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June 13, 2024 <br />HWA Project No. 2024-P180-21 <br />Proposal for Geotechnical Engineering Services <br />Everett Stormwater Conveyance Improvements 3 HWA GeoSciences Inc. <br />and will occupy one lane of travel. Pavement coring will be immediately followed by <br />advancement of the borehole at the core hole location. HWA anticipates that the pavement <br />coring and borehole advancement will collectively take up to six hours. Methodology for <br />advancing the borehole is discussed subsequently. <br />Conduct Geotechnical Explorations: HWA will complete four days of drilling consisting of up <br />to 11 geotechnical borings at the project sites to assess the subsurface soil and groundwater <br />conditions. The proposed borings will each be advanced to a depth of 25 feet or until practical <br />refusal of the drilling equipment, whichever is shallower. All borings will be drilled using hollow <br />stem auger drilling equipment. Four groundwater monitoring piezometers (two at each project <br />site) will be installed at select boring locations to allow for groundwater observations over time. <br />Each of the above-described geotechnical explorations will be logged by an HWA representative <br />who will monitor the explorations, collect representative soil samples, and prepare detailed logs <br />of the subsurface conditions observed. Soils will be characterized in general accordance with <br />ASTM D2488, Standard Practice for Description and Identification of Soils (Visual-Manual <br />Procedures). Geotechnical soil samples from the exploratory borings will be obtained in general <br />accordance with ASTM D1586, Standard Test Method for Standard Penetration Test (SPT) and <br />Split-Barrel Sampling of Soils at 2.5 ft or 5 ft intervals. <br />Conduct Groundwater Monitoring: HWA will visit the site on a roughly monthly basis to <br />collect measurements from the groundwater monitoring wells. Monitoring will be completed <br />over a 12-month period, for a total of 11 site visits following completion of drilling. HWA <br />assumes each visit will require 2 hours, including travel time and that traffic control devices and <br />personnel will not be required to access the monitoring wells. <br />Generate Exploration Logs and Assign Laboratory Testing: HWA will prepare summary <br />boring logs and perform laboratory testing to evaluate relevant physical properties of select soil <br />samples. HWA has included budget for 11 percent fines content determinations, 11 grain size <br />analyses, and 55 moisture content determinations. Geotechnical soil samples obtained from the <br />explorations will be held in HWA’s laboratory until submittal of a draft report after which time <br />they will be disposed of. <br />Geotechnical Engineering Analysis and Reporting: Information from the field investigations <br />will be analyzed by geotechnical engineers from HWA to develop geotechnical engineering <br />conclusions and recommendations for design and construction of the proposed stormwater <br />conveyance improvements. The results of HWA’s field explorations, laboratory testing, <br />engineering analyses, and geotechnical conclusions and recommendations will be summarized in <br />a draft geotechnical report that addresses both project sites. Upon receipt of consolidated <br />comments from the design team and the City, HWA will prepare a final geotechnical report, <br />which will be stamped by the project geotechnical engineer. The geotechnical report will include <br />the following: