(A) Applicability: The regulations of this section apply to all development, as described herein.
(B) Cost Of Construction: A properly designed storm sewer system must be provided at the expense of the owner or developer of a subdivision or other tract of land as required by this section.
(C) Permits:
1. Storm Sewer Permits:
(a) No connection to or extension of any storm sewer in the city may be made until a permit has been issued.
(b) Storm sewer application permits must be accompanied by three (3) sets of plans and specifications for review prepared by a registered professional engineer of Illinois.
(c) When the plans and specifications are approved and a permit has been issued, the applicant must furnish the city with an additional three (3) sets of plans and specifications.
(d) The city must be given an advance notice of forty eight (48) hours before any construction begins.
2. Excavation Permits:
(a) A permit is required for any excavation for constructing, repairing or replacing a storm sewer in any location.
(b) A cash deposit for ground restoration in the amount set by the city council must be paid prior to issuance of an excavation permit. The ground must be restored to the city's standards. If the ground is not restored to the city's specifications, restoration may be completed at the city's expense with costs deducted from a required deposit amount, with the balance of the deposit returned after all restoration has been completed.
(D) Certificate Of Insurance:
1. Any person, firm or corporation performing work under this section must take out and maintain during the construction of the project liability and property damage insurance that will protect him, the city and the city's representatives from claims from liability and property damages that may arise from construction of the work.
2. The city must be furnished certificates of insurance issued by the companies carrying the risk, and the certificates must be in form and substance satisfactory to and approved by the city.
(E) Design And Construction Standards: The design and construction of the storm sewer system and stormwater storage facilities within the jurisdiction of the city must conform to the most restrictive of the requirements contained in the latest edition of the following regulations, standards and specifications, which will be on file in the city clerk's office:
1. "Standard Specifications For Water And Sewer Main Construction In Illinois".
2. "Standard Specifications For Road And Bridge Construction", Illinois department of transportation.
3. "Design Manual", state of Illinois, department of public works and buildings, division of highways, bureau of design.
4. "Highway Standards", state of Illinois, department of public works and building division of highways, bureau of design.
5. "Manual Of Policies And Procedures", location and environment, Illinois department of transportation.
6. Standards adopted by the metropolitan sanitary district of Greater Chicago.
(F) Rainwater Drains: No rainwater drain may discharge onto any sidewalk or public way, and no drain may discharge onto any public street or alley at a height greater than eighteen inches (18") above grade.
(G) Storm Sewers For Impervious Areas:
1. Storm sewers and catch basins must be provided for all impervious surface areas larger than seven thousand five hundred (7,500) square feet when a public storm sewer is no more than one hundred feet (100') from the property line measured along a public right of way or sewer system easement.
2. One catch basin must be provided for the first thirty thousand (30,000) square feet of impervious area and one additional catch basin must be provided for every additional ten thousand (10,000) square feet of impervious area or fraction thereof.
3. All other impervious areas must be designed to drain to a public street or an existing open watercourse. No drainage may be allowed to pass onto adjoining property or over public sidewalks unless at the point where a driveway intersects the sidewalk.
(H) Subdivisions: No plat may be approved for a subdivision that is subject to periodic flooding or which contains poor drainage facilities and which would make adequate drainage of the lots and streets impossible. However, if the subdivider agrees to make improvements that will, in the opinion of the city engineer, make the area safe for residential occupancy and provide adequate lot and street drainage, the preliminary plat of the subdivision may be approved.
(I) Connection Of Sanitary Wastes To Storm Sewers Or Watercourses: No sanitary sewage may discharge into any portion of the city storm drainage system or any watercourse.
(J) Storm Sewer Capacity:
1. Storm sewer capacities must be designed for a minimum 10-year storm frequency. Storm sewer capacities will be determined using the rational formula (Q = CiA, where Q = peak runoff rate in cubic feet/second, C = runoff coefficient, i = average intensity of rainfall in inches/hour, A = drainage area in acres).
2. When stormwater storage is required, provision must be made to transport stormwater runoff from a 100-year storm frequency from the fully developed area of the site to the stormwater storage area. The additional stormwater runoff resulting from the design for a 100-year storm frequency may be transported to the stormwater storage area over streets, parking areas, parks, playgrounds or other open spaces, including utility easements.
3. The storm sewer system must have adequate capacity to adequately drain all tributary drainage areas through the property, and there will be no compensation to the owner or developer by the city for the increased pipe sizes and construction costs, if any.
4. In any subdivision, lot, or parcel of land where it is determined by the city engineer that the storm sewer would be larger than ninety six inches (96"), based on a 20-year storm frequency, then a ditch or drainage channel meeting the following standards may be used if the council so approves.
