A. Specifications And Design Criteria: Control of stormwater runoff and all stormwater management facilities shall be in accordance with the Kane County stormwater ordinance, adopted by the Village.
The proposed storm sewer system shall be sized, at a minimum, to convey the stormwater runoff generated during a rainfall event with a return frequency of not less than five (5) years. The design peak runoff shall be determined using the modified rational method. The design rainfall intensity shall be determined from "Illinois State Water Survey Bulletin 70", specifically appendix A (Aurora) and summarized below. Please note the table is only an excerpt from Bulletin 70 appendix A for Aurora and reflects the depth of rainfall in inches and the rainfall intensity (in/hr) for a 5-year frequency in northeastern Illinois. The provided values can be interpolated to determine incremental intensity for various times of concentrations.
5-YEAR FREQUENCY RAIN EVENT
Duration | Rainfall Depth (Inches) | Intensity (Inches Per Hour) |
Duration | Rainfall Depth (Inches) | Intensity (Inches Per Hour) |
5 minutes | 0.47 | 5.52 |
10 minutes | 0.86 | 5.04 |
15 minutes | 1.06 | 4.12 |
30 minutes | 1.45 | 2.82 |
1 hour | 1.85 | 1.79 |
2 hours | 2.32 | 1.12 |
3 hours | 2.52 | 0.81 |
6 hours | 2.95 | 0.48 |
The time of concentration used to determine the design rainfall intensity shall be calculated for the fully developed condition using Worksheet 3, as published in the SCS Technical 55 Manual.
The capacity of the storm sewer system must be determined by gravity flow only. The Village will not allow siphons or pump stations to convey stormwater runoff. The design shall disallow the effects of surcharging, with the exception of decreases in capacity due to tail water effects on outlets. The tailwater elevation of the receiving pond, or other body of water, to be used in storm sewer design shall be that which exists at the specific time being evaluated.
The storm sewer must be designed to have a minimum full flow velocity of two feet (2') per second. When storm sewers of different diameters enter or exit storm sewer structures, the controlling elevation shall be 0.8 times the respective diameters. Storm sewers smaller than the largest exit pipe may be raised above the controlling "0.8" elevation.
The composite runoff coefficient for the area tributary to each storm sewer structure collecting surface water shall be determined by the character of the land to be drained when fully developed using the following runoff coefficients:
Grass | 0.40 |
Impervious surfaces | 0.96 |
Water surfaces | 1.00 |
Storm sewers of sufficient capacity shall be constructed throughout the entire subdivision and shall be connected to an adequate outfall. Intercepting stormwater inlet or catch basin structures in streets shall be provided at maximum intervals such that the continuous length of flow along a gutter line is not in excess of three hundred feet (300'), as measured along the gutter line. However, additional inlets may be required, as determined by the Village Engineer, such that the width of flow during the design storm does not create a hazard to the motoring public. The Illinois Department of Transportation's Drainage Manual shall be used as guidance for allowed pavement encroachment.
All stormwater runoff which flows overland into or out of a storm sewer system must enter or exit through a curb inlet, catch basin, flared end section, slope box, or a cast in place, reinforced concrete headwall. Grates shall be required on all flared end sections twelve inch (12") diameter and larger. The minimum diameter of all storm sewers shall be twelve inches (12"), with the exception of closed lid systems which accept no surface water and which are solely designed for handling sump pump discharges, in which case the minimum size shall be six inch (6"). Two feet (2') minimum cover above the top of the pipe shall be provided for all storm sewers, unless otherwise approved by the Village Engineer due to unique circumstances. No pipe shall extend upward into the aggregate base course of a roadway.
Curb inlets, curb catch basins and rear yard catch basins shall not be constructed on storm sewers greater than eighteen inches (18") in diameter. Storm sewer trunk lines are encouraged in rear yards and limited longitudinal installation of storm sewer under roadways may be permitted by the Village Engineer. For each pair of curb inlet structures on opposite sides of a roadway, the downstream structure shall be a catch basin. No more than three (3) precast concrete adjusting rings, not exceeding ten inches (10") thickness, may be used on any structure. All storm sewer structures, other than curb inlets and curb catch basins shall be marked at the time of construction with a 4" x 4" hardwood post neatly installed vertically with a minimum four feet (4') bury and a minimum four feet (4') exposed. The top one foot (1') of the post shall be neatly painted green.
All manholes, catch basins, and inlets shall be reinforced precast concrete and shall be sealed with butyl rope joint sealant unless approved otherwise by the Village Engineer in high groundwater or high moisture soil areas. Storm sewer manholes shall be spaced at a general interval of four hundred feet (400'). All manholes shall be placed near the extension of side property lines whenever possible.
All stormwater from paved areas must pass through a catch basin prior to entering the storm sewer trunk line. All stormwater will also be required to pass through a catch basin prior to entering a detention/retention pond. Inlets or catch basins with a diameter of two feet (2') will not be allowed if more than one (1) 12-inch diameter pipe is proposed. The exception to this rule is if the other connections are four inch (4") diameter sump pump discharge lines. All catch basins and inlets will be backfilled with CA-7 crushed limestone or crushed gravel to allow for sub- grade seepage. If sub-grade conditions are excessively wet, excessively sensitive to moisture or special conditions exist as deemed by the Village or Village Engineer, a capped perforated pipe underdrain stubbed from the structure may be required.
