12728 19TH AVE SE BASE FILE Geotech Report 2025-07-29

' May 28, 2007 Proposed Office Building ' L&A Job No. 7A053 Page 14 ' (EFD) of 350 pcf (pounds per cubic foot) for the passive earth pressure be used for lateral resistance. The above passive pressure assumes that the backfill is level or inclines upward behind the foundations for a horizontal distance at least twice the depth of the foundations below final grade. A coefficient of friction of 0.60 between the foundations and the subgrade soils may be used. These are unfactored values, and a proper factor of safety should be used in calculating the resisting forces against lateral loads on the buildings. SLAB-ON-GRADE FLOORS Slab-on-grade floors, if used, should be placed on firm subgrade soils prepared as outlined in the SITE PREPARATION AND GENERAL EARTHWORK and the STRUCTURAL FILL sections of this report. Where moisture control is critical, the slab-on-grade floors should be placed on a capillary break which is in turn placed on the compacted subgrade. The capillary break should consist of a minimum four-inch-thick layer of free-draining gravel or crushed rock containing no more than 5%by weight passing the No. 4 sieve. We recommend that a vapor barrier, such as a 6-mil plastic membrane, be placed over the capillary break to keep moisture from migrating upwards. PARKING LOT AND DRIVEWAY PAVEMENT Performance of parking lot and driveway pavement is critically related to the conditions of the underlying subgrade soils. We recommend that the subgrade soils under the roadway be treated and prepared as described in the STI'E PREPARATION AND GENERAL EARTHWORK section of this report. Prior to placing base material, the subgrade soils should be compacted to a non-yielding state with a vibratory roller compactor and proof-rolled with,a piece of heavy construction equipment, such as a fully-loaded dump truck. Any areas with excessive weaving or flexing should be over-excavated and replaced with a structural fill or crushed rock placed and compacted in accordance with the recommendations provided in the STRUCTURAL FILL section of this report. LIU & ASSOCIATES, INC. p