8417 EVERGREEN WAY Geotech Report 2022-10-25

Geotechnical Engineering Report-Revised lierracon Proposed CFT Retail • Everett,Washington February 1, 2018■Terracon Project No. 81185002 Applicable conditions to the above include: a For active earth pressure, wall must rotate about base, with top lateral movements of about 0.002 H to 0.004 H, where H is wall height a For passive earth pressure to develop, wall must move horizontally to mobilize resistance a Uniform surcharge, where S is surcharge pressure in psf a Wall backfill weight a maximum of 130 pcf a Horizontal finished grade compacted to 95 percent of modified Proctor maximum dry density • Lateral earth pressures assume horizontal backfill surface behind the wall; consult Terracon for sloping backfill or unusual surcharge loading conditions a Loading from heavy compaction equipment not included • No hydrostatic pressures acting on wall a No dynamic loading a No safety factor included in soil parameters • Ignore passive pressure in frost zone. A minimum factor of safety of 1.5 is recommended for passive resistance. Reinforced concrete walls with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to those indicated in the above table. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction and/or compaction, and the strength of the materials being restrained. Two wall restraint conditions are shown. "Active" earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes some wall deflection. The "at-rest" condition assumes no wall deflection. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls. To account for increased lateral pressures on foundation and retaining walls due to seismicity, we recommend uniformly distributed pressures of 7H and 12H in pounds per square foot (rectangular distribution) to be applied to yielding and non-yielding walls, respectively. These pressures are in addition to the static pressures presented above. Backfill placed against walls should consist of granular structural fill. For these pressures to be valid, the structural fill must extend out from the base of the wall at an angle of at least 45 and 60 degrees from vertical for the active and passive cases, respectively. To calculate the resistance to sliding, a value of 0.42 should be used as the ultimate coefficient of friction between the footing and the underlying soil. A perforated rigid plastic or metal drain line installed behind the base of walls that extend below adjacent grade is recommended to prevent hydrostatic loading on the walls. The invert of a drain line around a below-grade building area or exterior retaining wall should be placed near foundation bearing level. The drain line should be sloped to provide positive gravity drainage or to a sump pit and pump. The drain line should be surrounded by clean, free-draining granular material having less than 5 percent passing the No.200 sieve.The free-draining aggregate should be encapsulated in a filter fabric. The granular fill should extend to within 2 feet of final grade, Responsive a Resourceful ■ Reliable 15