Twotree Island Channel, 0.2 mi (0.3 km) south 

 of Bartlett Reef, and Niantic River railroad bridge. 

 Continuous measurements were made for approx- 

 imately four days. Measurements in Twotree Is- 

 land Channel and Bartlett Reef consisted of cur- 

 rent speed and direction measurements at three 

 different depths. 



A study of the diffusion patterns of the circu- 

 lating water discharge effluent was made by 

 Bechtel Corporation (1966). The objective of 

 this study was to determine the flow and diffusion 

 patterns of the condenser discharge with the aid 

 of a small scale hydraulic model. The hydraulic 

 characteristics of the model were correlated with 

 local field data furnished by the Essex Marine 

 laboratory and the U.S. Coast and Geodetic Sur- 

 vey. The model study used tracers to indicate 

 the general flow patterns of the tidal current in 

 the vicinity of Millstone Point. Although the 

 variations of the water temperature in the effluent 

 were not predicted from this technique, the study 

 provided local flow patterns in the Millstone area. 



In May of 1966 Pritchard-Carpenter (1967) con- 

 ducted Rhodamine B dye tracer tests prior to the 

 operation of Unit 1 to determine the dilution off 

 Millstone Point that resulted from the natural 

 action of tides and wind. To simulate the action 

 of the Unit 1 circulating water system, which was 

 not functional at the time, Rhodamine B dye was 

 released through 1/8-in (3.2-mm) holes in a 5-ft 

 (1.5-m) pipe located 450 ft (137 m) offshore of 

 the proposed discharge point. The results pro- 

 vided estimates of the rates of mixing and dilution 

 of chemical discharges, and cooling of the heated 

 water. However, the thermal predictions did not 

 reflect induced entrainment due to discharge mo- 

 mentum nor did they reflect the effect that strat- 

 ification would have on the discharge of warm 

 water. Thus, the predictions were considered 

 conservative for design purposes. 



During August l968 and March 1969 "aytheon 

 Marine Research Laboratory (1968, 1969) made 

 temperature and salinity measurements at three 

 points in the greater Millstone bight to obtain 

 vertical temperature and salinity distributions. 



These points represented the general locations of 

 the ends of the Unit 1 thermal plume during ebb 

 and flood tide as predicted by Pritchard-Carpenter 

 (1967). The purpose of these surveys was to 

 obtain reference information on typical summer 

 and winter temperature-salinity characteristics. 



During February 1970 several tests were con- 

 ducted (Pritchard-Carpenter 1970) with the Unit 

 1 circulating water system operating at full flow, 

 but at ambient water temperature. A 30-percent 

 Rhodamine B solution was injected into the in- 

 take at 10 ml/min. The purpose was to evaluate 

 the combined effect of momentum entrainment 

 resulting from the velocity of the discharge and 

 the natural mixing characteristics produced by 

 tidal currents. Because there was no heat rejected 

 to the cooling water, the effects of stratification 

 were not determined. 



In June 1971, VAST, Inc. (1971a) conducted a 

 temperature survey of three-dimensional thermal 

 distribution patterns as they actually occurred 

 during full operation of Unit 1. The study used 

 a surface transect method to reduce the measure- 

 ment time required for each of four surveys; one 

 during maximum flood, maximum ebb, slack after 

 flood and slack after ebb. These surveys indicated 

 the position of the thermal plume and provided 

 the information necessary for the strategic collec- 

 tion of temperature at depth profiles. The result- 

 ing profiles indicated the three-dimensional struc- 

 ture of the thermal plume and, in deeper water, 

 determined the depth of the thermal plume. 

 However, no compensation was made for the 

 onshore warming temperature gradient character- 

 istic of the spring and summer months. Thus, 

 the areas enclosed by contours representing water 

 temperatures of 1.5°F and 4.0°F (0.83°C and 

 2.2°C) above ambient (AT) were overestimated. 



In November 1971 and March 1972, VAST, 

 Inc. (1972b) conducted temperature surveys to 

 define and map the thermal plume from Unit 1 

 independent of thermal inputs from natural 

 sources. Dye was injected at a constant rate into 

 the Unit 1 discharge while the unit was at full 

 load, and all four circulating water pumps and 



Hydrothemial Studies 325 



