A. General:
1. All developments or subdivisions shall include provisions for the construction of a storm water runoff conveyance system. The storm water runoff conveyance system shall consist of storm sewers, drainage ditches, swales, culvert pipes, detention and retention basins, individually or in combination. When public storm sewer exists on a property to be developed, or runs adjacent to the property, the sump pump shall be connected directly to the storm sewer.
2. All streams, channels or storm sewers shall be designed to accommodate storm water runoff from all areas that naturally flow to the area of development.
3. Storm water management facilities shall be designed and constructed in accordance with provisions of this title and the Beach Park watershed development ordinance (chapter 15.32 of this code).
4. Plans, specifications and all calculations for storm water runoff control as required hereunder, shall be submitted to the village as part of the review and approval of the preliminary and final plats. As built drawings shall be submitted for all stormwater and drainage facilities prior to village acceptance of the improvements.
5. The facilities for stormwater runoff control shall be constructed prior to any site grading, street or drainage construction and shall include provisions for siltation control.
B. Stormwater Drainage:
1. General: Storm sewers shall be designed and constructed in accordance with the latest edition of the Illinois department of transportation's "Standard Specifications For Road And Bridge Construction", the highway standards manual, and the highway design manual.
2. Design Runoff Rates: Storm sewers, swales, and ditches having a tributary area less than one hundred (100) acres shall be designed to convey storm runoff flows calculated using the rational method as follows:
Q = c x i x A
Where:
Q = Runoff flow in cubic feet per second
c = Runoff coefficient characteristic of the tributary area in dimensionless units
i = Average rainfall intensity in inches per hour
A = Tributary drainage area in acres
3. Drainage Area: The drainage area used for design shall be the entire watershed tributary to the point in the storm sewer system under consideration. It shall include any tributary area that may be outside the development or subdivision.
4. Rainfall Intensity:
a. The average rainfall intensity used for design shall be selected from rainfall intensity curves contained in Illinois state water survey bulletin no. 70.
b. The rainfall intensity for design of storm sewers or minor swales and ditches shall be based on a rainstorm with a 10-year recurrence interval and a duration equal to the time of concentration.
c. The rainfall intensity for design of major storm sewers in combination with streams and channels shall be based on a rainstorm with a 100-year recurrence interval and a duration equal to the time of concentration.
d. The "time of concentration" is defined as the time (in minutes) for the flow from the most remote point of the drainage area to reach the point under consideration.
e. For storm sewer design, the maximum time of concentration to a storm sewer inlet shall be twenty (20) minutes.
5. Runoff Coefficient:
a. The runoff coefficient is the ratio of runoff to rainfall and shall assume saturated conditions.
b. The runoff coefficient, C, for 10-year storms shall be a minimum of:
Water surface area = 1.00
Impervious areas = 0.95
Pervious areas = 0.30
c. The runoff coefficients for undeveloped areas outside of the limits of the proposed development shall be a minimum of 0.35 for 10-year storms, or as approved by the village engineer based on the zoning and land use of the tributary area.
6. Stream, Channel, And Storm Sewer Hydraulics:
a. Design Flow: Storm sewers, streams, and channels shall be designed to provide a design flow capacity based on Manning's formula:
Where:
Q = A x (1.486/n) x (R)2/3 x (S)1/2
Q = Flow rate in cubic feet per second
A = Area of the conduit in square feet
n = Roughness coefficient of the conduit in dimensionless units
R = Hydraulic radius, defined as the area of the conduit divided by the wetted perimeter
S = Slope in feet per foot
b. Design Velocities:
(1) Storm Sewers: Design velocities for storm sewers shall be greater than three feet per second (3 ft/s) and less than ten feet per second (10 ft/s).
(2) Lined Channels And Streams: Design velocities for lined channels and streams shall be greater than two feet per second (2 ft/s) and less than ten feet per second (10 ft/s).
