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Home My WebLink AboutGeotechnical Engineering Consultation 07.19.17tr CTL ITHOMPSON @ July 19,2017 Phil Vaughan Construction Management, lnc, 1038 County Road 323 Rifle, CO 81650 Attention: Mr.PhilVaughan Subject: Geotechnical Engineering Consultation Garage Building Vaughan Residence 1038 CountY Road 323 Garfield CountY, Colorado Project No. GS05694.000-1 45 Thís letter provides our geotechnical recommendations for the planned garage building to be constructed at 1038 County Road 323 in Garfield County, Óoloiado. Planned buitding construction, anticipated subsurface conditions, and our foundation recommendations for the building are provided below' Pla4ned Const-fuction The garage will have plan dimensions of 30 feet by 86 feet. Walls will be framed with} x 6 wood studs and the roof system willbe comprised of wood trusses that span âcross the shorter dimension. The building will have five overhead doors on the south wall, providing access to four parking bays, The finished floor slab elevatÍon in the building willbe 5309 feet. Existing ground surfacewithin the building footprint varies from about 5307 to 5310. The preferred foundation is a concrete slab-on-ground with turned down edges- Subsurface Conditions Subsurface conditions are anticipated to be similar to those observed in exploratory pits excavated as part of our field ínvestigation for a 2004 addition to the Vaughan Residence, Subsufface conditions consisted of 2.5 and 6 feet of silty sanðy clay underlain by clayey to silty gravel with basalt cobbles and boulders to the total åxplıred depth of 7,5 feet below existing ground surface. Free ground water was not observed in the exploratory pits. Site Earthwork Stripping depth will likely average about 6 incìes to remove topsoil and organics fiom below the planned building. We believe fillthickness of 2 feet or less w¡ìi ne required to achieve subgrade for finished floor. Significant overlot grading cuts and fill are not anticipated for building pad construction. 234 Center Drive I Glenwood Springs' Colorado 81601 Iefephone: 970-945-2809 F ax'. 97Ð'945-7 41 1 îffi Excavations for utilities and foundation walls can be accomplished using conventional, heavy-duty construction equipment. Excavation sides will need to be sloped or braced to meei local, state and federalsafety regulations. We believethe clay will classify as a Type B soil and the gravel will classify as a Type C soil based on 'OSH¡ stanáards governing excavations. Temporary slopes deeqerthan 4 feet (if requíred) should be nã steeperthan 1 to 1 (horizontal to vertical) in Type B soils and t.S to 1 in Type C soils. Contractors should identify the soils encountered in the excavations ând refer to OSHA standards to determinê appropriate slopes' Structural Fill The silty sandy clay soil at this site possesses the potential for. moderate consolidation when wêttedunder load. We recommend placement of at least 1 foot of structural fill below the slab-on-ground foundation. We recommend the granular, structural fitl consist of an aggregate base course, such as a CDOT Class 6 or similar soil. The subgrade surface that witl support structuralfill should be scarified to a depth of at leas[6 inches, moisture-treated, and compacted. Structuralfill should be moisture-treated to within 2 percent of optimum moisture content and compacted to at least g8 percent of maximum standard Proctor (ASTM D 698) dry density' Water required to increase the structuralfillsoil moisture contentto the specified moisture content should be uniformly mixed into the fill soil prior to compaclion We recommend loose fill lífts of i 0 inches or less. The actual thickness of fill lifis that can be properly compacted will depend on the type of compaction equipment' Slab-on Ground In our opinion, a slab-on-ground is a reasonable system for thefoundation and floor of the proposed garage at this site. We recommend supporting-the slab on a 1-foot thicknessóf densely-compacted, granular structural fill. Design criteria for a slab-on-ground foundation/floor system are provided below. 1. The slab-on-ground foundation should be constructed on a minimum 1 -foot thickness densely-compacted, granular structural f ill. Z. The slab should be heavily reinforced and preferably in a single monolithic configuration tô help maintain its integrity in the event of ground movement. The slab turned down edges sftot!! be " ãesigned for a maximum allowable soil pressure of 1,500 psf. 3, Modulus of subgrade reaction {Ks) is normally used for a slab-on- ground design. the modulus of subgrade reaction is dependent upon the coñrpressibility of the foundation soils and the size (or PHIL VAUSHAN CONSTRUCTION MANAGEMENT VAUGHAN RESIDENCE ADDITION PRoJËGT NO. GS05094.000-l 46 c:lus6|,6\cdownlng\EoxtPrcjoctslGlenwood sprlf,gE . PfoJôèt$6506694.0Û0t14613. Lêtters\G805öS',1.000 1¡Í6 Lz'docx 2 4 5. effective loaded area) of the foundation, lf the entire slab foundation is uniformiy loaded, then a Ks value of 200 pci' A friction coefficient of 0.45 can be used for lateral resistant between concrete and granular structural fill. Lateral loads can be resolved by evaluating passive resistance uring an equivalent fluid density o'r 325 pcf for the onsite soils, piàuioeo the backfill is compacted and is not removed' soils beneath the foundation must be protected from freezing. The granular structural fill and natural soils are not significantly ãusáãpt¡Ue to frost heave. We recommend the perimeter of the slab bä turned down to extend at least 24 inches below exterior grà0". The Garfield county building department should be ıontacted for specific frost depth requirements' Reviewed by: ffi ?e. Surface Drainage Surface drainage is critical to the performance of building foundations and slabs. Þrop"r surfacJdrainage can help controlthe amount of surface water that penetrates anJ wets the ãubgrade soils below the slab. The ground surface surróunding tne nuìtding should bä sloped to drain away from the building in all directions. Roof gutterã and downspouts should be provided. Limitations This geotechnical engineering consultation was provided in a manner consistent with that level of ð"t" "nd skill ordinarily exercised by geote-chnical ;gi;;rr currently practicing under similar conditions in the locality of this pro]ect. No warranty, express or lmplied, is made. lf we can be of further i"*i"" in discussing the'contents of this report, please call. Very truly rS crllr f--t, P-r,,+r J es D. Kellogg, P.E. n ManagerPri cc: :JDK;cd Via email to Phil@Pvcmi.com PHIL VAUGHAN CONSTRUCTION MÀNAGEMENT VAUGHAN RESIDENCE ADDITION PROJECT NO. GS05894.000'145 c:lussfs\cdowntngìBox\proJoctstc;nwood spf¡ngs . pfojocts\cso6694.000114513. LottofÊ1cs05094.000 l4ö L?'docl 3