The atmospheric release of hydrogen sulfide gas last week from a Texas Brine Co. LLC vent well in Assumption Parish did not require immediate reporting to state hazardous materials authorities, Louisiana State Police said.

Capt. Doug Cain, State Police spokesman, said the release of the gas, which is flammable and poisonous at high concentrations, did not go off the company’s site and did not trip community air monitors.

“As far as we’re concerned, it was not even a hazardous materials incident,” Cain said in a telephone interview this week.

Some state and parish agencies did not find out about the release on the evening of Nov. 19 until the next afternoon during a regular 3 p.m. telephone conference on the sinkhole response.

John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness, said his office was not told until then.

He said he has since asked State Police to see whether the company should have reported the incident sooner.

State Office of Conservation Commissioner James Welsh reported in a letter last week that hydrogen sulfide gas, abbreviated as H2S, was smelled by Texas Brine workers while water rising from the vent well was being routed to a storage tank.

The water had been separated from the vent well on Texas Brine’s leased site between Bayou Corne and Grand Bayou communities and south of La. 70 S.

An 8-acre sinkhole is also located in the same area.

The well was intended to burn off methane gas suspected of being trapped under the area after a Texas Brine salt cavern in the Napoleonville Dome failed in early August and caused the sinkhole.

The sinkhole prompted a mandatory evacuation of 150 homes in the Bayou Corne and Grand Bayou areas on Aug. 3. The evacuation remains in place.

The vent well had begun flaring gas earlier on Nov. 19 before the water was encountered later that day, Welsh wrote.

Texas Brine officials have said that once hydrogen sulfide’s presence in the water was confirmed — measurements were taken within the vent well separator unit — flaring was halted and the well was shut by 7 p.m. Nov. 19.

State right-to-know regulations require companies to report an emergency incident to the State Police hazardous materials hotline within an hour.

The regulations define an emergency as an event endangering public health and safety, creating “significant, adverse impact” to the environment or causing severe property damage.

When a nonemergency incident occurs, but a minimum amount of hazardous material, called a “reportable quantity,” has been exceeded, companies have 24 hours to report the incident.

More than 100 pounds of hydrogen sulfide must be released within 24 hours to require reporting in a nonemergency, regulations say.

Commissioner Welsh wrote that air sampling did not detect that hazardous concentrations of hydrogen sulfide escaped containment and that air sampling at Texas Brine’s site and in the surrounding community also did not detect such concentrations.

State Police’s Cain said that the incident was not “reportable” but State Police was notified later as a courtesy.

Like the parish, the Louisiana Department of Environmental Quality did not find out about the release until the 3 p.m. conference Nov. 20.

Officials said they are trying to calculate if the release could have reached more than 100 pounds to trigger formal reporting.

“We’re still looking to see if it could reach that level,” said Rodney Mallett, DEQ spokesman.

But he said the air release probably lasted less than a minute.

Sonny Cranch, spokesman for Texas Brine, said the total amount of hydrogen sulfide released was not measured but said it was minuscule.

He said the company has tried to keep the parish Office of Emergency Preparedness and other parish officials informed of every event on the company’s site.

“In this particular instance, we did not immediately notify them. It was 7 o’clock at night, and the well was closed,” Cranch said.

“We felt that procedurally, we handled the matter in the best possible way to assure that there was no threat at all to the public safety.”

Boudreaux said he reported the matter to State Police as part of his own due diligence.

“And if there is no finding, so be it. I am not going to pursue anything. I just wanted to make sure everyone was aware of” what happened, he said.

Texas Brine has plans to permanently plug the shut-in well, which contains hydrogen sulfide.