HomeMy WebLinkAboutItem 6.1 Schaefer Ranch GHAD
CITY CLERK
File # D[3][h]~-[~J~
AGENDA STATEMENT
CITY COUNCIL MEETING DATE: December 5,2006
SUBJECT:
Public Hearing: Approving the Formation of the Schaefer Ranch
Geologic Hazard Abatement District (GHAD) and Appointing the
City Council as the Board of Directors of the GHAD
Report Prepared by Melissa Morton, Public Works Director
. i" ;
ATTACHMENTS:
1)
Resolution Approving the Formation of the Schaefer Ranch
GHAD and Appointing the Dublin City Council as the Board
of Directors
November 7, 2006, Staff Report (without attachments)
June 21, 2005, Staff Report, Declaring the City of Dublin
Subject to State Law Relating to Geologic Hazard Abatement
Districts
Outline of Powerpoint Presentation
Plan of Control
2)
3)
4)
5)
RECOMMENDATION:
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Adopt the Resolution approving the formation of the Schaefer
Ranch Geologic Hazard Abatement District, and appointing the City
Council as the Board of Directors.
FINANCIAL STATEMENT:
There should be no fiscal impact. Once the Schaefer Ranch GHAD
has been formed, and a funding mechanism has been approved by
the Board of Directors and the affected property owners, the costs
associated with the operation of the Schaefer Ranch GHAD will be
offset by assessments paid by property owners within the District.
DESCRIPTION:
Division 17 of the California Public Resources Code establishes legal standards for geologic hazard
abatement district ("GHAD") formation, GHAD financing and the scope of GHAD authority (9 26500 et
seq.).
COPY TO: Doug Chen, Schaefer Ranch, LLC
Page 1 of2
ITEM NO.
fo.1
G:\DEVELOPISchaefer RanchlGHAD FormationlPublic Hearing StafIReport and Resolutionlagst Schaefer Ranch GHAD Approval.DOC
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V
California Public Resources Code S 26567 provides that after sufficient notice and a hearing at which
the owners of no more than 50 percent of the assessed valuation of the proposed district object to its
formation, a new GHAD may be formed by resolution of the City Council.
The adoption of the resolution approving the formation of the Schaefer Ranch GHAD, and the selection of
the initial Board of Directors are the next steps in the creation of the Schaefer Ranch GHAD.
ANALYSIS:
Pursuant to the Public Resources Code, the City Council adopted a resolution setting a public hearing and
noticing by mail the owners of real property to be included within the Schaefer Ranch GHAD at least
twenty (20) days before the date set for the hearing.
At the public hearing, if the owners of more than 50 percent of the assessed valuation of property within
the territory to be annexed do not object to the formation, at the close of the hearing, the City Council may
decide whether or not to form the Schaefer Ranch GHAD.
If the City Council wishes to approve the formation of the Schaefer Ranch GHAD, the City Council must
adopt a resolution approving the formation of the Schaefer Ranch GHAD and appointing members to act
as the Board of Directors for the Schaefer Ranch GHAD. Under the GHAD law, the City Council may
appoint five (5) real property owners within the District or the City Council itself, to act as the Board of
Directors. In this case, there is only a single property owner, and it is therefore only practical to appoint
the City Council as the Board of Directors.
As described in the Staff Report for the November 7,2006, City Council meeting, the City Council must
in future actions take additional steps to make the Schaefer Ranch GHAD operational. The Board
of Directors must pass a budget and levy an assessment. Levying the assessment requires two steps:
(a) approval of the engineer's report and the initiation of the assessment ballot proceeding, and (b)
following the 45-day notice period required by Proposition 218, a public hearing to tabulate the
assessment ballots and approve or deny the assessment.
RECOMMENDATION:
Staff recommends that the City Council adopt the Resolution approving the formation of the Schaefer
Ranch Geologic Hazard Abatement District, and appointing the City Council as the Board of Directors.
Page 2 of2
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RESOLUTION NO. -06
A RESOLUTION OF THE CITY COUNCIL
OF THE CITY OF DUBLIN
****************************************
RESOLUTION APPROVING THE FORMATION OF THE
SCHAEFER RANCH GEOLOGIC HAZARD ABATEMENT DISTRICT AND
APPOINTING THE DUBLIN CITY COUNCIL AS THE BOARD OF DIRECTORS
WHEREAS, on June 21, 2005, pursuant to the provisions of S 26550 of the Public Resources
Code, this Council adopted Resolution No. 139-05, declaring the Council to be subject to the provision of
Division 17 (Sections 26550 et seq.) of said Code, and forwarded a copy of said Resolution to the State
Controller; and
WHEREAS, pursuant to the provisions of Division 17 of the Public Resources Code, a Petition
("Petition") was filed with the City Clerk, dated November 1, 2006, for the formation of the Schaefer
Ranch Geologic Hazard Abatement District ("GHAD" or "District"); and
WHEREAS, on November 7, 2006, this City adopted Resolution No. 211-06 accepting the
Petition and setting a hearing on the filed Petition on December 5, 2006, at 7:00 pm; and
WHEREAS, notice of the hearing was given pursuant to the provisions of Public Resources Code
S 26561 through 26563; and
WHEREAS, a public hearing before the City Council on the formation of the GHAD was held on
December 5, 2006, at 7:00 pm, pursuant to the requirements of S 26557 of the Public Resources Code;
and
WHEREAS, at the time set for the hearing, no owner of real property within the proposed GHAD
had made a written objection to its formation in accordance with the provision of Public Resources Code
S 26564 through 26566; and
WHEREAS, at the hearing, the owners of more than 50 percent of the assessed valuation of the
GHAD did not object to the formation thereof, and the Board closed the hearing; and
WHEREAS, the formation of the GHAD is exempt from the provisions of the California
Environmental Quality Act (Public Resources Code S 21000 et seq.) in accordance with Public Resources
S 21080(b)(4) and S 26559;
NOW, THEREFORE, BE IT RESOLVED THAT:
Section 1. Pursuant Public Resources Code S 26567, the Council hereby orders the formation of
the GHAD, as described in the Petition.
Section 2. Pursuant to Public Resources Code Section 26567, the Council hereby appoints itself
as the Board of Directors of the Schaefer Ranch Geologic Hazard Abatement District (GHAD Board).
1
6. ) 12/5/[>i(~
ATTACHMENT I.
;?c ed-
Section 3. This resolution shall become effective immediately upon its passage and adoption. The
GHAD shall become operational only after the parcels within the boundaries of the GHAD have been
successfully assessed in accordance with Public Resources Code Section 26650 and Article XIII(D) of the
California Constitution. The GHAD Board intends to adopt separate resolutions to initiate the
establishment and authorization of an assessment on the real property included in the GHAD.
PASSED, APPROVED AND ADOPTED on this 5th day of December, 2006.
AYES:
NOES:
ABSTAIN:
ABSENT:
Mayor
ATTEST:
City Clerk
2
6v <6;;).-
CITY CLERK
File # D~[6][Q-!6O]
AGENDA STATEMENT
CITY COUNCIL MEETING DATE: November 7, 2006
SUBJECT:
Resolution Setting a Public Hearing on the Formation of the
Schaefer Ranch Geologic Hazard Abatement District
Report Prepared by Frank Navarro, Senior Civil Engineer
ATTACHMENTS:
Resolution Setting a Public Hearing on the Formation of the
Schaefer Ranch Geologic Hazard Abatement District, together with:
Exhibit "A" to the Resolution, Petition For Formation (including
Exhibit "A" to the Petition, Boundary Map, Exhibit "B" to the
Petition, Legal Description, and Exhibit "c" to the Petition, Plan of
Control), and Exhibit "B" to the Resolution, Notice of Public
Hearing
r-Adopt the Resolution Setting a Public Hearing on the Formation of
the Schaefer Ranch Geologic Hazard Abatement District.
RECOMMENDATION:
FINANCIAL STATEMENT:
There is no immediate fiscal impact. Once the Schaefer Ranch
Geologic Hazard Abatement District ("Schaefer Ranch GHAD") has
been formed and a funding mechanism has been approved by the
Board of Directors and affected property owners, the costs
associated with the operation of the Schaefer Ranch GHAD will be
offset by assessments paid by property owners within the District.
DESCRIPTION:
Division 17 of the California Public Resources Code establishes legal standards for geologic hazard
abatement district ("GHAD") formation, GHAD financing and the scope of GHAD authority (Section
26500 et seq.).
California Public Resources Code S 26550.5 provides that proceedings for the formation of a new GHAD
may be initiated by a petition signed by owners of at least ten percent (10%) of the real property to be
included within the proposed district.
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COpy TO:
Page lof2
G:\DEVELOP\Schaefer Ranch\GHAD Fonnation\agst Schaefer Ranch GHAD Formation 110706.DOC
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AnACmNT .2...
40 'l:t
The Schaefer Ranch GHAD annexation petition has been executed and submitted to the City Council of
the City of Dublin. The adoption of the resolution setting a public hearing on the formation of the
Schaefer Ranch GHAD is the first step in the formation process.
ANALYSIS:
Under the Public Resources Code, the City Council must adopt a resolution setting a public hearing and
noticing by mail the owners of real property to be included within the Schaefer Ranch GHAD at least
twenty (20) days before the date set for the hearing. Property owners may thereafter object in writing to
the proposed formation of the Schaefer Ranch GHAD.
The City Council of the City of Dublin will hold a public hearing on the proposed formation of the
Schaefer Ranch GHAD on December 5, 2006.' If it appears at the hearing that the owners of more than
50 percent of the assessed valuation of property within the territory to be annexed object to the fonnation,
the proceedings must be abandoned. At the close of the hearing, the City Council will decide whether or
not to form the Schaefer Ranch GHAD.
After the Schaefer Ranch GHAD is formed, the City Council must take additional steps to make the
Schaefer Ranch GHAD operational. Specifically, the City Council must then appoint members to act as
the initial Board of Directors for the Schaefer Ranch GHAD. The Board of Directors must then pass a
budget and levy an assessment. Levying the assessment requires two steps: (a) approval of the engineer's
report and the initiation of the assessment ballot proceeding, and (b) following the 45-day notice period
required by Proposition 218, a public hearing to tabulate the assessment ballots and approve or deny the
assessment.
RECOMMENDATION:
Staff recommends that the City Council adopt the Resolution Setting a Public Hearing on the Formation
of the Schaefer Ranch Geologic Hazard Abatement District.
Page 2 of2
CITY CLERK
File # D[8]~fI5l-r:2J[Q]
50f
"7
AGENDA STATEMENT
CITY COUNCIL MEETING DATE: June 21, 2005
SUBJECT:
Declaring the City of Dublin Subject to State La.w Relating to
Geologic Hazard Abatement Districts
Report Prepared by: Melissa Morton, Public Works Director
ATTACHMENTS:
Resolution declaring that the City of Dublin is subject to the
provisions of California Public Resources Code Division 17 relating
to Geologic Hazard Abatement Districts
RECOMMEiATIOY
1)
Adopt resolution declaring that the City of Dublin is subject
to the provisions of California. Public Resources Code
Division 17 relating to Geologic Hazard Abatement Districts.
Direct Staff to forward the adopted resolution to the State
Controller
2)
. FINANCIAL STATEMENT: None.
< DESCRIPTION: The City Council has participated in discussions with Staff regarding
the possible benefits of forming a Geologic Hazard Abatement Distriot (GHAD)in the City. The purpose
of such a District is to prevent, mitigate, abate and control geologic hazards in areas such as hillsides.
Given recent events where slides have occurred as the result of adverse weather conditions in various hill
areas of southern California, the City Council may wish to oonsider the formation of a GHAD at some
point in the future.
In order to confOm1 with California State Law related to the future formation of a GHAD, it is necessary
for the City to declare itself subject to provisions of the Law by adopting a resolution containing said
declaration. A copy of the adopted resolution must then be fot'W'arded to the State Controller in order to
establish the Cityis ~ligibility to fonn a GHAD. .
