Nonpoint source pollution has been identified nationally, in the State of California, and in the Bay Area as the leading source of degradation of natural waters. The magnitude of nonpoint source pollution is accentuated in coastal areas where human population is high and where pressures from urban development, industrial and commercial activities, and recreational use are the greatest. San Francisco Bay is listed as an impaired water body for PCBs and mercury under Section 303(d) of the federal Clean Water Act . The RWQCB has recently developed Total Maximum Daily Load (TMDL) reports for the Bay for mercury and PCBs.
For reports and data related to this project, please see this supporting page.
Both TMDLs assert the significance of urban runoff, call for load reductions of greater than 50% over the current estimates and call for improved and expanded implementation of best management practices (BMPs). However, there is presently no consensus on how this can be done. Some important, unanswered questions are:
- Where are the contaminated sites?
- What about sources such as atmospheric deposition?
- Will conventional source control, treatment control, or maintenance control BMPs work?
- If so – which BMPs, and when, and under what circumstances?
- How much will it cost?
This project was chosen to enhance the tools available to assist local environmental managers to evaluate and prioritize BMP methods for the control and treatment of nonpoint source mercury and PCB pollution. Municipalities are implementing a wide variety of actions including construction, erosion, and sediment control BMPs, site design, source control, and treatment control BMPs, and waste handling and disposal. However, in relation to Hg and PCBs many of these programs lack some important information:
- Region- or site-specific data to determine the optimal combination of BMPs
- Performance measures for success of BMPs
- Base maps for understanding the relationships between source areas and the point on the Bay margin where loads enter the Bay
Project Goal This project aims to assist Bay area municipalities in implementing the mercury and PCB TMDLs through the development of specific information on drainage systems, sediment loads, distribution of Hg and PCB contamination, urban runoff loads, BMP function in relation to trapping or removing Hg and PCBs.