394 



PECK AND WARREN 



41 "20' 



72"10' 



INTAKE 



DISCHARGE 



CUT- 



1 2 3 

 _J I I 



Nautical miles 



2 4 



I \ I  I 



km 



72 10' 



Fig. 1 Map of study area, Long Island Sound, showing nuclear 

 power plant. 



MATERIALS AND METHODS 



Study Area 



The Millstone Nuclear Power Station, Unit I, located on 

 northeastern Long Island Sound (Fig. 1), entrains 9.5 x 10"^ m'Vhr 

 (3.2 X 10^ ftVhr) of seawater (salinity 28 to 30%o) for cooling 

 from Niantic Bay at a depth of ^3 m. The AT from intake to 

 discharge is 13°C when the plant is operating at a capacity of 650 

 MW(e). The water passes through the plant in about 2 min, is 

 discharged into an effluent pond, and then enters Long Island Sound 

 via a cut. 



The fjord-shaped effluent pond, which was formerly a granite 

 quarry, has a volume of 850,000 m^, a maximum depth of ^30 m, 

 and a minimum depth at the shallow sill, the cut where entrained 

 water enters Long Island Sound, of ~3 m. When the plant is 

 operating, water in the effluent pond is both isothermal and 

 isohaline. Mean residence time of water in the pond is 6 to 9 hr. 

 Measurements with a surface float show that surface flow from 

 discharge to cut through the effluent pond occurs in ~1.5 hr to a 

 depth of 1 m. The surface-to-volume ratio of the pond is small, and 



