HomeMy WebLinkAboutB15-0147_B15-0147 Geotech report_1440600060.pdf~ech
HEPWORTH-PAWLAK GEOTECHNICAL
August 21, 2015
Keep Construction
Attn: Brian Claydon
P. 0. Box 3018
Edwards. Colorado 81632
thlclaydon@aol.com
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Job No. I 15 385A
Subject: Observation of Excavation, Proposed Lower Stairway Wall, Existing
Residence, Lot 50, Filing 2, Vail Village West, 1886 West Gore creek
Drive, Vail, Colorado
Dear Brian:
As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the
excavation at the subject site on August 18, 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 Keep
Construction, dated August 17, 2015.
The wall is lower downside wall of a new stairway from the street to the residence. The
wall has been designed to be supported on a spread footing assuming an allowable soil
bearing pressure of 2,000 psf. The upper wall has been constructed at this time.
At the time of our site visit, the foundation excavation had been cut from about 6 to 10
feet below the adjacent ground surface. The soils exposed in the bottom of the excavation
consisted of relatively dense, silly sand and gravel with cobbles and scattered small
boulders. The soils were too rocky to obtain undisturbed samples for swell-consolidation
testing. No free water was encountered in the excavation and the soils were generally
moist. The upper wall footing appears to be bearing on similar soils.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural coarse granular soil
designed for an allowable bearing pressure of 2,000 psf should be adequate for support of
the proposed wall. The continuous footings should be a minimum width of 18 inches.
Loose and disturbed soils in footing areas should be removed and the bearing level
ex.tended down to the undisturbed natural coarse granular soils. The footings should be
Parker 30.3-84 l -7119 • Colorado Springs 719-6 5 562 • Si!verthnme 970-468-l Q;)y
Keep Construction
August 21, 2015
Page 2
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 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 50 pcf for on-site granular soils (excluding
oversized rocks) soil as backfill. A foundation drain should be provided at the base of the
walls to prevent temporary buildup of hydrostatic pressure behind the wall. Structural fill
placed within slab areas can consist of the on-site sand and gravel soils 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 (95% in
pavement areas) 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.
If you have any questions or need further assistance. please call our office.
Sincerely,
Job No. 115 J85A