HomeMy WebLinkAboutMINUTES - 06062006 - C.7 BOARD OF SUPERVISORS, AS GOVERNING
BOARD OF THE FLOOD CONTROL & WATER 0 n t ra
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CONSERVATION DISTRICT _ Costa
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FROM: MAURICE M. SHIU, CHIEF ENGINEER Count_::_:-••�•
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DATE: June 6, 2006
SUBJECT: ADOPT the Stonebridge Estates Sedimentation Basin Desilt Project Mitigated Negative Declaration
and Mitigation Monitoring Program in compliance with the California Environmental Quality Act
(CEQA); APPROVE the project and AUTHORIZE the Chief Engineer, Flood Control and Water
Conservation District,or designee,to advertise the project,Alamo area.(District III)[CDD-CP#04-
56] Project No. 7576-6D91707.
SPECIFIC REQUESI'(S)OR RE-COMMENDATION(S)&BACKGROUND AND JUS'T'IFICATION
RECOMMENDED ACTION:
FIND on the basis of the Stonebridge Estates Sedimentation Basin Desilt Project Mitigated Negative Declaration
initial Study and all comments received, as well as the staff responses contained herein,that there is no substantial
evidence the project will have a significant effect on the environment, and
ADOPT the Mitigated Negative Declaration and Mitigation Monitoring Program in compliance with the California
Environmental Quality Act,(the custodian of which is the Community Development Director who is located at 651
Pine Street, Martinez), and
DIRECT the Director of Community Development to file a Notice of Detenninatio with the County Clerk, and
Continued on Attachment: SIGNATURE:
RECO• MENDATION OF COUNTY ADMINISTRATOR ❑ RECOMMENDATION OF BOARD COMMITTEE
[APPROVE THER
r'
SIGNATURE(S):
ACTION OF BOA N VGtf%Y)L Orp, oZQ1Ofi
APPROVED AS R OMMENDED 0' OTHER ❑
I hereby certify that this is a true and correct copy of an action
VOT,I OF SUPERVISORS taken and entered on the minutes of the Board of Supervisors on
UNANIMOUS(ABSENT the date shown.
AYES: NOES:
ABSENT: ABSTAIN: ATTESTED: 11144V-2'e— 404re i
C:D:sj JOHN CULLEN, Clerk of the Board of Supervisors and County
ii:`•.fneSvc`\.I NVIIZO`••13O`:2006,(06-06-06)CEQA—Stonebridge_Desilt.docAdministrator
Orig.Dic:Public works(Environmental Section)
Contact: C'ollecn Culver-Jaffe,(313-2236)
cc: Administrator—Atte.E. Kuevor
Auditor-Controller By ,Deputy
Community Development—11.1_i
Public works: Flood Control—P.Detjens
Maintenance—R.Tavenicr
Environmental C.Culver-Jaffe
SUBJECT: ADOPT the Stonebridge Estates Sedimentation Basin Project Mitigated Negative Declaration
and Mitigation Monitoring Program in compliance with the California Environmental Quality Act; APPROVE
the project and AUTHORIZE the Chief Engineer, Flood Control and Water Conservation District, or designee,
to advertise the project, Alamo area. (District ITI)[CDD-CP#04-56] Project No. 7576-6D9F07
DATE: June 6, 2006
PAGE: 2 of 2
RECOMMENDED ACTION (continued):
AUTHORIZE the Chief Engineer to arrange for payment of a$25 fee to Community Development for processing,
and a S25 fee to the County Clerk for filing the Notice of Determination, and
DIRECT the Chief Engineer to arrange for the S1,250 Fish and Game filing fee to be transferred to the County
Clerk, and
APPROVE the Stonebridge Estates Sedimentation Basin Desilt project, and AUTHORIZE the Chief Engineer to
advertise the project.
FISCAL IMPACT:
The project will not impact County General Funds. The estimated project cost is $20,000, and will be funded by
Drainage Area 76A (100%).
REASONS FOR RECOMMENDATIONS AND BACKGROUND:
The project consists of desilting the sedimentation and detention basins back to design grade,and restoring the level
of stormwater treatment capability and flood protection they were intended to provide. The project is comprised of
two parts: the immediate project and the long term maintenance.The immediate project will desilt the sedimentation
basin and the road-cross culvert(Seraf x Road)that joins the sedimentation basin to the detention basin.Longi tenn
maintenance includes desilting of the detention basin. Because the site is a known and occupied red-legged frog
habitat, desilting of the detention basin to design grade will take place in three stages over at least three summer
seasons. This will allow two thirds of the detention basin to remain untouched at any one time and provide refiige for
the resident red-legged frog population. In addition,to minimize impact,willow cuttings will be installed following
the desilting of each third of the detention basin. The Flood Control District will also conduct routine and ongoing
maintenance in the basins and culvert. Maintenance activities likely to be necessary in the project area consist of
debris removal and weed abatement activities and limited silt removal from the basin areas and culvert every few
years. Real property transactions and utility relocations may be necessary in support of this project.
The project has been determined to be in compliance with the General Plan. A Mitigated Negative Declaration of
environmental significance pertaining to this project was published on 04/04/06. The Board has considered the
Mitigated Negative Declaration together with all comments received during the public review period.
CONSEQUENCES OF NEGATIVE ACTION:
Delay in approving the project will result in a delay of design and construction and ultimately project
implementation.
CONTRA PUBLIC WORKS DEPARTMENT
COSTA INITIAL STUDY
COUNTY OF ENVIRONMENTAL SIGNIFICANCE
PROJECT#7576 6D 9F07
CP# 04-56
PROJECT NAME: Stonebridge Estates Sedimentation Basin Desilt Project
PREPARED BY: Colleen Culver-Jaffe DATE: 03/15/06
APPROVED BY: (vat..—` I�^�'`~''- DATE: 03- 7-1- a(.
RECOMMENDATIONS:
( ) Categorical Exemption ( ) Negative Declaration
( ) Environment Impact Report Required (X) Mitigated Negative Declaration
The project will not have a significant effect on the environment. The recommendation is based
on the following: There is no substantial evidence, in light of the whole record before the
agency, that the project as revised may have a significant effect on the environment. (Sec.
15070(b) (1 and 2)).
What changes to the project would mitigate the identified impacts: See attached mitigation
in Biological Resources Section
USGS Quad Sheet: Diablo Base Map Sheet#Q-16 Parcel # N/A
GENERAL CONSIDERATIONS:
1. Location: The project is located on an unnamed creek in Stonebridge Estates, adjacent
to Serafix Rd., in the community of Alamo, in central Contra Costa County, at the far
eastern extension of Livorna Road, on the lower, northwestern slopes of Mt. Diablo. The
site is characterized by steep hillsides surrounding a narrow northwest-trending valley
(Fig. 1).
2. Project Description: The project consists of desilting the sedimentation and detention
basins back to design grade, and restoring the level of stormwater treatment capability
and flood protection they were intended to provide. The project is comprised of two
parts: the immediate project and the long term maintenance.
The immediate project (Figure 2) is intended to desilt the sedimentation basin and the
road cross culvert (Serafix Road) that joins the sedimentation basin to the detention
basin. The culvert will be desilted and retrofitted with a steel plate to reduce the flow of
water and allow a greater percentage of the silt to drop out of the flow before it passes
into the detention basin. These activities will maintain the stormwater treatment
capability of the sedimentation basin, and ensure that high flows can move efficiently
into the detention basin. Additionally, the access road into the detention basin will be
restored to facilitate work in the detention basin and at the road cross culvert. Material
excavated from the sedimentation basin may be used as fill to restore the access road.
In addition to desilting the sedimentation basin and the road cross culvert, long-term
maintenance includes desilting of the detention basin.
Sedimentation Basin: The Stonebridge Estates sedimentation basin was designed to
allow for sediment loads in storm flows to settle 'out prior to entry into the adjacent
C:\DOCUME-1\TMoreira\LOCALS-1\Temp\notesBAAA25\IS(02-28-06)final.doc _ ._
detention basin, thereby improving water quality and minimizing dredging maintenance
required within the detention basin. The sedimentation basin was last desilted in 2001.
Based on the amount of measured accumulated sediment within the sedimentation
basin, desilting is necessary in order to maintain the stormwater treatment capability of
the basin. The project consists of removing approximately 200 cubic yards of sediment.
