estimation techniq

8/12/2019 Estimation Techniq

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Go Up to Table ofContents

Go ToChapter 4

(Labor,MaterialandEquipmentUtilization)

Go ToChapter 6

(EonomiE!aluation of"ailit#$n!estments)

Cost EstimationCosts %ssoiated &ith

Construted "ailities%pproahes to Cost

EstimationT#pe of Constrution

Cost EstimatesEffets of 'ale on

Constrution CostUnit Cost Method of

EstimationMethods for %lloation

of oint Costsistorial Cost *ataCost $ndies%ppliations of Cost

$ndies to Estimatin+Estimate ased onEn+ineer-s List of.uantities

%lloation ofConstrution Costs /!erTime

Computer %ided CostEstimation

Estimation of /peratin+Costs

0eferenes1roblems"ootnotes

5. Cost Estimation

5.1 Costs Associated with Constructed Facilities

The osts of a onstruted failit# to the o&ner inlude both the initial apital ost and

the subsequent operation and maintenane osts2 Eah of these ma3or ost ate+oriesonsists of a number of ost omponents2
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The apital ost for a onstrution pro3et inludes the epenses related to the initalestablishment of the failit#5

Land aquisition, inludin+ assembl#, holdin+ and impro!ement

1lannin+ and feasibilit# studies

%rhitetural and en+ineerin+ desi+n Constrution, inludin+ materials, equipment and labor

"ield super!ision of onstrution

Constrution finanin+

$nsurane and taes durin+ onstrution

/&ner-s +eneral offie o!erhead

Equipment and furnishin+s not inluded in onstrution

$nspetion and testin+

The operation and maintenane ost in subsequent #ears o!er the pro3et life #leinludes the follo&in+ epenses5

Land rent, if appliable

/peratin+ staff

Labor and material for maintenane and repairs

1eriodi reno!ations

$nsurane and taes

"inanin+ osts

Utilities

/&ner-s other epenses

The ma+nitude of eah of these ost omponents depends on the nature, size and

loation of the pro3et as &ell as the mana+ement or+anization, amon+ man#onsiderations2 The o&ner is interested in ahie!in+ the lo&est possible o!erall

pro3et ost that is onsistent &ith its in!estment ob3eti!es2

$t is important for desi+n professionals and onstrution mana+ers to realize that &hilethe onstrution ost ma# be the sin+le lar+est omponent of the apital ost, otherost omponents are not insi+nifiant2 "or eample, land aquisition osts are a ma3orependiture for buildin+ onstrution in hi+hdensit# urban areas, and onstrutionfinanin+ osts an reah the same order of ma+nitude as the onstrution ost inlar+e pro3ets suh as the onstrution of nulear po&er plants2

"rom the o&ner-s perspeti!e, it is equall# important to estimate the orrespondin+operation and maintenane ost of eah alternati!e for a proposed failit# in order toanal#ze the life #le osts2 The lar+e ependitures needed for failit# maintenane,espeiall# for publil# o&ned infrastruture, are reminders of the ne+let in the past toonsider full# the impliations of operation and maintenane ost in the desi+n sta+e2

$n most onstrution bud+ets, there is an allo&ane for ontin+enies or unepetedosts ourin+ durin+ onstrution2 This ontin+en# amount ma# be inluded &ithineah ost item or be inluded in a sin+le ate+or# of onstrution ontin+en#2 Theamount of ontin+en# is based on historial eperiene and the epeted diffiult# ofa partiular onstrution pro3et2 "or eample, one onstrution firm ma7es estimatesof the epeted ost in fi!e different areas5


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*esi+n de!elopment han+es,

'hedule ad3ustments,

General administration han+es (suh as &a+e rates),

*ifferin+ site onditions for those epeted, and

Third part# requirements imposed durin+ onstrution, suh as ne& permits2

Contin+ent amounts not spent for onstrution an be released near the end ofonstrution to the o&ner or to add additional pro3et elements2

$n this hapter, &e shall fous on the estimation of onstrution ost, &ith onl#oasional referene to other ost omponents2 $n Chapter 6, &e shall deal &ith theeonomi e!aluation of a onstruted failit# on the basis of both the apital ost andthe operation and maintenane ost in the life #le of the failit#2 $t is at this sta+ethat tradeoffs bet&een operatin+ and apital osts an be anal#zed2

Example 5-1: Energy project resource demands89:

The resoures demands for three t#pes of ma3or ener+# pro3ets in!esti+ated durin+the ener+# risis in the 9;92 These pro3ets are5 (9) an oilshale pro3et &ith a apait# of >=,=== barrels of oil produt per da#? (@) a oal+asifiation pro3et that ma7es +as &ith a heatin+ !alue of A@= billions of ritishthermal units per da#, or equi!alent to about >=,=== barrels of oil produt per da#? and(A) a tar sand pro3et &ith a apait# of 9>=,=== barrels of oil produt per da#2

"or eah pro3et, the ost in billions of dollars, the en+ineerin+ manpo&errequirement for basi desi+n in thousands of hours, the en+ineerin+ manpo&er

requirement for detailed en+ineerin+ in millions of hours, the s7illed laborrequirement for onstrution in millions of hours and the material requirement inbillions of dollars are sho&n in Table >92 To build se!eral pro3ets of suh an orderof ma+nitude onurrentl# ould dri!e up the osts and strain the a!ailabilit# of allresoures required to omplete the pro3ets2 Consequentl#, ost estimation oftenrepresents an eerise in professional 3ud+ment instead of merel# ompilin+ a bill ofquantities and olletin+ ost data to reah a total estimate mehaniall#2

