Rock Slough Water Quality Improvements Project

Contra Costa Water District, 
California

Rock Slough Water Quality Improvements Project

Service Type: 
Project Highlights: 
  • Implementation of an integrated modeling and monitoring approach to select alternatives to mitigate salinity in the raw water intake.
  • Correlations were developed between salinity trends and wet weather conditions, along with an initial salt balance for the study area.
  • Project includes a stakeholders' involvement program.

Carollo completed this watershed assessment and water resources study for the Contra Costa Water District (CCWD) as part of the CALFED Bay-Delta Program in the San Francisco Bay Delta. The goal of this project is to reduce, to the extent practicable, significant sources of water quality degradation in Rock Slough, which is where CCWD’s raw water intake is located. The major constituent of concern is salinity, but total organic carbon (TOC) and other trace contaminants are also an issue. Possible sources of degradation are primarily non-point sources of pollution (i.e., agricultural drainage, wet weather runoff, and groundwater seepage).

The project’s goal is to develop an approach and program that can be implemented elsewhere in the Delta to address similar concerns.

The project involves the implementation of an integrated modeling approach and a comprehensive water quality sampling program in order to develop an effective water quality improvement program.

The integrated modeling approach includes the use of a surface water model and potentially groundwater and receiving water models to characterize the complex hydrologic/hydraulic interaction among these water sources. Carollo will link these to test various alternatives for water quality improvement.

The project includes a stakeholder involvement program to help assure that a wide-range of potential alternatives are identified, and to develop a decision analysis framework for achieving consensus on the preferred solution. The public involvement program is an essential component of the project due to the many regulatory/resource agencies with jurisdictional authority in the San Francisco Bay-Delta. The project includes coordination with CALFED, the USEPA, the California Department of Water Resources, the California Department of Fish and Game, the California Department of Health Services, the U.S. Marine Fisheries Service, the State Water Resources Control Board, and local landowners.

An integrated monitoring and modeling approach is being implemented to select structural and non-structural alternatives to mitigate salinity loading to Rock Slough, a drinking water intake for CCWD.