HomeMy WebLinkAboutSoils Report 07.03.2017H.PryKUMAR
Gaotachnlcal Englneedng I Englneedng Goology
Malerials Tsst¡ng I Envimnmcnùrl
5020 County Road 154
Glenwood Springs, C0 81601
Phone: t970) 94S7988
Fax (970) 945-8454
Ernail: hpkglenwood@kumarusa.com
Offiæ Locations: Parker, Glenwood Springs, and Silveflhorne, Colorado
SUBSOIL STUDY
rOR FOUNDATION DESIGN
PROPOSED RESIDENCE
LOT 64, FILINC 2, PINyON MESA
TBD PAINTBRUSH WAY
GARFIELD COUNTy, COLORADO
PROJECT NO. 17-7-390
JULY 3,2t17
PREPARED FOR:
INTEGRATED MOUNTAIN DNVNLOPMENT, INC.
ATTN:.IIM GORNICK
P.O. BOX 908
GLENWOOD SPRINGS, COLORADO 81602
@)
RECEIVED
JUL z 3 20t8
GARFIELD COUNTY
COMMUNITY DEVELOPMENT
PURPOSE AND SCOPA OF STUDY
This report presents the results of a subsoil study for a proposed residence to be located at Lot
64, Filing 2, Pinyon Mesa, TBD Paintbrush Way, Garfield County, Colorado. Tlre project site is
shown on Figure L The purpose of the study was to develop recomrnendÍìt¡ons for the
foundation design. The study was conducted in accordance witl¡ our agreement for geotechnical
engineering services to Integrated Mountain Development, Inc. dated May I I,2017.
An exploratory boring was drilled to obtain information on the subsurface conditions. Samples
of the subsoils obtained during the field exploration were tested in the laboratory to determine
their classification, compressibility or swell and other engineering characteristics. The results of
the lield exploration and laboratory testing were analyzed to devclop recommendations for
foundation types, depths and allowable pressures for the proposed building foundation. This
report summarizes the data obtained during this study and presenl,s our conclu.sions, design
recommendalions and other geotechnical engineering considerations based on the proposed
construction and the subsurface conditions encountered.
PROPOSED CONSTRUCTTON
The proposed residence will be two story wood frame construÇtion above a basement and with
an attached garage. Basement and garage floors rvill be slab-on-grade. Grading for the structure
is a.ssumed to be relatively minor with cu( depths between about 3 to l0 feet. We assume
relatively light foundation loadings, typical of the proposed type of con.struction.
If building loadings, location or grading plans change significantly from those described above,
we should be notifïed to re-evnluate the recommendations contained in this report.
SITE CONDITIONS
The property is vacant and vegetated with sage brush, grass and weeds. Vegetation in the front
part of lot has been removed during the subdivision development. The ground surface in the
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Proiect No. 17-7-390
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test ¡s similar to the standard penetration lest described by ASTM Metlrod D- I 586. The
penetration resistance values äre an indication of the relative density or consistency of the
subsoils. Depths at which the samples rvere taken and the penetration resistance values are
.shown on the Log of Exploratory Boring, Figure 2. The samples lvere returned to our laboratory
for review by the project engineer and testing.
SUBSURFACE CONDITIONS
A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The
subsoils, below about 6 inches of topsoil, consist of very stiff sandy clay to I feet and sandy silt
and clay to 22 fee¡, underlain by hard to very hard siltstone bedrock to the boring depth of 31 feet.
Laboratory testing performed on samples obtained from the boring included natural moisture
content and density and percent fine¡' than sand size gradation analyses. Results of swell-
consolidation testing perfornred on relatively undisturbed drive samples of the clay and silt soils,
presented on Figures 3 and 4, indicate low conrpressibility under light loading and narural low
moisture conlent. The upper clay soil showed low expansion potential and the underlying silt
and clay soil showed moderate collapse potential (settlenrent under constant load) when wetted.
The laboratory testing is summarized in Table L
No free water wâs encountered in the boring at the Lime of drilling or when checked on June 15,
2017 and the subsoils and bedrock were slightly moist.
FOUNDATION BEARING CONDITIONS
The sandy clay and silt soils encounlered at typical shallow foundation depth mainly tend to
settle when they become wetted. A shallow foundation placed on these soils will have a risk o[
settlement if ¡he soils become u,etted and care should be taken in the surface and subsurl¿ce
drainage around the house Lo prevenl the soils frorn becoming wet. It will be critical to the long-
term performance of the structure that the recommendations for surface grading and subsurface
drainage contained in this report be followed. The âmount of settlement, if the bearing soils
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Projecl No. 17-7-390
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3)Exlerior footings and footings beneath unheated areas ,shoulcl he providecl with
adequate soil cover above their bearing elevation for frost protection. Placement
of f'oundations at le¿st 36 inches below exterior grade is typically used in this
¿trea.
