Section
51.01 Title, purpose, intent and policy
51.02 Applicability
51.03 Exemptions
51.04 Definitions
51.05 Drainage system components
51.06 Permits and applications
51.07 Drainage plan submittal requirements
51.08 Design requirement
51.09 Maintenance responsibility
51.10 Inspections
51.11 Approval of constructed facilities
51.12 Performance guarantee
51.13 Dry weather water outlets
51.14 Variances
51.15 Enforcement
51.16 Severability
51.17 Penalties
51.18 Appeals
51.19 Disclaimer of liability
51.20 Retroactivity
51.21 Administrative rules
51.22 Savings and applicability
(A) Title. This chapter shall be known, cited and referred to as the, “Stormwater Management Ordinance of the Village of Mahomet, Champaign County, Illinois”.
(B) Purpose. The purpose of this chapter is to guide developer’s attempts to control the transportation or movement of stormwater so as to reduce the likelihood of damage to property; prevent injury to persons; protect the public health, safety, and general welfare of the community; and to promote the orderly development of land and water resources within the Village of Mahomet.
(C) Intent. The intent of this chapter is to require temporary storage of stormwater runoff, to control the rate of release of stormwater runoff by implementation of “reasonable provisions” and “in accordance with generally accepted engineering practices”, to provide for adequate drainage of development sites and surrounding areas, and to protect existing agricultural drainage system. Further, it is intended that this chapter complement and coordinate with the Village of Mahomet Subdivision Ordinance and the Village of Mahomet Zoning Ordinance.
(D) Policy. This chapter establishes a stormwater management policy for the future control of stormwater runoff within the jurisdictional limits of the village. Accordingly, a combination of temporary storage and the controlled release of stormwater runoff shall generally be required for all new commercial and industrial developments, residential subdivisions, planned unit developments, and any redevelopment or other new construction, as further defined in this chapter.
(Ord. 15-12-02, passed 12-15-2015)
(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)
(A) The provisions of this chapter shall not apply to the following developments:
(1) Any development constructed totally upon a lot or parcel of land, recorded prior to December 14, 1981, that contains less than 20,000 square feet of land area, provided the development has less than 35% impervious surface area; or
(2) Any single-family residential or two-family residential development on any lot or parcel of land, which was recorded prior to December 14, 1981; or
(3) Modification of single-family residential or two-family residential structures which will continue to be used as single-family or two-family dwellings; or
(4) Modification of existing structures or appurtenances, other than a single-family dwelling or two-family dwelling, which do not increase the amount of impervious area of the lot or parcel upon which it is constructed; or
(5) Traditional agricultural land uses; or
(6) Improvement of any existing roadways which do not increase the number of traffic lanes in the typical cross-section of the roadway; or
(7) Any development greater than two acres in size which the total impervious area is less than 15% of the total area of the site.
(8) New development in which the total impervious area, including the area of the existing, adjacent public or private streets, is less than 20% of the total area or is less than 10,000 square feet, whichever is less.
(B) The exemptions set forth above shall not apply to the installation, repair, or replacement of dry weather water outlets.
(Ord. 15-12-02, passed 12-15-2015)
(A) For the purposes of this chapter, the following definitions are adopted.
ADMINISTRATOR. The Village of Mahomet Administrator or other person specifically designated by the President of the Board of Trustees to enforce the provisions of this chapter.
BOARD OF TRUSTEES. The Board of Trustees of the Village of Mahomet.
CAPACITY OF A STORMWATER DETENTION FACILITY. The maximum volume that can be stored by a stormwater detention facility without causing damage to the public or encroachment upon private property. The capacity of a stormwater detention facility is generally determined utilizing average end area or similar volume calculation methods.
CAPACITY OF A STORMWATER DRAINAGE FACILITY. The maximum flow at atmospheric pressure that can be conveyed by the facility without causing damage to the public or encroachment upon private property. The capacity of a stormwater drainage facility is determined utilizing “Mannings Equation” or similar approved formula.
CHANNEL. A natural or artificial watercourse of perceptible extent which periodically or continuously contains moving water, or which forms a connecting line between two bodies of water. It has a definite bed and banks which serve to confine the water.
