NORMAN — Lake Thunderbird’s well-earned nickname, “Dirtybird,” may not apply in six years according to computer model projections. The model projections and recommended requirements for reducing lake pollution were developed by the Oklahoma Department of Environmental Quality and Dynamic Solutions LLC and presented to the public Tuesday night at the Norman Public Library.
The computer modeling is part of a special study to look at pollution levels feeding into Lake Thunderbird, how much pollution the lake can theoretically handle and how to reduce the pollution to meet state and federal water quality requirements.
Known as the Lake Thunderbird TMDL Project, the study measured the Total Maximum Daily Load of pollutants going into the lake from various sources, as well as general run-off from the natural environment. Norman, Oklahoma City and Moore are the primary point sources of pollution.
In 1972, Congress adopted the Clean Water Act and, with it, some target dates for water-quality achievements.
“Congress set some pretty ambitious goals,” DEQ Watershed Manager Mark Derichsweiler said.
Goals included having fishable, swimmable water quality wherever it was attainable by 1983 and to eliminate the discharge of pollutants by 1985.
“We’re still a little behind on the 1983 goal, and we’re really behind on the 1985 goal,” Derichsweiler said. “We have somewhere over a thousand impairments in this state. Lake Thunderbird is one of the priorities.”
Thunderbird is designated as a sensitive water supply because it provides drinking water for Norman, Midwest City and Del City. It has been classified as impaired because of high levels of sediment (turbidity), algae (chlorophyll a) and low oxygen levels. The algae growth is a result of pollution by nutrients, in particular phosphorous and nitrogen.
“Lake Thunderbird doesn’t meet water-quality standards,” Derichsweiler said.
Thunderbird is a 6,070-acre reservoir and is part of the Upper Little River watershed.
Andrew Stoddard of Dynamic Solutions said the computer generated model is a numerical description of the lake’s watershed. Data was collected from various points and fed into the computer modeling program along with other relevant data such as weather, water temperature, water releases at the dam and surveys of the sediment bed.
The Oklahoma Water Resources Board, MESONET, U.S. Army Corps of Engineers and the Central Oklahoma Master Conservancy District contributed data.
The model describes the current conditions based on that data — a year-long segment during 2008-2009 — and makes future projections based on various scenarios, allowing DEQ to make recommendations for reducing pollution based on the model.
Samples taken at various points identified that urban development is the highest contributors to the loading of phosphorus and sediment in the lake. Hot spots for high levels of sediment and phosphorus loading into the lake were identified in northwest Norman, Moore and portions of Oklahoma City.
Norman, Moore and Oklahoma City discharge runoff into the lake’s tributaries through their stormwater systems.
Known as MS4s — Municipal Separate Storm Sewer Systems — these source point polluters will be required to reduce the amount of pollution they discharge into the watershed. DEQ’s proposed requirements include identifying potential sources of pollution, selecting a strategy for reducing the “wasteload” or amount of pollutants, implementing construction site inspections with enhanced enforcement and tracking progress.
Currently, the Central Oklahoma Master Conservancy District that manages the lake is experimenting with a oxygen injection project, and the DEQ recommend that be continued, along with expansion of shoreline revegetation. A more long-term project being recommended is the establishment of a treatment wetlands on Little River above the Twin Bridges.
Under the proposal, construction sites would have to maintain a 100-foot vegetative buffer for all streams, put in sediment basins (detention ponds) for sites five acres and larger, submit to weekly inspections, plant vegetation quickly and test the soil before using fertilizer.
DEQ’s full proposal is still in the comment period, and public comments will be taken through Aug. 1. After that, the TMDL model goes to the Environmental Protection Agency for final approval. Once approved, the plan will be incorporated as a water quality management plan.
All of the cities permitted for stormwater release in the Thunderbird watershed will have to comply. That means Moore and Oklahoma City will have to follow the plan, even though Thunderbird does not provide those municipalities with drinking water.
It is unclear how long the EPA approval is likely to take, so clearer waters for Lake Thunderbird could be way down the road. In the meantime, Norman has already taken steps to move toward cleaner waters by implementing a water quality protection zone and a fertilizer ordinance that limits the use of phosphorous.
Public education will be key as any plan is implemented. When changes result in progress, for a time, the lake may appear to get worse, Derichsweiler warned. When the sediment is reduced and the water becomes more clear, algae will increase in growth for a couple of years.
If pollutant nutrients such as phosphorous and nitrogen are reduced, that algae will slowly decrease. In addition to limiting the pollution sources of nutrients, cutting down on the sediment will reduce algae because sediment carries phosphorus into the water, Derichsweiler said. Reducing the sediment also increases the oxygen content of the lake.
Public comments can be mailed to Dr. Karen Miles, Water Quality Division, Oklahoma Department of Environmental Quality, P.O. Box 1677, Oklahoma City, OK 73101-1677, or email Karen.Miles@deq.
For more information, visit the project website, deq.state.ok.us/wqdnew/
The PowerPoint presentations will be on website soon.