Continuous loundation walls should be heavily reinforced top and botto¡n to spän
local anomalies such as by assuming an unsupported length of at least l4 feet.
The foundation should be configured in a box like shape to help resist differential
movements. Foundation walls acting as retaining structures should also be
designed to resist lateral earth pressures as discussed in the "Foundation and
Retaining \ü/alls" section of this report.
The topsoil, slrb-excavation depth and any loose or disturbed soils should be
removecl below the foundation area. The exposed soils in footing areas alter sub-
excavation should then be moistened and compacted. Structr¡ral fill should
consist of lorv permeable soil (such as the on-site sandy clay and silt soils)
cornpacted to at least 98Va of standard Proctor density within ZVa af optimum
moisture content. The slructural fill should extend laterally beyond the footing
edges equal to at leasl % the fill depth belorv the footing.
A representative of the geotechnical engineer should evaluate the fill placenrent
for compaction and observe all footing excavations prior to concrete placenrent.
4,
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6)
FOUNDATION AND RETAINING WALLS
Foundation ivalls and retaining struçt,ures rvhich are laterally supported and can be expected to
undergo only a slight amount of deflection shor¡ld be designed for a lateral earth pressure
con:puted on the basi.s of an equivalent fluid unit rveight of at lcast 55 pcf forl¡acklìllconsisting
of the on-site line-grained soils. Cantilevered retaining structures rvhicb are separate from the
residencc and can be expected to deflect suflìciently to mobilize the full active eðrth pressure
condition should be designed for a lateral carth pressure computed on the basis of an equivalent
fluid unit weight of at least 45 pcf for backfill consisting of thc on-site fìne-graincd soils.
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Projecl No. 17-7-390
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the effects of some differential movernent, floor slabs should be separated fronr all bcaring walls
and columns with expansion joints which allow unrestrained vertical movement. Floor slab
controljoints should be used to reduce damage due to shrinkage cracking. The requirements for
joint spacing and slab reinforcement should be eslablished by the designer based on experience
and the intended slab use. A minimum 4-inch layer of free-draining gravel should be placed
beneath basement level slabs to facilitate drainage . This material should consist of minus 2-inch
aggregate with at least 507o retained on the No. 4 sieve and less Lhan ZVo passing the No. 200
sieve.
All fill mâterials for support of floor slabs should be compacled Lo at least 957o of maximurn
sf andard Proctor density at a moisture contenl near optimum. Required fill can consist of the on-
site soils devoid of vegel.ation and topsoil.
UNDERDRAIN SYSTEM
Although free wafer was not encounfered during our exploration, it has been our experience in
the area and where clay soils âre present, that local perched groundwater can develop during
times of heavy precipitation or seasonal runol'f. Frozen graund during spring runoff can creûte a
perched condition. We recomnrend below-grade construction, such as retaining rvalls and
basement areas, be protected fron¡ rvetfing and hydrostatic pressure buildup by an underdrain
system. An underdrain should not be provided around slab-at-grade gâragc and crawlspace areas
to help lirnit potential wetting of bearing .sails from shallow u/aler sources.
The drains should consist of drainpipe placed in the bottom of the wall b¡ckfìll surrounded above
the invert level with free-draining granular nuterial. The drain should be placed at each level of
excav¿¡tion and ut leasl I loot below lowest adjacent finish grade and .sloped at a minimum l7o to
a suitable gravity outlet or surnp and pump. Free-draining granular materiäl used in the
underdrain systern should contain less than 27o passing the No. 200 sieve, less than 5û7r, passing
lhe No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at
least lth leel deep. An impervious membrane such as 20 mil PVC should be placed beneath the
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in the future. If the client is concerned about MOBC, then a professional in this special fîeld of
practice should be consulted. Our lindings include interpolation and extrapolarion of the
subsurface conditions identified at the exploratory boring and variations in thç subsurface
conditions may not become evident until excavation is performed. If conditions encountered
during construction appear different from those described in this report, we should be notified so
that re-evaluation of the recommendations may be made.
