By Wally Kennedy
wkennedy@joplinglobe.com
CARTERVILLE, Mo. — Workers with Snyder Construction Co. began clearing away piles of rock Wednesday at a former mining site along old Route 66 on the west side of Carterville.
The work kicks off a $1.9 million contract with the U.S. Environmental Protection Agency to clean up the mining field, which was abandoned nearly a century ago.
Motorists passing the site might be surprised to see a conveyor belt operating in the work zone. The conveyor belt is not part of the cleanup plan.
Blevins Asphalt, which operates in Joplin and Mount Vernon, purchased a chat pile in the field about three years ago. When the EPA recently announced that it was cleaning up the site, Blevins informed the EPA of its ownership of the small mountain of crushed rock.
“We learned about it in the pre-construction visit. We’ll just have to work around it until they are done,” said Mark Doolan, project manager with the EPA. “It put a kink in our plans, but it’s material we don’t have to handle.”
The EPA permits the use of chat as an aggregate material in the production of asphalt and concrete because the mining waste is encapsulated. The EPA does not permit the dispersal of loose chat on private driveways or on public roads because of the potential release of heavy metals.
The EPA, in this first phase, plans to restore 75 acres on the west side of the city. The project will take about eight months to complete. Eventually, more than 300 acres between Webb City and Carterville will be reclaimed.
The plan
The contract calls for Snyder to dig up mine waste and contaminated soil, and place the materials in abandoned mine pits. The EPA chose the plan after testing the approach a few years ago at a mining pit near Waco.
At the Waco test site, a two-acre pit that was 45 feet deep was filled with 560,000 cubic yards of highly contaminated mine waste. The metal of concern was zinc because it is far more mobile in water than lead.
“This was a worst-case scenario for the whole site,” Doolan said. “The mine wastes were highly contaminated with zinc. We are talking 30,000 parts per million. That’s one of the highest levels of zinc contamination we have found anywhere in the district.”
Before the wastes were moved, water samples were taken from the pit and from monitoring wells around the pit. After the pit was filled, a monitoring well was placed in the center of the pit. The levels of zinc in the well spiked for about a month or so after the pit had been filled.
“It went really high for a month, but now it’s less than before we filled the pit,” Doolan said. “The monitoring wells around the pit went up and then went down. The change did not amount to anything.”
A monitoring well drilled 200 yards east of the pit showed no change at all, he said.
Doolan said metal becomes soluble and leaches in the presence of oxygen. When the waste piles are rained on, the metals in them oxidize and leach into surface water.
“When you put it underground, it goes anaerobic because you take away the oxygen,” he said. “It makes the waste more insoluble than if it were sitting on the surface.”
To be on the safe side, the EPA is installing six monitoring wells around the pits that are being filled at Carterville. When the second phase closer to Webb City starts next year, the EPA will drill 12 monitoring wells.
“We are monitoring to make sure we are not having a groundwater problem,” Doolan said. “If we do have a problem, we will cease and desist, and do something else with the chat.”
Dust control
Another concern associated with the cleanup is dust. Doolan said dust-control measures will be a primary concern.
“We feel that Snyder knows how to move dirt and keep the dust down,” he said.
The contract is the first in a series to be awarded for cleanups that will cover about 7,000 acres over a 10-year period. The EPA estimates it will cost $57 million to reclaim and restore all the land.
The state of Missouri recently agreed to pay for 10 percent of the cleanup, which is required under the federal Superfund law. The EPA also will attempt to recover costs from mining and chemical companies that have been identified as potentially responsible parties for the contamination.
The second phase of the cleanup, planned for next year, will involve land closer to Webb City.
The waste comes from a variety of lead mining, milling and smelting operations, some dating to the mid-1800s. The wastes have contaminated groundwater, surface water and surface soil with cadmium, lead and zinc.
The area will be cleaned up to a standard that will allow mostly unrestricted development in the future.
Moving mountains
The EPA estimates that 350,000 cubic yards of mine waste will be put into mining voids on the 75 acres Snyder Construction will clean up. The EPA estimates that those voids will hold 355,000 cubic yards of material. No repository will be constructed.
