HomeMy WebLinkAboutSubsoils Report for Foundation DesignI'Ioveirrber i3,2C09
Tapesii-r, Builders
Attn: Jerre \,1/itt
P. C. Box 6065
Farachuie, C*lo;:adc 8 1 535
Job I.{o. i09 381A
Subjeci:Subsoii Study for Foundaticn Design and Fercola'ric* Tesi, Proposed
Coieman Residence, Lot 10, Ir4onumeni Rieige, Ivfcnuinent R.id.ge Road"
Garfi eld County, Colcracio
Dear Jere:
As requesteci, I-Iepv*orth-Pawlak Geotechnical,Inc. perfonneci a subsoil study arui
percclation test for foundation and septic disposal ciesigns at the subject site. Tire stuciy
was conducteci in accordance with cl.lr agreement for geaiechnicai engineering services to
Tapestr;r Buiiders d,ated October 27,2A09. The data obtained and our recornrnenclations
based on the proposed canstruction and su'hsurface conditions encountei"ed- are presenied
in this repoif.
Froposed Construetion: Tiie residence v.riil be a single siory \ ,666 franie strlrcture
located on the site as sho',rrn on Figui'e i. Ground fioors 'ui,ili be stmcturalii; sup-poileci
ot'er cra',arispace. Cut depths are expecied to iange betu,een about 1 to 5 feet. Foundaiion
ioadings for this t3zpe of consti'uction are assuialed ta be relatively iiglii an,i t_vpical of tlre
irroposed type of construction. The septic disposai systelll is protriosed io be iccated tc tiie
notthrarest of tile ,.'esidence and probably siigirti5r fuither v/est than that shor;.rn cn Figure i.
ii'];uiidiirg condi.iiens oi''ioundaticn icading-s are significantil'.iifferent fr'orr those
desci'ibed aborre, ';,'e shauici be notifieci to re-el'aluate ihe recomrnenciations irresented in
ilrrs repart.
Site Conclit'ions: Tiie ic"i is vaca*i ani'iire gr:cund sui'fbce appears il*siiy na'iui:ai. The
.e---:..' r:-. lhe bu;l:irr;= p-';ea it. r'eiatltei-,'fjai i.,iiii a Siiiirg slite dc;,i:r iC ilis',"'es'i
:.. ::.-'. :,:r:-:--l::lt':S::.r= ::'.,f -.-- ..;:lt-:.-l .=:,1',.- -i.- -: i.'-: i;e:. '..".,=.::r-:ti,:,,--;.::=ir,:
': --- -
-) -
Suhsui.face Conditions: The subsurface conditions at the site rvere evaluated by
excavati:ng two exploratory pits in the building area and one prof;-tre pit in ihe septic
disposai area at the approximate locations sholvrr on Figure i. The logs of the pifs are
presented on Figure 2.
TIre subsoiis encountered, below about Yz taoi of topsoii, consisted of medium dertse,
clayey to verSr clayey silty sand with scattered gravel and cobbles underlain at depths
fron: about 5 to 6Yz feet by mediun'r dense to dense, claliey sandy grarrel and cobbles with
snrall bculders ihat extended down to the inaximum depth explored af g 4 feet. Results of
srvell-consolidaticn testing perfurmed on relativeiy undisturbed sannples of the sand soils,
presenteci on Figure 3, indicate low cornpressibilit;u under existing moisture conditions
and lighi l6lding anci moderate compressibiiity rrrhen icaded after wetting. One oithe
samples sirovved a minor er,pansion potential a.nd the other sanple shorn ed a mincr
ccllapse potential when rn'e'ited un<ier a c.onstant 1,00C psf surcharge. Results of
gradatioir and hydrometer analyses perforrned on a disturbed bulk sampie of ciayey silty
sand sciis {millus lYt b:,ch fi'action} obtained from itre Frafile Pit are presented ori Figure
4. The laboratory test results are sum$le"rized in Ta'ble t. No free vrater rvas obseled in
flie pits atthe tiine oi'excai,ation and the soiis were slightiy inoisi.
