HomeMy WebLinkAboutObservation of Excavation 04.09.2018PKUMAR
Geotechnical Engineering 1 Engineering Geology
Materials Testing 1 Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado
April 9, 2018
Uriel Mellin
144 Cliffrose Way
Glenwood Springs, Colorado 81601
uriel.mellin@hotmail.com
RECEIVED
APR 12 2018
GARFIELD COUNTY
COMMUNITY DEVELOPMENT
Project No. 17-7-198
Subject: Observation of Excavation, Proposed Residence, Parcel A, Shelton Lot Boundary
Adjustment, County Road 110, Garfield County, Colorado
Gentlemen:
As requested, a representative of H-P/Kumar observed the excavation at the subject site on April
3, 2018 to evaluate the soils exposed for foundation support. The findings of our observations
and recommendations for the foundation design are presented in this report. We previously
conducted a subsoil study for design of foundations at the nearby proposed commercial building
on the property and presented our findings in a report dated April 12, 2017, Project No.
17-7-198.
The residence site is located about 150 to 200 feet south of the commercial building site. The
previous foundation recommendations were to place footings on siltstone bedrock or compacted
structural fill.
At the time of our visit to the site, the foundation excavation had been cut in 3 levels from 1 to 4
feet below the adjacent ground surface. The steps in grade between the levels were about 1 to 2
feet. The soils exposed in the bottom of the excavation consisted of sandy silt and clay which
appeared calcareous, gypsiferous and porous in places. Results of swell -consolidation testing
performed on samples taken from the site, shown on Figure 1, indicate the soils have variable
compressibility and expansion potential under conditions of loading and wetting. The test results
are summarized in Table 1. No free water was encountered in the excavation and the soils were
slightly moist.
The soil conditions exposed in the excavation are not consistent with those previously
encountered at the commercial building site. The residence area soils are variable and can be
Uriel Mellen
April 11, 2018
Page 2
considered for support of spread footings designed for an allowable bearing pressure of 1,500 psf
with a risk of differential settlement or heave. Loose disturbed soils should be removed in the
footing areas and the exposed undisturbed natural soils moistened and compacted. The bearing
soils should be protected from frost and concrete should not be placed on frozen soils. Other
recommendations presented in our previous report which are applicable, especially those to keep
the bearing soils dry, 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
commercial building site. Variations in the subsurface conditions below the excavation should
be expected and 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. 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,
H-PKUMAR
Steven L. Pawlak, P.E.
Rev. by: DEH
SLP/kac
Attachments: Figure 1 — Swell -Consolidation Test Results
Table 1 — Summary of Laboratory Test Results
fi'hr
H-P%KUMAR
Project No. 17-7-198
CONSOLIDATION - SWELL
CONSOLIDATION - SWELL
3
SAMPLE OF: Sandy Silt and Clay
FROM: Southwest Corner
WC = 16.2 %, DD = 106 pcf
—200 = 93
NO MOVEMENT UPON
WETTING
1.0 APPUED PRESSURE - RSV
100
SAMPLE OF: Sandy Silt and Clay with
Gypsum
FROM: North—Middle
WC = 9.2 %, DD = 110 pcf
—200 = 92
}F... 111{ n11..1. 6}'.l eMl. Y I"
ew.pin laYd, tA1 1.111.1 ,.p0.1
001 n01 b. np.vdned...Y.N in
Kwnerw M Iy(K.Il1. Ir lloyt. tin g A of
Con1n11rp.�• u1r..pp pwrpm..d H
c..k..c. win AS TI. 0-45.6.
17-7-198
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
1,0 APPLIED PRESSURE - KSF 10 - - -- -- - 100
H-PvKUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 1
TABLE 1
AR
SUMMARY OF LABORATORY TEST RESULTS
Project No. 17-7-198
SAMPLE LOCATION
BOTTOM OF
EXCAVATION
Southwest Corner
NATURAL
MOISTURE
CONTENT
(%)
16.2
NATURAL
DRY
DENSITY
(Pcf)
106
GRADATION
PERCENT
GRAVEL SAND PASSING
(%) (%) NO. 200
SIEVE
93
ATTERBERG LIMITS
LIQUID PLASTIC
LIMIT INDEX
(%) J (%)
UNCONFINED
COMPRESSIVE
STRENGTH
(PSF)
Residence
SOIL OR
BEDROCK TYPE
Sandy Silt and Clay
North -Middle 9.2
110
•
92
Southest Corner
6.6
88
87
Sandy Silt and Clay with
Gypsum
Porous Sandy Silt and Clay