The object of this paper is not primarily to describe the failure of a water main under earth pressure, but the writer desires to use this failure as an object lesson or warning against installing pipe lines with more than about 15 feet of earth cover without providing additional thickness of pipe wall to withstand the earth pressure. The writer has heard numerous expressions of the opinion that when earth is backfilled in a pipe trench, it forms an arch and prevents the full load from the weight of the earth bearing on the pipe. This opinion does not appear to be supported by either experiment or experience and the observed conditions as to breakage of pipes in 2000 feet of 48-inch main laid in 1891 and in 3500 feet of a double line of 48-inch main laid in 1895 the wall thickness being 1 inch. The failure of these pipes has been effectively described by Joseph Goodman in Engineering News-Record of August 25, 1927 and only a brief outline will be given herein.From the Kings County line to Ridgewood pumping station, about 4600 feet, the old Brooklyn Water Supply was carried in a lO-foot brick conduit constructed in 1857 and in a single 48-inch pipe 13.5 feet to the south and a double line of 48-inch pipe 18.5 feet and 25 feet, respectively, to the north, the distance given being between center lines. The pipes were laid about 2 feet above the flow line of the brick conduit. The hydraulic grade was at about the top of the pipes. The soil is a clean sand and water bearing with the water level about the top of the pipes. The depth of cover for a distance of about 3500 feet varied from 9 to 28 feet and was to be raised to 30 feet in grading for a proposed roadway. Computations of the strength of the pipe as an arch indicated a safe limit of cover of 9 feet. A 6-foot reinforced concrete circular conduit was planned to 1

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