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HomeMy WebLinkAboutRESOLUTIONS - 01012002 - 2002-023 THE BOAR OF SUPERVISORS OF CONTRA COSTA COUNTY,CALIFORNIA Adopted this Resolution on February 12,2002,by the following vote: AYES: Supervisors Uilkema, Gerber, DeSAulnier, Glover and Gioia NOES: None ABSENT: None ABSTAIN: RESOLUTION NO.20024. 23 SUBJECT: ACCEPT the Petition for Formation of the Wendt Ranch Geological Hazard Abatement District, Subdivision 8002,and FIX a Public Hearing on the Petition for Formation,Danville area.district III) The Board of Supervisors of Contra Costa County resolves that: 1. This resolution is made pursuant to Division 17(Section 26500 et seq.)of the Public Resources Code, 2. On January 15, 2002,this Board was presented with the Petition for Formation of the Wendt Ranch Geologic Hazard Abatement District (CHAD Petition), including a plan of control (Plan of Control). Pursuant to Public Resources Code Section 26554, the Clerk of the Board has determined that the Petition is substantially in the form required by Sections 26551 and 26552 and has verified that the signatures affixed to the CHAD Petition represent owners of not less than ten percent of the real property to be included in the proposed District. Upon recommendation of the Board Clerk, the Board concludes that the CHAD Petition is in the form prescribed by Sections 26551 and 26552 of the Public Resources Code. 3. The Board has reviewed the Plan of Control presented to it with the CHAD Petition and has determined that the health,safety,and welfare require formation of the District. 4. The Board will conduct a public hearing(Hearing)on the proposed formation of the CHAD on Tuesday,February 12, 2002, at 9:00 a.m., in the Board of Supervisors' Chambers, 651 Pine Street, Room 107, Martinez, California 94553. At the Hearing,any objections to the proposed formation shall be presented. 5. The Public Works Director shall mail notice of the Hearing to all owners of real property to be included within the proposed district as shown on the assessment roll last equalized by the County. Notice of the Hearing shall be mailed by first class postage, certified mail with return receipt requested, and postmarked at least 20 days preceding the date of the Hearing. Notice of the Hearing shall include a copy of the GHAD Petition. Notice of the Hearing shall indicate where the Plan of Control may be reviewed or duplicated. Notice of the Hearing shall also set forth the address where objections to the proposed formation may be mailed or otherwise delivered up to and including the time of the hearing. 6. Also on February 12, 2002, following the Hearing, the Board will consider resolutions appointing itself as the initial Wendt Ranch CHAD Board of Directors and appointing officers of the CHAD. 7. At any time not later than the time set for hearing objections to the proposed formation, any owner of real property within the proposed district may make an objection to the formation. Such objection shall be in writing, shall contain a description of the land owned by the objector by lot, tract, and map number, and shall be signed by such owner. Objections shall be mailed or delivered as specified in the notice procedure in Paragraph 5 of this Resolution. If the person whose signature appears on such an objection is not shown on the assessment roll last equalized by the County as the owner of the subject property,the written objection shall be accompanied by evidence sufficient to indicate that such person is the owner of such property. SE:sr I hereby certify that this is a true and correct copy of an Cr`CrrpDataLspDistNBoagl ordws\2002t01 7atatuy\01-15-02 Wena R=h,dac action taken and entered on the minutes of the Board of Contact skip Eppeely,(925)313-2253 Supervisors on the date shown. Oris, Div.: PW(special Districts) +��y/�r, co: AuditCountor -ConeCounsel Januar 15. 2002 Auditor-com++oi3cr ATTESTED:— Y Accounting JOHN SWEETEN,Clerk ofthe Board of EASia ing Services Supervisors and County Administrator Community Develupmant S.Zowd,McCutchen,Doyle,Brown&Emerson 1331 N.COfinnia Blvd,Walnut Creek,CA 46596 By Chris=shapell Sndustriet Pb Box 351169,Mitpitas,CA 95035 Efeputy U.Elishu,Engeo 3401 Crow Canyon Road,Ste.200,San Raman,CA 94583 RESOLUTION NO.20021 2 3 TO: BOARD OF SUPERVISORS 0. / FROM: MAURICE M. SHIU,PUBLIC WORKS DIRECTOR DATE: January 15, 2002 SUBJECT: ADOPT Resolution No. 2002! 23 accepting the petition for formation of the Wendt Ranch Geologic Hazard Abatement District and FIX. a public hearing on proposed formation, Subdivision 8002,Danville area. District IID Project Number 6X5082 Specltie Request(s)or Recommendations)&Backgm nd&Jmtlilcatian I. Recommended Action: 1. ACCEPT the Petition for the formation of the Wendt Ranch Geologic Hazard Abatement District (CHAD), and 2. ADOPT Resolution No. 2002/ 23 fixing Tuesday, February 12, 2002, at 9:00 a.m., in the Board of Supervisors' Chambers, 651 Pine Street, Room 107,Martinez, California, as the time and place for a public hearing to consider the proposed formation of the Wendt Ranch GRAD and to hear any Written objections to the proposed formation. 3. DIRECT the Public Works Director to mail notice of the hearing to all owners of real property to be included within the proposed District,as described in Resolution No. 2002/ 23 Continued on Attachment:X SIGNATURE: LLZ�VA ECOMMENDATION OF COUNTY ADMINISTRATOR _RECOMMENDATION OF BOARD COMMITTEE PROVE ER SIGNATURES : ACTION O;BO ail , 200APPROVED AS RECOMMENDED L&OTHER VOTE OF SUPERVISORS XX UNANIMOUS(ABSENT l AYES: .NOES: ABSENT: ABSTAIN: I hereby certify that this is a true and correct copy of an action taken and entered on the minutes of the Board of SE:sr G.\GrpData\SpDisttBoard Ordersl2002\01 January\01-15-02 Wendt Ranch.doc Supervisors on the date shown. Contact: Skip Epperly,(925)313-2253 Orig.Div.: PW(Special Districts) cc: County Counsel ATTESTED: January 15, .2,002 Auditor-Controller Accounting JOHN SWEETEN,Clerk of the Board of Supervisors Engineering Services and County Administrator Community Development S.Zo>vod,McCutchen,Doyle,Brown&Emerson 1331 N.Califomia Blvd.,Walnut Creek,CA 94596 Chris Truebridge,Shapell Industries By — PO Box 361169,Milpitas,CA 95035 Ereputy U.Eliahu,Engeo 2401 Crow Canyon Road,Ste.200,San Ramon,CA 94583 RESOLUTION NO. 2002/23 SUBJECT: ADOPT Resolution No. 2002/23 accepting the petition for formation of the Wendt Ranch Geologic Hazard Abatement District and FIX a public hearing on proposed formation, Subdivision 8002, Danville area. (District III)Project Number 6X5082 DATE: January 15, 2002 PAGE Page 2 II. FinancialImpact: There will be no impact to the General Fund. All costs will be covered with revenue generated through parcel assessments for the GHAD. III. Reasons for Recommendations and Background.: The Conditions of Approval for Subdivision 8002 (Wendt Ranch) require that the developer (Shapell Industries) form a GHAD in order to mitigate the potential for soil movement in this development. The District boundaries and the subdivision boundaries are the same. All of the subdivision parcels are currently owned by one owner, who is petitioning the Board to form the Wendt Ranch GHAD. The Plan of Control describes the work contemplated for the GHAD, including maintenance, monitoring, and funding. Funding for the GRAD will be based on a parcel assessment from each improved lot in the subdivision. It is anticipated that approximately $323,000 will be accumulated as a reserve during the initial four-year build-out period. This reserve will be used for general maintenance, repair of slides, and erosion control within the GHAD, as described in the GHAD Plan of Control. Parcel assessmentswill continue to be collected annually and used for maintenance and other GHAD purposes. Unexpended funds will augment the reserve for the following and subsequent years. The formation of the proposed GHAD requires several steps and the adoption of a number of resolutions. Below is a description of the process: First Step,the Board of Supervisors will: 1) Accept petition for formation 2) Adopt resolution setting hearing date on formation and ordering notice to be given Second Step, the Board of Supervisors will hold a public hearing on the formation. Immediately after closing