An independent analysis of sediment at the Gold King Mine adit found trace amounts of uranium isotopes, but at levels far below typical screening thresholds.
The study was done in September by Wright Water Engineers on behalf of La Plata County government. The analysis found results similar to those reached by the Environmental Protection Agency, but the independent analysis screened for elements that had not been sampled by the EPA, including radium and uranium.
Both the EPA and Wright Water Engineering collected surface water and sediment samples in September at a location about 50 feet inside the Gold King Mine. At the request of La Plata County government, Wright Water Engineering analyzed EPA’s samples to see if it drew similar results.
Overall, water quality and sediment sampling results were consistent with EPA findings.
La Plata County government decided to do its own testing to verify EPA results and quell concerns from residents who were distrustful of the federal agency following the Aug. 5 Gold King Mine blowout, said Commissioner Julie Westendorff. Commissioners also heard from people familiar with the mines above Silverton who said there may be other materials of concern that weren’t being tested, Westendorff said.
“There were some questions as to what may have been stored in those mines,” she said.
EPA officials did not return calls about why tests weren’t done for certain elements such as uranium. The EPA has since added uranium to its long-term monitoring.
Wright Water Engineering’s sediment sample detected not even one part (0.149 pCi/g) of uranium-238, which is the most common uranium isotope found in nature and can be used in nuclear weapons. By comparison, the EPA regional screening level for residential exposure for uranium is 155 pCi/g, according to the Wright Water Engineers report.
Radium concentrations also did not exceed the 1.1 pCi/g national average found in soil across the country, the report concluded.
Neither the EPA nor Wright Water Engineers found detectable amounts of cyanide, dioxins, furans, PCBs, volatiles, semivolatiles, thallium or chromium.
Gold King sampling analysis (PDF)
