Rule 1501:21-13-04 | Pipe conduit spillways, general requirements.
(A) All pipe conduits shall convey flow at the maximum design velocity without damage to the interior surface.
(B) Seepage control devices acceptable to the chief shall be installed.
(C) Adequate allowances shall be incorporated in the design to compensate for settlement and possible elongation of the pipe conduit.
(D) An anti-vortex device that is satisfactory to the chief shall be installed at the intake of all pipe and riser spillway systems. Anti-vortex devices may also be required for other spillway types as necessary to improve the performance of the spillway.
(E) A trash rack that is satisfactory to the chief shall be installed at the intake of all pipe and riser and/or drop inlet type spillway systems to prevent clogging the pipe conduit. Trash rack devices may also be required for other spillway types as necessary to ensure the performance of the spillway.
(F) An emergency overflow spillway is required, except when specifically exempted by the chief. A vegetated or unlined emergency spillway will be approved by the chief, but only after the applicant has demonstrated that it will pass the design flood without jeopardizing the safety of the structure. The average frequency of use for a vegetated or unlined emergency spillway must be predicted to be less than the following criteria unless otherwise approved by the chief:
(1) Once in fifty years for class I dams;
(2) Once in twenty-five years for class II dams; and
(3) Once in ten years for class III dams.
(G) The pipe conduit shall be of such size as to remove from the reservoir within ten days following passage of the design flood peak at least eighty percent of the water temporarily detained in the reservoir above the elevation of the primary (principal) spillway.
Last updated June 27, 2024 at 10:17 PM
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