3-99 



(2327 m^) (1.5 — ) {^=r^ — ) = 8.7 m"^ (11.6 yd"^) 

 mo 4 wks 



The rate at which the sediment could be scoured out (and the 

 resultant turbidity) cannot be easily determined. 



Analysis of measurements of water transparency (or depth of 

 visibility readings from Secchi disc measurements) and turbidity show no 

 distinct patterns relative to plant operations. 



Sumrnary of Impacts 



In summary, the impacts of New Haven Harbor Station opera- 

 tions appear to be slight. Minor alterations of local current patterns, 

 creation of 8-cm waves, and small, localized increases in turbidity near 

 the discharge during start-up after prolonged down-time probably occur, 

 though none of these have been measured. Dissolved oxygen concentra- 

 tions could be reduced slightly (<17%) when saturation is near or 

 greater than 100% — in effect, when minor alteration of DO is ecolo- 

 gically unimportant. Monitoring programs have detected no change in DO 

 concentrations attributable to New Haven Harbor Station operations . 



The only impact quantitatively measured was the establishment 

 of a thermal plume which: 1) is detectable (At > 1°F) over a maximum of 

 42% of the inner harbor surface, 2) creates a small "boil" where surface 

 temperatures may be elevated by as much as 4 F over ambient, 3) occa- 

 sionally covers the complete cross-sectional area of the navigation 

 channel with water 1-2 F warmer than ambient. 



The New Haven Harbor Station discharge may raise average 

 temperatures in the inner and outer harbors by less than 0.8 F and 0.5 F, 

 respectively. This increase is less than that induced by annual clima- 

 tological variation. 



