HomeMy WebLinkAboutObservation of Excavation 02.16.2024rcn *iffifi'f,1'trfttrn'yr; * *, *5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
An Employec Owncd Compony wwril.kumarusa.com
Office Locations: Denver (He), parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
February 16,2024
Wood Doctor Construction
Attn: Bruce Hasselbring
300 Oak Run Drive
Carbondale, Colorado 81 623
brucehG)sooris.net
Project No. 24-7-138
Subiect observation of Excavation, Proposed Addition, Low Residence, g7l county
Road 107, Carbondale, Colorado
Bruce:
As requested, a representative of Kumar & Associates observed the excavations at the subject
site on February 13 and February 15,2024 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 wood Doctor construction dated February 1,2024.
The proposed additions will be one-story wood frame structures over crawlspaces. Spread
footing foundations designed for an allowable soil bearing pressure of 1,500 psf were assumed
for design.
At the time of our visits to the site, the foundation excavations had each been cut to one main
level between about 2 lq and 4 feet below the adjacent ground surface for the east addition and
about 4 feetbelow the adjacent ground surface for the west addition. The soils exposed in the
bottom of the excavation for the east addition consisted of medium dense silty sand with
scattered gravel and boulders, and hard medium coarse sandstone bedrock in the excavation for
the west addition. Results of swell-consolidation testing performed on samples taken from the
site, shown on Figure 1, indicate the silty sand soils are moderately compressible under
conditions of loading and wetting.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
construction, spread footings placed on the undisturbed natural soil designed for an allowable
soil bearing pressure of 1,500 psfshould be adequate for support ofthe proposed additions.
The exposed soils tend to compress when wetted and there could be some post-construction
settlement of the foundation if the bearing soils become wet. Footings should be a minimum
width of 16 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' The bearing soils should be protected against frost and concrete should not be placed on
ftozen 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
Wood Doctor Construction
February 16,2024
Page2
to span local anomalies such as by assuming an unsupported length of at least l0 feet.
Foundation walls 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 granular soil as
backfill. Backfill placed around the structure should be compacted 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 10 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 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,
Kirmar & Ass*ciates, ine
David A. Noteboom, Staff
Reviewed by:
Robert L. Duran, P
RLD/kac
attachments Figure 1-Samples
Figure 2 - Swell Consolidation Test Results
Table I - Summary of Laboratory Test Results
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Kumar & Associates, lnc. o
Project No.24-7-138
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TABLE 1
SUMMARY OF LABORATORY TEST RESULTS
No.24-7-138
sotl 0R
BEDROCK TYPE
Silty Sand
Silty Sand
PSF)
UNCONFINED
COMPRESSIVE
STRENGTH
(/"1
Pt-ASTtC
INDEX
MI
LIQUID LIMIT
PERCENT
PASSING NO.
200 slEvE
2l
SAND
(V")
GRADATION
(/"1
GRAVEL
NATURAL
DRY
DENSITY
(pcll
85
95
(olol
NATURAL
MOISTURE
CONTENT
t9.7
9.8
SAMPLE LOCATION
East Side
Excavation @
z', g'))
Excavation @
4',