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Home My WebLink AboutSubsoils Report for Foundation DesignI(+A Xumar & Associatos, lns." Geotechnical and Matenals Engineers and Envrronmenlal Scientists An Employeo Orirnad Contpany 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com www.kumarusa.com Offiae l,ocations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado SUBSOIL STUDY FOR FOTTNDATION DESIGN PROPOSED GARAGE ADDITION 2074 COANTY ROAD 109 LOT 10, TELLER SPRTNGS GARFTELD COUNTY' COLORADO PROJECT NO.23-7-674 DECEMBER 28, 2023 PREPARED FOR: JACK KENNEDY 2074 COUNTY ROAD 109 CARBO|IDALE, COLORADO 81 623 ik@rof.net TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION ......... SITE CONDITIONS SUBSIDENCE POTENTIAL FIELD EXPLORATION SUBSTIRFACE CONDITIONS DESIGN RECOMMENDATIONS .. FOUNDATIONS FLOOR SLABS UNDERDRAIN SYSTEM SURFACE DRAINAGE.... LIMITATIONS 1 1 I -1- -2- n-L- a-J- -3- -4- 4- FIGURE 1 - LOCATION OF EXPLORATORY BORING FIGURE 2 - LOG OF EXPLORATORY BORING FIGURE 3 _ SWELL-CONSOLIDATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS Kumar & Associates, lnc. I Project No. 23-7-674 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed garage addition to the residence located at2074 County Road 109, Lot 10, Teller Springs, Garfreld County, Colorado. The project site is shown on Figure 1. The pulpose 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 Jack Kennedy dated November 24,2023. 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, compressibility and other engineering characteristics. The results of the field exploration and laboratory testing were analyzedto 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 garage addition will be a single-story skucture with slab-on-grade floor attached to the west side of the residence. Grading for the structure is assumed to be relatively minor with cut depths between about 2 to 3 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 proposed addition area consists of asphalt paved parking on the west side of the existing residence. The ground surface is relatively flat with a gentle slope down to the northeast. Nearby vegetation consists of irrigated lawn. SUBSIDENCE POTENTIAL Bedrock of the Pennsylvanian age Eagle Valley Evaporite underlies the Teller Springs subdivision. These rocks are a sequence ofgypsiferous 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 property. Dissolution of the gypsum under certain conditions can cause sinkholes to develop and can produce areas of localized subsidence. Sinkholes have been observed in the area of the Teller Springs subdivision which appear similar to others associated with the Eagle Valley Evaporite in areas of the lower Roaring Fork River valley. i I j I I I I Kumar & Associates, lnc. @ Project No. 23-7-674 ., 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 boring was 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 develop. The risk of future ground subsidence at the subject site throughout the service life of the proposed addition, 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 6,2023. 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 a truck-mounted CME-458 drill rig. The boring was logged by a representative of Kumar & Associates, Inc. Samples of the subsoils were taken with I% inch and 2-itch 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 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. The subsoils encountered, below the asphalt pavement, consist of about 4%feet of medium stiff, sandy silty clay overlying dense, silty sandy gravel and cobbles. Drilling in the coarse granular subsoils with auger equipment was difficult due to the cobbles and probable boulders and drilling refusal was encountered in the deposit. Laboratory testing performed on samples obtained from the boring included natural moisture content and density and finer than sand size gradation analyses. Results of swell-consolidation testing performed on relatively undisturbed drive sample of the upper clay soil, presented on Figure 3, indicate low to moderate compressibility under conditions of loading and wetting. The laboratory testing is summarizedinTable 1. No free water was encountered in the boring at the time of drilling and the subsoils were very moist to slightly moist with depth. t: ! I t, i I i I I I I I I I i I I t: I i I i I t, t' i l. Kumar & Associates, lnc. @ Project No. 23-7-674 J DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we recommend the building addition 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 granular soils should be designed for an allowable 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. Footings extended down to bear entirely on the dense gravel can be designed for an allowable bearing pressure of 3,000 psf with minor settlement potential. 2) The footings should have a minimum width of 18 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 atea. 4) Continuous foundation walls should be 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 (if any) should also be designed to resist a lateral earth pressure coffesponding to an equivalent fluid unit weight of at least 55 pcf. 5) All existing fill, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the firm natural soils. The exposed soils in footing area should then be moisture adjusted to near optimum and compacted. The clay soils have relatively high moisture content and care should be taken to not disturb them such as with wheel traffic or inundation from surface runoff. 6) A representative of the 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. 