The stormwater drainage system shall be separate and independent of the sanitary sewer system. Storm sewer shall be constructed of reinforced concrete pipe (RCP) conforming to the ASTM designation C-76, Class III or better. Other materials for storm sewers may be used in special cases upon the written approval of the Village Engineer. Any flexible pipe storm sewer systems so approved by the Village Engineer shall be subject to mandrell testing, for all sections, thirty (30) days following installation. Existing ground water drain tiles that enter the site from other properties shall be connected to the new storm sewer system with the use of a manhole or shall be restored to operating condition at the direction of the Village Engineer. The design capacity of the on-site storm sewer system shall consider all flows attributed to these drain tiles so connected. Joints for all concrete storm sewers shall be of the bituminous mastic or rubber gasket type, except when otherwise required by the Illinois Environmental Protection Agency or the Village Engineer. All storm sewers that encroach within fifteen feet (15') of any building foundation shall be "O"-ring, or other rubber, gasketed joints as per the ASTM C-443 specification.
Street grades and lot and block drainage shall be established so as to permit positive drainage to the storm sewer system. Parking lots shall be drained internally and directed to the storm sewer system where practical. Horseshoe drainage of individual lots should be avoided.
B. Manholes, Frames And Grates:
1. Inlet And/Or Catch Basin Castings: For M-3.12 curb and gutter under ponding or continuous grade conditions, inlet and/or catch basin frames and grates shall be Neenah R-3501-P, EJIW 7525, or approved equal. For B-6.12 curb and gutter under ponding conditions, inlet and/or catch basin frames and grates shall be Neenah R-3281-A, EJIW 7210 with type M2 grate and T1 back, or approved equal. For B-6.12 curb and gutter under continuous grade conditions, inlet and/or catch basin frames and grates shall be Neenah R-3281-AL, EJIW 7210 with type M4 vane grate and T1 back, or approved equal. All curb inlet frames shall be sealed with a hydraulic cement fillet between the frame and top adjusting ring or cone section.
When additional grate capacity is needed in ponding conditions to handle the tributary flow, additional inlet structures shall be utilized. In cases where storm sewer inlets are used in depressed barrier curb areas, use Neenah R-3339-1, EJIW 5130, or approved equal. In rear yards and all other turf applications (except roadside ditch drainage applications) catch basins shall use Neenah R-1713 with type D cover, EJIW 1050 with type M1 radial flat grate, or approved equal. Roadside ditch drainage structures shall be evaluated on a case by case basis.
All closed storm structure lids shall have "Village of Sugar Grove" and "STORM" cast into top and shall be the concealed pick hole type.
2. Sediment Control: All storm sewer inlet structures shall utilize Flexstorm Inlet Filters™, or approved equal, to properly manage sediment control and to minimize storm sewer televising and cleaning which would otherwise be required prior to Village acceptance of the storm sewer system. All inlet filters shall be properly maintained until such time as all areas tributary to a particular inlet have been adequately vegetated.
3. Manhole Castings: Construction and installation of all storm sewer manholes shall comply with the Standard Specifications for Water and Sewer Main Construction in Illinois. Storm sewer structures shall be sized such that a minimum of twelve inches (12") of precast concrete structure is provided between all pipe openings. When closed lids are needed, manhole castings shall be IDOT type 1 Neenah R-1713 frame with type B cover, EJIW 1050, or approved equal. In paved areas, cast in place concrete blocking, a minimum of ten inches (10") thick, extending eighteen inches (18") out from the frame is required. The surface of the concrete blocking shall be set at the elevation of the bituminous binder course. In concrete pavement applications, the surface of the blocking shall match the finish pavement surface. When open lids are needed, use Neenah R-1713 with type D cover, EJIW 1050 with type M1 radial flat grate, or approved equal. All type B covers shall have "Village of Sugar Grove" and "STORM" cast into the top and shall be the concealed pick hole type.
C. Sump Pumps: The connection to the storm sewer shall be through a structure. Stubs shall be provided as appropriate for all lots and shall extend at a minimum to the easement line to avoid excavation issues with other buried utilities. All pipe used for sump pump discharge collector lines shall be PVC (SDR-26) of the size specified by the engineer. Sump pump discharges to a closed pipe system shall be provided with an outside air break to facilitate flow.
All individual sump pump lines shall be connected to a storm structure or sump pump discharge collector line structure. Sump pump collection lines shall be six inches (6") diameter minimum. Sump pump discharge collector lines shall have a cleanout/inlet structure at the upstream end and shall have a cleanout/inlet structure every three hundred feet (300') maximum. Sump pump cleanout structures shall be two foot (2') diameter structures and will not be allowed to pick up surface drainage. All sump connections to the cleanout/inlet structure shall be precast or core drilled and shall be sealed inside and outside the structure with hydraulic cement. The minimum depth of cover for sump pump service lines is twenty four inches (24"). The frame and lid shall be Neenah no. R-1706-1 or approved equal. All sump pump service stubs shall be marked at the time of construction with a 2" x 4" wood post neatly installed vertically with the bottom set at the invert elevation of the capped stub, a minimum three feet (3') bury and a minimum four feet (4') exposed. The top one foot (1') of the post shall be neatly painted green. (Ord. 2018-02-20, 2-20-2018)