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TO: BOARD OF SUPERVISORS,AS BOARD OF
DIRECTORS FOR HILLCREST HEIGHTS GEOLOGIC a, Costa
HAZARD ABATEMENT DISTRICT
COUtH' �
FROM: JULIA R. BUEREN, PUBLIC WORKS DIRECTOR � County
DATE: June 24, 2008
SUBJECT: ACCEPT Petition for Annexation of the Spanish Trails subdivision into the Hillcrest Heights
Geologic Hazard Abatement District ("GHAD"), ACCEPT the proposed Hillcrest Heights GHAD
Plan of Control for Spanish Trails dated May 27, 2008, and ADOPT Resolution No. 2008Rglfixing
a hearing for July 22, 2008 at 9:30 a.m., to consider the Petition for Annexation and the proposed
Hillcrest Heights GHAD Plan of Control for Spanish Trails, El Sobrante area. (Hillcrest Heights
GHAD Funds) (District I) Project No.: 7756-6X5047.
SPECIFIC REQUEST(S)OR RECOMMENDATION(S)&BACKGROUND AND JUSTIFICATION
RECOMMENDED ACTION:
1. ACCEPT Petition for Annexation of the Spanish Trails Development into the Hillcrest Heights Geologic
Hazard Abatement District ("GHAD").
2. ACCEPT the proposed Hillcrest Heights GHAD Plan of Control for Spanish Trails ("Plan of Control");
3. ADOPT the attached Resolution No. 2008/ to do the following:
Continued on Attachment:X SIGNATURE: jl�Wv
RECOMMENDATION OF COUNTY ADMINISTRATOR
RECOMMENDATION OF BOARD COMMITTEE
APPROVE _OTHER
SIGNATURE (S):
ACTION OF BOARD ON APPROVC,6 AS RECOMMENDED OTHER
VOA E OF SUPERVISORS
UNANIMOUS(ABSENT ) I hereby certify that this is a true and correct copy of an
AYES NOES action taken and entered on the minutes of the Board of
Supervisors on the date shown.
ABSENT: ABSTAIN:
HH: rr��
G:\SpDist\Board Orders\2008\Board Orders 6-24-08\6-24-08 GHAD Board ATTESTED: d`T
Order Setting Hearing on Annexation Petition.DOC JOHN CULLEN,CIA of the Board of Supervisors and
Orig.Div:Public Works(Special Districts) County Administrator
Contact: Warren Lai(313-2180)
cc: Assessor �11 )
Community Development By
County Counsel Deputy
Engineering Service
SUBJECT: ACCEPT Petition for Annexation of the Spanish Trails subdivision into the Hillcrest Heights
Geologic Hazard Abatement District ("GHAD"), ACCEPT the proposed Hillcrest Heights GHAD
Plan of Control for Spanish Trails dated May 27, 2008, and ADOPT Resolution No. 2008/ fixing
a hearing for July 22, 2008 at 9:30 a.m., to consider the Petition for Annexation and the proposed
Hillcrest Heights GHAD Plan of Control for Spanish Trails, El Sobrante area. (Hillcrest Heights
GHAD Funds) (District I) Project No.: 7756-6X5047.
DATE: June 24, 2008
PAGE: 2
RECOMMENDED ACTION: (continued)
(a) FIX a Public Hearing for July 22, 2008 at 9:30 a.m. in Room 107 of the Board of Supervisors' Chambers,
651 Pine Street, Martinez, California, to consider the proposed annexation of territory into the existing Hillcrest
Heights GHAD and the proposed Hillcrest Heights GHAD Plan of Control for Spanish Trails, and to hear any
written objections thereto;
(b) DIRECT the Public Works Director, or her designee, to mail, by first class mail, a written notice of the
hearing to consider the proposed annexation and proposed Hillcrest Heights GHAD Plan of Control for Spanish
Trails to each owner of real property proposed to be annexed to the Hillcrest Heights GHAD and to each owner
of real property currently located within the GHAD boundaries.
FISCAL IMPACT:
There will be no impact to the County General Fund. Processing costs have been paid by the applicant. The
costs for any GHAD activities that occur within the boundaries of the land proposed to be annexed into the
Hillcrest Heights GHAD will be covered with revenue generated through parcel assessments for the Spanish
Trails Development. The proposed assessment of$1,567.17 for each of the 15 improved lots in the subdivision
will be considered at a subsequent assessment ballot proceeding.
REASONS FOR RECOMMENDATIONS AND BACKGROUND:
Due to the potential for land sliding, the Conditions of Approval for the Spanish Trails Development (DP 03-
3052, SD 02-8687) require the annexation into the existing Hillcrest Heights GHAD, or the creation of a new
independent GHAD.
To satisfy these requirements, the developer of the Spanish Trails subdivision has elected to petition the Board
of Directors of the Hillcrest Heights GHAD ("GHAD Board") to annex the subdivision into that existing
GHAD. The territory to be annexed pursuant to the Petition for Annexation is currently owned by the developer.
The boundaries of the territory to be annexed and the boundaries of the Spanish Trails subdivision are identical
but are not contiguous with the boundaries of the 66 unit Hillcrest Heights Subdivision 7582 that is already part
of the Hillcrest Heights GHAD.
In connection with the proposed annexation, the Hillcrest Heights GHAD Plan of Control for Spanish Trails
dated May 27, 2008, has been prepared. The proposed Hillcrest Heights GHAD Plan of Control for Spanish
Trails describes the work contemplated for the subdivision, including maintenance and monitoring, to address
the potential for land sliding. Funding for the land proposed to be annexed into the Hillcrest Heights GHAD
will be based on an assessment from each improved lot in the subdivision, which funding will be collected and
used in accordance with the Hillcrest Heights GHAD Plan of Control for Spanish Trails. The proposed
assessment of $1,567.17 for each of the 15 improved lots in the subdivision is supported by a detailed
Engineer's Report prepared by a registered professional engineer certified by the State of California, and will be
considered at a subsequent date in accordance with Proposition 218. County staff recommend that approval of
the proposed annexation be conditioned upon subsequent approval of the proposed assessment following an
assessment ballot proceeding. If adopted, the Hillcrest Heights GHAD Plan of Control for Spanish Trails will
SUBJECT: ACCEPT Petition for Annexation of the Spanish Trails subdivision into the Hillcrest Heights
Geologic Hazard Abatement District ("GHAD"), ACCEPT the proposed Hillcrest Heights GHAD
Plan of Control for Spanish Trails dated May 27, 2008, and ADOPT Resolution No. 2008/ fixing
a hearing for July 22, 2008 at 9:30 a.m., to consider the Petition for Annexation and the proposed
Hillcrest Heights GHAD Plan of Control for Spanish Trails, El Sobrante area. (Hillcrest Heights
GHAD Funds) (District I) Project No.: 7756-6X5047.
DATE: June 24, 2008
PAGE: 3
address geologic hazards within the Spanish Trails subdivision. The Hillcrest Heights GHAD Plan of Control
for Spanish Trails will not address geologic hazards within Hillcrest Heights Subdivision 7582.
CONSEQUENCES OF NEGATIVE ACTION:
The Planning Commission required the annexation into the existing Hillcrest Heights GHAD or the creation of
a new independent GHAD as a condition of approval for the Spanish Trails subdivision. The developer has
satisfied all of the remaining Conditions of Approval and has obtained building permits to commence
construction of the project. If the GHAD Board does not proceed with this matter, satisfaction of this condition
will be delayed and possibly may not occur.
NOTICE OF PUBLIC HEARING REGARDING PETITION BY THE
AUSTIN GROUP, LLC FOR ANNEXATION OF TERRITORY TO
THE HILLCREST HEIGHTS GEOLOGIC HAZARD ABATEMENT
DISTRICT AND FOR APPROVAL OF THE HILLCREST HEIGHTS
GHAD PLAN OF CONTROL FOR SPANISH TRAILS
YOU ARE HEREBY NOTIFIED THAT on July 22, 2008 at 9:30 a.m. in the Board of
Supervisors' Chambers located at 651 Pine Street, Martinez, California, the Contra Costa County
Board of Supervisors, acting as the Board of Directors for the Hillcrest Heights Geologic Hazard
Abatement District ("GHAD"), will hold a public hearing on the Petition for Annexation of
Territory to the Hillcrest Heights GHAD by The Austin Group, LLC pursuant to Division 17
(commencing with Section 26500) of the California Public Resources Code.
The purpose of the hearing will be for the GHAD Board to receive and consider all objections to
the proposed annexation and to the proposed Hillcrest Heights GRAD Plan of Control for
Spanish Trails, and to make a determination on whether to approve the annexation and Hillcrest
Heights GHAD Plan of Control for Spanish Trails. The proposed annexation will not change
or otherwise affect the assessment for the properties within the existing boundaries of the
Hillcrest Heights GHAD.
