http://www.stuarthsmith.com/fears-of-methane-explosion-rise-in-sinkhole-ravaged-la-town/Fears of methane explosion rise in sinkhole-ravaged La. town10/8/12
The people of Bayou Corne have been through a lot. It started this summer when residents of the small bayou community about 70 miles west of New Orleans began feeling tremors and reporting foul odors. Then in August, a large sinkhole — near the site of a cavern that has long been mined by the Texas Brine Co. — threatened the town and forced evacuations. And the news keeps getting worse:
Now officials are warning the residents of a powerful buildup of methane gas under Bayou Corne that could cause a massive explosion:
An as-yet undetermined amount of natural gas is trapped in the aquifer underneath the Bayou Corne community, state and parish officials have said.
The area has been rattled by earth tremors, has waterways with gas bubbling to the surface, and is in the vicinity of a 4-acre sinkhole south of La. 70 that has grown larger since its emergence Aug. 3. Bayou Corne’s 150 households have been evacuated since the sinkhole appeared just off the edge of the Napoleonville Dome, a 1-mile-by-3-mile underground salt deposit.
Local officials have told the Advocate they’re very concerned that the odorless and colorless gas is accumulating to the point where it could burst through the ground with explosive force:
Once the pressure in the aquifer reaches a pressure greater than 75 to 85 pounds per square inch, the clay layer might not be able to hold back the accumulated gas, according to Boudreaux and geologists.
“And then it could be a problem because you do not know where the weak point would be until after it has already done its thing,” Boudreaux said.
This alarming news comes amid news reports that tremors are now being felt in a wide area across the bayou. This happened late last week, roughly 45 miles from Bayou Corne:
Nobody quite knows what caused the ground in some parts of Lafourche and Terrebonne parishes to shake, but it certainly has people talking.
A little before 2 p.m. Wednesday, reports began flooding in to officials of tremors accompanied by a loud noise. The Lafourche Parish Sheriff’s Office and Office of Emergency Preparedness received reports, but nobody has been able to narrow down a cause.
Lockport resident Bryan Comardelle had just sat down to watch television when he felt the rumble.
“It was just a sudden vibration,” Comardelle said. “I live in a brick house, and it even made it shake.”
Indeed, there’s also mounting reports of methane bubbling up from underground throughout the region:
Methane bubbles have been emerging in the sinkhole vicinity for four months. There are now seventeen bubble sites percolating in the sinkhole vicinity. As far as 80 miles west, at Lake Peigneur, gas bubbling has also increased. A resident who has lived and fished in the sinkhole area for decades has reported that the entire 1-mile by 3-mile Napoleonville Salt Dome area has been sinking.
Some scientists believe the sinkhole was caused when a subterranean brine cavern in the 1-mile by 3-mile Napoleonville Salt Dome collapsed. The breached cavern floor, storing radioactive materials and brine, is over 1,000 feet underground. The bottom is now leaking hydrocarbons into the cavern. Other scientists say some other powerful force has caused the cavern to breach, the seismic activity and escaping gas.
This is an incredibly dangerous situation in the Louisiana bayou. Just ask the residents of Hutchinson, Kansas, where in 2001 an underground buildup of methane caused a serious of explosions that killed two people and destroyed several stores in a downtown area. (In that case, the methane came from an untapped brine well under a department store.) In 2003, a methane leak in Louisiana from the Napoleanville dome caused 50 residents to evacuate their homes for weeks.
In Bayou Corne, workers began this weekend drilling three vent wells. This may eventually relieve some of the pressure — but the mental pressure and anguish for those who own homes in the community must be hard to take. It didn’t have to be this way. State and Texas Brine officials knew about potential problems at the dome more than a year and a half ago, and the state Department of Environmental Quality was painfully slow to respond to the first reports of tremors and bubbling gases this summer. Let’s pray that the efforts to reduce the pressure are not too little — or too late.
