Lower Slate Lake Back Dam - AK00320-3593
Dam Name: Lower Slate Lake Back Dam
State: AK
Downstream Hazard Potential: S
Incident Type: Non-Failure
Incident Date: 09/18/2023
Incident Driver: Hydrologic/Flooding
Incident Mechanism 1: Overtopping
Incident Mechanism 2Spillway Deficiency
Incident Mechanism 3Other
Incident IDAK00320-3593
Incident Description9/18 a cofferdam protecting AK00320 embankment construction work was overtopped and an partially eroded allowing water to flow freely into the tailings reservoir. Water eroded portions fo the AK00320 construction works. On 10/8 A temporary diversion line failed due to high flows and pressure allowing water to flow freely into the tailings reservoir.
Named Hydrologic Event
EAP Enacted (Y/N) due to IncidentYes
Fatalities (Number)
Number of People Evacuated
Number of Habitable Structures Evacuated
Number of Habitable Structures Flooded
Other Infrastructure Impacts
Economic Damages (in $)
Response
Volume released at failure (ac-ft)
Additional Remarks or Updatesincident did not involve an uncontrolled release of contact water, but did have impact on the overall site water balance that took about a year to resolve.
Owner TypeP
Dam TypeER
Primary Purpose(s)T
EAPY
Dam Height44 ft
Max Storage (ac-ft)910.00
Surface Area (acres)75.00
Year Completed2024
NID NumberAK00320
River NameEast Fork Slate Creek
Latitude58.8136
Longitude-135.04
Year Modified
Regulatory Agency(ies)AK DNR
Incident Time7:00 AM
Incident Durationapprox 1 month
Incident Report ProducedUnknown
Information SourcesAK DNR
