Small hollow pipe buried near property line -- marker of some sort
Septic Tank/Absorption Field Systems: A Homeowner's Guide to Installation and Maintenance
Pipeline - Wikipedia
Mitigations
Carsonite Utility Posts Underground Pipeline Markers
Underground Cables - an overview
Designing and Building the Home Foundation – Mother Earth News
Marking Non-Metallic Pipe Locations
ii pipeline engineering spur lines of chainsa - GAIL (India) Ltd.
GME Wireline Catalog 24.1 by gmesco - Issuu
Building a Reliable Block Retaining Wall - Building Products Corp
Replacing a Sewer Line with Minimal Digging
DRemdo Pipe Hider Under Sink,PVC Decorative Pipe Line Cover Kit,U Shape Panel Lineset Cover/Heavy Duty Conduit Raceway Sheild Enclosure for Coarse Pipes Cords, Wide 10 15 20 25 cm Pipework Concealer
Trail Terms - American Trails