711 112TH ST SE 7 ELEVEN Geotech Report 2018-01-02 MF Import

d Subsurface Ecp7orntion and Proposed 7-Eleven Property Geotechnical Engineering Repaf Everett, War/iinRron Design Rccammendatfons II. DESIGN RECOMMENDATIONS SA INTRODUCTION Our exploration indicates that from a geotechnical standpoint, the parcels are suitable for thc proposed commercial buildings provided the recommendations discussed herein are properly� followed. Sincc the building areas arc underlain by uncontrolled fill material, including somc areas of compressible organic fill soil, excessive, long-tertn foundation settlement would bc exper,ted if conventional shallow footings were used. We recommend that the foundation IoaJs be extended through the fill material to bear inro the natural, firm sediment. The depth w thc bearing sediment (lodgemcnt till) for the proposed 7-Eleven building, represented by EP-1 and EP-2, was approximately 4 to 4�/: feet deep below the existing ground surface. Therefore, wc recommend either trenching along the footing lines to reach bearing soil or usin; piles or piers. The trenches may be backfilled with crushed quarry rock or controlled density fill (CDF) to transfer foundation loads to the bearing stratum, as described in the Foundation section of this report. According to the owner, the canopy foundations for the pump island arc required to be on thc order of 10 fcet deep to account for overmrning and lateral loads. We anticipate that drilled picr foundations will be used for support of the canopy. If desired, pier foundations could also support the 7-Eleven building. The Phase II office building may also bc supported on drilled piers or alternatively, small-di�meter, driven pipe piles. A slab-omgrade floor may eid�er be supported on rock- or CDF-filled trenches, as described above, or may be cast over the existing fill if the potential for some setdement-related cracking is tolerable. Further recommendations are presented in the section on Floor Suppon. 6.0 SITE PREPARr1T10N Si�e pmparation should include the removal of all trees, brush, debris, and any other dcleterious matcrial within the building and parking areas. Buried utilities that arc not a part of future plans and are under future building locations will need to be abandoned or relocated. Areas where loose, surficial soils exist due to grubbing operations should be considered as fill to the depth of disturbance and treated as subsequendy recommended for structural fill placement wl�ere they occur under slabs, sliallow foundation, or pavement. The on-site fill soils cont�in fine-grained material that makes them extremely moismre- sensitive and subject to dismrbance and erosion when wet. The contractor must use care h/nr�H l9. 200/ ASSOCIATED E1RTH SC1Eh'CES SFffnp - A"Ept91�41/ - U il4'P'�yrl� 0/ - I�'A' p�1gC 6�� `�y