HomeMy WebLinkAboutSubsoils Study for Foundation DesignI(+rtffiilc¡.**s020cdntyRoad 154
Glenwood Springs" C0 81ó01
phme: (97O)95J988
far (970) 95-8454
ern¡il: lrdenwororl@kum¡nrsa-com
COWorf wwwkumarusa.com
OtræI¡cmi¡re DmmtfQiffict Gemod ftirys" ild Sl"nnft Affiy" Oolcado
Ìvlay 2û,2A22
Donnople><, LLC
Atfir: Slawek Wojciuch
255CI Highway 82, Unit 108'4.
Glenwsod Springs, Colorado 81601
slawek@domoplex.com
Job No. 22-7-297
Subj"ecil Subsoil Study for Foundation Design, Propos,ed Residence, Lot 5tr, Filing 9,
Elk Springs, CI071 Vist¿ Place, Garfield Count¡r, Colorado
flear Slawek:
As requesûod K¡.rmar and Associates, Inc. perfonned a subsoil study for design of foundations at
the strb.iect site. T[re sttrdy w¿s conducted in accordance with our agreement for geotechnical
engineerimg senvices to Domropflex, LLC, dat€d April t8, 2022. The d¿t¿ obtained and our
nocommendations based on the proposed construction and subsurface conditions encountered are
pnesented in this report.
Proposed Construction: The pnrposed residence design had not been deterrnined at the time of
our shldy. In general, it is assurned to be a two story, wood frarne structure over crawlspace or
basemrent with slab-on-grade floor and with an attached slab-on-grade garag€. Cut depths could
r¿urg€ between about 3 to 8 feet. Foundation loadings for this type of construction are assumed
to be relatively light and typical of the proposed t¡rpe of construction.
If building conditions or foundalion loadings are significantly different from those described
a.bove, we should be notified to re-evaluate the recommendations presented in this report.
Site Conditions: The site is vacant and vegetated with juniper trees, small evergreen trees, and
gr¿ùss€s. The lot is bordered on the east by Vist¿ Place, and on the west by a common area. The
lot is near a natural hilltop and slopes moderately down to the south. The ground surface is
natt¡ral with basalt cobbles ¿rnd boulders visible on the surface.
Subsurface Conditions: The subsurface conditions ¿t the site were evaluated by excavating
throe exploratory pits at the approxinrate locations shown on Figure 1. The logs of the pits are
prosantd on Figuro 2- Below about L to ZYz feet of topsoil and organic sandy silt with basalt
nocks, dense basalt gravel, cobbles and boulders in a calcareous sandy silt matrix was
encotmtend down to the tnaximum explored depth of 5 feet. Digging in the basalt rock was
difficutt due to the cobbles and boulders and practical digging refusal was encountered in the
deposit in a[[ thrce pits at depths al I% to 5 feet. Results of a gradation analysis performed on a
samp[e of the coarse granular soils (rninus 5-inch fraction) obtained from the site are presented
on Figure 3. No ftee water was observed in the pits at the tirne of excavation and the soils were
sflightly rnoist.
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Foundation Recommendations: Considering the subsoil conclitio,ns ensounterscl in the
exploratory pits and the nature of the proposed constnrction, \Me recoñMnend spread f'ootings
placed on the undisturbed natural basalt roük soil designed for ar¡ alnuwablc uoiX bcaring pre$riuire
of2J00 psf f-or Epport of the proposed residence. .t-ootings should be a rninin¡urn width of
16 inches for continuous walls and 2 feet for columns. The topsoil, and any loose disft¡rbed soiXs
encountered at the foundation bearing level within the excavation should be rernoved and the
footing bearing level extended down to the undisturbed natural soils. Utility trenches and deep
cut areas may require rock excavating techniques such as chipping and blasting. Voids created
frorn boulder removal should be backfilled with road base compacted to at least 95%o of standard
Proctor density at a moisture content near optirnunn or with concrete. We should obsen¡e the
completed foundation oxcavation for bearing conditions. Exterior footings should be provided
with adequate soil cover above their bearing elevations for fiost protection. Placernent of'
footings at least 36 inches below the exterior grade is typically used in this area" Contim¡ous
--foundation wa-lls should be heavily reinforced top and bottom to span local anornalies such as by
assuming an unsupported length of at least 10 feet. Foundation walls acting as retaining
structures should be designed to resist a lateral earth pressure based on an equivalent fluid ur¡ít
weight of at least 45 pcf for the on-site soil or imported gravel as backfill, exclucling organics
and rock larger than 6 inches.
Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitahle to support lightly loaded
slab-on-grade construction. To reduce the effects of,sorne differential moverneilt, floor strabs
should be separated from all bearing walls and solumns with expansion joints which allow
unrestrained vertical movement. Floor slab control joints should be used to reduce darnage due
to shrinkage cracking. The requirerrents frr joint spacing and slab reinforcon¡ent should be
established by the designer bassd on experiense and the intended slab use. A rninin¡wn -inch
layer of fiee-draining gravel should be ptraced beneath basønerit levetr slabs to f'acilitate drainage.
This material should consist of minus 2-inch aggregate with less than 5CIYo passing the No. 4
sieve and less than 2% passing the No. 200 sieve. The 4-inch gravel layer placed below slab-at-
gracle such as the garage can consist of 3/¿-inch road base.
All fill materials for support of floor slabs should be cornpacted to at least 957o of maxirr¡urn
standard Proctor density at a moisture content near optimum. Required fill can consist of the
on-site soils or imported granular soils devoid of vegetation, topsoil, and oversizod rock.
Underdrain System: Although free water was not errcountered during our eryrÏoration, it has
been our experience in mountainou$ areas that local perched groundwater can develop during
times of heavy precipitation or seasor¡al rur¡off. Frozer¡ ground during sptring n¡r¡off'car¡ areate a
perched condition. We recommend below-grade construction, such as retaining walÏs,
crawlspace areas, and basements, be protected from wetting and hydrostatic pressure buiÏdup hy
an underdrain system.
The drains should consist of drainpipe placed in the bottorn of the wall baakfrll surro¡¡nded above
the invert level with free-draining granular rnaterial. Thc drain should be ¡rlacacÌ at cach lwcl of
lúmr&Aceociúr, læ.o F@þclto" &-T-Er
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€xcevation and at least I foot below lowest adjacent finish grade and sloped at a minimum l%ó ta
a suitable gravity outleL Free'draining granular material used in the tmderdrain system should
contain less than 2%o passing the No, 200 sieve, less than 50% passing the No. 4 sieve and have a
maaxirnum size of 2 inches. The drain gravel backfill should be at least IYzfeet deep.
Surface Drainagc Tlre fiollowing drainage precautions should be observed during construction
and maintained at all tiftrss after the residence has been completed:
[) lnund¿tion of tho foundaticn excavations and underslab areas should be avoided
during construction.
2l Extenior backfill should be adjusted to near optimurn moisture and compacted to
at least 95% of the maxirnum standard Proctor density in pavement and slab areas
and to at least 9Va/o af the maximum standard Proctor density in landscape areas.
Free-draining wall backfill should be covered with filter fabric and capped with
about 2 foet of the on-site, finer graded soils to reduce surface wate¡ infiltration.
3) The ground surface surrounding the exterior of the building should be sloped to
drain away fr,om the foundation in all directions. lVe recomrnend a minimum
slope of 6 inches in the first l0 feet in unpaved areas and a minimum slope of
3 inches in the first 10 feet in pavement and walkway areas.
4, Roof downspouts and drains should discharge well beyond the limits of all
backfilt.
5) t andscaping which rquires regular heavy irrigation should be located at least
5 feet ftom the building.
