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Home My WebLink AboutSubsoil Study for Foundation1-iEPWORTH-PAWfAK GEOTECHNICAL C 1 h_I'li,X16Ik-I.151.1.11. t.1S,1i41.11t1I4.k1. Itt- ll,� 154 t ilcin\l,ni,l 1'I ,n4: g7l1-li4;-;lay`• 970-945-'054 on ill: SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED BARN ADDITION AND RESIDENTIAL, TRI-PLEX ASPEN VALLEY POLO CLUB ASPEN EQUESTRIAN ESTATES COUNTY ROAD 100, GARFIELD COUNY, COLORADO JOB NO. 113 459A DECEMBER 18, 2013 PREPARED FOR: DIVIDE CREEK BUILDERS ATTN: MAX FILISS 1531 COUNTY ROAD 342 SILT, COLORADO 81652 niaNfilissrtvallao.cm€11 I\ RHP Parker 303-841-7119 ° Colorado Sl,rings 719-633-5562 m Silvertkome 970-468-1949 TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS - 2 - SUBSIDENCE POTENTIAL - 2 - FIELD EXPLORATION - 3 - SUBSURFACE CONDITIONS - 3 - FOUNDATION BEARING CONDITIONS - 4 - DESIGN RECOMMENDATIONS - 4 - FOUNDATIONS - 4 - FLOOR SLABS ... - 6 - UNDERDRAIN SYSTEM - 6 - SURFACE DRAINAGE - 7 - LIMITATIONS - 7 - FIGURE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURE 4 - SWELL-CONSOLIDATION TEST RESULTS FIGURE 5 - GRADATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed barn addition and residential tri-plex to be located at the Aspen Valley Polo Club, Aspen Equestrian Estates; County Road 100, Garfield County, Colorado. The project site is shown on Figure 1. 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 Divide Creek Builders dated December 11, 2013. Hepworth-Pawlak Geotechnical, Inc, previously performed a preliminary geotechnical study for the proposed development (Preshana Farms) and reported our findings under Job Number 198 501, dated August 31, 1998. We also provided a geotechnical engineering study for a proposed commercial area on the property, Job Number 104 739, dated November 30, 2004. 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 field exploration and laboratory testing were 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 • The proposed barn addition will be a tall one story wood frame structure. Ground floor will be slab -on -grade. Grading for the structure is assumed to be relatively minor with cut depths between about 2 to 4 feet. The proposed tri-plex will be one and two story wood frame construction above a crawlspace. Grading for the structures is assumed to be relatively minor with cut depths between about 2 to 4 feet. We assume relatively light Job No. 113 459A GateCh -2 - foundation loadings, typical of the proposed type of construction. The proposed building locations are shown on Figure 1. The existing pole barn, garage and residence will be razed prior to 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 property has recently been used for equestrian purposes and development has consisted of barns, sheds, indoor arena and outside stables and arenas. An existing pole barn, garage and residence constructed prior to the subdivision creation are located in the southeast corner of the property. An existing stable and indoor arena are located in the southwest corner of the property. The property is relatively flat with a slight slope down to the west. There was about 4 inches of snow cover at the time of our field investigation. SUBSIDENCE POTENTIAL Bedrock of the Pennsylvanian age Eagle Valley Evaporite underlies the Aspen Equestrian Estates subdivision. 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 massive gypsum deposits associated with the Eagle Valley Evaporite underlie portions of the lot. Dissolution of the gypsum under certain conditions can cause sinkholes to develop and can produce areas of localized subsidence. During previous work in the area, several sinkholes have been observed scattered throughout the lower Roaring Fork River Valley. Sinkholes were not observed in the immediate area of the subject property. No evidence of cavities was encountered in the subsurface materials; however, the exploratory borings were relatively shallow, for foundation design only. Based on our present knowledge of the subsurface conditions at the site, it cannot be said for certain that sinkholes will not Job No, 113 459A GeStech -3 - develop. The