HomeMy WebLinkAboutPreliminary Geotechnical Study 03.14.2008,ð 14
þ**a
l'l.r'r..,r¡!l l'r',i ì ; "'r¡' -it"r' :i. rlr'
','..: ' .,,,t,, l'l ,, i i; ì
i ,,. .' . ", : ' ¡ ¡: ,:" ' .'i. ,.r' i l':. I
l'Ì1, 'f : 'rl,' !r'ì -i ,') I .i
lJ Ë F'woi?f i-i - PÅ],ry L,*ì'd cirÛT Ë.t l-t hi i t'{t I ìr.r . ,i;ì-.!j,ri-..1:: i
. i¡r:ril. ilit,j,,ti'ii¡:r''¡! l'':'ìlll
GEOTECITNICAL STUDY
PROPOSED TCI RANCTI SUBDIVISION
HIGHWAY 82 EAST OF COUNTY ROAD lOO
COUNTY, COLORADCI
)B NO. 1û6 0920
ARCH 14,2008
:
PS,trPARED FOR:
TCI IIANE RI|NCH, LLC
C/CI NOBLE DT'SIGN STUDIO
ATTN: JON FRßDERICKS' ASLA
19351 HIGHWAY 82
CARBONDALE, COLORADO 81623
J{
N4
ì
l
i ,,!,,1;,ii', -,¡ ;irt,:'. , it' It i "' 1'r't.- '' -ìi ' ¡lil' itlr i'' ^i:' I
TABLE OF CONTENTS
PI.]RPOSE AND SCOPE OF.STUDY
SITE CONDITIONS
REGIONAL GEOLOGIC SETTING..,
PROJECT SITE GEOLOGY,......,.,
RIVER TERRACES AND DEPOSITS
EAGLE VALLEY EVAPORITE,......,,.......
GEOLOGIC SITË ASSESSMENT....
RIVER FLOODING
SINKHOLES ..........,.....
EARTHQUAI(E CONSIDERATION S
RADIATTON POTENTIAL............
IITELD EXPLORATION ....,......
SUBSURFACE CONDITIONS."-..,....
PRELIMINARY DESICN RECOMMENDA]TON S
FO{JNDATIONS .........
BELOÏY GRADE CONSTRUCTION...
FLOOR SLABS
SIJRFACE DRAINAGE
PAVEMENT SECT]ON
L|MITATIONS .............
REFARENCES ..............
FIGURE 1 _ PROJECT' SITE LOCATION
FIGURE 2 * GEOLOGICALLY YOLING FAULTS AND LARGER I'ITSTORIC
EART'I-IQUAKES
FICURE 3 * WESTERN COLORADO EVAPORTTE REGICIN
FIGURE 4 * PROJECT AREA GEOLOüY MAP
FIGUR.E 5 - LOCATION OF EXPI.ORATORY PITS
F}GURE ó_LOGS OF EXPLORATORY PITS
FIGL}RE 7. LEGEND AND NOTËS
FIÜURE B - SWELL-CÛNSCILIDATION TEST RESULTS
FIGURES 9, IO, I1 & i? - GRADATION TEST ITESULTS
TABLE I- SUMMARY OF LÂBORATOIII'TEST RESULTS
..., I -
... - I -
...-2-
J
4
4
5
5
5
6
_'7 -
...... - I -
...... - I -
...-B-
...-9-
...-9-
...-9-
.-10-
.-10-
....... _ l0 -
......" - 12 -
PTIRPOSIi ANI} SCOPE OF'SI'I.IDy
This report presents the results of a ¡:reliminary geotechnical study fol the proposed
residential subdivision at TCI Lane Ranch located north of the Roarfurg Folk l{iver and
east of the Blue Creek Ranch Subdivision, Garfîeld Courty, Colot'aclo. The pmject site is
shown on Figure l. Tlie puryose of the stucly was to evaluate the geologic antl subsurface
conditions and their potential inrpact on the project. The stucly was conducted in
accorclance with our proposai fôr geotechnical engineerùrg selvices to TCI Lane Ranch,
LLC, clated Dece urber 2A,2007. We previously conducted percolation testing for a septic
system design on the prcpeüy and presented our findings in a repoú dated Octobel 31,
2006, JobNo. 106 0920.
A fielcl exploration progräm consisting of a recorïlaissance and exploratoty pits rvas
conducted to obtain infbrmation on the site and subsurfbce couclitiolis. Samples of'the
subsoils obtained during the fiekl exploratiorr werê lssLsrl ,it the laboratory to dctcrminc
their classiûcation, compr-essibility or swell and other engineering characteristics. The
lesults of the freld exploration and labolatory testing were analyzecl to cleveiop
recommeudations fbl project planning ancl prelirninary clesign. This report sutlrmaLizes
the clata obtained during this study and presents our conclusions atrd recomntendatiotts
based on the proposec{ development and subsurface conditiolrs encounterecl.
StrTE CONDITIONS
Tþe TCI Lane Ilanch covers atrout i 00 acres and is located in lhe Roar:ing Fork River
valley about tltree ancl one-half miles upstream of Carl¡onclale, see Figule l. The
property lies to the nofth of the river and is entilely oir the nearly level valley floor. The
valley tloor has an averâg€ slope erf about 2 pei'cent down to lhe west. It is made up of
, -,,1,-:-,' -- l^--^1^ al^^¿ ^--- -^-^,--.^.^-1 l^,,l^.., ^^ã,ìr..rr1aôñ+ô 'l-lro o¡nnrrrmêrlfc qtês(jvçl¿ll ltvtil tç¡I¿lçc -ltivti¡s ul¿11 alg SrJlJdr¿tLçrr uy rL,w çrrd¡lJ¡¡¡w¡¡Lo' ¡ rrL vrvu^t/
typically about 6 to 20 fèet high and lrave slnpes of about 50 to 70 Fercent. llhe teruace
or,,-fì¡oo lia hotrr¡earr <¡k¡rrrf 1- t'¡ á"Á fppt nhnr¡e the tiver The Ft'¿rntaçte Road ltlr I-IishWaV
B2 is locatecl along tlre northeln ¡troperty line. Pafis of the southern property line are in
Jotr No. 106 0920 ceötech
2-
t¡e Roaring Fol.k l{ver.chan¡el. The Blue Creek Subdivision borders the ptlrperty on the
west ancl rural homes and agricultural land are located on the pïopeîties to tlie east. At
the tiure of this stucly several houses ancl r¿¡nch buildings wete located in the east-central
pafi of the TCI Ranch. Much of the ranch is imgatect hay fìelds and pasture which
are located ly on the higher terîaco suffüces. Cottotlwood lrees, other trees and brush
are typical of vegetatioll on the lower terraces. Poorly drained wetlands are also
plesent on t]te wet ten'aces
PROPOSED DEVELOPMtr]NT'
pment at the TCI Lane Ranch wìll be mostly a resiclential
development faciiities will füclude a network of streets, a comnunity
park and other ity làcilities.
