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SUBSOIL STTJDY
FOR FOLT{DATTON DESIGN
PROPOSED RESIDENCE
LOT H.35, ASPEN GLEN
GARFIELD COUNTY, COLORADO
JOB NO. il4 506A
NOVEMBER 28,2014
PREPARED F'OR:
WOODBRIDGE MORTGAGE IhTVESTMENT FUND z,LLC
ATTN: RICK SALVATO
22 CENTER STREET, FRONT SUITE
FREEHOLD, NEW JERSEY 01728
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TABLE OF CONTENTS
PURI'OSE AND SCOPE OF STUDY.....,.. ...
PROPOS ED CONSTRUCTION.
SITE CONDITIONS
SUBSIDENCE POTENTIAL,...
FIELD EXPLORATION.......,.....
SUBSURFACE CONDITIONS...
FOLNDATION BEARII{G CONDITIO].{S
DESIGN RECO}\,{MENDATION S......,..,..........
FOUNDATIONS......,..
FOLIhIDATION AND RETAINING WALLS
FI-OOR SLABS
LINDERDRAIN SYSTEM
SURFACE DRAINAGE ...,.".........
LIMITATIONS
REFERENCES
FIGURT 1 - LOCATIO}I OF EXPLORATORY BORINGS
FIGLIRE 2 - LOGS OF EXPLORATORY BORINGS
FIGTJRE 3 - LECEND AND NOTES
FIGURE 4 - SWELL-CONSOLIDATION'TEST RESULTS
FIGURE 5 - GRADATION TEST RESLTLTS
]'ABLE 1- SL'MMARY OF LABORA.TORY TEST RESLILTS
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PT]RPOSE.{.\'D SCOPE OF STUDY
This report presents the re.^ults o1'a suhsoil study for a prcposed residcnce to be l'cated ar
Lot H-35, Aspen Glen Subdivision, Garfield County, Colorado. The project site is shown
on Figure 1' The purpose of the sturiy rvas to develop recommendations tirr rhe
foundation design. Thc slirdv rvas conducted in accordance rvith our proposal fbr
gecrtcchnical engineerrng sen ices to Wootibridge Mortgage lnvestrnent Fund Z, LLC
dated November 6' 2014. Chen-Northern" Inc. {i991 and i9q3i previously conducted
preliminary geotechnical etgineering srudies for the der,elopment and preiig:inary plar
iiesign.
A tield exploration progrirm consislir:g of erplorarorv-borings was oonducted ro 'btarnilformatiort on the subsurtace conditions. Samples of the subsoils obtained durisg tle
field exploration wcre lested in the laboratory to dctermine their classification.
compressibility or sweli and other enginea-ing characteristics. The results of the field
exploration and laboralorrl testing were analyzed to develop recommendations lbr
fcrundation fypes. deprhs and allowable pressures for thc proposed builcting founciatii;n.
This report summarizes the data obtained ,luring this study and prese.nts onr conclusions,
design reootnmendations and other geotechnical enginecring consiclerations based on the
proposed construction and the subsurface conrjitions encountcreri.
PROPOSED CONSTRUCTIO]\
Building pliurs for the resrdence are ccinceptuai. Tlpical consrmction in the area consists
0f one and two story wood frame clrnsttlction above a basen:ent cir crawispace with an
atiached garage. Basement and garage floors are t,vpicaily slab-on-gra6e. Graciins fbr
this typc olstructure is assurned to be relatively minor with cut depths hetwcen about 3 tir
I 0 feet' we assune reiativeiy light foundation loadings. tlpicai of thc assumcd t-vpe oi'
construction.
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I1'building loadings, location or Eading pians cirange signilioantiy from those describcd
above, we should be notified to re-evaluate the reoornmer"idations cr-;ntained in this repoil.
SITE CONDITIONS
The vacant lot is kicated on Saddleback Road in tiie nor"tha'est corner of the subdivisicn.
