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HomeMy WebLinkAboutMINUTES - 07231996 - SD.7 JY THE BOARD OF SUPEOISORS OF CONTRA COSTA COU',*, CALIFORNIA Adopted this Resolution on July 9, 1996, by the following vote: AYES: Supervisors Rogers , Bishod, DeSaulnier , Torlakson , Smith NOES: None ABSENT: None ABSTAIN: None RESOLUTION NO. 96/329 SUBJECT: Approving Formation of Hillcrest Heights Geologic Hazard Abatement District Subdivision 7582 The Board of Supervisors of Contra Costa County RESOLVES THAT: 1. On May 21, 1985, pursuant to the provisions of Section 26550 of the Public Resources Code, this Board adopted Resolution No. 85/276, declaring that the Board is subject to the provisions of Division 17 (Sections 26500 et seq.) of said Code, and forward a copy of said Resolution to the State Controller. 2. Pursuant to the provisions of said Division 17 of the Public Resources Code, a Petition was filed with the Clerk of the Board, date May 8, 1996, for the formation of the Hillcrest Heights Geologic Hazard Abatement District ("GHAD") Subdivision 7582. 3. , On June 4, 1996, this Board adopted Resolution No. 96/256 setting a hearing on the filed Petition for formation on July 9, 1996 at 9:45 a.m. Notice of said hearing was given in accordance with the provisions of Public Resources Code Sections 26561 through 26563. 4. A public hearing before this Board on the formation of the GHAD for the Hillcrest Heights Subdivision 7582 was held on July 9, 1996 at 9:45 a.m. At the time set for the hearing, no owner of real property within the proposed GHAD had made a written objection to its formation in accordance with the provisions of Public Resources Code Section 26564. At the hearing the owners of more than 50 percent of the assessed valuation of proposed GHAD did not object to the formation thereof; the Board closed the hearing. 5. The formation of the GHAD for the Hillcrest Heights Subdivision 7582 area is exempt from the provisions of the California Environmental Quality Act(Public Resources Code Section 21000 et seq.) in accordance with Public Resources Code Sections 21080(b)(44) and 26559. 6. The Board hereby ORDERS the formation of the Hillcrest Heights Subdivision 7582 Geologic Hazard Abatement District, as described in the Petition for Formation of the GHAD. 7. In accordance with Public Resources Code Section 26567, the Board hereby APPOINTS itself to act as the Board of Directors for the Hillcrest Heights Subdivision 7582 Geologic Hazard Abatement District. SE:fp g:\EngSvc\SpDist\7582-9.t7 l►t2 ft to ft M a ttue and aetW aw d an acdw taken and entued on the mkv*e d-ft Orig.Dept.: Public Works Department(Special Districts) Board of taofs dat9 tdwrn. Contact: Skip Epperly,313-2253 TCH �"�'� d cc: County Administrator p$epayype Auditor-Controller DI/A OD Accounting Eugene C.Lee Cerrito Development Daniel J.Curtin,Jr. McCutchen,Doyle,Brown&Enersen 1331 N.California Blvd. Walnut Creek,CA 944596-1270 RESOLUTION NO. 961379 • • SO- 3 Y` THE BOARD OF SUPERVISORS OF CONTRA COSTA COUNTY CALIFORNIA Adopted this Order on July 9. 1996 by the following vote: AYES: Supervisors Rogers, Bishop, DeSaulnier, Torlakson, Smith NOES: None ABSENT: None ABSTAIN: None ----------------------------------------------------------------- ----------------------------------------------------------------- SUBJECT: Hillcrest Heights Geologic Hazard Abatement District, Subdivision 7582 This being the time, hearing on Hillcrest Heights Geologic Hazard Abatement District, Subdivision 7582, IT IS BY THE BOARD ORDERED that the hearing on said matter is continued to July 23, 1996, -at 10: 00 A.M. I hereby certify that this is a true and correct copy of an action taken and entered on the minutes of the Board of Supervisors on the date shown. ATTESTED: July 9. 1996 PHIL BATCHELOR, Clerk of the Board of Supervisors and County Administrator By eputy cc: Public Works (Skip Epperly) County Administrator Auditor Controller SD • 3 THE BOARD OF SUPEISORS OF CONTRA COSTA COIF, CALIFORNIA e Adopted this Resolution on July 9, 1996, by the following vote: AYES: NOES: ABSENT: ABSTAIN: RESOLUTION NO. 96/ SUBJECT: Approving Formation of Hillcrest Heights Geologic Hazard Abatement District Subdivision 7582 The Board of Supervisors of Contra Costa County RESOLVES THAT: 1. On May 21, 1985, pursuant to the provisions of Section 26550 of the Public Resources Code, this Board adopted Resolution No. 85/276, declaring that the Board is subject to the provisions of Division 17 (Sections 26500 et seq.) of said Code, and forward a copy of said Resolution to the State Controller. 2. Pursuant to the provisions of said Division 17 of the Public Resources Code, a Petition was filed with the Clerk of the Board, date May 8, 1996, for the formation of the Hillcrest Heights Geologic Hazard Abatement District ("GHAD") Subdivision 7582. 3. On June 4, 1996, this Board adopted Resolution No. 96/256 setting a hearing on the filed Petition for formation on July 9, 1996 at 9:45 a.m. Notice of said hearing was given in accordance with the provisions of Public Resources Code Sections 26561 through 26563. 4. A public hearing before this Board on the formation of the GHAD for the Hillcrest Heights Subdivision 7582 was held on July 9, 1996 at 9:45 a.m. At the time set for the hearing, no owner of real property within the proposed GHAD had made a written objection to its formation in accordance with the provisions of Public Resources Code Section 26564. At the hearing the owners of more than 50 percent of the assessed valuation of proposed GHAD did not object to the formation thereof; the Board closed the hearing. 5. The formation of the GHAD for the Hillcrest Heights Subdivision 7582 area is exempt from the provisions of the California Environmental Quality Act(Public Resources Code Section 21000 et seq.) in accordance with Public Resources Code Sections 21080(b)(44) and 26559. 6. The Board hereby ORDERS the formation of the Hillcrest Heights Subdivision 7582 Geologic Hazard Abatement District, as described in the Petition for Formation of the GHAD. 7. In accordance with Public Resources Code Section 26567, the Board hereby APPOINTS itself to act as the Board of Directors for the Hillcrest Heights Subdivision 7582 Geologic Hazard Abatement District. SE:fp g:1EngSvc\SpDist17582-9.t7 Orig.Dept.: Public Works Department(Special Districts) Contact: Skip Epperly,313-2253 cc: County Administrator Auditor-Controller Accounting Eugene C.Lee Cerrito Development Daniel J.Curtin,Jr. McCutchen,Doyle,Brown&Enersen 1331 N.California Blvd. Walnut Creek,CA 944596-1270 RESOLUTION NO. 96/ TO: BOARD OF SUPERVISORS FROM: J. MICHAEL WALFORD, PUBLIC WORKS DIRECTOR DATE: JUNE 4, 1996 SUBJECT: ACCEPT THE PETITION FOR FORMATION OF AND ADOPT THE RESOLUTION SETTING THE HEARING FOR THE FORMATION OF THE HILLCREST HEIGHTS, GEOLOGIC HAZARD ABATEMENT DISTRICT, SUBDIVISION 7582, EL SOBRANTE AREA. PROJECT NUMBER 6X5086 Specific Request(s)or Recommendation(s)&Background&Justification L Recommended Action: 1. ACCEPT the Petition for the formation of the Hillcrest Heights Geologic Hazard Abatement District (GRAD), and 2. ADOPT the Resolution SETTING the hearing date on the proposed formation of the Hillcrest Heights GHAD on Tuesday July 9, 1996, at 9:45 am. in Room 107 of the Board of Supervisors' Chambers, 651 Pine Street,Martinez, California, as the time and place for a public hearing to consider oral and written objections or comments concerning the Hillcrest Heights GRAD. U. Financial Impact: 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 7582 required that a GHAD be formed 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 individual, who is petitioning the Board to form the Hillcrest Heights GRAD. Continued on attachment: x Yes SIGNATURE: Z111,4.11 RECOMMENDATION OF COUNTY ADMINISTRATOR RECOMMENDATION OF BOARD COMMITTEE APPROVE OTHER SIGNATURE(S): ACTION OF BOARD ON: APPROVED AS RECOMMENDED_OTHER VOTE OF SUPERVISORS --,— UNANIMOUS(ABSENT AYES: NOES: ABSENT: ABSTAIN: SE-pesd t hereby t:crtiy that this Is a true and tronat.Kt�pyo! g:1Erig,Svcl.SpDist\BOUiHGHAD4.t6 an action token and entered on the minutes Of tft9 Boardof Supe isors on the date shown. Contact: Skip Eppedy,(510)313-2253 ATTESTED: 4 129 Orig.Div.: PW(Special Districts) PHIL BA HELGR,ClerV of the Board cc: Auditor-Controller of Supervis rs and County Administrator Accounting ) Engineering Services Community Development By putt D.Curtain,McCutchen,Doyle,Brown&Emerson T.Coats,Wollman&Associates HILLCREST HEIGHTS GEOLOGIC HAZARD ABATEMENT DISTRICT JUNE 4, 1996 PAGE TWO M. Reasons for Recommendations and Background: (Continued) The Plan of Control describes the work contemplated for this district, including maintenance, monitoring, and funding.Funding for the GHAD will be based on a parcel assessment from each improved lot in the subdivision. It is anticipated that approximately$60,000 will be accumulated as a reserve during the initial three year build-out period. This reserve will only be used for general maintenance, repair of slides and erosion control within the District. Parcel assessments will continue to be collected annually and used for maintenance. Unexpended funds will augment the reserve for the following year. It is anticipated that the homeowners of the subdivision will assume the responsibilities as the Board of Directors of the GHAD after the first four years. IV. Consequences of Negative Action: The project will not be able to proceed because no building permits may be issued without a GHAD being formed. THE BOARD OF SUPERVISORS OF CONTRA COSTA COUNTY, CALIFORNIA Adopted this Order on June 4, 1996, by the following vote: AYES: Supervisors Rogers, Bishop, DeSaulnier, Torlakson, Smith NOES: None ABSENT: None ABSTAIN: None SUBJECT: Setting a Public Hearing on the Petition ) for Formation of Hillcrest Heights ) RESOLUTION NO. 96/256 Subdivision 7582 Geologic Hazard ) (Pub.Res. C. § 26557, 26561-5) Abatement District ) The Board of Supervisors of Contra Costa County Resolves that: 1. On June 4, 1996, this Board was presented with the Petition for Formation of the Hillcrest Heights Subdivision 7582 Geologic Hazard Abatement District (the "GRAD Petition"). The Board concludes that the GHAD Petition is in the form prescribed by Sections 26551 and 26552 of the Public Resources Code. 2. The Board of Supervisors will conduct a public hearing (the"Hearing") on the proposed formation of the GHAD on Tuesday, July 9, 1996 at 9:45 a.m. in Room 107 of the Board of Supervisors' Chambers, 651 Pine Street,Martinez, California 94553. At the Hearing, any objections to the proposed formation shall be presented. 3. Notice of the Hearing shall be mailed 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 certified mail with return receipt requested and postmarked not less than 20 nor more than 30 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. 4. 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 a written objection to the formation. Such objection shall be in writing, shall contain a description of the land by lot,tract, and map number, and shall be signed by such owner. Resolution 96/256 Objections shall be mailed or delivered as specified in the notice procedure in Paragraph 3 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. I hereby certify that this is a true and correct em of an action taken and entered on the minutes of the Board of Supervisftrs on the date sh 4. wn. ATTESTED: '-- PHIL BAT EIGR,Cler of the oard of SupervISM and County Administrator By Deputy Orig. Dept.: Department of Public Works cc: Clerk of the Board County Counsel Daniel J. Curtin, Jr., McCutchen, Doyle, Brown& Enersen Eugene C. Lee, Cerrito Development Resolution 96/256 2 PETITION FOR FORMATION OF HILLCREST HEIGHTS SUBDIVISION 7582 GEOLOGIC HAZARD ABATEMENT DISTRICT PURSUANT TO DIVISION 17 (commencing with Section 26500) OF THE PUBLIC RESOURCES CODE OF THE STATE OF CALIFORNIA TO: The Clerk of the Board of Supervisors of Contra Costa County The undersigned owners of land within the boundaries of the district proposed in this petition hereby request that the Board of Supervisors initiate proceedings to form a Geologic Hazard Abatement District pursuant to the provisions of Division 17 of the Public Resources Code, Sections 26500 et seq. (a) This petition is made pursuant to Division 17 of the Public Resources Code with particular reference to Sections 26550.5, 26552 and 26553 of said Code. (b) Opposite the signature of each of the petitioners 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 proposed to be included within the proposed district. (c) Opposite the signature of each petitioner is an indication of the date on which said petitioner's signature was affixed to this petition. (d) The following documents are attached to this petition and are incorporated herein by this reference as if set forth in full in the petition: 1. As Exhibit A, a legal description of the boundaries of the territory proposed to be included within the proposed district; CA961060.012/73503-001 05/08/96 0212 PM 2. As Exhibit B, a map of the boundaries of the territory to be included within the proposed district; and 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 the actual or threatened landslides, land subsidence, soil erosion and other natural or unnatural movements of land or earth and the plan for their prevention, mitigation, abatement and control thereof. SIGNATURE ADDRESS DATE A portion of Lots 25 and 26, Secretary, Cerrito as shown on the Map entitled ,S U I 4 �v Map of North Richmond, Development Corporation Contra Costa County, California" filed on April 6, 1908, in Book 1 of Maps, at Page 18, Contra Costa Records, and a portion of Lot 126, as shown on the Map of Rancho San Pablo filed March 1, 1894, Contra Costa Records. 2 CA961060.012 Exhibit "A" G.H.A.D. District Subdivision 7582 Contra Costa County, Cil i _corm a legal Description All that real Property located in the unincorporated lands of Contra Costa County, State of California, described as follows: Being a portion of Lots 25 and 26, as shown on the Map entitled "Map of North Richmond, Contra Costa County, California" filed on April 6, 1908, in Book 1 of Maps, at Page 18, Contra Costa County Records, and a portion of Lot 126, as shown on the Map of Rancho San Pablo filed March 1, 1894, Contra Costa County Records, described as follows: R MNNING at the Northeast corner of said Lot 25 (1-M-18) ; thence from said Point of Beginning South 88033114" East, 249.81 feet to the Northwest corner of Lot 72, as said lot is shown on the map of "La Colina", filed April 14, 1941 in Book 25 of Maps, at Page 805, Contra Costa County Records; thence along the exterior boundary of said "La Colina" the following three (3) courses: South 01026'26" West, 345.17 feet; South 39051'24" East, 199.38 feet; South 59025'24" East, 45.11 . feet; thence leaving said exterior boundary South 29006'29" West, 136.00 feet to the North line of La Cima Road as designated on said "La Colina"; thence along said North line of La Cima along a non-tangent curve to the right, the center of which bears North 25006'38" East, having a radius of 40.00 feet, through a central angle of 0011'12", an arc length of 0.13 feet to a point of reverse curvature; thence along said reverse curve, the center of which bears South 25017'50" West, having a radius of 44.00 feet, through a central angle of 120041'14", an arc length of 92.68 feet to a goint of non-tangency, thence leaving said North line of La Cima South 84 36136" West, 35.10 feet; thence South 25054'18" West, 176.29 feet to the South line of said Lot 126; thence along the exterior line of said Lot 126 the following two (2) courses: North 89002'04" West, 180.04 feet; North 01021'02" East, 34.35 feet to the Southeast corner of said Lot 26 (1-M-18) ; thence along the exterior boundary of said Lot 26 the following four (4) courses: North 88049'38" West, 567.35 feet; North 31005130" West, 351.26 feet; North 73034'39" West, 99.35 feet; * North 16025'21" East, 125.00 feet to the Northwest corner of said Lot 26, said point being on the centerline of Hillcrest Road, a county road; thence along said centerline North 36045121" East, 309.72 feet; thence leaving said centerline South 19044'39" East, 96.89 feet; thence North 70015'21" East, 100.00 feet; thence North 19044'39" West, 163.08 feet to said centerline of Hillcrest Road; thence along said centerline North 3604521" East, 50.00 feet to the Northwest corner of said Lot 25 (1-M-18) ; thence along the North line of said Lot 25 South 89006'09" East, 535.51 to the POINT OF BEGMeuM. Excepting Therefrom: A11 that land described in the Deed to Bailey, recorded in Book 8120 of Official Records, at page 397, Contra Costa County Records. Containing 17.56 Acres, more or less. Exhibit "B" • f N .rn n D r 1 m Z /Amommum- 1 L' ,• 36• Ln w X �O sts, o �C r � � o SFS M<< N C •--1 m O � p Z D N • Ln po r O N y rn p N D UP00 �! O ; W N G7 I m o W D o m � Ln c7= Oo f i p C) O Ln o 0D CD Z O Z � co Z� r. O Z m ;u- D O U' Z O D —� W rn G7 m D C7 0 nO� D �� � D— z0 co p C 00 N Z O O N O I 0 OO ,N� C°! t� N cD D S2S• ► O w n P rri so 1-26'26"W 345. 