The 1930s-era buildings at Seaside State Park were designed in a grand style by Cass Gilbert, but years of neglect mean restoration could come with a hefty price tag. Photo courtesy of Connecticut DEEP | Justin Scalera photo

State environmental officials say they’ve been unable to find a private developer to transform a former 1930s-era tuberculosis sanatorium for children overlooking Long Island Sound into a lodge and spa.

The Department of Energy and Environmental Protection last year solicited proposals to redevelop four buildings at Seaside State Park in Waterford.

The agency announced Tuesday that neither of the two proposals it received met the criteria.

The aging structures are listed on the National Historic Registers of Historic Places. In return for renovating them, a developer would receive at least a 50-year lease to develop a lodge similar to ones found inside the Grand Canyon and Yosemite national parks.

Deputy Commissioner Susan Whalen says the agency remains committed to securing “the best possible future” for the state park. The park will remain open to the public for passive uses but the buildings will continue to be off-limits to the public.