HomeMy WebLinkAboutObservation of Excavation 10.28.2022
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
October 28, 2022
Hank Hayes
1962 County Road 132
Glenwood Springs, Colorado 81601
the4x4kid@hotmail.com
Project No. 22-7-696
Subject: Observation of Excavation, Proposed Detached Garage, 1962 County Road 132,
Mitchel Creek, Garfield County, Colorado
Dear Hank:
As requested, a representative of Kumar & Associates observed the excavation at the subject site
on October 20, 2022 to evaluate the soils exposed for foundation support. The findings of our
observations and recommendations are presented in this report. The services were performed in
accordance with our agreement for professional engineering services to you dated October 19,
2022.
The garage will be a single-story structure cut into the hillside slope. The floor will be slab-on-
grade. The building has been designed to be supported on spread footings sized using an
allowable soil bearing pressure of 2,000 psf. The foundation design was based on a previous soil
observation for the main residence at the site by Hepworth-Pawlak Geotechnical (H-P Geotech),
report dated November 30, 1999, Job No. 199 921. We have a copy of that report.
At the time of our site visit, the foundation excavation which was nearly complete had been cut
in one level up to about 20 feet below the adjacent ground surface daylighting to the west. The
south side of the excavation was not complete at this time. The soils exposed in the bottom of
the excavation consisted primarily of relatively dense, slightly silty sandy gravel with small
cobbles. In the deeper cut area along the east side, hard sandstone/siltstone bedrock was exposed
at subgrade. The results of a gradation analysis performed on a disturbed bulk sample of soils
(minus 3-inch fraction) obtained from the bottom of the excavation are presented on Figure 1.
Groundwater was encountered in the excavation in the northeast cut area and was being
controlled by a shallow trench gravity out-letting to the south. The soils and bedrock were moist
to wet.
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 2,000 psf. There is some risk of differential settlement due primarily to the
variable bearing conditions. Loose and disturbed soils should be removed in the footing areas to
expose the undisturbed natural granular soils or bedrock. The water seepage into the excavation
should continue be collected and diverted away from the footing areas and any softened soils and
mud removed before concrete placement. The bearing soils should be protected from frost and
Kumar & Associates