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Home My WebLink AboutSubsoil StudyKfif mrfim*lm1'#ü*." Áû &!pb}¡a Cnm¡dCompcrry 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 (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado }l4ay 7,2021 Domoplex, LLC Attn: Slawek Wojciuch 2550 Highway 82, Unit 1084 Glenwood Springs, Colorado 81601 slawek@domoplex.com Project No. 21 -7-280 Subject: Subsoil Study for Foundation Design, Proposed Residence, Lof 62, Filing 7, Elk Springs, 104 Aster Drive, Garfield County, Colorado Dear Slawek: As requested, Kumar & Associates, Inc. performed a subsoil study for design of foundations at the subject site. The study was conducted in accordance with our agreement for geotechnical engineering services to Domoplex, LLC dated March 18,202I. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presented in this report. Proposed Construction: Plans for the proposed residence were not available at the time of our study. The proposed residence will likely be a one- or fwo-story residence possibly over a lower walkout basement level with an attached garage located in the building envelope shown on Figure 1. Ground floors could be structural over crawlspace or slab-on-grade. Cut depths are assumed to range between about2 to 8 feet. Foundation loadings for this type of construction are assumed to be relatively light and typical of the proposed type of construction. If building 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 subject site was vacant at the time of our field exploration. The ground surface is sloping down to the south and southeast at grades estimated between 5 and 10 percent. Basalt cobble and boulders were visible at the surface. Vegetation consists of grass and sage brush with scatteredjuniper trees on the lower portion of the lot. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating three exploratory pits at the approximate locations shown on Figure l. The logs of the pits are presented on Figure 2. The subsoils encountered, below about Vzfoot of topsoil, consist of Yzto l%feet of medium stiff to stiff, sandy clay soils overlying dense, highly calcareous sandy silt a ancl gravel and cobbles to the maximum explored depth of .5 feet. Resr¡lts of a graclation analysis performed on a sample of highly calcareous sandy silt and gravel (minus S-inch fraction) obtained from the site are presented on Figure 3. No free water was observed in the pits at thc time of excavation and the soils were slightly moist to moist. Foundation Recommendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, we recommend spread footings placed on the undisturbed natural soil designed for an allowable bearing pressure of 2,000 psf for support of the proposed residence. The fine-grained soils tcnd to compress after wetting and there could be some post-construction foundation settlement. Footings should be a minimum width of 16 inches for continuous walls and 2 t-eet t.or columns. Topsoil, sandy clay 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 silt and basalt rock soils. Exterior footings should be provided with adequate cover above their bearing elevations for frost protection. Placement of footings at least 36 inches below the exterior grade is typically used in this area. Continuous t'oundation walls should be reinforced top and bottom to span local anomalies suoh as by assuming an unsupported length of at least l0 feet. Foundation walls acting as retaining structures 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, excluding topsoil and rock larger than 6 inches. 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 laycr uf fiee-tlraining gravel should be placed beneath basement level slabs to facilitate drainage. This material should consist of minus Z-inch aggregate with less than 50o/o passing the No. 4 sieve and less than 2%o passing the No. 200 sieve. All fìll materials for support of floor slabs should be compacted to at least 95% of maximr¡m standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site soils devoid of vcgctation, topsoil and oversized rock. Underdrain System: Although free water was not encountered during our exploration, it has been our experience in the area and where clay soils are prescnt, that local perched groundwater Kumar & Associates, lnc. o Projcct No. 21-7-280 -J- can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. We recommend below-grade construction, such as retaining walls, crawlspace and basement areas (if any), be protected from wetting and hydrostatic pressure buildup by an underdrain system. The drains should consist of drainpipe placed in the boffom of the wall backfill surrounded above the invert level with free-draining granular material. The drain should be placed at each level of excavation and at least I foot below lowest adjacent finish grade and sloped at a minimum lYoto a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than 2Yo passingthe 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: The following drainage precautions should be observed during construction and maintained at all times after the residence 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 95o/o 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. 