The Redridge Dam (Michigan)slis ofothes ei Among the notable masonry dams of the same general construction as the Ash Fork Dam. bgravity type may be instanced the following: It is 464 feet long and 741 feet highaq The face 19d1The Assouan Dam, across the Nile, in Egypt, members of the bents vary from 15-inch I-beams is the largest masonry dam in the world. It is on the low obents to 24-inch I-beams on the built of granite srubbleg is 16,400 feet long, and high ones asid jedt pauso aidt mort noitsbiloz -has a maximum height of 112 feet. Its mass The illustration shows a combination of steel contains 1,179,000 cubic yards of solid masonry. 1915 3d of Water Lever on пs em 01 sdt to ebno bas sbie bavius sy beat 21 00 of 02 mins Steel Rodss boot batab ng to batom s tedt 12"Concrete Buttresses loarspaced 6'apart ti 02 to beer s obпu ngit (qu bains Jog 1.) 026_2(Total length of dam-120 ft)bn Ingeniogin od ni ma viud Hodinovo-22gigniwa od ELEVATION vino s 57 bodi (Down stream ends of buttresses) ↑ ̄‚i !<-| Concrete-steel Dam, Theresa, N. Y. CROSS SECTION KAS PTHOUT2 ab antivui toCross-section through the Wachusett Dam at the deepest part of the valley. Metropolitan Water Supply, Boston, Mass. wish for! .ame Ists M and permanence, promises an era of high masonry dams. The approved cross-section has a thickness at top of 8 to 10 per cent of the height, a curved batter down stream and a slightly curved batter up stream, the conditions being that the locus of strain shall not pass outside the middle third, and that the greatest pressure in the masonry shall not exceed safe working limits, the latter being governed by the quality of the masonry. The construction is massive random rubble work with an avoidance of continuous beds and joints, the upstream face in courses with roughly dressed beds and joints, the downstream face of selected stone. The top of the dam is usually finished as a roadway with parapet walls, and the spillway is constructed on an independent location. The site is a rock gorge or canyon with a valley expanse above for the reservoir. The New Croton Dam (built 1892-1906), a part of the water supply works of New York city has a length of 1,168 feet, with a spillway of 1,000 feet connecting at right angles. The maximum height of the dam is 297 feet, and the head of water 136 feet. The dam is part rubble and part cyclopean masonry, and has a mass of 855,000 cubic yards-by far the largest in America and second only to the great Assouan Dam on the Nile. (See diagram on another page). The Ashokan, or Olive Bridge Dam (New York city water supply), across the Esopus Creek, is 1,000 feet long, with continuing core walls and embankment 4,800 feet in all. Its maximum height is 251 feet. It is of cyclopean masonry faced with concrete blocks. The I masonry mass has a content of 488,200 cubic Iyards. The Tansa Dam, in India (water supply of Bombay), is of rubble masonry, 8,800 feet long and 118 feet high, with a mass of 408,500 cubic yards. The Waldeck Dam across the river Eder, in Germany, is of rubble masonry. It is 900 feet long, 160 feet high and has a content of 392,400 cubic yards. The Poona Dam, in India, is of rubble masonry, 5,136 feet long and 108 feet high, with a mass of 362,000 cubic yards. The Roosevelt Dam, in Arizona (built 190511), is of rubble masonry with concrete in vertical joints. It is 680 feet long and 260 feet high. It is 158 feet wide at the base and 16 feet at the top. Its content is 344,000 cubic yards. The Mauer Dam, in Germany (built 190412), is of rubble masonry, 918 feet long and 208 feet high. It has a mass of 332,000 cubic yards. The Lake Cheesman Dam, of the Denver water supply, is one of the very high masonry dams carrying a free head of water second only to the Arrowrock Dam. It is 700 feet long on the crest, with a maximum height of 225 feet. It is built on a curve, the radius of which is 400 feet. It is of granite rubble, with a mass of 103,000 cubic yards. Of all-concrete dams of the gravity type, the following are examples: The Arrowrock Dam, over the Boise River, in Idaho (built 1912-16), is of concrete with 1 Keokuk Dam, 4,278 feet long, across the Mississippi river from Keokuk, Iowa, to Hamilton, Illinois 2 The 15 big generators turned by power from the Keokuk Dam 2 DAMS S$441 odas many plums" distributed through its mass of po ei (01-00er find) svi -lias could be conveniently placed. It is 1,160 feet died EL of Spillway 212 021 to 2uibst s Curved to Red 399.89 bis 1991 OIS to testo od ts 1991 II s completion.sbIt is built on a curve of 662 feet 916 2msb d 1997 970m odt gпomA gradius, though of gravity type, being 238 feet amoy W ni CHEESMAN DAM 26lguod zowide at the base, and 151⁄2 feet at the crest. -mol 1991 00 9dIts content is 530,000 cubic yardsobThebfree -ixsm 1991 28 brhead of water behind the dam is 248 feet31-90 lo olgns sob adT died mum 9 feet higher than at the Lake Cheesman Dam, te bidt eodoristnositod edt dtiw 29919 biwhich formerly held the record in this respect. -que admin teodoni A bas got t bimuThe Elephant Butte Dam, across the Rio 2599 31s 292297ttud gnitrog 99 Grande in New Mexico, is of cyclopean concrete or is 29rom 021 oidt 29roni S becarried up in huge block, sections. It is 1,310 00 bas 12 9 tq59b 1991 OI mottod -nfeet long and 305 feet high, with as cubical con- bootnissim Tasd sdt ts 1991 1stent amounting to 1608,000 cubic yards, making 19w oro ai sit the third largest masonry damein the world, arsurpassed in bulk only by the Assouan Dam in bristal asvuponsTO 1oEgypt and the New Croton Dam in New York. OS bns grol 1991 The Keokuk Dam on the Mississippi is a squab