920 MILLWRIGHT LOOP S BASE FILE Geotech Report 2023-12-29

m The concrete mixture for the rigid inclusions should have a minimum compressive strength (to) at 28 days of 4,000 pounds per square inch (psi). Refer to ground improvement specifications that are Included In a separate design drawing submittal for Parcel A17 for additional detalls. m Rigid inclusions should be overlain by a 2-foot-Nick layer of crushed surfacing base course (CSBC) to act as a load transfer pad (LTP) between the foundation elements and the rigid inclusions (compacted in accordance with the geotechnical engineers recommendations). m The CSBC should comply with Washington State Department of Transportation (WSDOT) Standard Speed cation Section 9-03.9(3), Base Course, and restrict fines to maximum 5 percent passing Number 200sieve. 52.2. Pest-Impmeemeirt RecommeMMkms The rigid inclusion design layouts for Parcel A17 were developed using the same approach that was used for Parcels AS, Al2, and A7, that both using diameter of rigid inclusion column of 2 feet, a required area replacement ratio of 8 percent, and a minimum compressive strength of 4,000 psi. And based on our review of the structural loads and the proximity of the proposed buildings to the existing bulkhead, we believe that the ground improvement design calculations completed for Parcels AS, AU, and A7 will be also valid for Parcel A17. Therefore, without additional ground improvement calculations, the same recommendations for Parcels A8, Al2, and A7 regarding the post -improvement design bearing capacity, static and seismic settlements were also proposed for Parcel A37. G221. paslgn Rearing p awl y We recommend an allowable bearing rapacity of 3,000 Psf with a FOS of at least 2.0 and a modulus of subgrode reaction of 200 pounds per cubic inch (poll be used for the foundations bearing on the improved ground. G222. Stetic eM aNamlc Geltlemerrb We anticipated that the static settlement will be less than 1 Inch with the implementation of rigid Inclusion ground improvement, and the differential static settlements between building foundations should be less than °/s Inch over a horizontal distance of 50 feet. Similar to Parcels AS, Al2, and A7, we anticipate that the post -improved seismic settlements of A17 will be less than about 3 inches and the differential settlement should be less than about %inch over a horizontal distance of 50 feet. a.223. Btllrquakslnduced lateral around pabrmatlan The post -improvement earthquake -induced lateral ground deformation was estimated by pedormingglobal slope stability and Newmark analyses that include the improved area with an increased overall strength. With a design area replacement ratio of 8 percent and a compressive strength of 4,000 psi, the increased composite strength of the improved ground was estimated as 23 ksf for the improved area for use in the post -improvement global slope stability analyses. As shown in Figure 8, the FOS corresponding to the slip surfaces going underneath the potential building footprint is higher than 2.8, which indicates a stable post -earthquake condition after ground improvement. With a stable post -earthquake condition, the post -improvement earthquake -induced lateral spreading is mainly due to the deformations happening during earthquakes. GEGENGINEEaS 67 Dadter21) 20m o1 Pgemm