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Lutzky Associates Development, LP - Geolechnical Investigation <br />MACTEC Project 4953-03-2631 <br />September 18,2003 <br />surcharges due to any other vertical surcharge loads behind the walls. For preliminary design, a <br />uniform lateral pressure equal to one-third of the vertical surcharge pressure may be used. <br />Seismic Lateral Earth Pressure <br />In addition to the above-mentioned lateral earth pressures, subterranean building walls more than 6 <br />feet higher than the opposite wall should be designed to support a seismic active pressure. The <br />recommended seismic lateral earth pressure distribution on walls below grade with allowable <br />maximum deflection of '/2 inches is illustrated in the following diagram with the maximum <br />pressure equal to 16H pounds per square foot, where H is the wall height in feet or the difference, <br />in wall height between the building wall and the opposite building wall. <br />V <br />H- <br />HEIGHT OF WALL OR <br />DIFFERENCE IN <br />BUILDING WALL <br />HEIGHT <br />IN FEET <br />E-3> <br />'4 Al.) 1 <br />Drainage <br />Although the historic high ground water at the project site is at 10 feet below the existing grade, <br />we recommend that the wallt below grade should be designed to resist, in addition to the lateral <br />1 earth pressure and other surcharge pressures,the hydrostatic pressure of water rising to the level,of <br />•the adjacent existing grade behind the walls due to a possible perchl water build-up #of' <br />0)filtrating water from the ground surface. The hydrostatic pressure on the walls could be <br />estimated by assuming a fluid density of 62.4 pounds per cubic foot. A waterproofing barrier may <br />be installed on the walls below grade, if desired. <br />27