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Home My WebLink AboutObservation of Excavation 11.12.2012;; :, i.' ll irl:, , .:,,:, ,|li,.,,.i-:- .i,. i i f. l r1,Vi )l.l i i. ¡ . i-'/¡\\rill,r\ Ìi i:; l: i-)'i'i: { l ii.,i i'. ¡ll íi,trlr.i'',,l,,, ' l ,'ni i.. 'il,,t.,.i !i,t-,rrr_rr. j., :',, ''-i.., ; ,,iì...,', ,i'r'r,,,i.lr rì,lr,,i November 12,2012 Down to Earth Landscapingand Construction Attn: Pat Seubert P. O. Box 680 Basalt, Colorado 81621 G¡l s ú¡lelqlutosrul¡Es.ça.rn) Job No, 112 4l3A Subject: Obsel'vation of Excavation, Proposed Shop Building, Lot 5 Hawkriclgc, 5 Red Wing Lane, Garf,reld County, Colorado Dear Pat: As requested, a representative of Hepworlh-Pawlak Geotechnical, Inc. observed theexcavation at the subject site on Novemb er 7,2012 to evaluate the soils exposed for foundation suppoft. The findings of our observations and recorrunendations for thEfoundation design are presented in this repoú. The services were perforrned in accordance with our agreemeut firr professional engineering serviôes to Down to Earth Landscaping and Construction, datecl November 6,-2012. The shop building will be located north of tlie existing residence and west of the existing gârage at the site. The building will be a single story steel û'ame and metal structure with a slab-on-grade floor- The structure has been designecl to be supported on spreacl footings assuming an allowable soil bearing pressure of 2,000 psfì An existing slab will be used aspart of the floor slab for tl-re building. At the time of our site visit, tlie foundation excavation which was essentially cornplete had been cut in one level about 3 feet below the adjacent ground surface. The soils exposed in the bottom of the excavation consistecl of stiff, sandy silty clay with scatterecl gravel and srnall cobbles. The soils were calcareous. Results of swcll-consoliclation testing performed on samples taken fi'om the site, shown on Figure l, indicate the soils are slightly to moderately cotnpressible under conclitions of loacting and wetting. The sample showed a minor swell potential when wetted under a constant 1,000 psflurcharge. No fi'ee water was encountered in the excavation and the soils were slightly inoist. Considering the conditions exposed in the excavation and the nature of the proposecl construction, spread footings placed on the unciisturbed natural soil clesigneà fot. un allowable bearing pl'essul'e of 2,000 psf can be used for support of the proposecl buildi¡g. The exposed soils may tend to expand or colnpress solne *ñ"n wetted and there could be some post-construction movetnent of the fbunclation if the bearing soils become wet. Precautions should be taken to prevent wetting of the bearing soils. i',,¡i,' j.ll ,.il,lr,, : i,,l,rlliirr'.i,¡,,,.,1. ri.,i,11,,,,, .,i.,,t.!1,,¡:,, r.-r 1i,., trì.rr Down to Earth Landscaping and Construction November 12,201? Page 2 Footings should be a minimurn width of 18 inches for continuous walls and 2 feet for columns. The minor swell potential encountered in the sample tested can be disregarded in the foundation design. Loose and disturbed soils in footing areas should be removed and the bearing level extended down to the undisturbed natural soils, and the subgrade compacted. The bearing soils should be protected against fiost and concrete should ¡ot be placed on frozen 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 spân local anomalies such as by assuming an unsupported length of at least 12 feet. A perirneter foundation drain around the "slab-át-grade,' building should not be needed. Structural fill placed within floor slab a.eas ian consist of the on-site soils compacted to at least 95Yo of standarcl Proctor density (SPD) at a moisture content near optimurn. There could be some differential movement between the existing slab and new floor areas especially if the subgrade becomes wetted which should be considered in the design. Backfill placed around the structure should be compacted to at least 90% SPD and the surflace graded to prevent ponding within at least tO feèt ofthe building. Landscape that requires regular heavy irrigation,ìuch as sod, and sprinkler heads should not be located within 5 feet of the foundation. The recommendations submitted in this letter are based on our obseryation 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 suppott than those exposed. The risk of foundation movement may be greater than indicated in this report because ofpossible variations in the subsurface conditions. In otder to reveal the nature and extent of variations in the subsurface conditions below the excavation, drilling would be requirecl. It is possible the data obtained by subsurface exploration could change the recommendations contained in this letter. Our serices do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developing in the fi¡ture. If the client is concerned about MOBC, then a professional in this special field of practice shoulcl be consulted. If you have any questions or neecl ñrrther assistance, please call our office. Sincerely, HEPWORTH _ PAWLAK CAL, INC David A. Young, P DAY/ljg attaclllent Figure 1, Jolr No. 112 413A n Test Results eåFtecn Moisture Content = Dry Density = -200= 17.4 105 88 Sample of Sandy Silty Ctay From: Bottom of Excar,ation percent pcÍ percent 1 rôo\ 2o a)z fLX UJ Izo U)Ø [rJEfLEoO 0 2 ù 4 5 10 APPL¡ËD PHES$URE ( ksf ) 0.1 1.0 100 112 413A SWELL-CONSOLI DATION TEST RESUTTS FIGURE 1