3610 W MUKILTEO BLVD Geotech Report 2022-10-25

Geotechnical Engineering Evaluation NGA File No. 1129119 .Zahler Residence Development October 14,2019 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. We performed one small-scale pilot infiltration test within the northeastern portion of the site. The subsurface soils generally consisted of surficial undocumented fill soils underlain by silty fine to medium sand with varying amounts of silt, gravel, and iron-oxide weathering, which we interpreted as native glacial soils. Based on our testing results and the relatively dense silty nature of the onsite soils, it is our opinion that traditional methods for stormwater infiltration are not feasible. Shallow, low impact systems such as pervious pavements, rain gardens, and shallow infiltration swales may be feasible for this site,but should be further evaluated during final design. In the attached report, we have also provided general recommendations for site grading, slabs-on-grade, structural fill placement, retaining walls, 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 NGA 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. Khaled M. Shawish,PE Principal Engineer