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 10 support the trench walls during utility installation. Utilities on this site below a depth of five feet should be designed to resist buoyancy forces. Site Drainage Surface Drainage: The finished ground surface should be graded such that stormwater is directed to an appropriate stormwater collection system. Water should not be allowed to stand in any area where footings or slabs are to be constructed. Final site grades should allow for drainage away from the structures. We suggest that the finished ground be sloped at a minimum gradient of three percent, for a distance of at least 10 feet away from the structures. Surface water should be collected by permanent catch basins and drain lines, and be discharged into an appropriate discharge system. Excavations below the groundwater table will require more elaborate dewatering. Subsurface Drainage: If groundwater is encountered during construction, we recommend that the contractor slope the bottom of the excavation and collect the water into ditches and small sump pits where the water can be pumped out of the excavation and routed into an appropriate discharge point. We recommend the use of footing drains around the planned structure. Footing drains should be installed at least one foot below planned finished floor elevation. The drains should consist of a minimum four- inch-diameter, rigid, slotted or perforated, PVC pipe surrounded by free-draining material, such as washed rock, wrapped in a filter fabric. We recommend that an 18-inch-wide zone of clean (less than three-percent fines), granular material be placed along the back of subsurface walls above the drain. Pea gravel is an acceptable drain material, or drainage composite may be used instead. The free-draining material should extend up the wall to one foot below the finished surface. The top foot of backfill should consist of impermeable soil placed over plastic sheeting or building paper to minimize the migration of surface water or fines into the footing drain. Footing drains should discharge into tightlines leading to an appropriate collection and discharge point with convenient cleanouts to prolong the useful life of the drains. Roof drains should not be connected to footing drains. USE OF THIS REPORT NGA has prepared this report for Mr. Adam Clark and his agents, for use in the planning and design of the development planned on this site only. The scope of our work does not include services related to construction safety precautions and our recommendations are not intended to direct the contractors' methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. There are possible variations in subsurface conditions between the explorations and also with time. Our report, conclusions, and interpretations should not be construed as a warranty of NELSON GEOTECHNICAL ASSOCIATES, INC.