- State & Regional Water Boards
- Decisions Pending and Opportunities for Public Participation
Guadalupe River Watershed Mercury TMDL
This update covers implementation actions at mercury mine sites, oxygenation to suppress methylation of mercury in reservoirs and lakes, and coordinated monitoring.
Mercury mine sites
As planned, we started implementation at the top of the watershed by requiring mine site owners to evaluate and report on the potential for mining waste to erode from their properties. These reports are posted below. The following erosion control work is underway:
Oxygenation to suppress methylation of mercury in reservoirs and lakes:
The Santa Clara Valley Water District continued its voluntary methylmercury production and control studies, which it initiated in 2005. Initially, the District tried solar powered circulators, which were effective in suppressing methylmercury production in Lake Almaden but not in Almaden or Guadalupe Reservoirs. Subsequently, the District installed more powerful hypolimnetic oxygenation systems in Calero, Guadalupe, and Almaden Reservoirs.
Low water levels due to the drought interfered with these studies. More information is available in their December 2015 biennial report, and previous December 2013 biennial report and December 2011 biennial report. (Their next report is due December 2017).
The four entities discussed above have established a coordinated monitoring program, led by Santa Clara County Parks. Monitoring data gathered thus far is inconclusive regarding changes in mercury concentrations. Prey fish were monitored at five locations in 2011 and 2012, and there was no statistically significant difference in prey fish mercury concentrations between these years. A cursory analysis of prey fish monitoring data shows that fish mercury concentrations were lower in reservoirs in 2011, as compared to 2004 (see comparison plot), but higher in Lake Almaden and creek sites (see comparison plot). The program submitted two interim reports, the January 2012 and January 2013 annual data reports. Mercury loads to San Francisco Bay were monitored in the 2014-2015 wet season, and prey fish monitoring is scheduled for 2016. A report on 2011 to 2016 monitoring is due in early 2017.
TMDL Approved by U.S. EPA
U.S. EPA gives final approval to TMDL and Water Quality Objectives for Mercury in the Guadalupe River Watershed
Regulatory DocumentsPreviously, the State Office of Administrative Law (OAL) approved the amendment on February 24, 2010, the State Water Board approved the amendment on November 17, 2009, and the Regional Water Board adopted the amendment on October 8, 2008.
Materials from Sept. 11, 2008 meeting with Alamitos Creek property owners
Questions and Answers about the Guadalupe River Watershed Mercury TMDL
Streambank Repair Guidance Manual for the Private Landowner (Santa Clara Valley Water District publication)
Final Conceptual Model Report, May 22, 2005 (Tetra Tech, Inc.)
Due to the size of the original PDF document (47.98 MB), we have made both the full document and each separate chapter available below for download. All these PDF files were created using Adobe Version 6. If you do not have this version (or higher), you will not be able to view the files.
Full Document (47.98 MB)
Individual Files (smaller-size documents):
Cover Page, Table of Contents, and Executive Summary (1.4 MB)
Chapter 1. Introduction (233 K)
Chapter 2. Watershed Characterization (15 MB)
Chapter 3. Data Summary (2.3 MB)
Chapter 4. Estimated Mercury Loads (4.3 MB)
Chapter 5. Conceptual Model of Mercury (5.9 MB)
Chapter 6. Summary (203 K)
Chapter 7. References (233 K)
Derivation of Numeric Wildlife Targets for Methylmercury in the Development of a Total Maximum Daily Load for the the Guadalupe River Watershed (USFWS 2005) (2.3 MB)
Reservoir Sediment Sampling, April 2005 (Tetra Tech, Inc., 203 KB)
Draft Project Plan, June 2004 (407 KB)
Preliminary Project Definition, August 2004 (45 KB)
Santa Clara Valley Water District (home page)
For extensive Guadalupe River Watershed information, scroll to the bottom of the page and click on "Healthy Creeks and Ecosystems", from the list on the left, first click on "Watersheds," then click on "Guadalupe."
CalFed (Bay-Delta Authority) Mercury Project
See especially the document "Mercury Strategy for the Bay Delta Ecosystem"
San Francisco Bay Mercury TMDL
For more information contact:
Water Resource Control Engineer
San Francisco Bay Regional Water Quality Control Board
1515 Clay Street, Suite 1400
Oakland, CA 94612