2416 61ST ST SE 2022-03-04 - Laserfiche WebLink

2416 61st Street SE Limited Subsurface Exploration and Geotechnical Everett, Washington Assessment for Slab and Foundation Repair Bedroom Floor Slab Repair We understand that the concrete slab located within the bedroom adjacent to the kitchen has experienced noticeable settlement toward one corner and is no longer level; however, no evidence of water intrusion or excessive cracking has been observed. The observed settlement is likely due to long-term settlement of the underlying fill soils that has occurred over several years since initial construction. Since no pipe leaks or other water intrusion issues are suspected below the slab, it is our opinion that the slab could remain in place and re-leveled with floor leveling compound or"lifted" using grout or polyurethane foam injection techniques. Alternatively, the floor slab could be removed and foundation soils remediated similar to the kitchen floor slab; however, this option does not appear warranted as the observed distresses are mostly cosmetic. Settlement Mitigation of Exterior Footings It is our opinion that the observed settlement and cracking of the exterior footings along the southeast and northeast corner of the building is likely due to settlement of the underlying fill soils and possibly the loose weathered horizon of the advance outwash soils. Given the age of the structure, we think it is unlikely that any significant additional settlement will occur during the remaining life of the structure. However, if desired by the Owner, further potential settlement of the exterior footings could be mitigated by underpinning the footings with small-diameter pipe piles. The pipe piles would be driven through the existing fill soils and penetrate the underlying medium dense to dense advance outwash sediments at depth. Our recommendations for pipe pile foundations are provided below. Pipe Pile Foundations Small-diameter pipe piles are lengths of steel pipe driven into the soil, usually by an air or hydraulically actuated jackhammer. The jackhammer may be hand-operated or mounted on a small excavator. The piles are driven in a series of small excavations. Once the piles have been driven into the soil, steel brackets are used to connect the piles to the concrete footings. The loads from the footing are then transferred to the pipe piles through the upper loose fill soils to the underlying bearing soils. A qualified structural engineer, using the design guidelines presented herein, should complete the design of the foundation system to determine the number and spacing of piles required to underpin the exterior footings. We anticipate that 2-inch-diameter pipe piles will be suitable for underpinning purposes and the anticipated structural loads.The piles should be galvanized steel pipe, driven with a suitable pneumatic or hydraulic hammer to the refusal criteria shown in Table 1 below. The following table provides required minimum hammer weight, refusal criteria, and allowable load for a 2-inch-diameter pipe pile. Based on our limited exploration depths and knowledge of the site geology, we anticipate that pile embedment depths may range from 10 to 15 feet. It should be noted that actual driven lengths are unpredictable and may be substantially longer or shorter than the estimated range. The piles must extend through the existing fill and loose native soils and penetrate the underlying medium dense to dense advance outwash sediments. October 26,2021 ASSOCIATED EARTH SCIENCES INC. BD/Id-20210370E001-002 1Pae 6/i(D