ML20056H052

NPDES Noncompliance Notification:On 930824,fish Observed Floating in Quarry Near Discharge Structure.Caused by Temp Variation in Quarry Due to Shut Down Resulting in Thermal Shock to Fish

ML20056H052
Person / Time
Site:	Millstone
Issue date:	08/31/1993
From:	Sears C NORTHEAST UTILITIES
To:	Keeney T CONNECTICUT, STATE OF
References
D06808, D6808, NUDOCS 9309080139
Download: ML20056H052 (4)

Text

l NORTHEAST UTILITIES ceners Omces . seioen street. Bernn. connect. cut l s *NaNw P.O. BOX 270 HARTFORD. CONNECTICUT 06141-0270 k k J $ 7. '$N.,7, (203) 665-5000 l

l August 31, 1993 006808 Mr. Timothy Keeney, Commissioner Department of Environmental Protection State Office Building 165 Capitol Avenue Hartford, CT 06115

Dear Commissioner Keeney:

Millstone Nuclear Power Station Fish kill in Millstone Ouarry Auoust 24. 1993 On August 24, 1993, fish were observed floating in the Millstone Quarry, near Unit 3 discharge structure. Station investigations found the remains of 50 to 100 badly decomposed fish. Due to the decomposition, accurate size and number estimates could not be obtained. The remains of the following types of fish l were identified: Morone Saxatilis, Huail sop., Centropristis striata, Morone l americana, Tautoa onitis. The quarry was monitored for three days subsequent

• l to the discovery, with no additional mortalities observed.

Verbal notification was made to the Nuclear Regulatory Commission, according to the Unit 3 Environmental Protection Plan, and to the Connecticut Department of Environmental Protection on August 25, 1993 by Dr. Milan Keser of NUSCO Aquatic Services. In addition, an unusual event " ECHO" notification was declared by the Station.

An investigation of Station discharges show no permit discharge exceedances, hcwever, due to unit shutdowns in August, condenser cooling water discharge conditions for both Unit 2 and 3 changed frequently. Unit 3 was shut down on July 31 to begin a refueling outage, and Unit 2 had a maintenance shutdown beginning on August 6. These operational changes caused temperature variations in the quarry. It is beliesed that a rapid rise in temperature from 31.4 degrees C on August 21, to 34.0 degrees C on August 22 thermally '

shocked the fish. The 34*C temperature is near or above the thermal tolerance limits of the identified fish. The decomposed remains of the fish were observed 2 days later, on the 24th.

The attached Table 1 lists the quarry water temperature as well as the Unit l flows for the month previous to the incident. Quarry flow, as well as Intake l l and Quarry temperature are portrayed graphically in Graph 1. The horizontal l line at 34' is the thermal tolerance limit of several of the fish.

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23 OS3421 REV. 448 93090B R A N 9$D 0

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Mr. Timothy Keeney

'D06808/Page 2 i August 31, 1993 Should you have any questions, please call Dr. Milan Keser, NUSCO Aquatic Services, Northeast Utilities Environmental Laboratory, at 444-4238.

Very truly yours, 1

NORTHEAST UTILITIES SERVICE COMPANY l As agent for Northeast Nuclear Energy Company l

b C. F. Sears l Vice President Enclosure cc: Mr. Charles Fredette Connecticut Department of Environmental Protection 122 Washington Street Hartford, CT 06106 Mr. Ernest Beckwith Connecticut Department of Environmental Protection State Office Building, Room 255 165 Capitol Avenue

• Hartford, CT 06106 Mr. Eric Smith Connecticut Department of Environmental Protection Marine Fisheries Office P.O. Box 714 Old Lyme, CT 0637:

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TABLE 1. Daily mean quarry water temperatures and flows through Millstone Nuclear Power '

plants, July 24,1993 through August 24,1993.

Quarry Water F 1 o w (cfs) ,

Date Temocrature ( C) Unit 1 Unit 2 Unit 3 Comments July 24 30.7 881 1276 2099 July 25 31.0 755 1276 2099 July 26 30.6 788 1276 2099 July 27 30.6 983 1276 2099 July 28 31.0 979 1276 2099 July 29 30.9 989 1276 2099 July 30 31.0 989 1276 2099 Jtily 31 27.6 989 1276 2099  :

Aug.1 28.6 989 1276 1118 U-3 shutdown Aug. 2 29.1 989 1276 1079 Aug. 3 29.9 989 1276 855 Aug. 4 33.5 989 1276 55 U3 all cire. water i Aug. 5 .' 32.0 989 1276 33 pumps off Aug. 6 26.4 989 1167 72 U-2 shut down Aug. 7 25.9 989 665 633 U-3 & U-2 shutdown Aug. 8 25.8 989 666 711 ,

Aug. 9 : 25.9 989 665 711 Aug.10 26.0 989 794 711 Aug.11 24.8 983 1276 711 Aug.12 25.3 989 1276 598  :'

Aug.13 26.0 989 1276 372 Aug.14 26.3 989 1276 372 Aug.15. 26.5 989 1276 566 Aug.16 . 30.0 989 1276 730 U-2 resumes operation Aug.17 30.5 989 1276 739 Aug.18 30.2 989 1276 744 Aug.19 30.4 989 1276 744 Aug. 20 30.8 989 1276 723 Aug. 21 31.4 989 1276 489 Aug. 22 34.0 989 1276 33 Aug. 23 34.5 982 1276 33 Aug. 24 34.7 989 1276 33 4

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