Excavated material may be used in the reestablishment of the detention basin access
road. Any excavated material not used in the detention basin road reestablishment will
be placed in trucks and legally disposed of at a legal off-site upland location. The
sedimentation basin is expected to be dry during construction.
Serafix Road Cross Culvert: The culvert that joins the sedimentation basin and the
detention basin is approximately 50% filled with sediment. The sediment will be removed
utilizing hand tools or a vacuum truck. The excavated material will be placed in trucks
and disposed of at a legal off-site upland location. The culvert will be retrofit with a steel
plate welded to the upstream end to reduce the flow of water and allow a greater
percentage of the silt to drop out of the flow before it passes into the detention basin.
This will increase the stormwater treatment capability of the upstream sedimentation
basin and, in turn, reduce the frequency of required sediment removal in the
downstream detention basin. The culvert is expected to be dry during construction.
Detention Basin Access Road: The detention basin access road has deteriorated and
needs to be re-established to facilitate work at the culvert with the least impact possible.
This work will require approximately 650 cubic yards of fill (50 cubic yards within Corps
jurisdiction). Material excavated from the sedimentation basin may be used for re-
establishment of the detention basin access road.
Detention Basin: The detention basin was designed to hold back flood flows and provide
flood protection. Because the site is a known and occupied red-legged frog (RLF)
habitat, desilting of the detention basin to design grade will take place in three stages
over at least three summer seasons (Figure 3). This will allow two thirds of the detention
basin to remain untouched at any one time, and provide refuge for the resident red-
legged frog population. Additionally, to minimize impact, willow cuttings will be installed
following the desilting of each third of the detention basin. Sediment will be removed
utilizing back hoes and dump trucks.
All work associated with the project will be conducted during the dry season. Real
Property transactions and utility relocations may be necessary in support of this project.
3. Does it appear that any feature of the project will generate significant public
concern?
[] yes [X] no [] maybe (Nature of concern):
4. Will the project require approval or permits by other than a County agency?
[X] yes [ ] no Agency Name(s): Regional Water Quality Control Board (Water Quality
Certification), Department of Fish and Game (Streambed Alteration Agreement), U.S.
Army Corps of Engineers Nationwide Permit (including Section 7 Consultation).
5. Is the project within the Sphere of Influence of any city? No.
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Environmental Checklist Form
1. Project Title: Stonebridge Estates Maintenance Project
2. Lead Agency Name and Address: Contra Costa County Community Development Department
651 Pine St., Martinez, CA 94553
3. Contact Person and Phone Number: Colleen Culver-Jaffe (925) 313-2236
4. Project Location: The project is located in central Contra Costa County near the
town of Alamo.
5. Project Sponsor's Name and Address: Contra Costa County Flood Control and Water Conservation
District
255 Glacier Dr., Martinez CA 94553
6. General Plan Designation: Residential
7. Zoning: Open Space
8. Description of Project:
The Contra Costa County Flood Control and Water Conservation District is proposing to desilt the existing
detention and sedimentation basins in Stonebridge Estates, returning them to design grade. This project will be
comprised of both short and long term maintenance components which will take place over several
construction seasons. The immediate maintenance needs address desilting the sedimentation basin and the
Serafix Road cross culvert, as well as reestablishment of the detention basin access road. The long term
maintenance consists of desilting the detention basin. These activities will maintain the storm water treatment
capability of the sedimentation basin, as well as ensuring that high flows can move:efficiently into the detention
basin.
Sedimentation Basin Desilt (short term maintenance):
The immediate maintenance need consists of desilting the sedimentation basin back to design depth in order
to restore the level of water quality treatment it was intended to provide. The culvert that joins the
sedimentation basin to the detention basin will be desilted and retrofitted with a steel plate to reduce the flow of
water and allow a greater percentage of the silt to drop out of the flow before it passes into the detention basin.
These activities will maintain the stormwater treatment capability of the sedimentation basin, as well as
ensuring that high flows can move efficiently into the detention basin. Additionally, the access road into the
detention basin will be restored to facilitate work in the detention basin and at the Serafix Road cross culvert.
Material excavated from the sedimentation basin may be used as fill to restore the access road. Following.
construction, all disturbed areas will be seeded with a mix including appropriate native species.
Detention Basin Desilt (long term maintenance):
The long term maintenance addresses the need to desilt the detention basin to design grade. Because the
detention basin is a known and occupied red-legged frog (RLF) habitat, desilting of the detention basin will take
place in three stages over at least three summer seasons. This will allow two thirds of the detention basin to
remain untouched at any one time and provide refuge for the resident red-legged frog population. In addition,
to minimize impact, willow cuttings will be installed following the desilting of each third of the detention basin.
Following construction, all disturbed areas will be seeded with a mix including appropriate native species.
9. Surrounding Land Uses and Setting: Land surrounding the project area consists of horse ranches
and grazing land to the north and northeast and Mt. Diablo
Regional parkland to the east. To the south and the west is
residential development.
10. Other public agencies whose approval California Department of Fish and Game, US Army Corps of
(e.g., permits, financing approval, or Engineers, US Fish and Wildlife Service, Regional Water
participation agreement). Quality Control Board.
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ENVIRONMENTAL FACTORS POTENTIALLY AFFECTED:
The environmental factors checked below would be potentially affected by this project, involving at least one
impact that is a "Potentially Significant Impact" as indicated by the checklist on the following pages.
Land Use & Planning Transportation/Circulation Public Services
Population & Housing Utilities &Service
X Biological Resources Systems
Geological Problems Energy& Mineral Resources Aesthetics
Water Hazards Cultural Resources
Air Quality Noise Recreation
Mandatory Findings of No Significant Impacts
Significance Identified
DETERMINATION
On the basis of this initial evaluation:
I find that the proposed project COULD NOT have a significant effect on the environment, and a NEGATIVE
DECLARATION will be prepared.
I find that although the proposed project could have a significant effect on the environment, there will not be a
significant effect in this case because the mitigation measures described on an attached sheet have been
X added to the project. A MITIGATED NEGATIVE DECLARATION will be prepared.
I find that the proposed project MAY have a significant effect on the environment, and an ENVIRONMENTAL
IMPACT REPORT is required.
I find that the proposed project MAY have a significant effect(s) on the environment, but at least one effect (1)
has been adequately analyzed in an earlier document pursuant to applicable legal standards, and (2) has been
addressed by mitigation measures based on the earlier analysis as described on attached sheets, if the effect is
a "potentially significant impact" or "potentially significant unless mitigated." An ENVIRONMENTAL IMPACT
REPORT is required, but it must analyze only the effects that remain to be addressed.
I find that although the proposed project could have a significant effect on the environment, there.WILL NOT be
a significant effect in this case because all potentially significant effects (a) have been analyzed adequately in
an earlier Elk pursuant to applicable standards and (b) have been avoided or mitigated pursuant to that earlier
EIR, including revisions or mitigation measures that are imposed upon the proposed project.
.e,�-•--a M-moo.,.
3- . o
Signature Date
Contra Costa County
t.M W M.o R E i 1z �4 Community Development Department
Print Name
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SOURCES
In the process of preparing the Checklist and conducting the evaluation, the following references (which are
available for review at the Contra Costa County Community Development Department, 651 Pine Street 5th
Floor-North Wing, Martinez) were consulted:
1. Contra Costa County Resource Mapping System - Quad Sheet Panels for Mount Diablo Quadrangles,
CA
2. The County General Plan (July 2005) and EIR on the General Plan (2005-2020)
3. Contra Costa County Important Farmland Map 1998, California Department of Conservation Division of
Land Resources Protection, 1999
4. Soil Survey of Contra Costa County, Soil conservation Service, 9/77
5. FEMA 100-Year Floodplain Map
6. California Natural Diversity Data Base, California Department of Fish and Game, September 2005
7. Field Reviews and Project Description
8. Stonebridge Estates Special-Status Species Assessment Report conducted by Zentner and Zentner,
December, 2005
9. Stonebridge Estates Detention Basin Section 404 Jurisdictional Delineation by Zentner and Zentner,
December, 2005
10. Stonebridge Estates Detention and Sedimentation Basins Vegetation Survey by Zentner and Zentner,
December, 2005
11. Contra Costa County Public Works GIS, July 2004
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EVALUATION OF ENVIRONMENTAL IMPACTS:
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
I. AESTHETICS. Would the proposal:
a. Have a substantial adverse effect on a scenic
vista? X
b. Substantially damage scenic resources,
including, but not limited to, trees, rock,
outcroppings, and historic buildings within a
state scenic highway? X
c. Substantially degrade the existing visual
character or quality of the site and its
surroundings: X
d. Create a new source of substantial light or
glare, which would adversely affect day or X
nighttime views in the area?