Copies of the Petition for Annexation, and Board Order and Resolution related to the setting of
the hearing are enclosed for your review. Copies of the proposed Hillcrest Heights GHAD Plan
of Control for Spanish Trails are available for review and copying, at a cost not to exceed the
cost of duplication, at the following locations: Contra Costa County, Clerk of the Board, Room
106, 651 Pine Street, Martinez, California; and Contra Costa County, Public Works Department,
255 Glacier Drive, Martinez, California.
Objections to the proposed annexation or to the Hillcrest Heights GHAD Plan of Control for
Spanish Trails may be made by any owner of real property proposed to be annexed into the
Hillcrest Heights GHAD or by any owner of real property within the existing Hillcrest Heights
GHAD boundaries. In order to be considered, objections must be in writing, contain a
description of the owner's land by lot, tract, and map number; contain the signature of the owner,
and be mailed or otherwise delivered to the address set forth below prior to the time set for the
hearing. Objections not received by the close of business on July 21, 2008, should be presented
at the hearing. If the person whose signature appears on the written objection is not shown on
the assessment roll last equalized by the county as the owner of the subject real property, the
written objection must be accompanied by evidence sufficient to indicate that such person is the
owner of such property.
Contact for information or written objections: Hillary Heard, Contra Costa County, Public Works
Department, 255 Glacier Drive, Martinez, California.
THE BOARD OF SUPERVISORS OF
CONTRA COSTA COUNTY, CALIFORNIA
AS THE GOVERNING BOARD OF DIRECTORS FOR THE
HILLCREST HEIGHTS GEOLOGIC HAZARD ABATEMENT DISTRICT
Adopted this Resolution on June 24, 2008 by the following vote:
AYES: SUPERVISORS GIOIA, UILKEMA, PIEPHO, BONILLA AND GLOVER
NOES: NONE
ABSENT: NONE
ABSTAIN: NONE
RESOLUTION NO. 2008/_q-4q
SUBJECT: ADOPT Resolution No. 2008/yyg fixing a hearing for July 22, 2008 at 9:30 a.m.,
to consider the Petition for Annexation of Territory to the Hillcrest Heights
Geologic Hazard Abatement District ("GHAD") and the proposed Hillcrest
Heights GHAD Plan of Control for Spanish Trails, El Sobrante area. (Hillcrest
Heights GHAD Funds) (District 1) Project No.: 7756-6X5047.
RECITALS:
A. On July 23, 1996, the Contra Costa County Board of Supervisors adopted Resolution No.
96/329, approving and ordering the formation of the Hillcrest Heights Subdivision 7582
Geologic Hazard Abatement District("Hillcrest Heights GHAD") and appointing itself to
act as the Board of Directors of the GHAD ("GHAD Board"). This formation was
described in the petition dated May 8, 1996 and in the GHAD Plan of Control dated May
8, 1996.
B. On June 24, 2008, the GHAD Board was presented with and reviewed the Petition for
Annexation of Territory to the Hillcrest Heights Geologic Hazard Abatement District
("GHAD Petition"), which is attached hereto as Exhibit 1. The territory proposed to be
annexed into the GHAD is described in the legal description set forth in Attachment A of
Exhibit 1 and identified in the boundary map as shown in Attachment B of Exhibit 1.
C. On June 24, 2008, the GHAD Board was presented with and reviewed the proposed
Hillcrest Heights GRAD Plan of Control for Spanish Trails dated May 27, 2008, which is
contained in Attachment C of Exhibit 1 and is on file at the office of the Clerk of the
Board and the Public Works Department. The proposed Hillcrest Heights GHAD Plan of
Control for Spanish Trails describes potential geologic hazards within the territory to be
annexed and addresses the prevention,mitigation, abatement and control of such hazards.
CERTI IED .
I certify that this is a full,true and correct or nal document which
is on file in my office. ATTEST, JOHN MLLEN, C�rerk of the Board of
Supervisors and county Administrator by Deputy Clerk. �/ ��Q
SUBJECT: ADOPT Resolution No. 2008/Wfixing a hearing for July 22, 2008 at 9:30 a.m.,
to consider the Petition for Annexation of Territory to the Hillcrest Heights
Geologic Hazard Abatement District("GHAD") and the proposed Hillcrest
Heights GHAD Plan of Control for Spanish Trails, El Sobrante area. (Hillcrest
Heights GHAD Funds) (District I) Project No.: 7756-6X5047.
DATE: June 24, 2008
PAGE: 2 of 2
THE BOARD OF SUPERVISORS OF CONTRA COSTA COUNTY CALIFORNIA
ACTING AS THE BOARD OF DIRECTORS FOR THE HILLCREST HEIGHTS
GEOLOGIC HAZARD ABATEMENT DISTRICT DECLARES, RESOLVES, FINDS
AND ORDERS THAT:
1. This resolution is made pursuant to the provisions of Division 17 of the Public Resources
Code with particular reference to Chapter 1 (commencing with section 26500), Article 3
(commencing with Section 26550) and Article 4 (commencing with Section 26561).
2. The Petition for Annexation of Territory to the Hillcrest Heights GHAD is substantially
in the form described in Sections 26552 of the Public Resources Code; and the proposed
Hillcrest Heights GHAD Plan of Control for Spanish Trails is substantially in the form
described in Section 26509 of the Public Resources Code.
3. The proposed annexation is exempt from the provisions of the California Environmental
Quality Act (Pub. Res. Code §§ 21000 et seq.) in accordance with Public Resources Code
sections 21080(b)(4) and 26559.
4. The GHAD Board has been presented with and reviewed the proposed Hillcrest Heights
GHAD Plan of Control for Spanish Trails and has determined that the health, safety and
welfare of the public requires annexation of the proposed territory to the Hillcrest Heights
GHAD.
5. A public hearing on the filed petition, above determination, and proposed annexation will
be held on July 22, 2008 at 9:30 a.m. in the Chambers of the GHAD Board, 651 Pine
Street, Martinez.
6. The Public Works Director, or designee, shall mail, by first class mail, a written notice of
the hearing on the Petition for Annexation, along with a copy of the Petition and this
resolution, to all owners of real property within the proposed district pursuant to Public
Resources Code Sections 26561, 26562 and 26563 to consider the proposed annexation
and the proposed Hillcrest Heights GHAD Plan of Control for Spanish Trails.
7. This Resolution shall become effective immediately upon its passage and adoption.
EXHIBIT 1
PETITION FOR ANNEXATION OF TERRITORY TO THE HILLCREST HEIGHTS
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 Hillcrest Heights Geologic Hazard Abatement District ("GHAD")
(Clerk of the Board of Supervisors)
The undersigned owner of land within the boundaries of the territory proposed to be annexed to
the GHAD hereby requests that the Board of Directors of the GHAD ("GHAD Board") initiate
proceedings to annex the territory described in Attachment A (Legal Description) and shown on
Attachment B (Boundary Map), attached hereto, to the GHAD pursuant to Article 3
(commencing with Public Resources Code § 26550) and Article 4 (commencing with Public
Resources Code § 26561) of Chapter 2 of Division 17 of the Public Resources Code (§ 26500 et
seq.). Said owner is the owner of all the territory proposed to be annexed.
(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 an
owner of land within the territory proposed to be annexed to the GHAD.
(c) Opposite the signature of the 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. A Legal Description of the territory proposed to be annexed to the GHAD
(Attachment A);
2. A Boundary Map of the boundaries of the territory proposed to be annexed to the
GHAD (Attachment B); and
3. The proposed Hillcrest Heights GHAD Plan of Control for Spanish Trails, dated
May 27, 2008, prepared be ineering geologist certified pursuant to Section 7822 of the
California Business and Pro7fe
.1
s Code, which describes in detail geologic hazards, their
location and the areas affect th b , and a plan for their prevention, mitigation, abatement and
control thereof(Attachment
_ APN #s
5 Z3 433-160-068 thru 085
Date WilliaF.ScIder,Jr.Managing Member Description of Property
The A stinGrp LLC
As M ager opanish Trails Associates LLC
Attachments:
A—Legal Description
B—Boundary Map MAY 21
C—Hillcrest Heights GHAD Plan of Control for Spanish Trails
MMB:10480-001:746922.2
ATTACHMENT A
Legal Description
MMB:10480-001:746922.2
Spanish Trail Annexation to GHAD-Geologic Hazard Abatement District
SD 8687
EXHIBIT A
The land referred to, is situated in the County of Contra Costa, State of California,and is
described as follows:
All that parcel of land described in the deed to Spanish Trail LLC,recorded November
21, 1995, document no 95-202230, Contra Costa County Official Records described as
follows.
Beginning at the Southwestern corner of said Spanish Trail LLC parcel said corner also
being on the eastern right of way line of Valley View Road. Thence, from said point of
beginning along the exterior boundary of said Spanish Trail LLC parcel as follow:
South 65°43' 42"East 202.94 ft; South 33° 13' 42"East 257.14 ft; South 44° 50'
44"West 13.05 ft; South 45° 56' 40"East 100.94 ft; South 34°49' 15"West 67.70 ft;
North 86° 13' 34"East 96.74 ft; South 380 28' 45"East 118.14 ft; South 64°28'
45"East 15.19 ft; North 420 0 P 15"East 516.12 ft; North 24°24'45"West 400.00 ft;
South 58° 16' 18"West 502.74 ft; North 42° 59' 10"West 185.83 ft;North 600 53'
21"West 195.82 ft, to said Eastern right of way line of Valley View Road;thence along
said right of way line of Valley View Road along a curve to the right having a center that
bears South 77°04' 57"West a distance of 565.00 ft., through a central angle of 19° 12'
58"an arc distance of 189.49 ft to the point of beginning.
Containing 7.12 acres more or less.
