HomeMy WebLinkAboutRevised Soil ReportlGrti' å:ffi#rni':,Íå'*"
An Ëmploycc Owncd Compony
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
fax: (970) 945-8454
email: kaglenwood@kumarusa. com
wwwkumarusa.com
Offce Locations: Denver (HQ), Parke¡ Colorado Springs, Foft Collins, Glenwood Sprirgs, and Summit County, Colorado
September 23,2A2I
Steve Reynolds
117 Ponderosa Drive
Glenwood Springs, Colorado 81601
steverevnol dswellness@.outlook. com
Project No. 2l-7-753
Subject: Subsoil Study for Foundation Design, Proposed Addition, 117 Ponderosa Drive,
Gl enwood Springs, Colorado
Gentlemen:
As requested, a representative of Kumar & Associates observed the excavation of an exploratory
pit at the subject site on September 2I,2021to evaluate the soils exposed for foundation support.
The fîndings of our observations and recommendations for the foundation support are presented
in this report. The services were performed in accordance with our agreement for professional
engineering services to Steve Reynolds dated September 15,202I.
The addition will be off the uphill, northwest comer of the residence and be up to about 10 feet
below the adjacent ground surface, roughly at the basement floor level. The addition will be
open initially with the option of being covered in the future.
At the time of our visit to the site, an exploratory pit was excavated near the middle of the
proposed addition to a depth of 10 feet, roughly the proposed design foundation bearing level.
below the topsoil and apparent shallow depth fill soils, the soils exposed in the pit consisted of
slightly clayey silty sand and gravel with cobbles and scattered small boulders. The results of a
gradation analysis performed on a sample of the gravel (minus 5-inch fraction) obtained from the
pit are presented on Figure l. No free water was encountered in the pit excavation and the soils
were slightly moist.
Considering the conditions exposed in the pit excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural granular soil designed for an
allowable soil bearing pressure of 2,500 psf can be used for support of the proposed addition.
A one-third increase in the allowable bearing pressure can be taken for eccenffically loaded
(retaining wall) footings. The matrix soils likely tend to compress r¡¡hen wetted under load and
there could be some post-construction settlement of the foundation if the bearing soils become
wet. Footings should be a minimum width of 18 inches for continuous walls arid 2 feet for
columns. Loose disturbed soils and existing fill in footing are¿N should be removed and the
exposed soils moistened and compacted. We should observe the completed foundation
excavation for bearing conditions prior to forming footings.
Steve Reynolds
Scptcmbcr 23,2AZl
Page2
Exterior ttrotings should be provided with adequate soil cover above their bearing elevations for
&ost protection or frost protected with rigicl insulation. Continuous foundation walls should be
reinforced top and bottorn to spam local anomalies such as by assuming an unsupported length of
at least 12 fbet. Foundation walls acting as retaining structures should also be designed to resist
alatercl earth pressure based on an equivalent fluicl unit weight of at least 45 pcf for on-site soil
as backfill, excluding rock larger than ó inches. A sliding coetficient of 0.45 and passive earth
pressure of 400 pcf equivalent fluid unit weight can be used to resist lateral earth pressr¡re
loading on retaining walls.
A perimeter foundation drain should be provided to prevent temporary buildup of hydrostatic
pressure behind the basemenlretaining walls and wetting of the lower level. Structural fill
placed within floor slab arcas can consist of the on-site soils compacted to at least 95% of
stanclarcl 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 5 feet of
the building. Landscape that requires regular heavy irrigation, such as sod, and sprinkler heads
should not be located within l0 feet of the foundation.
The recommeldations submitted in this letter are based on our obsen'ation of the soils exposed
within the pit excavation and our experience in the area. This study is based on the assunpticn
that soils beneath the footings throughout the addition have equal or better support than those
exposed in the pit. The risk of foundation movement may be greater than indicated in this report
because of possible variations in the subsurface conditions. Variations in the subsurface
conditions encountered in the excavation could change the recomtrendations contained in this
ietter. Our services do not include detemtining the presence, prevention or possibility of mold or
otherbiological contaminants (MOBC) developing in the future. If the client is concemed 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,
L¡¡¡ll:¡¡' "-Q ¡\ssoei¡tcs. lnç:
Steven L. Pawlak,
SLP/kac
Attachment: ligure I Results
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DIAMETER OF RS
CLAY TO SILT COBBLES
GRAVEL 50 % SAND 23 %
LIQUIO LIMIT - PLASTICITY INDEX
SAMPLE 0F: Slightly Cloyey silty Sondy Grovel wilh Cobbles
SILT AND CLAY 27 %
FROM;Pit1e7'-8'
Thosr lost rcsulls opply only lo lht
somDl.s whlch w.r. l.slad, Th.
to3tliìg raÞort gholl nol ba roproduc.d,
oxc€pl ln full, wllhoul lh6 wrltlon
opprovol of Kumor & Assoclolas, lnc,
sleve onolysls Lsllno ls p€rlormad ln
occordoncc vllh ASTM D6913' ASTM 07928,
ASTM C136 ond/or ASIM D1140.
SIEVE ANALYSISHYDROMEIER ANALYSIS
CEAR SQUARE OPENINGU.3. SIANDÆO SERIB
310 ¡â
TME RruINGS
i utN24 HRS 7 HRS
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FIN E MEDTUM lcOanse FIN E COARSE
21 -7 -753 Kumar & Associates GRADATION TEST RESULTS Fig. 1