Vegetation consists cf gSass and rveeds. The building envelcpe is locatecl above the
roadway grade and the ground surtbce is relatir,eiy flat with a slight slope down tc the
west. The rear part oi'the site gcntly 5lspes dorvn to tire east. A golf course fairwav
barders thc east side of the site.
SUBSIDENCE POTENTIAL
Betlrock of the Pcnnsylvanian age Eagle Vallcy Evaporite underlies the Aspen Clen
development. These rocks are a sequence of g1'psifcrous shale, fine-grainecJ
sandslone/siltstone and liurestone with some massir.e beds of gypsum. There is a
pnssibility that massive gypsun'l deposits associated ."vith the Eagle Valiey Evaporite
underlie portions of the lot. Dissrrlution of the g)?sulll under certain conditions can cause
sinkholes to deveiop and can produce areas ofiocalized subsidence. I)uring previous
sti"ldies in the alea, several broad subsi<ience arsas and srnaller size sinkhole areas were
r:bserved scattered thrcughout ihe Aspen Clen developmeni. prcdominantiy on the east
side of the Roartng Fork Rivcr qChen-Northem, Inc., 1gg3j. These sinkh*les appear
similar to others ass,:crated with the Eagle Va]le},Evaporite in areas af thc Roaring Fork
River valley.
The nearcst sinkhole lvas mapped about i "200 feet to the soufheasr of Lot l{-3i.
Sinkholes were not obsered in the imrnediate area of the subject iot. N<; evidcnce of
cavities was encountered in thc subsurface materials; howcver. the expltiratory bonngs
were relatively shallor'v. fbr foundation design only. Based on our present knowleclge o1'
the subsurface conditions at the site, it cannr)t be said lbr certain that sinkhclcs rviil not
dcvelop. The risk of fitture ground subsidcnce on l-ot F 7 thnrugirout the service iife of
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thc proposed residence, in our opinion, is low but the site should not be con.sidered tutall1,.
risk fi'ee. If further investigation of possible cavities in the tredrock belcw the site is
desired. we shouleJ be ccrntacted.
FIELD EXPLORATIOI\
The field exploration for the project was conducted on November I l, 2014, Tno
exploralory bcrilgs r,vere drilleil at the locations shown on Figure i ro evaluate the
subsurface conditiotts. The Lrorings were advanced with 4 inch diameter orntinuous fiight
augers pou"ered by a tr-Lrck-mounted CIVIE-458 rbill rig. The borings \,vere iogged by a
represenrati ve of H epworth- P aw iak C corechnical, In c.
Samples of the subsoiis were taken with 17i inch and 2 inch LD. spoon samplers. The
samplet's were driven intc the subsails at variaus depths ,"vith blows from a l.l0 pound
hamnrer falling 30 inches. This test is similar to the standard penetration test desoribed
by ASTM Method D-1586. The penetration resistance values are an indjcation of the
relatjve density'or consisiericy of the suhsoils. Depths at which the sampics were taken
and the penetraticrn resistancc vaiues are sholvn on the Logs of Exploratory Borings,
Figure 2' Thc samples were rehrrneci to our laboratory for review by the project engrneer
ancl testing.
SU BS URFACE COI{DITION S
Graphic logs of the subsurface conditions encountered at the sire are shc;wn on Figure 2.
The subsoils below about one foot of topsoil {ronsist of 2',\ to 4 feet of sanclv silty ciay
overlying I'tz to 6 feet of silty sandy gravel with cobbies and smail boujders dor,vn to rhe
maximunr depth explored, 1 I fbet. Drilling in thc dense granuiar soils with auger
equipmcni was ditficult due to the ccbbics anrl boulders and cir.llling refusal was
encourrlered in tlre deposit.
Ji-'i,r No. I l4 51i{:A HFGe<!:tech
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Laboratory testing pcrfcrrmed on samples obtaincd from the borings included natural
moisfure content, density and gradation analyses. Results of swcll-consolidation testing
performed an a relatively undisturbed drive sample of the clay soils. presented on Figure
4, indicate a low expansion potential under condltions of light loadilg and rr"'etting.
