Koehn Ranch Reservoir Reservoir Report

Last Updated: December 15, 2025

Koehn Ranch Reservoir, located in Grant, Washington, is a private earth dam structure designed by JUB Engineers for irrigation purposes.


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Summary

Completed in 2009, this reservoir has a storage capacity of 20 acre-feet with a normal storage of 16.7 acre-feet. With a surface area of 2.1 acres and a hydraulic height of 13 feet, Koehn Ranch Reservoir plays a vital role in supporting agricultural activities in the region.

Despite its relatively small size, Koehn Ranch Reservoir's high hazard potential and fair condition assessment make it an important water resource in the area. The dam structure, built with a core of rockfill on soil foundation, stands at a height of 13 feet and spans 850 feet in length. As a state-regulated facility under the jurisdiction of the Washington Dept of Ecology, regular inspections are conducted to ensure the safety and integrity of the reservoir.

In the event of emergencies, the reservoir's Emergency Action Plan (EAP) is periodically reviewed and updated to meet safety guidelines. With its strategic location and contribution to irrigation activities in the region, Koehn Ranch Reservoir serves as a valuable asset for water resource management and climate resilience efforts in Washington.

Year Completed

2009

Dam Length

850

Primary Dam Type

Earth

Surface Area

2.1

Hydraulic Height

13

Nid Storage

20

Structural Height

13

Hazard Potential

High

Foundations

Soil

Nid Height

13
       
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.