Loading...
Report (31) rCrAisJ GeoP ===1s Real-World Geotechnical Solutions Investigation• Design•Construction Support June 1, 2017 GeoPacific Project No. 14-3366 Biggi Construction, LLC 11605 SW Normandy Lane Wilsonville, OR 97070 Via email to: Vince Biggi (biggicon aC?.gmail.com) Subject: GEOTECHNICAL OBSERVATION OF FOUNDATION SUBGRADE OAK WOODS, LOT 1 (6920 SW LOCUST STREET) TIGARD, OREGON GeoPacific Engineering, Inc. (GeoPacific) performed a geotechnical engineering investigation of the site prior to development. We also conducted on-call testing and construction observation services during site development. This letter addresses the building pad subgrade for Lot 1 of the development. GeoPacific personnel visited the site on May 31, 2017 to observe footing subgrade soils. At the time of our visit, the foundation excavation was complete and extended 12 to 36 inches below the surroundinggrade. The foundation bearingsoils consisted of native silt soils, which were evaluated with a %2-inch steel soil probe. Probing efforts indicated very stiff consistency throughout the footing subgrade soils. The layout of Lot 1 is relatively flat; and the adjacent properties slope gently to the north. Wall and slope setbacks were not an issue. Based on observed conditions, the foundation soils are considered suitable for foundation support. Foundation subgrades as prepared are 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 1/2 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. 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 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. 14835 SW 72nd Avenue Tel(503)598-8445 Portland, Oregon 97224 Fax(503)941-9281 Oak Woods—Lot 1 GeoPacific Project No. 14-3366 We have prepared this report for Biggi Construction, LLC 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. \NE�RRoPes ' �0 IN6's. l©� 1477E 11/ � 'r OREGON :41.23 .1`) . EXPIRES:06/30/20a James D. lmbrie, G.E., C.E.G. Principal Engineer 2 GEOPACIFIC ENGINEERING, INC.