1707 SCENIC DR Geotech Report 2022-10-25

GEOENGINEER 8410 154th Avenue NE Redmond,Washington 98052 425.861.6000 March 31,2015 Snohomish County Public Utility District No. 1 P.O. Box 1107 • Everett,Washington 98206-1107ti Attention:Jim Simpson Subject: Geotechnical Engineering Services MAY LU i� MSE Wall Design Recommendations Beverly Park Substation Expansion Project CITY OF EVER Everett,Washington Permit II' File No.0482-027-02t✓r�iC�S INTRODUCTION This addendum letter summarizes our design recommendations for a mechanically stabilized earth (MSE) wall planned at the proposed Snohomish County PUD No. 1 Beverly Park Substation Expansion project in Everett, Washington.We previously completed a geotechnical report for the project titled, "Geotechnical Engineering Services, Beverly Park Substation Expansion, Everett, Washington,"dated,October 24, 2014. This letter is submitted as an addendum to our October 24,2014 report. PROJECT UNDERSTANDING The design team has requested design level geotechnical recommendations for a vegetated MSE wall planned along the northwest corner of the site(Retaining Wall 2).The wall is shown in the project drawings on Sheets S-10A-C36, S-10A-C37, and S-10A-C38. The MSE wall will step up in 1.5-foot increments to 13.5 feet in height and will retain fill planned as part of site grading for the 115kV yard.The wall is planned to be 130.5 feet long with a level fore slope and back slope. The planned bottom of wall steps up from Elevation 414.3 feet at STA 0+00 at the east end to Elevation 417.5 feet at STA 1+30.5 at the west end. The wall backfill will be reinforced with geogrid and will be constructed with fencing along the top of the wall. The wall will also be constructed with a batter by offsetting each Sierrascape facing unit row by 6 to 10 inches, as shown on the typical'section on Sheet S-10A-C36. The MSE wall will need to support a live load of 250 pounds per square foot(psf)for vehicle loading.