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Geotechnical Engineering Evaluation NGA File No. 1165620 Lyashenko Accessory Dwelling Unit Development April 10, 2020 Everett, Washington Summary - Page 2 Final stormwater plans have also not been developed, but we understand that on -site infiltration is being considered for this site. The subsurface soils generally consisted of surficial topsoil/undocumented fill soils underlain by granular fine to medium sand with varying amounts of silt, gravel and iron -oxide weathering that we interpreted as native advance outwash soils at relatively shallow depths. Based on our onsite testing and significant groundwater seepage encountered throughout the site, it is our opinion that stormwater infiltration is not feasible within the site. However, shallow, low -impact design infiltration systems and/or dispersion systems may be feasible at specific areas within the site depending on final layout as determined by the civil engineer. In the attached report, we have also provided general recommendations for site grading, slabs -on - grade, structural fill placement, erosion control, and drainage. We should be retained to review and comment on final development plans and observe the earthwork phase of construction. We also recommend that INGA be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed differ from those anticipated, and to evaluate whether or not earthwork and foundation installation activities comply with contract plans and specifications. It has been a pleasure to provide service to you on this project. Please contact us if you have any questions regarding this report or require further information. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. I Khaled M. Shawish, PE Principal Engineer