The URL can be used to link to this page

Home My WebLink AboutSubsoils Report for Foundation ReporttGrtiiffiåffiiffinl'i¡;-"' An Employcc Owncd Compony 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 Cotutty, Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE LOT 15, BLOCK 4, BATTLEMENT CREEK VILLAGE 195 BOULDER RIDGE DRIVE GARFIELD COUNTY, COLORADO PROJECT NO.23-7-220 MAY 16,2023 PREPARED FOR: ADA CHAVEZ 71 RIDGE VIEW PLACE BATTLEMENT MESA, COLORADO 81635 Adachavez6@,smail.com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITIONS FIELD EXPLORATION SUBSURFACE CONDITIONS ,..- 1 - 1 ...........- I - I .............-2 - DESIGN RECOMMENDATIONS ................2- FOUNDATIONS....2- FOLTNDATION AND RETAINING WALLS ...............- 3 - FLOOR SLABS .....- 4 - UNDERDRAIN SYSTEM 4- SURFACE DRAINAGE.....5- LIMITATIONS 5- FIGURE 1 - LOCATION OF EXPLORATORY BORING FIGURE 2 -LOG OF EXPLORATORY BORING FIGURES 3 aruJ 4 - SWELL-CONSOLIDATION TEST RESULTS FIGURE 5 _ GRADATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS Kumar & Associates, lnc, @ Proiect No.Z&.V-üM PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for the proposed residence to be located on Lot 15, Block 4, Battlement Creek Village, 195 Boulder Ridge 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 performed based on our agreement letter to Ada Chavez dated March 28,2023. An exploratory boring was drilled 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 residence will be a single-story wood frame structure over a walkout basement level with attached garage at the main level. Ground floors will be slab-on-grade. Grading for the structure is assumed to be relatively minor with cut depths between about2 to 8 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 lot was vacant and the ground surface appeared mostly natural at the time of our field exploration. The terrain is strongly sloping down to the south. Vegetation consisted of grass, weeds and sagebrush. The Colorado River is approximately % mile north of the site and considerably lower in elevation. F'IELD EXPLORATION The field exploration for the project was conducted on April 24,2023. One exploratory boring was drilled at the location shown on Figure 1 to evaluate the subsurface conditions. The boring was advanced with 4 inch diameter continuous flight augers powered by a truck-mounted CME- 458 drill rig. The boring was logged by a representative of Kumar & Associates. Kumar & Associates, lnc. @ Project No.23-7-220 -2 Samples of the subsoils were taken with l% inch and 2 inch I.D. spoon samplers. The samplers wcrc driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is sirnilar 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 Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory for review by the projcct engineer and testing. SUBSURF'ACE CONDITIONS A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The subsoils consist of about lYzfoot of topsoil overlying very stifflmedium denseo silty to very silty clayey sand down to l0% feet depth where relatively dense, silty clayey sandy gravel and cobbles with boulders down to the drilled depth of 16 feet. Laboratory testing performed on samples obtained from the boring included natural moisture content and density, and gradation analyses. Results of swell-consolidation testing performed on relatively undisturbed drive samples of the silty sand, presented on Figures 3 and 4, indicate low to moderate compressibility under existing moisture conditions and light loading, with a low hydrocompression potential when wetted under constant light surcharge. A gradation analysis, presented on Figure 4, was performed on a sample of the very silty sand and gravel from a depth of 15 feet. The laboratory testing is summarized in Table 1. No free water was encountered in the boring at the time of drilling and the subsoils were slightly moist. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we believe the building can be founded with spread footings bearing on the natural soils with some risk of movement. The risk of movement is primarily if the bearing soils were to become wetted and precautions should be taken to prevent weffing. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed natural soils should be designed for an allowable bearing pressure of 1,500 psf. Based on experience, we expect settlement of footings dcsigned and constructed as discussed in this section will be about I inch or less. Some additional settlement could occur if the bearing soils become wetted. 'lhe Kumar & Associates, lnc. o Froiect No.23.7-220 -J- magnitude of the additional settlement would depend on the depth and extent of the wetting but may be on the order of Vzto I inch. 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 area. 4) Continuous foundation walls should be well reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 14 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) All existing fill, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the firm natural soils. The exposed soils in footing area should then be moistened and compacted. 6) A representative ofthe geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FOUNDATION AND RETAINING WALLS Foundation walls and retaining structures 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 50 pcf for backfill consisting of the on-site 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 40 pcf for backfill consisting of the on-site soils. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge 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 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 maximum standard Proctor density at a moisture content near optimum. Backfill in pavement and walkway areas should be compacted to at least95Vo of the maximum standard Proctor density. Care should be taken not to overcompact the backhll or use large equipment near the wall, since this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall Kumar & Associates, lnc. o Project No. 23-7-220 -4 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 thc footing. Rcsistancc to sliding at the bottoms of thc footings can bc calculatcd based on a coefficient of friction of 0.35. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 325 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 95%o of the maximum 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 free- draining gravel should be placed beneath basement level slabs to facilitate drainage. This material should consist of minus 2-inch aggregate with at least 50% retained on the No. 4 sieve and less than2Yo passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least95o/o of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on-site soils devoid of vegetation, topsoil and oversized rocks. UNDERDRAIN SYSTEM Although free water was not encountered during our exploration, it has been our experience in the area that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoffcan also create a perched condition. We recommend below-grade construction, such as retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. The drains shoulcl consist of perforated drainpipe placed in the bottorn of the wall backfill surrounded above the invert level with t-ree-draining granular material. 'l'he drain should be Kumar & Associates, lnc. o Frojeei No.23"'iî-22ø -5- placed at each level ofexcavation and at least I foot below lowest adjacent finish grade and sloped at a minimum l%o to a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than 2%opassingthe No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least lYzfeetdeep. SURFACE DRAINAGE Positive surface drainage is a very important aspect of the project to prevent wetting of the bearing soils. The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: l) Inundation ofthe foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at leastg5Yo 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. Free-draining wall backfill should be covered with filter fabric and capped with about 2 feet of the on-site soils to reduce surface water infiltration. 