Oak Site Reservoir Report

Last Updated: December 5, 2025

Oak Site is a state-regulated dam located in Santa Cruz, California, specifically in the city of Swanton.


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Summary

Built in 1969, this earth dam stands at 43 feet high with a hydraulic height of 37 feet, providing essential water supply for irrigation and domestic use. With a storage capacity of 20 acre-feet and a surface area of 2 acres, Oak Site is a crucial infrastructure that supports water management in the region.

Managed by the California Department of Water Resources (DWR) under the Safety of Dams program, Oak Site has a low hazard potential and is currently in satisfactory condition as of the last assessment in September 2017. The dam is inspected annually to ensure its structural integrity and safe operation. While no emergency action plan (EAP) is currently in place, the dam's risk management measures and guidelines are continuously evaluated to meet safety standards and mitigate potential risks associated with its operations.

Despite its relatively modest size and hazard potential, Oak Site plays a significant role in the local water resource management system. As a vital infrastructure for water supply, this dam serves as a testament to California's commitment to safeguarding its water resources and ensuring the resilience of its hydraulic infrastructure in the face of climate change challenges.

Year Completed

1969

Dam Length

290

Dam Height

43

River Or Stream

Tr Big Creek

Primary Dam Type

Earth

Surface Area

2

Hydraulic Height

37

Drainage Area

0.08

Nid Storage

20

Hazard Potential

Low

Nid Height

43
       
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.