HomeMy WebLinkAboutObservation of Excavation 08.12.20221(+AKumar &Associates, Inc
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
August 12, 2022
Jack Wheeler
Conceptone Group
183 N. 12th Street
Carbondale, Colorado 81623
wheeler(&,,conceptonegroup. com
Project No. 22-7-563
Subject: Observation of Excavation, Proposed Residence, 48 Highpoint Drive, Lot 21,
Phase 1, Springridge Reserve, Garfield County, Colorado
Dear Jack:
As requested, the undersigned representative of Kumar & Associates observed the excavation at
the subject site on August 11, 2022 to evaluate the materials 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 August 11, 2022.
The proposed residence will be two stories with a slab -on -grade floor. The proposed detached
shop/garage will be 11/2 stories with a slab -on -grade floor.
At the time of our visit to the site, the foundation excavation had been cut in two levels from 1 to
8 feet below the adjacent ground surface. The garage/shop excavation was mostly complete and
the house excavation was still underway. The materials exposed in the bottom of the excavations
consisted of weathered to hard, Maroon formation bedrock. The bedding dip of the bedrock was
down to the southwest at about 45 degrees. No free water was encountered in the excavation and
the bedrock was slightly moist.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural bedrock designed for an
allowable bearing pressure of 4,000 psf can be used for support of the proposed residence and
garage/shop. The exposed bedrock should have only minor settlement potential. Footings
should be a minimum width of 16 inches for continuous walls and 2 feet for columns. Loose and
disturbed bedrock in footing areas should be removed and the bearing level extended down to the
undisturbed natural formation rock. Exterior footings should be provided with adequate soil
cover above their bearing elevations for frost protection. 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 should also be designed to resist
a lateral earth pressure based on an equivalent fluid unit weight of at least 45 pcf for on -site well -
broken bedrock or a suitable imported granular soil as backfill. A perimeter foundation drain
should be provided to prevent temporary buildup of hydrostatic pressure behind the basement
Jack Wheeler
August 12, 2022
Page 2
walls and prevent wetting of the lower level. Structural fill placed within floor slab areas can
consist of imported screened rock or road base 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 materials
exposed within the foundation excavation. This study is based on the assumption that bedrock
beneath the footings have equal or better support than those exposed. 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, In
:4
Daniel E. Hardin, P.
DEH/kac
Kumar & Associates, Inc. 0' Project No. 22.7-563