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Home My WebLink AboutSubsoils Study for Foundation DesignIluddleston-Berry EagûnGcrfqt ¡S T$tirg, l¿C December 7,2022 Project#02585-0001 Rob Ashcraft PO Box 867 Carbondale, Colorado 81 623 Subject:Geotechni cal Investi gati on Parcel 239503309026 Carbondale, Colorado Dear Mr. Ashcraft, This letter presents the results of a geotechnical investigation conducted by Huddleston-Berry Engineering & Testing LLC (HBET) at Parcel 239503309026 in Ca¡bondalg Colorado. The site location is shown on Figure l. The proposed constn¡ction is anticipaæd to consist of a new single-family residence. The scope of our investigation included evaluating the subsurface conditions at the site to aid in developing foundation recommendations for the proposed construction. Site Conditions At the time of the investigation, the site was open and sloping down towards the northeast. Vegetation consisted primarily of weeds and grasses. The site was bordered to the nortfi by a pedestrian pathway, to the west by avacantlo! to the east by a residential properly, and to the south by Laird Lane. Subsurface Investisation The subsurface investigation included two test pits as shown on Figure 2 - Site Plan. The test pits were excavated to depths of 4.0 and 7.0 feet below the existing ground surface. Typed test pit logs are included in Appendix A. As indicated on the logs, the subsurface conditions encountered at the site were slightly variable. The test pits encountered 1.0 foot of topsoil above brown, mois! very stiffto hard lean clay with sand soils. In TP-l, the lean clay with sand extended to the bottom of the excavation. However, in TP-2 , the lean clay with sand extended to a depth of 3.0 feet and was underlain by brown, moist, hard sandy lean clay with gravels, cobbles, and boulders to the bottom of the excavation. Groundwater was not encountered in the subsurface at the time of investigation. Laboratorv Testing Laboratory testing was conducted on samples of the native soils encountered in the test pits. The testing included grain size analysis, Atteóerg limits determination, naûral moisture content determination, and morimum dry density and optimum moisture content (Proctor) determination. The laboratory testing results are included in Appendix B. 2789 RiversidePukway Grand Jrmction" Colorado 8 150 I Phone: 97G255{005 Info@huddlestonberry.com Parcel 239503309026 #025854001 t2n7Í22 The laboratory testing results indicated that the native clay soils are moderately plastic. In addition, the native soils were shown to be slightly expansive, with up to approximately 0.7Yo expansion measured in the laboratory. Foundation Recommendations Based upon the results of the subsurface investigation and nature of the proposed construction, shallow foundations are recommended. Spread footings and monolithic (tumdown) sfir¡ctural slabs are both appropriate foundation alternatives. However, as discussed previously, the native soils were indicated to be slightly expansive. Therefore, in order to provide a st¿ble bearing stratum and limit the potential for excessive differential movements, it is recommended that the foundations be constructed above a minimum of 24-inches of structural fill. If a basement is proposed, IIBET should be retained to evaluate the subsurface conditions below the bottom of basement foundation elevation. Due to their plasticity, the native soils are not suitable for reuse as structural fill. Imported structural fill should consist of a granular, non-expansive, non-free drøìnínp material approved by HBET. For spread footing foundations, the footing areas may be trenched. However, for monolithic slab foundations, the stn¡ctural fïll should extend across the entire building pad area to a depth of 24- inches below the