Predictable debris in a predictable place
Container unpacking is not a random event. The site knows which days containers arrive, roughly how long each takes and where the work happens. That makes the debris one of the few things in a warehouse that can be planned for precisely, and it means an attendance timed to follow the unpack does far more than a fixed weekly sweep. Sites can usually give a week's notice without difficulty.
The material itself is consistent too: timber dunnage, inflatable airbags, corner boards, strapping, film and the dust and sweepings from the container floor. Knowing that in advance lets the method and the containers be arranged properly rather than improvised, and it lets the time allowance reflect the actual volume rather than an average. Airbags in particular take up far more space than their weight suggests.
