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HomeMy WebLinkAboutSoils Report for Foundation Design 03.14.2019If A Kumar & Atsn xtraa, luc. Geotechnical and Materials Engineers and Environmental Scientists 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com An Employee Owned Company www.kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado RECEIVED MAY 0 2 2019 GARFIELD COUNTY COMMUNITY DEVELOPMENT SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE AND BARN COUNTY ROAD 346, SOUTH OF SILT DIXON WATER FOUNDATION PARCEL 2179-114-00-733 GARFIELD COUNTY, COLORADO PROJECT NO. 19-7-119 MARCH 14, 2019 PREPARED FOR: ESAU RUIZ P. O. BOX 450 SILT, COLORADO 81652 E s a u ru ii9U [rr_ j.;unail.com Tl4&J.0 TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS - 2 - FIELD EXPLORATION - 2 - SUBSURFACE CONDITIONS - 2 - FOUNDATION BEARING CONDITIONS - 3 - DESIGN RECOMMENDATIONS - 4 - FOUNDATIONS -4- FLOOR SLABS -5- SURFACE DRAINAGE - 5 - LIMITATIONS - 6 - FIGURE 1— VICINITY MAP FIGURE 2 - LOCATION OF EXPLORATORY BORINGS FIGURE 3 - LOGS OF EXPLORATORY BORINGS FIGURE 4 - LEGEND AND NOTES FIGURES 5 through 7 - SWELL -CONSOLIDATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS Kumar & Associates, Inc. Project No. 19.7.119 r. :?: PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence and barn to be located on a parcel of land north of County Road 346, south of Silt, Dixon Water Foundation Parcel 2179-114-00-733, Garfield County, Colorado. The site is shown on Figures 1 and 2. The purpose of the study was to develop recommendations for the foundation design of the buildings. The study was conducted in accordance with our agreement for geotechnical engineering services to Esau Ruiz dated January 25, 2019. 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, 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 CONSTRUCTION The proposed residence will be a single story wood -frame structure over crawlspace. The attached garage will have a slab -on -grade floor. The barn is planned to be located a few hundred feet east of the residence. We assume the barn will be a pole or pad -and -beam style structure with a slab -on -grade floor. Grading for the buildings is assumed to be relatively minor with cut depths between about 3 to 4 feet. We assume relatively light foundation loadings, typical of the proposed type of construction. When building location, grading and loading information have been developed, we should be notified to re-evaluate the recommendations presented in this report. Project No. 19.7-119 -2 SITE CONDITIONS The project site is currently vacant. The proposed building sites are to the west of a rough graded road accessing the property from County Road 346. Topography is valley bottom with gentle slopes generally down to the north. An irrigation ditch is located to the north of the proposed building sites which was not flowing water at the time of our field exploration. The Colorado River is approximately 1/2 mile to the north of the proposed building sites. Vegetation at the site consisted of native grass and weeds below about 6 inches of snow that covered the site. FIELD EXPLORATION The field exploration for the project was conducted on January 25, 2019. Two exploratory borings were drilled at the approximate locations shown on Figures 1 and 2 to evaluate the general subsurface conditions. Boring 1 was drilled at the approximate barn location and Boring 2 was drilled at the proposed residence site. The boring locations were as directed by the client. 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. Samples of the subsoils were taken with 1% 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-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 3. