HomeMy WebLinkAboutSubsoils Report for Foundation Design6*bJ(r*
Geotechnical Engineering Report
Lot 83
lronbridge Subdivision
Garfield Countlr, Golorado
Proiect No.2St74
Augu*t 29, 2006
Preparad for:
Hr. Tom Buck
50E0 Orchard Court
Golden, Colorado 80403
Preprcd hy:
Ysh and Aseoclabr, lnc.
l7O llol Ray Road
Glemrood Sprlngr, Golorado 81001
Phone: 970-3E+15{t0Fax: g7l)€8+1501
LotE3,lmnbddge Pr{cd No.2S174
Table of Gontents
Page
Purpase and Scope of $fudy ....,..,,..r.,.'rrrrrr......t...t..t..r.t... I
Foundation Recommendations ,..!.,..r.,r.'rr 2
Figure
Approximate Locailonc of Eryloretory Borlnge ...
Aooendlcss
t{o=
1
A
B
No.
Lot 8i31, lronbrldge Prq,sdNo.2&174
Purpoee and Scopo of StttdY
This report presenb the rasults of our geotecfrnical investigation for a proposed single'
fumily residence on Lot 83 of lronbridge $ubdMsion in Garfield County, Colorado. The subjec't
site is presented on Figura I. The purpose of the sfudy was to develop rtoommendations for
design and constuction of a singl+.famlty residence on the subiect lot.
Ths field investigation consisted of drilling three exploratory borings near the buildlng
envolope. Test holes were drilled at the locations shown on Frgure 1. Samples of tha
subsurface materials nrere coltested and rctumed to our laboratory br testing. The results of
our field and labonatory prognams wero erraluat€d to dovelop r€oommendations fur building
foundations, belowgrade consfuriion and surfaca and subsurhce drainage. This report
summarizes the information obtained dudng our investigalion and presents our
recommendations based on ths proposed consbuc'tion and subsurhce conditions encountered'
Proposed Gonstruction
The proposed residence will be a on+.story wood framed shucture with a walkout
besement We anticipate bas€ment excarmtion on the oder of I to 10 feet deep. For the
garage area, excavations will likely be on the order of 3 to 4 feet deep. We anticipate the main
level floorwill be sbuc.turally supported. Foundation loads will likely be on the order of 1,000 to
3,000 pounds per linear foot
-Slta Conditions
The sitrs is located on Lot 83 in the lronbridge SubdMsion, wfiich is approdmately five
and on+half mtles southeast of Glenwood Springs, Colorado (Figure 1). The proposed building
site is on a vacant river-front lot wiilrin a new developmenl The lot is situated rvest of and iust
above the Roaring Fork River and east of and below the lronbridge Gotf Coursa. At the time of
our site visits, tre utrlitias rvere being installed and there wa$ an open tench on the site that
appeared to encroach lnto the building envelope. The lot is nearly level to gently sloping and
slopes down to the south at gmdes of less than 5 percenL The lot is bounded on the west by a
moderately steep slope wifir grades of about 30 percent up to the golf course and on he east by
a s6gp slope with essmated grades of 45 percont down to the river. Ths lot had been graded
and there was minor vegetation that mnsisted of natrral grass€s and weeds. There is a lift
station lo the south of the lot, and a vacant lot to the norlh. The sbeet was rough graded.
I
Lot8il, lronbddgp Fntect No.2&174
Subsurface Condifons
Exploratory borings were drilled neer the proposed building envelopa as shown on
Figure 1. The borings were drilled to dep$rs between 5 and 12 feeL The test holes werp
terminaled shallowsr than desir€d depths due to pnac-tical drill rig refusal. Modified Califumia
and Split Spoon samples were cotlected at specifred depths. Calibmia samplos were collected
using a 2-inch l.D" sampler driven into the subsoils wifir a 140{ound hammerfalling 30 inches'
Tho split spoon sampleo wero obtrincd lhr same way but urith a 1-31fr inch l"D- sampler. The
number of blows needed to drive the eampler constihrtes the blow count For example, a valuE
on the log (Appendix A) of 50/6 indicates the samplerwae driven 6 inctrcs wih 50 blows of the
hammer. The blow count cen be used as a ralatively measurc of material stiftiess or density.
The cotlec'ted samples were hansported to our laboratory where thay wera axamined and
classified. Laboratory tests included moisture content, dry densi$, grain size analysis and
Atterbbrg limit testing. Laboratory test results are pres€nted in Appendix ts.
