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Home My WebLink AboutSubsoils Study for Foundation DesigntGrtffiffiffiff'å-*SCANNED 5020 County Road 154 Glenr"'ood Springs, CO 81ó01 phone: (970) 945-7988 fax: (970) 945-8454 ernaíl : kagl en wooriØ)kumarusa.com An Emdoyee Ownsd Compony www'kumarusa'com Ofïice Locations: Denver (HQ), Parker, Colorado Springs, Fo¡t Collins, Glenrvood Springs, and Summit County, Colorado SI}BSOTL STT}DY FOR FOI}I{IDI\TIOIV IDESIGTV PROF(ÑTTD RE$IIDEFVCN 188 EAGT,.ES RIIDGD IDRIVD LOT 'ø'-ßAGLß,PIOINTBÄTrf,MMTMESI\ GARFIELT' q)f]ItrìITY, COLORAIX) PRO|ECT D{O.l9t-7464 srxtTwBER^ 'Jr,?frß, PREPA,RED FOR: LUCItv S,HOT BUILDERS, LLC ATTN: CASIE DUNLAP 591 COI]NTY ROAI} 259 RIFLE, COLROADO 81650 casie.dunla p(itluckvshotllc.com TÄBI,D OFCI)IYTENT]S PIJRFOSEAND SCOPE OF STIII)Y l- PROPOSED CONSTRUCTION 1 -1-SITE CONDITIONS GEOLOGY -2- FIELD EXPLORATION -2- SUBSURFACE CONDITIONS -2- FOUNDATION BEARING CONDITIONS ....- 3 - DESIGN RECOMMENDATIONS FOLINDATIONS ........ FOTINDATION AND RETAINING ÏVALLS FLOOR SLABS 5- LIMITATIONS 7- FIGURE 1 . LOCATION OF EXPLORATORY BORING FIGURE 2 - LOG OF EXPLORATORY BORING FIGURE 3 - GRADATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS ..................- 3 - .....- 3 - _a- Kumar & Aseociates, lnc. o Project No, 19.7.464 PT]RFOÑE A¡{TD SCOPß OF STT}IDY This report presents the results ofa subsoil study for a proposed residence to be located on Lot 12, Eagles Point, Battlement Mesa, 188 Eagle Ridge Drive, Garfield County, Colorado. The project site is shown on Figure L The purpose 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 Lucky Shot Builders, LLC dated July 31,2A19. An exploratory boring was drilled 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 and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for foundation tlpes, 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 At the time of our study, design plans for the residence were conceptual. ln general, the residence will be a2-story structure above crawlspace with a slab-on-grade garage floor. The building is proposed in the area roughly near exploratory boring location shown on Figure 1. We assume exeavation for the building will be relatively shallow, up to about 5 feet below the existing ground surface. For the purpose of our analysis, foundation loadings for the structure were assumed to be relatively light and 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. SITIU GOF{IIITIOFSS Tho site was vacant at &o timc ofm field qilordion- ThCI grormd ffifrc is mvsd urift ndwal grass and weeds, The þrãh g@€rally slopcs dovrn to fu soú ú.nqrymfuffiSVo Kumar & Associates, lnc.'q Project No, 19.7-464 a slope acrossmoúoffroldmdinswesto aboú a,\Vløsþrcdornrnüo adrainageditch southof fre properfy. mo*ry, singlÞ.fuily rcsik wift ffi grages sç úo fre east, west, atrd north, Eagle Ridge Drive is fre norfr" rnd vacd lmd is to ûc sorú of fte sirc- GETOLOGY l\ccording to froPrcfiminuy Cmlogic hdry offte C¡rand Val[ey aqadrqglq Grfield County, Colorado, ddsd n9&6,W l¡omell" Ymd, md Smilt, ts sits is mdslain by r.qqls End Formation, trúúty ñom lhe Bull Lake elacidim- Tb dqlæit is dceøäbod æ allur¡ial terrace md fan depoeüls msising ofgrayiúsrown" smüy gr¿\d ofhalt md localþ daived slabby siltstone, malgnne rul smdstme; mtety to pody suted, poody ffiifio¡l with angular b well-roundednoefraglffi- FIELD EXPLORATION The field exploration for the project was conducted on August 28,2019. One exploratory boring was drilled at the.location shown on Figure 1 to evaluate the subsurface conditions. The boring was advanced with 4 inch diameter continuous flight augers powered by truck-mounted CME- 458 drill rig. The boring was logged by a representative of Kumar & Associates, lnc. Samples of the subsoils were taken with a IVsínchl.D. spoon sampler. The sampler was driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is simila¡ to the standard penetration test described by ASTM Method D-l586. The penetration resistance values are an indication of the relative dørsity or consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. Underneath the minor organic growth, the subsoils consist of about 4 feet of medium dense/very stiff, clayey siit and sand with gravel overlying dense, silty, clayey, sandy gravel with cobbles Kumar & Aseociatoe, lnc.6 Project No, 19.7.464 J and possible boulders. Drilling in the coarse granular soils with auger equipment was difficult due to the cobbles and possible boulders and drilling refusal was encountered in the deposit. Laboratory testing performed on samples obtained from the boring included natural moisture content and gradation analyses. Results of gradation analyses performed