5720 EAST DR 2018-01-02 MF Import

Geote, finical Engineering Report Parcel 00471700002401- 57XX East Drive Everett, Washington December 12, 2009 RMI File No. 53409 Page 9 Slabs -On -Grade Slab -on -grade areas should be prepared as recommended in the Site Preparation and Grading subsection of this report. After removal of loose soil, the subgrade should be compacted to a dense, non - yielding condition. Prior to structural fill placement, the subgrade should be proofrolled with a heavy, rubber -tired piece of equipment, to identify soft or yielding areas that require repair. Areas observed to pump or weave should be reworked to structural till specifications or be excavated and replaced with properly compacted structural fill. We recommend that all floor slabs be underlain by at least 6 inches of free -draining sand or gravel for use as a capillary break. A suitable vapor barrier, such as heavy plastic sheeting (10-mil minimum is recommended), should be placed over the sand or gravel. A 4-inch-thick crushed rock blanket covered with visqueen may be used to cover the vapor barrier to protect it. The capillary break should be designed to drain into the foundation drain system. Subsurface Walls and Retaining Walls The lateral pressure acting on subsurface and retaining walls is dependent on the nature and density of the j soil behind the wall, the amount of lateral wall movement which can occur as backfill is placed, wall I{ drainage conditions, and the inclination of the backfill. For walls that are free to yield at the top at least one thousandth of the height of the wall (active condition), soil pressures will be less than if movement is limited by such factors as wall stiffness or bracing (at-rcst condition). We recommend that walls supporting horizontal backfill and not subjected to hydrostatic forces be designed using a triangular earth pressure distribution equivalent to that exerted by a fluid with a density of 35 pcf for yielding (active condition) walls, and 60 pef for non -yielding (at -rest condition) walls. These recommended lateral earth pressures are based on the assumption of a horizontal ground surface adjacent to the wall for a distance of at least the subsurface height of the wall, and do not account for surcharges. Additional lateral earth pressures should be considered for surcharge loads acting adjacent to the subsurface walls and within a distance equal to the subsurface height of the wall. This would include the effects of surcharges such as traffic loads, floor slab loads, slopes, or other surface loads. The lateral pressures on walls may be resisted by friction between the foundation and subgrade soil, and by passive RMI ASSOCIATES LLC �DI'