Generally, the subsoils encountered in our borings mnsisted of silty sands over clayey,
sandy gravel. The gravels contained cobbles and bouldors whicfr caused drill rig refusal"
B€drock was not encountersd on this lot. The silty sand had 20 percent fines (passing No. 200
sieve) and was non-liquid and non-plaslic. The gravel had 41 percent fines and had a liquid
llmit of 26 percent and a plasticity index of 7 peroent. The silty sand classified as an SM and the
clayey gravelas a GC, based on the Unifted $oil Classification Sptem-
Gmundwater uns not encountered during drilllng, and the subsoils were slightly molst'
Groundurater could not be checked several days afier drilling due to the consbuction of a lateral
s6wer line desfioyed lhe test hole locations. We belleve variations ln ground water conditions
Gan occur. The magnihrde of the variaffon will be largely dependent upon local inigation
practices, the dunation and intensity of precipitation, slte gnading changes, and the surface and
subsurfaca drainage clraracterietics of the sunuunding area.
Foundation Recommendations
We anticipate foundations wsuld be constucted on sand and/or gravel subeoils. These
materials are relatively favorable for foundation supporl Based on tha reeuhs of our subsurface
investigation, we believE the resHence can be supported on spread fuotirrg foundafions placed
on the natural solls or properly compacted fill. The fullowing design and consbrucilion details
should be obsarved for spread foolings placad on ths natrlral soils or propsrly compactad fill.
2
Lot 83, lronbridge Projed No.26-174
1. Foundations should be cons$r.uted on undlsfurbed, natural soils. Loo$e, distlrbed
soils encountered at foundation level should be removed and replaced wi$t
compacted fillorthe foundation should bg e)dsnded to undisturbed soils.
2. Footing foundations can be designed for a maximurn allowable soll
psf. The design pressure may be increased by 113 or as allowed
when consldering total loads that lnclude wind or seismic condi$ons.
g. Continuous wall footings should have a minimum widh of at least 16 inches.
Foundation pads for isolated columns should have a minlmum dimension of 20
inches.
4. Resistiance to sliding at the bottom of lhe fuoting can be calcilhted based on a
coefincient of fticiion of 0.35. Passive pressurp against the slde of the fuofing can
also bs considered for the sliding resistancp if lt is properly compacted. Passive
pressure can be estimated based on an equivalent fluid density of 300 pcf for a level
backfill.
5. Grade beams and foundalion walls should be reinforced to span undisdoeed loose
or soft soil araas. We recommend reinforcement suffident to span an unsupported
distance of at least 10 fg€t
6. The soils betow exterior footings or exterior edges of slabs should be protected ftom
fteezing. We recommend the bottom of footings be construc'ted at least 3 tuet below
finished exterior gnade oras required by local municipal code.
T. All foundation excavations should be observod by a representative of the
geotechnical engineer prior to placement of concrete-
Baeement Walls
Basement and belowgrade walls should be designed for lateral earth pressure. Walls
that can deffect or rotiate abut 0.5 to 1 percent of the wall height can be des'4;ned for "active'
earth pressure conditions. For a wry rigU wall where negligible deflec.tion will ocor, an'at-
rest' lateral earffr pnessure condiHon can bs used. Typically, basement walle can rotate under
normaldesign loads, and deflections re$ult in acceptrable performance.
lf on-site soils are used as baeJdll, w€r recommend using an equirralent ffuid density of
45 pcf for deslgn of basement walls fur "active' mndltions. The equivalent densi$ does not
account for sloping backfill, surcharges or hydrostatic pressure. This rralue assumes that some
minor craddng ls acceptable. lf negllglble deflections are desired, an equhralent fluid density of
55 pcf should be used br daoign.
3
3,000
LotS3,lrunbridge Projeti No" 2$174
Slabs-orr.Grade
Based on our lnvestigation, basement, garage and drivoway slabs will llkely be undErlain
by sandy and/or gravelly soils. We beliew there is a low risk of poor slehrrgrarte
performanoe due moisture sensitive soils. The on-site soils, free of organics and debris, are
suibble to support ligh0y loaded slabs-ongnado. Slabs should be separated ft,om all load
bearing walls and columns with expansion folnts Srat allow vertical movemenl Gonhol ioints
should be uaed to reduce damage hom shrinkage cracking. All fill below slabs should be
compac,ted to at leaet 95 percant of maximum standard Proc'tor dry density within 2 percant of
opfimum moisfure contenL
Subsurfiacg Dralnage
Groundwater ums not encountered during our investigation. Surf;aca water typically
flows through permeable wall backfill and collecls at the backfill and natural soil interf;ace
resulting in sahrrated foundation soils and/or damp basement or crawlspace conditions. To
reduce water accrrmulafion outside foundation walls and reduce the potantial fur water within
the basement and cravvlspace aneas, a foundalion drain should bs installed around the extedor
or interisr of foundation walls. Drains can bE installed in crawlspa@ ar€es after completion of
constuction, if groundumter develops. lf groundwater or highly safurated soils are encountered
during fuundation excavation on this lot, we should be contacted for additional
recommendations.
