3800 RIVERFRONT BLVD Geotech Report 2023-05-04

March 26, 2019 HWA Project No. 2015-061-21 Task 600-7 4.8 ILLUMINATION FOUNDATIONS We expect that street illumination and associated illumination foundations will be constructed per the City of Everett standard plans. These plans require a 4-foot deep and 3-foot wide foundation to support the proposed illumination poles. We expect that the existing near surface soils will provide adequate lateral support for the proposed illumination foundations, provided areas of shallower fill are not encountered. However, it should be noted that grade supported illumination foundations will settle with the surrounding roadway over time. 4.9 GENERAL EARTHWORK 4.9.1 Structural Fill Due to the moisture sensitivity of the existing fill soils and the potential for site grading to take place during the wet weather months, we recommend that structural fill for the roadway consist of Crushed Surfacing Base Course, meeting the requirements of Section 9-03.9(3) of the WSDOT standard Speciation(WSDOT, 2018). 111 4.9.2 Compaction Structural fill soils should be moisture conditioned and compacted to the requirements specified in Section 2-03.3(14)C, Method C, of the WSDOT Standard Specifications (WSDOT, 2018); except the standard of compaction achieved shall not be less than 95% of the maximum dry density(MDD) determined for the fill material by test method ASTM D 1557 (Modified Proctor). Subgrade compaction in road bed areas should conform to the requirements of Section 2-06.3(1) of the WSDOT Standard Specifications. At the time of placement, the moisture content of structural fill should be at or near optimum. The procedures required to achieve the specified minimum relative compaction depend on the size and type of compaction equipment, the number of passes, thickness of the layer being compacted and the soil moisture-density properties. When the first fill is placed in a given area, and/or anytime the fill material changes, the area should be considered a test section. The test section should be used to establish fill placement and compaction procedures required to achieve proper compaction. The geotechnical consultant should observe placement and compaction of the test section to assist in establishing an appropriate compaction procedure. Once a placement and compaction procedure are established, the contractor's operations should be monitored, and periodic density tests performed to verify that proper compaction is being achieved. Backfill compaction in any confined areas such as trenches, behind retaining walls, or within excavated confines should be performed on each layer no greater than 6 to 8 inches in thickness, depending upon the types of equipment employed. Geotechnical Report Revision 3 26 2019.doc 24 HWA GEOSCIENCES INC.