3500 TERMINAL AVE Geotech Report 2022-10-25

26 I Port of Everett—South Terminal Wharf&Electrical Upgrades—Phase 2 • Optically survey movement and monitor vibration of settlement-sensitive structures when driving piles nearby, • Monitor movement of adjacent piles when driving piles nearby;and • Provide PDA along with CAPWAP analysis for selected piles.We recommend performing dynamic testing on at least 5 percent of production piles and including at least one pile from each row along the slope.The first piles driven should be instrumented with the PDA to immediately assess the performances of the pile driving system. A suitable approach(such as the use of S.equation described above)should be developed to assess and verify pile capacity using the blow count observed during pile driving. Capacity during initial pile driving is typically less than the final static capacity.This occurs because: • In granular soil (sand),the vibrations from pile driving induce liquefaction in the nearby soil, reducing the shear strength;and • In cohesive soil (clay),the soil is remolded during driving. Remolded soil strengths are generally less than undisturbed soil strengths. These strength losses during initial driving are usually regained following installation; rapidly for granular soil (within several days), but more slowly for cohesive soil (weeks to months).The pile axial resistance values recommended on Figures 22 through 27 are representative of conditions after the strength losses during initial driving have been regained.We would recommend instrumented restrikes on a series of test piles at the beginning of driving with planned restrikes of 40-hours and, if needed,a second restrike 7-days later to assess geotechnical capacity.Alternatively,the piles could likely be driven slightly deeper such that the geotechnical capacity within 40-hours of driving is adequate for the required loading. Utilities In general,we recommend that utility trench cut design be the contractor's responsibility. For shallow trench excavations less than 4 feet deep,open cutting is not prohibited. In general,the on-site soils are OSHA Type C soil.Temporary shoring may be necessary if deeper excavation is required for utility placement, if the soils are unstable,and if room does not allow for a safe slope to be established.The contractor should verify the condition of the side slopes during construction,and lay back trench cuts as necessary to conform to current standards of practice.We can provide additional recommendations as required. Foundation Support for Underground Civil Structures The following foundation recommendations cover design and construction of proposed utility vaults: • Use a maximum allowable bearing pressure of 2,000 pounds per square foot(ksf). • For utility vaults bearing below design groundwater elevation,design for an uplift pressure of 400 psf. 19232-01 IN December 6,2017 HAWSER