Two companies have announced plans to decontaminate English Station, a non-operational power plant on an island in the nearby Mill River about a mile and a half east of Yale’s campus.

The United Illuminating Company and Iberdrola SA will have three years to rid the polluted power station complex of asbestos, other dangerous chemicals and heavy metals. English Station has long been an site of contention, with state and local government officials, along with three separate companies, advocating but unwilling to pay for the plant’s remediation. The power plant has continued to decay and pollute the nearby area for the last 15 years, and Connecticut Department of Energy and Environmental Protection analysts have argued that the plant is a threat to public health.

Originally built in 1929 by United Illuminating, English Station was shut down in 1992 because of financial issues. United Illuminating then paid Quinnipiac Energy $4.25 million in 2000 to assume ownership of the property. By selling the plant, United Illuminating strove to shed itself of the costly responsibility of decontaminating equipment and dismantling English Station.

Quinnipiac Energy originally hoped to fix and reopen the plant to provide additional energy support during periods of high energy demand in the area. However, the energy company failed to secure the environmental permits necessary to do so and sold English Station in December 2006 to two companies — ASNAT and Evergreen Power. These two companies’ plans to salvage scrap metal from the plant stalled in December 2012, when state Attorney General George Jepsen and DEEP filed an administrative order holding that ASNAT and Evergreen were obligated to first decontaminate the site before proceeding.

ASNAT and Evergreen eventually appealed the administrative order, claiming that United Illuminating, as the plant’s original owner, should take fiscal responsibility for the decontamination process.

Negotiations on English Station finally moved forward when United Illuminating applied to the Public Utilities Regulatory Authority — a state body charged with regulating the rates and services of Connecticut’s investor owned electricity, natural gas, water and telecommunication companies  — for permission to merge with Iberdrola SA. When the regulatory authority indicated that it would not approve the merger because it “failed to meet the burden of proof that [it] as presently structured, is in the public’s interest,” United Illuminating redrafted and resubmitted the application so that it included the deal to decontaminate English Station. The clean-up is contingent upon the regulatory authority approving the merger.

Keith Ainsworth, an attorney who represents both ASNAT and Evergreen, said his clients were disappointed that a deal had been struck without their input.

“Overall, though, we’re feeling a lot better about the situation because this breaks 15 years of paralysis,” Ainsworth added.

One area of disagreement between the companies is United Illuminating’s decision to only remediate English Station to commercial-industrial standards — the least thorough standards of decontamination. Ainsworth said ASNAT and Evergreen feel as if a more thorough clean-up would be appropriate given that there are many potential uses for the property.

ASNAT and Evergreen have reached out to DEEP and New Haven city officials to talk about potentially developing the land. The companies are considering converting the decontaminated plant into either a source of renewable (wind or solar) energy or into a combination of residential and commercial property.

In a statement released last week, Mayor Toni Harp also expressed support for the agreement.

“State regulators … have said all along, that UI is responsible for remediation and restoration of the property to productivity,” she said.