jplans change significantly fiorn those described, rve shoulci be notifìerl to
tecomlnendations presentecl in this lepoÉ'
REGIONAL GEOLOGIC SI'TTING
Tire ploject is in the Southern Rocky Moutttains to the west of the Rio Grande rift ancl
to the east of coloracJo Plateau, see Figure 2. The site is in the western colol'ado
and is in the Carbonclale collapse center, see Figure 3. Thc Carbollclaleevaporite
The proposeci
subdivision as
parl of the
undevelop
proposed.
ed
If developtnent
le-evaluate the
colla¡rse ceitter
Colorado. It is
vicinity of
the r"egions
on Figure 4. A piant ntu'sery will be located in the northwestetl
Tlie lowest tet.races along the rivel rvill not be developecl and
will lemain along Llighway 82. Eiglrty-nine residential lots are
the western of tr.vo |egional evaporite collapse cellters in rvestern
irregular-shaped, nor"thwest trencling region between the Wllite River
lram and others, 2002i. The or¡aporite is nrostly in tlie Ëagle Valley
uplil1 antl basin. It covcrs about 460 square miies. As lriuch as 4,000 feet i¡f
regional subsid is believecl to have occurted during the past i 0 mìllion years in the
ale as a |csult of dissolution and flowage of evaporite fi'ombeneath
Evalrorite witl"i in rhe Eagle valley Foruratio¡r. The Eagle vailey Evaporite is tlre
ileal stlrfacc roclc belorry the sur:ficial soil cleposits at the pr"Ûject site' It crcps
.lob No. 106 0920 Gäbtech
-J-
out on the steep valley side to the south ofthe river, see.[,igure 4. Much of t¡e evaporite
related subsidence in the Cal:bondale collapse center appears to have occurred within the
past 3 rnillion years which also conesponds to high incision rates along the Roaring For.k,
Colorado and Eagle Rivels (I(unk and others, 2002). This indicates thät long*ten*
subsiclence fates have been very slow, between about 0.5 and 1.6 inches per 100 years. It
is uncertain if regional evaporite sutrsidence is still occurring or if it is curen¡y inactive.
If still active these regiotral dsfornmtions because of their very slow rates should ¡ot have
a significant impact on the propose tleveropme,nt at trre TCI La'e Ra¡rch.
Geologically young faults related to erraporite tectonics are presed i' t¡e Carbonclaie
colla¡:se center btrt consiclering tlie nature of evapolite tectonics, these fault are not
consiclereci ca¡:atrle 0f generating large earthquakes. The closest geologically youug
faults that are less than about 15,000 years old ancl considered capable of generating large
eafihquakes ate located in the Rio Graude rift to the east of tire pr-oject site, see Figure 2.
'flte noúhetn scction ofthe Williams Fork h¡fountains fault zone e50 is locared about 60
rÏiles to thc nofiheast ancl tlre southern section of the Sawatch tàult zone e56b is locatecl
about 60 miles to the southeast. At these distances large earthquakçs o¡l these two
geologically youlig {ault zones shoukl not produce stlong ground shaking at the proiect
site that is greater than the ground slialcing shown on the Li. S. Geological Survey 2002
National seisrnic Flazards Maps (Þ'ra'kel a'd otliers, 2002).
PROJECT SITE GEOLOGY
Tlte geology irr tire project ¿r'ea is shown on Fìgure 4. This map is based on our field
obsenations a¡rd ìs a modifìcation of the r.egional geology rnap by lfirkham ancl
Widmann (1997)' Near surtirce ibrmation rock is the middle Pennsylvanian-agg Eagle
Valley Evaporite. This legional roch folmatiou was deposited in the centrai Coloraclo
ttough during the Ancestt'ai Rocky Mountain oïogeny about 300 million year.s ago. At
the prnject site the evaporite is covered by a ser ies of Roaring Fork Riyer telraces and
dcposits tlrat are associated with cyclic 1:eriocls of deposition ancl erosion relatecl to glacial
attd interglacial clirnatic tluctuations clur:ing about the past 35 thousand years.
Job No. 106 092i,G€òtech
4
RTVEIT'I'IRRACES AND DEPOSITS
Remnants of seven t'iver terace levels (Qtl tllnugli Qt7) are prcsent at tlie project site.
The loweÏ four temaces are prnbably related to post-Pinedale climatic fluctuations clur.ilg
the past 15 thousand years. Tetrace Qt1 lies within 4 ftet of the river. Tenace et2 lies
about 6 feet above the river, tenace Qt3 lies about l2 feet above the river and te¡.ace et4
is about 22 feet alrove the river. The Qtl terlaces are surall river 6ank tenaces a¡d
channel bar cleposits. The Qt2 telraces are olct alranclonecl river channels that lie bel.,,v
the Qt3 tetrace surface. The tliree higher ten'¿ìces are ¡rrobably associatecl with the late
Pleistocene-age' Pineclale glaciations between about l5 ancl 35 thousaud yeal-s ago.
