11229 19TH AVE SE SILVER LAKE TOWNHOMES WHOLE SITE Geotech Report 2022-10-25

Geotechnical Report Proposed Development: 11229 - 19th Avenue SE, Everett, WA September 16, 2016 The procedure to achieve proper density of a compacted fill depends on the size and type of compaction equipment, the number of passes, thickness of the lifts being compacted, and certain soil properties. If the excavation to be backfilled is constricted and limits the use of heavy equipment,smaller equipment can be used,but the lift thickness will need to be reduced to achieve the required relative compaction. Generally, loosely compacted soils are a result of poor construction technique or improper moisture content. Soils with high fines contents are particularly susceptible to becoming too wet and coarse-grained materials easily become too dry, for proper compaction. Silty or clayey soils with a moisture content too high for adequate compaction should be dried as necessary, or moisture conditioned by mixing with drier materials, or other methods. 6.6 WET WEATHER CONSTRUCTION In our opinion, the proposed site construction may be accomplished during wet weather (such as in winter) without adversely affecting the site stability, provided that surface water and erosion control will be properly managed. However, earthwork construction performed during the drier summer months likely will be more economical. Winter construction will require the implementation of best management erosion and sedimentation control practices to reduce the chance of off-site sediment transport. Some of the site soils contain a high percentage of fines and are moisture sensitive. Any footing subgrade soils that become softened either by disturbance or rainfall should be removed and replaced with structural fill, Controlled Density Fill(CDF),or lean- mix concrete. General recommendations relative to earthwork performed in wet conditions are presented below: • Earthwork should be performed in small areas to minimize subgrade exposure to wet weather. Excavation or the removal of unsuitable soil should be followed promptly by the placement and compaction of clean structural fill. The size and type of construction equipment used may have to be limited to prevent soil disturbance. • During wet weather, the allowable fines content of the structural fill should be reduced to no more than 5 percent by weight based on the portion passing the 0.75-inch sieve. The fines should be non-plastic. • The ground surface within the construction area should be graded to promote run-off of surface water and to prevent the ponding of water. • Geotextile silt fences should be installed at strategic locations around the site to control erosion and the movement of soil. 16-210 11229 19th Ave SE Rpt Page 15 PanGEO, Inc.