Staff recommends that the City Counc.il adopt the resolution declaring that the City of Dublin is subject to
the provisions of California Public Resources Code Division 17 relating to Geologic Hazard Abatement
Districts, and direct Staff to forward the adopted resolution to the State ControUer. .
__w____~~____~.~~-________~__________________.-----~-----------
COPIES TO:
G:\AOENMISC\ag~ GHAD State Laws 062105.doc
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ITEMNO.~
ATTACBHENT 3.
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RESOLUTION NO. -05
A RESOLUTION OF THE CITY COUNCIL
OF THE CITI' OF DUBLIN
***~********~***~*****
DECLARING THAT THE CITY OF DUBLIN IS SUBJECT TO THE PROVISIONS OF
CALIFORNIA PUBLIC RESOURCES CODE DIVISION 17 RELATING TO
GEOLOGIC HAZARD ABATEMENT DISTRICTS
WHEREAS, the City Council has discussed with City staff the useful role that Geologic Hazard
Abatement Districts can in some cases perform in the prevention, mitigation, abatement and control of
geologic hazards; and
WHEREAS, the Geologic Hazard Abatement District Law is only applicable where the City has
adopted a resQlution declaration that the City of Dublin is subject to the Law's provisions and forwarded a
copy of the resolution to the State Controller; and
WHEREAS, the City Council may wish to consider formation of Geologic Hazard Abatement
Districts in the future;
NOW, THEREFORE, BE IT RESOLVED THAT:
Section 1. Pursuant to Public Resources Code section 26550, the City Council of the City of
Dublin does hereby resolve and declare that it is subj ect to the provisions of California Public Resources
Code Division 17, "Geologic Hazard Abatement Districts" as that Division may from time to time be
amended.
Section 2.
A copy of this resolution shall be forwarded to the State Controller.
PASSED, APPROVED, AND ADOPTED this 21st day of June, 2005, by the following vote:
AYES:
NOES:
ABSENT:
ABSTAIN:
Mayor
ATTEST:
City Clerk
O:\AGENMISC\~eliU GHAD Law 062105.DOC
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PLAN OF CONTROL
FOR
SCHAEFER RANCH
GEOLOGIC HAZARD ABATEMENT DISTRICT
(GHAD)
DUBLIN, CALIFORNIA
SUBMITTED
TO
SCHAEFER RANCH, LLC
PREPARED
BY
ENGEOINCORPORATED
PROJECT NO. 4748.1.500.01
NOVEMBER 1, 2006
COPYRIGHT @ 2006 BY ENGEO INCORPORATED. THIS
DOCUMENT MAY NOT BE REPRODUCED IN WHOLE OR IN PART
BY ANY MEANS WHATSOEVER, NOR MAY IT BE QUOTED OR
EXCERPTED WITHOUT THE EXPRESS WRITTEN CONSENT OF
ENGEO INCORPORATED.
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TABLE OF CONTENTS
Page
I. Authority and Scope......................................................................................................... 1
Property Identification...................................................................................................1
II. Background............................................................................................. .......................... 2
Pregrading Site Conditions....................................................... .....................................2
Proposed Development.............................................................................. ....................2
Open Space....................................................................................................................4
GHAD Responsibilities.................................................................................................4
III. Site Geology ........................................................................................................... ............ 6
Geologic Setting.............................................................................................................6
Site Geo logy.. .. .. .. .. ... . .. .. .. . . . .. . . ... . .. . . . .. . .. . . . . .. .. . . . . . .. .. . . . . . . . .. .. . . . .. . . .. .. . . . ....... . .. . . . . ... . ... .... .. . .... 6
IV. Geologic Hazards................................................................................................. ............. 7
Slope Instability............................................................................................................. 7
Erosion and Sedimentation............................................................................................9
Seismically- Induced Ground Shaking........................................................................ ...9
V. Criteria for GHAD Responsibility ................................................................................ 11
Prevention, Mitigation, Abatement and/or Control of Geologic Hazards ...................11
Exceptions.................................................................................................................. ..11
Isolated or Remote Slope Instability......................... ................ ......... ....................... ...11
Single Property........................................................................ .................................... .11
Geologic Hazards Resulting From Negligence of Property Owner.............................12
Vertical Movement or Creep Due to Shrink Swell or Settlement ...............................12
Protected Wildlife Habitat.......................................................................................... .13
Property Not Accepted.............................................................................................. ...13
Damage to GHAD Accepted Property from Landslide Originating on Property not
Accepted by GHAD .................................................................................................... .13
GHAD Funding or Reimbursement for Damaged or Destroyed Structures or Site
Improvements............................................................................................................. .13
VI. Acceptance....................................................................................................................... 15
Activation of Assessment.................................................................................. ....... ...15
Responsibility for GHAD Activities..... ....................... ................... .............................15
VII. Schaefer Ranch GHAD Management Plan...................................................................... 16
Landslide Mitigation for Existing Landslides and Erosion Features........................... 17
Geotechnical Techniques for Mitigation of Landslide and Erosion Hazards ..............21
VIII. Priority of GHAD Expenditures................................ ................................... ................. 23
IX. Biotechnical Recommendations for Prevention and Mitigation of Existing or Potential
Erosion Hazards............................................................................................................... 24
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TABLE OF CONTENTS (Continued)
X. Maintenance and Monitoring Schedule............. ....................... .................................... 25
SELECTED REFERENCES
EXHIBIT A - GHAD Legal Description
EXHIBIT B - GHAD Boundary Exhibit
GHAD Open Space Exhibit
PLATE 1 - Parcel Designation Plan
PLATE 2 - Geologic Map
APPENDIX A - Water Quality - Detention Basin Monitoring and Maintenance
APPENDIX B - Site Geology
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I. Authority and Scope
The Schaefer Ranch Geologic Hazard Abatement District ("GHAD" or "District") is proposed to
be formed under authority of the California Public Resources Code (Division 17, commencing
with Section 26500). Formation of the GHAD has been proposed to provide a framework for the
prevention, mitigation, abatement, and control of identified or potential geologic hazards.
Development of a Plan of Control prepared by a State Certified Engineering Geologist is a
requirement for formation of a GHAD. Pursuant to Section 26509, this Plan of Control was
prepared by an engineering geologist certified pursuant to Section 7822 of the Business and
Professions Code and describes 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.
Property Identification
The boundary of Schaefer Ranch (Tract 6765), the legal description of the property, its parcel
designations, and the proposed boundary of the GHAD are shown in Exhibits A and B and Plate
I.
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II. Background
The Schaefer Ranch project is located on the north side of Highway 580 in west Dublin,
California. The east side of the property borders open space for an adjacent subdivision and East
Bay Regional Park District land. The northern side of the property borders East Bay Regional
Park District land and the Machado Property. The west side of the property borders the
DaVilla/Eden Canyon Family Partnership Property. Access to the site is currently provided via
Schaefer Ranch Road through an existing freeway underpass. The site is approximately
445 acres in area and is bordered on the west and north by undeveloped land (the "GHAD
Property"). The GHAD Property includes the area shown in Exhibit B.
Pregrading Site Conditions
The GHAD Property is located in an area dominated by a high ridgeline that reaches elevations
of over 1,100 feet (Plate 2). In plan view, the crest of the ridge forms a "V" shape, open to the
west. The high point on the property, Donlan Point at elevation 1,138 feet, occurs at the apex of
the "V", at the east end of the high ridgeline. East of Donlan Point, a single ridgeline continues
to the east at elevations of 750 to 900 feet. South of the ridge, the property slopes to Highway
580 at elevations of 600 to 700 feet. The center of the high ridge is drained by Marshall Canyon
and Kelley Canyon. Wagon Wheel Canyon flows from a saddle south of the main ridge. All
three canyons drain northwest, into undeveloped lands. The vegetation on site currently consists
of open grassland in upland areas and south-facing slopes, local brush and tree cover in the
canyon bottoms and some lower portions of north-facing slopes.
Proposed Development
The Preliminary Grading Plan for the subject property, developed by PIA Design Associates
currently shows single family residential units, interior subdivision streets, a leisure park, a
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sports park, three detention basins, three water quality basins, a water tank, an East Bay Regional
Park District trailhead, staging area and associated trails and an approximately 5.7 acre parcel at
the site. A Geotechnical Investigation dated October 1997 was completed for the Schaefer
Ranch site by Alan Kropp and Associates (AKA). ENGEO Incorporated performed a
supplemental exploration at the Schaefer Ranch site and provided supplemental geotechnical
recommendations in a report dated January 29, 2004, as well as subsequent documents listed in
the references section.
Grading plans for the subject site indicate that the majority of planned residential units will
occupy cut areas along the west-northwest and northwest trending ridgelines at the site.
Proposed residential units will also occupy building pads in fill areas in the southwest portion of
the site west of proposed Schaefer Ranch Road and within the west and northwest portions of the
site. In addition to the proposed residential development, a westward extension of Dublin
Boulevard is planned at the site.
Along the uphill side of the Dublin Boulevard Extension, 2: 1 (horizontal: vertical) slopes up to
180 feet in vertical height are planned. East of Station 30+50 the 2: 1 slopes are planned to be
rebuilt as engineered fill slopes. West of Station 30+50, portions of the 2: 1 slopes outside of
mapped landslide areas are not planned to be rebuilt. Landslides within the grading limits along
Dublin Boulevard are planned to be completely removed and replaced with drained engineered
fill. Benches with concrete-lined ditches and stormdrain systems are planned on graded slopes
steeper than 3: 1.
According to grading plans by PIA Design Resources, deep fill areas are planned at the
southwest and northwest portions of the Schaefer Ranch Project site. Engineered fill within the
above mentioned portions of the site are shown to extend up to approximately 150 feet above
original grades in some places. ENGEO provided recommendations for the monitoring of deep
fills in letters dated June 26, 2005, and August 17, 2005. Settlement instrumentation will be
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provided in the deep fill areas at the southwestern portion of the site west of Schaefer Ranch
Road and in the deep fill area in the northwest portion of the site. The developer will provide for
monitoring of the settlement instruments during grading as well as during the residential
construction period.
Open Space
Project Open Space includes Parcels AI, B1, C1, E, F, G, H, L, P, R, S, U and V as shown in
Open Space Exhibit. Title to these parcels will be conveyed to the GHAD approximately three
years after the recording of the first final map affecting the GHAD Property. Since long-term
maintenance and stability of the GHAD Property will protect the open space, which is an amenity
that will benefit all of the current and future property owners, the funding for the GHAD's
activities will be shared by all current and future property owners within the GHAD's
boundaries. All such activities shall be consistent with this Plan of Control.
According to the GHAD Boundary Exhibit prepared by P A Design Resources (August 16, 2006)
approximately 66 acres of open space designated as Parcel A has been deeded to the East Bay
Regional Park District and will therefore be outside of the GHAD's boundaries, although the
GHAD reserves the right to enter this property at its discretion in conjunction with maintenance
and repairs on the GHAD property (see attached Exhibit B).
GHAD Responsibilities
The GHAD will mitigate, prevent, abate or repair landslide or erosion hazards that could directly
affect property within the GHAD boundary, as necessary to implement this Plan of Control. The
GHAD will also assume open-space management responsibilities that are required for the
Schaefer Ranch Project. These responsibilities will include: vegetation management, erosion
control, vegetation removal (fire suppression), and selected other maintenance associated with
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open space. In addition, the responsibility of the GHAD includes: maintenance, repair and
replacement of detention basins (within the GHAD Property), vegetation control, armoring of
channels and desilting of detention basins.
The GHAD's responsibilities will include but may not be limited to monitoring and maintenance
for the following as appropriate.
· Detention Basins and Water Quality Basins on Parcels "R", "G" and "V", including
structures, vegetation and sediment removal.
· Maintenance and repair ofEV A and access Roads.
. Erosion repairs.
· Revegetation and vegetation control, including fire break mowing, weeding and additional
hydro seeding as deemed necessary.
· Sediment removal from concrete structures (applies only to open-space catch basins, field
inlets, V-ditches and stormdrain pipes).
· Slope stabilization (includes minor landsliding and debris bench clearing).
. Subdrain outfall maintenance.
