5901 23RD DR W Geotech Report 2025-07-29

i October 22, 2007 Project No. T-5922-1 Accordingly, for temporary excavations of more than 4 feet and less than 20 feet in depth, the side slopes in Type C soils should be laid back at an inclination of 1.5:1 or flatter. Temporary excavations in Type A soils can be laid back at an inclination of 0.75:1. If there is insufficient room or other conditions that restrict completion of the excavations in the manner described above,or if excavations greater than 20 feet deep are planned,temporary shoring will likely be required to support the excavations. 111 We did not observe indications of significant groundwater seepage in our site explorations. However, the development of a perched groundwater table is possible during the wet winter months. Based on our study, we expect that the volume and rate of flow of any perched groundwater into site excavations would be relatively minor and would not be expected to impact the stability of the excavations when completed, as described. In our opinion, if necessary, a system of shallow collection trenches and conventional sump pumping procedures should be capable of maintaining a relatively dry excavation for construction purposes. This information is provided solely for the benefit of the owner and other design consultants, and should not be construed to imply that Terra Associates, Inc. assumes responsibility for job site safety. It is understood that job site safety is the sole responsibility of the project contractor. 5.5 Foundations The buildings may be supported on conventional spread footing foundations bearing on competent native soils or on structural fills placed above competent native soils. Foundation subgrades should be prepared as recommended in Section 5.2 of this report. Perimeter foundations exposed to the weather should be a minimum depth of 1.5 feet below final exterior grades. Interior foundations can be constructed at any convenient depth. We recommend designing foundations supported by competent native soils or structural fill for a net allowable bearing capacity of 3,000 pounds per square foot (psf). For short-term loads, such as wind and seismic, a one- third increase in this allowable capacity can be used. With the anticipated building loads and this bearing stress, estimated total foundation settlement should be less than one-half inch. For designing foundations to resist lateral Ioads, a base friction coefficient of 0.35 can be used. Passive earth pressure acting on the sides of the footings may also be considered. We recommend calculating this lateral resistance using an equivalent fluid weight of 300 pounds per cubic foot(pcf). We recommend not including the upper 12 inches of soil in this computation because they can be affected by weather or disturbed by future grading activity. This value assumes the foundations will be constructed neat against competent native soil or the excavations are backfilled with structural fill as described in Section 5.2 of this report. The recommended passive and friction values include a safety factor of 1.5. 5.6 Slab-on-Grade Floors Slab-on-grade floors may be supported on subgrades that are prepared as recommended in Section 5.2 of this report. Immediately below the floor slabs, we recommend placing a four-inch thick capillary break Iayer of clean, free-draining, coarse sand or fine gravel that has less than three percent by weight of material passing the No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slabs. I Page No. 9 I