on small diameter drive samples (minus l%-inch fraction) of the coarse granular subsoils are shown on Figure 3. The laboratory testing is summarized in Table 1. No free water was encountered in the boring at the time of drilling and the subsoils were slightly moist. FOUNDATION BEARING CONDITIONS The natural subsoils encountered at the site possess moderate bearing capacity with generally low settlement potential. Shallow spread footings are recommended for support of the residence. DESIGN RECOMMENDATIONS FOUFSDATIO}qS Considering the subsurface conditions encountered in the exploratory boring 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 ased on experience, we expect settlement of footings designed and constructed as discussed in this section wiil be about 1 inch or less. 2) The footings should have a minimum width of 16 inches for continuous walls and 2 feet for 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 2,000 Kumar & Associates, lnc.'1 Project No. 19-7-464 4 of foundations 36 inches aÍea. 4) Continuous should be exterior grade is typically used in this reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 12 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. The topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the relatively dense natural soils. The exposed soils in footing area should then be moistened and compacted. Voids created by boulder removal should be backfilled with concrete or granular structural fill compacted to at least 98olo of standard Proctor density at near optimum moisture content. A representative of the geotechnical engineer should observe all footing excavations prior to concrete placernent to evaluate bearing conditions. FOTINDATION 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 soils. Cantilevered retaining structures which are separate from the residence and 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 soils. Backfill should not contain organics, debris or rock larger than about 6 inches. AJl foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will 5) 6) Kumar & Associates, lnc.,ì Project No. 19-7-464 5 increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain should be provided to prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lifts and compacted to at least 90o/o of the maximum standard Proctor density at a moisture content near optimum. Backfill placed in pavement and walkway areas should be compacted to at least9SYo 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 dishess to facilities constructed on the backfill. 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 0.40. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 350 pcf. The 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 a granular material compacted to at least 95o/o 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. 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. Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirernents forjoint 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 road base should be placed beneath interior slabs for Kumar & Associates, lnc. ù Project No, 19-7-464 -6- support. This material should consist of minus 2 inch aggregate with at least 50% retained on the No. 4 sieve and less than 12% passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least95Yo of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site granular soils devoid of vegetation, topsoil and oversized rock. UNDERDRAIN 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 basernent areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. Shallow crawlspace should not need an underdrain with proper backfill placement and compaction and positive surface grading as recofilmended below. Where provided, the drains 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 be placed at each level ofexcavation and at least I foot below lowest adjacent finish grade and sloped at a rninimum lo/o to a suitable gavity outlet. Free-draining granular material used in the underdrain system should contain less than 2ol passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at Ieast 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: t) Inundation ofthe foundation excavations and underslab areas should be avoided during construction. Kumar & Associates, ln6. c'Project No. 19-7.464 .f 3) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95o/o af the maximum standard Proctor density in pavement and slab areas and to at least 9OYo af the maximum standard Proctor density in landscape areas. The ground surface surrounding the exterior of the building 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. Roof downspouts and drains should discharge well beyond the limits of all backfill. Landscaping which requires regular heavy irrigation and sprinkler heads should be located at least 10 feet from foundation walls. 4) LIMITATIONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this areaat this time. We make no wa:ranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory boring drilled at the location 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 boring and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appear diflerent from those described in this report, we should be notified so that re-evaluation of the recornmendations may be made. This report has been prepared for the exclusive use by our client for design purposes. \Me 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 and 2) s) Kumar & Associates, lnc. {f Project No. 19.7-464 E moniftr frG i@memaim of our recorrrørenddiq md to veri$ iñat fu rmenddioro havebm WW¡m¿V itrerpreted. Sig[ificddesign"lungeqnayrcquircadditimal mal¡rsi$ c modificdims to Õe rmmrrendations ¡resctrod hcrcin- We rmad æ-sitc obserr¿atiom of øcandions md formduirn bearing süda ad tcßËing of sfructu¡¡l filt by a rqrcseffiive of tbeepdofuica[ogiffi- Rcryedutty Sutm¡no{ Kumar & Assocíates, Inc. ShmcJ- Rúd, P-E Rer¿iewoilby: Sûs\rcnL Pawlalç P-E SJRIk¡c Kumar & Associates, lnc. o Project No. 1S-7-464 t-l¿/ H ü (J Ø þJ <[5xoæ&&4 Õ ,1 ¿ l, II ;-__¡-_-J t I .i 4l :ïi tr d ä il ! '.1 "I'tu q L', f.-t ':ot-{6' . .iîoy""..r ' rllr,.+''* ¿l I.¡ I;"¡l* iq. ,, f I f t: ¡ t, t¡râ \:".... .+(o.+ Ir\ I(t) ano ñ'ı oø(n oð L G EãY () z.tr C) co u.() t-- x.oJo-X t¡J LLO z.() Ë C)() J (¡) t! 'l¿ ìi¡ tE ! å BORING 1 LEGEND 0 l,';zl r..:.) t.. )/.1tt..t F3 t/, '. 1li.''Al: -¿sìl/4. . 1 I ¡ SAND AND SILT (SM-ML); cLÀYtY wlTH 0RAVEL, MIDIUM DENSEIVERY ST|FF, SLIGHTLY M0|ST, 9R0WN. 1s/ 12 WC= 12.9 +4=8 -200=46 GRAVEL COEBLE (0M); AND SILTY CLÀYEY SAND MATRIX, BASÀLT ROCKS TO POSSIBLT BOULOER SIZE, DTNSE, SLIGHTLY MOIST, BROWN. Ã 47 /12 WC=7.0 +4=36 -200=33 DRTVE SÂMPLE, 1 3/8-INCH r.D, SPLIT SP00N STANDARD PENTTRAIION IEST.Fl¡l LdL I-¡-o- L¡ltf ro¡rc DRIVE SAMPLE BLOW COUNT, INDICÀTES THAT 19 BL0WS 0F'"1'. A 140-PoUND HAMMER FALLING 50 INCHIS WERE REOUIRED TO DRIVE THT SÀMPLIR 12 INCHTS. I rnlcrrclr AUGER RTFUSAL, 10 50/ 4 NOTES 1. THE EXPLORATORY EORING WAS DRILLED ON AUGUST 28,2AI9 WITH A 4-INCH DIAMETTR CONTINUOUS FLIGHT POWER AUGER. 15 2, THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITT PLAN PROVIDID. 3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT MEASURED AND THE LOG OF THE EXPLORATORY BORING IS PLOTÏED TO DEPTH. 4, THE TXPLORATORY EORING LOCATION SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED 8Y THT METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOG REPRESINT THE APPROXIMATE BOUNDARIES BETWTEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6, GROUNDWATER WAS NOT ENCOUNÏERED IN THT BORING AT THE TIME OF DRILLING. 7. LABORATORY ÏEST RESULÏS: wc = WATER CoNTENT (%) (ASTM D 2216); +4 = PERCTNTAGE RETAINED ON NO. 4 SIEVE (ASTM D 6915); -200 = PERCENTAGE PASSING N0. 200 SIEVE (ASTM D 1140). 19-7 -464 Kumar & Associates LOG OF TXPLORATORY BORING li1. 2 .t É Fè dJ :! rì d9 :ù SAND GRAVEL FINE MEDTUM lconnsr FINE COARSE HYDROMEÍER ANALYSIS SIEVE ANALYSIS I : I rre , ; ,t9 : Ïtt RüotNcs 100 90 80 70 60 50 40 90 20 to o HRS l.ltN 7 HRS t5 MtN ö8 ltil o to 20 to & a0 60 70 a0 90 t00 ú , P i -t ? I I I I ) l 't 1 : ; I .0t 1l r5 tl¡t-.l li tàtt52 DIAMETER OF IN CLAY TO SILT COBBLES GRAVEL 8 7" SAND 46 % LIQUID LIMIT PLASTICITY INDEX SAMPLË 0F: Cloyay Sond qnd Slli wiih Grovel SILT AND CLAY 46 % FROM:Boringl@2.5' CBR 1m 80 ao 10 60 50 40 50 20 10 o ¡{RS Mlli.0 10 20 !o 40 50 60 70 ao eo 6 2 Ë a Pt a I : : ..: -t I -1 I I I ,'].i I l, rl.. I1.75 ¡ Ll:l 9.5 !oo I .123 PARTICLES IN MILLIMTTERS CLAY TO SILT COBBLES GRAVEL 36 % SAND LIOUID LIMIT SAMPLE 0F: S¡¡ty, cloyey, Sondy Groval 51 % SILT AND CLAY PLÅSTICITY INDEX FRoM:Bor¡ng1O4,5' 33% Thoso losl result3 opply only lo lh6 somples Phlch w€rs l€slod. lhg losllng r.porl Þholl nol bo reproduced, dxcopl ¡ñ lull, wllhoul lhå wrlilGn opprovol ol Kumor & Aêsocloln¡, lnc. Slovg onqlygls losllng ls psrlorm.d ln occordonc! wllh ÀSTM D6915, ASTM D7928, ASTI, C156 ond/or ASÌM t1140. SAND GRAVEL F'NE MEDTUM lcOAnSr FINE COARSE SIEVE ANALYSISHYDROMETER ANALYSIS I I t 1 : : 19-7 -464 Kumar & Associates GRADAÏION TIST RESULTS Fig. 3 TABLE I SUMMARY OF LABORATORY TEST RESULTS No.'19. SOILTYPE ehyey, Sand urd Silt \4rith Gravel Silty, OlayEy, Sandy Gravel losf) ul{co1{Ft1{ED COMPRESSTVE STRENGTH {G LIIIITS (o/o) PtASrß INDEX At tÈ LIQUID LMT {oÄl PERCENT PASSTT'¡G NO. 200 stEvE 46 33 SAND (%) 46 1336 ('KAUAItOil (/,1 GRAVEL 8 I.IATURAT DRY DEI{SNY fDcfì 7.0 12.9 }IATURAL MOISTURE COT{TENTDEPTH 2Y, 4Yz saltPt BORING I