BAYOU CORNE — Kathryn Brown says her New Orleans upbringing instilled in her a responsibility to take care of her property.
While many residents have evacuated and 65 property owners have agreed to buyouts from Texas Brine Co., Kathryn and Tim Brown have not left their home of 14 years on the bayou despite the 25-acre Assumption Parish sinkhole just to the east and fears of rising methane gas.
The Browns have small air monitors in their house and a community-wide air monitor in their backyard along Bayou Corne. They also have a sinkhole display in front of their house on Sportsman Drive south of La. 70.
“That’s our way of dealing with it,” said Kathryn Brown, 64.
But scientists and officials working on the sinkhole response said they may have a way to greatly reduce the risk posed to people like the Browns by methane gas trapped under the communities near the sinkhole.
The failure of a Texas Brine Co. salt dome cavern that led to the formation of the sinkhole last year also unleashed methane from natural sources deep underground, scientists have said.
The gas has risen to the surface in more than 90 bubble sites on land and water. Fears of an explosion have been part of the motif for a more than yearlong evacuation by Bayou Corne and Grand Bayou residents, scientists and officials have said.
Methane is an odorless, invisible, flammable gas and can accumulate under slabs and in confined spaces.
Texas Brine and state scientists recently conducted tests on a bubble site, nicknamed “Stephanie and Her Sisters” which gurgles inside a pond on Texas Brine’s Bayou Corne-area site, with a form of technology often used to remove soil contaminated by petroleum from old, underground tanks.
Called dual phase vapor extraction, the system uses vacuum pumps to suck out water and gas underground.
Scientists and officials with the state Office of Conservation believe a system of dual-phase vacuum pumps and shallow wells could intercept the rising gas in a continuous layer of sand 20 to 30 feet deep, which was recently discovered after a recent round of — and at times controversial — geologic testing.
As proof of this concept, scientists set up a pump and wells near Stephanie and Her Sisters and began running the vacuum pump Aug. 28. Within four days, the bubbles were virtually gone and could not be detected, but within 90 minutes of turning off the pump, the bubbles returned, scientists said.
Gary Hecox, senior hydrogeologist with CB&I and a leading scientist on the sinkhole response, told residents in a small meeting Thursday in Bayou Corne that the technology provides an interim level of protection.
Hecox emphasized the pumps will have to be designed to run for the long term while scientists work on removing the actual sources of gas from deeper underground, which could take years.
“It’s not, ‘I come in today, it’s fixed tomorrow.’ But this is going to make it a lot safer to be in and around your homes because were getting the gas before it gets to your homes,” Hecox, also a member of a special state commission investigating the sinkhole, said.
The technology is a shift from earlier, deeper vent wells, which are still being used and have removed 17.5 million cubic feet of gas, parish officials said.
Those wells were drilled into the swampy Louisiana earth and were aimed at hitting known gas pockets, but some have had trouble by filling with water, which blocked the natural flow of the methane.
Drilling for an initial round of testing to help design the vacuum system could start late this week, said John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness.
The system could be in place and running in a few months, depending on how many wells have to be drilled to cover the community, Hecox said.
Gas removed by the vacuum system would be burned inside an oxidizer unit in the communities or sent to an off-site flare, officials said.
Scientists are also working to address gas deeper underground, located at the top of the Mississippi River Alluvial Aquifer at 90 to 125 feet, and in the deep, originating source at thousands of feet.
To attack the aquifer, officials plan to drill five new wells with improved designs in the Bayou Corne community south of La. 70 along Sportsman Drive.
The wells will use a similar vacuum technology to remove water and gas, Hecox said. Work could also take several months, though wells will be brought online as they are ready.
Texas Brine plans to discharge the water pumped by shallow and deeper wells into the sinkhole through a future system of lines, officials said.
Reaction to the plan Thursday was mixed as residents worried about aesthetics of the vacuum systems and new wells and where gas will be discharged during initial testing.
Tim and Kathryn Brown saw the presentation as a positive development.
“It’s got to be done. They’ve got to get the gas out. That’s our biggest worry. I’m not worried about the sinkhole swallowing us up,” Tim Brown, 65, said.
The Browns said they are comfortable with relying on the pumps to remain in their home.
“We’re here for the duration,” Kathryn Brown said.
Hecox said the amount of gas in the aquifer is more than the 45 million cubic feet first thought and has been found to be collected heavily in a dome-like high spot under the Sportsman’s Drive area, which is under the Browns’ house.
“There’s no kidding. There’s a lot more gas than I told you three months ago,” Hecox told residents Thursday.
Gas from that area is finding its way to the shallow sands and spreading out under the community. He said the new, deeper wells in the aquifer could be removing gas and water for years.
The state Department of Environmental Quality gave Texas Brine a permit Sept. 6. to discharge into the sinkhole at two points. According to the permit request, Texas Brine expects to pump about 360,000 gallons per day from each point, which is more than enough water to fill an Olympic swimming pool each day.
Patrick Courreges, spokesman for the state Department of Natural Resources, said it would be up to parish officials along with the commission to decide whether the new vacuum system could lead to a lifting of the evacuation order.