Ponderosa Lake Dam Reservoir Report

Last Updated: December 5, 2025

Ponderosa Lake Dam, located in Milan, Washington, is a privately owned structure designed by Hahn Engineering.


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Summary

Completed in 1969, this earth dam on Beaver Creek serves primarily for recreational purposes, offering a serene setting for water enthusiasts to enjoy activities such as fishing and boating. With a hydraulic height of 68 feet and a structural height of 55 feet, the dam provides a storage capacity of 710 acre-feet, with a normal storage level of 357 acre-feet covering a surface area of 75 acres.

Despite its recreational significance, Ponderosa Lake Dam poses a high hazard potential and has been assessed as being in poor condition as of the last inspection in 2015. The dam is regulated by the Washington Department of Ecology, with state permitting, inspection, and enforcement procedures in place to ensure public safety. In the event of an emergency, an Emergency Action Plan (EAP) may be activated, although details on its preparation and compliance with guidelines are currently unavailable.

As climate change continues to impact water resources and infrastructure, the maintenance and safety of dams like Ponderosa Lake Dam become increasingly crucial. With its location in a beautiful natural setting and its important role in providing recreational opportunities, ongoing monitoring and potential upgrades to address the dam's condition and hazard potential are essential to protect both the environment and the community that enjoys this picturesque water resource.

Year Completed

1969

River Or Stream

Beaver Creek

Primary Dam Type

Earth

Surface Area

75

Hydraulic Height

68

Drainage Area

7.7

Nid Storage

710

Structural Height

55

Hazard Potential

High

Foundations

Soil

Nid Height

68
       
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.