Margaret Lake Dam

Margaret Lake Dam is an earth dam located in King County, Washington, built in 1933. It carries a High hazard potential classification and has a fair condition assessment.

About Margaret Lake Dam

The primary purpose of Margaret Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Lake Margaret Purposes Community Club (private). It impounds the Margaret Creek.

The dam stands 41 feet tall and stretches 480 feet across, creates a reservoir covering 52 acres, has a maximum storage capacity of 1,210 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1933, the structure is well-established, with more than 75 years of service.

This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 07/21/2020.

At 41 feet, this dam is taller than 88% of dams nationwide.

Living Downstream

If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Washington dam safety program can provide more specific information about emergency planning for this structure.

Search for dams near your address to see all dams in your area with hazard classifications and safety data.

High HazardFair ConditionEmergency Action Plan: Yes

Location

StateWashington
CountyKing
River/StreamMargaret Creek
Coordinates47.76698, -121.90143

Physical Characteristics

Dam TypeEarth
NID Height41 ft
Dam Length480 ft
Year Completed1933 (93 years old)

Storage & Hydraulics

NID Storage1,210 acre-ft
Max Storage1,210 acre-ft
Normal Storage820 acre-ft
Surface Area52 acres
Drainage Area2 sq mi
Max Discharge750 cfs

Ownership & Safety

PurposeRecreation
OwnerLake Margaret Purposes Community Club
Owner TypePrivate
Hazard ClassificationHigh
Condition AssessmentFair
Last Inspection07/21/2020
Emergency Action PlanYes

Identifiers

NID IDWA00236
Federal IDWA00236
More InfoState Dam Safety Program

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