Results of gradation analyses performed on a small diameter drive sample (mipus I 14 inch
fraction) of the coarse granular subsoils are sholn on Figure 5. The laboratory tesrilg is
.sumrnarized in Tablc l.
llo fi'ee water was encountered in the borings at fie time of drillirig and the subsojls were
siightly mcist to moist.
FOL}IDATION B EARIN' G CONDITIO|{S
The naturai sandy gravels are adequate for support of spread focting tbundaticns. The
sand-v clay soils overiying the granular soils shcukl tre removcd iium beneath proposed
lboting areas.
DESIGN RECO$TMENDATIONS
FOLIhDATIONS
Considering the subsurface conditicns cncountered in the exploratory borings ancJ tire
nature of the proposed constn:ction, we recornmentl the buikling be founded wirh sprea4
ftrotings bearing on tl"le natural gpamrlar soils.
The design and construction cntcria presenteri belcw shouid be observed tbr- a spread
Iboting foundation svstem.
1) Footings placed ou the undisturbcd narural granular soiis sirould be
designed for an ailowabie bearing pressure of 2.500 psf. Based on
experience, we erpcct settlement of tbotings designerl ancl constructed as
discussed in this section will be ahout I inch or less.
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2i The footings should have a n'rinimum witJrh o1' l6 inches lar conlinuors
wails and 2 feet for isoiated pads.
3) Exterior footings and footings beneath unheated areas should he provided
w'ith adequate soil cover above therr bearing elevation firr frost protection
Flacenrent of fbundations at leasr 36 inches b_elorv exterior grade is
typically used in this area.
4) Continuous foundation walls should be reinforced top and bottcrn to span
lncal anamalies such as bv assuming an unsupported length af at least 10
feet. Foundation walls acting as retaining structures shouid aiso bc
designed to resist laleral earth pressures as discussecl in the "Fcr.rnriation
and Retarning Walls,, section cf this report.
-s] All topsoil, satrdy clay arrd any loose or disturbed soils should be reniov.ed
and the ftroting bea.ring level extended down to the relatively ciense natural
gfarrular soils" The exposecl soils rn tboting alea should then be moistened
and cornpacted. lf u'ater seepage is encountered. the footing arcas shoultl
be dervatered before concretc placement.
6) A representative of the geotecirnical engineer shouid ohserv-e all footilg
excavatioils prior to concrete placement tc evaluate bearing condittons.
FOUI\DATIO},i AND RETAIhING WALLS
Foundation walls and retaining structures w.hrclr are tateralll, suppi:rted and can be
expected to undergo only' a slight arnor-rnt of dellecrion should be clesigrecl fbr a lateral
eadh pressurc computcd on the basis of an equivalent lluid rxiit weight of'at least 45 pcf
firr backfill consisting of t"hc on-site granular soiis" Cantilevereciretailing strucalres
which are separale from the residence antl can be cxpecteei to deflect sufficientlrv to
mobilize the ftili active earth pressure ci_indition should be designed for a lateral earth
pressure cornputed on the basjs of an equivalcnt fiuicl unit rveight of ar least 40 pcf t6r
backfrll ccr:sisling cf the on-site gra-r:ular sorls.
Ail fbundaticn and retaining stt-uctures shculd be ejesignecl fbr appropriate hvdrostatic anrJ
surcharge pressures such as adjacent frrolings. traffic, constuction materials ancl
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6
equipnlent' The pressures recomrlended above assum€ ilraincd conciitiolrs behind the
walls and a horizontal backfill surface. The buildup olrvater behind a wall or an upward
sloping backf:ll surtace wiil increase the lateral pressure imposed on a tbundation r.vail or
retainirlg structure. An underdrain should be prcvided to preven{ hydrostatic pfessure
huiidup bchind walls.
