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Home My WebLink AboutSubsoil Study for Foundation Design 04.22.19tGrt -:' ACEC lfu¡ts & l¡soûffi, hc. Geotæhniæl and iíaterials Engineers and Envlronmenhl Scienüsrs kumarusa.com 5020CountyRoad 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com www.kumarusa.0omMEMßER Offìce Locations: Denver (HQ), Parke¡ Colorado Springs, Fort Collins, Glenwood Springs and Summit County, Çolorado Apnl22,2019 Gruenefeldt Construction Attn: Dan Gruenefeldt P.O. Box 1910 Basalto Colorado, 81621 dan@gruenefeldt.com Project No. 19-7-214 Subject:Subsoil Study for Foundation Design, Proposed Residence, Lot E19, Aspen Equestrian Estates, Equestrian Way, Garfield County, Colorado Dear Dan: As requested, Kumar & Associates performed a subsoil study for design of foundations at the subject site. The study was conducted in accordance with our agreement for geotechnical engineering services to you dated April 5,2019. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presørted in this report. Proposed Construction: The proposed residence will be a one to two story wood frame structure located on the site in the area of the pits shown on Figure l. Ground floor will be slab- on-grade. A monolithic slab foundation is being considered. Cut depths are expected to range between about l%to 3 feet. Foundation loadings for this type of construction are assumed to be relatively light and t¡pical of the proposed type of construction. If building conditions or foundation loadings are significantly different from those described above, we should be notified to re-evaluate the recommendations presented in this report. SÍte Conditions: The lot was vacant at the time of our site visit. The lot is flat, slopes slightly down to the south and is vegetated with grass and weeds. Eagle Valley Evaporite bedrock is exposed on the valley hillsides to the north and south of the property. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating five exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The subsoils encountered, below about I to lVz feet oftopsoil, consist of ap to 3Yz feet of medium stiff to stiff sandy silt and clay or I foot of medium dense, silty, sandy Gruenefeldt Construction Apn|22,2019 Page2 clay and gravel with cobbles, overlying relatively dense, silty sandy gavel with cobbles and small boulders down to the maximum depth explored, 2tA ta 6 feet. Results of swell-consolidation testing performed on a sample of the clay soil are presented on Figure 4 and results of a gradation analysis performed on a sample of the gravel are presented on Figure 5. The laboratory test results are summarized in Table 1. Free water was not encountered in the pits at the time of excavation and the soils were moist. Foundation Recommendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, we recommend spread footings or a thickened edge slab foundation placed on the undisturbed natural clay or natural gravel soil designed for an allowable soil bearing pressure of 1,500 psf for support of the proposed residence. The clay soils tend to compress under load and there could be some post-construction foundation settlement. Footings or the thickened slab edge should be a minimum width of 16 inches for continuous walls and2 feet for columns. The topsoil and loose disturbed subsoils encountered at the foundation bearing level within the excavation should be removed and the footing or thickened edge bearing level extended down to the undisturbed natural soils. V/e should observe the completed foundation excavation prior to concrete placement. Exterior footings should be provided with adequate cover above their bearing elevations for frost protection. Placement of footings at least 36 inches below the exterior grade is typically used in this area. Shallower footings or thickened slab edges should be protected from frost with insulation in accordance with the Intemational Residential Code. 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 (if any) should be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 50 pcf for the on-site soil as backfill. Non-structural 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 interior slabs to K+æ=¡ å Ães*cÊcË+c, lme. Gruenefeldt Construction Apttl22,2019 Page 3 act as a break for capillary moisture rise. This material should consist of minus 2-inch aggregate with less than 50% passing the No. 4 sieve and less than2o/o passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least gíYo of maximum standard Proctor density at a moisture content near optimum. Required fiIl can consist of the onsite gravel soils devoid of vegetation, topsoil and oversized rock or an imported gravel such as road base. Underdrain System: An underdrain should not be needed for the proposed slab-at-grade construction. