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1 of 8 <br /> LONGITUDE <br /> ONE TWENTYO <br /> ENGINEERING&DESIGN <br /> Helical Pile Review for Structural Compliance <br /> Date: February 5, 2024 <br /> Project Name: 4504 Evergreen Way- Foundation Stabilization Effort L120 Project#S220527-3XR <br /> Project Location: 4504 Evergreen Way, Everett, WA 98281 <br /> Client's Name: R&R Foundation Specialist, LLC <br /> To whom it may concern, <br /> The purpose of this letter is to confirm helical pile installation and capacity compliance with the structural <br /> requirements specified in the L120 Structural Calculation Package and Structural Site&Foundation Plan dated <br /> August 27, 2023. <br /> On September 12,2023,the installation of four(4) helical piles and ten (10)concentric piles to lift and stabilize <br /> areas of the residence located at 4504 Evergreen Way were finalized by R&R Foundation Specialists(R&R).The <br /> FOR from L120 Engineering was present on site during the pile installation. Helical piles were installed with a <br /> DIGGA 6k drive head to a maximum depth of 4ft.Concentric piles were installed with a Power Team C25C <br /> Hydraulic Cylinder drive head to a maximum depth of 5ft.These piles were installed by R&R certified installers in <br /> accordance with the cited structural package and ESR-3750 and ESR-4121. Please refer to the attached drive logs. <br /> With pile spacing at a maximum 8'-0"on-center,and 6'-0"on-center,the minimum required vertical capacity as <br /> determined by L120 was allowable loadings of 11 kips for helical piles, 12 kips for concentric piles#3-6, and 16 kips <br /> for concentric piles#1-2, 7-10.These demand requirements are as determined and specified in L120's structural <br /> calculation package cited above. <br /> As required by the referenced structural package, proof testing was performed to 200 percent of the specified <br /> design load.The installers utilized the dead weight of the existing structure to achieve the required reaction of the <br /> test piles. <br /> Pile capacities for helical piles have been calculated utilizing the torque correlation factors provided in ESR-3750.A <br /> torque/capacity chart detailing this calculation has been attached to this letter. Per the attached document,an <br /> Ideal Foundation Systems 2-7/8in diameter helical pile installed to minimum pressures of 1,250 psi results in an <br /> installation torque of 3,885 ft-lbs,and an allowable capacity of 17.5 kips including a safety factor of 2. <br /> Pile capacities for concentric piles have been calculated utilizing the torque correlation factors provided in ESR- <br /> 4121.A torque/capacity chart detailing this calculation has been attached to this letter. Per the attached <br /> document, piles shall reach a pressure that correlates with an allowable capacity, but shall not exceed the <br /> maximum allowable capacity,including a safety factor of 2. <br /> 4. •6)790 9502 <br />