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Home My WebLink AboutGeotechnical Investigation 01.11.2022Huddleston-Berry Ðr$it!ÈcriãrË f*í'I'tsiirl-9. i'i,C 2789 Riverside Parkway Grand Junction, Colorado 81 5û1 Phone: 97G255-8005 lnfo@huddlestorrbeny. com January lI,2022 Project#02406-0001 Mr. Lee Gehrett 864 County Road 323 Rifle, Colorado 81650 Subject: Geotechnical Investigation 864 County Road 323 Rifle, Colorado Dear Mr. Gehrett, This letter presents the results of a geotechnical investigation conducted by Huddleston-Berry Engineering & Testing, LLC (HBET) for 864 County Road 323 in Rifle, Colorado. The site location is shown on Figure 1 - Site Location Map. The proposed construction is anticipated to consist of a new steel building. The scope of our investigation included evaluating the subsurface conditions at the site to aid in developing foundation recommendations for the proposed construction. Site Conditions At the time of the investigation, an existing residence and a barn occupied the northern and eastern portions of the site, respectively. The remainder of the site \¡ias open and fairly flat. Vegetation consisted of grasses, weeds, and small to large n'ees. The site was bordered to the north, east, and south by rcsidential/agricultural properties, and to the west by Rulison Road. Sub surface Investigation The subsurface investigation included two test pits at the site as shown on Figure 2 - Site Plan. Test Pits TP-l and TP-2 were excavated to depths of 6.5 and 5.0 feet below the existing ground surface, respectively. Typed test pit logs are included in Appendix A. As indicated on the logs, the subsurface conditions at the site were consistent. The test pits encountered 1.0 foot of topsoil above tan, moist, medium dense silt with sand soils to depths of between 2.5 and4.0 feet. The silt soils were underlain by tan, moist, dense gravel, cobble, and boulder soils in a clayey sand matrix to the bottoms of the excavations. Groundwater was not encountered in the subsurface at the time of the investigation' Laboratorv Testine Laboratory testing was conducted on samples of the native soils collected from the test pits. The testing included grain-size analysis, Atterberg limits determination, natwal moisture content determination, and maximum dry density and optimum moisture content (Proctor) determination. The laboratory testing results ale included in Appendix B' 864 CR 323 #02406-û001 ù1111122 Hud¡llcston-Ben-l The laboratory testing results indicate that the native silt soils are slightly plastic. In general, based on the Atterberg limits and our experience with similar soils in the vicinity of the subject site, the native silt soils are anticipated to be slightþ collapsible. The matrix soils in the gravel, cobble, and boulder materials were indicated to be moderately plastic. Based upon the Atterberg limits of the material, the matrix soils are anticipated to be slightly expansive. Foundation Recommendations Based upon the results of the subsurface investigation and nature of the proposed construction, shallow foundations are generally recommended. Spread footings and monolithic (turndown) structural slab foundations are both appropriate alternatives. However, as discussed previously, the native soils are anticipated to range slightly collapsible to slightly expansive. Therefore, in order to provide a uniform bearing stratum and reduce the risk of excessive differential movements, it is recommended that the foundations be constructed above a minimum of 24- inches of structural fill. The native silt soils, exclusive of topsoil, are suitable for reuse as structural fill. However, due to their plasticity, the gravel, cobble, and boulder soils are not suitable for reuse as structural fill. Imported skuctural fil1 should consist of a granular, non-expansive, non-free drsÍning material approved by HBET. For spread footing foundations, the footing areas may be trenched. However, for monolithic slab foundations, the structural fill should extend across the entire building pad area to a depth of 24- inches below the tumdown edges. Skuctural fill should extend laterally beyond the edges of the foundations a distance equal to