Tenace Qt5 lies about 38 lèet above the liver, tenace Qr6 lies nbout 40 fbet above the
tiver and teüace Qt 7 lies about 46 &et above the river.
our exploratory pits show that the alluvial cieposits below terrace leveis et3 tluough et7
¿fe similar. They consìst of a thin, less than i -foot thiclc to 3-1bot thick, tgpsoil for.mccl ir¡
solì' silty clay over-bauk cleposits. The over*b¿urk cleposifs overlie river aliur¡ium that
consists of rouncled gravel- to boulcler'-size rocks iu a relatively clean sand matrix. The
river alluvitlm extenrlecl to the bottom of the exploratory pìts tlrat were excavatecl to
depths of around 9 feet. JLulging li'om water well rec¡lds in the Coloraclo State
Engineer's dafa base the rivct'alluvium is probably in the range o{'40 to 50 lèet deep i¡
thc project arrea.
ËAGLE VALLEY EVi\PORII-E
The Eagle Valley Fvaporite uncleriies the Roaring Fork Rivel alluviun iu the project area
ancl as cliscussed above tnav extertd to depths of'40 to 50 feet trelorry the teflace surià.ces.
The Eagle Valley Et'al:orite is a sequence of evaporite rocks consisti¡g olurassive to
laminated gypstllll' anhl'cirite, anil halite interbeddecl with light-colorecl uruclstoue, fìne-
grairiecl sanclstone, thin limestone and dolomite beds a¡rcl black shale (lfirkharn ancl
Widmalur, 1997)' The $'aporite minerals are relatively soluble in circulating grouncl
wâter anci subsurlàce.solution r¡oicls ancl relatecl surfhce sinkholes are locally present irr
tJtese rocks tluougltorrt fhe u'esteur Coioraclo eva¡:orite region rvliere the eva¡:orite is near
Jotr No. l0(r (ll)2(l
cåFtecl.
5-
the surface' see Figure 3' sinkholes wel'e ¡rot obseryect at the project site cluri¡g o'r field
work but the snow cover at tbat tirne niay have obscu¡:ed sinkiroles if pr.esent.
GEOLOGIC $ITN ASSESSNIENT
Geologic conditions that could present an unusually high r.isk to the prnposed
developurent v/ere not identifiecl by this sturly but there are geologic con¿itiçns that
should be considered in the prcrject ¡rlanning ancl clesign. These conditions, their potential
risks and possible mitigations to lerluce the risks are discussed below. ceoteclnical
e'gheering design eonsiderations are presentecl in the prerí'rinary Design
Recommendations section of this report.
RTVER FLOODING
The low lying ten'aces along tlie Roaring Fork River may be subject tti ¡:eriodic floocl¡g
during high river f'lows. ?he hydrologic stucly corrducted fbr the piqect stornl water
mãnagelneut plan desigrl shouitl evaluate the potential fbr river flooding ancl possi6le
methods to prctcct proiect facilities fi'om an appro¡:riate clesign flootl on the river.
SINIil{OLES
Geologically young sinkholes are present in the lvestenr Colorado evaporite region
mostly in areas where the Eagle valley Fornration ancl Eagle valley Evaporite are
shallow, see Figure 3. In this region a few silrkholes have collapsed at the grou¡d surfàce
with little or no wamiug during liistoric tímes- This inciicates that infi.equenf sinlc6ole
formation is still arr active geologic process in the region. Eviclence of sinkholes was not
observed at the proiect site during our lield recc¡lmaissance or aerial photogr.aplrs revierv
but coulcl have been obscurecl by the srlorv cover. A field review to look for sfurkholes in
tlte ¡:roposed builcling area sliould be macle after the site is clear of'snow cover. Alt¡g¡gh
geologically active fur the region, tire likelihoocl tlmt a sinkhole will development duri¡g a
reasonatrle exposure til¡e at tire prnject area is corLrsielerecl to be low. This inf'ere¡ice is
.f ob No. 106 0920 e&Ftectr
-6-
based on thc large extellt of sinlchoie prone areas in the region in comparison to the sulall
nr¡¡l'rber of sinldroles thnt havc developed Lr historic times.
Because of the cotnplex nature of the evaporite relatecl sililiholes, it r,vill not bc p0ssible to
avoitl all sirilchole risk at the project site. If conditions inclicative of sinkhole relatecl
pt'oblerns are encounterecl durirtg site specific soil and founclation studies for.{he houses
allcl other moveltteut sensitive faculties, an altenrative building site should be consiilerecl
or the feasibility of'mitigation evaluated. Mitigation rneasul"es could inclucle: (l) a rigid
rnat lòundation, (2) stabilization by grnutinø. (3) stabilizatiori by excavation ancl
backfîlling, (4) a clee¡: Jbu¡rclation system or'(5) stlrctural bri¿gi'g. Watçr fbatLrres
should not bc consicleretl close to builcling sites, unless evaluated ou a site specifîc basis.
The home Ûwllers coulcl purchase special insurance to reriuce their potential rislcs.
Ptospective owllers sllould be advised of the sinkhole potential, since early cletectiou of
builcling clistress ancl liniely remedial actions are impofant in reclucing the cosf of
building repair should alt uncletectecl subsurface voicl star1 to develop into a si*khole afler
construction,
EAI{TI-TQUAKE CON SIDEITATTON S
Historic eafthqualces withirt 150 nriles of the project site h¿ì\¿e tyi:rically Seen moderatelv
stlong witit magnitudes oI' M 5.5 ancl less and ulaxirnurn MoclifÌecl Mer.calli Inte'sities ofvi and less, see Figure 2. Thr: largest historic earthquake in the projecr r.egio, cicct¡r.r.e¡ in
1BB2' It was locatecl in the nofiirein Fro¡rt l{ange about I l5 nljles ro the northeast .l.the
project site arrcl hacl a estùnatecl magnitude of about M 6.2 ancl a nraximr¡llr inte'sity o1'vll" Ilistoric grountl shaki'g at the p'oject site associatecl witir the I gg2 ancl the other
larger lristolic earthtluakes in the regicu cloes not ap]leil to have excçeclecl Morlifìed
Mer-calli Interrsity vr {Kirkrram ancl Rogers, r gg5). Modi{Ìecl Mcrca¡i Intensity vI
ground shakillg sìrould be expectecl duli'g a reaso¡ralrle oxl]osure tilne lcrr-tlle houses a*c
ofher prcject làcilities ' but fhe ¡:rtbability of strongel grouncl slraking is low. Inte'sit,y
vI grnund shaking is li:lt hy rnost ¡:cople aucl causes gcneral ¿rrarrr, Lrul rcsults in
negligible clamage Io structur.es r:f goocl clesigl ancl construction.
