Timothy Lake Reservoir Report

Last Updated: December 13, 2025

Timothy Lake, located in Clackamas County, Oregon, is a captivating reservoir with a primary purpose of hydroelectric power generation.


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Summary

This private-owned lake, managed by the Federal Energy Regulatory Commission, holds a significant storage capacity of 66,000 acre-feet and covers an expansive surface area of 1,430 acres. The dam, completed in 1956, stands at a height of 100 feet and has a controlled spillway to manage water flow.

The Oak Grove River feeds into Timothy Lake, providing a vital water source for the surrounding area. The lake is not only essential for hydroelectric power but also serves as a recreational destination for visitors seeking outdoor activities such as fishing, boating, and hiking. With a maximum discharge capacity of 16,000 cubic feet per second, the dam plays a crucial role in regulating water flow and ensuring safety for downstream areas.

Despite its high hazard potential, Timothy Lake has not undergone a recent condition assessment. However, emergency preparedness measures are in place, with an Emergency Action Plan last revised in May 2021. With its strategic location and impressive infrastructure, Timothy Lake continues to be a significant contributor to water resource management and climate resilience efforts in the region.

Year Completed

1956

Dam Length

740

Dam Height

100

River Or Stream

Oak Grove River

Primary Dam Type

Earth

Surface Area

1430

Hydraulic Height

91.9

Drainage Area

54

Nid Storage

69000

Structural Height

100

Outlet Gates

Tainter (radial) - 2

Hazard Potential

High

Nid Height

100
       
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.