The public has a chance to learn about cleanup proposals at a former chemical plant in northern New Hampshire that was named a federal Superfund site in 2005. The Chlor-Alkali site is along the east bank of the Androscoggin River in Berlin. The plant had supported the production of paper in local mills. The Environmental Protection Agency says elemental mercury and other contaminants have migrated from the site and into the river, and continue to do so. An EPA investigation found sediment, fish and other organisms tainted with the same contaminants found in the soil at the site, and that exposure to the contaminants poses an unacceptable risk to human health. The public meeting is at 6:30 p.m. on Thursday, May 29, in the Berlin City Hall.