Abstract: This invention relates to a backfill compaction apparatus of a type particularly well suited to the puddling and compaction of loose soil around pipes laid in trenches, such apparatus being characterized by a self-propelled carriage adapted to straddle the pipe and advance therealong incrementally, a mast supported in upstanding relation on the front end of the carriage, a forwardly-extending boom mounted on the mast for vertical movement relative thereto, means operatively interconnecting the mast and boom for raising and lowering the latter, a tool-carrying platform suspended from the boom in overhanging relation to the trench to be backfilled, at least one pair of transversely-spaced combination puddling and vibrating subassemblies hanging from the tool-carrying platform adapted to enter the trench on opposite sides of a pipe laid therein, said subassemblies each including an elongate rigid nozzle for introducing water beneath the surface of the backfill and a vibrator connected to said nozzle for movement