two service water pumps were in operation. Dye 

 concentrations were measured continuously in the 

 quarry and from boats moving along prescribed 

 transects. The dye concentration and temperature 

 data were digitized at predetermined grid points 

 and converted to the equivalent temperature rise 

 to obtain synoptic patterns of the thermal plume. 

 These results were in closer agreement with pre- 

 dictions than the June 1971 study (NUSCO 1979). 

 The differences between the prediction of May 

 1966 and those of February 1970 in the near field 

 were attributed to the effects of momentum en- 

 trainment which had not been compensated for 

 in the 1966 study. 



VAST, Inc. conducted two other dye studies 

 (1971a, 1972c). Each was designed to determine 

 the natural flushing or renewal rate of Long Island 

 Sound water in the vicinity of Millstone Point 

 due to tidal exchange. The surveys were required 

 for use in the conceptual design of a multiport 

 diffuser system that might be located in Twotree 

 Island Channel or west of Twotree Island for 

 cooling water discharge. During both surveys 

 Rhodamine B dye was injected from boats in 

 these two areas and dye concentrations were sam- 

 pled continuously from boats moving along pre- 

 scribed transects. 



In 1972, Stone and Webster Engineering Cor- 

 poration (SWEC) completed a modeling effort 

 that resulted in preliminary thermal plume pre- 

 dictions presented in the Environmental Reports 

 for Unit 2 and Unit 3 (MFC 1972a, 1972b). 



Hydrograpliic surveys were conducted in the 

 Niantic Bay area of Long Island Sound during 

 August and September 1973 and February 1974 

 (Braincon 1975). Tide levels, tidal current speed 

 and direction, and wind speed and direction were 

 measured. These data were analyzed and the tide 

 levels were used as input for the SWEC two- 

 dimensional tidal circulation model; the current 

 data were used to verify this model. 



1977 Hydrothermal survey 



During 1977, as required by the Nuclear Reg- 

 ulatory Commission, a hydrothermal field survey 

 of the two-unit operational plume from MNPS, 

 was conducted (ENDECo 1978; TI 1978). The 

 objectives of this survey were to determine the 

 three-dimensional temperature characteristics of 

 the thermal plume resulting from the discharge of 

 condenser cooling water from Units 1 and 2 and 

 to verify the original 1972 predictions of the two- 

 unit plume. The details of these studies are best 

 described in contractor reports (ENDECo 1978; 

 TI 1978) but are summarized briefly. 



The dye study provided detailed information on 

 dilution rates and three-dimensional temperature 

 distributions (ENDECo 1978). Rhodamine WT 

 dye was introduced into the Units 1 and 2 circu- 

 lating water discharges during full plant load con- 

 ditions to achieve 16 ppb at the quarry cut 

 (ENDECo 1978). During a two-day period (one 

 complete tidal cycle each day) dye concentration 

 and temperature were monitored continuously at 

 each intake, the quarry cut and from boats that 

 followed six predetermined transects. It took the 

 boats about one hour to complete all six transects; 

 boat position was determined from four transpon- 

 ders. In the near field (an area defined as 500 ft 

 (152 m) from the center line of the discharge 

 plume out to 1000 ft (305 m)), dye concentration 

 and temperature were measured vertically (5-ft 

 (1.5-m) at intervals down to 30 ft (9 m)) and 

 horizontally 1.5 ft (0.5 m) below the surface. 

 These data were used to map the plume over a 

 complete tidal cycle. Temperature isotherms and 

 dye concentration isopleths were drawn manually 

 on a map. 



Thermal infrared scanning provided a synoptic 

 'picture' of the surface thermal plume at specific 

 tidal stages. The 8- to 14-micrometer portion of 

 the electromagnetic spectrum was scanned coinci- 

 dent with the dye study (TI 1978). Temperature 

 reference sources within the field-of-view provided 

 ground truth calibration. The recorded airborne 

 thermal infrared data were presented both quali- 

 tatively and quantitatively. 



326 



