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Home My WebLink AboutGeotechnical Investigation Report 10.16.2013I•lucldleston-Berry k'vt- it �ttiu; .l• rt,tiu;t. 1 1 t MountainView Construction Services, LLC 1413 Ivtunro Avenue Rifle, Colorado 81650 Attention: Mr. Jerry Caves Subject: Geotechnical Investigation Lot 1S-11 Aspen Glen Subdivision Garfield County, Colorado Dear Mr. Caves, Got} White Avenue Grand Junction, CO 8150 I Phone: 970-255-8005 Fax: 970 255 6818 11 uddlcstonl3erry6t. hresnan.net wu•atI-1I3E-GJ.com October 16, 2013 Projeci/I01273-0007 This letter presents the results of a geotechnical investigation conducted by Huddleston -Berry Engineering & 'Testing, LLC (1-113ET) for Lot IS -11 oI' the Aspen Glen subdivision near Glenwood Springs, Colorado. The proposed construction is anticipated to consist of a single- family residence. 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, the site was generally open with a gentle slope down In ihe north. Vegetation consisted primarily of field grasses. The site was bordered by Wild Flower Road to the south, by an existing residence to the east, by an unnamed paved road to the west, and by a vacant lot to ihe north. Subsurface Investigation The subsurface investigation included one test pit. The test pit was excavated to a depth of 8.5 feel below the existing ground surface. A typed test pit log is included in Appendix A. The test pit encountered 1.5 feet of sandy lean clay with organics topsoil above brown, moist, stiff sandy lean clay to n depth of 3.0 feet. The clay was underlain by brown, moist, dense clayey gravel and cobbles to the bottom of the excavation. Grounchvatcr was not encountered in the test pit at the time of the investigation. Laboratory Testing Laboratory testing was conducted on samples of the soils encountered in the test pit. The testing included grain size analysis, Attcrbcrg limits determination, and natural moisture content determination. The laboratory testing results are included in Appendix Ti. 1S-11 Aspen Glen #01273.0007 10/16/13 TiuddIrstan-Derry rei�m �f s rrr,�. lit The laboratory testing results indicate that the native clay soils are slightly plastic. These materials are anticipated to consolidate under loading. Foundation Recommendations Based upon the results of the subsurface investigation and nature of the proposed construction, shallow foundations are recommended. Spread footings and monolithic (turndown) structural slabs are both appropriate foundation alternatives. However, to provide a uniform bearing stratum, it is recommended that the foundations be constructed above a minimum of 12 -inches of structural fill resting on the dense gravel and cobble soils. The native clay soils, exclusive of topsoil, are suitable for reuse as structural fill. The native gravel soils are also suitable for reuse as structural fill; provided particles in excess of 3 -inches in diameter are removed. Imported structural fill should consist of a granular, non -expansive, non - free draining material such as crusher fines or CDOT Class 6 base course. Prior to placement of structural fill, it is recommended that the bottom of the foundation excavation in the dense gravel and cobble soils be moisture conditioned and proofrolled to the Engineer's satisfaction. Structural fill should extend laterally beyond the edges of the foundation a distance equal to the thickness of structural fill. Structural fill should be moisture conditioned, placed in maximum 8 -inch loose lifts, and compacted to a minimum of 95% of the standard Proctor maximum dry density for fine grained soils and modified Proctor maximum dry density for coarse grained soils, within ± 2% of the optimum moisture content as determined in accordance with ASTM D698 and D1557C, respectively. Pit -run or native gravel materials used as structural fill should be proofrolled to the Engineer's satisfaction. For structural fill consisting of the native soils or imported granular materials, and foundation building pad preparation as recommended, a maximum allowable bearing capacity of 2,000 psf may be used. In addition, a modulus of subgrade reaction of 150 pci may be used for structural fill consisting of the native clay soils and a modulus of 250 pci may be used for structural fill consisting of the native gravel soils, crusher fines, or base course. Foundations 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 -I1 sulfate resistant cement is recommended for construction at this site. Any stemwalls, basement walls, 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 fluid unit weight of 50 pcf in areas where no surcharge loads are present. 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 recommended that non-structural floor slabs and/or exterior flatwork be constructed above the native soils, below the topsoil and/or fill, that have been scarified to a depth of 12 -inches, moisture conditioned, and compacted to a minimum of 95% of the standard Proctor maximum dry density, within ± 2% of the optimum moisture content as determined in accordance with ASTM D698. SC 12066 ALL PROJECTS 01273. Mamuimieu ConHn:clion Smicti 0127J.0007 15- I 1 .Upt. G1 n•200 - Gee 01273-0007 LR 101531 dac 2 Is-I 1 Avon Gkil 401273-0007 10;16'13 ElliddFrVnn•ii�rr+ a I II Drainage Recommendations Grading and drainage are critical to the Tong -terns performance of I undations and slabs -on - grade. 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. Downspouts should empty beyond the backfill zone. It is also recommended that landscaping within three feet of the structures include primarily desert plants with low water requirements. In addition, it is recommended that automatic irrigation within ten feet of foundations be minimized. Groundwater was not encountered during the subsurface investigation. However, if a basement is proposed, a perimeter foundation drain is recommended. In general, the perimeter foundation drain should consist of prefabricated drain materials or perforated pipe and gravel with the flowline of the drain at the bottom of the foundation (at the highest point). The perimeter drain should slope at a minimum of 1.5% to daylight or to a sump. In addition, the gravel or other prefabricated drainage materials should extend along the basement walls to within 36 -inches of the finished ground surface. An impermeable membrane is also recommended at the base of the drain to limit the potential for moisture to infiltrate into the subsurface below the foundations. 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, only one test pit was conducted at the site. Therefore, the precise nature and extent of any subsurface variability may not become evident until construction. As a result, it is recommended that a representative of I IBET observe the foundation excavation prior to structural fill placement to verify that the subsurface conditions are consistent with those described herein. In addition, it is recommended that a representative of HBET test compaction of structural fill materials. 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. Respectfully Submitted: Huddleston -B rr Engineering and Testing, LLC Michael A. Berry, P.E. Vice President of Engineering R _rr3.'LL PRUJLC IS 01_'73•\leunramaSeni.ra 01273.00071$•11 'mot G'rn 21A. Licu 01173•CL6; LR1OI61.) Jaw 3 APPENDIX A Typed Test Pit Log