HomeMy WebLinkAboutObservation of Excavation 6.6.14HEPWORTH-PAWLAK GEOTECHNICAL
June6,20J4
Gabe Linehan
P.O. Box 11088
Aspen, Colorado 81612
(gaJ2elinehan /{1 gmail.com)
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Job No. 114 219A
Subject: Observation of Excavation, Proposed Residence, Lot B-10, Aspen
Equestrian Estates, 18 Equestrian Way, Garfield County, Colorado
Dear Gabe:
As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the
excavation at the subject site on June 3, 2014 lo 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 June 3, 2014.
The proposed house will be a 2 story wood frame structure with attached garage. The
lower floor will be slab-on-grade. Foundations were designed based on an assumed
allowable soil bearing pressure of2,000 psf.
At the time of our visit to the site, the foundation excavation had been cut in one level
from 3!6 to 5 feet below the adjacent ground surface. The soils exposed in the bottom of
the excavation consisted of medium dense, slightly silty sandy gravel with cobbles and
small boulders. About I to 2 inches of b1foundwater was observed in the bottom of the
northern portion of the excavation and the bearing soils in the rest of the excavation were
moist.
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
residence. 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 soils. A thin layer of screened
rock can be placed in the wet areas of the footing excavation as needed to provide for
construction in the dry. Exterior footings should be provided with adequate soil cover
above their bearing elevations for frost protection, typically 36 inches in this area.
Continuous foundation walls should be reinforced top and bottom to span local anomalies
such ac; by assuming an unsupported lenb1fh of at least l 0 feet. Foundation walls acting as
retaining structures (if any) should also be designed to resist a lateral earth pressure based
on an equivalent fluid unit weight ofat least 45 pcf for on-site gravel soil as backfill. A
Gahe Linehan
June 6, 2014
Page 2
perimeter foundation drain should not be installed for the proposed slab-on-grade floor
construction. Structural fill placed within floor slab areas can consist of the on-site sandy
gravel 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 foet 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
excavatio n, 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 he consulted.
If you have any questions or need further assistance, please call our oftice.
Sincerely,
Rev. by: SLP
DEH/ijg
cc: Dale Kaup (kaUJJC!l~t tlro[nct )
Bob Mehall (bohfil_rmnrchitccls net )
Job No I 14 :!191\
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