the public hearing,the Board may take the following steps: 1) As Board of Supervisors, adopt resolution approving formation and appointing Board of Supervisors as Board of Directors of the Wendt Ranch GHAD 2) As GHAD Board of Directors, adopt resolution appointing officers of the GRAD 3) As GRAD Board of Directors, adopt resolution approving GHAD budget and Repair, Maintenance, and Improvement Program(RMI') 4) As GHAD Board of Directors, adopt resolution of intention to order an assessment, set public hearing on proposed assessment, and order notice of the levying and assessment ballots mailed Third Step, the GHAD Board of Directors will then conduct a public hearing on the proposed assessment. Upon the close of that hearing, the ballots will be tabulated by the GRAD clerk. The CHAD Board may then take the following actions: 1) Adopt resolution accepting canvass of votes 2) Adopt resolution confirming assessments and ordering the levy and collection of assessments RESOLUTION NO. 2002/23 SUBJECT: ADOPT Resolution No. 2002/ 2 3 accepting the petition for formation of the Wendt Ranch Geologic Hazard Abatement District and PIX a public hearing on proposed formation, Subdivision 8002,Danville area. (District III)Project Number 6X5082 DATE: January 15, 2002 PAGE Page 3 III. Reasons for Recommendations and Background (continued): As indicated above, the proposed assessments will provide funding for the GHAD's budget and activities. Under Public Resources Code Sections 26651 and 26652, the CHAD Board of Directors must set the hearing for approval of the assessments. Therefore, the GHAD must be formed before the assessment hearing is set and the assessments are approved by the GHAD Board of Directors. To ensure that the GHAD assessments are properly approved and levied, formation of the CHAD should be conditioned on subsequent approval and levy of the assessments. If the developer wishes to file a final map before the assessments are levied, the subdivision lots should be deed-restricted until the assessments are approved and levied. Otherwise, subdivision lots could be transferred before levy of the assessments, and the landowner vote in favor of the assessments may not be assured. The developer has agreed to these conditions. IV. Consequences of Negative Action: The Board of Supervisors required the formation of a GHAD as a condition of approval of the Wendt Ranch subdivision. If the Board does not proceed with this matter, formation of the CHAD will be delayed, and the developer may not be able to satisfy the condition. RESOLUTION NO. 2002/23 NOTICE OF A PUBLIC HEARING You are hereby notified that on February 12, 2002, at 9:00 a.m., in Room 107, County Administration Building, 651 Pine Street, Martinez, California, the County Board of Supervisors will consider formation of a geologic hazard abatement district pursuant to the attached "Petition for Formation of the Wendt Ranch Geologic Hazard Abatement District pursuant to the Division 17 (commencing with Section 26500) of the Pubic Resources Code of the State of California" (Petition). This geologic hazard abatement district (CHAD) will be located in the area generally known as Wendt Ranch, as described in the Petition. The formation of the GHAD will require the levy of an assessment to pay for the cost and expenses of the activities described in the attached"Plan of Control for Wendt Ranch GRAD"(Plan of Control). The purpose of the lhearing is to receive and consider any and all objections to the formation of the GHAD. Valid objections can be made in writing, not later than the time set for hearing, by any owner of real property within the boundary of the proposed district. Objections shall contain a'description of the land owned by lot, tract and map number, and shall be signed by the owner of such property. Objections must be mailed or delivered to the address set forth below, and must comply with the provisions of the Public Resources Code Section 26564 (copy attached). The Plan of Control can be reviewed at the County's Public Works Department, located at 255 Glacier Drive, Martinez, CA 94553. It may be duplicated for the cost of duplication. For further details, contact the Contra Costa County Public Works Department, Special Districts Section, 255 Glacier Drive,Martinez, CA 94553, or phone Skip Bpperly at(925) 313-2253. Owner Notification: Shapell Industries, Inc. Attn: Chris Truebridge 100 Milpitas Boulevard, #100 Milpitas, CA 95035 SRSr GAGrpDatalsp1:11st113oard Orders12002101 January\01-15-02 Wendt Ranch.doe December 18,2001 RECETED PETITION FOR FORMATION OF THE DEC 2.0 2001 WENDT RANCH GEOLOGIC HAZARD ABATEMENT DISTRI 4ERK BOARD OF SUPERVISORS PURSUANT TO DIVISION 17 (commencing with Section 2650 OF THE PUBLIC RESOURCES CODE OF THE STATE OF CALIFORNIA TO: Clerk of the Board of Supervisors of Contra Costa County: The undersigned owner of land within the boundaries of the district proposed in this petition hereby requests that-the Board of Supervisors initiate proceedings to form a Geologic Hazard Abatement District("GHAD")pursuant to the provisions of Division 17 of the Public Resources Code, Sections 26500 et seq. Said owner owns all the land to be included within the GHAD boundaries. (a) This petition is made pursuant to Division 17 of the Public Resources Code with particular reference to Article 3 (commencing with Section 26550) and Article 4 (commencing with Section 26561). (b) Opposite the signature of the petitioner is an indication of the lot,tract and map number or other legal description sufficient to identify the signature of the petitioner as that of the owner of land within the territory to be included within the proposed GHAD. (c) Opposite the signature of the petitioner is an indication of the date on which the petitioner signed this petition. (d) The following documents are attached to this petition and are incorporated herein by reference as if set forth in full in the petition: 1. As Exhibit A, a map of the boundaries of the territory to be included within the proposed GHAD; 2. As Exhibit B, a legal description of the boundaries of the territory to be included within the proposed GRAD; and 1 30129633.in2272-6044 3. As Exhibit C, a Plan of Control prepared by an engineering geologist certified pursuant to Section 7822 of the Business and Professions Code which- describes hichdescribes the specific geologic hazards to be addressed by the GHAD and the plan for their prevention,mitigation, abatement and/or control. SIGNATURE ADDRESS DATE ? Assessor's Parcel No. 206- 030-006 J. Christian Truebridge, Assistant Mice President, Shapell Industries, Inc. 2 30129633.ln2272-0044 PLAN OF CONTROL FOR WENDT RANCH GEOLOGIC HAZARD ABATEMENT DISTRICT (GRAD) SUBMITTED TO SHAPELL INDUSTRIES OF NORTHERN CAI HORNIA PREPARED BY ENGEOINCORPORATED PROJECT NO.4063S.050.01 FEBRUARY 20,2001 t i COPYRIGHT 0 2002 BY ENGEO INCORPORATED. THIS DOCUMENT MAY NOT BE REPRODUCED IN WHOLE OR IN PART BY ANY MEANS WHATSOEVER, NOR MAY IT BE QUOTED OR EXCERPTED WITHOUT THE EUa?RESS WRIT'TEN CONSENT O ENGEO INCORPORATED. ENGEO GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS I NCORPO RATED MATERIALS TESTING Project No. 4063,5.050.01 February 20, 2001 Mr. Chris Truebridge Shapell Industries of Northern California P.O.Box 361169 Milpitas,CA 95035 Subject: Wendt Ranch CHAD Contra Costa County, California PLAN OF CONTROL FOR'W.ENDT RANCH Dear Mr.Truebridge: The Wendt Ranch Plan of Control has been prepared and is being submitted in conjunction with an Engineer's Report and a petition filed by Shapell Industries of Northern California to form the Wendt Ranch Geologic Hazard Abatement District(CHAD). Very truly yours, F.NGEO INCORPORATED Prepared by: YnElhia�hug Debra Care Carey dcljd:poc 2401 Crow Canyon Road •Suite 200•San Ramon,CA 94583-1545•(925)838-1600'Fax(925)838-742:4 www.engeo.com• E-mail:engstaff@engeo.com r Project No. 4063.5.050.01 February 20,2001 Mr. Chris Truebridge Shapell Industries of Northern California P.O. Box 361169 Milpitas,CA 95035 Subject: Wendt Ranch CHAD Contra Costa County, California. PLAN OF CONTROL FOR WENDT RANCH Dear Mr.Truebridge: The Wendt Ranch Flan of Control has been prepared and is being submitted in conjunction with an Engineer's Report and a petition filed by Shapell Industries of Northern