The following guidelines shall be used for street and local drainage within the development of a subdivision:
(A) Proposed stormwater channels shall be designed in accordance with the most current edition of the North Carolina Erosion and Sediment Control Planning and Design Manual;
(B) Channels shall provide positive drainage. The minimum slope shall be 0.5%;
(C) The minimum pipe diameter allowed, including driveway pipe, is 15 inches;
(D) Acceptable pipe materials outside of NCDOT right-of-way include Class III reinforced concrete pipe and HOPE, PASHTO M294 — corrugated exterior/smooth interior pipe (Type S). No HOPE end treatments are allowed. Reinforced concrete pipe/headwall shall be used for all end treatments. Pipe shall be installed according to the manufacturer’s requirements. Corrugated metal pipe is not allowed. Pipe inside NCDOT right-of-way shall be in accordance with Subdivision Roads Minimum Construction Standards published by NCDOT;
(E) Minimum cover for all pipes located outside traffic areas is one-half foot. Minimum cover for all pipes located in proposed traffic areas is one foot;
(F) At utility crossings, the minimum vertical separation between storm drainage and water and sanitary sewer lines shall be 24 inches or in accordance with 15A NCAC 2T .0305, whichever is more stringent;
(G) Storm structures are required where there is a change in pipe size, a change in grade, or changes in horizontal alignment greater than 45 degrees. All structures shall allow for access to the storm drainage system with a removable lid or grate;
(H) All local drainage systems shall be designed to convey the ten-year design storm;
(I) The minimum design storm frequency for cross drainage for streets shall be in accordance with the current edition of Subdivision Roads Minimum Construction Standards published by NCDOT; and
(J) All curb and gutter shall meet NCDOT, Division of Highways standards. Curb inlet and storm drainage design shall be in accordance with requirements outlined in NCDOT’s Best Management Practices for Construction and Maintenance Activities.
(Ord. passed 10-17-2011)