The Rotherhithe Tunnel. (Including Plates at Back of Volume).

Abstract

The levels under the river were governed by the fact that the Thames Conservancy have the right to dredge a width of 450 feet to a depth of 45 feet below Trinity high-water mark. A thickness of 4 feet was left between this level and the top of the tunnel, the actual minimum cover during construction being about 7 feet. GENERAL DESCRIPTION. Direct communication between two important streets is provided by the tunnel and its approaches. These streets are, on the south side of the river, Lower Road, Rotherhithe, and on the north side, Commercial Road, Stepney. The open approach leaves the former street at its junction with Union Road, and the latter near Stepney Station, which two points are more than 3 miles apwt by road ; by the tunnel this distance is 14 mile. Commencing on the south side, the open approach leaves the street on a gradient of l in 36.5 and is 930 feet long. Near its lower end the East London Railway is crossed by a bridge, the roadway being here about 25 feet below ground-level. The next 530 feet is brick tunnel, constructed by the " cut-and-cover " system, and terminating in No. 1 shaft. A t this shaft the cast-iron-lined tunnel begins, and, still descending on the same gradient for a distance of 890 feet, attains its maximum depth in No. 2 shaft, which is situated on the riverbank. At this point the roadway is 75 feet below ground-level. From No. 2 shaft to No. 3 is the subaqueous portion of the tunnel, 1,535 feet in length. The roadway rises 1 in 800 for the greater part of this distance, the up-gradient of 1 in 37 beginning about 270 feet from No. 3 shaft. Between this shaft and No. 4, a distance of 1,155 feet, the tunnel passes round a curve of 800 feet radius, and is under buildings for nearly the whole of the way. Beyond No. 4 shaft is a length of 600 feet of cut-and-cover, followed by 1,186 feet of open approach, at the end of which the street-level is once more attained.