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Report /o51-)12(4 - 0219 f�,off. q721`1GeoP this gG( ��22Engineering,Inc. Real-World Geotechnical Solutions Investigation • Design • Construction Support January 7, 2019 GeoPacific Project No. 15-4010 Riverside Homes, LLC 17933 NW Evergreen Parkway, Suite 370 Beaverton, OR 97006 Via email to Wes Boisvert(wboisvert@riversidehome.com) Subject: GEOTECHNICAL OBSERVATION OF FOUNDATION SUBGRADE ELDERBERRY RIDGE SUBDIVISION—LOTS 36 & 37 TIGARD, OREGON Reference: Summary Report of Geotechnical Observation and Testing, Elderberry Ridge Subdivision - Lots 1-40, Tigard, Oregon. Report dated November 8, 2018 GeoPacific Engineering, Inc. (GeoPacific) conducted on-call density testing and construction observation services for the Elderberry Ridge Subdivision site. This letter addresses the footing subgrade conditions for Lot 36 (7643 SW Cornutt Lane) and Lot 37 (7679 SW Cornutt Lane). It is our understanding that the planned structure at each lot will consist of a single- family residence utilizing conventional spread footings. GeoPacific visited the site January 4, 2019 to observe the foundation subgrade conditions at Lots 36 and 37. At the time of our arrival, the excavations were complete and extended approximately 12 inches below the surrounding grade at each lot. The subgrade soils were covered with approximately 2-3 inches of gravel as a protective cover. The foundation bearing material at each lot consisted of engineered fill soil which was stiff to very stiff consistency when evaluated with a Humboldt hand probe. The layout of Lots 36 and 37, and the adjacent • properties, is relatively flat. Footing-to-wall and footing-to-slope setbacks do not appear to be an issue. Based on observed conditions, the footing subgrade soils are considered suitable for foundation support. The foundation subgrade as prepared is considered suitable to support the planned allowable bearing pressure of 1,500 psf. Estimated settlement under the allowable bearing pressure is 1 inch total, and Y2-inch differential, measured over a horizontal distance of 20 feet. 14835 SW 72nd Avenue Tel (503) 598-8445 Portland, Oregon 97224 Fax (503) 941-9281 Elderberry Ridge— Lots 36 & 37 GeoPacific Project No. 15-4010 Care should be taken to avoid saturation or disturbance of footing subgrade soils during and after excavation. If footing bearing soils become saturated or disturbed, any softened soil or slough should be removed and replaced with crushed aggregate or additional concrete. In general, footing excavations should be cleaned such that no more than approximately %2-inch of loose soils are present prior to pouring concrete. Construction should include typical measures for controlling subsurface water beneath the homes, including positive crawlspace drainage to an adequate low point drain exiting the foundation, visqueen covering the exposed ground in the crawlspace, and crawlspace ventilation (foundation vents). The homebuyers should be informed and educated that some slow flowing water in the crawlspaces is considered normal and not necessarily detrimental to the home given these other design elements are incorporated into its construction. Appropriate design professionals should be consulted regarding crawlspace ventilation, building material selection and mold prevention issues, which are outside GeoPacific's area of expertise. We have prepared this letter for Riverside Homes, and it should not be relied upon by third parties without consulting GeoPacific. Within the limitations of scope, schedule and budget, GeoPacific attempted to execute these services in accordance with generally accepted professional principles and practices in the fields of geotechnical engineering and engineering geology at the time the report was prepared. The conclusions and interpretations presented in this report should not be construed as a warranty of the subsurface conditions. No warranty, expressed or implied, is made. The scope of our work did not include flood hazard evaluations, environmental assessments, the presence or absence of wetlands; or potential hazardous substances in the soil, surface water, or groundwater at this site. We appreciate this opportunity to be of service. Sincerely, GEOPACIFIC ENGINEERING, INC. co PR c-:;(°‘ GSN 96i0 y14743PE OREGI "Nt.2340 EXPIRES:06/30/20/ James D. Imbrie, P.E., G.E., C.E.G. Principal Geotechnical Engineer 2 GEOPACIFIC ENGINEERING, INC.