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 Kumar E Associates, lnc. o Project No. 23-7-674 -4- 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 CDOT Class 6 base course should be placed beneath slabs for support. This material should consist of minus 2-inchaggregate with at least 50% retained on the No. 4 sieve and less than l2o/o passing the No. 200 sieve. Due to the relatively high moisture of the natural soils, care should be taken not to disturb the natural clay subgrade such as with wheel loading. All fill materials for support of floor slabs should be compacted to at least 95o/o of maximum standard Proctor density at a moisture content near optimum. Subgrade fill can consist of the onsite soils devoid of vegetation, topsoil and debris when moisture conditioned to near optimum moisture content. Imported granular soil such as CDOT Class 6 base course could also be used. UNDERDRAIN SYSTEM We understand the proposed finished floor elevation of the addition at the lowest level is at or above the surrounding grade. Therefore, a foundation drain system is not required. It has been our experience in the area that local perched gtoundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff and the clay soils can create a perched condition. We recommend below-grade construction, such as retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain and wall drain system. If the finished floor elevation of the proposed addition is revised to have a floor level below the surrounding grade, we should be contacted to provide recommendations for an underdrain system. All earth retaining structures should be properly drained. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the addition has been completed: 1) Inundation ofthe foundation excavations andunderslab areas shouldbe avoided 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 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 hrst l0 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in paved areas. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. ,il iii ii :ll rii it :IIjit ,t! iiiiIiil ;ii ril rii rli itl ,li iii ill iii .I ,ltr;l,t' ;i ' ,ll,l; iii iii :li iii'il ,ii ii iti ,ii :ll jil ;ii ,il ili iil ilt :ll ill ili iti ili ii I ,ii :I I :ll :i iti,i, iit rll iii ii iI iii ;ii ;ii ;li iti :ii Ii ii! iir iii iil iii'tl .lr iil iil Kumar & Associates, lnc. @ Project No. 23.7.674 -5- 5) Landscaping which requires regular heavy irrigation should be Iocated at least 5 feet frorn foundation walls. LIMITATIONS This study has been conducted in accordance with generally accepted geotecturical engineering principles and practices in this area at this time. We rnake no warranty either express or implied. The conclusions and recommendations subrnitted in this report are based upon the data obtained frorn 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 lindings include interpolation and extrapolaticln of the subsurface conditions identified at the exploratory boring and variations in tire subsurface conditions may not become evident untii excavation is perfonned. If curditions encountered during construction appear dilferent frorn those described in this repofi, we should be notified so that re-erraluation of the recommendations may be rnade. This report has been prepared fbr the exclusive use by our client fbr design purposes. We are not responsible for technical inte4rretations 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 recomrnendatiotrs, and to veritl, that the recornmendations have been appropriately interpreted. Significant clesign changes may requile additional arialysis or rnodifications 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, (f, Steveu L. Pawlak, P. Revierved by: I I i..* -:' ,:r' '' b Daniel E. Hardirr, P.E. SLP,&ac cc: Palomino Desigri-Build - Jack Palomiuo (;;lr. ii1;;iii:r'rrliir;''i"i1'r ;:ijillti , ,ri,) if. 1^1i1i ;;1 |t. jr,::l:qrL iiiit'l.l, I ltt:,r tr,] :r i,r:'r .'.1' l:,1,i ,i il il BORING 1o PROPOSED ADDITION EXISTING EXISTING 1()E 6 0 APPROXIMATE SCALE-FEET 2rJ74. 23-7 -67 4 Kumar & Associates LOCATION OF EXPLORATORY BORING 1 I IFig BORING 1 (4)ASPHALT, THICKNESS IN INCHES SHOWN IN PARENTHESES TO LEFT OF THE LOG.0 (4) 5/12 CLAY (CL); Sllfi, SANDY, MEDIUM STIFF, VERY MOIST, BROWN. FlrJ u.l LL I-F(L LJo 5 10/12 WC=21.9 W GRAVEL AND CoBBtrS (GM); STLTY, SANDY, PRoBABLE BOULDERS, DENSE, MOIST, BROWN, ROUNDED ROCK. I oo=gg I F i I _t DRIVE SAMPLE, z-INCH I.D. CALIFORNIA LINER SAMPLE. 10 DRTVE SAMPLE, 1 5/8-|NCH t.D. SpLtT Sp00N STANDARD PENETRATION TEST, -l otsrunneo BUr.x sAMPt.e. I_t <rt.lDR|VE SAMPLE BL0W C0UNT. INDICATES THAT 5 BL0WS 0F"/ ''A 140-pouND HAMMER FALLINc 30 tNcHEs wERE REQUIRED TO DRIVE THE SAMPLER 12 INCHES. f enlcrrclr AUGER REFusAL. NOTES THE EXPLORATORY BORING WAS DRILLED ON DECEMBER 6, 2023 WITH A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. 2, THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT MEASURED AND THE LOG OF THE EXPLORATORY BORING IS PLOTTED TO DEPTH. 4. THE EXPLORATORY BORING LOCATION SHOULD BE CONSIDERED ACCURAIE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE TIME OF DRILLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (X) (ASTM D 2216): DD = DRY DENSITY (pcf) (ASTM D 2216); -2OO = PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D 1 1 40). WC=7,1 -200=26 Fis. 223-7-674 Kumar & Associates LOG OF EXPLORATORY BORING ,1 jj ;i 1l ! I rl :] {' ,li SAMPLE OF: Sondy Silty Cloy FROM:Boringl@4' \ttC = 21 .9 %, DD = 99 pcf ln ot NO MOVEMENT UPON WETTING 0x J4J -llr,l =vt t_2 zotr (f oazoo_4 -5 -6 1.0 APPLIED PRESSURE - KSF t0 Fig. 3SWELL_CONSOLIDATION TEST RESULTS23-7-674 Kumar & Associates rli K+n Kumar & Arstriates, lnn" ',lcrltrnl c 1r tr:1 I\4el?r,,1rs 1".:s:.r"+.:, an{ fifi rirrcrrilgr]lgt SCr{ifrti$t$ TABLE 1 SUMMARY OF LABORATORY TEST RESULTS SOIL TYPE Sandy Silty Clay Silty Sandy Gravel (psfl UNCONFINED COMPRESSIVE STRENGTH (%\ PLASTIC INDEX ATTERBERG LIMITS t%l LIQUID LIM]T PERCENT PASSING NO. 200 stEvE 26 SAND (%l GRADATION (%) GRAVEL {ocfl I'IATURAL DRY DENSITY 992t.9 7.1 NATURAL MOISTURE CONTENTDEPTHBORING 4 5-8 I No. 23-7-674