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Home My WebLink AboutPreliminary Subsurface Study 11.07.17H-PÈKUMAR 5020 Coung Road l3t Glenwood Springs, CO 81601 Phone: (970) 945.7988 Fax (e70) 945-8454 Emai[ hpkgenwood@kumarusa.com Geotechnical Engineering I Engineer¡ng Geology Îv'lalerials Testing I Environmenlal Office Locatlons: Parl€r, Gtenwood Springs, and Sllvarlhoma, Cotorado PRELIMINARY SUBSURFACE STUDY PROPOSED PRIMARY AND SECONDARY RDSIDENCE PI{ELAN PARCEL, BIG MOUNTAIN RÀNCH COUNTY ROAD 252 NORTHWEST OF RIFLE GARFIELD COUNTY, COLORADO RECE,YED æíi^ËÍ'ifw¿;rPROJECT NO. 16-7-485 NOVEMBER 7,2016 PREPARED FOR: JOHN PHELAN c/o LYMAN rOGEt 284 NORTTI STAR DRIVE ASPEN, COLORADO 8T611 lvman@284nsd.com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY............... PROPOSED CONSTRUCTION SITE CONDITIONS FIELD EXPLORATION ....- I - -7 - 2- 4 SUBSURFACE CONDITIONS ENGINEERING ANALYSTS ........... LMITATrONS........... FIGURE I - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LECEND AND NOTES FICURES 4 through I - SWELL-CONSOLIDATION TEST RESULTS TABLE I- SUMMARY OF LABORATORY TEST RESULTS )_ -?- H-P\ KUMAR Plojecl No. 16-7.485 PURPOSE AND SCOPE OF STUDY This report presents the results of a preliminary subsurface study for proposed primary and secondary residences to be located on the Phelan Parcel at Big Mountain Ranch, northwest of Rifle, Garfield County, Colorado. The project site is shown on Figure l- The purpose of the study was to develop preliminary recommendations for planning and site grading design. The study was conducted in accordance with our agreement for geotechnical engineering services to John Phelan c/o Lyman Fogel dated September 26,2A16. A field exploration program consisting of exploratory borings was conducted to obtain information on the subsurface conditions. Samples of the subsoils and bedrock obtained during the field exploration were te.sted in the laboratory to determine their classification, compressibility or swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop preliminary recommendations for foundation and site grading design for the proposed development of the site. This report summarizes the data obtained during this study and presents our conclusions, preliminary recommendations and other geotechnical engineering considerations based on the general proposed construction and the subsurface conditions encountered. PROPOSEÐ CONSTRUCTION Two separate buildings are planned in the area of our exploratory borings shown on Figure l. Vfe understand conceptual plans are to locate the main residence to the southwest of the existing game house on the property and be about 15,000 square feet in size. The secondary residence will be further to the southwest and about l0 to 20 feet lower in elevation than the main residence. The two buildings may be connected. Extensive cut and fill grading is planned at the site to provide relatively flat pads for the building construction. When building location, grading and loading information have been developed, we should be notified to re-evaluate the recommendations presented in this report, and perform additional exploration and analyses as needed. H-P+ KUMAR Pro¡ect No. 16-7-485 -2- SITE CONDITIONS The Big Mountain Ranch is located roughly 20 miles northwest of Rifle along the back, northeast side of the Grand Hogback. The Phelan Parcel is vacant and located along the top of a broad, northeast to southwest trending ridge. The existing building to the norrheast shown on Figure I is the game house at the property. The terain is moderately steep sloping along the ridge down to the southwest at grades estimated from about l0 to 157o. Elevation difference across the site borings ì¡/as approximated to be about 73 feet ranging from 8457 feet