The Environmental Protection Agency finished mercury-decontamination efforts July 29 at the Red Arrow gold mill site on Grand Avenue.
Workers removed 240 pounds of liquid mercury waste, and the EPA has spent an estimated $230,000 on the site, including $185,000 on the cleanup contractor, according to EPA documents and EPA on-scene coordinator Craig Myers.
The mill was closed last year after it was discovered mercury was being used to process gold in a building at 1000 West Grand Ave.
On June 10, workers started vacuuming the building and large equipment to remove mercury, according to an EPA report. They also used HgX solution on the mercury to keep it from vaporizing and leaching.
Special effort was made to save the amalgamation unit and an ore concentrator valued at more than $35,000.
Crews also scraped the floor and crevices because dust seemed to be a source of the airborne mercury, the EPA report said.
By June 17, the mercury levels were still well above the standard, so crews used an epoxy sealer on the floor and painted the walls. They later had to remove all the wood and metal in the building including the heater and painted every surface again with latex-based primer.
"(Painting) binds the mercury to the substrate material and prevents it from vaporizing and posing a health risk," said Myers.
While crews were not on site from June 25 to July 21, the building was vented by a fan in the furnace exhaust vent to help remove the vapors. Myers said this was standard practice and the total release would not have been more than 1 gram.
"The levels of mercury, once vented to the outdoor atmosphere, quickly dissipate to levels that are not detectable and pose no risk to human health," Myers said.
The building is now safe to use, and control has been given back to Boyd and Teri Sanders, the property owners who had leased out the building and were not part of the gold mine venture.
"EPA was very considerate to us," they said in an email.
Hazardous waste materials were taken to landfills in Arkansas, Nebraska and Deer Trail, Colo.
About 1,500 cubic yards of contaminated but non-hazardous soil was taken to the Montezuma County Landfill.
Government health officials still plan to hold a community meeting to talk about the work, but it has not been scheduled.
For a full description of the steps taken to decontaminate the mill site visit: www.epaosc.org/site/sitrep_profile.aspx?site_id=8837&counter=21950.
