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C. Compaction Requirements for Pipe Culverts and Storm Sewers: 1. The backfilling of pipe trenches shall be done in three stages as follows: a. In the first stage the CONTRACTOR shall provide adequate compacted fill beneath the haunches of the pipe, using mechanical tampers suitable for this purpose. This compaction applies to the material placed beneath the haunches of the pipe. b. In the second stage the CONTRACTOR shall obtain a well-compacted bed and fill along the sides of the pipe and to a point at lest one foot above the top of the pipe. The width of backfill and compaction to be done under this second stage shall be the width of the portion of the trench having vertical sides, or, when no portion of the trench having vertical sides, it shall be to a width at least equal to twice the outside diameter of the pipe. c. In the third stage the remainder of the trench shall be backfilled with suitable material, which shall be compacted in accordance with the requirements below. 2. Compaction: a. The backfill for the first and second stages shall be placed in six-inch layers (compacted thickness) and shall be compacted to 98% of maximum density as determined by AASHTO T180. Where the backfill lies within the roadway embankment or subgrade, it shall be compacted to the densities specified for these areas. b. When pavement is to be constructed over the pipe, the backfill for the third stage shall be placed in the manner and compacted to the degree required for the first and second stages. Where no pavement is to be constructed and vehicular traffic is not to pass over the pipe, the third stage backfill shall be compacted to a firmness approximately equal to that of the soil adjacent to the pipe trench. D. Backfill Under Wet Conditions: 1. Where wet conditions are such that dewatering by normal pumping methods would not be effective, the procedure outlined below may be used when specifically authorized by the ENGINEER in writing and noted in the job diary. In such specifically authorized cases the backfill material used below the elevation at which mechanical tampers would be effective shall be of the A-3 soil classification (based on AASHTO Designation M145-49). After the pipe is bedded properly, the A-3 material shall be placed, and rammed and compacted under the pipe haunches by the use of timbers or City of Sunny Isles Beach NE 174th Street Roadway Improvements 02630 - 16 Storm Drainage 14-1758 / 09-19-2014