CONTROL STRUCTURE. A facility constructed to regulate the volume and rate of stormwater that is released during a specific length of time.
CULVERT. A closed conduit for the passage of surface drainage water under a roadway, railroad, or other surface impediment.
DETENTION STORAGE. Temporary detention or storage of stormwater in storage basins, on rooftops, in parking lots, school yards, parks, open space, lakes, ponds, or other areas under predetermined and controlled conditions, with the rate of drainage therefrom regulated by appropriately installed devices.
DEVELOPMENT. Any man-made change to improved or unimproved real estate, including, but not limited to, construction of or substantial improvements to buildings or other structures, the placement of mobile homes, paving, mining, filling, or other similar activities.
DISCHARGE. The rate of outflow of water from a stormwater drainage or stormwater detention facility.
DIVERSION. The deflection of storm or stream waters in such a way that those waters flow into a watercourse to which they are not naturally tributary or that the point of discharge of these waters within a natural watershed is changed.
DRAINAGE AREA. The area from which water is carried off by a drainage system; a watershed or catchment area above a given point.
DRAINAGE EASEMENT. Authorization by a property owner allowing use of a designated portion of his/her property by others for drainage purposes.
DRY BOTTOM STORMWATER DETENTION BASIN. A facility that is designed to be normally dry and which accumulates stormwater runoff only during periods when the restricted stormwater runoff release rate is less than the stormwater inflow rate.
DRY WEATHER WATER OUTLET. A dry weather water outlet is an outlet from a sump pump, footing tile, field tile, or other source which may discharge at times other than during periods of rainfall and pursuant to direct surface runoff.
EXCESS STORMWATER PASSAGEWAY. A channel formed on the surface of the soil to carry excess stormwater runoff through a specific area from dominant to servient land areas.
EXCESS STORMWATER RUNOFF. That portion of stormwater runoff which exceeds the transportation capacity of storm sewers, swales, ditches or natural drainage channels serving a specific watershed.
FLOOD ELEVATION. The elevation of all locations delineating the maximum level of high waters for a flood of a given return period.
FLOODPLAIN. The special flood hazard lands adjoining a watercourse or channel, the surface elevation of which is lower than the flood elevation and which are subject to periodic inundation during floods.
FLOODWAY. A channel of a watercourse and those portions of the adjoining floodplain which are reasonably required to carry and discharge the design flood.
GRADE. The inclination or slope of a channel, canal, conduit, etc., or natural ground surface, usually expressing in terms of percentage of the vertical rise (or fall) as compared to the corresponding horizontal distance.
ILLINOIS URBAN MANUAL. This term shall mean “A Technical Manual designed for Urban Ecosystem Protection and Enhancement”, published by the United States Department of Agriculture, Natural Resources Conservation Service, latest edition thereof.
IMPERMEABLE. A term applied to material through which water cannot pass.
IMPERVIOUS. A term applied to material through which water cannot pass, or through which water passes with great difficulty or at a very slow rate. For purposes of this chapter, any surface which
would typically be assigned a Rational Method “C” value of 0.60 or greater shall be considered impervious.
INLET. An opening into a storm drainage system for the entrance of surface storm runoff, more completely described as a storm drainage inlet.
NATURAL DRAINAGE. Water flow by gravity in channels formed by the true surface topography of the earth prior to changes made by the efforts of man.
NATURAL DRAINAGE CONDITION. The situation whereby water flows by gravity in channels formed by the true surface topography of the earth prior to changes made by the efforts of man or as defined by the Illinois Compiled Statutes.
NATURAL SAFE STORMWATER DRAINAGE CAPACITY. The quantity of stormwater runoff that can be transported by means of a channel, passage, conduit, tube, duct, or combination thereof, in such a manner that the elevation of the water does not rise significantly above the level of the adjacent soil surface, and cause damage or encroachment upon public or private property. For the purposes of this chapter, it is presumed that the maximum NATURAL SAFE STORMWATER DRAINAGE CAPACITY for downstream stormwater drainage systems is the capacity required to carry the rate of stormwater runoff from a five year return period storm prior to December 14, 1981.
