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Home My WebLink AboutSubsoil Study for Foundation Design 01.30.2018H-PVKUMAR Geotechnical Engineering I Engineering Geology Materiels Teeting I Envlronmental 5020 County Road 154 Glenwood Springs, CO 81601 Phone: (970) 945-7988 Far (970) 94s8454 Email: hpkglenwood@kumarusa,com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RDSIDENCE LOT 5o SUN MEADOW ESTATES NORTH MEADOW DRIVE GARFIELD COUNTY, COLORADO JOB NO. L7-7-870 JANUARY 30,2018 PREPARED FOR: CHRIS AND MA.RIANNE STALLINGS 2Ol VISTA DRI\TE SILT, COLORADO 81652 northmeadowdrive @ smail.com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION ....... STTE CONDTTIONS FIELD EXPLORATION STIBSURFACE CONDMIONS ...... FOI.INDATION BEARING CONDITIONS DES IGN RECOMMENDATIONS FOTINDATIONS... FLOOR SLABS SURFACE DRAINAGE ...... LIMITATIONS FIGURE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATOR.Y BORINGS FIGURES 3 and 4- SWELL-CONSOLIDATION TEST RESLILTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS _1_ 1 ........-2 - n -2- ...............- 3 - 4 4 4 5 6- H-P&KUMAR Project No. '17-7-870 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 5, Sun Meadow Estates, North Meadow Drive, 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 io Chris and Marianne Stallings dated December 13,20i7. Hepworth- Pawlak Geotechnical (now H-PÆfumar) previously performed a preliminary geotechnical study for the Sun Meadow Estates development and submitted the findings in a report clated March 28, 2000, Job No. 100 169. A field exploration program consisting of exploratory borings was eonducted 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 CONSTR.UCTION The residence will be a two story wood frarne structure over crawlspace with an attached two story garage located on the lot as shown on Figure 1. The gârage ground floor will be slab-on- grade. Gradíng for the structure is assumed to be relatively minor with cut depths between about 2 ta 4 feet. lffe 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 notifîed to re-evaluate the recornmendations contained in this report. l{-P!KUlvlAR Project No. 17-7-870 -3- Laboratory testing performed on samples obtained from the borings included natural moisture content and density, and percent fincr than sand size gradation analyses. Results of swell- consolidation testing perforrned on relatively undisturbed drive samples of the upper soils, presented on Figures 3 and 4, indicate low compressibility under natural moisture condition and light loading. One sample (Boring 1 at 5') showed a low collapse potential and the other sample (Boring 2 at?Vz') showed a minor swell potential when the samples were wetted under a constant light surcharge. The samples showed moderate compressibility when loaded after wetting. The laboratory testing is summarized in Table i. No free water was encountered in the borings at the time of drilling and the subsoils were slightly moist. FOUNDATION BEARING CCINDITIONS The upper soils possess low bearingcapacity and generally tend to settle when wetted. The minor swell potential encountered in one of the samples is believed to be an anomaly and the soils in the area are typically not expansive. Spread footings bearing on the natural soils appear feasible for foundation support with some risk of movement and distress. The risk of movement is primarily settlement if the bearing soils were to become wetted and precautions should be taken to prevent wetting. Removal and replacement of a depth of the nalural soils (typically 3 feet) in a moistened and compacted condition below the footings could be done to reduce the risk of foundation movement and building distress. Use of a reiatively deep foundation system, such as helical piers or screw piles, that extend down to the less compressible sand and gravel soils would provide a relatively low risk of foundation movement. Provided below are recommendations for spread footings bearing on the natural soils. If recommendations for spread footings bearing on a depth of cornpacted structural fill, or for helical piers or screw piles are desired, we should be contacted. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we believe the building can be founded with spread footings bearing FI.PTKUMAR Proiect No. 17-7-874 -5- wetted as discussed above. To reduce the effects of some differential movement, floo¡ slabs should be separated from all bearing walls mcl columns with expzutsion joirits wtrich 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 sand and gravel road base should be placed beneath slabs for support and to faciiitate drainage. This material should consist of minus 2 inch aggregate with at ieast 50Vo retained on the No. 4 sieve and less than IZVo passing the No- 200 sieve. All fîll materials for support of floor slabs should be compacted to at least 95Vo of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site soils devoid of topsoii and oversized (plus 6 inch) rocks. SUR.FACE DRAINAGE Positive surface drainage is an irnportant aspect of the project to prevent wetting of the bearing soils. A perimeter foundation d¡ain around shallow crawlspace areas (less than 4 feet deep) should not be needed with adequate compaction of foundation wall backfill and positive surface slope away frorn foundation walls. The foilowing 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 backfilt should be adjusted to near optimum moisture and compacted to at least 957o of. the maximum standard Froctor density in pavement and slab areas and to at least 90Vo of the maximum standard Proctor density in landscape areas. . 3) The ground surface surounding the exterior of the building should be sloped to drain away from the foundation in all directions. Vy'e recommend a minimum slope of 12 inches in fhe first 10 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. 5) Landscaping which requires reguiar heavy irrigation should be located at least l0 feet from foundation wails. Consideration shouid be given to use of xeriscape to reduce the potential for wetting of soils below the building caused by irrigation. I.I.PÈKUÍVIAR Project No. 1 7-7-870 NORTH MEADOW DRIVE N 89'02',21" E 1"98.OO', Rebar and Cøp LS No. 36572 in Ptaee ín Place 10.4' I I !/ 3 oo(¡ $i e.ì c'j Ot$ F Otclì F-tr) o e A \o \ot\) t\) C¡l rû 6f Fence t0.o' N 88"44',21'E 198.00'Aluminum Tag LS No. 36572Rebar and Cop 198.2 I I I { I I 87.5' 2s.o' -+l I I 40.o' G)so L -rBt!&tg- r I {I I I I 70.5' 50.o' rÐ Í,ot 5 2.239r Aetes *_J BORING 2 APPROXIMATT SCALE-FETT H-PryKUMAR LOCATION OF EXPLORATORY BORINGS Fíg. 117 -7 -870 LEGEND N n n n F i ^ /.- DRIVE SAMPLE BLOW COUNT. INDICATES THAT 9 BLOWS OF A I4O.POUND HAMMER "/'" ÈALLtNc so tNcHES wERE REQUTRED To DRtvE THE cALTFoRNtA oR spr SAMpLER 12 rNcHES. NOTES 1, THE EXPLORATORY BORINGS WERE DRITLED ON DECEMBER 21,2017 WITH A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. 2. THE LOCATIONS OF THE EXPLORATORY EORINGS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLÄN PROVIOEO. 3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE NOT MEASURED AND THE LOGS OF THE EXPLORATORY BORINGS ARE PLOTTED TO DEPTH. 4. THE EXPLORATORY BORING LOCATIONS 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 EOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL, 6. GROUNDWATER WAS NOT ENCOUNTEREO IN THE BORINGS AT THE TIME OF DRILLING. FLUCTUATION IN THE WATER LEVEL MAY OCCUR WIÏH TIME. 7. LABORATORY TEST RESULTS: wC = WATER OONTENT (%) (ASTM D 2216); DD = ORY DENSITY (PCf) (ASTM D 2216); -ZQa= PERCENTÀGE PASSING N0' 200 SIEVE (ASTM D r 1 40). TOPSOIL; ORGANIC SILTY CLAYEY SAND, SLIGHTLY MOIST, 8R0WN, ROOT ZONE" SAND (SM); SILTY TO VERY SILTY, OCCASIONALLY CLAYEY, SCAÎTËREO GRAVEL, MEOIUM DENSE, SLIGHTLY MOIST, BROWN. stLT AND SAND (ML-SM)¡ INTERMTXED AND STRATIFIED, SCATTEREO GRAVEL, ST|FF/MEDTUM DENSE, SLIGHTLY MOIST, BROWN. SANO AND GRAVEL (SU-OU); WITH COSBLES, SILTY, MEDIUM DENSE TO DENSE, SLIGHTLY MOIST, MIXED BROWN. RELATIVELY UNDISTURBED DRIVE SAMPLE; 2-INCH l.D. CALIFORNIA LINER SAMPLE. DRIVE SAMPLE; STANDARD PENETRATION TEST (SPT), I 3/E INCH I.D. SPLIT SPOON SAMPLE, ASTM D-I586. LEGEND AND NOTES Fig. 317 -7 -870 H-PryKUMARÈ H-PTKUMARÏABLE 1SUMMARY OF LABORATORY TEST RESULTSProject No. 17-7-870SOILTYPEVery Silty SandSilty SandSilty Sand and GravelSilty Clayey SandVery Sandy SiltVery Sandy SiltUNCONFINEDCOMPRESSIVESTRENGTH{PSF}ATTERBERG UMITSPLASÎCINDEXlo/olLIQUIDLIMIT(o/olPERCENTPASSINGNO.200SIEVE4I265657GRADATIONSAND(o/"1GRAVÊL(volNATURALDRYDENSTTVfocfl110111Iô.1Ir07r08119NATURALMOISTURECONTENTlo/"13.95.1J.JJ._t3.94,7DCPTHlftì11./n510zYz510BORINGI2