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Home My WebLink AboutSubsoil Studyl$¡tåffi:ffir'*-' An Employcc Owncd Compony 502û CotmtXr Rod 154 Glenurood Spriagg CCI 816ûI phone: (970)%5-7988 far (970)%18454 emait kaglenmi'oo d@f wnanuacorn www.kumarusa.corn Ofrce Locstitxls: Ðenver ftIQ), krkæ, Colorado Springs, Fort Co[ins, Gl€ñ$Ðod Springs, anil ,Smmmit Counüg Coloado SUBSOIL STUDY F'OR F'OT]NDATION DESIGN PROPOSED RESIDENCE LOl2o RUBEN MINOR SUBDMSTON COT.INTY ROAD 346 GARF'IELD CO[]NTY, COLORADO PROJECT NO. 20-7-557 NOVEMBER 20,2020 PREPARED FOR: RUBEN RUIZ P.O. BOX 456 sILTo COLORADO 81652 rrtruckins1@hotmail.com TABI,B OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION......... SITE CONDITIONS....... FIELD ÐGLORATION SIJB SURFACE C ONDITIONS FOUNDATION BEARING CONDITIONS DESIGN REC OMMENDATTONS FOLTNDATTONS .......... FOUNDATION AND RETAINING WALLS FLOOR SLABS TINDERDRAIN SYSTEM SURFACE DRAINAGE LIMITATIONS FIGURE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF E)GLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURES 4 and 5 - SWELL-CONSOLIDATION TEST RESULTS TABLE I- SUMMARY OF LABORATORY TEST RESULTS 1 I I -2- 3 .-3- .-3 - .-4- .-5- .-5- .-6- -6- Kum¡r & Associateq lne. o ko¡ect ¡lo, ãt7.5ıl PURPOSE AND SCOPE OF'STUDY This report presents the results ofa subsoil study for a proposed residence to be located on Lot 2, Ruben Minor Subdivision, County Road 346, Garfield County, Colorado. The project site is shown on Figure 1. The putpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with our agreement for geotechnical engineering services to Ruben Ruiz dated September 25,2020. A field 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, compressibility or swell and other engineering characteristics. The results of the freld exploration and laboratory testing werc analyzed to develop recommendations for 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. PROPOSED CONSTRUCTION Development plans for the lot were conceptual at the time of our study In general, the proposed residence will be a single-story structure with an attached garage. Ground floor will be structural above crawlspace for the living area and slab-on-grade for the garage. Grading for the structure is assumed to be relatively minor with cut depths between about2 to 4 feet. We assume relatively light foundation loadings, typical of the proposed type of construction. 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 building site in the north part of the lot was partly graded atthe time of our site visit for an existing shed and gravel surfaced parking. The ground surface in the building area is relatively flat with around one foot of elevation difference. An irrigation ditch borders the west side of the lot. Vegetation consists of grass and cottonwood trees along the west side. Kumar & Associates, lnc. o Project No.20-7-557 a F'IELD EXPLORATION Tlre field exploration for the project was conducted on October I,202A. Two exploratory borings were drilled at the locations shou¡n on Figure I to evaluate the subsurface conditions. The borings were advanced with 4-inch diameter continuous flight augers powered by a truck- mounted CME-458 drill rig. The borings were logged by a representative of Kumar & Associates,Inc. Samples of the subsoils were taken with l%inch and 2-inch I.D. 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 stanclard penetrafion test describecl by ASTM Method D-I586. The penetration resistance values are an indication of the relative density or consistency of the subsoils. Depths at rnihich the samples 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. SUBSURT'ACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The subsoils encountered, below athin gravel base layer, consist of stiff to medium stiff with depth, sandy silty clay dor¡¡n to 2l to 2TYzfeet overlying dense, slightly silty sandy gravel to the boring depths of26feet. Laboratory testing performed on samples