risk of future ground subsidence on the property throughout the service life of the proposed barn addition and tri-plex, in our opinion, is low; however, the owner should be made aware of the potential for sinkhole development. If further investigation of possible cavities in the bedrock below the site is desired, we should be contacted. FIELD EXPLORATION The field exploration for the project was conducted on December 11, 2013. Four exploratory borings were drilled at the -locations shown on Figure.] to evaluate the subsurface conditions. Two borings were drilled at the barn addition and two borings in the area of the tri-plex. The borings were advanced with 4 inch diameter continuous flight augers powered by a truck -mounted CME -45B drill rig. The borings were logged by a representative of Hepworth-Pawlak Geotechnical, Inc. Samples of the subsoils were taken with 131 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 standard penetration test described by ASTM Method D-1586. The penetration resistance values are an 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 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 consist of about one to two feet of fill overlying a relatively thin layer of clay above sandy gravel with cobbles and small boulders, Drilling in the dense granular soils with auger equipment was difficult due to the cobbles and boulders and drilling refusal was encountered in the deposit. Job No, 113 459A G cptech -4 - Laboratory testing performed on samples obtained from the borings included natural moisture content and gradation analyses. Results of swell -consolidation testing performed on a relatively undisturbed drive sample, presented on Figure 4, indicate moderate compressibility under conditions of loading and wetting. Results of gradation analyses performed on a small diameter drive sample (minus 11/2 inch fraction) of the coarse granular subsoils are shown on Figure 5. 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 slightly moist to moist. FOUNDATION BEARING CONDITIONS A pit about 4 feet deep was observed alongside the existing stable. The existing footing was exposed and the bottom of the footing was about 2 feet below surrounding grade. The subsoils exposed consisted of sandy'clay fill above sandy clay overlying granular material at 3'/ feet below grade. The proposed barn addition excavation adjacent to the existing barn should expose the bottom of the existing footings and penetrate all fill material. The tri-plex footprint spans over the existing garage and a few feet of fill material should be expected in this area. All fill and sandy clay soils should be removed and the excavation extended down to granular soils. DESIGN RECOMMILNDATIONS 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 granular soils. Job No. 113 459A Gtech -5 - The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed natural granular soils should be designed for an allowable bearing pressure of 3,000 psf The barn addition can be founded the natural sandy clay soils and designed for a maximum soil bearing pressure of 1,500 psf. Based on experience, we expect settlement of footings designed and constructed as discussed 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 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. A shallower footing protecfe ffrohi frost -with insulation, designed in accordance with the International Building Code could also be constructed. 4) Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 10 feet. Foundation walls acting as retaining structures should also be designed to resist lateral a lateral earth pressure corresponding to an equivalent fluid unit weight of at least 45 pef. 5) All existing fill, topsoil; sandy clay in the tri-plex excavation and any loose or 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,should then be moistened and compacted. If water seepage is encountered, the footing areas should be dewatered before concrete placement. b) A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. Job No. 113 459A C- tech -6 - 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 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 free -draining gravel should be placed beneath slabs to provide a break for capillary moisture rise. This material should consist of minus 2 inch aggregate with at least 50% retained on the No. 4 sieve and less than 2% passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95% 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 mountainous areas 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 crawlspace areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. 