A Connecticut judge on Thursday ordered state officials to go back to their deliberations in a long-running dispute with United Illuminating over the cleanup of one of the utility’s former power plants, English Station.

The ruling — which is almost certain to add further delays to the remediation effort — came just days after officials in New Haven announced ambitious plans to tear down the dilapidated plant and develop the site into a waterfront park complete with walking trails and a public pool.

“While this is not the only dispute that has interfered with the remediation of the English Station site, originally contemplated to have been completed years ago, the parties’ dispute over the applicable cleanup standard inside the buildings is a significant impediment to completing that project,” Superior Court Judge John B. Farley wrote in his decision.

United Illuminating operated the plant for more than a half century, burning coal and later oil to produce electricity for its customers, before the plant was finally powered down in 1992. During its run, the site became heavily contaminated with polychlorinated biphenyls, or PCBs, resulting in a complex and costly remediation effort.

Over the years, the plant fell into disrepair and was subject to vandalism and thefts of leftover metal. As part of a deal with regulators to approve UI’s merger with Spanish utility giant Iberdrola in 2015, the company agreed to spend $30 million to clean up the site.

That agreement, however, quickly became subject to a dispute over the standard to which the property should be cleared of contaminants and made ready for development.

The Connecticut Department of Energy and Environmental Protection, led by Commissioner Katie Dykes, argued that the consent decree signed by both parties required UI to remediate PCB levels in the plant building to below 1 part per million, which would allow for a wider range of future uses, such as housing, businesses or recreation. Utility officials balked, arguing that doing so would require the complete demolition of the building — something they had not agreed to do during negotiations over the agreement.

Last year, Dykes issued a ruling requiring UI to abide by the higher remediation standard. UI promptly sued, arguing that Dykes had overstepped her authority and misconstrued the language in the consent decree to suit the state’s desire for a more robust cleanup.

In his decision on Thursday, however, Judge Farley opted not to side with either party’s interpretation of the consent decree, which he said was ambiguous as to the required level of cleanup.

Instead, Farley remanded the case back to DEEP for further proceedings. At the same time, he found that Dykes had not abused her authority by issuing a declaratory ruling, thus allowing her to make further decisions regarding the consent decree.

In a statement Friday, United Illuminating spokesperson Sarah Wall Fliotsos said the company appreciated the decision to sustain their appeal and send the case back to DEEP.

“In this case, DEEP wrongfully changed the standard for clean-up that was agreed upon nearly a decade ago,” Fliotsos said. “It is clear DEEP was wrong to try to enforce a standard that was not part of the original agreement, and they are wrong to continue to blame UI for delays.”

“Ultimately, clean-up of this site cannot be achieved without clarity on the standard we are working towards,” she added. “As this issue is remanded for further proceedings, we hope to be able to work in good faith with state officials to chart a clear path forward for UI’s role in the future of English Station.”

DEEP officials referred comment to Attorney General William Tong’s office, which represented the agency in the lawsuit. Tong told the CT Mirror on Friday that his office is still reviewing the judge’s decision and its impact on the cleanup process.

“We’re gonna keep fighting,” Tong said. “UI owes whatever it takes to remediate English Station, and I’m never going to come off that position.”

A spokesman for New Haven Mayor Justin Elicker said Thursday that the ruling would not impact the city’s plans to move ahead with the proposed redevelopment of English Station.

“As the City advances its proposal for Mill River Park, it’s critical that UI stop dragging its feet and complete the remediation of English Station so that this land can finally be put to good public use, and we’re confident the Attorney General and CT DEEP will continue to hold UI accountable for its longstanding failure to clean up this site,” the spokesman, Lenny Speiller, said in a statement.

“We hope the City’s proposal and intended use of the site brings a new focus and urgency on what needs to be done to help make this vision a reality,” he added.

The city’s proposal is part of a larger plan to redevelop former industrial areas along the Mill River, which surrounds the small island on which the power plant sits.

In order to make the land safe for walking, playing and swimming, the site would have to be cleaned to the 1 ppm level being sought by DEEP, Speiller said. Even then, the city has estimated it will cost at least another $25 million to develop its park proposal.

“After bearing the costs of industrial pollution and blight from the English Station power plant for decades, our community deserves a true treasure in its place,” Elicker said in his announcement of the city’s plans on Monday. “By replacing it with a new waterfront public park and recreation area, we will transform this site into an amazing public asset that will benefit our residents, improve our environment and strengthen our community for generations to come.”

Beyond the initial cleanup, however, other hurdles exist that could complicate the city’s plans.

New Haven still has to acquire the English Station property, which has changed hands several times over the last two decades. On Monday, city officials sent letters to the current owners of the island expressing their desire to “negotiate a fair purchase price” for the property. If the owners do not respond, Speiller said, the city will consider using eminent domain to acquire the property.

The owners are a pair of limited liability corporations tied to three people — George Goldstein, Esther Schiller and David Tropper — with business addresses listed in Brooklyn, Queens and Israel.

When reached for comment earlier this week, Goldstein at first denied being one of the owners of English Station before saying he had received the city’s letter and was reviewing it. “I have to get back to you on that,” Goldstein said when asked if he was interested in selling the property.

Schiller and Tropper could not be reached for comment. Goldstein hung up after being reached for comment a second time on Friday.

Local advocates have also questioned the need to tear down the hulking, brick-clad structure of English Station, which many argue carries historic and aesthetic significance to the city.

Anstress Farwell, the president of the New Haven Urban Design League, said this week that she supported the city’s efforts to take control of the power plant property, though she called its plans to raze the remaining buildings “premature” until further studies can be done to determine whether they are salvageable.

“In all of my talks with the city, it’s been about ‘the building is an asset,'” Farwell said. “It’s 110,000 square feet that city officials have said that they could never rebuild on the site but could use if it could be renovated.”

Nor did Thursday’s ruling put an end to the state’s ongoing legal battle against UI over English Station.

Tong filed a separate lawsuit last year, accusing the utility of failing to uphold its agreement to spend $30 million on the remediation effort. In response, UI officials have argued that the company has already spent millions toward the remediation of the site, including removal of asbestos, but that its efforts have been hampered by the ongoing dispute with DEEP.

That case is also assigned to Judge Farley, who issued a separate ruling on Thursday dismissing four out of the five defenses that the utility had raised. That case is currently set for trial in October 2026.

Lastly, there is the case involving the Public Utilities Regulatory Authority’s decision in 2023 to begin fining United Illuminating $2 million a year over what regulators called a failure to abide by the utility’s agreement to remediate English Station. Earlier this year, a judge upheld the legality of that penalty — a decision that the utility is appealing.