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Middle Fork Project Project Description. April 25, 2006. Middle Fork American River Hydroelectric Project. Provide a Project Overview Describe Major Project Features Describe Supporting Infrastructure Discuss Operating Constraints Describe General Operations and Maintenance
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Middle Fork Project Project Description April 25, 2006
Middle Fork American River Hydroelectric Project • Provide a Project Overview • Describe Major Project Features • Describe Supporting Infrastructure • Discuss Operating Constraints • Describe General Operations and Maintenance • Summary of Recreation Facilities • Questions
MFP - Overview • Developed as a Water Supply and Generation Project • Initial Operation 1967 • 224 MW Nameplate Generating Capacity • 120,000 Acre-Feet Water Supply • Operated by Placer County Water Agency • PG & E Acquires Power Output
Major Project Features • Two Large Dams and Storage Reservoirs • Two Medium Dams and Reservoirs • Three Small Dams and Diversion Pools • Five Powerhouses • Five Tunnels
Supporting Infrastructure • Electrical Switchyards and Substation • Access Roads and Trails • Communication and Power Lines • Stream Gages • Maintenance and Dormitory Facilities
Duncan Creek Diversion • Spillway Crest - 5,265 ft Elevation • Diversion - Concrete Gravity - 165 ft Long • Diversion Capacity - 400 cfs • Surface Area - Approximately 1 Acre • Gross Storage - 20 Acre-Feet
Duncan Creek - Middle Fork Tunnel • 1.5 Miles Long • 10 ft Horseshoe Cross-Section • Capacity 400 cfs* • Intake With Trash Rack
French Meadows Damand Reservoir • Spillway Crest at 5,273 ft Elevation • French Meadows Dam - Gravel and Earthfill - 2,700 ft Long • Surface Area - 1,404 Acres Maximum,434 Minimum • Gross Storage - 134, 993 Acre-Feet • Shoreline - 9 Miles
French Meadows - Hell Hole Tunnel • 2.6 miles long • 12.3 ft Horseshoe Cross-Section • Capacity 400 cfs* • Intake in French Meadows Reservoir and Trash Rack • Terminates in a 6.25 ft Diameter - 691 ft Long Penstock to the French Meadows Powerhouse
French Meadows Powerhouse • Located on Hell Hole Reservoir • Water Supply - Discharge from French Meadows - Hell Hole Tunnel • Single Francis Turbine • 15.3 MW / 60,000 Volts • Discharges to Hell Hole Reservoir
Hell Hole Dam and Reservoir • Spillway Crest at 4,650 ft Elevation • Hell Hole Dam - Rockfill - 1,570 ft Long • Surface Area - 1,253 Acres Maximum, 185 Acres Minimum • Gross Storage - 207,500 Acre-Feet • Shoreline - 11 Miles
Hell Hole Powerhouse • Located at Outlet from Hell Hole Dam • Water Supply - Hell Hole Dam Discharge Conduit • Single Francis Turbine • 0.725 MW / 12,000 Volts • Discharges to Rubicon River
Hell Hole - Middle Fork Tunnel • 10.4 Miles Long • 13.5 ft Horseshoe Cross-Section • Capacity 920 cfs* • Intake in Hell Hole Reservoir • Terminates in a 9 - 7.5 ft dia. - 3,653 ft Long Penstock to the Middle Fork Powerhouse
North Fork Long Canyon Creek Diversion • Dam Crest at 4,720 ft Elevation • Diversion - Concrete Gravity - 120 ft Long • Diversion Capacity 100 cfs • Surface Area - Less than 1 Acre • Pipe and Shaft to the Hell Hole - Middle Fork Tunnel
South Fork Long Canyon Creek Diversion • Dam Crest at 4,650 ft Elevation • Diversion - Concrete Gravity - 145 ft Long • Diversion Capacity 200 cfs • Surface Area - Less than 1 Acre • Pipe and Shaft to the Hell Hole - Middle Fork Tunnel
Middle Fork Powerhouse • Located on Middle Fork Interbay Reservoir • Water Supply- Hell Hole - Middle Fork Tunnel • Two Pelton Waterwheels • 122.4 MW / 60,000 Volts • Discharges to Middle Fork Interbay Reservoir
Middle Fork Interbay Damand Reservoir • Dam Crest at 2,536 ft Elevation • Interbay Dam - Concrete Gravity - 233 ft Long • Surface Area - 7 Acres • Gross Storage - 175 Acre-Feet