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the residence has 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 l0 feet in unpaved areas and a minimum slope of 2Y" inches in the first 10 feet in pavement and walkway areas. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from the building. 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 pits excavated at the locations indicated on Figure 1 and to the depths shown on Figure 2,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) deveioping in the future. If the client is concerned å{uæcr & A=seeietes, lne.Frajeet F*a. 1S"?-?f4 Gruenefeldt Construction Apnl22,2019 Page 4 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 pits 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 at once so 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 evolveso we should provide continued consultation and field services during sonstruction to review and monitor the implementation of our recommendations, and to veri$ 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 sfrata and testing of structural fïll by a representative of the geotechnical engineer. If you have any questions or if we may be of further assistance, please let us know. Sincerel¡ Kumar & Associates, lnc. Shane J. Robat, P.E. Project Manager Reviewed by: Steven L. SJRlkac attachments Pits Figure Pits Figure 3 - Legend and Notes Figure 4 - Swell-Consolidation Test Results Figure 5 - Gradation Test Results Table I - Summary of Laboratory Test Results Kuæe¡ å Åe=çeiates, lR+.Froject Ha, '8S"7-!14 -l I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I IJ I 2 Ptro Plïo LOT E-19 5 EOUESTRIAN WAY PITo 3 1 PIT O Ptlo r I I I I I I I I I I I I I I I I I I I I I I ! I I I I I I I I IL APPROXIMATE SCALE-FEET 19-7-214 Kumar & Assoclates LOCATION OF EXPLORATORY PITS Fig. 1 R PIT I PIT 2 PIT 3 0 0 1 +4=57 J -200=1 WC=18.5 DD= 1 05 -240=49 WC= .l6.0 DD= 1 04Fl¡J¡!l! I-|-ô-l¡¡ô 5 5 ¡.- l¡Jl¡¡l¡ Irl-o- LJo 10 10 PIT 4 Plï 5 0 0 t-.-l¡J t¿JL I-t-o-¡Jô 5 5 t-L¡ ¡¡Jl¡ ITFo- l¿¡o t0 f0 19-7 -21 4 Kumar & Associates LOGS OF EXPLORATORY PITS Fig. 2 t LEGEND TOPSOIL¡ ORGANIC, SANDY CLAY & S!LT, F|RM, MO|ST, BROWN. 9!4y_ AI'19-.9RAVEL (cL-cC); SILTY, SANDY wtTH coBBLEs, MEDTUM DENSE To sTtFF, MotsT,MIXED BROWN. 9L4I-&.:I-L.T (CL-ML); SANDY TO VERY SANDY, MEDIUM STIFF TO STIFF, MoIsT To VERYMOIST, BROWN. GRAVEL (GM' GP); SANDY, SLIGHTLY stLTy, wtTH coBBLEs, DENSE, Motsr, BRowN. F HAND DRIVE z-INCH DIAMETER LINER SAMPLE NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOT ON APRIL 9,2019. 2, THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROMFEAïURES SHOWN ON THE SITE PtiAN PROV|DED. 3. THE ELEVATIONS OF TI{Ë EXPLORATORY PITS WERE NOT MEASURED AND THE LOGS OF THEEXPLORATORY PITS ARE PLOTTED TO DEPTH. 4, THE EXPLORATORY PIT LOCATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREEIMPLIED BY THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESENT THEAPPR0XIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRAÑstTro¡¡S üÃi-¡iE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNIERED IN THE PITS AT THE TIME OF DIGGING. 7 LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216);DD = DRY DENSITY (pct) (lsrU D 2216):+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422); -200= PERCENTAGE PASSING NO. 2o0 stEVE (ASTM D il40). 19-7-21 4 Kumar& Associates LEGEND AND NOTES Fis. 5 I å I SAMPLE OF: Sllly Sondy Cloy FROM:PltSQ2' WC = 16.0 %, DD = 104 pcf d I I I I -l I I ! ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING ;I ¡ I I i;i'lr Itiiir.l rl I j.-..-ì I I 1-- 0 ^-1N J-zl¡¡ìØ l-3 zo l- 3-tovtzoo-5 -þ PRESSURE - 19-7-21 4 Kumar & Assoclates SWELL.CONSOLIDATION TEST RESULT Fig. 4 . 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Jeu¡n)sltnslu rsll Notlvovugg '6u l(+rlGeotechnical and Materials Engineersand Environmental Sc¡ent¡stskumarusa.comTABLE 1SUIIIIARY OF LABORATORY TEST RESULTSNo.197-214SOITTYPESandy Gravel with CobblesSiþ Clay and SandSilty Sandy ClayUIGOT¡FÛ{EDcotPRE56tVEsirn6rcfilodìPtASftcnDEXt%tLIOUþ LITITÍf%)PERCEMPASS|Í{G r{0.200 srEvE42149rAnoilSAI{D$tGRAIGRAYEL(%)57}IATUFAIDRYDENSTY{pctl105104iütTURÄ-iloñruREcoNtEf{IP.IrDEPIH18.316.034J2I23