· Open-space stormdrain pipe and V -ditch replacement.
In addition, the GHAD will have maintenance, monitoring and repair responsibilities for slopes,
which will include natural, reconstructed or partially-reconstructed landslides as indicated within
the referenced ENGEO reports and discussed below (Section V).
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III. Site Geology
Geologic Setting
The site is located within the Coast Ranges geologic prOVlllce of California, a senes of
northwest-trending ridges and valleys. Bedrock in the province has been folded and faulted
during regional uplift beginning in the Pliocene period, roughly 4 million years before present.
More specifically Schaefer Ranch is located in the central East Bay Hills, an area that is
characterized by folded and faulted Cretaceous to Pliocene-age sedimentary rocks (Plate 2). The
eastern and western geologic boundaries of the East Bay Hills are formed by the active Calaveras
and Hayward Faults.
Site Geology
Regional geologic maps of the area have been prepared by Dibblee (1980), Crane (1988) and
Graymer (1996). The most recent regional map prepared by Graymer indicates that the site is
underlain by late and middle Miocene rocks of the Briones Formation and undivided middle
Miocene marine rocks of the Monterey Group including the Rodeo Shale, Hambre Sandstone,
Tice Shale and Ours an Sandstone. A more extensive discussion of the site geology is included
as Appendix B of this Plan of Control.
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IV. Geologic Hazards
Geologic hazards identified for the site in the AKA and ENGEO reports include the following
items:
· Lateral stability or slope stability
· Erosion and sedimentation
· Seismically-induced ground shaking
Slope Instability
Earth stability is the GHAD's prime geotechnical concern at this site. This is not unique to this
project, but is of importance for hillside projects in the San Francisco Bay Area. This section
describes several types of slope instability which are within the GHAD's responsibility, subject
to the provisions of Section VI.
Landslides are a common geologic phenomenon and are part of the process of mass wasting.
Weathered or fractured bedrock and soil are transported downslope over geologic time as a result
of gravitational and hydrostatic forces. Landslides and earth movement in this bedrock formation
are typically rotational slumps and earthflows. Depth of movement is typically about 5 to
25 feet below the ground surface. In the winter rainy season, these earthflows can move at a rate
of several feet per day.
A landslide is a deposit of soil andlor bedrock moving downward from its original position under
the influence of gravity. Landslides include a variety of morphologies and are further defined by
type of materials, wetness, and mode of movement. They can consist of mass movements of
earth materials that are primarily intact, and occur along discrete shear surfaces. These surfaces
(shear or slip planes) can be rotational (conchoidal or concave), such as for earth slumps, or
planar, as for translational earth slide or bedrock block glides. Most landslides are truly
"complex landslides", sliding, falling and flowing with more than one type of movement andlor
material.
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According to the geotechnical reports for the project approximately 59 landslides have been
identified on the subject site. The geologic map showing the location of each of the landslides is
included as Plate 2. In general mitigation measures for the mapped landslides are to be
performed in accordance with the approved remedial grading plans for the project. The proposed
mitigation measures identified in the geotechnical report and the remedial grading plans include
the following: complete removal of the landslide and replacement with drained engineered fill,
removal and replacement of the lower portion of the landslide and replacement with a drained
engineered fill buttress, and removal and replacement of the upper portion of the landslide within
the grading limits and providing a keyway along the edge of the grading limits. According to the
geotechnical report for the project, landslides that are completely outside of the proposed grading
limits and pose no potential risk to the proposed development, will not be mitigated and will be
left in-place. As-built remedial grading plans are to be prepared following grading at the site to
show areas and locations where corrective grading was performed.
Slope failures are also often triggered by increased pore water pressure due to the infiltration of
rainwater. The resulting decrease of shear resistance (internal resistance to deformation by
shearing) can cause the slope to move. The level of the groundwater table varies with the
amount of rainfall for the area. If rainfall is higher than average during the winter season, the
water table will be higher than average on a hillslope and groundwater pressures may become
high. Under these conditions, hillside movement can be activated.
Soil creep is the slow, often imperceptible, deformation of slope materials under low stress
levels, which normally affects the shallow portion of the slopes, but can be deep seated where a
weak zone of soil or bedrock exists. It results from gravitational and seepage forces, and may be
indicative of conditions favorable for landsliding. Creep can be caused by wetting and drying of
clays, by solution and crystallization of salts, by the growth of roots, by burrowing animals and
by down slope movement of saturated ground. Colluvium refers to the thicker mantle of loose
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soil and weathered bedrock debris that progresses down hillsides by creep. Colluvial deposits
are typically the result of soil creep and may be in a weak, unconsolidated state, making them
susceptible to landsliding if undercut. Colluvium is generally approximately 8 to 15 feet in
thickness. Landslides and colluvial deposits located within open space areas are natural
landforms that do not require mitigation except where they affect man-made improvements.
Potential mitigation and repair measures for GHAD areas near development are discussed in
Section VII.
Erosion and Sedimentation
The District shall also be concerned with erosion and sedimentation in open space or affecting
established lots or improvements. Erosion is defined as the process by which earth materials are
loosened and removed by running water on the ground surface or in the subsurface.
Sedimentation is the depositing or settling of soil or rock particles from a state of suspension in a
liquid.
Hilly terrain in open space, either in a natural condit.ion or particularly on excavated slopes, can
be subject to erosion. Landslide deposits which are sometimes in a loosened condition are
particularly prone to erosion. Earth flow, debris flow and mud flow landslides typically have an
area of deposition or accumulation (sedimentation area) at their base. Graded slopes in the
District, particularly those in excess of 20 feet in vertical height or those not sufficiently
vegetated, can be subject to erosion and therefore, a source of transported sediment.
Seismically-Induced Ground Shaking
As identified in the geotechnical reports, an earthquake of moderate to high magnitude generated
within the San Francisco Bay Region could cause considerable ground shaking at the site, similar to
that which has occurred in the past. Seismic slope stability has been considered in the ENGEO
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remedial grading plans for engineered fill slopes at the site. On unimproved open space slopes,
seismically-generated slope failures may occur in open-space areas outside the development
limits.
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v. Criteria for GHAD Responsibility
Prevention, Mitigation, Abatement andlor Control of Geologic Hazards
Subject to the following exceptions, the primary mission of the GHAD shall be the prevention,
mitigation, abatement andlor control of geologic hazards within its boundaries that have
damaged, or that pose a significant threat of damage to site improvements within the GHAD
boundaries. As used herein, the term "site improvements" means buildings and outbuildings,
roads, sidewalks, utilities and associated facilitieslstructures and geologic stabilization features.
Exceptions
The intent of this Plan of Control is not to extend the GHAD's responsibilities to every potential
situation of slope instability. Specifically, the following are excluded from the GHAD's
responsibili ties:
Isolated or Remote Slope Instability
The GHAD shall not have responsibility to monitor, abate, mitigate or control isolated or remote
slope instability that does not involve damage to or pose a significant threat to damage (a) site
improvements or (b) off-site improvements if the threat of damage or damage is not caused by
property or site improvements for which the GHAD is responsible.
Single Property
The GHAD will not prevent, mitigate, abate or control geologic hazards which are limited in
area to a single parcel of property not owned by the GHAD unless the geologic hazard has
damaged, or poses a significant threat of damage, to site improvements located on other property
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within the GHAD boundaries. This exclusion does not apply to geologic hazards existing on
common area property owned by the HOA or within the GHAD-owned Property.
Geologic Hazards Resulting From Negligence of Property Owner
The GHAD may, in the GHAD manager's sole discretion, decline to prevent, mitigate, abate or
control geologic hazards which occurred or resulted from any negligence of the homeowner
andlor the homeowner's contractors, agents or employees in developing, investigating, grading,
constructing, maintaining or performing or not performing any post-development work on the
subject property.
Vertical Movement or Creep Due to Shrink Swell or Settlement
Vertical movement due to shrink -swell of expansive soils or settlement of fills is expected at the
site as with many residential developments in the area. Damage to site improvements resulting
from shrink swell or settlement of fills is not the responsibility ofthe GHAD.
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Protected Wildlife Habitat
The GHAD will not prevent, mitigate, abate or control isolated geologic hazards which are
limited to mitigation areas andlor protected wildlife habitat unless the geologic hazard has
damaged, or poses a significant threat of damage, to site improvements located on property
within the GHAD boundaries.
Property Not Accepted
The GHAD shall not have responsibility to repair damaged site improvements which are situated
on a parcel of real property that the GHAD has not accepted in accordance with Section VI,
below.
Damage to GHAD Accepted ProtJerty from Landslide Originating on Property not Accepted by
GHAD
The GHAD may monitor, abate, mitigate or control slope instability on a parcel of real property
which (1) the GHAD has not accepted in accordance with Section VI, below, and (2) that is not
excluded from GHAD responsibility by Paragraphs 1 and 2; provided that GHAD responsibility
on such parcel shall be limited to the extent necessary to address damage or a significant threat to
damage site improvements which are within a parcel of real property which the GHAD has
accepted in accordance with Section VI, below.
GHAD Funding or Reimbursement for Damaged or Destroyed Structures or Site Improvements
In the event that improvements (including residences, landscape, hardscape, or any other
structure) are damaged or destroyed due to, or as a result of, a geologic hazard, the GHAD may
fund or reimburse the property owner for the expenses necessary to repair or replace the
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damaged or destroyed structure, site improvement or landscaping. Unless authorized by the
Board of Directors, the dollar amount of the GHAD funding or reimbursement may not exceed
an aggregate of ten percent (10%) of the costs incurred by the GHAD in preventing, mitigating,
abating or controlling the geologic hazard responsible for the damage.
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VI. Acceptance
Activation of Assessment
An annual assessment shall be fully authorized, prior to recordation of the Final Map in
accordance with the Conditions of Approval, on all residential parcels in the GHAD and may be
increased as provided by law to achieve the purposes of the GHAD and this Plan of Control.
The assessment shall be levied by the GHAD on each individual residential parcel beginning the
first fiscal year following issuance of a building permit for that parcel.
Responsibility for GHAD Activities
Except as provided for in Section V, the party that, on the date the Final Map within the
boundaries of the GHAD is recorded in the Official Records of Alameda County, owns the
developable parcels shown on the Final Map shall have the responsibility to perform all the
activities of the GHAD on property within the Final Map prior to transfer of such property to the
GHAD. Pursuant to this Plan of Control, such responsibility shall automatically transfer to the
GHAD at 9:00 a.m. on the day exactly three years after the completion and city approval of the
grading for the Schaefer Ranch Project, or exactly three years, after the first occupancy permit
for the Schaefer Ranch Project is issued by the City, whichever is later, and provided the
improvements required by the Conditions of Approval for the Schaefer Ranch Project have been
accepted. This transfer date may be extended at the sole discretion of the owners of the GHAD
Property to be transferred, provided that the owners continue to perform the GHAD's activities
and that the assessments continue to be levied during the extension period and that notice of such
extension is delivered to the GHAD manager at least 30 days prior to the transfer date. The
approximate three-year period between the levying of the GHAD assessment and the GHAD
transfer will allow the GHAD to accumulate reserve funds without incurring significant
expenses.
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VII. Schaefer Ranch GHAD Management Plan
The GHAD will subject to the criteria outlined in Section V, monitor, mitigate and repair
landslide or erosion hazards within the GHAD boundaries. Subject to the same criteria, the
GHAD will also monitor, maintain, and repair the following within the GHAD boundary.
· Detention Basins and Water Quality Basins on Parcels "R", "G" and "V", including
structures, vegetation and sediment removal
· Maintenance and repair of EVA and access Roads.
. Erosion repairs.
· Revegetation and vegetation control, including fire break mowing, weeding and additional
hydro seeding as deemed necessary.
· Sediment removal from concrete structures (applies only to open-space catch basins, field
inlets, V-ditches and stormdrain pipes).
· Slope stabilization (includes minor landsliding and debris bench clearing).
. Subdrain outfall maintenance.
· Open-space stormdrain pipe and V -ditch replacement.
· Any other duties that the GHAD manager deems necessary for the management of areas
within the GHAD boundaries.