California to form the Wendt Ranch Geologic Hazard Abatement District(CHAD). Very truly yours, ENGEU INCORPORATED Prepared by: Reviewed by: Debra Carey Uri Eliahu dcljd:poc INCORPORATED TABLE OF CONTENTS Letter of Transmittal Pne I. Authority and Scope.......................................................................................................1 PropertyIdentification....................................................................................................... I ELBackground.....................................................................................................................2 M. Site Geology.....................................................................................................................4 GeologicUnits..................................................................................................................4 Landslides. .....................................................................................................................5 IV. Slope Instability...............................................................................................................6 V. Slope Stability Considerations........................................................................................8 VI. Criteria for'GELAD Responsibility...............................................................................11 I, Isolated or Remote Slope Instability....................................................................11 2. Singh Property....................................................................................................11 3. Geologic Hazards Resulting From Negligence Of Property Owner.....................11 4. Property Not Accepted........................................................................................12 5. Geologic Hazard Which Requires Expenditure in Amount Exceeding the Value of the Threatened or Damaged Improvement...................................... 12 6. GRAD Funding or Reimbursement for Damaged or Destroyed Structures orSite Improvements............................................................................................12 7. No Reimbursement of Expenses Incurred by PropertyOwners...........................13 VII. Acceptance.....................................................................................................................14 1. Activation of Assessment....................................................................................14 2. Responsibility for GHAD Activities....................................................................14 3. Process for Transferring Responsibility for GHATS Activities.............................14 VIII. Annexations to the GRAD............................................................................................16 IX. Wendt Ranch Open Space Plan of Control.................................................................17 GeotechnicalTechniques for Mitigation of Landslide and Erosion Hazards...................17 X. Priority of CHAD Expenditures..................................................................................19 M. Open Space Ownership and Management.................................................................. . XIL Biotechnical Recommendations for Prevention and Mitigation of Ensding or Potential ErasionIlazards.............................................................................................................21 XIII. Maintenance and Monitoring Schedule.......................................................................22 SELECTED REFERENCES LIST OF FIGURES 4063.5.050.01 February 20,2001 E7YGG0 INCORPORATED L Authority and Scope The Wendt Ranch Geologic Hazard Abatement District ("CHAD" or "District") is proposed to be formed under authority of the California Public Resources Code (Division 17, commencing with Section 26500). Formation of the CHAD is necessary to satisfy Conditions of Approval 18, 26 and 162 of Contra Costa County Board of Supervisors Approval of Subdivision and Final Development flan SD968002 and DP963004 on December 17, 1996. Preparation of a Plan of Control prepared by a State Certified Engineering Geologist is a requirement for formation of a GRAD. Pursuant to section 26509, this Plan of Control was prepared by an engineering geologist certified pursuant to Section 7822 of the Business and Professions Code and describes in detail the geologic hazards, their location, and who is affected by them. It also provides a plan for the prevention, mitigation, abatement, or control of said hazards. As used in this Plan of Control, and as provided in Section 26507, "geologic hazard" means an actual or threatened landslide, land subsidence, soil erosion, earthquake, fault movement, or any other natural or unnatural movement of land or earth. Ply Identification The proposed CHAD boundary is shown on Figure 1. 4063.5.050.01 February 20, 2001 1 FAnEO INCORPORATED II. Background The site is located to the south of Camino Tassajara Road, near Blackhawk Drive in unincorporated Contra Costa County, east of Danville. The irregularly-shaped parcel is about 164.8 acres in area. One branch of the Alamo Creek traverses the site in a northeast to southwest direction,and another borders the western site boundary. The subject site typically consists of a relatively-level area, with minor knolls in the northwest portion of the property and ridges and hillslopes in the southeastern half. Elevations range from a low of about 628 feet above mean sea level (msl) at the southwest comer to a high of about 915 feet above msl at the southern end. Currently, it is anticipated that title for the majority of the open space, including the detention basin, will pass to the Wendt Ranch Homeowner's Association (HOA). As the open space within and immediately adjacent to subdivision tracts is an amenity that benefits all of the property owners within those subdivisions, the funding of the maintenance of the open space should be shared by all current and future property owners within recorded subdivision tracts in the GHAD's boundaries. All activities in open space parcels within the GHAT}shall be subject to approval by the GHAD. Maintenance of habitat features and values will be the responsibility of the natural lands manager. The governing documents of the HOA will include provisions requiring cooperation and coordination with both the GRAD and natural lands manager. The CHAD will mitigate or abate landslide or erosion hazards that could directly affect improved, developed, and accepted properties (as defined in Section VII) within the Wendt Ranch Site, in accordance with Section VI. The CHAD will assume other peripherally-related open-space responsibilities, such as detention basin maintenance, erosion control, and selected 4063.5.050.01 February 20, 2001 2 EE:u INCORPORATED other maintenance associated with open space. Maintenance of the detention basin and open- space drainage facility shall be conducted by the CHAD in accordance with the Drainage Maintenance Plan, which will be prepared in accordance with Condition of Approval No. 155. Proactive maintenance, assessment, repair and replacement of creek improvements (including vegetation control and armoring of channels), natural slope maintenance and desilting of detention basins will be the responsibility of the CHAD subject to the limitations of this Plan of Control. In addition, the GRAD shall have the right to approve any construction, maintenance or repair in the open space which the GHAD determines has the potential to impact geologic stability. 