HomeMy WebLinkAboutExcavation Observation 07.31.2013Gtech
HEPWORTH - PAWLAK GEOTECHNICAL
July 31, 2013
Erica Gentry
c/o Tom Dyer Construction, Inc.
193 TZ Trail
Grand Junction, Colorado 81503
(tldyerl8[;msn.com)
Hepworth-Pau•lnk Geotechnical, Inc.
5020 County Road 154
Clermont Springs, Colorado 81601
Phone 970-945-7988
Far: 970-945-8454
email hpgco@hpgeurech.com
Job No. 113 256A
Subject: Observation of Excavation, Proposed Residence, Lot 8, Sun Meadow
Estates, 0530 North Meadow Drive, Garfield County, Colorado
Dear Ms Gentry and Mr. Dyer:
As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the
excavation at the subject site on July 24 and 29, 2013 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 October
19, 2006, Job No. 105 363.
At the time of our visit to the site on July 24, the foundation excavation had been cut in
one level from 7 to 9 feet below the adjacent ground surface, The soils exposed in the
bottom of the excavation consisted of stiff, sandy silty clay and desiccated hard clay.
Relatively undisturbed hand driven liner samples were obtained at two locations in the
excavation. Results of swell -consolidation testing performed on samples obtained, shown
on Figures 1 and 2, indicate the soils are variably compressible under conditions of
loading and wetting. No free water was encountered in the excavation and the soils were
slightly moist.
Due to the swell potential of the desiccated hard clay soils found during our geotechnical
exploration, we recommended over -excavation of the hard clay soil to a depth of 2 feet
below foundation grade (the northern portion of the excavation). We recommended
replacement of the over -excavated soils with'/" aggregate base course or similar granular
material compacted to a minimum of 98% of a standard Proctor density for the material at
near optimum moisture content. For the southern portion of the excavation, consisting of
sandy silty clays, we recommend scarifying, moisture conditioning and compacting the
existing soils in the foundation areas.
On return visits in the morning and afternoon of July 29, 2013 we observed that the
subgrade had been over -excavated to a depth of 2 feet below foundation grade in the
northern portion of the excavation, The over -excavated hard clay soils were replaced
with compacted i/1" aggregate base course. Compaction tests performed on the base
Parker 303-841-7119 • Colorado Springs 719-633-5562 • Silverthorne 970-468-1989
course at foundation grade are attached for reference. The native soil in the southern
portion of the excavation had reportedly been scarified, moisture conditioned and
compacted. Probing of the soils by hand with a metal rod in the southern portion of the
excavation resulted in minor penetration of the probe and the soils were judged to be firm
and suitable for placement of footings..
The soil conditions exposed in the excavation and prepared as noted above are suitable
for support of spread footings designed for the recommended allowable bearing pressure
of 1500 psf. Any loose and disturbed soils should be removed in the footing areas prior
to placement of concrete. 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,
HEPWORTH — PAWLAK GEOTECHNICAL, INC.
James A. Parker, P.E., P,G.
Rev. by: SLP
JAP/ljg
attachments: Figures 1 & 2 — Swell Consolidation Test Results
Earthwork Compaction Test Report
Job No. 113256A
Compression %
D
2
3
4
5
6
7
8
9
Moisture Content = 6.5 percent
Dry Density = 92 pcf
Sample of: Sandy Silty Clay
From: Bottom of Excavation - Southeast Corner
•
Compression
upon
wetting
r
0.1
1.0
APPLIED PRESSURE - kat
10
100
113 256A
Gatech
Hepworth—Pawlak Caatachnleal
SWELL CONSOLIDATION TEST RESULTS
Figure 1
Compression %
0
1
2
3
4
5
6
Moisture Content = 7.6 percent
Dry Density = 105 pcf
Sample of: Sandy Silty Clay
From: Bottom of Excavation- Northwest Corner
4
Compression
upon
welling
0.1
1.0
APPLIED PRESSURE - ksf
10
100
113 256A
%f
Hspwo th-Pawldc Gsot.chnrcd
SWELL -CONSOLIDATION TEST RESULTS
Figure 2
�CG'CI'1
HEPWORTH-PAWLAK GEOTECHNICAL
5024 County Road 154
Glenwood Springs, Colorado 81601
Phone: 970.945-7988
Fax: 970-045.8454
hpsreoehngeotech.com
Earthwork Compaction Testing Report
Client: Erica Gentry
c/o Tom Dyer Construction, Inc.
193 TZ Trail
Grand Junction, CO 81503
Job No.: 113256A Day: Monday
Date: 7/30/13
Page: 1 of 1
Project: Residence, Lot 8, Sun Meadow Estates, Garfield County, Colorado
Weather. Clear, calm, dry
Temperature:
84° at 4 pm
Earthwork Contractor. Tom Dyer Construction
Equipment Used: trackhoe, walk behind pad foot compactor
Description of Earthwork Basement level structural fill under slab and footings was tested for
Tested: compaction. Compaction tests were judged adequate based on an estimated
Proctor value of 135 pcf for the aggregate base course fill.
Verbal Communication: The contractor was informed of our compaction test results.
Placement and Compaction Procedure: Not Observed by HP Geotech.
Lift Thickness: Max. Rock Size:
Compactor(s) Used:
Moisture
Conditioning:
Number of Passes:
Test
No.
Location
Nuclear Gauge Moisture/Density Test Results
Basement Level of Building Area
Depth or
Elev.
Field
Dry
Density
(Pot)
Field
Moisture
Content
Feld
Comp.
(%)
Min.
Comp.
Req.
(%)
Proctor
Lab No.
1
West Side of North Half
Foundation
grade
141.4
5.3
100
98
Est.
2
North Side of North Half
Foundation
grade
135.6 4.0
100
98
Est.
3 East Side of North Half
Foundation
grade
135.3 3.9
100
98 Est.
Proctor Sample Reference:
Lab No.
Method
Description
Max. Dry
Dens. (94)
Opt.
Moist. (%}
Est.
ASTM D 698
3/4" aggregate base course
135
7
THIS REPORT PRESENTS OPINIONS AS A RESULT OF OUR OBSERVATIONSOF FILL PLACEMENT, WE HAVE RELIED ON THE CONTRACTOR TO CONTINJE APPLYING THE RECOMMENDED
COMPACTTVE EFFORT AND MOISTURE TO FILL DURING THE TIMES WI tEN OUR OBSERVER IS NOT OBSERVING OPERATIONS.
THE NUCLEAR DENSOMETER METHOD OF TESTING WAS USED IN SUBSTANTIAL ACCORDANCE WITH ASTM 0 6938.
Distribution: Erica Gentry — ericaaentrverifleco.ort
Tom Dyer — ildver180msn.c9m
James A. Parker, PE, PG Steven L. Pawlak, PE
Field Technician Reviewed By