17' n mVm I n rrrrrrrrrr C D m O (D Oo �l o) Un -P. W N Z n '- p r m < z m O D cn D v zzcnzZz � Ncn U4 v -- -- v o CO N cn -F'CD O� Ocorn ; cDCDm O — O O W N W 0 " n O r� cncn � cncn � � , NN rvLNm � �NO 1 z ---i N) 68, - to D r i Nm m m m mm rnz co D \\ N2906, Ln 0 w m W U4U4U4 (A � N 8N ?9'' 0CDa) ncD PU, rncn --i Np F 0 C) U4 L-4 - 0 — D o r,, 00 (Docncnoo -- � P � m � D i §26561 GEOLOGIC HAZARD ABATEMENT DISTS. Div. 17 i Article 4 NOTICE AND HEARING Section 26561. Certified mail; return receipt requested; postmark. 26562. Copy of petition or resolution; attachment to notice. 26563. Contents of notice. 26564. Objections to formation; time; form; mailing or delivery; evidence and determination of ownership of real property. 26565. Hearing of objections; adjournment. 26566. Abandonment of proceedings of formation. 26567. Order of formation; resolution; board of directors. Article 4 was added by Stats.1979, c. 1118, p. 4071, § 1. § 26561. Certified mail; return receipt requested; postmark Notice of the hearing set pursuant to Section 26557 or subdivision (c) of Section 26558 shall be mailed by certified mail with return receipt.requested and postmarked not less than 20 nor more than 30 days preceding the date of the public hearing. (Added by Stats.1979, c. 1118, p. 4071, § 1.) Library References Counties «52. C.J.S. Counties § 88. Municipal Corporations 0:-89. C.J.S. Municipal Corporations§§ 395 to 398. Time a2 et seq. C.J.S. Time § 2 et seq. § 26562. Copy of petition or resolution; attachment to notice A copy of the petition described in Section 26552 or the resolution de- scribed in Section 26558 shall be attached to the notice. (Added by Stats.1979, c. 1118, p. 4071, § 1.) § 26563. Contents of notice The notice shall set forth the time, date, and place of the hearing, briefly describe the purpose thereof, and indicate where the plan of control may be reviewed or duplicated, at a cost not to exceed the cost of duplication. The notice 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. (Added by Stats.1979, c. 1118, p. 4071, § 1. Amended by Stats.1981, c. 714, p. 2752, § 377.) Historical Note The 1981 amendment amended the section without change. i 510 i FORMATION §26567 Ch. 2 § 26564. Objections to formation; time; form; mailing or delivery; evi. dence and determination of ownership of real property 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 a written objection to the formation. Such objection shall be in writing, shall contain a description of the land by lot, tract, and map number, and shall be signed by such owner. Objections shall be mailed or delivered as specified in the .notice described in Section 26561. If the person whose signature appears on such objection is not shown on the assessment roll last equalized by the county as the owner of the subject real property, the written objection shall be accompanied by evidence sufficient to indicate that such person is the owner of such property. The determination by the legislative body of ownership for purposes of this section shall be final and conclusive. (Added by Stats.1979, c. 1118, p. 4071, § 1.) § 26565. Hearing of objections; adjournment At the time set for hearing objections, the legislative body shall be presented with all objections made pursuant to Section 26564. The legislative body may adjourn such hearing from time to time, but not to exceed 60 days from the date specified in the original notice. (Added by Stats.1979, c. 1118, p. 4071, § 1.) § 26566. Abandonment of proceedings of formation If it appears at the hearing that owners of more than 50 percent of the assessed valuation of the proposed district object to the formation thereof, the legislative body shall thereupon close the hearing and direct that proceedings for the formation of a district be abandoned. (Added by Stats.1979, c. 1118, p. 4071, § 1.) § 26567. Order of formation; resolution; board of directors At the close of the hearing or within 60 days thereafter, the legislative body may proceed by resolution to order the formation of the proposed district. Such resolution shall appoint five owners of real property within the district to the initial board of directors for terms not to exceed four years, or, as an alternative to the appointment of five such owners, the legislative body may r appoint itself to act as the initial board of directors for a term not to exceed four years. Thereafter, the board of directors shall be elected as provided by Section 26583. (Added by Stats.1979, c. 1118, p. 4071, § 1.) 147 511 MCCUTCHEN,DOYLE,BROWN&ENERSEN,LLP �� X996 K e®ARp OF SUPERVISORS CHER CONTRA COSTA CO. May 16, 1996 dcurtin@mdbe.com FEDERAL EXPRESS Ann Cervelli Deputy Clerk, Board of Supervisors Contra Costa County 651 Pine Street Martinez, CA 94553 Hillcrest Heights -- Subdivision 7582 GHAD Our File No. 73503-001 Dear Ms. Cervelli: I am enclosing the following document initiating proceedings for formation of the Hillcrest Heights Subdivision Geologic Hazard Abatement District (GRAD) pursuant to Division 17 of the Public Resources Code § 26500 et seq.: a Petition for the Formation of a GHAD including a Plan of Control. On behalf of my client, the petitioner and the owner of the land within the territory included within the proposed district, please set this on the Board of Supervisors' agenda for adoption of a resolution setting a public hearing pursuant to Government Code section 26557. Government Code section 26561 requires notice to be sent at least 20 days before the public hearing. At the close of the public hearing, I request that the Board of Supervisors, pursuant to Government Code section 26567, adopt a resolution ordering the formation of the District and approving itself to act as the Board of Directors. ATTORNEYS A T L A W 1331 N. California Blvd., P.O. Box V San Francisco Palo Alto Walnut Creek, California 94596-1270 Los Angeles Washington, D.C. Tel. (510) 937-8000 Fax (510) 975-5390 San Jose Taipei http://www.mccutchen.com Walnut Creek Contra Costa County Clerk May 16, 1996 Page 2 If you have any questions regarding this petition, please advise either me or my Associate Adam Lindgren. Very t 1 o s, an J. Curt' r. Enclosures cc: Victor J. Westman R. Mitch Avalon Skip Epperly Eugene Lee, Cerrito Development Corporation John Wollman, Wollman Associates, Inc. Tim Coats, Wollman Associates, Inc. William Wigginton, Geolex, Inc. Daniel B. Rosen, Alda Properties MCCUTICHEN : MCCUTCHEN,DOYLE,BROWN&ENERSEN,LLP May 16, 1996 dcurtin@mdbe.com FEDERAL EXPRESS Skip Epperly Special District Coordinator Contra Costa County Department of Public Works 255 Glacier Dr. Martinez, CA 94553 Hillcrest Heights -- Subdivision 7582 GHAD Our File No. 73503-001 Dear Skip: As you requested in our telephone call this morning, I am enclosing the a copy of the cover letter to Ann Cervelli and the documents initiating proceedings for the formation of the Hillcrest Height Subdivision Geologic Hazard Abatement District(GRAD). At your request, I have provided you with the/original copy of the Petition. Thank you for your continuing assistaethsr. V Dr. Enclosures CA961370.060 cc: Ann Cervelli Tim Coats A T T O R N E Y S A T L A W 1331 N. California Blvd., P.O. Box V San Francisco Palo Alto Walnut Creek, California 94596-1270 Los Angeles Washington, D.C. Tel. (510) 937-8000 Fax (510) 975-5390 San Jose Taipei http://www.mccutchen.com Walnut Creek i 1 1 1 1 ' HILLCREST HEIGHTS SUBDIVISION 7582 ' GEOLOGIC HAZARD ABATEMENT DISTRICT (GRAD) PLAN OF CONTROL MONITORING & MAINTENANCE MANUAL i 1 ' G E O L E X G E O E X 8 May 1996 Project No. 95117-1 ' Eugene Lee 2971 25th Ave. San Francisco, CA. 94132 ' Subject: Hillcrest Heights, Subdivision #7582 GHAD Dear Mr. Lee: Enclosed are the documents and figures necessary for the creation of the Hillcrest Heights (Subdivision 7582) Geologic Hazard Abatement District (GRAD). The proposed district is for the purpose of abatement of potential landslide and erosion hazards at the site. ' This report includes a legal description of the property, a map of district boundaries, and the required plan of control. The necessary forms for the Contra Costa County Board of Supervisors Resolutions are also included. Very truly yours, �G\NEER GEOLEX Inc. �Q� 5. 