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HomeMy WebLinkAboutSoils Report 05.20.2019g+p Wen & Associates, , i c.° Geolechniral and Materiels Engineers and Environmental St-:ntisls An Employee Owned Company 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com www.kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs. Fort Collins, Glenwood Springs, and Summit County, Colorado RECEIVED OCT 1 7 7.01 GARFIELD COL cowmen, DEVEL • SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE COUNTY ROAD 346, SOUTH OF SILT ASSESSOR'S PARCEL 217910300001 GARFIELD COUNTY, COLORADO PROJECT NO. 19-7-235 MAY 20, 2019 PREPARED FOR: JOEL RUIZ P. O. BOX 37 SILT, COLORADO 81652 Joel -i uiz(rr:live.coin TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS - 1 - FIELD EXPLORATION - 2 - SUBSURFACE CONDITIONS - 2 - FOUNDATION BEARING CONDITIONS - 3 - DESIGN RECOMMENDATIONS - 3 - FOUNDATIONS - 3 - FLOOR SLABS - 4 - SURFACE DRAINAGE - 5 - LIMITATIONS - 6 - FIGURE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURE 4 - SWELL -CONSOLIDATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS Kumar & Associates, Inc. 6 Project No. 19-7-235 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on a parcel of land north of County Road 346, south of Silt, Assessor's Parcel 217910300001, Garfield County, Colorado. The 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 to Joel Ruiz dated April 16, 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 two-story wood -frame structure with an attached garage and located generally between the exploratory borings shown on Figure 1. Ground floor will be structural over crawlspace in the living area and slab -on -grade in the garage. Grading for the structure 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. SITE CONDITIONS The project site is currently vacant. The proposed building site is to the northwest of the intersection of two two -track roads. The east road is proposed to be extended to the south to access the property from County Road 346. There are numerous unmaintained two -track roads Kumar & Associates, Inc. ,k, Project No. 19-7-235 -2 - and irrigation ditches throughout the property. Topography is valley bottom with gentle slopes generally down to the west. The Colorado River is approximately'/ -mile to the northeast of the proposed building site. Vegetation at the site consists of native grass and weeds. There is an undeveloped natural gas drilling well pad approximately 300 feet from the eastern edge of the proposed building area. FIELD EXPLORATION The field exploration for the project was conducted on April 23, 2019. 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 13A 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 2. 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 2. The encountered, below about 1 foot of topsoil, consist of about 15 to 18 feet of stratified layers of sandy silt and silty sand that was typically clayey and medium stiff/loose and underlain by dense, silty sand and gravel with cobbles and probable boulders. Drilling in the dense granular soils with auger equipment was difficult due to the cobbles and boulders and drilling refusal was encountered in the deposit. Laboratory testing performed on samples obtained from the borings included natural moisture content and density and percent finer than sand -size gradation analyses. Results of swell - consolidation testing performed on relatively undisturbed drive samples of the sand and silt soils, presented on Figure 4, indicate generally low to moderate compressibility under conditions of Kumar & Associates, Inc. 0 Project No. 19-7-235 3 loading and wetting. The samples typically showed a low collapse potential when wetted under a constant 1,000 psf surcharge load. The laboratory testing is summarized in Table 1. Free water was encountered in Boring 1 at a depth of 22 feet at the time of drilling. No free water was encountered in Boring 2. The upper soils were moist to slightly moist with depth. FOUNDATION BEARING CONDITIONS The fine-grained compressible silt and sand soils are expected to be encountered at excavation subgrade for the residence. 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 residence with a risk of settlement. The risk of settlement is primarily if the bearing soils were to become wetted and precautions should be taken to keep the bearing soils dry. 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 extended down to the low 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 evaluate their compressibility potential. If recommendations for a helical pier foundation system are desired, we should be contacted. DESIGN RECOMMENDATIONS FOUNDATION S Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, the residence can be founded with spread footings bearing on the natural soils or a minimum 3 feet of compacted structural fill with a risk of settlement. The design and construction criteria presented below should be observed for a spread footing foundation system. Kumar & Associates, Inc." Project No. 19-7-235 4 1) Footings placed on the undisturbed natural soils or compacted structural fill should be designed for an allowable bearing pressure of 1,500 psf. Based on experience, we expect initial settlement of footings designed and constructed as discussed in this section will be about 1 inch or less. If the natural soils were to become wetted, additional settlement estimated at on the order 1 inch could occur depending on the depth and extent of wetting. 