TA!E 5-10esoure 0equirements of 'ome Ma3or Ener+# 1ro3ets

/il shale(>=,===

barrelsBda#)

Coal +asifiation(A@= billions

TUBda#)

Tar 'ands(9>=,===

barrelsBda#)

Cost ( billion)

@2> 4 D to 9=

asi desi+n (Thousands ofhours)

D= @== 9==

*etaileden+ineerin+ (Millions ofhours)

A to 4 4 to > 6 to D

Constrution (Millions of

@= A= 4=
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hours)

Materials ( billion)

9 @ @2>

'oure5 Eon 0esearh and En+ineerin+ Compan#, "lorham 1ar7,

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5." Approaches to Cost Estimation

Cost estimatin+ is one of the most important steps in pro3et mana+ement2 % ostestimate establishes the base line of the pro3et ost at different sta+es of de!elopmentof the pro3et2 % ost estimate at a +i!en sta+e of pro3et de!elopment represents a

predition pro!ided b# the ost en+ineer or estimator on the basis of a!ailable data2%ordin+ to the %merian %ssoiation of Cost En+ineers, ost en+ineerin+ is defined

as that area of en+ineerin+ pratie &here en+ineerin+ 3ud+ment and eperiene areutilized in the appliation of sientifi priniples and tehniques to the problem ofost estimation, ost ontrol and profitabilit#2

Firtuall# all ost estimation is performed aordin+ to one or some ombination ofthe follo&in+ basi approahes5

#roduction $unction.$n miroeonomis, the relationship bet&een the output of aproess and the neessar# resoures is referred to as the prodution funtion2 $nonstrution, the prodution funtion ma# be epressed b# the relationship bet&een

the !olume of onstrution and a fator of prodution suh as labor or apital2 %prodution funtion relates the amount or !olume of output to the !arious inputs oflabor, material and equipment2 "or eample, the amount of output . ma# be deri!edas a funtion of !arious input fators 9, @, 222, nb# means of mathematial andBorstatistial methods2 Thus, for a speified le!el of output, &e ma# attempt to find a setof !alues for the input fators so as to minimize the prodution ost2 The relationship

bet&een the size of a buildin+ pro3et (epressed in square feet) to the input labor(epressed in labor hours per square foot) is an eample of a prodution funtion foronstrution2 'e!eral suh prodution funtions are sho&n in "i+ure AA of Chapter A2

Empirical cost in$erence.Empirial estimation of ost funtions requires statistial

tehniques &hih relate the ost of onstrutin+ or operatin+ a failit# to a fe&important harateristis or attributes of the s#stem2 The role of statistial inferene isto estimate the best parameter !alues or onstants in an assumed ost funtion2Usuall#, this is aomplished b# means of re+ression anal#sis tehniques2

%nit costs $or &ill o$ 'uantities.% unit ost is assi+ned to eah of the failit#omponents or tas7s as represented b# the bill of quantities2 The total ost is thesummation of the produts of the quantities multiplied b# the orrespondin+ unitosts2 The unit ost method is strai+htfor&ard in priniple but quite laborious inappliation2 The initial step is to brea7 do&n or disa++re+ate a proess into a numberof tas7s2 Colleti!el#, these tas7s must be ompleted for the onstrution of a failit#2

/ne these tas7s are defined and quantities representin+ these tas7s are assessed, aunit ost is assi+ned to eah and then the total ost is determined b# summin+ the
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osts inurred in eah tas72 The le!el of detail in deomposin+ into tas7s &ill !ar#onsiderabl# from one estimate to another2

Allocation o$ joint costs.%lloations of ost from eistin+ aounts ma# be used tode!elop a ost funtion of an operation2 The basi idea in this method is that eah

ependiture item an be assi+ned to partiular harateristis of the operation2 $deall#,the alloation of 3oint osts should be ausall# related to the ate+or# of basi osts inan alloation proess2 $n man# instanes, ho&e!er, a ausal relationship bet&een thealloation fator and the ost item annot be identified or ma# not eist2 "or eample,in onstrution pro3ets, the aounts for basi osts ma# be lassified aordin+ to(9) labor, (@) material, (A) onstrution equipment, (4) onstrution super!ision, and(>) +eneral offie o!erhead2 These basi osts ma# then be alloated proportionall# to!arious tas7s &hih are subdi!isions of a pro3et2

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5.( Types o$ Construction Cost Estimates

Constrution ost onstitutes onl# a fration, thou+h a substantial fration, of the totalpro3et ost2 o&e!er, it is the part of the ost under the ontrol of the onstrutionpro3et mana+er2 The required le!els of aura# of onstrution ost estimates !ar#at different sta+es of pro3et de!elopment, ran+in+ from ball par7 fi+ures in the earl#sta+e to fairl# reliable fi+ures for bud+et ontrol prior to onstrution2 'ine desi+ndeisions made at the be+innin+ sta+e of a pro3et life #le are more tentati!e thanthose made at a later sta+e, the ost estimates made at the earlier sta+e are epeted to

be less aurate2 Generall#, the aura# of a ost estimate &ill reflet the information

a!ailable at the time of estimation2

Constrution ost estimates ma# be !ie&ed from different perspeti!es beause ofdifferent institutional requirements2 $n spite of the man# t#pes of ost estimates usedat different sta+es of a pro3et, ost estimates an best be lassified into three ma3orate+ories aordin+ to their funtions2 % onstrution ost estimate ser!es one of thethree basi funtions5 desi+n, bid and ontrol2 "or establishin+ the finanin+ of a

pro3et, either a desi+n estimate or a bid estimate is used2

92 )esign Estimates."or the o&ner or its desi+nated desi+n professionals, thet#pes of ost estimates enountered run parallel &ith the plannin+ and desi+n

as follo&s5o 'reenin+ estimates (or order of ma+nitude estimates)

o 1reliminar# estimates (or oneptual estimates)

o *etailed estimates (or definiti!e estimates)

o En+ineer-s estimates based on plans and speifiations

"or eah of these different estimates, the amount of desi+n informationa!ailable t#piall# inreases2