SUMMARY:
Desilting the sedimentation basin will have no permanent impact on.Aesthetic resources as the project
consists only of desilting an existing water treatment facility to design grade and no tree removal is required.
After construction, all disturbed areas will be hydroseeded with a mix including appropriate native species to
ensure rapid reestablishment of vegetation cover.
Desilting the detention basin will require tree removal (willows); however, because the detention basin will be
desilted over a period of at least three years and because willows reestablish rapidly (willow cuttings will be
installed to facilitate the reestablishment of the willow cover), the project will not cause a significant aesthetic
impact.
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
II. AGRICULTURAL RESOURCES. In determining
whether impacts to agricultural resources are
significant environmental effects, lead agencies
may refer to the California Agricultural Land
Evaluation and Site Assessment Model (1997)
prepared by the California Dept. of Conservation
as an optional model to use in assessing impacts
on agricultural and farmland. Would the project: X
a. Convert Prime Farmland, Unique Farmland, or
Farmland of Statewide, Importance
(Farmland), as shown on the maps prepared
pursuant to the Farmland Mapping and
Monitoring Program of the California
Resources Agency, to non-agricultural use? X
b. Conflict with existing zoning for agricultural
use, or a Williamson Act contract? X
c. Involve other changes in the existing
environment, which, due to their location or
nature, could result in conversion of Farmland,
to non-agricultural use? X
SUMMARY:
The project will have no impact on Agricultural Resources as the project consists only of desilting an existing
water treatment and..stormwater_facility to.design__grade._______
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Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
III. AIR QUALITY. Where available, the significance
criteria established by the applicable air quality
management or air pollution control district may be
relied upon to make the following determinations.
Would the project:
a. Conflict with or obstruct implementation of the
applicable air quality plan? X
b. Violate any air quality standard or contribute to
an existing or projected air quality violation?
X
c. Result in a cumulatively considerable net
increase of any criteria pollutant for which the
project region is non-attainment under an
applicable federal or state ambient air quality
standard (including releasing emissions which
exceed quantitative thresholds for ozone
precursors)? X
d. Expose sensitive receptors to substantial
pollutant concentrations? X
e. Create objectionable odors affecting a
substantial number of people? X
SUMMARY
The project will have no permanent effect on air quality, as the project consists of desilting an existing water
treatment and stormwater facility to design grade. Short-term emissions may be generated during
construction; however, they will be minor and temporary. In order to minimize impacts due to construction
activities, contract specifications will stipulate the use of properly tuned and muffled equipment and the
elimination of unnecessary idling of equipment when not in use. Implementation of dust control practices
including general watering of exposed areas and/or use of chemical stabilizers will also minimize air quality
impacts. The minor temporary deterioration of ambient air quality at the construction site will have no
potentially adverse long-term impacts to air quality.
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
IV. BIOLOGICAL RESOURCES. Would the project:
a. Have a substantial adverse effect, either
directly or through habitat modifications, on
any species identified as a candidate,
sensitive, or special status species in local or
regional plans, polices, or regulations, or by
the California Department of Fish and Game or
U.S. Fish and Wildlife Service? X
b. Have a substantial adverse effect on any
riparian habitat or other sensitive natural
community identified in local or regional plans,
policies, regulations or by the California
Department of Fish and Game or US Fish and
Wildlife Service? X
c. Have a substantial adverse effect on federally
protected wetlands as defined by Section 404
of the Clean Water Act (including, but not
limited to, marsh, vernal pool. coastal, etc.)__
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Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
through direct removal, filling, hydrological
interruption, or other means?
d. Interfere substantially with the movement of
any native resident or migratory fish or wildlife
species or with established native resident or
migratory wildlife corridors, or impede the use
of native wildlife nursery sites? X
e. Conflict with any local policies or ordinances
protecting biological resources, such as tree
preservation policy or ordinance? X
f. Conflict with the provisions of an adopted
Habitat Conservation Plan, Natural Community
Conservation Plan, or other approved local,
regional, or state habitat conservation plan?
X
SUMMARY: Potentially Significant Unless Mitigation Incorporated. The project site is located in an area of
mixed residential, agricultural and open space uses. Zentner and Zentner conducted a special status species
assessment of the Stonebridge Estates detention and sedimentation basins. Site visits were completed in
October, November and December, 2005. This assessment included a review of the California Department of
Fish and Game (CDFG) lists of special animals and plants, California Natural Diversity Data Base (CNDDB)
occurrence records for Diablo and nearby Las Trampas Ridge, Walnut Creek and Clayton quads, California
Native Plant Society's Inventory of Rare and Endangered Vascular Plants of California (Skinner & Pavlik
1994), and United States Fish and Wildlife Service (USFWS) special status species lists for the above quads.
Sedimentation Basin: This assessment found that there are five special status species that have a low to
moderate potential to occur at the sedimentation basin. In addition, California red-legged frog, Rana aurora
draytonii, is known to occur in the vicinity of the project impact area.
Birds: There were five special status bird species identified in the assessment as having low to moderate
potential to occur on site. The site may provide foraging and nesting habitat for white-tailed kite Elanus
leucurus and for Allen's hummingbird Selasphorus sasin. Both these species have moderate potential to
occur on site. The site may also provide foraging habitat and limited nesting habitat for Nuttall's
woodpecker Picoides nuttallii, and for the California thrasher Toxostoma redivivum. Both these species
have low potential to occur on site. There is foraging and breeding habitat for the loggerhead shrike
Lanius ludovicianus, and it has low potential to occur on site.
Mitigation measure:
• The project is specifically timed to start after the nesting season is finished.
• A pre-construction survey will be conducted for these species two weeks prior to beginning work on
the project.
• If nesting birds are found during the pre-construction survey, the project will be delayed until the
birds have fledged.
California red-legged frog - Rana aurora draytonii:
The California red-legged frog (RLF) is a federally-listed threatened species and a California species of
concern. The general project area is a known and occupied habitat for RLF. RLF have not specifically
been observed in the sedimentation basin and, due to the lack of open water and riparian cover, they are
unlikely to utilize this area. No red-legged frog habitat will be taken by the sedimentation basin desilt
activity. In order to ensure impacts do not occur as a result of the sedimentation basin desilting, the
following measures will be implemented:
Mitigation measures:
• The removal of sediment will occur during the time between August and October when the
sedimentation basin is dry
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Because RLF are known to occur in the detention basin, in order to minimize any potentially adverse
effects to red-legged frogs or their habitat the following measures shall be taken (these measures are
taken from the RLF Programmatic Agreement):
1. At least 15 days prior to the onset of activities, the District shall submit the name(s) and
credentials of biologists who would conduct activities specified in the following measures.
No project activities shall begin until the District has received written approval from the
Service that the biologist(s) is qualified to conduct the work.
2. A Service-approved biologist shall survey the work site two weeks before the onset of
activities. If California red-legged frogs, tadpoles, or eggs are found, the approved biologist
shall contact the Service to determine if moving any of these life-stages is appropriate. If the
Service approves moving animals, the approved biologist shall be allowed sufficient time to
move RLF from the work site before work activities begin. Only Service-approved biologists
shall participate in activities associated with the capture, handling, and monitoring of RLF.
3. Before any work activities begin on the project, a Service-approved biologist shall conduct a
training session for all construction personnel. At a minimum, the training shall include a
description of the
RLF and its habitat, the importance of the RLF and its habitat, the general measures that
are being implemented to conserve the RLF as they relate to the project, and the
boundaries within which the project may be accomplished. Brochures, books and briefings
may be used in the training session, provided that a qualified person is on hand to answer
any questions.
