The U.S. Fish and Wildlife Service is seeking to build a low sea wall off Lido Beach in an effort to slow waves and preserve salt marshes and wildlife habitats in Reynolds Channel.

The construction, known as a “sill,” will involve building three separate rock footings about 3 1⁄2 feet tall about 25 feet from shoreline, officials said. They will be backfilled with sand and gravel underwater to slow crashing waves on the marshes and shoreline. The sills are to be separate from each other so as to not block wildlife and fish from passing through.

Fish and Wildlife officials submitted an application to the New York Department of Environmental Conservation this month for the Lido Beach Wildlife Management Area, north of Lido Boulevard and adjacent to Lido Golf Club in Lido Beach.

The proposal includes building the sea walls with clean sand and salt-tolerant vegetation. They will be connected to foot-deep channels connected to the marshes and allow the areas to drain, according to the Fish and Wildlife application.

Project officials said the renewed salt marshes should also reduce flooding near homes in the Lido Beach bay area during tidal surges.

The rock sills will stabilize the marshes and “hold the living shoreline together,” said Michelle Potter, the agency’s project leader for its Long Island Wildlife Refuge Project. The Lido Beach restoration is part of an $11 million superstorm Sandy recovery project that also includes salt marsh restoration off Heckscher State Park in Islip and in the Wertheim National Wildlife Refuge in Brookhaven.

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“When a marsh is functioning in a healthy manner, it can absorb a lot of water in the tide cycles and that is a natural occurrence that should be happening,” Potter said.

The sills are designed to keep the rocks and sand from getting ripped away by strong currents, Potter said.

Potter said the salt marshes have become battered over time by wind-fueled currents and boat traffic whipping up waves that uproot plants in the salt marshes. The marshes are created by decomposed plants and held together by the roots of underwater plants.

She said the salt marshes offer a large habitat for birds nesting in the channel. Migrating birds also use the marshes to rest.

“Salt marshes are critical for water quality and habitat purpose,” Potter said. “That particular site [in Reynolds Channel] is adjacent to a lot of contiguous salt marsh in the Long Beach area and provides a good amount of storm water protection from flooding.”

Fish and Wildlife Service officials said they hope to have a state permit issued in the next few weeks. The rocks will be visible during low tide, but be under water at high tide, Potter said.

The project is not expected to disrupt any activity for boaters, golfers at the Lido club or residents, Potter said. The project is expected to last at least 15 years, Potter said. Residents may see a barge working on the salt marshes for about four to six weeks, with one marsh buggy off the coast to build the rock footings, Potter said.