@2 id Estimates."or the ontrator, a bid estimate submitted to the o&ner either

for ompetiti!e biddin+ or ne+otiation onsists of diret onstrution ostinludin+ field super!ision, plus a mar7up to o!er +eneral o!erhead and


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profits2 The diret ost of onstrution for bid estimates is usuall# deri!edfrom a ombination of the follo&in+ approahes2

o 'ubontrator quotations

o .uantit# ta7eoffs

o Constrution proedures2

A2 (. Control Estimates."or monitorin+ the pro3et durin+ onstrution, aontrol estimate is deri!ed from a!ailable information to establish5

o ud+et estimate for finanin+

o ud+eted ost after ontratin+ but prior to onstrution

o Estimated ost to ompletion durin+ the pro+ress of onstrution2

)esign Estimates

$n the plannin+ and desi+n sta+es of a pro3et, !arious desi+n estimates reflet thepro+ress of the desi+n2 %t the !er# earl# sta+e, thescreening estimateor order of

magnitudeestimate is usuall# made before the failit# is desi+ned, and must thereforerel# on the ost data of similar failities built in the past2 %preliminary estimateorconceptual estimateis based on the oneptual desi+n of the failit# at the state &henthe basi tehnolo+ies for the desi+n are 7no&n2 The detailed estimateor definitiveestimateis made &hen the sope of &or7 is learl# defined and the detailed desi+n isin pro+ress so that the essential features of the failit# are identifiable2 The engineer'sestimateis based on the ompleted plans and speifiations &hen the# are read# forthe o&ner to soliit bids from onstrution ontrators2 $n preparin+ these estimates,the desi+n professional &ill inlude epeted amounts for ontrators- o!erhead and

profits2

The osts assoiated &ith a failit# ma# be deomposed into a hierarh# of le!els thatare appropriate for the purpose of ost estimation2 The le!el of detail in deomposin+the failit# into tas7s depends on the t#pe of ost estimate to be prepared2 "oroneptual estimates, for eample, the le!el of detail in definin+ tas7s is quite oarse?for detailed estimates, the le!el of detail an be quite fine2

%s an eample, onsider the ost estimates for a proposed brid+e aross a ri!er2 %sreenin+ estimate is made for eah of the potential alternati!es, suh as a tied arh

brid+e or a antile!er truss brid+e2 %s the brid+e t#pe is seleted, e2+2 the tehnolo+#is hosen to be a tied arh brid+e instead of some ne& brid+e form, a preliminar#estimate is made on the basis of the la#out of the seleted brid+e form on the basis of

the preliminar# or oneptual desi+n2 hen the detailed desi+n has pro+ressed to apoint &hen the essential details are 7no&n, a detailed estimate is made on the basis ofthe &ell defined sope of the pro3et2 hen the detailed plans and speifiations areompleted, an en+ineer-s estimate an be made on the basis of items and quantities of&or72

id Estimates

The ontrator-s bid estimates often reflet the desire of the ontrator to seure the3ob as &ell as the estimatin+ tools at its disposal2 'ome ontrators ha!e &ellestablished ost estimatin+ proedures &hile others do not2 'ine onl# the lo&est

bidder &ill be the &inner of the ontrat in most biddin+ ontests, an# effort de!otedto ost estimatin+ is a loss to the ontrator &ho is not a suessful bidder2


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Consequentl#, the ontrator ma# put in the least amount of possible effort for ma7in+a ost estimate if it belie!es that its hane of suess is not hi+h2

$f a +eneral ontrator intends to use subontrators in the onstrution of a failit#, itma# soliit prie quotations for !arious tas7s to be subontrated to speialt#

subontrators2 Thus, the +eneral subontrator &ill shift the burden of ostestimatin+ to subontrators2 $f all or part of the onstrution is to be underta7en b#the +eneral ontrator, a bid estimate ma# be prepared on the basis of the quantit#ta7eoffs from the plans pro!ided b# the o&ner or on the basis of the onstrution

proedures de!ised b# the ontrator for implementin+ the pro3et2 "or eample, theost of a footin+ of a ertain t#pe and size ma# be found in ommerial publiationson ost data &hih an be used to failitate ost estimates from quantit# ta7eoffs2o&e!er, the ontrator ma# &ant to assess the atual ost of onstrution b#onsiderin+ the atual onstrution proedures to be used and the assoiated osts ifthe pro3et is deemed to be different from t#pial desi+ns2 ene, items suh as labor,material and equipment needed to perform !arious tas7s ma# be used as parameters

for the ost estimates2

Control Estimates

oth the o&ner and the ontrator must adopt some base line for ost ontrol durin+the onstrution2 "or the o&ner, a budget estimatemust be adopted earl# enou+h for

plannin+ lon+ term finanin+ of the failit#2 Consequentl#, the detailed estimate isoften used as the bud+et estimate sine it is suffiient definiti!e to reflet the pro3etsope and is a!ailable lon+ before the en+ineer-s estimate2 %s the &or7 pro+resses, the

bud+eted ost must be re!ised periodiall# to reflet the estimated ost to ompletion2

