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HomeMy WebLinkAboutSoils Report for Foundation DesignGEOTECH NICAL INVESTIGATION REPORT Manufactured Home Foundation 146 Quicksilver Court Rifle, Colorado Geo Quest Project No.: 25-130 July 11, 2025 Prepared for: Vortex Engineering 851 Rood Avenue Grand Junction, CO 81501 970-245-905t \ $ N \ a\ -\ s Geo Quest Geotechnical Engineering - Testing (970) 3r8-6784 PO Box 1 372 Rifte, CO 81650 geoquestco@pm.me L 2 3 4 5 6 7 Table of Contents Purpose and Scope of Study Proposed Construction ....................... Site Conditions ............ Field lnvestigation Subsurface Conditions Earthwork Recommendations 7.7 Shallow Footing Foundations ... 7.2 Concrete Slab On Grade Foundations. 7.3 Below-Grade Walls .. 7.4 DrainageConsiderations................... 8 Limitations Figures Figure L - Project and Approximate Test Pit Location Map... Figure 2 - Test Pit Excavation, View looking North ............... Figure 3 - Profile of Testpit Figure 4 - Note Mudstone ln Red Circle ......,... Figure 5 - Note Basalt Grave1...,............... Figure 6 - Sample of Cemented Sand Below 7 Feet Depth Tables Table 1 - Compaction Criteria....... 1. 2 3 4 4 5 6 L L 2 2 3 5 6 6 7 7 7 8 Geo Quest Geotechnical Engineering - Testing (970) 318-6784 PO Box 1 372 Rifte, CO 81650 geoquestco@pm.me Soil Report-Manufactured Home Foundation 146 Quicksilver Ct, Rifle, CO Geo Quest No.25-130 7/Lrlzs 1, Purpose and Scope of Study This report presents the results of our geotechnical investigation for the planned construction of a new manufactured home foundation located at 146 Quicksilver Court, Rifle, Colorado. The purposes of this investigation were to evaluate the subsurface conditions at the site and to develop geotechnical recommendations to assist in design and construction. This report is not a foundation design and cannot be used as such. The type, thickness, reinforcing and other aspects of foundation elements should be designed by a structural engineer. Our scope of services included the following: Using an excavated test pit, observe the subsurface conditions and collect soil samples to identify and assess the material layers at the proposed building site. Estimate soil parameters including allowable bearing pressure, approximate depth to bearing stratum, and estimated foundation movement. Discuss earthwork, including recommendations for fill placement and compaction, suitability of the site soil for reuse as engineered fill, and subgrade preparation. Figure 1 - Project and Approximate Test Pit Location Map 2 ProposedConstruction The project proposes the construction of a concrete slab, slabs or footings with stem walls for a new manufactured home. Geo Quest (GQ) assumes a crawl space will exist between the foundation and the a a a I Approxlmate Test Pit Location Soil Report-Manufactured Home Foundation 146 Quicksilver Ct, Rifle, CO Geo Quest No. 25-130 7/Lrlzs floor of the new home. The location of the project site is presented in Figure I, Project and Approximote Test Pit Location Map. No plan sets or drawings were available at the time of this report. lf the proposed construction details change from those above, GQshould be contacted for review and re-evaluation of the recommendations in this report. 3 Site Conditions The property is located approximately 8 miles south of the town of Rifle in an area known as Grass Mesa on a 17-acre parcel. The parcel is near the western boundary of Grass Mesa where the land drops steeply into Ramsey Gulch to the west. The lot is relatively flat except for the western edge that extends into Ramsey Gulch. The property is very sparsely covered with native grass, sage brush, small basalt boulders along with pinion, juniper and cedar trees. Figure 2 - Test Pit Excavation, View looking North 4 Field lnvestigation On June 25,2025, GQ was at the property and one test pit was excavated to a depth of 8 feet below the ground surface using a John Deere 35G excavator. The site and approximate test pit location are presented in Figure 1. 2 Soil Report-Manufactured Home Foundation 146 Quicksilver Ct, Rifle, CO Geo Quest No.25-130 7/Lt/25 Bulk samples of the subsurface materials were obtained from the test pit at select depths for testing and identification of each material layer. The excavation was backfilled with the excavated soil when completed. 5 Subsurface Conditions Collected soil samples were classified by the geotechnical engineer in accordance with the Unified Soil Classification System (USCS) as described in ASTM D-2488 Visual Manual Procedure. The test pit encountered approximately 12 inches of topsoil over 1.5 feet of fine, white sandy silt that appears to be weakly to moderately cemented with calcium carbonate. The sandy silt is low-density, light weight material and clods can easily be broken by hand although it holds an excellent vertical face in the test pit. Figure 3 presents a profile of allsoil layers encountered in the test pit. Figure 3 - Profile of Testpit Below the silt was very dense silty gravel extending from 2.5 feet to 7 feet below the surface. The gravel contained small to large pieces that were subangular to angular and consisted of mudstone, basalt, 3 Topsoit Sandy Sitt Si tty