Each applicant shall submit the following information, to ensure that the provisions of this chapter are met. The submittal shall include sufficient information to evaluate the environmental characteristics of the property, the potential adverse impacts and benefits of the development on water resources, both on-site and off-site, and the effectiveness of the proposed drainage plan in managing stormwater runoff, and meet the provisions of § 291-2. The applicant shall 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 for all new development or redevelopment.
A.
Drainage plan requirements. A topographic survey of the property
at two-foot contours unless otherwise specified or approved by the
Village. If the mapping is compiled using a digital format and the
Global Positioning System (GPS), the applicant will provide both paper
and digital copies, including GPS points.
B.
Mapping and descriptions. An existing drainage and proposed drainage
plan for the property and 100 feet surrounding the property, at a
scale of not more than 100 feet to one inch, and including the following:
(1)
Property boundary, dimensions, and approximate acreage;
(2)
Building setback lines;
(3)
All existing and proposed structures and sizes;
(4)
Area in square feet of existing and proposed impervious surface;
(5)
All existing or proposed easements;
(6)
All existing, abandoned, or proposed water or monitoring well head
locations;
(7)
All sanitary or combined sewer lines and septic systems;
(8)
The banks and center line of streams and channels;
(9)
Shoreline of lakes, ponds, and detention basins with normal water
level elevation;
(10)
Known farm drains and tiles;
(11)
Soils classifications;
(12)
Location, size and slope of stormwater conduits and drainage
swales;
(13)
Depressional storage areas;
(14)
Detention facilities;
(15)
Roads, streets and associated stormwater inlets, including finished
grades;
(16)
Base flood elevation, flood fringe, and regulatory floodway;
(17)
Basis of design for the final drainage network components;
(18)
A statement giving any applicable engineering assumptions and
calculations;
(19)
A vicinity map showing the relationship of the site to its general
surroundings at a scale of not less than 2,000 feet to one inch (1:24,000);
(20)
Title, scale, North arrow, legend, seal of licensed professional
engineer, date, and name of person preparing plans;
(21)
Cross-section data for open channel flow paths and designated
overland flow paths;
(22)
Direction of storm flows;
(23)
Flow rates and velocities at critical points in the drainage
system (may be included in the supporting documentation);
(24)
A statement by the design engineer of the drainage system's
provision for handling events greater than the one-hundred-year, twenty-four-hour
runoff (may be included in the supporting documentation); and
(25)
A statement of certification of all drainage plans, calculations,
and supporting data by an Illinois licensed professional engineer.
C.
Environmental features. A depiction of environmental features of
the property and immediate vicinity, including the following:
In the selection of a drainage plan for a new development or
redevelopment, the applicant shall evaluate and implement site design
features which minimize the increase in runoff volumes and rates from
the site. The applicant's drainage plan submittal shall include evaluations
of site design features which are consistent with the following hierarchy:
A.
Preserve regulatory floodplains, floodprone and wetland areas;
B.
Minimize impervious surfaces on the property, consistent with the
needs of the project;
C.
Attenuate flows by use of open vegetated swales and natural depressions
and preserve the existing natural stream channel;
D.
Infiltration of runoff on-site;
E.
Provide stormwater retention structures;
F.
Provide wet or wetland detention structures;
G.
Provide dry detention structures; and
H.
Construct storm sewers.
A.
The drainage system should be designed to minimize adverse surface
water and groundwater quality impacts off-site and on the property
itself.
B.
Water quality shall adhere to the following:
(1)
Illinois Environmental Protection Act (415 ILCS 5/12);
(2)
Illinois Pollution Control Board Rules and Regulations (Ill. Admin.
Code): Title 35: Environmental Protection, Subtitle C: Water Pollution,
Chapter I: Pollution Control Board, Part 302: Water Quality Standards;
and
(3)
Illinois Pollution Control Board Rules and Regulations (Ill. Admin.
Code): Title 35: Environmental Protection, Subtitle C: Water Pollution,
Chapter I: Pollution Control Board, Part 304: Effluent Standards.
C.
