I've recently been looking at 2 huge outfalls that flow into the mersey, one at birkenhead, and one over in Liverpool.
They're both about 25 foot high, and both the same shape, but I only have a picture of the birkenhead one unfortunately.
The one in Liverpool is in line with a pumping station for MEPAS, so I think its possible it was originally a sewer that discharged straight into the mersey. Currently there is a constant trickle of water coming out of it, possibly overflow from the canal? I know it pre-dates the canal, as when they built the canal they cut into the tunnel.
Line in red shows the position of it:
Also, over the mersey at the birkenhead ferry terminal is a similar tunnel:
The line in red shows the position, and the line in purple shows the direction in which it stretches inland. If you use google maps and zoom in on where the purple line is, you see a series of grids in the floor. I went down and had a look at these yesterday, there is some serious flow of water coming through, the further you get inland the louder the roar gets. You can look through the grids and see a lot of turbulent water coming through, at a very fast rate. I presume it is because the water is flowing downhill, and hitting rocks etc within the tunnel.
The only problem is that I couldnt see where the water discharges. It definately doesnt come out of the tunnel mouth, and I couldnt see anywhere else along the front where it might empty out. Where could all that water be coming from anyway? As far as im aware there isnt any rivers in that area, so it seems odd!
Anyone have any ideas what either tunnel are for?