HomeMy WebLinkAboutObservation of Excavation 03.24.2016March 24, 2016
Divide Creek Builders
Attn: Dean Filiss
1531 County Road 342
Silt, Colorado 81652
(dead iv i dec reekbui lde rs .corn
Subject:
Dear Dean:
Job No. 116 071A
Observation of Excavation, Proposed Additions to Residence, Lot 13,
Wooden Deer, 499 Wooden Deer Road, Garfield County, Colorado
As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the
excavation at the subject site on March 17, 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. The services were performed in
accordance with our agreement for professional engineering services to Divide Creek
Builders, dated March 17, 2016. CTL/Thompson previously conducted a subsoil study
for design of foundations at this site and presented their findings in a report dated July 14,
1993, their Job No. GS -1115.
The proposed additions will consist of enlarging the west side of the garage and placing a
living area over it, a mudroom addition on the north side of the existing house and a front
entry/patio addition on the south side of the house. New foundations were designed for
2,000 psf allowable soil bearing pressure. The existing house is a one story wood frame
structure over a crawlspace with an attached garage on the north side.
At the time of our visit to the site, the addition foundation excavations had been cut in one
level from 31/2 to 5 feet below the adjacent ground surface in the garage/mudroom area
and 3 to 4 feet in the front entry area. The materials exposed in the bottom of the
excavations consisted of hard gypsum bedrock in the garage/mudroom area and stiff,
sandy silty clay in the front entry area. Results of swell -consolidation testing performed
on a sample of the clay taken from the site, shown on Figure 1, indicate the clay soils are
moderately compressible under conditions of loading and wetting with a minor collapse
potential (settlement under constant load) when wetted. No free water was encountered
in the excavation and the soils were moist. The footings were formed with reinforcing
bars in place at the time of our site visit. The footings were all formed at least 20 inches
wide.
Divide Creek Builders
March 24, 2016
Page 2
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an
allowable soil bearing pressure of 2,000 psf can be used for support of the proposed
additions. The exposed clay soils tend to compress when wetted and there could be some
post -construction settlement of the foundation if the bearing soils become wet. 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.
The recommendations submitted in this letter are based on our observation of the
materials exposed within the foundation excavation and the previous report by
CTL/Thompson. 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.
24443 z,
Daniel E. Hardin, P.E.
•
SS/ "11 11
DEH/ksw ��~,
attachment Figure 1 — Swell -Consolidation Test Results
cc: M.J. Mueller Company - Mark Mueller (mjr l@mjmlpe.cotO
K.H. Webb Architects - Kyle Webb (kv ie @khwebb.con )
Job No. 116 071 A
Compression %
0
1
2
3
4
5
Moisture Content = 17.1 percent
Dry Density = 102 pcf
Sample of: Sandy Silty Clay
From: Bottom of Excavation
Compression
upon
wetting
0.1
1.0
APPLIED PRESSURE - ksf
10 100
116 071A
SWELL -CONSOLIDATION TEST RESULTS
Figure 1