turndown edges. Sfuctt¡ral fill should extend laterally beyond the edges of the foundation a distance equal to the thickness of stuctr¡ral fill. Prior to placement of structural fill, it is recommended that the bottom of the foundation excavation be scarified to a depth of 6 to 9 inches, moisture conditioned, and compacted to a minimum of 95o/o of the standard Proctor manimum dry density, within + 2o/o of the optimum moisture conterit as determined in accordance with ASTM D698. Strucn¡ral fill should be moisture conditioned, placed in maximum 8-inch loose lifts, and compacted to a minimum of 95Yo of thest¿ndard Proctor mæ<imum dry density for fine grained soils and 90% of the modified Proctor mærimum dry density for coarse grained soils, within + 2Yo of the optimum moisture content as determined in accordance with ASTM D698 and D1557, respectively. Structural fill should be extended to within O.I-feet of the bottom of the foundation. No more than O.1-feet of gravel should be placed below the footings or turndown edge as a leveling course. For structural fill consisting of approved imported granular materials and foundation building pad preparation as recommended, a ma¡rimum allowable bearing capacity of-lr@b" used. However, if struch¡rat fill oaends below foundations to the lean clay with gravels, cobbles, and boulders soilq an allowable bearing capaøty of 2,000 psf may be used. In addition, a modulus of 200 pci may be used for approved imported structural fill materials. Foundations subject to frost should be at least 36-inches below the finished grade. ffiw 2Z:\20O8 ALL PROJECTI¡\02585 - Rob Ashcraft\02585-0ml Parcel 2i19503309026\200 - (ho\02585{001 LRl2Û722.doc #025854001 wffirn Any stemwalls or retaining walls should be designed to resist lateral earth pressures. For bacldrll consisting of the native soils or imported granular, non-free draining, non-expansive material, we recommend that the walls be designed for an active equivalent fluid unit weight of 55 pcf in areas where no surcharge loads are present. An at-rest equivalent fluid unit weight of 75 pcf is recommended for braced walls. Lateral earth pressures should be increased as nec€ssary to reflect any surcharge loading behind the walls. Water soluble sulfates are common to the soils in Western Colorado. Therefore, at a minimum, Type l-tr sulfate resistant oement is recommended for constn¡ction at this site. Non-structural Floor Slab, and Exterior Í'latwork Recommendations In order to reduce the potential for excessive differential movements, it is recommended that non-sfiuctural floating floor slabs be constnrcted above a minimum of 24-inches of stn¡ctural fïll with subgrade preparãtion, structural fill materials, and fill placement be in accordance with the Foundøtion Recommendafi'ons section of this report. It is recommended that exterior flatwork be constructed above a minimum of l2-inches of strucû¡ral fill- Draipase Recommendatioqs Grødins ønd ùqíltape üe Øítical.for the lonp-term oeqfor!Ìu;nce of tþe sfiucture and grading ato should be designed to carry precipitation and runoff away from the structure. It is recommended that the finished ground surface drop at least twelve inches within the fïrst ten feet away from the structure. It is also recommended that landscaping within fïve feet of the stnrcû.re include primarity desert plants with low water require,lnents. In addition, it is recommended that irrigatiın, including drip lines, within ten feet of foundations be minimized. I{BET recommends that downspout extensions be used which discharge a minimum of 15 feet from the structure or beyond the backfill zone, whichever is greater. However, if subsurface downspout drains are utilized, they shouldbe carefully constructed of solid-wall PVC and should daylight a minimum of 