HomeMy WebLinkAboutB13-0358 Soils testing report 001G661 tech
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March 6, 2014
Slopeside Construction, Inc.
Attn: Mike Dantas
2121 N. Frontage Road West
PMB 206
Vail, Colorado 81657
(ipikcdantj -, a co,mcast.nrO
Job No. 113 352A
Subject: Observation of Excavation, Proposed Residence, Lot 49, Vail Village
West Filing No. 2, 1896 West Gore Creek Drive, Vail, Colorado
Dear Mike
As requested, a representative of Hepworth - Pawlak Geotechnical, Inc. observed the
excavation at the subject site on March 4 and 5, 2014 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 general
accordance with our agreement for professional engineering services to Slopeside
Construction, Inc., dated March 3, 2014.
The residence will be two stories in height with the lower level a walkout basement
daylighting at street level to the north. The building has been designed to be supported on
spread footings using an allowable soil bearing pressure of 2,000 psf. The foundation
design was based on a previous subsoil study at the site by LKP Engineering dated July 1,
2013, Project No. 13 -2867. We have been provided a copy of that report. The site is a
relatively steep northerly facing hillside above West Gore Creek Drive. The upslope side
of the cut for the building excavation has been soil nailed up to about 26 feet high.
On March 4, the excavation was underway with natural granular soils being encountered.
At the time of our March 5 site visit, the foundation excavation was essentially complete
had been cut in multiple levels fi•om about 6 to 26 feet below the adjacent ground surface.
The soils exposed in the bottom of the excavation consisted of medium dense to dense,
silty to clayey sand and gravel with cobbles. The results of a gradation analysis
performed on a sample of the soils (minus 3 inch fraction) obtained from the site are
presented on Figure 1. No free water was encountered in the excavation and the soils
were generally moist.
The soils appear similar to those described in the previous LKP Engineering report.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural granular soils designed for
an allowable bearing pressure of 2,000 psf should be adequate for support of the proposed
residence. Footings should be a minimum width of 16 inches for continuous walls and 2
Slopeside Construction, Inc.
March 6, 2014
Page 2
feet for columns. All till and loose disturbed soils in footing areas should be removed
and the bearing level extended down to the undisturbed natural granular soils. The
subgrade should then be compacted. 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 fi-ost protection. Continuous
foundation walls should be reinforced top and bottom to span local anomalies such as by
assuming an unsupported length of at least 10 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 55 pcf for on -site soil, excluding topsoil and oversized (plus 8
inch) rocks, as backfill. A perimeter foundation drain should be provided to prevent
temporary buildup of hydrostatic pressure behind the basement walls and prevent wetting
of the lower level. The underdrain system should include at least 4 inches of free
draining gravel below the ground floor slabs. Structural fill placed within floor slab areas
can consist of the on -site sand and gravel soils, or a suitable imported granular soil,
compacted to at least 95% of standard Proctor density (SPD) at a moisture content near
optimum. Backfill placed around the structure should be compacted to at least 90% SPD
and the surface graded to prevent ponding within at least 10 feet of the building.
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 G t�TjlQICAL, INC.
David A. Young, P.E.
DAY /ljg
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Joh No. 113 3;2A
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