HomeMy WebLinkAboutSubsoils Report for Foundation DesignGEOTECHNICAL INVESTIGATION REPORT
Pre-fab Metal Building
1863 Six Lazy K Road
New Castle, Colorado 81647
Geo Quest Project No.: 25-120
May 28, 2025
Prepared for:
Edmundo Castillo
2400 Bob O Link Lane
Glenwood Springs, CO 81601
Mund74@gmail.com
970-309-3884
(970) 318-6784
EGeot�edtmical Quest PO Box 1372
Engineering - Testing Rifle, CO 81650
geoquestco@pm.me
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Table of Contents
1 Purpose and Scope of Study................................................................................................... 1
2 Proposed Construction........................................................................................................... 1
3 Site Conditions........................................................................................................................ 1
4 Field Investigation................................................................................................................... 2
5 Subsurface Conditions............................................................................................................ 2
5.1 Laboratory Test Results................................................................................................................4
6 Earthwork................................................................................................................................4
7 Recommendations.................................................................................................................. 5
7.1 Foundations.................................................................................................................................5
7.2 Concrete Slab on Grade.............................................................................................................6
7.3 Drainage Considerations............................................................................................................ 6
8 Limitations.... _ - _ . .................................................................................................................... 6
Figures
Figure 1 - Project and Approximate Test Pit Location Map.....
Figure 2 — Field Investigation, View Looking Northeast......--..
Figure 3 — Soil Layers ................... . . ...............
Tables
............................................................ 2
............................................................ 3
............................................................ 3
Table 1—Test Pit 1 Laboratory Test Results and Relative Density.................................................................4
Table2 —Compaction Criteria .. ... ................................................................................................................... 5
(970) 318-6784
EGeot�echtnical Quest PO Box 1372
Engineering - Testing Rifle, CO 81650
geoquestco@pm.me
Soil Report -Prefab Metal Building Geo Quest No. 25-120
1863 Six Lazy K Rd, New Castle, CO 5/28/25
1 Purpose and Scope of Study
This report presents the results of our geotechnical investigation for the planned construction of a pre-
fabricated metal building south of New Castle, 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 excavated test pits, observe the subsurface conditions and collect soil samples to identify
and assess the material layers at the proposed building site.
• Recommend foundation type(s) 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.
2 Proposed Construction
The project proposes the construction of a light weight, pre -fabricated metal building with a concrete slab
on grade floor. Geo Quest (GQ) understands the building to be non -living space and used for parking and
storage. The location of the project site is presented in Figure 1, Project and Approximate Test Pit Location
Map. If the proposed construction details change from those above, GQ should be contacted for review
and re-evaluation of the recommendations in this report.
3 Site Conditions
The property is located approximately 7.5 miles south/southeast of the town of Silt on a 19-acre parcel
and accessed by Garfield County Road 311 also known as Divide Creek Road and then Six Lazy K Road. The
property consists of rolling hills with sparse grasses and cedar trees. Sandstone outcroppings are visible at
some locations on the property. An existing cabin is on the property to the north of the proposed building
location which is the focus of this report.
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Soil Report -Prefab Metal Building Geo Quest No. 25-120
1863 Six Lazy K Rd, New Castle, CO 5/28/25
Figure 1- Project and Approximate Test Pit Location Map
4 Field Investigation
On May 12, 2025, GQ was at the property and one test pit was excavated to a depth of 7.0 feet below the
ground surface using a Caterpillar 305.5 excavator. The site and approximate test pit location are presented
in Figure 1 and Figure 2.
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
The test pit encountered approximately 10 inches of topsoil over 1 foot of medium dense clayey sand
above 3 feet of very stiff to hard sandy clay over weathered sandstone bedrock to the bottom of
excavation. The soil was dry to moist, brown/tan and had white calcareous streaking throughout the clay
layer. Sulfates are likely present and sulfate resistant concrete should be used in foundations. Figure 3
presents photos of the soil layers in the excavation when sampling at a depth of about 3 feet below ground
surface.
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Soil Report -Prefab Metal Building
1863 Six Lazy K Rd, New Castle, CO
Geo Quest No. 25-120
5/28/25
Ground water was not encountered in the test pit to the depth explored. 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.
Figure 2 — Field Investigation, View Looking Northeast
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Clayey Sand
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Figure 3 — Soil Layers
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Soil Report -Prefab Metal Building Geo Quest No. 25-120
1863 Six Lazy K Rd, New Castle, CO 5/28/25
5.1 Laboratory Test Results
Collected soil samples were classified by the geotechnical engineer in accordance with the Unified Soil
Classification System (USCS) as described in ASTM D-2488 and ASTM D-2487. Laboratory tests were then
performed on select samples to evaluate the pertinent engineering properties of the soil. The laboratory
testing was conducted in general accordance with the American Society for Testing and Materials (ASTM)
test procedures. The following laboratory tests were performed for this evaluation and presented in
Table 1:
• In -Situ Moisture Content ASTM D-2216
• Soil Particle Analysis ASTM D-422
• Plastic and Liquid Limits ASTM D-4318
Table 1— Test Pit 1 Laboratory Test Results and Relative Density
Sand Percent Finer Liquid Limit/Plasticity Index Relative
Depth In -Situ Moisture Than 200 Sieve (LL/PI) *
(ft) N N N Density
I%)
3.5 1 7.1 1 46 1 54
7 6.8 1 63 37
*Values estimated based on driving sample tube
6 Earthwork
25 LL
Very Stiff to
10 PI
Hard
32 LL
Dense to Very
15 PI
Dense
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 for fill throughout the project site. All fill should be free of organic matter, debris
and rocks larger than 3 inches. If weak, saturated and unsuitable soils are encountered at subgrade
elevations the material should be removed and replaced with imported granular material, to provide a
suitable platform for construction.
