HomeMy WebLinkAboutObservation of Excavation 06.25.2018H.PVKUMAR
Geotechnlcal Engineering I Engineering Geology
Malerials Testing I Envimnmental
RECEIVED
AUo I 4 2018
GARFIELD COUNTY 5020 Countv Road iS4
COMMUNITY DEVELOPMENT Glenwood Springs, CO 81601
Phone: (970) %5-7989
E ma i I : h p ks re.,"i'x*@fJ$jrt";:.Xfi
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit Coung, Colorado
July 25,2018
John Landry
288 Sun King Drive
Glenwood Springs, Colorado 81601
landryparty @ yahoo.com
Project No. 18-7-471
Subject: Observation of Excavation, Proposed Additions to Existing Residence, 288 Sun
King Drive, Above Oak Meadows, Garfield County, Colorado
Dear Mr. Landry:
As requested, a representative of H-P/I(umar observed the excavation at the subject site on
July 19, 2018 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 July 18, 2018.
The proposed additions will consist of a new garage on the west side, new decks on the south
and north sides and a bump-out on the east side of the existing house. New foundations were
designed for an allowable soil bearing pressure of 1,500 psf.
At the time of our visit to the site, the new foundation excavations had been cut in multiple levels
from3Vz to 6 feet below the adjacent ground surface. The soils exposed in the bottom of the
excavations consisted of gravel and cobbles with scattered basalt boulders in a sandy clay matrix.
Results of swell-consolidation testing performed on samples of the clay matrix soils taken from
the site, shown on Figures I and2, indicate the soils have low to moderate expansion potential
when wetted. No free water was encountered in the excavations and the soils were slightly moist
to moist.
Considering the conditions exposed in the excavations and the nature of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an allowable
soil bearing pressure of 3,000 psf and a minimum dead load of 1,000 psf can be used for support
of the proposed additions. The exposed soils tend to expand when wetted and there could be
some post-construction movement of the foundation if the bearing soils become wet. 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 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
John Landry
July 25, 2018
Page2
unsupported length of at least 14 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 as backfill. A perimeter foundation drain should be provided to prevent
temporary buildup of hydrostatic pressure behind the crawlspace and retaining walls. An
impervious membrane, such as 20 mil PVC should be provided below the drain gravel in a
trough shape and attached to the foundation wall with mastic to prevent wetting of the bearing
soils. Structural fill placed within floor slab areas should consist of imported 3/a-inchroad base
compacted to at least 957o of standard Proctor density at a moisture content near optimum.
Backfill placed around the structure can consist of the onsite soils excluding topsoil and rock
larger than 6 inches and should be compacted and the surface graded to prevent ponding within
at least 10 feet ofthe building. Landscape that requires regular heavy irrigation, such as sod, and
sprinkler heads should not be located within 10 feet of the foundation.
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 subsurfauc cxploral.ion 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,
H-P* KUMAR
I
i:.
Daniel E. Hardin
Rev. by: SLP
DEFVkac
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7
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attachments Figures I &2 - Swell-Consolidation Test Results
cc: JackPalomino jackpalominoSS@gmail.com
Dolf Gona gsc@sopris.net
H-P\I(JIVIAI?Project No. 18-7-471
SAMPLE OF: Sondy Cloy Motrix
FROM: Wesl Side of Goroge ct
Fooling Grode
WC = 14.5 %, DD = 1'l 0 pcf
.ot b Eprdrcd.
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
3
JJ
1ll3tn
I
zotr
(f
-lo
tt1zo(.,
2
1
0
1
2
-3
-4
1.0 APPLIEO PRESSURE - KSF IO
18-7 -471 H-PVKUMAR SWELL_CONSOLIDATION TIST RTSULTS Fig. 1
SAMPLE OF: Sondy Cloy Motrix
FROM: Eosl Side of Goroge cl
Fooling Grode
WC = 14.5 %, DD = ltO pcf
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
J
l4I
=an
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zo
F
o
Ioazo()
1
0
-1
-2
-5
-4
r.0 10 t00
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=v1
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-2
-3
I.O APPLIED 10 I
SAMPLE OF: Sondy Cloy Moirix
FROMr Norih Side House oi
Fooling Grode
WC = i2.3 %, DD = 112 pcf
in
EXPANSION UNDER CONSTANT
PRESSURE UPON WETTING
18-7 -471 H-PVKUMAR SWTLL_CONSOLIDATION TIST RESULTS Fig. 2