Storm sewers/pipes hydrologic/hydraulic design shall be undertaken by utilization of either the Rational Method, as discussed in the IDOT Drainage Manual, using Illinois State Water Survey Bulletin - 70, or by the Soil Conservation Service TR-55 or TR-20 methodology as applicable. Detention facilities shall be designed by the methodology discussed in the IDOT Drainage Manual Detention Storage Section or designed by utilizing the Corps of Engineers HEC-1 program or the WSPRO (Water Surface Profiles Program).
(A) Storm sewers/pipes shall be designed and installed by the Subdivider/Developer to satisfactorily accommodate the surface runoff incident to the twenty-five (25) year design storm.
(B) Design calculations showing velocity of the storm sewers, discharge velocity, and design of any rip rap in accordance with the Corps of Engineers HEC-1 program, shall be submitted to the Village for all storm sewer pipes. The Subdivider/Developer's engineer shall also submit the Engineer's Hydraulic/Hydrologic Drainage Summary and Certification form, included herein as Exhibit 34-3-E7.
(C) The minimum diameter of storm sewers shall be twelve (12) inches and the minimum diameter of pipe culverts shall be fifteen (15) inches.
(D) Storm sewers located under paved surfaces and right-of-way shall be of reinforced concrete pipe with rubber gasket joints and sufficient wall thickness and reinforcement to carry the intended loading, meeting the requirements of ASTM C-76 and ASTM C-443.
(E) Storm sewers/pipes located outside paved surfaces and right-of-way may be of any of the following materials:
(1) Reinforced concrete pipe with sufficient wall thickness and reinforcement to carry the intended loading and meeting the requirements of ASTM C- 76.
(2) Pre-coated galvanized corrugated steel culvert pipe and pre-coated galvanized corrugated steel pipe arch fabricated from pre-coated steel sheets, and conforming to ASSHTO M 246M (M246), Grade 10/3. The pre-coated culvert pipe and pipe arch shall conform to the requirements of AASHTO M 245M (M245), except that the sheet thickness for the respective diameters of pipe and fill heights shall be as specified in Tables 1B and IIA of Article 542.03 of the IDOT Standard Specifications. Pre-coating of the connecting bands will not be required.
(3) Bituminous coated corrugated steel culvert pipe and bituminous coated steel pipe arch conforming to the requirements of AASHTO M 190, Type A. Any bituminous coating damaged in shipment, during installation, or prior to final acceptance shall be repaired by the Subdivider/Developer to the satisfaction of the Village Engineer. Bituminous coating for the connecting bands will not be required.
(4) Polyethylene pipe conforming to AASHTO M294-94. This pipe shall have a smooth wall interior fitted with elastomeric gaskets conforming to ASTM F477-93.
(F) The Subdivider/Developer shall be responsible for providing the proper plate gauges for the particular loading situation encountered, and for increasing minimum plate gauges as the final loading dictates.
(G) All trenches for pipe/storm sewers that are located under paved surfaces shall be properly backfilled and properly compacted to a density not less than ninety percent (90%) of maximum standard lab dry density as prescribed by AASHTO T-99.
(H) Storm sewer manholes, designed in accordance with the Standard Specification Plan Sheets, shall be installed at all changes in vertical grade or horizontal alignment of storm sewers, if at locations other than inlets/catch basins.
(I) The spacing for inlets/catch basins shall be calculated so that the runoff from the design storm shall not encroach upon the pavement by more than four (4) feet; provided, however, that under no circumstances shall such spacing exceed five hundred (500) feet.
(1) Inlets/catch basins shall be constructed in accordance with the standards depicted on the Standard Specification Plan Sheets.
(2) No open throat inlet shall have an opening greater than five (5) inches high unless said opening is protected by a cross bar intended to prevent the entry of persons into the throat of the inlet.
(3) Vaned inlets shall be used within the curb and gutter on streets where the slope exceeds five percent (5%), in order to prevent the by-pass of storm water flows.
(J) The minimum and maximum gradients of pipes/storm sewers shall conform to the following criteria:
(1) Minimum grade shall be three-tenths percent (.3%).
(2) There is no maximum grade; provided, however, that rip rap and/or energy dissipaters shall be utilized at discharge points, as needed, to minimize erosion.
(K) The minimum and maximum gradients of earth drainage ways and/or swales shall conform to the following criteria:
(1) Minimum grade shall be one percent (1%), which may be reduced to thirty-five hundredths percent (.35%) if paved with concrete.
(2) Maximum grade shall be three percent (3%) with no protection other than sod, or twelve percent (12%) with paving, rip rap, and/or energy dissipaters.