The GHAD will be authorized to maintain the geologic stabilization features (e.g. ditches, benches,
walls, etc.) in the open space, and the unimproved areas including the hillside slopes extending
uphill from debris benches and common areas outside of the private lot boundaries except where
noted in section X. The GHAD's maintenance responsibilities include prevention, abatement, and
control of landslide and erosion hazards within the subdivision open space and hillsides, as provided
in Section V.
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General maintenance of the surface drainage improvements in the open space and on the hillsides,
such as the concrete V-ditches, will be the GHAD's responsibility. The GHAD is also responsible
for general maintenance of the stormdrain inlets and outlets in open space as well as the sub drain
outlets. Potential geologic hazards such as landslides and slope erosion within the open space,
including the unimproved hillsides, shall be the responsibility of the GHAD in accordance with
Section V of this report. Clearing of fire breaks and general maintenance of the open space (other
than hazard abatement) will be performed by the GHAD.
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Landslide Mitigation for Existing Landslides and Erosion Features
For existing landslide areas the following mitigation measures have been proposed within the
geotechnical investigation reports. General landslide mitigation measures and potential GHAD
maintenance and monitoring activities are shown below.
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Proposed Corrective
Measures
Com lete removal
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slide
ations
B-1
Remove and replace lower
portion of landslide
B-2 underlying improvements,
Provide intervening
deposition area
None Required
B-3 Outside of grading limits
and within 0 en s ace area
B-4 Com lete removal
B-5 Com lete removal
B-6 Com lete removal
None Required
B-7 Outside of grading limits
and within 0 en s ace area
L-l Com lete removal
L-2 Com lete removal
Removal of the upper portion
L-3 of the landslide within grading
limits
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4748.1.500.01
November 1,2006
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Potential GHAD Maintenance or Monitoring Activities
Routine observation durin eriodic site monitorin events.
Upslope portions of Bedrock Landslide above the repair
to remain. Observation of this area during periodic site
monitoring events. Higher potential for corrective work in
future if landslide debris movement impacts rebuilt portion
of slope or site improvements. See Section vn for potential
landslide mitigation techni ues.
Landslide to remain in place. Routine observation during
periodic site monitoring events.
Routine observation during
Routine observation durin
Routine observation durin
events.
events.
events.
Landslide to remain in place. Routine observation during
periodic site monitoring events.
Routine observation durin eriodic site monitorin events.
Routine observation during periodic site monitoring events.
Lower portion of landslide within open space area and
outside of grading limits to remain. Routine observation
during periodic site monitoring events.
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ENGEO
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dslide Proposed Corrective Potential GHAD Maintenance or Monitoring Activities
Designations Measures
None Required Landslide to remain in place. Routine observation during
L-4 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-5 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-6 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-7 Outside of grading limits
and within open space area periodic site monitoring events.
Shallow upslope margins of landslide above the repair to
remam. Observation of this area during periodic site
Removal of the lower portion monitoring events. Higher potential for maintenance or
L-8 of the landslide within cut corrective work in future iflandslide debris is shed on to
slope rebuild area. benches of rebuilt slope or shallow movement impacts
rebuilt portion of slope or site improvements. See Section
vn for potential landslide mitigation techniques.
Remove and replace lower Shallow upslope margins of landslide above the repair to
portion of landslide remain. Observation of this area during periodic site
L-9 underlying improvements, monitoring events. Higher potential for maintenance or
corrective work in future if landslide debris is shed into
Provide intervening intervening debris deposition area. See Section vn for
deposition area potential landslide mitigation techniques.
L-lO Complete removal Routine observation during periodic site monitoring events.
L-ll Complete removal Routine observation during periodic site monitoring events.
Remove and replace more Shallow upslope portion of landslide above the repair to
significant lower portion of remain. Observation of this area during periodic site
L-12 landslide underlying monitoring events. Higher potential for maintenance or
corrective work in future if landslide debris is shed into
improvements, Provide intervening debris deposition area. See Section vn for
intervening deposition area potential landslide mitigation techniques.
Remove and replace lower Upslope portion of landslide above the repair to remain.
portion of landslide Observation of this area during periodic site monitoring
L-13 underlying improvements, events. Higher potential for maintenance or corrective work
Provide intervening in future if landslide debris is shed into intervening debris
deposition area deposition area. See Section vn for potential landslide
mitigation techniques.
Remove and replace lower Upslope portion of landslide above the repair to remain.
L-14 portion of landslide Observation of this area during periodic site monitoring
underlying improvements, events. Higher potential for maintenance or corrective work
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Landslide Proposed Corrective Potential GHAD Maintenance or Monitoring
Desil!nations Measures
Provide intervening in future iflandslide debris is shed into intervening debris
deposition area deposition area. See Section VII for potential landslide
mitigation techniaues.
Shallow upslope margins of landslide above the repair to
Removal of the more remain. Observation of this area during periodic site
significant lower portion of the monitoring events. Higher potential for maintenance or
L-15 corrective work in future iflandslide debris is shed on to
landslide within cut slope benches of rebuilt slope or shallow movement impacts
rebuild area. rebuilt portion of slope or site improvements. See Section
VII for potential landslide mitigation techniques.
Shallow upslope margins of landslide above the repair to
Removal of the more remain. Observation of this area during periodic site
significant lower portion of the monitoring events. Higher potential for maintenance or
L-16 corrective work in future if landslide debris is shed on to
landslide within cut slope benches of rebuilt slope or shallow movement impacts
rebuild area. rebuilt portion of slope or site improvements. See Section
VII for potential landslide mitigation techniques.
Shallow upslope margins of landslide above the repair to
Removal of the more remain. Observation of this area during periodic site
significant lower portion of the monitoring events. Higher potential for maintenance or
L-17 corrective work in future iflandslide debris is shed on to
landslide within cut slope benches of rebuilt slope or shallow movement impacts
rebuild area. rebuilt portion of slope or site improvements. See Section
VII for potential landslide mitigation techniques.
None Required Landslide to remain in place. Routine observation during
L-18 Outside of grading limits
and within open space area periodic site monitoring events.
Removal of the upper portion Lower portion of landslide within open space area and
L-19 of the landslide within grading outside of grading limits to remain. Routine observation
limits during periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-20 Outside of grading limits
and within open space area periodic site monitoring events.
L-21 Complete removal Routine observation during periodic site monitoring events.
L-22 Complete removal Routine observation during periodic site monitoring events.
L-23 Complete removal Routine observation during periodic site monitoring events.
L-24 Complete removal Routine observation during periodic site monitoring events.
L-25 Complete removal Routine observation during periodic site monitoring events.
L-26 Complete removal Routine observation during periodic site monitoring events.
L-27 Complete removal Routine observation during periodic site monitoring events.
L-28 Complete removal Routine observation during periodic site monitoring events.
L-29 Complete removal Routine observation during periodic site monitoring events.
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Landslide Proposed Corrective Potential GHAD Maintenance or Monitoring Activities
Designations Measures
L-30 Complete removal Routine observation during periodic site monitoring events.
Upslope portion of landslide above the repair to remain.
Remove and Replace Observation of this area during periodic site monitoring
Portions Underlying events. Higher potential for maintenance or corrective work
L-31 Improvements, Construct in future if landslide debris is shed on to benches of rebuilt
Buttress and Debris slope or shallow movement impacts rebuilt portion of slope
Catchment Bench or site improvements. See Section VII for potential landslide
mitigation techniques.
L-32 Complete removal Routine observation during periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-33 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-34 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-35 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-36 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-37 Outside of grading limits
and within open space area periodic site monitoring events.
Lower portion of landslide within open space area and
Remove and Replace outside of grading limits to remain. Observation of this
Portions Underlying area during periodic site monitoring events. Higher potential
L-38 Improvements, Construct for corrective work in future if downslope movement of
Buttress Key at Upper landslide leads to regression of heads carp into areas of site
Landslide Limits. improvements. See Section VII for potential landslide
mitigation techniques.
None Required Landslide to remain in place. Routine observation during
L-39 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-40 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-41 Outside of grading limits
and within open space area periodic site monitoring events.
L-42 None Required Routine observation during periodic site monitoring events.
Outside of grading limits
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Landslide Proposed Corrective Potential GHAD Maintenance or Monitoring Activities
Desi2nations Measures
and within open space area
None Required Landslide to remain in place. Routine observation during
L-43 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-44 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-45 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-46 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-47 Outside of grading limits
and within open space area periodic site monitoring events.
None Required Landslide to remain in place. Routine observation during
L-48 Outside of grading limits
and within open space area periodic site monitoring events.
L-49 None Required Landslide to remain in place.
Outside of grading limits Routine observation during
and within open space area periodic site monitoring events.
L-50 None Required
Outside of grading limits Landslide to remain in place. Routine observation during
and within open space area periodic site monitoring events.
L-51 None Required
Outside of grading limits Landslide to remain in place. Routine observation during
and within open space area periodic site monitoring events.
L-52 None Required
Outside of grading limits Landslide to remain in place. Routine observation during
and within open space area periodic site monitoring events.
Geotechnical Techniques for Mitigation of Landslide and Erosion Hazards
The techniques which may be employed by the GHAD to prevent, mitigate, abate, or control
geologic hazards include, but are not necessarily limited to:
A. Removal of the unstable earth mass.
4748.1.500.01
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ENGEO
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B. Stabilization (either partial or total) of the landslide by removal and replacement with
compacted, drained fill.
C. Construction of structures to retain or divert landslide material or sediment.
D. Construction of erosion control devices such as gabions, riprap, geotextiles, or lined
ditches.
E. Placement of drained engineered buttress fill.
F. Placement of subsurface drainage devices; (e.g. underdrains, or horizontal drilled drains).
G. Slope correction (e.g. gradient change, biotechnical stabilization, slope trimming or
contouring).
H. Construction of additional surface ditches and/or detention basins, silt fences, sediment
traps, or backfill or erosion channels.
Potential landslide and erosion hazards can be mitigated best by controlling soil saturation and
water runoff and by maintaining the surface and subsurface drainage system. Maintenance shall
be provided for lined surface drainage ditches and drainage terraces including debris benches or
drop inlets.
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VIII. Priority of GHAD Expenditures
Emergency response and scheduled repair expenditures by the GHAD are to be assigned a
priority at the discretion of the GHAD manager based upon available funds and the approved
operating budget. GHAD expenditures shall be prioritized as follows in descending order of
priority:
A. Prevention, mitigation, abatement or control of geologic hazards that have either
damaged or pose a significant threat of damage to residences, critical underground
utilities or paved streets.
B. Prevention, mitigation, abatement or control of geologic hazards which have either
damaged or pose a significant threat of damage to ancillary structures, including but not
limited to the detention basins, or community buildings.
C. Prevention, mitigation, abatement or control of geologic hazards which have either
damaged or pose a significant threat of damage to open space amenities including
vegetation that part of the irrigated, maintained, ornamental landscaping.
D. Prevention, mitigation, abatement or control of geologic hazards existing entirely on
open-space property and which have neither damaged nor pose a significant threat of
damage to any site improvements.
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ENGEO
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IX. Biotechnical Recommendations for Prevention and Mitigation of Existing or Potential
Erosion Hazards
Maintenance of vegetative cover is important on all slopes cut or fill. Vegetation provides a
protective role on soil and exposed rock. It absorbs the impact of raindrops, reduces the velocity
of runoff, and retards erosion.
The GHAD may plant carefully selected and placed biological elements (plants). In addition, if
the GHAD manager determines that it is necessary, biotechnical slope protection may also
involve the use of mechanical elements or structures in combination with biological elements to
provide erosion control and help prevent small-scale slope failures. Locally, crib walls, welded-
wire walls, gabion walls, rock walls, riprap, and reinforced earth walls used in combination with
carefully selected and planted vegetation can provide high quality slope protection. The
vegetation may be planted on the slope above a low retaining structure or toe wall, or the
interstices of the structure can be planted.
