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Home My WebLink AboutObservation of ExcavationHrrwonrr¡-Pewrar GnorucrrNlc¿.r, INc. lv''f:ay 24, L994 5020 Road 154 Glenwood Springs, CO 81601 Fax 303 945-&454 Phone 303 94U7988 SCAIINED Subject D.M. Neuman Constn¡ction Attn: Rick Davis P.O. Box 2317 Glenwood Springs, Colorado 8L602 Job No. 194 250 Observation of Fxcavation, Proposed Guest House, 0284 Sunking Drive, Garfield County, Colorado. Gentlemen: As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the excavation at the subject site on May 13, L994 to evaluate the soils exposed for foundation support. The findings of our work and recommendations for the foundation design are presented in this report. The work was done in accordance with our agreement for geotechnical engineering services to D.M. Neuman Constn¡ction, dated May 12, 1994. The proposed guest house will consist of a 3 car garage with an upper level living area. The ground level will daylight from the hillside cut. Concrete walls and spread.footings sized for a maximum bearing pressure of 1,500 psf have been assumed for building support. At the time of our visit to the site, the foundation excavation had been cut in one level up to about 15 feet below the adjacent ground surface. The footings had been constructed. The soils exposed in the bottom of the excavation consisted mainly of stiff sandy clay. Results of swell-consolidation testing performed on sampies taken from the site, shown on Fig. 1, indicate the soils are slightly compressible under light loading. One of the samples showed a low expansion potential when wetted. No free water was encountered in the excavation and the soils were slightly moist to moist. Considering the conditions exposed in the excavation and the nature of the proposed constn¡ction, spread footings placed on the undisturbed natural soil designed for an allowable soil bearing pressure of 1,500 psf should be adequate for support of the proposed guest house. S/etting of the bearing soils could result in some post construction settlement or heave. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. Loose and disturbed soils at the foundation bearing level within the excavation should be removed to expose the undisturbed natural soils. Exterior footings should be provided with adequate soil cover above their bearing elevations for frost protection. Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 12 feet. Foundation walls acting as retaining structures should be deSigned to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 50 pcf for on-site soil backfill. A perimeter foundation drain should be provided to prevent temporary buildup of hydrostatic pressure behind the walls and prevent wetting of the D.M. Neuman Construction May 24, 1994 Page2 lower level. Structural fill placed within floor slab areas can consist of the on-site soils compacted to at least 957o of standard Proctor density at a moisture content near optimum. Bacldill placed around the strucnre should be compacted and the surface graded to prevent ponding within at least 10 feet of the building. 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 movement may be greater than indicated in this report because of possible variations in the subsurface conditions. In order to reveal the nature and 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 contained in this letter. If there are any questions or if we may be of further assistance, please let us know Sincerely HEPTVORTH - PAWLAK GEOTECHNICAL, INC. Steven L. Pawlak, P.E. SLP/ro Attachment H.P GEOTECH 0 2 3 è.e O .t') .J1 I,J.¡ú.o- =O(J 4 iI 10 z,O U) o-x L¡.l òs o v).J)lrl æ.ô-ãO(J 0 APPI_jEÐ PRESSURE - KSf APPLIEÐ PRESSURE - Ksf 1 I Mois¡ure Content = Ory Unit Weli¡nt ' Sample of: SAndy C I Ay From: $slfom of ExcavatiOno Southwest side 1E.7 percent 1AZ pcr lllr Compress ion Upon l.,letting \\l I llillil llll llt lllltlllttt lt IIII Morsrure Content . 15. 1 On7 Unrt Wergnl ' 107 Samoie of: Sandy ClAy From: Bottom of Excavation,st side percenl pci lrtilr l I llll iil IlI illliilliltiil r + Expansion Upon Wetting I ili aIIiI IIIII II HEPWOñTH.PAWLAK GEOTECHNICAL lnc.194 250 SWELL.CONSO LI DATION TEST R ESULTS Frg. I