Headwater Mercury Source Reduction Technical Advisory Committee (HMSR-TAC)

Next HMSR-TAC: HMSR Workshop, Spring 2020:
Thursday, May 14, 2020
10:00 am – 5:30 pm via Zoom
Topic: Hydraulic Mines and Mine Features and Mercury in Forest and Land Management

Contact Nick Graham for meeting location details.

Interested in joining the TAC? See the Membership section below.

To read the HMSR Strategy, click here.

To view past HMSR-TAC agendas, click here.


In 2006 The Sierra Fund (TSF) carefully assembled a Working Group of over 60 technical, policy and agency experts to provide sound advice and feedback to our work to assess and address legacy mining impacts in the Sierra Nevada. Since that time our project development strategy has been directed in part by outcomes of annual Working Group meetings which are used to offer critical insight to key agencies and the public about progress, direction, and planning processes to confront impacts from the California Gold Rush. Through our sustained efforts to inform and include members of the public we have conducted outreach on our work to address legacy mercury sources in all 22 counties of the Sierra Nevada and given more than 14 site tours of hydraulic mine sites for agency leaders and members of the public.

Since 2011, TSF has been working with a variety of partners to develop best practices for addressing headwater sources of mercury through the design and implementation of pilot projects. Project targets include:

Hydraulic Mines and Mine Features: Of the approximately 20 million pounds of mercury imported from the Coast Range to the Sierra Nevada for use in gold processing, an estimated 10-13 million pounds were lost to the environment. Hydraulic mine operations were associated with the highest levels of mercury loss. At the denuded sites of these mines, inorganic mercury adsorbs to fine silts and clays, which erode and become suspended during storm events. Despite the fact that unregulated hydraulic mining ceased in 1884, and many debris control dams were built to hold back the tailings, there is a significant amount of inorganic mercury washing off of legacy hydraulic mine sites, especially during storm events. This allows for mercury to be transported into aquatic ecosystems where it can methylate and become incorporated into the food web. See Malakoff Diggins.

Mercury Contaminated Sediment in Reservoirs: Until recently, addressing mercury loading associated with abandoned mines was not considered a high priority strategy for the Bay-Delta because there was the erroneous assumption that foothill reservoirs were holding back the mercury source. The reservoirs, however, are filling up with mercury-contaminated sediment and their trapping efficiency is decreasing. In addition, scientific advancements indicate that even low levels of mercury in sediment and water are prone to methylation, leading to high levels in fish through biomagnification and bioaccumulation. Subsequent research suggests that mercury bound (adsorbed) to fine silts and clays that originate from hydraulic mine sites can be transported over the top of dams, meaning that when reservoirs spill turbid water during storm events, mercury is being delivered to downstream waterways including the Bay-Delta. See Combie Reservoir.

Mercury Exposure: As a result of mercury transported off-site from legacy mines, the vast majority of water bodies in the Sierra Nevada and the Bay-Delta are listed as impaired for mercury under section 303(d) of the Clean Water Act. Numerous water bodies have state-issued fish consumption advisories for mercury warning sensitive populations, including women and children, to avoid consumption of predatory fish such as bass altogether. Consumption of mercury contaminated fish is the primary pathway of human exposure to this developmental neurotoxin. Exposure to mercury during pregnancy can cause permanent neurological deficits in children and the effects of mercury exposure during childhood include slow development, language and memory impairment, and attention disorders. See our Gold Country Angler Survey.

Mercury and Forest Management: Predominant forest management strategies for the Sierra Nevada region  have consistently included fire suppression in developed areas, clear-cut timber harvest practices in old growth areas, and reforestation using single species, even-aged planting in denuded areas. Together these factors have led to the development of stand structures and fuel loads that represent increasingly unhealthy forest conditions prone to fire. Legacy mines in the Sierra are a complicating factor for forest management. Hydraulic mines consist of altered landscapes where hilltops were excavated to recover gold.  These areas are typically partially vegetated with dense manzanita and madrone, leading to very high fuel loading.  Mercury remains in the soils at these sites, and can be transported into watersheds and downstream reservoirs. The effect of wildfire on watershed health in a region with numerous hydraulic mine sites and unprecedented fuel loads has resulted in sedimentation and volatilization events and unknown releases of mercury. Forest fires occurring in the hydrologic path between these sites and stream channels may result in swift and significant transport of sediment and mercury into vulnerable water bodies due to loss of the buffering function of the forest.

In 2014 TSF received funding from DWR to lead a regional Mercury Forum. From 2015 – 2017 the Forum met quarterly to share lessons learned around permitting, sampling, and remediation activities for a bundle of sediment and mercury abatement projects in the Cosumnes, American, Bear, Yuba (CABY) watershed region. To date seven M.S. theses that address legacy mercury and sediment in our headwaters have been completed by CSU, Chico graduate students under the direction of TSF’s Science Director (with the collaboration of technical experts) and four additional theses are currently underway.

