Just completed a 2000 yard flow fill job filling abandoned water and sewer lines.  The line size was 18" and 20".  Water was 20" cast iron and sewer was 18" HDPE.  The contractor cut the lines and installed a MJ cap with a 2" nipple with a valve.  We hooked up our 2.5" hose from my Olin 545 and started pumping.  The pipe was open ended in various lengths.  The first line we pumped 96 yards for a distance of 1200 feet.  The MJ cap was kicked off against the other section of pipe but at the 96 yard mark we blew off the cap and split the 4x4's like a log splitter.  After that we did the same except we placed a board across the pipe as to not have the pipe thickness act as a cutter.  Ended up being a total length of around 4 miles of each  pipe.  The concrete plant added 37% air to the sand, cement and ash mix.  This was the first time I ever pumped that low psi mix, normally I pump 1000 psi. but it did great.  Did find out that a distance of 800 lf was the optimal distance.  The concrete plant was 15 minutes away, so we asked for 3 trucks to be spaced every 15 minutes but that didn't work so we said to turn them as soon as they got back.  Ended up with 4 trucks and that keep us moving.