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1 of 6 <br />LONGITUDE <br />ONE TWENTY0 <br />ENGINEERING & DESIGN <br />Helical Pile Review for Structural Compliance <br />Date: July 25, 2022 <br />Project Name: 810 33rd St - Foundation Stabilization Effort L120 Project # S201013-2XR <br />Project Location: 810 33rd St, Everett, WA 98201 <br />Client's Name: Amanda Howe, Project Coordinator— 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 />March 29, 2021. <br />On May 16, 2022, eleven (11) helical piles were installed by R&R Foundation Specialists (R&R) to lift and stabilize <br />the residence located at 810 33rd St, Everett, WA 98201. Piles were installed with a DIGGA 10k drive head to a <br />maximum of depth of 10 ft. To the knowledge of L120, these piles were installed by R&R certified installers in <br />accordance with the cited structural package and ESR-3750. Please refer to the attached drive log provided by <br />R&R. <br />With piles centered under the posts, the minimum required vertical capacity as determined by L120 was an <br />allowable loading of 20.0 kips per pile. These demand requirements are as determined and specified in L120's <br />structural calculation package cited above. <br />As required by the referenced structural package, proof testing was to be performed to 200 percent of the <br />specified design load. It is L120's understanding that the installers utilized the dead weight of the existing structure <br />to achieve the required reaction of a test pile. <br />Pile capacities for helical piles have been calculated utilizing the torque correlation factors provided in ESR-3750. A <br />toque/capacity chart detailing this calculation has been attached to this letter. Per the attached document, an <br />Ideal Foundation Systems 2-7/8 in diameter helical pile installed to a minimum pressure of 1,500 psi results in an <br />installation torque of 5,220 ft-lbs and an allowable capacity of 23.5 kips including a safety factor of 2. <br />The results are summarized below: <br />Maximum Demand (allowable) = 20.0 kips/pile <br />Available Capacity (allowable) = 23.5 kips/pile <br />