MIAMI — University of Oklahoma professor Robert Nairn gave a presentation on “Passive Treatment Systems for Mine Water Quality Improvement” at the 18th annual Tar Creek Conference on Tuesday.
Nairn is director of the Center for Restoration of Ecosystems and Watersheds (CREW) and an associate professor in the School of Civil Engineering and Environmental Science at OU.
He is also an associated faculty member with the Ecology and Evolutionary Biology Program, Aquatic Research Facility, Institute for Oklahoma Technology Applications and Water Technologies for Emerging Regions Center at OU.
He gave an update on the work that has been ongoing since the early 1980s at a location southeast of Commerce. The following data is based on the results of CREW.
“I will be addressing 37 years of what we call 'reversible irreversible' damage,” Nairn said. “The focus I want to talk about is the artesian discharge.”
Artesian discharge is the process of water coming out from the ground naturally by pressure and the quantity of water released.
The 1984 Operable Unit 1 (OU1) Surface and Groundwater Decision was implemented after water began coming out of the ground in 1979 at a location in SE Commerce in the lowest spot in the watershed- Mayer Ranch.
In 1984, the United States Environmental Protection Agency (EPA) and Oklahoma Water Resources Board (OWRB) re-designated beneficial use classification as “impacts to (surface waters) are due to irreversible man-made damages resulting from past mining operation at the site.”
“Irreversible man-made damages allowed the Records of Decision (ROD) to use a fund-balancing waiver that essentially says it costs too much to address surface water contamination,” Nairn said. “Those are artesian discharges that have been flowing since 1979 throughout the mining district.”
CREW has been addressing and looking at the small watersheds including stream samples and selected artesian discharges. Its area of focus has been on five watersheds: Elm Creek, Lytle Creek, Tar Creek, Beaver Creek and an unnamed tributary referred to as UT.
“Our focus is on the point of discharge — where the waters are coming out of the mines — and there’s three areas of the mining district that it happens,” Nairn said. “There are a number of discharges in the Beaver Creek watershed. Beaver Creek of course drains to Spring River, so hydrologically surface water is disconnected from Tar Creek. We’ve sampled a number of discharges there in the past that we’ve put data on and we’ve worked with the Quapaw Tribe to potentially address some of those sometime in the near future.”
According to his data, the artesian discharges are where the increase in metals in the stream are found. Of course, Tar Creek carries the most amount of peak median loadings of metal than any of the five watersheds.
His team has been working on Mayer Ranch and compared data from the 1980s to 2015.
“The pH level has gotten a bit better in Mayer Ranch,” Nairn said. “Iron and zinc (levels) have gone down considerably. From a geochemical perspective, that makes sense. The mines fill up, we have a big first flush of bad water and has been ameliorating over time. Lead and cadmium levels are about the same, maybe a little bit more, but some of that has to do with the analytical techniques used back in the ’80s and the techniques we use today. Whether or not those are truly different is a good question.”
The most recent 2015 data still shows elevated concentrations that need to be addressed, which is where the Mayer Ranch Passive Treatment System comes into play.
Nairn said the treatment system is working with the ponds and wetlands working as filters. The biggest change occurs upfront in the first oxidation unit.
“The clay lined pond is oxidizing the iron flowing rust, and it’s filling up with iron oxides, but that’s the way it was designed,” Nairn said. “We’re tracking that and design life is about 25 years. We’re on track for that right now.
“The surface flow wetlands are starting to filter those solids out and the trace metals stick to the iron,” he added. “About 100 kg of iron per day comes in and about 4 kg goes out of that very first unit. The removal rate in our engineering design is 20 g per square meter per day and over eight years, we’re real close to that. It's working like it’s supposed to.”
Noticeable levels of lead, cadmium and arsenic have changed. Lead and cadmium both decrease significantly by the first unit and arsenic is completely filtered out. To filter out zinc, the system relies on microbes.
“We see some decreasing upfront for zinc but the big changes occur in the vertical flow bioreactors,” Nairn said. “These are the systems that incorporate a subsurface drain that’s all perforated pipe, buried in limestone and a mixture of mushroom compost, limestone sand and wood chips. The water flows vertically down into the compost and we rely on microbial action to help us treat the water.
“The microbes take the sulphate that’s naturally in the mine water and the organic matter in the compost, which produces metal sulfides,” he added. “These metal sulfides are where we retain the zinc, cadmium and the lead. It’s working like it was designed.”
Overall, pH has increased and iron, zinc and nickel have decreased considerably. There are still measurable amounts found but significantly lower than when it is released from the ground. Cadmium and arsenic are below their detection rates and cannot be measured.
Not only has there been remarkable changes in chemistry but also on the biological side, as well. The data shows marked improvements in water quality and early indications of return of fish communities.
“The numbers of fish species have increased,” Nairn said. “We have brand new species that we haven’t seen prior to construction. Not only do the number of species increase, but we’ve seen in increases in species’ diversity and richness.”
In 2000, a five-year review statement was released that said it’s expensive to treat the water and “there is no reason to revisit the fund-balancing waiver that was made in the 1984 OU1 ROD.” In 2015, the review said “treating mine water discharge via passive treatment appears to be economically feasible” and that the waiver is no longer valid and should be re-evaluated.
“Not only are we showing results with data, but there seems to be some movement on the decision making side, which is just as important if not more important,” Nairn said.
CREW hopes to implement the passive treatment system in another area of Commerce. Nairn said their next area of focus will be the southeast area next to the Mickey Mantle Field and Commerce High School. The surface was reclaimed in 2006 and the water currently discharges into the unnamed tributary.
Nairn said his team has implemented a conceptual design based on their success at Mayer Ranch. They put out request for the design/build proposals last year and were awarded the design/build in December 2015. Final engineering designs were scheduled for Sept. 2 and construction is set to begin on Thursday.
“Staking starts Thursday and construction will begin a week after,” Nairn said. “We will have a stormwater pond, a big oxidation pond, the wetland filter, the vertical flow bioreactor, the final polishing unit and will discharge back in the unnamed tributary upstream into its current location.
“Hopefully, it will be better than it is now,” he added. “If we do this, we would have addressed all of the artesian discharges in the unnamed tributary watershed. We would have addressed all of the orange water up-flowing out of the ground in the UT watershed.”
The passive treatment system has proved to reverse the irreversible.