by David J. MITCHELL
River Parishes bureau
November 09, 2012
Texas Brine Co. LLC is burning off natural gas being vented from an aquifer near a Bayou Corne-area sinkhole 24 hours a day, company officials said Wednesday.
The gas was forced into the Mississippi River Alluvial Aquifer through a chain of events arising from a Texas Brine salt cavern failure, which scientists think also caused the sinkhole to form during early August in swamps between Bayou Corne and Grand Bayou in Assumption Parish.
The continuous flaring represents a greater rate of gas removal since late last week when Texas Brine initiated gas flow from a “vent well” in the aquifer and then set up a system to remove the gas from the aquifer during daylight hours.
But Commissioner James Welsh of the Louisiana Office of Conservation announced Wednesday a joint effort between his agency and the Louisiana Department of Environmental Quality to test for methane in slab-built homes and structures in the Bayou Corne area.
Office of Conservation officials said in a statement that sampling results from 18 shallow monitoring wells, called Geoprobes, installed around the Bayou Corne community found gas in layers of sediment above the aquifer Texas Brine is now venting.
Five wells detected gas at low pressures, parish officials said.
The Geoprobes are 20 to 40 feet deep. The aquifer of permeable, water-bearing sand, gravel or rock, lies more than 100 feet deep.
A previous voluntary in-home testing program by DEQ found no instances of natural gas in 97 homes, but Office of Conservation officials are asking that residents grant permission for new testing.
“While analysis of the data we have available indicates that the risk of natural gas accumulation in homes is low, we want to have additional testing out of an abundance of caution. We will take no chances when it comes to public safety,” Welsh said in a statement.
Sonny Cranch, spokesman for Houston-based Texas Brine, said the company flared off 70,000 cubic feet of gas between noon Monday and 7 a.m. Wednesday from the vent well, which is the first of four completed wells to remove gas from the aquifer.
Three other wells drilled by a Shaw Environmental and Infrastructure subcontractor working for the Louisiana Department of Natural Resources are clogged.
A fourth is still being finished.
Office of Conservation officials said structures on piers, which create an open space between the building floor and the ground, allow air flow that prevents natural gas accumulation.
Natural gas is odorless and colorless and can be flammable at high enough concentrations.
Parish officials have said the fear of natural gas accumulation is one factor keeping an evacuation of the Bayou Corne and Grand Bayou areas in place.
Discovery of the sinkhole initially prompted the evacuation of 150 homes Aug. 3, following months of tremors and natural gas releases in area waterways. Gas was later found in the aquifer.
The Texas Brine cavern was mined from inside but near the western edge of the Napoleonville Dome, a 1-by-3-mile salt deposit that has been the focus of solution mining, gas storage and oil and gas exploration.
Now at least 7 acres at the surface but just 111 feet deep, the slurry-filled sinkhole sits off the edge of the dome, northwest of the cavern.
In January 2001, in Hutchinson, Kan., a gas leak from a well tied to an underground salt storage cavern caused a major downtown explosion, fires elsewhere and two fatalities.
Similar fears after a gas leak from a well tied to a Gulf South Pipeline Co. gas storage cavern led to the evacuation of Grand Bayou in 2003 and 2004.
Much of the gas involved in the Grand Bayou incident was removed. Recent isotopic testing found that gas from the 2003 Grand Bayou leak is not involved in the Bayou Corne incident, but scientists think the gas is instead from natural pockets along the dome unleashed by the Texas Brine cavern failure.
Patrick Courreges, DNR spokesman, said the risk that gas could escape from the upper sediments and accumulate in homes in Bayou Corne is very low, but officials want to “absolutely rule it out.”
“Let’s make sure something is not happening,” he said.
“We don’t want to assume it is not happening.”
John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness, said the parish has been speaking with the Office of Conservation about installing methane detectors in homes, in addition to the testing.
Gulf South Pipeline Co. provided gas detectors to Grand Bayou residents in 2004 while gas was removed from the aquifer.
DEQ has advised the public to call (225) 219-3015 to arrange for residential air monitoring services in the Bayou Corne community..