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Home My WebLink AboutSubsoils Report for Foundation DesginlGrtf;ffi ['ff*l:lr:fr'I3;'**' An Employac Owncd Compony 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970)945-7988 fax: (970) 945-8454 email : kaglenwood@kumarusa.com wwwkumarusa,com Office Locations: Denver (tIQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado RECEIVET'J AU{i 2 3 202rr GARFIELti COUF.ITV" COMI,{ UNITY DEVE!- ]PMENl STJBSOIL STUDY FOR FOUNDATION DESIGN TWO PROPOSED RESIDENCES 3s ACRE PARCEL NO.217729100011 EAST OF RIFLE VILLAGE SOUTH GART'IELD C OUNTY, COLORADO PROJECT NO. 20-7-434 SEPTEMBER 21, 2020 PREPARED F'OR: JOSE SALAZAR 26 NATIVE SPRINGS DRTVS RTFLE, COLORADO,81650 salazarcservices@gmail.com $ ,{tl a\ -\ N s' TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY., PROPOSED CONSTRUCTION ... SITE CONDITIONS FIELD EXPLORATION. SUBSURFACE CONDITIONS FOUNDATION BEARING CONDITIONS ........... DESIGN RECOMMENDATIONS FOLINDATIONS FLOOR SLABS UNDERDRAIN SYSTEM SURFACE DRAINAGE LIMITATIONS FIGURE I - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINCS FIGURE 3 . LEGEND AND NOTES FIGURES 4 &, 5 - SWELL-CONSOLIDATION TEST RESULTS TABLE I- SUMMARY OF LABORATORY TEST RESULTS I 1 a 4- 5 -3- .......- 3 - - 1- -a- .......- 4 - I I Kumar & Associates, lnc, o Project No.20-7434 PT]RPOSE A}[D SCOPE OF STT]DY This report presents the results of a subsoil study for two proposed residences to be located on the subject site. The project site is shown on Figure l. The pu{pose of the study was to develop recoilrmendations for the foundation design. The study was conducted in accordance with our proposal for geotechnical engineering services to Jose Salazar dated IuLy 29,2020. 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, compressibilify or swell 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 recofirmendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The proposed residences will be one and two-story wood frame structures located in the area of Borings 1 and 2 as shown on Figure 1. Ground floorwill be slab-on-grade. Grading for the structure is assumed to be relatively minor with cut depths between about 3 to 5 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 recofllmendations contained in this report. SITE CONDITIONS The 35-acre property is vacant of structures. The building sites had been stripped of vegetation. Surrounding areas were vegetated with grass and sage brush. The general topography is gently sloping down to the north. Adjoining properties to the south and west of Boring 2 were developed with residences. Kumar & Associates, lnc. @ Project No.20-7-434 -2- FIELD EXPLORATION The field exploration for the project was conducted on August 11,2020. Two exploratory borings were drilled at the locations shown on Figure I to evaluate the subsurface conditions. The borings were advanced with 4-inch diameter continuous flight augers powered by a truck- mounted CME45B drill rig. The borings were logged by a representative of Kumar & Associates, Inc. Samples of the subsoils were taken withlsh 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-l586. 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 fot review by the project engineer and testing. SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figwe 2. The subsoils consist of about %foot of topsoil overlying 60 to 73 feet of medium dense, sand and silt Dense gravel soils were encountered in the borings at roughly the same elevation, 60 feet in Boring I and73% feet in Boring 2. Approximately 5Yzfeet of sandy clay and silt soil was encountered below the topsoil in Boring 1. Laboratory testing performed on samples obtained from the borings included natural moisture content, density, Atterberg limits testing and percent finer than sand size gradation analyses. Results of swell-consolidation testing performed on relatively undisturbed drive samples, presented on Figures 4 and 5, indicate low to moderate compressibility under conditions of loading and wetting with a low expansion or collapse potential (settlement when wetted under constant load) when weffed under a constant light surcharge. Results of percent finer than sand size gradation analyses perfomred on small diameter drive samples of the sandy subsoils varied from 38 to 76 percent. Atterberg limits testing indicates the clay and silt soils have low plasticity. The laboratory testing is summarizedin Table 1. Kumar & Associates, lnc. @ Project No.20-7-434 -3- No free water was encountered in the borings at the time of drilling the subsoils were slightly moist. FOTJNDATION