the thickness of sttuctural fill for both foundation types. Prior to placement of structural fill, it is recommended that the bottom of the foundation excavation be scarified to a depth of 6 to 8 inches, moisture conditioned, and compacted to a minimum of 95Vo of the standard Proctor maximum dry density, within +ZYo of the optimum moisture content as determined in accord¿urce with ASTM D698. Structural fill should be moisture conditioned, placed in maximum 8-inch loose lifts, and compacted to a minimum of 95Yo of the standard Proctor maximum dry density for fine grained soils and 90% of the modified Proctor maximum dry density for coarse grained soils, within t2Yo of the optimum moisture content as determined in accordance with ASTM D698 and D1557, respectively. Structural fill should be extended to within 0.l-feet of the bottom of the foundation. No more than 0.l-feet of gravel should be placed below the footings or turndown edge as a leveling course. For structural filI consisting of the native soils or imported granular materials, and foundation building pad preparation as recommended, a maximum allowable bearing capacity of 1,500 psf may be used. In addition, a modulus of subgrade reaction of 150 pci may be used for structural fill consisting of the native soils and a modulus of 200 pci may be used for suitable imported structural frll. Fotmdations subject to frost should be at least 36 inches below the finished grade. Water soluble sulfates are common to the soils in Western Colorado. Therefore, at a minimum, Type I-II sulfate resistant cement is recommended for construction at this site. Ìoffrert\l)2406 fi)01 864 CR8l3\?g0 Gçg\0¡406-0001 LR0llll2.dùc 2 iislli.¡li!,! aÈrlnte. ¡,¡ (: 864 CR 323 #02406-0001 at¡11/22 Huddleston-tcny tiod¡r.crì¡¡ & -reiifu. l,l (; Any stemwalls or retaining'walls should be designed to resist lateral earth pressures. For backfill consisting of the native soils or imported granular, non-free draining, non-expansive material, we recommend that the walls be designed for an equivalent active fluid unit weight of 45 pcf in areas where no surcharge loads are present. An at-rest equivalent fluid unit weight of 65 pcf is recommended for braced walls. Lateral earth pressures should be increased as necessary to reflect any surcharge loading behind the walls. Non-structural Floor Slab and Exterior Flatwork Recommendations In order to limit the potential for excessive differential movements of slabs-on-grade it is recomrnended that non-structural floating floor slabs be constructed above a minimum of 18- inches of structural fill with subgrade preparation and fill placement in accordance with the Foundation Recommendations section of this reporf. It is recommended that exterior flatwork be constructed above a minimum of l2-inches of structural fill. Drainase R€commendations Gradíns and drainøge øre critical to the lone-term nerformance oÍ the structure. Grading around the structure should be designed to carry precipitation and runoff away from the structure. It is recommended that the finished ground surface drop at least twelve inches within the first ten feet away from the structure. It is also recommended that landscaping within five feet of the structure include primarily desert plants with low water requirements. In addition, it is recommended that automatic irrigation, including drip lines, within ten feet of foundations be minimized. HBET recommends that swface downspout extensions be used which discharge a minimum of 15 feet from the strucfure or beyond the backfill zone, whichever is greater. However, if subsurface downspout drains are utilized, they should be carefully constructed of solid-wall PVC and should daylight a minimum of 15 feet from the structure. In addition, an impermeable membrane is recommended below subsurface downspout drains. Dry wells should not be used. General Notes The recommendations included above are based upon the results of the subsurface investigation and on our local experience. These conclusions and recommendations are valid only for the proposed construction. As discussed previously, the subsurface conditions encountered in the test pits were consistent. However, the precise nature and extent of subsurface variability may not become evident until construction. As discussed previously, it is recommended that HBET provide conskuction materials testing and engineering oversight during the entire construction process. In addition, the builder and any subcontractors working on the project should be provided a copy of this report and informed of the issues associated with the presence of moisture sensitive subgrade materials at this site. 32:Þ008 A]-L PROJECTS\02406 -Lee Celuett\0240ó-0001 864 CR 823\200 - Gæ\02406-0001 LRol I 122.dùc 864 CR 323 #Ð2406-û001 $1/11122 //,E+1!