HomeMy WebLinkAboutObservation of Excavation 09.06.2022
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
September 6, 2022
Colonna Construction
Attn: Bernie Colonna
P.O. Box 1968
Rifle, Colorado 81650
colonna2012@hotmail.com
Project No. 19-7-709.A
Subject: Observation of Excavation, Proposed Residence, Lot 10, Sun Meadow Estates,
329 County Road 216 (Antonelli Lane), Garfield County, Colorado
Dear Bernie:
As requested, a representative of Kumar & Associates, Inc. observed the excavation at the
subject site on June 10, 2022 to evaluate the soils exposed for foundation support. The findings
of our observations and recommendations for the foundation design are presented in this report.
We previously conducted a subsoil study for design of foundations at the site and presented our
findings in a report dated January 2, 2020, Project No. 19-7-709.
The new house will be 2,500 square feet, one story wood frame structure over a crawlspace.
The attached 3-car garage will have a slab-on-grade floor.
At the time of our visit to the site, the foundation excavation had been cut in three levels from
2 to 6 feet below the adjacent ground surface. The soils exposed in the bottom of the excavation
consisted of stiff sandy silt. Results of moisture/density and percent finer than sand size
gradation testing performed on samples taken from the site, shown on Table 1, indicate the soils
have low collapse potential under conditions of light loading and wetting. No free water was
encountered in the excavation and the soils were slightly moist.
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 1,500 psf. Loose and disturbed soils should be removed in the footing areas
to expose the undisturbed natural soils. An underdrain should not be provided for the shallow
crawlspace and slab-at-grade garage floor. Other recommendations presented in our previous
report which are applicable, especially those to keep the bearing soils dry, should also be
observed.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavation and the previous subsurface exploration at the site. Variations
in the subsurface conditions below the excavation could increase the risk of foundation
movement. We should be advised of any variations encountered in the excavation conditions for
TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
Project No. 19-7-709.A
SAMPLE LOCATION NATURAL MOISTURE CONTENT
NATURAL DRY DENSITY
GRADATION
PERCENT
PASSING NO. 200 SIEVE
ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH SOIL TYPE SAMPLE DEPTH GRAVEL SAND LIQUID LIMIT PLASTIC INDEX (%) (%)
(ft) (%) (pcf) (%) (%) (psf)
HD-1 Footing
grade 4.5 99 86 Sandy Silt
HD-3 Footing
grade 9.2 97 83 Sandy Silt