Tailings from abandoned mines in Mohave and neighboring Yavapai County contaminate nearby streams and pose potential threats to the groundwater, a geologist with the federal Bureau of Land Management said at a meeting Wednesday.
However, the BLM is working in conjunction with the Arizona Department of Environmental Quality to clean up and reclaim the mine sites, Art Smith said.
He spoke for about a half-hour before a gathering of 20 people during a meeting of the Northwest Arizona Watershed Council at the BLM field office in Kingman.
The operators of the abandoned mines dumped the tailings – mine wastes – along slopes and sometimes into creeks, Smith told the gathering.
Heavy metals such as copper, cadmium and zinc have mixed with runoff and entered creeks.
The minerals affect the drinking water, Smith said.
"You have all these base metals" like arsenic, he said.
"They eventually get to the groundwater.
They do migrate downhill and eventually to the Colorado (River)."
Runoff into Boulder Creek from the former Hillside mine near Bagdad in Yavapai County may have destroyed aquatic life for a stretch of three miles to four miles to the confluence with Burro Creek, Smith said.
The operators of the former mine, inactive for some 40 years, extracted silver, copper, zinc and some gold.
"We do get copper color in Boulder Creek," he said.
He added the BLM is working on cleaning up and reclaiming Hillside and other mines.
Government agencies face challenges getting the landowners to clean up the sites, said Pete Foster, ADEQ's liaison in Mohave County.
"You don't know who the (property) owner is," Foster said.
Foster said that Phelps Dodge operates its copper mine in Bagdad "very responsibly." The mine poses little threat to the environment.
While a number of mine sites in Mohave County appear to be contaminated, none are serious enough to warrant placement on the federal Superfund list for sites that require cleanups, Smith said in response to a question.
However, he said Hillside is on a state Superfund list.
Smith, a geologist at the BLM office here for nine years, circulated aerial photos of mine tailings and presented a slide show that showed discolored creeks and runoff.
Samples of water taken from Boulder Creek show that the water exceeds the federal standards for arsenic concentration, Smith said.
The threshold is 50 pounds per billion for drinking water, Foster said.
Responding to a question, Smith said that cyanide – used in leaching ores – has not posed a contamination problem.
"It is the other heavy metals that are remaining, and possibly arsenic," Smith said.
Smith said he will have more to report in a year.
Contacted after Smith's speech, Earl Engelhardt, secretary of the watershed council, said he took the comments about contamination seriously.
"I think they are very real, underestimated long-term threats, and they need to be considered," Engelhardt said.
In other actions, the watershed council, a private, nonprofit organization, re-elected Engelhardt secretary, Elno Roundy chairman and Keith Curry of the BLM treasurer.
Dave Knisely, who comes from a ranching background, was elected vice chairman.
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