Detention basins shall incorporate design features to capture stormwater
runoff pollutants. When designers propose wet bottom and wetland type
designs, all flows from the development shall be routed through the
basin (i.e., low flows shall not be bypassed). When it is not practical
or feasible to route the entire project's flow to the detention basin,
the design of the basin shall compensate for the bypass flow. In cases
where detention facilities are practical and the long-term maintenance
of such facilities are provided for, detention of stormwater shall
be promoted throughout the property's drainage system to reduce the
volume of stormwater runoff and to reduce the quantity of runoff pollutants.
D.
The drainage system should incorporate multiple uses where practicable.
Uses considered compatible with stormwater management include open
space, aesthetics, aquatic habitat, recreation (boating, fishing,
trails, playing fields), wetlands, and water quality mitigation.
The following requirements shall be applicable and shall be
satisfied prior to the construction, improvement or development of
any structure, project or land which is subject to the provisions
of this chapter. All infrastructure included in this article shall
be designed and certified by an Illinois licensed professional engineer.
A.
Maximum release rate. The maximum controlled release rate for each
independent watershed area within the owner's land shall be determined
in the following manner:
(1)
For that portion of the watershed outside of an owner's land, the
peak rate of runoff which would have occurred for a five-year return
period storm under the state of development existing just prior to
application for development of an owner's land shall be calculated
and determined.
(2)
For that portion of the watershed within the lands of an owner, the
peak rate of runoff which would have occurred for a five-year return
period storm under a state of traditional agricultural usage shall
be calculated and determined.
(4)
The peak rate of runoff which would have occurred for a five-year
return period storm shall be determined using the Rational Method
or other substantial method acceptable to the Village Engineer.
(5)
The five-year and fifty-year storm shall be determined utilizing
Bulletin 70 of the Illinois State Water Survey, or the most recently
available information.
(6)
In the event that the downstream stormwater runoff drainage system
is inadequate to accommodate the maximum release rate provided above,
then the Village, at its option, may reduce the allowable release
rate to that rate permitted by the capacity of the receiving stormwater
runoff drainage system and additional storage, as determined by the
Village Engineer, may be required to store that portion of the runoff
exceeding the capacity of the receiving stormwater runoff drainage
system.
B.
Storm sewer systems.
(1)
Compliance is mandatory with the latest edition of the Standard Specifications
for Water and Sewer Main Construction in Illinois.
(2)
Capacity. All storm sewer systems shall be designed for the peak
rate of runoff from a minimum of a five-year return period storm in
accordance with the Illinois Department of Transportation Drainage
Manual. The five-year return period storm shall be determined utilizing
Bulletin 70 of the Illinois State Water Survey, or the most recently
available information. The minimum pipe diameter shall be 12 inches.
The system shall have a free outlet.
(3)
All design calculations must be submitted to the Village Engineer
for approval.
(4)
Grade. Sewer grades shall be such that, in general, a minimum of
two feet of cover is maintained over the top of the pipe. Pipe cover
less than the minimum may be used upon site-specific approval by the
Village Engineer. Uniform slopes shall be maintained between inlets,
manholes and inlet to manhole. Minimum and maximum allowable slopes
shall be those capable of producing velocities between two feet per
second and 10 feet per second, with three feet per second being desirable,
when the sewer is flowing full as calculated by Manning's Formula.
Velocities lower than the minimum or higher than the maximum may be
used upon site-specific approval by the Village Engineer.
(5)
Overland flow. The maximum distance for overland flow of stormwater
runoff to an underground storm sewer system shall be 600 feet.
(6)
Alignment. Storm sewers shall be constructed in a straight line between
manholes insofar as possible. Where long-radius curves are necessary
to conform to street layout, the minimum radius of curvature shall
be no less than 100 feet. Deflection of pipe sections shall not exceed
the maximum deflection recommended by the pipe manufacturer. The deflection
shall be uniform and the finished installation shall follow a smooth
curve.
(7)
Manholes. Manholes shall be installed to provide access to continuous
underground storm sewers for the purpose of inspection and maintenance.
