7800 EVERGREEN WAY HYUNDAI Geotech Report 2025-04-28

• The building addition can be supported on conventional spread footings bearing on: (1) suitable undisturbed dense to very dense glacial till deposits, (2)structural fill extending to the dense glacial till deposits, or(3)at least 2 feet of structural fill. Footings supported on undisturbed dense to very dense glacial till deposits may be designed using a maximum allowable bearing pressure of 5,000 per square foot(psf). Footings supported on structural fill that extends down to undisturbed dense glacial deposits or is supported on at least 2 feet of compacted structural fill may be designed using a maximum allowable bearing pressure of 3,000 psf. The allowable bearing pressures may be increased by one-third for short duration loads such as wind or seismic events. • Imported gravel borrow should be used as structural fill under all building addition elements. • We recommend that perimeter footing drains be installed arolihi( ri re exterior of the building addition. The perimeter drains should be installed at the base of the l:;peter footings. • The building addition floor slab and at-grade paverm.rr areas lr, v be supported on existing soils provided that the upper 12 inches of exposed sub^r;irie is evaluate: )nd recompacted (if needed) to at least 95 percent of the maximum dry density (P;ii)D) per ASTM Inten, (ASTM) D 1557. • Earthwork should be performed in the typical dry 'ason (June through Septern';Ter)to reduce earthwork costs and to provide the best opportunity to reuse <)rrsite soils jai ring construe Our specific geotechnical recommendations are presented if i !i tollowing sections of this report. 4.1. Earthquake Engineering We evaluated the site for seismic hazards in. ding liquefaction, lateinii ',Dreading and fault rupture. Our evaluation indicates the site does not have liquc ible soils present and,therefore, also has little to no risk of liquefaction-induce.I „round distur _ince including I-itr:ral spreadin,;. There are no mapped faults in the immediate vicinity of the ,rt?, although the Southern Whidbey Island fault zone is mapped approximately 9 miles southwest of the site. fecaus, of the thickne_r of the Quaternary sediments below the site, which are commonly more than 1,00u feet thick, the potential Hr surface fault rupture is considered remote. 4.1.1.2018 IBC Seismic Design Information We recomrr d the use of the f,;Ilowing 2018 IBC parameters for Site Class,short period spectral response acceleration ( .;,), 1-second peria 1 pectral response acceleration (Si) and seismic coefficients (FA and Fv) for the project site is shown in Tak 1 for design. TABLE 1. IBC SEISM RAMET 2018 IBC Parameter Recommended Value Site Class C Short Period Spectral Response Acceleration,Ss(percent g) 134.3 1-Second Period Spectral Response Acceleration,Si(percent g) 47.6 Seismic Coefficient, FA 1.000 Seismic Coefficient, Fv 1.820 GEOENGINEERS December6,2021 Page 3 File No.24459-003-00