HomeMy WebLinkAboutCT 04-26; ROBERTSON RANCH EAST VILLAGE 16 17 18; SUPPLEMENTAL RECOMMENDTIONS REGARDING PIER SUPPORTED BRIDGE ABUTMENTS; 2006-11-30•
Geotechnical, .. CO(i$tal • Geologic l\ Environmentai
5741 Palmer Way • Carlsb;:td, Califbfnia,92010 • (7<;30) 438~3155 • FAX (760) 93l-091-5
Calave~,Hilis II, L.LC
2750' Wamble Road
S~n Diego;, Califarnia 92106
Att~ntion:' Mr. Dbn Mitchell
November 30;2006
W.o. 3098-A2'-$C
Subject Supplemental Recommendations Ae'gardin-g 'pi~r Supported Bridge
Abutments, Robertson Ranch E?$t Project, City Qf Carlsbad, .san Diego
.county, Californ'ia '
'Reference: !'Updated Geotechn.ical Evaluation aftheHobertson RanehProperty, City of
Carlsbad, San Diego County', ·California;"W.O. 3098-A2-SC, dated
September 20, 2004, by GeoSoils, ,Inc.
DearMr., Mitchell:
Inaccordance with your request, GeoSoils, Inc. (GSI) pas reviewed.sjte cQndilions,and.0l;Jr
'referenced report regarding the construction of a bridge crossing near Ule'western edge
:Qf thi3, Hqbertson Ranch East project. Unless specifically' super;ceded herein., the, .
conClusions and recommendations presented in the referenced report remain valid and
~pplioable.
PROPOSED CONSTRUCTION,
It is our understanding that the purpose bf1he bridg~, is to:provide, m~!ntenance ac€;~ss
across"a pianned open space area. IUs' &lso,Qur understaocUng that the type of briqge
proposed wiiI utiliZe two recycled railroad flat cars. placed s~d~ by 'side,_ Information
prov.ided by others indicates that the flat cars-are on the 'order .of 65 feet :in length, and
weigh approximately 500 pounds per lineal footof br,idge. An additional railing, system· will
add 'another 30 pounds perlineaJ foot of bridge. There isa potentiaJ.tMatthe:flatcars will
also be re-surfaced. The unit weight of the .:e:..surfaCing materiEd ,isIlcllt known afthis time,.
Par pr.eliminary planning purposes, the weight of-any ad ditionaJ pi:l'.lehlent surfaCing may
be, assumed to be on the order 'Of 35 to 55 pound$ per 'Cubic foot (pef-[to be YE?tif!13d by
others]).
The,bridge;ablrtrhents are planned to be supported-on apier (€frilledpier) and grade beam
foundati.on system, which penetrates the near-surface aliuvia:1 dep:osits~ and embedded'into.
the uhdeilying bedrock. Reaction load, s.eismic loads and abutmsnt r~action were not
proVided to this office at the time this report was prepared.
ENGINEERING GEOLOGY
Earth~ Materials
Baseq on,allr review, and the limited data Tn the specific,ar'ea·,ofthRbrtdge" the abutments
will beunderlafn with approximately 15 to 20 feet of compressible a]Iuvium· (see
Reference). Bedrock underlying these alluvial .soils appears to consist of dense;
Weathered, undifferentiated metavolcanic/granitic bedrock bene,ath the 'abutments:
Variations itOhe depth·to bedrock are likely, but tend 10 refle~tthe.cbannel shape.
·Groundwater.
BC;lsed..Qrra, r~view of the 2004 referencedreportl groundWaterir;tthe,areamay potentially
be encountered at a depth of approximately 15 feet belowexistin{lgrades,withio'alluviai
soils; and/or very ·near the contact between allUvium and the underlying bedrock. Based
·on 'anlidpated caisson depths on the order of 20 to 30 'feet; groundwater should be·
anticipated. Variations in the depth to groundwater are'-likely, and may occur at shaliower
depths .{perched) due to up-gradient irrigation or pr<3cipitation.