(a)
Manholes shall be provided at the following locations:
[1]
Where two or more storm sewers converge;
[2]
At the point of beginning or at the end of a curve, and at the
point of reverse curvature (PC, PT, PRC) of a storm sewer;
[3]
Where pipe size changes;
[4]
Where an abrupt change in alignment occurs;
[5]
Where a change in pipe slope occurs;
[6]
At suitable intervals in straight sections of sewers.
(b)
The maximum distance between manholes shall be 400 feet.
(c)
All manholes shall be of precast reinforced concrete construction,
in accordance with the Illinois Department of Transportation Highway
Standards.
(8)
Inlets and catch basins. Inlets and catch basins on drainage structures
shall be utilized to collect surface water through grated openings
and convey it to storm sewers or culverts. All inlets and catch basins
shall be of precast reinforced concrete construction in accordance
with the Illinois Department of Transportation Highway Standards and
as approved by the Village Engineer.
(9)
Trench backfill. Trench backfill requirements shall conform to the
applicable portions of the Standard Specifications for Road and Bridge
Construction, Illinois Department of Transportation (latest edition),
or as otherwise approved by the Village Engineer.
(10)
(11)
Workmanship.
(a)
The specifications for the construction of storm sewers shall
not be less stringent than those set forth in either the latest edition
of the Illinois Department of Transportation Standard Specifications,
or the latest edition of the Standard Specifications for Water and
Sewer Main Construction in Illinois, by the Illinois Society of Professional
Engineers, et al. (latest edition).
(b)
Construction of any utility pipe or conduit such as gas, electric
and water through any storm sewer structure shall be prohibited, except
with approved conflict structures.
C.
Surface drainage systems. Surface drainage will be permitted for
stormwater, where cost estimates show storm sewers are not economically
feasible (including all life-cycle costs and the value of the land
consumed), where land use conditions indicate this method is feasible,
and where topographic conditions indicate there will be no difficulty
from this method of disposal of stormwaters. Such economic and feasibility
studies shall be reviewed and approved by the Village Engineer.
(1)
Capacity. All surface drainage systems of stormwater shall be designed
for the peak rate of runoff from a minimum of a ten-year return period
storm. The ten-year return period storm shall be determined utilizing
Bulletin 70 of the Illinois State Water Survey, or the most recently
available information. The system shall have a free outlet. All design
calculations must be submitted to the Village Engineer for approval.
(2)
Grade. Stormwater surface drains shall be constructed with uniform
bottom slopes along the entire length of the drains. Minimum and maximum
allowable grade shall be those capable of producing velocities between
0.5 foot per second and 10.0 feet per second, respectively, when the
surface drain is flowing full. A minimum slope of 0.3% is required.
In all cases, stormwater velocity shall be controlled to eliminate
problems of soil erosion or other damage which could detract from
the primary use of the area.
(3)
Side slopes and bottom widths. Surface drains shall be constructed
having side slopes of not less than three feet horizontal to one foot
vertical, or flatter. Side slopes steeper than three feet horizontal
to one foot vertical shall not be used without site-specific approval
by the Village Engineer. A channel bottom width of not less than two
feet shall be provided.
(4)
Erosion. Design of surface drains shall include control of soil erosion.
Temporary seeding or other soil stabilization measures shall be utilized
during construction to control erosion. Permanent erosion control
measures such as mulching, hydroseeding, conventional seeding, or
other similar measures shall be utilized upon completion of construction.
At the discretion of the Village Engineer, energy dissipaters, such
as riprap, may be required at storm inlet and outlet locations. Erosion
control practices identified in this chapter shall be constructed
in accordance with the Illinois Urban Manual, 1995.
(5)
Culverts. Culverts and similar structures shall have a capacity which
meets or exceeds the capacity of the surface drain, but shall be a
minimum of 12 inches in diameter. The flowline of a culvert shall
match the flowline of the surface drain. All culverts shall have flared
end sections or headwall treatments. Culvert materials shall be in
accordance with the Standard Specifications for Road and Bridge Construction,
Illinois Department of Transportation (latest edition).
(6)
Workmanship. The specifications for the construction of stormwater
surface drains shall equal or exceed those set forth in the Standard
Specifications for Road and Bridge Construction, Illinois Department
of Transportation (latest edition) or shall be as otherwise approved
by the Village Engineer.
