Blanchard-Offner Reservoir Report

Nearby: Heitz Duvall

Last Updated: December 5, 2025

Blanchard-Offner, also known as Lake Rodney, is a private dam located in Napa, California, specifically in the city of Aetna Springs.


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Summary

This earth dam was completed in 1963 and stands at a height of 47 feet, with a hydraulic height of 43 feet. It serves multiple purposes including flood risk reduction, irrigation, recreation, and water supply, with a storage capacity of 274 acre-feet.

Managed by the Natural Resources Conservation Service, Blanchard-Offner has a high hazard potential and is considered to be in satisfactory condition as of the last assessment in September 2017. The dam spans a length of 785 feet and has an associated surface area of 19 acres, with its primary function being flood risk reduction. The dam is regulated and permitted by the California Department of Water Resources, ensuring its safety and compliance with state standards.

Located near Tr Pope Creek, Blanchard-Offner plays a crucial role in managing water resources in the region. Its strategic placement and multiple functions make it a vital infrastructure for the community, safeguarding against floods while providing essential water for irrigation and recreation activities. Enthusiasts of water resources and climate management will find Blanchard-Offner to be a noteworthy example of sustainable infrastructure design and management in California.

Year Completed

1963

Dam Length

785

Dam Height

47

River Or Stream

Tr Pope Creek

Primary Dam Type

Earth

Surface Area

19

Hydraulic Height

43

Nid Storage

274

Hazard Potential

High

Nid Height

47
       
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.