Harriet Lake Reservoir Report

Last Updated: December 13, 2025

Harriet Lake, located in Clackamas County, Oregon, is a privately owned reservoir primarily used for hydroelectric power generation.


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Summary

Constructed in 1923, this arch dam stands at 68 feet tall and spans 186 feet in length, with a storage capacity of 400 acre-feet. The lake covers an area of 22 acres and is fed by the Oak Grove River, with a maximum discharge rate of 11,200 cubic feet per second.

Despite its age, Harriet Lake boasts a low hazard potential and a moderate risk assessment rating. While the condition assessment is not currently available, the dam is inspected annually by the Federal Energy Regulatory Commission to ensure its safety and compliance with regulations. The spillway, with a width of 134 feet, is uncontrolled, adding to the recreational opportunities and potential for downstream water management.

Although privately owned, Harriet Lake offers not only hydroelectric power but also recreational opportunities for visitors. With its scenic location and historical significance, this dam serves as a vital resource in the region's water management infrastructure while providing a picturesque backdrop for those who visit.

Year Completed

1923

Dam Length

186

Dam Height

68

River Or Stream

Oak Grove River

Primary Dam Type

Arch

Surface Area

22

Drainage Area

131

Nid Storage

400

Structural Height

68

Hazard Potential

Low

Nid Height

68
       
Seasonal Comparison

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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.