Why gas mains fail. Part 2. Deep excavations and tunneling

Deep digging and tunneling near gas mains can severely damage the distribution system by causing ground movement. To avoid this risk, BGC recommends (1) firmly supporting the excavated wall during digging and while the hole is open and (2) gradually withdrawing the support as the excavation is backfilled. A high degree of backfill compaction is essential to prevent further ground settlement months later.