A Weyerhaeuser Co. cleanup plan for land around an old munitions plant is under fire from historians, environmentalists and local officials. The area surrounds the locations of the Fort Nisqually, built in 1833; an early Methodist mission, early 19th century settlements and possibly burial sites for the Nisqually Tribe or other aboriginal peoples. The plan covers an area around the old DuPont Works, where E.I. du Pont de Nemours & Co. manufactured explosives from 1906 until the timber company bought the land near Fort Lewis in the 1970s. The site is now part of Northwest Landing, a 3,000-acre planned community. Lead and arsenic have been found in the soil, mostly where buildings once stood or near old rail lines. Pat Steel, a member of the Nisqually Point Defense Fund, and others want the right to perform so-called salvage archaeology while cleanup is under way. Some also want more than one archaeologist to monitor the site.