Bon Tempe Reservoir Report

Last Updated: December 5, 2025

Bon Tempe, also known as Bon Tempe Lake, is a vital water resource located in Marin, California, near Pt Reyes Station.


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Summary

Built in 1949 for flood risk reduction and water supply purposes, this Earth-type dam stands at a height of 98 feet, with a hydraulic height of 94 feet, and a length of 1150 feet. With a storage capacity of 4300 acre-feet and a surface area of 140 acres, this dam plays a crucial role in managing the water supply in the region.

Managed by the Public Utility, Bon Tempe is under the jurisdiction of the California Department of Water Resources for safety regulations, permitting, inspection, and enforcement. The dam, which impounds water from Lagunitas Creek, has a high hazard potential but is currently in satisfactory condition as per the last assessment in September 2017. With regular inspections and emergency action plans in place, Bon Tempe ensures the safety of the surrounding community and helps mitigate flood risks in the area.

The dam's location near a major water source and its significant storage capacity make it a key player in water resource management in the region. With Congressman Jared Huffman representing the area, Bon Tempe continues to be a critical infrastructure for flood risk reduction and maintaining a stable water supply for the residents of Marin County. Its historical significance, coupled with its modern safety measures, positions Bon Tempe as a resilient asset in the face of climate change and water resource challenges.

Year Completed

1949

Dam Length

1150

Dam Height

98

River Or Stream

Lagunitas Creek

Primary Dam Type

Earth

Surface Area

140

Hydraulic Height

94

Drainage Area

2.71

Nid Storage

4300

Hazard Potential

High

Nid Height

98
       
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.