+È\ ffiïß$)Hrrdall€ston BcHg t:¡d¡i.ri¡t ; -¡i.i:.:, !-!.,: It is imnortant to note that the recommendøtions herein s.re intended to redace the risk of structural movewent ønd/or dømøge. to vøwins desrees, assoeiøted teith volume chanse of the native soils. Howeven HBET cønnot oredict lons-term chanses i!, subsu(Íace moisture eonditìons ønd/gr the precíse møsnilude ot eñent of volume chunge. Where sisnificant fuicreases jn sabsurface moisture oecur d.ue to ooor grøding, imþroner stormwøter manøgement, utílitv line failare. excess írrìgøtion. or other cøuse, either darìng constraction or the result of actions of the orooertv owner. severøl inches of movement are oossible. I! uddition, snv føilare to comolv with the recommendøtions in this report releases Huddleston- Beyrv Ensineerins & Test¡ns, LLC qf anv liahílitv wÍth resard to the structure oerformønce. 'We are pleased to be of service to your project. Please contact us if you have any questions or comments regarding the contents of this report. Respectfu lly Submitted: Huddleston-Berry Engineering and Testing, LLC Michael A. Berry, P.E. Vice President of Engineering 42:\2008 AIL PROJECTS\02406 - L¿e Gelr¡ett\01406-0001 864 CR 823U00 - Geo\02406-000.1 LROI I l22.doc #@ t-j Å FIGURE 1 Site Locntion Map971ft ,Site Planr, rJ,i:t,,*sI 'q^'jI!I.,1*llif'ni: tll "ì'i I*ffi. *, " i':.i"ar,. .::.. . 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NEN ü(J ooo ô N [I Nøz É.o Hueldleston-Berry Engineering & Testing, LLC 2789 Riverside Parkway Grand Junction, CO 81501 970-255-8005 GRAIN SIZE DISTRIBUTION CLIENT Lee Gehrett PROJECT NAME 864 Countv Road 323 PRû'ECT NUMBER 02406-0001 PROJECT LOCATION Rifle, CO U.S. SIEVE OPENING IN INCHES I U.S. SIEVE NUMBERS I 14820t HYDROMETER6 4 3 21.5 1 50 t-T(, t¡I = co É. TUztrþzul C)t ITJ(L 100 s5 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 100 10 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS ll ll-úr I tt (--. \il \ \ h il il \J l li \il T lr \r \ COBBLES GRAVEL SAND SILT OR CLAYcoarsefinecoarsemediumfine Specimen ldentification Classification LL PL PI Cc Cu o TP-1, GB-1 12t15 SILTwith SAND(ML)26 22 4 a TP-1,GB,-z 12t15 CLAYEY SAND with GRAVEL(SC)43 26 17 Specimen ldentification D100 D60 D30 D10 %Gravel %Sand %silr %Clav o TP-1, cB-1 12115 l9 5.7 22.3 72.O tr TP-1,GB'-z 12t15 50 2.333 0.47 24.2 50.5 14.O Huddleston-Berry Engineering & Testing, LLC 2789 Rivøside Pa*way Grand Junction, CO 8t501 970-255-8005 ATTERBERG LIMITS' RESULTS PROJECTNUMBER 024064001 PROJECT NAIIIE 8il Countv Road 323 PROJECT LOCATION Rifle lll-l CLIENT I ee Gehrp;fl 50 40 30 20 10 CL-ML @@ 0 80 P L A S T I c I T I N D E X 60 LIQUID LIM¡T Specimen ldentification LL PL PI #200 Classificatian a 26 22 4 72 S|LTwith SAND(ML:TP.1, GB-{12115 4r 26 17 14 GLAYEY SAND w¡th GRAvEL(sclTP.1, GB.2 12115 ú,() @ ôo ô No oF J NNñ tsf)o úi 5 ØJ ¡-z(, I c? N ú.o @ ooô @ No zst-o =a MOISTURE-DENSITY RELATIONSH IP PROJECT NAlltE 864 Countv Road 323 PROJECT LOCANONPROJECT NUMBER 02406{100l CLIENT Lee Gehrett 970-255-8085 Jrarction, Ct 81501 Huddlesion-Bery Engineffing & Testing, LLC 2789 Riverside P*{ovay ,UI \ \ \ I \ \ \ \ .//\ \\/\\\\ \ Sample Date: Sample No.: Source of Material: Description of Material: 12t15t2022 GB-I 145 TP-1 S|LTwith SAND(ML) Test Method ASTM D6984 14A 135 TEST RESULTS Maximum Dry Density 119'0 PCF Optimum Water Content 11'5 % 130 GRADAfiON RESULTS (% PASS¡NG) #200 #4 314" 72 94 100125 oo"tþızuÕ É.o ATTERBERG LIMITS 1 20 LL PL PI 26 22 4 '115 Curves of 100% Saturation for Specific Gravity Equalto: 110 2.80 2.70 2.60 105 100 95 5 0 15 WATER CONTENT, % 90 0 2A 25 30