I'm just thinking, standards for fill around utilities range from no compaction to, at best 90% ASTM D1557. Projects I'm on usually require only 'hand-tamping', which is basically just the same as stomping with your feet. If you're thinking about moment, are you deciding whether to use thrust blocks? It seems like you'd need some pretty good compaction to be able to handle moment on a pipe, at least for the design.
Just some thoughts.
ds