Assumption sinkhole claims another patch of earth

The sinkhole near Bayou Corne sucked down another small patch of earth Monday afternoon as Texas Brine Co. released pressure again from its failed salt dome cavern near the 29-acre swampland sinkhole in Assumption Parish.

The edge collapse, or slough-in, came five days after six trees in the same area were pulled down into the hole’s watery depths. Texas Brine was releasing pressure from the cavern around the same time.

State regulators said Monday they are trying to determine to what extent reducing pressure in the cavern is linked to recent slough-ins.

State and Texas Brine officials are trying to reduce cavern pressure in measured amounts and watch for any consequences, said Patrick Courreges, spokesman for the state Department of Natural Resources.

“Any sudden, sharp change in condition that might have the potential to release additional gas/crude oil, or alter the sinkhole growth trend in some way that would pose a greater threat to the public or to Bayou Corne itself must be prevented,” Courreges said in an email Monday to a resident asking about the situation.

Video provided by parish officials Monday shows an estimated 40-foot by 10-foot section of the well pad slowly sink underneath the sinkhole’s surface at about 2:35 p.m.

The video was shot by John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness. He said he continued to see small bits of the well pad — once used by the company to work on the well — continue to be eaten away by the sinkhole Monday afternoon.

“Every now and then, I see a piece fall in,” he said.

The two sizeable slough-ins occurred just weeks after a scientist working for the state suggested cautiously that the sinkhole may be stabilizing and its growth slowing.

Scientists think the Texas Brine cavern, which was carved with fresh water from a large underground deposit of salt, had a breach or collapse in its supporting side wall. Rock surrounding that deposit flowed inside the cavern. The shifting rock underground resulted in the sinkhole in August 2012.

Scientists have described the connection between the sinkhole and the broken cavern as a U-shape. Rock moves down through the shattered earth under the sinkhole and into the 5,000-foot-deep breach near the cavern’s bottom inside the cavity and then up the cavern toward its roof.

The process has fueled the growth of the sinkhole, sometimes in dramatic fashion, but also puts pressure on the cavern and its well infrastructure. Liquid muck toward the top of the cavern is steadily being squeezed by the rock filling the cavern.

Like the steam relief valve on a tea kettle, the pressure in the cavern access well must be released to avoid further damage to the cavern. Courreges said Texas Brine has been doing that intermittently over the past few days.

Though possibly years away, scientists have speculated that the sinkhole will become stable once rock fills the cavern and it is compacted.

Courreges said some discussion has centered on releasing cavern pressure more often and hastening the flow of rock. But the concept is being reviewed with caution, he said, to avoid “unintended consequences” that might threaten the public or the environment.