Current through Register Vol. XLI, No. 24, June 14, 2024
Section 47-34-9 - Breaching of a Dam9.1. Application to Breach a Dam - The owner of a dam must obtain a certificate of approval from the Secretary prior to the breaching of the dam. A complete application in accordance with the provisions of subsection 5.1. must be submitted to and approved by the Secretary prior to the commencement of breaching activities. 9.1.a. Plan Package Requirements - The plan package submitted in order to breach a dam shall be in accordance with the applicable requirements of section 6 and must also include the specific requirements delineated in subsection 9.2 through subsection 9.10. Narratives, plans, or specifications required under section 6 which are clearly not applicable to the proposed breaching activities may be omitted from the submittal; however, the Secretary reserves the right to specify those items which must be included in the breaching plan package.9.2. Breach Dimensions - The breach opening in the dam shall be designed so that any water resulting from design storm inflows that is temporarily impounded behind the residual structure shall be less than the height and storage requirements of a "dam" set forth in subsection 2.12. The breach shall be to original stream bottom level, except that a small impoundment of less than one (1) acre-foot storage may be retained for sediment control purposes.9.3. Breach Channel - The embankment shall be breached with a designed channel having the capacity to carry the peak runoff from the design storm corresponding to the dam's hazard classification. The channel created by the breach shall have an erosion-preventive lining adequate to withstand the depth and velocity of the peak flows from a P100 rainfall event. The channel side slopes shall achieve a minimum stability factor of safety of 1.5.9.4. Safety - Reservoirs shall be completely drained before breaching operations begin. Breaching work shall be scheduled during dry weather using National Weather Service advice and proceed quickly to reduce the potential for impounding water.9.5. Blasting - If blasting is to be used in the breaching of a dam, a blasting plan shall be submitted to the Secretary for approval. The plan shall include the distance to existing structures and the measures that will be taken to minimize air blast and flying materials. A pre-blast survey of existing nearby structures and water wells which may be affected by blasting may be required by the Secretary.9.6. Erosion and Sediment Control - Erosion and sediment control measures sufficient to comply with the provisions of paragraph 8.1.m. shall be implemented during the breaching operation. The following measures shall also be implemented: 9.6.a. Reservoir areas, and the sediment deposits therein, shall be protected from erosion after the impounding capability has been eliminated by the breaching of the dam;9.6.b. Silt deposits and barren areas in the reservoir shall be stabilized and revegetated;9.6.c. Disturbed areas, including the faces on any remaining embankment, must be protected by vegetation or other means approved by the Secretary;9.6.d. A channel in the reservoir sediment may be required by the Secretary in order to reestablish a stream channel; and9.6.e. Permanent sediment basins, subject to ongoing maintenance, may be required by the Secretary if the dam owner cannot demonstrate the effectiveness of other structural and vegetative measures in stabilizing the reservoir area and dam site.9.7. Placement of Earthen Material - Material removed from the dam shall be placed in waste disposal areas delineated in the approved plan package. The material shall be graded and compacted as necessary and stabilized from erosion by vegetation or other means approved by the Secretary.9.8. Placement of Non-Earthen Material - Concrete rubble and other rock material shall be placed in waste disposal areas delineated in the approved plan package. The material shall be placed in a manner to reduce hazardous conditions; protruding metal, wire, or bars are prohibited. The requirements of subdivision 8.1.n. shall apply to the disposal of any other waste materials generated by the breaching operation.9.9. Galleries and Drains - The effect of flows through the breach and backwater pressure on galleries and drains shall be evaluated. The galleries and drains shall be vented or sealed as necessary to prevent failure of the remaining structure. 9.10. Safety of Remaining Structure - The remaining structure shall have sufficient strength to support the maximum hydraulic loading without failure. The engineer shall attempt to reduce or eliminate hazards associated with an "attractive nuisance."9.11. Construction Practices - The requirements of section 8 shall apply when breaching a dam unless clearly not applicable to the breaching operation; however, the Secretary reserves the right to specify which requirements are applicable.