The Louisiana Department of Environmental Quality (DEQ) on Tuesday expanded its investigation to determine the extent of natural gas contamination in area water wells.

More than 125 homes in Caddo Parish, LA, were evacuated Monday as a precaution after natural gas apparently leaked into an aquifer during a drilling test.

DEQ said gas apparently leaked into the Wilcox Aquifer during drilling operations by EXCO Resources Inc. Thirty-five of 45 private water wells sampled by DEQ Monday after the leak was detected tested positive for natural gas, a spokesman said.

On Tuesday DEQ said it now is examining water samples from a half mile from the drilling site to a five-mile radius around the EXCO well, which would include parts of DeSoto Parish.

“We have been testing the water and are not satisfied,” said Caddo Parish Sheriff Steve Prator. “We have not made any progress.” More residents may be asked to voluntarily evacuate the area depending on what more testing shows, Prator said.

According to EXCO, a crew was drilling early Monday on a “superpad” site where two other gas wells are sited at a depth of about 1,200 feet when it encountered “unexpected gas” from high gas pressure in the well. EXCO notified state officials, and a crew was able to relieve the high gas pressure.

DEQ said tests have not yet determined which drilling company may be responsible for the contaminated water wells. State officials tested the area water systems following EXCO’s report to emergency responders.

Officials are “erring on the side of caution” by informing residents that gas was found in several water wells, said Prator. He did not know how long it would take for the gas to dissipate from the wells.

EXCO offered to pay residents for temporary housing, food and other necessities if they decided to evacuate, the spokesman said. The company hoped to have the situation resolved by early Wednesday.

Last month Chesapeake Energy Corp. and its contractor, a subsidiary of Schlumberger Ltd., each agreed to pay the state $22,000 in fines for violating Louisiana’s environmental laws in connection with the deaths about a year ago of 17 cows at a natural gas well site in Caddo Parish.

DEQ said the settlement required the companies to advertise the agreement and invite public comment. In a joint statement Chesapeake and Schlumberger acknowledged entering into the agreement.

However, the companies in the agreement denied that any material discharged from the well site had killed the livestock, and they also denied that violations were committed. The fines, which they agreed to pay, carried a $1,300 penalty for each offense, DEQ said.

Last April area residents notified officials that cows were dying in a pasture owned by Cecil and Tyler Williams. The animals could be heard bellowing and were bleeding before they died, witnesses told authorities.

At the time, Schlumberger was performing a hydraulic fracture of a gas well on land that was leased by Chesapeake. DEQ determined following an investigation that fracturing fluid had leaked from a well pad and then flowed into an adjacent pasture after it had rained.

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