Backfill should be piaced in unifbrm lil1s and conrpacted tc at least 9{i9ro of the maxrmurn
standard Proclor clensity at a moisfure content near opiimum. Backfill in par,.ement g11d
walkwal; areas shculd he compacted ro at leasr g5o'o of the rnaximurn standar<i proctr:r
density'- Clare shoulrJ be taken not to overcolnpact the back{rll or use large cquipmelt
near the ivall, since this could cause excessive lateral pressur€ oil the wall. Some
settlement of deep foundatian w'a!l backfill should be expected. elen if the rnaterial is
placed correctly. and could result jn distress to facilities constructed on the backfiil"
The lateral resistance af foundaticn ar retaiirine wall footlngs wiii be a carnbinarion of the
sii,itng resrstance of the footing on the founclation materials ancl passiye earth pressure
against the side of the fboting. Rcsistance to slicling at the bottlrms of rhe footings can he
calculated based on a coefficient of f iction of 0"50. Passive pressur€ of compacted
backfill against the sides cf the fbotings can be calculated using an equivalent fluid unit
weight of 40fJ pcf. The coetficrent of f iction and passive pressurc rralues rccommended
above assume ultirnate soil strength" Suitable factcrs of safoty shouid be includcd in the
design to limit the sirain which will occur at ihe ultiftare strength. parlicularlv in the case
of passive resistance. Fill placed against the sides of the tborings to resist lateral l.ads
shoulti tre compacled to at ieast 95')i ot'the maximum stanclard Proctor densitv at a
moisrurc content ncar nptimum.
FLOOR SLABS
The narulal on-site soils, cxclusive of topscril. are suitahle ro support iightly loacied siab-
on-grade consfruction. To reduce the cffects of somc ciiJlerential trove.ment" flacr slabs
should be separatcd from aii bearing ."r,alls and columns with erpansion jcints which
allow unrestrainecl ventcal movement. Floor slab control joints should be userJ 1o re{iuce
damage due to shrinkagc cracking. The requirements ftrr joint spacing and slab
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reinftrrcement should bs established by the designer based on experience anri the inte,ded
slab use. A minimum 4 inch iayer of free-draining gravel shoukl be placed beneatir
basetncnt level slabs to facilitate drainage. Thrs rnaterial should consist af minus 2 inch
aggregate with at least 509/o retained on the Nn. 4 sieve and less than 20:ir passing the JrJr:.
?00 sieve.
All flll materials for support of floc,r slabs should be compacted tc, at lea.r-t g19h of
maxirnum standard Proctor density at a rioisture content near oSrtimum. Requircd fill can
consist af the on-site ,qranular soils devr-rid of vegeiation, topsoil arid oversizeci rock.
LINDERDRATN Sl'STEful
Althcugh free water r.vas nct encounteretl during our exploration, it has been our
experience in the area that local perched groun<lwater can clevelcp during times 6f heavy
precipitation or seasonal runoft. Frozen ground cluring spring nuroff'can also create a
perched condition, lVe recomrnend belol"u-gr-ade constructi(rr1, such as retaining wails.
crawlspace and basemertt areas, be protected from wetting ancl hydrostatic pressure
buildup by an undcrdrain system.
The drains should consist of drainpipe placed in the bottom of thc r,vall backfill
surrounded above the invert level with fiee-draining granular material. The drain shouli
be placed at each level of excavation and at least I foot beiow lowesr arijaccnt finish
grade and sloped at a minimum Ioti, ta a suitalrle gravrtv outlet or clrlrarell basecl in the
gravel soils. Free-draining granular material used in the underdrain system should
contain iess than 20..o passing thc No. 200 sieve. less than _500/o passing the No. 4 sieve alcl
have a maxjmum size of 2 jnches. l'he drain gravel backfill should be at ieast lrrz tc6;t
deep.
STJRFA{]E DRAI}{AGE
Tire fr:llowing drainage precautions should be observed during construction and
maintained at all times afler the residence has lreen completed.
