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Home My WebLink AboutSubsoil Study for Foundation Design 12.23.19K+tfTffiffir#'å* An Ëmploycc OqÀrnËd Çompony -502û County Roacl 15,1 Clcnrveroel Springs. C() fìli;û1 ¡rhone: (Ç70) 9/+5"7988 lbx: {*70) 945-84,54 ernai I : kagienwood(4likLrniarusa.conr wrvl.ku¡naru sa.ec¡;n ûi1ìce Locations: Þern er {HQ), Parker Coloracir¡ Springs. Fort Collius, Clenr.vood Springs. and Summrt County, Colorado REGEIVED l:i.i;; i Îi,;il GARFIELD COUNTY COMMUN¡TY DEVELOPMENT SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED SALES OFFICE BUILDING LOT t0, BLOCK 5, FILTNG 1 SADDLEBACK VILLAGE, BATTLEMENT MESA 14 TAMARISK TRAIL GARFIELD COUNTY, COLORADO PROJECT NO. 19-7-681 DECEMBER 23,2019 PREPARED F'OR: RIIP PROPERTIES ATTN: LIBBY MORROW 3 12OO NORTIIWESTERN HIGT{WAY FARMINGTON rrILLS, MTCIIIGAI\¡ 48334 trmorrow{& rår F- pro Þeriies.co¡¡¡ TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITIONS GEOLOGY FIELD EXPLORATION DESIGN RECOMMENDATIONS FOUNDATIONS FLOOR SLABS LIMITATIONS..... FIGURE I - LOCATION OF EXPLORATORY BORINGS FIGURE 2 . LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURE 4 - S}VELL.CONSOLIDATION TEST RESULTS FIGURE 5 . GRADATION TEST RESULTS TABLE 1. SUMMARY OF LABORATORY TEST RESULTS -t- I I -t _ -t - SUBSURFACE CONDITIONS -2- FOLINDATION BEARING CONDITIONS ......,..... 3 - J 3 4 5 .....- 6 - Kumar & Associates, lnc. tì Project No. 19.7.681 PURPOSE AND SCOPE OF'STT]DY This report presents the results of a subsoil study for a proposed sales office building to be located on Lot 10, Block 5, Filing 1, Saddleback Village, Battlement Mesa, 14 Tamarisk Trail, Garfield County, Colorado. The project site is shown on Figure 1. The pu{pCIse of the study was to develop recommendations for foundation design. The sfudy was conducted in general accordance with our agreement for geotechnical engineering services to RHP Properties, dated November 8,2019. A fieTd exploration program consisting of exploratory borings was conducted to obtain information on the subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their classification, colnpressibility or swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recoflrmendations ftrr foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSAD CONSTRUCTION At the time of this study, development plans for the property were preliminary. The building is proposed in the southwestem portion of the site as shown on Figure l. We have been informed that the proposed building will be a one-story, single-wide modular structure above crawlspace. For the purpose of our ånalysis, foundation loadings for the structure were assumed to be relatively light and typical of the proposed type of consffuction. If building loadings, location or grading plans change significantly from those described above, we should be notified to re-evaluate the recommendations contained in this report. SITE CONDITIONS The site was mostly vacant with a Saddleback Village sign and wooden fencing around the south and west site perimeter at the time of ow field exploration. The terrain is gently sloping down to Kumar & Associates, lne ,'-'Project No. 1S.7"681 -2- the west. The ground surface is vegetated with landscaped grass and trees. Double-wide modular homes are to the west and south, a gas station and Tamarisk Trail are to the north, and Stone Quarry Road and vacant land are to the east of the project. GEOLOGY According to the Preliminary Geologic Map of the Grand Valley Quadrangle, Garfield County, Colorado, by Donnell, J.R., Yeend, W.8., and Smith, M.C., dated 1986, the site is underlain by mudflow and fan gravel deposits of the Pleistocene period. Mudflow and fan gravel deposits are described as pebble, cobble, and boulder gravel in a gray matrix of coarse sand; poorly sorted; clasts primarily unweathered basalt, but contains some