(A) The Plan Commission shall not recommend the approval of any plat unless the City Engineer determines that the proposed provisions for storm water drainage are adequate within boundaries of the subdivision, and are in compliance with Chapter 157 of this code. Complete documentation of the area to be drained, including contributory areas outside of the subdivision, shall be provided by the subdivider's engineer. This documentation shall include at a minimum current topographic data of the land in question, and calculations showing the anticipated storm water run-off for given rain events.
(B) Drainage improvements in the subdivision shall be coordinated with existing and planned drainage improvements elsewhere so as to form an integrated city system. The storm water drainage system shall be separate and independent of the sanitary sewer system and shall meet the following design criteria:
(1) All arterial streets and major collector streets:
(a) Flow from a "ten-year storm" shall not inundate the center 20 feet of the pavement.
(b) Flow from a "50-year storm" shall be carried without damage to any building.
(2) Minor collector streets and local streets:
(a) Flow from a "ten-year storm" shall not inundate the center 18 feet of the pavement.
(b) Flow from a "50-year storm" shall be carried without damage to any building.
(C) Catch basins or inlets, if required, shall be constructed so that the majority of surface water shall be intercepted before reaching the intersection, and not carried for a distance of more than 400 feet of the pavement.
(D) Accommodation of upstream drainage areas. A culvert or other drainage facility large enough to accommodate potential runoff from the entire drainage area upstream from the proposed subdivision shall be provided in accordance with the city's standard specifications. Potential runoff shall be determined on the basis of the maximum development of the upstream area that is permitted or to be permitted under the Comprehensive Plan.
(E) Drainage easements. Adequate easements for storm water drainage shall be established along any natural drainage channel and in any other locations where necessary to provide satisfactory disposal of storm water from streets, alleys, and all other portions of the subdivision. The precise location and minimum widths of said easements shall be as approved by the City Engineer.
(Ord. 3265, passed 8-14-00)