This report has been prepared for the exclusive use by our client for design purposes. We are nol
responsible for technical interpretations by others of our information. As the project evolves, we
should provide continued consultation and field services during construction to review and
monitor the implementation of our recommendations, and to verify that the recomnrendations
have been appropriately interpreted. Significant design changes may require additional anatysis
or modifications to the recommendations prcsented hcrein. rvVe recommend on-site observation
of excavations and foundation bearing slrâta and testing of structural fill by a representative of
the geotechnical engineer.
Respectfully S ubmitted,
H-P* KUMAR
Louis E. Eller
Reviewcd by:
Steven L. Pawlak,
LEE/liac
cc: Oddo Engineering
*1&'¿2*. g
4
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Projecl No. 17-7-390
i
BORING I
EL=6199.3'
0
5
LEGEflÞ
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7¡717 ORlVt SAMPLE BLOW COUNT. INDICÀIûS lHÂl 26 8t0WS 0t Å--,'- I1O-POUNO HAMMTR FALLI}IG 30 TNCHTS WERE RTOUIRTO TO DR¡VT
THE SAMPL:R 12 INCHTS.
NOTES
I, THE EXPLORATORY 6ORIHG IVÂS DRILLTO ON MÅY t6,2017 W'TH À 1-INCH
O}ÂMT'TR CONTINUOUS ¡LIGI{T POWTR ÅUGSR.
2, T}IE IOCA]ION OF THT TXPTORAÎORY BORINû WAS IJTASUREO
ÂPFROXIMÂTELY 8T PACIIIG IROI' TEÂTURTS SHOWN ON THT SITE PI,AN
PRoVt0t0.
3. THE TLEVATION OF THE TXPLORATORY SORING WÂS I'TÂsURTO 8Y HÀND
LEVEL ÂNO REFTFS fO ROAOWÂY 6RADT STAKT.
4. IHT TXPLORÀTORY BOftITIG LOCÀTiON AND ILEVÀIION SHOULI) BE
COI{sIDCRID ACCURATT ONLY TO THT DTGRTE IHPLIED 8Y THE MITHOD
U5TD,
5, fHl L¡NIS BmVEEN [{ÂrtRlÅLS SHoWN 0N lHt EXPLoRÂT0RY BoR:f¡c LoG
RTPfl'5ENI THT ÀPPROX{MÂIE SOUNBAiITS SETWIEN MA1TRIAL ÎYPES ÂND
THT TRANSIÎIONS UÅY 8T CRADUAI.
6. ORÛUI¡OWATTR WÅS NOl T¡¡COUNTTRTO IN THE BORII¡C AT ftE T'UE OF
ORILLING.
7, tÂBOfiÁTORY TESI RTSI'LIS;
\{c = ttAIÊR cofiitNf (16) (ÀsrH û ?216);
0D = oRY DENSTTY {pcr) (ÀSrM 0 22rS);
-200 = PtRCtNrÁçE PASSrtt0 N0. 200 StEvt (ASTH Ð ll10).
T0PS0|L¡ 0R0AN|C SÂNDY SILI /ìN0 CL¡\T, nRM, StlCHltY ¡r0l5l, 8R0WN
CIAY (Ct); SILTY, SÂNÐY, vÉRY STFr, SLIGI{¡IY M0IST, 8R0WN, LoW
PLÂ:TEIÛ, sLIçIITLY CALCÀRIOUS.
5rL1 ÅND CUY (ML-CI); SANDY, vtRY Strf, SLEHTLY M06r, UcHt
0R0I{N, cÂtcÂRtous IFAcgs.
SILTSIONI BEÐROCX; HÂR0 I0 YIRY HÁRÐ WTH 0tP1H, SLÍGHiLY ¡¡015I,
LIGHT GRAY. EÀGLË VÅLLEY EVÁPORITT,
ORIVE sAMPI.E, 2-INCH I.O, CÂLIFORNIÂ UNÊR 5ÄMPLS.
10
15
20
25
3{t
35
?6/t2
tE/12
Y{C;7.9
0D=l 05
1a/12
Y/C-5. I
0l=107
-200=83
20/12
WC:3.9
DD=95
26112
5s/t2
WC=1.9
00. I 27
-2ÐA=22
5a/ 4
1 7-7-590 H-PryKUMAR LOG OF EXPLTRATORY BORING Fig. 2
SAMPLE OF: Sondy Slll ond Cloy
FROM: BorlnE I O 15'
WC = 3.9 Z, DD = 95 pcf
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ADOITIONAL COMPRËSSION
UNDER CONSTAI'IT PRESSUR€
DUE TO WETTINC
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17-7-394 H-PryKUMAR SWTIL-CONSOLIDATION TEST RESULTS Fig. 4
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