Fish Impingement and Survival on “Fish Friendly”

Traveling Water Screens

Alabama Water Resources Association ConferenceOrange Beach, Alabama

September 07, 2012

Justin B. MitchellAPC Compliance Studies

Introduction

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

Impingement

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:1. Cooling Towers2. Intake velocity <0.5 fps3. 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?

Modified Band Screen with Fish Buckets

Low and High Pressure Spray

Fish Trough

Debris Trough

Intake Flow

Fish Return and Aquaria System

Study Objectives

1. Characterize Fish Impingement Rates Debris trough Fish trough

2. Evaluate Screen Operational Efficiency

3. Investigate 48 hr Latent Impingement Mortality

4. Examine Rates of Sick or Moribund Fish

Impingement SamplesCollected to Date

Fish Return TroughDebris 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 Recreationall

y Important spp.

Fragile spp.

Common Species

Shad & Non-shad Composition

80%

0.9%

8%

11%

Fish Separation

87.6%

12.4%

92.5%

7.4%

Survivability Experimental Design

Biweekly ImpingementFish Return Trough only

Fish Collection2 days/week

48 Hourly Latent Impingement Mortality (LIM) Observations

Shift Monday Tuesday Wednesday Thursday Friday

0600-1400Fish Collection & LIM Observations

Fish Collection & LIM Observations LIM Observations LIM Observations

1400-2200Fish Collection & LIM Observations

Fish Collection & LIM Observations LIM Observations LIM Observations

2200-0600Fish Collection & LIM Observations

Fish Collection & LIM Observations LIM Observations LIM Observations

Other Study Components

Water Quality Intake Aquaria system

CWIS Flow Circ Pumps On,

Unit offline Intake Velocity Weather and River

Flow conditions

24 and 48 hrLatent Impingement

Mortality

Fish Health Diagnosis

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