HomeMy WebLinkAboutObservation of Pit Excavations 02.09.2024rcn $,'iffi'1ffi,#rn"'n3;'**'
An Employcc Orncd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email : kaglenwood@kumarusa.com
www.kumarusa.com
Ofiice Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
February 9,2024
Shane Wiescamp
1977 Covnty Road 210
Rifle, Colorado 81650
wiescamps@msn'com
project No.24-7-r4r
Subject Observation of Pit Excavations, Proposed Shop Building,1977 County Road 210,
East of Rifle, Colorado
Dear Shane:
As requested, a representative of Kumar & Associates observed the pit excavations at the subject
site on February 2,2024 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 February 2,2024.
The proposed shop will be a tall one-story steel frame strucflre with a slab-on-grade floor.
At the time of our visit to the site, two pits were excavated in the proposed building area. The
soils exposed in the pit excavations consisted of about 6 inches of road base over natural, sandy
silty olay down to the bottom of fhe pits at 3Yzto 4 feet. Results of swell-consolidation testing
performed on samples taken from the site, shown on Figures I and 2,indicate the soils are
moderately compressible under conditions of loading and wetting. The results of a percent finer
than sand size gradation analysis and Atterberg Limits testing performed on a sample obtained
from Pit 2 are shown on Table I and indicate the soils are sandy silty clay. No free water was
encountered in the pit excavations and the soils were moist.
Considering the conditions exposed in the excavation and the natwe of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an allowable
soil bearing pressure of 1,500 psf should be adequate for support of the proposed shop. 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 l8 inches for continuous walls and2 feet for columns. Loose and disturbed soils and
existing fill 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 frozen 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 (if any) should also be designed
Shane Wiescamp
February 9,2024
Page2
to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 55 pcf for on-
site soil as backfill. A perimeter foundation drain should not be needed for the proposed slab'on-
grade floor level. Structural fill placed within floor slab areas can consist of a suitable imported
sandy gravel soil such as %-inch road base compacted to at least 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 5 feet of the building.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the two pit excavations. 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. We should observe the footing subgrade prior to forming of footings. 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 concemed 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 & Associates, I
Daniel E. Hardin, P.
Rev. by: SLP
DEHlkac
attachments Figures 1 and2- Swell-Consolidation Test Results
Table I - Summary of Laboratory Test Results
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Kumar & Associates, lnc. o Project No.24-7-141
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SAMPLE OF: Sondy Sllty Clcy
FROM:PltloS'
WC = 7,7 %, DD = 108 pcf
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
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24-7-141 Kumar & Associates SWELL_CONSOLIDATION TEST RESULTS Fig. 1
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SAMPLE OF: Sondy Sllty Cloy
FROM:Pii2O2.5'
WC = 11,6 %, DD = 106 pcf
ADDITIONAL COMPRSSSION
UNDER CONSTANT PRESSURE
DUE TO WEfiING
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SWELL-CONSOLIDATION TEST RESULTS Fig. 224-7-141 Kumar & Associates
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lcn lfurmr & Associates, lnc. @
Geotechnical and Materials Engineers
and Environmental Scientists
TABLE 1
SUilITIARY OF LABOMTORY TEST RESULTS
lla. 2+7-141
2
1
PIT
2% -3
2%
J
m
DEPT}I
SAIPLE LOCATIOI{
10.3
.611
7.7
{%}
NATURAT
TOSTURE
coirTEhn
106
108
NATURAT
DRY
DENSlrY (%)
GRAVEL
(%)
SA}ID
64
PERCENT
PASSING NO.
2(nSEVE
20
MI
LKIIJID LITF
5
PLASTIC
INDB(
l0[]
ATIERBERGUTITS
(D6fl
UNCOf.IFINED
COilPRESSNE
STRENGTH
Sandy Silty Clay
Sandy Silty Clay
Sandy silty Clay
SOL TYPE