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1 of 7 <br />LONGITUDE <br />ONE TWENTY° <br />ENGINEERING & DESIGN <br />Pile Review for Structural Compliance <br />Date: June 5, 2023 <br />Project Name: 4332 Colby Ave - Foundation Stabilization Effort L120 Project #: S220906-1XR <br />Project Location: 4332 Colby Ave, Everett, WA 98203 <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 installation and capacity compliance with the structural <br />requirements specified in the L120 Structural Calculation Package and Structural Site & Foundation Plan dated <br />November 13, 2022. <br />On April 18, 2023, thirteen (13) helical piles were installed by R&R Foundation Specialists (R&R) to lift the <br />residence for 4332 Colby Ave, Everett, WA 98203. Helical Piles were installed with a DIGGA 10K drive head to a <br />maximum depth of 13ft. To the knowledge of L120, these piles were installed by R&R-certified installers in <br />accordance with the cited structural package, ESR-3750. Please refer to the attached drive log provided by R&R. <br />With pile spacing at a maximum of 6'-0" on -center at the exterior, the minimum required vertical capacity as <br />determined by L120 was an allowable loading of 10 kips per pile. These demand requirements are as determined <br />and specified in L120's 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 Ideal Manufacturing, Inc. helical piles have been calculated utilizing the torque correlation <br />factors provided in ESR-3750. A toque/capacity chart detailing this calculation has been attached to this letter. Per <br />the attached document, an Ideal Foundation Systems 2-7/8 in diameter helical pile installed to a minimum <br />pressure of 1,450psi results in an installation torque of 5,046 ft-lbs and an allowable capacity of 22.7 kips including <br />a safety factor of 2. <br />The results are summarized below: <br />Helical Piles: <br />Maximum Demand (allowable) = 10.0 kips/pile <br />Available Capacity (allowable) = 22.7 kips/pile <br />