Middle Fork TunnelRalston Tunnel • 6.7 Miles Long • 13.5’ Horseshoe Cross-Section • Capacity 924 cfs* • Intake in Middle Fork Interbay Reservoir / Trash Rack • Terminates in a 9.5 - 8 ft dia. - 1,670 ft Long Penstock to the Ralston Powerhouse
Ralston Powerhouse • Located on Ralston Afterbay Reservoir • Water Supply - Middle Fork Tunnel - Ralston Tunnel • Single Francis Turbine • 79.2 MW / 60,000 Volts • Discharges to Ralston Afterbay
Ralston Afterbay and Afterbay Dam • Dam Crest at 1,189 ft Elevation • Ralston Afterbay Dam - Concrete Gravity - 560 ft Long • Gross Storage - 2,782 Acre-Feet
Ralston - Oxbow Tunnel • 0.1 Miles Long • 13.25 ft Horseshoe Cross-Section • Capacity 1,075 cfs* • Intake in Ralston Afterbay Reservoir / Trash Rack • Supplies Oxbow Powerhouse
Oxbow Powerhouse • Located on Middle Fork American River • Single Francis Turbine • Generator - 6.1 MW / 60,000 Volts • Discharges to Middle Fork American River below Ralston Afterbay Dam
Other Project Components • Project Power and Communication Lines • Stream Gaging Stations • Project Roads and Trails • Microwave Reflector Stations and Radio Towers • Support Facilities
Project Operations • Operating Constraints • Water Rights (Storage and Diversion Allowances) • Minimum Pool Requirements • Stream Maintenance Flows (i.e. Minimum Instream Flows) • Dam / Diversion Discharge Capacities
MFP Operations • Operated to Meet Water Supply Requirements • Operated to Meet Minimum Instream Flow Requirements • Operated to Optimize Value of Generation
Operations Overview • Operations Governed By: • MF Project FERC License Conditions • Water Rights Permits • Contractual Obligations (Delivery of Water and Power) • Physical Constraints (Size of Tunnels, Capacity of Powerhouses) • Power Market – High Value Periods of Operation
Seasonal Pattern of Operations • Reservoir Storage: • French Meadows and Hell Hole Reservoirs, 343,000 Acre-Feet Total Storage • Seasonal Pattern of Operations: • Store Water During Winter and Spring Precipitation and Runoff Periods (Refill Period) • Releases During the Dry Summer and Fall Months (Drawdown Period) • Reservoirs are Operated to Maintain Relative Balance between Reservoirs • Dec. 31 Carry-Over Target for Dec. 31 of 150,000 Acre-Feet (Two Reservoirs)
Reservoir Operations • Operations during refill period to meet demands, fill reservoirs, avoid spill • Operations during drawdown to meet demands, hit end-of-year storage target • Reservoir storage targets through the year: • Generally based on historic practice • Refined during refill period based primarily on hydrologic conditions, with some consideration of power market conditions • Storage managed during drawdown period based on consumptive obligations and power market trends • At all times meet minimum release obligations
Generation Scheduling • Watershed provides sufficient water to operate about half of the time at full load (50% capacity factor) • Full-load operations are most efficient for generation • Project typically operates in “peaking” mode: 8-16 hours per day, during the most valuable time periods • Annual generation approximately 1 million MW hours.
Scheduling and Operations • Project operations have been much the same since the construction of the Project • Variation in specific operations practices through time in response to: • Project maintenance requirements • Changes in California power markets • Recreation demands downstream of the Project
Maintenance • Facility Testing (powerhouse equipment testing and maintenance, gate and valve testing) • Debris Removal Management • Sediment Management • Vegetation and Pest Management • Facility Painting • Road Maintenance
Recreation Facilities • Recreation Plan developed as required by the license • Recreation Facilities include campgrounds, picnic areas, boat launch areas, and one scenic vista • Operated by the Tahoe and Eldorado National Forests