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Home My WebLink AboutObservation of Excavation 03.21.17H-PVKUMAR Geotschnlcal Englnecdng I Englnasring Geology Maledals Tasting I Envlronmental 5020 County Road 154 Glenwood Springs, C0 81601 Phone: (970) 945-7988 Fax (970) 945-8454 Email: hpkglenwood@kumarusa.com March 2l,20l7 Office Locat'nns: Parkeç Glenwood SpÍngs, and Summit County, Colorado Patrick Morrissy l0 tüalnut Court South Orange, New Jersey 07079 natri ck.morrissvfi)cmai l.com Project No.l7-7-229 Subject:Observation of Excavation, Proposed Residencen 55 Cedar Street, Satank, Garfield County, Colorado Gentlemen: As requested, a representative of H-P/Kumar observed the excavation at the subject site on March l5 and 16,2017 to evaluate the soils exposed for foundation support. The findings of our observations and recommendations for the foundation design are presented in this report. The services were performed in accordance rvith our agreement for professional engineering services to you, dated March 10,2017. The residence will be a I and 2-story structure with a detached garage. Ground floors rvill be slab-on-grade. Spread footings placed on the gravel soils and sized for an allowable bearing pressure of 2,000 psf rvere assumed for the foundation support. At the time of our initial visit to the site, the building pad had been stripped of topsoil and compacted and excavation for footings had just started. When observed on March t6rh, the footing trench excavations for the house and detached garage rvere complete and had been cut in one level about 2V¡to 3 feet below the adjacenf ground surface. The soils exposed in the bottom of the excavation consisted of relatively dense,.silty sandy gravel and cobbles with scattered smatl boulders. There was about I to I % feet of moist silty clayey sand in the excavation sides above the gravel. The results of a gradation analysis performed on a sample of the gravel (minus S-inch fraction) obtained from the site are presented on Figure L No free water was encountered in the excavation and the soils were slightly moist. Consïdering 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 for support ofthe proposed residence and garage. Post-constructíon settlement of the foundation bearing on the dense gravel should be minor. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. Loose disturbed soils in footing areas should be removed or compacted. Exterior footings should be provided rvith adequate soil cover above their bearing elevations for frost Patrick Morrissy Marclr 21,2017 Page 2 protection. Continuous foundation walls should be reinforced top and bottom to span locat anomalies such as by assuming an unsupported lengtlr of at least 10 feet. Structural fill placed within floor slab areas can consist of the on-site soils excluding rock larger than about 6 inches compacted to at least 95% of standard Proctor density at a moisture content near optimum. Backhll placed around the structure should be compacted and the surface graded to prevent ponding rvithin at least l0 feet of the building. Landscape that requires regular heavy irrigation, such 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 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 movernent may be greater than indicated in this report because of possible variations in the subsurface conditions. In order lo reveal the nature and extent of variations in the subsurface conditions belorv the excavation, drilling would be required. It is possibte the data obtained by subsurface exploration could change the recommendations contained in this letter. The property is underlain by Eagle Valley Evaporite which is known to be associated rvith sinkhole development due to formation of solution cavities in the evaporite. The risk of future sinkhole development throughout the service life of the residence, in our opinion, is low but the owner should be aw¿re of the risk. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developÍng in the future. If the client is concerned about MOBC, lhen a professional in this special field of practice should be consulted. Ifyou have any questions or need further assistance, please call our office. Sincerely, H-P*t KUM.AR Steven L. Pawlak, P Reviewed by: DEH SLP/ltac Attachment: Figure I - Cradation Test Results a Ia 1622? H.P+ruMAR Projecl No. 17-7-229 I I t6 tö to 7C a¡ s E s :o to o t! t¡ to ¡ao tô a! ,o ¡g It t00 t I E ctÂY 10 stLT COEELES GRÂVEL 62 X SAND 22 * LTQUTD UUIï PLÂSflClIT INoEX SAtlPLl 8l: Sllly 5oñdy ßtov.l rllh CobblÉr StLl AX9 Ct¡Y 16 N Fioll: Sollam ol 8¡eovolia¡ lllo¡ l¡rl n¡ull¡ o¡rlt lnlt lo llr.tqnd[ rhlch r.Ð l.rl.d, TlrrIttlln¡ ñpcrl ú!n nel br ¡rpÞdscrC,a¡Ðal l¡ lull. rfítoül lh. rrlf6lppel cl f!ilar I ¡ttælobt, læ,lhn an¡lt¡l¡ larllñt lr þ¡rl!.Éd ln ¡Gccrdcñr. rlth ASll¡ Oll1, Àttu CllSqñd,/ûi ¡Sl1¡ Orr4o. HYDTöI¡ETEñ ÀNALTsIs st€Yq ^NALYtr¡it¡t tE¡oil6 la Hlt t ltÈr u5. tglm ¡Errt8 --l I l._--¡*l-t_.= --l ¡ -t-_t --::":1==f_- -t I_ryffi -Etæ-_*:T::=:::: t.-___l ---:--J::î*_*t__-_ t.-_=*-"-1 . : l-=-¡:::::l:: -t- _-_t-- gAND ÊRAYEL FINE MEDTUM ICoAESE FINE COAFSE l7 -7-229 H-PryKU]VIAR GRADATION TEST RESULTS Fig. 1