(a) With grades to four percent (4%), ditch may have earth bottoms and sod banks.
(b) With grades greater than four percent (4%), ditches must be paved.
(c) All ditches must have side slopes of not less than three to one (3:1).
(d) Easements for all ditches must be dedicated to the city and there must be provided in addition to the necessary width required for the ditch, a strip of land on each side of the ditch of a width of fifteen feet (15'), such distance to be measured perpendicular to trees, poles, structures and other obstructions. The slope of these side areas to the ditch may not exceed five percent (5%). There may be no trees, bushes, or obstructions of any kind placed in this area.
(e) Culverts or bridges must be provided at all street crossings and must be sized to eliminate flooding or ponding of water and must have a minimum cover of twelve inches (12"). Culverts or bridges must be reinforced concrete or precast reinforced concrete pipes with necessary headwalls. Culverts or bridges must extend a minimum of five feet (5') past each right of way line of the street and must extend far enough to provide a minimum slope of three to one (3:1) from the right of way line down to the invert of the pipe.
(f) All ditches, bridges and culverts must be located and designed in accordance with current applicable standards as amended from time to time and requirements of the city engineer.
(g) All culverts or bridges must be provided with suitable railings and/or guardrails as required and approved by the city.
(K) Manholes And Catch Basins: Manholes must be provided at all changes in direction and at intermediate points not exceeding three hundred fifty feet (350') apart. Catch basins with curb inlets must be provided as required by the "Design Manual", state of Illinois, department of public works and buildings.
(L) Stormwater Storage Facilities:
1. Where Required:
(a) Nonresidential Development: A properly designed stormwater storage facility must be provided by the developer of all nonresidential developments that contain an area greater than one acre or, if less than one acre, where fifty percent (50%) or more of the area is covered with impervious improvements, unless an approved facility exists for the property. This requirement does not apply to replacement of improvements on property in cases where the impervious coverage of the development is not increased.
(b) Residential Development: Stormwater storage must be provided for all residential developments larger than two (2) acres. This requirement does not apply to replacement of improvements on property in cases where the impervious coverage of the development is not increased.
2. Basis Of Design:
(a) The necessary volume of stormwater storage will be calculated on the basis of a 100-year storm frequency using the criteria established by the metropolitan sanitary district of Greater Chicago. The volume required will be that necessary to handle the runoff for a 100-year storm for any and all durations, from the fully developed drainage area of the site tributary to the reservoir less that volume discharged during the same duration as the allowable release rate.
(b) No stormwater storage will be required for off site upstream areas.
(c) Flows from off site tributary areas resulting from a 10-year storm frequency will be drained through the storm sewer system provided for the site. Off site flow in excess of the 10-year storm frequency must be bypassed through the site as overland flow and must be calculated using the 100-year storm frequency.
(M) Allowable Release Rate: The allowable release rate of stormwater runoff from the developed drainage area of the site must not exceed the existing capacity of the downstream storm sewer system or drainage channel, but in no case may the discharge be more than the runoff of the existing site using a "C" factor of 0.2 and a 5-year rainfall frequency in the rational formula. No outlet pipe may be of a diameter of less than eight inches (8") and of a diameter so as not to restrict the designed allowable release rate from any stormwater storage facility. Outlet control facilities other than pipes must be constructed of reinforced concrete. Outlet pipes from storage areas must be approved by the city. This limitation applies only to improvements constructed pursuant to building permits applied for after the effective date specified in section 14-1-2 of this title.
(N) Bypass:
1. The drainage system that is provided for the site must have adequate capacity to safely bypass through the development the flow resulting from a 100-year storm frequency from all upstream areas assuming the land is in a fully developed state under present zoning or proposed zoning outlined in the comprehensive plan. The flow must be calculated using a runoff coefficient of not less than 0.50. An allowance must be made for any upstream stormwater storage that has actually been provided.
2. The required bypass area for stormwater in excess of the volume handled by the storm sewer system may consist of streets, parking areas, parks, playgrounds or other open spaces, including utility easements. There may be no habitable structures located within this bypass area that is used as a floodway, and this bypass area may not be reshaped or restricted in any way to reduce its effective capacity.
3. The design of the bypass area must take into consideration the control of the stormwater velocity to prevent erosion. The side slopes on any drainage swale may not be steeper than three to one (3:1).
(O) Stormwater Storage Areas: The required volume of stormwater storage may be provided in paved parking areas and in reservoirs with either a wet or dry bottom. Alternate types of stormwater storage areas must be approved by the city engineer.
