Built sometime in the 1980s Bunker is a long concrete storm relief the outfalls to the Manchester Ship Canal. It's mainly RCP of comfortable walking height and a long sections have a ledge likely containing a small sewer.
I later returned with Nckt to walk the whole 3 1/2 odd miles to the plughole. This drain has some nice features including cast iron pipework, multiple stair chambers, junctions and the plughole.
Many more hours could have been spent as theres so much to see, only bad thing is the miles of monotonous RCP that makes up much of the length. Still, it's a great drain and sets a standard for concrete draining.
At the top of the plughole the pipe continues in a reduced form for an unknown distance.