% re!ised estimated ost is neessar# either beause of han+e orders initiated b# theo&ner or due to unepeted ost o!erruns or sa!in+s2

"or the ontrator, the bid estimate is usuall# re+arded as the bud+et estimate, &hih&ill be used for ontrol purposes as &ell as for plannin+ onstrution finanin+2 The

bud+eted ost should also be updated periodiall# to reflet the estimated ost toompletion as &ell as to insure adequate ash flo&s for the ompletion of the pro3et2

Example 5-": *creening estimate o$ a grouting seal &eneath a land$ill 8@:

/ne of the methods of isolatin+ a landfill from +round&ater is to reate a bo&lshaped

bottom seal beneath the site as sho&n in "i+ure >=2 The seal is onstruted b#pumpin+ or pressurein3etin+ +rout under the eistin+ landfill2 oles are bored atre+ular inter!als throu+hout the landfill for this purpose and the +rout tubes areetended from the surfae to the bottom of the landfill2 % la#er of soil at a minimumof > ft2 thi7 is left bet&een the +routed material and the landfill ontents to allo& forirre+ularities in the bottom of the landfill2 The +rout liner an be bet&een 4 and 6 feetthi72 % t#pial material &ould be 1ortland ement +rout pumped under pressurethrou+h tubes to fill !oids in the soil2 This +rout &ould then harden into a permanent,impermeable liner2
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Figure 5-1:Grout ottom 'eal Liner at a Landfill

The &or7 items in this pro3et inlude (9) drillin+ eplorator# bore holes at >= ftinter!als for +rout tubes, and (@) pumpin+ +rout into the !oids of a soil la#er bet&een4 and 6 ft thi72 The quantities for these t&o items are estimated on the basis of thelandfill area5

D ares H (D)(4A,>6= ft@Bare) H A4D,4D= ft@

(%s an approimation, use A6=,=== ft@to aount for the bo&l shape)

The number of bore holes in a >= ft b# >= ft +rid pattern o!erin+ A6=,=== ft@is +i!enb#5

The a!era+e depth of the bore holes is estimated to be @= ft2 ene, the total amountof drillin+ is (944)(@=) H @,DD= ft2

The !olume of the soil la#er for +routin+ is estimated to be5

for a 4 ft la#er, !olume H (4 ft)(A6=,=== ft@) H 9,44=,=== ftAfor a 6 ft la#er, !olume H (6 ft)(A6=,=== ft@) H @,96=,=== ftA

$t is estimated from soil tests that the !oids in the soil la#er are bet&een @=I and A=Iof the total !olume2 Thus, for a 4 ft soil la#er5


9/86

+routin+ in @=I !oids H (@=I)(9,44=,===) H @DD,=== ftA+routin+ in A= I !oids H (A=I)(9,44=,===) H 4A@,=== ftA

and for a 6 ft soil la#er5+routin+ in @=I !oids H (@=I)(@,96=,===) H 4A@,=== ftA+routin+ in A=I !oids H (A=I)(@,96=,===) H 64D,=== ftA

The unit ost for drillin+ eplorator# bore holes is estimated to be bet&een A and 9=per foot (in 9;@,=== to @,DD=,===for a 4 ft la#er &ith A=I !oids, +routin+ ost H 9,


10/86

TA!E 5-":Unit 1ries in T&o Contrators- ids for 0oad&a# Constrution

$tems Unit .uantit#Unit prie

9 @Mobilization ls 9 99>,=== >6;,>>4

0emo!al, berm lf D,=@= 92== 92>=

"inish sub+rade s# 9,@=== =2>= =2A=

'urfae dithes lf >@> @2== 92==

Ea!ation strutures # 2==

ase ourse, untreated, AB4-- ton A6@,@== 42>= >2==

Lean onrete, 4-- thi7 s# D@=,A9= A29= A2==

1CC, pa!ement, 9=-- thi7 s# 2== A=2==

Metal, end setion, 9>-- ea A; 9== 9@>

9D-- ea A 9>= @== 1ost, ri+htof&a#, modifiation lf 4,=

'al!a+e and rela# pipe lf 9,6D= >2== 9@2==

Loose riprap # A@ 4=2== A=2==

raed posts ea >4 9== 99=

*elineators, t#pe $ lb 9,AA= 9@2== 9@2==

t#pe $$ ea 94= 9>2== 9@2==

Construti!e si+ns fied sf >@,6== =29= =24=

arriades, t#pe $$$ lf @;,>== =2@= =2@=arnin+ li+hts da# 6,A== =29= =2>=

1a!ement mar7in+, epo# material

la7 +al 4 ;=2== 9==

ello& +al ;=2== =2== @=2==

Topsoil, ontrator furnished # @6= 9=2== 62==

'eedlin+, method % ar 9=A 9>= @==Eelsior blan7et s# >== @2== @2==


11/86



Corru+ated, metal pipe, 9D-- lf >D= @=2== 9D2==1ol#eth#lene pipe, 9@-- lf @,@>= 9>2== 9A2==

