HomeMy WebLinkAboutObservation of Excavation 10.10.2019KFA
Kumar & Anacleto, lac.
Geotechnical and Materials Engineers
and Environmental Scientists
An Employee Owned Company
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa.com
www.kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado
October 10, 2019
Colorado Carpentry
Attn: Vance Hutchinson
389 Grand Butte
New Castle, Colorado 81647
cocarpentiy(i msn.com
Subject:
Dear Vance:
Project No. 19-7-158.A
Observation of Excavation, Proposed Residence, Lot 94, Ironbridge Subdivision,
322 River Bend Way, Garfield County, Colorado
As requested, a representative of Kumar & Associates, Inc. observed the excavation at the
subject site on September 27 and 30, 2019 to evaluate the soils exposed for foundation support.
The findings of our observations and recommendations for the foundation design are presented
in this report. We previously conducted a subsoil study for design of foundations at the site and
presented our findings in a report dated March 13, 2019, Project No. 19-7-158.
At the time of our initial visit to the site, the foundation excavation had been cut in one level
from 3 to 6 feet below the adjacent ground surface. The soils exposed in the bottom of the
excavation consisted of dense, silty, sandy gravel and cobbles in the eastern part of the
crawlspace and what appeared to be mostly sandy silty clay in the rest of the excavation. An old
backfilled excavation for a "burn pit" was observed in the bottom and north side of the
foundation excavation near the northeast corner of the garage. There was about 2 to 3 feet of
ashes and wood remnants covered with a mixture of the on-site clay and gravel soils. The total
depth of the old burn pit appeared to be about 10 feet below the existing ground surface and
about 4 feet below the current excavated crawlspace grade. Two shallow pits had been dug
below crawlspace grade near the northeast corner of the garage. The burn pit appears to extend
out to the north of the house. Only the portion of the burn pit within the building excavation will
be excavated and replaced with compacted structural fill.
We returned to the site on September 30a' to observe several shallow pits excavated with a
backhoe to determine the depth of clay overlying the dense gravel soils recommended for
placement of footings. The pits excavated in the crawlspace indicated that outside the "burn pit"
area, the crawlspace subgrade consisted of up to 6 inches of compacted clay soil overlying
relatively dense silty sandy gravel with cobbles. No free water was encountered in the
excavation and the soils were slightly moist to moist. A pit excavated on the west side of the
garage showed about 2' feet of clay soils overlying the gravel. We recommended that the clay
Tim & Natalie McDonald
October 10, 2019
Page 2
soils be removed from below footing areas at the garage footing and "burn pit" areas and that
footing subgrade be re-established with compacted structural fill as recommended in our
previous report.
We tested the compaction of the road base placed as structural fill on October 3 and 4, 2019.
The results are attached in the Earthwork Compaction Testing Reports for those days and
indicated that compaction was satisfactory and suitable for support of footings.
The soil conditions exposed in the completed excavation are generally consistent with those
previously recommended for foundation design and suitable for support of spread footings
designed for the recommended allowable bearing pressure of 2,500 psf. The bearing soils should
be protected from frost and concrete should not be placed on frozen soils. Other
recommendations presented in our previous report which are applicable should also be observed.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavation and the previous subsurface exploration at the site. Variations
in the subsurface conditions below the excavation could increase the risk of foundation
movement. We should be advised of any variations encountered in the excavation conditions for
possible changes to 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,
Kumar & Associates, Inc.
O Li a'
'<e, He- -14,•,,
mac*-
P '° 24443 2.;
Rev. by: SLP ' .55„_ - ,
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attachments Earthwork Compaction Testing Reports dated October 3 and 4, 2019
Figure 1 - Laboratory Proctor Compaction Test Report
Figure lA — Particle Size Distribution Report
cc: Tim & Natalie McDonald cubuffbuff@icloud.com nataliemcdonald@niac.com
Patrick Stuckey stuaerh®comcast.net
Kumar & Associates, Inc.
Project No. 19-7-158.A
Kt11RAr 5020 County Road 154, Glenwood
Geotechnical and Materials Engineers Phone: (970) 945-7988,
ICAalld l"nvircnlri6nta15Cit7t11{slS Email:
1 ..
