101 E MARINE VIEW DR SEPA 018 - 011 Geotech Report 2025-04-15

Geotechnical Engineering Evaluation NGA File No. 988017 East Marine View Drive Warehouse May 19,2017 Everett,Washington Page 6 For planning purposes,we recommend that temporary cuts above the water table in the on-site soils be no steeper than 3 Horizontal to 1 Vertical (3H:1 V) if worker access is necessary. Cuts below the water table should be shored. We recommend that cut slopes be protected from erosion. These erosion protection measures may include covering cut slopes with plastic sheeting and diverting surface runoff away from the top of cut slopes. We do not recommend vertical slopes for cuts deeper than four feet, if worker access is necessary. We recommend that cut slope heights and inclinations conform to appropriate OSHA/WISHA regulations. Site Preparation and Grading After erosion control measures are implemented site preparation should consist of removing all remanence of the burnt down warehouse and all pavement surfaces. The stripped material should be removed from the site. Due to the proposed structure being supported on compacted rock aggregate piers, we would anticipate minimal depth excavations throughout the proposed building area but the resulting subgrade should be compacted to a firm surface state. If the ground surface, after site stripping, should appear to be 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. If soft soils are encountered in the building or pavement areas, these areas should be removed and replaced with rock spalls or granular structural fill. If significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed, and the exposed subgrades should be maintained in a semi-dry condition. 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. NELSON GEOTECHNICAL ASSOCIATES, INC.