330 ELM ST VIEW RIDGE ESTATES 2022-04-04

• ` Geotechnical Engineering Evaluation NGA File No. 1085419 View Ridge Estates 330 Building Settlement March 22,2019 Everett,Washington Page 7 For planning purposes, we recommend that temporary cuts in the on-site soils be no steeper than 2 Horizontal to 1 Vertical (2H:1 V). If significant groundwater seepage or surface water flow were encountered, we would expect that flatter inclinations would be necessary. We recommend that cut slopes be protected from erosion. The slope protection measures may include covering cut slopes with plastic sheeting and diverting surface runoff away from the top of cut slopes. We do not recommend vertical slopes for cuts deeper than four feet, if worker access is necessary. We recommend that cut slope heights and inclinations conform to appropriate OSHA/WISHA regulations. Foundation Underpinning Improvements General: We recommend that at a minimum, the eastern, and portions of the northern and southern foundations extending from the eastern side of the building, be supported on a deep foundation system such as pin pile or helical anchors, to transfer structure loads down into the underlying competent native bearing materials to limit future settlement and damage to the structure. Structural brackets should be used to attach the pin piles/helical anchors to the existing foundations. The structural engineer should design the new foundation supports and determine the location of the supports based on the recommendations provided in this letter. A qualified contractor specializing in foundation retrofit should be retained to complete the repairs. Considering the limited site access conditions, it is our opinion that the most feasible foundation underpinning systems are 2-inch diameter pin piles driven to refusal using a hand operated 140-pound jackhammer or hydraulically driven helical anchors. Extreme care should be taken during the proposed repairs as to not impact existing utilities within the vicinity of the residence. Our explorations encountered loose undocumented fills within the planned areas to be repaired. If large objects or debris are present within the fill, there is a possibility that this material may obstruct some piles or anchors at shallow depths. There should be contingencies in the budget and design for additional/relocated piles/anchors that may be obstructed by possible debris in the fill. Due to the rigid pile/anchor support, friction between the foundation and subgrade soil should not be considered for resisting lateral pressures on this structure. Also, passive resistance acting on the below- grade portion of the foundation should not be used to resist lateral pressures. We recommend that all lateral loads be transferred to the remainder of the structure. We should be retained to review final plans and to monitor installation of the pin piles/anchors during construction. 10 \ i.I NELSON GEOTECHNICAL ASSOCIATES, INC.