Yesterday’s Installment: Sinkhole Explosive Methane ‘officially’ Life Threatening, residents NOT told
Sinkhole Site, 10/07/12
9:45 a.m. Update October 7, 2012:
The first vent well is complete. Yesterday we were advised that The Shaw Group had drilled down to 178′ with a final goal of 200′. They met a refusal rate at 184′, which is 74′ below the aquifer. The aquifer is located at 110′ feet down, so the drilling of 74′ under it is satisfactory for the venting process. The second vent well was started this morning. If all activities at this site remain on schedule, venting can begin there as early as Thursday or Friday.
Now they can release these toxins into the air…
BUT as of 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.
The aquifer under Assumption Parish is not used as its major water source — Bayou Lafourche is — but some parish officials say they are concerned the odorless, colorless gas underground could accumulate unseen to explosive concentrations if left unchecked.
John Boudreaux, director of the Assumption Parish Office of Homeland Security and Emergency Preparedness, said there are concerns the gas can build up pressure under the clay layer that lies above the aquifer.
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.
* In 2001, in Hutchinson, Kan., and in late 2003, in Assumption Parish’s Grand Bayou community next door to Bayou Corne, natural gas also became trapped underground.
The gas prompted evacuations and, in the case of Hutchinson, caused a major downtown explosion, fires elsewhere and two fatalities, according to a Kansas Geological Survey report and Louisiana regulatory files.
* In late 2003, casing in a well tied to a underground salt storage cavern then leased by then Gulf South Pipeline Co. LP in the Napoleonville Dome leaked gas into the subsurface over the dome. Twenty-eight residents were evacuated on Christmas Day and kept out of their homes for 50 days.
* Two years earlier, in Hutchinson, Kan., the worst that could happen did. Hutchinson Fire Chief Kim Forbes said residents saw the roof of the former Decor Party Store do a summersault in the air from the initial gas explosion.
The blast, on Jan. 17, 2001, stemmed from an old uncapped brine well forgotten inside the downtown store that once was part of a turn-of-the-20th century spa.
Seven miles away, propane had escaped, unknown, through a failed well casing tied to the Yaggy field salt storage cavern belonging to Oneok Inc., of Tulsa, Okla.
The propane moved through the underground Milan Limestone formation, which tilted upward from the cavern toward Hutchinson, a city of almost 41,000 then, until the gas found the old well. An overhead furnace in the party store provided the ignition source, Forbes said. The explosion set fire to neighboring Woody’s Furniture Store, also part of the old spa.
The gas continued to move under the town, finding other old wells in an area once heavily solution-mined for salt, sparking a trailer fire that killed two people the next day and shooting geysers of water 100 feet high.