A typical foundation dnain should conslst of a 4-inctr diametsr, perforated pipe encasod
in free draining gravel. The gravel should be 5/t to l.finch rrashed ruck with less than 5
percent fines- The drain should be provided with a grawty discharge such as E sump pit where
water can be removed by pumping or be daylighted. The pipe should ba sloped at e minimum
of 0.5 peraent and should be installed 12 to 18 inches away from and parallel to the boting
foundation. The bottom of lhe pipe shouH be at least 2 in*es below the bottom of tuoting level
atthe high point Crawlspace sreas should also be provided wtth adequate ventilation.
a---r. .. - h---l- __--uutTace u|aiRagE
Surface dreinage is crucial to the performance of hundations and flatrvork We
recommend the gnound surf;ace sunounding the residenca be sloped to drain away ft,om the
stnrcfrrre. We racommend a slope of at least 12 inches in the first 10 fiaet Bacl<fill around
foundations slmuld be moisture conditioned and compaded to at least g5 percent of maximum
standard Proctor dry density within 2 percent of optimum mdsfure content. Care should be
4
Lot tli!, lronbrldge Prdatn No. 2S174
taken not to over-compac{ the backfillor us€ large equipment adracent to bundalion rralls that
could cause excessiva lateral earth pressure on the wall. Roof downspoub and drains should
discharge beyond lhe limits of lhe backftll. Failure to follow these ra@mmendations could result
ln hydrocompaction of the subsoils resuhing in setllement of the residence.
Limitations
The analyses and recommendations presentod in this report are based upon our dah
obtalned from the borings at the lndlcatsd locations, fieH obsenrations. labonatory testing, our
understanding of the proposed constudion and other inbrmation discussed in this rsport. lt is
possible that subsurface conditions may \Ery betriveen or beyond the points explored. The
nature and extent of such nariations may not become evident until construction. lf variations
appear, we should be contacted irnmediately so we can rsview our report in light of the
variations and provide supplemental recommendations as necessary. We should also revieut
the report if the scope of the proposed construction, including the proposed loads, finished
elevations or sFucture locations, change ftom those described in this roporl ThE conclusions
and recommendations conbined in this report shall not hs considered valid unlees Yeh and
Associates reviews the changes and either verifies or modiftes the conclusions of this report in
writing.
The scope of services fior this project did not indude, spedftcalty or by implication, any
environmental or biological (e.9., mold, fungi, bacteria) a$sessment of the site or itlentification or
prevention of pollutants, hazardous materials or conditions or biological conditions. The scop€
also did not indude invetigation of the bedrock conditions below the site. The site is underlain
by a bedrock forrna$on known to produce sink holes" The purpose of this investigation was to
investigate near surhoe condilions for design and consffudion of a res'xJence. This
investlgation did not evaluate the potentiel fur sink holes to develop and based on our
experience sink holes could develop anpvhere at anytime within ftis b€drock formation- lf the
ownsr is concemed about the potenUal for such contamination, conditbns, pollution or potential
sink holes, olher shldiss should be undertaken.
The report was prepared in substantial accordance with *te generally accepted
standards of pnac'tice for geobchnical engineering as exist in the site area at the time of our
investigation. No warranfies, express or implied, are intended or made. The recommendations
in this report are based on the assumption that Yeh and Associates will conduc{ an adequate
5
Lcil 83, lronbddge Pndsd No.2&174
program of consfuction testing and observation to evaluate compliance wift our
recomrnendalions.
Respectfr.tlly Submitted,
YEH AND ASSOCIATES. INC.
Keih Asay
Staff Engineer
Reviewed by:
35S*eRichard D.
Senior
(3 copies sent)
7.*f &
n
Vicinity ilap
NTS
--
.10 0 t0 .lE
\
SCALET l' = 40'
\\
TH.1
Lot 83
Proposed
Bulldlng
Envslope
Llno
\
\
\-/-<---\
\TH.2
o
\,
\
\
\
\
-tst*\
-rn--\..- - -
\e
Lot fXl. lronbridga
APPENDIX A
Prqpd No.2S174
TEST HOLE LOGS
n*1gWcfiiatbld0 f,nrdop!
TH.2
Crrt ru{lfiwdoP.
Tl{{
tiE !illsbldg.fl,nloFr
1
g
!
CLoo
t 6
YEH AHD AS$OGIATES, IHC.