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 boring drilled at the location 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 extrapolation of the subsurface conditions identified at the exploratory boring and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appear Kumar & Associates, lnc. @ Proipcü lllo" 23-7-220 -6- differult from those described i¡ rhis¡ netrnrt' we Sould be nr tifid so that ¡o-waluatim of ths recommendations may be made. This rc'port haq bee,n prcpared for thc ffidrnive rsu by our t:liqill, fi,r drrsign prrpucos. Wc uu nrt responsible for technical interpretatims hy oilhas of our informdion- l\s üe pojecÊ enolvesn we should provide continued consultatimmd frctd ecrniæ during mnstruction üo rwiew and moniûor the implementation of ourrMdionsç mnl to verifyftd ftermcnddions have been appropriately interpreted- $iigr¡¡frcrrt design drnnges m¿y ËIüirG additional malyßis or modifications to the recommenda{ñrrrmÍresdod hcr€in- \Perrur¡mend on sitc oüserndion of excavations and foundation bearing ffi md t€sing of trutual frll by a rryesmtative of the geotechnical engineer. Respectfu lly Submitted, Kumar & Associates, Robert L. Dura& P Reviewed by: T Daniel E. Hardin, P.E. RLDlkac Kumar & Associates, lnc.6'Project No. 23-7-220 0 60 APPROXIMATE SCALE-FEET 23-7-220 Kumar & Associates LOCATION OF EXPLORATORY BORING Fig. 1 I I 6 Ê I BORING 1 LEGEND 0 TOPSO|L; SAND AND SILT, FIRM, SLIGHTLY M0|ST, BROWN, ORGANIC. 24/12 WC=4.6 DD=97 SAND (SM); STLTY T0 VERY S|LTY, MtDtUM DENSE, SLTGHTLY MOIST, BROWN, SLIGHTLY CALCAREOUS. 5 12/12 WC=4.6 DD=94 W GRAVEL (GM); SILTY, SANDY, SCATTERED coBBLEs, MEDIUM DTNSE TO DENST, SLIGHTLY MOIST, TAN, SLIGHTLY CALCAREOUS. DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE. t- UJtd l! I-FfL ¡¡Jô 10 14/6,50/1 i DRTVE SAMPLE, r 3/8-|NCH LD. SPLTT SP00N STANDARD PENETRATION TEST. .1¡¡17DRIYE SAMPLE BLOW COUNT. INDICATES THAT 21 BLOWS 0F-./'-A 11o-POUND HAMMER FALLING 30 INCHIS WERE REQUIRED TO DRIVE THE SAMPLER 12 INCHES. 15 28/12 WC=7.3 +4=27 -200=41 NOTES 1. THE EXPLORATORY BORING WAS DRILLED ON APRIL 21, 2023 WITH A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. 2. THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 20 5. THE ELEVATION OF THE EXPLORATORY BORING WAS NOI MEASURED AND THE LOG OF THE EXPLORATORY BORING IS PLOTTED TO DEPTH. 1. THE EXPLORATORY BORING LOCAÏION SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE Ii4ETHOD USED 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE TIME OF DRILLING. 7, LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSITY (PCt) (ISTU D 2216); +4 = PERCENTAGE RETAINED ON NO.4 SIEVE (ASTM D 6913); -200 = PERCENTAGE PASSING N0. 200 SIEVE (ASTM D 1110). 23-7-220 Kumar & Associates LOG OF EXPLORATORY BORING Flg. 2 14,- tO:l¡om Sub.oll CoNSoLTDATTON - SWELL (%) ÞI @ I\¡I(t)I(,I (r,¡ I ¡\)I o !!trr0 ı8ä il=P È@r¡b'9oir Tl o\ (cì-1' s= : @; "Ng(f) (ln o_\¡ !o cz>oorî otor= Fgg -z>ci a,t- {å8rr! -{ <f-I Znr,lc)nanul ut2ıãz- rrt \ åãì É;r Ì í:.{.â ièt Êái e9tt - =Ét çg¡ 3 f¡ ÊË a*ı ô f.åcË *96í Èåsã N)(^ I\¡ I N) N)o i\c 3 0¡ eo U'Øo a.!¡ oa at =11t-t- I C)oz.tJlo1- I -.toz. -{fî a,/)-l Ðr1 rJlct--ltn =I (¡ P E! ı E¡ I I SAMPLE OF: Very Sllfy Sond FROM:Boringl@5' WC = 4.6 ?6, DD = 94 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING ) \ \ \( \ 2 òe JJ l¡J =tt', I z.otr ô Jolnzo C) 0 -2 -4 -6 -8 -10 -12 1.0 23-7 -220 Kumar & Associates SWELL_CONSOLIDATION TEST RESULTS Fig. 4 E SIEVE ANALYSISHYDROMETER ANALYSIS rXE RÉADITG ¡4 HRS 7 HRSu¡r ¡^vrx rovlx tl U.S. SIA¡DARD SERIES CLilR SQUARE OPENIXGS Iû H too 90 80 70 to 50 10 30 20 io o 0 to 20 30 40 50 60 70 ao 90 too I¡b I .123 132IN MILLIMETERS CLAY TO SILT COBBLES GRÂVEL 27 % SAND 32 % LIQUID LIMIT - PLASIICITY INDEX SAMPLE OF: Very Silty Sond ond Grovel SILT AND CI.AY 11 % FROM:BoringlO15' ThclG loll r.sull! opply only lo lhc rompb. whlch vcrc lc¡lcd. Thcl.rllno rGport lholl nol b. r.produc.d, arc.pt ln full, vllhoul lh. vrllLn opprovol ol Kumo¡ il Attocìolcr, lnc. Sl.v. onolysl! lcltlng l3 p.rfomld ln occorddnc. u¡th ASTI¡ 06913, ASTM 07928' ASTM C156 ond/or ASTM Dll,l0. SAND GRAVEL FINE MEDTUM lCOanSe FINE COARSE 23-7 -220 Kumar & Associates GRADATION TEST RESULTS Fig. 5 lCÄi;ffilå#r:ffiiiiäü-* :t TABLE 1 SUMMARY OF LABORATORY TEST RESULTS 23.7-220 SATPI LOCAT|Ot{tot AT'I i I trtTs BORING ffrì DEPfH t%t i¡ATURAL ¡t0tsTuRE COIITENT {octl iIATURAL DRY DENSITY GRAVEL (%) sAt{0 ftt PERCEI{T PASSING I{O. 200 stEvE LIQUID LIfIf toi6t f96t PLASÍIC [{DEX forn UNCOI{FINED cotPREsstvE STRËNGTI{SOIL TYPE I 2y,4.6 97 Silty Sand 5 4.6 94 Very Siþ Sand l5 7.3 27 32 4l Very Silty Sand and Gravel