Foundation Bearing Conditions: At assume<i eilcavation grades, the claye'v to \/ery
ciayerr siity ssn6 soils rvili probabiy be exposed at suLrgrade. Spread fooiings bearing on
ihese soils shor:id be feasible fcrfoundation suppcrt of the huildurg wiih some risk o1'
movement. The risk of movement is prirnariiy ifthe bearing soiis become wetted a:rd
precautions shculd be tai<en to prei.rent ra'etting ofthe bearing soils. The ioir e>ipansion
potential encountered in one of the samples is probabl3'an isolated ccndiiion and caii be
neglected ur the tbuirdation design" \"[/e shculd further erraiuate the soil bearing
ccnclitions ez,pcsed in the foun<iation excavation far exnansion pctential at the time cf
constn-rciion. A iora,er risk aiternative v.,ith respeci to ftiundation moverient rn,ouid be tc
bear ihe footings entirely on the uncieriying cla1tq, sanciy gravel arui cobble soils.
Foumcliation R.eeornnnendations: Spread fboiings bearing on'ihe undisturbed naturai
soils desisned for an aiio\a,abie bearing pressure of 1"5*$ nsf.can be used for support cf
the propcsed resicience. The sanci sails may rlend to srryeli or compress aiter rn'eiting and
there could be some post-construction foundatior: rroiieineni. The potential ntoveineitl is
expected to be up lo i inch depending on the depih anci extent cf the wetting and
settien:ent iriaire sails.
o a tillnllltul1i i4/o contmucus
cch:rnns. AIi topsaii a"nci icose ciisturbed soils eircauntered t'ltlie fcundr,iiorr bearing level
.icl- lvo. 1iJ9 i31A
a -:-71^i,- A-!zi=\:)tEr-l I
-J*
tvithin the excavation should be remorred and the footing bearing levetr e;itended dci"'n'io
the undlsiu6ed natural soils. The fociing subgrade should therr be nroistened and
corcpacted. Exterior footings should be provided with adequate cover above theil bearing
elevations for *ost protection. Placement of footings at least 36 inches below the exterior
grade is typicaily used in this area. Continuous foundatiot walis should be weil
reinforced top and bottom to span local anornalies and better withstand the effects of
some diff,erentlai morrement such as by assuming an unsuppo*ed length af eft.least 12
{bet. Found.ation waiis acting as retaining structures shouid also be designed to resisi a
iateiai eartii pressure baseC on an equivaient fluid unit weight cf at least 50 pcf for the orr-
site scil, excluding topsoil and overstze<i rocks, as backfiil.
Llnderdrain $pr5fgm; Although &ee rx;ater was not encountered durfug crir expicratiort, i''
has been oul experience in the area and v,rhere clayey soiis are present that local perched
gtoundrx'a.ter can develop during tirnes of heaw precipitaticn or seasonal prnoff Frozen
ground during spring nrnoff can aisc create a perched conditiorr. \1ie lecomnteird irelcw-
grade construction, such as reraining walis anci relatively rieei: crawlspace areas. be
protectsJ fiom ra'etthg and hydrostatic pressure buil<lup by air underdrain s3,ster.
The drains slroul<i consist of drainpipe placed in the bcttcin afthe wall backfili
surrounded above the urvert level with fi'ee-draining granular rnateriai. The drain sirouiil
be placed at each levei of excavation and at ieast tr f,oot belorn' lowesi adjacent finish
gra<ie end sioped at a minirnum lo/o tc e suitable gravity ouilet. Free-draining granutrar
material used in the underdrain systern should contain }ess than 2% passing the No. 200
sieve, iess than 50% passing the No. 4 sierre anci irave a maxii-num size oi'2 i*ches. Tire
drain glavei backfili should be at least i X ftet deep.
Surfaee Draimage: Fositive surface drainage is arr irnpoltant aspect ofthe projeci to
preveni ."i.siti!rg ofthe bearing soils. The folloi,r'ing clrainage precauiions shouid be
observeci durhg construction anci maintained at all times after the residence has beeir
eonpieted:
1) Inundation of the foundation excavaticns and underslair areas should be
al'o ided during construction.
2) Exterior backfill should be adjusted to near- aptimum mcisture and
conipacted to at least 95Ya af the inaximum siandard Pioctor density in
parrement and slab areas and to at least 90920 cf ihe ma:drnuni standard
Pnrctor density in landscape areas.
3l The grcund suriace sun'ounciirg the exieriol af the buiidirig sha,-ild be
Ii to awa"!ili 11 lli RS
ieccillitienci a ininii-lium slope cf 12 iircires iil t}-ie firsi 10 feet in unpaved
job No. 1Oil 33lA
ueGAibteCr-i
-5-
This report iias been prepared for the exclusive use by our client for design purposes. We
ai'e not responsible for tecirnical interpretations by others of our information. As the
project evoives. we should provide continued consulta-tion and field seryices dudng
constniction to revieu, and monitor the implementation of our recornmendations, and to
l'erify that the reconxnendations have been appropriately interpleted. Significant design
changes may require additional analysis or modifications to the recoinmenclaiiops
presented herein. We recontnend on-site observation of excavations and foundatioir
bearing strata and iesting of stirrctui'al fill by a representative of the geotechnical
engineer.
