So, the first job is to open every chamber on site, and clear it, either by hand, shovelling, or by suction into a big vacuum tanker, or by washing down with a high pressure jetter.
We did all that, and found problems outside the site's boundaries. Some of the city's drainage guys had a look, passed the buck, multiple agencies pointed responsibility at each other, and promised action, but not in this lifetime. We have tenants whose businesses are at risk if there's a repeat of the storm we had two weeks ago, so we decided to find the problems ourselves.
First job was clearing the spiky undergrowth from the edge of the mill.
The camera is on a four-wheel drive chassis, it clambers along, sending live video back to the van, via the cable it drags behind.