at Boring dorvn to 8384 feet at Boring 4. Vegetation consists of grass, weeds and oak brush with several scattered âspen trees. FIELD EXPLORATTON The field exploration for the project was conducted on October 5, 2016. Four exploratory borings were drilled at the locations shown on Figure I to evaluate the general subsurface conditions. The locations were as requested by the client. The borings were advanced with 4 inch diameter continuous flight augers powered by a rrucþmounted CME-45B drill rig. The borings were logged by a representative of H"p/Kumar. Samples of the subsoils and bedrock were taken with a 2 inch LD. spoon sampler. The sampler was driven into the subsoils and bedrock at various depths with blows from a 140 pound hammer falling 30 inche.ç. This test is similar to the standard penerration tesr desmibed by ASTM Method D-158ó. The penetration resistance values are an indication of the relative density or consistency of the subsoils and hardness of the bedrock. Depths at which the samples rvere taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the sitE are shown on Figure 2. The subsoils encountered, below about ltl¿ feet of organic topsoil, consisted of stiff to very stiff, .sandy clay with scattered gravel underlain at depth^s from about SVzto l5l: feet by nil to about l0 H-P+ XUtvlnR Project No. t6-7-485 -3- feet of medium hard to hard, weathered claystone. Below depths from about 7 to 25t/t feet, the bedrock became less weathered and hard to very hard claystone, contained some siltstone layers and extended down to the maximum depth drilled of 3l feet. Drilling in the bedrock with depth was difficult due to its hardness but auger drilling refusal was not encountered to the drilled depths of about 5 to 9 leet into the bedrock. Laboratory testing performed on samples obtained from the borings included natural moisture content and density, percent finer than sand size gradation analyses, and Atterberg limits. Results of swell-consolidation testing performed on relatively undisturbed drive samples of the clay soils, presented on Figures 4 and 5, indicate low compressibility under conditions of loading and wetting and a moderate to high swell potential when wetted under a constant 1,000 psf surcharge. Swell pressures from about 5,000 to 20,000 psf were measured on the clay samples. Results of swell-consolidation testing performed on drive samples of the hard to very hard bedrock, presented on Figures 6 through 8, indicate low to moderats compressibility under conditions of loading and wetting with low hydro-compression potential. The bedrock samples were probably partly disturbed due to the rock hardness and the sampling process, and based on our experience should not possess a hydro-compression potential, Undisturbed samples of the weathered bedrock for swell-consolidation testing were not possible due to its fractured and broken condition. The liquid and plastic limits testing indicates the clay and weathered claystone to have medium high plasticity. We expect the weathered claystone could possess a swell potential, possibly similar to the clay soils. The laboratory testing is summarized in Table L No free water was encountered in the borings at the time of drilling and the subsoils and bedrock materials were slightly moist. ENGINEERING ANALYSIS Based on our experience and the drilling conditions, excavation of the soils, weathered bedrock and a depth of the hard to very hard less weathered bedrock should be feasible with conventional heavy duty equiprnent commonly used in the area. Heavy duty excavation equipment typically used in the area includes relatively large track-hoe excavators and dozers with rippers. We H-P* KUMAR Project No. 16'7.4{t5 -4- exPect excavation of 5 to l0 feet into the hard