Jub lilr.r. Il)r) rlVl()
(' åötech
-7 -
The houses anci other 1àcilities subject to eafihquake clamage shoulcl be clesigned t.
u'ithstancl tnoderately sttong gtnund shalcing rvith little or no clarnnge ancl not to collapse
uncler stronger grcund shahírrg. F<>t./ìnn rctclç siles with shear wave rrelocities of 2,5û0
fus in the upper 100 feet, the U. S. Geological Survey 200? National Seismic llazarcl
Maps inclicate that a peak grounrl accelelation of 0.069 has a l0% exceeclence ¡rnbability
fbr a 50 yeâr exllosufe fime ancl a peak gïound acceleration of 0.239has a2yoexceeclence
probability fur a 50 year exposure time at the project site (Frankel ancl Others, 2002).
This collespOnds to a statistical recun'enre tirne c¡l' about -500 years anci 2,500 years,
respectively' The soil profiles at the builcling sites shouid be considerecl as Class C,Jïrnr
rocÌr 'vites as clescribed ill the 2006 Intenr¿tional Building code unless site specifìc shear
rvave yelocity studies show otlrerrvise.
RADIATION POTEÌ{TIAL
Iìegional studies by the Coloraclo Cìeological Survey inclicate that the closest rac1ioactive
ttiiuel'al occull'ences to the prajcct site are greater that trve¡ty miles fi-om the site
(Nelson-Moore alrcl otheru, lg78). Radioactive minerai occunences are present in the
Aspen-Lenaclo mining clistrict to the southeast aritl on the southwest flank ofthe White
Iìivel uplift to lhe nofthwest. Regior:al stuclics by the U. S, Geological Survey (Dubiel.
1993) for the u. S. Envil'ortnteutal Protection Agencl, (EpA) inclicate that the prnject site
is in a model'ate racloi gas ¡rotential zone. llhe 1993 EIIA regional radon stucty considerecl
data frorrr (l) irrdoorlaclon sur-veys, (z) ¿rcrial raclioaur.ivir.v surveys, (j) thegeneral
gcobgy. (4) soil permeability estinrates, ancl (5) regional arc¡itecrural practices. It is riot
possible to accut'ately flssess {i-itule t'ado:r ccurcentrations in builclings l¡efirre they are
construoted' Accurate tesfs of raclon co¡lcentl-ations cau only be macle when the buikJirrgs
have been contpleted. Ilecause of this, nei.i, l'¡uilclings in uroclel.ate to high raclorr areas are
oflcn clesigtted with ¡rrovisions fur ventilation of'the lower e¡rclosed areas s¡o¡icl ¡lgst
construction testi'g show u'acceptable r:aclon concentratìons.
.lotr No. lil(r O!?tl Gèötech
-8-
FINLD EXPLORATION
The field cxploratiÚtr lor the project was conductcd on Januar.y l0 ancl 15, 200g. Twelve
exploratoty pits were excavated at the locations shown on Figure 5 to evaluate t¡e
subsurface conditions. The pits were crug with a tmcrcrroe ancr wer.e loggecl by a
representative of He¡:worth-Pawlak Geoteclurical, Inc. samples of the su6soils were
talcen with relatively uutlisturbed ancl clisturbecl sarnpling metirocls. Depths at whjch the
sarnples were taken are shown on the Logs of Exploratory pits, Figure ó. The sarnples
were rctu'ned to t¡u. laboratory ror review by trre project engiueer ard testi'g.
SUBST.IRFACE CONDITIONS
Graphic ìogs of the subsurface conclifions encounterecl at the sitc are shown on Figure 6.
The subsoils consist of about tA to 3 feetof organic topsoil overlying 2 feet of silty sand
in Pit I and relatively clettsq silty sandy gravel containing cobbles and boulcler.s in the
renuining pits- pit 3 contai'ed a le's of slightly gravelly sand finm 4 ta Syz feet.
Laboratory testing perfbnned on sarnples obtaineci fì'om the ¡rits included natuml mojsture
content and density and gr-adation analyses. Results of swell-consolitlatio, testing
performed on a relatively trndisturbecl sarnple, presented on Figure g, indicate motlerate
compressibility under conclitions of loarling ancl wetting. Results olgr.aclatiop aualyses
perfuilIed on large distulbed samples (rninus 3 to 5 inch fi.action) of the natural coarse
granulaï soils are shown on Figures 9 tllnugh I ?-. The lalroraroq, testing is slr;rnrnarizecl
in Table L
No lì'ee water was encounterecl in the pits at the time of excavation and the subsoils were
slightly moist.
PRELIMINARY DESIGN RECOMMENDATIONS
Tire conclulsions ancl recolnmeudations ¡lesentecl belolv are basecl on the proposed
clevelopment, subsurlàce conclitions encormterecl in the explor.atory pii, an¿ nr¡r
expet'ience in the area' T'lie recolurrenclations are suitable for piamrng zurcl preliminary
design but site specifìc studies shoulcl be conducted fbr individual lot developrnent.
.lol) hl'r. l()fl {}920
r;ê¿bt€ch
9
FOUNDAT'IONS
Bearirrg conditions will vary depending on the sliecific locatio¡ of ttre building on the
plopeft)¿' Basecl oll tlte natul"e of the pro¡:rosecl construction, spreacl fcrotings bearíng on
the ttatural granulat'stlii.s should be suitable at the builcling sites. we expect tlie fìroti'gs
can tre sized fbr a' allorvarrre bearing pressure i' the'ange of 1.500 psi'to 3,000 psi.
cornpressible silty sands encountered iu builcling a¡:cas may need to be removed or tle
fbotings clesignecl accordingly âs pafi of the site specilic lot study. Nested boulders a¡d
loose matrix soils may neecl lreatment snch as enlarging footir:gs or ¡rlacing compacterl
strucfural fill. þ-cluntJation walls should be clesigned to span local anomalies antl to rcsist
lateral earth loadí:rgs rvhen acting as retaúring structures. The tiroti¡gs s¡ould haye a
rnininium depth of 36 inclies fol- fi-ost protection.
