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Report Main Office Branch Office P.O. Box 23814 4060 Hudson Ave., NE Tigard, Oregon 97281 Salem, OR 97301 Carlson Testing, Inc. Phone (503) 684 -3460 Phone (503) 589 -1252 FAX (503) 684-0954 FAX (503) 589 -1309 0 N qq0cf Xcz/nd ovember 16, 1998 CTI #97-G1155 �`" �f� SSI1 V 1 POD Harper Righellis, Inc. O� 1\G 5200 SW Macadam Ave. - Suite 580 C\ C� Portland, OR 97201 FINAL REPORT OF EARTHWORK OBSERVATION AND TESTING FILE COPY TIGARD WOODS SUBDIVISION Etici 9$ — oo %g TIGARD, OREGON Carlson Testing Inc. (CTI), has conducted on -call inspection services for the earthwork at the above residential development located on SW Landau Place & SW Landau Street in'Tigard, Oregon. This letter briefly summarizes our observations and testing during construction and the as -built soil conditions to the best of our knowledge. This letter also provides recommendations for foundation design and soil guidelines during construction of the single - family homes. SITE PREPARATION AND FILL PLACEMENT Based on our visual observations and our density test results no engineered fill was placed on any of the lots or the streets. Density tests were conducted on the storm and sewer trenches and the base course only. OBSERVATIONS From our observations and hand probing, the surface of the most lots are covered with approximately 18 to 24 inches of newer strippings, uncompacted material, and /or water softened soils that will require excavation prior to construction of foundations with the following exceptions: Lot 1 contains up to 4 feet of uncompacted material on it's surface. In addition, the utility trench along the east side of the lot appear to have been backfilled with on -site soils with no compactive effort and has settled nearly 10 inches. Approximately 3 feet of soft, old fill was encountered on Lot 5. A small stockpile of material was observed near the center of Lot 8. This pile should be removed prior to the foundation excavation. Lot 2 has an existing structure. HOUSE EXCAVATION GUIDELINES We anticipate foundation excavation depths to vary throughout the subdivision. The foundation excavation for Lot 1 is anticipated to range between 3 and 4 feet. In addition, the proposed foundation should have a minimum horizontal setback of 5 feet off the edge of the uncompacted trench. The foundation excavation for Lot 3 and 4 is anticipated to be 18 and 24 inches, respectively. Excavation depths ranging between 2 and 3 feet are expected on 5 through 8. We anticipate the deeper excavations (3 feet) will be necessary along the back side of the lots near the ravine. Some groundwater seepage and /or water flow should be anticipated. Perimeter footing drains may be required- -for Lots 5 through 8. CTI #97 -G 1 155 Tigard Woods Page 2 If excavated material is spread around the lot deeper than one foot and is expected to support appurtenant structures such as deck footings and sidewalks, it should be placed, compacted, and tested as engineered fill. The foundation excavations for Lots 5 through 8 .should be reviewed by a Geotechnical Engineer. FOUNDATIONS The proposed one- to two -story residential buildings will likely be founded on shallow spread footings bearing on competent native soils or engineered fill. Spread footing design and construction should generally conform to UBC Chapter 18 and /or Chapter 4 of the CABO One and Two Family Dwelling Code, except where we specifically recommend otherwise. For protection against frost heave we recommend that spread footings on nonexpansive soils have a minimum final embedment depth of 18 inches for exterior grades on level ground. The recommended minimum widths for continuous wall footings are tabulated below: Minimum Width for No. of Stories Continuous Footing (floors supported) (in) 1 -story 12 2 -story 15 As previously stated, the allowable bearing pressure can be taken as 1,500 Ib /ft for footings bearing on competent native subsoils or engineered fill. The recommended maximum load is 20 kips for column footings. For heavier column loads and masonry chimneys, a Soil Engineer should be consulted. The coefficient of friction between on -site soil and poured -in -place concrete may be taken as 0.35. The maximum anticipated total and differential footing movements are 1 inch and '/4 inch, respectively, over a span of 20 feet. If requested, CTI can provide inspection services to verify that suitable foundation subgrade is exposed prior to placement of concrete. II - I I . ' CTI #97 -G1155 Tigard Woods Page 3 CLOSING AND LIMITATIONS Our reports pertain to the materials tested /inspected only. This letter should be made available to each builder in the develo.ment• however information contained herein is not to be re.roduced exce.t in full without •rior authorization from this office. This letter should not be construed to relieve or lessen the responsibility of the contractor or owner's site representative for this site work, but is provided for the minimum required governmental assurance. Our support was given on an as- needed basis as requested. If conditions are encountered during foundation excavation which differ from this report, then the developer (Harper /Righellis) and CTI should be allowed to review the condition before corrective actions are taken. Corrective work performed by the builder without notifying the above parties will be interpreted as an acceptance of the conditions encountered. Respectfully submitted, CARLSON TESTING, INC. cig. ROFF 14743 -s7 "" OREGON � 9 0 ` ' e_ <F, �£S D. 10 L 3c. Brian D. L E.I. Engineering Associate James D. Imbrie, P.E. Principal Engineer Attachments: Summary report of in -place soil density tests cc: City of Tigard Bldg. Dept.