OWNER. The record title holder or a beneficiary of a land trust which is the record title holder, and includes singular or plural; if the owner is other than an individual, the term includes beneficiaries, agents, shareholders, officers and directors, partnerships, associations, firms, trusts, clubs, companies, or corporations.
PEAK FLOW. The maximum rate of flow of water at a given point in a channel or conduit resulting from a predetermined storm or flood.
PERSON. An individual, public or private corporation, unit of government, partnership, or unincorporated association.
POSITIVE GRAVITY OUTLET. A term used to describe the drainage of an area in a manner that will ensure complete removal of all surface water by means of gravity.
RECOGNIZED AGENCY. A governmental unit or agency which has statistically and consistently examined local, climatic, and geologic conditions and maintained records as they apply to stormwater runoff, e.g. National Weather Service, University of Illinois Engineering Experiment Station, and the Illinois State Water Survey.
RETENTION BASIN. A structure of feature design to retain stormwater over a period of time, with its release being positively controlled over a longer period of time than a typical stormwater “detention” storage facility.
RETURN PERIOD. The average interval of time within which a given rainfall event will be equaled or exceeded once. As an example, a flood having a return period of 50 years has a 2% probability of being equaled or exceeded in any one year.
RUNOFF COEFFICIENT. A decimal fraction relating the amount of rain which appears as runoff and reaches the storm sewer system to the total amount of rain falling. For example, a coefficient of 0.50 implies that 50% of the rain falling on a given surface appears as stormwater runoff.
STANDARD SPECIFICATIONS. The Standard Specifications for Road and Bridge Construction published by the State of Illinois Department of Transportation, latest edition.
STORM DRAIN. A closed conduit for conveying collected stormwater runoff.
STORMWATER DRAINAGE SYSTEM. All means, natural or man-made, used for conducting stormwater to, through or from a drainage area to the point of final outlet, including but not limited to any of the following: conduits, storm drains, swales, canals, channels, ditches, streams, culverts, street gutters and pumping stations.
STORMWATER RUNOFF. The water that results from precipitation which is not absorbed by soil or plant material, which does not evaporate and which flows over the surface of the ground or is collected in channels, conduits or ponds.
STORMWATER RUNOFF RELEASE RATE. The rate at which stormwater runoff is released from dominant to servient land.
STORMWATER STORAGE AREA. An area designated to temporarily accumulate excess stormwater.
STRUCTURE. Anything which is constructed or erected with a fixed location on the ground or attached to something having a fixed location on the ground. Among other things, structures include buildings, fences, signs, mobile homes, swimming pools, and walls.
TIME OF CONCENTRATION. The time required for stormwater runoff from the remotest part of the drainage basin to reach the point being considered. Minimum time of concentration requirements for design of stormwater drainage systems shall be 15 minutes.
TRADITIONAL AGRICULTURAL USES. Uses commonly classes as agricultural or horticultural, including forestry, crop farming, truck gardening, wholesale nursery operations, animal husbandry, the operation of any machinery or vehicles incidental to said uses, and the construction of a single-family dwelling and other farm structures incidental to and typically associated with said uses. The terms does not include commercial feed lots, commercial grain storage/processing facilities or other similar agriculturally related commercial and industrial land uses.
TRIBUTARY WATERSHED. The entire catchment area that contributes stormwater runoff to a given point.
VILLAGE. The Village of Mahomet, Champaign County, Illinois and its staff and elected officials.
WATERCOURSE. Any stream, creek, brook, branch, natural or artificial depression, slough, gulch, reservoir, lake, pond or natural or man-made drainageway in or into which stormwater runoff and flood waters flow either regularly or intermittently.
WET BOTTOM STORMWATER STORAGE AREA. A facility that contains a body of water and which accumulates excess stormwater during periods when the restricted stormwater runoff release rate is less than the stormwater inflow rate.
(B) Words not defined shall be interpreted in accordance with the definitions contained in Webster’s New Collegiate Dictionary.
(Ord. 15-12-02, passed 12-15-2015)
Loading...