ML19266A511
| ML19266A511 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 09/18/2019 |
| From: | Cheek T Tennessee Valley Authority |
| To: | Janjic V Document Control Desk, Office of Nuclear Reactor Regulation, State of TN, Dept of Environment & Conservation, Div of Water Resources |
| References | |
| TN0026450 | |
| Download: ML19266A511 (3) | |
Text
Tennessee Valley Authority, 1101 Market Street, BR2C, Chattanooga, Tennessee 37402-2801 September 18, 2019 Mr. Vojin Janjic Division of Water Resources Tennessee Department of Environment and Conservation (TDEC)
William R. Snodgrass Tennessee Tower 312 Rosa L Parks Avenue, 11th Floor Nashville, Tennessee 37243
Dear Mr. Janjic:
TENNESSEE VALLEY AUTHORITY (TVA) - SEQUOYAH NUCLEAR PLANT (SQN) -
NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES) PERMIT NO. TN0026450 - AMENDED PERMIT APPLICATION - REQUEST TO CONDUCT A PREDICTIVE CLEAN WATER ACT (CWA) SECTION (§) 316(a) DEMONSTRATION TVA is seeking to amend the existing Alternate Thermal Limit (ATL) for the SQN thermal discharge to include the transition months of October and April, in addition to the ATLthat currently exists for November through March. To support this proposal, TVA is requesting the NPDES permit renewal for SQN currently being drafted by TDEC include a provision for TVAto conduct a predictive CWA § 316(a) demonstration study within the first six months of the effective permit term for TDEC review and determination.
Background
TVA conducted a predictive CWA § 316(a) demonstration study in 1989 to support the existing ATLthat authorizes a temperature rise in the receiving water (Chickamauga Reservoir) of 5°C measured at the end of a mixing zone established 1,500-ft downstream of the SQN submerged multi-port discharge diffusers during the months of November through March. The state criterion for temperature rise is 3°C; thus, the current ATL represents a 2°C increase. TVA has conducted § 316(a) demonstration/monitoring studies at least every permit renewal cycle since 1989 to ensure that no appreciable harm has resulted to the protection and propagation of a balanced, indigenous population offish, shellfish, and wildlife (commonly referred to as a BIP) in Chickamauga Reservoir. These studies have formed the basis for the continuance of the ATL in subsequent NPDES permits for SQN for the months of November through March.
Mr. Vojin Janjic Page 2 September 18, 2019 Reason for the Request Originally, the current ATLwas soughtto avoid incurring significant and costly freeze damage to SQN's natural draft cooling towers during winter months. The ATL has been effective in that regardwhile also being protectiveof a BIPinthe receiving water.
Since the current ATLwas first approved, the plant has faced challenges in achieving the 3°C temperature rise criterion during Octoberand April even with havingcooling towers in operation.
It is during these two months of transitioning from summer to winter(October) and from winterto summer (April) that ambient conditions inthe reservoir, and the positions and hydrological attributes of the upstream and downstream compliancemeasuring points, combine to create challenges for temperature risecompliance. In the remainder of the year (i.e., May through September), the 3°Ctemperature rise criterion is maintained undernormal operations of the plant without the need for cooling tower use1.
In reviewing SQN cooling tower use-hours since 2007, average operation of the towers inthe transition months of October and April ranges from 26% to 40% of total annual tower operations. This is an excessive amount of cooling toweroperationsfor just two months occurringduring a time of generally mildwater temperatures inthe reservoir. Due to natural seasonal fluctuations inwater temperatures occurring during the Octoberand April transitional months, fish are exposed to a wide range of temperatures in the reservoir unrelated to SQN operations. As such,theremaybe nomaterial benefit provided by operation ofthe cooling towersduring thistime (October andApril) to ensurethe protection and propagation of a BIP.
A predictive CWA§ 316(a) demonstration study would be designed to analyze this hypothesis to support a TDEC decision on the requested ATL modification.
Proposed ATL and Supporting Demonstration TVA proposes to evaluate an ATL fortemperature rise of 4°C forthe transition months of October and April, just 1°C above the established state criterion of 3°C and 1°C below the currently authorized ATL for November through March of 5°C. We believe such a modest increaseduring these months will notthreaten the protection and propagation of a BIP in Chickamauga Reservoir.
The TDEC General Water Quality Criteria for temperature protective of fish and aquatic life provides that: "Asuccessfuldemonstration as determined bythe Department conducted for thermal discharge limitations under Section 316(a) oftheClean Water Act, (33 U.S.C. §1326),
shall constitute compliance with this paragraph" (Chapter 0400-40-03-.03(3)(e)). The state's temperature criteria arewaterquality-based as opposedto technology-based; that is, application erf cooling tower technology is not the basis for the state'stemperature criteria, rather the water quality impacts associated with temperature. The predictive CWA § 316(a) 1Cooling towers are, however, operated on an as-needed basis during summer months to meet the state criterion for maximum temperature (30.5°C) atthedownstream end ofthemixing zone asdefined intheNPDES permit.
Mr. Vojin Janjic Page 3 September 18, 2019 demonstration study will evaluate the water quality impacts associated with the proposed ATL with regard to the protection and propagation of a BIP in Chickamauga Reservoir.
TVA respectfully requests that the NPDES permit renewal for SQN currently being drafted by TDEC include provisions for TVA to conduct a predictive CWA § 316(a) demonstration study within the first six months ofthe effective permit term. Further, provisions in the renewal permit should provide for the application of the proposed ATL for temperature rise of 4°C for the months of October and April within the permitterm should TDEC determine TVA's predictive CWA § 316(a) demonstration study supports such a decision.
If you have questions or need additional information, please contact Travis Markum at (423) 751 -2795 or by email at trmarkum@tva.gov.
Sincerely rj^m ?- ^M Terry E^Cheek Senior Manager Water Permits, Compliance, and Monitoring cc:
Ms. Jennifer Innes Program Manager Chattanooga Environmental Field Office Division of Water Resources 1301 Riverfront Parkway, Suite #206 Chattanooga, Tennessee 37402 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555