Overflow of the Glamorganshire Canal (nprn 34425), passing under the towing path by a two-arched culvert and then in a short tunnel to the River Taff some 400m to the southeast. There is a sluice gate in the side wall of the canal some 20m to the south, possibly part of the water supply to Lucy Dock (nprn 91543).
Site visited B.A.Malaws, RCAHMW, May 1978.