HomeMy WebLinkAboutObservation of Excavation 06.26.2023.1~
l(+A Kumar& ,tnc.•
Geotechnical and Materials Engineers
and Environmental Scientists
5020 County Road 154
Glenwood Springs, CO 81601
phone: {970) 945-7988
fax: {970) 945-8454
email: kaglenwood@kumarusa.com
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An Employee Owned Company www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
June 26, 2023
Gerd Zeller
P.O. Box 37
Aspen, Colorado 81612
gmz52@aol.com
Subject:
Dear Gerd:
Project No. 23-7-380
Observation of Excavation, Proposed Residence, 55 River Park Lane, Lot F3,
Aspen Glen Filing 1, Carbondale, Colorado
As requested, a representative of Kumar & Associates observed the excavation at the subject site
on June 21, 2023 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 June 21 , 2023.
The proposed residence will be a one and two story wood frame structure over a walkout
basement level. The basement and garage will have slab-on-grade floors.
At the time of our visit to the site, the foundation excavation had been cut in four levels from 2 to
9 feet below the adjacent ground surface. The soils exposed in the bottom of the excavation
consisted ofrelatively dense, slightly silty sand and gravel with cobbles and small boulders. No
free water was encountered in the excavation and the soils were slightly moist.
Considering the conditions exposed in the excavation and the nature of the proposed
consh·uctio~ spread footings placed on the undisturbed natural oil designed for an allowable
soil bearing pressure of 3,000 psf can be used for suppmt of the proposed residence. Footings
should be a minimum width of 16 incl es for continuous walls and 2 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 1 O
feet. Foundation wall acting as retaining structures should also be designed to resist a lateral
earth pressure based on an equivalent fluid unit weight of at least 45 pcf for on-site soil as
backfill . A perimeter foundation drain should be provided to prevent temporary buildup of
hydrostatic pressure behind the basement walls and prevent wetting of the lower level.
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 optimwn. Backfill placed around the
structure should be compacted and the surface graded to prevent pond ing within at least 1 O feet
of the building.
GerdZeller
June 26, 2023
Page2
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
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. In order to reveal the nature and extent of variations in
the subsurface conditions below the excavation, drilling would be required. It is possible the
data obtained by subsurface exploration could change the recommendations contained in this
letter. 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 office.
Sincerely,
Kumar & Assoch
DEH/kac
Kumar & Associates, Inc. ® Project No. 23-7-380