0, 0`� o cn 3 No.855 Z �dS UP.12/31/1 Wig n 1 Certified Engineering Geologist, No. 855 OF CAUF�Q�� ' Copies: 4 to Client ' GFEE OLFEE X INC. ' W.13. W I G G 1 "T O N P.O. BOX 1149-132 APTOS, CALIFORNIA 95003 TELEPHONE 510.988.9428 FACSIMILE 408.662.0755 TABLE OF CONTENTS Hillcrest Heights, Subdivision 7582 CHAD, Plan of Control Letter of Transmittal Recital 1 GHAD (Description) 2 Description of Landslide Hazard 2 Other Potential Geotechnical/Geologic Hazards 3 Exclusion of Isolated Problems on a Single Lot 4 PLAN OF CONTROL A. Authority and Scope 5 ' B. Criteria for Inclusion or Exclusion 5 C. Funding 6 D. Description of Geologic Hazards and Repair 7 E. Definitions 9 F. Plan for Prevention, Mitigation, Abatement, or Control 9 G. Geotechnical Techniques for Mitigation 9 H. Operation and Maintenance Procedures 10 I. Monitoring Frequency 13 J. Annual Report 13 1 K. Initial Start-up Period 14 L. Future Modifications of Plan of Control 14 FIGURES 1. Vicinity Map 2. Site Map 3. Rough Grading Plan 4. Schematic of Remedial Grading 5. Eastern Landslide Repair Cross-section 6. Western Landslide Repair Cross-section 7. Subdrain Detail 8. Preliminary Remedial Grading Plan 9. B-58 Concrete Lined Ditch ' 10. J Concrete Lined Ditch GEOLOGIC AND SOILS MAP (Pre-Construction by Harlan Tait for EIR) BIBLIOGRAPHY HILLCREST HEIGHTS SUBDIVISION 7582 GEOLOGIC HAZARD ABATEMENT DISTRICT GHAD Plan of Control and Monitoring and Maintenance Manual 1 RECITAL The proposed project, Hillcrest Heights, is an R-6 single-family residential detached development (six units per acre) consisting of 66 lots on 17.5± acres. The subdivision is located within the unincorporated El Sobrante area of Contra Costa County on a north facing hillside of the San Pablo Ridge (see Figures 1 & 2). Two open space parcels within the subdivision are the 2.65 acre Parcel B and 0.13 acre Parcel A. These parcels lie outside of individual lot boundaries, and are to be under the ownership of the Hillcrest Heights Homeowners Association (HOA) together with the HOA maintained private streets. ' The project EIR recognized that a potential significant geologic hazard exists for this development in the form of landslides. "Slides on site need to be properly evaluated as to their hazard potential to site. Sites near Hayward fault and its or any other nearby faults effects need to be evaluated." Also since the site will be heavily graded this was considered a significant environmental impact and "the effect on this on underground water needs to be investigated". These issues raised in the EIR were addressed in the geotechnical reports by Alan Kropp and Associates (AKA 1988,1991,1995) and a geologic report by Darwin Myers Associates (1988). Other relevant publications used in preparation of this report are in the Bibliography in the Appendix. AKA came to the conclusion that "the site is suitable for the proposed development." This was with the provision that the conclusions and recommendations contained in their reports were followed. Corrective work to stabilize landslide materials is defined in these reports. Darwin Myers (1988) in his geologic report recognized the potential landslide hazard and stated " a network of subdrains, in combination with an efficient surface drainage system will be critical to stabilize the site." The County in its Conditions of Approval (6/13/93) for the Hillcrest Heights Subdivision, recognizing a need for post-construction maintenance of surface and subsurface drainage facilities, called for in Condition 21 (J): "A Geologic Hazard Abatement District (GRAD) or functional equivalent shall be developed to monitor and maintain the slope stability measures (e.g., subdrains) for this development." The Conditions of Approval place a requirement for an annual inspection report to be filed with ' the County by "a licensed Geotechnical Engineer." The intent of the Condition of Approval 1 i a N, a ?1co 'm 1 6 N Y a a Qu?1a� E IgM e1°dy CO) 6 J i n K ki O J S� S d . 1 1 r N a � to co Q m �t 1 'p d � � d 0 ul qO o. itto r r a 9 N 40 co 10 Z o 40dw O� r 6 3 o togo CA d �. o r co e+ j, Q/ N b 21 (J) is clearly to require the formation of a legal entity responsible for the long-term monitoring and maintenance functions needed for this development. GEOLOGIC HAZARD ABATEMENT DISTRICT (GHAD) Geologic Hazard Abatement Districts are property owner tax assessment districts which are created in accordance with the Beverly Act SB 1195 (1979) [California Public Resources Division 17 commencing with Section 26500]. A petition to the County Board of Supervisors is made by the developer. The district is formed with the passing of a resolution by the County Board. Annually a report is submitted to the board discussing the cost of operating of the district depending on the monitoring levels, repair costs, and inflation. The administration and field monitoring for the Hillcrest Heights GHAD would be accomplished by a professional private consultant(with possible assistance of the consultant's staff) retained by the district under the guidance of the enclosed Plan of Control and Monitoring & Maintenance Manual. The purpose of the district is for the functional life of the project, presumably 50 years, to monitor and maintain the specified subsurface drains (subdrains),surface concrete lined B-58 and 'J' ditches, permanent storm drainage facilities, the emergency vehicle access road, and certain retaining structures. A minimum of two subsurface monitoring devices (inclinometers) will be left in place which will require reading to demonstrate a lack of significant ground movement. 1 At least two piezometers will be monitored to determine if significant ground water level fluctuations have occured. Cleanouts will be placed during project site grading at appropriate locations to permit post-construction maintenance operations such as rodding, flushing or television camera monitoring of subsurface drain pipes. The District will also generate sufficient funds to build up a reserve to be used to mitigate landslide or adverse erosion damage in areas for which it has responsibility. DESCRIPTION OF LANDSLIDE HAZARD The most serious geologic hazard within the proposed GHAD district is believed to be potential slope instability. The EIR authors recognized that a stability analysis of both existing and reconstructed (graded) slopes in the project area was needed. This was done by AKA (January 19, 1996 and March 20, 1996) and the analyses were reviewed by Rodgers-Pacific, the peer review firm retained by the County for this project. An important product of this exercise was to define the level to which the ground-water surface can rise and still have the site retain adequate stability. The project Factor of Safety under static and seismic [earthquake] loadings drops for higher water table elevations. AKA (1995), in their appraisal of future performance, state that "the probability that landsliding will occur is substantially reduced by the proper maintenance of drainage measures at the site". Although the likelihood of landsliding is "very low", AKA states that even if proper maintenance is performed, landsliding may still occur during very heavy 2 1 rains, breaks in water lines, or other severe environmental conditions. For this reason the GHAD is responsible to make slope repairs that affect more than one property owner within the district. OTHER POTENTIAL GEOTECHNICAL/GEOLOGIC HAZARDS 1 Beside landsliding, several other geotechnical and/or geologic hazards are described for this project, including: 1. Erosion and sedimentation 2. Expansive soils and bedrock 3. Creep of slopes 4. Earthquake hazards such as ground shaking 5. Potential flooding 1 It is not the purpose of the Geologic Hazard Abatement District to take care of all potential soil P rP g and geologic problems or concerns within the project site. Potential landsliding is the primary ' hazard for which the district serves as the mitigation measure. Rapid removal of surface water resulting from precipitation by means of concrete lined ditches and storm drain facilities prevents 1 water