4. A Service-approved biologist shall be present at the work site until such time as all removal
of RLF, instruction of workers, and habitat disturbance have been completed. After this
time, the contractor or permitee shall designate a person to monitor on-site compliance with
all minimization measures. The Service-approved biologist shall ensure that this individual
receives training outlined above in measure 3 and in the identification of RLF. The monitor
and the Service-approved biologist shall have the authority to halt any action that might
result in impacts that exceed the levels anticipated by the Corps and Service during the
review of the proposed action. If work is stopped, the Corps and the Service shall be
notified immediately by the Service-approved biologist or on-site monitor.
5. During project activities, all trash that may attract predators shall be properly contained,
removed from the work site and disposed of regularly. Upon completion of the project, all
trash and debris shall be removed from work areas.
6. All fueling and maintenance of vehicles and other equipment and staging areas shall occur
at least 10 meters from the riparian habitat or water body. The District shall ensure
contamination of habitat does not occur during such operations.
7. A Service-approved biologist shall ensure that the spread or introduction of invasive exotic
plant species shall be avoided to the maximum extent possible.
8. All disturbed areas shall be hydroseeded with a mix including native grasses.
9. The number of access routes, number and size of staging areas, and the total area of the
activity shall be limited to the maximum necessary to achieve the project goal. Routes and
boundaries shall be clearly demarcated, and these areas shall be outside of riparian and
wetland areas. Where impacts occur in these staging areas and access routes, restoration
shall occur as identified in measures 8 and 9 above.
10. Work activities shall be completed by November 1.
11. To control erosion during and after project implementation, best management practices
shall be implemented, as identified by the Regional Water Quality Control Board.
Detention Basin:
The Special Status Species Assessment found that there are six special status species that have a low to
moderate potential to occur on the detention basin project site. The project site is a known and occupied
habitat for California red-legged frog (RLF).
Birds: There were five special status bird species identified in the assessment as having low to moderate
potential to occur on site. The site may provide foraging and nesting habitat for white-tailed kite Elanus
leucurus and for Allen's hummingbird Selasphorus sasin. Both these species have moderate potential to
occur on site. The site may also provide foraging habitat and limited nesting habitat for Nuttall's
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woodpecker Picoides nuttallii, and for the California thrasher Toxostoma redivivum. Both these species
have low potential to occur on site. There is foraging and breeding habitat for the loggerhead shrike
Lanius ludovicianus, and it has low potential to occur on site.
Mitigation measures:
• In order to ensure no impacts to nesting birds occurs, project construction will be timed to occur
outside of the nesting season
• A pre-construction survey will be conducted for these species two weeks prior to beginning work on
the project.
• If nesting birds are found during the pre-construction survey, the project will be delayed until the
birds have fledged.
• The basin will be desilted one third at a time over a period of three years.
California tiger salamander-Ambystoma californiense:
The California tiger salamander (CTS) is a federally-listed threatened species and a California species.of
concern. The only breeding habitat in the vicinity of the project site is the open water area located in the
north end of the detention basin; this area has a lengthy period of inundation and could provide breeding
habitat. Gopher and ground squirrel burrows were observed in the upland areas adjacent to the detention
basin and CTS could use these burrows for aestivation. Although no CTS have been observed anywhere
on site, there has been one sighting made approximately 3 miles form the site.
Mitigation measures:
• A pre-construction survey will be performed two weeks prior to commencement of both the short-
term and long-term maintenance (i.e. prior to work in either basin).
• Protocol level surveys will be conducted over two consecutive years prior to long-term maintenance
(desilting) work in the detention basin.
California red-legged frog - Rana aurora draytonii:
The California red-legged frog (RLF) is a federally-listed threatened species and a California species of
concern. The. detention basin area is a known and occupied habitat for RLF. No RLF habitat will be
permanently taken as a result of the detention basin desilt activity.
Mitigation measures:
• The removal of sediment will occur during the summer construction season.
• The basin will be desilted one third at a time over a period of three years, leaving 2/3 of the basin
as refuge.
• Willow cuttings will be installed to facilitate the reestablishment of the willow cover.
Because RLF are known to occur in the detention basin, in order to minimize any potentially adverse
effects to red-legged frogs or their habitat the following measures shall be taken (these measures are
taken from the RLF Programmatic Agreement):
1. At least 15 days prior to the onset of activities, the District shall submit the name(s) and
credentials of biologists who would conduct activities specified in the following measures.
No project activities shall begin until the District has received written approval from the
Service that the biologist(s) is qualified to conduct the work.
2. A Service-approved biologist shall survey the work site two weeks before the onset of
activities. If California red-legged frogs, tadpoles, or eggs are found, the approved biologist
shall contact the Service to determine if moving any of these life-stages is appropriate. If the
Service approves moving animals, the approved biologist shall be allowed sufficient time to
move RLF from the work site before work activities begin. Only Service-approved biologists
shall participate in activities associated with the capture, handling, and monitoring of RLF.
3. Before any work activities begin on the project, a Service-approved biologist shall conduct a
training session for all construction personnel. At a minimum, the training shall include a
description of the
RLF and its habitat, the importance of the RLF and its habitat, the general measures that
are being implemented to conserve the RLF as they relate to the project, and the
boundaries within which the project may be accomplished. Brochures, books and briefings
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may be used in the training session, provided that a qualified person is on hand to answer
any questions.
4. A Service-approved biologist shall be present at the work site until such time as all removal
of RLF, instruction of workers, and habitat disturbance have been completed. After this
time, the contractor or permitee shall designate a person to monitor on-site compliance with
all minimization measures. The Service-approved biologist shall ensure that this individual
receives training outlined above in measure 3 and in the identification of RLF. The monitor
and the Service-approved biologist shall have the authority to halt any action that might
result in impacts that exceed the levels anticipated by the Corps and Service during the
review of the proposed action. If work is stopped, the Corps and the Service shall be
notified immediately by the Service-approved biologist or on-site monitor.
5. During project activities, all trash that may attract predators shall be properly contained,
removed from the work site and disposed of regularly. Upon completion of the project, all
trash and debris shall be removed from work areas.
6. All fueling and maintenance of vehicles and other equipment and staging areas shall occur
at least 10 meters from the riparian habitat or water body. The District shall ensure
contamination of habitat does not occur during such operations.
7. A Service-approved biologist shall ensure that the spread or introduction of invasive exotic
plant species shall be avoided to the maximum extent possible.
8. All disturbed areas shall be hydroseeded with a mix including native grasses.
9. The number of access routes, number and size of staging areas, and the total area of the
activity shall be limited to the maximum necessary to achieve the project goal. Routes and
boundaries shall be clearly demarcated, and these areas shall be outside of riparian and
wetland areas. Where impacts occur in these staging areas and access routes, restoration
shall occur as identified in measures 8 and 9 above.
10. Work activities shall be completed by November 1.
11. To control erosion during and after project implementation, best management practices
shall be implemented, as identified by the Regional Water Quality Control Board.
Wetlands Impact— Sedimentation Basin
The sedimentation basin contains,some seasonal marsh habitat, portions of which may be impacted by the
project, including such species as cattail, Baltic rush (Juncus balticus) and rabbitsfoot grass (Polypogon
monspeliensis). The sedimentation basin is specifically designed to be a water treatment facility, and the
removal of sediment from the sedimentation basin will allow additional sediment to settle out, improving
water quality in the downstream system. Additionally, the removal of silt from the sedimentation basin will
allow the marsh to become more inundated, increasing habitat value. This impact is expected.to be limited
since the vegetation will reestablish rapidly.
Mitigation Measures
• The area will be reseeded with a mix including such wetland species as cattail, Baltic rush (Juncus
balticus) and rabbitsfoot grass (Polypogon monspeliensis) to minimize the impact.
_Wetlands Impact— Detention Basin
Portions of the detention basin have been delineated as wetlands. Following the desilting activities, the
area will retain its wetland characteristics.
Mitigation Measures
• In order to reduce the temporary impacts to the wetlands in the detention basin the desilting will be
done one third at a time over three years, leaving 2/3 of the basin as refuge.
• Additionally to reduce the impact willow cuttings will be installed to facilitate the reestablishment of
the willow cover.
All necessary regulatory permits will be obtained prior to construction activities to ensure that impacts to
the wetlands are minimal and any conditions in the permits will be complied with during construction.
