(Ord. 3281 - 8/16/99)
A. General.
1. All development, whether public or private, shall include provisions for the construction of storm sewers and appurtenances designed in accordance with this Section. Developers shall use either the public sewer system or an alternative sewer system, certified by an agency or municipality with jurisdictional authority, provided that the development is proximate to a transmission line that has adequate capacity to handle such proposed development.
2. All development designated by the Director of Engineering shall include provisions for storm water holding facilities designed in accordance with this Section. The storm water holding facilities should incorporate multiple uses where practicable.
The detention (dry pond), retention (wet pond), or depressional storage areas that are to be used as part of the drainage system for a property shall be constructed as the first element of the initial earthwork program. Any eroded sediment captured in these facilities shall be removed by the applicant before project completion in order to maintain the design volume of the facilities. (Ord. 3837 - 12/1/03)
3. Storm sewer systems shall be installed in accordance with Section 600 of the "Standard Specifications for Road and Bridge Construction," and "Standard Specifications for Water and Sewer Main Construction in Illinois," latest edition, unless otherwise modified in this Section.
4. Stormwater system designs should be in conformance with Illinois EPA stormwater permitting requirements. In particular, a state National Pollutant Discharge Elimination System (NPDES) Permit for Construction Site Activities is required for land disturbances of five or more acres. Permit requirements for a "stormwater pollution prevention plan" specifically reference the need for stormwater detention, vegetated swales and natural depressions, infiltration measures, and velocity dissipation devices to control runoff pollutants and to maintain pre development hydro logic conditions.
5. All dry basins with volume control and Best Management Practices (BMP’s) must have a minimum of 4" under drain or as required by the Director of Engineering. (Ord. 3837 - 12/1/03; Amd. Ord. 5822 - 7/17/23)
6. In wet ponds natural landscaping is required to be planted at not less than 5 feet wide at the normal water line for a 4:1 slope. (3837 - 12/1/03)
B. Service Areas. All storm sewers, streams or channels shall be designed to accommodate all areas which naturally flow to the area of the development and also any additional areas which are planned to contribute to the drainage area as identified by the Director of Engineering. The drainage areas as designated shall be designed to not adversely impact the capacity of the downstream system.
C. System Extension. The location of proposed extensions to the existing storm sewer system shall be approved by the Director of Engineering.
D. Submittal Requirements
1. Drainage Plan. Each applicant shall submit the following information as required by
the Director of Engineering, depending on development size. Properties smaller than 10 acres shall submit the Basic Drainage Plan. Properties larger than 10 acres shall comply with the submittal requirements of both the Basic Drainage Plan and the Advanced Drainage Plan. The applicant shall have a registered professional engineer certify on the drawings that all clearing, grading, drainage, and construction shall be accomplished in strict conformance with the drainage plan. The following information shall be submitted for both existing and proposed property conditions.
2. Topographic Map: A topographic survey of the property at one foot contours under existing and proposed conditions, and areas upstream and downstream, necessary to determine off site im pacts of the proposed drainage plan. The map shall be keyed to a consistent datum specified by the Director of Engineering.
3. Provide a narrative describing the existing conditions of the site, identifying previous permitting (if applicable), and requirements for meeting outside agency permitting, such as the MWRD Watershed Management Ordinance.
4.
Basic Drainage Plan: Mapping and descriptions, where relevant, of existing and proposed drainage system features of the property and immediate vicinity including:
a. The banks and centerline of streams and channels;
b. shoreline of lakes, ponds, and detention basins;
c. the limits of wetland areas;
d. any designated natural areas;
e. any proposed environmental mitigation features;
f. farm drains and tiles;
g. sub watershed boundaries within the property;
h. watershed soils classifications;
i. the property's location within the larger watershed;
j. location, size and slope of stormwater conduits and drainage swales;
k. depressional storage areas;
l. delineation of upstream and downstream drainage features and watersheds which might be affected by the development;
m. detention and/or retention facilities; (Ord. 3837 - 12/1/03; Amd. Ord. 5822 - 7/17/23)
n. roads and streets and associated stormwater inlets;
o. base flood elevation, and regulatory floodway where identified for the property; and
p. basis of design for the final drainage network components.
5. Advanced Drainage Plan: The same information as required under the Basic Drainage Plan is required for properties larger than 10 acres along with the following additional information for the minor drainage system's design runoff event and the 100-year runoff event of critical duration:
a. Elevations and maps of 100-year flooding;
b. cross section data for open channel flow paths and designated overland flow paths;
c. direction of storm flows;
d. flow rates and velocities at representative points in the drainage system; and
e. a statement by the design engineer of the drainage system's provisions for handling events greater than the 100-year's runoff.
