7010 COLBY AVE 2023-06-01 - Laserfiche WebLink

Mr. Paul Korenovsky ES-6067 June 20, 2018 Page 7 Foundations The proposed residential structures can be constructed on conventional continuous and spread footing foundation bearing on competent native soil, recompacted native soil, or new structural fill placed directly on competent native soils. In general, competent native soil, suitable for support of the new foundations, will likely be encountered beginning at depths of about one to three feet bgs. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of soils to the specifications of structural fill, or overexcavation and replacement with a suitable structural fill material, will be necessary. Provided the foundations will be supported as prescribed, the following parameters may be used for design: • Allowable soil bearing capacity 2,500 psf • Passive earth pressure 300 pcf(equivalent fluid) • Coefficient of friction 0.40 A one-third increase in the allowable soil bearing capacity may be assumed for short-term wind and seismic loading conditions. The above passive pressure and friction values include a factor-of-safety of 1.5. With structural loading as expected, total settlement in the range of one inch and differential settlement of about one-half inch is anticipated. The majority of the settlements should occur during construction, as dead loads are applied. Seismic Design The 2015 International Building Code recognizes the American Society of Civil Engineers (ASCE) for seismic site class definitions. Based on the soil conditions encountered at the test pit locations, in accordance with Table 20.3-1 of the ASCE Minimum Design Loads for Buildings and Other Structures manual, Site Class D should be used for design. The referenced liquefaction susceptibility map indicates the site and surrounding areas maintain "very low" liquefaction susceptibility. Liquefaction is a phenomenon where saturated and loose sandy soils suddenly lose internal strength in response to increased pore water pressures resulting from an earthquake or other intense ground shaking. In our opinion, site susceptibility to liquefaction may be considered negligible. The relative density of the site soils and the absence of a uniformly established, shallow groundwater table were the primary bases for this consideration. Slab-on-Grade Floors Slab-on-grade floors for the proposed residential structures should be supported on firm and unyielding subgrades comprised of competent native soil, compacted structural fill, or new structural fill. Unstable or yieldingareas of the subgrades should be recompacted, or 9 overexcavated and replaced with suitable structural fill, prior to slab construction. Earth Solutions NW,LLC