Impact Assessment, Inc. was contracted by the Commonwealth of Massachusetts to assess the adequacy of the proposed Seabrook Nuclear Reactor emergency response plans for evacuation of communities following a potential nuclear accident at the plant, and to identify and recruit appropriate expert witnesses for litigation in opposition to the NRC issuance of an operating permit. The reactor had been constructed without appropriate initial approvals and was now at the point where an operational permit was required. NRC approval of the operating permit required the applicant (Public Service Company of New Hampshire ("PSNH") owner – Seabrook Nuclear Power Station) to submit emergency response plans prepared by state and local governments whose jurisdictions lie within designated emergency planning zones ("EPZs") surrounding the plant. An applicant for a nuclear plant operating license must provide detailed plans for competently responding to radiological emergencies on the plant site and for ensuring offsite emergency preparedness. The NRC cannot authorize an operating license unless it finds "reasonable assurance that adequate protective measures can and will be taken in the event of a radiological emergency."

The full power licensing issues before the court principally involved the Licensing Board's approval of Seabrook's offsite emergency plans. The New Hampshire Radiological Emergency Response Plan Revision 2 ("NH Plan") is a state plan covering the New Hampshire communities within the plume exposure pathway EPZ. The Seabrook Plan for Massachusetts Communities ("Utilities Plan") was the plan developed by PSNH and the other owner-utilities pursuant to 10 C.F.R. Sec. 50.47(c) after Massachusetts and the Massachusetts communities within the EPZ declined to participate in emergency planning.

The heart of the “Commonwealth of Massachusetts v. United States Nuclear Regulatory” emergency response claim was delivered by the IAI expert witnesses at trial. Research conducted results were delivered in testimony arguing that neither the state (New Hampshire) nor existing utility (Seabrook) emergency plans met existing NRC, local government, or state requirements. Testimony was prepared and delivered to the Commission contending that: (1) the proponent’s generic emergency preparedness guidelines were developed on the basis of inadequate dose-distance assessments performed for an inappropriate range of accident scenarios; (2) the predicted level of protection the New Hampshire Plan was wholly inadequate to protect peak summertime beach population in terms of the potential radiation doses, since evacuation routes would have failed; (3) inadequate consideration was given to actual likelihood and characteristics of a catastrophic atmospheric release of radiation at Seabrook; and (4) inadequate consideration of the actual health consequences (dose consequences) of site-specific radiation exposures at those levels.

Issues on remand centered on the adequacy of evacuation plans for school personnel involved in evacuating schoolchildren; the adequacy of periodic identification of persons with special transportation needs; the accuracy of evacuation time assumptions for advanced life support patients in hospitals, nursing homes, and other special facilities; and the need for further implementing details in the plan for emergencies in which sheltering would be the preferred protective action for the beach population.

The U.S. Court of Appeals rendered its final decision in 1991. The conclusions of the court were rendered essentially moot the following year when the NRC removed the language requiring community emergency response planning requirements.