E. Basic Design Standards. The following criteria should be used in evaluating and designing the drainage system. The underlying objective is to provide capacity to pass the 10-year peak flow in the minor drainage system and an overland flow path for flows in excess of the design capacity. Whenever practicable, all areas of the property must be provided an overland flow path that will pass the 100-year flow at a stage at least 1 foot below the lowest grade adjacent to the foundation in the vicinity of the flow path. Overland flow paths designed to handle flows in excess of the minor drainage system capacity shall be provided drainage easements. Street ponding and flow depths shall not exceed curb heights by more than one inch, except as allowed by the Director of Engineering.
1. Drainage Area. The drainage area, in acres, used for design shall be the entire watershed service area tributary to the point in the drainage system under consideration. It shall include any tributary service area that may be outside the development.
2. Rainfall Intensity. The rainfall data source for computations of hydraulic and hydrologic analysis shall be based upon Frequency Distributions and Hydroclimatic Characteristics of Heavy Rainstorms in Illinois and the latest rainfall data source approved by the Illinois State Water Survey (ISWS) shall be used. The average rainfall intensity used for design shall be selected from a Rainfall Intensity Duration curve, as follows:
a. Underground storm sewer water conduits and swales shall be determined from the ten (10) year storm event curve.
b. Surface streams and open channels shall be determined from the one hundred (100) year storm event curve.
c. The elapsed duration time used in selecting a specific point on the rainfall intensity curve shall be equal to the time of concentration, defined as inlet time, plus the time of flow between the most distant inlet and the point in the system under consideration. (Amd. Ord. 5564 - 12/21/20)
3. Storm Sewer, Stream Improvement and Open Channel Hydraulics.
a. Storm sewers, stream improvements and open channels shall be designed to provide design flow capacity using Manning's formula:
Q = (A)(1.486) (R2/3)(S1/2)
n
n
b. Roughness coefficients (n) shall be as follows:
1. Concrete pipe – 0.013
2. Plastic pipe (PVC)(HDPE) – 0.010
3. Open channels concrete or asphalt lining – 0.013
4. Open channels sodded – 0.020
5. Improved stream – 0.025
6. Natural stream – 0.050
7. High-Density Polyethylene (HDPE) 0.012.
(Amd. Ord. 5653 - 11/1/21)
c. Design mean velocity shall not exceed the following:
1. Storm sewers – ten (10) feet per second.
2. Open channels, concrete or asphalt lining – ten (10) feet per second.
3. Open channels, sodded – five (5) feet per second.
4. Storm sewer, including manholes, shall be constructed so that infiltration shall not exceed thirteen hundred (1300) gallons per inch diameter of sewer per mile per twenty four (24) hour day at any time for any section of the system.
4. Natural Stream Channels. Natural stream channels that are designated by the Board of Trustees for the Village of Orland Park shall be retained in lieu of either constructed open channels or enclosed storm sewer pipes. Natural stream channels shall be regulated by provisions in Section 6-411 and Section 6-412 of these regulations. (Amd. Ord. 5312 – 7/16/18)
5. Manmade Open Channels.
a. Constructed open channels that are not designated as natural stream channels, and that will be draining an area eighty (80) acres or larger, may be provided on an optional basis in lieu of an enclosed storm sewer pipe.
b. All constructed open channels that are not designated as natural stream channels located within a development or located on public property or easements adjacent to the development and other open channels within one hundred fifty (150) feet of the development, shall be improved as follows:
1. Maximum slopes shall be six (6) horizontal to one (1) vertical.
2. An eight (8) foot wide bituminous concrete (IDOT – Class I) pathway, suitable for use by maintenance vehicles, with a minimum thickness of six (6) inches, shall be constructed a minimum of two (2) feet above the normal water level. The far edge of the pathway shall be a minimum of one (1) foot within the easement running along the open channel. The near edge of the pathway shall not be more than ten (10) feet from the edge of the normal water line.
3. A six (6) inch underdrain shall be constructed with a minimum cover of six (6) inches along the flowline of all open channels.
4. An easement for drainage, access and municipal utilities, shall be provided along the open channel with a width adequate to include the area covered by an one hundred (100) year storm.
