Seneca Reservoir Report

Last Updated: December 5, 2025

Seneca, located in Oakland, California, is a crucial water supply dam managed by a public utility.


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Summary

Completed in 1950, this earth dam stands at 40 feet high and has a storage capacity of 92 acre-feet. With a primary purpose of water supply, Seneca plays a vital role in providing water to the surrounding area.

Managed by the Department of Water Resources and Safety of Dams, Seneca is regulated and inspected regularly to ensure its safety and functionality. The dam has a low hazard potential and has been assessed to be in satisfactory condition as of September 2017. With a last inspection date in October 2019, Seneca is continually monitored to meet safety standards and emergency preparedness guidelines.

Situated in Alameda County, Seneca is part of the Sacramento District and serves as an offstream reservoir. With its strategic location and vital role in water supply, Seneca is a significant structure contributing to water resource management in the region. For water resource and climate enthusiasts, Seneca's presence highlights the importance of sustainable water infrastructure and the need for continuous monitoring and maintenance to ensure a stable water supply in the face of changing climate conditions.

Year Completed

1950

Dam Length

1520

Dam Height

40

River Or Stream

Offstream

Primary Dam Type

Earth

Surface Area

5

Hydraulic Height

36

Nid Storage

92

Hazard Potential

Low

Nid Height

40
       
Seasonal Comparison

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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.