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January 3, 2025 <br />HWA Project No. 2021-159-21 <br />Geotechnical Engineering Report 37 HWA GEOSCIENCES INC. <br />Port Gardner Storage Facility <br />• Due to the presence of groundwater, micropiles may be preliminarily designed and <br />installed in accordance with Case I, Type B requirements as specified in FHWA NHI-05- <br />039 (FHWA, 2005). <br />• Drilling methods should be determined by the contractor. Drilling methods shall be <br />capable of advancing through wood debris and dense glacial soils. <br />• Micropiles may be preliminarily designed using ultimate grout-to-ground interface bond <br />strength of 35 psi in dense glacial soils and 10 psi in the bay deposits. Grout-to-ground <br />strength should be neglected in areas where wood deposits and other fill is present. <br />• Down drag loads presented in Table 3 assume uncased micropiles and residual shear <br />strengths of liquefiable soils. Down drag values can be reduced for micropiles cased in <br />the liquefaction zone. <br />• To increase micropile capacity, the contractor's design may include permanent cased <br />sections through the non-liquefiable layer (i.e., crust) above the liquefiable layer to <br />reduce down drag loads; alternatively, the contractor may increase micropile embedment <br />below the liquefiable layer into dense outwash soils. Final pile depths will be determined <br />by the contractor. <br />• Pre-production testing should be performed as discussed in Section 4.6.7. <br />4.6.7 Micropile Construction <br />An experienced and competent contractor should be retained to install micropiles. Final design of <br />the micropile foundation systems should be based on available data and the results of pre- <br />production testing. <br />Verification load testing should be performed on one or more pre-production test piles per <br />structure near locations where the micropiles are planned (i.e. four areas). Load testing should be <br />performed prior to installation of the production piles and the test piles should be sacrificial. A <br />representative of HWA should be present during pre-production pile load testing to observe and <br />document testing conditions and results. Based on the results of the load tests, design axial <br />capacities may be reevaluated for planned production piles. The verification test is to verify the <br />design and adequacy of the contractor’s drilling, installation, and grouting operations. Each <br />verification micropile must be constructed with the identical materials, dimensions, tip <br />elevations, and installation methods as the production micropiles it represents (i.e. four areas).