HomeMy WebLinkAboutObservation of Excavation
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
email: kaglenwood@kumarusa.com
www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
November 3, 2025
Red House Architecture
Attn: Bruce Barth
815 Blake Avenue
Glenwood Springs, Colorado 81601
bruce@redhousearchitecture.com
Project No. 25-7-656
Subject: Observation of Excavation, Proposed Addition to Existing Residence, Lot 5,
Mountain Springs Ranch, 4544 Mountain Springs Road, Garfield County, Colorado
Dear Bruce:
As requested, a representative of Kumar & Associates observed the excavation at the subject
site on October 27, 2025 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 Red House Architecture dated October 27, 2025.
The proposed addition will be built on the uphill, east side of the existing residence. The addition
will be a single-story wood-frame structure with a slab-on-grade ground floor. The addition has
been designed to be supported on spread footings sized for an allowable bearing pressure of
3,000 psf with a minimum deadload pressure of 1,000 psf based on the subsoil study report by
Hepwroth-Pawlak Geotechnical, Job No. 199 272 dated April 15, 1999 for the existing residence.
At the time of our visit to the site, the foundation excavation had been cut in one level from 2½ to
4 feet below the adjacent ground surface. The soils exposed in the bottom of the excavation
consisted of natural sandy clay on the east side of the addition area with basement wall backfill
exposed on the west side of the addition area near the existing residence. When tested with a
T-probe at the time of our site visit, the natural clay was penetrated 3 to 6 inches and the fill was
penetrated between 12 and 30 inches (full probe length). Results of swell-consolidation testing
performed on a sample of natural sandy clay taken from the site, shown on Figure 1, indicate the
soils are slightly expansive when wetted under load. No free water was encountered in the
excavation and the soils were slightly moist to moist.
The foundation wall backfill is variable density and not suitable for support of the proposed
addition. The footing excavation can be deepened through the backfill to expose natural soils, or
the proposed footings on the west side of the addition can be designed to be supported on helical
piers installed into the natural clay soils below the fill.
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 3,000 psf with a minimum deadload pressure of 1,000 psf can be used for
support of the proposed addition. The exposed soils tend to expand when wetted and there could
be some post-construction movement of the foundation if the bearing soils become wet. Footings
should be a minimum width of 16 inches for continuous walls and 2 feet for columns. Loose
Kumar & Associates