Sylvia Lake Dam Pierce Co Reservoir Report

Last Updated: December 15, 2025

Sylvia Lake Dam in Pierce County, Washington, is a privately owned structure primarily used for recreation.


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Summary

Completed in 1963, this earth dam stands at a height of 16 feet and has a length of 390 feet, creating a reservoir with a storage capacity of 142 acre-feet. The dam is located in the Tr-Puget Sound watershed, with a drainage area of 0.95 square miles and a surface area of 6.4 acres.

Managed and regulated by the Washington Department of Ecology, Sylvia Lake Dam is inspected regularly to ensure its structural integrity and safety. The dam has been assessed to be in fair condition, with a significant hazard potential. The last inspection was conducted in July 2021, with an inspection frequency of 5 years. In case of emergencies, an emergency action plan (EAP) may be in place, although details on its preparation and guidelines compliance are not specified in the data.

Sylvia Lake Dam provides not only recreational opportunities but also serves as a crucial infrastructure component in the region. With its strategic location and importance in water resource management, the dam plays a vital role in the overall ecosystem health and climate resilience of the area. As water resource and climate enthusiasts, understanding the significance of dams like Sylvia Lake Dam in maintaining water supply, flood control, and environmental sustainability is essential for advocating for their proper maintenance and management.

Year Completed

1963

Dam Length

390

River Or Stream

Tr-Puget Sound

Primary Dam Type

Earth

Surface Area

6.4

Hydraulic Height

16

Drainage Area

0.95

Nid Storage

142

Structural Height

16

Hazard Potential

Significant

Foundations

Soil

Nid Height

16
       
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.