6202 ASSOCIATED BLVD Geotech Report 2022-10-25

Proposed Everett Warehouse Project No. 2152.01 March 5, 2019 encountered in borings B-1 through B-3, we estimate total foundation settlements on the order of 1 inch with differential settlements of about % inch in 40 feet. As discussed above, much of the soil encountered within our explorations is opined to be undocumented fill soils. Undocumented fill by nature can be highly variable and could vary greatly between exploration locations. Without completely removing the fill, or supporting the building on deep foundations that extend through the fill, there is a risk that compressible fill or unsuitable material buried within the fill could result in unanticipated building settlements. However, based on the composition and density of the fill observed in our borings and test pits, the risk of unanticipated settlement appears to be low. Our conclusion regarding risk associated with undocumented fill soils is not a guarantee or warranty that unanticipated settlement will not occur. Lateral Earth Pressures on Permanent Foundation Walls We expect the building will included backfill permanent foundation retaining walls. The lateral soil pressures acting on backfilled retaining walls will depend on the nature and density of the soil behind the wall, and the ability of the wall to yield in response to the earth loads. Yielding walls (i.e. walls that are free to translate or rotate) that are able to displace laterally at least 0.001H, where H is the height of the wall, may be designed for active earth pressures. Non -yielding walls (i.e. walls that are not free to translate or rotate) should be designed for at -rest earth pressures. Non -yielding walls include walls that are braced to another wall or structure, and wall corners. The 2015 IBC requires retaining walls be designed for dynamic seismic lateral earth pressures for sites with Seismic Design Categories D through F. Per the USGS, this site is Seismic Design Category D. Per the 2015 IBC, seismic lateral earth pressures need only be applied to walls with an exposed height of more than 6 feet. Our recommended lateral earth pressures are provided graphically in Figure 2. The lateral earth pressures recommended in Figure 2 are based on the assumption of no buildup of hydrostatic pressure behind the wall. Backfilled retaining walls should include a permanent drainage system to prevent the buildup of hydrostatic pressures. See the Permanent Drainage Measures section below for additional recommendations. Stormwater Detention Vault Current plans indicate an underground detention vault will be constructed in the northeast portion of the site. The lateral earth pressures provided in Figure 2 may be used for design of the vault. For bearing pressure and lateral resistance values, information provided above in the Building Foundations section of this report may be used. Footings for the building may impose a surcharge on the vault walls. If possible, we recommend building footings near the vault be planned such that they do not impose a surcharge on the vault walls by locating them in such a manner that a 1H:1V line projected from the bottom edge of a footing does not intersect Page 13