(A) All pipes shall be bedded in well compacted, moist aggregate bedding material at least four inches in depth below the pipe, placed across the entire width of the trench and for the length of the pipe. Material for granular pipe bedding shall be crushed limestone, washed gravel, washed sand, or other granular material authorized by the developer’s engineer. Granular pipe bedding shall be placed to the centerline of the rigid pipe and to one foot above the top of the pipe for flexible pipe.
(B) For rigid piping (iron, concrete, steel, and the like), the granular pipe bedding for firm, dry trench bottoms shall be crushed limestone, coarse aggregate gradation CA 6 or CA 9 as specified in the Standard Specifications for Road and Bridge Construction, IDOT.
(C) For flexible and brittle piping (plastic, clay, copper, corrugated metal pipe, and the like), the granular pipe bedding for firm, dry trench bottoms shall be washed sand, fine aggregate gradation FA 5 or FA 6 as specified in the Standard Specifications for Road and Bridge Construction, IDOT.
(D) PVC sewer pipe shall be bedded and backfilled in general accordance with Underground Installation of Flexible Thermoplastic Sewer Pipe, ASTM Standard D-2321. The embedment materials shall be Class III.
(E) When unsuitable soil conditions are encountered in the bottom of the trench, the contractor shall remove unsuitable materials below the depth of the bedding shown on the drawings, and shall replace the material removed with compacted pipe bedding materials authorized by the developer’s engineer.
(F) In cases where excessively wet conditions exist on the trench bottom, stone larger than those listed hereinabove (coarse aggregate gradation CA 1 as specified in the Standard Specifications for Road and Bridge Construction, IDOT) may be used as ballast to stabilize the bottom; however, the pipe shall not be laid on this large aggregate. Granular pipe bedding is required between the larger aggregate and the pipe.
(G) As soon as the condition of the pipe will permit, the entire width of the trench shall be backfilled with moist aggregate to the heights stated above. The aggregate shall be placed longitudinally along the pipe. The elevation of the haunching material on each side of the pipe shall be the same. Special care shall be taken to completely fill the space under the pipe haunches. The aggregate materials shall be placed in maximum six-inch layers, loose measurement, and compacted by ramming or tamping.
(Ord. 97-7, passed 7-1-1997, § 5.16)