They are plastic tubes, and it appears that some kind of tree is growing inside. I think the tubes are there to keep the deer from eating them until they get established, but I am not sure why they are only located adjacent to where the gas line crosses the stream and not elsewhere.
Peter
_________________________
Peter Kaufman NRA Life GOA SAF RKCC CM-023 RKS #5642 SHAG # 005 Ironwood Nut Life is too short to have ugly knives