HomeMy WebLinkAboutObservation of Excavation 11.30.2017H#'KUMAR
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
November 30, 2017
Gabe Brubacher
516 Honeysuckel Drive
New Castle, Colorado 81647
gbrubacher@gmail.com
Project No. 17-7-327.01
Subject: Observation of Excavation, Proposed Residence, Lot 19, Cedar Hills, 4261
County Road 214, Garfield County, Colorado
Dear Gabe:
As requested by James Martinez, a representative of H-P/Kumar observed the excavation at the
subject site on November 1, 2017 to evaluate the soils exposed for foundation support. The
findings of our observations and recommendations are presented in this report. The services are
supplemental to our agreement for professional services to you dated April 18, 2017.
We previously conducted a subsoil study for design of foundations at the site and presented our
findings in a report dated May 23, 2017, Project No. 17-7-327. The proposed construction is
generally similar to that discussed in our previous report. Spread footings bearing on the natural
soils designed for an allowable bearing pressure of 1,500 psf were recommended for foundation
support with some risk of settlement.
At the time of our site visit, the foundation excavation which was essentially complete had been
cut in two levels from about 1 to 4 feet below the adjacent ground surface. The soils exposed in
the bottom of the excavation consisted of stiff, sandy silty clay. Results of swell -consolidation
testing performed on samples taken from the site, shown on Figure 1, indicate the soils are
slightly compressible under conditions of natural moisture and light loading, with a moderate
collapse potential when wetted under a constant 1,000 psf surcharge. The sample showed
moderately high compressibility when loaded after wetting. The sample was probably partly
disturbed due to the sampling process. No free water was encountered in the excavation and the
soils were slightly moist.
Gabe Brubacher
December 1, 2017
Page 2
The soil conditions exposed in the excavation are consistent with those previously encountered
on the site and suitable for support of spread footings designed for the recommended allowable
bearing pressure of 1,500 psf. The risk of settlement is primarily if the bearing soils were to
become wetted and precautions should be taken to prevent wetting. Prior to the footing
construction, all loose disturbed soils should be removed to expose the undisturbed natural soils
and the subgrade 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 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 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 changes to recommendations contained in this letter.
If you have any questions or need further assistance, please call our office.
Sincerely,
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attachment Figure 1, Swell -Consolidation Test Results
cc: Garfield County Building Department - Jim Wilson (jwilsonC@garfield-countv.com)
H-P%KUMAR
Project No. 17-7-327.01