A.P.N.No 433-160-022, 030&059
ATTACHMENT B
Boundary Map
MMB:10480-001:746922.2
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ATTACHMENT C
Hillcrest Heights GHAD Plan of Control for Spanish Trails
MMB:10480-001:746922.2
ENGINEERS REPORT
for
ANNEXATION OF THE SPANISH TRAILS
SUBDIVISION
TO THE HILLCREST HEIGHTS
GEOLOGIC HAZARD
ABATEMENT DISTRICT
EL SOBRANTE,
CONTRA COSTA COUNTY,
CALIFORNIA
By
TERRASEARCH, inc.
Project No. 6034.G3
27 May 2008
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
TABLE OF CONTENTS
Palle No.
CERTIFICATIONOF FILING.......................................................................................................3
I. INTRODUCTION ...........................................................................................................5
II. BACKGROUND .............................................................................................................5
III. GEOLOGIC HAZARD ABATEMENT DISTRICT BOUNDARIES ............................5
IV. SERVICE LEVELS.........................................................................................................6
V. DESCRIPTION OF THE GHAD IMPROVEMENTS....................................................6
VI. ASSESSMENT METHOD..............................................................................................7
VII. ASSESSMENT LIMIT- BUDGET................................................................................8
EXHIBITA....................................................................................................................................11
EXHIBITB....................................................................................................................................14
EXHIBITC....................................................................................................................................16
TERRASEARCH,inc. Page 2 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
ENGINEER'S REPORT
ANNEXATION OF THE SPANISH TRAILS SUBDIVISION
TO THE HILLCREST HEIGHTS
GEOLOGIC HAZARD ABATEMENT DISTRICT (GHAD)
(California Public Resources Code sections 26500 et seq.)
CERTIFICATION OF FILING
Terrasearch, inc. makes this engineer's report for the Spanish Trails subdivision, as directed by
the Board of Supervisors, acting as the Board of Directors of the Hillcrest Heights GRAD. The
GHAD is intended to provide geologic hazard improvements for the Spanish Trails subdivision
and to levy and collect assessments sufficient to pay for those improvements.
The improvements to the Spanish Trails subdivision that are the subject of this report are defined
as any activity necessary or incidental in the prevention, mitigation, abatement, or control of a
geologic hazard, construction, maintenance, repair, or operation of any improvement; or the
issuance and servicing of bonds issued to finance any of the forgoing. Pub. Res. Code section
26505.
This report consists of seven parts, as follows:
I. INTRODUCTION
II. BACKGROUND
III. GEOLOGIC HAZARD ABATEMENT DISTRICT BOUNDARIES
IV. SERVICE LEVELS
V. DESCRIPTION OF GHAD IMPROVEMENTS
VI. ASSESSMENT METHOD
VII. ASSESSMENT LIMIT—BUDGET PROJECTION
TERRASEARCH,inc. Page 3 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
The undersigned respectfully submits the enclosed Engineer's Report.
Date: By: Terrasearch, inc.
, GE
I HEREBY CERTIFY that the enclosed Engineer's Report was filed on the day of
Clerk of the Board
Hillcrest Heights Geologic Hazard Abatement District
El Sobrante, Contra Costa County, California
I HEREBY CERTIFY that the enclosed Engineer's Report was approved and confirmed by the
GHAD Board on the day of
President of the Board
Hillcrest Heights Geologic Hazard Abatement District
El Sobrante, Contra Costa County, California
APPROVED
TERRASEARCH,inc. Page 4 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
ENGINEER'S REPORT
for
ANNEXATION of the SPANISH TRAILS SUBDIVISION
to the
HILLCREST HEIGHTS
GEOLOGIC HAZARD ABATEMENT DISTRICT
for the
ESTABLISHMENT OF AN ASSESSMENT LIMIT
I. INTRODUCTION
The Hillcrest Heights Geologic Hazard Abatement District ("GHAD or "District") was formed
under the authority of the California Public Resources Code,Division 17, Section 26500 et seq.
II. BACKGROUND
The County of Contra Costa Board of Supervisors adopted Resolution No. 96/329 on July 23,
1996, approving the formation of the Hillcrest Heights Subdivision 7582 Geologic Hazard
Abatement District ("Hillcrest Heights GHAD"). The Board of Supervisors, acting as the Board
of Directors of the Hillcrest Heights GHAD, adopted Resolution No. 2008/ on ,
2008, approving the annexation of the Spanish Trails subdivision to the Hillcrest Heights
GHAD. Under Public Resources Code section 26581, the Board of Supervisors then adopted
Resolution No. 2008/ on , 2008, approving the annexation of the Spanish Trails
subdivision to the Hillcrest Heights GHAD.
III. GEOLOGIC HAZARD ABATEMENT DISTRICT BOUNDARIES
The boundaries for the Spanish Trails subdivision are shown in the diagram attached hereto as
Exhibit A.
TERRASEARCH,inc. Page 5 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
IV. SERVICE LEVELS
The Hillcrest Heights GHAD provides for activity that is necessary or incidental to the
prevention, mitigation, abatement, or control of geologic hazards including construction,
maintenance, repair, or operation of any improvement, and the issuance and servicing of bonds
issued to finance any of the foregoing.
The Hillcrest Heights GHAD provides for the administration and review of facilities within
budgeted limits and including the following services:
1. Oversight of GHAD activities.
2. In conjunction with the County Assessor's Office, setting the annual levy of
assessments on the property tax rolls.
3. Retention of geotechnical professionals to perform the monitoring duties described in
the GHAD Plan Control for Spanish Trails.
4. Performance of GHAD maintenance activities in accordance with the Hillcrest
Heights GHAD Plan of Control for Spanish Trails. These maintenance activities
include:
• Lined surface drainage ditches.
• Storm drain inlet, outfalls and pipelines within common areas.
• Subdrains.
• Retaining wall and appurtenant drainage facility maintenance.
• Debris wall maintenance.
• Erosion management.
5. Slope reconstruction
6. Preparation of annual GHAD budgets.
V. DESCRIPTION OF THE GRAD IMPROVEMENTS
The GHAD improvements are described in the Hillcrest Heights GHAD Plan of Control for
Spanish Trails, dated 27 May 2008. In general, improvements include drainage systems
(including concrete v-ditches in open space, open-space storm drain inlets and outlets and
TERRASEARCH,ine- Page 6 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
subdrains), debris wall, retaining walls with appurtenant drainage systems, natural slopes and
reconstructed slopes and any improvements constructed by the homeowner after the builder has
constructed a house on the lot, that are accepted by the GHAD.
VI. ASSESSMENT METHOD
The improvements referenced in Section V are distributed within the boundaries of the Spanish
Trails subdivision. The District Engineer hereby finds that the properties within the Spanish
Trails subdivision receive approximately equal special benefit from the work and improvements
of the Hillcrest Heights GHAD. Maintenance and protection of these improvements provide a
special benefit to all of the real property within the subdivision. As a result, the assessment is
distributed equally among all of the properties annexed to the Hillcrest Heights GHAD.
The total number of residential units within the Spanish Trails subdivision is divided into the
annual GHAD budget to develop the annual assessment amount. A financial analysis was
performed to provide a framework for an operating budget for the on-going abatement,
mitigation, prevention and control of geologic hazards within the Spanish Trails subdivision. In
preparation of the budget, several factors were considered including:
• Site geology.
• Proposed remedial grading.
• Proximity of geologic hazards to proposed residences.
• Site access considerations.
• Elements requiring routine maintenance including:
1. Surface drainage facilities
2. Graded and natural slopes
3. Storm drain inlets, outfalls and pipelines within common areas
4. Retaining wall and appurtenant drainage facility maintenance
5. Debris wall maintenance
6. Erosion management
TERRASEARCH,inc. Page 7 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
VII. ASSESSMENT LIMIT-BUDGET
Upon annexation of the Spanish Trails subdivision to the Hillcrest Heights GHAD, the District
will be funded by property tax assessments levied upon each lot within the boundaries of the
subdivision. The assessment shall be levied on each individual parcel.
Grading and construction of all improvements has been completed. The first building permit
was issued in July 2007. It is our understanding that the developer will pay $100,000 once the
GHAD improvements have been accepted or 3 years after the assessment has been confirmed,
whichever happens first.
A summary budget was prepared for the purpose of estimating initial assessment levels and is
attached as Exhibit B. In order to establish a reasonable reserve in the early years following
formation of the GHAD, there will be an initial deferral of GHAD expenses as described in the
Plan of Control.
Administrative Costs
The possible repair and maintenance budget costs for the Hillcrest Heights Subdivision 7582 are
unique to that subdivision and were not considered in our review. However, the administrative
costs for the Hillcrest Heights GHAD were considered relevant and are used for this budget.
