New London — The Coast Guard, in seeking public comment on a review of the environmental impacts related to building the National Coast Guard Museum on the downtown waterfront, has released the museum's newest design.

The review, officially known as a supplemental environmental assessment, is required under the National Environmental Policy Act and outlines the environmental impacts of proposed construction. It also details the need for the acquisition of an additional 14,200 square feet of land, much of which is submerged land beneath the City Pier platform and along the Thames River adjacent to the proposed site of the museum.

A draft version of the assessment will be available for comment for 30 days beginning Aug. 1. After the public comment period, the Coast Guard will determine whether there is a finding of no significant impact, meaning the project can proceed, or will identify outstanding issues that need to be addressed.

The proposed site of the estimated $100 million museum is adjacent to Union Station on one-third of an acre of land that the city donated to the Coast Guard in 2014. The site is in a 100-year flood zone, which complicates the design and construction process.

Site testing began in mid-July and is expected to last about a month. The museum association recently hired two Connecticut based firms for pre-construction work.

An updated cost estimate for the project isn't expected until the design is finalized, with construction tentatively scheduled to begin in 2021. But that is subject to change. So far, $37.1 million has been raised by the National Coast Guard Museum Association, including $5 million from the federal government and $20 million from the state.

Environmental assessments were performed in 2002, 2008 and 2014, which concluded in a finding of no significant impact. It was after the 2014 assessment that the land adjacent to Union Station was transferred from the City of New London to the Coast Guard.

The latest assessment includes the newest design of the museum. Changes were made to address feedback from government agencies, such as the Federal Emergency Management Agency and the state Historic Preservation Office, and public comment solicited as part of the environmental assessment.

The first architectural designs unveiled in December 2016 envisioned a four-story building perched high on the waterfront with a glass facade facing the Thames River. The museum is being designed by Boston-based architecture firm Payette.

The new designs show a much more opaque structure on the waterfront side, with long metal panels, which resemble sails, breaking up the glass to help prevent bird strikes and to address concerns from the Coast Guard about upkeep.

The museum, originally oriented to the east, now looks toward the city with a south-facing main entrance that opens to City Pier Plaza. A Coast Guard rescue helicopter hangs from the ceiling inside, in view from the plaza, which museum organizers say provides an iconic image that people associate with the Coast Guard.

The museum is being designed for prekindergarten through adult audiences with a Science Technology Engineering and Math, or STEM, Discovery Center, multiple exhibit floors and gathering spaces.