11831 AIRPORT RD WHOLE SITE FILE Geotech Report 2022-10-25

INTRODUCTION AND PROJECT DESCRIPTION This report presents the results of GeoEngineers, Inc.'s(GeoEngineers')geotechnical engineering services for the proposed Community Transit Swift II Bus Rapid Transit (BRT) project to be constructed along a 12.4-mile route between Canyon Park in Bothell and Boeing/Paine Field in Everett, Washington. We understand the route will connect the future Seaway Transit Center near the Boeing Everett Plant to dense regional centers in Snohomish County, Everett, Mill Creek, and Bothell. The Swift II BRT line will also intersect key roadways (SR 99, I-5, SR 527, and 1-405), creating improved transit connectivity with the original Swift line on SR 99. The Swift II BRT line will begin at the Canyon Park Park-and-Ride and travel north along SR 527 for approximately 6.2 miles to 132nd Street SE.The line turns west on 132nd Street SE for about 1 mile,where the road becomes 128th Street SE. Continuing west on 128th Street SW for less than 1 mile, the BRT line turns north on Airport Road.The line continues about 3 miles on Airport Road to West Casino Road,turning east to Seaway Boulevard using the SR 526 off-ramp. The project will include construction of new stations, modifications to existing utilities, areas of roadway widening, traffic signal improvement, retaining walls and underground stormwater infiltration facilities. Most of the new retaining walls will be less than 4 feet in height with the exception of two new retaining walls near the on-ramps for I-5. The proposed project alignment is shown on the attached Vicinity Map, Figure 1,and Site Plan, Figures 2A through 2R. The purpose of this study was to complete subsurface explorations along the project alignment and to provide geotechnical engineering conclusions and recommendations for the design and construction of the proposed improvements. Our geotechnical engineering services were completed in general accordance with the subconsultant agreement executed January 12, 2016 and an amendment dated November 14,2016. FIELD EXPLORATIONS AND LABORATORY TESTING Field Explorations Subsurface soil and groundwater conditions were evaluated by drilling 22 borings (GEI-1 through GEI-24 excluding GEI-3 and GEI-7) and six hand holes (HA-1 through HA-6). The borings were completed on August 26 through November 16, 2016 using continuous-flight, hollow-stem auger drilling equipment.The hand holes were completed on November 28, 2016 using hand auger equipment. Three monitoring wells and two pilot infiltration tests (PITs)were subsequently completed in March 2017 to evaluate subsurface conditions at the proposed infiltration facility locations. The approximate locations of the explorations are shown on Figures 2A through 2R. Details of the field exploration program and logs of the explorations are presented in Appendix A, Field Explorations. GEOENGINEERS April 14,2017 ; Page 1 He No,2095-032-00