and decreased in summer and early fall. The impingement of winter 

 flounder is potentially of lesser concern for impact because the sluiceway 

 return systems to be provided at Units 1 and 3 will significantly reduce 

 mortality. 



The primary means of assessing impact of Millstone to date has been 

 a deterministic model developed by the University of Rhode Island. It 

 has been judged as an acceptible but conservative means of estimating 

 impact but recent advances in modelling have made it less acceptable. A 

 stochastic matrix model has been accepted as the basis for future 

 evaluations which should provide more realistic estimates. The needs of 

 this model should direct much of the future research on the winter 

 flounder as it is the best means to integrate and reduce the large 

 amount of available data to predict changes as a consequence of longterm 

 plant operations. 



IMPINGEMENT 1972 - 1982 



The primary objective of impingement monitoring at Millstone has 

 been to quantify total annual, species specific, mortality. In addition, 

 means of minimizing this mortality have been evaluated experimentally 

 and appropriate plant design changes recommended where cost-effective. 

 Routine impingement sampling began at Unit 1 in 1972. Monitoring at 

 Unit 2 was initiated just prior to full-power testing in September 1975. 



Throughout the ten years of study, various program changes have 

 been implemented. The principle changes to the routine impingement 

 program were made in each of three areas, the frequency of counting, the 

 manner in which lengths were recorded, and' the method for calculating 

 monthly totals. 



