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Project No. JB-20100 4 December 2000 J Page 10 We recommend that our representative observe pier drilling or deep excavations to confirm the soil characteristics of the materials encountered. Depending on the time of year of drilling and the foundation excavation location, groundwater may be encountered in the pier hole. In such cases, the excavation should be cleaned of loose slough and either pumped dry just prior to pouring concrete or tremied with concrete to "float' the water above the concrete with the tremie hose maintaining a minimum 5-foot head of concrete at all times during hose removal. If a different type of foundation system is desired, this office should be called for supplemental recommendations. Such recommendations will be presented as an addendum to this report. 5.3 Lateral Load Design Criteria Lateral loads may be resisted by soil friction and by the passive resistance of the soils. For properly compacted fill, we recommend the following lateral load design criteria: Coefficient of Friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.35 Passive Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 psf/ft The passive pressure and the frictional resistance of the soils may be combined without reduction in determining the total lateral resistance. These values are ultimate and an appropriate factor of safety should be applied by the structural engineer. 5.4 Concrete Slabs-on-Grade If the Earthwork recommendations are complied with, concrete slabs-on- grade may be protected from unwanted moisture vapor by an underlainment of a 4-inch thick capillary break of Class 2 drain rock, clean 1/2 by 3/4-inch crushed drain rock, or pea gravel. We recommend that Class 2 base rock not be used as the capillary break. If the potential for a damp slab is undesirable or if moisture sensitive floor coverings are used, we recommend that an impermeable membrane of 10-mil minimum thickness be placed on the drain rock and overlain by a minimum of 2 inches of clean sand to assist in the proper curing of the slab. The select material or sand should be moistened but not saturated prior to placement of concrete. IsKorbmacher Engineering. Inc.