infiltration into the subsurface and weakening of slope materials. Therefore proper operation of the concrete lined ditches, storm drains and detention pond is considered a long- term maintenance function suitable for the district. The surface ditches which total approximately 4,000 feet of aggregate length drain into a permanent stormdrain system. A sediment detention basin six feet deep and 60 by 100 foot in dimension is also present on-site. An erosion control plan is required for this project and details for post-construction maintenance should be given in this document. The geotechnical report (AKA 1995) states that the surficial clay soils and landslide debris are moderately to highly expansive and can undergo significant volume changes when shrinking and swelling. This can cause damage to homes, pavements, garage slabs, etc. Design mitigation will include the use of drilled pier and grade beam foundations for homes. In the EIR the authors also recognize the likelihood that the bedrock can also exhibit expansive (swelling) characteristics. The Hillcrest Heights Geologic Hazard Abatement District is not formed to undertake repairs resulting from the shrink-swell phenomena unless it directly effects the integrity and functioning of the drainage facilities for which it is responsible. Soil creep is differentiated from landsliding in that landslides have a distinct surface of sliding (slip plane), and creep does not. Creep may, however, in some cases be a precursor of landsliding. The rate of movement for creep is in fractions of an inch per year whereas landsliding occurs in inches or feet per day, month, or year. AKA (1995) state that "the surface ' soils tend to lose strength after prolonged rains, and when they are located on moderate slopes they have a tendency to creep". The mitigation measure chosen, given that the proposed homes are to be constructed on sloping terrain, is to design the foundation elements to resist the anticipated creep forces near the ground surface. The Hillcrest Heights GHAD is not formed 3 1 to undertake repairs resulting from the soil creep phenomena, unless it directly effects the integrity and functioning of the drainage facilities for which it is responsible. AKA is expected to place at least four slope inclinometers into the subsurface and periodic readings will be made by the District to record the depth and amount of any ground movement with time at the chosen installation sites. ' The Hillcrest Heights Subdivision is located approximately 0.7 to 1 mile northeast of the nearest strands of the active Hayward fault. The assumption is made (AKA, 1995) that the site will be subjected to at least one moderate to severe earthquake during the next 30 to 50 years. The likelihood of fault offset at the site is considered remote;however, ground shaking would occur. A secondary effect of earthquakes is seismically induced landsliding. The EIR authors under mitigation measure 4.2-1(g) recognize this possibility and call for: "A stability analysis of both existing and reconstructed project area slopes should be performed. Project area slopes should have a factor of safety greater than one under the effects of the design earthquake, assuming maximum possible groundwater levels during the life of the project" (underline added for emphasis in this document). A stability analysis (static and pseudostatic) was prepared by AKA. The maximum allowable level of groundwater is to be defined. Currently the stability analyses are based on an assumption that groundwater would remain below the repaired material at the base of the compacted fill. The GHAD monitoring responsibility is to assure that the ground water level in the subdrained areas does not rise above the maximum possible groundwater level as determined by the project 1 design. Personnel retained by Hillcrest Heights GHAD are used to inspect surface drainage facilities, concrete lined ditches, the inlets, subsurface storm drains, and the sediment detention basin. The Hillcrest Heights GHAD is not formed to undertake repair of earthquake damage unless it directly effects the integrity and functioning of the drainage facilities for which it is responsible. EXCLUSION OF ISOLATED PROBLEMS ON A SINGLE LOT The Hillcrest Heights Geologic Hazard Abatement District(GHAD) is not intended to treat landsliding or adverse erosion damage confined within a single lot boundary. If, however, a hazardous landslide or erosion condition encroaches from a lot into the open space (Parcels A or B) or crosses a property line, or threatens in the judgement of the District more than one ' property the District should act to mitigate the damage. 4 HILLCREST HEIGHTS GHAD PLAN OF CONTROL Maintenance and Monitoring Manual EXHIBIT C A. Authority and Scope ' Under authority of the California Public Resources Code(Division 17, commencing with Section 26500) the County of Contra Costa wishes to establish the Hillcrest Heights Geologic Hazard Abatement District (GHAD) in the El Sobrante area. Development of the Plan of Control by a state licensed Certified Engineering Geologist is a requirement for formation of a GHAD. The potential for long-term landslide and erosion are known to exist and this plan document provides a plan for their prevention, mitigation, abatement, or control. ' B. Criteria for Inclusion or Exclusion of a Given Property Within the GHAD Area of Maintenance Responsibility Inclusions 1. ' Two or more lots or properties( with at least one within established GHAD boundary) affected by a serious slope stability (landslide) or erosion problem which poses a clear-cut hazard to public health, safety and welfare. ' 2. Surface concrete lined ditches or, subdrainag a under compacted fill or behind retaining P walls that cross more than one lot or property within the established GHAD boundary. ' 3. Permanent storm drainage facilities, including storm drain pipes, catch basins, manholes, and detention pond are the districts' maintenance responsibility. The drainage terrace that serves as an EVA is also the district's maintenance responsibility. 5 Exclusions 1. Landslide or erosion damage within a single lot which does not pose a clear cut hazard to public health, safety and welfare. 2. Maintenance of privately maintained right of ways other than the EVA. 3. Property or lot which lies completely outside the GHAD boundary in which the landslide or erosion problem does not encroach or directly affect the improved lands within the district. 4. Surface concrete lined drainage ditches or homeowner installed subdrains that traverse only one lot. C. Funding 1 The GHAD District will be funded from the assessment of each lot within the GHAD boundaries. The tax assessment would commence upon the filing of the Final Subdivision Map. The owner of each lot which includes the developer would pay the full assessment whether or not a residence is constructed on the lot. a. Single Family Unit(lot size up to 1 acre )....$ 875 per year*(approximate) * Based on 1996 estimate. Automatic escalation according to US Dept. of Labor, Bureau of Labor Statistics, Consumer Price Index. .Open space and undeveloped land within the district will not be assessed. Streets, the detention basin, and any lands held in common by the homeowners association will not be assessed. The project is anticipated to be graded in 1996 and lot sales would commence in 1997. For the ' first year after grading the contractor is normally responsible for any defects or problems with drainage installations. The developer is expected within the three year buildout period to handle any minor landslide or erosion problems. It is therefore expected that a reserve can be established in the first three years on the order of$60,000. The reserve should only be tapped to repair shallow landslides or adverse erosion within the district areas of responsibility, to maintain ditches, or repair damaged pipes for which the district is responsible. . 