Yukon - Charley Rivers National PreservePage 13 of 63
Cleaning Up Coal Creek: Drums, Lead, Mercury and Petroleum Removed by 1998
A bucket-line dredge operation left the Coal Creek valley with numerous petroleum spills, stockpiles of drums, hazardous debris and areas of heavy metal contamination. When the Coal Creek claims passed to the National Park Service in 1986, the Park Service took on the cleanup. Linda Stromquist describes how it was done.
An example of mercury recovered in the cleanup (National Park Service photograph).
Surveying and clearing
The Park Service first investigated the valley to characterize the contamination and hazardous debris. In 1994 crews removed 830 55-gallon drums, 18 lead-acid batteries, 2,500 pounds of solid waste and 46,000 pounds of scrap steel. By 1996 park managers began work on soils contaminated with lead and mercury.
Three contaminants, three treatments
| Contaminant | Where | Treatment |
|---|---|---|
| Lead | About five cubic yards of soil from the historic blacksmith shop | Packed into drums and shipped to a licensed disposal facility in Washington State |
| Mercury | About 45 cubic yards of soil around the historic assay building | Washed on site; about 172 pounds of mercury concentrates left the site for disposal |
| Petroleum | Contaminated soil in and around the Coal Creek area, investigated in detail | Excavated and treated by thermal desorption in a portable unit flown to the site in the summer of 1998 |
How the mercury was washed out
Crews built a soil-washing facility on site, with a 4,000-square-foot work pad and a 14,000-gallon recycle pond in the maintenance yard of the main camp complex. They hauled the mercury-contaminated soil to the pad, mixed it into a slurry and treated it with an ore cleaning solution. The slurry then ran across a hydraulic jig, a copper plate and a series of sluice boxes. Process water went to the recycle pond, and the solids stayed on the work pad until laboratory analysis showed the cleanup standards had been met. An on-site laboratory used X-ray fluorescence analysis to monitor the excavation and washing, and Northern Testing Laboratory in Fairbanks analyzed samples and confirmed its findings.
With the close of the 1998 field season, the Park Service had completed the multi-year cleanup of the contaminants left by mining in the Coal Creek valley.
Sources
- Linda Stromquist (National Park Service), Mining and mitigation: The Coal Creek remediation project, Alaska Park Science, National Park Service; rewritten in hubnx's own words.