(3) Unlined Channels And Streams: Design velocities for unlined channels and streams shall be greater than two feet per second (2 ft/s) and less than five feet per second (5 ft/s).
7. Storm Sewers:
a. Storm sewers shall be designed using Manning's formula for a gravity flow condition with the downstream controlling elevation at the 10-year 24-hour return frequency storm level. The lowest structure frame shall be a minimum of twelve inches (12") above the high water level in the detention or retention basin.
b. Minimum storm sewer size shall be twelve inches (12").
c. Storm sewers shall be laid straight in both horizontal and vertical planes between structures unless otherwise approved by the village engineer.
d. Storm sewers of differing diameters or materials shall join at structures only. The invert elevations shall be adjusted to maintain a uniform energy gradient by matching the 0.8 depth points of the differing diameters.
e. Inlets shall be provided so that surface water is not carried across or around street intersections. Inlets shall be spaced such that overland flow shall not build up a flow rate exceeding one cubic feet per second; except, that curb inlets shall be located such that no more than three hundred feet (300') of gutter is tributary to an inlet or as otherwise approved by the village engineer. Inlets shall be as provided at all low points.
f. Manholes shall be provided at all changes in horizontal or vertical direction; changes in shape, material or size of pipe; and junctions of pipes. The maximum spacing of manholes shall be four hundred feet (400') for sewers forty two inches (42") in diameter and smaller, and five hundred feet (500') for sewers forty eight inches (48") in diameter and larger.
g. Storm sewer service stubs for existing, proposed and future sump pump connections shall be provided as required by the village engineer.
h. When a public storm sewer exists or is proposed on or adjacent to a property to be developed, the sump pump must be connected directly to the public storm sewer. Sump pump connections shall be made with a minimum four inch (4") diameter polyvinyl chloride pipe, SDR 26, installed in accordance with the village sanitary sewer installation policy. Connection to the storm sewer pipe shall be made by core drilling a clean hole into the pipe or manhole and connecting with a mission coupling or elastomeric boot. Connection to the storm sewer structure shall be made by core drilling a clean hole into the structure and grouting the sump pump connection pipe into place with waterproof cement grout.
8. Drainageways:
a. Existing streams and channels shall be maintained and stabilized and, if permitted, shall be realigned or channelized subject to requirements of the Illinois department of natural resources division of water resources, the army corps of engineers, the federal emergency management agency, the Lake County storm water management agency, and the village of Beach Park.
b. Where streams and channels are allowed to be realigned or channelized, the bottom shall be stabilized and the banks shall be protected from erosion by methods approved by the village engineer and in compliance with this title.
9. Floodplains:
a. No construction shall be permitted in the floodplain without village board approval.
b. Any construction in the floodplain permitted by the village board shall comply with the provisions of the Beach Park watershed development ordinance (chapter 15.32 of this code).
10. Culverts:
a. The minimum culvert size shall be twelve inches (12") for driveways and roadway crossings. At locations where culverts cross roadways, the cover over the culvert shall be designed to provide H20 loading capability. In no case shall cover be less than nine inches (9") between the top of the pipe and the roadway surface.
b. All roadway culverts shall extend a sufficient distance beyond the shoulder line so as to intersect the backslope of the culvert spring line at a minimum six to one (6:1) slope. Flared end sections shall be provided on all roadway and driveway culverts. Roadway and driveway culverts eighteen inches (18") or greater in diameter shall also require grates.
c. An overall map of the development or subdivision showing the culvert size and slope for each lot shall be included in the as built drawings submitted for the development or subdivision.