Cath basin +rate and frame ea A> A>= @D=

Equal opportunit# trainin+ hr 9D,=== =2D= =2D=

Granular ba7fill borro& # @=

arriade, 4D--4@-- ea 4= 9== 9==

ood post, road losed lf 9== A=2== A62==

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12/86

5., E$$ects o$ *cale on Construction Cost

'reenin+ ost estimates are often based on a sin+le !ariable representin+ the apait#or some ph#sial measure of the desi+n suh as floor area in buildin+s, len+th of

hi+h&a#s, !olume of stora+e bins and prodution !olumes of proessin+ plants2 Costsdo not al&a#s !ar# linearl# &ith respet to different failit# sizes2 T#piall#, sale

eonomies or diseonomies eist2 $f the a!era+e ost per unit of apait# is delinin+,then sale eonomies eist2 Con!ersel#, sale diseonomies eist if a!era+e ostsinrease &ith +reater size2 Empirial data are sou+ht to establish the eonomies ofsale for !arious t#pes of failit#, if the# eist, in order to ta7e ad!anta+e of lo&er

osts per unit of apait#2

Let be a !ariable representin+ the failit# apait#, and # be the resultin+onstrution ost2 Then, a linear ost relationship an be epressed in the form5

(>29)

&here a and b are positi!e onstants to be determined on the basis of historial data2ote that in Equation (>29), a fied ost of # H a at H = is implied as sho&n in "i+ure>@2 $n +eneral, this relationship is appliable onl# in a ertain ran+e of the !ariable ,suh as bet&een H and H d2 $f the !alues of # orrespondin+ to H and H d

are 7no&n, then the ost of a failit# orrespondin+ to an# &ithin the speifiedran+e ma# be obtained b# linear interpolation2 "or eample, the onstrution ost of ashool buildin+ an be estimated on the basis of a linear relationship bet&een ost and

floor area if the unit ost per square foot of floor area is 7no&n for shool buildin+s&ithin ertain limits of size2

Figure 5-":Linear Cost 0elationship &ith Eonomies of 'ale


13/86

% nonlinear ost relationship bet&een the failit# apait# and onstrution ost #an often be represented in the form5

(>2@)

&here a and b are positi!e onstants to be determined on the basis of historial data2"or = b 9, Equation (>2@) represents the ase of inreasin+ returns to sale, and forb ?+t 9, the relationship beomes the ase of dereasin+ returns to sale, as sho&n in"i+ure >A2 Ta7in+ the lo+arithm of both sides this equation, a linear relationship an

be obtained as follo&s5

Figure 5-(:onlinear Cost 0elationship &ith inreasin+ or *ereasin+ Eonomies of'ale

(>2A)

%lthou+h no fied ost is implied in Eq2(>2@), the equation is usuall# appliable onl#for a ertain ran+e of 2 The same limitation applies to Eq2(>2A)2 % nonlinear ost

relationship often used in estimatin+ the ost of a ne& industrial proessin+ plant fromthe 7no&n ost of an eistin+ failit# of a different size is 7no&n as the exponentialrule2 Let #nbe the 7no&n ost of an eistin+ failit# &ith apait# .n, and # be theestimated ost of the ne& failit# &hih has a apait# .2 Then, from the empirial

data, it an be assumed that5


14/86

(>24)

&here m usuall# !aries from =2> to =2;, dependin+ on a speifi t#pe of failit#2 %!alue of m H =26 is often used for hemial proessin+ plants2 The eponential rulean be redued to a linear relationship if the lo+arithm of Equation (>24) is used5

(>2>)

or

(>26)

The eponential rule an be applied to estimate the total ost of a omplete failit# orthe ost of some partiular omponent of a failit#2

Example 5-,: )etermination o$ m $or the exponential rule

Figure 5-,:Lo+Lo+ 'ale Graph of Eponential 0ule Eample

The empirial ost data from a number of se&a+e treatment plants are plotted on alo+lo+ sale for ln(.B.n) and ln(#B#n) and a linear relationship bet&een these

lo+arithmi ratios is sho&n in "i+ure >42 "or (.B.n) H 9 or ln(.B.n) H =, ln(#B#n) H =?and for .B.nH @ or ln(.B.n) H =2A=9, ln(#B#n) H =292 'ine m is the slope of the

line in the fi+ure, it an be determined from the +eometri relation as follo&s5

"or ln(#B#n) H =29, #B#nH 92>, &hile the orrespondin+ !alue of .B.nis @2 $n

&ords, for m H =2>D>, the ost of a plant inreases onl# 92> times &hen the apait# isdoubled2


15/86

Example 5-5: Cost exponents $or water and wastewater treatment plants84:The ma+nitude of the ost eponent m in the eponential rule pro!ides a simple

measure of the eonom# of sale assoiated &ith buildin+ etra apait# for future+ro&th and s#stem reliabilit# for the present in the desi+n of treatment plants2 hen

m is small, there is onsiderable inenti!e to pro!ide etra apait# sine sale

eonomies eist as illustrated in "i+ure >A2 hen m is lose to 9, the ost is diretl#proportional to the desi+n apait#2 The !alue of m tends to inrease as the number of

dupliate units in a s#stem inreases2 The !alues of m for se!eral t#pes of treatmentplants &ith different plant omponents deri!ed from statistial orrelation of atual

onstrution osts are sho&n in Table >A2

TA!E 5-( Estimated Falues of Cost Eponents for ater Treatment 1lants

Treatment plantt#pe

Eponentm

Capait# ran+e(millions of +allons per da#)

