HomeMy WebLinkAboutSubsoil Study for Foundation Design 07.10.2024lGrt#ffi,[mmi#d'*"
An Employcc Orncd Compsny
5020 County Road 154
Glenwood Springs, CO 81601
phone: (970) 945-7988
tax (970'1945-8454
email : kaglenwood@kumarusa,com
wwwkumarusa.com
Offcp Locations: Denver (HQ), Par*cr, Cdorado Spdngs, Fort Collins, Glcnwood Sprirys, and Summit County, Colorado
Iuly lo,2a24 REcElvEn
Luis Vargas
7 92 Castle Y alley Boulevard
New Castle, Colorado 81647
umbllc(Demail.com
Project No. 24-7-355
Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 31, First Eagles
Point, 177 Eagle Ridge Drive, Battlernent Mesa, Colorado
&ar Luis:
As requested, Kumar & Associates, Inc. performed a subsoil study for design of foundations at
the subject site. The study was corducted in accordance with our agreement for ge.oteehnical
engineering services to you dated June'1,2V24. The data obtained and our recommendations
based on the proposed constnrction and subsurface conditions encountered arc presented in this
report.
Proposcd Construcfion: Plans for the proposed residence pv€r€ conc€ptual at the time of our
study. The proposed residence is assumed to k a orrc- or two-story wood-frame strueturc with
aftached garagaloeatsd on the site in the area between the pits shown on Figure 1. Ground
floors could be slab-on- grade or structural over crawlspace. Cut depths are expeeted to range
between about 3 to 5 fcet. Foundation loadings for this type of construction are assumed to be
relatively light and typieal ofthe proposed type of construetion.
If building conditions or foundation loadings are significantly different ftom those deseribed
above, we shculd be notifred to re-evaluate the rccommendations presented in fhis report,
Sitc Conditions: The subject site was vasantatthetime ofour field exploration. The ground
surface was gently sloping down to the southwest at a grdla estimated at between 2 tn 3 pereent.
Vegetation consists of grass and weed with scattered sage brush"
Subsurfacc Conditions: The subsurface conditions at the site were evaluated by exeavating two
exploratory pits at the approximate locations shown on Figure l. The logs of the pits are
presented on Figure 2. The subsoils encountered, below about %foatof topsoil, consist of stiff,
slightly sandy to sandy silt down to betrreen 4 and 4Yz Mdeep u,trere dense, silty sand and
gravel was encountered to the manimum explored dcpth of lA feet. Results of swell-
consolidation testing performed on relatively undieturM samples of sandy silt, presented on
Figure S,ir:dricatrc low compressibility under existing moisture conditions and light loading anda
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GAilt-[r:LlJ t,C,-,'l L i
COMJJUNIIY TJEVEI- )PMENT
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low expansion potential when wetted. Our experience in the area indicates the expansion
potential is anomalous ard can be discounted in foundation design. Results of gradatian
analyses performed on samples of gravelly sand and silt (minus 3-inch fractian) obtained
from the site are presented on Figure 4" No free water was observed in the pits at the time
of excavation and the soils were slightly moist to moist.
Foundation Reeommendations: Considering the subsoil conditions encountered in the
exploratory pits and the nature of the proposed constructiorr, we recommend spread footings
placed on the undisturbed nafural relatively dense, granular soil below the sandy silt designed
far anallowable soil bearing pre$sure oJZ,OqO psf for support of the proposed residence. The
soilsgeneraIlytendtocompressan"'@E?'e'ecouldbesomepost-construction
foundation settlement. Footings should be a minimum width of 16 inches for continuous walls
and2 feet for columns" Loose and disturbed soils and existing fill encountered at the foundation
bearinglevel within the excavation should be removed and the footing bcaring level extended
down to the undisturbed natural soils. Exterior footings should be provided with adequate c.ov€r
above their bearing elevations for frost protection. Placement of footings at lgst 35 inches
belowthe exterio r gradeis typically used inthis area. Continuous foundation *-GttEid-Ut
reir$orcedtop and bottom to span local anomalies such as by assuming an unsupported lengfh
of af least l0 feet. Foundation walls actingasretainingstructures should be designed to resist
alateral earth pressure based on an equivalent fluid unit weight of at least 55 pcf for the on-site
soil as backfill.