4063.5.050.01 February 20, 2001 3 EAGEv INCORPORATED III. Site Geology QmIggic Units The geologic units mapped on the site include bedrock and surficial deposits consisting of colluvium, alluvium and landslides which are described below. Bedrock at the subject site is mapped by Dibblee (1980) as nonmarine sedimentary rock (Tps). This bedrock is described as consisting of late Miocene to Pliocene age (8.5 to 2.5 million years) claystone and siltstone interbedded with sandstone, pebble conglomerate, and volcanic tuff (Davenport, 1986). According to studies of these rocks by Issacson (1990), the depositional environment for these sedimentary rocks is believed to have been meandering and braided streams. Bedrock at the site strikes to the west to northwest with dips measured from 70 to 88 degrees to the northeast. One tuffaceous unit was mapped across the north-south trending ridge by Dibblee (1980). Highly-sheared and weak bedrock is known to occur in this area. Such conditions may result in a lower than normal stability of slopes. The flat-lying portion of the subject property is underlain by Quaternary age alluvial terrace deposits. These soils consist of unconsolidated gravel, sand, silt and clay. Incised into the terrace deposits are the existing stream channels that contain more recent alluvial deposits, similar to the terrace deposits,but currently subject to reworking by the modern streams. Mantling the bedrock and filling swales are colluvial deposits, which include landslides. These sediments are derived from weathering of the underlying bedrock and consist mostly of clay to silty clay. This material generally is expansive and has low strength. Where colluvium is located 4063.5.050.01 February 20, 2001 4 INCORPORATED on sloping ground, it is characteristically unstable. Within swales, the colluvial deposits tend to be relatively thicker and may be subject to flow or slip downslope. Im dslides Landslides were previously mapped on the site by Nilsen (1975) and Davenport(1986). ENGEO (1991, 1992, 1993, 1996) undertook more specific aerial photograph interpretations with field reconnaissance to map the site landslides. These landslides consist of active and inactive earthflows and larger slumpflow complexes. No debris flows were mapped on the site in an ENGEO (1992) debris flow study, and the potential for future debris flows is considered low. The most significant landslide activity on the property is located in the southern portion of the site, where much of the north-facing hillside is mantled by large active earthflows and slump flows. The relative landslide susceptibility map prepared by Davenport (1986) indicates that most of the hillside area of the site is classified as `generally' to `most susceptible' to landsliding. 4063.5.050.01 February 20, 2001 5 E Gr-v INCORPORATED IV. Slope Instability Earth stability is the GHAD's prime geotechnical concern at this site. This is not unique to this project, but is of importance for hillside projects in the San Francisco Bay Area. This section describes several types of slope instability which are within the GHAD's responsibility, subject to the provisions of Section VL Landslides are a common geologic phenomenon and are part of the process of mass wasting. Weathered or fractured bedrock and soil are transported downslope over geologic time as a result of gravitational and hydrostatic forces. Landslides and earth movement in this bedrock formation are typically rotational slumps and earthflows. Depth of movement is typically about 10 to 30 feet below the ground surface. Earthflows are confined to the upper 3-to 5-foot-thick clayey sail mantle. In the winter rainy season, these earthflows can move at a rate of several feet per day. A',landslide is a deposit of soil and/or bedrock moving downward from its original position under the influence of gravity. Landslides include a variety of morphologies and are further defined by type of materials, wetness, and mode of movement. They can consist of mass movements of earth materials that are primarily intact, and occur along discrete shear surfaces. These surfaces (shear or slip planes) can be rotational (conchoidal or concave), such as for earth slumps, or planar, as for translational earth slide or bedrock block glides. Most landslides are truly "complex landslides", sliding, falling and flowing with more than one type of movement and/or material. Falls are an abrupt free-fall of earth materials off cliffs, steep cuts, or steep stream banks while earthflows are mass movements of earth materials in which the type of movement is one of flowing. When composed of soil finer than gravel size, the flowing material is commonly called a mudflow. A debris flow/debris avalanche is composed of natural earth materials, artificial fill, 4063.5.050.01 February 20, 2001 6 EAGE) INGORPORAT D and/or organic debris which flow downslope with spud.. Most of the material is transported away from the area of initial ground failure. Sail creep is the slow, often imperceptible, deformation of slope materials under low stress levels, which normally affects the shallow portion of the slopes, but can be deep seated where a weak zone of soil or bedrock exists. It results from gravitational and seepage forces, and may be indicative of conditions favorable for landsliding. Creep can be caused by wetting and drying of clays, by solution and crystallization of salts, by the growth of roots, by burrowing animals and by down slope movement of saturated ground. Colluvium refers to the mantle of loose soil and weathered bedrock debris that progresses down hillsides by creep. The District shall also be concerned with erosion and sedimentation in open space affecting developed lots or improvements, subject to the provisions of Section H. Erosion is defined as the process by which earth materials are loosened and removed by running water on the ground surface or in the subsurface. Sedimentation is the depositing or settling of soil or rock particles from a state of suspension in a liquid. Hilly terrain open space either in a natural condition or particularly on excavated slopes can be subject to erosion. Landslide deposits, which are sometimes in a loosened condition are particularly prone to erosion. Earth flow-, debris flow- and mud flow-type landslides typically have an area of deposition or accumulation (sedimentation area) at their base. Graded slopes in the District, particularly those in excess of 20 feet in vertical height or those not sufficiently vegetated,can be subject to erosion and therefore a source of transported sediment. Creek banks can be oversteepened by natural processes such as stream cutting and erosion, which can cause the banks to slump. The slumped material can then be transported downstream. Additionally, this can lead to destabilization of areas above the creek banks. In flood stage, strearnls such as Alamo Creek can erode even vegetated stream banks. 4063.5.050.01 February 20,2001 7 Et:u INCORPORATED V. Slope Stability Considerations Wendt Ranch consists of open, rolling, grass-covered hills with scattered trees. Two branches of the Alamo Creek are located on or adjacent to the subject property. In general, the northwestern half of the site is topographically subdued,while steeper hills are situated in the southeastern half of the site. In the past, the property has been used for cattle grazing. The majority of the natural hillslopes in Wendt',Ranch are in a marginally stable to unstable condition. However, some of the mapped landslides are located in areas of proposed development. In general, mitigating measures for land instability include avoiding large landslide areas when placing structures, or stabilizing the landslides by removing the unstable soil to bedrock, constructing engineered keyways, and reeompaeting the soil as drained engineered fill. Another technique is to provide drained toe-of-slope buttress fills with debris benches of sufficient width to intercept the potential landslide debris. Debris benches may be constructed as a preventive measure on selected perimeter cut slopes surrounding the development area. The CHAD will maintain the debris benches, associated drainage facilities, and the hillslopes extending uphill from the benches. Generally, development of this site will be concentrated in the low-lying valley areas or on the southeastern ridgeline. The low-lying valleys will be filled to establish finish grades that are substantially higher than original elevations. Fill materials for grading will be generated from cuts on the surrounding hill slopes. This grading concept provides pad elevations above flood levels while, of the same time, improving the stability of the surrounding natural slopes through the use of buttress fills and flatter slope gradients. Known active landslides which will be adversely affected by the proposed grading or which constitute a threat to the proposed development will either be completely removed and replaced as subdrained engineered fills, or buttressed with drained, engineered fills. 