(A) Any person, firm, corporation or other entity proposing to construct buildings or develop land within the jurisdiction of the Village shall prepare, for review by the Village Engineer, a Storm Water Pollution Prevention Plan that describes the manner in which erosion, sediment and runoff resulting from the development will be controlled and managed. The provisions of this Section shall be applicable to the following developments:
(1) Any residential development having a gross aggregate of five (5) acres or more; or
(2) Any residential development of less than five (5) acres but with at least fifty percent (50%) impervious surface including roads, building, utility right-of-way and other improvements; or
(3) Any commercial, industrial, institutional or utility development that has a gross aggregate area of one (1/2) half acre or more.
(B) No building or construction permits, or plat approval shall be issued by the Village until the Storm Water Pollution Prevention Plan has been reviewed by the Village Engineer as meeting the requirements of this Ordinance, or the requirement for such Storm Water Pollution Prevention Plan has been waived by the Village Engineer.
(C) Downstream property owners, watercourses, channels, or conduits shall not receive storm water runoff from proposed upstream developments at a higher peak flow rate than would have resulted from the same storm event occurring over the site of the proposed development with the land in its natural, undeveloped conditions, nor shall storm water runoff exceed the capacity of the natural drainage system.
(D) Storm water runoff resulting from a proposed development shall be detained on- site;
(1) By wet or dry bottom reservoirs;
(2) By underground reservoirs;
(3) On flat roofs, parking lots, or streets; or
(4) By other detention methods reviewed by the Village Engineer.
(E) For purposes of designing adequate on-site detention facilities, the Illinois State Water Survey Bulletin 70 rainfall data for this region shall be used.
(F) Detention Basins. Detention basins may be constructed to temporarily detain the storm water runoff so that the rate at which it is released is the same rate as before development. The following features shall be incorporated into the design of any detention basin:
(1) The volume of storage provided shall be sufficient to store flows both during and immediately after the maximum storm event which can be expected to occur once every two (2) and one hundred (100) years.
(2) Outlet works shall be designated to limit peak outflow rates from detention storage areas to or below peak flow rates that would have occurred prior to the proposed development. Due to the potential for maintenance problems associated with small diameter outfall pipes from detention facilities, no outfall pipe smaller than four (4) inches in diameter shall be used.
(3) Outlet works shall not include any mechanical components or devices and shall function without requiring attendance or control during operation.
(4) Emergency spillways shall be provided to permit the safe passage of runoff generated from a 100-year storm.
(5) The maximum planned depth of storm water stored shall not normally exceed four (4) feet.
(6) The maximum side slopes for grassed basins shall not exceed one (1) foot vertical for three (3) feet horizontal (3:1 slope).
(7) In no case shall the limits of maximum ponding be closer than thirty (30) feet horizontally from any building and less than two (2) feet vertically below the lowest sill elevation.
(8) The basin bottom should be designed to drain expeditiously. If the bottom is to be grass, it should have a minimum slope of one percent (1%).
(9) Small flows through the detention basin should be handled by paved ditches from inflow structures to outflow structures to minimize erosion.
(10) If the detention basin is to have other uses, the design of the basin bottom should include under drains to expedite drying of the bottom between runoff events.
(11) Designs should result in aesthetically pleasing configurations that will enhance public acceptability.
(12) Outfall storm sewer structures for detention ponds and basins shall be piped through lots.
(G) Detention Ponds. Detention ponds may also be used to temporarily detain the differential runoff from the development. In addition to the general design features for detention basins as listed above, the following should also be incorporated into the design of any detention pond.
(1) In order to minimize weed growth, the normal pool depth should be four (4) feet minimum.
(2) If fish are to be kept in the pond, at least one-quarter of the area of the permanent pool should have a minimum depth of ten (10) feet.
(3) In order to ease cleaning of the pond or shoreline maintenance, the pond design should include provisions for emptying the pond.
(4) The design of any pond may include a low flow by-pass channel or pipeline to divert runoff that can be accommodated by downstream drainageways.
(5) In order to minimize the effects of waves or ice, some type of bank stabilization such as rip rap or concrete should be placed along the normal pool shoreline.
(6) The side slopes below the normal pool elevation may exceed the maximum side slope permitted above normal pool. The design shall, however, include provisions for a safety ledge having a depth of water not greater than three (3) feet immediately adjacent to the shoreline.
(7) Outfall storm sewer structures for detention ponds and basins shall be piped through lots.
(H) Rooftop Storage. Detention storage may be met in total or in part by detention on roofs. Details of such design, which shall be included in the Building Permit Application, shall include the depth and volume of storage, details of outlet devices and down drains, elevations of overflow scuppers, design loadings for the roof structure and emergency overflow provisions. Direct connection of roof drains to sanitary sewers is prohibited.
(I) Other Detention Methods. All or a portion of the detention storage may also be provided in underground or surface detention facilities, to include basins, tanks, or swales.
(J) Safety Features. The design of detention facilities shall incorporate safety features, particularly at outlets, on steep slopes, and at any attractive nuisances to include, as necessary, fencing, handrails, lighting, steps, grills, signs and other protective or warning devises so as to restrict access during critical periods and to afford some measure of safety to both authorized and unauthorized persons.
(K) The storm water detention facilities must be built in conjunction with the storm sewer installation and be fully operational after the clearing of vegetation.
(1) Silt and debris connected with early construction shall be removed periodically from the detention area to maintain full storage capacity.
(2) The maintenance responsibility of the detention area shall remain with the developer and/or contractor until final inspection and applicable escrows are released.
(3) Before plat approval, the developer shall submit his plan for future maintenance responsibility of the detention area.