Loon Lake Polishing Lagoon Reservoir Report
Last Updated: December 5, 2025
Loon Lake Polishing Lagoon in Stevens, Washington, is a vital water resource managed by the Washington Dept of Ecology.
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Summary
This Earth dam, completed in 1986, serves as a crucial part of the Tr-Loon Lake-Offstream water system, with a hydraulic height of 12 feet and a storage capacity of 41 acre-feet. The lagoon covers a surface area of 3.9 acres and plays a key role in water purification and quality control for the region.
Despite its satisfactory condition assessment and regular inspections, the Loon Lake Polishing Lagoon poses a high hazard potential, highlighting the importance of effective risk management and emergency preparedness. With a drainage area of 0.01 square miles and a maximum discharge rate of 2 cubic feet per second, the lagoon's impact on the surrounding environment and community cannot be understated. The presence of public utility ownership and state regulation further emphasize the significance of this water infrastructure in ensuring the well-being of local residents and preserving the natural ecosystem.
As climate change continues to impact water resources and infrastructure, the Loon Lake Polishing Lagoon stands as a critical component in maintaining water quality and availability in the region. With its earth dam structure and rockfill core, this lagoon serves as a testament to the ongoing efforts to manage and protect water resources in the face of evolving environmental challenges. As enthusiasts of water resources and climate resilience, understanding and supporting the maintenance and regulation of facilities like the Loon Lake Polishing Lagoon is essential for safeguarding our communities and natural surroundings for generations to come.
Year Completed |
1986 |
River Or Stream |
Tr-Loon Lake-Offstream |
Primary Dam Type |
Earth |
Surface Area |
3.9 |
Hydraulic Height |
12 |
Drainage Area |
0.01 |
Nid Storage |
41 |
Structural Height |
12 |
Hazard Potential |
High |
Foundations |
Rock, Soil |
Nid Height |
12 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Loon Lake Polishing Lagoon