Usibelli No. 2 Reservoir Report

Last Updated: December 5, 2025

Usibelli No.


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Summary

2 is a privately owned earth dam located in Pope Valley, California, specifically on the Tr Maxwell Cr river. Completed in 1973, this dam serves primarily for water supply purposes such as irrigation and water storage. With a height of 26 feet and a storage capacity of 900 acre-feet, it covers a surface area of 56 acres and has a drainage area of 0.23 square miles. The dam is regulated, inspected, and enforced by the California Department of Water Resources, Safety of Dams division.

Despite its satisfactory condition assessment as of September 2017, Usibelli No. 2 has a high hazard potential, highlighting the importance of regular inspections and maintenance. The dam has a designated emergency action plan (EAP) and a one-year inspection frequency to ensure its safety and functionality. The surrounding area, including Napa County, relies on this dam for crucial water supply needs, making it a vital infrastructure for the region's agricultural and environmental sustainability.

Owned by a private entity, Usibelli No. 2 plays a significant role in water resource management within the San Francisco District. Located in a picturesque setting, this dam not only supports local water supply but also showcases the intersection of engineering, water conservation, and climate resilience. As water resource and climate enthusiasts continue to monitor and advocate for sustainable practices, Usibelli No. 2 stands as a prominent example of infrastructure crucial for supporting communities and ecosystems in an ever-changing climate.

Year Completed

1973

Dam Length

3600

Dam Height

26

River Or Stream

Tr Maxwell Cr

Primary Dam Type

Earth

Surface Area

56

Hydraulic Height

20.5

Drainage Area

0.23

Nid Storage

900

Hazard Potential

High

Nid Height

26
       
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.