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M98168GE • . Level Backfill foundations in intimate contact with the formational material (pounds per cubic foot per foot of depth) Active L.E.P. 30 At-rest L.E.P. 45 Passive L.E.P. 500 Resistant forces used in the design of the walls will depend on the type of soil that tends to resist movement. We suggest that you consider a coefficient of friction of 0.3 for the on site soil and a coefficient of friction of 0.4 for foundations with intimate contact with the formational material. The lateral earth pressure values provided above, for design purposes, should be treated as equivalent fluid pressures. The lateral earth pressures provided above are for level well drained backfill and do not include surcharge loads or additional loading ae a result of compaction of the backfill. Unlevel or non-horizon- tal backfill either in front of or behind walls retaining soils will signif'_cantly influence the lateral earth pressure values. Care should be taken during construction to prevent construction and backfill techniques from overstressing the walla retaining soils. Backfill should be placed in thin lifts and compacted, ae discussed in this report to realize the lateral earth pressure values. Walls retaining soil should be designed and constructed so that hydrostatic pressure will not accumulate or will not affect the integrity of the walls. Drainage plane should include a subdrain behind the wall at the bottom of the backfill to provide positive drainage. Exterior retaining walls should be provided with perime- ter drain or weep holes to help provide an outlet for collected water behind the wall. The ground surface adjacent to the wall should be eloped to permit rapid drainage of rain, snow melt and irrigation water away from the wall backfill. Sprinkler systems should not be installed directly adjacent to retaining or basement walla. 9.0 DRAIN SYSTEM A drain system should be provided around building spaces below the finished grade and behind any walla retaining soil. The drain systems are to help reduce the potential for hydrostatic pressure 17 Lambert ana ~,o~otiateo COM WLTIMO OlOTlCMMIC~L f MOO1!!q •MO Y/Tl~I~L Tf/T~MO