Mill Creek Dam Cosmopolis is a gravity dam located in Grays Harbor County, Washington, built in 2019. It carries a High hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 20 ft20 ft tall and 200 ft long. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic concrete gravity section and the water level is illustrative.
About Mill Creek Dam Cosmopolis
The primary purpose of Mill Creek Dam Cosmopolis is fish and wildlife pond. The dam creates habitat for fish and wildlife, supporting local ecosystems and potentially serving conservation goals. The dam is owned by Cosmopolis City Public Works (local government). It impounds the Mill Creek near Cosmopolis.
The dam stands 20 feet tall and stretches 200 feet across, creates a reservoir covering 10 acres, has a maximum storage capacity of 20 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 2019, the structure is relatively new.
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 10/05/2005. That was 21 years ago — unusually long for a high-hazard dam, which typically requires more frequent inspections.
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 Washington 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 | Washington |
| County | Grays Harbor |
| Nearest City | Cosmopolis |
| River/Stream | Mill Creek |
| Coordinates | 46.95047, -123.77138 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 20 ft |
| Dam Length | 200 ft |
| Year Completed | 2019 (7 years old) |
Storage & Hydraulics
| NID Storage | 20 acre-ft |
| Max Storage | 20 acre-ft |
| Normal Storage | 10 acre-ft |
| Surface Area | 10 acres |
| Drainage Area | 1 sq mi |
Ownership & Safety
| Purpose | Fish and Wildlife Pond |
| Owner | Cosmopolis City Public Works |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 10/05/2005 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WA01730 |
| Federal ID | WA01730 |
| More Info | State Dam Safety Program |