HomeMy WebLinkAboutObservation of ExcavationKumar & Associates, Inc.® 5020 County Road 154
'� Geotechnical and Materials Engineers Glenwood Springs, CO 81601
and Environmental Scientists phone: (970) 945-7988
email: kaglenwood@kumarusa.com
www.kumarusa.com
An tmployee Owned Company
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
November 6, 2025
Marcelino Holguin
3655 County Road 100
Carbondale, Colorado 81623
holg u in m a reel i no2ya hoo. cam
Project No 25-7-442
Subject: Observation of Excavations, Proposed Residence and Barn/Accessory Dwelling
Unit (ADU), Lot 9, Gilead Gardens, Garfield County, Colorado
Dear Marcelino:
As requested, a representative of Kumar & Associates observed the excavations at the subject
site on October 27 and 28, 2025 to evaluate the soils exposed for foundation support. The
findings of our observations and recommendations for the foundation support are presented in
this report. The services were performed in accordance with our agreement for professional
engineering services to you dated June 24, 2025.
The proposed primary residence will be one and two stories of wood frame construction over a
crawlspace, with slab -on -grade in the garage area. The Barn/ADU building will be one and two
stories of wood frame construction with a slab -on -grade ground floor. Q
At the time of our visit to the site, the foundation excavation for the primary residence had been
cut into two levels from 2'/2 to 5 feet below the adjacent ground surface. The foundation
excavation for the barn/ADU had been cut to one level from 1 to 1'/2 feet below the adjacent
ground surface. The soils exposed in the bottom of the excavations consisted of very stiff, sandy
silt and clay with scattered gravel. Results of swell -consolidation testing performed on samples
taken from the site, shown on Figures 1 and 2, indicate the soils are slightly expansive under
conditions of loading and wetting. No free water was encountered in the excavations and the
soils were slightly moist to moist.
Considering the conditions exposed in the excavations and the nature of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an allowable soil
bearing pressure of 2,500 psf with a minimum dead load of 800 psf can be used for support of
the proposed residences. Alternatively, footings placed on a minimum of 3 feet of moisture -
conditioned and compacted structural fill can be designed for an allowable bearing pressure of
2,500 psf and no minimum dead load. The exposed soils tend to expand when wetted and there
could be some post -construction movement of the foundations if the bearing soils become wet.
Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns.
Loose disturbed soils in footing areas should be removed and the bearing level extended down
to the undisturbed natural soils. Exterior footings should be provided with adequate soil cover
above their bearing elevations for frost protection. Continuous foundation walls should be
reinforced top and bottom to span local anomalies such as by assuming an unsupported length
of at least 12 feet. Foundation walls acting as retaining structures should also be designed to
resist a lateral earth pressure based on an equivalent fluid unit weight of at least 55 pcf for on-
Marcelino Holguin Project No. 25-7-442
November 6, 2025 Page 2
site soil as backfill. A perimeter foundation drain should be provided around the main residence
to prevent temporary buildup of hydrostatic pressure behind crawlspace walls and prevent wetting
of the crawlspace. Structural fill placed within floor slab areas can consist of the on -site soils
compacted to at least 95% of standard Proctor density at a moisture content near optimum.
Backfill placed around the structure should be compacted and the surface graded to prevent
ponding within at least 10 feet of the building. Landscape that requires regular heavy irrigation,
such as sod, and sprinkler heads should not be located within 5 feet of the foundations.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavations and do not include subsurface exploration to evaluate the
subsurface conditions within the loaded depth of foundation influence. This study is based on the
assumption that soils beneath the footings have equal or better support than those exposed. The
risk of foundation movement may be greater than indicated in this report because of possible
variations in the subsurface conditions. In order to reveal the nature and extent of variations in
the subsurface conditions below the excavations, drilling would be required. It is possible the
data obtained by subsurface exploration could change the recommendations contained in this
letter. 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.
If you have any questions or need further assistance, please call our office.
Sincerely,
E.
7 "'24443
Daniel E. Hardin, :E.
Rev. by: JHP
DEH/kac
attachments Figures 1 through 4 — Swell -Consolidation Test Results
Table 1 — Summary of Laboratory Test Results
Kumar & Associates, Inc
SAMPLE OF: Slightly
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FROM: Main House
— West
WC = 16.0 %, DD
= 105 pcf
2
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SWELL —CONSOLIDATION TEST RESULTS
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SAMPLE OF: Slightly Sandy Silty Clay
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25-7-442 Kumar & Associates SWELL —CONSOLIDATION TEST RESULTS Fig. 2
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SAMPLE OF: Slightly
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