4920 EVERGREEN WAY STAPLES Geotech Report 2022-10-25

Geotechnical Engineering Report Staples Rockery Failure Everett,Washington lierracon March 8, 2019 Terracon Project No. 81175122 retain the unsupported soil. Furthermore, removal of the rockery in short sections, or slots, will help mitigate the potential for sloughing after the rockery is deconstructed and before lagging is placed. Backfilling. For temporary excavations, trenches,voids behind the retaining wall, and the headscarp of the failed section, backfilling should occur after temporary wood lagging has been placed for the full height of the retaining wall. This will help reduce the further loading on the building wall within the existing failed section. As of the publishing of this report, overhead utilities exist adjacent to the rockery and will be an obstruction during retaining wall construction. The contractor will need to work with the City and other public utilities to relocate the overhead utilities. Surface water should not be allowed to pond on the site and soak into the soil during or after construction. Construction staging should provide drainage of surface water and precipitation away from the retaining wall.Any water that collects over or adjacent to construction areas should be promptly removed. Surface water control in the form of sloping surfaces, drainage ditches and trenches, and sump pits and pumps will be important to avoid ponding and associated delays due to precipitation and seepage. 4.3 Seismic Considerations Code Used Site Classification International Building Code (IBC) and 2010 ASCE 71 D2 S5—Short Period Spectral Acceleration for Site Class B 1.378 g Si — 1-Second Period Spectral Acceleration for Site Class B 0.523 g Fa—Short Period Site Coefficient for Site Class D 1.0 Fv— 1-Second Period Site Coefficient for Site Class D 1.5 PGA-ASCE 7-10, Peak Ground Acceleration 0.570 FPGA-Peak Ground Acceleration Site Coefficient 1.0 1. The 2010 ASCE 7 document indicates that the seismic site classification is based on the average soil and bedrock properties in the top 100 feet. The current scope does not include a 100-foot soil profile determination. This seismic site class definition considers that soil encountered at depth in our explorations continue below the termination depths. Additional exploration to deeper depths would be required to confirm the conditions below the current depth of exploration. 2. Site Class D applies to an average soil profile within the top 100 feet consisting predominantly of stiff and dense to very dense soils. This soil is characterized by Standard Penetration Test blow counts between 15 to 50, a shear wave velocity of between 600 and 1,200 feet per second, and an undrained shear strength between 1,000 and 2,000 pounds per square foot. Responsive • Resourceful ■ Reliable 9