TSF launched the Headwater Mercury Source Reduction Technical Advisory Committee (HMSR-TAC) in 2017 as a way to leverage the outcomes of the Mercury Forum and facilitate the development and implementation of a regional Strategy to address mercury contamination in Sierra Nevada watersheds. The inaugural HMSR-TAC meeting, held in July 2017, focused on the inventory and assessment of hydraulic mines and mine features as key headwater sources of mercury. Refer to the top of the page for the date and topic of future meetings.

Planning and Operating of the HMSR-TAC

Vision: To reduce headwater sources of mercury, thus protecting and restoring ecosystem and community resiliency in the Sierra Nevada to the benefit of both regional and downstream stakeholders. See The Sierra Fund’s 2017 Strategic Plan, A Platform for Action for additional information about our organizational mission and approach.

Mission: To facilitate coordination, collaboration, and capacity building among scientists, regulators, landowners, resource managers, and interested stakeholders in the development and implementation of a strategy (HMSR Strategy) to assess and mitigate the impacts of headwater sources of mercury from the Sierra to the sea.

Objectives: The source and transport of mercury in Northern California watersheds, from hydraulic mine sites to foothill reservoirs and beyond, has detrimental implications for ecosystem resiliency and community health. The Sierra Fund has brought together the diverse stakeholders of the HMSR-TAC to create a forum that will:

  1. Showcase regional, local, and project-specific research, actions, and methods for the assessment and mitigation of headwater sources of mercury and associated downstream impacts.
  2. Identify and seize opportunities to address land and water management activities on mercury impacts to better ecosystem and human health objectives.
  3. Provide a cohesive platform for stakeholders to share, revise, and integrate best-practices for headwater mercury source reduction into the HMSR Strategy.

Geographic Area of Focus: The primary geographic scope of the HMSR-TAC is the 22 counties that form the headwater region of the Sierra Nevada. However, given watershed-wide mercury fate and transport processes, the forum welcomes participation by stakeholders and technical experts from all regions impacted by mercury statewide.

Membership: The role of the HMSR-TAC and the purpose of the Partnership is to direct and inform specific tasks and outcomes associated with the implementation of the HMSR Strategy. This collaborative effort is sustained by the participation of regional and topical experts through quarterly meetings convened and facilitated by The Sierra Fund. The HMSR-TAC is not open to the public; however, we aim to recruit additional experts and key stakeholders to the forum as relevant to the four strategic targets. Please contact The Sierra Fund if you are interested in joining the TAC or have suggestions for additional members.

Meetings: HMSR-TAC meetings are held quarterly. Proposed dates for future meetings will be identified during scheduled meetings and formal save-the-date and draft agendas will be sent to forum participants a minimum of 4 weeks in advance of the next scheduled meeting. Past meeting agendas will be made available on The Sierra Fund’s website.

Facilitation: HMSR-TAC meetings will be facilitated by staff of The Sierra Fund, at the will of the HMSR-TAC members. Facilitator(s) will guide participants in discussion in a manner that is focused and respectful and within the timeframe specified by the applicable forum agenda.

Ground Rules: HMSR-TAC members agree to follow and enforce ground rules, modeled after those of the Delta Tributaries Mercury Council (DTMC), to ensure that a collaborative and respectful environment is fostered and maintained at forum meetings:

  • Respect start and end times
  • Keep discussion focused
  • Give all participants a chance to speak
  • Be brief and to-the-point
  • Do not dominate the conversation
  • Do not interrupt fellow stakeholders
  • No side conversations
  • Share all relevant information
  • Active participation by all
  • Disagree openly

Document Review Process: The HMSR-TAC will review documents relevant to their mission as requested. Documents should be submitted in electronic form at least two weeks prior to a quarterly HMSR-TAC meeting for discussion at the meeting. Documents, with the exception of the HMSR Strategy, will not be a product of the HMSR-TAC. Individual review of relevant information may also be sought from HMSR-TAC members via email.

Organizations and Agencies Represented in the HMSR-TAC: 

  • California Department of Conservation
  • California Department of Public Health, Environmental Health Investigations Branch
  • California Department of Water Resources
  • California Office of Environmental Health Hazard Assessment
  • California State University, Chico
  • Central Valley Regional Water Quality Control Board
  • Forsgren Associates, Inc.
  • Great Lakes Environmental and Infrastructure
  • KTC Environmental
  • McCord Environmental, Inc.
  • Nevada Irrigation District
  • NV5
  • Public Policy Institute of California
  • Sierra Forest Legacy
  • The Sierra Fund
  • Sierra Nevada Conservancy
  • South Yuba River Citizens League
  • Teichert
  • United States Forest Service, Tahoe National Forest
  • United States Geological Survey
  • University of California, Berkeley
  • University of California, Davis
  • University of South Carolina

Carrie Monohan, Ph.D.
Science Director, The Sierra Fund
Email: carrie.monohan@sierrafund.org
Phone: (530) 265-8454 x214