With questions lingering about the rising cost and need for a new atomic weapons plant in South Carolina, federal officials plan to meet next week with environmentalists who sued several years ago over the plant’s potential impacts on the landscape.

Officials with the Savannah River Site, a 310-square-mile nuclear weapons complex near Aiken, are to host a rare tour for environmentalists of the partially built plutonium pit plant Tuesday. They also are expected to answer questions about the project’s cost, future and pollution threat to the public.