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<br />Geotechnical Engineering Report 1 HWA GEOSCIENCES INC. <br />Port Gardner Storage Facility <br />GEOTECHNICAL ENGINEERING REPORT <br />PORT GARDNER STORAGE FACILITY <br />CONSTRUCTION PACKAGE – WO# UP-3525 <br />EVERETT, WASHINGTON <br />1.0 INTRODUCTION <br />1.1 GENERAL <br />This report presents the results of a geotechnical study performed by HWA GeoSciences Inc. <br />(HWA) in support of the proposed Port Gardner Storage Facility (PGSF) project. The <br />approximate location of the project site is shown on the Site and Vicinity Map, Figure 1, and on <br />the Site and Exploration Plan, Figure 2. The purpose of this study was to evaluate the soil and <br />groundwater conditions within the project site and to provide geotechnical recommendations for <br />the proposed improvements. <br />This report presents a summary of the observed subsurface and groundwater conditions. The <br />elevations provided throughout this report are based on NAVD 88 project datum. The <br />geotechnical design and construction recommendations provided herein may be updated in future <br />iterations of this report as project plans progress so that modifications to our recommendations <br />can be made, as necessary. <br />1.2 PROJECT UNDERSTANDING <br />HWA understands that the City of Everett (City) acquired the Kimberly Clark Wastewater <br />Treatment Plant (KC WWTP) and developed a facility plan outlining future use of the PGSF. In <br />2021, the City completed the PGSF Engineering Report, which outlines how the KC WWTP <br />infrastructure will operate as a wet weather storage facility and integrate into the existing <br />collection system (BC/HDR, 2021a and 2021b). As part of this study, a seismic resiliency <br />assessment was conducted to determine the resiliency of the existing facility infrastructure <br />regarding the potential for failure or damage to the existing facility infrastructure due to a <br />seismic event. The results of that assessment indicated that the KC WWTP does not meet current <br />seismic design requirements outlined by IBC 2021 and ASCE-7-16. <br />Brown and Caldwell (BC; project civil and structural engineer) is designing the PGSF to provide <br />temporary combined sewer storage, which will reduce the frequency of combined sewer <br />overflows at Puget Sound Outfalls 4, 5, 6, and 7 to an average of less than one event per year. <br />The PGSF will also provide stormwater treatment for separated stormwater drainage basins with <br />conveyance to the City’s deep-water outfall (DWO) and local stormwater conveyance to the <br />Everett Water Pollution Control Facility. The PGSF is scheduled to be operational by December <br />31, 2027.