1415 BROADWAY CM HEATING 2023-09-25

Geotechnical Engineering Evaluation NGA File No.1213420 CM Heating Additions January 8,2021 Everett,Washington Page 10 Slab-on-Grade Slabs-on-grade should be supported on subgrade soils prepared as described in the Site Preparation and Grading subsection. 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. The capillary break should 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 be used to protect the vapor barrier membrane and to aid in curing the concrete. Pavements Pavement subgrade preparation and structural filling where required, 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 with a heavy, rubber-tired piece of equipment, to identify soft or yielding areas that require repair. Any pavement section should be underlain by a stable subgrade. We should be retained to observe the proof-rolling and recommend subgrade repairs prior to placement of any asphalt or hard surfaces. Utilities We recommend that underground utilities be bedded with a minimum six inches of pea gravel prior to backfilling the trench with on-site or imported material. Trenches within settlement sensitive areas should be compacted to 95%of the modified proctor as described in the Structural Fill subsection of this report. Trenches located in non-structural areas should be compacted to a minimum 90% of the maximum dry density.Trench backfill compaction should be tested. 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 areas where footings, slabs, or pavements are to be constructed. Final site grades should allow for drainage away from the residence. 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 residence. Surface water should be collected by permanent catch basins and drain lines, and be discharged into an appropriate discharge system. The overflow water should be dispersed to discharge into an appropriate location. NELSON GEOTECHNICAL ASSOCIATES, INC. 13I2 