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Home My WebLink AboutSubsoil Study for Foundation Design 06.14.2019&¿Æ-/hzþ7/â3 tcrt#mimff';*" Ån Employao Ownâd Company 5020 Clounty l{oad I 54 Clenwootl Springs. C() 8ló01 . phone: (-q70) 94-5-7S88 fax: (970) 945-8454 enrail ; kaglenwood(n)kurnalusa.cr:m wrvrv.kutnalusa.conl Office L¡cations: Denver {HQ). Parke¡, Coloradc Springs. Fort Collins. Cìenu,ood Springs, and Sununit County, Cok:ndo SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE LOT SD-13, ASPEN GLEN SUNDANCE TRAIL GARFIELD COUNTY, COLORÄDO PROJECT NO. 19.7-286 JUNE 14,2419 PREPARED FOR: WIIITNEY IVARI) P.O. BOX 870 EDWARTIS, COLORADO 81ó32 (wglygfdøme.com) àI r$ () erIo TABLE OF'CONTENTS PTJRPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITTONS SUBSIDENCE POTENTIAL. FIELD EXPLORATTON SUBSURFACE CONDITIONS ...... FOUNDATION BEARING CONDITIONS DESIGN RECOMMENDATIONS I 1 I 2- 3- .....,. - 3 - ..-3- ..-3-FOUNDATIONS FOUNDATION AND RETATNING V/ALLS ,., - 4 - FLOOR SLABS LINDERDRAIN SYSTEM .... I "'I r'¡. SURFACE DRAINAGE LIMITATIONS -7 - FIGURE 1 - LOCATION CIF EXPI,ORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORTNGS t*FIGURE 3 - GRADATION TEST RESULTS .....,.,...,, - 6 - ,"f i-d 'v :.i d. 'Í"¡ 1,..0'i' TABLE I- SUMMARY OF LABORATORY TEST RESULTS f ij t l rÈ*ð Kumar & Associates, lnc. ói Project No. 19-7-286 PURPOSE AIYD SCOPE OF STUDY This report presents the results ofa subsoil study for a proposed residence to be located on Lot SD-l3, Aspen Glen, Sundance Trail, Carfield County, Colorado. The project site is shown on Figure i. The purpose of the sfudy was to develop recommendations for the fcundation design. The study was conducted in accordance with our proposal for geotechnical engineering services to Whitney Ward dated lll{.ay 2,2419. A field exploration program consisting of exploratory borings was conducted to obtain information on the subsurtace conditions. Sarnples of the subsoils obtained during the field exploration were tested in lhe laboratory to determine their classification and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations tbr foundation t¡rpes, depths ald 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 Plans for the proposed residence were not available at the time of our study. The proposed construction is assumed to be a 2-story structure with attached garage. Ground floors are assumed to be structural over crawlspace or slab-on-grade. Grading for the strucfure is assumed to be relatively minor with cut depths between about 3 to S-feet We assume relatively light for¡ndation loadings, typical of the proposed type of construction. When building location, grading and loading information have been developed, we should be notified to re-evaluate the recommendations presented in this report. SITE CONDITIONS The subject site was vacant at the tirne of our field exploration. The ground surface is relatively flat with grades of less than 5Ya. Elevation difference across the building area is estimated at around I to 2 f'eet. Vegetation consists of gtass and weeds. There is an artificial pond on the Kumar &,Associates, lnc. {i Project No. 19-l-286 2- northeast boundary of the lot. To our knowledge, the pond is constructed with an impervious line.r to prevent leakage. SUBSIDENCE POTENTTAL Bedrock of the Penns5'lvanian age Eagle Valley Evaporite underlies the Aspen Glen Subdivioion. These rocks are a sequence of gypsiferous shale, fine-grained sandstone and siltstone with some massive beds of gypsum and limestone. There is a possibility that rnassive gypsum deposits associated with the Eagle Valley Evaporite underlie portions of the lot. Dissolution of the gypsum under certain conditions cân cause sinkholes to develop and can produce areas of localized subsidence. During previous work in the area, several sinkholes were observed scattered throughout Aspen Glen, mainly east of the Roaring For* River. A small sinkhole was mapped about 200 feet northwest of Lot SD-l3. These sinkholes appoar similar to others associated with the Eagle Valley Evaporite in areas of the middle to lower Roaring Fork River valley. Sinkholes were not obserued in the immediate area of the subject lot. No evidence of cavities wâs encountered in the subsurface materials; however, the exploratory borings wøre relatively shallow, for foundation design only. Based on our present knowledge of the subsurface conditions at the site, it cannot be said fcrr certain that sinkholes will not develop. The risk