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Home My WebLink AboutSoils Report 12.31.2019Kumar & As fates, Inc." Geotechnical and Materials Engineers and Environmental Scientists An Employee Owned Company 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kag]enwood@kumanisa.com www.kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado Assonant% 311Q0401, 1 989-201 SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE LOT 47, PINYON MESA 26 CLIFF ROSE WAY GARFIELD COUNTY, COLORADO PROJECT NO. 19-7-686 DECEMBER 31, 2019 PREPARED FOR: MIKE AUGUSTYNIAK AND CAROLINE BARNES 155 DAVENPORT DRIVE CHESTERFIELD, NEW JERSEY 08515 sii7iiieg ka v4hoo.ii7iii ca roll sie.barnes88(a,.yahoo. coin PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 47, Pinyon Mesa, 26 Cliff Rose Way, 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 conducted in accordance with our agreement for geotechnical engineering services to Mike Augustyniak and Caroline Barnes dated November 12, 2019. 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 At the time of our study, design plans for the residence had not been developed. The building is proposed in the area roughly near Boring 1 shown on Figure 1. We assume the residence will be two story wood frame structure over a basement or crawlspace with an attached garage, and the excavation for the building will have a maximum cut depth of one level, about 10 feet below the existing ground surface. For the purpose of our analysis, foundation loadings for the structure were 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 subdivision is located on a relatively flat topographic bench of alluvial fan deposits above the Roaring Fork River valley and below Spring Valley. The site is located at the base of a steep Kumar & Associates, Inc. i' Project No. 19-7-686 -3 - Samples of the subsoils were taken with a 2 inch I.D. spoon sampler. The sampler was driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is similar 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 and hardness of the bedrock. 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 project engineer and testing. SUBSURFACE CONDITIONS A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The subsoils consist of about 2 feet of topsoil overlying about 51 feet of slightly calcareous, stiff to very stiff, sandy clay and silt with occasional layers of silty sand and silty sand and gravel underlain by bedrock of the Eagle Valley Evaporite formation. Laboratory testing performed on samples obtained from the boring included natural moisture content, density and percent fines (percent passing the No. 200 sieve). Results of swell - consolidation testing performed on relatively undisturbed drive samples, presented on Figures 3 and 4, indicate low compressibility under conditions of loading and wetting and minor collapse (settlement under constant load) or low to moderate expansion potential when wetted under a constant light load. 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. FOUNDATION BEARING CONDITIONS The subsoils encountered in the boring at shallow foundation depth generally consist of sandy, clay and silt which are generally compressible when wetted under load. The subsurface profile is similar to that encountered in nearby lots. Shallow spread footings placed on the upper compressible soils could have a settlement potential of 2'/2 inches or more, resulting in building distress. A possible way to mitigate the building damage risk is to provide a heavily reinforced mat foundation to make the structure more rigid and better able to resist differential settlement. Kumar & Associates, Inc. , Project No. 19-7-686 -5 - 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) The topsoil and required soil depth for structural fill should be removed from beneath the building area and to at least 5 feet beyond the building perimeter. The exposed soils should then be moistened to near optimum and compacted to at least 95% of the standard Proctor density. The soils removed from the excavation should be replaced and compacted to at least 98% of standard Proctor density within 2 percentage points of optimum moisture content. The structural fill should extend out beyond the sides of the proposed foundation a distance equal to at least half of the fill depth below the footing. 