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1 of 5 <br />LONGITUDE <br />ONE TWENTYO <br />ENGINEERING & DESIGN <br />Pile Review for Structural Compliance <br />Date: April 29th, 2023 <br />Project Name: Foundation Stabilization/Lift — Everett Project Number: S220725-1XR <br />Project Location: 1007 49th P1 SW, 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 pile installation and capacity compliance with the structural require- <br />ments specified in the L120 Structural Calculation Package and Structural Site Plan dated September 2nd <br />2022. <br />During the week of January 13th, 2023, seven (7) helical piles were installed by R&R Foundation Specialists <br />(R&R) to stabilize areas of the single-family residence located at 1007 49th P1 SW, Everett, WA 98203. To <br />the knowledge of L120, these piles were installed by R&R certified installers in accordance with the cited <br />structural package, ESR-3750. Please refer to the attached drive log and photographs provided by R&R. <br />The helical piles were installed with maximum pile spacing of 6'-0" on -center, the typical minimum required <br />vertical capacity as determined by L120 is shown in the table below. These demand requirements are as <br />determined and specified in L120's structural calculation package cited above. <br />PILE SPACING & LOAD REQUIREMENTS TABLE <br />MAX O.C. SPACING, ft <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 />TYP <br />HELICAL <br />6'-0" <br />PER PLAN <br />14.0 k/PILE <br />28.0 k/PILE <br />EXTERIOR <br />Pile capacities for the helical piles have been calculated using a Digga HH-6K 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 1,800 psi results in a maximum allowable capacity of 25.2 kips including a safety <br />factor of 2. <br />