HomeMy WebLinkAboutObservation of ExcavationIC+A Geotechnical and Materials Engineers 5020 County Road 154
and Environmental Scientists Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
An Employee Owned Company www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
March 22, 2022
Ross Trulove
540 Cactus Flats Road
Carbondale, Colorado 81623
ross()tonkaexcavation.com
Project No. 22-7-235
Subject: Observation of Two Pit Excavations, Proposed Addition, 540 Cactus Flats Road,
Garfield County, Colorado
Dear Ross:
As requested, the undersigned representative of Kumar & Associates observed the excavation at
the subject site on March 16, 2022 to evaluate the soils exposed for foundation support. The
findings of our observations and recommendations for the foundation support are presented in
this report. The services were performed in accordance with our agreement for professional
engineering services to you dated March 16, 2022.
The proposed addition will consist of two stories of wood frame construction added to the north
side of the existing two-story house. Foundations will consist of spread footing foundations.
The ground floor will be slab -on -grade.
At the time of our visit to the site, two pits were excavated just west of the proposed addition.
The soils exposed in the pit excavations were similar and consisted of 1 to 1!/2 feet of organic
sandy silty clay topsoil overlying relatively stiff, slightly clayey sandy silt down to the pit depths
of 4 to 5 feet. No free water was encountered in the pit excavations and the soils were slightly
moist to 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
soil bearing pressure of 2,000 psf can be used for support of the proposed addition. The exposed
soils tend to compress when wetted and there could be some post -construction settlement of the
foundation if the bearing soils become wet. Footings should be a minimum width of 18inches
for continuous walls and 2 feet for columns. Loose and disturbed soils and existing fill in
footing areas should be removed and the bearing level extended down to the undisturbed natural
soils. The bearing soils should be protected against frost and concrete should not be placed on
frozen soils. Exterior footings should be provided with adequate soil cover above their bearing
elevations for frost protection (typically 3 feet). Continuous foundation walls should be
reinforced top and bottom to span local anomalies such as by assuming an unsupported length of
at least 10 feet. Foundation walls acting as retaining structures (if any) should also be designed
to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 50 pcf for
on-site soil as backfill. A perimeter foundation drain should not be needed for the proposed
Ross Trulove
March 22, 2022
Page 2
slab -on -grade ground floor construction. Structural fill placed within floor slab areas can consist
of the on-site soils compacted to at least 95% of standard Proctor density at a moisture content
near optimum. Backfill placed around the structure should be compacted and the surface graded
to prevent ponding within at least 10 feet of the building.
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,
Kumar & ".
Daniel E. I
DEH/kac
Kumar & Associates, Inc. Project No. 22-7-235