Floor Slebs: The natural on-site soils, exclnsive of topsoil,arc suitable to support lightly toaded
slab-on-grade construction" To reduce the effects of some differential movement, floor slabs
should be wpaated from all bearing walls and columns with expansion joints whieh allow
unrestrained vertical movement. Floor slab control joints should be used to reduee damage duc
to shrinkage cracking. The requirements for joint spacing and slab reinforeement should be
established by the designer based on experience and the intended slab use. A minimum 4=inch
layer of free-draininggravelshould be placed beneath basement level slabs tofaailitate drainage,
This material should eonsist of minus Z-inch aggregate with less ttnn 5Ao/o passing the No. 4
sieve and less than LYo passingthe No. 200 sieve"
Alt fill matefials for support of floor slabs should be compacted to atleast9St/o of maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the
on-site soils devoidof vegentioq topsoil and oversize"d,rsck.
Urdcrdrain $ystcm: A foundation underdrain should not be required in shallow crawlspace
areas less than 4 feet deep if foundation wall backfill is adequately campaeted and surfaee
drainage precautions we taken.
-3-
Surfacc Drainagc: The following drainage precautions should be observed during co'nstruetion
and maintained at all times after fhe residence has b€en completed:
l) Inundation of the foundation excavations and underslab areas should bc avoided
during construction.' Drying could increase the expansion potential of thc soils.
2\ Exterior backfill should be adjusted to near cptimum moisture and eompacted fo
atleast9l%af the maximum standard Proctor density in pavement and slab areas
and to at least 9AVo af the maximum standard Proctor density in landscape areas,
Free-draining wall backfill should be covered with filter fabric and capped with
about 2 feetof the on-site, finer graded soils to rcduce surface water infiltration.
3) The ground surface surrounding the exterior of the building should be sloped to
drainaway from the foundation in all directions. We recommend a minimum
slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of
3 inches in the first l0 feet in pavement andwalkway ar€as.
4\ Roof downspouts and drains should discharge well beyond the limits of alt
baskfill,
5) Landscaping which requires regular heavy irrigation should be located at least
5 fwt from the building. Consideration should be given to the use of xeriscape to
limit potential wetting of soils below the foundation caused by irrigation.
Limitations; This study has been conducted in accordance with generally accepted geotechnieal
engineering principles and practices in this area at this time. We make na warranty either
express or implied. The conclusions and recommendations submitted in this report are based
upon the data obtained from the exploratory pits excavate.d at the locations indieated on Figure I
and to the depths shown on Figure 2,the proposed type of construction, and our experienee in
the area. Our serviees do not include determining the prescnce, prevention or possibility of motd
or other biological eontaminants (MOBC) developing in the future" If the elient is coneerned
about MOBC, thenaprofessional in this special field of practice should be consulted. Our
frndings include interpolation and extrapolation of the subsurface conditions identified atthe
exploratory pits and variations in the subsurfac€ conditions may not become evident until
excavation is performed. If conditions encountered during construction app€ar different from
those describ€d in this reqrt, we should be notified at once so re-evaluation of the
recommendations may be made.
This report has b'een prepared for the exclusive use by our client for design purposes. We are not
responsible for technical interpretations by others of our information. As the project evolves, we
should provide continued consultation and field serviccs during construction to review and
monitorthe implementation of our recommendations, and to verify that the recommendations
have been appropridely interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presentsd herein. We recommend on-site observation
4
of excavations and foundation bearing strata and teting of strucdral fill by a representative of
the geotechnical engineer
If you have any questions o'r if we may be of further assistance, please let us know.
Respec'tftlly Submitted,
Kumar & Associatesn lnc,
James H. Parsons, P.E.
Reviewed by:
Daniel E. Hardin, P.E.
