NORMAN — The Oklahoma Department of Environmental Quality has completed the preliminary draft of the total maximum daily loads for Lake Thunderbird’s watershed and submitted that draft to the Environmental Protection Agency on Nov. 30.
A TMDL measures the amount of pollution a body of water can take without violating EPA standards and is particularly relevant as lake levels continue to fall below normal.
The EPA will review technical details of the draft TMDL, and changes are anticipated after the EPA review.
“We finished that preliminary draft and submitted it to EPA,” said Tim Ward, assistant director ODEQ/Water Quality Division. “There is no timeline on how long the EPA has to review it. Hopefully they’ll review it within the next few months, but we really don’t know.
“After we receive their comments, we will then make changes as we believe are necessary to that TMDL and will release that to public notice. At that time, not only will the public have an opportunity to comment but the EPA can comment again as well.”
Public comments are not being taken at this time.
“This is extremely early in the process,” Ward said.
Lake Thunderbird: Lake Thunderbird is the primary drinking water source for Norman and also serves Midwest City and Del City. It was designated as a Sensitive Water Supply lake by the state in 2002. The federal Clean Water Act and other regulations require TMDLs be developed for impaired bodies of water.
“It (the TMDL) characterizes the total maximum daily loads in the area,” Ward said. “At the same time, there are goals to a TMDL. It is a study that helps us to manage the amount of pollutants going into that basin.”
The first step of a TMDL is a modeling study for the lake and its watershed. To help accomplish that, a technical advisory committee was formed to provide recommendations and guidance for the development of the TMDL and watershed plan.
However, a lawsuit filed by the Central Oklahoma Master Conservancy District, which oversees the lake and serves as a guardian of the water quality, required ODEQ to complete the study by November. This timeline resulted in a more curtailed modeling study.
“ODEQ has determined that it could complete the TMDL by November 2012 only if it disbands the TAC and limits the number of times DEQ runs the models to a minimum,” according to TAC meeting notes on April 24 recounting input by ODEQ attorney Mista Turner-Burgess.
Officials on the COMCD staff and board believed water quality and pollution levels were quickly becoming critical concerns.
“They (DEQ) had delayed the TMDL a number of times,” COMCD District Manager Randy Worden said. “The district initially filed against the DEQ back in ’07, and that was to make DEQ perform a TMDL on Little River and Lake Thunderbird. The court ordered that done by April 2010 — it was supposed to be completed.
“DEQ didn’t even start by then. It was important for us to ensure by litigating this thing to have a set date for the TMDL to be completed,” he said. “Our discussions with the DEQ after the due date of 2010, we couldn’t pin them down to a date.”
Lake impairment: Lake Thunderbird is considered impaired because of “high turbidity, high levels of chlorophyll-a and low levels of dissolved oxygen,” according to DEQ.
High levels of chlorophyll-a result in too much algae growing in the lake, though this summer when high temperatures and drought conditions caused potentially toxic algal bloom in many small Oklahoma lakes, Thunderbird remained safe.
Runoff deposits nitrogen and phosphorus in the lake, which promotes high levels of algae growth. When algae die and decompose, oxygen is depleted in the water, contributing to the death of fish and aquatic organisms.
“Excess algae can also affect the taste of drinking water as well as increase the costs of treating the water,” according to DEQ.
Ironically, Thunderbird may have been protected from algal bloom this summer by another of its issues — turbidity.
“Turbidity doesn’t let the light in, and that’s why you get less algae,” Norman Utilities Director Ken Komiske said. “We have a very good water treatment plant that takes care of most of our issues. Right now, we’re doing a pilot project using ozone to help improve the taste and odor.”
In layman’s terms, turbidity is caused by sediment in the water. This sediment is easy enough to remove, though it can create mechanical wear on water supply pumps and systems, increasing treatment costs.
The bigger issue, however, is that the sediment transports pesticides or other chemicals into the lake which are difficult to remove in order to produce high-quality drinking water.