The subgrade should be proofrolled before placement of fill, concrete or foundation elements to check
for weak areas that need improvement. This may be accomplished with a loaded truck, backhoe, front
end loader or other heavy rubber -tired vehicle making multiple passes across the subgrade surface. Soil
rutting, pumping or movement that is greater than 0.75 inches needs to be addressed and improved
through compaction or the removal of soil to an appropriate depth and replacement with dryer soil or
gravel. GQ should be contacted if problems persist.
If fill is used below the structure it should be placed in loose lifts of 8 inches thick or less, moisture
conditioned and compacted to at least 95 percent of the maximum proctor dry density as shown in Table
2. Placement and compaction should be observed and tested by the geotechnical engineer.
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Soil Report -Prefab Metal Building Geo Quest No. 25-120
1863 Six Lazy K Rd, New Castle, CO 5/28/25
Table 2 — Compaction Criteria
fPercent Compaction Moisture Content
I
95% minimum Standard (ASTM D698) ± 2 % of optimum 1
Care should be used when compacting soil next to foundation walls, utilities or other sensitive areas to
prevent damage. If 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. Placement and compaction of fill should be observed and tested by
a representative of the geotechnical engineer.
7 Recommendations
7.1 Foundations
A stable foundation and proper structure anchorage is critical to the design life of the lightweight,
prefabricated metal building. Primary foundation types for these structures include concrete pier or post
in the ground foundations and anchorage to a slab on grade. The prefabricated metal building
manufacturers' design recommendations should be followed.
Post in the ground foundations may consist of small concrete piers that are excavated by hand or drilled
with a powered auger. Alternatively, the vertical building supports may extend to the bottom of the
excavations where the void space is then filled with concrete.
The following design and construction details should be observed for post in the ground construction:
1. Borings and excavations should be drained of water before placement of concrete.
2. Concrete with a minimum 28-day compressive strength of 3,500 pounds per square inch
should be used. Concrete should be properly vibrated, consolidated and distributed to
eliminate voids and seal the boring/excavation from surface water.
3. Concrete should be a fluid mixture that is appropriate to fill potentially small voids between
foundation elements and reinforcing. The concrete slump should be within 5 to 8 inches.
4. Sulfate resistant concrete should be used. The exposure category to sulfates should be
considered Severe and a Class of S2 should be used when selecting sulfate resistant concrete
as discussed in ACI 318-11.
5. The soil at this location is anticipated to adequately hold an open hole for the placement of
post and concrete. Cardboard forms such as Sono Tubes should be used if
borehole/excavation collapsing is experienced.
6. Piers or posts in the ground should extend to a minimum depth of 3 to 4 feet below the
surrounding ground surface for frost protection and structural integrity.
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Soil Report -Prefab Metal Building Geo Quest No. 25-120
1863 Six Lazy K Rd, New Castle, CO 5/28/25
7. A minimum amount of reinforcing steel should be used in concrete piers that extends the
entire length of borehole to resist tension forces.
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 during construction and
throughout the design life.
7.2 Concrete Slab on Grade
GQ recommends the concrete slab on grade (SOG) floor be a minimum thickness of 5 inches. Additional
slab design and construction recommendations are as follows:
• A subgrade modulus value of 150 pounds per cubic inch may be used in SOG design.
• Welded wire reinforcing may be used to maintain aggregate interlock when temperature and
shrinkage cracks occur. The reinforcing should be placed in the top 1/3 of the slab thickness and
extend laterally to within 2 inches of the side edge.
• Positive separations and/or isolation joints should be provided between slabs and all piers,
columns, or utility lines to allow independent movement.
• Control joints should be provided in slabs to control the location and extent of cracking.
• Interior utility trench backfill placed beneath slabs should be properly compacted in accordance
with Table 2.
• Slabs should not be constructed on frozen subgrade.
7.3 Drainage Considerations
We recommend the ground surface surrounding the building be sloped to drain away from the structure,
SOG and foundation elements 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 downspouts be used and discharge a minimum of 5 feet away from the
structure and beyond all structure backfill zones. These recommendations may require raising the site
grade slightly.
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. It 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.
Soil Report -Prefab Metal Building
1863 Six Lazy K Rd, New Castle, CO
Geo Quest No. 25-120
5/28/25
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. However, 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.
Respectfully submitted,
o L/"
Geo Quest r.57139
' E. of `rr^
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Kevin E. Dye, P.E. 4��ONAL
Founder
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