HomeMy WebLinkAboutSubsoils Report for Foundation DesignKumar & Associates, Inc.®
IUA
Geotechnical and Materials Engineers 5020 County Road 154
and Environmental Scientists Glenwood Springs, CO 81601
phone: (970) 945-7988
fax:(970) 945-8454
email: kaglenwood(akumarusa.com
An Employee Owned Company www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
June 19, 2025
Colonna Construction
Attn: Bernie Colonna
P.O. Box 1968
Rifle, Colorado 81650
colonna2012@hotmail.com
Project No. 24-7-635.A
Subject: Subsoil Study for Foundation Design, Proposed Residence, 3436B County Road
233, West of Silt, Garfield County, Colorado
Dear Bernie:
As requested, Kumar & Associates, Inc. performed a subsoil study for design of foundations at
the subject site. The study was conducted in accordance with our agreement for geotechnical
engineering services to you dated October 29, 2024. The data obtained and our \
recommendations based on the assumed construction and subsurface conditions encountered �1n
are presented in this report. ^�
Proposed Construction: The proposed residence is expected to be a one-story wood frame
structure over a walkout basement located on the site in the area of the pits as shown on Figure 1.
Ground floor will be slab -on -grade or structural over crawlspace. Cut depths are expected to
range between about 2 to 10 feet. Foundation loadings for this type of construction are assumed
to be relatively light and typical of the proposed type of construction.
If building conditions or foundation loadings are significantly different from those described
above, we should be notified to re-evaluate the recommendations presented in this report. `v
Site Conditions: The site slopes moderately down to the southeast. Vegetation in the area
consists of sagebrush with an understory of grass and weeds. The vegetation and topsoil had
been stripped from the building area and the building pad had been graded. Sandstone bedrock 1�
was observed outcropping on the hillside above the site to the east.
Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating
three exploratory pits in the graded driveway/building area at the approximate locations shown
on Figure 1. The logs of the pits are presented on Figure 2. The subsoils encountered, below
about Moot of topsoil/root zone consist of stiff to very stiff sandy silty clay down to the bottom
of the pits 2%2 to 7 feet. Results of swell -consolidation test results performed on samples taken
from the pits are shown on Figure 3. The samples showed a low expansion or collapse potential
when wetted. No free water was observed in the pits at the time of excavation and the subsoils
were slightly moist.
-3-
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the residence has been completed:
1) Inundation of the foundation excavations and underslab areas should be avoided
during construction.
2) Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95% of the maximum standard Proctor density in pavement and slab areas
and to at least 90% of the maximum standard Proctor density in landscape areas.
Free -draining wall backfill should be capped with about 2 feet of the on -site, finer
graded soils to reduce surface water infiltration.
3) The ground surface surrounding the exterior of the building should be sloped to
drain away from the foundation in all directions. We recommend a minimum
slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of
3 inches in the first 10 feet in pavement and walkway areas. A swale may be
needed uphill to direct surface runoff around the residence.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
5) Landscaping near the house should consist of low-water need plants and irrigation
should be restricted to be at least 5 feet beyond the foundation walls.
Limitations: This study has been conducted in accordance with generally accepted geotechnical
engineering principles and practices in this area at this time. We make no warranty either
express or implied. The conclusions and recommendations submitted in this report are based
upon the data obtained from the exploratory pits excavated at the locations indicated on Figure I
and to the depths shown on Figure 2, the proposed type of construction, and our experience in
the area. Our services do not include determining the presence, prevention or possibility of mold
or other biological contaminants (MOBC) developing in the future. If the client is concerned
about MOBC, then a professional in this special field of practice should be consulted. Our
findings include interpolation and extrapolation of the subsurface conditions identified at the
exploratory pits and variations in the subsurface conditions may not become evident until
excavation is performed. If conditions encountered during construction appear different from
those described in this report, we should be notified at once so re-evaluation of the
recommendations may be made.
This report has been prepared for the exclusive use by our client for design purposes. We are not
responsible for technical interpretations by others of our information. As the project evolves, we
should provide continued consultation and field services during construction to review and
monitor the implementation of our recommendations, and to verify that the recommendations
have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presented herein. We recommend on -site observation
of excavations and foundation bearing strata and testing of structural fill by a representative of
the geotechnical engineer.
Kumar & Associates, Inc. 0 Project No. 24-7.635A
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LOCATION OF EXPLORATORY PITS Fig. 1
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SWELL —CONSOLIDATION TEST RESULTS
Fig. 3
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SAMPLE OF: Sandy Silty Clay
FROM: Pit 1 ®
2'
WC=6.5DD=
114pcf
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ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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SAMPLE OF: Sandy Silty Clay
FROM: Pit 2 ® 2'
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WC = 4.3 %, DD = 114 pcf
1 EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
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