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HomeMy WebLinkAboutSoils Report-Main Res Patios 07.18.25CTL ITHOMPSON July 18,2025 Beck Building Company P.O. Box 4030 Vail, CO 81658 Attention: Steve Boderck Senior Project Manager Subject:Main Residence Patios Sweetwater Ranch 4894 Sweetwater Road Garfield County, Colorado Project No. G506935.000-1 45-11 ' CTLIThompson, lnc. (CTLIT) performed a geotechnical engineering investigation for the main residence planned at Sweetwater Ranch under our Project No. GS06935.000-125 (report dated January 20,2025). Subsequent to our report, CTLIT was asked to opine on backfill and fill soils that are proposed below two exterior patios that will be adjacent to the north and east sides of the residence. The proposed northern and eastern patios are indicated on the attached Figure 1. The backfill and fill will be thicker than 12 feet below parts of these patios. Additionally, an earth retaining wall is proposed on the fill slope that is downgradient of the patios (see Figure 1). The following sections provide our opinions and recommendations. Structural Backfill and Fill Foundation backfill and structural fill in areas that will support patios should consist of AASHTO Glass 4 or Class 5 aggregate base course or similar material. A sample of the proposed backfill/structural fill material should be submitted to our office for approval, prior to hauling to the site. Prior to placement of structural fill below proposed patios, the natural ground surface should be stripped of vegetation and organic soils. ln areas where existing slopes are 20 percent or steeper, relatively flat benches should be excavated into the slope prior to placement of structural fill. This facilitates compaction of the fill material and reduces the potential for subsequent sliding along the interface between the existing soils and the overlying fill. Bench widths of I to 10 feet should be considered to allow use of large compaction equipment. Excavation faces at the uphill side of benches should be no steeper than 1 to 1 (horizontal to vertical). CTLIT should be called to evaluate excavation slopes during construction. The backfill and structural fill soils should be placed in loose lifts of 10 inches thick or less and moisture-conditioned to within 2 percent of optimum moisture content. BacKill and structural fill should be compacted to at least 98 percent of ASTM D 698 maximum dry density. CTLIT should be called to check moisture content and density of backfill and structuralfill during placement. Observation of the compaction procedure is necessary, CTLITh omoson. lnc. Denver, Fort Collins, Colo-r.ado Sprinqq, Glenwood Sprinqs, Pueblo, Summit Countv - Colorado Chevenne, Wyoming and Bozeman, Montana ffi ffi CTLIT recommends that final slopes be no steeper than 2 to 1 (horizontalto vertical). Slopes at this inclination should be stable provided they are constructed properly, and erosion control measures are designed, constructed, and maintalned during and after construction. Erosion control blankets, such as RollMaxrM EroNet SC150 or similar, should be considered for permanent slopes to facilitate revegetation. The erosion control blankets should be installed according to the manufacturer's specifications. Earth ino Walls An earth retaining wall with is proposed on the slope down-gradient of the patios. ln our opinion, several earth retention systems could be utilized at the site. These include a mechanically stabilized earth (MSE) structure, a large-block retaining wall, and a reinforced concrete retaining wall. Brief comments on each of these systems are below. An MSE structure consists of alternating layers of compacted structural backfill and geogrid reinforcement. Mobilized friction between the geogrid and structural backfill results in a zone oF reinforced earth that essentially acts as a gravity retaining structure. The structure is faced with masonry blocks that are connected to the geogrid reinforcement. The facing blocks prevent erosion and sloughing of the materials at the front of the reinforced earth zone and create an aesthetically pleasing wall. The bottom course of blocks is typically placed on a layer of densely-compacted, granular structural fill. A drainage layer and drainpipe are required behind the facing blocks. MSE structures are relatively tolerant to ground movement. Large-block earth retaining walls (e.9., Redi-rock) are constructed with pre-cast concrete blocks that are available in a variety of styles and colors. Walls with maximum heights of 9 feet can often be designed without geogrid reinforcement behind the wall. For this type of wall, the weight and interlocking nature of tho blocks provides resistance to earth pressures in the retained slope. The bottom course of blocks is typically placed on a layer of densely-compacted, granular, structuralfill. A drainage layer, drainpipe, and some backfill soils are required behind the blocks. Large-block retaining walls are relatively tolerant to ground movement. A reinforced concrete retaining wall is a potential alternative to consider. These walls are constructed with two-sided forms, which must be stripped after the wall is cast. This could result in personnel in a trench{ype situation between the wall and the excavation slope. OSHA guidelines for trench safety apply. The footing foundation for the wall would likely need to be supported on a 2-foot thickness of densely-compacted, granular structural fill. A drain system is required behind reinforced concrete earth retaining walls to reduce potential hydrostatic pressure. CTLIT can assist with design of any of these earth retention systems. We can provide additional recommendations as architectural plans are further developed. A survey of existing and proposed grades will be important to facilitate design of the retaining wall systems. I imifafinnc CTLIT believes our consultation is being provided with that level of skill and care ordinarily used by geotechnical engineers practicing in this area at this time. No warranty, express or implied, is made. Please contact us if you have questions or need additional information. BECK BUILDING COMPANY SWEETWATER RANCH - MIAN RESIDENCE PATIOS cTLIT PROJECI Nu. GSune35.0u3-14b-L1 Pege 2 of 3 ffi CTLITHOMPSON, lNC.Reviewed by: \u%2{"h(:D. Kellogg, P Principal Engin Via email: steve@beckbuilds.com BECK BUILDING COMPANY SWEETWATER RANCH - MIAN RESIDENCE PATIOS cTLlr PROJECT NO. GS06935.003-145-Ll rbo Division Manag 1 .E. o m68s R Page 3 of 3 ffi 50 60 SCALE: l'= 60' NOTE:BASE IMAGE FROM SOPRIS ENGINEERING LLC (DATED MARCH 26, 2o2s) \ ../. rnrn9 \ ;l l (i ')l BECKBUILDING COMPANTY SWEETWATER RANCH - MAIN RESIDENCE PANOS ProJect No. GSO6935.OOO-1 4S-Ll Patios Proposed Above Backfill and Structural Fill FE.1 I I