An HDPE storm drain line is bedded in free-draining granular material with a minimum thickness of six inches below the pipe and six to nine inches along the sides. The pipe zone extends twelve inches minimum above the crown of the pipe using free-draining granular material with a sand equivalent of not less than thirty and ninety percent relative density compaction. The backfill zone requires twelve inches minimum of free-draining granular material with a sand equivalent of not less than twenty and ninety-five percent relative density compaction, topped by a twenty-four inch minimum depth to the new Portland cement concrete sidewalk constructed per landscape sheets.
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