Lemolo No 1 Reservoir Report

Last Updated: December 5, 2025

Lemolo No 1 is a captivating hydroelectric dam located in Idleyld Park, Oregon, along the picturesque North Umpqua River.


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Summary

Built in 1955 by Pioneer Service & Engineering, this rockfill dam stands at an impressive height of 120 feet and boasts a storage capacity of 19,000 acre-feet. With a primary purpose of generating hydroelectric power, the dam also provides opportunities for recreational activities in its vicinity.

Managed by the Federal Energy Regulatory Commission, Lemolo No 1 is a vital infrastructure for water resource and climate enthusiasts. The dam's controlled spillway, with a width of 100 feet, ensures the safe release of excess water during high flow events. With a hazard potential rated as high and a risk assessment indicating a very high risk level, the dam is closely monitored and inspected to ensure public safety and environmental protection.

Despite its age, Lemolo No 1 continues to play a crucial role in water management and renewable energy production in Douglas County, Oregon. Its strategic location, impressive height, and significant storage capacity make it a key player in the region's water resource infrastructure. For enthusiasts interested in water management and climate resilience, Lemolo No 1 is a fascinating example of engineering ingenuity and environmental stewardship.

Year Completed

1955

Dam Length

885

Dam Height

120

River Or Stream

North Umpqua River

Primary Dam Type

Rockfill

Surface Area

419.1

Hydraulic Height

109

Drainage Area

175

Nid Storage

19000

Structural Height

120

Outlet Gates

Tainter (radial) - 1

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

120
       
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.