The Use of Long-Term Databases in Evaluating Impingement and Entrainment Impacts at Nextera Energy Seabrook (NH) Nuclear Power Station

Seabrook Station, a 1,246 MWe net nuclear power plant located on the New Hampshire coast, became operational in 1990.  Preoperational studies to describe baseline conditions began as early as 1969 for some parameters and provide a unique long-term database necessary for Before-After-Control-Impact comparisons.  The power of statistical tests improved with the addition of each year, making ‘impact’ detection for some parameters more likely.  A long-term database can capture unusual, yet valid, data in the baseline period that has yet to occur in the operational period.  Long-term declines in groundfish abundance can appear to be significant impacts due to plant operation. Annual time series of winter flounder abundance included historically high levels in the preoperational period that have not occurred in the operational period due to overfishing.  Adult equivalency modeling indicated minimal impacts to fish populations.  A long-term database also documents natural variability and lends itself to scientific-based monitoring program iterations. Potential impacts to Jonah and Rock crabs became non-significant as natural variability was better described.  High impingement events appeared to occur during strong northeast storms.  There was no relationship between entrainment of softshell clam larvae and abundance of mature clams.