West Valley
West Valley is an earth dam located in Modoc County, California, built in 1936. It carries a High hazard potential classification and has a satisfactory condition assessment.
About West Valley
The primary purpose of West Valley is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by South Fork Irrigation District (public utility). It impounds the West Valley Cr near Alturas.
The dam stands 65 feet tall and stretches 305 feet across, creates a reservoir covering 1,050 acres, has a maximum storage capacity of 23,000 acre-feet, and collects water from a drainage area of 136 square miles. Completed in 1936, the structure is well-established, with more than 75 years of service.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 11/04/2025.
At 65 feet, this dam is taller than 96% of all dams in the United States.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The California dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | California |
| County | Modoc |
| Nearest City | Alturas |
| River/Stream | West Valley Cr |
| Coordinates | 41.22280, -120.41210 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 65 ft |
| Dam Height | 65 ft |
| Dam Length | 305 ft |
| Year Completed | 1936 (90 years old) |
Storage & Hydraulics
| NID Storage | 23,000 acre-ft |
| Max Storage | 23,000 acre-ft |
| Surface Area | 1,050 acres |
| Drainage Area | 136 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | South Fork Irrigation District |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 11/04/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00300 |
| Federal ID | CA00300 |
| More Info | State Dam Safety Program |