A sinkhole in a Louisiana bayou that caused four pipelines to be shut in this month expanded again on Thursday morning, swallowing more land as workers continue to assemble a rig to drill an exploratory well at the site.

According to Assumption Parish officials, about 50 feet of property along the southwest side of the sinkhole -- also known as a "slurry" -- fell into the hole at about 11 a.m. Thursday, while cleanup activities were taking place.

"Two cleanup workers in a boat, which was tied to a tree in that area, were rescued via airboat and shortly thereafter, their boat sunk into the sinkhole," the parish said. "All workers have been accounted for and no injuries have been reported. At the present time, cleanup operations at the site have been suspended."

The sinkhole first appeared in swampland on Aug. 3, devouring cypress trees and forcing the evacuation of homes in the areas of Bayou Corne and Grand Bayou, LA (see Daily GPI, Aug. 9). Assumption Parish Secretary-Treasurer Kim Torres told NGI on Thursday that 159 residences have been given orders to evacuate, and that 60% have complied.

The incident caused four pipelines -- owned by Florida Gas Transmission (FGT), Enterprise Products Partners LP's Acadian Gas Pipeline LLC and Crosstex Energy LP -- to be shut in and depressurized. It also prompted Chevron Corp.'s Bridgeline Holdings to declare a force majeure for its natural gas storage cavern near Napoleonville, LA (see Daily GPI, Aug. 7).

Workers with Texas Brine Co. LLC, which owns a brine cavern near the sinkhole, continued to assemble a rig Thursday about 950 feet away to drill an exploratory well. The Houston-based company and Torres both said 10 tractor trailers delivered components for the rig on Wednesday, and another 10 were expected on Thursday and four more on Friday.

"We are assuming that they will start drilling soon, maybe on Saturday," Torres said, adding that it could take Texas Brine about 40 days to drill the exploratory well. "They hope at the end to have some answers and more information."

The Associated Press reported Tuesday that regulators with the Louisiana Department of Environmental Quality (DEQ) have asked Crosstex to submit an updated risk management plan for its 940,000-barrel butane storage cavern by Wednesday. The facility is 1,600 feet from the sinkhole.

Jill McMillan, spokeswoman for Dallas-based Crosstex, could not be reached for comment Thursday.

DEQ spokesman Rodney Mallett told NGI that inspectors have visited the sinkhole twice to test for naturally occurring radioactive material, but "found nothing above background." He said "odors that people are getting are related to the hydrocarbons or the diesel that is on the hole. We're down there with our mobile air monitoring lab and are picking up low levels [of emissions] from time to time, but nothing that would be any kind of long-term health risk."

Torres added that the parish "has not been informed of any increase in seismic activity [near the sinkhole]. The only readings [scientists] are getting, that they have informed us about, are very small tremors that could just be with the work taking place in the area."

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