HomeMy WebLinkAboutObservation of Excavation 06.27.2016G&edh
HEPWORTH-PAWLAK GEOTECHNICAL
June 27, 2016
Brian Derkash
1618 Lincolnwood Drive
Glenwood Springs, Colorado 81601
brianderk ash (a)gm ai l .cam
Subject:
Dear Brian:
Hepworth-Pawlak Geotechnlcal, Inc.
5020 County Road 154
Glenwood Springs, Colorado 81601
Phone: 970-945-7988
Fax: 970.945.8454
Email: hpgeoehpgeotech.com
Job No. 1 1 5 591A
Observation of Excavation, Proposed Residence, Lot 51, Westbank Mesa,
Huebinger Drive, Garfield County, Colorado
As requested, the undersigned representative of Hepworth-Pawlak Geotechnical, Inc.
observed the excavation at the subject site on June 17 and 23, 2016 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
January 29, 2016, Job No. 115 591 A.
At the time of our initial visit to the site, excavation was just getting started and slab
subgrade was exposed in two areas near the northeast corner of the proposed house.
Results of swell -consolidation testing performed on two samples of clay taken from the
site, shown on Figures 1 and 2, indicate the soils have low compressibility under existing
low moisture content and light loading and have a low collapse potential (settlement
under constant load) when wetted. •rhe samples had moderate to high compressibility
under increased loading after wetting.
We visited the site again on June 23rd to observe the nearly completed excavation.
The foundation excavation had been cut in multiple levels from 3 to 10 feet below the
adjacent ground surface. The soils exposed in the bottom of the excavation consisted of
very stilf'to hard sandy silty clay. Results of swell -consolidation testing performed on
another sample taken from the southwest corner of the excavation, shown on Figure 3,
indicate the soils are slightly expansive when wetted under a constant light surcharge and
had low compressibility under conditions of loading and wetting. No fret water was
encountered in the excavation and the soils were slightly moist.
The soil conditions exposed in the excavation are consistent with those previously
encountered on the site and suitable for support of spread footings designed for the
recommended allowable bearing pressure of 2.500 psfwith a minimum dead load
pressure of 700 psi: Loose and disturbed soils should be removed in the footing areas to
Brian Derkash
.lune 27, 2016
Page 2
expose the undisturbed natural 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,
HEPWORTH — PAWLAK GEOTECI-CNICAL. INC.
Daniel L. Hardin, P.B.
Rev. by: SLP
DEI-Uksw
attachments Figures 1 to 3 -- Swell Consolidation Test Results
ec: Red House Architects -- Bruce 13arth(bruce(redhousearchitecture.com}
Kaup Engineering - Dale Kaup (jcaupena rofnet)
J(1)1411. 115 591A
Sl1f1S31:1 1531 NOLLV0170SNO0-113MS
m
0
c
[D
Is i 1dfSS38d 03IlddV
0
0
0
Compression %
o V O) CP -P. W NI 1
0
,_
1
r
d
_c,"
71
Moisture Content 7.0
Dry Density - 101
Sample of. Sandy Silty CIa
From: One foot above Foc
Northeast corner of
,moi
f
,
Compres
upon
wetting
Compression %
0
1
2
3
4
5
6
7
a
9
10
11
Moisture Content - 6.4 percent
Dry Dens ty = 93 pcf
Sample al- Sandy Silly Clay
From Onc foot above Footing Grade
North wall of house, 6/17/16
Compression
upon
wetting
01
1.0
APPLIED PRESSURE - ksi
10
100
115 591A
HCPWORTWPAWLA% GEOTECHNICAL
SWELL -CONSOLIDATION TEST RESULTS
Figure 2
Compression - Expansion
Moisture Content 8.4 percent
Dry Density - 97 pcf
Sample of. Sandy Silty Clay
From: Southwest corner at Footing Grade,
6/23/16
'acN
Expansion
upon
wet ing
01
10
APPLIED PRESSURE - its(
10
100