Citing continuing risk from rising, flammable gas unleashed by the Bayou Corne sinkhole, the state Office of Conservation ruled Friday that remaining residents in the swampland community must continue to receive weekly $875 checks for evacuation assistance.

The order says the checks from Texas Brine Co. should continue until the mandatory evacuation order in place since Aug. 3, 2012, is lessened to a voluntary evacuation order.

Late last year, Assumption Parish emergency officials instituted a voluntary order in a small part of the evacuation area — in the nearby Grand Bayou community — but the mandatory order remains in effect elsewhere, including all of Bayou Corne. Two residences remain occupied in the Grand Bayou area, but a Texas Brine spokesman said those residents stopped receiving checks when the order went voluntary.

Texas Brine began making the weekly payments about two weeks after the sinkhole was discovered and has spent nearly $12 million so far.

The ruling, which affects about 13 residents and landowners in Bayou Corne still receiving checks, came after Texas Brine petitioned the Office of Conservation in early January to end the payments, arguing the risk from the 31-acre sinkhole had been abated.

Office of Conservation scientists believe years of salt dome mining by Texas Brine triggered formation of the sinkhole when that mining got too close to the outer face of the salt dome. A breach opened up in the hollow cavern created by years of past mining, and surrounding sediments filled the void.

The sinkhole’s formation also opened natural deposits of methane gas that pose an explosive risk, scientists claimed, if the invisible and odorless gas built up inside or under the homes.

Texas Brine officials said in a statement Friday they are extremely disappointed with the ruling.

“We are considering our options, including a possible appeal of the Committee’s decision,” said Bruce Martin, vice president of operations for Texas Brine.

Company officials pointed out that the residents seeking the weekly checks have not evacuated and have not participated in direct buyouts through the company or a federal class-action lawsuit. Some opted out of the class-action; some were excluded.

Sidney Marchand III, a Donaldsonville attorney who represents some remaining residents with their own lawsuit against Texas Brine, said the ruling is fair. He said his clients, though they remain in Bayou Corne and do not wish to be bought out, still face having to leave at any time.

“The gas is still being vented. There’s tremors from time to time, and the evacuation is still in effect. Nothing too much has changed, so why should they (Texas Brine officials) be able to stop the payments?” Marchand said.

He has also pointed out that Texas Brine continued paying checks to bought-out residents until they closed on the sale of their homes.

Parish officials have long said the mandatory order meant that residents who remained in Bayou Corne were doing so at their own risk should things go awry but not that the parish would force them to leave.

Before an Office of Conservation hearing committee Jan. 28, Texas Brine experts had claimed that the risk from the methane and the sinkhole itself no longer existed. Texas Brine has been burning off the gas with vent wells, though area bayous and swamps continue to bubble at a reduced rate. Company experts contended a layer of clay under the community effectively sealed the gas off and keeps it from the homes.

In a response released Friday, conservation experts acknowledged there is little risk the sinkhole would ever grow to reach the community or La. 70 but also argued that residents still face a risk from the gas. Those experts disputed that the clay was as effective of a barrier to the gas as Texas Brine claimed, noting gas bubble sites still are active within the community.

In tying the continued issuance of checks to the evacuation order, the Office of Conservation ruling also rejected a central contention of Texas Brine’s.

Company officials had argued that its original 1982 permit to drill controlled when the checks should stop, not the status of the parish evacuation order. The permit called for evacuation assistance “if the area of collapse appears to threaten any residents. …”

Company officials contended 30 months of scientific and technical data gathered by state and Texas Brine contractors confirmed that the homes are not threatened by the sinkhole, so payments are no longer justified.

“The mandatory evacuation, which has never been enforced, is not representative of current conditions on the ground in Bayou Corne,” the company’s statement adds.

But the Office of Conservation tied continuation of the checks to the evacuation order, saying the gas, a key reason the order remains in place, still could “create hazardous conditions that could potentially affect the residents and put them at significant risk.”

Follow David J. Mitchell on Twitter @NewsieDave.