ol. t. -omassive concrete monolith, 4,6490 feet long and 91 9v53 feet high.Itbis 29 feet wide at the top and S 42 feet at the bottom. The spillway section or bis 4,278 feet in length and a height of 36 feet, 29251 allowing for a head of 11 feet over the crest. The deck of the dam above the spillway is supported on 119 arches, 36 feet from centre to centre, on 6-foot piers. From this deck are operated the steel gates (11 feet by 32 feet) which close the spillway openings. In building this dam concrete was poured 40 feet deep per day-a 15-foot lift, then 5 hours for setting, followed by the 25-foot lift. b335 feet. Its maximum height was 64 feet and Jeit was 20 feet thick at the base and 3.2 feet at ni bit received, it stood unimpaired until submerged 90feet at the crest. For the upper 30 feet the 191 III Imed limit of Ceck excavation s rfaces are parallel, the slight batter being below in eorul us 202201ind that section on the downstream side tool bs Thest Shoshone and Pathfinder dams, binelle deli Wyoming, depend in part upon their arch form boptotic for stability. Comparative Sections High Masonry Dams. 21 loog oft mort loib 1916W odt ts sont odom 1 i slob этотопоэ Shoshone Dam (built 1905-10) is of Pubble -qfeet. It is 108 feet thick at the base and 10 masonry, arched to a radius of 150 feet. It is te feet at the crest.1991 of 2nd vd botto 200 feet long, with a maximum height of 328 515 Pathfinder Dam, across the North Platte River (built 1906-10), is of masonry, arched to a radius of 150 feet. It has a maximum height of 210 feet and is 94 feet thick at the base and 11 feet at the crest. Among the more recent hollow dams are: Douglas or La Prele Dam, in Wyoming (built 1908-09), an open front dam of the Ambursen type, 360 feet long and 135 feet maximum height. The deck is at an angle of 40 degrees with the horizontal and is 12 inches thick at the top and 54 inches at the bottom. The supporting buttresses are 18 feet between centres, 12 inches thick at the top and 50 inches at the bottom, 10 feet deep at the crest and 160 feet at the base. The material is reinforced concrete. The whole batter is on the water face. Jordan River Dam, on Vancouver's Island, is of reinforced concrete, 756 feet long and 126 feet high. The buttresses are 72 feet deep at the crest and 148 feet at the base. They are placed 18 feet between centres and are 12 inches thick at the top and 42 inches at the bottom. The deck (cast after the buttresses 16 inches thick at the top and 31 inches at the bottom. A rock foundation not being available, the buttresses were built on a thick mattress of concrete. Adjuncts. The ordinary dam across a stream is its own spillway. For impounding dams of earth or rock-fill the necessity for independent spillway is obvious. It should be equally obvious for the high masonry dam, and this is now recognized by the best practice. Many errors have been made, especially in arid regions, through insufficient spillway. In humid regions the "greatest flood" occurs two or three times in a century, and if these are provided for, the margin is usually sufficient for any contingency. In the arid regions a flood as great may be possible, but the occurrence is far more erratic. Cloudbursts produce startling effects in small basins, but the results in basins of considerable area are not significant. The Yellow River of China has a large proportion of arid and semi-arid territory, and five times in its history it has devastated its valley, notwithstanding all the defenses of man, and Lake Cheesman Dam. Water Supply of Denver, Colorado. were built) is 15 inches thick at the top and 55 inches at the bottom. The Three Miles Falls Dam, in Oregon (built 1914), is a multiple-arch dam, curved to a radius of 1,200 feet, and 24 feet in height. It is composed of 40 arches sprung from the buttresses as piers with a radius of 18 feet. The buttresses are placed 20 feet from centre to centre, 2 feet wide at the crest and 34 feet at the base. They are 12 inches thick at the top and 24 inches at the bottom. The Big Bear Valley Dam, in California (built 1914-16), is 363 feet long and 92 feet high. It is a multiple-arch dam, consisting of 10 arches of 302 feet chord, sprung from buttresses 22 feet deep at the crest and 111 feet at the base. The buttresses are 18 inches thick at the top and 54 inches at the bottom. The Mathis Dam, at Tallulah Falls, Ga., is 650 feet long and 90 feet high, of reinforced concrete. The deck is 18 inches thick at the top and 39 inches at the bottom, and is supported by buttresses 16 feet deep at the crest and 148 feet at the base. The buttresses are changed its lower course to the sea. All the factors in flood flow will sometime conjoin, and a work that is to last through the centuries must recognize all the possibilities. Adjuncts in the way of gates, sluices and movable structures are much favored by some designers, especially where they serve to lessen cost. Such provisions should not be carried to a point where their failure to operate or be operated will produce damages amounting to a disaster. The location of service pipes and outlets through or beneath dams is shown by experience to be a source of danger, and the best practice now seeks an independent location. The tendency is now to avoid the long race for power purposes, to build the dam at the foot rather than the head of the rapids or descent, and to make the power station and forebays a part of the structure, taking the water directly from the pool. Outside of the main elements of a structure on which safety and permanency depend, many devices and constructions are permissible, as |