(A) All streets shall be provided with inlets and underground drainage facilities having a minimum design capacity adequate to carry off surface water falling or coming on the streets in a ten year storm event under the projected final state of development of the entire upstream watershed.
(B) The subdivision shall be laid out so as to provide proper drainage of the area being subdivided. Drainage improvements shall maintain natural watercourses and existing outlet/outfall locations. The subdivider shall provide for stormwater detention, or retention, for all additional runoff created through changes in imperviousness between the undeveloped and future full developed subdivision. The outlet restrictor shall be designed according to the following requirements:
(1) All subdivisions not releasing storm water into existing city storm sewer systems shall conform to Chapter 12 of the Illinois Drainage Manual.
(2) All subdivisions releasing water directly, or indirectly, into an existing city storm sewer shall conform to Chapter 12 of the Illinois Drainage Manual except that, the release rate shall be no more than a five-year rate of runoff for the undeveloped condition during a 100-year design storm frequency.
(3) An emergency overflow shall be provided and designed to safely accommodate flows in excess of the 100-year storm event. Calculations showing the undeveloped runoff, changes In imperviousness due to development, fully developed runoff, volume of storage required, volume of storage provided and design of the outlet restrictor and emergency overflow shall be prepared by a professional engineer, licensed in Illinois, and submitted to the City Engineer for review and approval.
(C) Alternate drainage systems developed by the subdivider may be considered for approval by the City Engineer if a detailed engineering study performed under the direction of a professional engineer, licensed in Illinois demonstrates that the alternate drainage system provides a level of service at least equal to that provided by the above requirements without increasing maintenance and operating costs to the city.
(D) Temporary drainage courses and structures that are not in the public right-of-way shall be maintained by the subdivider so as to safeguard the public welfare until such time as they are replaced with permanent facilities.
(E) Storm drainage, including drainage tile around basements, shall not be permitted to empty into any sanitary sewer. Where a public storm sewer is reasonably accessible, the subdivider shall connect with such storm drainage system and shall do such grading and provide such drainage structures including lateral connections as may be required. The subdivider shall analyze the existing storm sewer to ensure the system can adequately accommodate the flows being generated by the subdivision and submit those calculations for approval by the City Engineer. If the existing sewer is found to be inadequate to carry the runoff from the subdivision, some provisions must be made to accommodate the additional flow, such as a parallel storm sewer, additional storm water detention, or such other provision as approved by the City Engineer. Where a public storm water drainage system of the district in which the subdivision is located has been prepared and officially approved, the subdivider shall install drainage facilities as may be required in conformity with such official plats and the flood plan provisions of the zoning code.
(F) If the subdivision is in an area where a public storm water system is not available, the subdivider shall do such grading and provide such drainage structures as may be required to drain surface runoff and tiling around basements. Sump pumps shall not drain directly into roadside ditches or into the curb/roadway. See City of Tuscola Design and Construction Standards. Whenever the construction of streets and a necessary storm water system in a subdivision is such that the direction of storm water flow is diverted and affects surrounding properties, the subdivider shall obtain drainage easements to provide adequate disposal of the storm water.
(Ord. 81-0-19, passed 5-11-81; Am. Ord. 2011-O-4, passed 3-14-11)