LONG LAKE DAM - AK00044-2651

Incident ID AK00044-2651
Downstream Hazard Potential L
State AK
Incident Date 09/11/2015
Incident Type Non-failure
Incident Driver Hydrologic/flooding
Incident Mechanism 1 Gate/valve Failure
Incident Mechanism 2
Incident Mechanism 3
Incident Description Heavy rain event (7.73 in 24 hrs & 2.8 in earlier in the week) resulted in a rainfall induced flood event during which a section of the wooden flashboards failed.
Named Hydrologic Event
EAP Enacted (Y/N) due to Incident
Fatalities (Number) 0
Number of People Evacuated 0
Number of Habitable Structures Evacuated 0
Number of Habitable Structures Flooded 0
Other Infrastructure Impacts
Economic Damages (in $)
Volume released at failure (ac-ft)
Additional Remarks or Updates “The flashboards include a 20ft.x1ft. notch, near the south end of the dam, that will pass a nominal flow of 75 cfs. All additional flows will overtop the flashboards along the length of the dam. Based on the 1999 stability analysis, the flashboards are expected to fail at flood flows above 4500 cfs. This is a storm with a return interval of 10 years. The dam is located in a very remote area and there is no development downstream of the dam.
Incident Time
Incident Duration
Incident Report Produced Yes
Information Sources AK DNR
Owner Type U
Dam Type CNPG
Primary Purpose(s) H
Year Completed 1973
Year Modified 0
Dam Height 30 ft
Max Storage (ac-ft) 147000 ac-ft
Surface Area (acres) 1375 acres
Latitude 58.1667
Longitude -133.733
Regulatory Agency(ies) AKDNR
NID Number AK00044
Attachments Y