HomeMy WebLinkAboutObservation of Excavation 06.02.25l*n51ffih:'f,T*:*$n'"nr;;**'
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
email : kaglenwood@kumarusa.com
www.kumarusa.com
An Employcc Oumcd Compony
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
June 2,2025
DM Neuman Construction
Attn: Brad Dykema
310 1gth Street
Glenwood Springs, Colorado 81601
brad@dmneuman.com
Project No. 25-7-361
Subject Observation of Excavation, Proposed Deck lmprovements, Brettelberg
Condominium Building, 11101County Road 117, Garfield County, Colorado
Gentlemen
As requested, a representative of Kumar & Associates, lnc. observed the excavation at the
subject site on May 26, 2025, to evaluate the soils exposed for foundation support. The findings
of our observations and recommendations for the foundation design are presented in this report.
CTl/Thompson previously conducted a subsoil study for design of foundations at the site and
presented the findings in a report dated July 25, 2024, Project No. GS06866.000-120. The
current observation was conducted in accordance with our agreement for professional services
with DM Neuman Construction dated May 22,2025.
The proposed deck improvements are to the west side of the Brettelberg Condominium building
Spread footings placed on the natural gravel and cobble soils were designed for the foundation
support and sized for the recommended maximum allowable bearing pressure of 3,000 psf.
At the time of our visit to the site, the foundation excavation was mostly complete and had been
cut in 3 levels up to about 5/.feet below the adjacent ground surface. The soils exposed in the
bottom of the excavation mainly consisted of sandy clay with gravel and scattered cobbles.
Results of swell-consolidation testing performed on clay samples taken from the site, shown on
Figure 1, indicate the soils are slightly to moderately compressible under conditions of loading
and wetting. The results of a gradation analysis performed on a sample of the sandy clay and
gravel soil (minus 3-inch fraction) obtained from the site are presented on Figure 2. The
laboratory test results are summarized in Table 1. No free water was encountered in the
excavation and the soils were moist.
DM Neuman Construction
June2,2O25
25-7-361
Page2
The soils exposed in the excavation appear to have more clay than the soils previously
encountered in the exploratory pits dug at the site and spread footings are recommended to be
designed for a uniform allowable bearing pressure of 2,000 psf. A onethird increase in
allowable bearing pressure can be taken for maximum toe pressure of eccentrically loaded
retaining wall footings (total about 2,700 psf). The sliding coefficient should be taken as 0.40
rather than previously recommended 0.45. Footing pads adjacent to the existing building
should be doweled into the existing foundation. Loose and disturbed soils should be removed in
the footing areas to expose the undisturbed natural soils. Other recommendations presented in
the previous CTUThompson report which are applicable should also be observed.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavation and do not include subsurface exploration at the site.
Variations in the subsurface conditions below the excavation could increase the risk of
foundation movement. We should be advised of any variations encountered in the excavation
conditions for possible changes to recommendations contained in this letter.
lf you have any questions or need further assistance, please call our office.
Sincerely,
Kumar & Associates, lnc.
Steven L. Pawlak, P.E
Reviewed by: JHP
Attachments: Figure 1 - Swell-Consolidation Test Results
Figure 1 - Gradation Test Results
Table 1 - Summary of Laboratory Test Results
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25-7-361 Kumar & Associates GRADATION TEST RESULTS Fig. 2
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TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
No.25-7-361
ATTERBERG
LIMITS
SAMPLE
LOCATION GRADATION
BOTTOM OF
EXCAVATION
lo/ol
NATURAL
MOISTURE
CONTENT
(ocfl
NATURAL
DRY
DENSITY GRAVEL
(%)
SAND
(%)
PERCENT
PASSING
NO.200
SIEVE
t=tQUtD
LIMIT
(%l
PLASTIC
INDEX
(%l (PSF)
UNCONFINED
COMPRESSIVE
STRENGTH
sorL oR
BEDROCK TYPE
Southwest Part 18.3 109 Sandy Silty Clay
Sandy Silty ClaySouth-Central
Part
't7.0 106
Southeast Part 52 17 31 Sandy Clay and Gravel