6) A representative of the geotechnical engineer should observe the building excavation for bearing conditions and performed field compaction tests at the time of structural fill construction. 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 55 pcf for backfill consisting of the on-site fine-grained 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 45 pcf for backfill consisting of the on-site fine-grained 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. Kumar & Associates, Inc. c, Project No. 19-7.686 7 This material should consist of minus 2 -inch aggregate with at least 50% retained on the No. 4 sieve and less than 12% passing the No. 200 sieve. Fill material placed for support of floor slabs above footing bearing level should be compacted to at least 95% of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on-site soils devoid of vegetation and topsoil. 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 runoff can create a perched condition. We recommend below -grade construction, such as retaining walls and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. Shallow crawlspace or slab -on -grade areas (such as the garage) should not have a perimeter drain. 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 of excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum Moto 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 11/2 feet deep. An impervious membrane such as 20 mil PVC should be placed beneath the drain gravel in a trough shape and attached to the foundation wall with mastic to prevent wetting of the bearing soils. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: 1) 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 95% 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. Kumar & Associates, Inc. h Project No. 19-7-686 9 of excavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, Kumar & Associates, Inc. 241444, -- Shane J. Robat, P.E. Reviewed by: „ L- �` ,,0 2444' Z. Daniel E. Hardin, E. ` -0' 01 �0,' • SJR/kac ,,� _ (I._ . , �•ti4 cc: Cris Shaw (cshaV.,: „,,,, Iliiail.com) Julian Hardaker aulianhardaker(hotmail.com) Kumar & Associates, Inc. Project No. 19-7-686 BORING 1 0 10/12 WC=5.8 DD=121 i__J -200=90 5 1 15/12 7• WC=5.9 DD=101 15/12 10 /r WC=6.8 DD=101 -200=93 - 15 F%� 26/12 1 WC=7.4 DD=102 1- w ' 38/12 20 I We=5.8 / I _ V DD=105 a - /'� -200=86 Lu f — 25 30 — 35 40 LEGEND TOPSOIL; SANDY, CLAYEY SILT, FIRM, MOIST TO VERY MOIST, BROWN. SILT AND CLAY (ML); SANDY, STIFF TO VERY STIFF, SLIGHTLY MOIST TO MOIST, BROWN, SLIGHTLY CALCAREOUS. SAND AND GRAVEL (SM -GM); VERY SILTY, CLAYEY, DENSE, SLIGHTLY MOIST, LIGHT BROWN, SUB -ANGULAR GRAVEL. 1 EAGLE VALLEY EVAPORITE BEDROCK. I DRIVE SAMPLE, 2 -INCH I.D. CALIFORNIA LINER -I SAMPLE. 10/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 10 BLOWS OF A 140 -POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE THE SAMPLER 12 INCHES. NOTES _ 1. THE EXPLORATORY BORING WAS DRILLED ON NOVEMBER 20, 2019 WITH A 4 -INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. / 2. THE LOCATION OF THE EXPLORATORY BORING 38/12 WAS MEASURED APPROXIMATELY BY PACING / FROM FEATURES SHOWN ON THE SITE PLAN we=9,1 PROVIDED. DD=121 r 158/12 /f 7- 32/12 50/3.5 45 50-- 55 --- 3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT MEASURED AND THE LOG OF THE EXPLORATORY BORING IS PLOTTED TO DEPTH. 4. THE EXPLORATORY BORING LOCATION SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD 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. w w ▪ 7. LABORATORY TEST RESULTS: = WC = WATER CONTENT (%) (ASTM D 2216); a_ DD = DRY DENSITY (pcf) (ASTM D 2216); -200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140). 19-7-686 Kumar & Associates LOG OF EXPLORATORY BORING Fig. 2 CONSOLIDATION - SWELL 5 4 3 2 1 Masa larrl FOOlitir..jpglytro en'', the oio r * b. r.praduci.d. lift:pi In fuN, .dlhaYt IM +Mir. oppeav0 oT Kwna pad Mu cLplp. Inp S*pl Commto r.•rn..d In cerdanc• .111118M1$011$45. SAMPLE OF: Sandy Silty Clay FROM: Boring 1 0 25' WC = 9.1 %, DD = 121 pcf EXPANSION UNDER CONSTANT PRESSURE UPON WETTING 1.0 APPLIED PRESSURE - KSF 10 ;170 19-7-686 Kumar & Associates SWELL—CONSOLIDATION TEST RESULTS Fig. 4