A standard shallow storm manhole assembly utilizes precast concrete sections conforming to ASTM C478, supported on an eight-inch compacted base course. A twenty-four-inch heavy-duty traffic-rated lid and ring rest atop adjustable grade rings set over a standard concrete lid. The manhole barrel diameter ranges from four to six feet, featuring joint mastic at precast joints and a mortared bench shelf with a one-and-one-half-inch per foot slope draining to the invert pipe. Detail notes specify requirements for flexible gasket sealants, grout around pipe penetrations, and rubber water stops for plastic pipe connections.
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