§ 11-125. General drainage system requirements.

(a)

A drainage system shall be designed by a licensed engineer and constructed by the developer to provide for the proper drainage of surface water of the development and the drainage area of which it is a part, to permit the unimpeded flow of natural watercourses, and to provide positive drainage away from structures and on-site sewage disposal facilities. The subdivider/developer's responsibility shall include those drainage facilities to discharge his storm runoff to an existing facility outside the development area capable of receiving such runoff with no adverse effects.

(b)

A registered licensed engineer engaged by the developer shall prepare a drainage study and report. This report shall include both existing and proposed drainage conditions and shall include an evaluation of the ability of the proposed drainage facilities and other improvements pertaining to drainage or flood control within the development to handle the runoff, which would be generated by the development. The report shall also contain the following items:

(1)

Calculated estimates of the quantity of storm water entering the development naturally: also, estimates of such water when the upper watershed area shall have been developed for the maximum runoff anticipated under full development.

(2)

Existing conditions of the watershed that may affect the proposed development, such as subsoil type, positive drainage channels, obstructions and the like.

(3)

Quantities of flow at each pickup point.

(4)

Estimates of temporary erosion and pollution controls necessary while the development is under construction.

(5)

Description of the major, primary and secondary system. The report shall include evaluation of proposed facilities under both frequent and infrequent storms (ten-year, 50-year, 100-year), in such a way that required areas of ponding or flow ways are clearly indicated and protected from future encroachment. The report shall take into account, where applicable, chapter 26, article II, pertaining to flood damage prevention; chapter 59, pertaining to subdivisions; and the current stormwater management guidelines of the South Carolina Department of Health and Environmental Control.

(c)

In designing storm drainage facilities, special consideration shall be given to the avoidance of problems, which may arise on developed or undeveloped properties.

(d)

Storm drainage facilities shall be designed not only to consider the anticipated peak discharge from the property being developed, but also the anticipated increase in runoff that will occur when all property at a higher elevation in the same drainage area is fully developed consistent with the approved land use plan.

(e)

Where adequate existing public drainage facilities are accessible, the County shall require that the system proposed for the land being developed be connected thereto.

(f)

Drainage easements shall be provided in accordance with the following criteria:

(1)

Where development is traversed by a drainage facility, adequate areas for storm drainage, including ponding, shall be allocated, conforming substantially to the lines of such drainage facility, and of sufficient width to carry off storm drainage and provide for maintenance and improvement of the drainage facility. Adequate access for maintenance and equipment will be required. Generally, for underground storm drain pipe, the minimum width of the easement shall be not less than 20 feet or the outside diameter of the pipe in feet plus 15 feet on one side and four feet on the other side of the pipe, whichever is greater. In either case, a minimum of 15 feet shall be left on one side for maintenance access. Where pipes are installed at cuts greater than five feet in depth, soil conditions may dictate the requirement for additional easement widths. Where open improved drainage channels, paved or unpaved, are permitted, the width of the easement shall be in accordance with subsection 59-95(a) or as required by slope changes noted at subsection 11-126(b)(2). Deviations from the guidelines shall be based on considerations for public safety or sound engineering considerations (such as soil characteristics at the construction site).

(2)

The location of any surface or underground drainage facility shall not be changed without the approval of the county.

(Ord. No. 08-06-30, 6-23-2008)