sandstone, rnarlstone, siltstone, and claystone. FIELD NXPLORATION The field exploration for the project was conducted on November 26,20T9. Two exploratory borings were drilled at the locations shown on Figure I to evaluate the subsurf'ace conditions. The borings were advanced with 4 inch diameter continuous flight auger powered by a truck- mounted CME-458 drill rig. The borings \ryere logged by a representative of Kumar & Associates. Samples of the subsoils were taken withl% inch and 2 inch LD. spoon samplers. The samplers were driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-l586. The penetration resistance values are an indication of the relative density or consistency of the subsoils. Depths at which the sarnples were taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Figure 2. The samples were retumed to our laboratory for review by the project engineer and testing SUBSURFACE CONDITIONS ûraphic logs of the subsurface conditions encountered at the site are shown on Figure Z. The subsoils consist of about lz footof topsoil overlying about g ta l6t/z feet of stiff to very stifd sandy, silty clay with gravel layers underlain by dense, silty sanil and gravel that extended down to the boring depths of 21 feet. Kumar & Associates, lnc. '',Project No. 19.7"681 J Laboratory testing performed on samples obtained during the field exploration included natural moisture content, density, gradation analysis, and percent-fines (percent passing the No. 200 sieve), Swell-consolidation testing was performed on relatively undisturbed drive samples of the clay subsoils. The swell-consolidation test results, presented on Figure 4, indicate low compressibility under relatively light surcharge loading and a minor expansion potential when wetted under a constant light surcharge. The laboratory testing is summarized in Table 1. Free water was nÕt encountered in the borings at time of drilling. The subsoils were slightly moist. FOUNDATION BEARING CONDITIONS The natural {ine-grained silty, sandy clay soils possess a relatively low bearing capacity, and minor expansion potential. Spread footings bearing on the nab¿ral fine-grained soil can be used for foundation support with the accepted risk of movement and distress. Lower risk options include removal of a minimum of 3 fbet of the natural soil below the footings and replacement with compacted structural fill or use of a deep foundation, such as micropiles or drilled piers. Belc¡w are design recommendations for spread footings. If deep foundations are desired, we should bc contacted to provide design recommendations. All existing foundations, slabs-on- grade, utilities, and undocumerrted fill should be removed from the proposed building fooþrint prior to construction. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we recommend the structure be founded with spread footings placed on the natwal fine-grained soil or compacted structural fiIl. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed natural fine-grained soils can be designed for an allowable bearing pressure of 2,000 psf. Structural fill (if used) should be compacted to a minimun of gSYo of the standard Proctor density. Based on experience, we expect initial settlement of footings designed and constructed in Kumar & Associates, lnc. ,Project No. 19"7.681 -4- this section will be about I inch or less. Additional movement of around 1 inch could occur if the bearing soils are wetted. Less movement is expected for footings bearing on a minimum of 3 feet of compacted structural fill depending on the depth and extent of wetting. 