HomeMy WebLinkAboutObservation of Excavation 05.11.2022rcn Xuns&AsftffiAhc.@
Geotedrnicaland tulaierials Engineen 5020 County Road 154
and Environnentalscientists Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
An Employcc olmcd co,mpony www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
May 17,2022
Rob & Kim Velasquez
2906 County Road 113
Carbondaleo Colorado 81623
kimmer.velasq uez@ email. com
Project No. I 7-7-1 39.01
Subject: Observation of Excavation, Proposed Garage/ADU, Northwest of Existing
Residence, 3064 County Road 113, Carbondale, Colorado
Dear Rob & Kim:
As requested, the undersigned representative of Kumar & Associates observed the excavation at
the subject site on May 9, 2022 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 you dated May 9, 2022. We previously observed the excavation for the
existing residence as described in a letter dated June 9, 2017, Project No. 17-7-139.
The proposed garage/ADU will be a two-story wood frame structure with a slab-on-grade ground
floor. Foundations were designed for an allowable soil bearing pressure of 1,500 psf.
At the time of our visit to the site, the foundation excavation had been cut in one level from 3 to
7 feetbelow the adjacent ground surface. The soils exposed in the bottom of the excavation
consisted of medium stiff sandy silty clay with scattered rocks up to cobble size. No free water
was encountered in the excavation and the soils were moist.
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 1,500 psf can be used for support of the proposed building. Footings
should be a minimum width of 20 inches for continuous walls and2 feet for columns. Loose and
disturbed soils in footing areas should be removed and the bearing level extended down to the
undisturbed natural soils. Exterior footings should be provided with adequate soil cover above
their bearing elevations for frost protection. Continuous foundation walls should be reinforced
top and bottom to span local anomalies such as by assuming an unsupported length of at least
12 feet. A perimeter foundation drain should not be needed for the proposed slab-at-grade floor
construction. Structural fill placed within floor slab areas can consist of the on-site soils
compacted to at least 95% of standard Proctor density at a moisture content near optimum.
Backfill placed around the skucture should be compacted and the surface graded to prevent
ponding within at least 10 feet of the building.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavation and do not include subsurface exploration to evaluate the
Rob & Kim Velasquez
May 11,2022
Page2
subsurface conditions within the loaded depth of foundation influence. This study is based on
the assumption that soils beneath the footings have equal or better support than those exposed.
The risk of foundation movement may be greater than indicated in this report because of possible
variations in the subsurface conditions. Our services do not include determining the presence,
prevention or possibility of mold or other biological contaminants (MOBC) developing in the
future. If the client is concerned about MOBC, then a professional in this special field of
practice should be consulted.
If you have any questions or need further assistance, please call our offtce.
Sincerely,
Kumar & Associates. Inc
Daniel E. Hardin, P.E.
Rev. by: SLP
DEHlkac
Kumar & Associates, lnc. @ Project No. 17-7-139.01