Mystic — The Stonington Planning and Zoning Commission delayed a decision Tuesday night on Mystic Aquarium’s new $3.5 million conservation, education and research center on the eastern portion of its Coogan Boulevard campus.

Commission members said they wanted to more closely review drainage and other details of the plan.

Town Engineer Scot Deledda had raised a long list of concerns about the drainage, most of which the aquarium had addressed just before Tuesday’s public hearing.

Commissioners Lynn Conway, Curtis Lynch and Frances Hoffman also said they wanted more information about wetlands, erosion and traffic and wanted to see a three-dimensional or computer model of the building to see how it fits into the overall campus.

The commission continued the hearing for two weeks.

During the public hearing, Selectman Mike Spellman and Lisa Konicki, the executive director of the Ocean Community Chamber of Commerce, urged the commission to approve the special use permit needed for the project.

Spellman called the aquarium “a class operation” and told the commission the town was blessed to have the facility in the community.

Konicki called the aquarium a wonderful facility that continues to look to the future and make investments in not only the campus but the visitor experience. She called the aquarium a tremendous asset to the region’s tourist economy.

The two-story, 18,000-square-foot facility would be called the Milne Center for Ocean Science and Conservation.

Plans are to break ground for the facility in 2018, once fundraising is completed. The project is a revision of an earlier plan for an updated research facility at the aquarium.

The building, which will have a public exhibits and a viewing areas, would be connected to the existing Aquatic Animal Study Center.

Plans call for first floor to have a large area for animal holding, where newly arrived animals would acclimate before being moved into exhibits. It also would include a conference room and lobby.

The second floor would include a mezzanine that overlooks the animal holding area, three classrooms, office space and bathrooms.

David Holmes, the project architect, told the commission the building will fit the campus well and be an interesting piece of architecture.

The Milne center is one of the initial phases of what Mystic Aquarium officials envision as a $25 million to $50 million update of the institution and its exhibits over the next decade.

j.wojtas@theday.com