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HomeMy WebLinkAboutBuilding Correspondence 2013-6-11 Branch ENGINEERING . Since 1977 ,tune 11, 2013 civil • transportation structural geotechnical Mr. Derrick Westover S U R V E Y I N G' r' Bruce Wiecherl Custom Homes, Inc. 31)73 Skyview Lane Eugene, Oregon 97405 RE: BUILDING PAD SUBGIADEEVALUATION Sd( f Lppzo13-©0078 6132 GI4AYSTONI3 LOOP Cl LOT 78 MOUNTAIN GATE WEST SUBDIVISION(PHASE IV) SPRINGFIELD, OREGON BRANCII ENGINEERING INC PROJECT NO. 13-017 A geotechnical engineer visited the above referenced site on June 5, 2013 to observe the building pad excavation and assess the shrink/swell potential of the subgrade soil, and determine the bearing capacity of the final building pad grade for construction of a single-family residence. The flat, cut/fill pad has been scraped of vegetation exposing a hard miscellaneous stone fill subgrade. The pad was leveled by covering the subgrade with 2- to 3-inches of 3/4"-0 crushed aggregate. Testing of the subgrade soil indicated a low shrink/swell potential (IS 2720 result of <5%). The April 5, 200.4 by 13oire Associates Inc. indicates that Lot 78 is in a hard rock cut area as confirmed by our observations, with the exception of the south half fill of up to 4-feet in thickness. The slope stability of the lot is good and no other geologic/geotechnical factors will impede site development as planned. The subgrade is suitable for a conventional perimeter-style foundation, and an allowable soil bearing capacity of 2,000 psi'. 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 I/4-inch over a span of 20 feet. Footing drains are not required as the subject and adjacent lots area relatively flat. Surface drainage shall be conveyed to a suitable disposal area, and final perimeter landscape grades shall slope away I'roni the foundation and surface water not be allowed to pond adjacent to the foundation. Sincerely, Branch (Engineering Inc, - r' 6, 70 //,/ r� OREGON •9p�D Jck.0G� Ronald J. Derrick, P.E., G.E. Expires 12/31/2013 Principal Geotechnical Engineer EUGENE-SPRINGFIELD SALEM-KEIZER 310 S^ Street, Springfield, OR 97477 I p: 541.746.0637 www.branchengineering.com