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

Geotechnical Engineering Evaluation NGA File No.910814 Emerald Court Apartment Building November 21,2014 Everett,Washington Page 9 fill should contain no more than five-percent fines (soil finer than U.S. No. 200 sieve, based on that fraction passing the U.S. 3/4-inch sieve). The use of some of the on-site soils as structural fill may be feasible, but will be highly dependent on moisture and organic contents of the material at the time construction takes place. We should be retained to evaluate proposed structural fill material prior to placement. Fill Placement: Following subgrade preparation, placement of structural fill may proceed. All fill placements should be accomplished in uniform lifts up to eight inches thick. Each lift should be spread evenly and be thoroughly compacted prior to placement of subsequent lifts. All structural fill underlying building areas and pavement subgrade should be compacted to a minimum of 95 percent of its maximum dry density. Maximum dry density, in this report, refers to that density as determined by the ASTM D-1557 Compaction Test procedure. The moisture content of the soils to be compacted should be within about 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 Slabs-on-grade should be supported on subgrade soils prepared as described in the Site Preparation and Grading subsection of this report. We recommend that all floor slabs be underlain by at least six inches of free-draining gravel with less than three percent by weight of the material passing Sieve #200 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. An additional 2-inch thick moist sand layer may be used to cover the vapor barrier. This sand layer is optional and is intended to protect the vapor barrier membrane during construction. We also recommend that an underslab drainage system be incorporated into the basement slab. We have provided additional recommendations regarding this system in the Subsurface Drainage subsection of this report. Pavement Subgrade Pavement subgrade preparation should be completed as recommended in the Site Preparation and Grading and Structural Fill subsections of this report. The pavement subgrade should be proof-rolled NELSON GEOTECHNICAL ASSOCIATES, INC.