(7)
Tile drains. All major stormwater surface drains as designated by
the Village Engineer shall also be constructed with a subsurface drainage
tile or tubing encased to the surface with washed gravel in a nonwoven
geotextile envelope.
D.
Excess stormwater passageway.
(1)
An excess stormwater passageway shall be provided for the floodplains
of all natural watercourses and such man-made watercourses and storm
drainage systems as the Village Engineer may direct, which shall have
adequate capacity to convey the excess stormwater from the tributary
watershed. The capacity of this excess stormwater passageway shall
be adequate to transport the peak rate of runoff from the fifty-year
return period storm, assuming all upstream areas are fully developed
for uses specifically permitted by existing zoning. Emergency overflow
routes shall be located in permanent easements, dedicated commons,
or on public rights-of-way. Routes shall be designated on the face
of the preliminary plat and subsequent plans. No structures shall
be constructed within this passageway; however, streets, parking lots,
playgrounds, park areas, pedestrian walkways, open green space, and
utility and sewer easements shall be considered compatible uses.
(2)
Design of the excess stormwater passageway shall include control
of stormwater velocity to eliminate problems of soil erosion or other
damage which would detract from the primary use of the area. The entire
area of any excess stormwater passageway within the corporate limits
of the Village and 1 1/2 miles thereof shall be placed in a drainage
easement or remain under the jurisdiction of the Village, other governmental
unit, or Village-approved quasi-public agency (i.e., homeowner's association,
etc.). In the event this passageway is reshaped or its capacity to
transport excess stormwater is otherwise restricted, the Village may
cause to have any restrictions removed at the expense of the agency,
party, or parties causing or permitting these restrictions. Should
a natural drain exist, it shall be preserved and used to the extent
possible, as a part of the excess stormwater passageway. Where it
is necessary to reroute a natural drain, the rerouted drain shall
have a capacity equivalent to or greater than that which existed in
the natural drain and as otherwise required by this chapter.
E.
Stormwater storage. When the maximum controlled stormwater runoff
rate would be exceeded due to the development, redevelopment, or new
construction on the owner's land, stormwater storage methods shall
be provided and constructed by the owner. Any one or all of the stormwater
storage methods listed shall be provided and constructed.
(1)
General requirements.
(a)
The volume of required stormwater storage shall be calculated
on the basis of the maximum value achieved from the runoff of a fifty-year
return period storm less the volume of water released through the
outlet structure. The fifty-year return period storm shall be determined
utilizing Bulletin 70 of the Illinois Water Survey, or the most recently
available information. The method utilized for calculation of volume
of storage shall be the rational method or any other substantial method
acceptable to the Village Engineer. The release rate of the outlet
structure when 1/2 of the storage volume is filled may be used in
lieu of routing techniques in small drainage areas. The control structure
shall be designed to maintain as uniform a flow as possible, independent
of the stormwater storage volume. Where the proposed structure, project,
or land development forms only a portion of a watershed or contains
portions of several watersheds, the storage volume calculations shall
be based upon the area of the entire project, development, or land
use change.
(b)
The storage of excess stormwater runoff from a fifty-year return
period storm having a duration of 24 hours, released at the allowable
rate, shall not result in a storage duration in excess of 24 hours,
but storage duration may be as long as 48 hours upon site-specific
approval by the Village Engineer.
(c)
All design calculations must be submitted to the Village Engineer
for approval.
(d)
Plans shall clearly indicate normal and high water elevations,
design storage volume, minimum, maximum and typical slopes.
(e)
Each stormwater storage area shall be provided with a method of overflow in the event a storm in excess of the design capacity occurs. This overflow facility shall be constructed to function without special attention and can become a part of the excess stormwater passageway described in Subsection D of this section.
(f)
The entire stormwater storage area shall be designed and constructed
to fully protect the public health, safety, and welfare. If a condition
occurs in the stormwater storage area which is hazardous to the public
health, safety, or welfare, the person responsible for the condition
will be required to provide approved corrective measures. In the event
these corrective measures are not provided, the Village may eliminate
the hazard at the expense of the person responsible.
