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HomeMy WebLinkAboutObservation of Excavation 07.11.17H-PryKUMAR Geolechnlcãl Engineedng I Engineering Geology Materials Tesling I Environmental 5020 Coung Road 154 Glenwood $prings, CO 81601 Phone: {970} 945-7988 Far (970) 945.8454 Email: hpkglenwood@kumaruså.com July I l,2Ol7 Office Locations: Parker, Glenwood Springs, and Silverthome, Colorado Bruce Robinson 1548 County Road 137 Glenwood Springs, Colorado 81601 (ellican yonranch@ gnrai l.cpnr) Project No. l7-7-512 Subject:Observation of Excavation, Proposed Cabin Addition, 1548 County Road 137, Garf,reld County, Colorado Dear Mr, Robinson As requested, a representative of H-P/Kurnar observed the excavation at the subject site on July 7,2017 to evaluate the soils exposed for foundation support. The findings of our observations and recomrnendations for the foundation design are presented in this report. The services were performed in accordance with our agreement for professional engineering services to you, dated June 28, 2017, The existing cabin is one story log above a crawlspace. The addition will be one story log above a crawlspace and located on the south side (front) of the cabin. A spread footing imposing a maximum soil bearing pressure of 2,000 psf has been used for design. At the time of our visit to the site, the foundation excavation had been cut in one level from 272 to3Yz feet below the adjacent ground surface. The soils exposed in the bottom ofthe excavation consisted of sandy clny with scattered gravel and occasional cobbles. Results of swell- consolidation testing performed on a sample tahen from the site, shown on Figure l, indicate the soils are slightly to moderately compressible under conditions of loading and wetting. No free w¡¡ter was encountered in the excavation and the soils were slightly moist to moist. The excavation was compacted and firm. The top few inches of the existing footing was exposed in the excavation. Considering the conditions exposed in the excavation and the nature of the proposed construction, spread footings placed on the undisturbed natural soil designed for an allowable soil bearing pressure of2,000 psfshould be adequate can be used for support ofthe proposed :rddition, The exposed soils tend to compress when wetted and there could be some post- construction settlement of the foundation if the bearing soils become wet. Footings should be a minimum width of l6 inches for continsous walls and 2 feet for columns. Loose and disturbed soils in footing areas should be removed and the bearing level extended down to the undisturbed natural soils. Exterior footing.s should be provided with adequate soil cover above their bearing Bruce Robinson July I l,2Ol7 Page 2 elevations for frost protection. Continuous foundation walls should be reinforced top and bottom to spÂn local anomalies such as by assuming an unsupported length of at least 12 feet. Foundation walls acting as retaining structures should also be designed to resist a lateral eanh pressure based on an equivalcnt fluid unit weight of at least 50 pcf for on-site soil as backfill, A perimeter foundation drain should not be required provided the exterior backfill is properly placed and graded. Backfill placed around the structure should be compacted and the surf¡ce graded to prevent ponding within at least l0 feet of the building. Landscape that requires regular heavy irrigation, such as sod, and sprinkler heads should flot be located within l0 feet of the foundation. The recommendations submitted in this letter are based on our observation of the soils exposed within the foundation excavation and do not include subsurface exploration to evaluate the subsurface conditions within the loaded depth of foundation influence. This study is based on the assumption that soils beneath the footings have equal or better support than those exposed. The risk of foundation rnovement may be greater than indicated in this report because of possible variations in the subsurface condition,s. In order to reveal the nature ¿nd extent of variations in the subsurface conditions below the excavation, drilling would be required. It is possible the data obtained by subsurface exploration could change the recommendations contain€d in this letter. Our services do not include determining ihe presence, prevenlion or possibility of mold or other biological contaminants (MOBC) developing in the future. If the client is concerned about MOBC, then a professional in this special field of practice should be consulted. lfyou have any questions or need further assistance, please call ouroffice. Sincerely, H.P MAR Louis E. Eller, Staff Engineer Reviewed by: DanielE. Flardin, P LEE/kac attachment Figure I -Test Results cc: Kaup Engineerine: Attn: Dale H.Pt-KU¡VIAR Kaup (dulc @haupen gi0.Êerin g.cou) Proiect No. 17-7-512 Moisture Content * 16.5 percent Ðry Density = 91 pct Sample of; Sandy Silty Clay From: Bcttom of Excavation at Southwest Corner L- Compression JJpon wett¡ng \I \ \ û èS '-u, (tt o- Êo(J 1 2 3 4 5 ö 0t 1.0 10 100 APPIIÊD PRESSUFE -ksf 17-7-512 H-P\KUMAR SWE LL.CO NSOLI DATION TEST RESULTS Figure 'l