6. Swales. All swales shall be sodded and limited to a maximum water depth of twelve (12) inches. The maximum water depth shall be a minimum of one foot (1') below the lowest opening of an adjacent foundation along the flow path. Maximum side slopes of swales shall not be steeper than six (6) horizontal to one (1) vertical.
7. Alignment. Sewer shall be laid straight in both horizontal and vertical planes between manholes, unless otherwise approved by the Director of Engineering.
8. Pipe Design Flows. Unless otherwise approved by the Director of Engineering, storm sewer pipes and open channels shall be designed to carry storm water runoff flows determined by the Rational Method using the formula:
Q = C i A
Where Q = runoff flow in units of cubic feet per second.
C = runoff coefficient, characteristic of tributary drainage area in dimensionless units.
A = tributary drainage area in units of acres.
i = average rainfall intensity in units of inches per hour.
a. The runoff coefficient, C, is the ratio of runoff to rainfall and shall be assumed as follows:
1. All impervious areas (paved or hard surfaced areas of all types and buildings, inclusive of, but not limited to, patios, garage walks, stoned landscaped areas and pools), C shall equal 0.95.
2. All pervious areas (all areas not classified as impervious), C shall equal 0.45.
3. All bodies of water (wetlands, lakes, streams, and depressional storage areas), C shall equal 1.0.
b. The runoff coefficient used in design shall be the weighted average for the proposed tributary watershed.
c. Within a development, the runoff coefficient shall be computed assuming ultimate develop ment. Where ultimate development plans are not available at the time of the design of the storm sewer system, a runoff coefficient shall be selected by the Director of Engineering, based on the zoning classification, knowledge of the specific development and the previous experience of the Village with similar developments. The area within the watershed, but outside the development, shall be computed for existing conditions, the runoff coefficient shall be approved by the Director of Engineering.
9. Minimum Sewer Size.
a. Storm sewer shall not be less than ten twelve (12) inch diameter except where existing storm sewer pipe is smaller in size downstream.
b. Private storm sewer serving sump pumps and roof drains shall not be less than eight (8) inch diameter.
(Amd. Ord. 5653 - 11/1/21)
10. Sewer Size Changes. Storm sewer of different diameters shall join only at structures. The invert elevations shall be adjusted to maintain a uniform energy gradient by matching the 0.8 depth points of the different diameter.
11. Storm Water Inlets.
a. Surface drainage inlets shall be provided so that surface water is not carried across any street intersections or parking lot drives. Surface runoff shall not extend a distance of more than four hundred (400) feet along the surface of the ground and shall not build up a flow of more than two (2) cubic feet per second (with no more than 1.0' of head) in a ten (10) year storm before being intercepted by drainage inlets. Inlets shall discharge into storm sewers which shall not discharge into side lot or rear lot drainage ditches. Inlets shall be provided at all low points.
b. Rear yard inlets having a minimum depth of two (2) feet shall be provided where necessary.
12. Storm Sewer Manholes.
a. Manholes shall be located as follows:
1. At the termination of all sewers which do not terminate at an inlet.
2. Changes in direction, horizontal or vertical.
3. Changes in shape or pipe size.
4. Junctions with other storm sewers.
5. Access spacing shall be:
Sewer Pipe Size (in inches) | Maximum Interval (in feet) |
6 - 24 | 350 |
27 - 36 | 400 |
42 - 54 | 500 |
60 or larger | 1000 |
b. Where flows and other conditions dictate, special manholes or junction chambers shall be designed and constructed.
(Amd. Ord. 5653 - 11/1/21)
13. Sewer Depth. Storm sewers shall be constructed sufficiently deep so as to prevent freezing and provide an outfall for all storm water within the ultimate service area, both existing and future. The minimum cover shall be three (3) feet.
14. Sewer Pipe Class. Sewer pipe class shall be determined based upon the specifications of Section 603 of the "Standard Specifications for Road and Bridge Construction," latest edition.
15. Sewer Pipe Bedding.
a. Sewer pipe bedding shall, as a minimum, conform to the requirements shown on Exhibit No. SS 07.
b. Sewer pipe concrete cradle, arch, or fill encasement shall be constructed whenever dictated by trench or embankment conditions.