obtained from the borings included natural moisture content and density, Atterberg limits and finer than sand-size gradation analyses. Results of swell-consolidation testing performed on relatively undisturbed drive samples, presented on Figures 4 and 5, generally indicate low to moderate compressibility under conditions of loading and wetting. Some of the samples showed minor expansion potential when wetted under light loading. Atterberg limits testing indicated that the shallow clays ale low to medium plasticity. The laboratory testing is summarized in Table 1. No free water was encountered in the borings at the time of drilling and the subsoils were typically moist. Ku¡mr & Associateo, lrm. o Projccf t{o.2fl7-557 -3 - T'OUNDATION BEARING CONDITIONS The upper clay soils are generally stiff and suitable for support of lightly loaded spread footings with low movement potential, mainly if the bearing soils are wetted. Some of the soils may exhibit expansion potential when wetted and should be further evaluated for footing heave risk at the time of excavation. DESIGN RECOMMEIIDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural soils. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed natural soils should be designed for an allowable bearing pressure of-lJgbsL Based on experience, we expect settlement of footings designed and constructed as discussed in this section will be about I inch or less. There could be potential for post-construction movement up to around I inch. 2) The footings should have a minimum width of 16 inches for continuous walls and W, isolated Pads' 3) 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 36 inches below exterior grade is typically used in this area. 4) Continuous foundation walls should be heavily reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 14 feet. Foundation walls acting as retaining structures should also be designed to resist lateral earth pressures as discussed in the "Foundation and Retaining Walls" section of this report. 5) The existing fill, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the undisturbed natural clay soils. The exposed soils in footing area should then be moistened and compacted. Ku¡nar & Associafes, Inc. o Proiec't No.20-7-55I 4 A representative ofthe geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FOUNDATION AND RETAINING WALLS Foundation walls and retaining structures which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 55 pcf for backfill consisting of the on-site fine-grained soils. Cantilevered retaining structures which are separate from the residence arid can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 45 pcf for backfill consisting of the on-site fine-grained soils. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, trafflrc, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill suface. The buildup of water behind a wall or an upward sloping backfill surface will inclease the latelal plessule ilrpused ulr a fuuldatiun wall ur retaining struuture. An untlerdrain should be proviclecl to prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lifts and compacted to at least 90% of the maximum standard Proctor density at near opûmum moisture content. Backfill placed in pavement and walkway areas should be compacted to at least 95% of the maximum standard Proctor density. Care should be taken not to overcompact the backfill or use large equipment near the wall, since this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall backfill should be expected, even if the material is placed correctly, and could result in distress to facilities constructed on the backfïll. Backfill should not contain organics, debris or rock larger than about 6 inches. The lateral resistance of foundation or retaining wall footings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated based on a coefficient of friction of 0.30. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 300 pcf. The 6) Kumar &Associates, lnc. ð Pfojsct ¡{r. ä17-5ll -5- coefficient of friction and passive pressure values recommended above assume ultimate soil strength. Suitable factors of safety should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should be compacted to at least 95% of the maximum standard Proctor density at a moisture content near optimum. FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade construction with low movement potential. To reduce the effects of some differentlal movement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab control joints should be used to reduce damage 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 relatively well graded sand and gravel such as 3/¿-inch base course should be placed beneath interior slabs for subgrade support. This material should consist of minus 2-inch aggregate with at least 50olo retained on the No. 4 sieve and less than 12o/o passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95%o of maxtmum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site soils devoid ofvegetation, topsoil and oversized rock. TINDERDRAIN SYSTEM Although free water was not encountered during our exploration, it has been our experience in the area that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. We recommend below-grade construction, such as retaining walls and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. The proposed relatively shallow crawlspace should not need an underdrain provided the perimeter wall backfill is well compacted and the surface is adequately sloped to drain away from the foundation. Where an underdrain is provided, it should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free-draining granular material. The drain should Kumar & Associates, lnc. o Project No.2&7-557 6 be placed at each level of excavation and at least I foot below lowest adjacent finish grade and sloped at a minimum lo/oto a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than 2olo passing the No. 200 sieve, less than 50oá passing the No. 4 sieve and have a maximum size of 2 inches. The dlain gravel backfill should be at least lYz feet deep. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: I ) Tnr¡ndation of the foundation excavations and unclerslab areas shoulcl be avoiclecl during construction. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95Yo of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proctor density in landscape areas. 3) The ground surÊace surrouncling the exterior of the builcling should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in paved areas. Free-draining wall backfill should be covered with filter fabric and capped with about 2 feet of the on-site soils to reduce surface water infiltration. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy inigation should be located at least 5 feet from foundation walls. Consideration should be given to use of xeriscape to reduce the potential for wetting of soils below the building caused by irrigation. 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 warrant¡r 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 Kumar & Associataa, lnc. 3 Pmjec{ No.2l}-7óft -7 - 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 iu this special fietd 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 conclitions may not becorne evident u¡tii excavation is performed, If conditions encountered during construction appear different from those described in this report, we should be notified so that re-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for clesign pwposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued consultation and field services during construction to review ancl monitor the implunentation of our lecommendations, and to veri$r that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendatiors presented herein. We recommend on-site observation of excavations and foundation bearing strata and lesting of structural ñll by a representative of the geotechnical engineer. Respectfully Subrnitted, Kunr¿¡r & Ass¡rcinfes. Inc. Steven L. Pawlak, P.E Reviewed by: Daniel E. Hardin, P.E. SLPlkac Cc: High Country Kumar & Associates, lnc. t' om S cott (!,t¡_@:lfçç.ng-rp m ) Project No. 20"7-557 ç 6 I I I I II I I I I I I I -t-Csfr¡¡$f Ro¡d Nı, 3,46 .fr6, ûrtÈcf --.