San Pablo Dam Road - La Honda Storm Drain and Slide Repair Project
Summary
SCH Number
2026050969
Lead Agency
Contra Costa County
Document Title
San Pablo Dam Road - La Honda Storm Drain and Slide Repair Project
Document Type
MND - Mitigated Negative Declaration
Received
Present Land Use
Storm drain, road/right-of-way, creek / R-7 Single-Family Residential / RC, Resource Conservation
Document Description
The San Pablo Dam Road–La Honda Road Storm Drain and Slide Repair Project proposed project) involves the stabilization of an embankment failure, the repair of the northern side of San Pablo Dam Road, and replacement of an existing culvert approximately 200 feet southeast of La Honda Road in unincorporated El Sobrante, Contra Costa County, California. The proposed project would install a stitch pile wall 50 feet north of San Pablo Dam Road between the roadway and San Pablo Creek with an approximate length of 150 feet. The wall consists of cast-in-drilled-hole concrete piles about 50 feet in depth that are spaced six feet apart. The slope between the proposed stitch pile wall and San Pablo Dam Road would be excavated to a maximum depth of 24 feet. The slope would be rebuilt with the excavated material reinforced with layers of geogrid placed at 2-foot vertical spacing to provide long-term stabilization.
The 18-inch existing culvert outfall within the embankment failure area would be relocated west of the proposed stitch pile wall with the installment of two manholes and 75 feet of reinforced concrete pipe intended to convey stormwater to the outfall location. The existing 18-inch culvert under San Pablo Dam Road would be repaired using cured-in-place-pipe lining through the installation of a flexible liner inside the culvert to restore previous hydraulic conditions while the damaged segment towards San Pablo Creek would be removed. The 18-inch relocated culvert outfall would be reinforced concrete pipe enhanced with a concrete flared end section outfalling to a rock slope protection pad to disperse flow and to prevent bank erosion around the inlet. Approximately 200 feet of San Pablo Dam Road would be repaired along the embankment failure including restriping and placement of a 170-foot guardrail.
Demolition and Construction Activities
Construction of the proposed project is expected to begin in mid or late 2026 and would last approximately 100 working days. Construction activities would involve excavations 50 feet in depth for the installment of the cast-in-drilled-hole concrete piles associated with the stitch pile wall and excavations 24 feet in depth between the stitch pile wall and San Pablo Dam Road, minimal grading in front of the stitch pile wall, the removal of approximately 67 trees, and roadway repairs including restriping and placement of approximately 170 feet of guardrail. Construction activities would require the establishment of three temporary staging areas with the first on the northbound lane on La Honda Drive, a second on the north shoulder of San Pablo Dam Road, and a third smaller staging area south of San Pablo Dam Road directly across the embankment failure (Exhibit 1 of CEQA document).
Contact Information
Name
Christina Kelleher
Agency Name
Contra Costa County Public Works Department
Job Title
Environmental Analyst
Contact Types
Lead/Public Agency / Project Applicant
Phone
Name
Syd Sotoodeh
Agency Name
Contra Costa County Department of Conservation and Development
Job Title
Senior Planner
Contact Types
Lead/Public Agency
Address
Phone
Location
Coordinates
Cities
El Sobrante
Counties
Contra Costa, San Bernardino
Regions
Unincorporated
Cross Streets
Approximately 200 feet southeast of La Honda Road and San Pablo Dam Road intersection
Zip
94803
Total Acres
1.62
Parcel #
433-242-018
State Highways
Interstate 80
Railways
N/A
Airports
N/A
Schools
De Anza High School
Waterways
San Pablo Creek, San Pablo Reservoir
Township
1N
Range
4W
Section
3
Base
MtDiablo
Other Location Info
The Project is located on the northern side of San Pablo Dam Road, approximately 200 feet southeast of La Honda Road in unincorporated El Sobrante, Contra Costa County, California
Notice of Completion
State Review Period Start
State Review Period End
State Reviewing Agencies
California Department of Conservation (DOC), California Department of Fish and Wildlife, Bay Delta Region 3 (CDFW), California Department of Forestry and Fire Protection (CAL FIRE), California Department of Parks and Recreation, California Department of Pesticide Regulation (DPR), California Department of Toxic Substances Control (DTSC), California Department of Transportation, District 4 (DOT), California Department of Water Resources (DWR), California Fish and Game Commission (CDFGC), California Governor's Office of Emergency Services (OES), California Highway Patrol (CHP), California Native American Heritage Commission (NAHC), California Natural Resources Agency, California Regional Water Quality Control Board, San Francisco Bay Region 2 (RWQCB), California State Coastal Conservancy (SCC), Delta Protection Commission, Delta Stewardship Council, Office of Historic Preservation, State Water Resources Control Board, Division of Drinking Water, University of California Natural Reserve System (UCNRS)
Development Types
Other (Road and Embankment Repair)
Local Actions
Site Plan, Road and Embankment Repair
Project Issues
Biological Resources, Cultural Resources, Geology/Soils, Tribal Cultural Resources
Public Review Period Start
Public Review Period End
Attachments
Draft Environmental Document [Draft IS, NOI_NOA_Public notices, OPR Summary Form, Appx,]
Notice of Completion [NOC] Transmittal form
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