5720 EAST DR 2018-01-02 MF Import

Gcotechnical Engineering Report Parcel 00471700002401- 57XX East Drive Everett, Washington December 12, 2009 RMI File No. 53409 Page 5 across any slopes as erosion or weakening of surface soils could occur. Surface water should be collected by permanent catch basins and drain lines and be taken to the City (storm sewer. Subsurface Drainage It is good practice to use exterior footing drains around all of the structures where moisture control is important. Footing drains should be installed at least 1 foot below the planned finished floor slab or crawl space elevation. The drains should consist of 4-inch-diameter, rigid, perforated PVC pipe surrounded by free -draining material, such as pea gravel wrapped in a non -woven filter fabric such as Mirafr 140NSL. footing drains should discharge into tightlines leading to an appropriate collection and discharge point. In addition, the "high" end and all 90-degree bends of the subdrain pipe should be connected to a riser, which extends to the surface and acts as a clean -out. Crawl spaces should be sloped to drain, and a positive connection should be made into the foundation drainage system. Roof drains should be tightlined separately of footing drains. All drainage should be routed to an appropriate discharge point such as the City's storm sewer. Site Preparation and Grading The new building area should be stripped of vegetation, topsoil, loose soils, and fill (if any). The subgrade below any planned slab -on -grade and/or foundations should be compacted to a dense, non -yielding condition. Areas observed to pump or weave, should be repaired by over -excavating and replacing with thoroughly compacted granular fill (structural fill). Erosion Control Measures The erosion hazard for the on -site soils is considered moderate. The erosion hazard will be dependent on how the site is graded and water is allowed to accumulate. Best Management Practices (BMPs) should be used to control erosion. Measures taken may include diverting surface water away from the stripped area but not over the slope. Silt fences or straw bales should be erected to prevent muddy water from leaving the site. RMI ASSOCIATES LLC 4