Green Oaks #1 Reservoir Report

Last Updated: December 5, 2025

Green Oaks #1 is a privately owned earth dam located in San Mateo County, California, along Green Oaks Creek.


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Summary

Completed in 1936, the dam stands at 39 feet high and has a storage capacity of 322 acre-feet. Its primary purpose is flood risk reduction, with additional benefits including hydroelectric power generation and water supply.

The dam is regulated and inspected by the California Department of Water Resources under the Safety of Dams program. As of the last inspection in March 2021, the dam was deemed to have a low hazard potential and satisfactory condition. The surrounding area has a drainage area of 1.08 square miles and a surface area of 22 acres, providing essential protection against flooding for the community.

Overall, Green Oaks #1 serves as a vital infrastructure for water resource management in the region, contributing to flood control, water supply, and environmental protection along Green Oaks Creek. With a history dating back over 80 years, the dam continues to demonstrate its importance in safeguarding the surrounding area from potential risks associated with extreme weather events and climate change impacts.

Year Completed

1936

Dam Length

880

Dam Height

39

River Or Stream

Green Oaks Creek

Primary Dam Type

Earth

Surface Area

22

Hydraulic Height

36

Drainage Area

1.08

Nid Storage

322

Hazard Potential

Low

Nid Height

39
       
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.