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Report psi aoJ5 - 00-2-C-C i7sw 8ELU & !F GeoPacific Engineering.Inc. Real-World Geotechnical Solutions Investigation• Design•Construction Support September 25, 2019 GeoPacific Project No. 15-4010 Riverside Homes, LLC 17933 NW Evergreen Parkway, Suite 370 Beaverton, OR 97006 Via email to Brett Groves (BGroves@riversidehome.com) and Amilian Avgi (AAvg i@ riversidehome.corn) Subject: GEOTECHNICAL OBSERVATION OF FOUNDATION SUBGRADE ELDERBERRY RIDGE SUBDIVISION—LOT 5 TIGARD,OREGON 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 5 of the development. It is our understanding that the planned structure will consist of a single-family residence utilizing conventional spread footings. GeoPacific personnel visited the site September 23rd and 24th, 2019 to observe subgrade preparation for the foundation excavation at Lot 5. The excavation depth was approximately 12- 18 inches below the surrounding grade. The foundation bearing soils consisted of engineered fill soils, which were evaluated with a Humboldt hand probe. Probing efforts indicated stiff to very stiff soils throughout the footing subgrade layout, with the exception of the south footing. Approximately 2-3 feet of unsuitable soils was removed from the south footing to expose stiff subgrade conditions. This area will need structural backfilling after the foundation is poured. Also, approximately one foot of additional unsuitable soil was removed from a small area within the south footing due to a previous stump removal. This small area at the middle of the south footing was backfilled with compacted granular fill. Density testing indicated the granular backfill was compacted to project specifications (95% of AASHTO T-99). The footing layout of Lot 5 and the adjacent lots is relatively flat. Footing-to-slope and footing-to-wall 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 %-inch differential, measured over a horizontal distance of 20 feet. 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. 14835 SW 72nd Avenue Tel (503)598-8445 Portland,Oregon 97224 Fax (503) 941-9281 Elderberry Ridge- Lot 5 GeoPacific Project No. 15-4010 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 crawispaces 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 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. ��� � PROI=essi �2 ,\GINE, g r i f 1474li pr . OREGON EXPIRES:06/30/20V James D. Imbrie, P.E., G.E., C.E.G. Principal Geotechnical Engineer 2 GEOPACIFIC ENGINEERING, INC. GeoPacific Engineering,Inc. Real-World Geotechnical Solutions 14835 SW 72nd Avenue Tel (503)598-8445 Investigation• Design•Construction Support Portland, Oregon 97224 Fax(503)941-9281 PROJECT MATERIAL DESCRIPTION DATE Elderberry Ridge %"-0 Crushed Aggregate September 24,2019 PROJECT NUMBER (Tigard Sand&Gravel) WEATHER 15-4010 Overcast,60s CLIENT NUCLEAR GAUGE SERIAL S CONTRACTOR Riverside 34418 Renner PERMIT NUMBER METHOD OF TEST PAGE S -- Troxier Gauge,AASHTO T-99 1 of 1 TEST ELEV FIELD FIELD DENSITY MAX DRY COMP COMP OPTIMUM PASS TEST LOCATION MOIST (PCF) DRY DENSITY SPEC RESULT MOISTURE LAB ID OR TYPE (FT) % WET (PCF) % % % FAIL SF Lot 5, —middle of south footing FG 6.1 132.7 125.1 124.7 95 100+ 11.9 P19-110 P SF Lot 5, —middle of south footing FG 5.2 131.3 124.8 124.7 95 100+ 11.9 P19-110 P TEST TYPE: LF=Lot Fill SF=Structural Fill ST=Sanitary Trench DT=Storm Trench WT=Water Trench RF=Roadway Fill RW=Retaining Wall Backfill PS=Pavement Subgrade BC=Base Course FT=Franchise Trench REMARKS: GeoPacific engineering technician was onsite to conduct density testing of backfill material following over-excavation of soft soils from the south footing of Lot 5. Approximately 2-3 feet of rock was placed. Test results met project specifications for compaction at the locations tested. TESTED BY: Eric Merritt REVIEWED BY: Information contained herein pertains to materials tested/inspected only. The fact that any particular work has been observed or tested does not waive the contractor's responsibility for the means and methods of construction,job site safety,or to comply with the contract documents. This information contained herein should be considered preliminary until review by the project engineer.