This culvert is found on the upper reaches of the River Irk. Unlike the massive downstream culverts like Optimus Prime, the river here demands only a small conduit.
The outfall is stone and around 7ft high, the pipe continues like this for a short distance before shrinking down to 5ft RBP.
This RBP makes up the majority of the length, seepage has created flowstone in places and a black tar like coating in others.
The shape changes twice more before finally shrinking to around 3ft, I called it a day at that point.
Although small and stoopy this drain has great character and it's interesting to see the Irk in it's younger stages.