By David J. Mitchell
River Parishes bureau
November 02, 2012
Updated at 12:10 p.m.
Assumption Parish and Texas Brine Co. officials issued estimates Wednesday that disagree on how much land a 5.5-acre sinkhole swallowed during the slurry hole’s eastern-bank collapse Tuesday.
Parish officials offered an estimate Wednesday nearly 19 times the size of their initial estimate on Tuesday, while Texas Brine officials suggested Wednesday the amount of land that crumbled into the sinkhole actually was a bit less than the parish’s initial estimate.
The dispute dates back to Tuesday, when the parish announced that 1,600 square feet of land fell into the sinkhole about 4:45 p.m. that day. Wednesday, parish officials raised their estimate of the land loss to almost as much as 0.7 acre, or 30,000 square feet.
For a more precise measurement, parish officials said, they plan a flyover Thursday of the sinkhole located in wooded swampland between Grand Bayou and Bayou Corne south of La. 70 South.
John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness, said measurements calculated on Wednesday comparing current and prior maps showed the area of collapse extends 300 feet along the sinkhole’s bank and extends 75 to 100 feet inland on the eastern rim.
Boudreaux’s original estimate issued less than an hour after the Tuesday event suggested a strip of land 80 feet by 20 feet had fallen into the sinkhole.
Sonny Cranch, Texas Brine spokesman, said Wednesday that the company estimates about 50 to 75 linear feet of sinkhole bank extending inland about 15 to 20 feet had been swallowed Tuesday by the sinkhole, an area possibly as small as 750 square feet.
Cranch declared the parish overstated the size of the sinkhole’s latest land grab.
“That’s our measurement,” he said of the 750-square-foot estimate.
Scientists with Shaw Environmental and Infrastructure and the Louisiana Department of Natural Resources believe a Texas Brine salt cavern underwent a wall breach that led to the formation of the sinkhole 200 feet to the northwest.
Discovery of the sinkhole on Aug. 3 triggered orders the same day evacuating 150 homes in the area.
The evacuation orders still stand.
The cavern is located inside the Napoleonville Dome but was carved near its western edge. The sinkhole sits just off that edge.
The 1-by-3-mile salt deposit has been used for years for solution mining of brine for industrial uses and hydrocarbon storage while its perimeter has been the focus of oil and gas exploration.
Despite the bank-sloughing incident Tuesday, Cranch said, cleanup workers were able to continue skimming oil from the surface of the sinkhole Wednesday and so far have collected a total of more than 900 barrels.
The cavern wall breach and a subsequent release of brine from inside the plugged cavern caused oil and gas from natural pockets along the dome to escape, scientists believe.
The latest zone of banksloughing starts just east of a mat road Texas Brine has installed for cleanup purposes.
Texas Brine’s main facilities are east of the sinkhole, but Cranch said the eastward migration of the sinkhole rim is not a threat to those facilities or to the damaged Texas Brine cavern to the south.
“It’s a concern, but it’s not endangering operations yet,” he said.
The sloughing-off process has been expected, DNR and Texas Brine officials have said, as the banks of the funnel-shaped sinkhole — 550 feet in diameter before the latest collapse and 449 feet deep — gradually seek an angle of repose.
A worst-case scenario projects the sinkhole would reach 1,500 feet across, scientists have said, while also noting that the main area of weakness is the western edge of the sinkhole, not the eastern edge.
Before the collapse, Texas Brine had largely finished removal of vegetation but Boudreaux said the company now has more work to do.
“There’s plenty of debris back in the hole now,” he said, including another 15 trees pulled into the slurry Tuesday.
While a recycling company is hauling away the crude oil for resale, Rodney Mallett, Louisiana Department of Environmental Quality spokesman, said the oily sinkhole debris is being hauled to the Colonial Landfill near Sorrento.
The Type I and II landfill on La. 70 is authorized by DEQ to accept residential, commercial and industrial solid waste, DEQ records say, and has received oil leak cleanup waste from BP’s Deepwater Horizon disaster in 2010.