I asked on another forum ( there are some advantages to being a dingle
)
Somebody has posted this map from 1911, you can see the arm going off to the left in to a basin which is where they loaded the coal. The bridge ( tranway from the colliery ) is also shown. There was also a dry dock for repairing the barges shown on the map. Apparently the pipe for draining that dock came out in Thompsons Park and is still around.