Ongoing defect preceded sinkhole
By DAVID J. MITCHELL
River Parishes bureau
August 13, 2012
Louisiana Department of Natural Resources and Texas Brine Co. officials knew at least since January 2011 that one of the company’s salt dome caverns may have developed problems now suspected of possibly causing a large sinkhole and unexplained natural gas venting in northern Assumption Parish swamps.
For more than two months, as gas bubbles and tremors rattled the Bayou Corne community. DNR and other officials had asked for patience while pipelines, oil and gas wells and other salt caverns were tested.
The problems with the salt cavern were not disclosed to the public and some parish officials involved with the response effort.
An examination of DNR records, interviews, public statements and public meetings established the following:
- The possibly failed salt cavern may be closer to the outer wall of the Napoleonville Dome than Texas Brine officials believed.
- DNR defended the timing of its disclosures about the history surrounding the salt cavern as matching the emerging facts of the incidents in Bayou Corne.
- Sonny Cranch, Texas Brine spokesman, said company officials have been as surprised as anyone about a possible collapse of their salt cavern.
- DNR officials allowed Texas Brine to deposit naturally-occurring radioactive material arising from drilling into two company salt caverns, including the one that may have breached in the Bayou Corne area. As of Wednesday, state environmental officials had not tested the sinkhole for radioactivity.
In a Jan. 21, 2011, letter, Mark J. Cartwright, Texas Brine Co. Saltville LLC president, informed DNR about a failed integrity test of the cavern and company officials’ subsequent suspicion that the cavern may have breached the Napoleonville Dome’s outer wall, possibly explaining a loss of pressure in the cavern during the test. (Read letter.)
“One obvious concern is the cavern’s proximity to the edge of salt,” Cartwright wrote to DNR’s Joseph “Joe” S. Ball Jr. “There have been several studies in this regard, and Texas Brine has mapped the salt boundary near the cavern applying available well log data, seismic data, and most recently, vertical seismic data gathered during the workover. At this time, a breach out of the salt dome appears possible.”
Ball is the director of the DNR Injection and Mining Division, which oversees salt caverns.
Texas Brine officials also met with DNR officials on Jan. 21, 2011, concerning their work on the salt cavern that may have failed, DNR records show.
On Friday evening, the same day the sinkhole emerged, releasing a foul diesel odor, DNR officials made public the first indication that the cavern may have failed and caused the sinkhole, also known as a slurry area.
On Tuesday night, DNR and Texas Brine officials further explained that the cavern appeared to be closer to the edge of the Napoleonville Dome than thought when the cavern was issued a state permit 1982 and that the cavern wall could have failed. The failure could allow a connection between the brine contents of the cavern and sediments surrounding the dome.
The 422-foot-deep, 372-foot-diameter sinkhole is largely filled with salty water and, on its surface, has traces of diesel mixed with mud and vegetation. Diesel is floated atop brine in salt caverns to prevent unwanted erosion, officials have said.
DNR officials speculated natural gas, which is found inside salt formations, accumulated in the cavern and was released, accounting for the bubbles.
The January 2011 Texas Brine letter served as formal notification to DNR of the problems that led to the cavern well being plugged in June 2011, but Texas Brine officials had been examining the cavern’s wall at least since June 2010, DNR records show.
In early September 2010, Texas Brine began reworking the cavern well, milling a section of salt higher than the existing cavern roof, at 3,400 feet deep, to see if the upper strata could be mined. A DNR permit for that work was issued in May 2010.
Ball explained Wednesday that officials believe that area, which extended for about 100 feet through the well casing above the cavern roof, may be the source of the possible salt dome wall breach.
On Wednesday, DNR officials defended the agency’s handling of the issue and the broader investigation surrounding the problems in and around Bayou Corne.
They pointed out the agency was following the evidence that started with natural gas bubbles seen directly over a natural gas pipeline corridor under Bayou Corne and only recently turned to the slurry area.
Ball said DNR officials were focused on finding a source of the natural gas large enough to send gas bubbling up in the bayous and focused on the natural gas pipelines and two salt caverns known to store natural gas under pressure.
“We were looking for a single gas source. We never anticipated that gas that would naturally accumulate in a cavern would have that much driving force behind it to move gas so far away from it,” Ball said. “That is why we never focused on anything other than the two caverns that stored natural gas under high pressure.”
The same kind of pressure test that led Texas Brine officials to speculate that “a breach out of the salt dome appears possible” in January 2011 were used on those two high-pressure wells and found the wells were not leaking.
Ball said DNR officials first started looking at the Texas Brine cavern a few days before the slurry area emerged when seismic data from the U.S. Geological Survey indicated tremors appeared to be coming from an area near where the sinkhole would later develop.
When asked if he could see how some might see DNR as hiding information with the disclosure of the letter, Ball replied he could, but that would not give a fair impression.
“Yes, I can, but you are playing Monday morning quarterback. That is always going happen,” Ball said.
Sonny Cranch, spokesman for Texas Brine, said company officials did not make the connection between the observations described in Cartwright’s letter and the events of the past few months in Bayou Corne.
“There still may not be connection,” Cranch said. “I’m serious. This collapse is as much a surprise to Texas Brine as anybody else.”
Cartwright’s letter was found in a review Wednesday of DNR regulatory files for the cavern. Ball and other DNR officials provided the files Wednesday at agency offices in Baton Rouge after a verbal request earlier this week.
John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness, said he was not informed about possible problems with the salt cavern until Friday after the sink hole emerged.
Boudreaux, who is the incident commander for the gas bubbles, sinkhole and other issues in Bayou Corne, began fielding calls about 6 a.m. Friday about the diesel smell, determined a half-hour later to be from the sink hole.
He said the Texas Brine letter is news to him.
“They have never told me anything. We have been fighting this since it began, and this is very concerning to me,” Boudreaux said.
John Achee Jr. is a community activist who runs two Facebook sites that have become community forums on Bayou Corne where feelings that officials are not giving all the information are aired.
“I know that this was certainly a possibility, but I am kind of shocked to be honest with you,” Achee said.
While Texas Brine plugged the cavern well, Ball confirmed no other monitoring of the cavern was required under the closure plan.
DNR records show that on Aug. 31, 1995, the agency authorized Texas Brine to dispose of 20 cubic feet of naturally occurring radioactive material by pumping it into the cavern and another Texas Brine salt cavern in Lafourche Parish. (Read letter.)
A Texas Brine letter dated Aug. 25, 1995, requesting the disposal says the radioactive “scale” had accumulated in soils around the two cavern wells. (Read letter.)
The radioactivity of scale, a common byproduct of oil and gas exploration and production, can vary widely from background levels to much higher, the U.S. Environmental Protection Agency says.
DEQ officials said Wednesday NORM materials can be harmful if ingested and confirmed they had not been testing the sinkhole for radioactivity.
Ball declined comment on the DNR correspondence without first reading it.