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Home My WebLink AboutMiscellaneous Field Test & Inspection Report 2011-1-28 <& W SflClQtl - bU '(<67- &) sY ~evt ~;rJ.1-l ed K & A Engineering, Inc. .91051 S. Willamelte Street P. O. Box 8486, COburg, OR 97408 (541) 684-9399 Voice (541) 684-9358 FAX kaengineers.com engineering January 28, 2011 Project: WCH1003 Walter Custom Homes 2863 Riverwalk Loop Eugene, OR 97401 SUbject: Foundation pad construction Springfield .permit: 811-SPR201 0-00987 6154 Forest Ridge Dr., Springfield, Oregon PURPOSE AND SCOPE As requested, K & A Engineering, Inc. has inspected construction of the foundation pad for a new single-family residence at the subject project site. The purpose of our evaluation was to verify subsurface soil conditions, provide on-site recommendations during construction, and test the suitability ot constructed tills.' The scope of our services included several site visits during toundation pad construction, in-place density testing of fills, and this report. . FOUNDATION PAD General Subsurface Soil Conditions Soils observed during foundation pad construction agreed with our observations in the geotechnical report' and consisted of approximately 1.5 to 2.0-feet of dark brown, loose, organic silty topsoil over approximately 1.5 to 2.0-feet of tan, moist, soft to stiff, plastic clay; over tan/orange stained decomposed sandstone. Groundwater was not observed in the excavation which was as deep as 4-feet below the original ground surface. Road fill covered the foundation pad along the south side ofthe foundation pad. Consfruction Foundation pad construction involved stripping and removing from the site all organic silty topsoil, road fill, and soft plastic clay and grading a benched subgrade on dense decomposed sandstone (on the east half of the foundation pad) or on stiff tan clay (on the west half of the foundation pad). The depth of excavation ranged from approximately 2.5-feet on the north half to over 5-feet on the south side (where road fill was removed).. After grading the subgrade irito approximately 3 level benches (stepping up toward the south) on stiff or hard undisturbed native clay or sandstone, well-graded % " - 0 crushed aggregate was placed on the sub grade in lifts less than '12-inches and compacted using a vibratory steel drum roller. The depth of this granular fill ranged , This site was characterized in a level I geotechnical investigation and report made at the request of Walter Custom Homes for the project site, dated December 21, 2010. l' , K & A Engineering, Inc. trom approximately 1 to 2-teet. The till was tormed into approximately 4 to 5 level benches that stepped uphill . toward the south. We tested the in-place density ot the constructed granular till and have determined that the average dry density exceeds 95% ot maximum as determined by ASTM 0698. SUMMARY AND RECOMMENDATIONS General Suitability The toundation pad, as constructed, is suitable to support the proposed new single-tamily residence supported by a conventional cast-in-place concrete spread tooting toundation. We recommend acceptance of the foundation pad, as constructed, by the local building official. Foundation Support We recommend a design allowable bearing pressure ot 1.500-pounds per square toot and that the edge of footings be located behind the top edge ot benches a minimum distance equal to 4/3 of the bench height. Expansive Soils The stiff clay and decomposed sandstone subgrade has a moderate to high potential tor volume change with changes in water content. The toundation pad, as constructed, mitigates this hazard by placing the native subgrade a minimum ot 2.5-teet below the proposed tinal grade around the perimeter foundation. The hazard ot toundation heaving is low tor this toundalion pad. Drainage We recommend that a perimeter tooting drain be installed around the perimeter foundation the tooting drain consists ot a 3-inch minimum diameter perlorated drain pipe covered with at least 12-inches ot drain rock that is enveloped in a separation geotextile. We recommend that the perlorated drainpipe be placed as low as possible, preterably near the subgrade. We also recommend that a low-point crawlspace