Gravet-Fou n dation BearingZone Cemented Sand Soil Report-Manufactured Home Foundation 146 Quicksilver Ct, Rifle, CO Geo Quest No. 25-130 7/1,r/25 sandstone and other particles as presented in Figures 4 and 5. The voids between the gravels were filled with silt and fine sand. Figure 4 - Note Mudstone ln Red Circle Figure 5 - Note Basalt Gravel 4 Soil Report-Manufactured Home Foundation 146 Quicksilver Ct, Rifle, CO Geo Quest No.25-130 7ht/2s From 7 feet to the bottom of the excavation at 8 feet a moderately to strongly cemented sand was encountered that may be described as conglomerate, hardpan or caliche. This material had particles that showed signs of oxidation and samples were very difficult to break by hand. Excavation was so slow in this material that bucket refusal was called out. Figure 6 - Sample of Cemented Sand Below 7 Feet Depth No ground water was encountered in the test pit. Variations in groundwater conditions may occur seasonally. The magnitude of the variation will be largely dependent upon the amount of spring snowmelt, duration and intensity of precipitation, site grading changes, and the surface and subsurface drainage characteristics of the surrounding area. Perched water tables may be present but were not encountered in the test pit. 6 Earthwork Geo Quest anticipates that fill placement, outside of foundation excavation areas, will be minor. Areas to receive fill should be stripped of vegetation, organic soils and debris. The on-site soils encountered in the test pit may be used as fill throughout the site with the exception of the white sandy silt layer. This low- density material is not suitable for use below any structural area due to its very poor engineering cha racteristics. Fill used at the site should be placed in loose lifts of 8 inches thick or less, moisture conditioned and compacted to at least 95 percent of the maximum standard Proctor dry density as shown in Table 2. Placement and compaction should be observed and tested by the geotechnical engineer, 5 Soil Report-Manufactured Home Foundation L46 Quicksilver Ct, Rifle, CO Geo Quest No.25-130 7hrlzs Table 1- Compaction Criteria Percent Compaction Moisture Content 95% minimum Standard (ASTM D698)+ 2% of optimum Care should be used when compacting soil next to foundation walls, utilities or other sensitive areas to prevent damage. lf utility trenches are backfilled with granular soil, a clay plug of adequate thickness should be placed in the trench adjacent to the building to reduce the potential for water flowing through the trench back under the structure. 7 Recommendations 7.1" Shallow Footing Foundations Typical shallow foundations may be used at this location such as spread footing with stem walls and slabs on grade. Foundations should bear in the very dense silty gravel below the fine, white sandy silt layer that was encountered directly below topsoil in the test pit as shown in Figure 3. lf the white, sandy silt layer is discovered at the foundation bearing depth this material should be removed and replaced with the silty gravel excavated from other locations at the site or the excavation should be extended into the silty gravel. The following design and construction details should be observed. L Weak, disturbed or unsuitable material encountered at the base of foundation excavations should be removed and replaced with properly compacted fill or the subgrade should be extended to undisturbed soils. Fill should be processed, treated and compacted according to Section 6 Earthwork. 2' Footing foundations that bear in the silty gravel can be designed for a maximum allowable soil pressure of 2,500 pounds per square foot (psf). 3. Continuous wall footings should have a minimum width of at least 15 inches. Foundation pads for isolated columns should have a minimum dimension of 24 inches, 4. Resistance to sliding at the bottom of the footing can be calculated based on a coefficient of friction of 0.40. Passive pressure against the side of the footing can also be considered for the sliding resistance if it is properly compacted. Passive pressure can be estimated based on an equivalent fluid density of 300 pcf for a level backfill. 5' Grade beams and foundation walls should be reinforced to span undisclosed loose or soft soil areas. We recommend reinforcement designed to span an unsupported distance of at least 12 feet. 5. The soils below exterior footings should be protected from freezing. Foundation footings should be constructed at least 36 inches below finished exterior grade for frost protection in 6 Soil Report-Manufactured Home Foundation 146 Quicksilver Ct, Rifle, CO Geo Quest No. 25-L30 7/1.1/2s this area 7. All foundation excavations should be observed by a representative of the geotechnical engineer prior to placement of concrete. Total foundation movement is estimated to be on the order of one (1) inch or less. Differential movement is anticipated to be on the order of % to % of the estimated total movement. These estimated foundation movements are dependent on proper construction practices, drainage and following the recommendations in this report, Therefore, proper drainage should be provided in the final design and during construction. 