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HomeMy WebLinkAboutMiscellaneous Field Test & Inspection Report 2013-6-6 i ✓ • • ��3 �1 Gr Branch sk �� q ( E NGINEERING Since 1977 ,.3 doll • transportation June 6, 2013 (r/ structural •I geotechnical SURVEYING Mr. 'Tom Walter Walter Custom Homes 2863 Riverwalk Loop Eugene, Oregon 97401 RE: FOUNDATION INVESTIGATION Lot 33 FERNHILL CT-MTN.GATE SUBDIVISION SPRINGFIELD,OREGON Branch Engineering Inc Project No. 13-116 Pursuant to your request Branch Engineering, Inc. (BEI) has performed a geotechnical engineering foundation investigation for the planned single-family residence on Lot 33 of the Mountain Gate Subdivision on Fernhill Court in Springfield, Oregon. On May 15, 2013 a small trackhoe provided by Casey Jones Excavating dug three test pits within the building pad that was roughly staked on . the northeast facing slope. The residential lots on either side of the site have been developed. The purpose of our site investigation was to assess the subsurface conditions with respect to future foundation construction. The test pits were 3- to 4-feet deep and located in the front (south), northeast and northwest corners of the pad. The lot was moderately covered with trees and scrub brush. The soils present in the excavations were visually classified in accordance with the American Society of • Testing and Materials (ASTM) Method D-2488 and representative samples collected for Free Swell (IS 2720) testing. Field log summaries of the exploratory pit are shown below: Test Pit - 1 (south front) 0 - 14" Dark brown, soft, slightly moist silty clay topsoil with roots 14" - 36" Brown to gray, soft, moist, clay colluvium 36" - 48" Light brown, hard, dry claystone Test Pit - 2 (northeast corner) 0 - 18" Dark brown, soft, slightly moist silty clay topsoil with roots 18" - 36" Light brown, hard, dry claystone Test Pit - 3 (northwest corner) 0 - 18" Dark brown, soft, slightly moist silty clay topsoil with roots 18" - 40" Brown to gray, soft, moist, clay colluvium 40" - 48" Light brown, hard, dry claystone The topsoil and colluvial clay material are unsuitable for foundation bearing and are recommended to be removed from below footings. The claystone is hard and will provide an allowable bearing capacity of at least 2,000 psf. A sample of the claystone was collected, dried, pulverized, and tested for Free Swell with a result of 60%, which is moderate to high. The in-situ • i shrink/swell potential of the soil is less since it will not be in a pulverized condition under the footings. • EUGENE-SPRINGFIELD SALEM-KEIZER • 310 5'h Street,Springfield, OR 97477 I p: 541.746.0637 I www.branchengineering.com • • Lot 33 Mtn Gate (13-116) June 6, 2013 • l3ased on our test pit observations, the recommended depth of excavation below footings is 18- to 40-inches; additional excavation may be required in areas of tree removal. The allowable bearing capacity of the native claystone is 2,000 psf with a coefficient of friction of 0.3. A passive soil pressure of 200 pcf may be used for overlying colluviurns, not including the topsoil. The lateral active earth pressure is 38 pcf. There was no indication of gross land movement in the vicinity of the site and only slight soil creep in the upper 2- to 3-feet was evident by the minor "pistol-butting' of the trees. No Perimeter landscape tgradessshalll be sloped away recommend rom the foundation onaand aterrnotallowed lto pond adjacent to the foundation. Sincerely, Branch Engineering Inc, GcP PROpe`�S� /a c�9 6 0 OREGON VLo15,'04- J,DE# Ronald J. Derrick, P.E., G.E. Expires December 31, 2013 Principal Geotechnical Engineer • • 2 Branch Engineering, Inc.