Dimension “A” must always be wide enough to allow for adequate space to ensure proper placement of backfill in the haunch region and to operate compaction equipment. Typically dimension “A” is a minimum of (0.75*DN)/2. The depth limit tables are based on a trench width of 1.75*DN. For larger diameter pipes a smaller value for
“A” may be adequate depending on the native soil, backfill material and compaction technique. As an example for native soil groups 1,2 and 3 and backfill materials A and B which require limited compactive effort, a narrower trench could be considered. Consult the pipe supplier for specific guidance and modifications.
Note: