In December 2018, The Sierra Fund (TSF) closed out a $1.5 million grant from the California Department of Water Resources (DWR) that funded a suite of projects to address mercury and sediment in the Cosumnes, American, Bear, Yuba (CABY) watershed region. The funding was awarded in 2014 as part of a much larger ($5.5 million) grant managed by TSF on behalf of the CABY Integrated Regional Watershed Management (IRWM) group.
Mercury and Sediment Abatement Initiative
Mercury contamination is pervasive in the CABY region, a legacy of the 19th century Gold Rush. Of the estimated 26 million pounds of mercury applied at mining operations in the Sierra Nevada, approximately 13 million pounds were lost to the environment. Today, with each storm event, mercury-contaminated sediment washes off of abandoned mine sites and is transported downstream.
Mercury-contaminated sediment poses significant issues: 1) it reduces water storage capacity in reservoirs, complicating operations for reservoir managers and 2) the mercury can methylate into a bioavailable form and become incorporated into the food web, often accumulating at dangerously high levels in long-lived, predatory sportfish like black bass. Eating contaminated fish is the primary human exposure pathway to mercury, a developmental neurotoxin, and impacts are most significant on pregnant women, infants and children.
Funded Projects and Key Outcomes
Below are goals and outcomes of the projects that made up the Mercury and Sediment Abatement Initiative and which together informed the development of a regional approach to address legacy mercury in the headwaters:
- Relief Hill Hydraulic Mine Remediation Project, led by the Tahoe National Forest
- Goal: Halt sediment and mercury discharge from a hydraulic mine in the South Yuba River watershed using remediation activities designed to control erosion.
- Outcome: Check dams and rock-armored spillways were installed to control the release of sediment offsite from a complex system of tunnels and sluices. Post-construction, disturbed areas were revegetated to curtail additional erosion.
- Malakoff Diggins Hydraulic Mine Feasibility Study, led by The Sierra Fund
- Goal: Quantify erosion and deposition patterns to inform the engineering design for remediation options of the hydraulic mine at Malakoff Diggins State Historic Park.
- Outcome: The United States Geological Survey (USGS) used remote sensing equipment (T-LiDAR) to investigate erosion and deposition rates in the hydraulic mine pit. A comprehensive sediment budget was developed, which informed the design and engineering of remediation options led by NV5 (formerly Holdrege and Kull). TSF helped secure over $8 million awarded in the 2017/2018 state budget to implement the remediation plan at Malakoff Diggins State Historic Park.
- Omega Diggins Hydraulic Mine Assessment, led by the South Yuba River Citizens League
- Goal: Establish baseline data about suspended sediment and mercury concentrations in the Scotchman Creek watershed in order to inform future clean-up activities.
- Outcome: Mercury and sediment data were collected across the watershed and the contribution of mercury and total suspended solids (TSS) during storm events from Alpha and Omega Diggins was quantified. Results indicate that the Red Creek sub-watershed, which includes Omega Diggins is a high priority for future remediation efforts.
- Spring and Shady Creek Assessment, led by the South Yuba River Citizens League
- Goal: Monitor water quality on public lands heavily impacted by hydraulic mining activities in order to establish baseline conditions in the event of the reopening of the San Juan Ridge Mine.
- Outcome: Data were collected on stream flow, annual sediment and mercury loads, the relative proportion of different forms of mercury and the correlation between particulate-bound mercury and suspended sediment. Findings indicate that for these watersheds mercury is primarily transported in particulate-bound form, demonstrating the continued impact of erosion from hydraulic mines sites on these watersheds.
- Combie Reservoir Sediment and Mercury Removal Project, led by the Nevada Irrigation District
- Goal: Determine the water quality treatment process necessary to return clean water back to Combie Reservoir in the Bear River watershed following the removal of mercury-contaminated sediment.
- Outcome: This project successfully refined the sediment and mercury removal process through pilot testing of the effect of polymer use at Combie Reservoir. Nine demonstration trials utilizing sediment removed from two locations facilitated this process, which is now being scaled up to full implementation with $6.3M in funding approved in the Governor’s 2017/2018 budget.
- Mercury-Contaminated Fish: Data Collection and Public Education Project, led by The Sierra Fund
- Goal: Fill critical information gaps on mercury levels in fish that are being consumed from CABY region water bodies and the quantity of fish being consumed in order to increase the amount and accessibility of public health information.
- Outcome: Over 200 fish were collected from six waterbodies in the CABY region, along with 220 angler surveys. These data demonstrate that Gold Country anglers are catching and eating locally caught fish, many species of which contain mercury at levels unsafe for consumption by sensitive populations including children and women who are or could become pregnant. This new information will be provided to public health officials including the Office of Environmental Health Hazard Assessment (OEHHA) in an effort to reduce human exposure to mercury.
- CABY Mercury Forum, coordinated by The Sierra Fund
- Goal: Integrate CABY region projects working to address mercury and sediment and showcase best practices and results, building a regional strategy for addressing contamination from legacy hydraulic mining activity.
- Outcome: Mercury Forum partners convened for 12 quarterly meetings, providing project updates, participating in site tours and sharing best practices and lessons learned. As a result of this collaboration, a regional Headwater Mercury Source Reduction (HMSR) Strategy has been developed that provides a technical basis for identifying, quantifying, and evaluating best management practices (BMPs) for reducing mercury in the CABY region.
To learn more about these and other projects that have been funded through the CABY IRWM, visit: http://cabyregion.org/
TSF is thrilled to wrap up this DWR grant, and we look forward to continued collaboration with CABY and other partners to address the legacy of the Gold Rush in California’s headwaters.
