1. Martin Rule Curve Study Ashley McVicar, APC Maurice James, Water Resources Consulting LLC

2. Martin Rule Curve Study Design Flood Study Approach –Determine flood to model for the 100 year design flood –Replicate operations for the actual flood event in an operation spreadsheet Model looked at both change in inflow and elevation to determine number of gates to open limited by 2 an hour –Compare Results

3. Martin Rule Curve Study APC Flood Frequency Analysis –Model developed by US Army Corps of Engineers – Hydrologic Engineering Center in Davis, CA –Utilizes the Corps 1939-2001 unimpaired flow database created as part of the ACT Comprehensive Study –Submitted to the COE by APC in November 2005

5. Martin Rule Curve Study Martin flow –100 yr flow unregulated = 130,000 cfs-days –March 1990 flow unregulated = 125,019 cfs- days (96% of 100 year flood) –March 1990 inflow regulated used in Martin Rule Curve evaluation (with Harris and Martin in place) = 92,307 cfs-days (71% of 100 year unregulated flood)

9. Current Martin Flood Control Guidelines

10. Martin Rule Curve Study General Assumptions –Martin Turbine Capacity = 16500 (based on observed data from recent past events) –Yates Turbine Capacity = 12400 –Thurlow Turbine Capacity = 13200 –20 lift gates 6 alternate (based on opening schedule) 11 adjacent Assumed we would not use last 3 gates as they flood out the powerhouse –Ability to open 2 spillway gates an hour to be conservative

12. Martin Rule Curve Study Design Flood Evaluation –Operational criteria set forth in model accurately replicated historical conditions

13. Martin Rule Curve Study Evaluation of Winter Pool of 480’ vs. 483’ –Used current operational criteria set forth by March 1990 flood historical operations and began pool at both 480’ and 483’ –No operational criteria was changed

14. JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

16. Martin Rule Curve Study Elevation 480’ vs 483’ Results –Martin pool kept below top of easement elevation 490 for both –Beginning winter pool elevation of 483’ results in earlier releases as well as approximately 25-30k higher discharge during the peak Results routed with HEC-RAS model downstream to determine effects

18. Martin Rule Curve Study Results –Elevations downstream result in a 1’ – 3’ higher elevation downstream to Alabama River. –Corps of Engineers uses FEMA’s requirement of no increase of peak elevation downstream –FERC defers to the Corps for flood analysis –FERC would require a full analysis of impacts of proposed vs. current operation including Environmental Erosion etc

19. Martin Rule Curve Study Further Study during Relicensing Required –Look at different operational plans Pass % of inflow in zones Open gates based on a lower starting elevation –Look at different winter pool elevation and/or shape of Rule Curve 484’ Change in summer pool duration –Further evaluate downstream flood & environmental impacts and present these effects and any mitigation to FERC –FERC will then evaluate and balance the proposal