(A) Principal spillways. Shall be designed to meet the following requirements.
(1) The principal spillway shall be designed to function without requiring attendance or operation of any kind or requiring use of equipment or tools.
(2) All discharge from the detention facility when inflow is equal to or less than the 100-year inflow shall be via the principal spillway(s).
(3) The design shall allow for discharge of at least 80% of the detention storage volume within 24 hours after the peak or center of mass of the inflow has entered the detention basin. On basins less than 100 acres, this shall not apply.
(4) The design discharge rate via the spillway shall continuously increase with increasing head and shall have hydraulic characteristics similar to weirs, orifices or pipes.
(B) Emergency spillways. The emergency spillway shall be provided to pass a 100-year storm without damaging any property and, where applicable, designed to Illinois Department of Water Resources Dam Safety Requirements.
(C) Outlet works. Shall have an outlet works consisting of valves, gates, pipes and other devices as necessary to completely drain the facility in 72 hours or less when required for maintenance or inspection on normally wet basins.
(D) Sediment storage. Shall be designed to provide for five years of sediment accumulation. All other detention facilities shall provide storage for two years of sediment accumulation, except, for those using roofs of buildings, paved parking areas or other facilities designed to preclude the deposition or accumulation of sediment. Sediment storage volume shall be in addition to the volume required for temporary storage of storm water to properly size the detention facility on normally wet basins.
(E) Erosion control. Principal spillways and outlet works shall be designed to prevent erosion and if necessary equipped with energy dissipating devices to slow the water to normal velocity as called out in the IPSUSESC Manual. Special measures shall be taken by the developer to not permit sediment from tilling the proposed detention basin during all construction of the proposed development.
(F) Public detention facilities. The owner shall dedicate the detention facility and easements as set forth upon completion of the one-year warranty period and approval by the Village Engineer, except:
(1) When multipurpose wet facilities are planned or are suitable for use for private aquatic recreation or for aesthetic enhancement of the owner’s property; and
(2) When multipurpose dry facilities incorporate surface recreational improvements.
(G) Private detention facilities.
(1) Shall be designed requiring the same criteria as the public detention faculties.
(2) The amount of easement shall be equal to the land occupied by the facility plus a 20-foot wide strip around the perimeter of the highest elevation attained by the design storage volume, plus an excess easement 20 feet in width between the facility and public street. This easement shall be shown as common ground or be dedicated to the trustees of the subdivision or owner of the property for the purpose of maintenance of the storm water detention facility.
(3) A plan for perpetual maintenance and designating responsibility for the maintenance shall be provided for its continuing performance to the standards established by this criteria.
(1999 Code, § 34-5-63)