The URL can be used to link to this page

Home My WebLink AboutSubsoils Report for Foundation DesignlGrti'ffifimfmrïfü-* An Emdoycc Chrncd 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 Collínq Glenwood Springs, and Summit County, Colorado Iune 6,2022 F?ECE¡VËffi Justin Sanford 200 Mountain Shadows Drive ,{iji, I þ ;1¡¡.lli Glenwood Springs, Colorado 81601 GArtF tËi-u Çüt,iu ¡- /iustin@eorentals'com iloMMrJNiTy !jr:i/El"rjpi!ïrjr,:i Project No.22-l-304 Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 12, Rapids on the Colorado, Rapids View Lane, Garfield County, Colorado Dear Mr. Sanford: 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 you dated April 20,2022. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presented in this report. Proposed Construction: The proposed residence will be one and two story wood frame construction above a crawlspace with an attached Earage. The residence will be located in the building envelope shown on Figure 1. Garage floor will be slab-on-grade. Cut depths are expected to range between about 3 to 5 feet. Foundation loadings for this type of construction are assumed to be relatively light and fypical 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 building site was vacant and vegetated with grass and weeds and a single tree. Numerous cottonwood trees line the river bank to the north. The ground surface is relatively flat with a slight slope down to the north. The Colorado River crosses the north part of the lot. The adjoining lots are vacant. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two exploratory pits at the approximate locations shown on Figure I The logs of the pits are presented on Figure 2. The subsoils encountered, below about %foot of topsoil, consist of sandy clay to 3 feet, silty sand to 4/, feet at Pit 1 and 6% feet atPit? overlying sandy gravel with scattered cobbles. Results of swell-consolidation testing performed on relatively undisturbed samples of sandy clay and silty sand, presented on Figures 3 and 4, indicate low compressibility under existing moisture conditions and light loading and moderate to high compressibility under a-L- additional loading when wetted. No free water was observed in the pits at the 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 gravel soil or compacted structural fill designed for an allowable soil bearing pressure of 2 for support ofthe proposed residence. The upper ay after wetting under load and should be removed down to the gravel soils. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. The upper clay, sand and loose disturbed soils encountered within the footing excavation should be removed and the footing bearing level extended down to the undisturbed natural gravel soils. Structural fill can be used to reestablish design bearing level compacted to at least 98% standard Proctor density to at least llzfeet beyond footing edges, We should observe the completed excavation for bearing conditions. Exterior footings should be provided with adequate cover above their bearing elevations for frost protection. Piacement of footings 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 should be designed to resist alateral 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, can be used 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 relatively well graded sand and gravel such as road base should be placed beneath slabs for support. This material should consist of minus 2 inch aggregate with less than 50% passing the No. 4 sieve and less than 12o/o passing the No. 200 sieve. All fill materials for of to at least 9 standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site soils devoid of vegetation, topsoil and oversized rock. Underdrain System: Although free water was not encountered during our exploration, it has been our experience in the areathat local perched groundwater can develop during times of heavy precipitation or seasonal runoff Frozen ground during spring runoffcan create a perched Kumar & Associates, lnc. o Projec{ No. n7-304 a-J- condition. We recommend below-grade construction, such as retaining walls, deep crawlspace and basement areas (if provided), be protected from wetting and hydrostatic pressure buildup by an underdrain system. Shallow crawlspace of around 3 feet high does not need protection by an underdrain. Where provided, the drains should consist of drainpipe placed in the bottom of the wall backfill surrounded 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 2o/o passíngthe No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. T'he drain gravel backfill should be at least 1%feetdeep. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: l) 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 95Yo of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proctor densify in landscape areas. Free-draining wall backfïll 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 12 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 backfill. 5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from the building. Consideration should be given to the use of xeriscape to limit potential wetting of sorls below the foundation caused by irrigation. Limitations: This study has been conducted in accordauce with generally accepted geotechnical engineering principles and practices in this area at this time, We 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 1 and to the depths shown on Figure 2,the proposed type of construction, and our experience in Kumar & Associates, lnc. o Project No, 22-7-304 ,4- the area. Our services do not include determining the presence, prerrention 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 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 recomrnendations may be made. This report has been prepared for the exclusive use by our client for design purposes. Vy'e 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 veriff 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, If you have any questions or if we may be of further assistance, please let us know. Respectfully Submitted, Kumar & Ässociateso lnc. Louis Eller Reviewed by: Steven L. Pawlak, LEElkac attachments Cc: Figure I Exploratory Pits Figure 2 - Logs of Exploratory Pits Figures 3 and 4- Swell-Consolidation Test Results Table 1 - Summary of Laboratory Test Results Brad Jordan (b radj o rd anarchitect@qnail. corl1) L ß2n Kumar & Associales, lnc, o Project No. 22-7-304 :.\1 I I I I I I\ \ \ \ \ \ Colorado Bilçr *r*I Iç¿t\ \ \ \ \I $ø{beriy cci{,/ihe öî lrte hta ilìcti !3 ioc{{rd þI *urve¡ 0,i"1fisi'l uoscrnenl per plat --***{r I ¡ 50 0 APPROXIMATE SCALE-FEET i:ct¡ad r*bor vlth qlumir:um ro¡, PLS I'lo, l.ïrûl 25d ll¡.ne¡s caa¡te¡ €d--déê€êadê 22-7 -304 Kumar & Associates LOCATION OF EXPLORATORY PIÏS Fig 1 PIT 1 Ptï 2 U n WC=8.0 DD=9 1 l- L¿JLI LL I :Êr-o- l¡Jo WC=3.4 DD=85 -2OO-31 WC=5.3 DÐ=90 ¡- LÀJIJtr I-t-û- L¡J Él E 5 10 10 LEGEND TOPSOIL; ORGANIC SANDY SILT AND CLAY, FIRM, SLIGHTLY MOIST, DARK BROWN CLAY (Ct-); SANDY, SILTY, STIFF, SLIGHTLY MOIST, BROWN SAND (SM); STLTY, LOOSE, SLIGHTLY MOIST, BROWN. GRAVEL (cM); SANDY, SILTY, SCATTERED COBBLES, ÐENSE, SLIGHTLY MOIST, LIGHT BROIVN, SUBROUNDED ROCKS. þ t HAND DRIVE z_INCH DIAMETER LINER SAMPLE DISTURBED BULK SAMPLE NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A DEERE 55G MIN¡_EXCAVATOR ON MAY 12, 2022. 2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATICINS OF THE EXPLORATORY PITS WERE NOT MEASURED AND THE LOGS OF THE EXPLORATORY PITS ARE PLOTTED TO ÐTPTH. 4. THE EXPLORATORY PIT LOCATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO 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. GROUNÐWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF EXCAVATION. 6. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM Ð 2216); DD = DRY ÐENStrY (pci) (nSrU Ð 2216): -2OQ= PERCENTAGE PASSING NO.2o0 SIEVE (ASTM D 1140)' 22-7 -304 Kumar & Associates LOGS OF TXPLORATORY PITS lis. 2 SAMPLE OFr Sondy Silty Cloy FROM;Pli19-2' WC = 8.0 %, DÐ = 91 pcf l¡ ol ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING I l i j l I 1 itl i I i i - t '..i I i i) iÌli l I I I-i'1 L l t I I I I I 1.. j I I ì ì I I 1,0 APPLIED 1 àe JJ!l =Ø I z.otr ô:io TAzoo 0 -1 -2 _a -4 -5 -6 22*7 -3CI4 Kumar & Associates SWELL-CONSOLIDATION TEST RTSULTS Fig. 3 SAMPLE OFr Silty Sond FROM:Plt2@5.5' WC = 5.3 %, DD = 90 pcf iìl AÐDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING I I l I ¡ I l r-i I I l i -i -Ì l ¡J l, ln tút d. 1 bq JJ lJJ =Ø I zo t- ô Jo at',zo() 0 -1 -2 -3 4 -5 -o -7 1 t0 Fig. 4SWELL-CONSOLIDATION TTST RESULTS22*7-304 Kumar & Associates I I Ê l{3rt :t lü¡E&ls6oslôirs,lno.o Geotechn¡cal ard Materials Ësg¡noers and Environm€ntal Sdentists TABLE 1 SUMMARY OF LABORATORY TEST RESULTS AI Lil¡tTSSAMPTtocaTtoN PERCENT PASStttG NO. 200 stEvE LIQUID IIMIT l%l PLASTIC IMDEX t9.)IGO UNCONFIIiED cot PREssrvE STRENGTI{SOIL TYPEPIT {ftt DEPTH IIATURAL M0tsfuRE COI{TEilT NATURAL DRY DENSFY loclì GRAVEL {%} SAND (e4 Sandy Silly ClayI28.0 91 31 Silty Sand33.4 85 Silty Sand9023Y,5.3 No.22'7.304