JHP/kac
attachments Figure I - Location of Exploratory Pits
Figure 2 *bg of Exploratory Pits
Figure 3 - Swell-Consolidation Test Results
Figure 4 - Gradatron Test Results
Table 1 - Summary of Laboratory Test Results
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APPROXIMATE SCAL€-FEET
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24-7-356 Kumar & Associaters LOCATION OF EXPLORATORY PITS Fia. 1
PIT 1
EL 103.5'
PIT 2
EL. 104'
o 0
ttlC=2l.6
DD=83
tftC=Zl.7
DD=73
-2OA=34t-tdIJt!
I-Fo-
l4Jo
5 -, wc=7.2
.) +4=21
-200=3E
I wc=o.o- +1=15
-20O=41
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LEGETTID
N TOPSOIL; SLIGHTLY GRAVELLY SANDY SILT WITH ROOTS AND ORGAI{ICS' FiRM' SIIGHTIY
htotsT, LTGHT sRowN.
SII-T (ML)' SLIGHTLY SANDY TO SAHDY, SCATTER€O GRAVEL, STIFF, SI-|GHTIY MOIST, TAN.
SAHD AND GRAVEL (Sv-ev); SltW, WITH BASATT eOBBtEs At{D BOUIDERS, SO}IE
SANDSTONE FRAGMENTS, OENSE, SLIGHTIY MOIST, TAN.
F
t
HAhID DRIVE 5AMPLE.
DISTURBED BULK SAI{PLE.
rtoTEs
1. THE EXPLORATORY PITS WERE EXCAVATED WTH A hIEW HOLLAH0 E37E MINI-EXEAVATOR ON
JUNE 1 1, 2421.
2, THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PAEING FROM
FEATURES SHOWH OT.{ THS SITE PLAN PROVIDED"
3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE I'EASURED BY HAND LEVEL AND REFER TO
THE MAHHOLE Oil Ft6 I AS 100,, ASSUMED.
4" THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SHOULD 8E EONSIDERED ACEURATE ONLY
TO THE DEGREE IhIPLIEO BY THE METHOD USED.
5. THE LINES BETWEEN ITATERIALS SHOWN OI{ THE EXPLORATORY FIT LOGS REPRESENT THE
APPROXIMATE BOUHDARIES BENflEEN MATERIAL WPES AND THE TRAhISITIONS MAY BE GRADUAL.
5. GROUNOWATER WAS }IOT ENCOUhITERED IN TH€ PITS AT THE TII/IE OF EXCAVATION. PITS WERE
BACKNLLED SUBSEQUEI{T TO SAI'PUNG.
7. TAEORATORY TEST RESI}LTS:
WC = WATER CONTEI-IT (Z) (ASTM D 2216};
DD = DRY DENSITY (pcf) (ASTH D 2216],t
+4 = PERCE}ITAGE RETAINED ON HO. 4 SIEVE (ASThI D 422J2
-26A= PERCENTAGE PASSING HO. 200 SIEVE (ASTM D 1140).
24-7-356 Kumar & Associates LOGS OF EXPLORATORY PITS Fig, 2
I
SAiIPLE 6F: Scndy Sllt
FROI/:Pltlg2.5'
WC = 21.6 %, DD = 83 pcf
EXPAHSIOH UTIDER EONSTAhIT
PRESSURE UPON WETTING
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Fig. 3SWELL-CONSOLIDATION TEST RESULTS24-7-336 Kumar & Associates
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24-7-356 Kumar & Associates GRADATION TEST RESULTS Fig. 4
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G€otodlnical and iral€lals Engine€tl
ald Eruircomontal Scientrtg
TABLE t
SUTTARY OF TABONATOEY TEST RESULTS
Proj.et ilo,2&t"3ff
8mt alclTril flnnL
roFtrnE
corlEilt
l.tl
ilANNAL
tgY
DEXdIY
ldt
PENCErf
Frst6t{L
1f6 SEVE
an LTTI tffioflFns
GffiR€EAVE
finH6rH
/nA
SOIITYFEPfiDFru
ltll
GNAIEL
fLt
8 il|'
(it rnlrDttrr
gt
pulttr
illEr
!cl
I 2%21.6 83 Sandy Silt
5 7.2 u 38 38 Gravelly Sand and Silt
)2%21.7 73 34 Silty Sand
5 9.0 l5 u 4l Qravelly Sand and Silt