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NEVADA CITY, Calif. May 18, 2017 – The Tahoe National Forest is requesting public comment on the Engineering Evaluation/Cost Analysis (EE/CA) for a non-time-critical removal action at the Marall Chrome Mine Site (Site) located on the American River Ranger District in Placer County. All public comments are welcome and will be accepted until the close of business June 16, 2017. Following this 30-day public comment period, a final decision will be made by the Pacific Southwest Region’s Regional Forester, which will be documented in a Removal Action Memorandum identifying the removal action decision.
The purpose of the EE/CA is to present a detailed analysis of cleanup/removal action alternatives that can be used for decision-making. The analysis presented in this document includes discussion of site background information, a summary of the site investigation, a preliminary risk screening, applicable or relevant and appropriate requirements (ARARs), removal action objectives and goals, and the analysis and comparison of removal action alternatives.
The Marall Chrome Mine Site is located approximately six miles north of Foresthill within the American River Ranger District of the Tahoe National Forest, in Placer County, California. The U.S. Forest Service is the federal agency in charge of the Site.
The Site is a former open pit chromite mine characterized by an open excavation and a relatively small tailings pile. Historical information regarding mine operation is limited. Large scale chromite mining at the site is believed to have occurred during the war years of 1915-1919 and 1941-1945. Approximately 85 percent of the chromite in Placer County was reportedly produced during these periods. Chromite is an iron chromium oxide mineral used to induce hardness, toughness and chemical resistance in steel.
Historical mining activities appear to have been conducted within a shallow pit that was most likely excavated to remove chromite-bearing materials. The pit floor occupies an area of approximately 1.3 acres; however, the entire area of disturbance related to the pit is approximately 7.8 acres.
The area around the Marall Chrome Mine pit has been developed for recreational use, with many native surface roads and OHV trails across the site. These roads and OHV trails are on serpentinite derived soils and bedrock that contains naturally occurring asbestos (NOA). A tailings pile that remains in place on the floor of the pit provides evidence that material extracted from the pit was processed onsite. There is no evidence of processing equipment remaining at the mine, so the method used to produce the tailings cannot be determined. Since the mine was abandoned, the open pit has been used extensively by the public as an unofficial shooting range, resulting in the widespread distribution of shot and ammunition across the tailings pile, pit floor, and pit walls.
During storm events, exposed soils containing fine particles of lead and copper from within the open pit are eroding into Pagge Creek, which flows into North Shirttail Canyon Creek, a tributary of the North Fork of the American River.
The presence of lead is regarded as the primary indicator of materials that are contaminated with lead shot. The metals antimony, arsenic and copper are also potentially related to bullets, shot, and casings.
Based on investigation findings and preliminary risk screening, the Forest Service is exercising its authority as lead agency under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) to undertake a non-time-critical removal action at Marall Chrome Mine that best meets the Removal Action Objectives (RAO):
- Reduce the potential for metals release to occur from source materials (i.e., lead shot present in tailings, as well as the pit walls, floor, and drainage).
- Reduce the exposure of human and wildlife receptors to metals in source materials to acceptable levels.
- Reduce the potential for NOA exposure related to the heavy use of the trails by ATV riders.
Based on available site information and data, three types of general response actions were considered for the Marall Chrome Mine:
- No Action
- Institutional and Engineering Controls
- Offsite Disposal
The following removal action alternatives were identified for Marall Chrome Mine based on the general response actions and screening discussed in the EE/CA and are listed in order of feasibility:
Alternative 1: No Action
Alternative 2: Prevent Access to Mine Pit; Signage on Roads and Trails
Alternative 3: Separate Lead from Mine Waste; Signage on Roads and Trails
The removal action alternative recommended in the EE/CA for the Marall Chrome Mine is Alternative 3. The final remedy selected by the Forest Service could be a combination of Alternatives 2 and 3.
To review copies of the EE/CA or other documents in the Administrative Record, visit the Tahoe National Forest headquarters in Nevada City, California, during office hours (Monday – Friday from 8:00 a.m. – 5:00 p.m.). Comments can be provided to: Tahoe National Forest, Attn: Rick Weaver, 631 Coyote St., Nevada City, CA 95959, or (530) 478-6241.