2400 33RD ST GEOTECHNICAL INVESTIGATION 2018-01-02 MF Import

The scope of work completed for this phase of the project included the following: • Proof -rolling the site using loaded dump tn::ks; • Coring and potholing the pavement and subgrade along the pipeline route; • Performing chemical laboratory testing of the on -site soils for arsenic levels with respect to landscaping suitability; • Formulate geotechnical engineering design recommendations for the site grading, and assist in cut and fill evaluation while minimizing the amount of material removed from the site; and • Prepare this addendum report on the findings of our investigations, including earthwork recommendations for the filling of the site pond, areas of over - excavation, and pavement analyses. REFERENCES AND PREVIOUS EXPLORATIONS The following reference was used in preparation of this report: • City of Everett, "Standards for Streets and Related Work", April 2002. • Milbor-Pita & Associates, "Geotechnical Report: Proposed Sounder Everett Station Facility, Everett, Washington (ZGF Project No. 90524.01)", for Zimmer Gunsel Frasca Partnership, 4 October 2001. FIELD PROGRAMS Site Explorations Proof Rollins In addition to the investigations outlined in the October 2001 report, MPA was on site on 5 January 2006 to observe proof rolling of the site. Proof rolling was done with fully loaded dump trucks. Successive passes of the dump trucks were spaced to provide complete coverage of the subgrade. The proof rolling provided visual information for the assessment of the subgrade and its acceptability as a bearing stratum. Subgrade conditions were also evaluated using a steel probe. In general, the subgrade performed well. In localized areas, there was some rutting of the top 2 to 3 inches of surticial soil; however, probing the soil showed that the underlying material has adequate density. The construction monitoring report is included in Appendix A of this report. Corine and Potholine On 26 January 2006, MPA explored 9 locations along the proposed pipeline route on 33"t Street and Hill Street Avenue, and adjacent to the Pacific Avenue Overpass. The locations of these corings are shown on Figure 1; the field report is included in Appendix A The purpose of this exploration was to determine the thickness and makeup of the pavement section and the subgrade material. Applied Professional Services (APS) performed the coring and potholing investigations. APS either cored or jackhammered through the asphalt and concrete. Then they used a VacMaster Vac-n-Dig to pothole the subgrade. This machine blows air at high pressure into the hole and dislodges the soil. Tien a vacuum attachment is lowered into the hole, and the soil is sucked out into the tank on the rig. MPA took grab samples at discrete depths in the hole to identify the soils. Two samples were also taken to send to an analytical laboratory to test for arsenic levels. Geolecllnical and Tunnel Consultants 17270 WoW inville-Redmond Rd, Sic 703 Phone (425) 486-6561 WoodinviHe, WA 98072 Page 2 Fax (425) 488 2660