(g)
Detention basins and their fifty-year high water shall be contained
within platted lots dedicated for drainage purposes. Said lots shall
have a minimum thirty-foot street frontage at a minimum of two locations.
For infill redevelopment, detention basins and their fifty-year high
water shall be contained within a drainage easement with thirty-foot
public roadway frontage where possible. All detention basins shall
include the following design parameters:
[1]
A twenty-foot minimum setback from all property lines to the
normal pool elevation.
[2]
A minimum of one foot of freeboard above the one-hundred-year
design water elevation.
[3]
Any buildings within 100 feet of a detention basin shall have
the lowest water entry point a minimum of two feet above the one-hundred-year
design water elevation.
(2)
Dry bottom stormwater storage.
(a)
Dry bottom stormwater storage areas may be designed to serve
a secondary purpose for recreation, open space, or similar types of
uses which will not be adversely affected by occasional intermittent
flooding;
(b)
Minimum grades for turf areas shall be 0.5% (200 units horizontal
to one unit vertical), and maximum side slopes shall be 25% (four
units horizontal to one unit vertical). Storage area side slopes shall
follow the natural land contours as closely as practicable, and a
minimum of earth excavation shall be used to create the storage facility.
Geometrics of dry bottom stormwater storage areas shall be approved
by the Village Engineer.
(c)
Erosion control measures.
[1]
Temporary seeding or other soil stabilization measures shall
be established in the stormwater storage area and excess stormwater
passageway immediately following the construction or reconstruction
of these areas. During the construction of the overall development,
it is recognized that a limited amount of sediment buildup may occur
in the stormwater storage area due to erosion. In no case shall the
volume of the storage area be reduced to less than 90% of the required
volume during the construction phase of the development.
[2]
Permanent erosion control measures such as mulching, hydroseeding,
conventional seeding, fertilizing, or sod installation shall be utilized
to control soil movement and erosion within the storage area and excess
stormwater passageway. These measures shall meet or exceed the standards
established by the Illinois Urban Manual, 1995. The installation of
these permanent measures shall take place only after the majority
of construction and other silt- and sediment-producing activities
have been completed. Prior to the establishment of the permanent erosion
control measures, the required capacity of the stormwater storage
area and the excess stormwater passageway shall be restored.
(d)
The control structure shall be provided with an interceptor
for trash and debris, and it shall be designed and constructed to
prevent soil erosion and not to require manual adjustments for its
proper operation. The control structure shall be designed to operate
properly with little or no maintenance and/or attention. The control
structure shall be provided with safety screens for any pipe or opening
to prevent children or large animals from crawling into structures.
The control structure shall be constructed to allow access to it at
all times, including times of flood flow.
(e)
Adequate impact stilling basins shall be provided to ensure
that downstream soil erosion is mitigated as much as practical and
the regime of the downstream drain facility is not disturbed.
(f)
Low-flow conduits or channels shall be provided in stormwater
storage areas; these conduits or channels shall be so constructed
that they will not interfere with any secondary usage of the storage
area and will reduce the frequency of time that the storage area will
be covered with water. Low-flow conduits shall facilitate complete
interior drainage of the stormwater storage area.
(g)
Pipe outlets of less than six inches in diameter shall not be
allowed. Pipe outlets shall not exceed 100 feet in length. Multiple
outlets from a storm storage area shall be avoided if they are designed
to be less than 12 inches in diameter.
(h)
The maximum planned depth of stormwater stored shall not exceed
four feet.
(i)
Tile underdrains shall be provided in dry bottom stormwater storage areas in accordance with Subsection C(7) of this section. These tile underdrains shall be so constructed that they will not interfere with any secondary usage of the storage area. Tile underdrains shall be so constructed that they shall facilitate dewatering of the soils in the stormwater storage area to avoid marshy or saturated soil conditions. Tile underdrain systems may be combined with the low-flow conduits or channel systems and shall be as approved by the Village Engineer.
(j)
Fencing may be required whenever storage depths exceed four
feet, or when side slopes are greater than four horizontal to one
vertical.
