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1 <br />- 17 - <br />A satisfactory alternative could be spread footings placed on the <br />natural, coarse granular material designed for a maximum bearing <br />pressure of 8,000 psf. A mini•myn footing dimension of 3 Eeet is <br />' recommended. Footings should be placed below potential scour depth. <br />' Riprap material, such as currently in place, could also be used to <br />reduce potential scour depth. Abutment walls should be designed to <br /> resist an equivalent lateral earth pressure of 35 psf per foot of <br /> depth above the water table and 80 psf per foot of depth including <br />' hydrostatic pressure below the ~.vater level. These pressures assume <br /> cort~acted backfill material. Additional lateral pressures due to <br /> vehicular traffic should also be considered <br />Unit wei <br />hts <br />an be <br /> . <br />g <br />c <br /> assumed as 125 pcf troist and 70 pcf submerged. If extensive wing <br /> walls are provided, a positive joint should be provided between the <br /> abutment to allow for some differential rtovement. Resistance to <br /> sliding can be calculated utilizing a base friction coefficient of <br />' 0.5. Backfill material would consist of granular soil having a <br /> maximm 8-inch size arr] percent passing the #200 sieve less than 58. <br /> <br />WATER TREATMFNP PLANE <br />Subsoils encountered within the proposed treatment site consist <br />of stiff to very stiff clays to the maximum depth drilled, 20 feet. <br />Results of swell-consolidation tests, presented on Figures 23 and 24, <br />' indicate negligible swell potential and minor settlement potential <br />' under natural rtoisture and density conditions. However, a swell <br />potential is indicated if the upper moist clays were to becone dry. <br />We understand that foundation loadings will be relatively light and <br />cut depth will be minimal. <br />1 <br />