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HomeMy WebLinkAboutTC Ord 1980-08-20 ORDINANCE NO. 229 N.S. AN ORDINANCE OF THE TOWN COT~CIL OF THE TOWN OF TIBURON APPROVING VON DER WERTH MASTER PLAN BE IT ORDAINED BY THE TOWN COUNCIL OF THE TOWN OF TIBURON AS FOLLOWS: SECTION 1. FINDINGS: A) A Master Plan has been submitted by Albert Von der Werth for the development of a five lot subdivision on 2.4 acres of land off Gilmartin Drive. B) The Master Plan is described as follows: 1) Map entitled, "Master & Precise Development Plan -- Vista De Aves Subdivision" by Robert C. Martin, dated April 27, 1979, and revised November 23, 1979. 2) Environmental checklist and supporting information. C) A focused Environmental Impact Report was prepared by HKS Associates for this project, and it has been reviewed by the Planning Commission (Commission). D) The EIR points out that the project site is comprised of moderate-to-steep southwest and southeast-facing slopes with elevations that vary from approximately 30 feet above sea level near Tiburon Boulevard to 200 feet along the upper limit of the site. The EIR notes that there are two landslides on the site and that when the soil on the site becomes saturated, it loses much of its strength; that the site illustrates conditions which are susceptible to winter landsliding; that new instability can develop in previously stable areas; and, in addition, old landslide zones can be reactivated to instability created by grading the natural slopes and from heavy groundwater flow. E) The EIR reveals that construction of dwelling units and the proposed access road will increase the potential for land- sliding in this active and recently active landslide area; land construction of the proposed roadway which would provide access from Gilmartin Drive would remove the support from most of the already unstable areas. F) The EIR points out that damage to foundations could result from the effects of expansive soils as well as the instability problems identified and that construction of the proposed developments would result in exposure of the proposed buildings and other facilities to strong earthquake shocks. -2- G. The project as proposed is feasible but geotechnically difficult. The major geotechnical considerations are the presence of weak, compressible and creeping colluvium which is unsuitable for support of fills or foundations; existing and possible new landslides could flow into and/or undermine improvements; and numerous springs on the property can contribute to pavement failure, dampness beneath houses, and instability. H. Implementation of the development as proposed would require that extensive corrective measures be taken. I. Development as proposed will require grading and earth moving of some 13,800 cubic yards of dirt, which the Council finds to be excessive and contrary to the Tiburon General Plan. J. The adverse environmental impact of the earthwork proposed can only be mitigated by reducing the number of lots to a maximum of four. This will allow for siting of the structures in areas less susceptible to on-site environmental constraints to development, thus offsetting significant adverse geologic and biotic impacts found to result from the proposed development as submitted. This reduction in density would also result in reducing hydrology, traffic, visual quality, and public finance impacts of the project. K. The Project is located in the RPD-2 zone which provides for a density of not less than 1.1 or more than 2.5 dwelling units per gross acre. The Zoning regulations futher provide that the maximum number of units that can be developed on this site is two unless findings are made that maximum effort has been made to minimize grading and that there has been maximum retention and preservation of natural elevations, ridgelands, natural features, lands too steep for development and land that is geologically unstable. The Council cannot make the necessary findings unless the density is reduced from five to four lots. L. Section 21081 of the Public Resources Code provides that the Town may not approve a development project which has a significant adverse effect unless measures to mitigate the adverse effect are infeasible; the conditions herein imposed are the minimum necessary to enable tne Town to comply with Section 21081 of the Town's General Plan. M. The Planning Commission has held a duly noticed Public Hearing on the application. N. The Planning Commission has recommended that the Town Council approve the Master Plan provided certain conditions are imposed. o. The Town Council has held a duly noticed Public Hearing for the purpose of reviewing the EIR, the Master Plan and the recommendations of the Commission and to receive comments and recommendations from the Public -3- SECTION 2, APPROVAL: THE MASTER PLAN DESCRIBED ABOVE IS APPROVED, SUBJECT TO THE CONDITIONS SET FORTH HEREIN: SECTION 3. CONDITIONS: A. Development be restricted to a maximum of four lots; B. Applicant submit a Precise Plan in compliance with applicable provisions of the zoning ordinance; C. Applicant comply with all applicable subdivision regulations; D. Applicant comply with mitigation measures as contained in the