HomeMy WebLinkAboutObservation of Excavation1( Kumar & Associates, s En
Geotechnical and Materials Engineers 5020 County Road 154
and Environmental Scientists Glenwood Springs, CO 81601
phone: (970) 945-7988
"" �- fax: (970) 945-8454
email: kaglenwood@kumarusa.com
An Employee Owned Company www.kumarusa.com
Office Locations: Denver (HO), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
July 15, 2024
Ron Friemel
226 Dolores Circle
Glenwood Springs, Colorado, 81601
Project No. 24-7-410
Subject: Observation of Excavation, Proposed Garage, Lot 34, West Bank Ranch PUD,
226 Dolores Circle, Glenwood Springs, Colorado
Dear Ron:
As requested, a representative of Kumar & Associates observed the excavation at the subject
site on July 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 you dated July 15, 2024.
The proposed garage will be a one- or two-story wood frame structure with a slab -on -grade floor.
We understand the foundations were designed for an allowable soil bearing pressure of
1,200 psf.
At the time of our visit to the site, the foundation excavation had been cut in one level from
about 1'/2 to 7 feet below the adjacent ground surface. The soils exposed in the bottom of the
excavation consisted of very sandy silty clay. Results of swell -consolidation testing performed
on a relatively undisturbed drive sample taken from the site, shown on Figure 1, indicate low
to moderate compressibility 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 1,200 psf should be adequate for support of the proposed garage.
The exposed soils tend to compress when wetted and there could be some post -construction
movement of the foundation if the bearing soils become wet. Footings should be a minimum
width of 18 inches 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 12 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 55 pcf for on -site soil as backfill.
Structural fill placed within floor slab areas can consist of the on -site soils compacted to at least
Ron Friemel
July 15, 2024
Page 2
95% of standard Proctor density at a moisture content near optimum. 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 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 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 (MDBC) developing in the future. If the client is concerned about
MDBC, 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 & AssoS::iates, Inc.
David A. Noteboom, Staff Engineer
Reviewed by: % Owl( I -EqS
Daniel E. Hardin, P. y
DANtkac
Attachments: Figure 1 — olidation Test Results
cc: Dave Doolan (ci a efi% lfx lanconstructi �n.c(, nm)
Kumar & Associates, Inc. a Project No. 24-7.414
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SAMPLE OF: Silty, Very Sandy Clay
FROM: Footing Grade — SE Corner
WC = 11.0 %, DID = 97 pcf
—200 = 58
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
These lest results apply only to the
amples tested. The testing report
shall not be reproduced, except in
lull, without the written approval of
Kumar and Associates, Inc. Swell
Consolidation testing performed in
accordance with ASTM D-4546.
— Arr LILU rKLJJUKL — RJh lU
100
it 24-7-410 1 Kumar & Associates I SWELL —CONSOLIDATION TEST RESULTS I Fig. 1 I