BAYOU CORNE — Nearly a week after Assumption Parish homeland security officials lessened the severity of a 3-year-old evacuation order stemming from the sinkhole near La. 70, lunchtime customers Tuesday at the Gator Corner gas station and restaurant were a bit indifferent.
As the drama over the sinkhole that appeared three years ago Aug. 3 has played out and most residents have moved away, gasoline continued to be pumped and po-boys dressed at the Gator Corner in spite of a mandatory evacuation order issued less than 24 hours after the sinkhole was discovered in the nearby swamp.
Correy Joffrion, 35, of White Castle, who was watching his friend eat his french fries after Joffrion had finished off his fried chicken, said Tuesday that he continued going to the Gator Corner for lunch after the discovery of the sinkhole and will keep on frequenting the eatery.
Other customers and employees had similar sentiments as the Gator Corner has become a popular spot with contractors working on the sinkhole.
Assumption Parish Homeland Security Director John Boudreaux reduced the mandatory evacuation order to a voluntary one Sept. 2 in an area west of Grand Bayou. That area has no residences but does include the gas station and some salt dome operators.
Officials say the latest evacuation order change — the second since December — indicates the ever-present risk of flammable methane gas is being reduced.
A mandatory evacuation order remains for the Bayou Corne community, where about a dozen families and camp owners remain, Boudreaux said.
The mandatory order means remaining in Bayou Corne poses a risk. While no one is forced to evacuate, if the sinkhole were to take a turn for the worse, parish officials could not guarantee people’s safety.
State scientists believe the sinkhole’s formation unleashed gas from natural deposits and allowed it to collect in an aquifer about 100 to 125 feet underground. Scientists have attributed the watery hole’s creation to an underground breach in a Texas Brine salt dome cavern. Texas Brine claims nearby oil drilling contributed to the cavern breach.
While the 31-acre sinkhole captured worldwide attention when video captured it sucking down a patch of cypress trees into its murky depths, the sinkhole’s rumbling has calmed, but fears that the methane gas could accumulate in homes have largely kept the evacuation order in place.
Parish and Texas Brine officials have different views about how long it will take to collect and burn off the remaining gas through special wells.
Bruce Martin, Texas Brine’s vice president for operations, said the daily rate of gas removal from so-called “vent wells” has fallen to just 3 percent of the gas removed at the peak of those efforts.
Martin said that in late 2013 and early 2014, some 150,000 cubic feet of gas was removed each day. For the past three weeks, gas removal has been closer to 4,000 to 6,000 cubic feet per day.
“We think we’re close to the end. We’re just running out of gas to vent,” Martin said.
At the same time, Martin could not say when the monitoring and remediation efforts would end or when the parish would lift the remaining evacuation orders.
Boudreaux didn’t dispute that gas flow from vent wells had dropped or that bubbling methane sites in area waterways have diminished, but he suggested gas removal could continue at least another year.
He noted that more than a year ago, facing residents’ opposition, Texas Brine committed not to pump water from the gas-containing aquifer, a method that could have sped up gas removal. Residents aired concerns about subsidence from pumping.
Boudreaux said Texas Brine is left with managing vent wells so gas flows as the amount of gas shrinks and pressure pushing the gas upward drops.
“It’s a back-and-forth kind of thing, which is a very time-consuming process,” he said.
A state panel formed after the sinkhole set the standard to declare the area free of gas risk.
Texas Brine does not have to remove all methane but must reduce gas pressure below a benchmark known as hydrostatic pressure.
That means if the gas were at the bottom of a 100- to 125-foot-deep swimming pool — a depth equivalent to the depth of the aquifer where the gas has collected — the pressure of all that water pushing down on the gas would keep it from rising.
The aquifer is covered by layers of clay, which exerts more pressure than water, so the benchmark is potentially a more rigorous safety standard than actual conditions.
Martin said company experts believe the clay contains the remaining gas, but state scientists have questioned whether the clay has cracks and pockets that could allow methane to reach the surface.
Boudreaux said the new voluntary order remains until state and parish officials can confirm through further testing that gas risk in that area has been abated completely.
Peter Graffagnino, comptroller for Roland J. Robert Distributor Inc., owner of the Gator Corner, said the latest change is another positive sign the sinkhole threat is diminishing. Worries remain for the gas station, he said, once response workers finish up and most residents have gone.
“The big next thing for us and the concern for us is what will the business numbers be,” he said.
Follow David J. Mitchell on Twitter, @NewsieDave.