Dams and Reservoirs - Permitting Process
The requirement to obtain a permit applies to construction of new dams that meet the size to be regulated, as well as to alterations, repairs, and removals of existing dams that are regulated. Any new dam or repair, alteration, or removal of an existing dam that is 25 feet or more in height and/or impounds 50 acre-feet must be permitted before any work may begin unless the dam is exempt from regulation.
The process to follow in obtaining a permit is covered in the Dams and Reservoirs Safety Act Regulations, R72-1. An outline of that process is given here.
After submittal of a complete application package, the first step taken by the Department in the permitting process is determination of the hazard potential classification that will be assigned to the proposed dam. As covered in the Regulations, dams are classified into one of three hazard classifications (determined by what is located below the dam in the area that would be impacted by potential failure of the dam): high hazard, significant hazard, or low hazard. Final decision on the proper classification to be assigned to the dam is made by the DHEC Dams and Reservoirs Safety Section. Please note that the design engineer (or the NRCS, as appropriate) should consult with DHEC on the classification before spending a lot of design time that might have to be redone, because the hazard classification of the dam determines minimum spillway requirements, testing that may be required to be done at the site, and other engineering requirements. For example, if the dam is classified as high hazard or significant hazard, the engineer is required to do a computer-generated breach analysis of the dam to determine the specific area below the dam that would be impacted by a potential failure of the dam, and to prepare maps (called flood-inundation maps) that locate this area. These maps then become part of the Emergency Plan that will be activated in case the dam later fails.
Minimum spillway requirements are also determined by the classification assigned to the dam, and these minimum spillway requirements are specified in the Regulations. In addition to submitting a permit application, site location of the dam on a portion of a USGS quad sheet, copy of the plans and specifications that will be used to construct the dam, the engineer is required to submit his computer runs indicating that minimum spillway requirements are met. DHEC normally requires that one foot of freeboard be maintained at the dam during passage of the design storm, i.e., water never rises higher than one foot below top of dam. DHEC does not specify the computer software that the engineer must use in making his analysis, but the engineer's computer analysis will be checked using the U. S. Army Corps of Engineer's HEC program.
The process that is followed by DHEC in evaluating the permit request is shown on the Permit Flow Chart.
There is no permit fee associated with obtaining a dam safety permit.
The process for alterations, repairs, and removal of existing dams is essentially the same as given above for new dams.
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