A drainage system adequate to serve the needs of the proposed new streets and the entire subdivision will be required in the new subdivisions. Where an adequate public storm sewer main is available at the plat boundary, the subdivider shall construct a storm sewer system and connect it with such storm sewer main. If such storm sewer systems are not accessible, adequate storm water drainage shall be provided by natural drainage channels with easements of adequate width as approved by the City Engineer. A drainage plan shall be submitted simultaneously with the plat of any subdivision, showing the proposed scheme of surface drainage.
(a) Standards and Specifications for Drainage Facilities. The construction of storm water drainage improvements shall be subject to the approval of the City Engineer.
(1) The drainage ditch must have at least a one percent grade, or otherwise approved.
(2) If the roadway ditch is in excess of four percent, an approved type gutter using concrete, stone, sod or underground drainage must be used, with sufficient inlets spaced so as to keep the volume of water at a low level.
(b) Culverts and Bridges. When natural drainage channels intersect any street right of way, it shall be the responsibility of the subdivider to have satisfactory bridges and culverts designed and constructed. Where culverts are required, the following minimum requirements shall be observed:
(1) All culverts shall extend across the entire right-of-way width of the proposed road. The cover over the culvert and its capacity shall be approved by the City Engineer. The minimum diameter of a culvert pipe shall be twelve inches. Head walls, depending on existing drainage conditions, may be required.
(2) Driveway culverts shall have a minimum length of twenty feet. Driveway culverts shall be reinforced concrete pipe or its equal with scaled joints having a diameter of not less than twelve inches. When special drainage designs are necessary, such as masonry or concrete structures, etc., such designs in detail must be submitted to the City Engineer Department for approval in advance of the completion of the construction plans. The driveway culverts shall be laid so as to maintain the flow line of the ditch or gutter. Head walls may be required.