15 feet from the stnrcture. In additior\ an impermeable membrane is recommended below subsurface downspout drain lines. Dry wells should notbe used. A perimeter foundation drain is recommended to reduce the risk of surface moisture adversely imþacting the structure. In general, the perimeter foundation drain should consist of préfabti"ãted drain materials or perforated pipe and gravel with the flowline of the drain at the bottom of the foundation (at the highest point). The perimeter drain should slope at a minimum of 1.0% to daylight or to a sump with pump. The drain should also include an impermeable membrane at the base to limit the potential for moisture to infiltrate vertically down below the foundations. Gener¡l Notes The recommendations included above are based upon the results of the subsurface investigation and on our local experience. These conclusions and recommendations are valid only for the proposed con$tn¡ction. ffiw J2:\2008 ALL PROJECTS\02585 - Rob Ashsraft\02585-0001 Parcel 2395033@026U00 - G€o\02585-0001 LR120722.doc Pacel 239503309026 #0258s4001 wfftn2 As discussed previously, the subsurface condition encountered at the site were slightly variable. However, the precise nature and ertent of any subsurface variability may not become evident until consfuction. As a resulL it is recommended ttrat HBET provide consfiuction materials testing and engineering oversight during the entire construction process. In addition, the builder and any subcıntractois working on the prqiect should be provided a copy of this report and informód of the issues associated with the presence of moisû¡re sensitive subgrade materials at this site. It is ittgottant to note that the rccorunendalíory hereín arc ínteFdei4 to -leútce,the rist-^ lf @ datmase. to vømíns dcsrees. associoled.tt¡t!, volqftre chønee qf the ffi. HBET cønnot oredíct lols-tqrrn chpnsqs in suÞ,surføce wilture @ irecíse mapnítudc or úent of volume cþanse Where sísníficønf ¡ncreøsii li iubsyrface moisture occur ù¿e to pqor qadìn*,. ittÐlopet slorftMa'ln itre, æcess íníualíon. or qther,cøu,sç, eíther úaríns consWct¡o! or the result of actíons òf tþe prooe4v øvner, sevelaLínches gf tnoveryF! are P?sst!.!e IJ @nulv wíth the recommenfutíons ín lhís leport releøses Huddleston- Bern Èns¡neerins &. Testins, LLC oÍ anv líøbílilv wíth resord ø the structute perforwønce. We are pleased to be of service to your project. Please contact us if you have any questions or comments regarding the contents of this report. Respecffirlly Submitted: Engineering and Tesúing, LLC @w 4Z:r2008 ALL PROJECTS\02585 - Rob Ashc¡aft\02585-0001 Parcel 239503309026U00 - G€o\025E5-0001 LRl20722.doc ÐqPilHþ.noff Garfield CountY, CO ÐaEüeeþ.ûtln7l2fl.z Last Data Udoade d: 11121Íþ2. 2ß&73 lffi F'IGURE 2 Site Plan Deverored bv{Ff FsågB#rt TEST PIT NUMBER TP.I PAGE I OF 1 PROIECil IOCAIION Cerbordaþ. CO PRfìtECr ilAfi,E Parcel PRorECrrütþER æ58S(ml CUENT Rob Ashcrafr RirËrsid€ Engin€€ring & T€sting LLIC Junotio,@ y7ù255-8005 cmrMrEr-EvAnoN _ TE8T PlrSæ GÐT'iDWATERLEI'EI9: CTIECIGDBY MAB ATIITIEOF EXCAVAIIOÍ{I)rv EXGAVAÌ}OI{ OOñITRA¡ TOR lMeeland EXGAVATTOil trtElltof)Trad<h/tsackhoe ITOGGEDBY TC MTESTARTED fN1T2, æÍIIPI.EÏED 1 AT ENDOF EXCAVAIId{nru AFTEREXCAVATþT{NOTE9 ATTERBERG LIMITS t-zt¡¡þzooot¡lztr 5 =EÉô u9 Êao2 =o() OL -c¡= J otrÞ 3=fL È añ 42I fL>É.l- ut 5g ä2U' s q8 8sl¡¡ú. øû> F-:) ^zJ;aso2 zluÈ hDYV c)ofL r¡l :Et-o- t¡Jc¡ o o Ir^ 3so MATERIAL DESCRIPTION ¡r t'.$ !'-.rü' iig,:l L.:!:t' rtr/ T '-..? 