drain be installed near the north perimeter foundation to ensure that any groundwater that may develop trom seeps or springs or trom water not intercepted by the perimeter drain effectively drained. The crawlspace drain inlet should be located at the base ot the granular till (at the subgrade elevation) with the granular till sloped away trom the drain inlet to avoid soil or gravels tailing into the drain.' A grate should be installed over the inlet. All tooting drains low point crawlspace drain should be routed to a suitable storm drain disposal point, downhill ot the foundation. SPECIFICATIONS Foundation Drain Perlorated drainpipe should consist rigid schedule 40 PVC or ADS 3000 Triple Wall or an equivalent rigid pipe. The perlorations should be placed down. The foundation drain should NOT be connected to the root drain unless the connection is made downhill ot the foundation utilizing a backtlow prevention device that prohibits root drainage trom backing up into the toundation drain system. Project WCH1 003 6154 Forest Ridge Dr., Eugene, OR Client Walter Custom Homes Page 2 of 3 . January 28, 2011 K & A Engineering, Inc. Drain Rock Drain rock should consist of clean, durable, 1 %-inch (maximum) angular or rounded washed rock. The rock should be placed over and to the side of the perforated pipe so that the pipe has a minimum of 12-inches of cover. The drain rock should be covered with separation geotextile . Separation Geotextile Separation geotextile should be placed on the grade (at footing level) prior to placement of the perforated pipe so that after the pipe is laid and drain rock place, the geotextile can completely wrap around the drain rock. Separation geotextile shall consist of a polypropylene non-woven needle-punched fabric that is stabilized against degradation from ultraviolet light exposure (sunlight). The fabric should have a maximum apparent opening size (ADS) of 0.212 mm (US Std. Sieve 70). LIMITATIONS OF THIS REPORT This report has been prepared for the exclusive use of Walter Custom Homes and its design consultants or subcontractors for the subject proposed structure. This geotechnical investigation, analysis, and recommendations meet the standards of care of competent geotechnical engineers providing similar services at the time these services were provided. We do not warrant or guarantee these recommendations, site surface, or subsurface conditions. Exploration test holes indicate soil conditions only at specific locations (i.e. the test hole locations) to the depths penetrated. They do not necessarily reflect soil/rock materials or groundwater conditions that exist between or beyond exploration locations or limits. The scope of our services does not include construction safety precautions, techniques, sequences, or procedures, except as specifically recommended in this report. Our services should not be interpreted as an environmental assessment of site conditions. . Thank you for the opportunity to be of service. Please call us if you have questions or need further assistance. Sincerely, EXPIRES 12/31/2012 Michael Remboldt, P.E., G.E. K & A Engineering, Inc. Project: WCH1003 6154 Forest Ridge Dr., Eugene, OR Client: Walter Custom Homes Page 3 of 3 January 28, 2011 ,.. . . ' Density of Soil and Soil-Aggregates In-Place ASTM 02922 and 03017 Project: WCH1003 Site Address: 6154 Forest Ridge Drive Permit No: 811-SPR2010-00987 Date: Jan. 20,2011 . Density Test Type ': DT-8" Operator: CCD MalerialType: 3/4" minus, dense graded crushed agQ., Delta S&G Maximum Dry Densliy, pel 125.0 Standardization and Reference Check ~ Density I It Moisture, I (Standard Deviations) (S.D.) 0.4 (S.D:) 0.35 Moist Dry Density, Density, Water Compaction, . Test No. pet pel Content, % % Remarks 1 130.9 121.4 7.8 97.1% 2 1421 131.7 7.9 105.4% 3 144.5 133.4 8.3 .106.7% 4 138.4 129.0 7.3 103.2% 5 130.9 121.7 7.6 97.4% 6 140.6 129.3 8.7 103.4% . . . " Average: Std. Dev.: 102.2% 4.05% 1 Direct Transmission (DT) (specify depth, in.) or Air Gap Backscatter (AGB) (specifiy(T)ouchable or (U)ntouchable mode . Test pertormed using Seaman Nuclear Corp model C-300, SN 21113 Client: Thomas Walter Custom Homes Project: WCH1003 K & A Engineering, Inc. 1/25/2011