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 3 with legend and notes of the boring logs on Figure 4. The subsoils encountered, below about 'A foot of topsoil, consisted of about 22 and 11 feet of stratified layers of sandy silt and silty sand that was typically clayey and stiff/medium dense, and underlain by dense, silty sandy gravel and cobbles with probable small boulders at Boring 1 and by medium dense, silty sand and gravel Kumar & Associates, Inc. Project No. 19-7-119 3 with cobbles at Boring 2. Drilling in the coarse granular soils with auger equipment was occasionally difficult due to the cobbles and probable boulders. Laboratory testing performed on samples obtained from the borings included natural moisture content and density, and percent finer than sand size gradation analysis. Results of swell - consolidation testing performed on relatively undisturbed drive samples, presented on Figures 5 through 7, indicate generally moderate compressibility under conditions of loading and wetting. The samples typically showed a low collapse potential when wetted under a constant 1,000 psf surcharge. One sample (Boring 1 at 2.5') showed a low expansion potential but this is considered an anomaly and the soils are not expected to be expansive at this site. The laboratory testing is summarized in Table 1. Groundwater was encountered in Boring 1 at a depth of 221/2 feet at the time of drilling. No groundwater was encountered in Boring 2. The subsoils were slightly moist becoming wet near and below groundwater level in Boring 1. FOUNDATION BEARING CONDITIONS The fine grained compressible silt and sand soils are expected to be encountered at excavation subgrade for the buildings. These soils possess low bearing capacity and, in general, moderate settlement potential, especially when wetted. Lightly loaded spread footings bearing on these soils should be feasible for foundation support of the buildings with some risk of settlement. The risk of settlement is primarily if the bearing soils were to become wetted and precautions should be taken to prevent wetting. The low expansion potential encountered in one of the samples can probably be neglected in the foundation (and floor slab) design but should be evaluated turther at the time of construction. A lower risk of foundation settlement would be to remove a depth of the on-site soils (typically at least 3 feet) and replace the soils in a moisture controlled and compacted condition as structural fill, or a relatively deep foundation system such as helical piers extending the bearing down to the less compressible coarse granular soils. Provided below are recommendations for spread footings bearing on the natural soils or a minimum 3 feet of compacted structural fill. We should observe the bearing soils once the excavation for the foundation has been completed, before the placement of concrete, to further Kumar & Associates, Inc. Project No. 19.7-119 -4 - evaluate their compressibility/swell potential. If recommendations for a helical pier foundation system 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 buildings can be founded with spread footings bearing on the natural soils or a minimum 3 feet of compacted structural fill with some risk of settlement. 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 or compacted structural fill 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. If the bearing soils were to become wetted, some additional settlement could occur estimated at on the order 1/2 to 1 inch. The lower expected settlement value is for footings bearing on the structural fill. 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 area. 4) Continuous foundation walls should be well reinforced top and bottom to span Local anornalies and better withstand the effects of some differential settlement such as by assuming an unsupported length of at least 12 feet. Foundation walls acting 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. 