NOI and NOA for Delta Dams Rodent Burrow Remediation Project


Notice of Intent to Adopt a Mitigated Negative Declaration

and Notice of Availability of the Draft Mitigated Negative Declaration

for the Delta Dams Rodent Burrow Remediation Project

Notice is hereby given that the California Department of Water Resources (DWR) Division of Operations and Maintenance, Environmental Assessment Branch intends to adopt a Mitigated Negative Declaration (MND) for the Delta Dams Rodent Burrow Remediation Project.

Notice is also hereby given that the Draft Initial Study (IS) and Proposed MND prepared by DWR have been released for a 30-day public review.

Project Title: Delta Dams Rodent Burrow Remediation Project

Project Summary, Background, and Impacts: The DWR California State Water Project (SWP) is a water storage and delivery system that consists of many reservoirs, aqueducts, power plants, and pumping plants. The California Aqueduct is a central feature of the SWP; it begins at Clifton Court Forebay, located in the southwestern portion of Contra Costa County, and extends over 400 miles to the south. Another feature of the SWP, the South Bay Aqueduct begins at Bethany Reservoir, which is located south of Clifton Court Forebay, and carries water to communities in Alameda and Santa Clara Counties, passing through Dyer Reservoir, located west of Bethany Reservoir, and passing through Patterson Reservoir, located south of Dyer Reservoir.

The earthen embankment dams at Clifton Court Forebay, Dyer Reservoir, and Patterson Reservoir have been subject to ongoing rodent burrowing throughout their service life. Rodent burrows are a recognized hazard to dams and levees because they can promote piping and internal erosion that can ultimately lead to dam failure. DWR proposes to undertake the Delta Dams Rodent Burrow Remediation Project (Project) to remove/fill in existing burrows and improve the integrity of each of these dams. The Project would involve rodent burrow remediation and restoration measures, ongoing monitoring, and permanent measures to prevent future burrowing where warranted.

The proposed burrow remediation and dam restoration involves collapsing and/or excavating burrows, backfilling the dam surface, and compacting the soil. Measures to prevent future burrowing include placing wire and rock over the earthen dam face.

Each dam is unique in its design, construction, operation, downstream consequences, and severity of burrowing activity; thus, while the remediation program is similar across all three dams, there are differences in the application of the remediation strategies to specific sections of each dam. These strategies are based on the location and density of the burrows on each dam or dam reach, complexity of burrow clusters, the phreatic surface (water level), slope stability, and other factors.

The IS did not identify any significant and unavoidable impacts. The IS analysis determined that the Project would result in potential adverse impacts associated with Biological Resources, Cultural Resources, Geology and Soils, Hydrology and Water Quality, and Tribal Cultural Resources, but that these impacts would be reduced to less-than-significant levels with implementation of mitigation measures.

Location: The proposed Project activities would occur at three DWR facilities—Clifton Court Forebay, Dyer Dam and Reservoir, and Patterson Dam and Reservoir. Clifton Court Forebay is located in Contra Costa County, and the Dyer and Patterson facilities are located in Alameda County. Each is located within the unincorporated area of the respective county, and lands surrounding each facility are primarily in agricultural production, grazing, and/or open space. A water treatment plant is located south of Patterson Dam and Reservoir. All of the Project activities would occur within DWR property or rights-of-way

Review: The 30-day public review period for this Draft IS and Proposed MND begins December 3, 2021 and ends January 3, 2022. The Draft IS and Proposed MND can be reviewed by accessing the links below:

Paper copies of the Draft IS and Proposed MND are available for review during normal business hours at:

Department of Water Resources

Division of Operations and Maintenance Headquarters

715 P St, 5th Floor

Sacramento CA 94236-0001

Department of Water Resources

Delta Field Division

5280 Bruns Road

Byron CA 94514

Submittal of Comments:

Comments regarding the Draft IS and Proposed MND should be submitted in writing to:

Sara Paiva-Lowry

Environmental Regulatory Compliance Section Manager

Division of Operations and Maintenance

or via email at

Comments are due no later than 5 p.m. local time on January 3, 2022.

If comments are provided via email, please include the project title in the subject line, attach comments in Microsoft Word format, and include the commenter’s U.S. Postal Service mailing address.


All comments received will be made available for public review in their entirety, including the names and addresses of the respondents. Individual respondents may request that their name and/or address be withheld from public disclosure. DWR will honor such requests to the extent allowable by law. If you wish us to withhold your name and/or address, you must state this prominently at the beginning of your comment.