92 ater treatment =26< 99==

@2 aste treatment

1rimar# &ith di+estion (small) =2>> =299= 1rimar# &ith di+estion (lar+e) =2 =2


16/86

Equalization mil2 +al2 @

eutralization m+d 6=,=== =2


17/86

92 *u&contractor uotations2 The deomposition of a pro3et intosubontrator items for quotation in!ol!es a minimum amount of &or7 for the+eneral ontrator2 o&e!er, the aura# of the resultin+ estimate depends on

the reliabilit# of the subontrators sine the +eneral ontrator selets oneamon+ se!eral ontrator quotations submitted for eah item of subontrated

&or72@2 uantity Ta2eo$$s2 The deomposition of a pro3et into items of quantities

that are measured (or taken off) from the en+ineer-s plan &ill result in aproedure similar to that adopted for a detailed estimate or an en+ineer-s

estimate b# the desi+n professional2 The le!els of detail ma# !ar# aordin+ tothe desire of the +eneral ontrator and the a!ailabilit# of ost data2

A2 Construction #rocedures2 $f the onstrution proedure of a proposed pro3etis used as the basis of a ost estimate, the pro3et ma# be deomposed into

items suh as labor, material and equipment needed to perform !arious tas7sin the pro3ets2

*imple %nit Cost Formula

'uppose that a pro3et is deomposed into n elements for ost estimation2 Let .ibethe quantit# of the ithelement and uibe the orrespondin+ unit ost2 Then, the total

ost of the pro3et is +i!en b#5

(>22D)

&here n is the number of ma3or equipment omponents inluded in the pro3et2 Thefatored method is essentiall# based on the priniple of omputin+ the ost of

anillar# items suh as pipin+ and !al!es as a fration or a multiple of the osts of the

ma3or equipment items2 The !alue of Cima# be obtained b# appl#in+ the eponential


18/86

rule so the use of Equation (>2D) ma# in!ol!e a ombination of ost estimationmethods2

Formula ased on !a&or3 0aterial and E'uipment

Consider the simple ase for &hih osts of labor, material and equipment areassi+ned to all tas7s2 'uppose that a pro3et is deomposed into n tas7s2 Let .ibe the

quantit# of &or7 for tas7 i, Mibe the unit material ost of tas7 i, E ibe the unitequipment rate for tas7 i, Libe the units of labor required per unit of .i, and ibe the

&a+e rate assoiated &ith Li2 $n this ase, the total ost # is5

(>2;)

ote that iLi#ields the labor ost per unit of .i, or the labor unit ost of tas7 i2

Consequentl#, the units for all terms in Equation (>2;) are onsistent2

Example 5-4: )ecomposition o$ a &uilding $oundation into design and

construction elements.

The onept of deomposition is illustrated b# the eample of estimatin+ the osts ofa buildin+ foundation eludin+ ea!ation as sho&n in Table >> in &hih thedeomposed desi+n elements are sho&n on horizontal lines and the deomposed

ontrat elements are sho&n in !ertial olumns2 "or a desi+n estimate, thedeomposition of the pro3et into footin+s, foundation &alls and ele!ator pit is

preferred sine the desi+ner an easil# 7eep tra7 of these desi+n elements? ho&e!er,

for a bid estimate, the deomposition of the pro3et into form&or7, reinforin+ barsand onrete ma# be preferred sine the ontrator an +et quotations of suh ontrat

items more on!enientl# from speialt# subontrators2

TA!E 5-5 $llustrati!e *eomposition of uildin+"oundation Costs

*esi+nelements

Contrat elements

"orm&or7 0ebars Conrete Total ost

"ootin+s >,=== 9=,=== 9A,=== @D,===

"ootin+s 9>,=== 9D,=== @D,=== 69,===

"ootin+s ;,=== 9>,=== 96,=== 4=,===

Total ost @;,=== 4A,=== >


19/86


20/86

(>29A)

Example 5-7: #rorated costs $or $ield super8ision and o$$ice o8erhead

$f the field super!ision ost is 9A,@4> for the pro3et in Table >6 (Eample >D) &itha total diret ost of DD,A==, find the prorated field super!ision osts for !ariouselements of the pro3et2 "urthermore, if the +eneral offie o!erhead har+ed to the

pro3et is 4I of the diret field ost &hih is the sum of basi osts and fieldsuper!ision ost, find the prorated +eneral offie o!erhead osts for !arious elements

of the pro3et2

"or the pro3et, # H DD,A== and " H 9A,@4>2 ene5

z H 9A,@4> O DD,A== H 9=9,>4>G H (=2=4)(9=9,>4>) H 4,=6@

& H 9=9,>4> O 4,=6@ H 9=>,6=


21/86

fe& o!erhead epenses in pratie, but this phenomenon &ould not be refleted in thestandard ost report2

TA!E 5- 'tandard Cost 0eport for a T#pe of Fal!e

(9) Materialost

(@) Laborost

(A) /!erheadost

(4) Totalost

1urhased part 929;D= 929;D=

/peration

*rill, fae, tap (@) =2=4AD =2@4=4 =2@D4@

*e+rease =2==A9 =2=AA< =2=A6D

0emo!e burs =2=>;D@ 92;==D

/ther subassemblies =2A>@A =2@;;4 92D>9; @24@AA =24=4= @24>=9 42ADA

Total ost, thisitem

92>@AA =2>29D9A

Cost omponent, I @;I 99I 6=I 9==I

'oure5 2 T2 ohnson and 02 '2 Kaplan,Relevance lost: The Rise and Fall ofManagement ccounting, ar!ard usiness 'hool 1ress, oston2 0eprinted&ith permission2

a7 to top

5.4 istorical Cost )ata

1reparin+ ost estimates normall# requires the use of historial data on onstrutionosts2 istorial ost data &ill be useful for ost estimation onl# if the# are olleted

and or+anized in a &a# that is ompatible &ith future appliations2 /r+anizations&hih are en+a+ed in ost estimation ontinuall# should 7eep a file for their o&n use2The information must be updated &ith respet to han+es that &ill ine!itabl# our2

