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HEPWORTH -PAWLAK GEOTECHNICAL
November 20, 2012
Stewart Custom Builders
Attn: Peter Stewart
100 Elk Run Drive, Suite 215
Basalt, Colorado 81621
peter@stewartcustombuilders.com
Subject:
Dear Peter:
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Thune: 0711-945-7988
Fax: 970-94i-8-1'14
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Job No. 112 408A
Observation of Excavation, Proposed Residence, Lot 1, Sunlight View 1I,
382 Meadow Wood Road, Garfield County, Colorado
As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the
excavation at the subject site on November 5 and 8, 2012 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 you, dated
October 29, 2012.
The residence will be single story above a basement level in the living area with the
garage at the main level. Floors will be slab -on -grade. Spread footings placed on dense
granular soils and designed for an allowable bearing pressure of 3,000 psf were assumed
for the building support.
At the time of our initial visit to the site, the foundation excavation had been cut in 2
levels from 2 to 10 feet below the adjacent ground surface. The soils exposed in the
bottom of the excavation consisted of basalt cobbles and boulders in a clayey sand and
gravel matrix in the basement area and sandy clay in the northwest garage area. There
was a step down of 4 feet between the garage and basement levels. When observed on
November 8, the garage footing area had been stepped down about 1 l/2 feet onto the basalt
rock soils. No free water was encountered in the excavation and the soils were slightly
moist to moist.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural basalt rock soil designed
for an allowable bearing pressure of 3,000 psf can be used for support of the proposed
residence. The basalt rock soils should have minor compressibility and minor foundation
settlement potential. Footings should be a minimum width of 16 inches for continuous
walls and 2 feet for columns. Loose and disturbed soils in footing areas should be
removed and the bearing level extended down to the undisturbed natural basalt rock soils.
Voids created by boulder removal should be backfilled with compacted structural fill.
Parker 303-841-7119 • Colorado Springs 719-633-5562 • Silverthorne 970-468.1989
Stewart Custom Builders
November 20, 2012
Page 2
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. Continuous foundation walls should be reinforced
top and bottom to span local anomalies such as by assuming an unsupported length of at
least 12 feet. Foundation walls acting as retaining structures should also be designed to
resist a lateral earth pressure based on an equivalent fluid unit weight of at least 50 pcf for
on-site soil as backfill excluding rock larger than about 6 inches. A perimeter foundation
drain should be provided around the basement level to prevent temporary buildup of
hydrostatic pressure behind the basement walls and prevent wetting of the lower level.
The drain can discharge into a perforated sump below the basement floor. Structural fill
placed within floor slab areas can consist of the on-site soils compacted to at least 95% of
standard Proctor density at a moisture content near optimum. Backfill placed around the
structure should be compacted and the surface graded to prevent ponding within at least
10 feet of the building. Landscape that requires regular heavy irrigation, such as sod, and
sprinkler heads should not be located within 5 feet of the foundation.
The recommendations submitted in this letter are based on our observation of the soils
exposed within the foundation excavation and do not include subsurface exploration to
evaluate the subsurface conditions within the loaded depth of foundation influence. This
study is based on the assumption that soils beneath the footings have equal or better
support than those exposed. The risk of foundation movement may be greater than
indicated in this report because of possible variations in the subsurface conditions. In
order to reveal the nature and extent of variations in the subsurface conditions below the
excavation, drilling would be required. It is possible the data obtained by subsurface
exploration could change the 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 NICAL, INC.
Steven L. Pawlak, P.
SLP/ksw
Job No. 112408A
Gtech