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.
Heaton Park has various small waterways snaking through it, when I first saw the sunken channel I presumed culvert. It was in a clearing in a wood, and had concrete surface structures that suggested something going on underneath.