Rhode Island’s attorney general is supporting a court case that challenges the proposed Burrillville power plant.

Attorney General Peter Kilmartin filed an amicus brief, or letter of support, Aug. 3 saying the town of Johnston isn’t allowed to sell water it buys from Providence to the proposed Clear River Energy Center.

Kilmartin cited the state’s 1915 Act, which limits municipal water use from the Scituate Reservoir to “domestic, fire and other ordinary municipal water supply purposes” and therefore prohibits resale outside its boarders.

“The attorney general is keenly concerned, on behalf of current and future Rhode Islanders, with the legal protections providing for the sustainability of the Scituate Reservoir,” Kilmartin wrote in the court filing.

On Jan. 10, 2017, the Johnston Town Council voted to sell a portion of the water it buys from the Scituate Reservoir to the power plant for $18 million over 20 years. In March 2017, the town of Burrillville and the Conservation Law Foundation sued Johnston and the developer, Chicago-based Invenergy Thermal Development LLC, over the legitimacy of that water deal.

Water has been a contentious issue for the $1 billion Clear River Energy Center. When it first proposed the natural-gas/diesel project, Invenergy was counting on a water agreement with the Pascoag Utility District to cool the nearly 1,000-megawatt power plant. The Pascoag Utility District rejected a water plan that included using contaminated well water. The Harrisville Fire District in Burrillville and the city of Woonsocket also rejected selling water to Invenergy.

In 2016, the Energy Facility Siting Board suspended the application process for 90 days so that Invenergy could secure a water source. Invenergy also changed its proposed cooling system for the proposed fossil-fuel power plant to one that reduces daily cooling water use from 200,000 gallons to about 20,000.

Both Invenergy and the town of Johnston filed motions to dismiss the Superior Court case that were later rejected by Judge Michael A. Silverstein. Silverstein recently announced that he is retiring Sept. 30.

Invenergy and Johnston later filed a motion for summary judgement, meaning they are asking the judge to rule that the case has no merit. Oral arguments for the motion are scheduled for Aug. 20 at Superior Court in Providence.

Invenergy declined to comment on this development in the court case.

The Scituate Reservoir is owned and managed by the Providence Water Supply Board and provides water to 60 percent of Rhode Island’s population.