Guadalupe River Watershed Mercury TMDL


The Guadalupe River Watershed supports many beneficial uses, such as drinking water supply, sport fishing, and habitat for wildlife and endangered species. Santa Clara County has issued a fish consumption advisory for mercury contamination. Mercury concentrations in fish tissue that exceed the U.S. EPA human health mercury fish criterion (0.3 mg/kg), have been measured at numerous creeks and reservoirs in the Guadalupe River Watershed. Elevated mercury concentrations in fish tissue may also pose a threat to wildlife, such as birds, amphibians, and mammals.

The Guadalupe River Watershed Mercury TMDL examined this water quality problem and provided a watershed-wide mercury management strategy. The main source of mercury in the Watershed is the New Almaden Mining District, the largest-producing mercury mine in North America. Other sources include atmospheric deposition from global and local sources, soil erosion from areas not known to contain mines, urban stormwater runoff, seepage from landfills, and Central Valley Project water inputs to Calero Reservoir. In addition to being the primary regulatory means of achieving water quality goals in the watershed, the Guadalupe River Watershed Mercury TMDL will simultaneously reduce the amount of mercury in the Bay in accordance with the San Francisco Bay Mercury TMDL's proposed requirements.
The Guadalupe River, downstream

May 2016 TMDL Implementation Update

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:

  • In 2009, the Midpeninsula Regional Open Space District and San Francisco Estuary Partnership jointly received a grant from the Water Board and U.S. EPA Clean Water Act Section 319(h) funds. In fall 2014, the grantees completed remediation of an eroding slope of mercury mining waste at Hicks Flat. Before and after photos can be found on the Partnership’s website.
  • In June 2013, the Board adopted Site Cleanup Requirements Order No. R2-2013-0024 (SCRs) for Guadalupe Mine, owned by the Guadalupe Rubbish Disposal Company (GRDC). The SCRs require GRDC to complete appropriate mercury mining waste cleanup and stabilization measures. GRDC has submitted a report that includes detailed mapping of mining waste and slope erodability evaluation. Next, Water Board staff will visit the site to discuss the report in the field with GRDC and its consultant team.
  • The Santa Clara County Department of Parks and Recreation and San Francisco Estuary Partnership have jointly received several grants for mine cleanup projects. These projects are underway and staff will continue to work with them on these projects.
    • Senador Mine: County Parks has completed design plans to reduce erosion of mercury mining wastes at Senador Mine. This project is funded by U.S. EPA’s San Francisco Bay Water Quality Improvement Fund. The project will restore a headcut and other targeted features in a creek channel, remediate several small calcine piles (piles of roasted mercury ores), and reduce erosion of mercury mining wastes. Nearly 300 pounds of mercury will be removed or stabilized. Construction is expected to be undertaken and completed in the 2016 dry season.
    • Calcine-paved roads: County Parks completed design plans to remediate calcine-paved roads in Almaden Quicksilver County Park. Approximately 4 miles of historic mine roads were paved with calcines, and are one of the last areas of eroding calcines in the Park. Concurrent with Senador Mine, construction is expected to be undertaken and completed in the 2016 dry season.
    • Upper Jacques Gulch: In April 2015, County Parks and the Partnership received a grant award from the Water Board and U.S. EPA Clean Water Act Section 319(h) funds. This grant will be used to complete remediation design for the portion of Jacques Gulch that was not previously remediated. (The lower portion of Jacques Gulch was remediated in 2010 by Santa Clara Valley Water District under a Natural Resource Damages Assessment legal settlement unrelated to the TMDL.)
  • The Santa Clara County Department of Parks and Recreation is working on another mine cleanup project.
    • Creeks adjacent to Hacienda Furnace Yard: Under a Natural Resource Damages Assessment legal settlement unrelated to the TMDL, County Parks is developing designs to restore creeks adjacent to the Hacienda Furnace Yard, by far the largest mercury ore processing facility at New Almaden. This would remove calcines from about 500 feet of creek bed, and restore these stretches of creeks. More information on the New Almaden Mine CERCLA Site is available at: Construction is planned for the 2017 dry season.
  • Reports from mine site owners are available here:

Guadalupe Rubbish Disposal Company

Santa Clara County Department of Parks and Recreation

Midpeninsula Regional Open Space District

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).

Coordinated Monitoring:

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
On June 1, 2010, the U.S. Environmental Protection Agency approved the Basin Plan amendment adopted by the Regional Water Board in October 2008. These actions establish New Water Quality Objectives and Total Maximum Daily Loads (TMDLs) and an Implementation Plan for mercury in waters of the Guadalupe River Watershed. The amendment is now part of the Water Quality Control Plan for the San Francisco Bay Basin (Basin Plan), the master planning document for water quality in the Bay Area.

Regulatory Documents

Previously, 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
Slide presentation
Streambank Repair Guidance Manual for the Private Landowner (Santa Clara Valley Water District publication)

Reference documents
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:
Carrie Austin
Water Resource Control Engineer
San Francisco Bay Regional Water Quality Control Board
1515 Clay Street, Suite 1400
Oakland, CA 94612
Phone: 510-622-1015
Fax: 510-622-2460