4748.1.500.01
November 1,2006
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ENGEO
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X. Maintenance and Monitoring Schedule
Geologic features and GHAD maintained facilities should be inspected by GHAD staff or
GHAD-assigned consultants as presented below. The annual budget should be calculated so that
inspections will be scheduled to occur two times per year and as necessary after heavy rainfall
events that is defined as greater than 1 inch of rainfall in a 12-hour period. The inspections
should be scheduled to take place in October, prior to the first significant rainfall; mid-winter as
necessary during heavy rainfall years or events; and in early April, at the end of the rainy season.
The frequency of the inspections should be increased in years of higher than average rainfall
intensity and recurrence. The timing, frequency and other details regarding such maintenance,
inspection and similar activities will be set forth in the Management Plan prepared by the GHAD
manager.
It is our understanding that in some instances slopes, benches and drainage structures which are
to be maintained by the GHAD shall extend across private parcels. Access for maintenance and
repair of these features shall be granted to the GHAD through easements established in favor of
the GHAD.
The GHAD shall obtain copies of geologic or geotechnical exploration reports related to site
development and keep these reports on file in the records of the GHAD. In addition, copies of
any earthwork-related testing and observation reports that will be finalized at the completion of
grading, when as-built drawings are available, shall be maintained as part of the GHAD records.
Following are guidelines for a monitoring plan. The actual scope and frequency of monitoring
events shall be at the discretion of the GHAD manager.
· The General Manager's engineer andlor geologist should inspect the lined surface ditches on
a regular schedule. If possible, inspections should be scheduled twice each year, budget
permitting. One inspection should be in the fall prior to the onset of winter rains. The
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inspector should check for sedimentation, cracking or shifting of the concrete-lined ditches.
Repairs and maintenance should be performed on a regular schedule. Excess silt or sediment
in ditches should be removed and cracked or broken ditches should be patched or repaired as
required prior to the beginning of the next rainy season.
. Subsurface drain outlets and horizontal drilled drain outlets, if any, should be inspected on a
regular basis. Water flowing from these outlets should be measured and recorded during
each inspection. If possible, inspections should be scheduled twice each year, preferably in
the fall and spring. Any suspicious interruption in flow should signal a need to unplug or
clean the affected drain.
· Inlets, outfalls or trash racks, if used, must be kept free of debris and spillways maintained.
Attention should be given to plantings or other obstructions which may interfere with access
by power equipment.
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The detention basins and water quality ponds on Parcels "R", "G" and "V" should be monitored
4 times each year, as appropriate. The monitoring schedule should occur in January, April,
October, and as necessary during heavy rainfall events. A more detailed schedule of monitoring
items and sample monitoring report forms are included in the detention basin monitoring and
maintenance section presented in Appendix A.
An annual inspection shall be made by the engineer andlor engineering geologist to assess the
effectiveness of the preventive maintenance program and to make recommendations as to which
landslide or erosion measures should be undertaken in the next fiscal year. Any appropriate
site-specific study of landslide or erosion conditions shall be determined at that time.
Consultants, if necessary, will be retained to undertake the needed studies. An annual inspection
report shall be prepared by the GHAD Engineer andlor engineering geologist for the GHAD.
Distribution of the annual report along with the budget information shall include City of Dublin
Public Works Director.
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ENGEO
INCORPORATED
SELECTED REFERENCES
Alan Kropp & Associates, 1997, Geotechnical Investigation, Schaefer Ranch Subdivision,
Dublin, California, Dated October, 1997, Project Number 1051-1C.
California Department of Conservation, 1996, California Fault Parameter, Division of Mines and
Geology, Open File Report 96-08.
Crane, R., 1995, Geology of the Mount Diablo Region, in Geology of the Mount Diablo Region
Guidebook, Northern California Geological Society.
Dibblee, T.W., 1980, Preliminary geologic map of the Dublin quadrangle, Alameda and Contra
Costa Counties, California: U.S. Geological Survey, Open-File Report OF-SO-537, scale
1 :24000.
ENGEO Inc., 2004, Supplemental Geotechnical Recommendations, Schaefer Ranch Project,
Dublin, California, dated January 29,2004, Project No.4748.1.00l.01
ENGEO Inc., 2005, Geotechnical Recommendations for Existing Mitigation Pond PP10 at
Marshall Canyon, Schaefer Ranch Project, Dublin, California, dated April 14, 2005,
Project No.4748.1.001.01
ENGEO Inc., 2005, Geotechnical Review of Mitigation and Watershed Enhancement Planting and
Grading Plans and Supplemental Geotechnical Criteria, Schaefer Ranch Project, Dublin,
California, dated June 9, 2005, Project No.4748.1.001.01
ENGEO Inc., 2005, Recommendations for Settlement Monitoring of Planned Deep Fill Areas,
Schaefer Ranch Project, Dublin, California, dated June 26, 2005, Project
No.4748.1.001.01
ENGEO Inc., 2005, Recommendations for Settlement Monitoring of Planned Deep Fill Areas,
Schaefer Ranch Project, Dublin, California, dated August 17, 2005, Project
No.4748.1.001.01
Graymer, R. W., Jones, D. L. and Brabb, E. E., 1994, Preliminary Geologic Map Emphasizing
Bedrock Formations in Alameda County, California: OFR 96-252.
Federal Emergency Management Agency, 1982, National Flood Insurance Program, Flood
Insurance Rate Map (FIRM), Panel Number 065048 0025 B.
4748.1.500.01
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ENGEO
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SELECTED REFERENCES (Continued)
Unruh, J. R. and Sawyer, T. L., 1997, Assessment of Blind Seismogenic Sources, Livermore
Valley, Eastern San Francisco Bay Region: Final Technical Report by William Lettis
Associates and Piedmont Geosciences Inc. for the U. S. Geologic Survey National
Earthquake Hazards Reduction Program.
Unruh, 2000, Characterization of Blind Seismogenic Sources in the Mt. Diablo-Livermore
Region, San Francisco Bay Area, California: Final Technical Report by William Lettis &
Associates for the U. S. Geologic Survey National Earthquake Hazards Reduction
Program.
Wagner, J. R., 1978, Late Cenozoic History of the Coast Ranges East of San Francisco Bay,
Ph.D. Dissertation, University of California, Berkeley.
Working Group on California Earthquake Probabilities, 1999, Earthquake Probabilities in the
San Francisco Bay Region: 2000 to 2030 - A Summary of Findings: USGS Open-File
Report 99-517.
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EXHIBIT A
PIA Design Resources
Legal Description
4748.1.500.01
November 1, 2006
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ENGEO
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EXHIBIT" A"
GRAD
LEGAL DESCRIPTION
ALL THAT REAL PROPERTY SITUATE IN THE COUNTY OF ALAMEDA, STATE
OF CALIFORNIA, DESCRIBED AS FOLLOWS:
A PORTION OF SECTIONS 3 AND 4, TOWNSHIP 3 SOUTH, RANGE 1 WEST,
MOUNT DIABLO BASE AND MERIDAN, MORE PARTICULARLY DESCRIBED
AS FOLLOWS:
BEGINNING AT THE NORTHWEST CORNER OF SAID SECTION 4; THENCE
ALONG THE NORTH SECTION LINE OF SAID SECTION 4, SOUTH 89029'04"
EAST 2594.67 FEET TO THE NORTH ~ CORNER OF SAID SECTION 4; THENCE
CONTINUING AWNG SAID NORTH SECTION LINE SOUTH 89033'52" EAST
1715.15 FEET; THENCE ALONG THE ARC OF A NON-TANGENT CURVE, THE
RADIUS POINT OF WInCH BEARS SOUTH 79006'33" EAST, CONCAVE TO THE
EAST, HAVING A RADIUS OF 172.50 FEET, THROUGH A CENTRAL ANGLE OF
59027'40", AN ARC LENGTH OF 179.02 FEET; THENCE SOUTH 48034'13" EAST
145.11 FEET; THENCE ALONG THE ARC OF A CURVE, CONCAVE TO THE
SOUTHWEST, HAVING A RADIUS OF 237.50 FEET, THROUGH A CENTRAL
ANGLE OF 38035'04", AN ARC LENGTH OF 159.94 FEET; THENCE SOUTH
09059'09" EAST 35.93 FEET; THENCE ALONG THE ARC OF A CURVE
CONCAVE TO THE WEST, HAVING A RADIUS OF 237.50 FEET, THROUGH A
CENTRAL ANGLE OF 26018'25", AN ARC LENGTH OF 109.05 FEET; THENCE
SOUTH 16019'16" WEST 108.23 FEET; THENCE SOUTH 73040'44" EAST 25.00
FEET; THENCE SOUTH 41019'00" EAST 438.12 FEET; THENCE SOUTH 32004'20"
EAST 249.89 FEET; THENCE SOUTH 18005'49" EAST 497.44 FEET; THENCE
SOUTH 02020'33" EAST 502.81 FEET; THENCE SOUTH 18035'08" EAST 176.93
FEET; THENCE SOUTH 00034'07" WEST 178.88 FEET; THENCE SOUTH 19009'21"
WEST 338.98 FEET; THENCE SOUTH 84055'54" WEST 227.56 FEET; THENCE
SOUTH 05004'06" EAST 174.32 FEET; THENCE SOUTH 15029'10" WEST 205.73
FEET; THENCE NORTH 89042'48" EAST 816.74 FEET; THENCE SOUTH 72027'42"
EAST 573.68 FEET; THENCE SOUTH 76044'06" EAST 299.82 FEET; THENCE
NORTH 86001 '31" EAST 565.57 FEET; THENCE SOUTH 90000'00" EAST 118.45
FEET; THENCE NORTH 52015'21" EAST 238.87 FEET; THENCE SOUTH 80023'31"
