In S.D., re-routing 7.2kV overhead distribution underground to a 6 residence transformer, although only 2 or 3 homes will ever be served by it. Terrain from 40' pole is 100' along a road edge, 45' steep drop from road down to creek, 35' creek then 200' lawn and gravel driveway. Approx. 380' underground (plus pole and transformer connection lengths) with two turns - one at creek/lawn and one at hilltop/road. Drilling under creek is not an option since attempts elsewhere have not went well (e.g. broken bits). A longer run involving a steel pipe mounted to a steel bridge railing is permitted, but is too expensive. So, wondering what best (reliability/longevity/maintenance, material/labor install cost) alternative is in view of code. Is 4' open trench with direct bury all the way the "best" or only option? Are PVC and/or steel pipe runs "better"? Even if conduit is sealed and water blown out seems likely water will creep in over time. A key question is can steel pipe be used under the creek and/or on the steep hillside to bury less than 4' (less labor, but higher material cost) or does code prohibit this? If anyone has preferred brand/model of direct bury or other underground 7.2kV distribution cables please advise on that too? Thanks for any advice.