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Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant .
Impact Incorporation Impact No Impact
V. CULTURAL RESOURCES. Would the project:
a. Cause a substantial adverse change in the
significance of a historical resource as
defined in §15064.5? X
b. Cause a substantial adverse change in the
significance of an archaeological resource
pursuant to §15064.5? X
c. Directly or indirectly destroy a unique
paleontological resource or site or unique
geologic feature? X
d. Disturb any human remains, including those
interred outside of formal cemeteries?
X
SUMMARY
The project will have no impact on Cultural Resources as the desilting activities in both basins will only be
done to the previously established design grade. There are no residences or other structures that will be
impacted by the project. No new right of way will need to be required in order to complete the project.
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
VI. Geology and Soils. Would the project:
a. Expose people or structures to potential
substantial adverse effects, including the risk of
loss, injury, or death involving:
1. Rupture of a known earthquake fault, as
delineated on the most recent Alquist-Priolo
Earthquake Fault Zoning Map issued by the
State Geologist for the area or based on
other substantial evidence of a known
fault? Refer to Division of Mines and
Geology Special Publication 42. X
2. Strong seismic ground shaking? X
3. Seismic-related ground failure, including
liquefaction? X
4. Landslides? X
b. Result in substantial soil erosion or the loss of
topsoil? X
c. Be located on a geologic unit or soil that is
unstable, or that would become unstable as a
result of the project, and potentially result in on-
or off-site landslide, lateral spreading,
subsidence, liquefaction or collapse? X
d. Be located on expansive soil, as defined in
Table 18-1-B of the Uniform Building Code
(1994), creating substantial risks to life or
property? X
e. Have soils incapable of adequately supporting
the use of septic tanks or alternative waste
disposal systems where sewers are not
available for the disposal of wastewater? X
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SUMMARY
According to the Contra Costa County Soil Survey, soils of the site consist of Alo Clay, a non-hydric soil. Alo
Clay is a well-drained soil underlain by soft sandstone and shale and is commonly located on steep hillsides.
This soil also has very slow permeability. The project will have no impact on Geology and Soils as the desilting
will only be done to a previously established design depth in previously disturbed areas. All areas left exposed
due to the project will be seeded with a mix including native grasses and wildflowers upon completion of the
project in order to stabilize exposed soil.
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
VII. HAZARDS AND HAZARDOUS MATERIALS.
Would the project:
a. Create a significant hazard to the public or the
environment through the routine transport, use,
or disposal of hazardous materials? X
b. Create a significant hazard to the public or the
environment through reasonably foreseeable
upset and accident conditions involving the
release of hazardous materials into the
environment? X
c. Emit hazardous emissions or handle hazardous
or acutely hazardous materials, substances, or
waste within one-quarter mile of an existing or
proposed school? X
d. Be located on a site which is included on a list
of hazardous materials sites compiled pursuant
to Government Code Section 65862.5 and, as a
result, would it create a significant hazard to the
public or the environment? X
e. For a project located within an airport land use
plan or, where such a plan has not been
adopted, within two miles of a public airport or
public use airport, would the project result in a
safety hazard for people residing or working in
the project area. X
f. For a project within the vicinity of a private
airstrip, would the project result in a safety
hazard for people residing or working in the
project area? X
g. Impair implementation of or physically interferes
with an adopted emergency response plan or
emergency evacuation plan? X
h. Expose people or structures to a significant risk
of loss, injury or death involving wildland fires,
including where wildlands are adjacent to
urbanized areas or where residences are
intermixed with wildlands? X
SUMMARY
The project will have no impact on Hazards or Hazardous Materials as the project consists only of desilting an
existing water treatment and stormwater facility to design grade. All fueling and maintenance of equipment will
occur on Serafix Road in order to ensure no water quality impacts to the creek.
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Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
VIII. HYDROLOGY AND WATER QUALITY.
Would the project:
a. Violate any water quality standards or waste
discharge requirements? X
b. Substantially deplete groundwater supplies or
interfere substantially with groundwater
recharge such that there would be a net deficit
in aquifer volume or a lowering of the local
groundwater table level (e.g., the production
rate of pre-existing nearby wells would drop to a
level which would not support existing land uses
or planned uses for which permits have been
granted)? X
c. Substantially alter the existing drainage pattern
of the site or area, including through the
alteration of the course of a stream or river, in a
manner, which would result in substantial
erosion or siltation on or off-site? X
d. Substantially alter the existing drainage pattern
of the site or area, including through the
alteration of the course of a stream or river, or
substantially increase the rate or amount of
surface runoff in a manner, which would result
in flooding on- or off-site? X
e. Create or contribute runoff water which would
exceed the capacity of existing or planned
storm water drainage systems or provide
substantial additional sources of polluted
runoff?
X
f. Otherwise substantially degrade water quality? X
g. Place housing within a 100-year flood hazard
area as mapped on a federal Flood Hazard
Boundary or Flood Insurance Rate Map or other
flood hazard delineation map? X
h. Place within a 100-year flood hazard area
structures, which would impede or redirect flood
flows? X
i. Expose people or structures to a significant risk
of loss, injury or death involving flooding,
including flooding as a result of the failure of a
levee or dam? X
J. Inundation by seiche, tsunami, or mudflow? X
SUMMARY
This project will have less than significant impact. Desilting the basins and the culvert, retrofitting the culvert,
and reestablishing the detention basin access road will not increase exposure of people or property to
flooding. In fact, one of the goals of the project is to lessen the potential exposure of people and property to
flooding. The project will not impair the flow of water; nor will it alter the course or flow of floodwaters. The
amount of surface water in the unnamed creek will not change significantly as a result of the project. Desilting
of the basins and culvert, retrofitting the culvert, and reestablishing the detention basin access road will not
Iadversely affect the quantity or quality of surface water, ground water or public water supply.
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In order to ensure that impacts to water quality remain less than significant, Best Management Practices
(BMPs) will be incorporated into the.desilt of the basins and culvert and reestablishment of the detention basin
access road. These BMPs include the following:
• All construction equipment will be stored, serviced and fueled outside of the basins. Standard
construction safety practices will be incorporated into the project to reduce the possibility of a spill of
gasoline, oil, or other pollutant that could have a significant impact on water quality. In addition,
stockpiled materials will be located far enough from the edges of the basins and channel to prevent
construction materials from entering the basins and channel.
• In order to ensure the work can be conducted with limited impact to water quality, in the event that the
basin is not dry, flows will be bypassed around the desilting activities and culvert retrofitting activities
and detention access road reestablishment and the immediate work areas will be dewatered.
Dewatering will likely entail installation of cofferdams to isolate the work areas and a silt settling area to
allow sediment—laden work area water to settle prior to release into the basins. Normal flows will be
maintained around the work site at all times through either a gravity flow or pumping system. The
dewatering system will function effectively to isolate the work areas from any flowing water and ensure
water quality is not impacted by the construction activities.
• At the completion of the project, all disturbed areas will be stabilized through the use of hydroseeding
with a mix including native grasses and wildflowers and/or erosion control blanketing, as appropriate.
Water Quality Certification will be obtained from the San Francisco Bay Regional Water Quality Control
Board (SFBRWCB) prior to construction of the project. Special conditions required by the certification
will be complied with during construction in order to minimize the possibility of water quality impacts.
Routine maintenance activities (i.e., debris and cattail removal, weed abatement, and minor silt removal) will
be conducted on an as-needed basis and are not expected to cause a significant impact to water quality.
Based on the rate at which sediment has built up in the basins historically, it is anticipated that the desilting
cycle of the sedimentation basin will be every 4 to 6 years, and the detention basin will only need to be done
every 5 to 10 years. In order to avoid water quality impacts as a result of maintenance activities, the basins will
be dewatered (if needed) prior to any desilting activities.
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
IX. LAND USE AND PLANNING. Would the project:
a. Physically divide an established community? X
b. Conflict with any applicable land use plan,
policy, or regulation of an agency with
jurisdiction over the project (including, but not
limited to the general plan, specific plan, local
coastal program, or zoning ordinance) adopted
for the purpose of avoiding or mitigating an
environmental effect? X
c. Conflict with any applicable habitat conservation
plan or natural community conservation plan? X
SUMMARY
The project will have no impact on Land Use and Planning as the project consists only of desilting an existing
water treatment and stormwater facility to design grade.
