(A) Scope of application. A combination of stormwater storage and controlled release of stormwater runoff is required for all non-agricultural development activities within the boundaries of the village involving:
(1) All non-agricultural developments greater than two acres in size.
(2) All non-agricultural developments between 20,000 square feet and two acres in size with greater than 35% impervious surface area.
(3) All new or expanded subdivisions which require approval of the village pursuant to the provisions of the Village of Mahomet Subdivision Ordinance, as amended.
(4) Generally, any new construction within the village’s area of zoning jurisdiction, pursuant to the provisions of the Village of Mahomet Zoning Ordinance, that increases the amount of pervious area of the lot or parcel of land upon which it is constructed.
(5) Except as may otherwise be provided herein, all structures erected hereafter, all uses of land or structures established hereafter, all improvements to water courses, all structural alterations or relocation of existing structures occurring hereafter, and all enlargement of, or additions to, existing uses which increase the amount of pervious area, occurring hereafter, shall be subject to the provisions of this chapter. Therefore, except as provided in § 51.03, no building permit may be issued, no subdivision or plat of land may be approved or recorded; no mobile home, independent travel trailer, or recreational travel trailer park permit may be issued; no planned unit development may be approved; no watercourse, stormwater drainage system, storm sewer, or stormwater control structure may be constructed; and no paved or compacted area designed to be used for loading, open storage, or the parking or movement of vehicles may be constructed without first having complied with the applicable provisions of this stormwater management chapter.
(B) Whenever storage and controlled release of stormwater is required for existing developed parcels, and where improvements upon such parcels were constructed prior to 1972, such storage and the required controlled release rate shall apply to the net increase in the amount of runoff since January 1, 1972.
(C) Any area proposed for development, consisting of a tract of land of three or more acres in common ownership or interest and upon which phased development is proposed, shall be required to provide a combination of storage and controlled release of stormwater runoff for future development of the entire tract.
(1) Where phased development is proposed, the owner may construct, after receiving site specific approval from the Administrator, one stormwater detention facility which is built larger than initially needed in order to anticipate subsequent phases of development and/or is designed to be enlarged at later dates as additional portions of the overall site are developed. Phased construction shall include implementation of sufficient and enforceable covenants upon the land to properly document the phased implementation. The form of covenant shall be approved by the Village Attorney, and the substance of the covenant shall reflect the approved overall stormwater detention plan for the site.
(2) Where a subdivision plat or a planned unit development involves new lots which are more than three acres in size that are zoned for commercial or industrial purposes, the developer/owner may provide for storage and controlled release of stormwater runoff for the developed lots by sufficient and enforceable covenant upon the individual lots. The covenant shall require construction of on-site stormwater detention facilities upon each lot at the time of subsequent development of that lot. The form of covenant shall be approved by the Village Attorney, and the substance of the covenant shall require construction of on-site stormwater runoff storage and controlled release of stormwater runoff from each lot in a manner approved by the Administrator, and in accordance with the provisions of this chapter.
(D) Any property or development falling within the scope of the provisions of this chapter shall be subject to review by the Administrator in order to establish and determine, in the opinion of the Administrator,that no adverse consequences will arise downstream as a result of construction of improvements under the sought-after permit. Any property located within floodplain areas, as defined in the flood hazard area development ordinance of the village shall be governed by such ordinance in the event of and to the extent of conflict with the provisions of this stormwater management ordinance.
(E) All applications for building permits shall contain a statement that such buildings or structures and appurtenances connected therewith include facilities for the orderly runoff or detention of rain and melting snow, as required herein. Plans submitted with said application shall include a signed statement issued by the owner and by an Illinois professional engineer that the plans include facilities adequate to prevent hazardous runoff, as required herein. For single family dwellings to be located in a subdivision meeting the requirement of this chapter, the signed statement may, in lieu of the above procedure, be placed on the face of the final plat or upon the required subsidiary drainage plat for the entire subdivision.
(F) Existing conditions.
(1) It is anticipated in this chapter that a land owner shall be allowed to pass through existing excess stormwater runoff from tributary areas upstream from that owner’s land without storage or controlled release of such runoff. It is further anticipated that this chapter will require the controlled release of excess stormwater runoff resulting from development on an owner’s land. The controlled release rate of excess stormwater runoff from an owner’s land shall not exceed the rate of runoff which would have occurred from that owner’s land prior to the development or redevelopment of that owner’s land.
(2) It is presumed by this chapter that prior to development, the owner’s land had a traditional agricultural use. It is further presumed that the maximum safe stormwater drainage capacity for downstream stormwater drainage systems is the capacity required to carry the peak rate of stormwater runoff from a five year return period storm event prior to December 14, 1981.
(Ord. 15-12-02, passed 12-15-2015)