New London — Advocates of the Environmental Protection Agency’s proposal to approve a site in eastern Long Island Sound for silt, sand, rocks and mud dredged out of channels and harbors are joining forces to counter plans by New York Gov. Andrew M. Cuomo to sue the federal agency to stop open-water disposal.

Rep. Joe Courtney, D-2nd District, is among lawmakers planning to attend a news conference at 11 a.m. Wednesday at City Pier to demonstrate wide support for the EPA’s plan, announced earlier this summer.

“This is not to turn this into a Connecticut-versus-New York issue, because that’s a dead end,” Courtney said Friday. “It’s to show there’s been a lot of dialogue on this plan with a coalition of stakeholders.”

Gov. Dannel P. Malloy is expected to attend the news conference, along with representatives of marine trades, the Navy, Electric Boat and the state Department of Energy and Environmental Protection.

On July 30, Cuomo’s chief legal counsel, Alphonso David, told Newsday that the New York governor would sue the EPA if it finalized its proposal to approve a 1.5-square-mile site between the mouth of the Thames River and the southwestern end of Fishers Island for disposal of dredge material from the eastern Sound.

The area is adjacent to the current disposal site, which will close along with a site off Cornfield Shoals near Old Saybrook on Dec. 23, when their permits expire.

Officials at the New York Department of State, which governs coastal issues, did not respond Friday to a request for comment or for a written statement on the issue.

In a July 18 letter to the EPA, however, the Department of State said it “is fully supportive of dredging for maintaining” water-dependent uses and navigation infrastructure, and is “committed to working with all partners to secure a path forward for achievable, measureable reductions in open water disposal over time.”

The agency said that while it did not support the EPA’s chosen site, which is in Connecticut waters but near the boundary between the two states, it would support designating a site in Niantic Bay as the long-term disposal site.

It also took issue with the EPA’s analysis of the amount of dredge material that would need to be disposed of in open water areas over the next 30 years, and argued that two existing open sites in the central and western Sound have sufficient capacity for this material.

The agency also advocated for greater use of methods to expand on-land disposal, and faulted the EPA for its analysis of the effects of the new dredge site on sensitive habitats near Fishers Island.

Using the Niantic Bay site, it stated, “would reduce vessel use conflicts ... since this location is not on top of vessel traffic lanes ... and is farthest from the two most dynamic areas in the vicinity, Plum Gut and The Race.”

Courtney said New York’s objections are being raised late in the process, which began five years ago.

“I’m disappointed that at the 11th hour, they’re taking this position,” he said. “I really think the EPA and the Army Corps of Engineers have done a painstaking job of balancing the various interests.”

He noted that the EPA’s proposal includes creation of a stakeholder panel that would review and consult with the Army Corps before any permits are issued for individual projects.

Sediment also must be tested before disposal permits are issued.

Contaminated material cannot be deposited in open-water sites.

“To have a blanket opposition to the eastern Connecticut site is disruptive,” Courtney said. “It just adds to the cost and it doesn’t eliminate open water disposal” if the material is just taken to the western or central Sound sites instead.

William Spicer, owner of Spicer’s Marina in Noank and who was active in the EPA’s process, said transporting dredge material to the other sites would make the cost prohibitive for marinas such as his.

New York state, he said, is “taking advantage” of Connecticut’s smaller size and greater need for dredging because of its location on the north side of the Sound.

“This proposal has been very thoroughly vetted,” he said. Both he and Courtney said analysis of the Niantic Bay site showed it is too small and not suitable for long-term disposal.

Brian Thompson, director of DEEP’s Office of Long Island Sound Programs, said there are at least eight marinas in Eastern Connecticut with pending dredging projects that would face higher disposal costs if they were forced to transport material to the central or western Sound sites.

Emily Bender, spokeswoman for the EPA, said the agency is reviewing comments on its proposal and plans to take action to either finalize the designation or modify the proposal by early October.

She noted that the proposal includes restrictions that “support the goal of reducing or eliminating open water disposal in the Sound, and to promote the beneficial re-use of dredged material, such as using sand for beach nourishment.”

“The agency is confident that its proposal to designate an open-water disposal site strikes an appropriate balance between the need for dredging to maintain safe and efficient navigation, and the mandate to restore and protect Long Island Sound,” she said.

j.benson@theday.com