A. Inlet Capacity and Type.
Inlets shall be 4 foot or 6 foot special inlets as indicated in PennDOT Design Standards Publication 72 - Plate RC - 34. The design capacity of all 4 foot special inlets shall be 5.5 CFS, and for all 6 foot special inlets shall be 6.5 CFS.
B. Straight Pipe Sections.
Wherever possible all storm drain pipes shall be designed to follow straight courses. No angular deflections of storm sewer pipe sections in excess of 5° shall be permitted. No vertical curves shall be permitted in the storm drain pipe system. Storm pipes shall be either fully coated bituminous corrugated metal pipe or reinforced cement concrete pipe.
1. Minimum Grade and Size - All storm drain pipes shall be designed to maintain a minimum grade of 0.5%. All storm pipes shall have a minimum inside diameter of 15 inches or a cross-sectional area of 176 square inches, except that pipes under a 25 foot or greater fill shall not be less than 24 inches or a cross-sectional area of 453 square inches.
2. Pipe Capacity - The capacity of all pipe culverts shall, as a minimum, provide the required carrying capacity as determined by the Manning Equation indicated in Section V, Paragraph E.
3. Pipe Arches - Where headroom is restricted, equivalent pipe arches may be used in lieu of circular pipe.
4. Horizontal Pipe Deflections - A manhole or inlet shall be provided at all horizontal deflections in the storm pipe system exceeding 5°.
5. Minimum Cover - a minimum of 2 feet of cover shall be maintained over all storm pipes. In extreme case, when approved by the Township Engineer, this minimum may be reduced, but in no case shall the top of the pipe be higher than 0.5 foot below the sub-grade elevation of the roadway.
6. Match Crowns - The crowns of all pipes tying into an inlet or manhole shall be set at equal elevation.
7. Diversion of Runoff - Where required by the Township, all storm drain pipes shall be designed to carry the runoff into a detention basin or similar facility utilized to control the rate of runoff.
(as amended by Ord. 239, 2/9/1990, § 2; by Ord. 242, 4/4/1990; and by Res. 1992-29, 8/19/1992)