Since the Spanish Trails subdivision will be annexed into the existing Hillcrest Heights GHAD,
the administration is in place and there will be some additional administration associated with
the Spanish Trails subdivision. It is anticipated that the additional administration costs
associated with the Spanish Trails subdivision will be lower than those currently in place for the
Hillcrest Heights Subdivision 7582. We have applied an additional administrative cost of 30%
more than the current yearly budget, as set forth below:
General Manager $5,000.00
County Public Works Personnel $1,500.00
Legal &Accounting $ 500.00
TERRASEARCH,inc Page 8 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
GHAD Association Membership $7.50 (existing membership)
TOTAL YEARLY ADMINISTRATION BUDGET $7,007.50
Monitoring and Maintenance Costs
Based on the frequency of monitoring outlined in the Hillcrest Heights GHAD Plan of Control
for Spanish Trails, the cost for administrating, performing the monitoring and minor cleaning
and/or grouting and preparation of a report for one year without any major repairs is estimated to
be $8,700 per year and is itemized as follows:
1. Coordination $ 500
2. Average four site visits per year(4 visits @ 4 hrs/visit @ $160/hr) $ 2,560
3. Contractor(most likely required for small repair and cleaning items
At most one time per year—estimate $ 4,000
4. Follow up observation of repair/cleaning work
1 visit @ 4 hours @ $160/hr $ 640
5. Reporting 1,000
TOTAL YEARLY MONITORING& MAINTENANCE BUDGET $ 8,700
Maior Repair(s) Costs
Major repair items will include small, moderate and large scale soil slumps/slides, erosion,
blockage of surface and subsurface drains, damage to surface and subsurface drains and
replacement of debris fences during an unusually high rainfall period or earthquake event. The
occurrence of such events is considered to be rare, and a precise estimate cannot be made at this
time. The additional cost with such repairs could range from $8,000 to $100,000 depending on
the magnitude of the event(s), extent of damage and access. The following estimates are based
on our experience with similar size repairs that have been performed recently in the Bay Area. It
may be advisable to set up an initial fund account or increase the amount of yearly funds as a
contingency to cover any future eventualities.
TERRASEARCH,inc. Page 9 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
However, for estimating purposes, it is hypothetically assumed that one small slump will occur
every 5 years, a moderate slide (up to 50 feet by 30 feet in plan area) will occur every 10 years
and one large scale slide (at least 100 feet by 100 feet in plan area) will occur in 50 years. Once
a large scale slide is repaired the likelihood of future instabilities would decrease as a large area
of the slope would have been repaired. The total estimated cost over 50 years is summarized as
follows:
1. Repair of v-ditches and other drainage facilities
(Once every two years)25 events @ $ 2,000 $ 50,000
2. Repair of Debris Fence 6 events @ $10,000 $ 60,000
3. Small scale slumps 10 events @ $ 8,000 $ 80,000
4. Moderate scale slides 5 events @ $40,000 $ 200,000
5. Large scale slide 1 event @ $100,000 $ 100,000
TOTAL ESTIMATE $490,000
Summary of Costs
The above cost estimates are for 2008 dollars and an appropriate inflation rate of approximately
three percent (3%) should be applied. Based on 2008 dollars, the expected total cost over the
next 50 years including total administrative costs plus total yearly monitoring and maintenance
costs plus the total of major repairs, is estimated to be $1,275,375 (50 years x $7007.50 + 50
years x $8,700 + $490,000). Deducting the $100,000 initially paid into the reserve, the
remaining cost to be assessed is $1,175,375 over 50 years. This is equivalent to $23,505.50 per
year for all 15 lots and equates to an assessment of$1,567.17 per lot per year. Accordingly, the
District Engineer recommends an annual assessment limit of$1,567.17 per residential unit to be
levied upon the completion of the annexation process. This limit will escalate annually based on
San Francisco-Oakland San Jose Consumer Price Index. Please note these estimated expenses
are only for preparing assessment levies and may not represent actual costs of actual specific
hazard occurrences or maintenance.
TERRASEARCH,inc. Page 10 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
EXHIBIT A
GHAD Boundary
Plat and Legal Description
TERRASEARCH,inc. Page 11 of 17
Spanish Trail Annexation to GHAD-Geologic Hazard Abatement District
SD 8687
EXHIBIT A
The land referred to, is situated in the County of Contra Costa, State of California,and is
described as follows:
All that parcel of land described in the deed to Spanish Trail LLC,recorded November
21, 1995, document no 95-202230,Contra Costa County Official Records described as
follows.
Beginning at the Southwestern corner of said Spanish Trail LLC parcel said corner also
being on the eastern right of way line of Valley View Road. Thence, from said point of
beginning along the exterior boundary of said Spanish Trail LLC parcel as follow:
South 650 43' 42"East 202.94 ft; South 33° 13' 42"East 257.14 ft; South 44° 50'
44"West 13.05 ft; South 45° 56' 40"East 100.94 ft; South 34°49' 15"West 67.70 ft;
North 86° 13' 34"East 96.74 ft; South 38°28' 45"East 118.14 ft; South 640 28'
45"East 15.19 ft; North 421 01' 15"East 516.12 ft; North 24° 24'45"West 400.00 ft;
South 58° 16' 18"West 502.74 ft; North 42° 59' 10"West 185.83 ft;North 600 53'
21"West 195.82 ft, to said Eastern right of way line of Valley View Road; thence along
said right of way line of Valley View Road along a curve to the right having a center that
bears South 77°04' 57"West a distance of 565.00 ft.,through a central angle of 19° 12'
58"an arc distance of 189.49 ft to the point of beginning.
Containing 7.12 acres more or less.
A.P.N.No 433-160-022, 030&059
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Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
EXHIBIT B
Summary of Budget Costs
TERRASEARCH,inc Page 14 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
EXHIBIT B
ANNEXATION OF SPANISH TRAILS DEVELOPMENT
TO THE HILLCREST HEIGHTS GHAD
BUDGET MAY 2008
Assumptions
Total No. of Units 15
Total Budget for Major Repairs over 50 Years $490,000.00
Reserve Paid by Developer $100,000.00
Remaining Budget for Major Repairs over 50 Years $390,000.00
Estimated Annual Expenses
Average Yearly Budget for Repairs($390,000/50 yrs) $7,800.00
Yearly Estimate for Administration $7,007.50
Yearly Estimate for Monitoring& Minor Maintenance $8,700.00
$23,507.50
ANNUAL ASSESSMENT PER UNIT $1,567.17
TERRASEARCH,inc. Page 15 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
EXHIBIT C
Notice of Assessment
TERRASEARCH,inc. Page 16 of 17
Project No.6034.G3 Engineers Report/Spanish Trails 27 May 2008
EXHIBIT C
NOTICE OF ASSESSEMENT
Pursuant to the requirements of , the undersigned Clerk of the
Hillcrest Heights Geologic Hazard Abatement District, State of California, hereby gives notice
that a diagram and assessment were recorded in the office of the County Recorder of Contra
Costa County as provided for in said section, more particularly described on that certain
assessment diagram filed in accordance with the section in Book of Maps of
Assessments and Community Facilities Districts at Page in the Office of the County
Recorder of Contra Costa County and relating to the following described real property:
The subdivision generally known as Spanish Trails, is to be annexed into the Hillcrest Heights
Geologic Hazard Abatement District. This subdivision is described Lot_in Block_, as said lot
and block are shown on the Map of Tract , El Sobrante, Contra Costa County, California,
filed Contra Costa County Recorders.
Notice is further given that upon the recording of this notice in the Office of the County
Recorder, the several assessments assessed on the lots, pieces and parcels shown on said filed
assessment diagram shall become a lien upon the lots or portions of lots assessed respectively.
Reference is made to the assessment diagram and assessment roll recorded in the office of the
County Recorder of Contra Costa County.
Dated:
ATTEST:
Owner Notification:
TERRASEARCH,ina Page 17 of 17
HILLCREST HEIGHTS GEOLOGIC HAZARD
ABATEMENT DISTRICT
PLAN OF CONTROL
for
SPANISH TRAILS
5315 Valley View Road
El Sobrante, Contra Costa County
California
for
The Austin Group,LLC
By
TERRASEARCH, inc.
Project No. 6034.G3
27 May 2008
Project No. 6034.G3
27 May, 2008
Mr. William Schrader
The Austin Group LLC
164 Oak Road
Alamo, California 94507
Subject: Spanish Trails
APN 433-160-022; -030 & -059
5315 Valley View Road
El Sobrante, California
HILLCREST HEIGHTS GEOLOGIC HAZARD ABATEMENT
DISTRICT PLAN OF CONTROL for SPANISH TRAILS
Dear Mr. Schrader:
In accordance with your authorization, TERRASEARCH, inc. has prepared a
Geologic Hazard Abatement District ("GHAD") Plan of Control for the above
referenced site. The Spanish Trails subdivision will be annexed into the existing
Hillcrest Heights GHAD.
This document presents the results of our plan of control and associated costs for
maintenance of open space areas that contain potential geologic hazards.
Should you have any questions relating to the contents of this report or require
additional information,please contact our office at your convenience.
Very truly yours,
TERRASEARCH, inc.
Simon Makdessi, P.E.
Senior Engineer
Robert Campbell, C.E.G.
Senior Geologist
Copies: 6 to Austin Group
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
TABLE OF CONTENTS
Pate No.
