PCWA MAY 16 2006 HANDOUT 4 Middle Fork

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

MF Project Facilities May 2006 2

Outline n n 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 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 May 2006 3

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

MF Project Storage Facilities May 2006 5

May 2006 6

French Meadows Reservoir May 2006 7

Hell Hole Reservoir May 2006 8

Reservoir Operations Considerations n Hydrologic variability: § Spill Avoidance § Current-year minimum releases & consumptive demands § Carry-over to meet following year demands Avg. inflow to Folsom Variability = <30% to >240% May 2006 9

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

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

May 2006 12

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

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

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

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

May 2006 17

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

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

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

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

May 2006 22

“Peaking” Generation May 2006 23

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

Key Elements for Peaking Operations n Available water in Hell Hole reservoir n Middle Fork and Ralston units operate “as one” § Long tunnels and small Interbay mandate closely coordinated operations n 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 2006 25

Historic Total Generation Avg generation ~ 1. 1 M MWhr/yr May 2006 26

Project Operations Overview Questions May 2006 27

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