HomeMy WebLinkAboutObservation of Excavation 03.26.2024I &n hwfift ng',*t'F;,'*u,,
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email : kaglenwood@kumarusa.com
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Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood $prings, and $ummit County, Colorado
March 26,2024
Sam Jurmu
699 Bristlecone Way
Silt, Colorado 81652
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Project No.24-7-204
Subject: Observation of Excavation, Proposed Shop, 164 Scutter Ridge Road, Rifle
Colorado
Dear Mr. Jurmu:
As requested, a representative of Kumar & Associates observed the excavation at the subject site
on March 20,2024 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 March 19,2024.
The proposed shop will be 32 feet by 48 feet in plan size. We understand that a thickened edge
slab foundation is proposed, The footings were designed for an allowable soil bearing pressure
of 2,000 psf and alateral earth pressure based on 50 pcf equivalent fluid unit weight.
At the time of our visit to the site, the foundation excavation had been cut in two levels from
l%to 6 feet below the adjacent ground surface. The materials exposed in the bottom of the
excavation consisted of weathered claystone on the north side and low density, clayey silty
sand in the rest of the excavation. Results of a swell-consolidation test performed on a sample
of the clayey silty sand taken from the site, shown on Figure 1, indicate the soils are highly
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 bedrock designed for an allowable
bearing pressure of 2,000 psf can be used in the deeper cut area. The rest of the footing areas
should be sub-excavated 3 feet and replaoed and compacted to at least 98% of standard Proctor
density. The exposed soils tend to compress when wetted and loaded and there could be post-
construction settlement of the southem portion of the excavation relative to the north side of the
foundation, which is on weathered claystone bedrock, particularly if the bearing soils become
wet. Footings bearing on the sandy soils should be a minimum width of 2 feet for continuous
walls and 3 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 frozen soils. Exterior footings
should be provided with adequate soil cover above their bearing elevations for frost protection.
Sam Jurmu
March 26,2024
Page2
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. A perimeter foundation drain should be
provided to prevent temporary buildup of hydrostatic pressure behind the retaining walls.
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 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 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,
:i :
Daniel'E. Hardin, P.E
Rev. by: SLP
DEH/kac
attachments Figure I - Swell-Consolidation Test Results
cc: ErnieKollar( : i )
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Soil Compaction Report crient:
TestMethod:ASTMD6938 SamJurmu
699 Bristlecone Way
sitt, co 81652
Proiect:
24-7-204
Scufter Ridge Shop Bldg
164 Scutter Ridge Road
Rifle, CO 81650
GlerpoodSprings
5020 County Road 154
Glenwood Springs, CO 81601
Phone: 97O-94t7988
Test Results
Remark
DP/T,lP
DPIMP
Test lnformation
Field Technician
Justin Orgill
Justin
Optimum
Moisture
Tolerance
P/ol
-2 l2
-2 l2
Min Comp.
(o/"1
98
98
Gauge
Make / Model / SN / Calibrated
Troxler13440 / 23f18 lO4lOAn23
Traxler 1344O 12ffi18 lO4rc3ln23
Percent
Compaction
99
99
Probe
Depth
(in)
't2
12
ln Place
Wet
Density
(pcf)
128.9
127.9
Refercnce
2'below lootin
2'below
Comments
are "Dire(t Transmission" (Method depth rS noted as
'Backscattef calibration data on
ln Place
Dry
Ilensity
(pc0
115.2
114.5
ln Place
Moisture
(/",
11.9
11.7
Elevation
Maximum
Dry Density
{ocfl
't 16.2
'116.2
Test Location
Structural Fill: Footing: Under footings, northeast corner
southeast corner
Optimum
Molsture
(%l
11.8
11.8
Soil
Classification
SC-SM
SC.SM
Bemarks
DP/MP: Density Pass / Moisture Pass
Method
B tD6e8)
B (D6e8)
Proctor lD
05*24
05+24
Test Date
o4la3l24
o4la3l24
Retest
of
1
2
Test #
3
4
Test #
3
4
Thb report presents opinions formed as a result of our observations of soil compaction. We have relied on the contractor to continue applying the recommended
compactive effort and moisture to the fill during times when our observer is not observing operations. Tests are made of the soils only as believed necessary to
calibrate our observer's judgement, Test data are not sole basis br opinions on whether the soils meets specifications. These test results only apply to the
samples which were tested. The testing report shall not only be reproduced, except in full, without trte written approval of Kumar and Associates, lnc. Nuclear
gauge density testing performed in accordance with ASTM D6938.
Page 1 ol 1
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Soil Compaction Report oient:
Test Method: ASTM D 6938 SamJurmu
699 Bristlecone Way
sirt, co 81652
Proiect:
24-7-204
Scutter Ridge Shop Bldg
164 Scutter Ridge Road
Rifle, CO 81650
Glemood Springs
5g2o County Rmd 1g
Glenwmd Springs, CO 81601
Phone: 970-94$7988
Test Results
Remark
DP/MP
DP/IilP
DP/MP
DP/MP
Test lnformation
Field Technician
Justin Orgill
Optimum
Moisture
Tolerance
(/"1
-2/2
-2 l2
-2 l2
-zt 1
Min Comp.
Phl
98
98
98
98
Gauge
Make / Model / SN I Galibrated
Troxlerl344O / 23818 lMn3ln23
Troxler / 3440 I 23E18 I O4l}3l?f.?3
Troxler I 34zl0 / 23€1 I I Mlu3ln23
Troxler 13444 1236'18t C/.lgglz02s
Percent
Compaction
99
98
98
98
Probe
Depth
(in)
12
12
12
12
ln Place
Wet
Density
(Pcf)
127.5
127.9
127.5
127.7
Relercnce
1'below footino qrade
1' below looting grade
footinq qrade
Comments
ln Place
Dry
Density
(ocf)
114.7
113.9
113.6
113.8
ln Place
lloisture
{/"1
11.2
12.3
12.2
12.2
Elevation
Maximum
Dry Density
(pcf)
116.2
116.2
116.2
116.2
Test Location
Structural Fill: Footing : Under footinqs, southeast corner
Under 3' north of southwest comer
Structural Fill: Footing: Under footings, 5' north of southwest corner
Filt:Under comer
Optimum
Moisture
l/"1
11.8
11.8
't 1.8
11.8
Soil
Classification
SC-SM
SC-SM
SC.SM
SC-SM
Remarks
DP/llP: Density Pass / Moisture Pass
Method
B (D698)
B {D698)
B {D698}
B {D698)
Proctor lD
05F24
05$24
055-24
055-24
Test Date
o4t04t24
Mla4l24
Mlur24
MIO4l24
Retest
ofTe$t #
5
6
7
I
Test #
5
6
7
8
This report presents opinions formed as a result ol our observations of soil compaction. We have relied on the contractor to c,ontinue applying the recommended
compactive effort and moisture to the fill during times when our observer is not obseMng operations. Tests are made of the soils only ai 6efieved necessary to
calibrate our observer's iudgement. Test data are not sole basis for opinions on whether the soils meets specifications. These test results only apply to the
samples which were tested. The testing report shall not only be reproduced, except in tull, without the written approval of Kumar and Associatbs, liri. Nuclear
gauge density testing performed in accordance with ASTM D6938.
Page 1 of 1