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Home My WebLink AboutSubsoils Report for Foundation DesignT(FN Kumar & Associates, lnc.@ Geotechnical and Materials Engineers and Environmental Scientists 5020 County Road 154: Glenwood Springs, CO 81601 phone: (970) 945-7988, , ) fax: (970) 945-8454 ' omai{: kaglenwood@kumarusa.com www.kumarusa.comAn Employcc Oryncd Compony Office Locations: Denver (JQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado May 20,2024 Stephen Zanetich 8 Oakview Terrace Swedesboro, New Jersey 08085 sjz26@.comcast.net Project No. 24-7-259 Subject: Subsoil Study for Foundation Design, Proposed Residence, Parcel Number 218528200033, Mountain Springs Road, Garfield County, Colorado Dear Stephen: As requested, Kumar & Associates, [nc. 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 23,2024. 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 conceptual at the time of our study. The proposed residence is assumed to be a one- or two-story structure with a lower walkout basement level and attached garage located in the area of the pits shown on Figure 1. Ground floor could be structural over crawlspace or slab-on-grade. Cut depths are expected to range between about 3 to 10 feet. Foundation loadings for this type of construction are assumed to be relatively light and 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 subject site was vacant at the time of our field exploration. The ground surface is moderately sloping down to the south at grades estimated at between l0 and 40 percent. Vegetation consists of fir and juniper trees, scrub oak, grass and weeds. There was patchy snow cover up to 2 inches deep. The ground surface was graded for a rough access road and there was evidence of cut and fill grading in the proposed building area. A creek is flowingon the west side of the lot. Due to the snow, mud and steep slopes, access to the site was limited for the mini excavator and the pits were placed where accessible. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The subsoils encountered, below about I foot of topsoil and up to 2/z feet of clay fill, consist of stiff to very stifi sandy clay to between 3Yz and 7 feet deep where weathered to hard claystone was encountered down to the maximum explored depth of 8 feet. \ $ '{e (N -\\ a\ N -L- Results of swell-consolidation testing performed on relatively undisturbed samples of the clay and claystone, presented on Figure 4, indicate low compressibility under existing moisture conditions and light loading and a low expansion potential when wetted under constant light surcharge. The laboratory testing is summarized in Table 1. 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 subsurface 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 psfof for support of the proposed residence. The soils tend to expand after wetting and there be some post-construction foundation movement if the soils become wet possibly resulting in distress. A lower movement risk option would be to place 3 feet of structural fill below spread footings. Footings should be a minimum width of 16 inches for continuous walls and2 feet for columns. The topsoil, existing fill 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. If structural fill is used, foundation areas should be sub- excavated to 3 feet below proposed bearing levels and the sub-exoavated depth backfilled with compacted structural fill. Structural fill can consist of imported granular material such as CDOT Class 5 or Class 6 base course. The onsite soils free of organics and plus 6-inch rock may also be suitable as backfill. Structural fill should be moisture conditioned to near or slightly above optimum moisture content and compacted to at least 98% maximum standard proctor density. 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 foundation walls should be heavily reinforced top and bottom to span local anomalies and resist differential movement such as by assuming an unsupported length of at least 14 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 60 pcf for the on-site soil as backfill. Floor Slabs: The on-site soils possess an expansion potential and slab heave could occur if the subgrade soils were to become wet. Slab-on-grade construction may be used provided precautions are taken to limit potential movement and the risk of distress to the building is accepted by the owner. A positive way to reduce the risk of slab movement, which is commonly used in the area, is to construct structurally supported floors over crawlspace. 