Mill Creek Dam Cosmopolis Reservoir Report

Last Updated: December 15, 2025

Located in Cosmopolis, Washington, the Mill Creek Dam serves as a vital structure for the local community, primarily functioning as a Fish and Wildlife Pond.


°F

°F

mph

Wind

%

Humidity

Summary

Completed in 2019, the Earth-type dam stands at a height of 20 feet with a hydraulic height of 20 feet. The dam's purpose extends beyond wildlife conservation, providing opportunities for recreation as well.

Managed by the Washington Department of Ecology, the Mill Creek Dam is subject to state regulation, inspection, and enforcement. With a high hazard potential, the dam's condition was last assessed as satisfactory in August 2019. Despite its critical role in water resource management, the dam does not have a spillway system or outlet gates, highlighting the importance of regular inspection and maintenance to mitigate potential risks.

As a key component of the local ecosystem, Mill Creek Dam plays a crucial role in preserving the surrounding environment and supporting recreational activities. With its strategic location in Grays Harbor County, the dam serves as a testament to the intersection of water resource management and climate conservation efforts in the region.

Year Completed

2019

Dam Length

200

River Or Stream

Mill Creek

Primary Dam Type

Earth

Surface Area

10

Hydraulic Height

20

Drainage Area

1.68

Nid Storage

20

Structural Height

20

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

20
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.