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
X. MINERAL RESOURCES. Would the project:
a. Result in the loss of availability of a known
mineral resource that would be of value to the
_region a.nd.the residents of the state?__. _._
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Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
(Source #)
b. Result in the loss of availability of a locally
important mineral resource recovery site
delineated on a local general plan, specific plan
or other land use plan? (Source #) X
SUMMARY
The project will have no impact on Mineral Resources as the project consists only of desilting an existing water
treatment and stormwater facility to design grade.
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
XI. NOISE. Would the project result in:
a. Exposure of persons to or generation of noise
levels in excess of standards established in the
local general plan or noise ordinance, or
applicable standards of other agencies?
X
b. Exposure of persons to or generation of
excessive ground borne vibration or ground
borne noise levels? X
c. A substantial permanent increase in ambient
noise levels in the project vicinity above levels
existing without the-project? X
d. A substantial temporary or periodic increase in
ambient noise levels in the project vicinity above
levels existing without the project? X
e. For a project located within an airport land use
plan or, where such a plan has not been
adopted, within two miles of a public airport or
public use airport, would the project expose
people residing or working in the project area to
excessive noise levels? X
f. For a project within the vicinity of a private
airstrip, would the project expose people
residing or working in the project area to
excessive noise levels? X
SUMMARY
The project will have no permanent impact on noise levels. Temporary minor increases in noise level may
occur during the project due to operation of construction equipment, however, much of the work will be done
with hand tools. Any desilting activities requiring the use of heavy equipment will occur during the hours of 8
AM to 5 PM. All equipment will be appropriately muffled.
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
XII. POPULATION AND HOUSING. Would the project:
a. Induce substantial population growth in an area,
either directly (for example, by proposing new
homes and businesses) or indirectly (for X
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Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
example, through extension of roads or other
infrastructure)?
b. Displace substantial numbers of existing
housing, necessitating the construction of
replacement housing elsewhere? X
c. Displace substantial numbers of people,
necessitating the construction of replacement
housing elsewhere? X
SUMMARY
The project will not have any impact on the population or housing of the region as the project consists only of
desilting an existing water treatment and stormwater facility to design grade.
Potentially
Significant
Potentially. Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
XIII. PUBLIC SERVICES
a. Would the project result in substantial adverse
physical impacts associated with the provision
of new or physically altered governmental
facilities, need for new or physically altered
governmental facilities, the construction of
which could cause significant environmental
impacts, in order to maintain acceptable service
ratios, response times or other performance
objectives for any of the public services:
1. Fire Protection? X
2. Police Protection? X
3. Schools? X
4. Parks? X
5. Other Public facilities? X
SUMMARY
The project will not impact any public services as the project consists only of desilting an existing water
treatment and stormwater facility to design grade. Serafix Road will remain open to traffic during the project.
Emergency vehicles will have access to and beyond the site at all times.
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
XIIII. RECREATION
a. Would the project increase the use of existing
neighborhood and regional parks or other
recreational facilities such that substantial
physical deterioration of the facility would occur
or be accelerated? X
b. Does the project include recreational facilities or
require the construction or expansion of
recreational facilities, which might have an
adverse physical effect on the environment? X
SUMMARY
The project will not impact any recreation resource as the project consists only of desilting an existing water
treatment and stormwater facility to design grade.
C:\DOCUME-1\TMoreira\LOCALS-1\Temp\notesBAAA25\MitNegDec(03-14-06)final.doc-Page 15 of 18
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
XV. TRANSPORTATION/TRAFFIC. Would the project:
a. Cause an increase in traffic, which is substantial
in relation to the existing traffic load and
capacity of the street system (i.e., result in a
substantial increase in either the number of
vehicle trips, the volume to capacity ratio on
roads, or congestion at intersections)?
X
b. Exceed, either individually or cumulatively, a
level of service standard established by the
county congestion management agency for
designated roads or highways? X
c. Result in a change in air traffic patterns,
including either an increase in traffic levels or a
change in location that results in substantial
safety risks? X
d. Substantially increase hazards due to a design
feature (e.g., sharp curves or dangerous inter-
sections) or incompatible uses (e.g., farm
equipment)? X
e. Result in inadequate emergency access? X
f. Result in inadequate parking capacity?
X
g. Conflict with adopted policies, plans, or
programs supporting alternative transportation
(e.g., bus turnouts, bicycle racks)? X
SUMMARY
The project will not significantly impact transportation or traffic. It is anticipated that Serafix Road will remain
open to traffic at all times during the construction. Truck trips are estimated at approximately ten trips per day
over a very short duration (2-4 days).
C:\DOCUME-1\TMoreira\LOCALS-1\Temp\notesBAAA25\MitNegDec(03-14-06)final.doc-Page 16 of 18
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
XVI. UTILITIES AND SERVICE SYSTEMS.
Would the project:
a. Exceed wastewater treatment requirements of
the applicable Regional Water Quality Control
Board? X
b. Require or result in the construction of new
water or wastewater treatment facilities or
expansion of existing facilities, the construction
or which could cause significant environmental
effects? X
c. Require or result in the construction of new
storm water drainage facilities or expansion of
existing facilities, the construction of which
could cause significant environmental effects? X
d. Have sufficient water supplies available to serve
the project from existing entitlement and
resources, or are new or expanded entitlement
needed? X
e. Result in a determination by the wastewater
treatment provider, which serves or may serve
the project that it has adequate capacity to
serve the project's projected demand in addition
to the provider's existing commitments?
X
f. Be served by a landfill with sufficient permitted
capacity to accommodate the project's solid
waste disposal needs? X
g. Comply with federal, state and local statutes
and regulations related to solid waste? x
SUMMARY
The project will not impact any utilities and service systems.
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
XVII. MANDATORY FINDINGS OF SIGNIFICANCE
a. Does the project have the potential to degrade
the quality of the environment, substantially
reduce the habitat of a fish and wildlife species,
cause a fish or wildlife population to drop below
self-sustaining levels, threaten to eliminate a
plant or animal community, reduce the number
or restrict the range of a rare or endangered
plant or animal or eliminate important examples
of the major periods of California history or
prehistory? X
b. Does the project have impacts that are
individually limited, but cumulatively
considerable? ("Cumulatively considerable"
means that the incremental effects of a project
_ _.._are.considerabJe when viewed_in_.connection_____.__._____. X .
C:\DOCUME-1\TMoreira\LOCALS-1\Temp\notesBAAA25\MitNegDec(03-14-06)final.doc_Page 17 of 18
Potentially
Significant
Potentially Unless Less than
Significant Mitigation Significant
Impact Incorporation Impact No Impact
with the effects of past projects, the effects of
other current projects, and the effects of
probable future projects)?
c. Does the project have environmental effects,
which will cause substantial adverse effects on
human beings, either directly or indirectly? X
SUMMARY:
Although this project site is in known red-legged frog habitat, the methodology to be utilized and mitigation
measures to be implemented will protect the population of the species in the area. Five special status bird
species were identified as having low to moderate potential for occurring on the site; the methodology to be
utilized and mitigation measures to be implemented will protect any of these species that may be in the area.
California tiger salamander (CTS) habitat exists in the detention basin; therefore methodology will be utilized
and mitigation measures implemented to protect any CTS that may be in the area. The wetland impact will be
minimal and will be mitigated by reseeding with wetland species in the sedimentation basin, and by desilting
one third at a time in the detention basin and installing willow cuttings following each desilting.