16. Building Drainage.
a. The point of discharge of sump pumps is allowed to be connected to storm sewer system for each building served, to the approved storm structure as shown on the Engineering Plans, unless approved otherwise. Storm sewer service lines from that point shall be provided to the storm sewer system. At no point, shall a discharge be directly connected to a storm sewer pipe.
b. Lots shall be graded in such a manner as to cause positive drainage away from the building up to lot line swales or ditches, which shall merge as quickly as possible and then discharge into a storm sewer. The route of flow of storm water away from each building into swales, ditches and storm sewers to where it leaves the site shall be shown on the Engineering Plans.
c. No lot shall be allowed to divert, modify, or change grade elevations from an approved engineering plan without written approval from the Director of Engineering. (Amd. Ord. 5822 - 7/17/23)
17. Vacant Lot Drainage. Positive drainage shall be established for each lot whether or not it is the owner's intention to construct a building on that lot.
18. Storm Water Detention Facilities.
a. Detention Basin (dry pond) Outlet Design: Backwater on the outlet structure from the downstream drainage system shall be evaluated when designing the outlet. (Ord. 3837 - 12/1/03)
b. The volume of detention facilities shall be determined as follows: the maximum volume of storm water generated by the 100 year frequency storm, less the volume of storm water released through the outlet pipe at the calculated peak of the 100 year frequency storm. The design maximum storage to be provided in a detention basin shall be based on the runoff from the 100 year, 24 hour event and reservoir routing or equal. Detention storage shall be computed using hydrograph methods as described in this section. The Director of Engineering may designate an alternative design computation for detention storage.
c. The outlet pipe(s) shall be designed to allow a maximum discharge of no more than 0.15 cubic feet per second per gross acre of development for a 24-hour 100-year storm event and shall include design to allow a maximum discharge of no more than 0.04 cubic feet per second per gross acre of development for a 24 hour 2-year storm event. If the restrictor for the 24-hour, 2-year storm event is deemed too small for practical use by the Director of Engineering, the Director of Engineering will have the authority to determine an appropriate restriction method. Where a single pipe outlet or orifice plate is to be used to control discharge, it shall have a minimum diameter of 4 inches. If this minimum size permits release rates greater than those specified in this section, and regional detention is not a practical alternative, the Director of Engineering may require an alternative outlet design which shall utilize self cleaning flow restrictors. If the receiving storm system is determined to be unable to accept the above calculated discharge rate, a lesser discharge rate may be required, as approved by the Director of Engineering.
d. In order to prevent soil erosion and weed problems, "dry" detention basins must be landscaped including the establishment of a groundcover over all unpaved areas through sodding of native natural growth plant material or material as designated by the Director of Engineering. Such groundcover shall not be of a plant type which can be carried by water plow to aggressively invade other downstream lands or properties, and crown vetch shall be prohibited. Native natural plant growth may comprise a variety of techniques that employ in concert according to the needs of the site. Some of these include biologs, aquatic plants, wattles, natural native grasses, tri lok, and vegetated geogrids. Detention Basins shall be designed so that the portion of their bottom area which is intended to be dry shall have standing water no longer than seventy two (72) hours for all runoff events less than the 100-year frequency storm.
Additional underdraining may be required at the discretion of the Director of Engineering. Pipe runs and spacing shall be designed to ensure good drainage. Detention facilities shall be designed so that the cross slope is at least two (2) percent. The bottom of the facility shall be provided with an underdrain (minimum four (4) inch diameter perforated drain tile) covered on all sides with a minimum of six (6) inches of crushed stone conforming to ASTM C33, Size No. 67. The underdrain shall be installed to drain the basin below grade during periods of low flow and shall connect to a storm sewer outfall pipe. Detention facilities shall be designed with side slopes not steeper than four (4) horizontal to one (1) vertical (4:1). The inflow storm piping system shall be constructed in such a manner so as to allow for "low" flows to bypass the basin. (Ord. 2959 – 11/18/96; Amd. Ord. 5167 – 2/20/17; Amd. Ord. 5653 - 11/1/21; Amd. Ord. 5822 - 7/17/23)
