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Home My WebLink AboutSubsoils Report for Foundation Designrc n $N;1f;'ff:":'flr:f*iiyi'*" An Emplcygs Owned Compony 5020 Counfy Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com www.kunarusa.com Office Locatiors: Denver- (lIQ), Parker, Colorado Springs, Fort Collins, Glenvood Springs, and Summit Coutty, Colorado SUBSOIL STUDY FOR X'OUNDATION DESIGN PROPOSED RESIDENCE 240 RIPPY LANE NEW CASTLE, COLORADO PROJECT NO.23-7-568 NOVEMBER 20, 2023 PREPARED F'OR: TIM F'INHOLM P.O. BOX 503 NEW CASTLE, COLORADO 81647 tfi nholm@uniq ueprop.com TABLE OF CONTENTS PIIRPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITIONS FIELD EXPLORATION SUBSURFACE CONDITIONS DESIGN RECOMMENDATIONS ........--.. FOI.INDATIONS FOLTNDATION AND RETAINING WALLS ......... FLOOR SLABS UNDERDRAIN SYSTEM .............. SURFACE DRAINAGE LIMITATIONS.......- FIGTIRE I - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURE 4 - GRADATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS -1- I 1 ", a-L- -2- -3- -4- 4- 5- 5 Kumar & Associates, lnc. o Project No.23-7-568 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be locate d at 240 Rippy Lane, New Castle, Colorado. The project site is shown on Figure l. 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 Tim Finholm dated September 26,2023. 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 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 Plans for the proposed residence were conceptual at the time of our study. The proposed residence is assumed to be a one- or two-story stmcture located on the site in the area of the borings shown on Figure 1. Ground floor could be slab-on-grade or structural over crawlspace. Grading for the structure is assumed to be relatively minor with cut depths between about 2 to 4 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 subject site was developed with an access drive, single-story residence and shop at the time of our field exploration. The ground surface was gently sloping down to the southeast at a grade of between 3 and 5 percent. Vegetation consists of landscaped grass and aspen trees. The Colorado River borders the property to the southeast. Kumar & Associates, Inc. @ Project No.23-7-568 -2- F'IELD EXPLORATION The field exploration for the proj ect was conducted on October ll , 2023 . Two exploratory borings were drilled at the locations shown on Figure 1 to evaluate the subsurface conditions. 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 Kumar & Associates, Inc. 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 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. SUBST]RFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The subsoils consist of about 4 to 6 inches of topsoii overlying dense, very sandy silty gravel with cobbles and possible boulders to the maximum explored depth of 3Yz feet. Drilling in the coarse granular soils with auger equipment was difficult due to the cobbles and possible boulders and drilling refusal was encountered in the deposit. Laboratory testing performed on samples obtained from the borings included natural moisture content and gradation analyses. Results of gradation analyses performed on samples (minus i%- inch fraction) of the coarse granular subsoils are shown on Figure 4. The laboratory testing is summarized in Table l. No free water was encountered in the borings at the time of drilling and the subsoils were slightly moist. DESIGN RECOMMENDATIONS FOLINDATIONS 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. Kumar & Associates, lnc. @ Project No. 23-7-568 3- 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. Based on experience, we expect settlement of footings desigrredfidfficted 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. 4) Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least l0 feet. Foundation walls acting as retaining structures should also be designed to resist lateral earth pressures as discussed in the "Foundation and Retaining Walls" section of this report. 5) Topsoil and any 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 should then be moistened and compacted. If water seepage is encountered, the footing areas should be dewatered before concrete placement. 6) A representative ofthe geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FOTINDATION AND RETAINING WALLS Foundation walls and retaining structwes which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 45 pcf for backfill consisting of the on-site granular soils. Cantilevered retaining structures which are separate from the residence and can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 35 pcf for backfill consisting of the on-site granular soils. Backfill should not contain organics, topsoil or rock larger than about 4 inches. All foundation and retaining sffuctures should be designed for appropriate hydrostatic and swcharge pressures such as adjacent footings, traffic, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will Kumar & Associates, lnc. @ Project No.23-7-568 -4- increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain should be provided to prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lifts and compacted to at least 90% of the maxlmum standard Proctor density at a moisture content near optimum. Backfill placed in pavement and walkway areas should be compacted to at least 95Ya of the maximum standard Proctor density. Care should be