Part of the Elan Aqueduct (nprn 95469), itself part of the Elan Valley Water Scheme (nprn 96459), Dolau Tunnel is about 6.8km long and carries the aqueduct under the uplands between the villages of Dolau and Bleddfa. Two shafts, presumably used during the construction of the tunnel, stand on the route: Graig Shaft (nprn 413073) and Bleddfa Shaft (nprn 413075).
B.A.Malaws, RCAHMW, 17 February 2011.