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 construction equipment, building materials, excavated soil, and vehicular traffic should not be allowed within a distance equal to 1/3 the slope height from the top of any excavation. 6.3 GROUNDWATER CONTROL Groundwater was encountered at about 6V2 feet below grade at PG-1, 6 feet below grade at PG-3, and 9 feet below grade at PG-4. We anticipate minor amounts of groundwater could be encountered during foundation excavation in the winter season. We anticipate that the use of sumps and pumps will likely be adequate for controlling the groundwater. All collected groundwater should be properly discharged as required by the City or County. The presence of groundwater seepage could also result in an unstable working subgrade. Depending on the actual groundwater conditions at the time of excavation, it may be necessary to place a layer of crushed rock to provide a stable working subgrade. The need to improve the subgrade will be determined during construction. 6.4 MATERIAL REUSE In the context of this report, structural fill is defined as compacted fill placed under footings, concrete stairs and landings, and slabs, or other load-bearing areas. In our opinion, the on-site soils are not suitable as structural fill. Structural fill should consist of imported, well-grade, granular material, such as WSDOT Gravel Borrow(WSDOT 9-03.14(1)) or approved equivalent. Well-graded recycled concrete may also be considered as a source of structural fill. Use of recycled concrete as structural fill should be approved by the geotechnical engineer. The on-site fill may be used as general fill in the landscaping areas. If use of the on-site soil is planned, the excavated soil should be stockpiled and protected with plastic sheeting to prevent softening from rainfall in the wet season. 6.5 STRUCTURAL FILL AND COMPACTION Structural fill should be moisture conditioned to within about 3 percent of optimum moisture content, placed in loose, horizontal lifts less than 8 to 10 inches in thickness, and systematically compacted to a dense and relatively unyielding condition and to at least 95 percent of the maximum dry density, as determined using test method ASTM D 1557. Depending on the type of compaction equipment used and depending on the type of fill material, it may be necessary to decrease the thickness of each lift in order to achieve adequate compaction. PanGEO can provide additional recommendations regarding structural fill and compaction during construction. 16-210 11229 19th Ave SE Rpt Page 14 PanGEO, Inc.