HomeMy WebLinkAboutObservation of Excavation 04.12.2021rc iiry*å#itrtin""r;;*'*
An Employos Owned Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email : kaglenwood@kumarusa.com
www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
April12,202t
Jose Salazar
26 Native Springs Drive
Rifle, Colorado 81650
salazarservices@qmail.com
Project No. 20-7-434.4
Subject: Observation of Excavation, Proposed Residence, Area of Boring 2,East of Rifle
Village South, Garfield County, Colorado
Dear Jose:
As requested, a representative of Kumar & Associates, Inc. observed the excavation at the
subject site on April 7,2021 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 site and presented our
findings in a report dated September 2l,2020,Project No. 20-7-434.
At the time of our visit to the site, the building site had been graded relatively flat with cut from
2 feet below the adjacent ground surface on the south side to about llz feet of fill on the north
side. The soils exposed in the bottom of the excavation consisted of stiff sandy clay and silt on
the south side to sandy silt and clay fill on the north side. Results of swell-consolidation testing
performed on samples of the natural and fill soils taken from the site, shown on Figures I and2,
indicate the natural soils and fill soils are collapsible (settlement when wetted under light load)
and have significant settlement under additional loading. No free water was encountered in the
excavation and the soils were slightly moist.
The natural soil conditions exposed in the excavation are generally consistent with those
previously encountered on the site and can be used for support ofspread footings designed for
the recommended allowable bearing pressure of 1,200 psf with significant settlement risk. We
did not provide recommendations for footings on fill in our previous report. Loose and disturbed
soils should be removed in the footing areas to expose the undisturbed natural soils. The
previous test results on the native soils indicated much lower collapse potential so precautions to
keep the bearing soils dry will be critical to limiting foundation settlement and building distress.
Other recommendations presented in our previous report which are applicable should also be
observed.
The recommendations submitted in this leffer 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
Jose Salazar
Apnl 12,2021
PageZ
frrundation rnovçmont. We nhoukl hc aclvised of any variations encountered ilr the oxoavation
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,
Kumar & Associates, Inc.
Daniel E.
Rev. by: SLP
DEH/kac
attachments Figures I and2 - Swell-Consolidation Test Results
Kumar & Associates, lnc. 6'Project No. 20.7.434.A
SAMPLE OF: Sondy Silt ond Cloy
FROM: South West Corner
WC = 1O.8 %, DD = 87 pcf
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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SWELL-CONSOLIDATION TEST RESULTS Fig. 120-7 -434.4 Kumar & Associates
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APPLIED PRESSURE - KSF 10 t00
SAMPLE OF: Sondy Silt ond Cloy Fill
FROM: North Wesl Corner
WC = 8.3 o/o, DD = 95.7 pcf
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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20-7 -434.A Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Flg. 2
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