1. Parking Areas: The stormwater storage areas must be designed so that the accumulation of water at any point in the parking lot during peak rainfall does not exceed eight inches (8"). The parking lot must be sloped to drain at a minimum of one percent (1%). The finished floor elevation of all buildings must be set so that no damage would occur if a storm in excess of the 100-year storm frequency occurs or if the drainage outlet becomes plugged.
2. Dry Bottom Reservoirs:
(a) A dry bottom type of reservoir may be designed to serve a secondary purpose for recreation, open space or other types of uses that will not be adversely affected by periodic flooding.
(b) A paved ditch with a slope of not less than 0.50 percent will be required from the inlet pipe or structure to the outlet pipe or structure to prevent erosion of the bottom of the reservoir when the capacity of the inlet pipe exceeds five (5) cfs or when the inlet pipe has a constant flow, even during dry weather. In certain cases, dry bottom reservoirs must have a pipe underdrain system as required by the city engineer. The paved ditch must meet the requirements for paved ditches contained in the "Highway Standards", state of Illinois, department of public works and buildings, division of highways, bureau of design.
(c) The grassed bottom of the reservoir must slope to drain to the outlet or paved ditch at a minimum of one percent (1%) slope. The side slopes on the earth berm around the reservoir must not be steeper than four to one (4:1) and the earth berm at the top may not be less than ten feet (10') wide.
(d) The inlet and outlet pipes or structures from the reservoir must be self-operating and require very limited maintenance. An emergency overflow spillway must be provided from the reservoir in the event a storm in excess of the 100-year storm frequency occurs. The inlet and outlet pipes or structures must be provided with safety bars with maximum openings of six inches (6") to provide for the safety of children.
3. Wet Bottom Reservoirs:
(a) Wet bottom storage reservoirs must be constructed to conform to the current applicable requirements. The minimum depth from the normal water level to the bottom of the side slope must be four feet (4'). A minimum of twenty five percent (25%) of the pond area must be constructed to a minimum depth of ten feet (10') to provide for fish.
(b) Proper measures must be provided by the developer to prevent the water from becoming stagnant.
(c) Where the soil in the bottom of the reservoir is too permeable to hold water, the bottom must be sealed by an accepted method approved by the city engineer.
(d) The inlet and outlet pipes or structures from the reservoir must be self-operating and require very limited maintenance. An emergency overflow spillway must be provided from the reservoir in the event a storm in excess of the 100-year storm frequency occurs. The inlet and outlet pipes or structures must be provided with safety bars with maximum openings of six inches (6") to provide for the safety of children.
(P) Requirements During Construction: Construction operations must be conducted in such a manner as to minimize erosion potential on the site. Silting of off site downstream areas must be controlled through the appropriate use of sedimentation basins, including retention/detention facilities designed for that purpose, provided that such facilities will be restored to their prior design configuration upon completion of construction operations. The developer must indicate the methods and timing of construction to be used for the control of siltation during construction operations at the time that final engineering plans are submitted for approval.
(Q) Approval: All work required to be done under this section must be periodically inspected by and approval obtained from the city superintendent in charge, or city engineer as the work progresses. When the work is completed, final approval must be obtained from the city superintendent in charge or city engineer. Before final approval can be obtained, the superintendent in charge or city engineer must inspect all work and see that it has been completed in accordance with the approved plans and specifications.
(R) Stormwater Management Facility Maintenance:
1. Routine Maintenance: The homeowners' association whose property or common area includes all or a portion of an open drainage swale, channel, detention basin or other stormwater management facilities will be held responsible for the mowing of grass, removal of debris or obstructions to the flow of water in or through such facilities, removal of silt, and maintenance and repair due to erosion.
2. Nonroutine Maintenance:
(a) Nonroutine maintenance, including maintenance activities that are expensive but infrequent, such as pond dredging or major repairs to stormwater structures, must be performed on an as needed basis based on information gathered during regular inspections.
(b) A legally binding covenant specifying the parties responsible for proper maintenance of all stormwater management facilities must be provided by the developer and approved by the city prior to final plat approval, or for properties not subject to the plat approval process, prior to the issuance of site plan approval or building permits, whichever comes first.
(c) The maintenance agreement must include a description of maintenance and repair procedures to be completed, including identification of components that need to be maintained and standards for maintenance.
3. Inspections:
(a) The persons or organizations responsible for maintenance must inspect stormwater management facilities on a regular basis, as outlined in the maintenance agreement.
(b) Authorized representatives of the city of Spring Valley may enter at reasonable times upon any time to conduct on site inspections or routine maintenance. (Ord. 1379, 6-9-2008)