PROVIDENCE — The U.S. District Court has made a ruling to expedite a trial on charges by North Tiverton residents that a subsidiary of the utility giant Southern Union contaminated the soil on their properties.

In a decision this week, Senior Judge Ernest C. Torres separated a trial on the claims of about 120 residents from third-party complaints by the defendant, New England Gas, which contends that others should be held liable for the pollution.

In the 12-page ruling, Torres said that separate trials would “greatly simplify the issues, avoid confusion, expedite the proceedings and more efficiently resolve the case.”

Gail Corvello, a spokeswoman for the plaintiffs, said she believes Torres’ decision is “good news.

“It allows us to keep moving forward” toward a trial date in April, Corvello said.

In August 2002, construction workers installing a sewer line underneath Bay Street in North Tiverton encountered soil tinged a bright blue — a telltale sign of cyanide.

The state Department of Environmental Management has designated Southern Union the responsible party for the soil contamination.

DEM found that the contamination came from the burning of coal to manufacture gas at the former Fall River Gas Co., the predecessor of New England Gas, which in turn is owned by Southern Union.

Testing has determined that the soil contains not only elevated levels of cyanide but other contaminants, including arsenic, lead and benzo(a)pyrene, a probable carcinogen.

Southern Union has denied responsibility, both in the civil case pending in the court and in administrative proceedings now under way at DEM.

In November, two and a half years after the residents sued, Southern Union filed a third-party complaint which seeks indemnity from several other entities, including the municipalities of Fall River and Tiverton.

Torres said that if the separate trials were not held, the trial of the residents’ claims against New England Gas would be delayed while the recently notified third-party defendants request postponements to conduct discovery.

The trial date already has been delayed once, from this month until April.

Torres said the presence of “significant quantities of hazardous substances” in the soil on or near the residents’ properties is “undisputed.”

And a moratorium on disturbing the soil prevents the residents from excavating or building on the properties until the contamination is remediated.

In addition, he said, summarizing the allegations, residents say the contamination has diminished their property values and that continued exposure to the hazardous chemicals is adversely affecting the health of some of them.

Torres also noted that one of the plaintiff’s principal witnesses is an elderly man in poor health who may not be able to testify if the trial is postponed.

The witness, Jose Souza, would provide eyewitness testimony to the dumping of coal gasification wastes from the former Fall River Gas Co. in the Bay Street area of North Tiverton during the 1940s.

Even if the residents do not prevail at trial, Torres said in the decision, New England Gas would still have the opportunity to pursue damages from third parties.

Andrew M. Teitz, the Tiverton town solicitor, said the town participated in a conference to get the issue of the separation of trials before the judge.

He said the town looks on the decision “as a good thing.”

“It’s a victory in one of the minor skirmishes of this war,” he said.

The town has filed a counterclaim against Southern Union, essentially for contaminating the earth under town-owned streets, Teitz said.

He said that last month Southern Union scheduled two simultaneous depositions of plaintiff residents and representatives of other defendants every weekday for three weeks, concluding only four days before Christmas Day.

The depositions, which lasted all day, were either a “fishing expedition,” an attempt at intimidation, or both, Teitz said.

Southern Union’s lawyers asked residents questions like whether any automotive oil they might have used in an oil change on a car ever seeped into the ground, or what kind of stain they might have used to stain a deck on a house, Teitz said.

Besides Tiverton and the City of Fall River, Southern Union’s third-party complaint names as defendants Bridgestone Firestone North American Tire LLC; Bridgestone Americas Holdings Inc.; Honeywell International Inc.; Gulf Oil Corp.; Inland Fuel Terminals Inc.; Dominion Resources Inc.; and Dominion Energy Brayton Point LLC.

Efforts to reach a Southern Union spokesman were unsuccessful yesterday.

gmacris@projo.com