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west coast prior to World War II, <br />they have received increasing accept- <br />ance during recent years. The author <br />alone has supervised the design of <br />more than 30 reservoirs of this type, <br />all of which were built in the western <br />United States. Figure 4 illustrates <br />an earlier design which combines a <br />12-ft vertical wall and a 2:1 sloping <br />side. Because of the difficulty in pro- <br />ducing a dense concrete on a steep <br />slope, Iater designs employ 5:1 slopes. <br />Concrete can be placed almost as easily <br />on a 5:1 slope as on the level. A later <br />design is illustrated in Fig. 5. <br />result in a perpetual maintenance ex- <br />pense if not properly designed. Fig- <br />ure 7 illustrates a type of expansion <br />joint which is suitable for an exposed <br />concrete roof which is not a tension <br />member between walls. Figure 8 il- <br />lustrates an expansion joint in a roof <br />that acts as a tension member between <br />opposite walls and as a tension tie to <br />the tops of the walls. <br />Cost Data <br />Table 1 is a tabulation of construc- <br />tion cost data on numerous concrete <br />Fig. 4. Walteria Reservoir, Torrance, Calif. <br />The capacity of this reservoir is 10 roil gal. <br />Because of site limitation, it is some- <br />times impractical to bury a reservoir <br />completely. Figure 6 illustrates such <br />a reservoir. With reservoirs of this <br />type, the design of the roof should in- <br />clude a careful analysis of the effects <br />of temperature changes. In small res- <br />ervoirs, such temperature changes are <br />not likely to require any special pro- <br />visions in the design, but in large res- <br />ervoirs expansion joints in the roof <br />may be necessary. Such joints can <br />C <br />reservoirs of various types which have <br />been built in California and Nevada <br />since World War II. The costs in- <br />clude all appurtenant items such as <br />earthwork, piping, paving, fencing, and <br />so forth, and therefore reflect higher <br />unit costs than would be the case if the <br />structure alone were considered. The <br />current Engineering News -Record <br />construction cost index has been ap- <br />plied to indicate approximate current <br />unit costs. Engineering, inspection, <br />RICHARD BRADY &ASSOCIATES, INC. F-54 <br />25B-132 <br />