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

May MF Project Facilities

May Outline 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

May 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

May MF Project Storage Facilities

May

7 French Meadows Reservoir

May Hell Hole Reservoir

May 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%

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

May Water Flow and Generation Pathway Middle Fork Project Duncan Diversion French Meadows Reservoir Hell Hole Reservoir Rubicon River Middle Fork MF powerhouse 850 cfs 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

May

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

May 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

May Main generation facilities encompass most of the vertical elevation of the Project

May 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

May

May Main generation facilities encompass most of the vertical elevation of the Project

May 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

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

May Typical Generation Dispatch to meet Load Most Responsive Units Least Responsive Units

May

May “Peaking” Generation

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

May 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

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

May Project Operations Overview Questions

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