In the latest step of a protracted legal battle between East Lyme's Water and Sewer Commission and the developer of a proposed housing development, an appellate court in Hartford has ruled that the commission must grant the developer more access to the town's sewer system than the commission wants to give it.

The town's lawyers plan to petition the state Supreme Court to appeal the Aug. 21 ruling, which affirms a state Superior Court judge's 2016 order that the commission must reconsider the amount of sewage capacity it is willing to grant for a proposed 840-unit residential development adjacent to the Oswegatchie Hills Nature Preserve along the Niantic River.

Over more than a decade, Landmark Development has sought to develop houses on the 236 acres it owns in the Oswegatchie Hills.

The plan has generated local opposition, which in recent years has taken the form of a coalition between Connecticut Fund for the Environment and two local groups arguing that the development would pollute the Niantic River and degrade wetlands on the property.

Landmark Development and its president, Glenn Russo, also have hit speedbumps before the town's Water and Sewer Commission, which regulates new connections to the pipes and pumps that bring sewage from East Lyme buildings through Waterford to a sewage treatment plant in New London.

A deal between East Lyme, Waterford and New London allows each town to send a certain amount of sewage to the New London sewage treatment plant — 15 percent of the plant's capacity, or about 1 million gallons a month in East Lyme's case — and limits the towns' ability to grant permission to build new sewer lines or allow new developments to connect to the existing ones.

In 2014, the Water and Sewer Commission denied Landmark's request for a guaranteed 118,000 gallons of sewage capacity per day for the development.

Landmark appealed that decision in New London Superior Court in 2014, kicking off the five-year ongoing debate in several courts over the commission's claims that the town's sewage system can't handle the amount of wastewater that a development the size of the Landmark proposal would generate.

The commission's members said that year that it could allow Landmark to generate only 14,434 gallons per day in sewage for the proposed houses, a fraction of the 118,000 gallons per day Landmark asked for in 2014.

Landmark's lawyers have argued that the commission granted the developer of a different housing complex in East Lyme, Gateway Commons, about 70,000 gallons of sewage capacity per day and told Gateway developers that the town had the capacity to handle about 100,000 additional gallons per day from the development. The commission's decision to grant that capacity to the Gateway development shows the town has "ample" sewage capacity for the Oswegatchie Hills proposal, they said.

Hartford Superior Court Judge Henry S. Cohn said in his 2016 ruling that 14,434 gallons per day is "excessively low" in light of the allocation to Gateway, and remanded the issue to the commission.

Town lawyers say the Gateway development's sewer capacity has no bearing on the Landmark case, because Gateway Commons is near one of the town's existing sewer lines and was relatively easy to connect to the system, whereas Landmark's proposal would require the construction of a new line.

The two development projects are "like apples and oranges," said East Lyme First Selectman Mark Nickerson, who is also the chairman of the Water and Sewer Commission as directed by the town's charter. "There's a difference between a connection and an extension," he said.

The appeals court dismissed that argument last month.

"Although the commission concluded that it did not have sufficient capacity to grant the plaintiff's application for up to 118,000 gallons per day, (Gateway) had effectively been granted an allocation of approximately 166,000 gallons per day," the court wrote in its ruling.

"At the end of the day that's not a valid argument," said Timothy Hollister, an attorney with the Hartford law firm Shipman & Goodman representing Landmark in the case. "The Water and Sewer Commission ... determined that the town as a whole has so much capacity that they can grant 166,000 gallons to Gateway ... but they have fought Landmark tooth and nail on every gallon of our request."

Nickerson said he is confident in the town's appeal.

The commission should have the ability to oversee management of its sewage systems without court interference, he said.

"The judges can't force us to put the sewer in there," he said.

He added that the extension of the sewer lines to the Oswegatchie Hills would constitute an unsuitable use of the town's increasingly limited capacity for adding new inputs to the sewer system and would eat up sewage capacity the town is saving for other neighborhoods where the houses still use septic systems.

The Department of Energy and Environmental Protection has put pressure on the town to expand sewer capacity to those neighborhoods to alleviate pressure on aging septic systems, which takes priority over development proposals like the Landmark plan, Nickerson said.

"If we had unlimited capacity and unlimited funds, we would give out all sorts of capacity," he said.

m.shanahan@theday.com