karohemd | [Riverside Bridge] A big sandbox

That's what the construction site looks like outside and they're doing pretty much the same things (digging holes, making neatly shaped heaps patted down nice and even), only their tools are diesel powered and cooler. ;o)
I think my orginal assumptions are correct and the series of ditches on the West side of the site will be the foundations for the supports as most of the ditches have been filled, redug, had steel reinforcments inserted and concrete poured in.
There's now also a much larger, roughly square ditch on the East side and on the edge of the trees alongside the river. Not sure what that's going to become.

There are various digs on the Riverside side, too but I can't see those from here as the trees are in the way and last time I was over there, it wasn't quite obvious what was what.

I'm sure there will be more exciting things to come. :o)