New London — The National Coast Guard Museum Association and the project's lead architect on Monday unveiled proposed architectural designs that envision a four-story building perched high on the New London waterfront.

The public unveiling at the Garde Arts Center, which several officials called a milestone in the development of the estimated $100 million museum, was cohosted by the Chamber of Commerce of Eastern Connecticut and the Southeastern Connecticut Cultural Coalition.

Charles Klee, principal at Boston-based architecture firm Payette, and members of the museum association stressed that the concept is in its infancy, and that a forthcoming environmental review, which will include public hearings to solicit comment, will ultimately determine the final design of the museum.

"These are design concepts that are likely to change dramatically over the course of the next year, year-and-half, two years as we design this building," Klee said.

Those who spoke Monday seemed set on using the event as evidence that the museum project is moving along. Some members of the public have raised concerns about the site given its location in a flood plain and lack of parking in the area, and have said Fort Trumbull would be a more viable option.

Museum association CEO Dick Grahn pointed to a collaboration among stakeholders "that really has fostered a feeling that this thing is going to get done."

New London is "working very hard to help you fulfill this dream," Mayor Michael Passero said. Monday's audience of about 100, was full of people investing in the city and rebuilding its economic base, Passero said.

The proposed site of the museum— adjacent to Union Station on one-third of an acre of land that the city donated to the Coast Guard in 2014 — is in a 100-year flood zone, so labeled because it has a 1 percent chance of flooding in a given year. It's predominantly located in a "velocity hazard" zone, the most hazardous of the federally designated Special Flood Hazard Areas because it could be impacted by waves during a storm.

Grahn said the museum association is working to satisfy the requirements of a 500-year flood zone given the sensitive nature and national importance of the artifacts expected to be on display in the museum.

Klee and the museum association have spent months working through environmental concerns and regulations with the Federal Emergency Management, the state Department of Energy and Environmental Protection, and the Army Corps of Engineers.

Those involved in developing the museum had hoped to build it over water, but that didn't comply with environmental regulations, so it will have to be built over land.

The main entryway to the museum will be at least 13 feet above City Pier Plaza to comply with flood plain regulations. The state has committed up to $20 million for a pedestrian bridge to provide access to the museum. The plan is for the bridge to connect from Water Street, in the vicinity of the Greyhound Bus Terminal, to the entryway plaza of the museum. If funding allows, the bridge will be extended to Water Street Garage.

The designs shown Monday propose a 70,000- to 80,000-square-foot building built on stilts that Klee said would engage the waterfront and not take away from the Henry Hobson Richardson-designed Union Station, which is on the National Register of Historic Places. The chairman of the museum association's board, Jimmy Coleman, a resident of New Orleans who was in attendance Monday, purchased the train station for $3 million in early 2015.

The roof of the building could serve as an event space and could host a stationary helicopter.

On the waterfront side, the building would have a glass facade that would allow visitors to engage with activity on the water through interactive exhibits such as a bridge simulator or a way to listen to radio traffic as ferry captains navigate in and out of slips, Klee said.

The Coast Guard barque Eagle would be moored at the pier, and there's also talk of a band shell being built on the side of the building for the Coast Guard Band.

The plan has received the approval of Coast Guard Commandant Adm. Paul Zukunft. On Friday, Rear Adm. Jack Vogt, who previously served as assistant superintendent of the Coast Guard Academy, briefed Zukunft who gave the proposals a "huge two thumbs up," he said. Vogt is now the director of governmental and public affairs for the Coast Guard, and is the lead for the Coast Guard Advisory Council for the museum project.

G. Roger Clements, a local architect who lives in New London, said he liked the concepts presented Monday, but there's still a ways to go. Clements said he went back and forth between Fort Trumbull and the downtown waterfront site, as his preferred site for the museum, but ultimately thinks the waterfront site is best given its proximity to the railroad and its closeness to the water.

Museum organizers still face a large fundraising goal. So far, they've raised $9 million in private donations towards their estimated $100 million goal. They anticipate securing $13 million in private donations in 2017, and have "approached" various individuals and corporations for $19 million.

It was announced Monday that Stonington First Selectman Rob Simmons and Mohegan Tribal Chairman Kevin Brown will co-chair a regional fundraising campaign to raise $2.5 million by summer 2018. The $700,000 in local donations already received will go toward that goal. Additionally, museum organizers are hoping for $30 million from the federal government.

U.S. Sens. Richard Blumenthal, D-Conn., and Chris Murphy, D-Conn., and U.S. Rep. Joe Courtney, D-2nd District, all who were present Monday, worked to change federal law so that the federal government can now contribute funding to the interior aspects of the museum such as displays and exhibits. Funding is still prohibited for the bricks-and-mortar aspects of the museum.

That was the first step, Murphy said adding that "We are on the precipice of the second step, which is to commit for the first-time federal funding."

j.bergman@theday.com