Excavation, Underground Services and Reinstatement
Excavations
An excavation is a temporary structure and must be treated as one. Support or batter the sides where people work - a common threshold is anything deeper than about 1.2 m, and shallower where ground is poor or there is vibration, traffic loading or previously disturbed ground. Keep spoil and materials back from the edge (a metre is a sensible guide), provide a ladder for access at frequent intervals, edge-protect the opening, and never leave it unattended and unguarded. A competent person inspects at the start of each shift, after any event likely to affect stability, and records the inspection. Watch for buried services, voids, contaminated ground and water.
Underground services
Before breaking ground, obtain service plans, use a cable avoidance tool and signal generator, mark the line, and hand-dig to confirm. Treat every service as live until proven otherwise; a common rule of thumb is no mechanical excavation within about half a metre of a marked service, and never use a pickaxe or spike. If you strike a service: stop, keep people away, warn others, and call the relevant utility - for gas, no smoking, no vehicles, no mobile phones in the hazard zone.
Reinstatement
Reinstatement must meet the Specification for the Reinstatement of Openings in Highways: correct materials, layer thicknesses, compaction and surface level. Undertakers carry a guarantee period during which a failed reinstatement must be put right, and records must be kept.
Traps: assuming a CAT scan alone proves nothing is there; backfilling with spoil containing sharp rubble around a duct; and leaving a plate over an excavation without securing or signing it.