Argyle No. 2 Reservoir Report

Last Updated: December 5, 2025

Argyle No.


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Summary

2, also known as Sobrante Reservoir, is a public utility water supply dam located in El Sobrante, California. Constructed in 1970, this offstream dam stands at a height of 27 feet and has a storage capacity of 22 acre-feet. Managed by the California Department of Water Resources (DWR), this dam is crucial for providing water to the surrounding communities in Contra Costa County.

With a high hazard potential, Argyle No. 2 is regularly inspected and maintained to ensure its safety and structural integrity. The dam has been assessed as satisfactory, with the most recent inspection conducted in March 2021. The Emergency Action Plan (EAP) for this dam was last revised in January 2018, highlighting the importance of preparedness and risk management measures in case of emergencies. As a vital water resource structure in the region, Argyle No. 2 plays a key role in water supply and management efforts, especially in the context of changing climate conditions and increasing water demand.

Year Completed

1970

Dam Length

875

Dam Height

27

River Or Stream

Offstream

Primary Dam Type

Other

Surface Area

1

Hydraulic Height

26

Nid Storage

22

Hazard Potential

High

Nid Height

27
       
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.