C:\DOCUME-1\TMoreira\LOCALS-1\Temp\notesBAAA25\MitNegDec(03-14-06)final.doc_Page 18 of 18
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ICP
Community Contra Dennis MyDevel Development
Community Development Director
DevelopmentCOSta - - -
i�
Department County -
County Administration Building i I
1
651 Pine Street
4th Floor, North Win - ' \ l APR 0 3 2006 L
Martinez, California 94553-0095 J� . '
S.L. WEIR, COUNTY CLERK
Phone: M 6 CONT C TA COUNTY
LBY
EPUTY
NOTICE OF PUBLIC REVIEW AND INTENT TO ADOPT A PROPOSED
MITIGATED NEGATIVE DECLARATION
County File # CP 04-56
Pursuant to the State of California Public Resources Code and the "Guidelines for Implementation
of the California Environmental Quality Act of 1970" as amended to date, this is to advise you that
the Community Development Department of Contra Costa County has prepared an initial study on
the following project:
i
STONEBRIDGE ESTATES SEDIMENTATION BASIN DESILT PROJECT, CP#: 04-56. The
Contra Costa County Flood Control and Water Conservation District is proposing to desilt the
existing detention and sedimentation basins in Stonebridde Estates, returning them to design
grade. This project will be comprised of both short and longterm maintenance components which
will take place over several construction seasons. The immediate maintenance needs address
desilting the sedimentation basin and the Serafix Road cross culvert, as well as reestablishment of
the detention basin access road. The long term maintenance consists of desilting the detention
basin. These activities will maintain the storm water treatment. capability of the sedimentation
basin, as well as ensuring that high flows can move efficiently into the detention basin.
Sedimentation Basin Desilt (short term maintenance): The immediate maintenance-need consists
of desilting the sedimentation basin back to design depth in order to restore the level of water
quality treatment it was intended to provide. The culvert that joins the sedimentation basin to the
detention basin will be desilted and retrofitted with a steel plate to reduce the flow of water and
allow a greater percentage of the silt to drop out of the flow before it passes into the detention
basin. These activities will maintain the stormwater treatment capability of the sedimentation basin,
as well as ensuring that high flows can move efficiently into'the detention basin. Additionally, the
access road into the detention basin will be restored to facilitate work in the detention basin and at
the Serafix Road cross culvert. Material excavated from the'sedimentation basin may be used as
fill to restore the access road. Following construction, all disturbed areas will be seeded with a mix
including appropriate native species.
Detention Basin Desilt (long term maintenance): The long term maintenance addresses the need
to desilt the detention basin to design grade. Because the detention basin is a known and occupied
red-legged frog (RLF) habitat, desilting of the detention basin will take place in three stages over at
least three summer seasons. This will allow two thirds of the detention basin to remain untouched
at any one time and provide refuge for the resident red-legged frog population. In addition, to
minimize impact, willow cuttings will be installed following the desilting of each third of the
detention basin. Following construction, all disturbed areas will be seeded with a mix including
appropriate native species.
Pagel of 2
Office Hours Monday- Friday:8:00 a.m. -5:00 p.m.
Office is closed the 1 st, 3rd & 5th Fridaysi of each month
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PROJECT LOCATION: The project is located on an unnamed creek in-Stonebridge--Estates-1-
adjacent to Serafix Rd., in the community of Alamo, in central--Contra Costa County;•at the-far —
eastern extension of Livorna Road
I
ENVIRONMENTAL EFFECTS: The Initial Study for the proposed project identified potentially
significant impact in the environmental area of biology. Environmental analysis determined that
measures were available to mitigate potential adverse impacts to insignificant levels. As a result, a
Mitigated Negative Declaration (MND) has been prepared' pursuant to Public Resources Code
Section 21080(c), 21063.5, and Article 6 of the California Environmental Quality Act (CEQA)
Guidelines.
Pursuant to the requirements of CEQA (CEQA Guidelines Section 15071) the MND describes the
proposed project; identifies, analyzes, and evaluates the potential significant environmental
impacts, which may result from the proposed project; and identifies measures to mitigate adverse
environmental impacts. The mitigations identified in this document, designed for the proposed
project, will ensure that the project will not cause a significant impact on the environment.
A copy of the Mitigated Negative Declaration and all documents referenced in the Mitigated
Negative Declaration may be reviewed during business hours at the offices of the County Public
Works Department, Environmental Division, at 255 Glacier Drive, Martinez.
Public Comment Period — The period for accepting comments on the adequacy of the
environmental document extends to Thursday, May 4, 2006; at 5:00 pm.
ANY COMMENTS SHOULD BE IN WRITING AND SUBMITTED TO THE
FOLLOWING ADDRESS:
j
Colleen Culver-Jaffe, Planner II
Contra Costa County Public Works Department
255 Glacier Drive
Martinez, CA 94553
Theenvironmental document is expected to go before the County Board of Supervisors on or
around June 6, 2006. To confirm the Board date, please (contact Colleen Culver-Jaffe at (925)
313-2236. The hearing is anticipated to be held at the McBrien Administration Building, Room 107,
Pine and Escobar Streets, Martinez.
Any questions regarding the project itself, should be directed,to:
i
Paul Detjens, (925) 313-2394
Contra Costa County Public Works Department
255 Glacier Drive
Martinez, CA 94553
G:\GrpData\EngSvc\ENVI90\Flood Control\Stonebridge Estates\Notice of Public Review Letter.doc
Cc: County Clerk's Office
Public Works—
P.Degens,FC
L.Chavez-Enviro
Pau 2 of 2
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EAST BAY
MUNICIPAL UTILITY DISTRICT
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April 24, 2006
CON WORKS CLc SEP R-TMENro T
Colleen Culver-Jaffe, Planner II Pua�1C WORx'
Contra Costa County Public Works Department
255 Glacier Drive
Martinez, CA 94553
Re: Notice of Public Review and Intent to Adopt a Proposed Mitigated Negative
Declaration— Stonebridge Estates Sedimentation Basin Desilt Project, Alamo
Dear Ms. Culver-Jaffe:
East Bay Municipal Utility District (EBMUD) appreciatesithe opportunity to comment
on the Mitigated Negative Declaration for the Stonebridge,Estates Sedimentation Basin
Desilt Project located in Alamo. EBMUD has the following comments.
The project area is currently served from EBMUD's Round Hill Pressure Zone, with a
service elevation between 720 and 920 feet. EBMUD owns and operates an 8-inch water
main located in an EBMUD right of way.(R/W 4564 - Summit Ranch Road) adjacent to
the proposed project construction activity that provides continuous service to EBMUD
customers in the area. The integrity of this pipeline must be maintained at all times. Any
proposed construction activity in Summit Ranch Road needs to be coordinated with
EBMUD and may require relocation of the water main and/or right of way, at the project
sponsor's expense.
If you have any questions concerning this response, please icontact.David J. Rehnstrom,
Senior Civil Engineer, Water Service Planning at(510) 287-1365.
Sincerely,
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W" iarn . irk
patrick�
`• anager of Water Distribution Planning
WRK:DVC:sb
sb06_113.doc
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375 ELEVENTH STREET. OAKLAND . CA 94607-4240. TOLL FREE 1-866-40-EBMUD
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Contra Costa County Maurice M. Shiu
•� I ex officio Chief Engineer
FLOOD CONTROL
I 255 Glacier Drive, Martinez, CA 94553-482
� �• & Water Conservation District Telephone: (925) 313-2000
FAX (925) 313-2333
I
William R. Kirkpatrick
Manager of Water Distribution Planning
East Bay Municipal Utility District
375 Eleventh Street
Oakland, CA 94607-4240
Our File: Stonebridge Estates Sedimentation Basin Desilt Project
i Project Number: 7576-6D-9F07
Dear Mr. Kirkpatrick:
The Flood Control District has received your letter dated April 24, 2006 regarding the
Stonebridge Estates Sedimentation Basin Desilt Project initial study. Thank you for
reviewing the CEQA document. Following is the response to your comment.
i
I
The project activity will be limited to the area within the sedimentation and detention
basins, and will not impact Summit Ranch Road. We will forward your continent
regarding the location of the East Bay Municipal Utility District (EBMUD)pipeline
located in an EBMUD right of way(R/W 4564—Summit Ranch Road) to the project
engineer. We will also recommend that the project engineer contact your Design division
for pipeline plans to ensure that there is no impact to the pipeline.
I
I hope this adequately addresses your concern with the project. If you have any further
concerns, please feel free to contact me at (925) 313-2236 or eculva�pw.cecount .111 for
additional discussion. Thank you.
