MITIGATING NON-POINT SOURCES OF DEGRADATION: A CALFED PROGRAM TO IMPLEMENT STRUCTURAL AND NON-STRUCTURAL ALTERNATIVES IN ROCK SLOUGH

This paper presents the findings, conclusion and recommendations for the evaluation of structural and non-structural alternatives to reduce non-point sources of salinity to a drinking water source. An integrated monitoring and modeling approach was taken to evaluate the alternatives to reduce non-point sources (agricultural drainage and groundwater seepage) of salinity in Rock Slough, California. Rock Slough and Contra Costa Canal were identified by CALFED Bay Delta Program and California Department of Water Resources as having degraded water quality and included the Rock Slough Water Quality Improvement Project (project) as an integral part its CALFED program. The goal of this project is to reduce, to the extent possible significant sources of water quality degradation along Rock Slough and CCC. The major constituent of concern is salinity and possible sources of degradation are primarily non-point sources of pollution (i.e. agricultural drainage, wet weather runoff and groundwater seepage). This project is setting the precedent in the San Francisco-Bay Delta on how to address other nonpoint source pollution issues related to salinity, as water quality degradation of Delta waterways is becoming a bigger issue.CCWD and the Carollo Engineers team (Project Team) are implementing a multi-year integrated modeling and monitoring program (including a stakeholder program) to identify and quantify the sources of degradation and to develop an effective water quality improvement plan for Rock Slough. The Project Team decided to implement a phased approach, with the anticipation that there may be a need to advance to a more complex modeling approach as warranted. Phase I of the project included conducting a comprehensive study to identify and quantify the sources of degradation. Phase II of the project included the identification and development of structural and non-structural alternatives, identification of water quality improvements (including cost effectiveness), estimation of redirected impacts, and selection of a preferred alternative. Phase III entailed the preparation of environmental documentation and permitting of the identified alternative. Phase IV includes design of the selected alternative and construction.