The Hartsville, Tennessee nuclear reactor site, the coal plant at Wheatland, Wyoming, and the nuclear plant at Skagit, Washington have mitigation plans developed in response to a federal, state, and local regulatory agency, respectively; the three mitigation plans aim at internalizing community-level social costs and benefits during the construction phase of large new energy supply facilities. Among the social costs included in the mitigation plans are public and private sector services such as schools, utilities, planning, public safety, transportation, housing, and community services at power generation construction sites. Viewed as new institutional responses to social impact mitigation planning, the plans have both variances and similarities in terms of origins, goals, scope, local participation, financing and costs, adequacy and significance. The plans are highly significant because of their pioneer status, their similarity of scope despite highly diverse regulatory environments, and their custom tailoring to local circumstances. Policies providing impetus for comprehensive assessment of the effects of public development projects, including the National Environmental Policy Act of 1969, court rulings, and various state laws, are presented. (Author/NEC)