The U.S. Environmental Protection Agency is taking public comment through May 13 on its proposal for addressing contamination at the Iron King Mine-Humboldt Smelter Superfund site in Dewey-Humboldt.
The mine produced silver, zinc, gold and lead for about 70 years before closing in 1970, while the adjacent smelter ran from the late 1890s to 1937.
The activity at both sites produced mine tailings, wastes called dross and slag and lead and arsenic contamination, with lead and arsenic also reaching the Agua Fria River and contaminating surface water and soil farther away from the site.
Most of the cleanup work would happen at the mine and smelter sites. Waste and contaminated soil would be gathered up and buried in two waste repositories, which would be lined and capped to keep any harmful substances from escaping into the air, spreading farther into soil or reaching waterways.
One repository would be placed on each side of state Route 69; loading the waste into them would take at least a year. When finished the waste would no longer threaten human health, wildlife or the environment, the EPA said.
Eventually, some of the filled areas could become parks or open space.
There have been three cleanup efforts in surrounding residential yards over the last 16 years where contaminated soil was replaced by clean soil, and the EPA plan would do this for additional yards in the area. The total cost of the cleanup is estimated at $72 million.
Public comments can be submitted via email to Remedial Project Manager Jeff Dhont at firstname.lastname@example.org or Community Involvement Coordinator Georgia Thompson at email@example.com or sent to Dhont at 75 Hawthorne St. (Mail Code: SFD-8-1), San Francisco, CA 94105. A public meeting was held at Dewey-Humboldt Town Hall on March 29.