A hazardous material cleanup crew from the federal Bureau of Land Management has been cleaning up hazardous chemicals at a former gold and silver mill site about 10 miles west of the Golden Valley area.
The most serious hazardous materials found at the site during an inspection in May was about 30 pounds of a highly concentrated cyanide used in the processing of gold and silver ore shipped to the site from local mines, said BLM specialist Lowell Jeffcoat.
The mill operators, who were not identified, had applied for but never completed applications to lease the site from the BLM last year to begin operations at the site, said BLM geologist Art Smith.
Because of the recent interest to reopening the milling operation, BLM began an inspection in May leading to the discovery of the cyanide, Smith said.
The site first opened in 1980 or 1981 and shut down in 1984.
There was no knowledge of cyanide being stored at the site, Smith said.
An investigation is underway as to when the cyanide was stored and who stored it.
Cyanide is used to separate the valuable minerals from the rock ore.
The chemical was found in a locked cement room at the 20-acre Tyro Mill site, Jeffcoat said.
The most toxic cyanide, found in a gelatin-like sludge in several barrels, was taken to a waste site near Boulder, Colo., for disposal.
Residue was also found in four nearby hoppers, Jeffcoat said.
The six-person crew wear protective suits during the cleanup, which began last week.
Enough cyanide coming in contact with human skin or by inhaling the fumes could cause death.
Jeffcoat said there are four levels of cleanup suits used with level A used for the most hazardous chemicals and level D as the lowest level.
The Tyro cyanide cleanup required level B suits, consisting of full body coverage and airpacks, Jeffcoat said.
"We're almost done cleaning up," Jeffcoat said.
"We've already removed the immediate threat to Colorado."
Water with a high concentrate of bleach is used to wash down the cyanide residue.
The remainder of the less hazardous materials that included arsenic, lead and cadmium were dumped in a five-acre pond near the site for future removal, Jeffcoat said.
There was no immediate threat to humans, unless anyone would have come in direct contact with the chemicals at the remote site about five miles north of Highway 68.
The site is roughly 10 miles east of Davis Dam and the Colorado River in the Black Mountains.
Other toxic materials found at the site included a caustic soda chemical with a pH of 14, the highest degree of acidity, dangerous enough to cause chemical burns.