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HEPWOR T H-PAWLAK GEOTECHNICAL
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August 6, 2015
BW-ANE, Inc.
Attn: Steve Sandoval
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Job No. 115 355A
Subject: Observation of Excavation, Proposed Maintenance/Storage Building,
Potato Patch Club, 950 Red Sandstone Road, Vail, Colorado
Gentlemen:
As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the
excavation at the subject site on July 31, 2015 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 BW-ANA, Inc, dated July 30, 2015.
The building is proposed to be supported on shallow spread footings with an allowable
bearing pressure of 1,500 psf and slab-on-grade floor.
At the time of our visit to the site, the foundation excavation had been cut in 2 levels from
3 to 61/2 feet below the adjacent ground surface and consisted of a perimeter trench cut.
The front, south half was about 2 feet lower than the uphill, north half. The soils exposed
in the bottom of the excavation consisted of relatively dense, silty clayey sandy gravel
with cobbles. The natural soils were observed below about 3 to 6 feet of apparently
onsite soil fill in the sides of the excavation. The results of a gradation analysis
performed on a sample of the gravel (minus 3 inch fraction) obtained from the excavation
bottom are presented on Figure 1. No free water was encountered in the excavation and
the soils were slightly moist.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural gravel soil designed for an
allowable soil bearing pressure of 1,500 psf should be adequate for support of the
proposed building. The exposed soils could tend to compress when wetted under load
and there could be some post-construction settlement of the foundation(and floor slab) if
the bearing soils become wet. Footings should be a minimum width of 16 inches for
continuous walls and 2 feet for columns. Loose disturbed soils in footing areas should be
removed and the bearing level extended down to the undisturbed natural 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
Parker 303-841-7119 ® Colorado Spring,s 719-633-5562 0 Silverthorne 970- 168-1989
BW-ANE, Inc.
August 6, 2015
Page 2
earth pressure based on an equivalent fluid unit weight of at least 45 pcf for on-site soil as
backfill. A perimeter foundation drain should be provided at the uphill side to prevent
temporary buildup of hydrostatic pressure behind retaining walls and prevent wetting of
the lower level. 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 GEOTECHNICAL, INC.
40-<:i416.070.
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Steven L. Pawlak, P.E.i ;. 3
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Attachment: Figure 1 —Gras a': 'st Results
Job No. 115 355A
GE�Urtech