BLAIRS POND DAM - DE00070-1205

Incident ID DE00070-1205
Dam Name BLAIRS POND DAM
Downstream Hazard Potential H
State DE
Incident Date 08/28/2011
Incident Type Non-failure
Incident Driver Hydrologic/flooding
Incident Mechanism 1 Erosion
Incident Mechanism 2
Incident Mechanism 3
Incident Description Prolonged discharge at a higher than normal rate through a concrete overflow spillway exacerbated erosion of a known void in the soil beneath the spillway.
Named Hydrologic Event Irene
EAP Enacted (Y/N) due to Incident No
Fatalities (Number)
Number of People Evacuated 0
Number of Habitable Structures Evacuated
Number of Habitable Structures Flooded 0
Other Infrastructure Impacts
Economic Damages (in $) None
Volume released at failure (ac-ft) 0 ac-ft
Response
Additional Remarks or Updates Void was discovered under the left downstream edge of the spillway during an inspection in August 2011, and had not been repaired prior to Irene. The immediate post-Irene inspection did not reveal any change in the size of the void, but 11 days after the storm a sinkhole developed near the left upstream corner of the spillway. The remaining flashboards were removed from the spillway to lower the pond level below the spillway elevation and the void was filled with concrete on 9/9/2011. Subsequent repairs will be made to seal open construction joints and cracks in the spillway slab, which are thought to be the source of leakage through the slab that caused the void to develop.
Incident Time
Incident Duration
Incident Report Produced
Information Sources
Owner Type S
Dam Type REPG
Primary Purpose(s) RF
EAP N
Year Completed 0
Year Modified 0
Dam Height 14 ft
Max Storage (ac-ft) 611 ac-ft
Surface Area (acres) 48 acres
River Name BEAVERDAM BRANCH
Latitude 38.904
Longitude -75.4848
Regulatory Agency(ies) DNREC
NID Number DE00070
Attachments