1. 30m length x 6m height x 6m wide. Single span round arch & traverses Nant Madog. E-W orientation.(RSJ 2000)
2. Small aqueduct carrying the Elan Aqueduct over the Nant Madog. It is part of the Elan Aqueduct (nprn 95469), itself part of the Elan Valley Water Scheme (nprn 96459), and it includes the Filter Beds (nprn 32524), Nant Madog Aqueduct (nprn 261743), Nant yr Haidd Aqueduct (nprn 261740) and a Washout Chamber (nprn 309607).
B.A.Malaws, RCAHMW, 03 December 2003.