BELOW GT{ÄDE CONSTRUCTION
Frecr water was etlcottltteretl iu some of the ex¡rlolatorypirs arrcl it has been our ex¡:er.iencc
in the area that tlie water lcvel catr Lise anci local perchecl grounclwater carr clerrelop cl¡ring
times ol'seasonal tulloff ancl heavy in'igation, In general. all below gmcle ar.eas sl:oulcl be
protected li'om wetting anel hydlostatic pressure builclup by rme of an u¡clerdrai¡ system.
We reconrtrlend thal slnb-on-grade floors be placecl ¡rcar to abclve exist jng gr.ade ancl
crau'lspaces be kept shallow. Basentent levels rnay not be ßasible iu the lçl,er lyirg
areas with a shallc¡w grouuchvatl:r lerrel. Potential groundrvater. inr¡:acts ou prol:rr.rsc:cl
cicvelo¡rr*c't should be e'aluated äs paft of the site s¡:ecilic building stutly.
FLOOR SL¿\BS
Siab-orl-gratle construction should be t'easible for bearing on the natulal granular soils
beiou' tlre t0¡:sÛil. Therc cor¡lcl be some post consiruction slab settlement at sites with
c0tn¡:ressible silts ancl sancls. To reduce thcl effects of'some diff"el-ential nrovemcnt, fìc¡or
siab.ç shoulclbe sepnt'aletl li'onl all bearing walJs arrcl coluurns rvith cxpausiçn.ioi¡ts.
Flool' slab cotitrol.ioints shoLrld be usecl to reduce clanagc clue to slririlcage cr.ackilrg. A
Jol.r No. i0fi 0920 GêiStech
_ 10-
tnhimum 4 inclr thick layer of ûee-draining g.ravel should undel.¡ie building slabs to
break capillary waf.er rise ancl facilitate drainage,
SURFACE DRAINAGE
The gracling plan f'or the subdivision should conside¡ runuff tlrcugh the ploiect and at
individr¡al sites. water shoulel not be allowed to pond next to buildings. To lirnit
infiltration into the bearing sc¡ils nexf to builclings, exterior backfìll sliould be rvell
cotnpacted and have a positive slope away fi'onr the building for a distance of at least l0
feet' Roof dr:rvnspouts and clrains should ctischarge well beyoncl the limits of all backfill
and landscape irrigation should be restricted.
PA\¡EMENT SECTION
Tite near suffàce soils encountered in the exploratory pits below the topsoil typicallv
sonsistcd of silty sa.tly gravel' The pavement section for the site access roads can be
talçen as inches of asphait parrentent on B inches of class ó aggregate base course for
preliminary design pul'poses' The subgtacle shoulcl be evaluated for pavernent srqrport at
fhe time of construction. surrexcavation of trre topsoil and fine-grainecr soils and
replaceurent with coarse grauular subbase rnaterial may be needecl to achieve a stable
subgtadc in some areas.
LIMITAT'IONS
?his study has lreen cr¡ncluctecl accorcling to generally accepted geoteclmical engi'eeri.g
pdnciples ancl practices fur this a.ea flt this tinre. we marce no war.ranty either express or
inrplied' The conclusions ancl recommenclations submitterl irr this report are hasecl upon
the clata olrtained û'our the field recoruaissancg review of published geologic repofis, tlie
exploratory pits locatecl as shorvn on Figure 5 ancl to the depths shown on Figure 6, tìre
pt'oposed [ype of'corrstl'uction altd or¡l'experieiice iii thç area. our consulti¡g ser.vices clo
not ilclucle deternining the pLesence, preventiori or possibility of rnolcl or ot¡er biological
contamilrants IMOBC) de,velniring ur tlre fìrturc. If-thc ciie¡ii is co¡rce¡.ilcri aboui ìvÍûBu,
then a professional in tlris special field of ¡rlactice shoulcl bc consulteci. our lindings
Job No. l0ú 0920
cê{btech
* t1-
include interpolation and extlapolation of the subsurface conditions identified a'd the
exploratory pits and variations in the subsurface conditions may not become evide¡t until
excavatio¡l is perfbrrned. If collditions encountored cluring construction appear differ.ent
fi'om thosc described in this report, rve should be r:otified so that le-evaluaticur of the
recon:mendations may be rnacle.
This reporl has been prepared fbr the exolusive use by our client for.plarrning and
plelir:rinaly design purposos. We are irot lesponsible for teclurical interpretations 6y
others of our inftrrmatioll. As the ploject evolves. we slrould prnvide co¡lti¡rued
consultation, cotrduct additional evaluations and review and monitor the irnplernentation
of our tecommenclations. Signi{icant design changes may require aclditional analysis or
utodifications to tlle reconmendafions presented herein. we recomrnend on-site
obseruaticur of excavations ancl foundation bearing strata ând testing of structural till bv a
representative of the geoteclmical engirieer.
Respect fully Sub¡nittecl.
HEPÏYORTH - PAWLAK GEOTECHNICAL. INC
Scott W. Richards, E.I
-llcvicwyd iry
Steven L. Pawlalc, P.E
SW.Rlvad
Jrlh No. l0ó t)920 eåEtectr
-t2-
REFERENCBS
Dubiel, R' F', 1993, PreÍímínary Geologíc Ratlon Patentíal .lssessntent of coloraclo irtGeologic Ratlon Pc¡.tential Ep,A Region g, Colotudo, Àrîontana, North f)rtkoru,sauth Dakota, utah anrr. wyoming: u. s. Georogicar survcy open File Report g3_
292_H.
Frankel, A. D. ¿nd othem, ztaz, DocuntentatianJitr tke 2002 rlpdate of the NarionalSeìsmic Hazard Maps; U. S. Geological Sirvey Opcn Fiie Report AZ_42A.
Kirklram, R' M' and Rogers, w' It., 1985, coloracla Earil,tc¡uake I)ata and lttterytrctarians1867 ro /98J: Colorado Geological Survey Bulletin 46.