'l'o retluce the efl'ects of some differential movement, nonstructural floor slabs should be senarafed from qll hecrino urqllc qnrl nnlrrmnc.rrifh o-^o-cinn inintc."L;^L ^ll^"',,-.^-+-^;-^jvrrrrr vrr|JsrrJrvrr JvrrrLo vYlllvrr grlvyY utltwott4tttvu vertical movement. Interior non-bearing partitions resting on floor slabs should be provided with a slip joint at the bottorn of the wall so that, if the slab moves, the movement cannot be transmitted to the upper structurc. This detail is also important for wallboards, stairways and door frames- Slip joints which will alluw at least I %-inches of vertical movement are recommended. Floor slab control joints should be used to rcducc damagc due to shrinkage Kumar & Associates, Inc. o ProieeJ No 2tr,7959 a-J- cracking. Slab reinforcement and control joints 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 immediately beneath basement level slabs-on-grade. This material should consist of minus 2-inch aggregate with less than 50Yo passing the No. 4 sieve and less than2%o passing the No. 200 sieve. The free-draining gravel will aid in drainage below the slabs and should be connected to the perimeter underdrain system. Required fill beneath slabs should consist of a suitable imported granular material, excluding topsoil and oversized rocks. The fill should be spread in thin horizontal lifts, adjusted to at or above optimum moisture content, and compacted to at least95Yo ofthe maximum standard Proctor density. All vegetation, topsoil and loose or disturbed soil should be removed prior to fill placement. The above recommendations will not prevent slab heave if the expansive soils underlying slabs- on-grade become wet. However, the recommendations will reduce the effects if slab heave occurs. All plumbing lines should be pressure tested before backfilling to help reduce the potential for wetting. Surface Drainage: Providing and maintaining proper surface drainage will be critical to the long-term satisfactory performance ofthe proposed residence. 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. Drying could increase the expansion potential of the soils. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95%o of the maximum standard Proctor density in pavement and slab areas and to at least 90o/o 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 12 inches in the first 10 feet in unpaved areas and a minimum slope of 3 inches in the first l0 feet in pavement and walkway areas. A swale will be needed uphill to direct surface runoffaround the residence. 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 l0 feet from the building. Limitations: This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area atthis time. We make no warranty either Kumar & Associates, lnc. o Project No. 2't-7-259 -4- express or implied. The conclusions and recommendations submiued 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,theproposed t1rye of conskuction, and our experience in the area. Om 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 concemed 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 recommondations mtry be madc. This report has been prepared for the exclusive use by our client for design puqrcses. 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 constuction to review and monitor the implernentation of our recommendations, and to v€riry that the recommendations have been appropriatcly interpretetl. 