Limitations: This sttrdy has been conducted in accordance with generally accepted geotechnical
engineering principles and practices in this area at this time. We make no warranty either
€xpress on impliod- The conclusions and necornrnendations subrnitted in this report are based
upon the d¿ta obtained from the exploratory pits excavated at the locations indicated on Figure I
and ûo the depths shown on Figure 2, the assumed type of construction, and our experience in the
are,a Our services do not include detennining the presence, prevention or possibility of mold or
other biologiaal contarninants (MOBC) deveþing in the future. If the client is concerned about
MOBC, then a prof,essional in this special f,reld of practice should be consulted. Our findings
include interpolation and extrapolation of ttrc subsurface conditions identified at the exploratory
pits and variations in the strbsurface conditions may not becorne evident untitr excavation is
penformod. [f conditions encounúer€d during construction appear different frorn those described
in this r€pod, we should be notified at once so rc-evaluation of the recomrnendations rnay be
made-
This report has been prepand 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 consulüation and field services during construction to review and
r¡aonitor the implementation of our recommendations, and to verify that the recommendations
lnave been apprcpriately interpreted. Significant design changes rnay require additional analysis
or modifrcations to the recommendations presented herein.
IúnrtAsso*,hco P@¡sxo. n-l-ln
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Vy'e recommend on-site obsorvation of excavations and foundation bearing strata and testing of
stn¡chrnl fill hy a representative of the geotechnical engineer.
If you have any questions or if we may be of furthor assistance, please let us know.
Respectfully Submitted,
Kurtltlr & .As*r¡{itr{rs, fme"
}Jd-
David A. Noteboom, StaffEngineer
Reviewed by:
Steven L. Pawlak, P.E.
attachments Figure 1-
Figure 2 -
Figure 3 -
Pits
Pits
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UTILITY
22-V-29V Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1
PIT 1 Ptl 2
EL. 104.5'
PIT 3
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LEGEND
TOPSOIL; SANDY GRAVELLY SILT WITH ORGANICS, COBBLES AND BOULDERS, FIRM, SLIGHTLY
MOIST, BROWN.
GRAVEL (GM) WITH COBBLES AND BOULDERS IN A HIGHLY CALCAREoIJS SANDY SILT MATRIX,
DENSE, SLIGHTLY MOIST, PALE TAN, BASALT ROCKS.
DISTURBED BULK SAMPLE.
I PRACT]CAL DIGGING REFUSAL.
NOTES
1. THE EXPLORATORY PITS WERE EXCAVATED WITI] A BACKHOE ON MAY 5, 2022.
2, THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM
FEATURES SI+OWN ON THE SITE PLAN PROV]DED.
3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE MEASURED BY I.IA.ND LEVEL AND REFER TO
PIT 1 AS ELEVATION 1OO, ASSUMED.
4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SHOIJLD BE CONSIDERED ACCURATE ONLY
TO THE DEGREE IMPLIED BY THE METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESENT THE
APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF EXCAVATION.
7, LABORATORY TEST RESULTS:+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ISTU O +ZZ);
-2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D 1140).
22-7 -297 Kumar & Associates LOGS OF EXPLORATORY PITS Fig. 2
6
100
s0
ao
70
50
50
40
EO
20
lo
o
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIYE READINGS u.s.CER SQUARE OPSNINGS
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.019 9.5 19 5A.t.125 2.O
OF PARTICLES IN MILLIMETERS
CL,AY TO SILT COBBLES
GRAVEL 32 % SAND 34 %
LIQI,ID LIMIT - PLASTICITY INDEX
SAMPLE OF: Highly Colcoreous Sllty Grovel ond Sond
SILT AND CLAY 54 %
FROM:Pit1O4.5'-5'
Th€sê tssl rosulls qpply only lo lhe
sompler whlch wor6 l€slod. The
lællñg reporl sholl not b€ r€produced,
excspl tn full, wllhoul lh6 wdtlo¡
opprovol of Kumor & Assooiolo3, lñc.
Slovo qnoly3¡s le3llng i! porformod in
occordonc€ wfth ASÏM 069,13, AslM 07928,
AsTl¡ c136 oñd/or ASTM D1140.
SAND GRAVEL
COARSEFINEMEDTUM ICOARSE FINE
Fig. 3GRADATION TEST RESULTS22-7 -297 Kumar & Associates