HomeMy WebLinkAboutObservation of Excavation 08.15.2022
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
August 15, 2022
Mountain Town Builders LLC
Attn: Wes Miller
P. O. Box 405
New Castle, Colorado 81647
wes@mountaintownbuilders.com
Project No. 21-7-303.01
Subject: Observation of Excavation, Proposed Residence, 1214 County Road 238, Garfield
County, Colorado
Dear Wes:
As requested, a representative of Kumar & Associates observed the excavation at the subject site
on June 23, 2022 to evaluate the materials exposed for foundation support. The findings of our
observations and recommendations are presented in this report. The services are supplemental to
our agreement for professional services to Mountain Town Builders LLC dated We previously
conducted a subsoil study for design of foundations at the site and presented our findings in a
report dated March 26, 2021, Project No. 21-7-303.
The proposed construction is similar to that discussed in our previous report. Spread footings
sized for an allowable soil bearing pressure of 2,000 psf were recommended for foundation
support with some risk of movement.
At the time of our site visit, the foundation excavation which was essentially complete had been
cut in two levels from about 2 to 13 feet below the adjacent ground surface. The materials
exposed in the bottom of the excavation consisted of weathered to hard claystone/siltstone with
some interlayered sandstone bedrock in about the southern ⅔ and medium dense, very clayey
silty sand in about in the northeastern ⅓. Results of swell-consolidation testing performed on
samples taken from the site, shown on Figure 1, indicate the weathered claystone/siltstone is
slightly compressible under conditions of loading and wetting with a minor swell potential when
wetted under a constant 1,000 psf surcharge. The results of the laboratory testing are
summarized in Table 1. No groundwater was encountered in the excavation and the soils and
bedrock were slightly moist.
The 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. The risk of movement is due to the variable bearing conditions
and especially if the bearing soils or bedrock were to become wetted, and precautions should be
taken to prevent wetting. Prior to the footing construction, all loose disturbed soils and bedrock
should be removed and the subgrade moistened and compacted. Other recommendations
presented in our previous report which are applicable should also be observed.
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 21-7-303.01
SAMPLE LOCATION NATURAL MOISTURE CONTENT
NATURAL DRY DENSITY
GRADATION
PERCENT PASSING NO. 200 SIEVE
ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH SOIL OR BEDROCK TYPE IN BOTTOM OF EXCAVATION GRAVEL SAND LIQUID LIMIT PLASTIC INDEX (%) (%)
(%) (pcf) (%) (%) (PSF)
South-Central
Portion 8.2 116 Weathered Claystone/
Siltstone
Northwest Portion 6.8 104 Very Clayey Silty Sand