4063.5.050.01 February 20,2001 8 GM--.r-u INCORPORATED The cuts will be viewed by the project geologist during grading to provide mitigation schemes for unsuspected slope conditions which could decrease the slope stability. Such conditions include unfavorable bedrock attitudes and seepage conditions. A geology map will be prepared by the project geologist for use by the GRAD. In repaired or buttressed landslide areas, the landslide debris will be overexeavated to firm undisturbed materials below the landslide plane as determined by the Geotechnical Engineer or Engineering Geologist at the time of grading. In the case of the complete removal of a landslide, systems of surface and subsurface drains will be installed to collect the surface and subsurface waters which may have initially caused the landslide. The configuration of each subdrainage system will be tailored to the individual landslide at the time of grading. The Geotechnical Engineer and/or the Engineering Geologist will determine the location and depths of subdrains at that time. A Licensed Land Surveyor will record the location and elevation of subdrains and outlets. Each landslide subexcavation then will be reconstructed to final grade by keying and benching below the landslide plane with compacted, drained engineered fill. Landslides that will not be completely removed either will be stabilized in place or are situated outside of the proposed development areas. Buttress fills will be constructed at the toes of major cut slopes near the base of known landslide areas. These fills consist of drained-engineered keyways, excavatedto firm bedrock, with an overlying engineered fill. Debris benches will generally be constructed with concrete-lined ditches discharging into approved outlets. It is important to note that to preserve the natural topography, wildlife habitat, and vegetation of the site, stabilization of landslide masses is currently planned only for landslides that directly threaten the proposed improvements. Slope instability in open-space parcels which does not have the potential to directly affect the GRAD-accepted homesites, roadways, or other improvements will not be repaired, as provided in Section VL 4463.5.050.01 February 20,2001 9 E1 GEE0 INCORPORATED Monitoring of the creek banks will be performed on a regular basis to identify areas of possible instability or future erosion. Proactive maintenance of creek banks will be performed at the discretion of the CHAD Manager. Creek bank erosion that does not directly threaten site improvements, as provided in Section VI, will not be repaired, and the creeks will be allowed to mature naturally. Any repair work required for creek bank erosion will utilize biotechnical repair techniques(Section XII)in favor of engineered structures, where practical. 40635.050.01 February 20, 2001 10 E INCORPORATED Vr. Criteria for GHAD Responsibility In forming the CHAD and establishing the assessment levels and budgets for the District, it is important to define clearly the limits of the GHAD's responsibilities. The CHAD will accept responsibility for property as described in Section VII of this Plan of Control. However, the intent of this Plan of Control is not to extend the GHAD's responsibilities to every potential situation of slope instability; rather,the following are exclusions from CHAD responsibility: 1. Isolated or Remote Slone Instability The CHAD shall not have responsibility to monitor, abate, mitigate or control slope instability that does not involve damage to or pose a significant threat to damage site improvements. 2. Sin lg a Proms The GHAD will not prevent, mitigate, abate or control geologic hazards which are limited in area to a single parcel of property unless the geologic hazard has damaged, or poses a significant threat of damage to site improvements located on other property within the CHATS boundaries. As used herein, the term "site improvements" means buildings, mads, sidewalks, utilities, improved trails, swimming pools,tennis courts, gazebos, cabanas, geologic stabilization features, or similar improvements. 3 Geologic Hazards Resulting From Negligence Of Pm=y Owner The GHAD may, in the general manager's sole discretion, decline to prevent, mitigate, abate or control geologic hazards which occurred or resulted from any negligence of the homeowner and/or the homeowner's contractors, agents or employees in developing, investigating, grading, 4063.5.050.01 February 20, 2001 11 GJGEO INCORPORATED constructing, maintaining or performing or not performing any post-development work on the subject property. 4 Property Not Accepted The CHAD shall not have responsibility to repair damaged site improvements, which are situated on a parcel of real property, which the CHAD has not accepted in accordance with Section Vft, below. The CHAD, however, may monitor, abate, mitigate or control slope instability on a parcel of real property which (1) the GRAD has not accepted in accordance with Section VII, below, and (2) is not excluded from GHAD responsibility by paragraphs 1, 2 and 3; provided, however, that CHAD responsibility on such parcel shall be limited to the extent necessary to address damage or a significant threat to damage site improvements which are within a parcel of real property which the CHAD has accepted in accordance with Section VTI, below. 5. Geologic HazaW VM-uch RcQ-uires Ex-pmdi= in AMunt Exceeding the Value of the lhm=e,d or Drn W impmymmt The CHAD may elect not to prevent, mitigate, abate or control a geologic hazard where, in the general manager's sole discretion, the anticipated expenditure required to be funded by the GRAD to prevent, mitigate, abate or control the geologic hazard will exceed the value of the structure(s) and site improvements)threatened with damage or loss. b. GHAD Funding glR ' fgr D r Sikv In the event a residence, commercial office building, or any other structure, site improvement or landscaping is damaged or destroyed due to, or as a result of, a geologic hazard,the CHAD may fund, or reimburse the property owner for the expenses necessary to repair or replace the damaged or destroyed structure, site improvement or landscaping. Unless authorized by the 4063.5.050.01 February 20,2001 12 EEO INCORPORATED Board of Directors, the dollar amount of the GHAT) funding or reimbursement may not exceed twenty percent (20%) of the costs incurred by the GHAD in preventing, mitigating, abating or controlling the geologic hazard responsible for the damage. In the event the geologic hazard damaged or destroyed a structure, site improvement or landscaping which violated any provisions of the County Building code or County Ordinance Code at the time of its installation or improvement, the GHAD may decline to provide any funding, or reimbursement to the property owner,for repair or replacement of the damaged structure, improvement or landscaping. 7. No Reim u rse M11 of Enenses Incurred by l p,My Owners The GHAD will not be obligated to reimburse a property owner for expenses incurred for the prevention, mitigation, abatement, or control of a geologic hazard absent a written agreement between the property owner and the GHAD to that effect, which agreement has been executed prior to the propertyowner incurring said expenses, and following an investigation conducted by the GRAD. 4063.5.050.01 February 20,2001 13 E:I!V�EC) INGORi ORATED VII. Acceptance 1. Activation of Assessment An annual assessment shall be promptly authorized on all residential parcels in the GHAD. The assessment shall be levied by the GHAD on each individual residential parcel beginning the fiscal year following issuance of a building permit for that parcel. 