HomeMy WebLinkAboutObservation of Excavation 04.29.55rcrf fj,ffi1lffifffi1ii:'i*'"
:=
An Employcc Orvncd Compony
5020 County Road 154
Glenwood Springs, CO 8160'1
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
www.kumarusa.coI!
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
Apnl29,2022
Melissa Behlow
89 Fairway Drive
Glenwood Springs, Colorado 81601
melis sa. s.behlow€D qmail. com
Project No.22-7-298
Subject: Observation of Excavation, Proposed New Roof, Existing Residence, 89 Fairway
Drive, Lot32, Westbank Ranch Subdivision #2, Garfield County, Colorado
Dear Melissa:
As requested, the undersigned representative of Kumar & Associates observed the excavation at
the subject site on Ap-"il2l, 2022 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 2I,2022.
A new roof is planned for the existing residence. The house was built in 1976. Additional
loading of the existing foundations is expected for the new roof. A backhoe pit was excavated
near the northeast comer of the house to evaluate the exiting footing size and soil bearing
conditions.
At the time of our visit to the site, the pit excavation had been dug near the northeast comer of
the existing house down to bottom of existing footing which was about 4 feet below the adjacent
ground surface. The exposed part of the footing was bout 8 inches thick and extended out from
the foundation wall about 4 inches. The soils exposed in the bottom of the bottom of the
excavation consisted of medium stiff, sandy silty clay. Results of a swell-consolidation test
performed on a sample taken from the bottom of the pit, shown on Figure l, indicate the soils are
moderately compressible under conditions of loading and wetting and have a moderate collapse
potential (settlement under constant load) when wetted. No free water was encountered in the
excavation and the clay soils were moist. The depth of clay soils below footing grade is
unknown.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, the existing spread footings placed on the undisturbed natural clay in this area are
typically designed for an allowable soil bearing pressure of 1,000 to 1,500 psf. The exposed clay
soils tend to compress when wetted and there could be some post-construction settlement of the
foundation if the bearing soils become wet. The existing exterior continuous footing appears to
have an overall width of 16 inches.
In order to evaluate the potential settlement of the bearing soils, we would need an estimate of
what the existing loads on the footing are and the increase in load due to the new roof.
s
\
\
\\
\
Melissa Behlow
Apnl29,2022
Page2
If we assume that the existing wall load is 1,500 plf, that would be a bearing pressure of
something less than 1,200 psf at the bottom of the footing. Increasing the wall load by a third to
2,000 plf would result in an increase in bearing pressure of 300 psf on the bottom of the footing.
We expect that initial settlement would be small,less than Yz-inch. If the soils were to become
wet, the settlernent could be 1 to 2 inches, although that risk already exists under the current
loading conditions.
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 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 gleater 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 excavation, 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,
Kumar & Associates,
E. Hardin, P
Rev. by: SLP
DEHlkac
attachment Figure I - Swell-Consolidation Test Results
cc: JessPedersen(pedarch@email.com)
Kumar & Associates, lnc, ti Project No, 22-7-298
]
:
I
I
SAMPLE OF: Sondy Silty Cloy
FROM: Existing Footing Grode NE Corner of House
WC = 14,4 %, DD = 82 pcf
-2OO = 82 %
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
Thotsdsd.
in
D-{46.
2
0
JJ
LJ
=a
I
zotr
o
Jo
U1zoO
-2
-4
-6
1 0
-12
-14
-16
-18
1.0 APPLIED PRESSURE - KSF I 100
22-7 -298 Kumar & Associates SWELL_CONSOLIDATION TEST RESULT Fig. 1