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 strucfural 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 & Associates, James H. Parsons, Reviewed by: ffi-/" Steven L. Pawlak, P.E. JHPlkac attachments Figure I - Location of Exploratory Pits Figure 2 - togs of Exploratory Pits Figure 3 - Legend and Notes Figure 4 - Swell-Consolidation Test Results Table I - Summary of Laboratory Test Results l.L F 586dt Kumar & Associates, Inc. o Prolect No. 24-7-259 itf tJ! :i lI { I J ati t, 0 30 60 APPROXIMATE SCALE_FEET 24-7-259 Kumar & Associates LOCATION OF EXPLORATORY PITS 1Fig. PIT 1 EL. 100' PIT 2 EL. 98' o 0 WC=15.4 DD=1 1 5 -200=39 FbJt!h IIFIL Lrl Cf 5 WC=15.0 DD=1 1 3 WC=9.3 DD=1 1 9 5 FI!tJt! I-F-o- LJolwc=tr.o- LL=28 Pl=16 10 t0 ^d 24-7-259 Kumar & Associates LOGS OF EXPLORATORY PITS Fig. 2 LEGEND TOPSOIL; CLAY, SANDY, ORGANICS, SOFT, VERY MOIST, DARK BROWN- K n t-l_l FILL; CLAY, SCATTERED COBBLES, MEDIUM STIFF TO STIFF, MOIST, DARK BROWN. CLAY (CL); SANDY TO VERY CLAYEY SAND, SCATTERED COBBLES AND BOULDERS WITH DEPTH, STIFF, MOIST, BROWN. CLAYSTONE; WASATCH FORMATION, WEATHERED TO HARD, MOIST, TAN TO GRAY. F Ir t HAND DRIVE SAMPLE. DISTURBED BULK SAMPLE PRACTICAL DIGGING REFUSAL TO THE EXCAVATOR. NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A MINI EXCAVATOR ON MAY 8, 2024. 2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE MEASURED BY HAND LEVEL AND REFER TO PIT 1 AS AN ASSUMED 1OO' BENCHMARK. 4. THE EXPLORATORY PIT 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 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 BACKFILLEO SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM O ZZTE); DD = DRY DENSITY (PCt) (ISTU O ZZTA); -2QO= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D LL = LIQUID LIMIT (ASTM D A318); Pl = PLASTICITY INDEX (ASTM D 4318). 1 1 4o); 24-7-259 Kumar & Associates LEGEND AND NOTES Fig. 3 I SAMPLE OF: Sondy Cloy FROM:PitlO5' WG = '15.0 %, OD = 115 pcf I I i I 1 .t- I EXPANSION UNDER CONSTANT PRESSURE UPON WETTING 1i l I N JJlrl =a I z.o F o Jovtz.o C) x JJlr, =tn I z,otr o =o anz.oo 1 o I 2 -5 -4 1 o I 2 -3 1 .t APPUED PRESSURE - XSF I.O APPUED t00 SAMPLE OF: Weolhered Cloyslone FROM:PitZA4' WC = 9.5 %, DD = 119 pcf ot EXPANSION UNDER CONSTANT PRESSURE UPON WETTING I I il rl i I , 24-7-259 Kumar & Associates SWELL_CONSOLIDATION TEST RESULTS Fis. 4 lc^[iry*[.mfffi1il;-- TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No.24'7.259 2 I PIT 4 2 6to7 5 DEPTH {ft1 9.3 t5.4 11.6 15.0 NATURAL MOISTURE CONTENT lol 119 113 1 I 3 NATURAL DRY DENSITY locfl GRAVEL l'lt SAND (:/"1 39 PERCENT PASSING NO. 200 srEVE 28 LIQUID LIMIT lohl ATTERBERG LIMITS 1 6 PLASTIC INDEX (%) UNCONFINED COMPRESSIVE STRENGTH (psf) Weathered Claystone Very Clayey Sand Sandy Clay Sandy Clay SOIL TYPE cLAy (cL); sANDy TO VERY CLAYEY SAND, SCATTERED COBBLES AND BOULDERS WITH DEPTH, STIFF, MOIST, BROWN. CLAYSTONE; WASATCH FORMATION, WEATHERED TO HARD, MOIST, TAN TO GRAYl HAND DRIVE SAMPLE. DISTURBED BULK SAMPLE. PRACTICAL DIGGING REFUSAL TO THE EXCAVATOR. NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A MINI EXCAVATOR ON MAY 8, 2024. 2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 5. THE ELEVATIONS OF THE EXPLORATORY PITS WERE MEASURED BY HAND LEVEL ANO REFER TO PIT 1 AS AN ASSUMED lOO' BENCHMARK. 4. THE EXPLORATORY PIT 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 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 EXCAVATTON. PITS WERE BACKFILLED SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSITY (PCt) (ISTU D 2216)i _2QO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D 11AO); LL = LIQUID TIMIT (ASTM D 4518); Pl = PLASTICITY INDEX (ASTM D 4318). F li t I Fig. 3Kumar & Associates LEGEND AND NOTES24-7-259 E ,8 I SAMPLE OF: Sondy Gloy FROM:Pit1O5' WC = t5.0 %, DD = 115 pcf EXPANSION UNDER CONSTANT PRESSURE UPON WETTING I I I I I I I I I x JJlrf =U' I z.o F o Jov,z.o() N JJIJAo I z.o_, F (f =oannz.oq) 1 0 1 2 -3 -1 1 -5 .t APPUED PRESSURE - APPUED SAMPLE OF: Weothered Cloyslone FROM:Pit2O4' WC = 9.5 %, DD = 119 pcf L ljl I lb h ot l 1 I I l I I iii I I EXPANSION UNDER CONSTANT PRESSURE UPON WETTING I l 1 t00 24-7-259 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 4 lGrt$iffilmfmtifd-* TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No. 24.7.259 2 PIT I SAMPLE LOCATION 4 2 6to7 DEPTH -_r$l- 5 9.3 rs.4 11 .6 NATUML MOISTURE CONTENT 1s.0 119 113 NATURAL DRY DENSITY 113 GRAVEL (%) GMDATION SAND t%l 39 PERCENT PASSING NO. 200 stEVE 28 LIQUID LIMIT -lId- ATTERBERG LIMITS I 6 PLASTIC INDEX -JYel- UNCONFINED COMPRESSIVE STRENGTH Weathered Claystone Very Clayey Sand Sandy Clay SOIL TYPE Sandy Clay