e. Permanent retention ponds ("wet basins") shall be designed in accordance with Exhibit No. STS 13. Native natural plantings are recommended for shorelines and banks. Prior to the construction of the basin, soil testing must be done to determine the need for a clay or synthetic liner and to determine the minimum side slopes required to prevent soil erosion. In order to prevent shore erosion and muskrat digging or denning, a fiber mat or other acceptable material shall conform to any applicable State specifications. The slopes that are inundated by the storm water levels shall be covered with this fiber. Native natural plant growth is recommended and may comprise a variety of techniques according to the needs of the site. Some of these include biologs, aquatic plants, wattles, natural native grasses, tri lok, and vegetated geogrids. Ponds shall have a minimum of four (4) foot horizontal to one (1) foot vertical side slopes (4:1). All slopes that are 4:1 should be sodded. Slopes greater than 4:1 and bottoms of ponds may be hydro-seeded. Sediment basins are required in dry ponds. Access for maintenance purposes should be at least 15 feet wide at the top of the pond property starting at any point above the high water level. At the toe of the slope, a twelve (12) foot wide safety ledge sloped toward the shore at four (4) percent shall be provided. See Exhibit STS 13. Beyond the safety ledge, the pond bottom shall slope at two (2) horizontal to one (1) vertical (2:1) down to the pond bottom elevation. The minimum pond bottom elevation shall be fifteen (15) feet below normal water level for a minimum of 25% of the surface area. Points of inflow to the pond shall be accessible to construction equipment for dredging as necessary. If retention facilities are designated for recreational purposes, appropriate consideration shall be reflected in the design for maintenance of fish life, boating, and safety. Wet basin ponds may be required to have aeration equipment installed to ensure adequate water quality. (Ord. 2959 11/18/96; Amd. Ord. 3837 12/1/03)
f. Detention basins within the floodplain is strongly discouraged. However, the stormwater detention requirements of this ordinance may be fulfilled by providing detention storage within flood fringe areas on the project site provided the following provisions are met.
1. Development in a Special Flood Hazard Area (SFHA) shall require compensatory storage for 1.5 times the volume below the base flood elevation fill placed in the SFHA. If a detention basin is placed in the SFHA, the release from the detention storage provided shall still be controlled consistent with the requirements of this section. The applicant shall demonstrate its operation for all streamflow and floodplain backwater conditions. Excavations for compensatory storage along watercourses shall be opposite or adjacent to the area occupied by detention. All floodplain storage lost below the 10-year flood elevation shall be replaced below the ten year flood elevation. All floodplain storage lost above the existing 10- year flood elevation shall be replaced above the proposed 10-year flood elevation. All compensatory storage excavations shall be constructed to drain freely and openly to the watercourse. (Amd. Ord. 5822 - 7/17/23)
2. On stream Detention: On stream detention basins and detention basins located within the regulatory floodways are discouraged but allowable if they provide regional public benefits and if they meet the other provisions of this ordinance with respect to water quality and control of the two year and 100 year, 24 hour events from the development. If on stream detention is used for watersheds larger than one square mile, a Conditional Letter of Map Amendment approved by the Federal Emergency Management Agency is required prior to any construction and a Letter of Map Amendment from the Federal Emergency Management Agency is required prior to any building construction. The applicant will submit modeling to demonstrate that the design will not increase stage for any properties upstream or downstream of the property. Also, impoundment of the stream as part of on stream detention:
a. shall not prevent the migration of indigenous fish species, which require access to upstream areas as part of their life cycle, such as for spawning,
b. shall not cause or contribute to the degradation of water quality or stream aquatic habitat,
c. shall include a design calling for gradual bank slopes, appropriate bank stabilization measures, and a pre sedimentation basin,
d. shall not involve any stream channelization or the filling of wetlands,
e. shall require the implementation of an effective nonpoint source management program throughout the upstream watershed which shall include at a minimum: runoff reduction BMPs; 2 year detention/sedimentation basins for all development; and a program to control nonpoint sources at the source for prior developments constructed without appropriate stormwater BMPs.
g. Methods for Generating Runoff Hydrographs Runoff hydrographs shall be developed incorporating the following assumptions of rainfall amounts and antecedent moisture.
1. Rainfall: Unless a continuous simulation approach to drainage system hydrology is used, all design rainfall events shall be based on the Illinois State Water Survey's Bulletin 70 or 71. The first quartile point rainfall distribution shall be used for the design and analysis of conveyance systems with critical durations less than or equal to 12 hours. The third quartile point rainfall distribution shall be used for the design and analysis of detention basins and conveyance system with critical durations greater than 12 and less than or equal to 24 hours. The fourth quartile distribution shall be used in the design and analysis of systems with durations greater than 24 hours. The first, third, and fourth quartile distributions described by Huff are presented in Table 37 of Bulletin 70. The SCS Type II distribution may be used as an alternate to the Huff distributions.
