Last updated on November 28th, 2022
36. Inconclusive Investigation
Investigators could not pinpoint an exact cause. However, they found 24 possible triggers of spillway failure. The main suspects were uneven concrete thickness, faulty drainage system, and rebar corrosion.
37. The Money Trail
Spillway repairs began in the summer. The expected total cost was $400 million, with most funds coming from the Federal Emergency Management Agency. Kiewit Construction won the primary contract worth $275 million. Estimates increased as more damage came to light.
38. Weighing the Options
Repair ideas fell into three categories. They could “Bridge the Hole” and bypass the eroded valleys, but it would be costly and complex. They could also “Use the Hole” carved by the water to minimize cost, but a scale model revealed its flaws. Finally, they could “Fill the Hole” by replacing the eroded foundation and returning to the original path. The third option won.
39. The Reconstruction Plan
Only the center of the spillway foundation gave out, but even undamaged parts were structurally defective. They had to demolish all of it and start from scratch. They also extended a cutoff wall beneath the emergency spillway to avoid future erosion.
40. The 2020 Safety Assessment
After a lengthy analysis, the Department of Water Resources concluded that the Oroville Dam is suitable for continued operation. However, officials are no longer complacent. The Federal Energy Regulatory Commission demands plans in case of heavier rainfall in the future.
Operation and Benefits
41. Power Generation Capacity
The Edward Hyatt Pump-Generating Plant under the dam was the largest underground power station in the US when it started its operation. It has a total capacity of 819 megawatts.
42. Recycling Water
The Hyatt Powerplant can lift water back up to Lake Oroville using surplus power. The flow rate ranges from 159 to 480 cubic meters per second.
43. Oroville-Thermalito Complex
In the west of Oroville, you will see two off-stream reservoirs. Surplus energy from the Hyatt plant lifts water from the lower to the upper reservoir in Thermalito. It lets the Thermalito plants generate up to 114 megawatts.
44. Traveling to the Coast
It is a long journey. Water travels from the Oroville Dam down to the Feather River, the Sacramento River, and the San Joaquin Delta. The California Aqueduct lifts the water onto the valley and the Tehachapi Mountains, allowing it to reach coastal Southern California.
45. Crucial Irrigation
The Oroville Dam serves both rural and urban areas. The dam irrigates 755,000 acres of land around the arid San Joaquin Valley. It also provides municipal water to roughly 25 million people.
46. Flood Control Protocol
The dam is on high alert every winter. Water can rise fast, so the operators do everything to catch rainfall without overflowing. The Oroville Dam frees up at least 20% of the reservoir capacity. That is roughly 930 billion liters!
47. The Great New Years Flood
The Oroville Dam helped avert disaster in 1997 when storms hit California. Inflows to the reservoir exceeded 331,000 cubic feet per second, yet it limited outflows to 160,000 cubic feet per second. It saved large parts of the Sacramento Valley from flooding.
48. The Feather River Fish Hatchery
Before the Oroville Dam came along, the area was part of the annual migration of Chinook salmon and steelhead trout. The California Department of Fish and Game compensated for the lost habitat by building the Feather River Fish Hatchery.
49. The Fish Barrier Dam
In 1962, they built a Barrier Dam to intercept the fish and guide them to a ladder leading to the Hatchery. The successful project produces 10 million salmon and 450,000 trout smolts.
50. Fish Releases
Fishermen love fall and spring. There is plenty to celebrate, including the bi-annual releases of salmon and trout into the Feather River. These provide exciting recreational fishing opportunities in the area.
Oroville Dam – quick facts and statistics
|Official name||Oroville Dam|
|Purpose||water supply, flood control, power|
|Number of turbines installled||3x conventional
|Installed capacity||819 MW|
|Type of dam||Zoned Earthfill|
|Opened||May 4, 1968|
|Owned by||California Department of Water Resources|
Total capacity: 3,537,577 acre⋅ft (4.363537 km3)
|Height||770 ft (235 m)|
|Length||6,920 ft (2,109 m)|
|Volume||77,619,000 cu yd (59,344,000 m3)|
|Spillway||150,000 cu ft/s (4,200 m3/s)|
|Last updated||November 28, 2022|