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HEPWORTH-PAWLAK GEOTECHNICAL
July 13, 2015
Mandy and Travis Tiffany
961 County Road 266
Silt, Colorado 81652
psf6251a1gmai I .com
Hcpworth-P11wlok Gcotcchnicat, Inc
5020 County Road I 54
Glenwood Springs, Colorado 8 I 60 I
Phone; 970-945-7988
Fax: 970-945-8454
Email hpgco@hpgcotcch .com
Job No . 115 124A
Subject: Observation of Excavation, Proposed Residence, Parcel No.
212732400145 , Silt Mesa Road, Garfield County, Colorado
Dear Mandy and Travis:
As requested by Blake Piland, a representative of Hepworth -Pawlak Geotechnical
observed the excavation at the subject site on June 30, 2015 to evaluate the materials
exposed for foundation support . The findings of our observations and recommendations
for the foundation design are presented in this report . The services are supplementa l to
our agreement for professional services to you dated April 2, 2015.
We previously conducted a subsoil study for design of foundations at the site and
presented our findings in a report dated April 30, 2015, Job No. 115 124A. The proposed
construction is similar to that described in our previous report . Spread footings bearing
enti rely on the bedrock materials designed for an allowable bearing pressure of2,000 psf
were recommended for foundation support with some risk of movement .
At the time of our site visi t, the foundation excavation had been cut in two le vels from
about 3 to 10 feet below the adjacent ground surface. The materials exposed in the
bottom of the excavation consisted of weathered claystone, and hard sandstone/siltstone
bedrock primarily in the deeper cut areas. Results of swell-consolidation testing
perfonned on samples taken from the site, shown on Figure 1, indicate the weathered
claystone is slightly compress ible under conditions of loading and wettin g with a low
expansion potential when wetted under a constant 1,000 psf surcharge. No free water was
encountered in the excavation and the bedrock materials were slightly moist.
The conditions exposed in the excavation are generally consistent with those prev iously
encountered on th e site and suitable for support of spread footings designed for the
recommended allowable bearing pressure o f 2,000 psf with some risk of foundation
movement, primarily if the weathered claystone becomes wetted and precautions should
be taken to prevent wetting . Prior to the footing construction, loose disturbed materials
should be removed . There is also some risk of slab movement in areas underlain by the
weathered claystone if the subgrade were to become wetted. To help prevent wetting of
the foundation bearing materials and slab subgrade, the foundation backfill should be
Moisture Content = 7.2 percent
Dry Density = 130 pcf
Sample of: Weathered Claystone
From : Bottom of West Central Portion of
Excavation
~
c
0 1 "iii c
fO a.
d1
0 ---I
15 ,~ ,~ r--,)
"iii en
~ 1 \
a. \ E
0
CJ
expansion
upon
wetting
0 .1 1.0 10 100
APPLIED PRESSURE -ksf
115124A ~ Heoworth-Powlak Geotechnlc:ol
SWELL-CONSOLIDATION TEST RESULTS Figure 1