Fern Ridge Dam Reservoir Report

Last Updated: December 10, 2025

Fern Ridge Dam, also known as Fern Ridge Lake, is a Federal-owned structure located in Eugene, Oregon, along the Long Tom River.


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Summary

Completed in 1941, the earth dam stands at a height of 46 feet and serves primarily for Flood Risk Reduction. With a storage capacity of 121,000 acre-feet and a surface area of 9360 acres, the dam plays a crucial role in mitigating flood risks in the region.

However, the dam faces a high Hazard Potential due to its proximity to the Cascadia Subduction Zone fault, which poses a risk of significant earthquake-induced damage. To address this risk, the US Army Corps of Engineers (USACE) is conducting advanced risk assessments to better understand potential damages and the likelihood of an uncontrolled release of water post-earthquake. USACE is also implementing risk management measures, including routine inspections, instrumentation for monitoring dam performance, and emergency action plans to safeguard the community in case of an emergency.

Despite the potential risks, USACE remains confident in the integrity of Fern Ridge Dam and its ability to reduce flood risks for the region. The ongoing efforts to assess and manage risks associated with the dam reflect USACE's commitment to ensuring the safety and security of the surrounding communities in the face of potential natural disasters.

Year Completed

1941

Dam Length

6610

Dam Height

46

River Or Stream

LONG TOM RIVER

Primary Dam Type

Earth

Surface Area

9360

Hydraulic Height

40

Drainage Area

275

Nid Storage

121000

Structural Height

49

Hazard Potential

High

Foundations

Soil

Nid Height

49
       
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.
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Area Campgrounds