Green Peter Dam Reservoir Report

Last Updated: December 13, 2025

Green Peter Dam, located on the Middle Santiam River in Oregon, was completed in 1967 by the US Army Corps of Engineers for flood risk reduction, hydroelectric power generation, irrigation, navigation, and recreation purposes.


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Summary

The gravity dam stands at 320 feet tall and has a storage capacity of 430,000 acre-feet, covering a surface area of 3,720 acres. Despite being classified as having a high hazard potential, a recent risk assessment conducted by USACE in 2020 deemed the dam's risk level to be low, with no immediate need for modifications or short-term measures.

USACE continues to monitor and evaluate the condition and risks associated with Green Peter Dam through routine inspections and advanced studies. The dam is equipped with instrumentation for performance monitoring and seismic activity detection. In the event of an earthquake, post-earthquake procedures are in place for inspection and evaluation of any damages. The Emergency Action Plan (EAP) for Green Peter Dam outlines emergency response procedures, and USACE is committed to updating the EAP based on the latest risk assessment results and inundation maps, as well as increasing community awareness of flood risks and dam-related risks.

Although the Willamette Valley dams, including Green Peter Dam, play a crucial role in reducing flood risks for the region, they cannot completely eliminate the potential for flooding during extreme weather events. USACE remains confident in the structural integrity of the dams and their ability to mitigate flood risks, but acknowledges the possibility of flooding downstream in communities along the South Santiam River in the event of extreme rainfall or snowmelt.

Year Completed

1967

Dam Length

1517

Dam Height

320

River Or Stream

MIDDLE SANTIAM RIVER

Primary Dam Type

Gravity

Surface Area

3720

Hydraulic Height

319

Drainage Area

277

Nid Storage

430000

Structural Height

378

Hazard Potential

High

Foundations

Rock

Nid Height

378
       
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.