5) All existing fill, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to firm natural soils. If structural fill is planned below the footings, the necessary amount of soil to provide a minimum of Kumar & Associates, Inc. Project No. 19.7.119 -5- 3 feet depth of structural fill should also be removed. The exposed subgrade in footing area should then be moistened and compacted. Structural fill below footing areas should be compacted to at least 98% standard Proctor density at a moisture content near optimum. 6) A representative of the geotechnical engineer should observe all footing excavations and test structural fill compaction 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. At the time of construction, we should further evaluate if any expansive soils exist below slab areas that may require removal. 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 sand and gravel base course should be placed beneath floor slabs "at -grade" for support and to facilitate drainage. This material should consist of minus 2 inch aggregate with at least 50% retained on the No. 4 sieve and less than 12% passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site soils devoid of topsoil and oversized rocks, or a suitable granular material such as road base can be imported. SURFACE DRAINAGE A perimeter foundation drain around shallow (less than 4 feet deep) crawlspace areas should not be needed with adequate compaction of foundation backfill and positive drainage away from foundation walls. The following drainage precautions should be observed during construction and maintained at all times after the residence and barn have been completed: Kumar & Associates, Inc. Project No. 19-7-119 -6- 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 12 inches in the 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 regular heavy irrigation, such as sod, and lawn sprinkler heads should be located at least 10 feet from foundation walls. 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 Figures 1 and 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) developing in the future. If the client is concerned 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 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 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 monitor the implementation of our recommendations, and to verify that the recommendations -7 - 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. Respectfully Submitted, Kumar & Associates, Inc. Ate Robert L. Duran, E. I. Reviewed by: (7. David A. Young, P. E. `'t�' RLD/kac iI4410.310 iO)V L il� 11.31 cc: Jeff Johnson Architectural — JeffJohnson (jeff@jjarchitecturaJ.com) Kumar & Associates, Inc. Project No. 19-7-119 TORTAA 2171.061-07 177 ID'S -RENDES AWIOEG ! 1 217 M OP iffi O`: 1 °T p 7A. IR 1100 R1.0 i(i1 / -- 1 1 AMMO e1riWr1•W-L4I j4A/1['i1I i r �- -Y 1.1. — r- FM/KWIC/1 TO DC 1011! Cr 9LT / 1 _ 7171-10-00-008 r .4 1 f 11 1 �IIEieRA.1 ! w -- -_--r OKI 1 RANCEI G . 6AS •-003-Ea716. RTA -100 h+.l — . . . - — . — ti 1. `1 1 1� R ) \ ISLAND f — 7f 044TOIr-00.-7u �� ,. r w 444, •-..p 4 r yo ___\ — — —1 �P \ + I 0113 �'ll]9 ` \ :!: -' —Iv MX M SIAM �n A'Ri7l71Y ' A)A. RR' _ e 43.365# Ary aftg010 A 0LT 2174-O04-00-733 NOT TO SCALE 19-7-119 X44§ , • BORING 2 BORING 1 • C. • 1E1 0100N WA0IEA1FOUN0AT0N II 2179-114-00-111 COUNTY ROAD 346 , I� Kumar & Associates '1[AMC61 taw. SIM MTh • 11 CM' HOLLOW 0702 .1 2129-001-00-t VICINITY MAP Fig. 1 d dvn'WeInniAfn' PROPOSED RESIDENCE 100 0 100 200 APPROXIMATE SCALE -FEET 19-7-119 COUNTY ROAD 346 Kumar & Associates BORING 1 • LOCATION OF EXPLORATORY BORINGS Fig. 2 UJ LJ X kT. xw 0 5 10 15 20 25 BORING 1 12/12 WC=4.8 DD=104 10/12 WC=2.