Technical Manual: Conduits through Embankment Dams (FEMA 484)

Table 11.1.—Assessing emergency classification and urgencyLevel of urgency and responseIncidentNon emergency Potential dam failure Embankment dam failure iscondition.—New or developing.—Possible embankment dam imminent.—Embankment dam failureincreased problem. Change failure is developing. Condition of has occurred, is occurring, or is about toin existing condition. embankment dam is deteriorating occur.rapidly.Response and Monitor condition and call Monitor condition; take appropriate Commence the appropriate emergencynotification for assistance. Contact the remedial actions; emergency response operations and response and evacuationpriority State dam safety officials personnel on standby-alert status; and of affected downstream residents.and/or design consultant. begin mobilizing for failure, if required. Contact emergency manager andContact design consultant, general response personnel, design consultant,construction contractor, the State dam general construction contractor, and thesafety officials, and emergency manager State dam safety officials.and response personnel.Problem orconditionExamples of possible observationsInternal Small amount of sediment in New, stable or slowly increasing seepage Rapidly increasing seepage transportingerosion and seepage or drains. rates transporting some sediment. large amounts of sediments. Sinkholesbackward Significant amount of sediment in on embankment dam or abutments,erosion piping seepage, drains muddy water. Reservoir whirlpool in reservoir, significantlevel is falling without apparent cause settlement of embankment dam,(such as outlet works or spillwaysignificant muddy water. Whirlpool orreleases).other signs of the reservoir drainingrapidly through the embankment dam orfoundation.Seepage Downstream slope of Significant new or increasing seepage or Rapidly increasing seepage and/orembankment dam is wet, sand boils downstream from the transporting large quantities ofsoft; minor sloughing; water embankment dam. Seepage is causing materials. Sand boils rapidly increasingrunning down dam face or slides, which narrows the embankment in size or number and/or rapidlyabutment groins. dam cross section, or settlement of dam increasing flows. Seepage has causedcrest and loss of freeboard.large slides, which have reducedfreeboard to the reservoir level, and/orembankment dam is overtopping due toloss of freeboard.Sinkholes Small depressions on Significant new or larger sinkhole(s) or Sinkhole(s) or settlement rapidlyembankment dam, abutment crest settlement. Large sinkhole over increasing in size or number. Unstableor foundation. outlet works, or on embankment dam, or increasing sinkhole over outlet works,abutment or foundation (larger than 8 or on embankment dam, abutment orin. in diameter). Stable or notfoundation. Whirlpool in reservoir.increasing in size.Settlement Minor settlement or Moderate settlement of embankment Significant settlement of thedepressions (less than 1 ft). dam crest or embankment slope (one- embankment dam crest, reservoir ishalf of normal freeboard).overtopping the dam.Conduit failure Broken gate or operator, Cracked or perforated conduit, sediment Significant, muddy seepage from orminor conduit deterioration, in seepage, deeply scoured or adjacent to conduit; sinkholes inseepage adjacent to conduit. undermined conduit. embankment over outlet conduit.266