EAST 145.72 FEET; THENCE SOUTH 57059'05" EAST 338.94 FEET; THENCE
SOUTH 86040'56" EAST 324.50 FEET; THENCE SOUTH 64023'41" EAST 479.65
FEET; THENCE ALONG THE ARC OF A NON-TANGENT CURVE, THE RADIUS
POINT OF WHICH BEARS NORTH 69000'53" EAST, CONCAVE TO THE
NORTHEAST, HAVING A RADIUS OF 559.94 FEET, THROUGH A CENTRAL
ANGLE OF 16017'59", AN ARC LENGTH OF 159.29 FEET; THENCE SOUTH
37017'05" EAST 53.18 FEET; THENCE SOUTH 52046'22" WEST 54.55 FEET;
THENCE SOUTH 62026'35" EAST 64.98 FEET; THENCE ALONG THE ARC OF A
NON-TANGENT CURVE, THE RADIUS POINT OF WHICH BEARS NORTH
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01024'28" EAST, CONCA VB TO THE NORTH, HAVING A RADillS OF 450.00
FEET, THROUGH A CENTRAL ANGLE OF 11006'30", AN ARC LENGTH OF 87.24
FEET; THENCE NORTH 77029'03" WEST 57.82 FEET; THENCE ALONG THE ARC
OF A CURVE , CONCA VB TO THE SOUTH, HAVING A RADillS OF 1175.00
FEET, THROUGH A CENTRAL ANGLE OF 16041 '54", AN ARC LENGTH OF
342.44 FEET, TO A POINT OF NON-TANGENCY, THE RADillS POINT OF WHICH
BEARS SOUTH 04010'57" EAST; THENCE SOUTH 24046'42" WEST 41.26 FEET;
THENCE SOUTH 79018'27" WEST 36.60 FEET; THENCE NORTH 34014'51" WEST
45.12 FEET; THENCE SOUTH 84049'07" WEST 386.53 FEET; THENCE ALONG
THE ARC OF A CURVE, CONCAVE TO THE NORTH, HAVING A RADillS OF
1525.00 FEET, THROUGH A CENTRAL ANGLE OF 12024'50", AN ARC LENGTH
OF 330.42 FEET TO A POINT OF COMPOUND CURVATURE; THENCE ALONG
SAID COMPOUND CURVE, CONCAVE TO THE NORTH, HAVING A RADillS
OF1175.00 FEET, THROUGH A CENTRAL ANGLE OF 01050'23, AN ARC
LENGTH OF 37.73 FEET, TO A POINT OF NON-TANGENCY, THE RADTIJS
POINT OF WHICH BEARS SOUTH 05023'34" WEST; THENCE SOUTH 27037'39"
WEST 122.22 FEET; THENCE SOUTH 64056'28" WEST 152.60 FEET; THENCE
NORTH 54005'20" WEST 225.92 FEET; THENCE SOUTH 87040'43" WEST 91.81
FEET; THENCE ALONG THE ARC OF A NON-TANGENT CURVE, THE RADTIJS
POINT OF WHICH BEARS NORTH09~53'56" WEST, CONCAVE TO THE NORTH,
HAVING A RADTIJS OF 1225.00 FEET, THROUGH A CENTRAL ANGLE OF
06025'39", AN ARC LENGTH OF 137.42 FEET, TO A POINT OF NON-TANGENCY,
THE RADillS POINT OF WHICH BEARS NORTH 03028' 17" WEST; THENCE
SOUTH 23037'03" WEST 164.40 FEET; THENCE SOUTH 74001'35" WEST 195.64
FEET; THENCE NORTH 82039'32" WEST 204.10 FEET; THENCE NORTH
53044'04" WEST 255.59 FEET; THENCE SOUTH 82018'54" WEST 105.06 FEET;
THENCE SOUTH 19051'38" WEST 170.84 FEET; THENCE NORTH 89~7'OT'
WEST 115.61 FEET; THENCE NORTH 24059'58" WEST 154.13 FEET; THENCE
SOUTH 88055'16" WEST 216.17 FEET; THENCE SOUTH 19052'26" WEST 178.82
FEET; THENCE SOUTH 85017'16" WEST 320.99 FEET; THENCE NORTH
24024'25" WEST 140.61 FEET; THENCE SOUTH 86020'13" WEST 294.72 FEET;
THENCE SOUTH 48049'53" WEST 102.97 FEET; THENCE NORTH 66031'21"
WEST 232.99 FEET; THENCE NORTH 43002'38" WEST 241.96 FEET; THENCE
NORTH 74041 '36" WEST 484.10 FEET; THENCE SOUTH 81008'09" WEST 378.64
FEET; THENCE NORTH 41039'34" WEST 426.98 FEET; THENCE NORTH
60033'37" WEST 260.44 FEET; THENCE SOUTH 78003'55" WEST 380.38 FEET;
THENCE SOUTH 53016'10" WEST 2.43 FEET; THENCE ALONG THE ARC OF A
CURVE, CONCAVE TO THE SOUTHEAST, HAVING A RADillS OF 389.00,
THROUGH A CENTRAL ANGLE OF 26002'14", AN ARC LENGTH OF 176.78
FEET; THENCE SOUTH 27013'56" WEST 74.74 FEET; THENCE, ALONG THE ARC
OF A NON-TANGENT CURVE, THE RADillS POINT OF WHICH BEARS SOUTH
69001'00" EAST, CONCAVE TO THE EAST, HAVING A RADillS OF 650.00 FEET,
THROUGH A CENTRAL ANGLE OF 04029'19", AN ARCH LENGTH OF 50.92
FEET; THENCE SOUTH 16029'42" WEST 18.85 FEET; THENCE NORTH 74030'24"
WEST 300.19 FEET; THENCE NORTH 67022'45" WEST 458.31 FEET; THENCE
NORTH 76011 '25" WEST 458.62 FEET; THENCE NORTH 87058'44" WEST 407.40
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FEET; THENCE NORTH 76012'50"WEST 301.13 FEET; THENCE NORTH 81006'38"
WEST 222.75 FEET; THENCE NORTH 55021'20" WEST 274.44 FEET; THENCE
SOUTH 70039'55''WEST 123.83 FEET; THENCE NORTH 03008'04" EAST 558.44
FEET; THENCE SOUTH 88022'02" EAST 890.26 FEET; THENCE NORTH 01037'58"
EAST 583.44 FEET; THENCE NORTH 62027'25" EAST 539.69 FEET; THENCE
ALONG THE ARC OF A NON-TANGENT CURVE, THE RADIUS POINT OF
WHICH BEARS NORTH 24024'16" EAST, CONCAVE TO THE NORTHEAST,
HAVING A RADIUS OF 8030.00 FEET, THROUGH A CENTRAL ANGLE OF
00020'22", AN ARC LENGTH OF 47.56 FEET TO A POINT ON A REVERSE
CURVE; THENCE ALONG THE ARC OF A REVERSE CURVE, CONCAVE TO
THE SOUTHWEST, HAVING A RADIUS OF 1570.00 FEET, THROUGH A
CENTRAL ANGLE OF 06024'00", AN ARC LENGTH OF 175.37 FEET, TO A POINT
OF NON-TANGENCY, THE RADIUS POINT OF WHICH BEARS SOUTH 18020'38"
WEST; THENCE SOUTH 62027'25" WEST 341.72 FEET; THENCE NORTH
75052'39" WEST 963.67 FEET; THENCE NORTH 00030'45" WEST 319.35 FEET;
THENCE NORTH 00050'31" EAST 1362.44 FEET TO THE POINT OF
BEGINNING.
CONTAINING 444.83 ACRES ( 19,376,631- SQ.. FT.) MORE OR LESS.
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EXHIBIT B
P / A Design Resources
GHAD Boundary Exhibit
4748.1.500.01
November 1,2006
~) l) g :;)...
ENGEO
INCORPORATED
DRAFT
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MANUEL MACHADO
APN 85A-1400-001-03
EAST SA Y REGIONAL
PARK DISTRICT
APN 85A-2400-001-05
ACCEPTED 1/4 CORNER
ACCEPTED 1/4 CORNER
COUNTY OF ALAMEDA
S89029'04UE 2594.61'
S89033'52"E 1715.15'
CITY OF DUBLIN
444.83t ACRES TOTAL
EXISTING
SCHAEFER
RESIDENCE
SERIES NO.
99-131918
5 30r ?;z.
EAST SA Y REGIONAL
PARK DISTRICT
APN 85A-2400-004-01
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4 3
TRACT 6765
SCHAEFER RANCH
A PORTION OF SECTIONS 3 & '" TOWNSHIP 3
SOUTH, RANGE 1 WEST,
MT. DIABLO BASE AND MERIDIAN.
CITY OF DUBLIN
ALAMEDA COUNTY, CALIFORNIA
ft~ Design Resources, Inc.
'714. Plonlng _ Eng/nHrlng _ SUtWylng
~
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T.2S.
R.1.W.
34
ACCEPTED 1/4 CORNER
T.SS.
R.tW.
2700 YgntJclo VtJlley RotJd, Suite '00
WtJlnut Creek. CtJllfornltJ 94598-3462
SCALE: 1" :: 400'
TEL (925} 210-9300
NOVEMBER, 2006
EAST SA Y REGIONAL
PARK DISTRICT
APN 941-0018-008
~
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800
EAST SA Y REGIONAL PARK DISTRICT
APN 941-0018-009
INTERSTATE 580
COUNTY OF
ALAMEDA
EXHIBIT '8'
GHAD BOUNDARY EXHIBIT
SHEET 1 OF 2
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LINE TABLE
LINE LENGTH BEARING
Lt 145.11 S48 "34 '13 "E
L2 35.93 S09"59'09"E
L3 108.23 SI6"19'16"W
L4 25.00 S73"40'44"E
L5 438.12 S41"19'00"E
L6 249.89 S32"04'20"E
L1 497.44 SI8"05'49"E
L8 502.81 S02 "20 '33 "E
L9 176.93 SI8"35'08"E
LtO 178.88 SOO "34 'orw
LtI 338.98 SI9"09'21"W
Lt2 227.56 S84 "55'54"W
Lt3 174.32 S05"04'06"E
Lt4 205.13 SI5"29'10"W
Lt5 816.14 N89 "42'48 "E
Lt6 573.68 S72"21'42"E
Lt7 299.82 S76"44'06"E
Lt8 565.57 N86"0 1'31"E
Lt9 118.45 S90 "00 '00 "E
L20 238.87 N52"15'21"E
L21 145.12 S80"23'31"E
L22 338.94 S5r59'05"E
L23 324.50 S86"40'56"E
L24 479.65 S64"23'41"E
L25 53.18 S3rl1'05"E
L26 54.55 S52"46'22"W
L27 64.98 S62"26'35"E
L28 57.82 N7r29'03"W
L29 41.26 S24"46'42"W
L30 36.60 S79"18'2rW
L31 45.12 N34"14'51"W
L32 386.53 S84"49'OrW
L33 122.22 S2r37'39"W
L34 152.60 S64"56'28"W
L35 225.92 N54"05'20"W
L36 91.81 S8r40'43"W
L37 164.40 S23"31'03"W
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P:\Orawings\03024-20 Schaefer Ranch\Final Map\03024-FM.dwg, 11/1/2006 1:58:47 PM, Station e. PIA Design Resources, Inc.
LINE TABLE
LINE LENGTH BEARING
L38 195.64 S74"01'35"W
L39 204.10 N82"39'32"W
L40 255.59 N53 "44 '04"W
L41 105.06 S82"18'54"W
L42 170.84 SI9"51'38"W
L43 115.61 N89"21'OrW
L44 154.13 N24"59'58"W
L45 216.17 S88"55'16"W
L46 178.82 SI9"52'26"W
L47 320.99 S85"11'16"W
L48 140.61 N24 "24 '25"W
L49 294.12 S86"20'13"W
L50 102.97 S48 "49'53 "W
L51 232.99 N66"31'21"W
L52 241.96 N43"02'38"W
L53 484.10 N74"41'36"W
L54 378.64 S81'08'09"W
L55 426.98 N41"39'34"W
L56 260.44 N60 "33 '3rW
L57 380.38 S78"03'55"W
L58 18.85 SI6"29'42"W
L59 300.19 N74"30'24"W
L60 458.31 N6r22'45"W
L61 458.62 N76"11'25"W
L62 407.40 N87'58'44"W
L63 301.13 N76"12'50"W
L64 222.15 N81"06'38"W
L65 274.44 N55 '21'20 "W
L66 123.83 S70"39'55"W
L67 558.44 N03"08'04"E
L68 890.26 S88"22'02"E
L69 583.44 NOI'31'58"E
L10 539.69 N62'27'25"E
L11 341.12 S62'27'25"W
L12 319.35 NOO"30'45"W
L13 2.43 S53"16'10"W
L14 74.14 S21"13'56"W
CURVE
CI
C2
C3
C4
C5
C6
C7
C8
C9
C10
CII
C12
C13
EXHIBIT 'B'
GHAD BOUNDARY EXHIBIT
CURVE DATA
DEL TA RADIUS
59"27'40" 172.50'
38'35'04" 237.50'
26"18'25" 237.50'
16'11'59" 559.94'
11'06'30" 450.00'
16"41'54" 1175.00'
12"24'50" 1525.00'
1"50'23" 1175.00'
6"25'39" 1225.00'
26'02'14" 389.00'
0"20'22" 8030.00'
6'24'00" 1570.00'
4'29'19" 650.00'
510 z~
LENGTH
179.02'
159.94'
109.05'
159.29'
81.24'
342.44'
330.42
37.73'
137.42'
176.18'
47.56'
175.31'
50.92'
TRACT 6765
SCHAEFER RANCH
A PORTION OF SECTIONS 3 & 4, TOWNSHIP 3
SOUTH, RANGE t WEST,
MT. DIABLO BASE AND MERIDIAN.
CITY OF DUBLIN
ALAMEDA COUNTY. CALIFORNIA
ft~ Design Resources, Inc.
'7"~ PI.nnlng - Engineering - Surveying
2700 Ygnaclo Vall"y Road. Suit" 100
Walnut Cr"ak, California 94598-3462
TEL (925) 210-9300
NOVEMBER, 2006
SHEET 2 OF 2
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ENGEO
INCORPORATED
PIA Design Resources
Open Space Exhibit
4748.1.500,01
November 1,2006
DRAFT
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PLATE 1
PIA Design Resources
Parcel Designation Plan
4748.1.500.01
November 1, 2006
670 r ~;<,
ENGEO
INCORPORATED
DRAFT
G.H.A.D. PARCEL DESIGNA TION PLAN
CITY OF DUBLIN, CALIFORNIA
DATE: AUGUST 16, 2006
PLA TE 1
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'/'
EXIST. SCHAEFER
RESIDENCE
PARCEL '/'
L__
Ul
lk.