& D0=104 13/12 WC=4.5 00=102 14/12 WC=4,2 DD=107 BORING 2 6/12 WCr-13.6 00=103 -200=72 7/12 WC=6.9 00=103 13/12 WC=4.1 DD=110 29/12 44/12 0 5-- 1 0 15 20 25 30 30 19-7-119 Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 3 LEGEND avz TOPSOIL; ORGANIC SANDY CLAYEY SILT, FIRM, MOIST, DARK BROWN. y� SILT AND SAND (ML—SM); STRATIFIED, TYPICALLY CLAYEY, STIFF/MEDIUM DENSE, SLIGHTLY /.' MOIST, BROWN, STRATIFIED. GRAVEL AND COBBLES (GM); WITH PROBABLE SMALL BOULDERS, SANDY, SILTY, DENSE, WET, BROWN, SUBROUNDED TO ROUNDED ROCKS. GRAVEL AND SAND (GM—SM); WITH COBBLES, POSSIBLE SMALL BOULDERS, SILTY, MEDIUM DENSE TO DENSE, SLIGHTLY MOIST, MIXED BROWN, SUBROUNDED TO ROUNDED ROCKS. DRIVE SAMPLE, 2—INCH I.D. CALIFORNIA LINER SAMPLE. 11 DRIVE SAMPLE, 1 3/8—INCH I.D. SPLIT SPOON STANDARD PENETRATION TEST. 12/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 12 BLOWS OF A 140—POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE THE SAMPLER 12 INCHES. Q DEPTH TO WATER LEVEL ENCOUNTERED AT THE TIME OF DRILLING. — I► DEPTH AT WHICH BORING CAVED IMMEDIATELY FOLLOWING DRILLING. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON JANUARY 25, 2019 WITH A 4—INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. 2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE APPROXIMATED 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 BORING LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER LEVELS SHOWN ON THE LOGS WERE MEASURED AT THE TIME AND UNDER CONDITIONS INDICATED. NO GROUNDWATER ENCOUNTERED IN BORING 2. FLUCTUATIONS IN THE WATER LEVEL MAY OCCUR WITH TIME. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSITY (pcf) (ASTM D 2216); —200= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140). 19-7-119 Kumar & Associates LEGEND AND NOTES Fig. 4 CONSOLIDATION - SWELL CONSOLIDATION - SWELL 0 — 1 — 2 —3 — 4 1 0 — 1 —2 —3 — 4 h..d 1.11 tn.Ars appy' Iv fin 1 •ampl.i lnl.d: 11w Ik11Y.q r.pwl liar rwl 6e l.p11.4 114 e.lcyl In IA opal ' Inn .Hl1in ufwi6.w or Humor and Annefelu, Inc, SooN Cemaldetlon fading oc1nrmed In eeeeldenee •IIr, ASIVI 111-4511 19-7-119 SAMPLE OF: Sandy Clayey Silt FROM: Boring 1 CSP 2.5' WC = 4.8 %, DD = 104 pcf EXPANSION UNDER CONSTANT PRESSURE UPON WETTING 1.0 APPLIED PRESSURE - KSF 10 1 DO SAMPLE OF: Sandy Clayey Silt FROM: Boring 1 @ 10' WC = 4.5 %, DD = 102 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1.0 APPLIED PRESSURE - KSr 10 100 Kumar & Associates SWELL -CONSOLIDATION TEST RESULTS Fig. 5 Kumar & Associates CONSOLIDATION - SWELL 1 0 —1 — 2 — 3 — 4 �,ei> -lees ..nm. NW! l" ao..ror• 4141•. ILO Witi.y .rpwl MN i411[w uC "3✓.�a. exv4l .n fall .01.11 11H •,4140 pro'et I(1'Imv •nY M3.0•44-4 4t S.r. eii14�e�.111F 11 MNWA 54Ik SAMPLE OF: Silty Clayey Sand FROM: Boring 2 ® 5' WC = 6.9 %, DD = 103 pcf ADDITIONAL COMPRESSION CINDER CONSTANT PRESSURE DUE TO WETTING 1.0 APPLIED PRESSURE - NSF 1C 1 19-7-119 SWELL -CONSOLIDATION TEST RESULTS Fig. 6 CONSOLIDATION - SWELL —3 — 4 — 5 — 6 — 7 SAMPLE OF: Silty Sand FROM: Boring 2 © 10' WC = 4.1 %, DD = 110 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1MmE•int muxa.omo6.. •Vr .w ul�p.}.�. ..— lm,,,fGsneeoo n1wS. I * en$ hs MplJ 4.migo En fi14 . U Nt 1n� Ntn, ne. So of itonw hr' -In 19-7-119 1.0 APPLIED PRESSURE — KSF 10 100 Kumar & Associates SWELL—CONSOLIDATION TEST RESULTS Fig. 7 11. -ran Geotechnical and Materials Engineers and Environmental Scientists kumarusa.com TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No. 19-7-119 SAMPLE LOCATION NATURAL MOISTURE CONTENT I%) GRADATION ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH lasf] SOIL TYPE BORING DEPTH (ft) NATURAL DRY DENSITY (acf) GRAVEL — SAND CA) PERCENT Pry SIEVE • I LIQUID LIMIT PASSING 1 (%1 Rpm INDEX N 1 21 4.8 104 Sandy Clayey Silt 5 2.8 104 Silty Clayey Sand 10 4.5 102 Sandy Clayey Silt 15 4.2 107 Silty Clayey Sand 2 21/2 8.6 103 72 Sandy Clayey Silt 5 6.9 103 Sandy Clayey Silt 10 4.1 110 Silty Clayey Sand