Springs, CO 81601
Fax: (970) 945-8454
kavlepwoodfc kumarusa.@om
Earthwork Compaction Testing Report
Client: Colorado Carpentry Project No.: 19-7-158.A Day: Thursday
Attn: Vance Hutchinson Date: 10/3/19
389 Grand Butte Page: 1 of 1
New Castle, Colorado 81647
Project: Proposed Residence, Lot 94, 322 River Bend Way, Ironbridge Subdivision, Garfield County,
Colorado
Weather: Clear, calm, dry Temperature: 44° at 9:00 am
Earthwork Contractor: Silt Excavation
Equipment Used: Trackhoe, vibratory double drum roller, water truck
Description of Earthwork We visited the site today to observe under footing backfill operations and to
Tested: perform compaction testing. Compaction was judged to be adequate based on
our test results and observations.
Sample(s) Obtained:
Verbal Communication: Vance Hutchinson with Colorado Carpentry and Tommy with Silt Excavating
Placement and Compaction Procedure: Observed by Kumar Associates
Lift Thickness: 6" Max. Rock Size: 3/4" Moisture water truck at stockpile
Conditioning:
Compactor(s) Used: vibratory double drum roller Number of Passes: 10+
Nuclear Gauge Moisture/Density Test Results
Test
Location
Depth or
Field Dry
Densit
Field
Moisture
Field
Com
Min.
Comp.
Proctor
No.
Elev.
y
Content
o p'
Req.
Lab No.
Under Footing Backfill
(pcf)
%
(/o)
(%)
1
Center of old fire pit
2' below
footing grade
122.1
8.4
98
100
418-19
2
N.W. corner
1' below
footing grade
123.0
8.8
99
100
418-19
1A
Retest (10-03-19)
2' below
footing grade
124.2
8.8
100
100
418-19
2A
Retest (10-03-19)
1' below
footing grade
124.8
8.5
100
100
418-19
3
Center of fire pit
1' below
footing grade
123.8
8.6
100
100
418-19
-
Proctor Sample Reference:
Lab No.
Method
Description
Max. Dry
Opt.
Dens. (pcf)
Moist. (%)
418-19
ASTM D 698
United e/4" Aggregate Base Course
123.9
8.7
THIS REPORT PRESENTS
OPINIONS ASA RESULT OF OUR OBSERVATION.SOF FILL PLACEMENT, WE HAVE RELIED ON THE CONTRACTOR TO CONTINUE APPLYING THE RECOMMENDED
COMPACTIVE EFFORT AND MOISTURE TO FILL DURING THE TIMES WHEN OUR OBSERVER IS NOT OBSERVING OPERATIONS.
THE NUCLEAR DENSOMETER METHOD OF TESTING WAS USED IN SUBSTANTIAL ACCORDANCE WITH ASTM D 6936.
Distribution:
Tim McDonald (cubuflhuffk@icloud.eom)
Natalie McDonald (nataliemcdonald(semac.com)
Patrick Stuckey
(stucarch mcpmcsm. nor)
Vance Hutchinson
(cacarponfryamsn.com)
/Imo
Philip Orgill Daniel E. Hardin, P.E.
Field Technician Reviewed By
5020 County Road 154, Glenwood
Geotechnical and MaterialsEnginet>rs
1(±A& A'ssad/dm+inc•n Phone: (970) 945-7988,
and FnvironmenlaE ScleRlisls Email:
"Z.
Earthwork Compaction Testing Report
Client: Colorado Carpentry Project No.: 19-7-158.A
Attn: Vance Hutchinson
389 Grand Butte
New Castle, Colorado 81647
Project: Proposed Residence, Lot 94, 322 River Bend Way, Ironbridge Subdivision,
Colorado
Springs, CO 81601
Fax: (970) 945-8454
kagfenwoodd:4kumarusa.com
Day: Friday
Date: 10/4/19
Page: 1 of 1
Garfield County,
Weather: Clear, calm, dry Temperature: 44° at 9:00 am
Earthwork Contractor: Silt Excavation
Equipment Used: Trackhoe, skid steer vibratory double drum roller
Description of Earthwork Under footing backfill operations are complete. Compaction was judged
Tested: adequate based on our test results and observations
Sample(s) Obtained:
Verbal Communication: Vance Hutchinson with Colorado Carpentry via telephone of our field
results
to be
test
Placement and Compaction Procedure: Not observed by Kumar Associates
Lift Thickness: 6" Max. Rock Size: 3/4" Moisture water truck at stockpile
Conditioning:
Compactor(s) Used: vibratory double drum roller Number of Passes: 8-10
Nuclear Gauge Moisture/Density Test Results
Test
No.
