Sylvia Lake Dam Grays Harbor Cnty
Sylvia Lake Dam Grays Harbor Cnty is a buttress dam located in Grays Harbor County, Washington, built in 1918. It carries a Significant hazard potential classification and has a poor condition assessment.
About Sylvia Lake Dam Grays Harbor Cnty
The primary purpose of Sylvia Lake Dam Grays Harbor Cnty is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Wa Parks (state). It impounds the Sylvia Creek near Montesano.
The dam stands 23 feet tall and stretches 120 feet across, creates a reservoir covering 32 acres, has a maximum storage capacity of 550 acre-feet, and collects water from a drainage area of 5 square miles. Completed in 1918, the structure is over a century old.
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. An emergency action plan is in place for this dam. The most recent inspection on record was 11/12/2024.
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Location
| State | Washington |
| County | Grays Harbor |
| Nearest City | Montesano |
| River/Stream | Sylvia Creek |
| Coordinates | 46.99608, -123.59838 |
Physical Characteristics
| Dam Type | Buttress |
| NID Height | 23 ft |
| Dam Length | 120 ft |
| Year Completed | 1918 (108 years old) |
Storage & Hydraulics
| NID Storage | 550 acre-ft |
| Max Storage | 550 acre-ft |
| Normal Storage | 320 acre-ft |
| Surface Area | 32 acres |
| Drainage Area | 5 sq mi |
| Max Discharge | 1,510 cfs |
Ownership & Safety
| Purpose | Recreation |
| Owner | WA PARKS |
| Owner Type | State |
| Hazard Classification | Significant |
| Condition Assessment | Poor |
| Last Inspection | 11/12/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WA00132 |
| Federal ID | WA00132 |
| More Info | State Dam Safety Program |