BEARING CONDITIONS The subsoils at the two building sites have moderate bearing capacity and low to moderate settlement potential. Due to the depth of the settlement-prone soils, future deep subsurface wetting could result in excessive settlement, potentially causing distress and cracking of the proposed houses. It will be critical to the long-term performance of the structures to keep the subsoils from getting wet. Recommendations for site grading and routing of roof runoff away from the building are provided in this report. DESIGN RECOMMENDATIONS FOIJNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we recofirmend the buildings be founded with spread footings bearing on the natural sand and silt 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 ";fl"]00 ptf Based on experience, we expect settlement of footings designed and constructed as discussed in this section will be about I inch or less. 2) The footings should have a minimum width of 20 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 14 feet. Kumar & Associates, lnc. @ Project No.20-7-434 -4- Foundation walls actrng as retaining structures should also be designed to resist a lateral earth pressure corresponding to an equivalent fluid unit weight of at least 50 pcf. All existing fiIl, topsoil andany loose or disturbed soils should be removed and the footing bearing level extended down to the firm natural silt and sand soils. The exposed soils in footing areas should then be moistened and compacted. 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 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 gravel should be placed beneath slabs for support. This material should consist of minus 2-inch aggtegate with at least 50% retained on the No. 4 sieve and less than 12% passing the No. 200 sleve. 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. Required fill can consist of the on- site granular soils devoid of vegetation, topsoil and oversized rock. UNDERDRAIN SYSTEM We understand that the proposed slab-on-grade ground floors will be at or slightly above th surrounding ground surface. A perimeter underdrain system is not needed and we recommend that it not be installed. The following recommendations for surface drainage around the building exterior should be followed. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the residences has been conrpleted: 5) 6) Kumar & Associates, lnc, o Project No.20-7'434 5 l)Inundation ofthe foundation excavations and underslab areas should be avoided during construction. Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95Yo of the maximum standard Proctor densrty in pavement and slab areas and to at least 90% of the maximum standard Proctor density in tandscape areas. The ground surface surrounding the exterior of the building should be sloped to drain away from the fotrndation in all directions. We recommend a minimum slope of 12 inches in the first l0 feet in unpaved areas and a minimum slope of 3 inches in the first l0 feet in paved axeas. Roof downspouts and drains should discharge well beyond the limits of all backfill and water should not be allowed to pool within 10 feet of the foundations. Landscaping which requires regular heavy irrigation should be located at least l0 feet from foundation walls. Consideration should be given to use of xeriscape to reduce the potential for wettrng of soils below the building caused by inigation. 3) 4) 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 fuhre. If the client is concerned about MOBC, then aprofessional in this special field 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 recolnmendations 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 2) s) Kumar & Associates, lnc. o Project No.20-7.434 -6- monitor the implementation of our recommendations, and to veriff 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. Respectfu lly Submitted, Kurnar & Aseociateso Inc. Daniel E. Hardin, P DEH/kac Kumar & Associales, lnc. ") Project No,20-7"434 :J .i.;' SORING 1 Q,r.:'. i ;i..' ':.i : ar.ll:i ':l r;.::i..r r ! -: I ri i,: :':!'j; ?-il/j ; .l': ,' .t ,' ,.". i '.f.;1 : { ri: >!''; '1: ;1 .trli.i ,:1 'lii,;{;,:'l i:i;:l !.. , itr:: ; r,Li ,ta i ''i ,,' : ', .' i .:.;i!'4 BORING 2 a i.\i'i.'..',:: : i .;'.;;;.; flF!;;r ji! crl{i}i,{*',a1':ll:4 ,. ',.,4?{}i#t 'iei.':f.\" ""' il'.'.-li .i. i- t-. lbi;Jr:i. lr'.r+'ri'i ldl;+:' ,,..,.s.r'' .. ri.. rr,.'.,..,...i1rd/.