If irou harie anlr questions or ifrn'e rnay be of further assistance. please lei us know
F.espect fu litr Subrnitted,
HEP\ /ORTH - PAWtr-AK GEOTECHNICAL. INC
qr\t g$f l lrfltr
,r\ ... '':'. \-4.--
David A. Y
RevieiveC by:
DAY/ksw'
attachments Figure i,I-ocation of Expioratcry Pits and Percolation Test Hoies
Figure 2.. Logs of Exploratory Pits
Figure 3, Sv'ell-Consolidation Test Results
Figule 4, Gradaiion Test Results
Tabie i. Summary of Lairolatory Test Results
Tabie 2, Percalation Test R.esuits
IJ Ld Engineering - Aiirr : Darrid Cliase (cl chas erT{;i,ist a eir occ i-i:. co nr)
.ir-rb No. 109 381A
c-e$tecir
TIME READINGS U.S. STANDAFD SERIES
#50 #30 #16
CLEAFI SQUARE OPENINGS
24 HFI- 7 HR
o 45 MtN- 15 MtN.60MlN19MlN.4 MtN. 1 MtN. #200 #iCO #8 #4 3/e" 314" 1 'tl?" 3" 5"6" 8"J00
802A
30
n!J 40z€F
UJE
F502
lrj{Ja:tds60
s0 v6ffi{
i-7
tl.J(1
E
Lels-4c
7*
BO
100
r!
0
001 .002 .00S.00S .01S .0i7 .AiA .1s0 .s00 .60$ i.lB 2.36 4.75
DIAMETER OF PARTICLES IN MILLIME|ERS
9.5 19.0 37.51t R
75.2 152 243
cirv I
I sAm l ^"^* l
r vFrs I ns I MmM lmmcilucnffil svrr! f MmntM I t^ffi I cc6BIFS
GRAVEL 24 %SAND 52 O/*slLT 17 %f'l fiV a a/\/|-./-l I r /O
Ll0utD Lli/iiT %PLASTICIry INDEX O/O
USDA SOIL rt'F[: Sandy Loain FROI'I: Profile Pit from 3 Feei io 4 Feei
109 381l\USDA GRADATIOhJ TEST RE$ULTS Figure 4
H EPWORTE"{-PAWLAK GECITECH N ICAT. I NE.
TABTE !
SqJNNffiARY OF LABORATORY TEST RESUTTS
.fob No.l09 38lA
SQETOR
BEDNOCI( TYPE
Very elayey silty sand with
gravel
Clayey silty sand
Very clayey silty sand
Sandy Loarn
{PSF}
UNCONFINED
EOiNPRESSlvE
$TREN6I}I
l%l
P!.ASne
IND9(
TIQUID
ilfrtUT
l%l
PERCEN'
PASSIN6
NO.200
SIB/E
245224
SAND
l%l
GRAVEI-
l%l
NATURAL
DRY
DENSITY
NATURAT
NNOlsIURE
qOMIN?
108
B5
102
5.8
7.2
1.7
tlepil
lfr!
4.
1t2
4
3-4.
SAMPP-E LOCANOh
Pii
1
2
Frofile
LCIT 1C
PROF'ILE
Fti-
I
PIT 2 PROPOSEU
RESSDENCEPRCIPOSED
PCl:[ BAI?N
n
n PIT i
rl@ rE Ol rEr,g/\l\A
FLEV l$ZtftEf 679633
LEGEi{D:
T PROFILE FfT'
A FERcoL/r.Tioht r[sr riclr
APPROXIM/I,TI SC,ALI
1t! I nt'\tI - ILJLJ
ffiLL
luttrl-E
BEI\ICH Ir4T\RK: ,;ROUI.,!D I,J PRCIPERTY
CCftl'lEF;; [L[ir. = 100.f;', ASSUMED.
1 09 38iA LCCATION OF E}{PLORATORY PITS A[',ID
PERCOLA. i-icN TEST F|CLES Figure i
${EPWORT$"{.PAWLAK GEOTEGF{IIICAL. INC"
TAtsLE 2
PER,COLATION TEST' RESULTS
JOB N0. ,t09 38rA
Note: FereoEation test froles were hand dug in the bottom of backhoe pEts arad soaked
on ft{ovember 2,20@9" Fercofa€ion tests wefi'e eonducted ora illevemrben 3, 2009.
