Koa Dam No 1 is an earth dam located in Lewis County, Washington, built in 1965. It carries a Low hazard potential classification.
Dam profile
NID height · 18 ft18 ft tall and 330 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 Koa Dam No 1
The primary purpose of Koa Dam No 1 is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Mhc Ltra Inc (private). It impounds the Tr-mill Creek near Salkum.
The dam stands 18 feet tall and stretches 330 feet across, creates a reservoir covering 50 acres, has a maximum storage capacity of 67 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1965, the structure is well into its service life at over 50 years old.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life.
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Location
| State | Washington |
| County | Lewis |
| Nearest City | Salkum |
| River/Stream | Tr-mill Creek |
| Coordinates | 46.54932, -122.58488 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 18 ft |
| Dam Length | 330 ft |
| Year Completed | 1965 (61 years old) |
Storage & Hydraulics
| NID Storage | 67 acre-ft |
| Max Storage | 67 acre-ft |
| Normal Storage | 50 acre-ft |
| Surface Area | 50 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 162 cfs |
Ownership & Safety
| Purpose | Recreation |
| Owner | Mhc Ltra Inc |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Not assessed |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | WA00110 |
| Federal ID | WA00110 |
| More Info | State Dam Safety Program |