The 19th century California Gold Rush is considered the primary source of mercury contamination to the Sacramento River and the San Francisco Bay-Delta. An estimated 26 million pounds of mercury were used in the Sierra Nevada during the California Gold Rush. Of these, an estimated 10 million pounds were lost to the environment in placer or hydraulic mining operations and another 3 million pounds were lost from hard rock mining. The CABY region in particular was the scene of the most intensive mining and most extensive mercury pollution in California.
Mercury from historic gold mining can still be found at dangerously high levels in Sierra Nevada waterways and fish tissue. Continuous and ongoing erosion of mine sites in the headwaters, especially with strong winter storms, washes mercury-contaminated sediment into downstream reservoirs such as Englebright or Combie Reservoir. In these reservoirs, the sediment reduces water storage capacity while the mercury transported with it has the potential to methylate and permeates the aquatic ecosystem, becoming a serious health hazard to the humans and wildlife that rely on the water body and downstream environments.
In addition to mercury contamination, massive amounts of sediment draining from eroding hydraulic mining pits also impacts water quality and water storage in the CABY region.
This mercury-contaminated sediment discharged from hydraulic mines is deposited in the upstream reaches of CABY region reservoirs, where it occupies valuable water storage space. It is estimated that 2.1 billion cubic meters of sediment have filled reservoirs across the state of California (Minear and Kondolf, 2009). In other words, sediment is filling 1.7 million AF of water storage space in California’s reservoirs, decreasing the capacity of about 200 reservoirs to half their original capacity.
The ongoing and complex problem of mercury and sediment discharge in Sierra Nevada waterways results in a broad range of interconnected needs for the Sierra Nevada foothills, and the CABY region in particular.
After seven years of working to assess and address legacy mining’s impacts on the region, the organizations and agencies that have partnered to form the CABY Mercury and Sediment Abatement Initiative have identified two places the drainage from abandoned mines can viably be treated:
- Upland sources such as abandoned hydraulic mining sites where the barren badlands topography and heavy historic mercury usage contribute to high amounts of mercury-contaminated sediment washing downstream with every rain; and
- Reservoirs downstream from abandoned hydraulic mines where the discharged sediment accumulates, occupying water storage space and bioaccumulating in the aquatic food chain.
The CABY Mercury and Sediment Abatement Initiative includes: A) Implementation of sediment reduction and mercury remedial activities at three sites impacted by former mining sites; B) Completion of planning and design for two additional remedial sites; and C) Coordination of regional mercury and sediment abatement efforts through the CABY Mercury Forum. In addition, the Project includes implementation of a monitoring component to evaluate fish mercury levels in water bodies impacted by mercury sediment, and education and outreach to local communities to help minimize mercury exposure.
The projects included in the CABY Sediment and Mercury Abatement Initiative are:
Upland Abandoned Mine Sources
- The Relief Hill Hydraulic Mine Remediation Project will implement Best Management Practices to reduce sediment and mercury drainage from this abandoned mine into the South Yuba River watershed.
- The Malakoff Diggins Hydraulic Mine Feasibility Study has undergone a three-year water quality and historical records assessment process, and is using these established baseline data to evaluate treatment options for this mine that drains into the South Yuba River just downstream of the Relief Hill drainage.
- The Scotchman Creek Assessment Project has collected preliminary baseline data for the Scotchman Creek watershed, and is now utilizing the assessment protocols established by the Malakoff Diggins project to conduct continuous stage and turbidity monitoring that will be used to quantify sediment and mercury loads in the highest mining-impacted tributary (Scotchman Creek) of the South Yuba River watershed in order to inform treatment options.
- The Spring and Shady Creek Assessment Project is utilizing the assessment protocols established by the Malakoff Diggins project to conduct continuous water quality monitoring in two tributaries of the South Yuba River watershed just downstream of the Malakoff Diggins drainage that are also heavily impacted by historic mining.
Downstream Reservoir Deposits
- The Combie Reservoir Treatment Facility project is demonstrating an innovative technology to remove mercury-contaminated sediment that is building up in reservoirs downstream of historic hydraulic mines on the Bear River, a technique that may be applied to numerous reservoirs in the mining-impacted CABY region and beyond.
