(http://img841.imageshack.us/img841/2350/seweraccess.png) (http://imageshack.us/photo/my-images/841/seweraccess.png/)
If you look at the minimap showing the level below (top right), the sewer access seems to be connected to the river, which sucks for me. There is no stairwell or anything else.
Just wanted to post this in case it helps, i'ma head in there if I can manage to not drown.
(Edit)
Drowned. But it does connect to the sewer.
Does anyone know how to open floor hatches? I can't figure it out. I thought you would stand next to them and press 'u' like with wells...
I thought you just go down them like they're a stairway - if what I was going through last night was a floor hatch, which I think it was.