LETTEROF TRANSMITTAL....................................................................................................................2
1.0 INTRODUCTION...........................................................................................................................4
1.1 Proposed Development.......................................................................................................5
1.2 Site Description...................................................................................................................5
1.3 Description of Mitigated Conditions ..................................................................................6
1.4 Existing Hillcrest Heights Plan of Control.........................................................................7
2.0. GEOLOGIC CONDITIONS............................................................................................................8
2.1 General Geologic Setting....................................................................................................8
2.2 Site Specific Geology.........................................................................................................8
2.3 Seismic Setting...................................................................................................................9
3.0 DESCRIPTION OF GEOLOGIC HAZARD................................................................................ 10
3.1 Landsliding....................................................................................................................... 10
3.2 Erosion.............................................................................................................................. 11
3.3 Earthquake Shaking.......................................................................................................... 11
3.4 Settlement of Engineered Fill...........................................................................................12
3.5 Expansive Clay Soil Movement........................................................................................ 13
3.6 Flooding............................................................................................................................ 13
4.0 CONTROL OF HAZARDS........................................................................................................... 14
5.0 MONITORING AND MAINTENANCE PROCEDURES........................................................... 16
6.0 FREQUENCY OF MONITORING............................................................................................... 17
7.0 MITIGATION OF HAZARD........................................................................................................ 18
8.0 ACCEPTANCE
8.1 Activation of Assessment................................................................................................. 19
8.2 Responsibility for GHAD Activities................................................................................. 19
8.3 Process for Transferring Responsibility for GHAD Activities......................................... 19
9.0 PRIORITY OF GHAD EXPENDITURES....................................................................................21
REFERENCES ..........................................................................................................................................22
FIGURES1 THROUGH 4.........................................................................................................................23
EXHIBIT A—GHAD Boundary(Plat and Legal Description)..................................................................27
EXHIBIT B—(Hillcrest Heights Plan of Control prepared by Geolex).............................................29
TERRASEARCH,inc. Page 3 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
GEOLOGIC HAZARD ABATEMENT DISTRICT
PLAN OF CONTROL
1.0 INTRODUCTION AND LEGAL AUTHORITY
As required by the planning commission for the County of Contra Costa, the Spanish Trails
subdivision will be annexed into the existing Hillcrest Heights Subdivision 7582 Geologic
Hazard Abatement District ("Hillcrest Heights GHAD") under the authority of California Public
Resources Code Section 26500 et seq.
Section 26553 of the Public Resources Code requires a Plan of Control, prepared by a state
certified engineering geologist, as a prerequisite to formation of or annexation into a GHAD.
Under Public Resources Code 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 the area affected by them. It also
provides a plan for the prevention, mitigation, abatement, or control thereof. 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."
The Spanish Trails Conditions of Approval (Final Development Plan #DP03-3052, Condition
16) relating to GHAD annexation are as follows:
I. Prior to the issuance of a building permit for a single family residence, the applicant
shall provide as a printed note on each set of building permit plans the statement that
construction inspections may only occur up to but not including the inspection Phase
#110 (insulation-framing). This Hold on further inspections shall remain in effect
until such time that the area of Subdivision 8687 is annexed to the existing Hillcrest
Heights Geological Hazard Abatement District (GHAD), or the applicant has created
a new independent GHAD acceptable to the Board of Supervisors. Prior to the release
of the Hold on further inspections, the applicant shall provide written evidence from
the Public Works Department that the subject property is within a GHAD. The
GHAD conditions and responsibilities shall be included in the recorded documents
TERRASEARCH,inc. Page 4 of 31
Project No.6034.G3 Hillcrest Heights GRAD Plan of Control for Spanish Trails 27 May 2008
for the subdivision and shall run with the land. Evidence of such recording shall be
provided to the Zoning Administrator prior to final inspection of any house in
Subdivision 8687.
J. An easement shall be granted to the Geological Hazard Abatement District (GHAD)
along the top of the bank within the rear yards of Lots 10-15, acceptable to the Public
Works Department, and limited to the purpose of providing access for inspection,
maintenance and repair required by the specified activities of the GHAD.
K. A recorded deed disclosure shall provide notice to all the owners of Lots 1-15 of the
existence of the Geologic Hazard Assessment District (GHAD) and its
responsibilities. For Lots 10-15 there shall be an additional recorded notice that any
improvements within the easement granted to the GHAD, required by Condition 16-
J, including landscaping and fences may be removed or damaged by the GHAD
without permission of, or compensation to, the lot owners.
This Plan of Control specifically addresses geologic related issues in planned open space areas
that may potentially affect the public and private improvements of the Spanish Trails
subdivision. The GHAD will collect sufficient revenue to finance the inspection and
maintenance of planned drainage improvements and/or facilities installed to mitigate known
geologic hazards or for the potential future geologic hazards for the useful life of the subdivision.
This will also include the costs of any repairs and/or construction of improvements as needed.
The purpose of this Plan of Control is to describe potential geologic hazards and to provide a plan to
address prevention, mitigation, abatement and control of such hazards, and estimate the associated
costs of those hazards.
1.1 Proposed Development
The proposed Spanish Trails subdivision consists of 15 single-family residential units, an
associated interior street and two emergency vehicle access roads.
1.2 Site Description
The Spanish Trails subdivision site is located in the eastern portion of El Sobrante within the
jurisdiction of the County of Contra Costa. It consists of an irregular shaped parcel
TERRASEARCH,inc. Page 5 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
approximately 7.5 acres in size. The site is accessed by a road off Valley View Drive. The
location of the site is shown on the site vicinity map attached as Figure 1.
Topographically the site is located on the south west facing slopes of a hill feature that slopes
down to San Pablo Creek. The center line of the creek generally forms the southern property
line.
The site is bounded by open space areas to the west, north, and east. The open space area to the
west is owned by E.B.M.U.D., the open space area to the north and north east portion is owned
by PG&E and the open space area bounded to the south east is owned by the City of Richmond.
The eastern portion of the site is located within a topographic bowl. Three swale features
originating offsite from the north and east sides of the site, drain into the topographic bowl. A
large ancient landslide is mapped within the topographic bowl feature. Several smaller landslide
features were present prior to development. Up to 40 feet of undocumented fill was present
along the south western side of the site prior to development. The undocumented fill forms the
northern bank of the creek within the majority of the development area. The geologic site plan
of the site prior to development is attached as Figure 2. The boundary of the land to be annexed
into the GHAD is attached as Exhibit A.
1.3 Description of MitiEated Conditions
In order for development of the subdivision to proceed, mitigation of the site was needed.
Mitigation essentially consisted of removal of all old undocumented fill and replacement with
engineered fill, buttressing of the large ancient landslide, and sub-excavation and reconstruction
of a cut-slope. Some of the engineered fill was reinforced with geogrid. At the time of writing
of this document, the construction of improvements has been completed and house structures are
under construction. The as-built mitigation plan and cross section are attached as Figures 3 and
4,respectively.
In general, some mapped slides will still remain along the creek bank and upslope of the buttress.
New slides may occur upslope of the buttress. The buttress has been designed with a flat run out
TERRASEARCH,inc. Page 6 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
catchment area and debris fence to contain any future upslope slides from impacting the
properties downslope of the buttress. Subdrains have been constructed as part of the remedial
grading and clean outs have been provided. Concrete lined v-ditches are planned throughout the
site to control surface water runoff from affecting the properties and preventing surface flow
over the creek bank.
1.4 Existing Hillcrest Heights Plan of Control
The existing Hillcrest Heights Plan of Control Monitoring and Maintenance Manual, a copy of
which is attached hereto as Exhibit C, was prepared by Geolex in 1996 for a residential
development consisting of 66 single-family residences located on the east side of Hillcrest Road
in El Sobrante. The existing development is located upon a hillside with prior landslides that
have been repaired.
The primary hazard of concern for the Hillcrest Heights GHAD is the potential for land sliding.
Monitoring and maintenance requirements were listed as follows:
I) Surface ditches.
I1) Subsurface drains in landslide repair areas.
111) Subsurface drains behind common retaining walls.
IV) Slope indicators.
V) Debris or impact wall.
TERRASEARCH,inc. Page 7 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
2.0 GEOLOGIC CONDITIONS
2.1 General Geologic Setting
The site of the Spanish Trails subdivision is within the Coast Ranges geomorphic province, a belt
of sedimentary, volcanic, and metamorphic rocks, which extend from southern California to
Oregon. The structural geology of the Coast Ranges is complex and dominated by transpressive
stress (combined transform and compressional) concentrated along faults within the San Andreas
Fault system. On the eastern portion of the San Francisco Bay, bedrock geology consists of
sedimentary and metamorphic rocks ranging from Cretaceous through Quaternary periods (up to
144 million years to present).
The subject site is located in East Bay portion of the San Francisco Bay Area, in the eastern
Richmond Hills, immediately west of San Pablo Dam in El Sobrante. Based on published
materials by Dibblee (1980), the materials underlying the site consist of Pliocene non-marine
sedimentary rocks, including weakly consolidated pebbly conglomerate sandstone, siltstone and
claystone, which strike approximately north 60 degrees west (N60W) and dip northeast at angles
from 10 degrees to 35 degrees from horizontal. In addition, un-engineered fill exists on the
southern portion of the property, in the relatively flat area, immediately north San Pablo Creek.
2.2 Site Specific Geolou
Prior to development, the majority of the northern portion of the site was underlain by a large
ancient landslide up to 60 feet in depth and the southern portion of the site including the creek
banks was underlain by up to 40 feet of undocumented fill.
As a result of the grading mitigation, the majority of the development area is underlain by
engineered fill ranging in thickness from 10 feet to 60 feet overlying bedrock material. The
bedrock material is a weak, highly weathered, fractured, sheared, interbedded claystone, siltstone
and sandstone. The bedrock becomes less weathered, less sheared, and less sheared with depth,
and has a slight increase in strength.