Ki'kharn. R- M. and widmaur, B. L., rgg7, Glorogy Map af the carbondare euadrangre,Gutfiekl coun\,, corararro: colo'ado Geologicaf survey open File 97-3.
Kirklram, R. M. anct scott, R. 8., 2002, rnrro¿r,ction to Lctte cetnzoic EtaporiîeTectonísm atd vorcnnism in rilest-cetttrar, cororarlo, in Iürkhu,r, ir". M., scott. R.
Job No. 10ri 092t1
cåFteclr
¡ f il-i¡:.l'.j¿.', i.i.,.i,i:i-;ÈII' ,!a¡¡g ¡ce[o¿'/.. -¡t'f.it-',rl,, ..tt.,l , ';,.l ¡:t.:1...t.t. ì"i"'i,','!'., li,...,':..¡i-'. ¡l-. .*..-&-. tt[!Hfll)-::Írì';¡ i4¡!'':,t'.u'g Qf = pilaful lnoluoQ'Ð 000e ='ul I :8lBrsû000ÊCI260 9ûr.Ltââlfi5rÐtcefoJd qcueu êue-l lCluor¡Bco-l slls| êJn6lJ
I
ì
vt
lnt6rmountaln
SoiEmlc Bslt
WY
Lilamie Mtfl
1984
M 6.6
''
i:
l¡04
tJ| s.1
."t-j¡i:;Irf.li,
Môåb
Axial Basin
Río Btan@
{Explosion)t973M57 llÊ
Gl6nwood
Spfings
0'r
nruronf R¡llu
G(E¡plæioû) project
M 5.3 s. Grand : Síte
Hoûbnol( - '- !19{4 / \vt (',)\_-/
cmnd Ji¡¡lct¡on
Psgosa SFrin0$
Ulv Pa¡k
fB?1
vt
Waldenü
Lovela¡dnN.
ló vll
3.2 to
Ìla¡0Fly
M
ñtaekgr
tl
Denvateðgle
#sl"
Rock,4sprn
Rldocwâv19f¡
:
:i:l
Sleambôåt
Sflrlngs.l
1882
M 6.2
E
'' flFarl¡er
j C¡maron
!c60
M 5.5
1l
\ouuo
,)¡
Sêllds
Q8¡
*63Ð
Cì6gtr
ûsl{q:
Ridgè GunÍson
tlManlfos if
â?T**
{"t
l-aks dly
1955
a
Krgmnllngn.
, (f,sfr!
Vall ::lr
L'I
rl
Côrte4
QSqdD!@¡0Ò
Sp.
Wals6nburt
13
ílÌf¡inidad
a
Pqshlo
ú
Explanatlon:
\ Post.Glacial Faults:\.. Fault younger than abouf 15,000 y6âß.
Largor Historic Earthquakesi
Earthquakas witlr maximum int€ns¡ly gÌ€alsr thsn Vt
or magnitr¡de o€aler than M 5.0 from 186¡ lôprqssnt.
* NuctearExplosion:
Large unds¡grôund nus,aãr exploÊion for nålural gãs
reseryo¡r anhance$enl.
H¡stor¡c Seismic Zones:
Areas with hislor¡cal¡y high s€lsmic acl¡v¡ty.
M Locaf, surface wave or ilody wave magnitudôVl Moclified Mercaili inlensity
References:
Widmarìn and Others (tS9g)
U. S. Geologiual Survey Sarìhqrrnke t,:alâlogs
0 ã0 rni,
Scale; 1 in. = 50 mi.
106 0920 Lane Ranch ProjectTÇI
Faults and Historic Figure 2
Explanation* P*i*.15itÉEaqleCollapseCenter(960 sq. mi.)Shâllow EvapÕdte in EagleValley Fonnat¡on and EagleValley Evaporite,;-ìi',,*riil't:lioijpiiit\-/ãiiûPirldãt'rt3i{c'.raliãr rlrrj.¡iÊiíi:*cpriñ_e*.:'ll i¿t*.ilt')¡'lll3ðð*a-eirCarboCollapseCenter{460 sq. mi.}Ëã$;l¡10 MilesRefarences:Twêto and Others {fg?g}Kirkham ãnd Scott (2002)ßu¡t:.Èn;.i,;t:,i:Ìr..'//,".n1.ù;i{1"l,.iür hli!o',c)(or$ãIII!çoIıf)Qr\z1lffifr-Tão@o:cjc)_9[-oiooó¡m3<c,o, :räË.oo;s9o(aı'J-rt(ocıcd
0t7
at6Jl'i_;3,
roÊôo-
ü
at3
Qt2
Fot\r
8r3:.',
âf Man-Placed Fitl
First Post Gtac-¡al Tqrrace
$åcond Pgst.Glacial Teråce
Ihird Pgst Glacial Tsrrgce
Fourth lgst Gl¡cìal Terrace
å¡iuv¡a¡ Fans
Qrs-7
Qt1
Q12 lhW colluvium over Eaqle vallev Evaporig
Çon¡,acli
Approx¡mate brundåry of måp un¡ls.
pl I çxplorâtgry pltsj
Approx¡matê localions.
Qt3
Q14
8f
0
Modiñed from t(irklìå¡ll Ënd Wdmâûn {1US/)
400 fr.
Explañat¡on:
ltt
Scale: 1 in. = 400 ft.
rlontour tnlerval: l0ft. and40
March 200e
elnedale Outwash Terraoes:
5 - towesl, 6 - intermBdiate, 7- highest
106 0s20 <;&Fteclr Ranch DevelopmentTCI Lane
Area Figure 4
APPROXIMATE SCALE
1":300'
rillr r *l
NURSERY PABCEL
J
a
4
I
of,
1,,.' L,ti-'¡*_!-ì
.Lr'PITl T
¡4)I)
mü$r\f,lY
cÊ¡r¡É r..+t¿':l
tr',lx )¿ Ì:¡¡¡:j
t_
\
t-_
L-t
.,'¡ r'"',J
::'I icf 5\
ó3 loca[ion of
ç
previous pÊfcÖlation tost
10130/2006
L-J
'f': I
I r a
I rl-l
I
J
ítl
L
I
I
J
\
---1
\i.-, -., I
10fì 0920 LOCATION OF TXPLORATCIHY PITS FIGURE 5
PIT 1
ËLFV.:
PIT 2
ELEV -Ptï 3
ELEV.*
PIT 4
ELEV.:
0 u
ı0)tL
-c
o-
0)Õ
WC=8.9
DD=96
-200_.-41 ()
0)
LL
ç
o_
c)o
5
5I I +¿=ts
-200=2
l I r-a:66
-200=2
t0 l
ll +¿=os
'200=2 10
PIT S PIT 6 PIT 7 PIT 8
0
U
0)
c)u_
o-
a)ô
5
o(¡)
LL
I
!
o-
0)o
l I +,t=¡¡
-24û=2
I .r+=or
- -200=3
't0 l
10
PIT 9 PIT 1Û PIT 11 PIT 12
0
0
0.)