to very hard, bedrock should be feasible with this type of equipment. It should be feasible to use the onsite soils mixed with well broken bedrock, excluding topsoil and oversized (plus 6 inch) rock fragnrents, as structural fill for the site grading. The fill may possess a swell potential especially if placed to a high degree of compaction at moisture contenr dry of opt¡mum, and then subsequently becomes wetted. Typically, structural fill of potentially expansive materials is placed at between gS ¡ogïEo standard Proctor density at moisture contents at to slightly above optimum to help mitigate the heave potential. Some Iong term settlement of deeper fill areas can occur even though the f¡ll mater¡al is properly placed and compacted which could result in distress to facilities constructed on the fill. Based on the above considerations, trye expect drilled piers end-bearing in bedrock will likely be needed for foundation support of the residences. Structurally supported floors over crawlspace may also be needed for residential living areas due to potentially expansive subgrade conditions. Less movement sensitive areas such as garage fioors may be feasible as slahs-on-grade provided some movem€nt is acceptable along with mitigation of the swell potential. Placing the buildings entirely on cut into the less weathered and hard to very hard bedrock encountered below depths from about 7 ¡o 25Vz feet could possibty allow use of spread footing foundations for support of the buildings. Cut and fill slopes.should typically be graded at 2 horironral to I vertical or flatrer. Steeper curs made entirely into bedrock may be feasible and can be studied on an individual basis. po.sitive surface drainage will be an important aspect of the project to prevent wetting of the bearing rnilterials below the building and fill areas. When preliminary building and grading plans have been developed, we should conduct additional exploration and analysis to develop design level recommendations. LIMITATIONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area at this time. We make no warranty either expre.çs or implied H.P \ KUMAR Proiect No. 16.7-¡185 -5- The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory borings drilled at the locations indicated on Figure l, the general proposed construction and our experience in the area. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory borings and variations in the subsurface conditions between the borings should be expected. This report has been prepared for the exclusive use by our client for planning and preliminary design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should drill additional borings, perform additional analyses, and provide continued consultation to review and monitor the implementation of our recommendations. We recommend on-site observation of excavations and foundation bearing str¿tâ and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, H.P\ KU David A. Young, P.E Reviewed by: **/. Steven L. Pawlsk, P.E. DAY/ksw H.P* KUMAR Proiect No. 16-Z¡185 PHEIAN PARCEL. BIG MOUNTAIN RANCI{ PROPOSED RESIDENCE SITE 1 APFRçXIMATE SCALE.FÊET 1 6-7*485 H.PryKUMAR LOCAÏION OF EXPLORATORY BORINGS Fig. 1 BORING I EL. 8457' BORIN6Et. 843 2 2' BORING 5 EL. 8402' SORING 4 EL. 8384' 0 0 25/12 WC=6.4 DD=l 1 1 -200=58 t6/12 24/t2 161 t2 5 s7 /12 3e/12 WC=l1.3 0D=115 2s112 l{C=10,8 DD:l15 -200=85 LL=49 Pl=21 s8/12 IVC= I 2.1 DÐ= I 20 -2ßO=97 5 10 sa/12 WC=l 1.8 DD=1 t 3 sal4 5a/s 54112 ttlC=8.2 00= 1 30 f0 t5 4t /12 s3/6 WC=7.5 D0=1 I 6 5A/4 WC=6,6 00=1 1 4 30/3 WCs5.5 DD=l l9 t5 I Fâ" a¡J0 s2/t2 WC=10.3 OD=l 24 LL=4¿t Pl=23 20 50/3 WC=8.0 D0=.l14 20 25 26/6,5a/5 WC*9.9 D0= I 25 25 50 s0l1 50 55 35 I 6-7-485 H.PVKUMAR LOGS OF TXPLORATORY BORINGS Fig. 2 ¡ LEGEND ñ n wI þ 2s1r2 PÍIIFNåg\i,.F,.