A culvert that travels under much of St Helens with a dirty big sewer overflow at one end.
A set of stairs drops down from a small dry RCP and joins after the outfall, the whole setup looking like a 'Y' from above.
A balancer between the A and B Outfall sewers with penstocks to enable throttling between pipes.
The brook emerged from a tiny brick culvert around a foot high, but downstream a few meters was the outfall for what I presume to be the brook's bypass.
Prestwich clough had a promising looking if not slightly dodgy culvert. The brick filled wire cages sagged rather in the middle and the concrete roof beams looked compromised from the weight above.