1910 W MUKILTEO BLVD Geotech Report 2022-10-25

• Geotechnical Engineering-Evaluation Spencer Garage Addition Development 1910 West Mukilteo Boulevard Everett, Washington INTRODUCTION This report presents the results of our geotechnical engineering investigation and evaluation of the planned Spencer garage addition project in Everett, Washington. The project site is located at 1910 West Mukilteo Boulevard, as shown on the Vicinity Map in Figure 1. The parcel number for the subject property is 004171-000-003-03. The purpose of this study is to explore and characterize the site's surface and subsurface conditions and to provide geotechnical recommendations for the planned site development. The property extends south from West Mukilteo Boulevard and covers approximately 0.45 acres in area. It is currently occupied by a single-family,residence on the northern portion, and a detached garage and sports court in the southern portion.The property is bordered by a shared access driveway to the east, and by residential properties to the west and south.Topographically,the site slopes gently to the north, but includes 5-to.8-foot tall north- and east facing slopes at the extreme southwestern'corner, likely associated with site grading for the level sports court.Final stormwater plans have also not been developed, however,we understand that stormwater may be directed to on-site infiltration systems, if feasible.The existing site layout is shown on the Site Plan in Figure 2. SCOPE The purpose of this study is to explore and characterize the site surface and subsurface conditions and provide general recommendations for site development. Specifically,our scope of services included: 1. A review of available soil and geologic maps of the area. 2. Exploring the subsurface soil and groundwater conditions on the north ard'west=facing slopes with hand tool explorations,where possible. 3. Exploring the subsurface soil and conditions within the site and prepare the Small-Scale PIT using trackhoe-excavated test pits. Excavation services were provided by NGA. 4. Providing long-term design infiltration rates based on on-site Small Pilot Infiltration Testing(PIT) per the 2014 SWMMWW, if feasible. 5. Performing laboratory grain-size sieve analysis on soil samples,as necessary. 6. Providing recommendations for structure setbacks from geologic hazards,as necessary. 7. Providing recommendations for earthwork and foundation support. NELSON GEOTECHNICAL ASSOCIATES, INC.