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HomeMy WebLinkAboutBuilding Miscellaneous 2014-4-23 (Branch April 23, 2014 E'NtINEERING= Since 1977 • Mr.Rick Proden civil • transportation Proden Homes structural • geot ethnical 3287 North 16th Street S U R V E Y I N G Springfield, Oregon 97477 ]//� RE: SUBGRADE EVALUATION A i / 804- 572S E WAY SPRINGFIELD,OREGON TV " BRANCH ENGINEERING INC PROJECT NO.14-098 FIELD PERSONNEL: MATTHEW RENNER P.E April 18, 2014: A Branch Engineering, Inc. (BEI) geotechnical representative visited the above referenced site to observe the building pad excavation, assess the shrink/swell potential of the subgrade soil and the suitability for placement of fill for the construction of a level building pad. The site is situated below adjacent lots to the west on an east facing hillside. At the time of the visit the topsoil had been removed across the majority of the building pad and the subgrade soil was exposed. The subgrade soil consists of brown silty clay overlying decomposed alluvial terrace deposits. The subgrade was probed with a steel hand probe and found to be consistently stiff across the building pad. The subgrade material was identified as suitable for the placement of compacted crushed rock aggregate fill and has a low shrink/swell potential. April 21, 2014: A BEl geotechnical representative returned to the site to document the placement of compacted crushed rock aggregate fill and perform compaction testing with a nuclear densometer (ASTM D-6938). The completed building pad consists of two level tiers with upper tier on the western portion of the site sitting approximately 30- inches in height above the lower eastern tier. Fill thickness increases from west to east on the building pad tiers and varies from approximately 4- inches along the western boundaries, up to 24- inches along the eastern boundary of the upper tier, and about 12- inches along the eastern boundary of the lower tier. Field compaction tests were conducted along portions of the pad containing fill in excess of 12- inches in thickness, using a nuclear densometer. An AASHTO T-180 Proctor curve (modified Proctor) was used to evaluate relative compaction. 90% relative compaction of a modified Proctor curve is required for a passing test, results are listed below. Moisture Dry Density Content Relative Location (pcf) (%) Compaction(%) Lower tier,eastern side 128.6 5.0 95 Upper tier,eastern side 125.9 5.9 93 Table-1: Compaction Test Results The building pad is suitable for a conventional perimeter-style foundation, and an allowable soil bearing capacity of 1,500 psf. We recommend that the foundation perimeter be backfilled and graded to slope away from the structure as soon as concrete curing allows. Differential settlements are expected to be less than 1/2-inch over a span of 20 feet. Footing drains are recommended as the subject lot lies below adjacent lots to the west and may receive runoff. Surface drainage shall be conveyed to a suitable disposal area, and final perimeter landscape grades shall slope away from the foundation and surface water not be allowed to pond adjacent to the foundation. EUGENE-SPRINGFIELD SALEM-KEIZER 310 5°^Street,Springfield,OR 97477 I p: 541.746.0637 I www.branchengineering.com 14-098 5725 Peridot Way April 23, 2014 Sincerely, Branch Engineering Inc, '\�0 PRO - c, G1NE.e / •� #16,170��►�- OREGON b 'rep MCP% �\Li EXPIRES: DECEMBER 31, 2015 Ronald J. Derrick, P.E., G.E. Principal Geotechnical Engineer • Branch Engineering,Inc.