Gold Hill Mill - draft Environmental Evaluation / Cost Analysis

The draft Environmental Evaluation / Cost Analysis (EE/CA) analysis hazards to people and the environment posed by the former Gold Hill Mill, located in Warm Springs Canyon in the Panamint Mountains, Death Valley National Park. Gold Hill Mill was active from the 1930s to 1950s. The area includes a well-preserved mill and arrastra, is adjacent to an unpaved road, and is near a perennial stream. The site covers less than one acre.

Arsenic and lead were identified as the primary contaminants of potential concern (COPCs) by comparing maximum detected concentrations in each media to the lowest appropriate human health risk-based screening levels. Arsenic concentrations in the mine tailings within the mill foundation area and mill tailings generally adjacent to the mill structure were found to represent an incremental cancer risk probability of 1 in 25,000 (for the Mining Enthusiast group). This exceeds the target de minimis excess lifetime cancer risk of 1 in 1 million. Non-carcinogenic health impacts can occur as a result of lead exposure. At Gold Hill Mill, lead concentrations were found at 13,900 mg/kg, which exceeds the 1,200 mg/kg comparison level. However, the use of this model to assess short-term exposures is uncertain, since it was designed for long-term occupational or residential exposures.

Ecological risks were assessed using Site-specific exposure factors and information regarding species known or likely to be present at or near the Site. Contaminants of ecological concern identified include antimony, arsenic, cadmium,
chromium, copper, lead, mercury, selenium, vanadium and zinc. Compared to the minimum acceptable hazard quotient level of 1, lead was 130, zinc was 202 and antimony was 327.

Four alternatives were initially considered:
1) No action
2) Excavation and off-site disposal in a landfill licensed to accept this waste material
3) Institutional controls: Institutional controls (i.e., restrict access to the site or other means to limit current and/or future land uses)
4) In-situ solidification/ stabilization

Alternative 2 (excavation and off-site disposal) is selected as the recommended alternative because it is the most protective of human health and the environment, is the most effective in both the short and long-term, is feasible to implement, and can be completed at an estimated cost of approximately $334,000.

If this alternative is selected, further design will proceed, along with consultation under Section 106 of the National Historic Preservation Act. A design concern will be how to remove contaminated soils from the mill's foundation area without destabilizing the mill.

A link to the full document is provided. The public is invited to comment. Comments entered in this website are preferred. Thank you!
Comment Period: Closed        Nov 19, 2021 - Dec 26, 2021
Document Content:
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