Red Rock Road Mercury Mine Tailings Cleanup Project

Red Rock Road is a former railroad bed that was constructed in the 1930s of mercury mine tailings for a railroad that transported logs from the forest until 1966. Although most of the mercury was removed from the ore during processing, arsenic was not, resulting in high concentrations in the soil around the railbed. Complicating the cleanup effort was the fact that the land surrounding the former railbed had been sold to more than 100 adjacent property owners and served a number of uses.

GSI conducted a site investigation, land use evaluation, dust migration study, ecological risk assessment, both deterministic and probabilistic human health risk assessments, and a feasibility study.

Because of the high risk to human health, a laboratory bioavailability study was conducted to predict the actual arsenic adsorption for incidental ingested mine tailings. Findings indicated that impacts to human health were nearly 10 times lower than would have been predicted using conventional U.S. Environmental Protection Agency guidelines. GSI then completed a probabilistic human health risk assessment to address the wide range of potential exposures on the many properties that contained the mine tailings, providing a more accurate assessment of risk than the more conservative deterministic methods. GSI was able to successfully demonstrate to the Oregon Department of Environmental Quality (DEQ) that railroad grade material could remain in place on all but three properties without being a threat to human health and the environment, thus avoiding the disruption and cost of removing and replacing large quantities of the railroad grade material. This probabilistic human health risk assessment was the first of its kind to be accepted by DEQ.

The team finalized the feasibility study, which called for removing railroad grade materials on three properties. Implementation of the remedy was completed in 2018. The team prepared other technical documents to support reaching DEQ closure for the site and completion of the record of decision (ROD). DEQ issued a No Further Action (NFA) memorandum for closure of the site in early 2019.

GSI’s work involved:

• Conducting a site investigation, dust migration study, and ecological risk assessment.
• Evaluating local land use plans and ordinances to complete a probabilistic evaluation of future land use patterns along the railbed.
• Completing deterministic and probabilistic human health risk assessments, and successfully demonstrating that arsenic did not present an unacceptable hazard to property owners along the railbed
• Negotiating with DEQ and the Oregon Health Authority.
• Conducting a feasibility study, which called for removing railroad grade materials on three properties.
• Preparing technical documents to support reaching DEQ closure for the site and completion of the ROD and NFA memorandum.