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Enhancing Fish Survival: Implementing Fish-Friendly Water Screens

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Learn about innovative modifications to water screens for reducing fish impingement and mortality rates while ensuring compliance with Clean Water Act regulations. Study objectives cover fish impingement rates, operational efficiency, morbidity rates, and survival. Preliminary findings indicate shad comprise most impingement cases, with implications for future research. Contact Justin Mitchell for inquiries.

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Enhancing Fish Survival: Implementing Fish-Friendly Water Screens

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  1. Fish Impingement and Survival on “Fish Friendly”Traveling Water Screens Justin B. Mitchell APC Compliance Studies Alabama Water Resources Association Conference Orange Beach, Alabama September 07, 2012

  2. Introduction Impingement- The death of fish and aquatic organisms that are pinned on the cooling water intake structure (CWIS).

  3. Impingement

  4. Proposed Impingement Rule • Section 316(b) of the Clean Water Act • Withdraw >2 MGD from waters of the US • >25% used for cooling purposes • Primary Compliance Options: • Cooling Towers • Intake velocity <0.5 fps • Traveling Screen Modifications and Biological Monitoring • Fish Buckets • Fish Return System • 48 hr Mortality Limit Criteria: Average annual mortality rate <12% Monthly maximum mortality rate <31%

  5. Gorgas Steam Plant • Walker County, AL • Black Warrior River (Mulberry Fork) • 1,200 MW • 5 generating units • FGD (scrubber) • 2 separate CWIS • Units 6-7 • Units 8-10

  6. Gorgas Approach SSI Band Screen Retrofit • Cost effective, $1.3M • Operationally feasible • Moribund fish (i.e. fish health) exceptions • Entrapment • Can this technology achieve the mortality limits?

  7. Modified Band Screen with Fish Buckets

  8. Low and High Pressure Spray Fish Trough Debris Trough Intake Flow

  9. Fish Return and Aquaria System

  10. Study Objectives • Characterize Fish Impingement Rates • Debris trough • Fish trough • Evaluate Screen Operational Efficiency • Investigate 48 hr Latent Impingement Mortality • Examine Rates of Sick or Moribund Fish

  11. Impingement SamplesCollected to Date • Fish Return Trough Debris Trough • 3 8-hr sample/day • Day • Evening • Night • 4 days/week (Jan-Feb) • 2 days/biweek (Mar-Jun) • Total Samples = 72 8-hr samples/trough

  12. Species Diversity • 5,300 fish • 30 species • 11 families • Recreationally Important spp. • Fragile spp.

  13. Common Species

  14. Shad & Non-shad Composition 80% 0.9% 8% 11%

  15. Fish Separation 92.5% 87.6% 7.4% 12.4%

  16. Survivability Experimental Design • Biweekly Impingement Fish Return Trough only • Fish Collection 2 days/week • 48 Hourly Latent Impingement Mortality (LIM) Observations

  17. Other Study Components • Water Quality • Intake • Aquaria system • CWIS Flow • Circ Pumps On, Unit offline • Intake Velocity • Weather and River Flow conditions

  18. 24 and 48 hrLatent Impingement Mortality

  19. Fish Health Diagnosis

  20. Preliminary Conclusions • Impingement comprised mostly of shad • 24 hr and 48 hr Impingement Mortality > 12% Limit • Shad (89-100%) • Non-shad (20-60%) • Disease prevalence among all survival categories • LIM studies are time and labor intensive • Future Research: Explore ways to optimize impingement survival

  21. Questions? Justin Mitchell (205)664-6184 jusmitch@southernco.com

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