The good: There are no elevated concentrations of mercury vapor.
The bad: Three soil samples had above-average or excessive mercury levels.
The ugly: Nearly a quarter of soil samples exceeded arsenic levels.
That’s what scientists have uncovered at the illegal Red Arrow gold milling site on Grand Avenue just outside Mancos. According to an Environmental Protection Agency report released Monday, the agency’s assessment included air monitoring for mercury vapors and collection of soil samples for arsenic and mercury.
“The results of air monitoring indicated no elevated concentrations of mercury vapor present escaping from the units of the storage facility to the west of the site or the septic system on the site,” wrote project leader Elliott Petri of Weston Solutions Inc.
Weston Solutions is an EPA-designated superfund technical assessment and response team.
At depths of 1 foot and 1½ feet, 31 sites were targeted for soil sampling in October at the mill site and across the street. All of the sampling was conducted before excavation and stockpiling of contaminated materials, according to the report.
Accutest Laboratories in Golden analyzed the samples for metals and mercury, finding that seven locations exceeded screening levels of arsenic, and one location exceeded screening criteria of mercury. Nearly two dozen sites registered above average for background levels of arsenic, and two contained above-average background levels for mercury.
The Colorado Department of Reclamation and Mining Safety discovered the unpermitted Red Arrow milling site, and in June, placed several injunctions against the former mining company and current owner, Craig Luikko. The company is in the process of a receivership claim and bankruptcy filing.
Before the EPA sampling, a stabilizing removal action, conducted as a cooperative effort between EPA and state mining officials, was completed to consolidate and stabilize waste material that had migrated off site. Additional assessment activities, including a public-health consultation, are ongoing, the report indicates.
The EPA evaluation was initiated to determine whether the site poses an immediate threat to human health or the environment stemming from milling operations and potentially contaminated materials on the property.
While milling practices and other details of the former operation at this location are unconfirmed, about 50 to 75 cubic yards of partially covered mill tailings and a container labeled “21.5 pounds mercury” were present at the site. The origin of the tailings is unconfirmed but is assumed to be the Red Arrow milling operations.
The rock composition in ore used for gold mining often contains high levels of arsenic. The mercury likely was used to process ore. Those chemicals and wastes, or their residues, are present at the facility and contained within the tailings materials, Petri wrote.