HomeMy WebLinkAboutObservation of Excavation 11.01.2016-P�INMAR
Geo echnical Engineering i Engineering Geology
Materials Testing 1 Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fa,c (970) 945-8454
Email: hpkglenwood@kumarusa.com
November 1, 2016
Glen McPherson
2291 County Road 311
New Castle, Colorado 81647
gmcpherson@mastetpetroleum.com
Office Locations: Parker, Glenwood Springs, and Silverthome, Colorado
Project No. 16-7-546
Subject: Observation of Excavation, Proposed Addition to Garage, 2299 County Road 311
(Divide Creek Road) South of Silt, Garfield County, Colorado
Dear Glen:
As requested, a representative of HP/Kumar observed the excavation at the subject site on
October 27, 2026 to evaluate the soils exposed for foundation support. The findings of our
observations and recommendations for the foundation design are presented in this report. The
services were performed in accordance with our agreement for professional engineering services
to you, dated October 26, 2016.
The addition will be attached to the south side of the existing garage and be a single story of
wood frame construction with a slab -on -grade floor. The building has been designed to be
supported on spread footings.
At the time of our site visit, the foundation excavation which was essentially complete had been
cut in one level from about 21/2 to 3' feet below the adjacent ground surface. The soils exposed
in the bottom of the excavation consisted of medium dense, silty sand with scattered silty clay
pockets. Results of swell -consolidation testing performed on samples taken from the site, shown
on Figure 1, indicate the soils are moderately compressible under conditions of loading and
wetting with a low hydro -compression potential. No free water was encountered in the
excavation and the soils were generally moist.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an allowable
bearing pressure of 1,500 psf can be used for support of the proposed addition. There may be
some foundation settlement, especially if the bearing soils were to become wetted, and
precautions should be taken to prevent wetting. The settlement may be differential with respect
to the existing structure which should be considered in the design. Footings should be a
minimum width of 16 inches for continuous walls and 2 feet for columns. Loose and disturbed
soils in footing areas should be removed and the bearing level extended down to the undisturbed
natural soils, and the subgrade compacted. Exterior footings should be provided with adequate
Glen McPherson
November 1, 2016
Page 2
soil cover above their bearing elevations for frost protection. Continuous foundation walls
should be well reinforced top and bottom to span local anomalies such as by assuming an
unsupported length of at least 12 feet. Structural fill placed within floor slab areas can consist of
the on-site soils compacted to at least 95% of standard Proctor density (SPD) at a moisture
content near optimum. Backfill placed around the structure should be compacted to at least 90%
SPD (95% in slab areas) and the surface graded to prevent ponding within at least 10 feet of the
building. Landscape that requires regular heavy irrigation, such as sod, and sprinkler heads
should not be located within 10 feet of the foundation.
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 greater 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,
H-P� KUMA -, tiim
F r .�
1 �� . i
•
E INr i
-
David A. Young, P.E;
DAY/ksw s': 4ba%.,.�..r. a '
attachment Figure 1, S,ettitYriMdation Test Results
H -P KUMAR
Project No. 16-7-546