10111 9TH AVE W EMERALD COURT APARTMENTS Geotech Report 2022-10-20

Geotechnical Engineering Evaluation NGA File No.910814 Emerald Court Apartment Building November 21,2014 Everett,Washington Page 6 Site Preparation and Grading After erosion control measures are implemented, site preparation should consist of removing loose soils, topsoil,and any undocumented fill,to expose medium dense or better native soils in foundation, slab, and pavement areas. The stripped soil should be removed from the site or stockpiled for later use as landscaping fill. Based on our observations, we anticipate native, medium dense or better soil to be encountered approximately six inches to two feet across the site, but this depth could be greater in unexplored areas of the site. After site preparation, if the exposed subgrade is deemed loose, it should be compacted to a non-yielding condition and then proof-rolled with a heavy rubber-tired piece of equipment. Areas observed to pump or weave during the proof-roll test should be reworked to structural fill specifications or over-excavated and replaced with properly compacted structural fill or rock spalls. We encountered up to two feet of loose soil within the test pits in the parking lot area. If loose soils are encountered in the pavement areas after removing the topsoil, the loose soils should be removed and replaced with rock spalls or granular structural fill, or compacted to structural fill specifications. If significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed, and the exposed subgrades maintained in a semi-dry condition. If deeper areas of unsuitable soils and/or undocumented fill are encountered in the unexplored areas of the site, we recommend that the soil be removed to expose dense native soil and replaced with structural fill or rock spalls. If wet conditions are encountered, alternative site grading techniques might be necessary. These could include using large excavators equipped with wide tracks and a smooth bucket to complete site grading, and covering exposed subgrade with a layer of crushed rock for protection. If wet conditions are encountered or construction is attempted in wet weather, the subgrade should not be compacted, as this could cause further subgrade disturbance. In wet conditions, it may be necessary to cover the exposed subgrade with a layer of crushed rock as soon as it is exposed to protect the moisture sensitive soils from disturbance by machine or foot traffic during construction. The prepared subgrade should be protected from construction traffic and surface water should be diverted around areas of prepared subgrade. Temporary Slopes Temporary cut slope stability is a function of many factors, including the type and consistency of soils, depth of the cut, surcharge loads adjacent to the excavation, length of time a cut remains open, and the presence of surface or groundwater. It is exceedingly difficult under these variable conditions to estimate a stable, temporary, cut slope angle. Therefore, it should be the responsibility of the contractor to NELSON GEOTECHNICAL ASSOCIATES, INC.