Phoenix Lake Reservoir Report

Last Updated: December 5, 2025

Phoenix Lake, located in Marin County, California, is a vital water resource managed by a public utility.


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Summary

The dam, completed in 1907, stands at 90 feet high and has a storage capacity of 612 acre-feet. The primary purpose of the dam is water supply, serving the surrounding area through Ross Creek.

With a high hazard potential, Phoenix Lake is under the regulatory oversight of the California Department of Water Resources, Safety of Dams division. Regular inspections ensure the dam's structural integrity, with the most recent assessment in September 2017 deeming its condition satisfactory. The dam's emergency action plan is up-to-date, reflecting the commitment to maintaining safety and preparedness in the face of potential risks.

Enthusiasts of water resources and climate will find Phoenix Lake to be a fascinating example of a century-old earth dam supporting crucial water supply infrastructure in California. Its history, design, and ongoing management showcase the importance of effective regulation and maintenance to ensure the continued resilience of our water resources in the face of changing climate conditions.

Year Completed

1907

Dam Length

320

Dam Height

90

River Or Stream

Ross Creek

Primary Dam Type

Earth

Surface Area

23

Hydraulic Height

74.8

Drainage Area

2.2

Nid Storage

612

Hazard Potential

High

Nid Height

90
       
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.