Feb. 5--PROVIDENCE -- North Tiverton residents are expected to ask a federal court tomorrow to enforce the terms of a tentative $12-million settlement with the Texas-based utility Southern Union for the cleanup of toxic soil in about 100 properties.

According to U.S. District Court records, Southern Union agreed last April to pay $9 million in damages and $3 million for the cleanup of cyanide, lead, arsenic and other contaminants -- as long as the town and the state Department of Environmental Management signed off on any claims against the utility.

But a dispute has developed over details of the tentative agreement.

Since blue-tinged soil contaminated with cyanide was discovered by sewer construction workers under Bay Street in August 2002, residents have been unable to sell, refinance or improve their properties or enjoy their yards, not even to plant flowers or vegetables. About 150 residents in the working-class Bay Street neighborhood filed suit four years ago.

The resident plaintiffs say the contingencies spelled out in the deal have now been met.

But Southern Union says the talks put into the court record April 22 were an "outline of settlement terms."

"The outline was not a settlement agreement, but rather a road map or plan requiring a four-party settlement" involving not only the plaintiffs and Southern Union, but the town and the DEM, according written arguments submitted recently to the court by lawyers for the utility.

Former Senior Judge Ernest C. Torres, who oversaw the case until recusing himself in December, has said that he believes the homeowners will probably get the order to enforce the settlement.

Since last April, homeowners have said, they've received bids for the cleanup that meet the $3-million ceiling set by Southern Union.

The plan satisfied everyone involved -- the residents, the town and the DEM -- that the remediation would make the properties safe, they said.

Contaminated soil, which covers about 50 acres, would be removed to a depth of two feet, and residents would accept deed restrictions requiring property owners to refrain from disturbing the earth still containing toxins.

The DEM has said the toxic wastes resulted from the burning of coal to manufacture gas decades ago at the former Fall River Gas Co., acquired by Southern Union in 2000.

Once the soil is cleaned up, the DEM would drop a separate administrative case against Southern Union, and the town would lift a moratorium on excavation in the area that has been in place since the wastes were discovered.