The URL can be used to link to this page

Home My WebLink AboutSubsoils Study for Foundation Designl*rtiiffififfiffiifiå;å*'" An Employcc olrncd Compqny 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 May 8,2t23 RECËruEn Jesse Flughson : , : ',i l:l ' P.O. Box 102 De Beque, cororado 8163û Snni,lfiiftff,ï;;',, jrhughsS6@gmail.com Project No, 22-7-785 Subject: Subsoil Study for Foundation Design, Proposed Buildings, 3241 County Road 237, Garfield County, Colorado Jesse: As requested, Kumar & Associates, Inc. performed a subsoil study for design of foundations at the subject site. The study was conducted in general accordance with our agreement for geotechnical engineering services to you dated December2l,2022. Additional exploratory pits were observed at the site as requested by you. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presented in this report. Proposed Construction: The proposed buildings will be located as shown on Figure L Ground floors could be slab-on-grade or structural above crawlspace. The shop building will be a Quonset hut-type structure designed to be supported by a monolithic slab foundation. Cut depths are assumed to be shallow, around 2 to 4 feet below existing ground surface. Foundation loadings for the proposed construction are assumed to be relatively light and typical of the proposed type of construction. If building locations, conditions or foundation loadings are significantly different from those described above, we should be notified to re-evaluate the recommendations presented in this report. Site Conditions: The property was vacant with a rough-cut driveway to the proposed building areas and covered with up to one foot of snow at the time of our site visit. The terain is south facing, hogback hillside of generally moderate slope and vegetated with pinon and juniper forest and sagebrush. Subsurface Conditions: The subsurface conditions at the site were evaluated by observing 5 exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The subsurface conditions encountered, below aboutYz to I foot of topsoil or silty sand, mainly consist of very steeply to near vertical bedded sandstone, siltstone and claystone bedrock. At Pit l, about 2Yzfeetof stiff clay above silty clayey gravel and cobble soil was encountered to the pit depth of 6 feet. Results of swell-consolidation testing performed on relatively undisturbed samples of the clay and weathered claystone/siltstone" presented on -') - Figures 4 and 5, indicate low compressibility under existing moisture conditions and light loading and a minor collapse or expansion potential when wetted. The laboratory test results are summarized in Table l. No free water was observed in the pits at the time of excavation and the materials were slightly moist to moist. Foundation Recommendations: Considering the subsurface conditions encountered in the exploratory pits and the nature ofthe proposed construction, we recommend spread footings placed on the undisturbed natwal soil designed for an allowable bearing pressure o,!!9@¡|for support of the proposed buildings. A monolithic slab foundation with a frost protected perimeter thickened edge 18 inches deep can be used for the shop building support. The soils tend to compress after loading and wetting and there could be around I inch of post-construction differential foundation settlement. In the other buildings, where spread footings are placed on the undisturbed natural bedrock, an allowable bearing pressure of 3,000 psf can be used for foundation support. Settlement potential should be relatively minor, less than I inch. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. The topsoil and loose disturbed soils encountered at the foundation bearing level within the excavation should be removed and the footing bearing level extended down to the undisturbed natural soils or bedrock. We should observe the completed excavations for foundation bearing conditions. Exterior footings should be provided with adequate cover above their bearing elevations for frost protection. Placement of footings (excluding frost protected monolithic slab) at least 36 inches below the exterior grade is typically used in this area. Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 12 feet. Foundation walls acting as retaining structures (if any) should be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 50 pcf for the on-site soil as backfill. 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, non-structural 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 (if any) to facilitate drainage. This material should consist of minus 2-inch aggregate with less than 50% passing the No. 4 sieve and less than2o/o 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 onsite soils devoid of vegetation, topsoil and oversized rock. Kumar & Associates, lnc. o Project No. 22-7-785 -3- Underdrain System: Although free water was not encountered during our exploration, it has been our experience in the area where bedrock is shallow that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoffcan create a perched condition. We recommend below-gtrade construction, such as retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. ïVhere provided, the drains should consist of drainpipe placed in the bottom of the wall backfill surounded above the invert level with free-draining granular material. The drain should be placed at each level ofexcavation and at least I foot below lowest adjacent finish grade and sloped at a minimum lo/o to a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than 2% passing the 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 lYz feet deep. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after each building has been completed: 1) 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 least 95Ya of the maximum standard Proctor density in pavement and slab areas and to at least 90% ofthe maximum standard Proctor density in landscape 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. 3) The ground surface sumounding 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 10 feet in unpaved areas and a minimum slope of 3 inches in the f,rst l0 feet in pavement and walkway areas. A swale will may be needed uphill to direct surface runoff around each building. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy inigation should be located at least 5 feet from the building. Limitations: This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area at this time. lVe make no waranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory pits excavated at the locations indicated on Figure I and to the depths shown on Figure 2, the proposed type of construction, and our experience in the æea. Our services do not include determining the presence, prevention or possibility of mold Kumar & Associates, lnc. o Projec-t No. 22.7.785 -4- 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 pits 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 at once so re,evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for design purposes. V/e are not responsible for technical interpretations by others of our infonnation. 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 veriry 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 rçresentative of the geotechnical engineer. If you have any questions or if we may be of further assistance, please let us know. Respectfi,rlly Submitted, Kumar & Associates, lnc. I,QFA Steven L. Pawlak, P.E. Reviewed by: Daniel E. Hardin, SLPlkac Attachments: Figure I Exploratory Pits Figure 2 - Logs of Exploratory Pits Figure 3 - Legend and Notes Figures 4 and 5 - Swell-Consolidation Test Results Table I - Summary of Laboratory Test Results ¡' l¡a!,'.t Kumar & Associates, lnc. ¡Project No. 22"7-785 ti Ì NOT TO SCALE 22-7-785 Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1 e WC=13.9 DD=1 O8 UC=1,200 WÇ=28.7 DD=79 PIT 1 EL. 100' Ptf z PIT 5 EL. 99 EL. 100' 0 FVffiT 0 WC=f 8.2 DD=1 02 F,:LI l4ll! I-F-& t¡JÕ 5 5 Ft¡l l¿lL I:rt-û- LJo 10 10 PIT 4 E1.100' PIT 5 EL. 104' 0 o FLd t¡Jt! I-þ-L LdÕ F- a¡¡ldlÀ I-+-û- TJê 5 22-7-785 Kumar & Associates LOGS OF EXPLORATORY PITS Fig. 2 E !. LEGEND TOPSOIL; ORGANIC SANDY SILT AND CLAY, GRAVELLY, FIRM, MOIST, DARK BROWN CLAY (CL); SILTY, SANDY, MEDIUM STIFF, VERY MOIST, BROWN, MEDIUM PLASTIC¡TY GRAVEL AND OOBBLES (GC); S|LTY, CLAYEY, SANDY, MEDIUM DENSE, MOIST, MIXED BROWN, BLACK ORGANIC LAYER AT 3.5 FEET. FM m 8..8ill;ip!::1E!Í¡ålzüw ÊÉtzìt rÅlÆÅ Y) I F t SAND (SM); SILTY, SCÄTTERËD COBSLES, LOOSE, MOIST, BROWN. SANDSTONE BEDROCK; VERY HARD, STEEPLY DIPPING BEDDING, SLIGHTLY MolST, BROWN WEATHERED SILTSTONE/CLÀYSTONE; MEDIUM HARD TO VERY HARD wlTH DEPTH, MOIST, 8ROWN, STEEPLY DIPPING BEDDING. HAND DRIVEN 2_INCH DIAMETER LINER SAMPLE. PRACTICAL DIGGING REFUSAL. NOTÈS 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON MARCH 28, 2023. 2. THE LOCATIONS OF THE EXPLORATORY PIÏS WERE MEASURED APPROXIMATELY BY PACING FROM FEAÌUKES SHOWN ON THE SITE PLAN PROVIDED AND AT THE BUILDING SITES DESIGNATEÐ BY ÏHE CLIENT. 5. THE ELEVATIONS OF THE EXPLORATORY PIÍS WERE MEASURED BY HAND LEVEL AND REFER TO PIT 1, PIT 5 AND PIT 4 AS 1OO FEET, ASSUMED AT THE RESPECTIVE BUILDING SITE. 4. ÏHE EXPLORATORY PlI LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY fO THE DEGREE IMPLIED BY THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PIÏS AT THE TIME OF EXCAVATION. PITS WERE BACKFILLEÐ SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSITY (PCf) (ASTM Ð 2216): UC = UNCONFINED COMPRESSIVE STRENGTH (PSf} (ASTM D 2166). 22-7-785 Kumar & Associates LEGEND AND NOTES Fis. 3 E I SAMPLE OF: Orgonic Sondy Silty Cloy FRQM:Pitlg3.5' ttlC = 28.7 %, DD = 79 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1 o ¡s j-1 l¡¡ =tn t_2 zI,-{ô =-JoØzo<J-4 -5 7 ,|t.0 - KSF t0 22-7-785 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fis. 4 SAMPLE OF: Weolhered Sillstone/Clcyslone FROM:Pit3q-2' WC = 1E.2 %, Dù = 102 pct h rö Þ4ff_ ñot h ryùd, EXPANSION UNDER CONSTANT PRESSURE UPON WETTING I AOx J J l¡, =Ø t_2 zotr ã f-Jovlzoç_4 -6 ,|!.0 APPLIED PRESSURE - KSF 't0 22-7-785 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 5 E 9. l(+rlm,[mrff';*'' :' TAELE I SUMMARY OF LABORATORY TEST RESULTS GRAOAÍþiT AT'ERBI ¡ LtiilTs Prt OEPfH (41 IIATURAL f{or$unE cottTEl{T 1{ATURAL DRY DEI¡SITY læll GRAVEL (96) sÁltD {*} PERCEI{Í PASSÍ|G ¡r0. 20t¡ slEtE LQU[}ultrf f%t PLASNC IXDEX t*t ¡*R UNCOilFfiED cotFREssfi,E $rnEttcllt SOIL T'IPE I 1 13.9 108 1,2a0 Sandy Silty Clay 3/,28,7 79 Organic Sandy Silty Clay 3 2 18.2 t02 Weathered Siltstone/Clavstone l$o. ¡¿"t+Ht