Decommissioning and cable mining.
Every task elsewhere in this series starts from a one-line that is presumed true. Decommissioning starts from the opposite premise: fifteen years of churn under the floor, and documentation that lies. The governing rule is the oldest one in the book — unverified means energized.
The verification is the work
Article 120's logic does not scale down for cable that is 'supposed to be dead.' An electrically safe work condition exists only after the source is opened, locked, and absence of voltage is verified at the point of work — and in a mining job, the point of work is every conductor the saw or the shears will touch, individually. Where circuits cannot be positively identified to a source — the defining condition of a mined floor — identification itself becomes the first task: tracing, tone, and lifting terminations at the source end until the conductor in hand and the breaker in hand are provably the same circuit.
Cutting is the moment of commitment. The habit that survives audits and funerals alike: no conductor is severed until it has been verified dead at the cut point, that shift, by the person cutting. A verification from Tuesday does not cover Thursday's cut — re-energization is exactly the failure mode churn produces.
Temporary grounding earned its Yes
Table 130.5(C)(3) lists the application of temporary protective grounds after a voltage test as a task likely to cause an arc flash event — the possibility being guarded against is precisely that the test missed something, and the ground makes the discovery violent. Where mining work near medium-voltage feeders or long parallel runs calls for grounding against induced or inadvertent re-energization, the installation of those grounds is itself an arc flash task, suited and bounded accordingly. The likelihood table's honesty here is worth teaching on its own: the safety measure is hazardous to apply.
Abandonment is a records decision
What separates a controlled decommission from an archaeology dig is whether abandonment was ever recorded. The site's power-path documentation — one-lines, panel schedules, whip registers — are safety documents in this work, and every removed circuit should exit through them: identified, verified, severed at both ends, and struck from the record in the same evolution. Cable abandoned in place with terminations intact is the debt this page exists to collect; it presents to the next crew as a live circuit, costs a verification every time it is touched, and eventually meets someone who skips the verification.
The 2027 edition's cutting and conductor-removal provisions in Article 130 formalise what the trade already knew: cutting into anything that could be energized is energized work until proven otherwise, with the full decision walk in front of it.
A mining crew three days into a floor pull, working from as-builts, finds a 100 A whip warm to the touch in a bundle marked decommissioned — fed from a panel in another room, through a tie nobody drew, serving one forgotten cabinet that never made the migration list. The crew's verify-before-cut discipline is the only reason the story is a finding and not an incident report.
Mining or demo scope? The walk's verification and source questions govern every cut. Run it per circuit, not per project.
This is the material of the 8- and 16-hour NFPA 70E classes — taught on the 2027 edition, against data center topology, about 55 times a year. Private onsite days run against your one-lines.