2. Antecedent Moisture: Computations of runoff hydrographs which do not rely on a continuous accounting of antecedent moisture conditions shall assume a normal antecedent moisture condition (2), unless otherwise directed by the Director of Engineering.
h. Inlet and Outlet Orientation: To the extent feasible, the distance between detention inlets and outlets shall be maximized. If possible, they should be at opposite ends of the basin.
i. Wetland and Dry Detention Basin Design: In addition to the other requirements of this ordinance, wetland and dry basins shall be designed to remove stormwater pollutants, to be safe, to be aesthetically pleasing and as much as feasible to be available for multiple uses.
Wetland and dry basins shall be designed so that the portion of their bottom area which is intended to be dry shall have standing water no longer than seventy two hours for all runoff events less than the 100 year event. Underdrains directed to the outlet may be used to accomplish this requirement. Grading plans shall clearly distinguish the wet/wetland portion of the basin bottom from the dry portion.
j. Velocity Dissipation: Velocity dissipation measures shall be incorporated into dry basin designs to minimize erosion at inlets and outlets and to minimize the resuspension of pollutants.
k. Stilling/Sedimentation Basins: A stilling/sedimentation basin should be constructed at each major inlet to a wetland or dry basin. The volume of the basins should be at least 500 ft3 per acre of impervious surface in the drainage area. Side slopes of the basins shall be no steeper than 4 horizontal to 1 vertical and basin depths should be at least 3 feet to minimize resuspension of accumulated sediment.
l. Overflow Structures: All stormwater detention basins shall be provided with an overflow structure capable of safely passing excess flows at a stage at least 1 foot below the lowest founda tion grade in the vicinity of the detention basin. The design flow rate of the overflow structure shall be equivalent to the 100 year inflow rate, or as designated by the Director of Engineering.
m. Stormwater runoff from areas tributary to the property shall be considered in the design of the property's drainage system. Whenever practicable, flows from upstream areas that are not to be detained should be routed around the basin being provided for the site being developed.
1. Upstream Areas Not Meeting Ordinance Requirements When there are areas not meeting the storage and release rates of this ordinance, tributary to the applicant's property, regionalized detention on the applicant's property shall be explored by the applicant. The following steps shall be followed.
a. The applicant shall compute the storage volume needed for his property using the release rates of this section.
b. Areas tributary to the applicant's property, not meeting the storage and release rate requirements of this ordinance, shall be identified.
c. Using the areas determined in 2) above plus the applicant's property area, total storage needed for the combined properties shall be computed.
Allowable release rates shall be computed using the combined property areas. If tributary areas are not developed, a reasonable fully developed land cover, based on local zoning, shall be assumed for the purposes of computing storage.
2. Upstream Areas Meeting Ordinance Requirements When there are areas which meet the storage and release rate requirements of this ordinance, tributary to the applicant's property, the upstream flows shall be bypassed around the applicant's detention basin, or be routed through the applicant's detention basin if this is the only practicable alternative.
n. All storm water inflow pipes must be constructed to inverts that are at or above the normal water level in "wet basins".
o. Setback for stormwater detention/retention facilities must meet requirements stated in section 6-305.8.b.4. (Amd. Ord. 5312 – 7/16/18; Amd. Ord. 5822 - 7/17/23)
p. Streets or habitable structures that are built with adjoining detention facilities shall meet those vertical clearance requirements provided in the flood plain regulations of the Village and other applicable laws.
q. Detention facilities designed and built in accordance with wetland mitigation plans approved by the U.S. Army Corps of Engineers shall be maintained to meet those criteria. Interpretive signage may be required by the Village. Wetlands must also meet the criteria provided in Section 6-413 of these regulations.
Existing wetlands and depressional storage areas shall not be modified for the purposes of storm water detention unless it is demonstrated that the existing wetland is low in quality and/or the proposed modifications will maintain or improve its habitat and ability to perform beneficial functions.
1. Existing storage and release rate characteristics of wetlands and other depressional storage areas shall be maintained and the volume of detention storage provided to meet the requirements of this section shall be in addition to this existing storage.
2. The existing wetland shall be protected during construction by appropriate soil erosion and sediment control measures.
3. All runoff from the development shall be routed through a preliminary detention/sedimentation basin designed to capture the two-year-24-hour event before discharging into the wetland.