PRELIMINARY DRILLED PIER.AND
GRADE BEAM FOUNDATION RECOMMENDATIONS
Th~' pr:opo&ed abutments, underlain by left":in-pJace 'alluviUm, . may be supported by a
driUep, .Gast::il1-place concrete pier and grade beam system. All drilledpiers·.should extend
·a minimum of7 feerinto competent formational materials undetlyimg the alluvium. Aotual
pier embedment should be finalized by the project's structural.engirieerbased on·thepier
.capacitY chart. (see Figure 1), and the structural' (;apacity:of the pier;(s) used~ The'structural
strengtn: ,of the piers should be checked by the struct(..lrAl engineer Qr civil engineer
spe'ci~izing in struptl,Jral analysis. Pier holes shOUld b~ ddl!e~:f':straight ·apd plumb"
Locations (both plan and elevation) anq plumbness ~holilld be .tbl?} ·contractors:
.respOri.sipUity .
The.grade beam should be ala minimum .of 24 inches by ·24 ihches in.:cr.0ss'"section and
.sqpPGrted by drilled .caissons 24 inches in diameter ·which are, placed at a mirlimliin
spacing of 6 feet on center and .supporting all abutments. Oiffictllt drilling shptild 'be
antiGipated. Independent drill holes, completed:b.ythe'cootrae.tof, ~ta·em:ouraged.in:order
to ,confirm drill rates and the type of equipment reqUired.
~Caiavera. Hills II, llC
:Robertson Ranch East Project
Flfe,e\wp9\3oo0\3098a2.srr
W.O. 309~~~-SC
N.ov~mbt;lr ~O, 2006
"P;:,iQe2'
ALLOWABLE:pIER CAPACITY
(KIPS)
o 10 20 30 4.0 5.0, 60 90
2: 10
,0
fi >' ~ is ,x ,W
IJ.. 0 'ill rn <p-IPw 20 3:W ou:,
..;J ,...-
~ ,/l! W 25 0:
IJ.. Q'
':J: f.,-n. 'W
1;:1 ~O
,5 ."" ' ' ~ ..... /2.4-NCHDIA JlETERC( 'NCRETE PIER
'\
" '" "-' ,
"\ .......
" ~ "-" ~ ~ ~ ,
12·.:fNCI DlAMET RCONC ETE PIEf, i---" ." ,
.~
" "-' -
~:
,3,5
40 , ,-
1. Minimum 'pier lengths should be 5 feet.
'2. Capacities are allowable capacities (based on Factor'of'Safety =:2) and m~y be 'Increased by-one-third
for short-term wind or seismic loads.
,3~FDr, uplift" use 75 percent of these capacities for sing.lepiers and 50 percen~ fOr piers in diJsters~
RIVERSID&CO.,
ORANGE--CO. SAN p,lEGO co.
PI.ER CAPACITY CHART
Th~· design' .of the grade beam and caissons 'shol,llcJ be :in accordance with the
recommendations of the proJect .structural engineer,~n(:l utilize the' folloWing lninililUm
geotechnical parameters:
Passive. Resistance
Passive 'earth pressure of 500 pcf per foot of caissoh depth, toa. llIaxirtlum value of
4;0'00 pounq~ per square foot (pst) may be used :to determine pier depth and spacihg~
provideq tnat they meet or exceed the minimum requirements stated above. No' friction ..
component·shouid pe used with drilled pier caps or interconnected grade be;:lms.
Point of Fixity
The :point offixity should be located at a distance eqtiivcdent. to one-thitq of the, caissons
length below the bottom ofthe grade beam.
Allowabie)~xial Capacity
.A shaf,t,qapacity pfAOO psf should be :applie'd over the .surrace area bfthe shaft located if!
bedtock:only. The tip bearing c.apacity should be limited to 6,0'00: pst.
·Caisson Construction
1. Th~ excavation and installation of tile drilled c;:lisson's .$ho.\.,lkf be obserVed and
documented by the project geotechnical engineer to verifY the recommended
depth. .
.2.., The drilled holes should be cased, specifically beloW the ··Water table, to prevent
caving. The bottom of the casing should be at least 4 feet below the top of fl;re
¢on<~tete as the concrete is pOl.{red 'and the Casing is withdrawn. DewaterjAg I1l~Y
be required for concrete placement if significant ,seepage or grouhdwater· ·is'
eRC0uhtered during construction. This. sh-o(Jld be considered during project
planning. The bottom of the drilled caisson shouldbe·efeare'd.of ariyloose or soft
soils before ·concrete placement
3., Site specific borings are not present Within the pJann?d abl:!tm,s.nt areas, Based:,on
'lhe·avanable information, caisson depths oothe order of20.tQ35 feet. pelowexisting
Qrades should be anticipated.