't;H, ir ¡l'{1 Silty Claywith Organics 0OPSOIL) ) l9 t8 79gGB 1 11 g7 3 *E¡rcavation R€lt¡sal dr¡e to Boulders at 4.0 Feet lean CI-AY with brown, moist, ræry G&l: [¡b Cbseified to I Bottom of te* pit at 4.0 feet. dqo g g EoN d()É fL ôê -@Í û b l¡,1o PruECf lf)GAnOil Carbon&þ. CO TEST PIT NUMBER TP-z PAGE I OF f PRO'ECTNA ,E Paroel 2395ffÍXl9(Þ6 FMIECf,I{ITÚBER 02585{þ1 CUENT ñlalr Aehcnaft Huddlesm-Berry Engin€€ring & T€sting LL,C v70-2553N5 EXCJIVAIIONCO{TRAú"IOR Wlseland Gþt iITWATERIEUELS: TEST PITSZEOOItIPI"EIED fnlmTNTESTARIEDfin1m cHECI(ED BY ÌTIAB AFTEREXCÂVATION EXCåVATtOlrt ¡lEIllOD Tradrh/tsacddtæ ATntlEOF EXCåVAI|OÍ{t}Ú AT ENDOF EXCAVANq{DrvUOGGEDBY TC GRd']IÍ} ËLEIIATION M)TE9 ATTERBERG LIMITS F2 l¡JFz 88 (t, t¡,z TL røû> Þ-:) ^z-t;3soz- z IJJÀr-ê¡¡r.g C)oÀ FÞ^ =EÉ.ô ,"FÉ.: 6fro2 =oo ôu e= J o LF 1=E È9ñ 42À fL>É. F- l¡l sg ä2(tt * É.^ Eä 8s r¡JE. o *so MATERIAL DESCRIPTION.C :Et-fL t¡Jo o-o Nt'.s i.o+ '*!.'J b..'j¿ -{ r-. '-l Silty Claywith Oryanics CIOPSOIL) üc 1 97 9 'E - l¡an Cl¡y with Sand (cl), brcwn, mok*, very s*ifito hard I 7 æ 18 12 67GB 1 Gravels, Cobbles, and Boulderc (CL), "Excavation Refr¡sal due to Bouldere at 7.0 Feet Sandy l-ean CLAY wiüì brov¡n. moid, hard GB'1: Lab Classified Gorte*p¡tatz.oteet ATTERBERG LI]UITS' RESULTS PRO'EGT [{A¡UE Parcel 23ñ150€B(þ026 PRf}'ECf, IIITIIBER û258&(ml PRf}'EgT I.oGATK'N Cerbondale. CO CUENT Flob Ashc¡eft Rirmside Engineering & Testing LLC qru255-affi5Junction,CO 8l50l @ @ P L A s T Ic I T Y I N D E X 40 20 o 10 CL-ML @ @ 0 20 LIQUID LIMIT PL PI #200 ClassificationSpecimen ldentilTcation LL LEA[{ CLAY rvith SAND(CL)37 l9 t8 79oTP-I, GB.1 11t21 SANDY LEA[{ C|¡Y(CL}30 18 12 87ETP.2, GB.I 11t21 E r¡lI o attt =:: Engin€aring & T€sting LI.C GRAIN SIZE DISTR¡BUTION Riwrsie Ju¡ctim,CO 8l50l vtù2st8ú5 CUENT Rob Ashcraft PROIECf tllAME Parcel 2$l5llXl09026 PRO'ECf,NTftIBER ø86{æI PROTECf, LOGÂIþI{ Carborìdale. CO u.s. srEvE oPEMh¡G tN tìrClrES I U.S. SIEVE NI'úBERS FÍYÍ)RChIETER 3 14 85 FToñI !o Éul2tr F-z 1¡¡oÉ l¡J(L 75 70 65 60 56 50 ¿t5 40 35 30 % æ 15 10 5 0 l0 0.1 0.ml GRAIN SIZE IN MILLIMETERS I Fr¡T- \I \ t: t: \ .li I\t\ r li li t: COBBLES GRAVEL SAND SILT OR CLAY coaf3e fine coarse medium fine Specimen ldentification Classification LL PL PI Cc Cu a TP-í, GB-l 11121 LEAN cLAYwffi SAND(GL)97 t9 t8 E TP-2, GB-1 11121 SANDY LEAfìl clÁY{cL)30 t8 12 Specimen ldentification D100 D60 D30 Dl0 ToGravel ToSand oÁs¡lt %Clay o TP-î, GB-l 17121 4.76 0.0 20.f 79.3 E TP-z, GB-t 11121 12.6 1.2 31.9 67.0 CONSOLIDATION TEST FRÍ}'EC*r fllA¡/IE Paroel 2ff)503FXXXÌ26 PRO.'ECTillnIBER ø8É(mf PROtEgf lJocATroil C.arhorxlala Cô CUENT Rob Ashcraft Huddlesûm-Berry Engin€ering e, Testing LLC v7u2554û5 Ritmside Parkway .hmotim,C,o 81501 I \\ \ \ \ \ \ () \ \ \ \ \ 10,000 MCo/o I \ 1,000 STRESS, p6f Specimen ldentification 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 100 * ¿ É. t--U' 97 Classification TP-2, MC-l 2.0 2 6 g ò ENozeÉ ft JoÎtzoo J ¡¡¡() É. o- PRCUECf, IOGATIOÍ{ Carbondale. CO MO¡STURE.DENSITY RELATIONSHIP PR(}JECI l,lAItlE Parcel æ9500€[X¡026 PRÀ'EGT NI'ÍtIEER lTrSSFl(YIll CTIENT Rob Ashcraft n89 y70-255-8W5 Huddle*oo-Bery Engine€ring & Testing L[,C ¡l \I \ \ \ \\ \\ I \ t \ \\ \ \ \ \\ \ \ \\ \ \\\\\ \ \ \ \ \ \ -a 7 \ /\7 /\ I \ Sample Date: Sample No.: Source of Material: Description of Material: fnlnoxz 22{/9ß 145 140 135 130 125 120 115 f10 105 100 95 TP-I. GB-I LEAN CLAY with SA[ì|D(CL) Test Method (manual):ASÏM Dô984 TEST RESULTS Maximum Dry Density 105.0 PCF Optimum WaterGontent 15'6 olo GRADAT|ON RESULTS (% PASSTNGI #2oo u. 9lË 79 100 100 .,(L È U)zl¡¡o ú.o ATTERBERG LIMIIS LL PL PI l837t9 Curves of 1000,6 Saturation for Specific Gravity Equalto: 2.80 2.7A 2.60 90 5 15 WATER CONTENT, % 0 t0 25 30 GlqPïHlc.rpt* Garfield Countv, CO Rmo35$ n0ûu¡t0 I I Rmæ1 þ-lGl Ëü .gffi* a 2¡!¡ü014006r Rür0$ ü lr¡ ilþ sC' nü0¡41 23û50lxl0tu0t R0û00tt Rmao ã¡9f0rÛ0?!0t R0üt¡ü0t zlgtßa00ü2 tR0000{¿ æeä0û:mû0t R0800{0 2lts¡ciloffi3RIF{H8O Ên5æ{0ütlû RûÛOE!' 2ttã{lill000Gı Bt RËAUOË LållD t lllÂcEtËtlï ft åR0mn0t ft DaE(r'eeþú77nLfñ22 tåst Deta Uploåded: t1!ZlÍÑ22fr&13 1Ñl I Location DevcrÇ€dbí¡[¡:)ftffi+|ff