helpful if an additional column was added to this table indicating design load values for each of the various sizes of wall tieback bars. We have presented these comment to the Project Structural Engineer. Prior to issuance of permits allowing initiation of roadway construction, we recommend that the following Condition 1 be satisfactorily addressed. 1. Geotechnical Plan Review - The applicants geotechnical consultant should review and approve, all geotechnical aspects of the project building and grading plans and supporting wall design calculations (i.e., site preparation and grading, site drainage improvements and design parameters for retaining walls and pavement to ensure that their recommendations have been properly incorporated. The results of the plan review should be summarized be the geotechnical consultant in a letter and submitted to the Town Engineer for review prior to issuance of building permits. 2. Geotechnical Field Inspection- the geotechnical consultant should inspect, test (as needed), and approve all geotechnical aspect of the project construction. The inspections should include, but not necessarily be limited to: site preparation and grading, site surface and subsurface drainage improvements, and excavations for foundations and retaining walls prior to the placement of steel and concrete. The consultant should also inspect the testing of wall tiebacks. The results of these inspections and the as -built conditions of the project shall be described be the geotechnical consultant in a letter Angelica Herrera Olivera Page 3 LIMITATIONS July 23, 2004 L043 1H and submitted to the Town Engineer for review prior to final (as built) project approval. This review has been performed to provide technical advice to assist the Town with discretionary permit decisions. Our services have been limited to review of the documents previously identified, and a visual review of the property. Our opinions and conclusions are made in accordance with generally accepted principles and practices of the geotechnical profession. This warranty is in lieu of all other warranties, either expressed or implied. Respectfully submitted, COTTON, SHIRES AND ASSOCIATES, INC. TOWN GEOTECHNICAL CONSULTANT Ted Sayre Supervising Engineering Geologist CEG 1795 David T. Schrier Senior Geotechnical Engineer GE 2334 POS:DTS:tr