7.2 Concrete Slab On Grade Foundations A concrete slab will provide a suitable bearing platform for manufactured home foundations. Slab on grade design and construction recommendations are as follows: ' A modulus of subgrade reaction value of 200 psi/in may be used on the silty gravel. r Positive separations and/or isolation joints should be provided between slabs and all foundations, columns, or utility lines to allow independent movement. . Control joints should be provided in slabs to control the location and extent of cracking. ' lnterior trench backfill placed beneath slabs should be properly compacted in accordance with Table 2. . Slabs should not be constructed on frozen subgrade. 7.3 Below-Grade Walls The foundation walls should be designed for lateral earth pressure of the surrounding soil where backfill is not present to the same level on both sides of the wall. For walls that can deflect or rotate about 0.5 to L percent of the wall height, the wall can be designed for "active" earth pressure conditions. For a very rigid wall where negligible deflection can occu[ an "at-rest" lateral earth pressure condition can be used. Typically, below-grade walls for residences may rotate a small amount under normal design loads, and this deflection results in acceptable performance. lf on-site soils are used as backfill we recommend using an equivalent fluid density of 40 pcf for design of below grade walls for "active" conditions. This value assumes that some minor cracking is acceptable. lf this is unsuitable, then a higher ("at-rest") equivalent fluid density should be used for design. For "at rest" conditions, an equivalent fluid density of 50 pcf can be used for design. These equivalent fluid densities do not account for sloping backfill, surcharges or hydrostatic pressure. 7,4 DrainageConsiderations We recommend the ground surface surrounding the building be sloped to drain away from the structure with a minimum slope of 10 percent or a drop of 12 inches in the first 10 feet for landscape areas. We recommend a slope of 2 percent away from the structure beyond this. We recommend that roof drain 7 Soil Report-Manufactured Home Foundation 146 Quicksilver Ct, Rifle, CO Geo Quest No.25-130 7/ruzs downspouts discharge a minimum of 5 feet away from the structure and beyond all structure backfill zones. These recommendations may require raising the overall structure elevations. 8 Limitations The analyses and recommendations presented in this report are based upon our data obtained from the test pit, field observations, soil classifications and our understanding of the proposed construction and other information as discussed in this report. lt is possible and likely that subsurface conditions may vary outside of the limits explored. The nature and extent of such variations may not become evident until construction. We should review the report if the scope of the proposed construction, including the proposed loads, finished elevations or structure locations, change from those described in this report, and provide supplemental recommendations as necessary. It is important to note that the recommendations herein are intended to reduce the risk of structural movement and/or damage associated with volume change of the subsurface materials. Howevet GQ cannot predict the long-term changes in subsurface moisture conditions and/or the extent of potential damaging effects. Where significant increases in subsurface moisture occur due to grading changes, utility line break, leaks from any source, excess irrigation or other causes, excessive movement is possible. This report was prepared in substantial accordance with the generally accepted standards of practice for geotechnical engineering as exist in the site area at the time of our investigation. No warranties, express or implied, are intended or made. These recommendations are based on the assumption that GQ will conduct an adequate program of testing and observation to evaluate compliance with our recommendations. Respectful ly su bmitted, Geo Quest Kevin E. Dye, P.E, 8 L 571 39 /lt/2 House Staking Report Bona Fide Surveying LLC Field Date 5129125 CMH Project: Beisner Rifle BFS Project2025.0029 Scale:1"=125' Lot 1 Quicksilver Court Subdivision Rec# 806669 s89'26'57"E 711.19' EJ -F JUo> J- IIJ6U):l<il trl o 7"W 196.87' ; UJzJt!o- (L oz a,IF I ulJo E.dt o =o otao lrJ()o Fzoulq>OUgU, U rl 10.00 EASEMENT UTILITIES AND PIPELINE BOOK 628 PROPOSED HOUSE I I I I I--l I I _l-: a trJz 9.- rB(LzO6 EESE7vtr ?ftffiko(L ?go e,m 20.00 UTILITY EASEMENT 30.00 EASEMENT CCESS ROADWAYS PATHS AND PIPELINES owt-uz ^ZFJNouiu@ Ffrstr nff?o N8919'32"W 568.1 G Gadield county Driveway Exemption Letter Date 6/121202s To Whom it May Concern: Parcel Number Property Owner Property Acldress 2L7727ZjTOOL Tamla & Steve Beisner L46 Quicksilver Ct, Rifle, CO 81650 V n The above address is exempt from needing a Driveway Permit from Garfield County Road and Bridge because: The Driveway will not directly access a County maintained road The driveway meets current CoLrnty standards Approved By: T. Terry Garfield County Representative For questions, please call: Garfield County Road Bridge @ 970-625-860I 0298 County Road 333A Rlfle, CO 81550 Phone: 970.825-8601 Fax: 970-625-8627