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B1: Impaired Water Bodies Improvement

This project helps the District meet surface water quality standards and reduces pollutants in streams, groundwater, lakes and reservoirs. Efforts are carried out in compliance with the Regional Water Quality Control Board (RWQCB) Total Maximum Daily Loads (TMDLs) standards as they continue to evolve (TMDLs are the maximum amount of a pollutant that a water body can receive and still safely meet water quality standards). Under this project the District employs treatment systems in reservoirs to reduce methylmercury formation, and helps create realistic plans and expectations for reducing contaminant loads by engaging in the regulatory development process with the RWQCB for new and emerging contaminants.


  • Reduces contamination in creeks and reservoirs
  • Improves water quality, including water going to drinking water treatment plants
  • Reduces mercury in reservoirs to prevent its entry into the food web
  • Improves fisheries by reducing mercury contamination
  • Supports regulatory compliance of TMDL standards affecting District operations

Project Status

(As of September 2017)

  • The project is on schedule and within budget.

Treatment Systems in Reservoirs

  • Oxygenation systems are operated continuously all summer and were shut down in September when reservoirs were no longer stratified. Stratification occurs in the summer when the reservoirs have distinct layers based on temperature. The bottom layer (hypolimnion) is where mercury is converted to methylmercury under anoxic (no oxygen) conditions. 
  • Performing monthly to twice monthly water quality monitoring at Almaden, Guadalupe, Calero, and Stevens Creek reservoirs and Lake Almaden.
  • Coordinating with project partners (County of Santa Clara, Midpeninsula Regional Open Space District, and Guadalupe Rubbish Company) and the San Francisco Regional Water Quality Control Board to plan the second 5-year phase of the Coordinated Monitoring Program for the Guadalupe River Mercury TMDL project. For more information on the Guadalupe Mercury TMDL project, please see here
  • Published a Request for Proposal for the next phase of coordinated monitoring. The resulting consultant contract will develop a monitoring plan and implement monitoring requirements shared by all partners in the Guadalupe River Mercury TMDL. The contract will be funded by all partners via a cost share agreement. 
  • Obtained services for scientific review of mercury data relating to oxygenation system efficacy and reduction of methylmercury in fish.
  • Presented interim results of technical studies of methylmercury controls at the International Conference on Mercury as a Global Pollutant in July. (ICMGP Presentation)

Prioritization plan and pollution prevention activities

  • Updated the B1 Prioritization Plan with revised analysis of impaired water bodies. 
  • Pollution Prevention Activity #1:
    Accumulation Point Mapping (Guadalupe River): trash was cleaned up on the FY16 accumulation map, removing approximately 78 cubic yards of trash. Cleaned up about 2 cubic yards of trash raft material on September 13, 2017. Guadalupe River Trash Mapping: Updated the Guadalupe River Trash Accumulation Point GIS mapping with 2017 data.

  • Pollution Prevention Activity #2:
    Funding a City of San José Park Ranger: Continued financial support of a Park Ranger to monitor and discourage the re-establishment of encampments along Guadalupe River and Coyote Creek.

  • Pollution Prevention Activity #3:
    Coyote Creek Trash Mapping: Began planning for Coyote Creek Trash Accumulation Point GIS mapping.

  • Pollution Prevention Activity #4:
    Completed first phase of angler survey at mercury impaired reservoirs and lakes to help inform outreach and signage. 

Key Performance Indicators

  1. Operate and maintain existing treatment systems in 4 reservoirs to remediate regulated contaminants, including mercury
  2. Prepare plan for the prioritization of pollution prevention and reduction activities
  3. Implement priority pollution prevention and reduction activities identified in the plan in 10 creeks

Prioity B-200

FY 17 Annual Report Status 

Status On Target
Project Start FY 2014
Project Finish FY 2028
Safe Clean Water
Program funding
 $25.1 M**

(2015 Dollars)

**More financial information: 5-Year Implementation Plan, pages: 19-27 

Location Countywide

For more information:

 Calero oxygenation station

Calero Dam oxygenation station treatment system

Map of reservoir oxygenation systems [PDF]

Oxygenation system

Guadalupe Trash Raft Clean-Up on September 13, 2017

D2_Guad trash Clean-up 3

D2_Guad trash Clean-up 2

D2_Guad trash Clean-up 1