The digger waits for the truck all day. What the arithmetic actually says about a spoil run.
The most common way an island job runs over is not weather and it is not the machine. It is one excavator loading one tipper.
A five tonne machine fills a seven cubic metre tipper in about eight minutes. The round trip from a plot in the village to the spoil ground and back, allowing for the lane, the harbour road and turning, is rarely under twenty five. So for seventeen minutes in every twenty five the excavator sits with its engine running and your operator sits with it.
Two tippers with one excavator roughly doubles what comes off the plot in a day. It does not double the cost, because the second tipper travels on the same barge and the excavator day is already being paid for.
We say this when we quote, and a fair number of customers hear it as an attempt to sell a second machine. So work it yourself: take your spoil volume, divide by seven, multiply by your round trip time, and compare that with eight minutes a load. The number will decide it.
There is a version of this where one tipper is right, and it is a short haul. If the spoil ground is two hundred metres away and the round trip is six minutes, one truck keeps up and a second one queues.
The same arithmetic applies to a pour with mixers. Two mixers and four people is not twice one mixer and two people; it is about three times, because the bottleneck moves from mixing to placing.