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MainPlace Mall Transformation Project 12126.001 <br />Retaining wall foundation may be designed as continuous strip foundations. <br />The earth pressure coefficients for seismic increment were derived based <br />on a PGAM of 0.53g. The above values are nominal values with no safety <br />factor. <br />Cantilever walls that are designed for a deflection at the top of the wall of at <br />least 0.001 H, where H is equal to the wall height, may be designed using <br />the active earth pressure condition. Rigid walls that are not free to rotate, <br />walls that are braced at the top, and walls that provide indirect support for <br />foundations should be designed using the at -rest condition. <br />We recommend that the backfill soils for earth retaining structures consist <br />of onsite or import soil with Expansion Index (EI) of not greater than 50 <br />(per ASTM D 4829). The in -place compacted soil weight may be assumed <br />as 125 pounds per cubic foot (pcf). <br />4.2.6 Surface Drainage <br />Positive drainage of surface water away from structures is very important. <br />Positive drainage may be accomplished by providing a minimum of 2 <br />percent gradient for a lateral distance of at least five feet and further <br />maintained by a swale or drainage path at a gradient of at least 1 percent. <br />Where necessary, drainage paths may be shortened by the use of area <br />drains and collector pipes. <br />Irrigation of landscaping should be controlled to maintain, as much as <br />possible, consistent moisture content sufficient to provide healthy plant <br />growth without over watering. <br />4.2.6 Corrosion Protection Measures <br />A composite sample of shallow onsite soils was tested for screening <br />corrosion potential to buried concrete and metals. The chemical analysis <br />test results are summarized in the table below. <br />�'♦� <br />16 / <br />Leighton <br />