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 heavily reinforced top and bottom to span local anomalies 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) The topsoil and 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 3 feet depth of structural fill should also be removed. The exposed subgrade in footing area should then be moistened and compacted. Structural fill placed 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, can be used to support lightly loaded slab -on -grade construction with a settlement risk. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow Kumar & Associates, Inc. c Project No. 19-7-235 -5 - 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: 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. Consideration should be given to the use of xeriscape to limit potential wetting of soils below the foundation caused by irrigation. Kumar & Associates, Inc. au Project No. 19-7-235 6 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 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 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. Robert L. Duran, E. I. Reviewed by: —_� Steven L. Pawlak, RLD/kac cc: Jeff Johnson Ar A-- (jL' ot:nct) Kumar & Associates, Inc. Project No. 19-7-235 ‘br I. f - V:VIVAcrY\ bli0j1-7-1b5 ,vbxpE Shah, ...aped held... C.* Rood sempossv v JewnN LOCATION OF EXPLORATORY BORINGS 133A-31V3S 31Vi1lX0elddV 0 0 0 o • • 1 t •?..„.. • : p,s : U-• - 10 7... 2 c; 0 0 ;k1 4 1. j a j \ • ••••••.. 1 • n A r • 411 . ! 1/ ko .- .......,- ) 1 / /• t I t / / / 1 / / 4v / .•')• r / / :P A 111 . i/' -,1 ,••• • / / ..-, . .i k :::t• i / / 1 • '.,-...1i •.".,` • 71-. 1 • / --. ..:.--. , ALI / I .1 / .4•''• ' ,..... •;.:.. I'• . ; I i 4 --!'• fie'rx, , ,--i .- - fg __ , I : I .•• f i 1 1 / t, _ -- _qii-ii.,;-•--,.-- -- ,rj A n DEPTH -FEET ana.o,»rxsa.oz w.e.o -- 0 -5 10 - 15 -- 20 BORING 1 EL. 100' 7/12 WC=13.2 1 DD=116 1 -200=73 8/12 WC=8.8 DD=109 7/12 WC=13.4 DD=97 7/12 50/4 50/3.5 BORING 2 EL. 97' 8/12 WC=13.9 DD=111 7/12 WC=6.9 DD=104 5/12 WC=11.3 DD=100 50/4 0 5 -- 10 15 --- 20 — - 25 25 1- 1- a - aa w 0 19-7-235 Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 2 LEGEND G TOPSOIL; ORGANIC SANDY CLAYEY SILT, FIRM, MOIST, DARK BROWN. SILT AND SAND (ML—SM); STRATIFIED, TYPICALLY CLAYEY, MEDIUM STIFF/LOOSE, SLIGHTLY MOIST TO MOIST, BROWN. GRAVEL AND SAND (GM—SM); WITH COBBLES AND SMALL BOULDERS, VERY DENSE, MOIST, MIXED BROWN. DRIVE SAMPLE, 2—INCH I.D. CALIFORNIA LINER SAMPLE. DRIVE SAMPLE, 1 3/8—INCH I.D. SPLIT SPOON STANDARD PENETRATION TEST. 7/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 7 BLOWS OF A 140—POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE THE SAMPLER 12 INCHES. DEPTH TO WATER LEVEL ENCOUNTERED AT THE TIME OF DRILLING. t PRACTICAL AUGER REFUSAL. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON APRIL 23, 2019 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 MEASURED BY HAND LEVEL AND REFER TO BORING 1 AS ELEVATION 100', ASSUMED. 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 LEVELS SHOWN ON THE LOGS WERE MEASURED AT THE TIME AND UNDER CONDITIONS INDICATED. FLUCTUATIONS IN THE WATER LEVEL MAY OCCUR WITH TIME. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D2216); DD = DRY DENSITY (pcf) (ASTM D2216); —200= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D1140). 19-7-235 Kumar & Associates LEGEND AND NOTES Fig. 3 Z —1 0 J 0 <nZ —2 0 0 — 3 —4 CONSOLIDATION - SWELL —1 — 2 — 3 SAMPLE OF: Slightly Clayey Sand and Silt FROM: Boring 1 0 5' WC = 8.8 %, DD = 109 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1.0 APPLIED PRESSURE — KSF 1a +00 SAMPLE OF: Slightly Clayey Sand and Silt FROM: Boring 2 © 3' WC = 13.9 %, DD = 111 pcf Inn! feet nwa. eppy teey to the nen** I.Iled. The teglep mewl shoe not W r.e.odutee, wept In NM, without the enItcn epprv..8 of MAW. ono Patetkloe, Int. Swee Cd,*.Idl ten t.Hig peMmned N OOOMQertte .ale +WO O -434e. ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1.0 A'PLIED PRESSURE — KSF 10 100 19-7-235 Kumar & Associates SWELL—CONSOLIDATION TEST RESULTS Fig. 4 ICA Kumar & Associates, Inc. °° Geotechnical and Materials Engineers and Enviranmrental Scientists TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Pro act No. 19.7-235 SAMPLE LOCATION NATURAL MOISTURE CONTENT PA) NATURAL DRY DENSITY (pcf) GRADATION PASSINGPERCENT NO. 200 SIEVE ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH (psf) SOIL TYPE BORING i DEPTH 1 (ft) GRAVEL (off) SAND (°/i) LIQUID LIMB (%) PLASTIC INDEX (%) 1 21/2 j 13.2 116 73 Slightly Clayey Sandy Silt 5 8.8 109 Slightly Clayey Sand and Silt 10 13.4 97 Slightly Clayey Sand and Silt 2 3 13.9 111 Slightly Clayey Sand and Silt 5 6.9 104 Slightly Clayey Sand and Silt 10 11.3 100 Slightly Clayey Sand and Silt a 1 • • t