HomeMy WebLinkAboutObservation of Excavation 01.03.2017H-PÈKUMAR 5020 County Road 154
Glenwood Spdngs, CO 8'1601
Phone: (970) 945-7988
Far: (970) 945-8454
Email: hpkglenwood @ kumarusa,com
Geol€chn¡cal Engineering I Engineenng Geology
lrlaterialc Tesling I Ertvirttrtrrretrlal
Office Localions: Parker, Glenwood Springs, and Silverthome, Colorado
January 3,2Ot7
Shane Smith
2995 County Road 3l I
New Castle, Colorado 81647
elh5x6x6@hu_shps.nej
Project No. l6-7-308.01
Subject Observation of Excavation, Proposed Residence,2995 County Road 3l l, South
of Silt, Garfield County, Colorado
Dear Shane:
As requesled, a representative of H-PlKumar observed the excavation at the subject site on
December 22 and 31, 2016 to evaluate the soils exposed for foundation support. The fÏndings of
our observations and recommendations are presented in this report. The services are
supplemental to our agreement for professional services to you dated August 9, 2016.
We previously conducted a subsoil study for design of foundations ât the site and presented our
findings in a report dated August 22,2016, Project No. l6-7-308. The proposed construction is
similar to that discussed in our previous report. The building has been designed to be supported
on spread footings u.sing an allowable soil bearing pressure of 1,000 psf based on
recommendations provided in our subsoil study report.
At the time of our December 22 site visit, the foundation excavütion had been cut in one level
from about 3Vzto 4 feet below the adjacent ground surface. The soils exposed in the bottom of
the excavation consisted of sandy to very sandy clay and silt. The subgrade soils were soft to
medium stiff, muddy and wet in areas, and contained some frost. No free water was encountered
in the excavation and the soils were moist to very moist. The footing forms were in place and
the excavation was blanketed. At this time, we recornrnended the subgrade soils in footing areas
be sub-excavated at least one-foot depth and replaced with compacted minus lVzinch
crushed/screen rock or a similar type mâterial. When we returned to the site on December 31,
we observed the subgrade in footing areas consisted of minus lVzinch rock that appeared
compacted and firm. Based on our discussions with you, we understand the sub-excavation and
gravel depth was about I foot, groundwater level is about 2 feet below footing bearing elevation
and the dense gravel with cobble soils are about 5 feet below footing bearing elevation.
The soil condition.s exposed in the excavation are generally consistent with those previously
encountered on the site, and the subgrade adequately improved and suitable for support of spread
footings designed for the recommended allowable bearing pressure of 1,000 psf. There is some
risk of settlement due to the compressible nature of the fïne grained bearing .soils. There is also a
risk of frost heave due to the silty nature of the bearing soils and relatively shallow groundwater
Shane Smith
January 3,2017
Page2
at the site, and extreme care should be taken to prevent freezing of the bearing soils until
adequately backfilled for frost cover. Prior to the footing construction, all loose disturbed
materials and any softened soils and mud removed before concrete placement. The bearing soils
should be protected from frost and concrete should not be placed on frozen soils. Other
recomrnendations presented in our previous 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 the previous limited 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 cbanges to 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,
¡{.P\ KU
David A. Young, P
DAY/ksw
cc Garfield County - Jim Wilson {jWilson @#¿rlield:çqUnty.cçm)
H.P+ KUMAR Projsct No. 1 ô-7.3{18.01