F. Material Specifications. All storm sewer system elements shall conform to the following specifications:
1. Sewer Pipe.
a. Sump pump service connection and storm sewer extension (4" and 6") – ABS sewer pipe or PVC sewer pipe ASTM D2751, SDR35, or ASTM D3034, SDR35, or flexible plastic drain pipe.
b. Concrete sewer pipe (10" diameter and smaller), minimum Class 3, ASTM C14.
c. Reinforced concrete pipe (12" diameter and larger), circular reinforcement, minimum Class 3, wall B, ASTM C76.
d. High Density Polyethylene (HDPE) Pipe (12" diameter to 60" diameter), ASTM D3350, ASTM F2648"
e. HDPE Pipe - ASTM F2648, ASTM F477, Fittings per ASTM F2306.
f. Reinforced concrete arch culvert pipe – double line reinforcement, minimum Class 3, ASTM C506.
g. Reinforced concrete elliptical culvert pipe –minimum class HE-III or VE-III, ASTM C507.
h. PVC underdrain pipe (4", 6", and 8") – ASTM D2729, SDR35.
(Amd. Ord. 5653 - 11/1/21)
2. Sewer Pipe Joints.
a. ABS pipe – ASTM C443.
b. PVC pipe – ASTM D3212, push on type, except underdrain pipe which shall have solvent welded joints.
c. Reinforced concrete pipe – ASTM C443. ("O" ring)
d. Reinforced arch or elliptical pipe – ASTM C877.
3. Casing Pipes for Augered Sleeves. Steel pipe – ASTM A120, 3/8" minimum thickness.
4. Manholes and Catch Basins. (Exhibit Nos. STS-01 and STS-02).
a. Precast reinforced concrete – ASTM C478 and ASTM C443.
b. Size: For sewer 18" diameter or less, manhole shall have a 48" inside diameter.
For sewer 21" to 36" diameter, manhole shall have a 60" inside diameter.
For sewer greater than 36" diameter, manhole shall have an offset riser pipe of 48" inside diameter.
c. Adjustment: No more than two (2) precast concrete adjusting rings with six (6) inch maximum height adjustment shall be allowed.
d. Pipe and frame seals: All pipe connection openings shall be precast with resilient rubber water tight pipe to manhole sleeves or seals. External flexible water tight sleeves shall also extend from the manhole cone to the manhole frame.
e. Bottom sections: All bottom sections shall be monolithically precast including bases and invert flowlines.
5. Inlets. (Exhibit No. STS 05).
a. Precast reinforced concrete ASTM C478 and ASTM C443.
b. Size: Inlets shall have 24" inside diameter and a maximum depth of four (4) feet.
c. Adjustment: No more than two (2) precast concrete adjusting rings with six (6) inch maximum height adjustment shall be allowed.
d. Only one (1) pipe connection is allowed and it shall be precast with resilient rubber water tight pipe to manhole sleeves or seals.
e. Bottom sections: All bottom sections shall be monolithically precast including bases and invert flowlines.
6. Castings.
a. Manhole frame and cover East Jordan Iron Works, Inc. #1022Z3, 1020A HD.
b. Manhole steps East Jordan Iron Works, Inc. #8518.
c. Six (6) inch curb and catch basin inlet East Jordan Iron Works, Inc. #1051Z3 and 1020M1 grate.
d. Three (3) inch inlet and catch basin inlet East Jordan Iron Works, Inc. #7525Z Frame and 7525M grate.
e. Yard inlet East Jordan Iron Works, Inc. #6527 grate.
7. Crushed Granular Bedding. (Exhibit No. STS 11). Crushed gravel or crushed stone course aggregate ASTM C33, Size No. 67.
8. Headwalls and Precast End Sections (Exhibit Nos. STS 08, STS 09). All pipes shall terminate at reinforced concrete headwalls or precast end sections.
G. Inspection and Testing.
General site grading shall not begin until the Project Engineer has certified in writing to the Village that any necessary detention facilities are in place and operational. The Director of Engineering or his representative will also conduct periodic inspections of the work in progress to be certain that the drainage system is being built as designed. If any violations of the provisions or requirements of this ordinance are noted during such inspections, the Director of Engineering shall notify the property owner in writing of the items needing correction. The property owner shall have ten (10) calendar days to make such corrections unless given a specific extension of time in writing by the Director of Engineering. Failure to complete such corrections within the specified time period shall constitute a violation of this ordinance
1. Cleaning. All sewers and appurtenances shall be cleaned prior to inspection and testing required by this Section.
2. Visual Inspection.
a. All sewer and appurtenances shall be visually inspected by representatives of the developer during and following construction.
b. Contractor must perform a high pressure jetting of sewer system in order to determine if any repairs must be made prior to lamping or testing.
c. Sewers designed to be straight between manholes will be tested for straightness by flashing a light from manhole to manhole, lamping or by other suitable means.
