Olson Reservoir Report

Last Updated: December 5, 2025

Olson, located in Napa, California, is a privately owned dam on Ledgewood Creek with a primary purpose of water supply for irrigation and other uses.


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Summary

Completed in 1955, this earth dam stands at a height of 45 feet and spans 646 feet in length, with a storage capacity of 200 acre-feet. The dam has a high hazard potential but is currently in satisfactory condition, last assessed in September 2017.

Regulated by the California Department of Water Resources for safety, Olson undergoes regular inspections and enforcement to ensure its integrity and compliance with state regulations. The dam's location in Palo Cedro, near San Francisco District, makes it a critical water resource for the region. While the dam has not been modified in recent years and lacks certain features like spillways and locks, its importance for water supply in the area cannot be understated.

Water resource and climate enthusiasts can appreciate the significance of Olson as a vital infrastructure for water management in California. With its historical significance, high hazard potential, and regulatory oversight, Olson serves as a key player in the state's water supply system. As climate change continues to impact water resources, understanding and monitoring dams like Olson is crucial for ensuring sustainable water management practices in the face of environmental challenges.

Year Completed

1955

Dam Length

646

Dam Height

45

River Or Stream

Ledgewood Creek

Primary Dam Type

Earth

Surface Area

13

Hydraulic Height

40

Drainage Area

0.45

Nid Storage

200

Hazard Potential

High

Nid Height

45
       
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.