Environmental Cleanup at Former Gold Processing Site in Nome, Alaska

Nome, Alaska is a coastal town of less than 4,000 people 500 miles northwest of Anchorage that experienced a great boom during the Alaska gold rush in the early 1900s. Placer gold mining continued to be one of the leading economic activities in Nome through the 1960s, with more than 3.6 million ounces of gold processed in the area.

At the height of gold processing, a mining company used a processing facility to physically and chemically consolidate and extract gold from dredged ore, which led to concentrated levels of mercury and arsenic in the soils surrounding the site.

GeoEngineers, on behalf of the former gold processing facility operator, completed an investigation, characterization and exploration program to clean up soil contaminated by metals in the area.

Approach

GeoEngineers characterized contamination at the site, including determining the vertical and lateral extent and nature of contamination present. The investigation process included reviewing historic studies, a detailed field investigation, and installing and/or rehabilitating the groundwater monitoring well network. Working in subarctic conditions with limited access, GeoEngineers used track-mounted drill rigs to complete the subsurface fieldwork.

The project also included collecting and evaluating sediment samples from Dry Creek, which runs adjacent to the site, and collecting samples within the site boundary and upstream and downstream of the site to evaluate any potential threats posed by the presence of methylmercury.

GeoEngineers also conducted a hydrologic study of the Dry Creek watershed to evaluate the potential for stabilizing and solidifying mercury-contaminated soil at the site, and used data collected from the field investigation to develop background concentrations of arsenic in site soils. We also completed an ecological evaluation for the facility, setting the stage for a proposed risk assessment.

We recently completed a feasibility study for remedial alternatives at the site, evaluating the full range of possible cleanup alternatives available for addressing the metals-contaminated soil.

Results

Pending regulatory acceptance of the preferred remedy, GeoEngineers will prepare a Cleanup Action Plan and remedial design for implementing cleanup at the site.