ML20054E907

Notification of 820515 Noncompliance W/Effluent Limitations Re Diffuser Gate Discharge to Tn River.Cause Unknown. Increase in Release Vol from Chickamauga Dam Initiated to Increase Riverflow Past Plant to Increase Mixing Ratio

ML20054E907
Person / Time
Site:	Sequoyah
Issue date:	06/10/1982
From:	Elashry M TENNESSEE VALLEY AUTHORITY
To:	Marlar J ENVIRONMENTAL PROTECTION AGENCY
References
NUDOCS 8206150022
Download: ML20054E907 (7)

Text

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TENNES9EE VALLE3 AUlitORITY K N( WVil I l'.

f r N N f

• t F: :t /m d TVA Mailroom JUN 101982 Mr. John Marlar, Chief Facilities Performance Branch Water Management Division U.S. Environmental Protection Agency, Region IV 345 Courtland Street, NE.

Atlanta, Georgia 3C365

' ear Mr. Marlar:

NOTIFICATION OF NONCOMPLIANCE WITil EFFLUENT LIMITATIONS - NPDES PERMIT NO. TN0026450 - SEQUOYAll NUCLEAR PLANT (SQN)

Description of the discharge--Discharge No. 024 - Diffuser gate discharge to the Tennessee River. The temperature rise between the upstream and downstream temperature monitors exceeded the maximum permit limitation of 3'C f rom 5:30 p.m. to 8:45 p.m. on May 15, 1982. The maximum temperature rise during this period was 3.9'C at 6:45 p.m.

The maximum downstream temperature during this time was 26.15 C at 7:25 p.m.

Cause and period of the noncompliance--During the period of noncompliance,

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upstream temperaturIe remained fairly constant at 22*C.

The temperature of the discharge trior to diffuser-induced mixing averaged 25.1*C, showing little variation between 24.8'C and 25.4*C.

The downstream temperature exhibited an upward trend throughout the hy starting at 23.l*C at 4:00 a.m. and reaching a maximum of 26.15*C at 7:25 p.m.

The dilution factor during the noncompliance period varied from approximately 2.6 to 8.5, based on discharge volumes and riverflows. The design of the diffuser discharge pipe should have provided a mixing ratio of approximately 6 to I for the flow and temperature conditions prevailing at the time of the noncompliance.

The existing thermal stratification within the Chickamauga Reservoir near the SQN site is such that there exists a 10-foot layer of cooler bottom water (T less than 18.9'C) in which much of the initial mixing of the thermal discharge occurs. Consequently, the upstream temperature at the 5-foot depth is not representative of the ambient water temperature conditions. This stratification results in the discharge jet entraining sufficient cool bottom water that it reaches its point of neutral buoyancy at an elevation substantially helow that of the surface.

Euclosed are data graphs showing upstream, downstream, and diffuser pond release temperatures plus dam releases, riverflows, and dilution factors during the period of noncompliance from 5:30 p.m.

to 8:45 p.m.

The exact cause of this noncompliance is not known.

Ilowever, we believe it was not plant induced.

It is evident from the diffuser pond temperatures measured (that were less than the downstream temperature between 6 p.m.

and 9 p.m.) and the field verified diffuser performance that the downstream temperature measured was not plant induced but the result of a combination of solar heating, low riverflows, and stratification as discussed above.

Ad 8206150022 820610 M 7]3 PDR ADOCK 05000327 S

PDR

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. Mr. John Marlar, Chief JUN 101982 Steps taken to reduce eliminate, and prevent recurrence of the noncomplying discharge--At the time the noncompliance was noted, an increase in release volume from Chickamauga Dam was initiated to increase riverflow past the plant, thus increasing the mixing ratio.

Sincerely, Ms Mohamed T.

h.D.

Assistant Manager of Natural Resources (Environment)

Enclosure cc (Enclosure):

Tennessee Department of Public Ilealth Division of Water Quality Control 150 Ninth Avenue, North TERRA Building Nashville, Tennessee 37203 Mr. lia rold R. Denton. Director (5)

Of fice of Nuclear Reactor iter;ulat ion U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Washington, DC 20555 Mr. James P. O'Reilly, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region 11 101 Marietta Street Atlanta, Georgia 30303 Mr. Jack McCormick, Basin Chief Chattanooga Basin Office Division of Water Quality Control 2501 Milne Street Chattanooga, Tennessee 37406

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