Design & Construction Specifications - Town of Kernersville

10. Maximum storm drainage pipe grade is 10.0%. Steeper grades may beconsidered at outlets and other substantial grade changes.11. Minimum grade for tail-ditching is 1.0%.12. Manholes are required at changes in grade, changes in alignment, andat intersection of drainage pipe.13. A concrete grout invert slide is required in all drainage boxes andmanholes.14. Recommended manhole drops:a) Change in alignment 0 degrees to 45 degrees, 0.10 ft.b) Change in alignment greater than 45 degrees, 0.20 ft.c) Change in pipe size, match inverts.d) Reverse flow conditions in a storm sewer system created by a tie-inat a structure will not be allowed unless a manhole drop equal to thediameter of the outgoing pipe is provided.15. End walls or flared-end sections, plus an appropriate energy dissipaterwill be required at the release point of all pipe systems. Open endedpipes are acceptable where flow rates are low and erosion can becontrolled with proper outlet protection.B. Drainage for Subdivisions and Other Developments:1. Site drainage will be required to tie into existing storm drainage systemwhere possible.2. The following must be included on Site Drainage Plans:a) Location of inlets, manholes, pipe lines.b) Clearly defined lines delineating areas drained to each inlet.c) Existing and proposed contour lines shall be extended a minimum oftwo hundred (200) feet beyond the project limits.d) Ditches, swales, pipes, and drainage easements which are adjacentto the proposed project.e) Drainage calculations.3. Minimum Drainage Easement widths, where required:Closed system15" - 30" pipe = 15 feet36" - 60" pipe = 20 feet66" - 96" pipe = 30 feet