HomeMy WebLinkAboutReview of Cut Slope Conditions 02.27.2015G&ech
HEPWORTH-PAWLAK GEOTECHNICAL
February 27, 2015
Jeff Nalley
10918 County Road 245
New Castle, Colorado 81647
jeffnalley[a7,gmail.com
Hepworth-Pawtak Geotechnical, Inc.
5020 County Road 154
Glenwood Springs, Colorado 51601
Phone: 970-945-7988
Fax: 970-945.5454
Email: hpgeo@hpgeotech.com
Job No. 114 527A
Subject: Review of Cut Slope Conditions, Proposed ADU Residence, 10918
County Road 245 (BufordlWest Elk Road), Garfield County, Colorado
Dear Jeff:
As requested, we are providing comments regarding general stability conditions of the
existing cut slope above the proposed ADU at the subject site. Our comments and
recommendations regarding the slope are presented below. Hepworth-Pawlak
Geotechnical previously prepared a subsoil study for design of foundations at the site and
presented our findings in a report dated December 19, 2014, Job No. 114 527A.
The cut slope is on a moderately steep, south facing to the north of the proposed ADU
building. The material from the cut slope was used to level the building pad area for the
ADU. The cut slope is about 15 to 25 feet high and was made by a series of five
relatively flat benches with 4 to 5 feet high near vertical cuts between the levels. The top
of the cut slope is about 6 to 8 feet high and near vertical. The overall effective grade of
the cut slope is about 11/2 horizontal to 1 vertical. The soils exposed in the cut are
primarily silty clayey sand and gravel with cobbles. No free water seepage was observed
from the slope and the exposed cut slope soils are slightly moist.
It is planned to retain the bottom approximately 5 feet high cut on the slope with the
building foundation. The remaining near vertical 4 feet high cuts on the slope are planned
to be retained with wooden crib walls. The upper, tallest near vertical cut is not planned
to be retained.
The overall existing slope appears stable. The proposed retaining of the lower vertical cut
areas should be feasible. The retaining walls should be designed for appropriate lateral
earth pressures. Some raveling and erosion of the upper, taller unretained cut slope
should be expected unless the slope is graded back to a flatter grade and revegetated to
reduce or prevent erosion. If the upper unretained cut slope were to fail, it does not
appear the failure would affect the proposed ADU building. The relatively flat
Jeff Nalley
February 27, 2015
Page 2
intervening terrace areas on the cut slope should act to catch any soil or cobbles falling
from the slope before reaching the ADU. Other recommendations in our report that are
applicable should also be observed.
The recommendations submitted in this letter are based on our observation of the soils
exposed on the cut slope and our experience in the area. The analyses did not include
subsurface borings at the slope and a detailed stability analyses of the slope.
If you have any questions or need further assistance, please call our office.
Sincerely,
HEPWORTH PAWLAK GEOTECHNICAL, INC.
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David A. Young, P.E ;; '8242ia ice:
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G&Etech
ODDO ENGINEERING, INC.
713 Cooper Avenue, Suite 200
Glenwood Springs, CO 81601
(970) 945-1006 Fax 945-2966
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