2. RMonsibift fQr GHAD Activities The party that, on the date each Final Map within the boundaries of the GHAD is approved by Contra Costa County, owns the developable parcels shown on that Final Map shall have the responsibility to perform all the activities of the CHAD on property within that Final Map. Such responsibility shall automatically transfer to the GRAD at 9:00 a.m. on the day exactly four years after the first residential building permit is issued by Contra Costa County. This turn-over date may be extended at the sole discretion of the project developer provided that the assessments shall continue to be levied during the extension period and that notice of such extension is delivered to the District Manager at least 30 days prior to the turn-over date. The petitioners for formation of the GHAD intend that the approximately four year period between the levying of the GHAD assessment and the GHAD becoming responsible to perform activities on property within each Final Map will allow the District to accumulate reserve funds without incurring significant'expenses. 3. 'Process for Transferring Responsibility for GRAD Activities After the Transfer Eligibility Date for parcel(s), the process for transferring responsibility for performing CHAD activities on such parcel(s) shall be as follows: 4463.5.050.01 February 20, 2001 14 EAIGM INCORPORA°TSD (a) In the calendar year of the Transfer Eligibility Date or in any subsequent year, at its discretion, the developer may apply to the GHAD ("Transfer Application")to transfer the responsibility for performing CHAD Activities for parcel(s)to the District. (b) Within 30 days of receiving such notice, a representative of the GHAD shall verify that all the facilities for which the GRAD will have maintenance responsibility have been constructed and maintained according to the County-approved plans and specifications, and that such facilities are operational and in good working order. (c) Within 15 days of such inspection, the GHAD will send the developer a list("Punchlist") of all of the items that need to be constructed, repaired or otherwise modified in order to comply with the County-approved plans and specifications. (d) The developer may notify the GHAD when it has completed the items identified on the Punchlist. (e) Within 14 days of receipt of such notice, the CHAD shall verify that all Punchlist items have been completed and notify the developer that the District accepts responsibility for performing all future GRAD Activities on the parcel(s). 4063.5.050.01 February 20,2001 15 INCORPORATED VIII. Annexatlons to the CHAD Annexation of properties not currently within the CHAD boundaries must be approved by the CHAD Board of Directors. The annexation shall be approved by the CHAD Board of Directors in accordance with the annexation policy which is current at the time of the application to annex. 4063.5.050.01 February 20,2001 16 EEO INCOR�+DRATED DL Wendt Ranch Open Space Plan of Control The CHAD shall be responsible for maintenance of geologic stabilization features (e.g. ditches, benches, walls, etc.) in the common open space, including the unimproved areas and hillside slopes extending uphill from debris benches and outside of the private lot boundaries. The GHAD's maintenance responsibilities include prevention, abatement, and control of landslide and erasion hazards and vegetation control within the subdivision open space and hillsides,as provided in Section VI. General maintenance of the surface drainage improvements in the open space and on the hillsides, such as the concreteV-ditches, will be the GHAD's responsibility. The CHAD is also responsible for general maintenance of private storm drain inlets and outlets in open space and creels corridors and subdrain outlets. Potential geologic hazards such as landslides and slope erosion within the open space,including the unimproved hillsides, shall be the responsibility of the GHAD. Clearing of Tire breaks and maintenance of the open space (other than hazard abatement) will be the responsibility of the Homeowner's .Association. The GHAD's creek maintenance duties will include monitoring and proactive maintenance at the discretion of the GHAT}manager and repair of`substantial bank failures that directly damage or threaten actual site improvements (including buildings, utilities and roads). Such creek bank repairs will be undertaken by the GHAD as necessary, and only to abate actual or threatened impact to site improvements. Biotechnical repair techniques will be the preferred method prior to any engineered structures. Habitat management will be the responsibility of a Natural Lands Manager. All creek bank repairs will be coordinated with the natural lands manager to minimize habitattspecies impacts. Qwtsdnioi T frtin of Lmdshde andErosion Hazards The techniques which may be employed by the GHAD to prevent, mitigate, abate, or control geologic hazards include,but are not limited to, the following. 4063.5.050.01 February 20,2001 17 EGO INCORPORATED A. Removal of the unstable earth mass. B. Stabilization (either partial or total) of the landslide by removal and replacement with compacted,drained fill. C. Construction of structures to retain or divert landslide material or sediment. D. Construction of erosion control devices such as gabions, riprap, geotextiles, or lined ditches. F. Placement of drained engineered buttress fill. F. Placement of subsurface drainage devices; (e.g.underdrains, or horizontal drilled drains). G. Slope correction (e.g. gradient change, biotechnical stabilization, slope trimming or contouring). H. Construction of additional surface ditches and/or detention basins, silt fences, sediment traps, or backfill or erosion channels. Potential landslide and erosion hazards can be mitigated best by controlling soil saturation and water runoff and by maintaining the surface and subsurface drainage system. Maintenance shall be provided for linedsurface drainage ditches and drainage terraces including debris benches or drop inlets. 4063.5.050.01 February 20,2001 18 FEV INCORPORATED X Priority of GHA D Expenditures Emergency response and scheduled repair expenditures by the CHAD are to be prioritized by the General Manager, utilizing his discretion,based upon available funds and the approved operating budget. When available funds are not sufficient to undertake all of the identified remedial and preventative stabilization measures, the expenditures are to be prioritized as follows in descending order of priority: A. Prevention, mitigation, abatement or control of geologic hazards that have either damaged or pose a significant threat of damage to residences, critical underground utilities or paved streets. B. Prevention, mitigation, abatement or control of geologic hazards which have either damaged or pose a significant threat of damage to ancillary structures, including but not limited to the detention basin,pool cabanas or restroom buildings. C. Prevention, mitigation, abatement or control of geologic hazards which have either damaged or pose a significant threat of damage to open space amenities. D. Prevention, mitigation, abatement or control of geologic hazards which have either damaged or gyrose a significant threat of damage limited to loss of landscaping or other similar non-essential amenities. E. Prevention, mitigation, abatement or control of geologic hazards existing entirely on open-space property and which have neither damaged nor pose a significant threat of damage to any site improvements. In performing its duties as described above, the CHAD shall seek all available reimbursements from any and all public and private entities including, but not limited to, FEMA, County Flood Control, insurance companies,etc. 4063.5.050.01 February 20,2001 19 EGu INCORPORATED M. Open Space Ownership and Management Ownership, funding sources and maintenance responsibilities shall be as shown on Table XI-1. TABLE X1-1 WENDT RANCH LONG-TERM MANAGEMENT MATRIX FACILITY/FUNCTION MAINTENANCE ENTITY FUNDING OWNERSHIP 1. Open Space HOA a. Open Space--Vegetation Land Manager Endowment HOA b. Open Space—Slopes GRAD GRAD Assmt HOA c. Conservation Easement Land Manager Endowment HOA 2. Species Mgt Land Manager Endowment HOA 3. Detention Basin GHAD GHAD Assmt HOA 4. Creek Banks GHAD GHAD Assmt HOA 5. Landscape a Camino TassajaraContra Costa County/HOA LL-2,Zone 68 Contra Costa County b Parkstrips HOA HOA Assmt Contra Costa County c. Fuel.Transition Zone HOA HOA Assmt HOA Firebreak d Riparian/Savanha Land Mgr Endowment HOA 6. Roadway,Sidewalks,etc. Contra Costa County Road Fund Contra Costa County 7. Street Lights Contra Costa County Lighting District Contra Costa County 8. Police Services Contra Costa County Police Services Contra Costa County District 9. Buffalo Wetland Land Mgr Endowment HOA The GHAD shall coordinate with the natural lands manager, whose responsibility includes preservation of the habitat values of the open space. The GRAD shall also coordinate with the HOA in all of its open space activities including fire prevention and general open space maintenance. 