6 1 D. Description of Geologic Hazards and Re air ' The site is on "a northwest facing slope that contains two swales. Elevations on the property range from 340 feet near the southeast corner of the site to elevations of about 120 feet near the northwest corner of the site. Natural slopes at the site are at inclinations of 2:1 (horizontal to vertical) to 5:1 over broad areas "(AKA, 1995). The average slope is slightly steeper than 5:1, ie 22%. The majority of the site appears hummocky suggesting soil creep or shallow soil slippage (AKA, 1995). Beneath a soil cover of colluvium landslide deposits, existing fill or terrace deposits is the P � g � P bedrock of the Pliocene Contra Costa Group (Tcc). This unit consists chiefly of a weakly lithified nonmarine claystone, siltstone, sandstone, and pebble conglomerate. Where exposed bedrock dips of approximately 35 to 40 degrees to the southwest. For more detail on site geology refer to the geologic reports referenced in the Bibliography. Harding Lawson and Associates (HLA, 1988) prepared the first site specific geologic map and outlined two significant large landslide deposits (15 to 20 foot thick) on-site which have become identified as the eastern slide and western slide. A smaller on-site active slide (northeastern slide) is also mapped. The Hillcrest Heights Subdivision 7582 Grading Plan was prepared by Wollman Associates and is included as Figure 3. A major portion of the site is to be graded with approximately a ' balanced 100,000 cubic yards of cut and fill. Slope repairs could take an additional 110,000 cubic yards (Simonitch, 1992). Depth of cut is up to 26 feet and thickness of fill can be up to 32 feet. The corrective work solution for the existing landslides by the project geotechnical consultant AKA is to remove the landslide material on-site. "Corrective work should include the construction of a keyway at the downslope boundary of the work, construction of benches in the slope where material is to be placed, installation of subsurface drainage systems, placement and compaction of the materials onto the prepared slope, and construction of surface drainage features" (AKA,1995), see Fig. 4. Two idealized cross-sections are presented in Figures 5 and 6 that show the regrading concept. They illustrate replacement of landslide debris with compacted engineered fill. Figure 7 shows the detail of the subsurface drainage installations at ' the base of a subexcavated slope. During site grading some temporary shoring work will be necessary along the southern property line to prevent upslope buildings from being adversely affected by excavations necessary for the slope reconstruction work. Darwin Meyers (1988) in his report for the landslides on-site recognized that "a network of subdrains, in combination with an efficient surface drainage system will be a critically important component of any plans to stabilize the site" (DMA, 1988). The primary function of the Hillcrest Heights GHAD is to ' provide the post-construction long-term maintenance and monitoring of the subdrainage, surface drainage, and buried storm drainage systems. Provided the drainage systems perform as designed ' the landslide hazard is prevented, mitigated, or controlled. 16 ,110 f � 6l, f �,t • ,�' � "` � _ � i'�" \�a• 1" ;111 ,�'' �' j ,r�lw• 60 �-�¢ � � r 11-. 1 4,� n ��:d1F S`�°`^'S :..t � 4b3z \ J$r �� �Q� l; `V.,V s�,`. `! �'. ..ra8_e w � � �`' k i� — •..__' .i j1.r, �1� t e 1,V ;} �, �;!' 2• '� ,A3 S!� �� 1 +��y� e' ;9:��yn •��� �� ",'F_'"-' ,. ,�,Ty.�'�fi"" �1 ^ y" . f� '-�J�_\ -'�_ _ e�fi� 8�S:Y :d�•` �� ;;�{"" � f�r � ,'t�-'` ���� � i �,:V'''a \1 � r ''S ` X1'1`��/f ^ �.,� _� L 1�t: { .,3d �• : �,� �`�. 'y. 1\M z::a 1 ! _> ' )Pry %� ' ��'1'"...- .! � � i as � • - � _ �>t` j'i� `'� � �/ !,61Y' n s�. ! L�dr a,•� -ri� b � 't'^1 »' \-,�-=1-'""q:�i.�:\ .z�',e { } Iarp I' /J�/��i t � ,'. E c.•a� .'r i� _yf�, _ ;r" i �'1 y��. t �! 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ROUGH GRADING PLAN By WOLLMAN ASSOCIATES, 75132 SugpNIS10N �. EL SMFtAt4TE, CALFCf"A ev WSW DALE 4/15/961111111 GOR�QRA a PROJECT N0. 95117 y W B-. WIGGINTON r ZV 3 1 Z OO to o cc to e- 0 ^Q ;::;,4o �. .9 �� Xp O J '1' r� � a •- v Ca O O O 1 � D O Q` 1 c q q r o d � q Os. Cl m vy O 2 ■ 3, m 3 W D N Z Q 1" N ccO ,tOr, LL'� rn d � C c Z U t11 Sr- r ©n Z U p d co m N N CD �y N v Y . O lU R 3 5 U X1 Q N ww °' a w C > a 1 0 z o z a Z. m m � � [� ` � � -- tom•- O N W to -i rn 1 \ N � a ul W S Q cr6 zz- �N�• c�4 ( ca R• Q ` \ �' � ,U N \ u Y � N W \ +LLC m � ; •i4 VP v w Z a o CL 3 o Q � 7 •� � a �z � °•y � r o •� � � 7 .II CD V y G G O O U a � Nm r L' tu' 'i6 d Q l r O 0 co - "`�' geotextile overlapped '/.-inch, clean, open-graded drainrock; wrapped in an a: ° approved non-woven polyester geotextile s�Q O o • p '° . 6-inch rigid, perforated, plastic pipe, placed with o holes down, on maximum 6 Inches of bedding, a ° o , sloping 200 minimum to solid pipe system (Joints glued where sloping>3:1). Provide o,'. • ° cleanouts at 'high' ends r AS PER A. KROPP & ASSOCIATES N.T.S. r - SUBDRAIN DETAIL EicuRE No. G E=— 0 I— fi= X SUBDIVISION 7582 INCOFiF'ORATE=� EL SOBRANTE, CALIFORNIA W.B. WIGGINTON PROJECT NO. 95117 DATE 4/15/96 BY wBw iSubdrainag_e System Figure 8 illustrates the current concept of the subdrainage system envisioned currently by the project geotechnical consultant. Approximately 12,000 feet of piped subdrains are anticipated by AKA ( see remedial grading plans dated Jan. 1996). It is expected that the project geotechnical engineer will ultimately determine the extent and layout of the subdrains in the field during grading. It is recommended by AKA that the project surveyor locate all subsurface drains, solid pipes, and cleanouts on an AS-BUILT DRAWING OF REPAIR AREAS. These 1 drawings are definitely needed by the Hillcrest Heights GHAD to assist the district in locating the pipes in the future should any repair work be necessary. i Clean-outs for the subsurface drains are to be provided at the upslope boundary of each subdrainage pipe and at intervals of no more than 100 feet for solid discharge pipe. Additionally a cleanout should be provided at each 90 degree elbow. The collected water is taken to a suitable "appropriate discharge facility". ' Concrete Lined Surface Drainage Ditches ' Current grading plans show an aggregate length of 4,000 feet of concrete lined ditches of the County B-58 and/or J design (see Figs. 9 & 10). B-58 ditches are typically placed on a 8 foot width drainage terrace (see detail). AKA has called for no surface water being allowed to flow over the top of cut or fill slopes. Drainage berms or interceptor ditches should be provided to prevent surface water from flowing over the slopes. Drainage terraces on the surface of cut or fill slopes should be provided with paved "V" ditches (in accordance with Contra Costa County ' specifications for a 13=58 ditch). AKA calls for the use of reinforcing bars rather than wire mesh in the concrete lining of the ditches. The ditches are to slope at a gradient of at least 5%. Collected water is to be carried in solid pipe to an "appropriate discharge location". A cleanout should be installed at the "high" end of the solid pipe and at 100-foot intervals along the length of the solid pipe. The project surveyor should survey in and place the location of this solid pipe on the As-built drawing of the repair areas. Project Improvement Plans should designate the 1 discharge storm drain facilities that the Hillcrest Heights GHAD is not responsible to maintain. 1 The EIR describes that a LEGAL ENTITY ( which is in this case is the Hillcrest Heights Geologic Hazard Abatement District) should be established to fund the needed maintenance of concrete lined ditches, inlets or drainage pipes located on slope benches or along rear lot lines 1 in accordance with Division 914 of Title 9, Subdivision Ordinance. All drainage facilities that drain more than one lot before entering the storm drain system would be maintained by the district. Drainage facilities that drain more than one lot located within lot boundaries need to ' have specified easements to permit the district to enter to perform the needed maintenance. Early implementation of the district is facilitated by developer funding in the form of assessment 1 on improved lots before homeowner occupancy. This together with the periodic inspection called i 8 ,. 1 ;;^g,ii kw r}YEaPY•� ri xi 4=.. E( �t ''�'ar.:��,v5�>f�,'a-,'xr��ftC`•> xr _ t - �°zr tI�``r rr�," ._ ;,.-,�„� f..' r. .. . �srvr?.t�F';1 r `u � r't+•^.i"�;{r j�".ti' rt. �T .�;y'�-., '�':hrot� r"s��,�-:i f�s�.$1 ,.9r ';t rEtx:'s-� �'�r.:'slls €�'���r!r5$'N-, r ;� EIt ur k 3'?il' t :.4N, .}w r�'- •,1.*.,: i 1 rrlt :, j - F '{� r tf J l._..3::es" Y�l - LV S'". ,F' .4 s�'T ( ��''h- � 'N '•,.i I� 7 7 .M' 1 Y� •.