2712 TAYLOR DR 2023-11-01 - Laserfiche WebLink

October 6, 2019 Page 3 of 6 Limited Geotechnical Investigation Temporary cut slopes should be covered with visqueen to help reduce erosion during wet weather, and the slopes should be closely monitored until the permanent retaining systems or slope configurations are complete. 'M terials should not be stored or equipment operated within 10 feet of the top of any temporary cut slope. Soil conditions may not be completely known from the geotechnical investigation. In the case of temporary cuts, the existing soil conditions may not be completely revealed until the excavation work exposes the soil. Typically, as excavation work progresses the maximum inclination of temporary slopes will need to be re-evaluated by the ;geotechnical engineer so, that supplemental recommendations-- can be -made., -Soil and -groundwater : conditions can be highly , variable. Scheduling for soil work will need to be adjustable, to deal with unanticipated conditions, so that the project can proceed and required deadlines can be met. If any variations or undesirable conditions are encountered during construction, we should be notified so that supplemental recommendations can = be made. If room constraints or groundwater conditions do not permit temporary slopes to be cut to the maximum angles allowed by the WAC, temporary shoring systems may be required. The contractor should be responsible" for developing temporary shoring systems, if needed: We recommend that Cobalt Geosciences and the project structural engineer review temporary shoring designs prior to installation, to verify the suitability of the proposed systems. Foundation Design The proposed single-family residence may be supported on a- shallow -spread- footing foundation system bearing on undisturbed medium dense or firmer native soils or on properly compacted structuralfill placed on the suitable native "soils. If"structural-,fill is used to support -foundations, then the zone of structural fill should extend beyond the faces of the footing a lateral distance at least equal to the thickness of the structural fill. Any and all undocumented fill must be removed below new foundation elements. The fill should be replaced with structural fill compacted •to ;at least 95 percent of the modified proctor and verified through testing. Clean angular rock could be used as fill in these areas. For shallow foundation support, we recommend widths of at least 16 and 24 inches, respectively, for continuous wall and isolated column footings supporting the proposed structure. Provided that the footings are supported as recommended above, a net allowable bearing pressure of 2,500 pounds per square foot (psf) may be used for design. A /3 increase in the above value may used for short duration loads, such as those imposed by wind and seismic "events. Structural fill placed on bearing, native subgrade should be compacted to'at least 95, percent of the maximum dry2ierisity based on, ASTM Test Method D1557:: `Footing excavations should be inspected to verify that the foundations will bear on suitable material. Exterior footings should have a minimum depth of 18 inches below pad subgrade (soil grade) or - adjacent exterior grade, whichever is lower. Interior' footings, should have a minimum depth of 12 inches below pad subgrade (soil grade) ,or adjacent exterior grade, whichever is lower. If constructed as recommended,` the total foundation settlement is not expected to exceed 1 inch. .Differential., settlement, along a 25-foot exterior wall footing, or between adjoining column footings, Should be less than 1/2 inch. This translates to an angular distortion of 0.002. Most settlement is expected to occur during construction, as the loads are applied. However, additional post -construction settlement may occur if the foundation soils are flooded or saturated. All footing excavations should be observed by a qualified geotechnical consultant. www.cobaltgeo.com (206) 831-1097