|f...n??i-åtåi',1Êå'iå Ëär"'-F'3lrìr3[nå "1h'..?H-?rüiiEg.NOTES r 1 40); TOPSOIL¡ 0RcANlC SILTY CLAY WTH GRAVEL, F|RM, SLtct{TLy tdOfST, DARK BROWN. 9!4I lc_!)i sANDy, .sLtGHTLy GRAVELLy ro occAStoNALLy cRAvELLy, STTFF To VERY STIFF. SLIGI{TLY MOIST. MIXËO EROWN TO GRAY-BROWX, UCO¡úU Ft-45ïtCtTY. !^E¡I¡FEEÐ ,CLÂYSIoNE; MED|UM HARD To I{ARD, sLtcHTLy MOtsT, LtGt{T SROWN TO ORAY-BROTVN, MEBIUM PLASTICITY. q$Yl_lg.Nt qllRocK¡ wlIH occAStoNAL stLrSToNE t-AyERs, vERy HARD.SLIGHTLY MOIST. LIGI{T BROWN TO GRAY, UEDIUM TO OCCAåIONÀLLY IOW PLASTtCtW. RELATIVELY UNDISTURBEO ORIVE SAMPLEI z-INCH ].0. OALIFORNIA LINER SAMFLE. t. 2. 3. 1. 5. 6. 7. Tl{E EXPLORAIoRY EOR|NGS WERE DRILLED ON OCTOBER 5, 20'15 t¡vlTH A /t-tNCH DTAMETERCONIINUOU5 FLIGHÎ POWER AUGER. THË LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPFOXIMATELY BY PACINGFROM FEATURES SHOWN ON THE SITE PLAN PROVIOEO. THE EL€VATIONS O¡ TI{E EXPLORATORY BORINGS WERË AFPROXIMÂTEO FROM GOOGLS EÂRTHANO SY I{ANÐ LEVEL. TI{E ËXPLORATORY SORING LOCAÎIONS ANO ELEVATIONS SIIOUTD 8S CONSIDEREO ACCURATEONLY TO TI{E OEGREE IMPLIEO gY THE METI{OD USED. THE LIN€s BETWEEN MATERIÀLS SHOWN ON THE SXPLORÀTORY BORING LOGS REPRTSENT THEAPPROXIMAÎE EOUNDARISS EETWEEN MATERIAL ¡YPES ANo TI{E TRANSITIoNS MAY eÈ Gi$UÁ.. GROUNOWATER WÀS NOT ENCOUNTERED IN THE 8ORINGS AT THE TÍME OF DRILLING. LAEORATORY T€ST RESULTS: WC = WATER CONTENT (X) (ASTM D 2216);DD = DRY DENSIW (PCr) (ASTM D 2216)¡ -200= PERCENTACE PASSING N0. 2o0 stEVE (ASTM DLl- = LlOUlD LIMIT (ASTM D 4IiB);Pl = PLASTICITY INDEX (ASTM D 4JtE). 1 6-7-485 H-PrylCfMAR LEGEND AND NOTES Fig. 3 SAMPLE OF: Sondy Cloy FROM:Borlng 1 C 10' WC = ll.8Z, DD = 115 pcf 3 2 Ix Jol¡Jìa^ I -lzc o otftzou-3 t,0 t0 I 6-7-485 H-PryKUÍVIAR SWELL-CONSOLIDATION TIST RESULT Fig. 4 SAMPLE OF: Sondy Cloy FF0M;Boring 2 C 5' WC = 11.3%, ÐD = 115 pcf I t 1 l I ti tl: ...:. a: ',ì ritl EXPANSION UNDER CONSTANT PRESSURE UPON WETTINC I i j 1 a i l 1 ;! I)t:: l "'1 ,a : t : a:..: a' , 1 : I' I t l I t I : 1 I t 1 t t t I t t t :i 1 . I , , I I I t : t t t a , 1 a ¡ I 7 6 5 J f¿¡* an 4 J 2 o o Joattzo(J 0 -t *2 1 6-7-485 H.PryKUMAR SWELL-CONSOLIOATION TEST RESULT Fig. 5 I l Ilri¡ t SAMPLE OF: Cloyslone FROM:Sorlng 2e20' ItrC = 8.0 %, OD = 111 pcf AODI'IONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO IVETIING t t : : : 1 : 1 L :tt1 :t I t , 2 It t l : l i I I I I : I 1 t t I '' ) ) I :,. 1 a , i t i I ) I 1 I a t t I t 1 o Þt JJl!3 v1 I et- o =oØ2o(J -l -1 -5 -6 t.0 1 6-7-485 H-PryKUMAR SWELL.CONSOLIDATION TEST RESULT Fig. 6 SAMPLE OFt Cloyslone FROMIBoring 5 O 15' V/C = 6.6 %, DD = ll4 pcl ADOITIONAL COMPRESSION UNOER CONSÍANT PTESSURE DUE TO WËTIING î \ \ I I t\ \ \ å I trtttrlh 1 0 ^-l)q j-z t3 an l-3 2ot-I =. -4ovlzo{J _5 -þ -7 r 6-7-485 H-PryKUMAR SWELL-CONSOLIOATION TEST RTSULT Fig. 7 SAMPTE OF: Slllstonc FROM: Boring 4 O 'l 5' WC = 6.5 %. D0 = llg pcf th d ADOITIONAT COMPRESS'ON UNDÉR CONSÎANT PRESSURE DUE TO WETTING t I I , 1 t I , t I t ', t t , i , I t : , a I : i : I I I t :,:1,a1: ,l,, tat:1l :t1lll'| '. 1ata 1:.i t a I I I 1 , , : 1 1 I l : : I , , l .: I I I l I t , 1 t , 't t a , I I 1 I a l l 0 ^-2 j-¡ l¡JFvl t-4 zotr !-so anzo(J_6 -7 1 6-7-4Bs H-PryKUMAR SWTLL*CONSOTIDATION TEST RESULT Fig.8I H-P\KUMARTABLE 1SUMÍTIARY OF LABORATORY TEST RESULTSProject No.1&7485sotLoRBEDROCKTYPESandy Clay with GravelSandy ClayWeathered ClaystoneWeathered Clay.stoneSandy CIayClaystoneClaystoneSandy ClayClaystoneWeathered ClaystoneClaystoneSiltstoneUNCONFINEDcoÍtPREsstvESTRENGTH.PSRATTERBERG LI¡IIITSPLASNCINDEXP/"t2324L¡qUÞLIHITl9t"l4449PERCENTPASSINGNO.200SIEVE588597NATURALDRYDENSlTYGRAVELlololSANDlv"llllI13124t25n5l16l141t5il4120t30It9NAÎURALMOISTURECONTENTlt/"\6.4r 1.810.39.9ll.37.58.0I0.86.6I)I8.26.5DEPTI.I{fr,tzvzt020255I52A5I55t0I5BORINGI234