The average percotration nates were based on the [ast tralo readings of each test.
l-roLE No"8-to[-E
DEFTH
{TNGFTES}
8-ENGThI OF
INTERVAL
{MrN}
WATER
EEPTF{ AT
ST'ART OF
INTERVAE-
{rNe}NES}
WAT'ER
DEPTI.I AT
ENB OF
INTERVA[-
{rr{cHEs}
DROP IN
WAT'ER
LFVEI-
(rhrcHEs)
AVERAGE
PERGOI.ATIOh!
RATE
{Mthg.rrr{Gt!}
P-4 48 {5
refilled
'l3s/a 10%TYz
8Y"
1A%63la 3y,
6sia 4T"2
4V"3Y^"t1/z
13Y4 9T4 211^
gY4 '1 ?31"
5
5 3'fz {rt
p-5 4E ts
rcfilled
133/a frIva ?Yz
J
2
nYz
2%
.5
I
7Yz
10Y4 7Y4
7Ya 5Y4
5Y1 33/a
XZrla 'f;0
,?0 7
{A
J
P-3 48 .tR 7$Ya ffi{E 41.t,
lt
14Y"SY4 t3/,'
93/a 8n NT,
81k 6%nYz
634 $Yz ftY4
4Y".t
4Tz 3%3/o
a3/"2%I
PIT 1
ELR/.:107.6'
PIT 2
ELEV.:'102.4'
PHOFILE PIT
ELEV.:99.3'
e)q)
l!
I
!
s)clI
-l
5
()
c)LL
I
o_
C]
tl
LEGENS
\hta.--J t
DD:85
VttC:1.7
DD=102
t )-4:24
' -2AO=24
0
1n
WC:5.8
DD:'108
13
TOPSOIL; organic siliy cla.y, slightly mcist, brcwn.
CLa.Y {CLi; sil\,'sandy, scattered gravel and cobbles, stiff, slighily mcisi, brov';n, low plasiiciiy
GIIAVEL AtJD COBBLE$ (GC); with small boulciers, sandyr, ciailey, medium dense tc' dense, sliglrtll' moist,
brown. rccks are primarillr subanguiar and a miu of basali, sandsione and shaie fiagnrents.
F 2" Diameter hand driven liner sample.
Disiurbed bulk sampie.
l,!OTES:
1. Exploratory piis v/ere excavated on November 2, 2009 with a Terex Ty.760B backhoe
f. iocaiions of exploraiory pits \Afere measured approximaieiy b,v pacing fro;'n features shovun on the site plan
prorrided.
3. Elevaticns of exploratory pits were n'leasured b;r instrument ievel and refer tc ihe Bench h.4ai-k s!'rrwn on Figui'e 1.
Logs of ihe pits are all drawn to depth.
4. The expioratory pii locations and elevaiions should be consiciered accurate cniSr i6 the deEree irnplied by ihe meii-rci
used.
5. The lines between rnaierials shown on the exploratory oii logs i'epreseni the appro:tinlaie bcundaries belween
material types and iransitions ma)/ be graduai.
6. l{e free water lr\ras encountered in the piis at the time of excavating. Fiuciuaiion in rrvater ieve! may accur with iime.
7. Lauhoraiory Testing Results:
WC : Vlaier Content (?6)
DD = Dry Density (pcfl
+4 = Percent Gra\rel
ffiffi
L__t,t;i--J
I
L*GS CF Ei{PL'SRATORY PITS Figui"e 2i0g 3B1A
U
;sc
'6
C(6
CL
UJ
r=
'=
a
a)e
E
I
I
4
ot i!IUU
AFPL|E] PRISSLIRE - hsf
Moisiure Conter-ri : 7.2
Dry Dansity': B5
Sampie of: Clayeir Siit1,52n6
Frrrl Pil I zi tA Fr't
percent
pcf
i^,
i
rOc\
Co
@q)
EU
1
Compression
upon
wetiinQ
"l
4
APPLIED PRESSUfrE - i<sf
Moisiure Content : 5-8 percent
Dry Density = i6B Pcf
$arnple of: Very Clayey Siliy Sand wlih Gravel
Frorn: Pit 1 at 4 Feei
\It \L
I
J
fI
Exprinsion
upsn
wettinE
t
a
n1 100
Figure 3109 38'iA S\ffTLL-CChISOLIDATi CN TEST NESULTS
H