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Report (30) _vo D055 1 soz.Z ,5t-t) L%( . GeoP*1110 1110 ngifleCttflg.Inc. Real-World Geotechnical Solutions Investigation•Design• Construction Support February 20, 2017 Project No. 15-3808 JT Roth Construction, Inc. do Mr. Tim Roth 12600 SW 72nd Avenue, Suite 200 Portland, Oregon 97223 Via email to: timr ,"trothinc.cQm Subject: GEOTECHNICAL OBSERVATION OF FOUNDATION EXCAVATION CORBIN ESTATES—LOT 0 TIGARD, OREGON GeoPacific Engineering, Inc. (GeoPacific) conducted on-call easesthe building pad subgrade for ing and construction observation services for the Corbin Estates development. This letter a Lot 10. It is our understanding that the planned structure at Lot 10 will consist of a single-family residence utilizing conventional spread footings. GeoPacific visited the site February 17, 2017 to observe the subgrade soils following the foundation excavation for Lot 10. At the time of our site visit, the excavation was complete and The foundation bearing soils consisted of extended 12 to 36 inches below the surrounding grade e by native silt soils, and engineered fill soils which were observed and dennd testetlnd Gated acific during mass grading of the site. Probing efforts with a 2 layout of Lot 10 slopes gently downward to the east, and the footing layout in the subgrade several steps.eFooting-to wall and footing-to-slope setbacks were not the footing includes an issue. Based on observed conditions, the footing subgrade soils earree con sidere support the planned d suitable for allowable bearing pressure of 1,500 pon support. The foundation subgrade asprepared t Estimated settlement under the allowable bearing pressure is 1 inch total, and %2-inch differential, measured over a horizontal distance of 20 feet. e soils g Care should be taken to avoid saturation or disturbance off footing any sof ened soil ran and after excavation. If footing bearing soils become saturated ate or additional concrete. In general, should be removed and replaced with crushed aggregate approximately 'e.inch of loose footing excavations should be cleaned such that no more than app Y soils are present prior to pouring concrete. Tel (503)598-8445 14835 SW 72nd Avenue Fax(503)941-9281 Portland, Oregon 97224 Corbin Estates-Lot 10 GeoPacific Project No. 15-3808 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 report for J.T. Roth Construction, 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. PROpp c 3 0GINFFgs' 14743PE ' OREGON SEs D.c EXPIRES:06/30/2011 James D. lmbrie, P.E., G.E., C.E.G. Principal Geotechnical Engineer 15-3808,Corbin Estates—Lot 10 2 GEOPACIFIC ENGINEERING, INC.