With the right size crew, 120 should be right on schedule, but not with my crew. I would be off by my typical 2 months.
#4 sch.40 PVC and crushed rock? I understand the cedar pipe, maybe the Hemlock is a extra layer to help direct water to the pipe? Filter matt? Is it hemlock bark? I wonder what is left underground? Am I in the wrong ball park in assuming this is a drainage system.
#5 I will have to google coal tar. That doesn't sound like a fire retardant either. Tim