4. 'We reGornmend that concrete be piaced through' the: tretnie pipe immediately
subsequentto approvedexcavation·and ste,el placement. :tat~"shouldbe taken to
prevent striking the walls of the excavations with the tretnie pipe dUring concrete
placement.
CalaVera Hills II, LLC
Robertson Ranch East Project
File:e\Wp9\3000\3098a2.srr
W.o.' 3098-A2-SC
November' 30,2006
Page 4
5'. All' excavations should be observed and approved by ,th'~"g~ot~chnicar consultant
prior to placement of concrete forms and reinforcement.
6. Drilled pier steel reinforcement cages should have spacers to allow for a minimum
spaGing of' $teel from the side of the pier exeavation. The need for epoxy-coated
stearin below grade piers and grade beams should be evaluated bY'a structural, or
corrosion consultant.
7. During' pier placement, concrete should not be allowed to free fall ,more than 5·feet
a. Concrete used in the bridge foundation .sh'Ould be tested by a qualified rnalerials
testing consliltant for strength and mix d.esign.
'Drilled Pier"and Grade Beam Foundation Settlement
Oril(<?d pi.~r and grade beam foundations should be minimally designed to accommodate
1h inch over aAQ-fQot horizontal span.
'Corrosion and Concrete Mix
Cbrrosio8.:testirm was performed in preparation of the referenced report. To ,summarize,
testlhg. indicates that site soils present a negligible sldfate·eXposure (per tab lei 1 Q-A-4 oftlie
UBC, '1i99,Tedition) to concrete and are corrosive, to' ferrous metals:vJ,hen.saturated.
RETAiNING STRUCTURES
Retaining 'elements of the planned bridge (lbutments 'may be designedlConstructed iii
accordance with recommendations presented in the referenced report. '
,EARTHWORK
Settlement of the approach ramps supported on cOfllpacted fill spould beanticipateq
r~lati\te·to,a>piei"supported bridge bearing>on bedrock. 'In orderto redt;Jcethe ~ettleJTlent
p,f ,fiIJ s6J1's used 'in the construction of ,the approach ramps, com'Pacti,on of the,:fills to at
le&51:95 per'c~nt relative compaction Should be considered. Additional recommendations
reg~rdif.lg site· earthwork (both' remedial arid .planned) are ptesented'ln the referenced
report. The ,use of structural approach slab for the bridge, ~ubdraii1s. abutment rip rap~
etc." vyill. be designed by others. Channel scour should also be evaluated by the desigA
civil erTgin~er.
C'abiveraliills II, LLC
Robertson Ranch East Project
File:e\Wp9.\3000\.3098a2.srr
, , W:O. 3098~M-SC
November 30, 2(j06
Page'5:
· ..
SUMMARY OF RECOMMENDATioNS' REGARDING
GEOTECHNICAL CONSULtATIONS. OBSERVAtiON AND TESTING
We .recommend that observation and/or testing be Performed by Gsr at each of the
following construction stages: .
'. burirl'g: gradin,g/recertification.
'" During: excavation .
• , DurIng placement of subdrains, toe drains, or other sJ;.Ibdrairrage devices,. prior to
pl~cing fiJi and/or backfill.
• Aft~r exc~vation'of building footings, retaining'walifootings~ and free standing walls
Jo.otihgs., prior to the placement of reiflfor.Cing ste.el ,O(,cohtrete.
.. Prior to pouring any slabs or flatwork, after pre$.oaking/PfesaturatiQn of 'bundiflQ
pads,' alid other flatwork subgrade,before the placement of'~conc[ete; reinforcirl'g
:steel, ,capillary break (Le .• sand, pea-gravel, etc.), or vapor barriers (i.e~, visqueen,
·etc.):.'
'~ During retaining wall subdrain installation, prior to. backfill' placement..
• During placement of backfill for area draih, interior plumbing. utility line trenches,
'and retaining wall backljll.
• During:sfope construction/repair.
,~Wheh any unusual soil conditions' are encount~reQ dl,lr,ing' ,?ny 'construction
op'eratj.ons, subsequent to the issoance oflhis report
• When any developer or homeowner-improvements" SUGh ,as buildings, f!atwork;,
spas, pools, walls, etc., are constructed, prior to construttiott.. GSl sf;iotiJd review
clnq ?pprove such plans prior'to construction.