Job No. I l4 5{}6A c&Ftecn
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r)lnundation o1'the foundation e.xcavations and under.slab areas shoulcl be
avoided during ceurstructir;n.
Exterior backfill should be adjusted ro near optimum moisfure and
compacted to a1 le ast g5"ta rsf the maximum stanciard prcctor density in
pavement and siab areas and to at least 90o,'o of the maxiilum .qtandard
Proctor density in landscape areas.
The ground surface surrounding the exterior of the building should be
sloped to drain awav from fte foundation in all directions. we
recommend a minimu'n slope of 12 inches irr the first l0 feet in unpaved
areas and a minimum slope of 3 inches in the first l0 feet in paved areas.
Free-draining wall backfili should be cappetl wirh about z teet r:1" the on_
site soils to rertruce surface u'ater infiliratian.
2)
4) Roof downspouts and drains should discharge well beyond the limirs of all
backfili.
LIIVIITATIOTiS
T'his study has bcen conducted in accordance with generaliy accepteii geotechnical
engineenng principles and practiccs in lhis area at this time. We make no r,r,alTanty either
expiess or iniplied. The conclusions ancl recon:nencJations submitted in this report are
based upon the data obtained from the exploratory barings rlrilled at the locations
indicated on Figure 1, the proposed typc of construction eurtJ our experience ir the area.
Our se:'viccs do not include determining the presence, preventir:n or possibilit-v ,:f mold gr
r:ther bioloEcai contaminants (lv{OBC) developing in the future. If thc client is
concemed about \.{OBC, then a professional rn ilris special fiel<i cf practicc shculd be
consulted, Our findings include inte4rolation ancl extrapolation of the subsurf'ace
conditions identified af the cxpior-atory borings and variations jn the subsurface
conditrons nray not irecorne evident until cxcavation is performed. tf colrlirions
cncLlurrtel'ed during conslntclion appear djffbrent litrm those riesclibed in this report, we
should he notified so that re-eveduation rif the recon'rmen<Jations may be made.
3)
Joir ii*. i 14 ,i0ir {c&Ftecn
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This report has been prepared fbr the exclusive use by'cur client lbr design purposes. We
are not responsible for technical ir:terpretations b1, others of our infbrmation. As the
project evolves, we siroulclprovide continued consultation and field services during
cotlstructiotr to review and monitor the impiernentaticn of our recornmendations, and to
verifu tlrat the recornmendations have beer appropriaielv interpreted, Significant design
cltanges may reqriire additional analysis or modifications to the recr:rnmcndations
presented herein. We recommend on-site observation of excavations and ftrundafion
hearing strata and testing of struetural fill brv a represenlative of the geotechnicaj
engineer,
Respectfull3, S ubrrritted.
HEPWORTH - PAWLAK GEOTEC]HNICAL, INC.
Louis E. Eller
Reviewed by:
Daniel E. Hardin. P.E
LEE,"irsw'
REFBRENCES
Chen-Nor-thern, Inc., 1991. Pretintinary Gerstechnicul Engineering Study, propo.ter)
Aspen GIen Development, GarJield county, colarado, prepared for Aspen cler:
Company, dated December 20, I 991, Job No. 4 l lZ gZ.
Chen-Northern, lnc., 1993, Geotedznica{ Engineering Studl' jbr Preliminar"v* plat Design,
Aspen Glen Der;elepwent, carfield crrunty, colorado, prepared for Aspep Glen
Company. dated l\{a1' 28" 199,1. Job Nc. 1 1lZ 92.
Jcb No. i l4 ,{{,{j/\c&Ftect
APPROXIMATE SCALE
l' = 30'
GOLF COURST FAIRWAY
LOT H.35
a
BORING 1
LOT H-34 LOT H.36
a
BORING 2
SADDLEBACK ROAD
114 5064 LOCATION OF EXPLORATORY BORINGS Figure 1
BORING 1 BOFING 2
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19112
WC=15.8
DD= 10s
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6
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WC=i0.3
t4=54
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15 15
Note: Explarntion o{ symbCIls is shown on Figure 3
1 14 s06A LOGS OF EXPLORATORY BORINGS Figure 2
LiGt\lrr
t:=lH TOPSOIL; organic sanoy silt and clay. iirni, slightly rnorst, iai'k red,Oro'rn
63v (CL), sandy. silty, stiff io very stiff, slrghtiy morst to rriois1. red-brown.
