Grasmere North Dam is a dam located in Owyhee County, Idaho, built in 1936. It carries a Significant hazard potential classification and has a poor condition assessment.
Dam profile
NID height · 22 ft22 ft tall and 1,520 ft long. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Grasmere North Dam
Grasmere North Dam is a dam in Owyhee, Idaho. The dam is private-owned. It impounds the Rattlesnake Creek Marys Creek near Highway 51.
The dam stands 22 feet tall and stretches 1,520 feet across, creates a reservoir covering 86 acres, has a storage capacity of 657 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1936, the structure is well-established, with more than 75 years of service.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. The most recent inspection on record was 08/27/2020.
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Location
| State | Idaho |
| County | Owyhee |
| Nearest City | Highway 51 |
| River/Stream | Rattlesnake Creek Marys Creek |
| Coordinates | 42.36340, -115.90890 |
Physical Characteristics
| NID Height | 22 ft |
| Dam Height | 22 ft |
| Dam Length | 1,520 ft |
| Year Completed | 1936 (90 years old) |
Storage & Hydraulics
| NID Storage | 657 acre-ft |
| Normal Storage | 657 acre-ft |
| Surface Area | 86 acres |
| Drainage Area | 1 sq mi |
| Max Discharge | 55 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Other |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Poor |
| Last Inspection | 08/27/2020 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | ID00190 |
| Federal ID | ID00190 |
| More Info | State Dam Safety Program |