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 surrounding 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 first 10 feet in pavement and walkway areas. 4) Roof downspouts and drains should discharge well beyond the limits of all backflrll. 5) Landscaping which requires regular heavy inigation should be located at least 10 feet from the building. Consideration should be given to the use of xeriscape to limit potential wetting of soils below the foundation caused by inigation. 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 pits excavated at the locations indicated on Figure 1 and to the depths shown on Figure 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 Kumar & Associates, lnc. @ Project No. 21-7-280 -4- or other biological contaminants (MOBC) developing in the future. If the client is concerncd about MOtsC, then a protbssional in this special field of practicc should be consulted. Our lindings include interpolation and extrapolation of the subsurface conditiotls identified at the exploratory pits and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during constuction 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. 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 recommendationso 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 shata and testing of struchral fill by a representative of the geotechnical engineer. If you have any questions or if we may be of further assistance, please let us know. Respectfully Submitted, Ke¡mar & Assoeiates, James H. Parsons, P.E. Reviewed by: Steven L. Pawlak, P.E. JHP/kac attachments Figure I - Location of Exploratory Pits Figure 2 - Logs of Exploratory Pits Figure 3 - Gradation Test Results Table I - Summary of Laboratory Test Rosults Kumer & AsEociates, lnc. s'Fmj*ct No. ?1"7"?ü0 PIT 2Pfr } LOT 80 50 0 50 APPROXIMATE SCALE-FEET LOCATION OF TXPLORATORY PITS Fig. 121 -7 -280 Kumar & Associates PIT 1 PIT 2 PIT 3 0 0 t-l¡Jt¡ll¡- IIt-- o_t¡lô _j WC=21.0 -2OO=72 t---U l¿lL I-t-IL LJo 5 I WC= f 9.2 +4=39 -2OO=23 c LEGEND TOPSOIL; SAND, SILTY, SLIGHTLY CLAYEY, ORGANICS, FIRM, MOIST, BROWN. CLAY (CL); SANDY, SILTY, SCATTERED ORGANICS, MEDIUM STTFF TO ST|FF, MO|ST, BROWN GRAVEL HIGHLY (GC-GM); SANDY, SILTY, CLAYEY, BASALT GRAVEL AND COBBLES, SANDY SILT, CALCAREOUS MATRIX, DENSE, SLIGHTLY MOIST, LIGHT TAN. l I l I DISTURBED BULK SAMPLt PRACTICAL DIGGING REFUSAL. NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON MARCH 29, 2021. 2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM FEAÏURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE NOT MEASURED AND THE LOGS OF THE EXPLORATORY PITS ARE PLOTTED TO DEPTH. 4. THE EXPLORATORY PIT LOCATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5. TIIE LINES BETWEEN MATERIATS 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 PITS AT THE TIME OF EXCAVATION. PITS WERE BACKFILLED SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216);+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422); -200= PERGENTAGF PASSING NO^ 200 SIEVE (ASTM D 1140). 21 -7 -280 Kumar & Associates LOGS OF EXPLORATORY PITS Fis. 2 I HYDROMETER ANALYSIS SIEVE ANALYSIS U.3. SÎANDARO SERIES CUAR SOUARE OFENINGltuE RE^OIN6 T' HRS 7 HRS vlN '_,!'i --_ .............r.....i......................-----1--i-------' ''' I .i '- l i - -- ----f-i----- ::..:.:.::.:i..r1..:.......:......:... ---i--l --- -- --;ã-i: :.-t---.1-.i.-.- t---'--'t¿i. + 1.--i--------l--i-ri . ......1 ... . _ ......... .. t_ ................i............ ... . '''lli .................:.....t..._...................tl ì lJ 'r-- ------i- l------- ' '--) .i----.'-'----1.-----^-l'- --.- -l'--'---.1-, ,-. i-t-, ., i.,-f-rr Id f g too 90 ao 70 60 5ô 10 36 20 lo o o 10 2A 30 10 50 60 70 ao eo ro0 ã E DIAMETER OF IN MI CLAY TO SILT COBBLES GRAVEL 39 % SAND 38 % LIQUIO LIMII PLASTICIÏY INDEX SAMPLE OF: Sflty Cloyey Sond ond Grovcl SILT AND CLAY 23 % FROM:Plt1O,+'-4.5' Th.!. l.!l r.sull. ôpÞly ônly lo th. somplcs whlch wGrc lcal.d. Tha l.sllng roporl 3holl nol bô raproducad, .xcGpl ln lull, vllhoul thr vrltl.h oÞÞrcvol ol Kumor ¡l Arroclot r' lnc. Slôv6 oôolylls lGsllng Ir pârtormôd ln ôccordôñco wlth ASIM 06913, ASTM D7928, ASTM C136 o¡d/or ASTM Dll,l0. SAND GRAVEL MEDIUM ICOARSE FINE COARSEFINE 21 -7 -280 Kumar & Associates GRADATION TEST RESULTS Fis. 3 lcnlura & lssoohb,lnc,'Gæbhnical and M¿tøials Engineersand Environmental S¡ientistsTABLE 1SUMMARY OF LABORATORY TEST RESULTSHo,2l-7-280sotlrlPESiltv Clayey Sand andGravelSandy ClaylosflUNCONFINEDCOMPRESSfVESTRENGTHlalolPl-ASilCINDEXATTERBERG LIMITS(alolLIQUID LIMfTPERCENTPASSING NO.200 stEVE23723839('l"lSANDtf/"|GRAVELNATURALDRYDENSlTYNATURALMOISTURECONTENT19.22t.0DEFTH4-4Y"1SAMPLE LOCATIO}¡PIT1J