A group of shoreline government and industry organizations plan to file a joint brief in a federal lawsuit, supporting the Environmental Protection Agency's opening of a 1.3-square-mile area in Long Island Sound as a site for disposing of silt dredged from waterways near the Sound.

Electric Boat, the Connecticut Port Authority and Connecticut lawmakers already had spoken in support of the EPA's decision to allow dredge material deposits at the mouth of the Thames River, and have joined Connecticut's congressional leaders and Gov. Dannel P. Malloy in opposing a lawsuit New York filed to overturn that decision.

As sites used by the U.S. Army Corps of Engineers and private dredging companies have filled up with silt, the EPA researched and in 2016 designated three new sites in the Sound for disposing of dredged material, including an area between the Thames River and Fishers Island.

The new site was established over the objections of New York State, which has argued that introducing a new dredging disposal site there would harm the Sound's ecosystem, introduce contaminants into the food chain of animals like lobsters and would interfere with the flow of ferry traffic between New York and New England.

Last summer, New York filed a lawsuit in U.S. District Court seeking to overturn the EPA decision creating the new site on those grounds. The state has not objected to the creation of two other sites in the western and central parts of the Sound.

U.S. Rep. Joe Courtney, U.S. Sens. Richard Blumenthal and Chris Murphy, Malloy, state Attorney General George Jepsen and local business and government leaders have dismissed New York's concerns. They say that having access to a nearby dredging disposal site is crucial to keeping the waterways near the Sound free from sediment buildup that could impede submarine movement and shipping traffic.

Taking the dredged material to disposal sites farther away would be expensive for companies from Electric Boat to small marinas up and down the rivers off the Sound, Courtney and other local officials said at a news conference Thursday in Union Station.

"This city is just in the middle of a tremendous economic boon right now, and I can't think of a greater threat to what's going on here than New York's completely irresponsible lawsuit," New London Mayor Michael Passero said at the conference.

On April 2 an attorney representing the group, which includes the Connecticut Port Authority and Electric Boat, along with the Connecticut Marine Trades Association, Cross Sound Ferry Services and three regional councils of government, submitted a letter outlining its intent to submit a brief supporting the EPA and DEEP in the suit.

The attorney with law firm Robinson & Cole plans to file the brief once the judge in the case gives his approval and the defendants — the EPA and the state Department of Energy and Environmental protection — officially respond to the New York appeal before Oct. 31.

The group signing on to the proposed amicus brief includes four of the five regional councils of government that represent towns on the shoreline.

Jim Butler, the executive director of the Southeastern Council of Governments, which represents 22 towns, cities and boroughs in New London and Windham Counties, said Thursday that the council voted to join the industry representatives and the port authority in signing the amicus brief to show their support for the New London dredging site.

The fifth shoreline council of governments, which represents Bridgeport and five nearby towns, has not signed on to the brief because its director has not yet brought the issue up for a vote, Butler said.

A handful of New York communities already have filed to join the lawsuit in support of New York's appeal.

m.shanahan@theday.com