GEOTECI{NIf, AL ENGINEERING CONSULTANT$
ioiI fi/tI llrll
6tul
t'llrnfi# ?S,174
Lot 8S, lronbrldga
Ho. A1
lTlvex Al.rD AssocrATEs, rnc.
tfl G€OrEctl$Clt nenrmnrecolsuliirrns
Pntect Lot 8[], lronbddge
PmJ€clNumben 2*174
Legend for Symbols Used on Test Hole Logs
Sample Types
I +nr Sn""., Samplcr. Thc aymbc{ 508 hdcabs thaf 50 Hffis frsn e 14{l pornd hammsr
I bktg 30 hdrc$ was uscd b *hr€ 1.5&dr l.D. rampler 6 incfta.
ltodfed Cafifunh Semder. The slrnlol 6112 lrdtdes that 6 bbtvs from I 1/{} pound
hammrh$ng 3{l hdrss was us€d b &ir€ 2.ttdr l.D- sanple 12 hdte&
ffi "* *tttr c,8s obtah€d lhun arqor urflfEr at the deplhs lndcabd.
Soil Lithology
[H] *. * sardy, taca sraud, lmo b medum d€ns€, dbhty mdst, brorur (Mt).
m t *. dtty. faoe day. bec6 griaird, bose ro mefirm dense, clghlymob( broryn (sM).
ffi *"*sbpy, eandy, mbbles, wry dense, dlghuy molst b{orfln (Gc}.
t lndcabe pacdcal drii rlg refttsal.
Flgurs l.lo.A.2
LotS3,lmnbddge
APPENDIX B
Pral€d No. 2S174
I.ABORATORY TEST RESULTS
Prcject No:2*174
YEH & ASSOCIATES rNc
Summary of Laboratory Test Roaults
ProJect NEme:Lst 83, lronMdge
SollDescdpUon
Sand, allty{SM}
Gmvol, clayey, aandy (GC!
Unconf.
Comp.
$berutr
{osf}
% Swell(+)l
Conrollda$on (-)
under 1Offi pef
mlls
PI
7
PL
1g
LL
28
Flner
< #200
(%)
2A
4 I
Sand
(%)
80
24
Gravsl
>#4
(%)
0
35
Dry Denel$
(pc'r)
Mol*hrc
Conlent
t%)
{9.6
5.0
lon
Sample
Typa
CEI
Bulk
Sa
Deph tft)
d-5
5.S
Bodng
Number
TH.2
TH.3
trane 'l rrf 'l
HydrornstsrAnalyds
Flza of Paddm ln mmU.$. Stsndard $tevssin lneheeSlevs
Slsve
tr |:.fr r' 3r{' 12. YA' 4 I 10 1! 30 {o !0 100 200
100
s]
80
70
Fso
ct66o s{l
otb40
o.
30
?0
10
0
1000 100 10 1 0.1 0.01
Padlcle $lre {mm}
-F{-t_t_i--J-
IIlt I II
Iltt
'i
*r--#
:r II
'
i
tt I
ii i If
tr I ttII
IItttlII
IIrl tjI{t II
IIrli II
Itt I IIII
III
ttI1
tlt I
l l lL r '++-{-+-
TL-I_L_:_L_-+]+l_F.;.*
*FFt*+-
-fi-fi-i:-:i-
-+*+-+--"i*,+-i--
J
olo
Pasalns
g5
2A
Elava
Slza
3"
2%'
4
1Yz.
I
?4d
Ya'
Yail
M
#10
#0
#200
w Yeh & Assocla Inc.
Gcolccbricet Engincsring Conmltanu
$IEVH ANALYSIS
2&174
B-1
Pmject No,:
Flgurs l*,1o.;
Drawn By:
Checked By:
SAW
RDJ
Prdect Name: llot 83, lronbrldge
TH.2Sample lD:
gamFIe
Deoth {fi.}:4-5
Sampla
Descrlotlon:Sand, ellly($M)
L]L I
PL
Pg
Gravel(t{} I 0
Sand (Yo) I eo
Flnes (%) | 20
9ndrsl nil?7DnnA
Hydrailcttr fuElytlt
| $ha of Partelas ln mrnU.$. Stsndatd Slsvoa
$leva
Slevs Opanlng ln lnchae
IT f J'r* cl' t/? !/!. 1 810 t6 ts$ is r00 m0
1{X}
90
80
70
g6s
6
f,tss
ollb404
30
20
10
1000 100 {0 1 u. I 0.01
Partlcls $Ee {mm}
olb
Prselns
94
8g
78
73
a5
82
58
4 1
Slsva
Slze
ei
2Yz"
2"
1Y2'
1
Y1'
llatT3
34"
H
#10
#40
#200
It Yeh & Associrtee.Inc.
Gcobchnical Enginc€ring Cons{trsb
SIEVE ANALYSIS
28-174
8.2
Pr{ect No.:
Flgure No.:
Drawn By:
Checked By:
SAW
RDJ
Prolect Name: Lot 83, lronbrldge
TH.3Sam$e lD:
Sample
Deoih ffi.l:5.10
Gravel, clayey, sandy (GC)
LL 26
1 g
PI 7
PL
Graval(7o)35
24
Flnes (%)41
Eand (Yo)
Rrvfrarl O#?7nfifiA