HomeMy WebLinkAboutObservation of Excavation 04.17.20215020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
An Employea Ownod Compony www'kumarusa'com
Office Locations: Denver (HQ), Parke¡ Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
April27,202l
Christina Venzor
4l County Road221
Rifle, Colorado 81650
cristvffr@yahoo.com
Project No. 21-7-368
Subject: Observation of Excavation, Proposed Residence, Tl92 County Road 210,
Garfield County, Colorado
Dear Christina:
As requested, a representative of Kumar & Associates observed the excavation at the subject site
on April 2l and 27 , 2021 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 April 20,2021.
The proposed residence is a one story, wood frame structure over a crawlspace. Foundations
were designed based on an assumed allowable soil bearing pressure of 1,500 psf.
At the time of our initial visit to the site, the foundation excavation had been cut in four levels up
to 3 feet below the adjacent ground surface. The soils exposed in the bottom ofthe excavation
consisted of natural, stiff, sandy silty clay in the northwestern two-thirds of the excavation and
fill composed of 3 to 6 inch cobble rock in the southeastern third of the excavation. Results of
swell-consolidation testing performed on clay samples taken from the site, shown on Figure 1,
indicate the soils are compressible under conditions of loading and wetting with a low collapse
potential (settlement under constant load) when wetted. No free water was encountered in the
excavation and the soils were slightly moist to moist. Footing forms and rebar were in place on
the April 21't site visit.
Considering the conditions exposed in the excavation and the nature of the proposed
constructiono spread footings placed on the undisturbed natural soil designed for an allowable
soil bearing pressure of 1,500 psf can be used for support of the proposed residence with a risk of
building settlement. We recommended via telephone on April 23'd thatthe cobble rock should
be removed from the excavation and the footings placed directly on the underlying natural clay
subgrade. We returned to the site on April2TTh and observed that the cobble rock had been
removed to expose the natural clay subsoils. The excavation had been cut in 3 levels from Yzto
5 feet below the surrounding grade. The exposed soils tend to compress when wetted and there
could be some post-construction settlement of the foundation if the bearing soils become wet.
Footings should be a minimum width of 20 inches for continuous walls and2 feet for columns.
Loose and disturbed soils in footing areas should be removed and the bearing level extended
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APPLIED PRESSURE - KSF 10
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SAMPLE OF: Sondy Silty Cloy
FROM: Fooling Grode of Soulhwesl Corner
WC = 5.4 o/", DD = 104 pcf
I ADDITIONAL COMPRESSION
UNDER CONSTANÎ PRESSURE
DUE TO WETTING
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SAMPLE OF: Sondy Silty Cloy
FROM: Footing Grode ot North Side
WC = 4.6 "Á, DD = 110 pcf
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ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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21 -7 -368 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 1
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