GRAVEL. COBBLES AND BOULDERS {GP-Glvl). sandy. siitv, dense siightly moist, brown
Reiativeiy undisturbeci drive sample: 2-rnch l.D. Caliionia linersampie.
Drrve sarnple, sianoard penetration tesi {SP'f ,1 3rr8:ncn i D split spoon $ampie, A.STM D-1586
Drive sampie blow count; indicates that 19 biows of a .1 40 pound hamrner falling 30 inches were
requrred lo drive the Caiifornia or SPT sanrpler 12 inches
Praciicat or,llinc refirsal
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1 Exploralory borings were drilled cn November 11 , 2014 with 4-inch d jameter continuous fiight powei. ar,ger.
2 Locations of exploratory bcrings \rere rfieasured approximaiely by pacing from leatures shown on lhe siie pian
provided.
3 Elevations oi expioratory borings were not measured and the logs ol exploratory borings are drawn to depth.
4 The exploratory boring iccalions shouid be considered accurate only to the degree irnp|ed by the melho6 useil.
5 The lines between materials shown on the exploratory boring logs represent the approxirr;ale boundaries between
material lyoes and transitions may be graduai.
6. h,o lree waler'!vas encounlered in the borings at the time of dfilirng. Firrctuaiion iir vveter tevei may occur with time
7 Laboratory Testrng Resuits:
WC : Water Content {%)
DD : Dry Densrty (pci)
i4 : Percent retained on the No, 4 sieve
-200 : Percent passing No. 200 sieve
114 5064
H
LEGEND AND NOTES Figure 3
MoisfureConlent:'16"8
Dry Denslty : 109
Sample of $andy Silly Cray
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1 14 5064 SWELL-CONSOLIDATION TEST RFSULTS Figure 4
A
TIME FEADII.JGS ti S STANDAFi-j SEaIES CLIAR SOUAfr E OPtNitrrGS
2.4 iR. 7 HFI a5 Mlt\ .15 trJlN 60h,llNlgMjt\J.4 fuf.l. 1 t\4lN #200 # iOc *r50 #3c #i6 *8 *4 318', 3i4" 1 1!2" 3' 5'6' 8'-'0r:
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llAlvlETf F OF PAF-l'lC LES il.i Mr Li-lf'l [TEFtS
19 {.j ;}7 .n 7f, 2 1 52 233
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GRAVEL 54 '/"sA,l'.iD 34 0/o SILT AND []LA,Y 'i2 %
L|QUID LII./IT %PLASTICITY INDEX oh
FROM Bcring 2 at 4 FeetSAI/PLE OF: Slightly Silty Sandy Gravet
1 14 5064 GRADATION TEST RESULTS Figure 5
HEPWORTH.PAWTAK GEOTECH N ICAL, I NC,
TABLF 1
SUMMARY OF LABORATORY TEST RESULTS
Job lrlo. 114 5064
ATTERBERG IIMITS
GRAVET
DEPTH
SAMPLE TOCATION
BORING
(%)
NATURAI
DRY DENSITY
GRADATION
SOIL OR
BEDROCK TYPT
UNCONFINED
COMPRSSSIVE
STRENGTH
PTASTIC
INDEX
PERcENT : '
PASSING NO. I,IQUID LIMIT
200 stEVr
NA'I'URAL
MOISTURE
CONTENT
SAND
{%)
LVt 16.8 109 Sandy Silty Clay
1 -- '..' *
2 4 10.3
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54
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34 L2 Slightly Silty Sandy Gravel
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