taken not to overcompact the backfill 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 450 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strength. Suitable factors of safety should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should be compacted to at least 95Yo of the maxjmum 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 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 relatively well graded sand and gravel such as road base should be placed beneath slabs for support. This material should consist of minus 2-inch aggregate with at least 50% retained on the No. 4 sieve and less than 12o/o passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95% of maxlmum standard Proctor density at a moisture content near optimum. Required fiIl can consist of the on- site granular soils devoid of vegetation, topsoil and oversized rock. TINDERDRAIN SYSTEM Kumar & Associates, lnc. @ Project No.23-7-568 5 The proposed shallow foundations should not need a perimeter foundation drain, provided that the exterior foundation wall backfill is well-compacted and good surface drainage, as described below, is maintained around the houses. SURFACE DRAINAGE The following drainage precautions should be observed during consffuction and maintained at all times after the residence has been completed: l) Inundation ofthe foundation excavations andunder slab areas shouldbe avoided during consffuction. 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 ieast 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 2/' inches in the first l0 feet in paved areas. Free-draining wall backfill should be covered with filter fabric and capped with about 2 feet of the on-site finer graded 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 warrantlr 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 concerned about MOBC, then a professional in this special field of practice should be consulted. Ow 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 pulposes. 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 Kumar & Associates, lnc. @ Project No.23-7-568 -6- 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 ofexcavations and foundation bearing strata and testing ofstructural fill by a representative of the geotechnical engineer. Respectfully Submitted, Kurnar & Associates, lnc. James H. Parsons, P.E. Reviewed by: fl*_/- Steven L. Pawlak, P.E. JHP/sls t\. w 58663 /ht Kumar & Associates, lne. 6 Project No. 23-7-568 50 50 100 APPROXIMATE SCALE-FEET 23-7 -568 Kumar & Associates LOCATION OF EXPLORATORY BORINGS Fig. 1 I +4=51 -2OO=1 1 BORING 1 BORING 2 0 0 FUU t! II Fo- LJo I FL!htt! IIFo- LIo 73/12 WC=2,2 *4=51 tnn-a 25/12 5 q LEG END TOPSOIL; SAND, GRAVELLY, CLAYEY, ORGANICS, FIRM, MOIST, DARK BROWN GRAVEL AND COBBLES (GM); VERY SANDY, VERY SILTY, PROBABLE BOULDERS, DENSE, SLIGHTLY MOIST, LIGHT BROWN. I t DRTVE SAMpLE, 1 3/8-|NCH r.D. SPL|T SP00N STANDARD PENETRATION TEST. DISTURBED BULK SAMPLE. 1'/4' DRIVE SAMPLE BLOW COUNT. INDICATES THAT 73 BLOWS OF A 14o-POUND HAMMERtr/ tz FALLTNG Jo TNCHES WERE REQUIRED To DRtvE THE SAMpLER t2 tNcHES. i PRACTICAL AUGER REFUSAL. WHERE SHOWN ABOVE BOTTOM OF BORING, INDICATES THAT MULTIPLE ATTEMPTS WHERE MADE TO ADVANCE THE HOLE. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON OCTOBER 1 1, 2023 WITH A 4-INCH-DIAMETER CONTINUOUS-FLIGHT POWER AUGER. 2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 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 BORINC LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D2216); +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTU OOSIS); -200= PERCENTAGE PASSING N0. 200 SIEVE (ASTM D1140). Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 223-7-568 too 80 80 70 60 50 40 so 20 10 0 I{YDROVETER ANALYSIS SIEVE ANALYSIS lME RADINCS I,' HRS 7 HRSMrN aduttr lvlx IMIN U.S. STANDARD SERIES CLEAF SQUARE OPENINCS :/rr tl^. 1 t/t. -, i----- - t- --1- 'l,tl .i. f -/ "t' t- 'I SAND CRAVEL FINE MEDIUM lcoanss FINE COARSE o d to 20 30 ir{t 50 a0 80 90 E E E F 100 .150 ,600 32 DIAMETER OF IN MILLI CLAY TO SILT COBBLES GRAVEL 5' % SAND 41 % LIQUID LIMIT - PLASTICITY INDEX SAMPLE OF: Sllghlly Sllly V€ry Sondy Grqval SILT AND CLAY A % FROM:BorlnglO2' z a I I t00 t0 ao 70 €0 50 40 !o 20 to o 0 t0 20 t0 10 50 50 70 a0 90 100 az E fi .ool 1,75 DIAMETER OF IN MI CLAY TO SILT COBBLES GRAVEL 51 % SAND 38 X SILT AND CLAY LIQUID LIMIT - PLASTICITY INDEX SAMPLE OF. Slightly Silty Very Sondy Grovel FROM: Boring 1 O 1'-2' 11 X Th6.c t6sl rcrulls opply only lo lhc romplor whlch wore leslsd. lhe lesllhg ropod eholl nol bo r.produced, cxcepl ln full, wllhoul lhc wrlllen opprovol of Kuhqr & A!!oolol.!, lnc. Slove onolylb losllng l3 pirform.d ln ocqordqnca wlth ASTM D6913, ASIM D7928, ASIM Cl36 ond/or ASTM D1t40. HYDROMETER ANALYSIS SIEVE ANALYSIS U.S. SANDARD SERIES CI.EAR SqIARE OPENINGS r/rx 1/^. 1 1/D.i Mtx at24 HRS 7 HRSr( vt[ ri ul! TME RETDINCS doltN !eltx avl! I 'll t1 rrr I r i '; ' 1"" SAND GRAVEL FINE COARSEFINEMEDTUM ICOARSE 23-7 -568 Kumar & Associates GRADATION TEST RESULTS Fig. 3 lGn#**'ffin[i:nii:"d'.-' ,--_._""-__1- TABLE 1 SUMMARY OF LABORATORY TEST RESULTS No.23-7-568 ATT LIMITSSAMPLLOCATIONGRADATION SAND (%) PERCENT FASSING NO- 200 stEvE LIQUID UMIT lolJ trhl PLASTIC INDEX (Dsfl UNCONFINED COMPRESSIVE STRENGTiI SOIL TYPEBORING lftl DEPTH NATURAL MOISTURE CONTENT locll NATURAL DRY DENSNY GMVEL ("kl 51 41 8 Slightly Silty Very Sandy GravelI22.2 Slightly Silty Very Sandy Gravel51381t7to2