§ 154.134  STORM SEWERS.
   (A)   A drainage system adequate to serve the needs of the proposed new streets, natural waterways and overland flow will be required in new subdivisions.  A drainage system may be composed of conduits, waterways, swales, ditches and curb flow areas, as required.  When a public storm sewer main is available at the plat boundary or within 500 feet, the subdivider shall connect the drainage system with such storm sewer main if the grade permits and other more economical solutions are not possible.
   (B)   Bridges or culverts shall be designed to support and carry loads according to the requirements of the city, but not less than AASHTO Loading HS-20, and shall be constructed the full width of the cartway plus additional length as necessary to provide a proper installation.
   (C)   Where open watercourses are planned, adequate safety, erosion control, drainage, protection of capacity and appearance measures shall be taken by the developer to ensure proper safe and healthful disposal of storm water.  All open watercourses must be approved by the Commission.
   (D)   Minimum grade of drainage courses shall be designed to create a minimum cleaning effect (velocity of two feet per second). Lesser grades may be permitted where such required grades cannot be achieved and the city approves lesser grades.
   (E)   Storm sewers shall have a minimum diameter of 15 inches and a minimum grade on .5%.  Lesser grades may be permitted when substantiated with calculations which prove that cleaning velocities will be maintained.
   (F)   Manholes shall normally be spaced at 400 feet maximum spacing where pipe sized of 24 inches or less are used, and not over 600 feet where larger sizes are installed.  Inlets may, if approved by the Commission and municipality be substituted for manholes.
   (G)   All phases of construction of open ditches, gutters, or storm sewers including width, depth, shapes, erosion control, minimum grade, size and area shall be in accordance with the requirements of these regulations and all storm drainage facilities shall be inspected and approved by the city.
(Ord. 1286, passed 6-7-1982)