Engineering Wonders of the World
Volume III

_____________ ______ ____ ___ _____________ ____ 106 ENGINEERING WONDERS OF THE WORLD. SECTION OF OLIVE BRIDGE DAM. cubic yards of embankment materials. On the crest of the dam, which will be 610 feet above sea-level and 20 feet higher than the flow line in tho west basin of the reservoir, will be built a roadway, 26 feet wide. The amount of the contract for the con- struction of the Ashokan Reservoir, including nearly four miles of main dams and accessory works, is about £2,570,000. The date set for the completion of the contract is February 19, 1915, with a provision, however, that the work must be sufficiently advanced by August 1912 to permit of the storing of water in the west, or Esopus, basin, and its delivery into the aqueduct. The following are approximate estimates of the excavation and material re- quired :— Earth excavation...............2,055,000 cubic yards. Rock......................... 425,000 Embankment and refilling.......7,200,000 „ Masonry....................... 874,000 „ Rubble paving and riprap....... 105,000 „ Portland cement...............1,100,000 barrels. The masonry structures for the most part will be “ cyclopean ”—that is, to quote the language of the specifications, “ concrete, into which stones of various sizes, Features of . ., . , ,, , the Dam u? to 'arSeSG can be conveniently handled/’ will be embedded. The main dam will bo faced with concrete blocks, and the same kind of material will be used as a lining for the inspection wells and at the expansion joints—two novel and interesting features in dam construction. All masonry dams, however well built, are liable to seepage, which, entering from the up-stream side, passes through the masonry, and issues from the down-stream face, pro- ducing a discoloration not only unsightly, but liable to create an impression that the structure is not tight. To prevent this, in the case of the Ashokan Dam, vertical drain- age wells will be built into the masonry, terminating at top and bottom in inspection galleries. The position of these will be ob- served in the cross-section of the dam printed on the opposite side of the page, TYPICAL SECTION OF DIKES, ASHOKAN RESERVOIR. The expansion and contraction joints are designed to localize the effect of changes of temperature. When cement is setting, the VIEW ALONG LINE OF OLIVE BRIDGE DAM, SHOWING TRENCH FOR FOUNDATIONS.