18-29-306.2.2 Rock removal.
   Where rock is encountered in trenching, it shall be removed to a minimum of 3 inches (75 mm) below the installation level of the bottom of the pipe, and the trench shall be backfilled to the installation level of the bottom of the pipe with sand tamped in place so as to provide uniform loadbearing support for the pipe between joints. The pipe, including the joints, shall not rest on rock at any point.