Y is ebay I think...
Also a circle of 1.8m radius seems way out to me... I just poured a litre of water on the ground outside and it spread to ~0.5m radius circle, now that was on concrete slabs but I also reckon that half of it went down the cracks between each one.
We ended up with three puddles:
1.8m radius (at 10mm depth)
2.5m radius (at 5mm depth)
5.6m radius (at 1mm depth)
if we add some more:
8m radius (at 0.5mm depth)
17m radius (at 0.1mm depth)
If someone could be so kind as to go out and pour a litre of diesel on some tarmac, we can see what sort of depth the puddle is and then extrapolate from there for a 100l puddle.