• A report of geotechnical obselVation and t~stiQg ,should be provided at ,the
'Conclusion of each of the above stages, in ord~r to provide cOl1cise and clec;lt
doclJrnentation of site work,and/or to comply \o/ith coge reqUirements, .
• ' ~Sl' should review project sales, documents. to, 'homeownersltipmeowne.rs
a,ssociations for geotechnical aspects, including irrigation:pra,ctie~s~-tlfle cQn~itiQns
outlined:apove, etc., prior to any saies. At that stage", GShvill, pro'vio$ homeowners·
majntenance guidelines which 'should be incorporated Into such documelit$.
'. Final project plans should be re.viewed by GSJ, prior'to' construction.
C~lavera HOis If, LLC
HQbe{tson Ranch East project
RI~:e.\wp9\~QOO\3Q98a?srr
w.o. :a09S-A2-SC
November 30, 200~
PageS
-~
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LIMITATIONS
Inasmucn.as,ouf,studyis based upon bur review andengi'neering~analyses and laboratory
data. the'C()hClusions and recommendations ,are' professional' opinions. These opinions'
havEi:peen derive:ci in accordance with current standards of practice", and no warranty Is
express or implied. Standards of practice are subiect'to change with timEt GSI' assumes
no respnnsibility or liability for work or testing performed by' others~. or their inaction; or
work 'performeq when GSI is not 'requested to be ons,ite, to,evalu,ate if our
reGQmmendations have been properly implement~d. Use of tni~ repqrt constitutes' an
<:i9reerj1ent:l::tnq Consent by the userto aU the limitations outlined above, notwithstanding'
,any oth$r agreements that may be in place. In addition, this report may be subject to'
review by the ,controlling authorities. Thus, this, report brings' to' completion our scope of
services ,for this project.
The"opportUnityto be of servic,e. is appreciated. Should 'you'haVea:ny questions'.r~gardihg
this document, please· do not hesitate to contact this office ..
GeoSoils, ·Ioc ..
RGc/bWS/JPF/jk
Distripution: (2) Addressee'
Calavera Hills II, LLC
Robertson Ranch East Project
'File:e\wp9\3000\3098a2:srr
GeoSoilsj Ine.
W.O. 30~i3~A2-SC'
November jOi2006
Page'?'
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.15'741 Palm'er Way • Carlsbad, California 92008 .. (760)438-31'q5 • FAX.(160)931--0915
MEMORANDUM
DATE: November 15, 2006 W.o. 3098-A2-SC
TO: Calavera Hills, LLC, Attn: Mr. Don Mitchell
FROM~ Robert Crisman, CEG; Oavid Sk.eliy' pe;
SUBJECT: Update QUhe Geotechnical Report with Respect to Site Gradihgand'the
Curr~nt ,Grading Plan, Robertson Ranch East, City of 'Carlsbact,
California '
References! .1. "Updated Geotechnical Evaluation ofthe Robertson Ram;;h,Property, Carlsbad; San Diego
County, California," W.O, 3098-A2-SC: dated,September 20,2004, by'Geo$oils"lnc.
2. '~Grading plans for: RobertsQn ranch East viflag~, M.P, Oi2~Oa, C.T: 02-16, " Project Nb,
C.T. 02-16, Drawing No. 433-6A, Job No. 011014, dat~d Augu:;>t 16, 2006, by' O~Day
Consultants.
,In ac.cQ,rdancewith your request, GeoSol!s, Inc. (~St}has,revj~wed fhe'geQt~chniGal reporl
(Reference No.1), and the current grading plan for Robertson Ranch East Village,
(Reference No~ 2). Based on our review, the geotechniccd: rE?Port (Reference No.1).' is
'cornsidered valid and applicable with respect. to the planned site grading;, as-shown on
Reference. No. '2.
The·concldsibnsand recommendations;presented:hereiri:are pr.ofessiCmal opinions. These
,opini€ms' have been derived in accordance with current standards of practice, ~md ho .
Warranty, 'ei~her express or implied, is given. Standarc;is of practice are SUbject to change
with time,.
The' 'opport!lnity to pe of ~ervice is greatly:appreci?ted, should YOll have "any'questi,oris,:
please contact this office. ' .
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