TERRASEARCH,ina Page 8 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
2.3 Seismic Setting
The closest active fault is the Hayward Fault, which is located approximately 2.9-miles (4.7-
kilometers [km]) west of the subject site. The Hayward Fault is considered active according to
the Alquist-Priolo Earthquake Fault Zones Act (AP Zone). The site is not located within an AP
zone, but is located within a Seismic Hazard Zone (DMG, 1997), as the site will undergo strong
seismic shaking. Other faults located within a 50 km radius of the site are shown on Table 1,
based on the EQFAULT computer program by Thomas Blake.
Table 1
Earthquake Fault Zone Data
Hayward Strike-Slip 4.7 7.1
Rogers Creek Strike-Slip 15.4 7.0
Concord-Green Valley Strike-Slip 20 6.9
West Napa Strike-Slip 23 6.5
San Andreas(1906) Strike-Slip 32 7.9
San Andreas(North Coast) Strike-Slip 33 7.6
San Andreas(Peninsula) Strike-Slip 33 7.1
San Gregorio Strike-Slip 35 7.3
Great Valley 6 Blind Thrust 36 6.7
Great Valley 5 Blind Thrust 39 6.5
Great Valley 4 Blind Thrust 43 6.6
Point Reyes Strike-Slip 48 6.8
TERRASEARCH,inc. Page 9 of 31
Project No.6034.G3 Hillcrest Heights GRAD Plan of Control for Spanish Trails 27 May 2008
3.0 GEOLOGIC HAZARDS
The following geologic hazards have been identified and are expected to remain after grading of
the site:
a) Landsliding
b) Erosion
C) Earthquake shaking
d) Settlement of deep Engineered Fill
e) Expansive clay soil movement
Some of the foregoing hazards (earthquake shaking and expansive soil movement) are common
to most or all residential developments within the Bay Area and are typically addressed in the
residence structure design. Expansive soil movement of the on-site soil materials cannot be
prevented. The Hillcrest Heights GHAD will not perform repairs on structures or facilities
within the Spanish Trails subdivision that are affected by ground shaking or expansive clay
movement unless such geologic events directly affect a drainage facility or improvement for
which the Hillcrest Heights GHAD is responsible.
Since the ground around and beneath all improved areas has undergone mitigation, the only areas
of potential hazards exist within the un-repaired portions of the creek bank, the slopes off-site to
the north and east and the on-site portion of the project upslope of the buttress.
3.1 Landslidinlz
Based on the conclusions presented in the Geologic and Geotechnical Update report by
Terrasearch, Inc., dated January 20, 2003, the buttressed ancient landslide has acceptable
stability under static and seismic conditions. However, the slope stability analysis of the native
slopes behind the buttress, have marginal stability even under dry conditions. It is anticipated
that surficial slumps similar to those that have already occurred on the hillside will occur in the
future. These surficial slumps are not expected to create high velocity debris flows due to their
TERRASEARCH,inc. Page 10 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
clayey nature and moderate slope. However, the debris wall planned immediately upslope of the
buttress will provide protection to the residence structures in the event that a slump or slide
reaches the top of the buttress.
The slopes off-site beyond the property line within the City of Richmond property may have the
potential for future sliding. The sliding is expected to be relatively small in nature given the
relatively gentle sloping topography. The grading and mitigation in this area has extended
approximately 50 feet into the property and given the likelihood of only small and shallow
features potentially occurring, such features will not impact the subject site.
The creek banks comprise of undocumented fill. The banks currently have a number of existing
slides and are susceptible to potential future landsliding. The mitigation for the site in this area
consists of a geogrid reinforced fill beneath the lots to protect the lots from any instabilities of
the creek bank.
3.2 Erosion
Risk of erosion is greatest in areas where there exists concentrated storm runoff on natural
slopes, graded slopes, building pads, and un-vegetated cut and/or fill slopes. It is presumed that
all graded slopes within the open space area of the Spanish Trails subdivision will be
hydroseeded prior to the onset of the following year's winter season. Revegetation of private
lots will be the responsibility of the homeowner. Some erosion potentially exists on recently
graded slopes if vegetation growth does not root properly, particularly during the first rainstorm
of the fall or after a fire. Since a creek exists along the southern margins of the site creek bank,
erosion may be a possibility. We understand that an evaluation of creek bank erosion has been
performed by Engeo Incorporated, and indicates that the likelihood of creek bank erosion is low.
3.3 Earthquake Shaking
Ground shaking is a complex phenomena related to velocity, amplitude, and duration of
earthquake vibrations. Damage from ground shaking is caused by the transmission of earthquake
TERRASEARCH,inc. Page 11 of 31
Project No.6034.G3 Hillcrest Heights GRAD Plan of Control for Spanish Trails 27 May 2008
vibrations from the ground to the structure. The most destructive effects of an earthquake are
usually seen where the ground is unstable and structures are poorly designed and constructed.
Maximum accelerations in rock and soil are based on the attenuation relationships formulated by
Sadigh and Chang (1997) and Abrahamson and Silva (1997). FRISKSP computer program by
Blake (2001) was used to calculate site-specific probabilistic peak ground accelerations (PGA)
for the site. FRISKSP is a computer program for the probabilistic estimation of seismic hazard
using three-dimensional faults as earthquake sources.
Using a 10% probability of exceedance within 50 years with maximum-horizontal ground
acceleration was calculated for the site of the Spanish Trails subdivision at 0.72g. This
calculation considered all active earthquake fault zones within a 100-kilometer radius of the site
and a return period of 475 years.
3.4 Settlement of Engineered Fill
All engineered fill placed during grading will experience settlement due to its own weight. The
main impact of settlements will be at the south western part of the site (Lots 10 through 15)where
up to 40 feet of undocumented fill was removed and replaced with engineered fill. Lots 12 through
15 received greater than 15 feet of engineered fill. Due to actual grading conditions for these lots, a
differential fill thickness occurs across the building pads of these lots. The maximum differential
fill thickness is approximately 30 feet, and the anticipated differential fill settlement across the
building footprint is of the order of 2 to 2'/2 inches, of which one inch is anticipated to occur within
the first two years. This level of differential settlement can be designed into the structure and
therefore no monitoring of this hazard is proposed. Total settlement of 40 feet of fill is estimated to
be of the order of 3 inches. It is estimated that some of the settlement will occur during
construction,however, at least 1'/2 to 2 inches of settlement may occur after homeowner occupation
of a lot in this area. The proposed structures will be founded on a slab foundation system which will
adequately tolerate this estimated settlement.
TERRASEARCH,ina Page 12 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
3.5 Expansive Clay Soil Movement
The on-site near surface materials are highly expansive clay materials. Highly expansive clays are
prone to heave and shrink movements with changes in moisture content. Changes in moisture
content may be the result of seasonal influences where little irrigation is present and causing
shrinking of the soil during the summer months and swelling or heaving of the soil during the wet
winter months;planting of certain species of trees near structures that can remove the moisture from
the soil and create shrinking of the soil; variations in irrigation patterns, cycles and frequency; and
areas of poor drainage where water is allowed to pond for extended periods of time. If water is
allowed to pond near foundations, structures or improvements, excessive swell movement will
occur and will cause damage to the structure or improvement. In addition, persistent ponding of
water adjacent to foundations could cause water to seep under the structure into the crawl space and
create conditions for mold growth. It has been recommended that a subdrain system be constructed
around the perimeter of the residence structure to minimize such an occurrence. The structures and
improvements must be designed to consider the effects of expansive soil movement.
3.6 Flooding
Flooding of San Pablo Creek, which is located within the boundaries of the Spanish Trails
subdivision,may occur. However,the northern banks of the creek within the subdivision boundaries
are higher in elevation than the southern banks, which are outside the subdivision boundaries, and
therefore the hazard of flooding is remote for the site and is not considered in this Plan of Control.
TERRASEARCH,inc. Page 13 of 31
Project No.6034.G3 Hillcrest Heights GRAD Plan of Control for Spanish Trails 27 May 2008
4.0 CONTROL OF HAZARDS
The Hillcrest Heights GHAD will be authorized to retain geologic and/or geotechnical
consultants to make periodic inspections within the Spanish Trails subdivision to evaluate the
performance of the natural and graded slopes, the surface drainage and ditches, and subdrains,
and provide recommendations for repair or mitigation measures. The inspections generally
would look for signs of slope failure, accelerated erosion, or drainage blockages, both surface
and subsurface. The property beyond the subdivision boundaries is the responsibility of the
actual property owners.
The Hillcrest Heights GHAD may repair or maintain properly permitted and maintained
improvements or structures on individual lots that are damaged by landsliding and erosion. As
used herein, the term "improvements" means modifications to landscaping, drainage and
structures on the lot including those constructed by the homeowner after the builder has
constructed a house on the lot and that are accepted by the GHAD. Factors that the GHAD
general manager may consider in deciding whether to approve such repairs or maintenance
include, but are not limited to, funding limitations, project priorities, and weather related risks.
The Hillcrest Heights GHAD will not repair or maintain improvements as follows:
• Geologic hazards that commence or occur off-site beyond the GHAD boundary, unless
such hazards damage or pose a significant threat to damage improvements or structures
located within the GHAD boundary.
• Any landslide that occurs on the creek bank, unless it threatens an improvement that is
maintained by the district, such as the v-ditches and drain inlets near the top of the bank.
