Coen C-3 Reservoir Report

Last Updated: December 5, 2025

Coen C-3 is a privately owned earth dam located in Healdsburg, California, along the Tr Dry Creek.


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Summary

Built in 1982, this dam stands at a height of 97 feet and has a storage capacity of 480 acre-feet, primarily serving the purpose of water supply for irrigation and other uses in the area. With a low hazard potential and a satisfactory condition assessment as of September 2017, Coen C-3 is regulated by the California Department of Water Resources (DWR) and undergoes regular inspections to ensure its safety and functionality.

Situated in Sonoma County, Coen C-3 boasts a surface area of 16 acres and a drainage area of 0.32 square miles. Despite its relatively small size, this dam plays a crucial role in providing water resources for the surrounding community. Managed by a private entity, Coen C-3 is subject to state jurisdiction, permitting, inspection, and enforcement to meet regulatory standards set by the DWR. The dam's location within the San Francisco District and its proximity to Healdsburg highlight its significance in water management and supply for the region.

With its efficient design and satisfactory condition, Coen C-3 stands as a testament to effective water resource management in California. The dam's low hazard potential, along with its regular inspections and state regulatory oversight, ensures the safety and reliability of its water supply operations. As climate change continues to impact water resources, structures like Coen C-3 play a vital role in securing and managing water supplies for the future, making it a key asset for water resource and climate enthusiasts alike.

Year Completed

1982

Dam Length

627

Dam Height

97

River Or Stream

Tr Dry Creek

Primary Dam Type

Earth

Surface Area

16

Hydraulic Height

91.5

Drainage Area

0.32

Nid Storage

480

Hazard Potential

Low

Nid Height

97
       
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.