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Page 11 <br />kimley-horn.com 2828 Colby Avenue, Suite 200 Everett, WA 98201 425-708-8275 <br />·Investigation Derived Waste (IDW): Soil cuttings, purged groundwater, and <br />decontamination water from borings will be placed in steel 55-gallon drums. These IDW <br />drums will be stored on-site pending chemical analysis, or at a City provided location <br />that is within three (3) miles of the proposed bridge site. Once laboratory results for the <br />environmental samples are obtained, HWA will coordinate the disposal of drummed IDW <br />using a waste disposal subcontractor. Waste profile documentation required for disposal <br />of the IDW will need to be signed by the property owner or a City representative. <br />·Conduct Phase 2 Explorations (Geophysical Survey): HWA shall perform geophysical <br />investigations of subsurface soils using Refraction-Microtremor (ReMi) or Extended <br />Spatial Autocorrelation Method (ESPAC) to collect shear wave velocity measurements of <br />the soils in the upper 100 feet of the site, to assess the most appropriate seismic site <br />class for the site. One geophysical investigation (either ReMi or ESPAC) will be <br />performed at each side of the bridge alignment (two locations). Work shall be conducted <br />by an HWA Geologist proficient in these geophysical methods, who will also determine <br />the appropriate locations for the test and the methods to be used. <br />·Generate Boring Logs and Assign Laboratory Testing: HWA will prepare summary <br />boring logs and perform laboratory testing to evaluate relevant physical properties of the <br />site soils. Laboratory testing would include moisture content, grain-size distribution, <br />Atterberg Limits, and direct shear testing. <br />·Groundwater Monitoring: HWA shall install a groundwater monitoring transducer in both <br />proposed monitoring wells. These transducers will be set to acquire groundwater <br />elevation readings every half hour for a duration of twelve (12) months. A geologic <br />representative from HWA shall make two (2) site visits to download and process the <br />groundwater data. This data will be used to provide geotechnical design <br />recommendations and to provide prospective contractors with an accurate <br />representation of the seasonal groundwater variations across the site. <br />Geotechnical Engineering Analysis <br />·Evaluate Field and Laboratory Data: Based on the borings and the laboratory test results <br />of selected samples, HWA will generate estimates of the soil strength and other <br />properties needed to evaluate the effects the subsurface conditions will have on the <br />proposed improvements. <br />·Develop Geologic Cross-Section: HWA will construct a geologic cross-section along the <br />centerline of the project. This cross section will show HWA’s interpretation of soil <br />conditions along the bridge alignment and will be provided in a geotechnical report. <br />·Evaluate Geophysical Data and Identify Seismic Site Class: HWA shall evaluate the <br />geophysical data collected at both abutments. The data will be reduced to develop a <br />shear wave velocity profile to determine the appropriate seismic site class for the new <br />AASHTO code. <br />·Generate AASHTO Seismic Design Parameters: Based on the Site Class determined <br />from the geophysical study, HWA will develop seismic design parameters. The design <br />spectral acceleration parameters will then be selected in accordance with the AASHTO <br />Load and Resistance Factor Design (LRFD) Bridge Design Specifications.