`;qi � �, r f ... -i " L x t a t �7p{ k.� s "`�' r- 'r � •?` n,�, e , f ,. r A s r .f J � { f. I 1t { ✓ s 4.'. 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W r s t "7 � :-0 J*M,r7.�1 'E 33'tt SI l st. t} ;.� w Ji �,"t h }>1{ �` y_.� t i:n is •'`9 Dx i'^��ryrsf�- �y'jl LEGEND +' '"^ !A A 11.:, y k {, 4 aN 1 f '� Y ' 'y``� yL: •"'"'" t Y rasa iw y.APPROX.LIMITS OF REMEDI p. TO MODIFICATION DURING C { MF t.. t i„ : , G Z`L*...i h 'h �P �L 1 r•,I _____ APPROXIMATE SUBORAIN TO 4r� YI H.r'"^}�n y: V,. F 11v"• } ALA KEYWAY LOCATIOt. AND ND LANOSUOC ftCPA1R5 ay .r 4 a.-t. '"� u R C i L"�h L , 3 S y•} `a } R .1 �`i, `s ffl .l ''+� SUB ORAIN CONNECTION PO f : S x•RL �, '{ai 4 S €�1 �. 5 J W�A� yt-, t � yet }�L.,. t ', vry '-er'.s. y + t 70 STORM DRAIN SYSTEM '? S� w � � �•L .; t Fu rts 4 £ 3 d k �.ty } Y l .Y� 7 NY L J 5. tl ,} 5 ; �.....�s�r a+F x, ✓ „2�i c, T»..:� nt r'^' .t* ..�.j• ,<4}ae' c,�' ,s s2' r 1C .F'L k l � �'', t F ^• A iL � �=• L 4 x ''w t s; .. � a > �'}�''+� �.'� t C (-• } s,..7+ ��� f'� f�t�: r -- � �"�lEf`, c:*'s> 5� �€� 5 � ,t�� a'�zf F #' 7::?k.fpf,.caY�. 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WIGGINTO'N PROJECT NO. 95117 DATE 4/15/96 By WB' T —� 32* 6. -� 3' min. WS 3' min. 12' Cb ,�\ 6Lip on uphill side -3' min. ' 6x6x10 Ga. mesh* NOTE: Use rebar, see. -12' min. comment below t C.C. CO. STD. B-58 DITCH * Lined surfa. ce ditch sloping 5% minimum to suitable discharge facilities. .Line ditches should be reinforced with reinforcing bars (not wire mesh) ' and have score Joints spaced appropriately. 8 feet minimum ' 2% minimum r ' DRAINAGE TERRACE DETAIL N.T.S. ' - B-58 CONCRETE LINED DITCH DETAIL AND DRAINAGE TERRACE FIGURE NO. Gi E=— O L_ E X SUBDIVISION 7582 w ' INCOF2POFiATE=� EL SOBRANTE, CALIFORNIA W.B. WIOC,INTON PROJECT NO. 95117 DATE 4/15/96 BY WBW 1 1 1 1 N ion IoM -3- ifliv Ole 1 ,l f ♦ ( I Q 7 ��' Z4 S M t M. SLOPE OM A L.L 1 0tTc. V•1Cr PEfZ SO1LS 1 1 1 1 . . 1 N.T.S. 1 - TYPICAL V CONCRETE LINED DITCH FIGURE NO. C1 E <Z> L I-= X SUBDIVISION 7582 INCORPORAT�� EL SOBRANTE, CALIFORNIA 10 ' W.B. WIGGINTON PROJECT NO. 95117 DATE 4/15/96 BY WBW ' for in this manual should provide adequate "proof that periodic maintenance" will be done. The maintenance should reduce the impact of long-term erosion and sedimentation on-site. Required ' monitoring should determine that the groundwater levels are maintained below a critical level where slope stability could be jeopardized. E. Definitions ' LANDSLIDE - is defined as a deposit of soil and/or rock moving downward from its original position under the influence of gravity. Slides are mass movements of earth materials, primarily intact, which occur along discrete shear surfaces. These surfaces (shear or ' slip planes) can be rotational such as for earth slumps, or planar as for translational earth slides or block glides. Flows 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. When the material flows downslope with speed the mass movement is called a debris flow or avalanche. EROSION - is defined as the process by which earth materials are loosened and removed by running water on the surface or in the subsurface. Sedimentation is the depositing or settling of soil or rock particles from a state of suspension in a liquid. F. Plan for Prevention, Mitigation, Abatement, or Control of Existing or Potential Landslide and Erosion Hazards The district will retain a professional registered geotechnical/civil engineer and/or a certified engineering geologist to identify potential landslide and erosion hazards. The professional ' consultant or consultants or their staff shall monitor existing or potential slide and erosion hazards and take action if authorized by the GHAD Board of Directors to repair or stabilize slides; and to mitigate,abate, or control the effects of sliding. The erosion hazard and adverse ' sedimentation effects are also to be monitored, mitigated and controlled. The ongoing annual maintenance is to be limited to that designated in the annual budget. ' G. Geotechnical Techniques for Mitigation of Landslide and Erosion Hazards If a hazardous landslide or erosion condition affects more than a single property, one of which is within District boundaries, or threatens in the judgement of the District more than one property, the Plan of Control is to be followed to mitigate the damage. This can include but may ' not be limited to: a. removal of the geologic hazard. ' 9 b. stabilization (either partial or total) of landslide by removal and replacement with compacted drained fill. ' C. construction of structures to retain or divert slide material or sediment. ' d. construction of erosion control devices such as gabions, riprap, geotextiles, or lined ditches. ' e. placement of drained engineered buttress fill. ' f. placement of subsurface drainage devices; e.g. underdrains, or horizontal drilled drains. g. slope correction (i.e. gradient change, biotechnical stabilization, slope trimming or contouring). h. construction of additional surface ditches and/or detention basins, silt fences, sediment traps, backfill or erosion channels. ' Potential landslide and erosion hazards can best be mitigated by controlling soil saturation and water runoff by maintaining the surface and subsurface drainage system. Operation and maintenance procedures for district operation are given along with a proposed monitoring schedule in the following sections. 1 H. Operation and Maintenance Procedures ' Once formed the Hillcrest Heights Geologic Hazard Abatement District through its retained professional consultant, would be responsible for implementation of the monitoring and maintenance program. The Consultant retained by the District could either be a Registered ' Geotechnical/Civil Engineer or Certified Engineering Geologist with experience in landslides and erosion and capable of maintaining civil engineering works. The administration required is limited and can be done by the subcontracted private consultant. Funding initially is from ' assessment of the lots (primarily developer's money in the beginning) and as the lots are sold the individual homeowners tax assessment would fund the district's annual budget. ' Concrete Lined Ditches The retained professional consultant and/or the consultant's designated representative would ' make the recommended periodic inspections (see next section for monitoring frequency). This ' 10 ' to placement of inclinometers behind and upslope of these structures to monitor the slope along the property line during grading. Provided the shoring materials are durable materials it is appropriate to leave this shoring material in-place rather than pulling the shoring out as fill is placed. This would be up to the project geotechnical consultant to determine. If the inclinometer casings upslope of the temporary shoring wall are left in place and are accessible, these installations should be integrated into the GHAD monitoring network. ' Retaining Wall Subdraina e Some proposed retaining walls cross a number of property lines or are in open space. These tmost likely would have a subdrainage system planned behind as wall and possibly a concrete lined ditch running behind the top of wall. The grading plan calls for criblock walls which are concrete crib type structures. If a retaining wall is confined to one lot it is the responsibility of the homeowner. If a wall has a subdrain which crosses a number of lots or is in open space, it is the district's responsibility to maintain the wall and to keep the drain functioning. ' Adequate drainage may be provided by a subdrain system consisting of a 4-inch rigid perforated pipe bedded in 3/4-inch clean, open-graded rock. The entire rock/pipe unit should be wrapped in an approved non-woven, polyester geotextile. The rock and fabric placed behind the wall should be at least one foot in width and should extend to within one foot of finished grade. The upper one foot of backfill should consist of on-site, ' compacted, relatively impervious soils (an impermeable plug). We should note that flexible, perforated pipe (flexline), 2000-Pound Crush, Leachfield, and ASTM FS 10 pipe are not acceptable for use in the ' subdrain because of the likelihood of damage to the pipe during installation and the difficulty of.future cleaning with mechanical equipment without damaging the pipe. We recommend the use of