(3)
Wet bottom stormwater storage. Wet bottom stormwater storage areas
shall be designed in compliance with all the regulations which are
applicable and govern the construction of dry bottom stormwater storage
areas. The following additional regulations shall apply:
(a)
Protection of the shoreline must be provided to alleviate soil
erosion due to wave action. This protection shall extend down the
side slope to an elevation one foot below the normal water surface
elevation and up the side slope to an elevation one foot above the
normal water surface elevation. Approved shoreline protection methods
include vegetative turf reinforcement mats constructed in accordance
with the manufacturer's recommendations, riprap revetment constructed
in accordance with the requirements of the Illinois Department of
Transportation Standard Specifications for Road and Bridge Construction,
latest edition, or retaining walls constructed from Allen Block or
Portland cement concrete. Alternative methods may be submitted to
the Village Engineer for approval.
(b)
Above-water side slopes shall be a maximum of four horizontal
to one vertical. If retaining walls are used, their height is limited
to four feet. Retaining wall design and material type shall be approved
by the Village Engineer.
(c)
In accordance with Section 204 of the Standard Specifications
for Road and Bridge Construction, Illinois Department of Transportation
(latest edition), below-water slopes shall be a maximum of four horizontal
to one vertical, except that slopes of two horizontal to one vertical
will be permitted below a point where the proposed water depth will
be eight feet or greater.
(d)
Wet bottom basins shall have a natural or artificial means of
aeration to prevent pond stagnation.
(e)
If fish or other aquatic wildlife are desired, a minimum depth
of eight feet shall be maintained over at least 25% of the pond's
surface area.
(f)
An outlet structure shall be provided to allow dewatering of
the pond for maintenance and cleaning. Gravity dewatering is strongly
preferred.
(g)
Wet bottom basin design shall include an evaluation of soil
permeability. A basin liner shall be included in the design if needed
to ensure water retention to normal pool elevation.
(h)
The control structure for stormwater release shall be designed
to operate at full design release rate with only a small increase
in water depth in order to minimize the land surface wetted by frequent
minor stormwater runoff conditions.
(i)
The volume of water permanently stored shall not be considered
to be part of the required excess stormwater storage volume.
(4)
Paved stormwater storage. Design and construction of the pavement
base must ensure that there is no pavement damage due to flooding.
Control structures in paved areas must be readily accessible for maintenance
and cleaning. Vortex control devices will be required.
(5)
Automobile parking lot storage areas. Automobile parking lots may
be designed to provide temporary detention storage on a portion of
their surfaces. Automobile parking facilities used to store excess
stormwater must be constructed having a maximum depth of stored stormwater
of 0.5 foot; and these areas shall be located in the most remote,
least-used areas of the parking facility. Design and construction
of automobile parking in stormwater areas must ensure that there is
no damage to the parking facility due to flooding, including damage
to the subbase. Warning signs shall be mounted at appropriate locations
to warn of possible flood conditions during storm periods.
(6)
Underground stormwater storage. Underground stormwater storage facilities
must be designed for easy access in order to remove accumulated sediment
and debris. These facilities must be provided with a positive gravity
outlet.
(7)
Stormwater storage areas which will be filled to capacity by frequent
storms shall be designed in a manner that will protect immediate downstream
properties, and all overflow structures shall be designed to function
properly and effectively without the necessity of making manual adjustments.
A larger outlet for a stormwater storage area may be permitted by
the Mayor or his designee for the orderly management of stormwater
runoff where large tributary areas were developed without detention.
(8)
If the orderly management of the stormwater runoff cannot be achieved
by passing the entire tributary area runoff through the stormwater
storage area, then the stormwater storage area may be constructed
to exclude the runoff from the tributary area originating outside
of the area to be developed.
(9)
Where the owner has a large tract of land upon which development
is to occur in several phases, the owner may construct, upon site-specific
approval by the Village Engineer, one stormwater storage facility
which is designed to be enlarged at later dates as additional portions
of the owner's lands are developed and as additional stormwater storage
is required due to that development.