Location
Depth or
Elev.
Field
Dens
ry fl
(pc
Field
Moisture Moisture
Content
%
Fieldo
(% p )
Min.
Comp.
Req.
(°%)
Proctor
Lab No.
1
Fire pit center
Footing
grade
124.2
8.0
100
100
418-19
2
10' S. of N.W. corner
Footing
grade
123.8
7.8
100
100
418-19
Proctor Sam le Reference:
Lab No.
Method
Description
Max. Dry
Dens. (pcf)
Opt.
Moist. (%)
418-19
ASTM D 698
United 3/:' Aggregate Base Course
123.9
8.7
THIS REPORT paesewS
COMPACTIVE EFFORT
THE NUCLEAR DENSOMETER
Distribution:
Tim McDonald (cubuffbuffiRlclaud.corn)
Natalie McDonald
Patrick Stuckey
Vance Hutchinson
AMC
OPINIONS AS A RESULT OF OUR
AND MOISTURE TO FILL DURING
METHOD OF TESTING WAS
(Da;atlemcdonaldeitmac.com)
(stucarch rC�.comcast.neti
CBSERVATIONSOF
THE TIMES WHEN
USED IN SUBSTANTIAL
FILL PLACEMENT. WE HAVE RELIED ON THE CONTRACTOR TO CONTINUE APPLYING THE RECOMMENDED
OUR OBSERVER IS NOT OBSERVING OPERATIONS.
ACCORDANCE WITH ASTM D 6938.
Philip Orgill Daniel E. Hardin, P.E.
(cocarnentrv@msn.com)
Field Technician Reviewed By
Laboratory Proctor Compaction Test Report
126
1
125-\
'^
Dry density, pcf
VN N A
-� N W -a
---13,7%.
1.2.9
N.\\\:\.\\\,
\
\-U
ZAV wi
Sp.G. _
2.48
$ 7 8 9 10 11 12
Water content, %
Test specification: ASTM D 698-12 Method C Standard
Elev/
Classification
Nat.
S G.
LL
PI
% >
% <
Depth
USCS
AASHTO
Moist.
p'
3/4 in.
No.200
SP -SM
A -1-a
NV
NP
0
5.5
TEST RESULTS
MATERIAL DESCRIPTION
Maximum dry density = 123.9 pcf
Optimum moisture = 8.7 %
Class 6 Aggregate Base Course
Project No. 19-7-158.A Client: Tim & Natalie McDonald
Project: Lot 94, Ironbridge Subdivision, 322 River Bend Way, Garfield County,
Colorado
o Location: Site Stockpile - United. Sievers Pit Sample Number: 418-19
Remarks: 1
See Figure lA for classification results.
Figure 1
Kumar & Associates, Inc.
Glenwood Springs, Colorado
Tested By: KO
Checked By: DEH
Particle
C C C ' , . m
N
Size Distribution Report
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100 10 1
GRAIN
01 0.01 0.001
SIZE - mm.
% +3"
% Gravel
% Sand
% Fines
Coarse
Medium
Fine
Silt 1 Clay
Coarse
Fine
0
0
44
16
23
11
6
r SIEVE
PERCENT
SPEC.*
PASS?
Material Descrlpt1o0
SIZE
FINER
PERCENT
(X=NO)
Class 6 Aggregate Base Course
1
3/4"
3/8"
100
100
78
100
95 -100
65
Atterberg Limits#4
#8
#16
56
43
32
30
25 - 55
PL= NP LL= NV PI= NP
Coefficients
#30
#50
#100
#200
22
12
8
5.5
3.0 - 12
D90= 13.9015 D85= 11.8754 D60= 5.3906
050= 3.4394 D30. 1.0307 D15= 0.3693
D10= 0.2121 Cu– 25.41 Cc= 0.93
Classification
USCS= SP -SM AASHTO= A -1-a
Remarks
See Figure 1 for standard Proctor compaction results.
4 3/4" ABC Class 6
Location: Site Stockpile - United, Sievers Pit
Sample Number: 418-19 Date: 10/2/2019
Kumar & Associates, Inc.
Glenwood Springs, Colorado
Client: Tim & Natalie McDonald
Project: Lot 94, Ironbridge Subdivision, 322 River Bend Way, Garfield
County, Colorado
Project No: 19-7-158.A Figure 1A
Tested By: KO
Checked By: DEH