3000 41ST ST Geotech Report 2025-12-31

PNW Home Builders, LLC ES-2598.03 May 2, 2013 Page 4 DISCUSSION AND RECOMMENDATIONS General In our opinion, construction of the residential buildings at this site is feasible from a geotechnical. standpoint. The primary geotechnical considerations associated with the proposed development include foundation support, slab-on-grade subgrade support, seismic design, and mitigation of consolidation and post-construction settlements. The proposed residential buildings should be supported on a conventional foundation system underlain by at least two feet of structural fill following the successful completion of a surcharge or preload program. Slab-on-grade areas should be supported on a suitable capillary break underlain by at least one foot of structural fill. This report provides recommendations for settlement mitigation, grading, foundation preparation, drainage, pavement sections, and other project-specific geotechnical recommendations. This study has been prepared for the exclusive use of PNW Home Builders, LLC and their representatives. No warranty, expressed or implied, is made. This study has been prepared in. a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Settlement:Considerations. As reported on the exploration logs, the subsurface conditions are generally characterized by 11 to 20 feet of fill overlying younger alluvium deposits consisting of silts, sands, and organic silts and peat. Due to the highly compressible nature of the younger alluvium deposits, consolidation settlement is to be expected with any site improvements, including foundations, retaining walls, utility trenches, and other necessary elements. The referenced geotechnical report indicates settlement estimates of 4 to 12 inches based on two to four feet of anticipated fill. Based on our review of the attached boring logs, we are in agreement with this estimate. Fills in excess of four feet will increase the magnitude of the anticipated settlement. Long-term secondary settlement estimates are in the range of one to two inches over a period of 50 years. Mitigation of consolidation settlement should be incorporated into design considerations. The use of a successful preload or surcharge program, as indicated in the following section, can reduce the anticipated post construction settlement to acceptable ranges. Surcharge and Preload Programs Depending on the required fill amounts to achieve final grades, either a surcharge or preload program should be incorporated in the foundation design. As stated previously, we anticipate fills on the order of six to seven feet will be needed to achieve finish grades; Due to the abundance of fill material and the presence of loose and moist to wet younger alluvium deposits reported at the site, it is our opinion that a surcharge and preload program be implemented as applicable by observing the following guidelines. Earth Solutions NW,LLC