• Damage to improvements located on individual lots due to improper homeowner
maintenance, including without limitation leaning fences, cracked or moved concrete
flatwork or decks, or any other landscape type improvements.
• Hazards or damage resulting from negligent activities performed by individuals, public
or private entities or government agencies, as long as the hazard is limited to a single lot.
The Hillcrest Heights GHAD is not intended to treat landsliding, adverse erosion, adverse
drainage confined within a single lot boundary. If, however, a hazardous landslide, erosion or
TERRASEARCH,inc. Page 14 of 31
Project No.6034.G3 Hillcrest Heights GRAD Plan of Control for Spanish Trails 27 May 2008
drainage condition encroaches from a lot into the open space areas or crosses adjoining property
lines, or in the judgment of the District threatens more than one property the District should act
to mitigate the damage.
Based on the discussion in Section 3.0, the main geologic hazards that exist and require some
control or mitigation during the life of the project are landsliding and erosion. The potential
occurrence of the erosion and landslide hazards can be minimized by ensuring that adequate
drainage and vegetation cover exists. Drainage will control the flow of water over natural and
filled land, while vegetation will reinforce the surface soil, increase the soil infiltration rate, and
reduce the extent and velocity of surface (overland) flow.
The drainage facilities that will be constructed as part of the development will consist of concrete
lined v-ditches and a subdrain system within the buttress. The ditches prevent overland flow
over the top of slope. The ditches will essentially intercept storm water runoff flows over the
face of the slope such that the velocity of flow is reduced to levels that minimize the potential for
erosion, sedimentation, and development of soil slumps. Some sedimentation is expected to
occur within the ditches and, should the ditches become blocked due to sedimentation, soil
slumping, debris, or vegetation and the accumulation of water cannot discharge to the drain, then
there exists the possibility of concentrated flow over the bench and onto the slope causing
erosion and/or soil slumping. It is therefore important that the concrete lined ditches be
inspected periodically to ensure that they are free of any debris, and that no cracks exist in the
concrete lining that may divert the flow of water away from the discharge point. Approximately
2,000 feet of v-ditches and 500 feet of debris fence are planned. Several drain inlets are also
proposed as part of the drainage facilities. The approximate total length of subdrains constructed
is in the range of 2,000 feet. Several clean outs have been provided. The actual length and
number of these facilities will be provided later after all improvements are complete and a final
as built plan is prepared.
Landsliding above the buttress may potentially occur and a debris bench and fence will provide a
system to prevent any of these landslide features from affecting the residence properties. If large
scale landslides occur, they may damage the fence and create sedimentation on the run out area
at the top of the buttress.
TERRASEARCH,inc. Page 15 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
5.0 MONITORING AND MAINTENANCE PROCEDURES
Monitoring of the hillside slopes, creek banks and drainage system would consist of walking the
length of all benches and concrete lined ditches, walking the areas above and below the slopes,
and observe the condition of the slopes. Access to the entire creek bank may be limited due to
vegetation cover and presence of water in the creek. Observations may be limited to
observations made at certain points along the top of the bank or certain areas within the bank.
The surface of the open space slope areas would be observed in the fall for wide shrinkage
cracks, bare unvegetated areas, any man-made surface grade changes, or significant rodent hole
activity. During the winter season, the slope areas would be observed for tension cracks,
localized bulging or water seeps.
The concrete ditches would be observed for evidence of cracks, heave, or settlement of the ditch
such that water flow direction has been altered. The ditches would be observed for the presence
of any debris or sedimentation. In addition, the uphill lip of the ditch will be checked to ensure
that it is below the ground surface and that water from the slope does not flow underneath the
ditch. The subdrain discharge point will be observed for any flow that is present. If any cracks
larger than hairline are observed, these will be sealed with grout or epoxy and if any debris is
observed in the ditches, the debris will be removed. If subdrain discharge typically occurs and it
is observed during a visit that no discharge is present, then cleaning/flushing of the subdrain will
be performed.
In order to assist in the monitoring and maintenance of facilities, an as-built grading/sub-
drainage plan is attached as Figure 3.
If subdrain discharge points that have historically shown water discharge are absent of discharge
at any time during the monitoring, then videoing of the subdrain must be performed to evaluate if
there is a blockage.
TERRASEARCH,inc. Page 16 of 31
I
Project No.6034.G3 Hillcrest Heights GRAD Plan of Control for Spanish Trails 27 May 2008
6.0 FREQUENCY OF MONITORING
It is recommended that the above monitoring program be initiated in the fall of each year just
prior to the onset of winter. After the initial visit, two visits during the winter are recommended.
An additional visit should be made during or immediately after a major storm event ('/2 inch of
rain in 24 hours). If any problems develop, additional visits will be required. In addition, a site
visit should be made after a major local earthquake event along the Hayward Fault occurs. This
is expected to occur only once or twice during the life of the project.
TERRASEARCH,inc. Page 17 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
7.0 MITIGATION OF HAZARDS
Should erosion or landsliding occur, temporary and permanent mitigation measures may include
the following:
Temporary Mitigation:
a) Covering soil failure and/or erosional surface with plastic sheeting
b) Installation of hydroaugers
C) Sandbagging around affected area
d) Additional inspections to monitor site conditions
e) Revegetation of disturbed area
f) Re-routing any adverse surface drainage
Permanent Mitigation
a) Complete removal and replacement of the failed zone with or without subdrains
b) Partial repair involving a buttress fill with or without subdrains
C) Repair of surface drainage facilities
d) Construction of additional surface or subsurface drainage facilities
Pa e18of31
TERRASEARCH,inc. g
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
8.0 ACCEPTANCE
8.1 Activation of Assessment
Upon annexation of the Spanish Trails subdivision to the Hillcrest Heights GHAD, an annual
assessment shall be promptly authorized on all residential parcels in the subdivision. The
assessment shall be levied on each individual parcel.
8.2 Responsibility for GHAD Activities
Once the annexation process is completed, the developer(party that owns the parcel(s) shown on
the Final Map) shall have the responsibility to perform all the activities of the Hillcrest Heights
GHAD on such property. That responsibility shall become eligible for transfer to the GHAD as
specified in Section 8.2 ("Process for Transferring Responsibility for GHAD Activities"). 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
Board of the GHAD intends that the period between the levying of the GHAD assessment and
the GHAD becoming responsible to perform activities on property within the Final Map will
allow the District to accumulate reserve funds without incurring significant expenses.
8.3 Process for Transferring Responsibility for GHAD Activities
Beginning on the Transfer Eligibility Date for parcel(s), the process for transferring
responsibility for performing GHAD activities on such parcel(s) shall be as follows:
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 GHAD 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 GHAD will have maintenance responsibility have been constructed and
maintained according to the city-approved plans and specifications for the individual
improvements, and that such facilities are operational and in good working order.
TERRASEARCH,inc. Page 19 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
C. Within 15 days of such inspection, the GHAD will send the developer a list("Punch List") of
all of the items that need to be constructed,repaired or otherwise modified in order to comply
with the city-approved plans and specifications.
D. The developer may notify the GHAD when it has completed the items identified on the
Punch List.
E. Within 30 days of receipt of such notice, the GHAD shall verify that all Punch List items have
been completed and notify the developer that the District accepts responsibility for performing
all future GHAD Activities on the parcel(s).
TERRASEARCH,inc. Page 20 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
9.0 PRIORITY OF GHAD EXPENDITURES
Scheduled repair and emergency response expenditures are prioritized by the General Manager
in his or her discretion, based on available funds, the approved operating budget, and the nature
of the hazard and its impact on life and safety. In general, scheduled maintenance must always be
performed as such maintenance can limit or prevent possible hazards from occurring. The
following list of general hazard situations are listed in order of highest priority to lowest,to assist
the General Manager in allocating funds for repair.
• Any hazard that occurs that directly affects or imminently threatens life and safety.
• Any hazard that affects access to the site or access to a residence.
• Any hazard that affects a development drainage improvement (v-ditches, and associated
drains and debris fence).
• Any hazard that affects individual lot improvements such as drainage retaining walls and
fences.
• Any hazard that occurs in the open space areas that will not affect any site or individual
lot improvement or structure.
TERRASEARCH,inc. Page 21 of 31
I
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
REFRENCES
Geoloex(1996), Hillcrest Heights Subdivision 7582, Geologic Hazard Abatement District
(GHAD), Plan of Control Monitoring &Maintenance Manual, Project No. 95117-1,
dated May 8, 1996.
Terrasearch, Inc., (2003), Geologic and Geotechnical Update, Spanish Trails, APN 433-160-022,
-030 and-059, Valley View Road, El Sobrante, California, Project No. 6034.G2,
dated January 20, 2003.
Terrasearch, Inc., (2005), Supplemental Recommendations, Spanish Trails, APN 433-160-022, -
030 and-059, Valley View Road, El Sobrante, California, Project No. 6034.G2,
dated May 27, 2005.
