A properly designed stormwater management system is required for all developments and shall conform to county, and any other applicable, comprehensive stormwater management plans, this article and all other ordinances of the City. All developments, whether public or private, shall include provisions for the construction of a stormwater runoff conveyance system. When required, a storm sewer system shall be separate and independent of the sanitary sewer system. All streams, channels, or storm sewers shall be designed to accommodate stormwater runoff from all areas which naturally flow to the area of development.
Design. All storm sewer shall be designed to handle a ten-year, sixty-minute storm in accordance with the requirements of the Berrien County Drain Commissioner.
Storm sewers shall be designed such that the hydraulic gradient shall not be above the gutter flow line.
Minimum storm sewer size shall be 12 inches.
Storm sewers shall be laid straight in both horizontal and vertical planes between structures unless otherwise approved, in writing, by the City Engineer.
Storm sewers of differing diameters 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.
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 exceeding two cubic feet per second except that curb inlets shall be located such that not more than 350 feet of gutter is tributary to an inlet or as otherwise approved by the City Engineer. Inlets shall be provided at all low points.
Perforated storm drains may be required in areas of high water levels, as determined by the City Engineer.
A four-inch stormwater connection shall be required at every lot, in a location approved by the City Engineer.
Reinforced concrete pipe (RCP) shall conform to the requirements of ASTM C76. Use Class III for depths of 14 feet or less and Class IV for depths greater than 14 feet.
Elliptical concrete pipe (ECP) shall conform to the requirements of ASTM C507. Use Class HE-II, as a minimum.
Solid-wall PVC sewer pipe: Sizes twelve-inch though fifteen-inch shall conform to the requirements of ASTM D303 fr. Type PSM polyvinyl chloride sewer pipe of the minimum wall thickness SDR 35. Sizes eighteen-inch through twenty-four-inch shall conform to the requirements of ASTM F679 for large diameter sewer pipe minimum wall thickness T-1.
ADS pipe installed per the manufactures requirements will also be acceptable.
Castings. Inlet and catch basin frames shall meet the standard specifications of MDOT, 1996 edition, converted to English units.
Storm sewers shall be constructed in accordance with the "MDOT Standard Specifications for Construction," 1996 edition, converted to English units, and the pipe manufacturer's recommendations.
All sewers and appurtenances shall be cleaned prior to inspection and testing.
PVC pipe testing. A mandrel shall be pulled through a minimum of 5% of all PVC pipe to test for deflection. Deflection shall be limited to 5.0% of the base inside diameter of the pipe. Failed test sections shall be uncovered and repaired, and the embedment and backfill properly recompacted prior to retesting.