1004 BROADWAY EVCC STUDENT HOUSING - PUBLIC WORKS 2017-01-13

Geotechnical Report - Revised Proposed Apartments; ] 002, 1006, and 1008 Broadway Street, Everett, Washington May 12, 2015 liquefaction are typically cohesiontess, predominately silt and sand sized, must be loose, and be below the groundwater table. The site is predominantly underlain by very dense silty sand with gravel without a defined groundwater tablc. Based on these conditions, in our opinion the liquefaction potential of the site is negligible and design considerations related to soil liquefaction are not necessary for this project. 4.2 BUII.DING FOUNDATIONS Based on the subsurface conditions encountered at the site and our understanding of tlie planned development, it is our opinion the proposed building may be supported on conventional spread and continuous footings. The foatings should bear on the dense to very dense, undisturbed native soil underlying the site, or on properly compacted structural fill placed on undisturbed native soil. Exterior foundation elements should be placed at a minimum depth of 18 inches below final extei•ior grade. Interior spread foundations should be placed at a minimum depth of 12 inches below the top of concrete slabs. We c•ecommend that a maximurn allowablc soil bearing pressure of 4,OU0 pounds per syuare foot (ps fl be used for sizing %undation elements bearing on dense to very dense native soil, or on structural fill. PanGEO should be retained to determinc the adequacy of footing subgrade during construction. The recommended allowable soil bea�ting pressure is for dead plus live loads. Por allowable stress design, the recommended bearing pressure may be increased by one- third for transient loading, sucll as wind or seismic fot•ces. Continuous arid individual spread footings should have minimum widths of 18 and 24 inches, respectively. Footings designed and constructed in accordanee with the above recoinmendations should expei•ience total settlement of less than one inch aild diffei•ential settlement of less than %z inch. Most of the anticipated settlement should occur during construction as dead loads are applied. 4.2.1 Lateral Resistance Lateral loads on the structure may be resisted by passive earth pressure deveioped againsT tlie embedded portion of` the foundation syste�n and by fi'ictional resistance between the bottorn of the foundation and the supporting subgrade soils. For footings bearing on thc dense to very dense silty sand, a fi•ictional coefficient of 0.35 may be used to evaluate IS-O44 IQ03 C3roadway, Rcviseci 1�8�TE', �7 P311iiE�, II1C.