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HEPWORTH—PAWLAK GEOTECHNICAL
June 9, 2014
Terrell & Patty Tankersly
c/o Jack Palomino
815 Blake Avenue
Glenwood Springs, Colorado 81601
iackpalomino55@amail.com
1 -ler; i.stil I':)tcl.)l, Ciento. Inc.
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FaN: 970.945-5454
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Job No. 111 021B
Subject: Observation of Excavation, Proposed Detached Garage, Parcel 1,
Simmons Subdivision, 2068 County Road 137, Canyon Creek Road,
Garfield County, Colorado
Dear Mr. & Mrs. Tankersly:
As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the
excavation at the subject site on June 3 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
accordance with our agreement for professional engineering services to you, dated June 3,
2014. We previously provided a subsoil study for an addition to the existing house at this
site in a report dated July 29, 1999, Job No. 199 512.
The proposed garage will be a 11/2 story wood frame structure with a slab -on -grade floor.
Foundations were designed based on our previous recommendations for design of the
house foundations: an allowable bearing pressure of 3,000 psf and retaining walls
designed to resist a lateral earth loading based on an equivalent fluid unit weight of at
least 45 pcf for the on-site soil used as backfill.
At the time of our initial visit to the site, the foundation excavation had been cut in one
level from nil to 4 feet below the adjacent ground surface. The soils exposed in the
bottom of the excavation consisted of relatively dense, silty clayey sand and gravel with
cobbles and boulders. The southern, downhill side of the excavation had about 1 to 11/2
feet of fill composed of the on-site gravel soils. No free water was encountered in the
excavation and the soils were slightly moist.
Parker 303.841-7119 • Colorado Springs 7I9-633-5562 • Silverthome. 970-4681989
Terrell & Patty Tankersly
June 9, 2014
Page 2
We met with Kevin Freed (excavator/builder) at the site on June 5th to clarify the
proposed construction. We understand the entire excavation was cut to footing grade,
which is 3 feet below proposed floor slab grade. The slab will be supported on
compacted structural fill consisting of'/ -inch road base. We understand that soil will be
placed around the structure to provide frost protection. We recommended that the
existing excavation subgrade be moistened and compacted prior to footing construction,
particularly the fill placed on the south side of the garage and any subgrade soils loosened
by boulder removal.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural soil or a limited depth of
compacted structural fill designed for an allowable soil bearing pressure of 3,000 psf can
be used for support of the proposed detached garage. The compacted fill soils below
footings could 'settle relative to the natural subgrade soils, particularly if the bearing soils
become wet. We expect that this differential settlement will be less than % inch.
Footings should be a minimum width of 16 inches for continuous walls and 2 feet for
columns. Loose and disturbed soils and existing fill in footing areas should be moistened
and compacted or 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 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 45 pcf for
on-site soil as backfill. A perimeter foundation drain should not be needed for the
proposed slab -on -grade construction. Structural fill placed within floor slab areas should
be 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.
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
Job No. 111 021B
Terrell & Patty Tankersly
June 9, 2014
Page 3
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.
Daniel E. Hardin, P.E.
Rev. by: SLP
DEH/ksw
cc: Kaup Engineering — Dale Kaup (kaupenu a,rof.net)
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Job No. 111 02113