Humann Company Inc., (2005) Improvement Plans, Subdivision 8687, Spanish Trails, Contra
Costa County, June 2005
TERRASEARCH,inc. Page 22 of 31
Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
FIGURE 1 THROUGH 4
Figure 1 - Vicinity Map
Figure 2—Pre-Development Site and Geology Plan
Figure 3 —Progress As-Built Geology Map
Figure 4—Progress As-Built Mitigation Cross Section
TERRASEARCH,inc. Page 23 of 31
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EXHIBIT A
GHAD Boundary
Plat and Legal Description
TERRASEARCH,inc. Page 28 of 31
Spanish Trail Annexation to GHAD-Geologic Hazard Abatement District
SD 8687
EXHIBIT A
The land referred to, is situated in the County of Contra Costa, State of California,and is
described as follows:
All that parcel of land described in the deed to Spanish Trail LLC,recorded November
21, 1995, document no 95-202230, Contra Costa County Official Records described as
follows.
Beginning at the Southwestern corner of said Spanish Trail LLC parcel said comer also
being on the eastern right of way line of Valley View Road. Thence, from said point of
beginning along the exterior boundary of said Spanish Trail LLC parcel as follow:
South 650 43' 42"East 202.94 ft; South 330 13' 42"East 257.14 ft; South 44° 50'
44"West 13.05 ft; South 45° 56' 40"East 100.94 ft; South 34°49' 15"West 67.70 ft;
North 86° 13' 34"East 96.74 ft; South 381 28' 45"East 118.14 ft; South 64°28'
45"East 15.19 ft; North 421 01' 15"East 516.12 ft; North 24°24' 45"West 400.00 ft;
South 58° 16' 18"West 502.74 ft; North 42° 59' 10"West 185.83 ft;North 600 53'
21"West 195.82 ft, to said Eastern right of way line of Valley View Road;thence along
said right of way line of Valley View Road along a curve to the right having a center that
bears South 770 04' 57"West a distance of 565.00 ft.,through a central angle of 19° 12'
58"an arc distance of 189.49 ft to the point of beginning.
Containing 7.12 acres more or less.
A.P.N.No 433-160-022, 030&059
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Project No.6034.G3 Hillcrest Heights GHAD Plan of Control for Spanish Trails 27 May 2008
EXHIBIT B
Hillcrest Heights Plan of Control Monitoring and Maintenance Manual prepared by Geolex
TERRASEARCH,inc. Page 31 of 31
HILLCREST HEIGHTS
SUBDIVISION 7582
GEOLOGIC HAZARD ABATEMENT
DISTRICT (GHAD)
PLAN OF CONTROL
ONS fORING & MAINTENANCE MANUAL
F
E L
8 May 1996 Project No. 95117-1
Eugene Lee
2971 25th Ave.
San Francisco, CA.
94132
Subject: Hillcrest Heights, .Subdivision #7582 GRAD
Dear Mr. Lee:
Enclosed are the documents and. figures necessary for the creation of the Hillcrest Heights
(Subdivision 7582) Geologic Hazard Abatement District (GHA.D). 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, ERR
GEOLEX Inc.
GGG
85
UP.No.2/31
William B. Wigg' n
Certified Engineering Geologist, No. 855 OFCA�IF�Q�
Copies: 4 to Client
GFEE OLEX INC.
W.B. W I G G I N T O N
P.O_ P30X 1149-132 AP-FOS, GALiFO FiN IA 95003 TELEPHONE 510.988.9428 FACSIMILE 408.662.0755
Exhibit C
HILLCREST HEIGHTS
SUBDIVISION 7582
GEOLOGIC HAZARD ABATEMENT
DISTRICT (GRAD)
PLAN OF CONTROL
MONITORING & IfiENANC-EMANUAL
G E L E X
TABLE OF CONTENTS
Hillcrest Heights, Subdivision 7582
GHAD, 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 5
A. Authority and Scope 5
B. Criteria for Inclusion or Exclusion 6
C. Funding 7
D. Description of Geologic Hazards and Repair 9
E. Definitions 9
F. Plan for Prevention, Mitigation, Abat meet, or Control 9
G. Geotechnical Techniques for Mitigation 10
H. Operation and Maintenance Procedures 13
I. Monitoring Frequency 13
J. Annual Report 14
K. Initial Start-up Period
L. Future Modifications of Pian of Control
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. 3 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
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 i & 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.
Inc project ETR 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 (7):
"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
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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 (GRAD)
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
'.i' ditches, permanent storm drainage facilities, the emergency vehicle access road, and certain
retaining structures. A minimum of two subsurface monitoring devices (inclinometers) will be
Itft in place which will require reading to demonstrate a lack of significant ground movement.
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 adveTse ereston damaQP �*' areas
damage
for which it has responsibility.
DESCRIP'T'ION 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 Iandsliding 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
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
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
It is not the purpose of the Geologic Hazard Abatement District to take care of all potential soil
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
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 giver:
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 ETR 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
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 Auld 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 GRAD 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
design.
Personnel retained by Hillcrest Heights GRAD are used to inspect surface drainage facilities,
concrete lined ditches, the inlets, subsurface storm drains, and the sediment detention basin. The
Hillcrest Heights GRAD is not formed to undertake repair ofrthquake 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 GRAD
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 (GLAD) 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 GRAD. 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 CHAD 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 subdrainage under compacted fill or behind retaining
walls that cross more than one lot or property within the established GRAD 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. Fundin
The GHAD District will be funded from the assessment of each lot within the GRAD
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 Umt(lot size up to 1 acre )....$-375 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
D. Description of Geologic Hazards and Repair
The site is on1 a northwest facing slope that contains two swales. Elevations on the property
range from 340feet 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 5A,
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
bedrock of the Pliocene Contra Costa Group (Tcc). This unit
ntconsists chiefly
of a ere exposed
lithified nonmarine claystone, siltstone, sandstone, and pebbleconglomerate.
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.
Li Tie coriecti'v2 ,work solution for the existing landslides by the project geot-.,chnlcal 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.
7
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geotextile overlapped
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.6-Inch rigid, perforated, plastic pipe, placed with
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cleanouts at "high' ends
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AS PER A. KROPP & ASSOCIATES N.T.S.
y
SUBDRAIN DETAIL FIGURE NO,
G E=— O I. f= X SUBDIVISION 7582
IIVCdFtPORAT�p EL SOBRANTE, CALIFORNIA
W_E3_ WIC;C;INTnN ' PDA WrT Mn nc1K7 +. .,.r• _.. ... ...
Subdrainage Svstem
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
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.
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 Drainaee 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 B-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
discharge storm drain facilities that the Hillcrest Heights GHAD is not responsible to maintain.
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
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
on improved lots before homeowner occupancy. This together with the periodic in spection'called
a
32' — 6'
3' min. WS 3' min.
�2• 6' Lip on uphill side
Cb
y \
l .3' min.
6x6x10 Ga. mesh*
NOTE: Use rebar, see 'jl 2' min.'
comment below
C.C. CO. STD. 6-58 DITCH
r �
* Lined surface ditch, slog[ng 5% minimum to suitable discharge facilities.
Lined ditches should be reinforced with reinforcing bars _(not wire mesh)
and have score joints spaced appropriately.
L
t 8 feet minimum
F2�_ minlmum
AM
DRAINAGE TERRACE DETAIL
N.T.S.
B-58 CONCRETE LINED DITCH DETAIL AND DRAINAGE TERRACE FIGURE N0.
C E=_ C> L_ F-': X SUBDIVISION 7582
iNcoR�oRA"r�� EL SOBRANTE, CALIFORNIA `''
{
PIT
11 A
c5"
Ir _ -
S `Xa M t 1. S LO FE QM ALL
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N.T.S.
TYPICAL 'J' CONCRETE LINED DITCH rIGURC NO.
C� i= O L_ EL-- X SUBDIVISION 7582
COF� �®
IF�lF�OF�AT�D EL SOBRAN-M, CALIFORNIA
W.B. WIGGINTON FROJECi N0. g$117 WE 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 renin a professional registered acotarhnicMY ild! "n,Qr,; .Pr °^djor a certified
b"' b"v....... v++p i+ cut r
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 Mitization 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 Pian 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.
t
g. slope correction (i.e. gradient change, biotechnical stabilization, slope'trimming or
contouring).
i
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.
H. Operation and Maintenance Procedures
f
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 GRAD monitoring network.
Retaining Wall Subdrainaae
Some proposed retaining walls cross a number of property lines or are in open space. These
most 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/-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 plus). We should note that flexible, perforated
pipe (flexline), 2000-Pound Ciush, Leachfield, and ASTM F810 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 inhere 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-decree
bends. "Sweep" 90-decree 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 slopin�y surface steeper
than.4:1 behind them. These ditches, which will collect runoff water from the slopes, should be sloped
to.drain•to suitable discliarge.facilities. The top of the walls should extend at least one foot above the
ditch.(one foot offreeboard),
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.
M
f I. Monitoring Frequency
SURFACE(B-581J)DITCHES and solid pipe outfalls....................................Semi-annually
SUBSURFACEDRAINS 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 twb 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 I a
License- Gevtechnieal Engineer should be consulted to deterimaine 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
z 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 Report
An Annual Report shall be preparers 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
4� 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
E._
years.
After 3 years a reserve of $60,000 could be established. The reserve should only be used to
r 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
4 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
CHAD.
14
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N sem`'" ., ! ,. ` �• 4^:R..E!_N_ .r T GEOIAGIC AND SDnS MAY
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Solace:R.I-Tait Acsooa,.
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 Enviommental Impact Report, Hillcrest Heights.
6. Contra Costa County, 3/93, Response to Comments on EIR.
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.
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