11-106 



Impingement 



Aside from other intake features designed to minimize finfish 

 impingement including low intake velocity (see Section 1) , to discourage 

 demersal fish from entering the intake structure, a "fish lip" was incor- 

 porated into the design. This "lip" rises six feet above the bottom of 

 the intake channel, which in turn extends approximately 900 feet from 

 the eastern edge of the main ship channel to the intake site (Introduction 

 Section 1.0) . Diver observations in June 1975 indicated no buildup of 

 sediment on the intake channel bottom prior to the plant beginning 

 operation; thus, it appears that at least in the initial period of 

 operation the lip structure functioned as designed, although its effect 

 on impingement is unknown. 



Since New Haven Harbor Station began operation in July 1975, 

 there have been 91 weekly, 24-hr surveys of fish impinged on the traveling 

 screens (Table 11-4) . From these data it is possible to estimate the 

 approximate average impingement rate on a daily and annual basis, as 

 shown in Table 11-5. One resident species, winter flounder, and one 

 summer migrant, menhaden, were impinged in relatively large numbers at 

 the New Haven Harbor Station intake. Five other species, windowpane, 

 bay anchovy, blueback herring, weakfish and summer flounder, were 

 impinged in lesser numbers (Table 11-5) . Thirty-one additional species 

 were also impinged, but were either uncommon or not included among the 

 representative species chosen for detailed analysis. 



It is evident from Table 11-5 that one species, the winter 

 flounder, stands out as having incurred losses large enough to be con- 

 sidered potentially important. Both winters of the plant operation 

 (1975-1976) witnessed equally high numbers of winter flounder impinged 

 (Figure 11-5) ; it is inferred from this that the fish lip is not effect- 

 ive in eliminating winter flounder impingement. We believe that, 

 although impingement mortality of approximately 27,000 juvenile winter 

 floiinder per year is high compared to other Long Island Sound generating 

 stations, this number is not important compared to the natural and 

 fishing mortality of the species. Using published values for survival. 



