Ashton
Ashton is an earth dam located in Fremont County, Idaho, built in 1917. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Ashton
The primary purpose of Ashton is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Pacificorp (private). It impounds the Henrys Fork, Snake River near Chester.
The dam stands 65 feet tall and stretches 252 feet across, creates a reservoir covering 404 acres, has a maximum storage capacity of 9,900 acre-feet, and collects water from a drainage area of 1,040 square miles. Completed in 1917, the structure is over a century old.
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 10/20/2022.
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 Idaho 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 | Idaho |
| County | Fremont |
| Nearest City | Chester |
| River/Stream | Henrys Fork, Snake River |
| Coordinates | 44.07850, -111.49680 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 65 ft |
| Dam Height | 65 ft |
| Dam Length | 252 ft |
| Year Completed | 1917 (109 years old) |
Storage & Hydraulics
| NID Storage | 9,900 acre-ft |
| Max Storage | 9,900 acre-ft |
| Normal Storage | 9,800 acre-ft |
| Surface Area | 404 acres |
| Drainage Area | 1,040 sq mi |
| Max Discharge | 46,100 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | PacifiCorp |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 10/20/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | ID00178 |
| Federal ID | ID00178 |
| More Info | State Dam Safety Program |