1. May 2006 1 Middle Fork Project Project Operations Overview May 2006 PCWA MAY 16, 2006 HANDOUT #4

2. May 2006 2 MF Project Facilities

3. May 2006 3Outline Major storage is at high elevation in the Project watershed Major storage is at high elevation in the Project watershed Project reservoirs store winter precipitation and spring runoff for use through the dry summer and fall Project reservoirs store winter precipitation and spring runoff for use through the dry summer and fall Water released through Project tunnels and powerhouses flows downhill to generate power Water released through Project tunnels and powerhouses flows downhill to generate power Withdrawals from the river to meet PCWA customer demand are at the bottom (downstream end) of the Project Withdrawals from the river to meet PCWA customer demand are at the bottom (downstream end) of the Project

4. May 2006 4 Upper Diversion & Storage Facilities Duncan diversion into FM Reservoir Duncan diversion into FM Reservoir French Meadows Reservoir French Meadows Reservoir Hell Hole Reservoir Hell Hole Reservoir Collect and store water, total about 340 TAF Collect and store water, total about 340 TAF Pattern of collection & filling: Pattern of collection & filling:  Collect in winter & spring  Release in summer and fall Duncan Diversion inlet in winter

5. May 2006 5 MF Project Storage Facilities

6. May 2006 6

7. 7 French Meadows Reservoir

8. May 2006 8 Hell Hole Reservoir

9. May 2006 9 Reservoir Operations Considerations Hydrologic variability: Hydrologic variability:  Spill Avoidance  Current-year minimum releases & consumptive demands  Carry-over to meet following year demands Avg. inflow to Folsom Variability = 240%

10. May 2006 10 Typical Reservoir Storage Curves Targets: - Fill with minimal spill - Carry-over 150TAF total

11. May 2006 11 Water Flow and Generation Pathway Middle Fork Project Duncan Diversion French Meadows Reservoir Hell Hole Reservoir Rubicon River Middle Fork MF powerhouse 850 cfs - 122 MW Ralston powerhouse 920 cfs - 80 MW Oxbow powerhouse 1050 cfs - 6 MW Middle Fork Duncan Creek French Meadows pwrhse 400 cfs - 15 MW Interbay Reservoir Afterbay Reservoir

12. May 2006 12

13. May 2006 13 Main Power Generation Facilities Hell Hole reservoir to Interbay via Middle Fork powerhouse Hell Hole reservoir to Interbay via Middle Fork powerhouse

14. May 2006 14 Main Power Generation Facilities Interbay to Afterbay via Ralston powerhouse Interbay to Afterbay via Ralston powerhouse Release from Afterbay via Oxbow Powerhouse Release from Afterbay via Oxbow Powerhouse

15. May 2006 15 Main generation facilities encompass most of the vertical elevation of the Project

16. May 2006 16 Secondary Generation facilities French Meadows powerhouse: flows from FM to HH reservoirs French Meadows powerhouse: flows from FM to HH reservoirs Hell Hole power house – stream maintenance flows Hell Hole power house – stream maintenance flows Oxbow power house – releases to Middle Fork Oxbow power house – releases to Middle Fork

17. May 2006 17

18. May 2006 18 Main generation facilities encompass most of the vertical elevation of the Project

19. May 2006 19 Operations - Generation Drivers to generation scheduling: Drivers to generation scheduling:  Water availability – reservoir level and downstream demands  Power grid needs – responsiveness to load and price

20. May 2006 20 Water Rights Permits Hydrology Power Market FERC License Terms Physical Constraints Window of Operations Project Operations – Framework for Operations Variable Factors Non-Variable Constraints

21. May 2006 21 Typical Generation Dispatch to meet Load Most Responsive Units Least Responsive Units

22. May 2006 22

23. May 2006 23 “Peaking” Generation

24. May 2006 24 Project Operations for Peaking Primarily MF & Ralston stations Middle Fork Project Profile

25. May 2006 25 Key Elements for Peaking Operations Available water in Hell Hole reservoir Available water in Hell Hole reservoir Middle Fork and Ralston units operate “as one” Middle Fork and Ralston units operate “as one”  Long tunnels and small Interbay mandate closely coordinated operations Afterbay fluctuates for re-regulation Afterbay fluctuates for re-regulation  MF & Ralston may only generate 8 ~12 hrs/day  Downstream requirements and minimum flows are 24 hrs/day  Afterbay fills during peaking generation operations, empties when generation off-line

26. May 2006 26 Historic Total Generation Avg generation ~ 1.1M MWhr/yr

27. May 2006 27 Project Operations Overview Questions

28. May 2006 28 Middle Fork Project Project Operations Overview May 2006 PCWA MAY 16, 2006 HANDOUT #4