HomeMy WebLinkAboutObservation of Excavation
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 25, 2021
Abel Esteban 461 North Midland Avenue
New Castle, Colorado 81647
ae@impseg.com Project No. 17-7-245.01
Subject: Observation of Excavation, Proposed Shop Building, near 6303 County Road 214, West of New Castle, Garfield County, Colorado
Dear Abel:
As requested, a representative of Kumar & Associates observed the excavation at the subject site
on October 14, 2021 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 13,
2021.
H-P/Kumar (now Kumar & Associates) prepared a subsoil study for foundation design of a
previously proposed residence at the site and presented our findings in a report dated April 21,
2017, Project No. 17-7-245. The shop building, which will be a single story steel frame and
metal structure with a slab-on-grade floor, will be located a few hundred feet southwest of our
previous boring at the site. The shop building has been designed to be supported on spread
footings using an allowable soil bearing pressure of 3,000 psf by the structural engineer.
At the time of our site visit, the foundation excavation which was essentially complete had been
cut in two levels from about 1½ to 3 feet below the adjacent ground surface. The soils exposed
in the bottom of the excavation consisted of stiff, very sandy silty clay. Results of swell-
consolidation testing performed on samples taken from the site, shown on Figure 1, indicate the
soils are moderately compressible under conditions of loading and wetting with no swell
potential. The laboratory testing is summarized in Table 1. No groundwater was encountered in
the excavation and the soils were slightly moist to moist.
The soil conditions exposed in the excavation are generally consistent with those previously
encountered on the site and suitable for support of spread footings designed for an allowable
bearing pressure of 3,000 psf. A minimum dead load pressure on the footings due to potentially
expansive clay soils does not appear needed. There could be some movement (likely settlement)
if the bearing soils were to become wetted and precautions should be taken to prevent wetting.
Prior to the footing construction, all loose disturbed soils should be removed in the footing areas
to expose the undisturbed natural soils, and the subgrade compacted. The bearing soils should be
protected from frost and concrete should not be placed on frozen soils. Other recommendations
and precautions presented in our previous report which are applicable should also be observed.
Kumar & Associates
TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No. 17-7-245.01
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)
Southwest Portion 17.8 94 51 Very Sandy Silty Clay
Northeast Portion 12.0 95 Very Sandy Silty Clay