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Sincerely,
Colleen Culver-Jaffe
Planner II
Environmental Section
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CVC:cvcj
G:\E•n-Svc\ENVIRO\Flood Control\Stonebridge Estates\CEQA\LtrEBMUD(05-08'-06).doc
Cc: P.Detjens,Flood Control
A.Knapp,Maintenance
L.Chavez,Environmental
I
CALIFORNIA ENVIRONMENTAL QUALITY ACT
NOTICE OF DETERMINATION
CONTRA COSTA COUNTY COMMUNITY DEVELOPMENT DEPARTMENT
651 PINE STREET 4TH FLOOR NORTH WING MARTINEZ, CALIFORNIA 94553-0095
Telephone: (925)313-2296 Contact Person: Cece Sellgren, Environmental Planner
Project Description,Common Name(if any)and Location: Stonebridge Estates Sedimentation DesHt Project County File#
CP 04-56,Project Description: The Contra Costa County Flood Control and Water Conservation District is proposing
to desilt the existing detention and sedimentation basins located in Central Contra Costa County, near the city of
Alamo.The project consists of desilting the sedimentation and detention basins back to design grade,and restoring
the level of stormwater treatment capability and flood protection they were intended to provide. The project is
comprised of two parts:the immediate project and the long term maintenance.The immediate project is intended to
desilt the sedimentation basin and the road-cross culvert(Serafix Road)that joins the sedimentation basin to the
detention basin. The culvert will be desilted and the upstream end will be retrofitted with a steel plate to reduce the
flow of water and allow a greater percentage of the silt to drop out of the flow before it passes into the detention
basin.These activities will maintain the stormwater treatment capability of the sedimentation basin,and ensure that
high flows can move efficiently into the detention basin.Additionally,the access road into the detention basin will be
restored to facilitate work in the detention basin and at the road-cross culvert. Material excavated from the
sedimentation basin may be used as fill to restore the access road. Any excavated material not used in the
detention basin road reestablishment will be placed in trucks and legally disposed of at a legal off-site upland
location. The sedimentation basin is expected to be dry during ,construction. In addition to desilting the
sedimentation basin and the road cross culvert, long-term maintenance includes desilting of the detention basin.
Because the site is a known and occupied red-legged frog habitat,desilting of the detention basin to design grade
will take place in three stages over at least three summer seasons.This will allow two thirds of the detention basin
to remain untouched at any one time and provide refuge for the resident red-legged frog population. In addition,to
minimize impact, willow cuttings will be installed following the desilting of each third of the detention basin.
Excavated material will be placed in trucks and legally disposed of at a legal off-site upland location. The Flood
Control District will also conduct routine and ongoing maintenance in the basins and culvert.Maintenance activities
likely to be necessary in the project area consist of debris removal and weed abatement activities and limited silt
removal from the basin areas and culvert every few years. Real property transactions and utility relocations may be
necessary in support of this project.
Project Location: The project area is located on an unnamed creek that flows southwest through the site,
upstream of Stonebridge Estates development before entering San Ramon Creek.The project site is adjacent to
Serafix Rd., in the community of Alamo, in Central Contra Costa Co6nty.
The project was approved on
Pursuant to the provisions of the California Environmental Quality Act:
( ) An Environmental Impact Report was prepared and certified (SCH # )
( ) The Project was encompassed by an Environmental Impact Report previously prepared
for (SCH # ).
(✓) A Mitigated Negative Declaration was prepared following identification of a potentially significant
impact.
Copies of the record of project approval and the Negative Declaration or the final EIR may be examined at the
office of the Contra Costa County Public Works Department.
(✓)The Project will not have a significant environmental effect with incorporated mitigation measures
( ) The Project will have a significant environmental effect.
( ) Mitigation measures were made a condition of approval of the project.
( ) A statement of overriding considerations was adopted.
( ) Findings were adopted pursuant to Section 15091 of,the State CEQA Guidelines.
( ✓ ) A mitigation reporting or monitoring plan was adopted for this project.
Date: By: _
Community Development Department Representative
AFFIDAVIT OF FILING AND POSTING
1 declare that on _ _I received and posted this notice as required by
California Public Resources Code Section 21152(c). Said notice will remain posted for 30 days from the filing
date.
i
Signature Title
Appllcant:
Public Works Department EIR-$850 Total Due: $
255 Glacier Drive,Martinez;CA 94553 _X Neg.Dec.-$1,250 Total Paid $
Attn:Colleen Culver-Jaffe DeMinimis Findings-$0
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I
Y �
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CALIFORNIA ENVIRONMENTAL QUALITY ACT
NOTICE OF DETERMINATION.
CONTRA COSTA COUNTY COMMUNITY DEVELOPMENT DEPARTMENT
651 PINE STREET 4TH FLOOR NORTH WING MARTINEZ, CALIFORNIA 94553-0095
Telephone: (925)313-2296 Contact Person: Cece Sellgren, Environmental Planner
I
Project Description,Common Name(if any)and Location: Stonebridge Estates Sedimentation Desilt Project County File#
CP 04-56,Project Description: The Contra Costa County Flood Control and Water Conservation District is proposing
to desilt the existing detention and sedimentation basins located in Central Contra Costa County, near the city of
Alamo.The project consists of desilting the sedimentation and detention basins back to design grade,and restoring
the level of stormwater treatment capability and flood protection they were intended to provide. The project is
comprised of two parts:the immediate project and the long term maintenance.The immediate project is intended to
desilt the sedimentation basin and the road-cross culvert(Serafix Road)that joins the sedimentation basin to the
detention basin.The culvert will be desilted and the upstream end will be retrofitted with a steel plate to reduce the
flow of water and allow a greater percentage of the silt to drop out of'the flow before it passes into the detention
basin.These activities will maintain the stormwater treatment capability of the sedimentation basin,and ensure that
high flows can move efficiently into the detention basin.Additionally,the access road into the detention basin will be
restored to facilitate work in the detention basin and at the road-cross culvert. Material excavated from the
sedimentation basin may be used as fill to restore the access road. Any excavated material not used in the
detention basin road reestablishment will be placed in trucks and legally disposed of at a legal off-site upland
location. The sedimentation basin is expected to be dry during ,construction. In addition to desilting the
sedimentation basin and the road cross culvert, long-term maintenance includes desilting of the detention basin.
Because the site is a known and occupied red-legged frog habitat, desilting of the detention basin to design grade
will take place in three stages over at least three summer seasons.This will allow two thirds of the detention basin
to remain untouched at any one time and provide refuge for the resident red-legged frog population. In addition,to
minimize impact, willow cuttings will be installed following the desilting of each third of the detention basin.
Excavated material will be placed in trucks and legally disposed of at a legal off-site upland location. The Flood
Control District will also conduct routine and ongoing maintenance in the basins and culvert.Maintenance activities
likely to be necessary in the project area consist of debris removal and weed abatement activities and limited silt
removal from the basin areas and culvert every few years. Real property transactions and utility relocations may be
necessary in support of this project. I
Project Location: The project area is located on an unnamed creek that flows southwest through the site,
upstream of Stonebridge Estates development before entering San Ramon Creek. The project site is adjacent to
Serafix Rd., in the community of Alamo, in Central Contra Costa County.
The project was approved on
Pursuant to the provisions of the California Environmental Quality Act:
( ) An Environmental Impact Report was prepared and certified (SCH # )
( ) The Project was encompassed by an Environmental Impact Report previously prepared
for (SCH # ). I
(✓) A Mitigated Negative Declaration was prepared following identification of a potentially significant
impact.
I
Copies of the record of project approval and the Negative Declaration or the final EIR may be examined at the
office of the Contra Costa County Public Works Department. I
(✓)The Project will not have a significant environmental effect with incorporated mitigation measures
( ) The Project will have a significant environmental effect.
( ) Mitigation measures were made a condition of approval of the project.
( ) A statement of overriding considerations was adopted.
( ) Findings were adopted pursuant to Section 15091 of'the State CEQA Guidelines.
( ✓ ) A mitigation reporting or monitoring plan was adopted for this project.
I
Date: By:
Community Development Department I Representative
AFFIDAVIT OF FILING AND POSTING
I
I declare that on I received and, posted this notice as required by
California Public Resources Code Section 21152(c). Said notice will remain posted for 30 days from the filing
date.
I
i
Signature Title
Applicant:
Public Works Department EIR-$850 Total Due: $
255 Glacier Drive,Martinezi CA 94553 _X Neg.Dec.-$1,250 Total Paid $
Attn:Colleen Culver-Jaffe DeMinimis Findings-$0
I
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