An Assumption Parish official said Sunday the deepest part of the 22-acre sinkhole near the Bayou Corne Community is at least 500 feet deep, and not between 110 to 220 feet deep that has been estimated by Texas Brine.
John Boudreaux, director of the Assumption Parish Office of Homeland Security and Emergency Preparedness, said previous depth reports released by Texas Brine Co., the company may have been inaccurate because the company’s sonar did not penetrate debris fields inside the sinkhole.
The swampland hole emerged last August after a Texas Brine salt dome cavern failed deep underground. That failure forced the evacuation of 350 residents for almost a year.
Texas Brine spokesman Sonny Cranch said Sunday he is confident the company’s depth findings are correct. A Texas Brine contractor has said the sinkhole is from 110 feet to 220 feet deep, according to previous monthly depth-finding surveys.
The most recent sonar test on June 7 found the depth of the sinkhole to be 140 feet deep.
Boudreaux likened the bottom of the sinkhole to a swimming pool with the deepest part located in the middle.
Boudreaux said he did not use a sophisticated method like sonar to measure the sinkhole. Instead, he said, he took a 10-pound crowbar with the ends cut off and attached it to a 500-foot surveyor’s tape measure, drove out to the center of the sinkhole in an amphibious vehicle and let the crowbar go, unspooling the tape measure until it could not go any further.
“It’s the simplest of the simple,” Boudreaux said of the device.
He performs these checks periodically to confirm the numbers Texas Brine is finding using sonar testing.
Boudreaux said he took six other measurements and found the floor in other areas to be between 125 and 180 feet before he found what he described as an “upside-down witches hat,” a deep cone with a pointed end.
He said there is debris, including trees, in the sinkhole and the sonar Texas Brine is using is bouncing off the debris, leading officials to find a false bottom.
“I made it through the debris and it continues to go down,” Boudreaux said of his measuring device.
He said he bounced the crowbar about two or three times — which he does to determine whether he has hit the bottom — before the device broke through and continued to fall.
Boudreaux said he thinks he ran out of tape before the crowbar hit the bottom of the sinkhole, so he is trying to find a 750-foot tape measure this week to see if he hits the bottom with it.
Accurately finding the true depth of the sinkhole is significant, Boudreaux said, because scientists can use that to try to determine the actual size of the sinkhole.
He also said if the sinkhole is bigger than previously estimated, then it may affect other areas such as fishing spots south of the sinkhole.
Cranch said he is confident in Texas Brine’s numbers and said surveyors have found holes in the past that he believes are similar to what Boudreaux found.
Cranch said surveyors found cone-shaped holes in October and December that extended far deeper than recorded depths of the sinkhole’s floor.
Those holes were 410-feet and 440-feet deep, respectively, data provided by Cranch shows.
But surveyors were not able to find those cones again and those numbers are considered outliers.
Consistantly, Texas Brine’s sonar contractor has determined the depth is approximately 160 feet deep, according to data the company has collected.
Cranch stressed that the depths change because the sediment in the sinkhole is constantly shifting and changing.
“He may find it again, he may not,” Cranch said.