(A) Bridges and culverts. The size and capacity of all drainage structures shall be computed using Talbot’s Formula for runoff. Wherever practical, pipe culverts shall be used. The minimum length of culverts shall be at least equal to the distance from edge of shoulder to edge of shoulder, plus six times the vertical distance from the edge of shoulder to the flow line of the culvert. No culvert shall have a diameter of less than 12 inches. In no case shall entrance culverts be less than 20 feet in length. The design of all bridges and culverts shall be approved by the Village Engineer.
(B) Storm sewers. The storm sewer system shall be designed by the rational method, with self-cleaning velocities as follows.
(1) The part of the system which serves as main or terminal collectors shall be of sufficient capacity to carry the maximum stormwater flows which may occur in a ten-year period.
(2) The part of the system which serves as lateral collectors, and which can readily be augmented by future additions, shall be of sufficient capacity to carry maximum stormwater flows which may occur in a five-year period.
(3) The system shall include all necessary appurtenances such as inlets, catch basins and manholes as may be required for proper operation and maintenance.
(4) The coefficients of runoff shall be based on the types of development anticipated in all parts of the watershed affecting the drainage structure, and shall be subject to approval of the Village Engineer.
(5) Where the main storm sewer serving a subdivision can be expected to carry a substantial amount of stormwater from adjoining lands higher in the drainage area, and where the runoff from these lands can be expected to increase in the future because of more intense development, the developer shall provide an underground storm sewer adequate to serve the entire drainage area above the subdivision. The developer shall provide on-site retention in compliance with the design promulgated by the Metropolitan Sanitary District of Greater Chicago.
(6) No sewer line shall be less than ten inches in diameter.
(2000 Code, § 155.082) (Ord. 876, passed 8-4-1975) Penalty, see § 154.999