LEGEND
PARCEL 'C-1'
G.H.A.D. OPEN SPACE PRESERVED WITH
CONSERVA TlON EASEMENT OVERLA Y ( ZONE ~')
G.H.A.D. OPEN SPACE WITH CONSERVATION EASEMENT OVERLAY (ZONE 'B')
@,1i.c
E.B.R.P.D. STAGING AREA WITH NO CONSERVA TION EASEMENT
CITY PARK PARCELS
STORM WATER DETENTION BASIN AND ACCESS
ROAD
Design Resources. Inc.
Planning _ Engineering _ Surveying
POND
DEVELOPMENT
SCALE: 1 If = 200 '
~ I
o 100 200 400
2700 Ygnacio Valley Road, Suite 100
Walnut Creek, California 94598-3462
TEL 1925} 210-9300
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PLATE 2
ENGEO Incorporated
Geologic Map of Schaefer Ranch
4748.1.500.01
November 1,2006
5'~ .L: 0--.,
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ENGEO
INCORPORA TED
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ENGEO
INCORPORATED
APPENDIX A
ENGEO Incorporated
Water Quality - Detention Basin Monitoring and Maintenance
Schaefer Ranch, Dublin, California
August 15,2006
4748.1.500.01
November 1, 2006
DRAFT
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Project No.
4748.1.500.01
November 1, 2006
Mr. Albert Seeno III
Schaefer Ranch Holdings LLC
4061 Port Chicago Highway, Suite H
Concord, CA 94520
Subject:
Schaefer Ranch
Dublin, California
WATER QUALITY - DETENTION BASIN MONITORING
AND MAINTENANCE
Dear Mr. Seeno:
As requested, we have prepared monitoring and maintenance recommendations for three Water
Quality-Detention Basins within the Schaefer Ranch development property in Dublin, California.
This is intended as a working document for use during maintenance of the water quality-
detention basins. The basins are designed as water quality and detention facilities to control peak
flood flows from the site. Maintenance of the basins will include, but not be limited to,
erosion/slope protection, vegetation management, sediment accumulation, trash/debris removal
and inspections of the inlet and outlet structures. The detention basins will be owned and
maintained by the Schaefer Ranch Geologic Hazard Abatement District (GHAD).
We are pleased to have been of service to you on this project and are prepared to consult further
with you and your design team.
Very truly yours,
ENGEO INCORPORATED
Prepared by:
Reviewed by:
J. Brooks Ramsdell
Senior Engineering Geologist
Theodore P. Bayham
Principal Engineer
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INTRODUCTION..................................................................... .......................................... .... ...... 1
Monitoring Schedule.................................................................................................... ........... 2
General Maintenance and Monitoring ............ ....... .............................. ............................. ....... 3
Inlet and Outlet Structures................................................................................................ 3
Detention Basin Embankments................. ....................................................................... 4
Vegetation................................................ ......................................................................... 4
Maintenance of Access Roads................................................................................ .......... 4
Fencing Repair.................................................................................................................. 5
Mosquito Abatement........................................................................................................ 5
Desilting and Clearing of Basin....................................................................................... 5
Detention Basin Catchment Area Inspection and Monitoring ......................................... 6
Emergency Response and Scheduled Remedial Repair .......................................................... 6
MONITORING REPORT
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INTRODUCTION
The purpose of this document is to provide a framework for the management and maintenance of
the Water Quality - Detention Basin at the Schaefer Ranch development. The three detention
basins are located throughout the Schaefer Ranch development property-one being near Dublin
Boulevard on the western edge of the property, one being near Dublin Boulevard in the south-
central portion of the property, and one east of 'Road A' on the eastern portion of the property.
The detention basins will be used to mitigate peak flows from the surface runoff on the subject
site.
Basin A is located in the western portion of the development, directly north of Dublin Boulevard.
The surrounding northwestern to eastern slopes serve as inlets for the detention basin. The outlet
for this basin is centrally located on the southern boundary of the basin, and runs westerly.
Interior slopes for the basin are planned to be up to 30 feet high with a slope gradient of
2: 1 (horizontal:vertical). An approximately 15-foot-wide bench extends around the top of the
debris basin berm on the south western boundaries of the basin. Slopes on the other side of the
road are proposed at a 2.5:1 gradient, sloping down to the west. Slopes to the east of the basin are
at a 2: 1 gradient, and are approximately 30 feet high.
Basin B, consisting of a water quality basin and a detention basin, is located in the south-central
portion of the development between Schaefer Road and Dublin Boulevard. The inlets for Basin
B are located northeast and east of the basin. The outlet for this basin is centrally located on the
western boundary of the basin, and runs westerly. The outlet for Basin B discharges into a new
closed conduit system. Interior slopes for the basin are planned to be up to 30 feet high with a
slope gradient of 3:1 (horizontal:vertical). An approximately 15-foot-wide bench extends around
the top of the debris basin berm on the south and western boundaries of the basin.
Basin C, consisting of a water quality basin and a detention basin, is located on the eastern
portion of the development, directly southeast of Road 'A.' The inlets are centrally located on
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the western side of the basin. The outlet for this basin is located on the northern point of the
basin, and runs northwesterly. The outlet for Basin C discharges into a new closed conduit
system. Interior slopes for the basin are planned to be up to 40 feet high with slope gradients of
2.5: 1 (horizontal:vertical).
Monitoring Schedule
Quarterly monitoring during January, April, July and October is planned, with additional
monitoring within two working days after significant storm events (i.e. one inch of rainfall in a
12-hour period). Technicians retained by the GHAD will carry out site inspections and utilize the
Monitoring Report Form included at the back of this manual. Personnel and subcontractors
involved in detention basin management will be trained on reading the staff gauge, proper
pruning/cutting techniques, and inspection measures by the GHAD. A sample Inspection Report
is included at the end of this letter.
Each water quality basin has been designed to meter out detained runoff over 48 hours when the
basin water surface elevation is at the side opening flowline ofthe inlet pipe riserloverflow
structure. At this water surface elevation, residence time longer than 48 hours could be an
indication of sediment buildup (resulting in loss of actual water storage volume) or blockage of
outlet pipe. In this case actions should be taken to investigate the cause and corrective actions
should be implemented.
Sediment accumulation measurements will monitor the rate of sedimentation quarterly in the
detention basin and identify the need for removal. Some sedimentation is expected within the
basin; however, removal is planned only to the extent necessary for proper basin function.
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General Maintenance and Monitoring
Procedures for the following maintenance and monitoring items are presented in the following
section:
. Inspection and repair of inlet and outlet structures.
. Stabilization andlor repair of eroded areas or failures of the embankment surrounding the
Detention Basins.
· Pruning/cutting ofthe vegetation within and surrounding the Detention Basin.
. Maintenance of all access roadways.
· Monitoring any perimeter fencing for public safety.
· Mosquito Abatement.
· Sediment accumulation measurement and removal.
Inlet and Outlet Structures. Maintenance of inlet and outlet structures will involve the clearing
of debris and repair of the trash rack structure, as required to allow passage of storm flows. The
inlet and outlet structures should be observed during or immediately after large storm events to
avoid prolonged blockage. Any observed damage or apparent inoperability of the structures will
be reported to the GHAD Manager immediately.
In the event that the primary detention basin outlet is rendered inoperable during a major storm
event, the emergency overflow spillway should be allowed to operate as designed to pass the
storm flows. Emergency maintenance of the inoperable outlet structure should be undertaken at
such time, and with the equipment, that the GHAD Manager deems appropriate.
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Detention Basin Embankments. Maintenance shall involve observation of the detention basin
embankment. The detention basin slopes should be inspected for obvious signs of vertical andlor
horizontal displacements. All embankment sides should be free of erosion, rills, slumps or
landslides. Any observed slope displacement should be reported to GHAD Manager
immediately. Any irrigation systems are to be monitored for proper function. Leaking or
malfunctioning irrigation systems will be repaired within two days of inspection.
Vegetation. Vegetation that does not preclude the proper functioning of the Detention Basins
should be allowed on the floor of the basin to aid in the trapping of sediment. Although
vegetative growth is generally encouraged, excess vegetation (defined as shrub and tree growth
in excess of 5 feet in height) must be removed from the basin floor by pruning. Herbicides will
not be used in the basin unless absolutely necessary. Such use shall be governed by all
applicable rules and regulations.
Vegetation removal will be accomplished by prulllng with hand labor, unless aggreSSIve,
non-native species become pervasive, in which case other methods of removal can be initiated at
the discretion of the GHAD Manager. Activities will involve only the cutting and removing of
vegetation above the ground, e.g. mowing, rotary cutting, and chainsawing, where the activity
neither substantially disturbs the root system nor involves mechanized pushing, dragging, or
other similar activities. No heavy equipment will be used within the detention basin for routine
vegetation control. The pruning debris will be removed from the basin in burlap or canvas
bundles and trucked to an authorized dump site reviewed and approved by the GHAD Manager.
Vegetation removed or destroyed during maintenance will be allowed to re-establish naturally
without replanting.
Maintenance of Access Roads. Maintenance of access roads and top of berm bench, as shown on
the improvement plans, will involve repair of excessive bumps, cracks and depressions such that
maintenance vehicles can easily navigate the roads. The roadways will be inspected on a
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semi-annual basis and repaired as needed. Any damage to or failures of the embankments near
the road will be reported to the GHAD Manager immediately.
Fencing Repair. Maintenance of fencing involves repair of all gaps, tears, sags and breaks such
that public safety is provided. All perimeter fencing will be monitored quarterly and maintained
in good condition without breaks or damage.
Mosquito Abatement. It is possible that mosquito abatement will not be required in the water
qualityldetention basins due to the drying cycle in the summer months; however, if homeowner
complaints are received by the GHAD, the GHAD will contact Alameda County Vector Control.
Desilting and Clearing of Basin. Detention basin floors must be regularly cleared of excess
sediment and excess vegetation to enable proper flow characteristics. Failure to do so can create
flood hazards. The floor of the detention basin should be monitored on a semi-annual basis. If
sediment in excess of 18 inches or 10 percent of the storage capacity, whichever is greater, has
accumulated above design grades, the sediment should be removed. Sediment accumulation will
be measured with installed staff gauges. If vegetation in excess of 5 feet in height is present, it
will require removal as described in the Vegetation section. Vegetation accumulation will be
measured with a tape measure in at least four locations within the basin floor. Prior to sediment
removal or vegetation pruning, the procedure should be reviewed and authorized by the GHAD
Manager.
If sediment in excess of 18 inches or 10 percent of the storage capacity, whichever is greater, has
accumulated above design grades, sediment removal shall be undertaken before the next winter
season. The dry season is the preferred time of year for sediment removal. Sediment removal
for routine maintenance will be with small mechanized equipment, hand labor and wheelbarrows
as much as possible subject to compliance with regulatory agency requirements. Emergency
repairs may require use of larger equipment including, but not limited to, excavators. Sediment
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will be removed in small sections, with as little disturbance to existing vegetation as possible.
No heavy equipment will be used within the detention basin without permission from the GHAD
Manager.
The sediment should be disposed of in a legal manner. In general, due to the steepness of the site,
limited areas will be available to place the material from the detention basin on open space areas
of the parcel and any proposed disposal areas should be reviewed by the GHAD Manager in
consultation with a qualified biologist as necessary. The sediment will not be placed within
20 feet of a creek or drainage. The sediment will not be placed on sloping ground, or any area of
sensitive wildlife habitat. After spreading, the sediment will be hand seeded and covered with
straw mulch.
Detention Basin Catchment Area Inspection and Monitoring. Monitoring of the detention basin
shall involve visual inspection of the detention basin containment area and piezometer
measurement if installed. The detention basin catchment area should be inspected for obvious
signs of vertical andlor horizontal displacements. The base of the detention basin should be free
of erosion, rills, slumps or landslides.