E.I.R. and modified in Exhibit "A" attached; E. All utilities be undergrounded and that service be guaranteed by the agency providing the utilities in writing prior to recordation of the final map; F. Applicant comply with all requirements of the Marin Municipal Water District necessary to insure adequate water pressure including the requirements outlined in the letter from Mr. Stroeh dated February 4, 1980; G. Applicant satisfy requirements of the Tiburon Fire Protection District, including those set forth in the letter from Mr. Barber dated January 30, 1980; H. All streets be offered for dedication; I. Applicant submit all proposed deed and title restrictions including future roadway easements and scenic easements to the Department of Community Development for review and approval by the Town Attorney prior to the filing of the final map; J. No building permits be issued for construction of any structures until they have received site plan and architectural approval; K. Applicant comply with the provisions of any ordinance of the Town requiring contribution to a Tiburon Boulevard traffic improvement fund; L. All requirements and standards, including but not limited to drainage, grading, soils, conditions listed on exhibit "A" attached hereto, and traffic, should be to the approval of the Town Engineer. SECTION 4. SEPARABILITY If any section, subsection, sentence, clause or phrase of this ordinance is for any reason held to be invalid or unconstitutional by a decision of a court of competent jurisdiction, such decision shall not affect the validity of the remaining portions of the ordinance. The Town Council of the Town of Tiburon hereby declares that it would have passed this Ordinance, any section, subsection, sentence, clause or phrase thereof, irrespective of the fact that anyone or more other sections, subsections, sentences, clauses or phrases may be declared invalid or unconstitutional. -4- SECTION 5. EFFECTIVE DATE: This ordinance shall take effect and be in force thirty days after the date of passage, and before the expiration of fifteen (15) days after its passage; the same shall be published, with names of the members voting for or against the same, at least once in a newspaper of general circulation published in the Town of Tiburon. PASSED AND ADOPTED at a regular meeting of the Town Council of the Town of Tiburon on August 20 , 1980, by the following vote: AYES: COUNCILMEN: Edelstein, Rockey, Bergsund, Hanson NOES: COUNCILMEN: None ABSENT: COUNCILMEN: Bass ATTEST: Date revised: August 14, 1980 EXHIBIT "A" Von der Werth A. Geologic Considerations - Mitigation Measures 1. Stabilization of the landslide areas should include excavation and compaction of the landslides, installation of subdrainage systems, and buttressing. 2. To ensure stabilization of any cut made into the expansive clay soils, the bottom of any excavation should be benched into firm supporting materials and, in some locations subdrains may be required. Fill should be placed within lifts, moisture condensed as required for compaction, and compacted to at least 90 percent relative compaction. For preliminary planning, cut and fill slopes should not be inclined steeper than two horizontal to one vertical (2:1) or 50 percent slope. 3. Specific requirements for the stabilization of the deeper land- slides occurring on lots in Subdivision A would depend on final grades and slope steepness and require further detailed sub- surface exploration. 4. Foundation design must take expansive soil effects and instabil- ity problems into account. Control methods could include: - Addition of lime to the soil. - Compaction to low densities, maintaining water contents on the wet side of optimum. 1 - Replacement of the upper layer of expansive soils found throughout the study area with non-expansive imported materials. Construction of special drilled pier and grade beam founda- tions with supported floors. Specific foundation design would depend on relative costs and specific lot conditions. On sloping areas, foundations for structures can include cast-in-place concrete piers with grade beams to provide lateral support. In leveled areas underlain by compacted fill or by shallow bedrock, satisfactory support could be obtained from conventional shallow spread footings. 5. Residential structures and other on-site facilities, such as utilities, should be designed to include proper earthquake resistant features. B~ Hydrologic Considerations - Mitigation Measures 1. Impervious surfaces should be limited by minimizing street widths and driveway areas. 2. The drainage systems should be designed to reduce discharge of post-project peak-volume flows to pre-project volumes by incorporating runoff delay mechanisms, such as plunge pool sumps or detention ponds. 3. In addition to on-site drainage improvements, the project developer should be responsible for upgrading the portion of lCompaction of expansive soil when it is wet reduces the swelling characteristics of the soil. Exhibit "A" p. 4 Von der Werth D. Visual Considerations - Mitigations (cont'd.) 3. Landscaping, including vegetating with native species, should be provided to buffer the development from the adjacent open space.