(10)
Where portions of the owner's land are tributary to the same
drain for an outlet, but which are within two or more tributary areas
to that drain, the owner may construct, upon site-specific approval
by the Village Engineer, compensatory stormwater detention facilities
within one tributary area which offset the lack of construction of
stormwater detention facilities in another tributary area. Such compensatory
storage shall be designed and constructed such that the net effect
of these facilities shall be to limit the amount of stormwater runoff
released into the drain to that which would have occurred had stormwater
detention facilities been constructed for all the tributary areas.
(11)
Stormwater storage areas may be planned and constructed jointly
by two or more landowners so long as compliance with this chapter
is maintained.
(12)
Where fringe portions of the owner's land are, in the opinion
of the Village Engineer, difficult or impractical to drain to the
detention facilities to be constructed for the rest of the property,
the owner may apply for a variance of the requirements of this chapter.
Such a variance may be granted for an area of land equal to up to
2% of the total property involved. In such cases, a variance may be
granted without owner's proof of the avoidance of an unnecessary hardship
and without specifically stating the public's interest in granting
the variation.
F.
Other requirements.
(1)
Automobile parking lots and other land uses with significant portions
of paved and roofed areas as determined by the Village Engineer shall
be constructed with internal stormwater runoff drainage systems.
(2)
Sump pumps. Sump pumps installed to receive and discharge groundwaters
or stormwater runoff shall be connected to the storm sewer where possible
or discharged into a designated stormwater runoff drainage facility.
No discharge of stormwater runoff or groundwater by a sump pump into
a sanitary sewer shall be allowed. No discharge of sanitary sewage
into a storm drain shall be allowed.
(3)
No sump pump, footing drain, or downspout shall discharge onto a
street surface, paved curb and gutter system, or public sidewalk.
(4)
Downspouts. Downspouts and roof drains shall discharge onto the ground
or be connected to a storm drain. No downspouts or roof drains shall
be connected to a sanitary sewer.
(5)
Footing drains. Footing drains and drainage tile shall discharge
into a storm sewer or other storm drainage facility. No footing drains
or drainage tile shall be connected to a sanitary sewer.
(6)
Sump pump drains. Any newly constructed or installed structure equipped
with a sump pump and located on property, any part of which is within
100 feet of a sump drain line or storm sewer outlet, shall be required
to connect to tie-in to such line or outlet.
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.
A.
Upstream areas not meeting code requirements.
(1)
When there are areas not meeting the storage and release rates of
this chapter, tributary to the applicant's property, regionalized
detention on the applicant's property shall be explored by the applicant
or the Village. When it is deemed beneficial by the Village or the
applicant to explore such a design, the following steps shall be followed:
(2)
Allowable release rates shall be computed using the combined property areas. Storage shall be computed as described in § 291-14. If tributary areas are not developed, a reasonable, fully developed land cover, based on local zoning, shall be used for the purposes of computing storage.
(3)
Once the necessary combined storage is computed, the Village may choose to pay for over-sizing the applicant's detention basin to accommodate the regional flows. The applicant's responsibility will be limited to the storage for his property as computed above. If regional storage is selected by the Village, then the design produced in § 291-13 shall be implemented. If regional storage is rejected by the Village, the applicant shall bypass all tributary area flows around the applicant's basin whenever practicable. If the applicant must route upstream flows through his basin and the upstream areas exceed one square mile in size, the applicant must meet the provisions of Subsection B for on-stream basins.
B.
Upstream areas meeting requirements. When there are areas which meet the storage and release rate requirements of this chapter, tributary to the applicant's property, the upstream flows shall be bypassed around the applicant's detention basin if this is the only practicable alternative. Storage needed for the applicant's property shall be computed as described in Subsection A. However, if the Village decides to route tributary area flows through an applicant's basin, the final design stormwater releases shall be based on the combined total of the applicant's property plus tributary areas. It must be shown that at no time will the release rate from the combined property exceed the allowable release rate for applicant's property alone.
Where detention, retention, or depressional storage areas are
to be used as part of the drainage system for a property, they 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 on a regular basis and before project completion
in order to maintain the design volume of the facilities.
