(A) General principles.
(1) Development should be related to the topography and soils of the site so as to create the least potential for erosion. Areas of steep slopes, where high cut and fills may be required, should be avoided and natural contours should be followed as closely as possible.
(2) Natural vegetation should be retained and protected. Clearing of natural ground cover and/or trees within a buffer area as defined in § 151.24 should be left undisturbed wherever possible.
(3) The smallest practical area of land should be exposed at any one time.
(4) Prior to site clearing and grading, sediment basins or traps, filter barriers, diversions, and other appropriate control measures shall be installed and functional.
(5) Permanent vegetation and structures should be installed and functional as soon as practical during development. Native vegetation is preferred for developments near, or adjacent to high quality natural areas, wetlands, and streams.
(6) Those areas being converted from agricultural purposes to other land uses shall be vegetated with an appropriate protective cover prior to development.
(7) All waste generated as a result of site development shall be properly disposed of and shall be prevented from being carried off the site by either wind or water.
(B) On-site control measures. The on-site control measures shall be designed based on the size of the disturbed area as follows:
(1) For disturbed areas draining less than one acre, filter barriers (including filter fences, straw bales, or equivalent control measures) shall be constructed to control all off-site runoff as specified in referenced handbooks. Vegetated filter strips, with a minimum width of 25 feet may be used as an alternative where runoff in sheet flow is expected.
(2) For disturbed areas draining more than one acre, a sediment trap or equivalent control measure shall be constructed at the downslope point of the disturbed area in conjunction with other filter barriers.
(3) Sediment basin and trap design shall provide for both detention storage and sediment storage. The detention storage shall be for equal volumes of "wet" detention storage and "dry" detention storage. Each shall be sized for the two-year, 24-hour runoff from the site. The release rate shall be the rate required to achieve a minimum detention time of 10 hours. The outlet structure shall be placed such that it only drains the wet detention storage.
(4) The sediment storage shall be sized to store the estimated sediment load generated from the site over the duration of the construction period with a minimum storage equivalent to the volume of sediment generated in one year. A sediment removal schedule is required for construction periods exceeding one year.
(C) Storm water conveyance channels. Stormwater conveyance channels, ditches, swales, and diversions shall convey a 10-year frequency storm without erosion. All channels shall be stabilized within 48 hours, consistent with the following standards:
(1) For grades up to 4%, seeding in combination with mulch or erosion blankets shall be placed along the channel sides with sod or erosion control blanket applied to the bottom.
(2) For grades of 4% to 8%, sod shall be used.
(3) For grades greater than 8%, use rock or rip-rap, or reduce the grade using drop structures.
(D) Channel protection.
(1) A vegetated buffer strip of at least 25 feet in width shall be preserved and/or re-established, where possible, along existing channels.
(2) Land disturbance activities in stream channels and construction vehicle use of channels shall be minimized.
(3) Temporary stream crossings shall be constructed, where necessary, to minimize erosion. Temporary crossings shall be constructed of non-erosive materials such as rip-rap or gravel.
(4) The temporary stream crossing shall be completely removed and the stream restored to its pre-construction condition within 48 hours after completion of construction, incorporating appropriate native vegetation.
(E) Additional requirements.
(1) Storm sewer inlets and culverts shall be protected by sediment traps or filter barriers meeting accepted design standards and specifications.
(2) If dewatering devices are used, discharge locations shall be protected from erosion. Water pumped or otherwise discharged from the site during construction shall be filtered and a means provided to reduce erosion. All pumped discharges shall be routed through appropriately designed sediment traps, or basins, or equivalent.
(3) Each site shall have graveled entrance roads, access drives, and parking areas of sufficient length and width to prevent sediment from being tracked onto public roadways. Any sediment reaching a public or private road shall be removed by shoveling or street cleaning (not flushing) before the end of each workday and transported to a controlled sediment disposal area.
(F) References adopted.
(1) Specifications for erosion control measures shall be in accordance with the Illinois Urban Manual latest edition.
(2) Sediment and erosion control planning shall be in accordance with Procedures and Standards for Urban Soil Erosion and Sedimentation Control in Illinois (revised July 1988) by the Urban Committee of the Association of Illinois Soil and Water Conservation Districts (the "Green Book") Chapters 1-5.
(3) Where the requirements of §§ 10, 2-10, 5 of this chapter, the Illinois Urban Manual or the "Green Book" conflict, the more restrictive requirement shall prevail.
(G) Plan requirements. An erosion and sediment control plan shall include the following:
(1) Proposed sequencing schedule, including dates, for:
(a) Stripping;
(b) Installation of temporary on-site control measures and perimeter control;
(c) Clearing and grading;
(d) Construction;
(e) Installation of storm drainage and paving; and
(f) Final grading, removal of temporary measure, and landscaping.
(2) Location, standard details, and design specifications of sediment basins and traps. The design specifications should include outlet details and the drainage area.
(3) Location and description of all control measures, including seeding mixtures and rates, types of sod, method of seedbed preparation, expected seeding dates, kind and quantity of mulching for both temporary and permanent vegetative control measures and types of non-vegetative stabilization measures.
(4) Description of dust and traffic control measures and location and specifications for construction entrances.
(5) Locations of stockpiles and description of stabilization measures.
(6) Volumes, locations, and methods of stabilization for off-site fill or borrow.
(7) Provisions for maintenance of control measures, including a maintenance schedule.
(8) Description of permanent stabilization measures.
(9) Identification (name, address and telephone) of the person(s) or entity responsible for maintenance during and after construction.
(H) Extended construction shutdown period. Disturbed areas shall be stabilized with temporary or permanent measures within 14 calendar days following the end of active disturbance or re-disturbance. The condition of the construction site for the winter shut down period shall address proper sediment and erosion control early in the fall growing season. Stabilization measures include seeding, mulching, sodding or erosion control blankets.
(I) Final site stabilization. All temporary control measures shall be disposed of within 30 days after permanent soil stabilization measures have been installed. Trapped sediment and other disturbed soils resulting from the temporary measures shall be permanently stabilized to prevent further erosion and sedimentation.
(Ord. O-14-03, passed 2-18-03)