8525 EVERGREEN WAY BURGER KING 2021-05-10

Geotechnical Engineering Evaluation NGA File No. 998317 Burger King Restaurant Development August 2,2017 Everett,Washington Page 6 should be planted as soon as practical, and the vegetation should be maintained until it is established. The erosion potential for areas not stripped of vegetation should be low. Site Preparation and Grading After erosion control measures are implemented, site preparation should consist of stripping the development areas of organics, undocumented fill, and loose soils to expose medium dense or better native glacial soils for structural fill subgrade, and in foundation, slab, and pavement areas. Our explorations generally encountered medium dense or better native soils approximately 2.0 and 3.0 feet below the existing ground surface. However, additional stripping may be required if thicker layers of undocumented fill, loose soil, or organic materials are encountered in unexplored areas of the site and areas near the existing utility lines within the property. The stripped materials should be removed from the site or be stockpiled for later use as landscaping fill. The exposed subgrade should be compacted to a non-yielding condition. We recommend that any fill encountered in the structure and pavement areas be removed and replaced with structural fill or rock spalls extending to competent native material. If significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed and the exposed subgrade maintained in a semi-dry condition. This may require dewatering systems or sump and pumps to remove the seeping water from the excavations. If wet conditions are encountered, alternative site stripping and 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 prepared subgrade. The near surface soils are considered to be moisture-sensitive, and will disturb when wet. We recommend that construction take place during the drier summer months if possible. However, if construction takes place during the wet season, additional expenses and delays should be expected due to the wet conditions. Additional expenses could also include the need for placing a blanket of rock spalls on exposed subgrades and construction traffic areas. The on-site soils will be very difficult to compact to structural fill specifications in wet conditions. We should be retained to evaluate proposed structural fill materials prior to construction. NELSON GEOTECHNICAL ASSOCIATES, INC.