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 of excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum 1% to a suitable gravity outlet. Free -draining granular material used in the underdrain system should contain less than 2% passing the No: 200 Job No, 113 459A -7 - sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least 1 % feet deep. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the barn addition and tri-plex have been completed: 1) Inundation of the foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optimum 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 maximum 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 a minimum slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of TA inches in the first 10 feet in paved areas. Free -draining wall backfill should be 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. 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 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 Job No. 113 459A Gtech -8 - concerned about MOBC, then a professional in this special feld 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 so that 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 information. As the project evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to verify that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommend on-site observation of excavations and foundation bearing strata and testing of structural fill by a. representative of the geotechnical engineer. Respectfully Submitted, HEPWORTH - PAWLAK GEOTECHNICAL, INC. Louis E. Eller Reviewed by: 0.00111111111110,,, "00, Daniel E. Hardin, P.E. LEE//ksw 19/13 ►►hnrnno Job No. 113 459A C rttch ¢m 2 • 11 2 71.1 z. ai U • b 4 8 BOR 0 / / / PROPOSED L . r/ BARN ADDITION (SHADED) COUNTY ROAD 100 PEW MN= 6280 EXISTING BARN 1 1 PROPOSED BORING ORING 3 (SHADED) BORING 4 EXISTING RESIDENCE EXISTING BARN BOR •r / / / / 1 2 EXISTING INDOOR ARENA / 0 co o 0p ra oD 0)U Z 0. 11w -J mul EXISTING GARAGE APPROXIMATE SCALE 1n= 80' 113 459A H chHepwwt INK:h[ak eatechnlcol LOCATION OF EXPLORATORY BORINGS Figure 1 BORING i ELEV.= 99.2' '.a416,1216 WC=18.3 :• DD=109 5 n. 0 BORING 2 BORING 3 BORING 4 ELEV.= 97.2' ELEV.= 6275.6' ELEV.= 6275.9' --7 57112 WC=2.9 +4=63 -200=7 r 10 i 10/12 WC=16.8 -200=56 0 716,1510 WC=7.0 -200=66 65112 5 BARN ADDITION TRI-PLEX Note: Explanation of symbols is shown on Figure 3. 10 0 113 459A H ch Hepworth-Pawlak eatechnlcat LOGS OF EXPLORATORY BORINGS Figure 2 LEGEND: FILL; clayey silty sand and gravel with cobbles, loose, moist, mixed browns. About 6 inches of road base above fill at Boring 3. ® TOPSOIL; organic sandy clay and silt, firm, moist, dark brown. CLAY (CL); sandy, silty, medium stiff, moist, reddish brown to brown. GRAVEL, COBBLES AND BOULDERS (GM -GP); sandy, slightly silty to silty, dense, moist, brown, subrounded rocks. Relatively undisturbed drive sample; 2 -inch I.D. California liner sample. Drive sample; standard penetration test (SPT), 1 3/8 inch I.D. split spoon sample, ASTM D-1586. 57/12 Drive sample blow count; indicates that 57 blows of a 140 pound hammer failing 30 inches were required to drive the California or SPT sampler 12 inches. T Practical drilling refusal. Where shown above bottom of log, indicates that multiple attempts were made to advance the boring. NOTES; 1. Exploratory borings were drilled on December 11, 2013 with 4 -inch diameter continuous flight power auger. 2. Locations of exploratory borings were measured approximately by pacing from features shown on the site plan provided. 