Bean Hollow #2 Reservoir Report

Last Updated: December 5, 2025

Bean Hollow #2, also known as De Los Frijoles Reservoir, is a privately owned dam located in San Mateo, California.


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Summary

This earth dam was completed in 1938 and serves primarily for water supply purposes, including irrigation. The reservoir has a storage capacity of 900 acre-feet and covers a surface area of 43 acres, with a drainage area of 1.38 square miles along the Ar De Los Frijoles stream.

With a dam height of 31 feet and a hydraulic height of 26 feet, Bean Hollow #2 has a low hazard potential and is considered to be in satisfactory condition as of the last assessment in September 2017. The dam is regulated and inspected by the California Department of Water Resources (DWR) under the Safety of Dams program. The last inspection was conducted in February 2020, with a frequency of one inspection per year to ensure the safety and integrity of the structure.

Located near the Pacific Ocean, Bean Hollow #2 plays a crucial role in providing water supply for the surrounding area. With its historical significance dating back to the late 1930s, this reservoir continues to be a vital resource for the community while also maintaining a low risk profile and meeting regulatory guidelines set forth by the state.

Year Completed

1938

Dam Length

325

Dam Height

31

River Or Stream

Ar De Los Frijoles

Primary Dam Type

Earth

Surface Area

43

Hydraulic Height

26

Drainage Area

1.38

Nid Storage

900

Hazard Potential

Low

Nid Height

31
       
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.