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Middle Fork American River Hydroelectric Project Overview

This project was initiated in 1967 and is operated by Placer County Water Agency. With a nameplate generating capacity of 224 MW and other significant features, it plays a crucial role in water supply and renewable energy generation. The project comprises various dams, reservoirs, powerhouses, and supporting infrastructure, contributing to its efficient operations. Recreation facilities are also available for visitors to enjoy. Operating constraints are discussed along with the general maintenance procedures and the project's historical background.

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Middle Fork American River Hydroelectric Project Overview

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  1. Middle Fork Project Project Description April 25, 2006

  2. 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

  3. 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

  4. Major Project Features • Two Large Dams and Storage Reservoirs • Two Medium Dams and Reservoirs • Three Small Dams and Diversion Pools • Five Powerhouses • Five Tunnels

  5. Supporting Infrastructure • Electrical Switchyards and Substation • Access Roads and Trails • Communication and Power Lines • Stream Gages • Maintenance and Dormitory Facilities

  6. 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

  7. Duncan Creek - Middle Fork Tunnel • 1.5 Miles Long • 10 ft Horseshoe Cross-Section • Capacity 400 cfs* • Intake With Trash Rack

  8. French Meadows Damand Reservoir

  9. 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

  10. 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

  11. French Meadows Powerhouse

  12. 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

  13. Hell Hole Dam and Reservoir

  14. 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

  15. Hell Hole Powerhouse

  16. 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

  17. 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

  18. North Fork Long Canyon Creek Diversion

  19. 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

  20. South Fork Long Canyon Creek Diversion

  21. 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

  22. Middle Fork Powerhouse

  23. 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

  24. Middle Fork Interbay Damand Reservoir

  25. 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

  26. 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

  27. Ralston Powerhouse

  28. 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

  29. Ralston Afterbay and Afterbay Dam

  30. 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

  31. 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

  32. Oxbow Powerhouse

  33. 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

  34. Other Project Components • Project Power and Communication Lines • Stream Gaging Stations • Project Roads and Trails • Microwave Reflector Stations and Radio Towers • Support Facilities

  35. 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

  36. Minimum Pool Requirements

  37. Minimum Instream Flow Requirements

  38. Minimum Instream Flow Requirements

  39. Minimum Instream Flow Requirements

  40. Dam and Diversion Discharges

  41. Dam and Diversion Discharges

  42. Dam and Diversion Discharges

  43. MFP Operations • Operated to Meet Water Supply Requirements • Operated to Meet Minimum Instream Flow Requirements • Operated to Optimize Value of Generation

  44. 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

  45. 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)

  46. 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

  47. 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.

  48. 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

  49. 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

  50. 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

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