11. Allowable Materials:
a. Storm sewers shall be reinforced concrete pipe conforming to ASTM C-76 wall B standards for round pipe or ASTM C-507 for elliptical pipe. Class of pipe shall conform to the class IV for round pipe and class HE III for elliptical pipe. The village engineer may approve alternate storm sewer materials.
b. Pipe joints shall be O-ring joints conforming to ASTM C-443 or asphaltic compound joints except where the storm sewer crosses a water main. At these locations the pipe joint shall be an O-ring joint.
c. Manholes, catch basins, and inlets shall be precast reinforced concrete conforming to ASTM C-478. Each manhole shall have a poured class SI concrete bench shaped to drain the outlet pipe.
d. Joints between manholes, catch basins, and inlet sections shall be completely sealed with preformed bitumastic joint filler.
e. Adjusting rings shall be precast concrete rings.
f. Inlet and catch basin frames and grates shall be subject to the approval of the village engineer.
g. Manhole frames, grates, and steps shall be subject to the approval of the village engineer. Grates shall be embossed "Storm" and "Village of Beach Park".
h. Bedding and trench backfill for storm sewers shall conform to the "Standard Specifications For Road And Bridge Construction" and shall conform to gradation CA-5 or CA-7 washed gravel (uncrushed).
12. Construction:
a. Storm sewers shall be constructed in accordance with the "Standard Specifications For Road And Bridge Construction", the "Standard Specifications For Water And Sewer Main Construction In Illinois", the pipe manufacturer's recommendations, and this title.
b. Trenches for stone sewers located under or within the influence area of a paved surface, structure, or utility shall be backfilled with trench backfill (CA-6) and compacted by mechanical means in lifts not exceeding eight inches (8") to ninety five percent (95%) standard proctor laboratory density.
c. Adjusting rings for manholes, catch basins, and inlets shall be limited to a maximum of two (2) rings and a maximum height of eight inches (8").
d. When adjusting rings are required on structures, a cement mortar or bituminous material coating shall be applied to the outside of the rings.
e. Lifting holes in structure sections and sewer pipe shall be plugged with appropriate sized concrete lift plugs and coated with bituminous material. Storm sewer pipe shall not have lifting holes at water main crossings.
D. Storm Water Management:
1. General: A properly designed storm water management system is required for all developments or subdivisions and shall conform to the Beach Park watershed development ordinance (chapter 15.32 of this code). The provisions of the Beach Park watershed development ordinance shall be deemed as additional requirements to the minimum development standards, this title and all other ordinances of the village.
2. Storm Water Detention Facilities:
a. All storm water detention facilities, other than roof tops, and/or underground storage, shall be located not less than fifty feet (50') from any building or structure to be occupied and shall not be less than thirty feet (30') from any roadway unless otherwise approved by the village engineer.
b. Detention basin storage volume shall be determined in accordance with the requirements of the Beach Park watershed development ordinance (chapter 15.32 of this code).
c. The design and construction of the detention basins shall meet the requirements of the village engineer.
d. No paved areas such as parking lots shall be used for storage of storm water.
e. A minimum of two feet (2') of freeboard shall be provided from the high water level to the top of the berm on all basins unless otherwise approved by the village engineer.
f. Detention basins shall be landscaped including the establishment of ground cover through sodding or hydroseeding.
g. Dry bottom storm water storage areas:
(1) Dry bottom storm water storage areas may be designed to serve a secondary purpose for recreation, open space or other use that will not be adversely affected by occasional or intermittent flooding and will not pose a safety hazard to users of the space. These areas may not count towards required active recreation area but may be included in open space requirements.
(2) A method of carrying the low flow through dry bottom storm water storage areas (such as a concrete paved channel) shall be provided in addition to a system of drains, and both shall be provided with a positive gravity outlet to a natural channel or sewer.
(3) The combination of storage of the water from a 100-year storm and the design release rate shall not result in a storage duration in excess of seventy two (72) hours.
(4) The maximum depth shall not exceed four feet (4') unless the existing natural ground contours and other conditions lend the area to greater storage depth as approved by the village engineer.
(5) Side slopes shall not be steeper than four horizontal to one vertical (4:1). The basin floor shall have a slope of not less than two percent (2%) to convey storm water to the paved channel or the basin outlet.
