If it was me and I want to make sure it is in speck I would get the specks in writing then go an inch or 2 deeper. Use your machine with a compaction bit go about 1 to 1 1/2 inches bigger than your conduit and it will slide right in. If it is a townhouse community do the trenches first then bore.
![(snipper)](/content/images/smiley/original/snipper.gif)