0)
LL
c
OJo
5
0)(l)lr-
o-q)o
Ä
l
-'t
I
l +4=54 l -t-4=68
-200=5
10
Nute:is shown on aot
10
106 0920
L
LOGS OF EXPLORATOBY P S Figure 6
LËGEND:
þ
TOPSOIL; organic silty clay, soft, moist, dark brown.
SAND (SM-SP ); silty, trace gravels, loose, slighfly moist, brown.
GRAVEL AND COBBLES {GM-GP); with lroulders, clean sancl, dense to very dense, slighily moist, tightbrown to brown, subrorinded rock.
2" Diameter hand driven lirier sample
Disturbed bullr sanrple.
I
I
J
a= Free waler in pit at lime of excavaling.
NOTES:
1. Exploratory pits were excavated on January 1s, 200g with a kack excavator
2' Locaiions of exploratory pits were nreasured approximately by pacing frorr features shown on the s¡e planprovided.
3' Elevations of exploratory pits were not measured and the logs of exploralory pits are drawn to deplh.
4' The exÞloratory pit locations and elevations shoulcj be considered accurate only to flre degree impliecf by the metlrcd
5' The línes between *ui"lþll shown on theexploratory pit logs represent the approximate boundaries betweenmaterial types and lransilions may be graUual.
6' waler-level readings shown on the logs were made at the time ancl under the conditions indicated. Fluctualions inwater level rnåy occur with tirte.
7. Lalroratory ïesting Results:
WC : Water Content (%)
DD : Dry Density (pcf)
+4 * Percenl retained on the No. 4 sieve
-200 : Percenl passing No. 200 sieve
106 0920 LEGEND AND NOTES Figure 7
MoiçlureCr)literrL: g.ûl
Dry Density - 96
$ample ol: Silty Sand
From: p¡ 1 aIZl¿ Feet
percetìt
prf
0 ilil
7 ilil^3-(
wetting
lliIt
ilt
ill\t\t\i ilt
(
ilt
Iil
lit
ilt
ilt
ilil
II
llII
II
¿
.ôo\
c
.e
.Ag,
a)aç
o
LJ
4
tJ
I
ct
0.1
10
APPLIËD PHESSURL. ksf
I.û
1Ofl
106 0920 SWELL-CONSOLIDATION TIST RESULTS f:igure B
ÏIME READINGS STANDÁRD SËRIES7Hñ
15 MtN.gMlN.4 h/tN. 1 MfN.It10a #$ #30 #]6 #B #.4
CLËAR SOUARE OPENINGS
3Ì8', 314" 1 llt 3- 5'6" S"
(tzıu)
o-t-ztU()
G
LU
o_
a
z
þ-<tUE
t"-z
Lrl(JÉ
LlJ
0_
10
20
3ô
40
100
9{t
8û
m
BO
5t)
40
l0
0
50
60
7A
80
s0
100
.æ5 üt or9 o3T .o74 t5g 1m _6m ì.rB 7.3S {.75 ù5
DIAMET€R OF PABTICIES IN MILLIÍüËTERS
le.g lgû 375 tun ,nrtao â3
c{ Y rÕ sill
GRAVEL 66 %
LIQUID LIMIT
SAMPLE OF; Sandy Gravel
7HR
15 MtN,
.00r AaZ .005 .00S
TIME RËADINGS U,S. STANDABD SERIES
6OMINJSMIN,4 MIN- 1 MIN.#100 #50 N|30
.019 .037 07.1 .150 .3C0 .60ü 1.18 2.36
DIAMETËH OF PARTICLES IN MILLIMETERS
32 "/" S¡LT AND CLAy a
PLASTICITY INDEX O/O
FROM: pn Z at B to I )¿ Feet
CLEAR SOUARE OPENINGS
4^75 9.q2.51s.0 37.5 76 2 1p152 203
t4'tß #8 1t4 3/8' 3/4' 1',t12' 3' 5"6. 8"
SAND
CCB¡T-Eg
ól/oot
24
46
0
100
90
80
7Az
tt>(nuoÉ
F50ñ
C)u0ffi
o-
30
otrJz
F
UJ
ctr
t--zylr
u.Jo-
10
20
30
40
50
Ân
7A
80
90
100
t0
U
ir"ÀY to $r¡
GRAVEL 15 9"
LIQUID LIMIT
SAMPLE OF:Gravel
SAND B3 ?å SILT AND CLAY 2
PLASTICITY INDËX %
FROM; Pit S at 5 to s Feet
cÕåBrEs
o/to
/o
1 06 0920 GRADATION TEST RESULTS Figure g
SIEVE
].I[4Ë READINGS
r l1n
r6 MrN-9M¡N.4 MIN, 1 MIN.
