U.S. Fish & Wildlife Service Low Hazard Dams - Association of State ...

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U.S. Fish & Wildlife Service Low Hazard Dams - Association of State ...

STANDING OPERATING PROCEDURES1. Notification of RDSO and SDSO. This is essential, if time permits, since development offailure could vary in some or may respects from previous forecasts or assumptions, andadvice may be needed.2. Initiation of Remedial Action. It is recommended that at least one technically qualifiedindividual, previously trained in problem detection, evaluation, and remedial action, be at theproject or on call at all times. Depending on the nature and seriousness of the problem andthe time available, emergency actions can be initiated.6.2 Identifying and Understanding Emergency ConditionsRefuge personnel should be knowledgeable of the potential problems which can lead to damfailure. In an emergency situation, various individuals may be involved in the decision-makingprocess. If a problem is noted early, the RDSO and SDSO can be contacted to recommend andhelp implement corrective measures. If there is any question as to the seriousness of anobservation, the RDSO should be contacted. Acting promptly may avoid a possible dam failure.Since only superficial inspections of a dam can usually be made, it is important that Refugepersonnel be aware of the prominent types of failures and their revealing signs. The manner inwhich a dam fails and the particular causes of failure are usually varied, multiple, complex, andinterrelated. However, failure modes may be divided into three general categories.6.2.1 Embankment OvertoppingOvertopping failures result from the erosive action of water overtopping theembankment. Erosion is due to the uncontrolled flow of water over, around and adjacentto the dam. Earth embankments are generally not designed to be overtopped andtherefore are particularly susceptible to erosion. Once erosion has begun duringovertopping, it is almost impossible to stop. A well vegetated earth embankment maywithstand limited overtopping if its top is level and water flows over the top and downthe face as an evenly distributed sheet without becoming concentrated.Figure 6-1: Dam Overtopping During a Flood6-2Revision No. 0October 2008

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