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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. Introduction.
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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
Introduction Impingement- The death of fish and aquatic organisms that are pinned on the cooling water intake structure (CWIS).
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%
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
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?
Low and High Pressure Spray Fish Trough Debris Trough Intake Flow
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
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
Species Diversity • 5,300 fish • 30 species • 11 families • Recreationally Important spp. • Fragile spp.
Shad & Non-shad Composition 80% 0.9% 8% 11%
Fish Separation 92.5% 87.6% 7.4% 12.4%
Survivability Experimental Design • Biweekly Impingement Fish Return Trough only • Fish Collection 2 days/week • 48 Hourly Latent Impingement Mortality (LIM) Observations
Other Study Components • Water Quality • Intake • Aquaria system • CWIS Flow • Circ Pumps On, Unit offline • Intake Velocity • Weather and River Flow conditions
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
Questions? Justin Mitchell (205)664-6184 jusmitch@southernco.com