By Krista Duhon
news@joplinglobe.com
COMMERCE, Okla. — Data derived from a passive water treatment system designed to reduce contaminants in surface-level mine water indicates that the system is working, although the impact is marginal.
Robert W. Nairn, an associate professor of civil engineering and environmental science at the University of Oklahoma in Norman, said the university’s treatment project in Commerce is significantly reducing the amount of iron, zinc, cadmium and lead in about 20 percent of the mine water entering Tar Creek from surface-level seeps.
“I consider this success,” Nairn said. “It is a demonstration project, and it is working.”
Nairn on Wednesday led a group of local officials and reporters through the network of filtering ponds as the site — known as the Mayer Ranch Passive Treatment System — nears its one-year anniversary of operation.
Data from water-quality testing at the site indicates that water captured from three controlled seeps is entering the system with arsenic concentrations of 0.062 milligram per liter; cadmium concentrations of 0.017 milligram per liter; iron concentrations of 172.51 milligrams per liter; lead concentrations of 0.063 milligram per liter; and zinc levels of 8.093 milligrams per liter. A liter equates to 0.26 of a gallon. An ounce equals about 28,350 milligrams.
Three of the five contaminants are below detectable levels when the water exits the system, Nairn said. Those include lead, which has drawn the largest amount of concern in recent years.
Iron concentrations have been reduced to 1.05 milligrams per liter, and traces of zinc are leaving the system at 0.232 milligram per liter.
The metal-laden water enters the system at about 160 gallons per minute. It is pushed to the surface through punctures made decades ago when mining companies searched for veins of lead and zinc through the mining district. Since then, water from the Boone aquifer has filled the mine workings and caused the mine water to seep to the surface through myriad outlets, including the drill holes on the Mayer ranch.
Nairn said the $1.2 million project that allowed for the capture of the seeping water is funded through the Environmental Protection Agency and the U.S. Geological Survey.
He said the overall impact of the project, given its small scale, on the quality of water in Tar Creek is marginal. He said he hopes the documented success of the project will send a message to politically powerful people who can bring about change and embrace the concept of passive treatment.
“Traditional ‘active’ treatment systems typically involve chemical mixing and aeration,” Nairn said in a press release. “This ‘passive’ system requires minimal maintenance and provides a naturally occurring biogeochemical, biological and physical process to positively impact water quality.”
The Mayer project has a projected duration of about 30 years, Nairn said, but his graduate students are looking at ways to determine if there is a beneficial use for the heavy-metal sediments that will be stacking up in the ponds.
If beneficial uses can be found, he said, it is possible that the time span of the system could be extended.
“This is fascinating,” said Miami Mayor Brent Brassfield as he concluded the tour. “I have been aware of the project, but I had not seen it firsthand. It makes me optimistic to see a water-quality process that is working.”
Brassfield said the project offers promise in the region of restored water quality to an area damaged by years of mining.
Commerce officials were at the site Tuesday, including Mayor Michael Hart and Councilwoman Lena Enochs.
“I think this is great,” Hart said. “I was here a year ago when the ponds were empty. It is nice to see the progress made.”
How it works
It takes three weeks for water particles to work their way from the top of the experimental system to an unnamed tributary of Tar Creek, according to Robert Nairn. They are cleaned in a series of ponds that naturally pull the heavy metals out of the water through wetland plantings, microorganisms that eat zinc, cadmium and lead, aeration ponds, and limestone beds that polish the water.
