The soffite of the viaduct. Beams span across the space between the piers. It would have been normal to have built brick voussoirs between the beams, to act as a stiffener and to support the road fill material. It appears to me to be partly foundry waste; the underside of the structure has been spray surfaced, a popular remedial technique in the recent past, but I have found there to be some problems that ensue, not the least of which is that the condition of the structure cannot be seen, nor can the state of attachment between the structure and the coating. I suspect that that is the purpose of the cross trench, to inspect the state of the structure. 2nd February 2009.