Fish Mercury Data Collection and Public Education
- The Mercury-Contaminated Fish: Data Collection and Public Education Project is working to fill critical information gaps on mercury tissue levels in fish that are being consumed from CABY water bodies, and the quantity of fish being consumed, in order to allow adequate public health information to be issued.
Current Progress: December 2016
Relief Hill: During the 3rd quarter, the final design plans and project work plans were received and approved by the Forest Service.
Malakoff Diggins: Monthly project partner calls continue to help project partners coordinate the analysis and data releases planned over the next year. In addition, more detailed project meetings have also taken place.
In the third quarter of 2016, Jason Muir at Holdredge and Kull (H&K) presented to a small group. The presentation summarized H&K’s investigation and analysis to date, including the infiltration study and the hydrologic model. Discussion that followed included new ideas for diversion of flows, and collection and containment of flows through the pit, that would minimize contaminant transport. Additional analysis is planned.
Scotchman Creek: The Sierra Fund in collaboration with the South Yuba River Citizens League (SYRCL) has conducted analysis of stream, mercury and sediment data and prepared a draft report. Additional sampling will take place in 2017.
Spring and Shady Creek: The Sierra Fund in collaboration with SYRCL has conducted data analysis of stream, mercury, and sediment data and prepared a draft report.
Combie Reservoir: The first demonstration tests for the Combie sediment and mercury removal equipment were completed in early December 2014 and demonstrations continued into 2015. In preparation for the demonstrations, Nevada Irrigation District (NID) coordinated and arranged demonstrations; excavated and transported sample material to the site; and leased, mobilized and set-up equipment. They then demonstrated the effectiveness of mercury removal using various polymers; monitored and sampled flow process; conducted safety briefings for workers and guests; and conducted Q&A meetings on-site. Since then, NID has been monitoring the effects of the operation on water quality and biota, analyzing results and working with fabricators and equipment manufacturers to refine the process. An updated dredge and treatment process plan was sent to DWR in the third quarter of 2016. Additionally, NID has continued to work with soils consultants to design a sampling and boring pattern to characterize the sediment and to determine the depth of native bed material in the reservoir.
Data Collection and Public Education:
- Fish Sampling: The Sierra Fund has been collecting fish samples since 2015 as part of an effort to collect the necessary data for OEHHA to develop species inclusive site-specific fish consumption advice for six reservoirs and three stream/river segments. Thus far data has been collected from the following water bodies: Lake Clementine, Rollins Reservoir, Combie Reservoir, Scotts Flat Reservoir, and the South Yuba River. Fish species collected include green sunfish, bluegill, pumpkinseed, small mouth bass, largemouth bass and spotted bass and rainbow trout. In 2016, carp and pikeminnow were added to the sampling plan for select water bodies based on the results of angler surveys.
- Angler Surveys: The Sierra Fund has been collecting angler surveys in collaboration with the Sierra Native Alliance since early 2015 at Scotts Flat Reservoir, Camp Far West Reservoir, Lake Clementine, Bullards Bar Reservoir, Rollins Reservoir and Lake Englebright. In 2015 and 2016 TSF executed volunteer-led events and posted over 140 fish consumption advisory signs at local lakes and reservoirs in the Bear/Yuba watershed. Since the posting of the advisories, TSF has worked to collect angler surveys using a revised format that will facilitate evaluation of whether posting fish advisories improves angler knowledge about healthy fish consumption. To date 204 surveys have been collected.
- CABY Mercury Forum: The lead partners of TSF-sponsored CABY projects continue to meet on a quarterly basis – either in person, by phone, or on field trips to project sites – in order to develop a regional strategy for addressing mercury and sediment contamination from legacy mining activity. Each Mercury Forum begins with a recap of the necessary scientific, cultural, and technical considerations required for collecting high-quality data. Participants in the forum include representatives from NID, Department on Conservation, USGS, California State Parks, Holdredge and Kull consulting, Friends of Malakoff Diggins, Tahoe National Forest and the South Yuba River Citizens League. To date eight forums have convened, with the most recent forum, held on October 24, consisting of a field trip to hear about assessment activities at Malakoff Diggins State Historic Park.
Lead Agency: The Sierra Fund
Contact: Dr. Carrie Monohan, 530-265-8454 x 214, firstname.lastname@example.org
Measurable Physical Benefits: Ecosystem Restoration
Watersheds: Yuba and Bear