3. Elevations of exploratory borings were measured by instrument level and refer to the Bench Marks shown on Figure 4. the exploratory boring locations and elevations should be considered accurate only to 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 transitions may be gradual. 6. No free water was encountered in the borings at the time of drilling. Fluctuation in water level may occur with time. 7. Laboratory Testing Results: WC = Water Content (%) DD - Dry Density (pcf) +4 = Percent retained on the No, 4 sieve -200 = Percent passing No. 200 sieve 113 459A �H�cHeworth-Aawln Geotechnical LEGEND AND NOTES Figure 3 Compression 0 1 2 3 4 5 0.1 1.0 APPLIED PRESSURE - ksf 10 100 113 459A Hepwart—Pawlok Geatechnicol SWELL -CONSOLIDATION TEST RESULTS Figure 4 Moisture Content = 18.3 percent Dry Density = 109 pcf Sample of: Sandy Silty Clay From: Boring 1 at 2 Feet - -i--e r No movement upon wetting 9 r T - 1 r1 0.1 1.0 APPLIED PRESSURE - ksf 10 100 113 459A Hepwart—Pawlok Geatechnicol SWELL -CONSOLIDATION TEST RESULTS Figure 4 • • l YFi DROMETERANALYSIS SIEVE ANALYSIS NN�R� HH 11ME READINGS 1 U.S. STANDARD SERIES CLEAR SQUARE OPENING5 0 45lViIN.15M N. 60MINi9MIN.4 MIN. 1 MIN. #200 #100 #50 #30. #16 #8 #4 318" 314` 1 112" 3' 5"6" 8" 100 10 20 30 40 50 60 70 to 90 100 Mill ` II i_ -M1 MI im IMmM1_M MI • !M1.11 ii a mmMm M IMI i MEM r_rrM_Mm- !- ROME ANIMEmn.wm moim /11 •illmJm_NmMmmmMMmMs a• mM -M•= • - mE•mmMm••M••M w_• - IMIMMOIilM IMIIMM••_!alMERMmmm••EMMIa- a•M�•MM�N--MEED Mw•m il•MI NliM-w�-EMmmI1!•Mq --m••MMMm=WMM- _•mM MI! lama ME J✓•Mml•a■M= IIWMMN� cess N -= Mi- 1 111 Mime mwE•M_Ram•_ M� Mielff Mina M••AMEWIMMmEr M•MMM NMmml-- m_!Mm• M W --a •mini =NM MEMOK I MMI•IN. .• !i•--■mmle MMmI E•MamammM_ ___ _ ! •m1 ■ �• mmEm ImM• a 'WOW MIWW �MIIMMnfti o.m mr MMMllMrr MMMME.EIEr mMa•l mMem r .SOY w•a• MamammwwiR --- M_I••ME._IME�•.twm.mmm.. m iliMINImmM.MMM -•._mM fm•I.•..•- m!f !MIM l• 14=•. 1M!!M••i MMm ImlaW/ Mai M•!MMr !`mM•a•MmlMmiMWMMarra!IMIm•_•I- i IMEIWIIM•mwilMff �!M�•IMMO --M•m MI r Mme- IM `'yIImWP-lM•WIM N »-M- Yr=M _•rI�MMrM .M= IIM_M•l-MmRMmM=M!•mmm mMrl_mmImm___ MOrlmm•N•rm ae!_ ammM -MINNI. ^!i_MINamlM=I MMIMIIM Mims- MMII•I- MOM! 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M ila it ^_M!• IMOMMI An r0. -mMlMr�- •Mmm••MM!•1 10 1W=M11, ••• ••-a!•I Wi i r»_mmMi__ MUMm!! —mm_M_M SIREm•mm•_NM=.11 •M!•IN • • 1='Ill MRMM— INEmI.armsEMME.M•11 M� �— . 11•=1 IMMMIIlWai 01• I14l /-MMm I llII'r mlm IM••lill i M-MIMMWI--IMI AMM Oa•••• -Mir -i w•WI w.lm•••m III •�.PI IIMM•I•I••MI• M•...._ e mm.[ 1�I E MIMPO a rM•m ••R•_E rmmm• Mliff • _. M•r• Jmws __ •_Wff mgl.m ••MINI _ •am Mi •M MMM••!- IIIIIMIr•MmmIm .•M11• 1;• • • Min= a •!M .1.•MI•• 1rMm•N•Mm•=0 Mr!•fMW=Mk• Mamma •ff I•m m•rr•Mmm••rMM• Ill mtrom m.mmr•saIMS Mmmm•MOMm maM-wwwi MMmt1i-•MOMS- i/.Mlm MPowmm•m maiiimr -MMM Mm Mir-•• l MOS M•M•i IMSmm•I•mM••MLima• M.mM•M bra rMmmmM`•_ i M•� I mmll.. _J - r!_••M!M___a_ ••••_•••MEm• 11 M-MEa-gyral lO Mm• -M••_ - r_ Mir-Mar•••1Wm---M_M•!•Mam __ �__-l_SMM Mm•me �miM�M`m_O �MI.I� �mmMMmlE•a!•r_•Mmili_Mmmmr,.MM•MIEms_MEP MIN __MRS__ -_•int• MiMMINE MMM-M•••mi ..E. MMS - •••EI• s•rN lr !IMM•_ M•••m! Ml --O M=OMR --_---•0=Im -MMSMMMMMI MMM!•m!•M•MMm = rMMS- M•il=••^ 10 1=11•11 MM. MMOW iml.MM .111 i - --i. a Ira _aMm•M_»__MI .001 .002 .005 .009 .019 .037 .074 .150 .300 .600 1.18 2.36 DIAMETER OF PARTICLES IN MILLIMETERS 4,75 CLAY TO SU GRAVEL 63 % LIQUID LIMIT 96 SAND 9.5 19.0 37.5 12.5 762 152 203 127 GRAVEL COBBLES FINE 1 IEOIL+M j OQ SE FINE { COARSE SAND 30 % SILT AND CLAY 7 % PLAST€C[ Y INDEX SAMPLE OF: Slightly Silty Sandy Gravel FROM: Boring 2 at 2 Y2 Feet 113459A H Hepworth--Pawlak Geotechnical GRADATION TEST RESULTS 90 80 70 80 50 40 30 20 10 0 Figure 5 HEPWORTH-PAWLAK GEOTECHNICAL, INC. TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Job No. 113 459A SAMPLE LOCATION NATURAL MOISTURE CONTENT (%) NATURAL DRY DENSITY06) fpcf) GRADATION PERCENTATTTERBERG PASSING NO. 200 SIEVE LIQUID LIMIT N. LIMITS PLASTIC INDEX (%) UNCONFINED- COMPRESSIVE STRENGTH (PSF) SOIL OR BEDROCK TYPE BORING DEPTH (ft) GRAVEL SAND (%) _ 1 _ 2 18.3 109 Sandy Silty Clay 2 2 112 2.9 L 63 30 7 Slightly Silty Sandy Gravel 3 1 16.8 56 Silty Sandy Clay - Fill 4 1 7.0 66 Sandy Silty Clay - r _ r