of ftrture ground subsidence on Lot SD-13 tlnnughout the service life of the proposed residence, in our opinion, is low; howevsr, the owner should be made a\ryare of the potential for sinkhole development. If further investigation of possible cavities in the bedrock below the site is desired, we should be contacted. F'IELD EXPLORATION The field exploration for the project was conducted on May 8,2019. Two exploratory borings were drilled at the locations shown on Figure I to evaluate the subsurface conditions. The borings were advanced with 4-inch diamcter continuous flight augers powered by a kuck- urounted CME-458 drill rig. The borings wore loggcd by a rcprcscntativc of Kumar & Associates. Samples of the subsoils were taken with a l%-inch I.D. spoon sampler. The sampler was driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This Kumar & Associates, lnc, t Projeet No. 19.7-2E6 -J test is similar to the standard penetration test described by ASTM Method D-l586. The penetration resistance vaiues are all indication of the relative density or consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Figure 2. The samples were refurned 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 or Figure 2. The subsoils consist of about ó inches of topsoil overlying relatively dense, silty sand and gravel with cobbles and possible boulders. The sand and gravel with cobbles continued down to the maxiinum drilled depth of 11 feet in both borings. Drilling in the dense, coarse granular soils was difficuit due to cobbles and possible boulders resulting ir near plactical auger drilling refusal. Laboratory testing perfbrmed on samples otrtained from the borings included natural moisfure content and gradation analyses. Rcsults of gradation analyses perfcrrmed on small diametor drive samples (rninus lYz-inch ffaction) of the c(,arse granular subsoils are shown on Figure 4. The laboratory testing is summarized in Table 1. No fi'ee water was encountered in the borings at the time of drilling and the subsoils were slightlymoist. FOUNDATION BEARING CONDITIONS The natural sand and gravel soils possess moderate bearing capacity and typically low settlement potential. At assumed excavatíon depths we expect the subgrade will expose the silty sand and gravel. Spread footings should be tb¿sible for foundation support of the residence with a low risk of settlement potential. DESIGN RECOMMENDATIONS FOTINDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nafure of the proposed construction, we recomrnend the building be founded with spreatl footings bearing on the natural gtanular soils. Kumar & Associates, lnc. t'Project No. 19-7-286 -4- The design and constnrction criteria presentecl trelow shoulcl be observed fbr a spread fcroting forurdation systern. I ) Footings placerl on the unclishrrhed natural granular soils should he dcsigncd fcrr au allorvable bearing pressure o$åQLpS! Based on experience, we expect settlement of footings designed and constructed as tliscussed in this section will 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 tbotings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection, Placement of ti¡undations at least.l{inches below exterior grade is typically used in this afea. 4) Continuous foundation walls should be reinforced top and bottom to span iocal anomalies such as by assuming an unsupported length of at least i2 feet. Foundation r.valls acting as retaining strucfures should also be designed to resist lateral earth pressures as discussed in the "Founclation and Retai¡ring Walls" section ofthis report. 5) The topsoil, any low-density clay and silt soils and loose disturbed soils should be removed and the footing bearing level extended down to the relatively dense natural granular soils. The exposed soils in footing area shoulcl then tre moistened and compacted. 6) FOL'NDATION AND RETAiNINC 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 tbr a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 50 pcf for backfill consisting of the on-site gyanular soils. Cantileverecl retaining structures which are sepârate fiom the resirlence and can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be designed for a lateral earth pressure computed r>n the basis of an equivalent A representative ofthe geotechnicai engineet should observe all footing excavations prior to concrete placement to evaluate bearing conditions. Kumar & Associates, lnc. i Project No. 13-7-286 -5- fluid unit weight of at least 40 pcf for backfill consisting of the on-site granular soils. Backfill should not contain organics or rock larger than about 6 inches. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffic, construction materials and equiprnent. The pressures recolnmended above âssume clrained conditions behind the walls ând a horizontal backiill surface. The buildup of water behind a wall or an upward slopiag backfill surface wili increase thc lateral pressure imposed on a foundation wall or retaining structure. An underdrâin should be provided to prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lifts ærd cornpacted to at least 95% of the maximum standard Proctor density at a moisture content near optimum. Backfill placed in pavement and walkway areas should be compacted to at least 95% of the maximurn standard Proctor density. Care should be taken not to overcompact the backfiil 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 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 0.50. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 400 pcf. The coeflicient of friction and passive pressure values recommended above assume ultimate soil skength. Suitable factors of safety should be included in the design to limit the strain which will occur at the ultimate strerrgth, 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 95a/a of the rnaximum 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 et'fects of some dífferential movement, floo¡ slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained Kumar & dssociates, lnc. r''Project No, 19-7-286 6- vertical movement. Floor slab control joints should be used to reduce darnage due to sluinkage cracking. The requirernents for joint spacing and slab reinforcement should be established by the desigxrer based on experience and the intended slab use. A minimum 4 inch layer of free- draining gravel should be placed beneath basement level slabs to fàcilitate drainage. This materiai should consist of minus 2 inch aggregate with at least 50% retained on the No. 4 sieve and less than?Vo passing the No, 200 sieve. All frll materials fbr support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a moisture content near optimum. Required lill can consist of the on- site granular soils clevoid of vegetation, topsoil aod oversized rock. IINDERDRAIN SYSTEM Altliough free w¿ter was uot encc¡unlered during our exploration, it has been our experience in fhe area that local perclied groundwater can develop during times of ireavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. We recommend below-grade construction, such as retaining walls, crawlspace and basernent areas, be protected fi'om wetting and hydrostatic pressure buildup by an underdrain system. The drains should consist of drainpipe placed in the bottom ot'the wall backfìll surroundecl above the invert level with &ee-draining granular material. The drain should be placed at each level i¡f excavation and at least I foot below lowest adjacent finish grade and sloped at a minimum lgo to a suitable gravity outlet or drywell. Free-draining granular material used in thç underdrain system should contain less th¿n 2% passing the No. 200 sieve, less than 50olo passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least lYz feet deep. SURFACE DRAINACE The fcrllowing drainagc prccautions should be,]bserved durilg çonstructir¡n and nraintained at all times after fhe resiclence has been completed: 1) Inundation of the foundation excavations and underslûb oreûs should bc avoidcd during construction. Kumar & Associates. lnc. "Project No. 19-7-286 -7 - 3) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95a/o of themaximum standard Proctor density in pavement and slab areas and to at least 90Yo of 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 6 inches in the first 1û 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 wifh about 2 feet ofthe on-site finer graded soils to reduce surface w¿ter infiltration. Roof downspouts and drains shoulcl discharge well beyond the iimits of all backfill. Landscaping which requires regular heavy irrigation should be located at least 5 feet from foundation walls. 