2) The footings should have a minimum width of l6 inches for continuous footings and,24 inches fbr isolated pads. 3) Continuous foundation walls should be reinforced top and bottom to span local anomalies and limit the risk of ditferential movement. One method of analysis is to design the foundation wall to span en unsupported length of at least 12 feet. Foundation walls acting as retaining structures should also be designed to resist a lateral earth pressure corresponding to an equivalent fluid unit weight of at least 55 pcf for backfill consisting of the onsite soils. 4) Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundations at least 3ó inches below the exterior grade is typically used in this afea. 5) Prior to the footing constructioil, ffiy existing fill, topsoil and loose or disturbed soils should be rernoved and the footing bearing level extended down to the firm natural soils, 6) A representative ofthe geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade construction with the accepted risk of movement as described above for foundations. The risk of movement can be reduced by placing slabs-on-grade on a minimum of 2 feet of compacted structural fill or by using structural floors over crawlspace, which is commonly done in the area. The structural fill should consist of a granular soil such as CDOT Class 5 or ó base course material. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Kumar & Associates, lnc. :'Projeet No. 19"7.681 5 Floor slab control joints should be used to reduce darnage due to shrinkage cracking. The requirements.for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A minimum 4 inch layer of sand and gravel base course should be placed beneath floor "slabs at grad€'for support and to facilitate drainage. This 4 inch thickness can be included in the recommended 2 feet of base course below the slabs. All fill materials for support of floor slabs should be compacted to at least gïYo of maximum standard Proctor density at a moisfure content near optimum. Required fill, below the recommended depth of base course, can consist of the on-site soils devoid of debris, topsoil and oversized rocks (plus 4-inch). SURFACE DRAINAGE Proper surface grading and drainage should be provided to prevent wetting of the bearing soils. An underdrain should not be needed for the proposed crawlspace with proper backfill placement and positive surface grading. The following drainage precautions should be observed during construction and maintained at all times after the structure has been cornpleted: l) Inundation of the foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optirnum moisture and compacted to at least 95% of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the m¿ximum standard Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend aminimum slope of 12 inches in the first 10 feet in unþaved areas and a minimum slope of 2% inches in the first 10 feet in paved âreas. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from foundation walls. Consideration should be given to the use of xeriscape to limit potential wetting of soils below the foundation caused by irrigation. Kumar & Associates, lnc. :i Project No" 19"7-681 -6- LIMITATIONS This study has been conducted in accord¿nce with generally accepted geotechnical engineering principles and practices in this areaatthis time. V/e make no warranty either express or implied. 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 1, the proposed type of construction and our experience in the area. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developing in the future. if the client is concerned about MOBC, then a professional in this special field of practice should be consulted. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory borings and variations in the subsurface conditions may not become evident until excavation is performed. If conditions enc¿untered during construction åppear to be different from those described in this report, we should be notified at once so re-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for design purposes. We are not responsible for technical interpretations by others of our infonnation. As the project evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recoûtmendations, and to veri$r that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications of the recommendations presented herein. We recommend on-site observation of excavations and foundation bearing strata and testing of structural fil1 by a representative of the geotechnical engineer. Respectfully Submitted, Kumnr & Associateso Tnc. Shane J. Robat, P.E. Reviewed by: Steven L. SJR/kac cc: Biil Wilde 15221,, Kumar & Associates, lnc. ".Project No, 19"7"681 =7tn^{7t-*-,-,it---'l¡-.II{IIIIIIII!.s+ö.irS(Þ**^"JsgÞ{t6aN A0.56.34" E 94.76'c{ç'IliiIIIl_lrIII¡ùåiq,å¡i5-Io-Û.Dnox-{fîØ()-rïI-ïrftm-{!9drIIII--ì-þs'r^\3\-r''\¡¡-\-\)/Á)ìt*-::ìz6)a!3alel€STONE QUARRY ROAD(oI{IO)@x3o-9ooaoo.oou,rOc)-{oz.oT1rflxTron_Jon@()nz.c)U'-ï1(o ¡ ü E :l I BORING 1 EL. 5562'BORING 2 EL. 5563' 0 0..* 26/12 WC=9.6 DD=116 8/ 12 WC=14.8 DD= 1 04 -200=90 5 5-23/ 12 WC=7.f DÐ=f12 -200=84 21 /12 WC= 10.8 DD=117 't0 10 t-- L¡J l¿Jlr I¿F-o- L¡Jc¡ s0/12 WC=9.0 DD=112 -20Q=77 21/6,s0/5 t-LJLIl! I-Fo- l¡Jô -f 15 526/ 12 64/12 20 2040 / 6,50/ 4 52/12 25 25- WC=5.5 +4=39*200=24 1 9-7- 68 1 Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 2 I f I f ¡ o' LEGEND ñNI TOPSOIL; SOD, SILTY, SANDY CLAY WITH OROANICS, FIRM, MO|ST, DARK BROWN. !!{v {ct-)¡ SANDY, SILTY wlrH GRAVEL LAYERS, srlFF To vERy sïFF, sLroHTLy Motsr, BROWN, LOW TO MEDIUM PLASTICITY, SAND AND GRAVEL (SM-GM); SILTY, DENSE, SLIGHTLY MoIsT, MIXED BRowN. SUBANGULAR ROCK TRAGMENTS. DRIVE SAMPLE, 2.INCH I.D. CALIFORNIA LINER SAMPLE, I DRTVE SAMPLE, I 3/8-|NCH t.Ð. SpLtT SPOoN STANDARD PENETRATTON TEST, 26/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 26 BLOWS Or A 14O-P0UND HAMMER FALLING 50 INCHES WERE REQUIRED TO DRIVE THE SAMPLER 12 INCHES. NOTES THE EXPLORATORY BORINGS WERE DRILLED ON NOVEMBER 26, 2019 WITH A 4-INCH_DIAMETER CONTINUOUS-FLIGHT POWER AUGER. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIÐED. 3. THE ELEVATIONS OT THE EXPLORATORY BORINGS WERE OBTAINED BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN PROVIDED. 4, THE EXPLORATORY BORING LOCATIONS AND ELEVATIONS SHOULD BT CONSIDERED ACCURATE ONLY TO THE DEOREE IMPLIED BY THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE APPROXIMATE BOUNÐARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6, GROUNDWATER WAS NOT ENCOUNTERED IN THT BORINGS AT THE TIME OF DRIILING. 7, LAEORATORY TEST RËSULTS: WC æ WATER CONTËNT (%) (ASTM D2216);DD = DRY DËNSITY (pcf) (ASTM o2216)t+4 = PERCENTAGT RETAINED ON NO. 4 SIEVE (ASTM 06913)¡ -200= PERCENTAGE PASSING NO. 200 SIEVE (ASTM 01140). 2. 1 9-7-681 Kumar & Associates LTGTND AND NOTTS Fig. 3 î: 9 f. SAMPLE OF: Sondy, Sttty Cloy wlth Grovel FROM:Boringl@2.5' WC = 9.6 )6, DD = 1 16 pcf EXPANSION UNDER CONSTANT PRESSURE UPON WETTING JJl¡l =t I zI C¡ fonz()(J 2 0 -2 -3 .t 100 às JJ l¡J!UI I z.o l- o Jov,zo(.) 0 2 -5 APPLIED PRESSURE -t0 SAMPLE OF: Sondy, Silty Ctoy FROM:Boring2@5' WC = 1O.8 %, DD = 1 17 pcl EXPANSION UNDER CONSTANT PRESSURT UPON WETTINO 1 9-7-681 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 4 ¡I srÊvE ANALYSTS t' I ilxE iEADrltos HYDROMETÊR SAND GRAVEL FINE MEDTUM lcoansr FINE COARSE å Ê F 't00 t0 lo 70 t0 !o ,t0 ¡0 ¡o t0 0 o rg 20 to Æ lo tô 70 l0 90 roo I E F I 1 i I I iJil .c00 JI ¡r CLAY TO SILT COBBLES CRAVTL 39 ,X SAND LIQUID LIMIT SAMPLE Of: Sllly Sond ond Grovol 37 '( PI¡STICITY INDEX SILT AND CI-AY 21 '( FROM: Bor¡ng 2 O 15' & 20' (Coñblnod) Thc¡. llst ruulls aÞÞly only lo lherompld whlch r.r. l¡sled. Th.l.rl¡ng ruporl rholl nol ba ruprcduc.d,cxccpl ln lull *¡lhou,l lh! wrllltn opprovol ol Kumor & Asoclotr!, lnc,Sbv! onolyrlt lldln! lr Þ.rtorm.d ln oooordono. wlth ASIM D6915, ASTì¡ D79281ASil Ctl6 ond,/or ASTM Dll,t0, 1 9-7-681 Kumar & Associates GRADATION TTST RESULTS ilg. þ