London Main Drainage: Concrete foundation for the northern outfall tunnels, 1861. The northern outfall sewer is about five miles long. For the first mile it consists of two lines of tunnel inclosed in a raised embankment, and for the remainder of the distance three lines of tunnels, each nine feet in diameter. It crosses, by iron aqueducts, over seven branches of the River Lea...The whole of the upper soil is first excavated, then a solid embankment of concrete is formed. In some places this embankment is as much as twenty feet in depth and one hundred feet in width. It is formed by carrying out a staging upon which several lines of rails are laid. The concrete is made of the best Portland cement...[which] is conveyed in trains of waggons drawn by locomotives to the tip or head of the bank, where it is pitched from the staging to the required level below. The upper surface of this concrete is prepared to a proper shape to receive the inverts of the three tunnels...This extraordinary bank was necessary on account of the treacherous nature of the soil upon which the drains were to be placed. It will be a magnificent work when finished, and one that may almost endure for ever. From "Illustrated London News", 1861.