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I of 8 <br />LONGITUDE <br />ONE TWENTYO <br />ENGINEERING & DESIGN <br />Pile Review for Structural Compliance <br />Date: April 9th, 2021 <br />Project Name: Foundation Stabilization/Lift — Everett Project Number: S200831-1 <br />Project Location: 4514 Seahurst Ave, Everett, WA 98203 <br />Client's Name: Andi Holm, Project Coordinator — R&R Foundation Specialist, LLC <br />To Whom It May Concern: <br />The purpose of this letter is to confirm pile installation and capacity compliance with the structural require- <br />ments specified in the L120 Structural Calculation Package and Structural Site Plan dated November 20th <br />2020. <br />On March 29th, 2021, ten (10) helical and two (2) concentric piles were installed by R&R Foundation <br />Specialists (R&R) to stabilize areas of the single-family residence located at 4514 Seahurst Ave, Everett, <br />WA 98203. To the knowledge of L120, these piles were installed by R&R certified installers in accordance <br />with the cited structural package, ESR-3750 and ESR-4121. Please refer to the attached drive log and <br />photographs provided by R&R. <br />The helical and concentric piles were installed at the locations as specified on Level Survey, the typical <br />minimum required vertical capacity as determined by L120 is shown in the table below. These demand <br />requirements are as determined and specified in L120's structural calculation package cited above. <br />PILE SPACING & LOAD REQUIREMENTS TABLE <br />MAX O.C. SPACING, R <br />MIN VERTICAL CAPACITY, kips <br />PROOF TESTING LOAD, kips <br />PILE # <br />PILE TYPE <br />BTWN PILES <br />END OFFSET <br />ALLOWABLE LOADING <br />200% MIN VERTICAL CAPACITY <br />(MIN ULTIMATE CAPACITY) <br />LOCATION <br />1-10 <br />HELICAL <br />PER PLAN <br />PER PLAN <br />16.0 k/PILE <br />32.0 k/PILE <br />TYP EXTERIOR <br />1-2 <br />CONCENTRIC <br />PER PLAN <br />N/A <br />22.0 k/PILE <br />44.0 k/PILE <br />CHIMNEY <br />Pile capacities for the helical piles have been calculated using a Digga MM-10K drive head with a torque <br />correlation factor, Kt, of 9 as prescribed in ESR-3750. A chart showing the resulting capacities is attached <br />to this letter. Per the attached document, an Ideal Foundation Systems 2-7/8" diameter helical pile installed <br />to a minimum pressure of 1,200 psi results in a maximum allowable capacity of 18.8 kips including a safety <br />factor of 2. <br />