4063.5.050.01 February 20,2001 20 EAGE-v INCORPORATED IM Bioterhnicai Recommendations for Prevention and Miidgadon of Exisfing or Potendal Erosion Hazards Fill slopes on this project may be expected to be as erodible as the cut slopes in bedrock. `herefore, maintenance of vegetative cover following grading is especially important on all slopes. Vegetation provides a protective role on soil and exposed rock. It absorbs the impact of raindrops, reduces the velocity of runoff, and retards erosion. In many instances, adequate erosion protection for slopes can be accomplished solely with carefully selected and placed biological elements (plants) without the use of biotechnical structures (e.g. brush layering and willow waddling), or hard engineering solutions (gabions, riprap). Biotechnical slope protection may involve the use of mechanical elements or structures in combination with biological elements to provide erosion control and help prevent small-scale slope failures. Biotechnical slope protection may be utilized in both creek bank areas and open space slope areas. Locally, crib walls, welded-wire walls, gabion walls, rock walls, riprap, and reinforced earth walls used in combination with carefully selected and planted vegetation can provide high quality slope protection. The vegetation may be planted on the slope above a low retaining structure or toe wall, or the interstices of the structure can be planted. Biotechnical solutions will be utilized before engineered structures are employed. Engineered structures will be used if there is an imminent danger to public improvements or human safety and,in the opinion of the GRAD manager, biotechnical solutions would not be sufficient. 40635.050.01 February 20, 2001 21 EGu INCORPORATED M. Maintenance and Monitoring Schedule The site inspections should be undertaken at appropriate intervals as determined by the GRAD manager. The GHAD budget should provide for four or more inspections in years of heavy rainfall. Generally, inspections should take place in October, prior to the first significant rainfall; mid-winter as necessary during heavy rainfall years; and in early April at the end of the rainy season. The frequency of the inspections should increase depending upon the intensity and recurrence of rainfall. Site inspections should increase sufficiently to provide for mitigation of potential hazards. The GRAD Manager shall keep these reports on file in the records of the GHAD. Following are guidelines for a monitoring plan. The actual scope and frequency of monitoring events shall be at the discretion of the CHAD manager. • The engineer and/or geologist retained by the District should carry out an inspection of lined surface ditches at least twice a year. One inspection should be in the fall prior to the onset of winter rains. The inspection shall check for sedimentation and cracking or shifting of the concrete lined ditches. Repairs and maintenance as needed should be undertaken including removal of excess silt or sediment in ditches and patching or replacement of cracked or broken ditches,prior to the beginning of the next rainy season. • Subsurface drain outlets and horizontal drilled drain outlets, if any, should be checked. Water flowing from these outlets should be measured and recorded during each inspection. The inspections should take place at least twice annually, preferably in the fall and spring. Any suspicious interruption in flow should signal a need to unplug or clean by flushing the affected drain. • Piezometers to measure ground-water levels, or instruments such as inclinometers or tiltmeters measuring potential slope instability should be monitored quarterly,if installed. • Settlement monitoring devices should be measured annually and tracked. In the event of anomalous readings or excessive settlement, the monitoring frequency should be increased to once per quarter. 4063.5.050.01 February 20,2001 22 EME ZORPORATED •'' ]Inlets, outfalls or trash racks, if used, must be kept free of debris and spillways maintained. It is anticipated that initially at least once every two (2) years, cleanup of vegetation and removal of silt would be in order. Attention should be given to plantings or other obstructions which may interfere with access by power equipment. • The creek corridors should be inspected at least twice a year. One inspection should be in the fall prior to the onset of winter rains. A second inspection should be undertaken during the rainy season to monitor potential creek bank failures which could imminently threaten or damage site improvements. The maintenance program should include the monitoring of subdrain outfalls from the grading operations which may outlet to the creek, and proactive maintenance of the creek banks at the discretion of the{CHAD Manager. • An annual inspection shall be made by the engineer and/or engineering geologist to assess the effectiveness of the preventive maintenance program and to make recommendations as to which landslide'repair or erosion control measures should be undertaken in the next fiscal year. Any appropriate site-specific study of landslide or erasion conditions shall be determined at that time. Consultants, if necessary, will be retained to undertake the needed studies. An annual inspection report to the CHAD shall be prepared by the District Engineer and/or engineering geologist. 40633.050.01 February 20,2001 23 rJncia INCORPORATED SELECTED REFERENCES Association of Bay Area Governments (ABAG), 1981, Manual of Standards for Erosion and Sediment Control Measures. Axelrod, D. L, 1944x,The Back Hawk Ranch Flora, in Pliocene Floras of California and Oregon, R. W.Chaney, ed. Carnegie, Inst. Washington Publication No.553: 91-101, 2 pls. Axelrod, D. I., 1944b,The Pliocene Sequence in Central California. Ibid.: 207-224, 1 Fig., 1 tab. Blake, T. F., 1994, EQFAULT, A Computer Program for the Deterministic Prediction of Peak Horizontal Acceleration from Digitized California Faults. Bonilla, M. G., 1982, Evaluation.of Potential Surface Faulting and Other Tectonic Deformation, USGS Open-File Report 82-732. Borcherdt, R. D., J. F. Cribbs, and R. Lajoie, 1975, Prediction of Maximum Earthquake Intensity in the Southern San Francisco Bay region, California, for larger Earthquakes on the San Andreas and Hayward Faults, USGS MF 709. Brabb, E. E., H. S.'Sonneman, and J. R. Switzer, Jr., 1971, Preliminary Geologic Map of the Mount Diablo-Byron Area, Contra Costa, Alameda and San Joaquin Counties, California: U.S. Geol. Survey Basic Data Contr. 28, scale 1:62500. Brabb, E. E., H. S. Sonneman, and J. R. Switzer, Jr., 1974, California Oil and Gas Fields, 1974, Vol. II, South Central Coastal and Offshore California: Cal. Div. Oil and Gas, Report. n, Tr. 12. California Division of Mines and Geology, January 1, 1982, State of California Special Studies Zone, Diablo 7-V2' Quadrangle. Clark, M. M., 1980,',Ground Rupture and Seismic Shaking as Separate Hazards of Active Faults (A Study of Active Faulting in the Ojai Valley, Southern California), in Proceedings of the Eighteenth Annual Engineering Geology and Soils Engineering Symposium. Contra Costa County,1975, Seismic Safety Element, Technical Background Report. Crane, Ron and Craig Lyon, 1995, Geology of the Mount Diablo Region Field Trip Guidebook: Northern California Geological Society,Diablo 7-Y2' Quadrangle, Scale 1:24,000. 4063.5.050.01 February 20,2001 EAGEO INCORPORATED SELECTED.REFERENCES(Continued) Darrow,R. L., 1976,Moub�l_c�Sent of the Meganc�,�Channel: in: Keith Drummond,ea., Pac. Secs. A.A.P.G.