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(A) Design. All subdivisions shall be designed so the proposed storm water drainage system does and accomplished the following:
(1) Extends the storm system through the proposed subdivision to serve upstream properties in the natural drainage area. The storm system should reflect the ultimate development of the drainage area.
(2) The storm system should be designed to provide positive drainage. This will provide a convenience system to pass frequent floods, and an emergency system to pass more severe floods.
(3) The storm system is assumed to consist of such components as sewers, channels, swales, natural drainageways, inlets, catch basins, manholes, streets, detention/retention basins, and other necessary facilities.
(4) The drainage plans shall have a certification by a registered professional engineer as follows:
"I, , hereby certify that adequate storm water storage and drainage capacity has been provided for this development, such that surface water from the development will not be diverted onto and cause damage to adjacent property for storms up to and including the one hundred (100) year event, and that the design plans are in compliance with all applicable state, county, and village ordinances."
(5) All storm sewer systems shall be entirely separate from the sanitary sewer system. Storm sewers shall be designed to convey the peak flow from a ten-year rainfall event. Rainfall frequency data shall be obtained from the Rainfall Frequency Atlas of the Midwest, Bulletin 71, or any subsequent revision thereof. Storm sewer outfalls shall be designed to function at their design capacity during flood conditions on the receiving stream or other body of water. The minimum size of storm sewer shall be 12 inches in diameter.
(a) Public storm sewer systems. All storm sewer systems to be dedicated to and accepted by the village as public improvements shall be constructed of reinforced concrete pipe, without exception.
(b) Private storm sewer systems. All private storm sewer systems constructed in residential areas shall meet the requirements set forth in division (A)(5)(a) above. Storm sewer systems in non-residential areas (excluding parks, open areas or any areas developed in connection with or intended for use as an amenity to or facility for any residential area) may be constructed of materials other than reinforced concrete pipe, provided that the applicant, developer, contractor, or any other entity proposing to install a storm sewer system provides the Village Engineer with sufficient technical data illustrating the storm sewer system meets or exceeds characteristics and performance capabilities of reinforced concrete
pipe. Any material proposed other than reinforced concrete pipe must have approval of the Director of Public Works and the Village Engineer.
(6) Culverts under thoroughfare streets shall be designed to pass the 100 year peak flow with no adjacent property damage. Culverts under collector streets shall be designed to pass the 50 year peak flow without damage. Culvert material shall consist of reinforced concrete sewer pipe or corrugated metal pipe.
(7) No ditch system shall be permitted. Drainage shall be provided through storm sewers with a ten year design capacity. Additional storm water sewer shall be conveyed through street and surface grading to pass up to the 100 year discharge without damage. Bypass channels shall use natural drainageways as much as possible, and shall convey up to the 100 year peak flow without damage. Modified or artificial channels shall be lined with concrete up to the ten year stage, with adequate capacity to pass up to the 100 year peak flow without damage. Channel modifications will be permitted only if the following conditions are met:
(a) The hydraulic capacity is maintained.
(b) The existing flood storage is maintained.
(c) The banks are adequately stabilized.
(d) The appropriate permits have been obtained.
(e) Swales in backyards and other areas shall be permitted provided the following conditions are met:
1. The maximum side slopes shall be a six to one (6:1) ratio.
2. Appropriate easements are provided, a minimum of 20 feet wide.
(8) Inlets will be located as necessary to collect surface water, but shall be spaced a maximum of 400 feet. Catch basins before a storm sewer enters a manhole. Manholes shall be located at the junction of two storm sewer pipes, or at any change in grade alignment or size of the pipe. Maximum spacing of manholes shall be 400 feet.
(9) Streets and parking lots should be designed and their grades established such that they can convey or store up to the 100 year rainfall event without damage. The maximum allowable depth in the street shall be nine inches, measured in the curb and gutter. The maximum allowable depth in parking lot shall be nine inches. Streets and parking lots shall be designed to provide positive drainage.
(B) Right-of-way/easement dedications.
(1) All drainageways shall be located in dedicated public rights-of-way. All storm sewers shall be located in public easements or dedicated public rights-of-way.
(2) Easements and rights-of-way shall be of sufficient width and storm and/or sanitary sewer shall be installed at such locations therein as to permit open cut installation, maintenance, and repair within the confines of the easement or right-of-way without relocation or other unreasonable interference with other public utilities located therein, and so as to meet the following minimum standards: 15 feet in width, plus five feet for each additional utility, plus, for storm and/or sanitary sewers in excess of 24 inches in diameter, two additional feet for each 12 inches or portion thereof of additional storm and/or sanitary sewers diameter provided; however, if storm and/or sanitary sewers exceed 15 feet in depth, additional right-of-way may be required.
(C) Construction standards. All storm sewers shall use materials and be installed in the manner meeting or exceeding the requirements, standards, and specifications contained in the "Standard Specifications for Water and Sewer Main Construction in Illinois," the most current edition as amended, supplemented and amended by the Village Engineer. These standards and specifications, with the modifications, amendments, and amplifications of the Village Engineer, are available at the Public Works Department.
(D) Oversizing. Where applicable, the developer/subdivider shall install storm systems sufficient in size and depth to carry the storm runoff from upstream properties naturally tributary to the proposed subdivision. The village shall make special provisions for that developer/subdivider to recapture those additional costs incurred as a result of oversizing and over-excavating the storm system.
(Ord. 2313-95, passed 2-1-95; Am. Ord. 2421-96, passed 5-15-96; Am. Res. 0007-02, passed 2-20-02; Am. Ord. 12-1014, passed 11-7-12)