4) LIMITATIONS This study has been conducted in aocordance with generally accepted geotechnical engineering principles and practices in this area at this time. \Me make no warranty either express eir implied. The conclusions and reconunendations 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 áo 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 prcfessional 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 encountered during construction appear different from those described in this report, we should be notified scr that re-evaluation of the recornmendations may be made. This report has been prepared fbr the exclusive use by our client for design purpCIses. We are not responsible for technical interpretations by others of our intbrmation. As the project evolves, we shoulcl provide continued consultation and field services during conskuction to review and monitor the implementation of our reconrmenclations, and to verify that the recommendations 2t s) Kumar & Associates, lnc. '"Project No. 19-7-286 -8- have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendatious presented herein. We recommend on-síte observation of exoavotions and foundation bearing slrata flrd testing of strusturul ûll by a rcpn:suntative of the geotechnical engineer. Respectfrrlly S ubrnittetl, Kumar & Assoeiate$. Inr- James H. Parsons, E.I. Reviewed by: Steven L. Pawlak, JHPlkac cc: Sam Augustine t,$3SS rl, : t.i Kum¿r & Associales, lnc, o Profect No, 19-7-286 APPROXIMATE SCALE_FEET SD-I 4 ) l5 s'/ ,E9t ,-g/ ,-*t'/ ô",' ,t ,'/ / lots.-'\ -_-_-'r!v)r- \ -.' \ -'r- \\ , PONO / / I / +% SD-13 t \-.----V/ \\ SUNDANCE ÎRAIL ----'\, \ L \\ \ \ \\ \¡\ \\ \t \ Y î \ sD-r2 \ \ \ \\ \ o gonnc z a BORING I PROPOSED RESIDENCE (TYPTcAL) 19-7-286 Kumar & Associates LOCATION OF EXPLORATORY BORINGS Fig. 1 fi BORING 1 E1.100'BORING 2 EL. 101' 0 0 3a/6,s0/s,s 44/6,5o/s WC=4.3 +4-44 -200= 1 65 5-- l-LI tilL I-F-ô- LJo 81 /12 1s/ 1z l-l¡l LrlL ITF-o-l¡lâ WC=2.0 f4=56 -200=9 10 10 --48/ 12 31/6,50/4.5 15 It LEGEND Fia N TOPSO|L; SILTY SAND W|TH GRAVEL, 0RGAN¡CS. BRowN FN tril l,:: .1 SANÐ, GRAVEL AND c08Bl"E$ (Gtyl-cP); SLIGHTLY StLTY, PRoBABLE BoULDERS, DENSE, SLIGHTLY MOIST, BROWN, ROUNDED ROCK. I DRIVE SAMpLE, 1 3/8-|NCH LD. SpLtT SPOON STANDARD PCNEIRAT|ON TEST so./s.s DRIVE SAMPLE BLOW COUNI. INDICATES THAT 50 ELOWS OF A 140-POUND HÀMMER- FALLING 50 INCHES WERE REQUIRED TO DRIVE THE SAMPLER 5,5 INCHES. NOTES 1, THE EXPLORATORY BORINGS WERE DRILLED ON MAY 8,2019 WITH A 4-INCH-ÞIAMETER CONTINUOUS-FLIGHT POWER AUGER, 2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY 8Y PACING FROM FEATURES SHOWN ON THE SITE PLAN PRTIVIUED. 3, THT ELEVATIONS OF THE EXPLORATORY BORINGS WERE MEASURED BY HAND LEVEL AND REFER TO BORING I AS ELEVATION .IOO' ASSUMEO, 4. THE EXPLORATORY BORING LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPL¡ED BY THE METHOD USED, 5. THE UNES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRAÕUAL. 6. GROUNDWATER WAS ÑOT ENCOUNTEREO IN THE BORINGS AT THE ÍIME OF DRILLING. 7, LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASïM D2216);+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D6913); -200= PERCENTAGE PAsstNG Nc. 200 S|EVË (ASTM Dlt4O). 19-7-286 Kumar & Associates LOCATION OF EXPLORATORY BORINGS Fig. 2 åg Èg too 90 !o 70 ¡o 50 10 to 20 to HYÞROME1'ER ANALYSIS SIEVE ANALYSIS 1}rE t.B, st^xoÀRù t I I SAND GRAYEL FIXE MEDIUM COARSE 0 ro 20 !ð 4 50 m 70 to 90 b- F Ë A ,*-"- .oor te DIAMETER OF CLAY IO SILT co8SLESrINE GRÅVTL 56 'I SAND LIOUID TIMIT SAMPLE OF: Slfghlly Slltf Sqndy çrsy6l 35X PL,ASTICITY INDEX SILI ÂND CLÁY g ?. FROM: Borlng 1 6 5'& t0' SIEVS ANALYSIS * g E Ë 10q ¡o EO 70 æ 50 40 JO n lo ó 20 ¡0 ß 50 50 2ç 80 90 fm = F Ëf it .?50 CLÂY TO SILT SANO FINE COBELES GRAYEL 44 % SAND LIQUIÐ LII¿IT SAIIPLE 0F: Sllty Sond ond Grdv¿l .+0 ,4 PIÁSIICITY ¡NDEX SILT AND CI.ÀY 1ç% Th6e. l.3l rosull! qpÞly orly t¡ lho somplos whlch wors ,.lod. Thslc.l¡ng Þpo.t shd¡l hÒt bo róptoCucld,.xê.pl lñ lull, vllhoul öB wrlltrnqÞÞþvdl of Kumqr & ÅÊ¡oolqlôr, lnc.sbr! onoly¡¡s fcrllng t9 F.rrorñod i¡.ccordonc. últh ^SÎt{ 08915. AsrM Þ792E, ÀS1g Cl56 ohdlor ASTi¡ Dtlrl0. FROMIEorlhg2ø2.5'&3' HYDROT¡ETER ANALYSIS lUe RE OHOS ta ¡lls ?ã6 ¿too)o g.s. s¡ ND^RD $Rr€S 150 ¡ao ¿50 ara aro 4 cl¡ÁF SôUARI OXN|Ë / / I I GRAVEL MEDIUI'COARSEI FINE COARSE 1 9-7-286 Kurnar & Associates GRADATION TEST RISULTS Fig. 5 lG-rtl(umar & Â¡*otln&. lns.üeriXsçhnicål änd Mäteriírl$ Ërx¡inçr.rrsãnd Íìnvir 0nm{Tnlål lìcisnti$lskumaru*a.*omTABLE 1SUMþIARY OF LABORATORY TEST RESULTStlc. 19-7-286SOILTYPESlightly Silty Sandy GravelSilty Sand and Gravelfmf)UHCO}¡FINEDCOTIPRESSNESIREHGTHPLASÍICr{DEXt%)ÂTTÊRBERG LMÍTSt%tL]QUID LIi{TfPÉRCÊNTPÁSSING NO.200 stEvE96ISANDl'/"'l3540GRADAÏIONf/')GRAVEL5644IIATURALDRYDEilSAY{DcOM)NAÏURAtilGfSTURECOIIlE¡¡T2.04.3ffrlÐEPTH5&10combined2.Vz 8.5combinedsÄflptE LocÀTf5¡¡Bon${G12