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Quality control

Cities could bear a big bill for Lake Thunderbird pollution.

Carol Cole-Frowe June 6th, 2012

Steep penalties could face the cities of Norman, Oklahoma City and Moore if drastic reductions in stormwater pollutants going into the Lake Thunderbird watershed are not achieved.

Lake Thunderbird
Credit: Mark Hancock

Up to $10,000 a day in penalties eventually could be assessed on watershed cities if a 75 percent reduction of pollution in Little River and Hog Creek is not achieved, according to state Department of Environmental Quality officials.

At a public meeting in Norman last month, DEQ representatives said that figure represents how serious the watershed pollution problem is at Lake Thunderbird, which long has been designated a “sensitive water supply” by the U.S. Environmental Protection Agency.

Little River is one of the primary watersheds flowing into Lake Thunderbird, which provides 70 percent of Norman’s drinking water, plus drinking water for Midwest City and Del City.

About 40 percent of the Little River and Hog Creek watersheds are in Moore and Oklahoma City, with the balance in Norman city limits. Each city has a five-year stormwater permit from the EPA to discharge into Lake Thunderbird. The 75 percent reduction would affect suspended solids and pollutants, including phosphorus, sediment, nitrogen and other organic compounds.

In 2007, the agency entered into an agreement with the Central Oklahoma Master Conservancy District (COMCD) to do a study of the lake’s total maximum daily load, or TMDL, but fell behind partially because of lack of federal funding. TMDL is the amount of pollutants a water body can receive without violating water quality standards. The TMDL study is two years overdue, and in 2011 the COMCD and the Oklahoma Homebuilders Association sued the agency in district court to force its completion.

“We have been in negotiations with COMCD,” said Mark Derichsweiler, engineering manager of DEQ’s water quality division for watersheds. “We were put in a very awkward position.”

The new completion date is Nov. 30, with the study then to be forwarded to the EPA for review with a public comment period.

“This end result of this process means that there would be some regulation for Norman, Moore and Oklahoma City,” said Derichsweiler. “EPA will insist that we have some outline of what cities are to do.”

Lake Thunderbird is impaired by high turbidity, or murkiness; low dissolved oxygen, which increases mortality in fish and other aquatic life; and high chlorophyll, which has a direct relationship with algae presence. High amounts of algae make it more difficult to meet Clean Water Act standards.

What’s next

Next steps for DEQ include refining pollution-flow models and simulating the limited number of treatment scenarios, including water flow, sediment losses and nutrient movement.

“The point is we look at all these sources that could be contributing,” Derichsweiler said.

DEQ water quality engineer Andrew Fang said ideally the agency would like to know how to get the pollutants’ reduction in the most cost-effective ways.

“You have urban development. You fertilize your lawn, that’s one thing,” he said. “You put more concentration on the land. That will basically change the hydrological process of your watershed. That creates a lot of erosion on your land.”

Andy Stoddard of Dynamic Solutions of Knoxville, Tenn., a company contracted to help with the study, said the model can be used to do “what if” scenarios. He said Lake Thunderbird’s “sensitive water supply” designation means it has additional protections “over and above.”

“The model matches physical observations in the lake. … Oxygen from the air doesn’t make it to the bottom layer,” he said. “One big piece of the puzzle is when you get oxygen low, it triggers a big release of phosphorus and ammonia into the lake.”

Experts caution that when the watershed cities implement best practices such as building wetlands in the watersheds, it will take time for those to work.

“How long might it take for the lake to attain compliancy?” said Stoddard. “You’re talking in the order of a few years. … It may seem hopeless at first, but it can be achieved.”

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