HomeMy WebLinkAboutObservation of Excavation 04.11.2023lGrtffii,[mmifü'-"
An EmÞloycc Ournsd Compony
5020 Gounty Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945.8454
email: kaglenwood@kumarusa.com
www.kumarusa.com
O'ffice Locations: Denver (HQ), Parker, Colorado Spings, Fort Cdlins, Glenvrcod Søtngs, and Summit C.;q¡nty, Colorado
April 11,2023
Mark Bunchman
2859 County Road 335
New Castle, Colorado 81647
mbunchman@grnail.com
Project No.23-7-231
Subject:Observation of Excavation, ProposedGaragelShop Building, 2859 County Road
335, Garfield County, Colorado
Dear Mark:
As requested, a representative of Kumar & Associates observed the excavation at the subject site
on April 7,2023, 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 April 5,2023.
The garagelshop building will be a single-story structure detached from the main residence. The
building has been designed to be supported on a thickened slab foundation assuming an
allowable soil bearing pressure of 1,500 psf by the structural engineer.
At the time of our site visit, the foundation excavation had been cut in one level up to about 2
feet below the adjacent ground surface and daylighting to the northwest. The soils exposed in
the bottom of the excavation consisted of stiff, sandy siþ 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. No groundwater was
encountered in the excavation and the soils were generally moist.
Considering the conditions exposed in the excavation and the nature of the proposed
constructiono a thickened slab foundation placed on the undisturbed natural soils designed for an
allowable bearing pressure of 1,500 psf can be used for support of the proposed building. The
exposed soils may tend to compress some when wetted and there could be some post-
¿onstruction settlement of the foundation if the bearing soils become wet. Precautions should be
taken to prevent wetting of the bearing soils. A reduced frost cover for the foundation should be
feasible provided ground insulation for the foundation is provided and some risk of frost heave is
Mark Bunchman
April 11,2023
Page2
acceptable. Prior to the foundation construction, all loose disturbed soils should be removed, and
the subgrade compacted. The foundation should be well reinforced with both longitudinal and
transverse steel to reduce the effects of some settlement or heave. Structural fill placed below
the slab can consist of the on-site soils compacted to at least 95% of standard Proctor density
(SPD) at a moisture content near optimum. Backfill placed around the structure should be
compacted to at least 90% SPD and the surface graded to prevent ponding within at least 10 feet
of the building. Landscape that requires regular heavy irrigation, such as sod, and sprinkler
heads should not be located within 5 feet of the foundation.
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 excavation 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.
If you have any questions or need further assistance, please call our ofñce.
Sincerely,
Kumar & AssoeÍate$" Inc.
David A. Young, P.E.
DAY/ljf
Attachment Figure l, Swell-Consolidation Test Results
Kumar & Associates, lnc. É Project No.23"7.231
SAMPLE OF: Sondy Silly Cloy
FROM: Bottom of NE Footing Pod Excqvotion
WC = 18.7 96, DD = 93 pcf
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ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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23-7-231 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS 1Fig.
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