- BORlNG t¡J tæ.| tI;6Fr hrúul¡¡¡lÈlblÈlabbtúlfr-¡.rqbt'?troaa NG2 I,at.2 Itøl¡bdblÉtûtrr¡¡rt räíFËt æ.øqlh*ihrûm;l{t L_ _ I¡t 3 z s 49.59'16'3t7.65' fdthtlrM-Snbl*l|ctüa U APPROXIMATE SCALE-FEET 2A-7 -557 Fig. 1Kumar & Associates LOCATION OF EXPLORATORY BORINGS BORING 1 EL. 1 00' BORING 2 EL. 99.5' 0 0 1A/ 12 WC=15.9 DD=1 1 7 -2OO=74 20/ 12 WC=7.6 -2QQ=76 LL=32 Pl=17 5 24/12 WC=9.6 DD=1 25 -200=89 5t2/ 12 1o 11 /12 WC=15.4 DD=1 12 5/ 12 10 10/12 WC= 1 9.3 DD= 1 09 t--LJ LJl! I-F(L L¡lÕ 15 15 t-LIl¡ll! I-t-(L LIô s/ 12 WC= 17.8 DD= 1 09 _a ^^--, ^ 4/ 12 Y'lC=21 .7 DD=1 O5 -2QA=92 20 20 8/ 12 e/12 25 25ß/6,5a/5 5A/ 4.5 30 30 20-7 -557 Kumar & Associates LOGS OF IXPLORATORY BORINGS Fîs. 2 g I Ë i ¡ & 3 E LEGEND FILLI COMPÁCTED SILTY GRAVEL AND SAND, MEDIUM DENSE, DRY TO SLIGHTLY MOIST, GRAY AND BROWN. CLAY (CL), SLIGHTLY SANDY TO VERY SANDY, SILTY, CLAYEY SAND LAYERS, STIFF TO MEDIUM STIFF WITH DEPTH, MOIST, BROWN, CALCAREOUS TRACES. rÍr.ã Ê)GRAVEL (GM), SANDY, SLIGHTLY SILTY, VERY DENSE, SLIGHTLY MOIST TO MOIST, LIGHT BROWN, ROUNDED ROCK. DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE, i DRrVE SAMPLE, 1 3/8-INCH l.D. SPLIT SPOON STANDARD PENETRATTON TEST 1¡71.¡ DRIVE SAMPLE BLOW COUNT. INDICATES THAT 10 BLOWS 0F A 140-P0UND HAMMER'"/'- FALLTNG 30 tNcHES WERE REQUIRED To DRtvE THE SAMPLER 12 INCHES. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON OCTOBER 1,2O2O WITH A 4-INCH DIAMETER CONTINUOUS-FLIGHÏ POWER AUGER. 2. THE EXPLORATORY BORINGS WERE LOCATED BY THE CLIENT 3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE MEASURED BY HAND LEVEL AND REFER TO THE GROUND SURFACE AT BORING 1 AS 1OO" ASSUMED. 4. THE EXPLORATORY BORING LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY ÏO THE DEGREE IMPLIED BY THE METHOD USED, 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D2216); DD = DRY DENSITY (pcf) (ASTM D2216); -2OO= PERCENTÀGE PASSING NO. 2OO SIEVE IASTM 01140):LL = LIQUID LIMIT (ASTM D4318);Pl = PLASTICITY INDEX (ASTM D4318). 2A-7 -557 Kumar & Associates LEGEND AND NOTES Fîg.3 SAMPLE OF: Sondy Silty Cloy FROM:Boringlc^2.5' WC = 13.9 %, DD = 1 17 pcl -2OO = 74 % EXPANSION UNDER CONSTANT PRESSURE UPON WETTING-JJ L¡l =<n I zo F ô:o anz.oo 0 -1 2 -3 -4 LIED PRESSURE - KSF 100 -J -Jt! =tn I zo l-. Õ Jo v'tzoo 1 0 -1 2 -3 -4 1.0 APPLIED - KSF l0 1 SAMPLE OF: Sondy Silly Cloy FROM:Boringl@10' WC = 19.3 %, DD = 109 pcf ln lnê. Sïdl EXPANSION UNDER CONSTANT PRESSURE UPON WETTING 20-7 -557 Kumar & Associates SWELL_CONSOLIDATION TEST RTSULTS Fig.4 : 3 Ê I t 2 ,| 0 -1 -2 -3 1 0 -1 -l -3 -4 às JJl¡l =Ø I z,o t-- ô JoØz() (J ñ JJtd3th I zotr â Jo U}zo() 100 - KSF SAMPLE OF: Slightly Scndy Sllty Clcy FROM:Boring2@5' WC = 9.6 %, ÐD = 125 pcf -200 = 89 % l I l 1 1: i i ) : l I I l I 1 I l ì I I I i EXPANSION UNDER CONSTANT PRESSURE UPON WETTING I i.. -. i: ) i l i; 1:::i t,i I I l I I tr i I i- -r.- l tr t-j ll lì : SAMPLE OF: Slightly Sondy Silty Cloy FROM: Boring2@7.5' WC = 15.4 ,4, DD = 112 pct l l : j i l 1 '' I -t- J j'i): , : I NO MOVEMENT UPON WEÏTING .t I I Th.tæt!d, lî D-4544. l 1 f' 100 20-7-557 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Flg. 5 I (+rt i.ffi[#:nürn'vËü**TABLE ISUMMARY OF LABORATORY TEST RESULTSPNo.20-7-557Slightly Sandy Silty ClaySlightly Sandy Silf ClaySOIL TYPESandy Silty ClaySandy Silty ClaySandy Silty ClaySandy Silty ClaySlightly Sandy Silty Claylosf)UNCONFINEDCOfiIPRESSIVESTRENGTH74r17(o/olPLASTICINDEX7IJ¿ATTERBERG LIMITS(o/olLIOUID LIMIT70768992PERCENTPASSING NO.200 stEvESAND(wGRADATIONGRAVEL('/ù(pcf)NATURALDRYDENSITY109109t25Tt2103f/o)NATURALMOISTURECONTENT13.91931787.69.615.42T.7(ft)DEPTH2Y2105I057Y251SAMPLE LOCATIONBORINGI2