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Report Nov. 9. 2006 12:38PM i- Asrzoo -ooh -4j3 /COW r, ■ 1122) SW IIST' GeoP die fniinecring, Inc. Real -World Geotechnical Solutions Investigation • Design • Construction Support January 26, 2005 Job No. 04 -9001 Pays Custom Homes, Inc. 17481 SW Hoodoo Ct'. Beaverton, OR 97007 Fax 503 -214 -8500 RE: SOIL ENGINEER'S SUMMARY AT CONCLUSION OF EARTHWORK FEHRENBACHER SUBDIVISION CITY OF TIGARD, OREGON GeoPacific Engineering, inc. recently completed on -call testing and construction observation services for the above - referenced residential subdivision during the development construction portion of the project. The purpose of this report is to provide a summary of the information generated from our services and to make general conclusions regarding the suitability of the site for single - family home development. This report does not supersede any actual soil observations made during single - family home construction. SITE PREPARATION AND FILL PLACEMENT Based on our site observations during construction, no engineered fill was placed on the lots, BUILDING EXCAVATION AND RECOMMENDED ENGINEERING REVIEW No more than one foot of uncompacted fill should have been placed on level areas. Based on hand probing, we anticipate 12 to 24 inches of excavation will be required to reach bearing soils. Foundation excavations should be carried through any rain - softened fill or loosely compacted excess soils placed over the surface of the lots, and any soft or organic native soils. For foundation excavations performed during the wet weather season, we expect that additional excavation of 6 inches and placement of a thin layer of compacted rock fill will likely be necessary for improved spread foundation support and protection of the subgrade. FOUNDATIONS No geotechnical investigation has been performed on the lots and the site has been previously developed. One area of buried debris was removed within the street; however shallow, conventional isolated or continuous spread footings will likely be appropriate to support the proposed structures, provided they are founded on competent native soils. We recommend a maximum allowable bearing pressure of 1,500 pounds per square foot (psf) for designing the footings. A maximum column load of 30 kips is recommended, subject to a geotechnical engineers review. For heavier loads or any masonry walls or chimneys, the geotechnical engineer should be consulted. The recommended maximum allowable bearing pressure may be increased by 1/3 for short -term transient conditions such as wind and seismic loading. All footings should be founded at least 12 inches below the lowest adjacent finished grade. Minimum footing widths should be determined by the project engineer /architect in accordance with applicable design codes. We recommend minimum footing reinforcement of two No. 4 bars in the footing and one in the stem wall. 7312 SW Durham Road Tel (503) 598 -8445 Portland, Oregon 97224 Fax (503) 598 -8705 ► Nov. 9. 2006 12:38PM No. lbtlU r. 1 Project No. 04-9001 Fehrenbacher Subdivision Assuming construction is accomplished as recommended herein, and for the foundation loads anticipated, we estimate total settlement of spread foundations of less than about 1 inch and differential settlement between two adjacent load - bearing components supported on competent soil of less than about /.;inch. We anticipate that the majority of the estimated settlement will occur during construction, a$ loads are applied. Wind, earthquakes, a I nd unbalanced earth loads will subject the proposed structure to lateral forces. Lateral forces on a structure will be resisted by a combination of sliding resistance of its base or footing on the underlying soil and passive earth pressure against the buried portions of the structure. For use in design, a coefficient of friction of 0.35 may be assumed along the interface between the base of the footing and subgrade soils. Passive earth pressure for buried portions of structures may be calculated using an equivalent fluid weight of 400 pounds per cubic foot (pcf), assuming footings are cast against dense, natural soils or engineered fill. The recommended coefficient of friction and passive earth pressure values do not include a safety factor, The upper one foot of soil should be neglected in passive pressure computations unless it is protected by pavement or slabs on grade. All footing excavations should be trimmed neat and the bottom of the excavation should be carefully prepared. Loose or softened soil should be removed from the footing excavation prior to placing reinforcing steel bars. Excavations near structural footings should not extend within a 1H:1V plane projected downward from the bottom edge of footings. If footing excavations are open during the winter season or periods of wet weather, it may be helpful to provide a layer of brushed aggregate to help preserve the subgrade until the footings are cast. Crushed aggregate should consist of 1'/2" — 0 crushed aggregate per the Oregon Department of Transportation (ODOT) Standard Specifications. ROADS, UTILITY TRENCHES GeoPacific performed periodic testing of roadway fill and trench backfills during placement of the water line, and sanitary sewer. Density test results generally indicate that backfill and base rock tested were compacted in accordance with our recommendations and county standards (See the attached Summary of Field Soil Density Tests). Asphaltic concrete density tests are also attached. Page 2 • Nov. 9. 2006 12:38PM No /btlH V. j Project No. 04-9001 • Fehrenbacher SubdiYision CLOSING AND LIMITATIONS Our reports pertain tq the materials and locations tested /inspected only. This letter should be made available to each hojsebuilder in the development. This letter should not be construed to relieve or lessen the responsibility of the earthwork contractor or owner for site work, but is provided to meet the minimum requir d governmental assurance in accordance with local engineering standards of practice. Our semis were provided on an as- requested basis. If conditions are encountered during foundation e6ccavation, which differ from this report, then the developer, the earthwork contractor, and GeoPacific should be allowed to review the condition before corrective action is taken. Corrective work performed by the builder without notification of the above parties will be considered as an acceptance of the conditions encountered. It is the housebuilder's responsibility to educate homeowners for reasonable expectations on foundation performance and standard levels of acceptable concrete cracking and crawispace drainage. Sincerely, GeoPacific Engineering, Inc. � PR0p *GIMEe cib` �"? i p )* ' 147143 -1 /. /� OREGO '� Et1 J ix James D. Imbrie, P.E., C.E.G. Geotechnical Engineer Attachments: Site Plan Field Soil Inspection Summary Summary of Field Soil Density Tests Summary of Field Asphaltic Concrete Density Tests cc: AEI Community Development Washington County Revcon Page 3