7505 SEAWAY BLVD Geotech Report 2022-10-25

FINAL GEOTECHNICAL REPORT SEAWAY TRANSIT CENTER EVERETT,WASHINGTON 1. INTRODUCTION 1.1 GENERAL This report summarizes the results of the geotechnical engineering study performed by HWA GeoSciences Inc. (HWA), in support of the proposed Seaway Transit Center in Everett, Washington. The approximate location of the project site is shown on the Site Vicinity Map, Figure 1, and on the Site and Exploration Plan, Figure 2. HWA previously conducted a Phase I exploration program as part of a feasibility study to evaluate the practicality of constructing the proposed transit facility at the subject project site. The Phase I exploration consisted of drilling four machine-drilled borings. Our Phase II study was performed in support of design of the proposed Seaway Transit Center. Phase II explorations included site reconnaissance, drilling two machine-drilled borings, and performing five hand borings in support of various site improvements associated with construction of the transit center. Engineering analyses were conducted to develop design recommendations for proposed bus bay and maintenance facilities, retaining structures, new pavement sections, stormwater facilities, and signal pole foundations. 1.2 PROJECT UNDERSTANDING We understand the proposed Seaway Transit Center will provide a centralized facility for several regional transit providers, and will serve as the terminus for the second line of the Swift bus. It is our understanding that the Seaway Transit Center will consist of a raised center island surrounded by a raised pedestrian platform; with bus lanes situated between the center island and platform. We understand that a buried detention vault near the middle of the site will be used to store treated runoff; from whence it will be conveyed off site. We understand that a single-story maintenance building will be constructed on the south side of the center island; and that two pedestrian shelters will be located along the western platform, adjacent to Seaway Boulevard. It is our understanding that the transit center pavement,platform, and center island will be constructed with Portland cement concrete (PCC). The eastern half of the site is currently covered with a 10-to 15-feet-tall mound of fill material. Site grading plans indicate a significant portion (if not all) of this fill material will be removed; and that one retaining wall will be constructed along the southern edge of the property. Six new traffic signals are proposed near the eastern entrance and PUD driveway to facilitate access from the transit facility to 75th Street SW.