The format of ost data, suh as unit osts for !arious items, should be or+anizedaordin+ to the urrent standard of usa+e in the or+anization2

Constrution ost data are published in !arious forms b# a number of or+anizations2These publiations are useful as referenes for omparison2 asiall#, the follo&in+

t#pes of information are a!ailable5

Catalo+s of !endors- data on important features and speifiations relatin+ to

their produts for &hih ost quotations are either published or an beobtained2 % ma3or soure of !endors- information for buildin+ produts is

!"eets' Catalogpublished b# MGra&ill $nformation '#stems Compan#2 1eriodials ontainin+ onstrution ost data and indies2 /ne soure of suh

information isE#R, the MGra&ill Constrution ee7l#, &hih ontainsetensi!e ost data inludin+ quarterl# ost reports2 Cost Engineering, a


22/86

3ournal of the %merian 'oiet# of Cost En+ineers, also publishes useful ostdata periodiall#2

Commerial ost referene manuals for estimatin+ +uides2 %n eample is the

$uilding Construction Cost %atapublished annuall# b# 02'2 Means Compan#,$n2, &hih ontains unit pries on buildin+ onstrution items2 %odge Manual

for $uilding Construction, published b# MGra&ill, pro!ides similarinformation2

*i+ests of atual pro3et osts2 The%odge %igest of $uilding Costs and

!pecificationspro!ides desriptions of desi+n features and osts of atualpro3ets b# buildin+ t#pe2 /ne a &ee7,E#Rpublishes the bid pries of a

pro3et hosen from all t#pes of onstrution pro3ets2

istorial ost data must be used autiousl#2 Chan+es in relati!e pries ma# ha!esubstantial impats on onstrution osts &hih ha!e inreased in relati!e prie2Unfortunatel#, s#stemati han+es o!er a lon+ period of time for suh fators arediffiult to predit2 Errors in anal#sis also ser!e to introdue unertaint# into ost

estimates2 $t is diffiult, of ourse, to foresee all the problems &hih ma# our inonstrution and operation of failities2 There is some e!idene that estimates ofonstrution and operatin+ osts ha!e tended to persistentl# understate the atual

osts2 This is due to the effets of +reater than antiipated inreases in osts, han+esin desi+n durin+ the onstrution proess, or o!eroptimism2

'ine the future pries of onstruted failities are influened b# man# unertainfators, it is important to reo+nize that this ris7 must be borne to some de+ree b# all

parties in!ol!ed, i2e2, the o&ner, the desi+n professionals, the onstrution ontrators,and the finanin+ institution2 $t is to the best interest of all parties that the ris7 sharin+

sheme impliit in the desi+nBonstrut proess adopted b# the o&ner is full#understood b# all2 hen inflation ad3ustment pro!isions ha!e !er# different ris7

impliations to !arious parties, the prie le!el han+es &ill also be treated differentl#for !arious situations2 a7 to top

5. Cost ndices

'ine historial ost data are often used in ma7in+ ost estimates, it is important tonote the prie le!el han+es o!er time2 Trends in prie han+es an also ser!e as abasis for foreastin+ future osts2 The input prie indies of labor andBor materialreflet the prie le!el han+es of suh input omponents of onstrution? the output

prie indies, &here a!ailable, reflet the prie le!el han+es of the ompletedfailities, thus to some de+ree also measurin+ the produti!it# of onstrution2

% prie inde is a &ei+hted a++re+ate measure of onstant quantities of +oods andser!ies seleted for the pa7a+e2 The prie inde at a subsequent #ear represents a

proportionate han+e in the same &ei+hted a++re+ate measure beause of han+es inpries2 Let ltbe the prie inde in #ear t, and l tO9be the prie inde in the follo&in+

#ear tO92 Then, the perent han+e in prie inde for #ear tO9 is5

(>294)


23/86

or

(>29>)

$f the prie inde at the base #ear tH= is set at a !alue of 9==, then the prie indies l 9,l@222lnfor the subsequent #ears tH9,@222n an be omputed suessi!el# from han+es in

the total prie har+ed for the pa7a+e of +oods measured in the inde2

The best7no&n indiators of +eneral prie han+es are the Gross *omesti 1rodut(G*1) deflators ompiled periodiall# b# the U2'2 *epartment of Commere, and theonsumer prie inde (C1$) ompiled periodiall# b# the U2'2 *epartment of Labor2

The# are &idel# used as broad +au+es of the han+es in prodution osts and inonsumer pries for essential +oods and ser!ies2 'peial prie indies related toonstrution are also olleted b# industr# soures sine some input fators for

onstrution and the outputs from onstrution ma# disproportionatel# outpae or fallbehind the +eneral prie indies2 Eamples of speial prie indies for onstrutioninput fators are the &holesale uildin+ Material 1rie and uildin+ Trades Union

a+es, both ompiled b# the U2'2 *epartment of Labor2 $n addition, the onstrutionost inde and the buildin+ ost inde are reported periodiall# in the Engineering#e"s&Record E#R(2 oth E0 ost indies measure the effets of &a+e rate and

material prie trends, but the# are not ad3usted for produti!it#, effiien#,ompetiti!e onditions, or tehnolo+# han+es2 Consequentl#, all these indies

measure onl# the prie han+es of respeti!e onstrution input factorsas representedb# onstant quantities of material andBor labor2 /n the other hand, the prie indies of