(6) Outlet control structures shall be designed as simply as possible and shall require little or no attention for proper operation. Each storm water storage area shall be provided with a method of emergency overflow in the event that a storm in excess of the 100-year frequency storm occurs. This emergency overflow shall be designed to function without attention and shall discharge to the natural surface channel system. All points of inflow and outflow to and from the storage area shall be accessible to equipment for maintenance. Hydraulic calculations shall be submitted to the village engineer for all design features.
h. Wet bottom storm water storage areas shall be designed in accordance with the requirements for dry bottom storm water storage areas except for specified slopes and the need to provide a low flow conduit and drain system. The following additional requirements apply:
(1) Basin side slopes shall be subject to the approval of the village engineer.
(2) The village engineer may require shoreline protection in areas deemed subject to wave erosion.
(3) Minimum normal water depth shall be four feet (4'). If fish are used to keep the pond clean, a minimum of twenty five percent (25%) of the pond area shall have a minimum depth of ten feet (10').
(4) Facilities shall be made, if possible, to allow the pond level to be lowered by gravity flow for cleaning purposes and shoreline maintenance.
(5) Control structures for storm water release shall be designed to operate at full capacity with only a minor increase in the water surface level. Hydraulic calculations shall be submitted to the village engineer to substantiate all design features.
(6) Aeration facilities may be required by the village engineer to prevent pond stagnation. If aeration facilities are required, agreements for the perpetual operation and maintenance of the aeration facilities by an entity other than the village shall be prepared to the satisfaction of the village.
(7) In the event that the water surface of the pond is to be raised for purposes of storing water for irrigation or in anticipation of the evapotranspiration demands of dry weather, the volume remaining for storage of excess storm water runoff shall still be sufficient to contain the 100-year storm runoff.
i. As built drawings for detention areas shall be delivered to the village engineer before the village will accept these improvements.
j. Construction:
(1) Where development of a property presents the threat of flooding or damage by flash runoff to downstream properties, the facilities for storm water runoff shall be constructed prior to any earth moving or drainage construction on the project site.
(2) During the construction phase of land development, facilities shall be provided to prevent the erosion and washing away of the earth. Silting of downstream areas shall be prevented through the strategic use of stilling basins, of runoff channels, and by limiting the period of time during which the earth is stripped of vegetation.
D. Inspection And Testing:
1. All storm sewers and appurtenances shall be thoroughly cleaned prior to final inspection and prior to testing.
2. The developer shall have an employee in charge on site at all times that the construction of the storm sewerage system and storm water management system is under way. The developer shall be fully responsible for the quality of the materials and methods of the construction work and shall bear full responsibility for ensuring that the storm sewerage and storm water management systems meet the stated requirements of the village in every way.
3. Upon completion of construction and prior to the beginning of the maintenance guarantee period, and, if deemed necessary by the village engineer, due to difficulties during construction of the storm sewers, a videotaped television inspection shall be performed on sections or portions of the storm sewer as directed by the village engineer. Videotapes and written reports for all television inspections shall be provided to the village prior to acceptance. The village engineer shall approve the form of the report and the videotape. All fees and costs involved in this television inspection shall be borne by the developer.
4. The village engineer will inspect the storm sewerage and storm water management systems during construction as it deems necessary. The village engineer shall not be responsible to direct the work of the developer but shall be responsible only to assess the acceptability of the improvement as constructed. In no case shall the village engineer be responsible for day to day quality control at the site of construction.
5. Repairs made to the storm water management system to meet the requirements of this section shall be permanent and shall be equal in quality to new work constructed in accordance with this section. All such repairs shall be performed at the expense of the developer and shall require repetition of all tests.
E. Submittal Of Engineering Design Data: Plans, specifications, and all calculations for storm water runoff control shall be submitted to the village engineer for review and approval prior to the village approval of a final plat or issuance of a building permit. (Ord. 2004-O-14 § 1)