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

} F Geotechnical Engineering Evaluation NGA File No.910814 Emerald Court Apartment Building November 21,2014 Everett,Washington Page 10 with a heavy, rubber-tired piece of equipment to identify soft or yielding areas that require repair. We should be retained to observe the proof-rolling and recommend repairs prior to placement of the asphalt or other surfaces. Site Drainage Surface Drainage: The finished ground surface should be graded such that runoff is directed to an appropriate stormwater collection system. Water should not be allowed to collect in any areas where footings,slabs,or pavements 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 routed into an appropriate discharge system. 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 from the excavation and routed to a suitable discharge point. We recommend the use of footing drains around the structure and behind all retaining walls. Footing drains should be installed at least one foot below planned finished floor elevation. The drains should consist of a minimum 4-inch-diameter, rigid, slotted or perforated, PVC pipe surrounded by free-draining material wrapped in a filter fabric. We recommend that the free-draining material consist of an 18-inch wide zone of clean (less than three-percent fines), granular material placed along the back of footings. Washed rock is an acceptable drain material. The free-draining material should extend up the footings to one foot below the finished surface. The top foot of backfill should consist of low permeability soil placed over plastic sheeting or building paper to minimize the migration of surface water or silt 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 wall or footing drains. Due to the potential for perched groundwater to develop within the site, we recommend that an underslab drainage system be incorporated into the building design. The underslab drainage system should consist of 4-inch diameter,rigid,perforated, PVC pipes placed within the capillary break layer no greater than 20 feet apart. The perforated drain pipes should be connected to a 6-inch diameter, rigid, solid, PVC pipe NELSON GEOTECHNICAL ASSOCIATES, INC.