-S.E.G.S.E.P.M. Joint Annual Field Trip San Francisca, April 24, 1976,p. 2533. Davenport,C. W., 1986, Landslide Hazards in Parts of the Diablo and Dublin 7-Y2'Quadrangles, Contra.Costa County,California,CDMG Open-File Report 86-7 SF. Dibblee, T. W. Jr., 1980, Preliminary Geologic Map of the Diablo Quadrangle, Alameda and Contra Costa Counties,California,USGS Open File Report 80-546. ENGEO Inc., 1991, Preliminary Geologic Mapping, TVPOA Property, Contra Costa County, California,Project No.3294-W 1. ENGEO Inc., 1992, Debris Flow Hazard Characterization, TVPOA Planning Area, Tassajara Valley, Contra Costa County, California, Project No.N2-3293-W3. ENGEO Inc., 1993, Preliminary Geotechnical Field Exploration, TVPOA Planning Area, Tassajara Valley,Contra Costa County, California, Project No. 3284-W4. ENGEO Inc., 1996,'{".geotechnical and Geological Assessment, Wendt Ranch, Subdivision 8002, Contra Costa.County,California;Project No.4063-W l. ENGEO Inc., 1996,'Geotechnical Exploration, Wendt Ranch, Subdivision 8002, Contra Costa County,California; Project No.4063-W1, October 15, 1996. Federal Emergency Management Agency, 1987, National Flood Insurance Program, Flood Insurance Rate Map(FIRM),Panel Number 060025 04758. Graham, S. A., C. Gavigan, C. McCloy, M. Hitzman, R. Ward, and R. Turner, 1983, Basin Evolution during the change from convergent to Transform Continental Margin: An Example from. the Neogene of Central California, in Field Trip Guidebook, Pacific Section SEP ,May 1983. Gaymer, R. W., D. L. Jones and E. E. Brabb, 1994, Preliminay Geologic Map Emphasizing Bedrock Formations in Contra Costa County, California, Open-File Report 94--622. Hart, 1981,Fault Evaluation Report 110,Diablo Quadrangle, C.D.M.G.unpublished report. Helley, E. J., and D G. Herd, 1977, Faults with Quaternary Displacement, Northwestern San Francisco Bay Region,California,USGS MF 818. 4063.5.050.01 February 20,2001 - - EEw INCORK ATED SELECTED REFERENCES (Continued) Herd, E. G., 1977, Geologic Map of the Las Positas, Greenville and Verona Faults, Eastern Alameda County, California: U.S. Geology Survey Open-File Report 77-689, 25 p. Herd, E. G., 1978, Map of Quaternary Faulting Along the Northern Calaveras Fault Zone: Las Trampas Ridge, Diablo Dublin, Niles and La Costa 7V2-minute Quadrangles, California, Sheet 1 USGS Open-File Report 78-307. Idriss, L M., 1993, Procedures for Selecting Earthquake Ground Motions at Rock Sites, National Institute of Standards and Technology,NIST GCR 93-625, 7pp. International Conference of Building Officials, 1994, Uniform Building Code. Isaacson, K. A., 1990, Late Tertiary Sedimentation in the Northern Livermore Basin, California; Unpublished Masters Thesis, San Jose State University. Lawson, A. C., 1914, Description of the San Francisco District: U.S. Geol. Survey Atlas, Folio 193,24 p., scale 1:62500. Limerinos, J. T., J. S. Lee, and P. E. Lugo, 1975, Flood Prone Areas in the San Francisco Bay Region, USGS Open-File Report(Water Resources Invest 37-73). Majmundar, H. H., 1996, Landslide Hazards in the Las Trampas Ridge Quadrangle and Parts of the Diablo Quadrangle, Alameda and Contra Costa Counties, California, California Division of Mines and Geology OFR 95-15. Nilsen, T. H., and S. H. Clarke, Sedimentation and Tectonics in the Early Tertiary Continental Borderland of Central California: U.S. Geol. Survey Prof. Paper 925, 64 p. Nilsen, T. H., 1975, Preliminary Photointerpretation Map of Landslide and Other Surficial Deposits of the Diablo 7117' Quadrangle, Alameda and Contra Costa Counties, California; USGS Open File Map 75-277-14. Pacific Aerial Surveys, October 1, 1991, Aerial Photographs, Tassajara Valley 1-3 and 1-4. Pampeyan, E. H., 1963, Geology and Mineral Deposits of Mount Diablo, Contra Costa County, California: California Division of Mines and Geology Special Report 80, 31 p., 5 pis. Richey, K. A., 1938, Osteoborus Diabloensis, a new dog from the Black Hawk Ranch fauna, Mount Diablo,California. The Cordon, 24: 303-308, 1 Figure. 4063.5.050.01 February 20, 2001 INCORPORATED SELECTED REFERENCES (Continued) Richey, K. A., 1948. Lower Pliocene Horses from Black Hawk Ranch, Mount Diablo, California. Ibid.,28: 1-44, 3 pls., 13 figs. Rogers, J. D., 1986, Landslide Processes of the East Bay Hills and San Francisco Bay Region, California, AEG Field Trip Guidebook, 29h Annual Meeting. Ruggeri-Jensen-Azar&Associates, Wendt Ranch, Key Map, dated March 26, 1996. Sarna-Wojicki, A. M., 1976, Correlation of Late Cenozoic Tuffs, in the Central Coast Ranges of California by Means of Trace— and Minor—Element Chemistry: U.S. Geologic Survey Professional jPaper 972, 30 p. Saul, R. B., 1967, The Calaveras Fault Zone in Contra Costa County, California, California Division of Mines and Geology Mineral Information Service, Volume 20,Number 3. Savage, E. E., B. A. Ogle, and R. S. Creely, 1951, Subdivision of Vertebrate-Bearing Non- Marine Pliocene Rocks in West Central Contra Costa County, California. Geologic Society America Bulletin, V.62. Savage, E. E., B. A. Ogle, and R. S. Creely, 1955, Nonmarine Lower Pliocene Sediments in California,A Geochronologic-Biostratigraphic Classification.Ibid., 31: 1-26, 13 figures. Savage, E. E., B. A. Ogle, and R. S. Creely, 1982, Stratigraphy of Upper Tertiary, Nomnarine Rocks of Central Contra Costa Basin, California, in SEPM-Cenozoic Nonmarine Deposits of California and Arizona. State of California, Department of Conservation, 1987, Erosion and Sediment Control Handbook, EPA 44013-78-003. Taff, J. A., 1935, Geology of Mount Diablo and Vicinity: Geol. Soc. America Bull. v. 46, p. 1029-1100,map. USDA, 1977, Soil Survey of Contra Costa County, California; U.S. Department of Agriculture, Soil Conservation Services. Varnes, D. J., 1978, Slope Movement Types and Processes, in Landslides, Analysis and Control, Special Report 176,Transportation Research Board. 4063.5.050.01 February 20, 2001 EhGEO INCORPORATED SELECTED REFERENCES (Continued) Wagner, J. R., 1978, Late Cenozoic History of the Coast Ranges East of San Francisco Bay, Unpublished Ph.D., U.C. Berkeley. Wentworth, C. M., S. Ellen, V. A. Frizzell, Jr., and J. Schlocker, Map of Hillside Materials and Descriptions of their Engineering Character, San Mateo County, California., USGS Miscellaneous Investigation Series Maps I-1275-D. Wesnousky, 1986, Earthquakes, Quaternary Faults, and Seismic Hazard in California, Journal of Geophysical Research,Vol.91 No.B12. 4063.5.050.01 February 20,2001 _. 1 r �` tJ LJ .R ................ shn.E0 INCORPORATED LIST OF FIGURES Figure 1 Grading Plan and GRAD Boundary Figure 2 Geology Map 4063.5.050.01 Fury 20, 2001 RECEIVED DEC 2,0 2001 PETITION FOR FORMATION OF THE WENDT RANCH GEOLOGIC HAZARD ABATEMENT DIS1. K CONTRA ARD OF SUPERVISORS PURSUANT TO DIVISION 17(commencing with Section 265 COSTA OF THE PUBLIC RESOURCES CODE OF THE STATE OF CALIFORNIA TO: Clerk of the Board of Supervisors of Contra Costa County: The undersigned owner of land within the boundaries of the district proposed in this petition hereby requests that the Board of Supervisors initiate proceedings to form a Geologic Hazard Abatement District("GHAD")pursuant to the provisions of Division 17 of the Public Resources Code, Sections 26500 et seq. Said owner owns all the land to be included within the GRAD boundaries. (a) This petition is made pursuant to Division 17 of the Public Resources Cade with particular reference to Article 3 (commencing with Section 26550) and Article 4 (commencing with Section 26561). (b) Opposite the signature of the petitioner is an indication of the lot,tract and map number or other legal description sufficient to identify the signature of the petitioner as that of the owner of handwithin the territory to be included within the proposed CHAD. (c) Opposite the signature of the petitioner is an indication of the date on which the petitioner signed this petition. (d) The following documents are attached to this petition and are incorporated herein by reference as if set forth in full in the petition: 1. As Exhibit A, a map of the boundaries of the territory to be included within the proposed GHAD; 2. As Exhibit B, a legal description of the boundaries of the territory to be included within the proposed GHAD; and 1 30129633.1172272-0044 3. As Exhibit C,a Pian of Control prepared by an engineering geologist certified pursuant to Section 7822 of the Business and Professions Code which describes the specific geologic hazards to be addressed by the CHAD and the pian for their prevention,mitigation,abatement and/or control. SIGNATURE ADDRESS DATE Assessor's Parcel No. 206- C�d"'''"s 030-006 ! .. !`�'• �'J J Christian'Truebridig e, Assistant Vice President, 5hapell Industries,Inc. 2 30129633.1172272-0044