-E,J Err. i.F ?.ri:::j-i 1 APPROXIMATE SCALE-FEET 20-7 -434 Kumar & Associates LOCATION OF EXPLORATORY BORINGS Fig. 1 I BORING 1 EL. 87.5' BORING 2 EL. 100' 0 24/t2 Y,IC=4.2 -2OO=76 LL=22 Pl=8 o 10/ 12 WC=5.7 DD=1 1 1 5 31 /12 WC=4.5 DD=1 18 28/12 WC=4.6 DD=1 10 -2OO=68 5 17 /12 WC=3.9 DD=97 -200=54 10 10 24/12 tNC=2.7 DD=1 17 -2O0=58 s/12 WC=3.2 DD=97 15 1535/t2 35/6, 25/6 20 ,-lrj lJIu- IxFo-LIo 20 27 /12 WC=3.3 DD=1 05 s/6, 15/6 WC=2.8 F UJtd l! I :EFo-IJo -200=39 LL=17 Pl=2 25 25 30 s2/12 30 50 53/12 WC=3.9 DD=110 50 41/6, 50/636/t2 55 55 70 60 75 5o/2, 1Oo/3.5 65 13/6, 50/4 Fig. 220-7-434 Kumar & Associates LOGS OF EXPLORATORY BORINGS N TOPSOIL; ROOTZONE, CLAYEY SANDY SILT, ORGANIC, STIFF, SLIGHTLY MOIST, BROWN. n n ffi CLAY AND SILT (CL_ML); SANDY, VERY STIFF, SLIGHTLY MOIST, LIGHT BROWN. SAND ANO SILT (SM_ML); SLTGHTLY CLAYEY TO CLAYEY LAYERS, OCCASTONAL GRAVELLY LENSES, MEDIUM DENSE TO DENSE, SLIGHTLY MOIST, LIGHT BROWN, CALCAREOUS. GRAVEL (OV); SIHOY, SILTY WITH COBBLES, VERY DENSE, SLIGHTLY MOIST, BROWN. F i DRIVE SAMPLE, 2_INCH I.D. CALIFORNIA LINER SAMPLE DRTVE SAMPLE, 1 3/$-INCH l.D. SPLIr SPOoN STANDARD PENETRATION TEST. ^, /4^ DRIVE SAMPLE BLOW COUNT. INDICATES THAT 24 BLOWS OF A 140-POUND HAMMERz'j/ tz FALLTNG J0 TNcHES wERE REQU|RED To DRtvE THE sAMPLER 12 tNcHES. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON AUGUST 11,2O2O WITH A 4_INCH-DIAMETER CONTINUOUS_FLIGHT POWER AUGER. 2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE PROVIDED BY THE CLIENT. 5. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE MEASURED BY HAND LEVEL WITH THE GROUND ELEVATION AT BORING 2 ASSUMED TO BE ELEVATION lOO FEET. 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 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); DD = DRY DENSITY (PCI) (ISTU D2216); .2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM Dl140); LL = LIQUID LIMIT (ASTM D4318); PI = PLASTICITY INDEX (ASTM 0451E). 20-7 -434 Kumar & Associates LEGEND AND NOTES Fig. 3 I E !t I N Jl4l =v, I z.o F o =otnzo(J 1 SAMPLE OF: Sondy Silty Cloy FROM:Boringl@5' WC = 4.5 %, DD = '118 pcf EXPANSION UNDER CONSTANT PRESSURE UPON WETTING ) I l I I I 0 -t -2 100 N JJ l4J =a I zo F o =onz.o() 1 0 -1 -2 1 SAMPLE OF: Cloyey Silly Sond FROM:Boringl@20' WC = 5.3 %, DD = 106 pcf iiilr1 i1ilrj l EXPANSION UNDER CONSTANT PRESSURE UPON WETTING -1 - Thr t d @ft! opoly only b tMmgh. tdt d- th. t dfiE cFt droll rct ba dFodue4 aeopt in firl, vltftout iha rdttan opprwol ot Xumd @d Aeclota, lm. Sr.I CoMofdotid blffE p.rtd@d in@tu rith ASIU tF45,46. -3 t.0 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 420-7 *434 ; E I SAMPLE OF: Sondy Silt FROM:Boring2@2.5' WC = 5.7 %, DD = 111 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING ( ( ) ------- j i I I I l i N Jlrl =V, I zo F o =olnzo C) JJ lrJ =at't I zot- cf, Jolnzo() I 0 -1 -2 -5 -4 1 0 -l -2 -3 -4 -5 - KSF t0 t00 SAMPLE OF: Silly Sond FROM: Boring 2 @ 10' WC = 3.2 %, DD = 97 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING .f I 100 Fig. 5Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS20-7 -434 lGrt[iffi,rffi*#fn'$$-"' TABLE 1 SUIIMARY OF I.ABORATORY TEST RESULTS Silty Sand Very Silty Sand Silt and Sand SOILWPE Sandy Silty Clay Sandy Silty Clay Sandy Silt Clayey Silty Sand Clayey Silty Sand Sandy Silt Sandy Silty Clay (ps0 UNCONFINED coilPRESSIVE STRENGTH 2 PLASNC INOEX t%l 8 LrQU[t Ltilfr {o/o) 22 71 ATTERBERGLftITTS 38 54 39 PERCENT PASSING NO, 2@SIWE 76 68 (%) SAND GRADATION (",6) GRAVEL tt7 106 lll 97 97 110 {ocfl NATURAL DRY DENSITY ll8 1104.6 2.7 3.3 3.7 3.9 3.2 2.8 3,9 (ohl NATURAL ilIOISTURE CONTENT 4.2 4.5 7Y, 10 20 2% 5 l0 20 30 {ftI DEPTTI 0 5 1 2 BORING No.20-7434 Garfield Coanty Community Developmem Department rOg $h Street, Suite 401 Glenwood Springs, CO 81601 19701945-82L2 www.garfield-cou ntv.com GRADING PERMIT REQUIREMENTS A permit is required for any excavation, grading, or earthwork construclion including fills and embankments. A grading permit does nol permit the construction of retaining walls or other structures. EXEMPTION FROM GRADING PERMIT: . AgriculturalLand: Grading, excavation and earthwork, including fills and embankments that are constructed solely for agricultural purposes on lands that are farms or ranches.. Small Proiects: Grading that does not exceed 50 cu. yds of earfrwork materialor 6000 sq.ft. of graded area as long as grading does not change drainage patterns with respect to adjacent properties. . $ee Amended IBC Appendix J for other exemptions. TYPES OF GRADING PERMITS AttlD FEES: Payment is due at time of submittal. Make Check payable to: Garfield County Treasurer . Maiorgrading: over20,000 sq. ft. orover5000 cubic yards.. .....$400.00r Minor grading: less than 20,000 sq. ft. and under 5000 cubic yards................