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January 3, 2025 <br />HWA Project No. 2021-159-21 <br />Geotechnical Engineering Report 38 HWA GEOSCIENCES INC. <br />Port Gardner Storage Facility <br />Installation of micropiles should be observed by a representative of HWA to confirm depth, <br />vertical alignment, subsurface conditions, reinforcing steel placement, and grout placement. <br />Grout used in piles should be sampled and tested for strength. <br />4.6.8 Construction Considerations and Monitoring of Pile Installation <br />The installation of piles may be impeded by the presence of buried logs, tree stumps, or other <br />obstructions. Where vibration-sensitive structures are present, HWA recommends pile locations <br />be predrilled through the existing fill to avoid hard driving through the relatively dense fill to <br />reduce vibration on adjacent structures. HWA recommends that pile installation begin with piles <br />closest to any existing structure and proceed away from it, wherever applicable. Additionally, if <br />sensitive structures are identified, HWA recommends that the contractor assess the nearby <br />sensitive structures and implement a vibration monitoring program during the pile diving <br />process. <br />Selection of an appropriate pile driving hammer will depend on the pile types and sections <br />selected for use on the project, the contractor’s methods, and other factors. Fixed leads should be <br />utilized to reduce the potential for the pile being driven out of alignment or struck <br />asymmetrically, which could damage the pile. <br />HWA recommends that a pile test program using PDA be specified for the project. Benefits of <br />the pile test program include confirming or refining pile wall thicknesses, pile length and <br />optimizing pile capacity estimates with pile setup/load transfer measurements using the PDA <br />technology. HWA recommends a minimum of three test piles be driven to evaluate the field <br />conditions in conjunction with the contractor's pile driving equipment. Recommended locations <br />for the test piles will be selected during construction. Test piles may be located such that they <br />also serve as production piles. Test piles should be re-struck 1 to 7 days after initial driving, at <br />the direction of the engineer. Ultimate capacities of these piles should then be evaluated using <br />penetration resistance during re-striking. Following completion of the test pile program, the <br />geotechnical engineer should provide final driving criteria, using the Wave Equation Analysis of <br />Pile Driving (WEAP). Production piles should be ordered based on the results of the test pile <br />driving. <br />In addition, HWA recommends at least 5 percent of the production piles be re-struck. The <br />geotechnical engineer should select piles designated for re-striking, and the re-strikes should be <br />performed at time intervals after initial driving as determined by the engineer. Re-striking <br />normally will consist of driving the pile an additional 3 to 6 inches, while noting the number of <br />blows required for each inch of penetration. <br />All pile driving should be observed by an engineer from HWA.