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 9 two percent of optimum so that a readily compactable condition exists. It may be necessary to over- excavate and remove wet soils in cases where drying to a compactable condition is not feasible. All compaction should be accomplished by equipment of a type and size sufficient to attain the desired degree of compaction. Slab-on-Grade Due to the very loose/soft nature of the soils that underlie the site,we recommend the slab be designed as a structural element and supported directly on the compacted rock aggregate piers. The aggregate piers within the slab should be spaced no more than eight feet on center. The slab should be additionally reinforced to limit potential impacts from settlement and should be doweled into the building foundation near door openings to limit differential settlement in these areas. We recommend that all floor slabs be underlain by at least six inches of free-draining sand or gravel for use as a capillary break. We recommend that the capillary break be hydraulically connected to the footing drain system to allow free drainage from under the slab. A suitable vapor barrier, such as heavy plastic sheeting(6-mil minimum), should be placed over the capillary break material. Pavements Pavement subgrade preparation, and structural fill placement where required, should be completed as recommended in the Site Preparation and Grading and Structural Fill subsections of this report. We recommend that the proposed pavement areas be overexcavated by a minimum of 18-inches and the entire resulting subgrade should be covered with a non-woven filter fabric overlain by a Tensar TX160 geogrid. The geogrid should then be covered with the overexcavated material if it meets structural fill specifications and should be compacted to structural fill specifications. A minimum 8-inch thick base course layer should be placed over the prepared subgrade and the pavement placed on the crushed rock. The pavement subgrade should be heavily compacted and proof-rolled with a heavy, rubber-tired piece of equipment, to identify soft or yielding areas that require repair prior to placing structural fill and prior to placing the pavement base course. We should be retained to observe the proof-rolling and recommend subgrade repairs prior to placement of the asphalt or hard surfaces. Underground Utilities Heavy groundwater seepage may be encountered within the utility trench excavations, depending on final depths. If groundwater is encountered in the utility excavations,we recommend that adequate dewatering measures be implemented to allow installation of the utilities. At a minimum, pump and sump systems should be utilized to keep water out of the excavations, but more elaborate dewatering may be needed depending on final depths. Adequate shoring, such as the use of trench boxes, should also be utilized to NELSON GEOTECHNICAL ASSOCIATES, INC.