Mid draction Auguat 1 

 TJorST' 



Fig. 3. Frequency of l5-min observations of wind direction as measured al the 30-m level on the melerological tower, 

 August through October. 



have a much greater impact on the thermal plume. 



0) turns' 

 I 125 

 .S 100 

 o. 75 

 8 50 

 o 25 



AUG87 AUG87 SEP87 SEP87 0CT87 N0V87 • 

 Date 



Fig. 4. Station cooling water usage ( — , million m /sec- 

 ond) and power production (--, MWe) August through 

 October 1987. 



Temperature and dye plume mapping 



As expected the the MNPS 3-unit thermal 

 plume moved and shifted in the direction of the 

 prevailing currents (Attachment Figs. 10 - 13). 

 Under the survey conditions on 26 August 1987, 

 the discharge water cooled to 4°F (2.2°C) above 



ambient within 3,750 ft (1,143 m) of the quarry 

 cut on all tidal stages. At low slack, the plume 

 pooled in an area from southwest to east of Mill- 

 stone Point and extended toward Twotree Island. 

 During maximum flood the plume was swept by 

 the tide along Millstone Point, westward into 

 Niantic Bay. At high slack the plume again 

 pooled in an area southeast of Millstone Point 

 but did not extend as far as Twotree Island. Dur- 

 ing maximum ebb the plume extended into and 

 followed Twotree Island Channel. 



Low slack 



During the low slack survey (0657 - 081 1 hours), 

 the plume was fairly well distributed about the 

 quarry cuts. The 4''F (2. 2''C) isotherm extended 

 out to 3,500 ft (1,067 m) off the cuts; it also 

 extented at the north into the eastern part of 

 .lordan Cove to 3,760 ft (1,146 m. Attachment 

 Fig. 10). The 6 and ST (3.3 and 4.4°C) isotherms 

 defined the edges of the discharge jet. The 4°F 

 (2.2°C) isotherm extended to the bottom out to 

 500 ft (152 m) from the quarry cuts (LSI and 



332 



