The riverside footpath has been closed while Durham County Council carries out stabilisation work, and the river itself is being dredged to remove flood debris.
The stuff is put through a strainer to remove random debris, then sucked via tubes into a vacuum system that blends it with other polyurethane scraps recovered from car dashboards and shipping materials.
He said he saw residents take chain saws to remove trees that lay across city streets, pile them along the side of the road and clean debris from culverts.