,w .cû5 .61
U,S. STANDARD
/t t0{) #$0 #30 /t tE
ÛLEAR SQUAHE OPENINGS
3/0" t/4, 1 \l?', 3" 5"0"#0 #4 Õ
10
l&
00
BO
10
69
50
{û
3ü
t0
¡t
L$4v)Ø
o_
t--z
LUf'ì
cc
UI
o_
20Utu230
F-
H40
t--250
IU
tr60u¡o-
70
80
90
1C,Ð
.Otg û17 .û?4 .150 .l@ (iS 1.t8 2.38 4.?5 9.5 ¡?5 190 31.5 18.2 152t2l 2ß3
DIAMETEF OF PARTICLËS IN MILLIMETEBS
CIÂY 1¡f SLT
GRAVEL 69 %
I IQUID LIMIT %
SAMPLE OF: g¿¡¡¡y g¡¿yp¡
7 t-tR T|ME READ|NGS
15 MlN.60MlN19MlN.4 lvttN. l
SAND 29 % SILI'AND CLAY 2
PLASTCIry INDFX %
FflOM: pit 4 aI g Jza to g t_eel
cú¡iÞiÊs
CLEAR SOUARE OPENINûS
,ZI"203
24
c5
0
10
MlN. lÉ200 //100
DIAMETER OF PARTICLES INI h/ILLIMETERS
U.S. STANDARD SERIËS
t/54 /r30 #16 tÉB 44 3/8" 3!4" 1 1/2' 3" 5'6' a'
10Ò
10
90
BO
{97Az
U)60s
t--50ñ
t)n0ffi
{)_
3û
tf
LU230af-tlj /nE
t--250
LU
860
tlJ0-
70
80
90
100 0
'0Û1 002 005 .0og .019 .o37 .ar| 150 300 600 1 18 2.36 4-75 9.q2.51'c),0 37.5 76.2
-_r|._|-.t_*
__+_*_*|-___
-..,Á-.| ---J-
cL4Y l0 s{ i cÖgå.ES
GRAVEL 73 9ó
LIQUID LIMIT
SAMPLb OF Gravel
SAND 25 ?å SILT AND CLAY 2 YO
PL,ASTIÜI]-Y INDEX A/O
FHOlvl; Pit 6 at 8,fp to g Feet
1 06 û920 GRADATION TEST RESULTS Figure i 0
TIME READINçS U.S, STANDARD SEÊIES¡ ttR
15 MtN.l,¡lN. 1 #200 #100 #50 #30 #16 1t8 tr4
.o02 ,005 009 .019 û37 0?4 .tS ,100 600 1.18 2.30
DIAMETER OF PAFTIÇLES IN MILTIMETERS
CLEAR EQUABE OPENINGS
318' 3t4" 1 112', 3" 5'6"B'
(nz6tn
L
l--ztllO
cc
LLI
o_
.t0
?0U
uJ230
l--
Cj 40[L
Lz5û
tlJa't
860
UJL
70
80
s0
100
1tx)
80
7ô
&
û
(0
;0
æ
t0
{.7Sæ¡95 t25 l9-0 37,$ tU' ,ort*203
--¿--F-
-tr-f-
_-t-_*
clnY to s[r
GRAVEL 61 O/O
LIQUID LIMIT %
SAMPLE OF: Sandy Gravel
7 HR TtMË FEÂDINGS
15 MlN. 60M¡NtgMtN.4 MtN.
U.S. STANDARD SÊFIES
{t50 #30 tþ16 *s
cô5ttss
CLËAR SOIJARE OPENINGS
SAND 38 % SILTANDCLAY 3
PLASTICITY INDEX O/O
FROM: pit I ai T lz to Blz Feet
24
0
I MtN. #200 #100 tÍ4 3/8" 314' 1 1lz' 3' 5"6" 8'
100
9C)
80 \)702(n(/)
60 à{
F50ñ()
00ffi
o-
30
tllz
F
l.¡Jæ
t--z
IU()
LU
û_
10
30
40
50
60
70
80
90
100
20
TO
0
.001 .004 .00s .çfJs .019 03? .o74 .t5g .300 .600 1.19 2.36 4.75 s.qe.sl9.tl 37.5 76.P f#2 203
DIAMETER OF PARTICLES IN MILLIMETERS
ci¡lY TG 5U.r cGsBrÈ$
GRAVEL 54 %
LIQUID LIMIT
SAMPLE OF;Gravelwith Cobble
SAND 41 ?'. SILT AND CLAY 5 %
PLASTICITY INDEX %
FROM: Pit 10 ar 6 to 7 Feet
%
1 06 0920 GFADATION TEST RESULTS Figure 11
24 HR. 7l'ln
0 45 MlN. 15 MtN.
TIME READINGS U.S. STANDARD SERIES
#50 llSa #16 J¡B
CLËAÊ SOUARE OPENINGS
60MlNrsMtN.4 MtN. 1 MtN. /1200 #100 tt| 318' 3/4' 1 112', s', 5"6" B'100
Bt)
70
60
50
40
30
2ñ
'I ¿ì
!U
r0
30
oL¡J 40z
l-
Lrtv.
t".- 50z
l¡J()E
l,¡Jô_ 60
ozı
U)
o-
l-.-.zf¡J(J&
ÛJô-
70
BO
00
t00 0.001 .c02 005 _009 .019 .037 .Q-?4 150 .300 .600 1.18 2.36 c.75 nUrr.urno
DIAMETER OF PARTICLES IN MILI.IMETERS
37.5 76.2 152 2(13
cuv it sill toaBEs
GRAVEL 68 %SAND 31 "/"SILT AND CLAY 1 %
LIQUID LIMIT O/O PLASICIry INDEX %
SAMPI-E OF: Sandy Gravet FROM: Pit 12 at 7 b lo I FeeI
-ffi----{-
1 06 0920 GRADATION TEST RESULTS Figure 12
H EPWORTH-PAWLAK GEOTECHNICAL, INC.TABLE 1SUMMARY OF LABORATORY TEST RESULTSJob No. 106 0920LIMTTSGR,AVEL(n/o)SANDf/o)PTRCsNTPASSiNG¡to. 2005¡EVEL!QUIDLIMTTPLASTICINDÊXUNCONFINETCOMPRESSTVESTRENGTH50iL oRBEDROCK TYPE41Silty sand66327Sandy gravel15832Gravelly sandSandy gravelSandy gravelSandy gravelSandy gravelSandy gravel2aLtJ5I2925364LJI69736t5468NATURALDRYDENSITY-{pcf)96Í{ATUR¡,1MOIS,TURECONTTNT(slo\8.97.'lDEPTHfftr71/zB-87¡5-SVzïVz -9\Vz-97 L/z - BVz6Vz -77t/z - B\trtrLPITI2J+oI101?