The Santa Clara Valley Water District is the lead agency on behalf of the Santa Clara Basin Watershed Management Initiative (WMI) for the development of a Total Maximum Daily Load (TMDL) for mercury in the entire Guadalupe River Watershed.

Former mercury mines are located in the upper Guadalupe River Watershed, which have contributed mercury to downstream surface waters and San Francisco Bay. The New Almaden Mining District in the Guadalupe Creek and Alamitos subwatershed was the largest producer of mercury in North America. Mercury in the mining district is primarily present as the mineral cinnabar. Mercury in downgradient water and sediment can be present in dissolved or particulate forms. Under appropriate conditions, bacteria can convert inorganic mercury to the organic form, methylmercury, which is the form of primary concern from a human health and ecological perspective due to its greater
toxicity and ability to bioaccumulate.

Other sources of mercury to the watershed include atmospheric deposition from global and local sources, stormwater runoff, and seepage from contaminated sites and landfills.

The following documents have been completed and are available for downloading. Future documents related to the study will be posted as they are completed:

• The Data Collection Report presents the wet and dry weather sampling of the Guadalupe River Watershed described in the Data Collection Plan (Technical Memorandum 5.3). The primary objective of Part 1 of the sampling effort was to assess the magnitude of mercury loading to the Guadalupe Watershed during the wet season. The major objectives of the dry weather sampling effort were to determine the changes in methylmercury concentrations due to stratification of the reservoirs and to measure mercury concentrations in fish tissue throughout the watershed.

  • Volume I (PDF 7 MB) February 2005

  • Volume 2 (PDF 800 KB) February 2005

• The Administrative Record includes all information sources cited in the technical memoranda of the Guadalupe River Watershed Mercury TMDL Project.
  • Administrative Record (PDF 147 KB)

• The Conceptual Model: From analyses of the historical data and synoptic survey results, a conceptual model is emerging for mercury behavior in the Guadalupe River Watershed. All chapters below are PDF files.

• The Data Collection Plan is the culmination of considerable effort to identify, obtain, and evaluate essential information for the development of a Total Maximum Daily Load (TMDL) for Mercury in the Guadalupe River Watershed.

• Data Collection Plan Technical Memorandum 5.2.3
  ( PDF 5 MB) posted 4/21/04

• The Synoptic Survey was designed to meet two primary objectives. First, to provide a general view of mercury contamination in the watershed. The survey had wide spatial coverage. Sampling and chemical analysis was conducted at 24 different locations, using a consistent set of sampling and analytical methods.
  
  The second objective was to produce an early indication of where key mercury transformations of solid phase mercury to bioavailable mercury are and are not occurring in the surface waters of the Guadalupe Watershed.
  
  
  • Download the final survey report (PDF 2.6 MB)
    Sept. 9, 2003
    
    
  • Download the survey plan (PDF 2 MB)
    July 30, 2003
    
    
  • Survey of Alamitos Creek from McKean Road to Almaden Reservoir - Sept. 27, 2003 - Addendum to Synoptic Survey Report
    (PDF 4.5 MB) Posted April 21, 2004

• Neighborhood work notice for the Guadalupe Watershed mercury study (PDF 971 KB) posted 8/15/03

• The Preliminary Problem Statement is an important first step in the development of the Guadalupe River Watershed Mercury TMDL. The purpose of this document is to provide a concise description of the current understanding of the processes or factors that are most relevant to controlling mercury in the Watershed. (PDF 1.15 MB)

• Project Quality Assurance Plan
  (PDF 851 KB)

• Project Management Plan
  (PDF 2 MB)