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• 2 to 3 feet of the ground surface. Imported granular soils should be free draining and have less than 10 <br />percent passing the No. 200 sieve. The upper 2 to 3 feet of fill should be a relatively impervious soil or <br />pavement structure to prevent surface water infiltration into the backfill. <br />The wall backfill should be cazefully placed in uniform lifts and compacted to between 90 and 95 percent of <br />the maximum modified Proctor density, near the optimum moisture content. Care should be taken not to <br />overcompact the backfill since this could cause excessive lateral pressure on the walls. Some settlement of <br />deep foundation wall backfill materials will occur even if the maietia! is placed correctly. <br />Surface Draina¢e-Structures: Proper surface drainage at this site is of paramount importance for <br />minimizing the infiltration of surface drainage into the wall backfill and bearing soils, which could result in <br />increased wall pressures, differential foundation and slab movement. The following drainage precautions <br />should be observed during construction and at all times after the building has been completed: <br />1) The ground surface surrounding the buildings should be sloped (minimum of 1.0 inch per foot) to <br />drain away from the building in all directions to a minimum of 10 feet. Ponding must be avoided. <br />If necessary, rnising the top of foundation walls to achieve a better surface grade is advisable. <br />2) Non-structural backfill placed around the building should be compacted to at least 90% of the <br />maximum standard Proc[or density at or neaz the optimum moisture content in order to minimize <br />future settlement of the fill. The backfill should be placed immediately after the braced foundation <br />• walls aze able to structurally support the fill. Puddling or sluicing must be avoided. <br />3) The top 2 to 3 feet of soil placed within 10 feet of the foundation should be impervious in nature to <br />minimize infiltration of surface water into the wall backfill. <br />4) Roof downspouts and drains should discharge well beyond the limits of all backfill. Roof <br />overhangs, which project two to three feet beyond the foundation, should be considered if gutters <br />are not used. <br />S) Landscaping, which requires excessive watering and lawn sprinkler heads, should be located a <br />minimum of ] 0 feet from the foundation walls of the building. <br />6) Plastic membranes should not be used to cover the ground surface adjacent to foundation walls. <br />Limitations: This report has been prepared in accordance with generally accepted soils and pavement <br />engineering prnctices. The recommendations given in this report are based on the soils and bedrock <br />materials encountered at this site, our understanding of the proposed construction and the behavior of <br />structures at neighboring, similar sites. We believe that this information gives a high degree of reliability <br />for anticipating the behavior of the proposed strvcnues; however, our recommendations are professional <br />opinions and cannot control nature, nor can they assure the soils profiles beneath those or adjacent to those <br />• observed. No warranties expressed or implied are given on the content of this report. <br />Job Number: 03-5838 NWCC, Inc. Page 8 <br />