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 be constructed by over-filling past the design limits of the slopes and cutting back to the design slope to provide adequate compaction at the edge of the slope. 6.0 CONSTRUCTION CONSIDERATIONS 6.1 SITE PREPARATION Site preparation for the proposed project mainly includes removing the existing structures, site clearing, and excavations to the design subgrade. All debris resulted from site clearing should be hauled away from the site. The stripped surface materials should be properly disposed off-site or be "wasted" on site in non-structural landscaping areas. Following site clearing and excavations, the adequacy of the subgrade where structural fill, foundations, slabs, or pavements are to be placed should be verified by a representative of PanGEO. The subgrade soil in the improvement areas, if recompacted and still yielding, may need to be over- excavated and replaced with compacted structural fill or lean-mix concrete. The need for overexcavation should be determined by PanGEO in the field. 6.2 TEMPORARY EXCAVATIONS As currently planned, we understand that temporary excavations will be on the order of 4 feet or less for the proposed development. However, foundation soil over-excavation for Building E, if the over-excavation and shallow footing option is used, will be up to about 8 feet. We anticipate the excavations to mainly encounter loose fill over dense to very dense sand and gravel. All temporary excavations should be performed in accordance with Part N of WAC (Washington Administrative Code) 296-155. The contractor is responsible for maintaining safe excavation slopes and/or shoring. All temporary excavations with a total overall depth greater than 4 feet should be sloped or shored. Based on the soil conditions at the site, for planning purposes, it is our opinion that temporary excavations for the proposed construction may be sloped 1 H:1 V or flatter. Based on our conceptual building layout, in our opinion, unsupported open cut excavation is likely feasible for the proposed development. In the event that space is not available for unsupported open cuts and temporary shoring is needed to support excavations, PanGEO can provide temporary shoring design recommendation, as requested. The temporary excavations and cut slopes should be re-evaluated in the field during construction based on actual observed soil conditions,and may need to be modified in the wet reasons. The cut slopes should be covered with plastic sheets in the raining season. We also recommend that heavy 16-210 11229 19th Ave SE Rpt Page 13 PanGEO, Inc.