Schedule 40 PVC, SDR 35 PVC or ABS, Contech A-2000 PVC drainpipe, or equivalent for the drain system. The subdrain pipe should be connected to a system of closed pipes (non-perforated) that lead to suitable discharge facilities. At the location where the perforated subdrain pipe connects with the solid discharge drainpipe, drainrock backfill should be discontinued. A "clay plug" should be constructed out of relatively impervious soils to direct and collected water into the perforated pipe and minimize the potential of water collecting around the solid drainpipe and saturating the adjacent soils. In addition, the "high" end and all 90 degree bends of the subdrain pipe should be connected to a riser which extends to the surface and acts as a cleanout. The number of cleanouts can be reduced by installing ' "sweep" 90-degree bends or pairs of 45-degree bends in succession instead of using "tight" 90-degree bends. "Sweep" 90-degree bends are similar to those used in sanitary sewer pipe connections. ' Lined surface ditches should be provided behind any walls that will have an exposed sloping surface steeper than 4: 1 behind them. These ditches, which will collect runoff water from the slopes, should be sloped to.drain to suitable discharge facilities. The top of the walls should extend at least one foot above the ditch,(one foot of freeboard). f 12 Deflection or Impact Structure The EIR authors as a mitigation measure discuss the need of impact and deflection structures below the Parcel B at the rear of Lots 35 and 36. Current grading plans show upslope retaining walls behind Lots 38,39, and 40. An Emergency Vehicle Access Road and concrete lined ditches are present on this slope upslope of the lots. The possibility of a debris flow is the reason for the need of deflection or impact structures to protect downhill lots. If the graded slope is steeper than 3:1 the possibility of more rapid debris flow movements is increased. The potential buildup of slide debris against the upslope side of the wall as well as possible encroachment of slide ' debris on the uphill ditches or EVA should be checked after heavy storms. ' I. Monitoring FLe qugncy ' SURFACE(B-585)DITCHES and solid pipe outfalls....................................Semi-annually SUBSURFACE DRAINS in LandslideRepair Areas......................................Semi-annually ' SUBSURFACE DRAINS behind Common Retaining Walls...........................Annually SLOPE INDICATORS........... .......................................................5years* *first set after one year and then every 5 Years. ' DEBRIS OR IMPACT WALL......................................................................Annually As a minimum two permanent piezometers should be placed by the Project Geotechnical ' Consultant, one in the Eastern and one in the Western Landslide Repairs. Preferably these should be placed in proximity to the two inclinometers in readily accessible locations. Initial readings of ground water level should be taken after completion of grading. and then Red Flag ' Levels should be established by the project geotechnical engineer. At Red Flag Level 1 a Licensed Geotechnical Engineer should be consulted to determine what if any remedial measures should be undertaken. At Red Flag Level 2 the district should take some action to lower the ' ground water such as by pumping or installing horizontal drains. Monitoring frequency should be increased should a Red Flag water level be reached. Inclinometers should be placed in grouted holes. If in excess of 2 inches of movement takes place or if the rate of movement is ' in excess of 1 inch per year, monitoring frequency should be increased and a Licensed Geotechnical Engineer consulted as to the significance of these measurements. ' For annual inspections, the timing should preferably be in the spring, following the end of winter rainfall. For semi-annual monitoring, the inspection should include a fall pre-winter storm inspection and one in the spring following winter rains. For major (once every 5 year type) ' storms that occur subsequent to 10 inches of rainfall within one winter season, a storm damage check of the site would be appropriate by a district representative. ' J. Annual Re ort ' An Annual Report shall be prepared by the Professional Registered or Certified Consultant ' 13 retained to administer the District. The scope of the work in preparation of the annual report would be to: a.) Prepare annual assessment roll. b.) Prepare a Quarterly financial report. c.) Coordinate with the Hillcrest Heights Homeowners Association President or appropriate Board Member so as to obtain maintenance plans of the association. d.) Review monthly expense records for district. e.) Calculate the level of taxation for the coming year. The Annual Report and proposed budget for the Fiscal Year is to be submitted to the County Board of Supervisors. ' K. Initial Start-up Period The project is anticipated to be graded in 1996 and lot sales would commence in 1997. It is expected that all lots would be sold in 3 years. The tax assessment would commence after the filing of the Final Subdivision Map. The owner of each lot would pay the full assessment ' whether or not a home is constructed on the lot. For the first year after grading the contractor is normally responsible for any defects or problems with the drainage installations. The developer is expected to handle any minor landslide problems during the 3 year buildout. The ' first three years should permit a buildup of a reserve. Assuming an assessment per unit(lot) of approximately $875 per year the annual initial budget is on the order of$57,750. Provided that $20,000 goes to a Reserve, $37,750 is the first year budget for administration and normal maintenance. This is in 1996 dollars and a 6% inflation rate can be assumed for subsequent years. After 3 years a reserve of $60,000 could be established. The reserve should only be used to repair shallow landslides or adverse erosion within the areas of district responsibility, to replace ditches, or repair damaged pipes for which the district is responsible. L. Future Modifications of Plan Of Control ' This document is to be considered as the initial Plan of Control to serve as a guide for the operation of the district. With time it may become necessary to update or expand this plan to meet changed conditions present at some point in the future. The current document was prepared ' based on available information from the project consultants (see Bibliography). No independent study of the site conditions was made by William B. Wigginton, CEG or GEOLEX Inc. and the document was prepared for the sole use of the client Eugene Lee and the Hillcrest Heights ' GHAD. ' 14 r r r r �' 1111 r ■"" AL I`ll COID �_-..�"" tett...+ a _ � / J ` / 1, ..l \\. � �� o/• ���i� 9 J i w Co o � al CD / _ ,/ ,,w•. n -ice\ 7 '\ ? �1 1 y , 1 D" r 0 to 1 to soya ? * o Our 'Mal All IL �r• Of'j��I L� '-/ }� .!�//.✓ t'J'/� f .%' W to v 7" @ C) N Cl • 1 Ui v li r A r O �; u) r p w O i= O ;lftl p 0 O Z C m Gt p o O w r y o r p m m x, w < r v q o c o O w N Ct WTI A O @n ( Z 9 v <wn wttt p m C-l 7N� nA z n a VwwNo 0 o a O A O n to cn A u w n C CA u, x p C/1 m y w O 3 ✓ v � m o a R £ O _ -- N z. r•{j . o 01 BIBLIOGRAPHY 1. Alan Kropp and Associates, 5/21/91, Geotechnical Evaluation Update (Appendix C of 4/28/95 report). ' 2. Alan Kropp and Associates, 4/28/95, Geotechnical Investigation, Hillcrest Heights. 3. Alan Kropp and Associates, 1/19/96, Supplemental Geotechnical Analysis, Hillcrest Heights. 4. Alan Kropp and Associates, 3/20/96, Response to 3rd Party Review, Hillcrest ' Heights. 5. Contra Costa County, 10/92, Draft Enviornmental Impact Report, Hillcrest Heights. f6. Contra Costa County, 3/93, Response to Comments on EIR. 1 7. Margason, E. M., 1984, Landslide Repair in Orinda Claystone Utilizing Geogrid Reinforcement, International Symposium of Landslides, ISSMFE, Toronto, Volume 1 (Hillcrest Road Slide Repair). 8. McCutcheon, Doyle, Brown and Enerson, 1996, Draft Articles of Incorporation and CC&R's, Hillcrest HOA. 9. Myers, Darwin, 11/15/88, Subsurface Investigation, Hillcrest Heights. ' 10. Wollman Associates, 9/94, Grading Plan, Hillcrest Heights. 11. Wollman Associates, 2/96, Improvement Plans, Hillcrest Heights. ' 12. Wollman Associates, 1/96, Preliminary Remedial Grading Plan, Hillcrest Heights.