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Texas Brine Co.’s push for a five-year state permit to discharge salty groundwater with traces of benzene and toluene into the Bayou Corne-area sinkhole has drawn concerns from environmentalists and landowners near the swampland hole in Assumption Parish.

The process has been underway for a year through short-term permits to help remove potentially dangerous methane gas collecting beneath the Bayou Corne community.

But environmentalists say the discharge introduces contaminated groundwater into the sinkhole and poses a risk to the surrounding freshwater swamp if sinkhole containment levees fail.

They point out that the levee around the lakelike, 37-acre sinkhole, which itself has high salt levels and other trace contaminants at its deepest levels, has failed before because of stirrings under the sinkhole and is just feet from the Bayou Corne waterway and sensitive aquatic life.

“We don’t know what all is going on underground,” Darryl Malek-Wiley, Sierra Club representative, said Wednesday.

Testing has shown that the water from the aquifer, which is no longer used for drinking water in Assumption Parish, contains trace amounts of toluene and benzene and other contaminants and has a high salt content. Continual testing in waters around the sinkhole have not shown contamination leaking out, Texas Brine officials have said.

Levee failures also only have resulted in surrounding water flowing into the sinkhole, not the reverse, because sinkhole water is often below the water level outside the levee.

Scientists studying the sinkhole believe it opened up natural oil and gas deposits when it formed underground more than two years ago due to the failure of a Texas Brine salt dome cavern. The gas spread in the aquifer and under the Bayou Corne community, posing an explosion risk to homes.

The state Office of Conservation has ordered Texas Brine to remove the gas and the company has been using nearly five dozen wells to collect and burn it. But those wells also pull up groundwater from the aquifer, depressing the flow of gas. The water must be removed periodically to keep the gas flowing.

Wells, pipelines and trucks take water from the aquifer and put it back into the sinkhole which is connected to the same aquifer.

DEQ has already granted tentative approval for the new permit and argues in a draft permit, as Texas Brine has argued in its submissions to DEQ, that the discharge is a closed loop that does not affect surrounding swamps and bayous.

“Berms surrounding the sinkhole provide total containment of existing water and new discharges within the sinkhole,” DEQ says in the permit. “The sinkhole remediation operation is a fully recirculating system.”

Scientists believe the sinkhole is separated from the surface by a levee and is connected underground to the aquifer, known as the Mississippi River Alluvial Aquifer. Texas Brine says the aquifer, at 100 to 130 feet deep, is also geologically sealed off from the surface by layers of clay.

But a hydrogeologist, working for owners of large properties in litigation with Texas Brine, claimed the state Department of Natural Resources, not DEQ, has the authority to permit discharges into groundwater aquifers. He also claimed the aquifer water is oil and gas exploration waste and state law bars its disposal in a groundwater aquifer or an underground source of drinking water.

“I see discontinuity with regulatory requirements from several different programs administered by different regulatory agencies within the state of Louisiana,” the hydrogeologist, Gregory Miller, said during a public hearing on the permit Tuesday night in Napoleonville.

After the sinkhole emerged in early August 2012, in addition to the gas, a foul-smelling hydrocarbon akin to diesel also rose for several months, leaving oil sheens on the sinkhole.

Some people are also arguing against the reduced frequency of aquifer water testing proposed in the permit and want a requirement that Texas Brine test waterways around the sinkhole.

Malek-Wiley, who testified at the hearing Tuesday, said Wednesday it is not clear how much of the aquifer contaminants arose from the sinkhole’s formation and how much was already in the aquifer.

“We don’t know if we are adding to the pollution or not unless we have detailed testing, so that is one of the issues,” Malek-Wiley said.

For its part, Texas Brine says it “is committed to an effective sinkhole response,” according to a company statement.

Issuance of the permit “is an important part of that response.”

DEQ officials declined comment Wednesday with the draft permit in the public comment period. It ends 4:30 p.m. Tuesday, Sept. 16.