Emergency Response and Scheduled Remedial Repair
Emergency response and scheduled repair expenditures are to be prioritized at the discretion of
the GHAD Manager based upon available funds and the approved operating budget. When
available funds are not sufficient to undertake all of the identified remedial and preventive
stabilization measures, the expenditures are to be prioritized as follows in descending order of
priority:
A. Prevention, mitigation, abatement or control of hazards that have either damaged or pose a
significant threat of damage to the detention basin embankments or spillway.
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B. Prevention, mitigation, abatement or control of hazards which have either damaged or pose a
significant threat of damage to ancillary structures, including but not limited to the inlet and
outlet pipes.
C. Prevention, mitigation, abatement or control of geologic hazards which have either damaged
or pose a significant threat of damage to the detention basin.
The techniques which may be employed by the Schaefer Ranch GHAD to prevent, mitigate,
abate, or control hazards include, but are not limited to, the following:
1. Repair, maintenance or replacement of inlet or outlet control valves and structures.
2. Stabilization (either partial or total) of levee embankments by removal and replacement with
compacted, drained fill.
3. Construction of erosion control measures. Whenever feasible, bioengineering techniques
will be utilized and are preferred over hard armor.
4. Placement of subsurface drainage devices (e.g. underdrains, or horizontal drilled drains).
5. Slope correction (e.g. gradient change, slope trimming or contouring).
6. Construction of additional surface ditches andlor detention basin, sediment traps, or backfill
of eroded channels.
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MONITORING REPORT
Schaefer Ranch
Dublin, California
WATER QUALITY - DETENTION BASIN OPERATIONS AND MAINTENANCE
SITE MONITORING AND MAINTENANCE
REPORT FORM
(TO BE COMPLETED QUARTERLY IN JANUARY, APRIL, JULY AND OCTOBER AND
AS NECESSARY DURING HEAVY RAINFALL)
Inspector:
Weather Conditions:
Days since last rainfall:
Basin Water Level:
Date:
Dry season? _ Wet season?
Sediment Accumulated since Last Monitoring Event
I~TORED YES NO NIA COMMENTS/ SUGGESTED MA. .."'TnT.'
ROL
1. Are inlet and
outlet structures
functioning properly,
allowing the basin to
drain and are they in
satisfactory
condition?
2. Are access roads
in satisfactory
condition?
3. Is all perimeter
fencing in good
condition without
breaks, gaps or
damage?
4. Have the debris
racks been cleaned
and are they in good
condition?
5. Are embankments
surrounding the
basin in good
condition without
rills or failures?
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MONITORED YES NO N/A COMMENTS/ SUGGESTED MAINTENANCE
CONTROL
6. Is the vegetation
less than 5 feet in
height?
7. Are embankment
slopes protected with
mulch or vegetation?
8. Has sediment
removal been
undertaken in the
last 3 months?
9. Is there evidence
of chemical sheen or
odor, contaminated
runoff, litter or
blowing debris in or
near the basin?
10. Do any basin
devices require
maintenance to
provide more
effective function?
11. Are there signs
of leaking irrigation
systems?
12. Are there any
signs of vandalism?
13. Are mosquitoes
evident?
14. Has mosquito
abatement been
undertaken since the
last monitoring
event?
15. Are there
remedial/repair tasks
that should be
undertaken in the
near future?
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MONITORED
CONTROL
16. Is there evidence
or information
received in the last 3
months to indicate a
len hy drain time?
YES NO N/A COMMENTS/SUGGEST
"No" answers to Items 1-7 or "Yes" answers to Items 8-16 require a corrective action noted
on Page 3.
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WATER QUALITY - BASIN OPERATIONS AND MAINTENANCE
SITE MONITORING AND MAINTENANCE
REPORT FORM (CONTINUED)
CORRECTIVE ACTIONS UNDERTAKEN
(If none required, enter date and "none")
DATE
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DEFICIENCY NOTED
CORRECTIVE ACTION
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DATE
DEFICIENCY NOTED
CORRECTIVE ACTION
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APPENDIX B
ENGEO Incorporated
Site Geology
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Site Geology
Regional geologic maps of the area have been prepared by Dibblee (1980), Crane (1988) and
Graymer (1996). The most recent regional map prepared by Graymer indicates that the site is
underlain by late and middle Miocene rocks of the Briones Formation and undivided middle
Miocene marine rocks of the Monterey Group including the Rodeo Shale, Hambre Sandstone,
Tice Shale and Ours an Sandstone.
Major folds in the site vicinity include the Kaiser Creek Syncline and the Knife Anticline,
located north of the property, as shown on Plate 2. Two smaller unnamed folds that form a
syncline-anticline pair are present on the south limb of the Kaiser Creek Syncline as shown on
Plate 2. The axis of the syncline passes through the center of the Schaefer Ranch Property in a
northwesterly direction, trending along the center of Marshall Canyon, passing through the ridge
under Donlan Point (the "axis" is the center line of the fold; beds dip in opposite directions on
either side of the fold axis). The synclinal axis extends to near the south site boundary, passing
below the proposed Dublin Boulevard Extension. In the site vicinity, the major folds are
commonly associated with low-angle compressional faults known as "thrust faults", including
the Bollinger and Miller Creek Faults (Crane, undated, Dibblee, 1980, and Wagner, 1976). The
thrust faults are thought to be the result of the same regional compressional forces that have
caused the folding of the rocks in the East Bay Hills block. None of the thrust faults mapped in
the site vicinity are considered to be active by the State.
Detailed mapping of the property included within the GHAD boundaries was completed as part
of the Geotechnical Investigations completed by AKA (1997) and ENGEO, Incorporated (2004).
The results ofthese investigations are included in the geologic descriptions.
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Geologic Units
Undocumented Fill. There are existing undocumented fills on the property associated with stock
ponds, roads, and existing structures. The most extensive undocumented fill deposit appears to
be at the entrance to the property at Schaefer Ranch Road. Approximately 25 feet of stiff clay
interpreted to be undocumented fill was encountered in this location. It appears that this fill is
likely associated with the construction of the adjacent Interstate 580. Proposed remedial grading
includes the complete removal and replacement of this undocumented fill as well as other less
extensive undocumented fill deposits on the site within the grading limits ofthe project.
Alluvium. Most of the creeks typically have steep, V-shaped channels incised into bedrock or
landslide debris, with no significant alluvial deposits. Minor deposits of modern alluvium
associated with the existing creeks occur in the lower reaches of Marshall Canyon and Wagon
Wheel Canyon. These deposits appear to consist of 10 to 20 feet of relatively compressible,
sandy to gravelly clay. A more significant deposit of alluvium occurs at the entrance to the
property at Schaefer Ranch Road, where the base of the stiff silty to sandy clay was encountered
at 35 feet and 45 feet below the surface.
A soil deposit identified as an old alluvial terrace occurs along the existing entrance road on the
south side of the ridge, and is well exposed in a deep erosion gully. Exposures in the gully
consist of stratified silty sand with pebble lenses. ENGEO and AKA borings in the terrace
deposit record thicknesses varying from less than 10 feet to 44 feet. The deposit is dense and
relatively incompressible.
Residual Soil and Colluvium
The site bedrock is typically mantled with 3 to 5 feet of residual soil formed from weathering
and decomposition of the underlying bedrock. The weathering of the bedrock on the site
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typically produces a fine-grained soil containing expansive clays. Colluvium is a soil deposit
formed from downslope movement and deposition of residual soil by such processes as
slopewash, sloughing/shallow sliding and creep. Mappable deposits of colluvium (typically
thicker than 5 feet) occur in most swales and ravines and at the bases of many slopes on the
property. The colluvium typically consists of expansive silty clay with rock fragments. The
composition of the colluvium varies with the composition of the underlying bedrock. Within
swales, the colluvial deposits tend to be relatively thicker and may be subject to flow or slip
downslope.
Landslides
Landslide deposits consist of masses of unconsolidated material andlor bedrock that have moved
downslope by sliding, falling, or flowing. Many landslides, ranging in size from very small to
large, occur on the site. The landslides include earth flows, debris flows, bedrock slumps and
translational landslides.
Shallow (less than 5 feet thick) to moderately deep (5 to 20 feet thick) earth flows are the most
prevalent types of landslide at the site. Shallow landslides occur on the steeper slopes, along
drainages and in swales. Larger, deep (greater than 20 feet) and deep-seated landslides (greater
than 30 feet) were also identified at the site.
Bedrock
Upper Miocene Marine and Nonmarine Sediments, Undifferentiated
The rocks underlying the center of the syncline, on the southwest side of Marshall Canyon,
appear to consist of interbedded claystone, siltstone and clay-cemented sandstone, including both
marine and nonmarine deposits. This unit was previously mapped by Dibblee (1980) as Pliocene
nonmarine rocks and by Graymer (1996) as "unnamed Miocene continental rocks". The
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sandstone and siltstone units are weak to moderately strong and highly to moderately fractured.
Based on our experience with this mapped unit in the site vicinity and in projects to the north, we
would expect that it could contain occasional layers of weak, relatively expansive claystone.
Briones Formation
The marine Briones Formation, which underlies the upper portions of the highest site ridges,
consists mainly of brown, thickly-bedded, moderately-strong to strong, clay-cemented, fine- to
medium-grained lithic sandstone. Some units contain minor thin beds of siltstone, friable
sandstone and pebble conglomerate.
The most resistant beds in the Briones Formation are gray-brown, strong to very strong,
carbonate-cemented, medium- to coarse-grained sandstone that contains abundant shell
fragments.
Miocene Marine Sediments
In the south and east portions of the property, the slopes are underlain by interbedded marine
sandstone and siltstone of the undivided Monterey Group. As mapped by Dibblee (1980) this
unit is divided into an upper unit of sandstone with interbedded siltstone (Tmss) and a lower unit
consisting mainly of siltstone with minor interbedded sandstone (Tmsl). The sandstone is thickly
bedded, brown, weak to moderately strong, fine grained and clay cemented. The near-surface
exposures of sandstone are moderately to highly fractured; fracture spacing decreases with depth.
The siltstones are gray-brown to gray, massive to thinly bedded and weak. The siltstone locally
grades to clayey siltstone and claystone.
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Groundwater
At the time of subsurface work groundwater has been encountered between 12 to 30 feet below
the ground surface. In general, the shallow groundwater was encountered locally within areas of
colluvium or deeply weathered bedrock. This water appears to be perched on the underlying
bedrock. Fluctuations in groundwater levels may occur seasonally and over a period of years
because of precipitation, changes in drainage patterns, irrigation and other factors. Future
irrigation may cause an overall rise in groundwater levels.
Seismic Sources
The seismicity of the Bay Area is dominated by the major active strike-slip faults. No State of
California-zoned active I faults are mapped crossing the GHAD property. The nearest State of
California-zoned, active2 faults are the Calveras fault located approximately 1 mile northeast of
the site and the Hayward Fault located approximately 6 miles southwest of the site. The Dublin
fault, a local strike-slip fault that passes 2,500 feet east of the property, is not considered active
by the State..
The Working Group on Northern California Earthquake Probabilities (WGEP, 2003) recently
evaluated the seismicity of the Bay Area. The WGEP estimated a 30-year probability of a
moment magnitude (Mw) 6.7 earthquake on one of the active Bay Area Faults of 62 percent. The
30-year probability of a 6.7 Mw earthquake for the Calaveras and Hayward Faults were estimated
at 11 percent and 27 percent, respectively. As discussed in the geotechnical investigations, there
1 An active fault is defined by the State Mining and Geology Board as one that has had surface displacement within
Holocene time (about the last 10,000 years) (Hart, 1994). The State ofCalifomia has prepared maps designating zones for
special studies that contain these active earthquake faults.
4748.1.500.01
November 1, 2006
DRAFT
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is a high probability that the site and any improvements will be subject to strong ground shaking
and some deformation of the site slopes during the lifetime ofthe project.
4748.1.500.01
November 1, 2006
DRAFT