HomeMy WebLinkAboutObservation of Pits Excavations 08.21.2020IN A
Kumar & A cIat , In .
t;aotethnical snd Materials Engineers
and Environmental Scientists
An Employee Owned Company
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwoodfp.,lcuniarusa.com
www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
August 21, 2020
Carlos Leyba
156 Cindy's Way
Rifle, Colorado 81650
etleyba@irosn .coni
Subject:
Gentlemen:
Project No. 20-7-449
Observation of Pit Excavations, Proposed Shop Building, 156 Cindy's Way,
Garfield County, Colorado
As requested by Matt Bilson, a representative of Kumar & Associates, Inc. observed the pit
excavations at the subject site on August 17, 2020 to evaluate the soils exposed for foundation
support. The findings of our observations and recommendations for the foundation design are
presented in this report. Hepworth-Pawlak Geotechnical (now Kumar & Associates) previously
conducted a subsoil study for design of foundations for the existing residence at the site and
presented the findings in a report dated April 30, 2003, Job No. 103 205.
The shop building will be located near the existing residence and is designed to be supported on
a monolithic slab foundation with 2 feet deep thickened edges which has been built. We
understand there was ground treatment done to prepare the building site for the slab and
foundation. The maximum bearing pressure of the foundation was assumed as 1,500 psf.
At the time of our visit to the site, two pit excavations had been dug along the north side of the
slab. The western pit was about 31/2 feet deep and the eastern pit was about 2'/2 deep. The soils
exposed in the bottom of the pits consisted of very clayey sand in the western pit and silty sandy
clay in the eastern pit. Results of swell -consolidation testing performed on samples taken from
each pit bottom, shown on Figures 1 and 2, indicate the soils are compressible under conditions
of loading and wetting. No free water was encountered in the pit excavations and the soils were
slightly moist to moist.
The clayey soils exposed in the pit excavations are generally consistent with those previously
encountered on the site and can be used for support of the thickened edge slab designed for the
assumed allowable bearing pressure of 1,500 psf with a risk of differential settlement, mainly
under wetted conditions. The ground surface should have positive slope to drain at least 10 feet
away from the building. Other recommendations presented in the previous report which are
applicable should also be observed.
The recommendations submitted in this letter are based on our limited observation of the soils
exposed within the pit excavations and the previous subsurface exploration at the site.
Carlos Leyba
August 21, 2020
Page 2
Variations in the subsurface conditions could increase the risk of foundation movement. 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, lnc.
Steven L. Pawlak, P
Rev. by: DAY
SLP/kac
Attachments: Figures
y'+ •L` ~~e 1_Consolidation Test Results
cc: Matt Bilson (I i
Kumar & Associates, Inc.
}
1
0
SAMPLE OF: Very Clayey Sand
FROM: Bottom of West Excavation, 3.5'
WC = 11.5 %, DD = 114 pcf
—4
Thaea tit 000 opplf only w inn
semen 1.ebd. TOO l.dGaq 004
.MY
01 do r.produc.d..s..Al In
MIL •i16.ut 110 wain' approval of
Num" and .Nlodoi... Ix. Sxa
aordvde t r' p . In
oacWdont..IN 'Mr
i I
'----• --- •- —I
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
- T I r 1"1
1.0 APPLIED PRESSURE — KSF 10 1G
20-7-499
Kumar & Associates
SWELL—CONSOLIDATION TEST RESULTS
Fig. 1
2
0
J —2
W
O
1-
SAMPLE OF: Silty Sandy Clay
FROM: Bottom of East Excavation, 2.5'
WC = 10.3 %, DD = 99 pcf
° —8
—10
—12
Td.., 1491 r.pA. pp only to the
rn
epin S.n.d. Th. I ep* t
read not b. r.pr.eyefd...s.0 In
IA without 1M •riSlm tpprOVol ar
xumdr dn0 .p.pcipI.,. too. Sr.lr
Cane I:7 yMwm.d In
Gcsalaarts nt. Hn A5T11 D-4546.
I..________L___._ 1._. L.L 1 ..
1 ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
. 1 1 1 1 1.
II
1.0 APPUED PRESSURE — KSF 10
100
•
20-7-499
Kumar & Associates
SWELL—CONSOLIDATION TEST RESULTS
Fig. 2