3. T.V. Inspections.
a. Upon completion of construction and prior to initiation of the maintenance guarantee period, and upon recommendation of the Director of Engineering, a T.V. inspection shall be performed on the sections or portions of the sewer. Video tapes and a written report of all television inspections shall be provided to the Village prior to the initial acceptance provided for by this Section. The form of the report and type and format of the video tape shall be approved by the Director of Engineering. T.V. Inspections and reports shall be completed for all storm systems and sanitary systems installed in the Village of Orland Park. (Ord. 3837 - 12/1/03)
b. Fees and costs connected with T.V. inspections shall be paid for by the developer or owner.
c. All dips, cracks, leaks, improperly sealed joints, and departures from approved grades and alignment shall be repaired by removing and replacing the involved sections of pipe.
d. All defects and corrective work required as the result of T.V. inspection shall be performed by the developer without delay. Upon completion thereof, the sewer shall be re tested and such further inspection made as may appear warranted.
H. Acceptance of Storm Sewers and Storm Water Detention.
1. Once the storm sewer system has been completed according to the specifications set forth in this Section, the Engineering Department along with the Public Works Department shall, upon the request of the developer, inspect the system and prepare a list of items for repair (punch list). The list shall be given or sent to the developer and when repairs have been made, the Engineering Department and Public Works Department shall accept the system for operational use only. During the time after the approval by the Village for maintenance, the developer shall be responsible for any delinquencies incurred within the system, including but not limited to siltation within the pipe, manholes and inlets, adjustment to manhole frames and leaking joints. Upon reaching approximately eighty (80) percent development of building construction, the Engineering Department and Public Works Department will reinspect the storm sewer system for any delinquencies which may have occurred and prepare a list of items for repair. The list shall be given or sent to the developer and when the repairs have been made to the satisfaction of the Engineering Department and Public Works Department, the Engineering Department shall accept the system for the Village. (Ord. 2570 - 5/2/94; Amd. Ord. 5653 - 11/1/21; Amd. Ord. 5822 - 7/17/23)
2. All construction shall meet the requirements and acceptance by the Metropolitan Water Reclamation District of Greater Chicago prior to the acceptance by the Engineering Department and Public Works Department. (Ord. 2570 5/2/94; Amd. Ord. 5822 - 7/17/23)
3. a. Maintenance of stormwater drainage facilities located on private property shall be the responsibility of the owner of that property in the case of a single lot development and the combined responsibility of the property owners for developments with more than one lot. Before a permit is obtained from the Village, the applicant shall execute a maintenance agreement with the guaranteeing that the applicant and all future owners of the property propert(ies) will maintain its stormwater drainage system. The maintenance agreement shall also specifically authorize representatives of the Village to enter onto the property for the purpose of inspections and maintenance of the drainage system. Such agreement shall be recorded with the Recorder of Deeds of Cook and/or Will Counties in Illinois as applicable. The maintenance agreement shall include a schedule for regular maintenance of each aspect of the property's stormwater drainage system and shall provide for access to the system for inspection by authorized personnel of the Village. The maintenance agreement shall also stipulate that if the Village notify notifies the property owner(s) in writing of maintenance problems which require correction, the property owner(s) shall make such corrections within 30 (thirty) calendar days of such notification. If the corrections are not made within this time period, the Village may have the necessary work completed and assess the cost to the property owner(s).
b. Subdivisions containing two or more lots shall establish a Homeowners' Association or similar governing body which shall be responsible for all maintenance, repair, and/or replacement of the stormwater management system, including but not limited to: detention ponds, green infrastructure, and related storm water management facilities located on and serving the private property. The property owners shall establish a dormant Special Service Area (SSA), including all properties that benefit from the storm water management facilities. The purpose of the dormant SSA is to fund the Village of Orland Park's costs of maintaining, repairing and/or replacing the storm water management facilities located in the subject property in the event that the Homeowners' Association or the owners of the property fail to maintain, repair and/or replace said storm water management facilities as required. (Amd. Ord. 5653 - 11/1/21)
I. Penalties
Any person convicted of violating any of the provisions or requirements of this section of this ordinance shall be guilty of a misdemeanor and shall be subject to a fine of not more than One Thousand Dollars ($1,000.00). Each day the violation continues shall be considered a separate offense.