Selecting and accommodating inflow design floods for dams

Chapter 2 Selecting and Accommodating Inflow Design Floods for Dams, (Final Version) The Division of Dam Safety and Inspections, Office of Energy Projects, has revised Chapter 2 of the Engineering Guidelines on Selecting and Accommodating Inflow Design Floods for Dams.

The revised guidelines state HEC-RAS is the recommended one-dimensional model to use for performing dam break analyses but allow the use of the other one-dimensional and two-dimensional models if pre-agreed to by the Commission.

The guidelines state that existing analyses using NWS DAMBRK and FLDWAV are still acceptable, but any new or revised analyses should not use these models.

These inspections determine the extent of any damage and the need for emergency repair or other action.

Low hazard dams are inspected every 6 years, alternating between a formal SEED inspection and an Intermediate SEED inspection.

See section 2.4 for more information about the SEED inspection program The RDSO must review the SEED report and approve it before it can be included with the Engineering Assessment.

The Engineering Assessment must clearly state any significant deficiencies and costs associated with the dam(s) and must be included in the Decision Document the Regions Engineering Division gives to the Regional Director for approval (see 341 FW 1).(The SDSO may change the frequency based on size and condition of the dam.) The frequency of special inspections depends on the occurrence of an unusual event (e.g., seepage through the dam has become turbid).Those responsible for the dam must be alert to identify situations or events that may require special inspections.The Division of Engineering will set priorities and completion dates to correct deficiencies in accordance with the relative level of failure potential and downstream consequences.To determine priorities for maintenance, repair, or removal, the Division of Engineering looks at the adequacy of structures and facilities to continue serving the purpose for which they were constructed and identifies the extent of deterioration.Formal inspections are comprehensive searches for evidence of deterioration of materials, developing weaknesses, and unsafe hydraulic or structural conditions.

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