$100.00 PERMIT APPLICATION & SUBiIfnAL REOUI RFMFNTS (1 copy required) : r Comolete application (a one page form is available fom fte County). Vicinity Map indicating section, township and range of site, proposed location of grading, and the site's relation to surrounding roads, municipal boundaries, and water bodies.. Site plan that shows the following within 100 feet of the proposed grading: i. Existing and proposed contours (see exemption belowfor pipelines) ii. Delineation of area to be disturbed by grading activities iii. Existingstructures iv. Existing and proposed roads and driveway v. Property boundades, right+f-ways and easements vi. Floodplains, intermittenl streams, welland$ and other bodies of water r Erosion Conkol Plan and Qetails. Plan shows the location of allerosion control measures. . MAJORGMDINGPERMITONLY:i. Revegetation and Reclamation Plan. Seeattached requirements, ii. Financial security for site reclamation. Please allow County to review reclamation cost estimate before providing security. iii. For major grading permits, the plans must be prepared and stamped by a qualified Colorado Professional engineer.. PIPELINES ONIY: The site plan does not need to show topographic contours if he installation of pipeline will not result in changes to the surface grade.r Approved State Stormwater Permit if area disturbed by grading is greater than one acre.. Soils Report: A soils report may not be required if the maximum depth of cut or fill deplh is less than 15 feet and native slopes are less than 25%.. Drainage Report: willbe required if the County believes that grading may change drainage pattems with regard to adjacent properties, wellands/water bodies or slopes greater than 2570 (Applicant's Copy) ALL PERMITS MUST GOMPLY WTH THE FOLLOWNG REQUIREMENTS: . AppendixJ- lnternationalBuilding Code as amended.. Garfield County Land Use Code.. Applicable Colorado Department of Public Health and Environment, Water Quality Control Division requirements.. UTILITY LOCTION IS REQUIRED PRIORTO ANYGRADING. Garfield Countv Vegetation & S,ite Reclamation Reouirements (Long-Term Disturbed Areas, One Acre or More) Overview: Grading Permits typically require the submission of:. A Site Specific lnventory and Map of county and State Listed Noxious Weeds.. A Weed Management Plan.. A Revegetation and Reclamation Plan.. A Cost Estimate. A FinancialSecurity. The purpose of the plan is to ensure that the development does not result in: (i) erosion and dust generation, (ii) the propagation of noxious weeds, (iii) the excessive loss of wildlife habitat and food sources, and (iv) long-term visual eyesores. The financial security allows the County to perform redamation in the case that the developer abandons the project or does not perform adequate reclamation. Section 1 - Soil Handling. lncludes: (i) provisions for salvaging on-site topsoil, (ii) a timetable for eliminating topsoil and/or aggregate piles, (iii) plan that provides for soil cover if any disturbances or stockpiles sit exposed for a period of g0 days or more, and (iv) erosion control barriens and dust suppression measures. Section 2 - Weed Management Plan. lndudes: (i) a site specific weed inventory along with a site plan showing County Listed Noxious Weeds and Colorado Listed A & B Noxious Weeds (Contact Garfield County Vegetation Management for updated list), (ii) weed management plan that addresses inventoried weeds in a timely and effective manner. (Note: Garfield County may require the submittal for treatment records.) Sec'tion 3 - Site Revegetation and Restoration. lndudes: (i) plant material list (be specific, scientific and commsn names require), (ii) planting schedule (to include timing, methods, and provisions for watering, if applicable.) Section 4 - Gost Estimate. Cost estimate is used to determine the amount of the financial security. Line items within the cost estimate include: (i) mobilization, (ii)earthmoving, (iii) seed and planting, (iv)weed- fee mulch, erosion control, and dust suppression, (v) irrigation, and (vi) weed management. (Note: For pipelines and projects in which existing grade is the same as final grade, a cost of $2,500/acre can used to determine the financial security.) Financial Security: Bonds, Letter of Credit valid for a minimum of 2 years or Cash. County lnspection and Release of Financial Security: $/hen grading has been completed and vegetation reestablished, the developer (permit holder) phones County Vegetation Manager (970-94$1377 Ext. 4305) and requests an inspection. lf restoration is determined to be adequate, the county will inform the development and release the financialsecurity. (Applicant's Copy)