Yuba–Bear Hydroelectric Project
The project area encompasses approximately 400 square miles (1,000 km2) in Nevada, Placer, and Sierra Counties.
[2][3] The Yuba–Bear Project introduced additional canals, reservoirs, ability to generate power, and 145,000 acre-feet of water storage to be utilized by residents of the district.
[4] The Yuba–Bear Hydroelectric Project is located within the Sierra Nevada mountain range, which experienced uplift beginning 3 to 5 million years ago, and contains faults resultant of tectonic collision during the late Paleozoic and Mesozoic eras.
[5] This uplift and tilting of the Sierra Nevada created drainage patterns and channel incisions that shaped the landscape, including the Yuba and Bear rivers.
Incision of the modern Yuba River began 5 million years ago, compounded by glacier erosion in the Quaternary period.
[6] The Yuba River creates an incision through metamorphic bedrocks, including Mesozoic igneous rocks (granodiorite), Paleozoic phyllite, and slate from the Shoo Fly and Calaveras Formations.
Over time, these channels were filled with Tertiary deposits of gravel, large boulders, and sands that were rich in gold.
[7] The Yuba River has been heavily influenced by gold mining activity, with lingering effects such as abandoned mines, residual mercury sequestered in sediment, erosion, and alteration of sediment transport through the river system, with resulting consequences to channel structure.
In addition to gold, major minerals of the area include copper, chromium, tungsten, and manganese.
The Bear River has been severely impacted by hydraulic mining, and struggles with mercury contaminationleft over from the gold rush.
Jackson Meadows Dam stores water from the Middle Yuba, which is diverted southward through the Milton-Bowman Diversion Conduit into Bowman Lake, an impoundment of Canyon Creek.
In addition to Jackson Meadows and Bowman reservoirs, the Yuba–Bear project derives water from fourteen smaller high elevation Sierra lakes, which have been dammed to increase their size.
[11] After passing through Bowman Powerhouse, the water continues south via the Bowman–Spaulding Conduit to Lake Spaulding, which is part of the heavily interconnected Drum-Spaulding Hydroelectric Project owned by PG&E.
Lake Spaulding is an impoundment of the South Yuba River, and is an important hub of the system as nearly all the water used by both projects passes through it.
[11] Below Lake Spaulding water passes through Drum-Spaulding Project canals through Emigrant Gap into the upper Bear River, where it powers six hydroelectric plants on its long descent to Rollins Reservoir, the lowermost major reservoir of the Yuba–Bear project.
[12] NID was granted the Federal Energy Regulatory Commission (FERC) license for the Yuba–Bear project in June, 1963.
The four developments discussed in detail below compose the Yuba–Bear Project, with a total of 13 mains dams and 207,865 acre-feet of gross combined storage capacity.
Sawmill Dam Spillway and Lake allow for 3,030 ac-ft storage capacity, and create 79.4 acres of surface area.
2 Conduit is a combination of flume, tunnel, siphon, and canal that takes water from PG&E's Drum-Spaulding Project (at Drum Afterbay), and channels it into Dutch Flat No.
[14] Six miles upstream from where the Bear River meets Rollins Reservoir, is the Dutch Flat Afterbay Dam.
