Engineering Wonders of the World
Volume III

HOW LONDON GETS ITS WATER. 199 channel from the Lee, an outlet channel 1| miles long, and an overflow conduit. The clay wall and the clay substratum form the sides and bottom of a gigantic and abso- SIX-FOOT DIAMETER MAINS THROUGH WHICH WATER IS PUMPED INTO THE GREAT RESERVOIRS AT STAINES, NEAR LONDON. {Photo, by courtesy of Messrs. Thomas Piggott and Sons, Birmingham.) The largest constructional item is the rais- ing of the miles of embankment required to impound th© water. In the middle of the embankment is a vertical core The Embank- n r £C i ,, . ,, , wall oi puddled clay, Gar- ments. . 1 J ried down at all points to the bed of London clay which, underlies the sur- face of the ground at an average depth of about 20 feet. Up to ground-level the core wall is formed in a trench ; above the surface it is built up simultaneously with the em- bankment. This last has a water slope of 1 in 3 and 1 in 4, and an outside slope of 1 in 2|. The earth needed for its construction— some 3,000,000 tons—is excavated by steam navvies and grabs and by hand from the bed of the reservoir, at a distance not less than 200 feet from the toe of the inside slope. lutely water-tight tank. The outward pres- sure of the water is borne by the embank- ment, which has on the reservoir side a facing of concrete slabs and bricks set in cement. In order that the water may be drained away entirely if necessary, the bed of the reservoir will be given a gentle slope towards the southern outlet. The old bed of the Lee has been cleared out and filled up with, hard earth of the same nature as the rest of the bottom. An army of twelve hundred men, a multi- tude of locomotives and trucks—for which many miles of rails have been laid—and a large equipment of excavating machines, electric motors, and Excavating. pumps, are, and will be for many months to come, engaged in the task of forming an arti-