!arious t#pes of ompleted failities reflet the prie han+es of onstrution output

inludin+ all pertinent fators in the onstrution proess2 The buildin+ onstrutionoutput indies ompiled b# Turner Constrution Compan# and and#hitman

Utilities are ompiled in the U2'2 !tatistical bstractspublished eah #ear2

"i+ure >< and Table >; sho& a !ariet# of United 'tates indies, inludin+ the Grossational 1rodut (G1) prie deflator, the E0 buildin+ inde, the and# hitmanUtilities uildin+s, and the Turner Constrution Compan# uildin+ Cost $nde from

9; 9=A2< 9=D 99@2> 99> 99D2< 9@@

and#hitman1ubli Utilit# A9 >4 99@ 99> 99D 9@@ 9@A

G1 *eflator A> 4; 9=D 99= 99A 994


24/86


25/86

the ost in #ear t epressed in base#ear dollars and %t- be the ost in #ear t epressedin thenurrent dollars2 Then5

(>296)

Con!ersel#

(>29


26/86

(>2@9)

More sophistiated foreastin+ models to predit future ost inreases inludeorretions for items suh as eonomi #les and tehnolo+# han+es2

Example 5-1": Changes in highway and &uilding costs

Table >9= sho&s the han+e of standard hi+h&a# osts from 9;4= to 9;;=, and Table>99 sho&s the han+e of residential buildin+ osts from 9;


27/86

$n the sreenin+ estimate of a ne& failit#, a sin+le parameter is often used to desribea ost funtion2 "or eample, the ost of a po&er plant is a funtion of eletriit#

+eneratin+ apait# epressed in me+a&atts, or the ost of a se&a+e treatment plant asa funtion of &aste flo& epressed in million +allons per da#2

The +eneral onditions for the appliation of the sin+le parameter ost funtion forsreenin+ estimates are5

92 Elude speial loal onditions in historial data@2 *etermine ne& failit# ost on basis of speified size or apait# (usin+ the

methods desribed in 'etions >2A to >26)A2 %d3ust for inflation inde

42 %d3ust for loal inde of onstrution osts>2 %d3ust for different re+ulator# onstraints62 %d3ust for loal fators for the ne& failit#

'ome of these ad3ustments ma# be done usin+ ompiled indies, &hereas others ma#require field in!esti+ation and onsiderable professional 3ud+ment to reflet

differenes bet&een a +i!en pro3et and standard pro3ets performed in the past2

Example 5-1(: *creening estimate $or a re$inery

The total onstrution ost of a refiner# &ith a prodution apait# of @==,=== bblBda#in Gar#, $ndiana, ompleted in @==9 &as 9== million2 $t is proposed that a similar

refiner# &ith a prodution apait# of A==,=== bblBda# be built in Los %n+eles,California, for ompletion in @==A2 "or the additional information +i!en belo&, ma7e

an order of ma+nitude estimate of the ost of the proposed plant292 $n the total onstrution ost for the Gar#, $ndiana, plant, there &as an

item of > million for site preparation &hih is not t#pial for otherplants2

@2 The !ariation of sizes of the refineries an be approimated b# theeponential rule, Equation (>24), &ith m H =262

A2 The inflation rate is epeted to be DI per #ear from 9;;; to @==A242 The loation inde &as =2;@ for Gar#, $ndiana and 9294 for Los

%n+eles in 9;;;2 These indies are deemed to be appropriate forad3ustin+ the osts bet&een these t&o ities2

>2 e& air pollution equipment for the L% plant osts < million in @==A

dollars (not required in the Gar# plant)262 The ontin+en# ost due to inlement &eather dela# &ill be redued

b# the amount of 9I of total onstrution ost beause of the fa!orablelimate in L% (ompared to Gar#)2

/n the basis of the abo!e onditions, the estimate for the ne& pro3et ma# be obtainedas follo&s5

92 T#pial ost eludin+ speial item at Gar#, $ is

9== million > million H ;> million

@2 %d3ustment for apait# based on the eponential la& #ields


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(;>)(A==,===B@==,===) =26H (;>)(92>)=26H 9@92@ million

A2 %d3ustment for inflation leads to the ost in @==A dollars as

(9@92@)(92=D)4H 96426 million

42 %d3ustment for loation inde +i!es

(96426)(9294B=2;@) H @=426 million

>2 %d3ustment for ne& pollution equipment at the L% plant +i!es

@=426 O < H @9926 million

62 0edution in ontin+en# ost #ields

(@9926)(9=2=9) H @=;2> million

'ine there is no ad3ustment for the ost of onstrution finanin+, the order ofma+nitude estimate for the ne& pro3et is @=;2> million2

Example 5-1,: Conceptual estimate $or a chemical processing plant$n ma7in+ a preliminar# estimate of a hemial proessin+ plant, se!eral ma3or t#pes

of equipment are the most si+nifiant parameters in affetin+ the installation ost2 Theost of pipin+ and other anillar# items for eah t#pe of equipment an often be

epressed as a perenta+e of that t#pe of equipment for a +i!en apait#2 The standardosts for the ma3or equipment t#pes for t&o plants &ith different dail# prodution

apaities are as sho&n in Table >9@2 $t has been established that the installation ostof all equipment for a plant &ith dail# prodution apait# bet&een 9==,=== bbl and4==,=== bbl an best be estimated b# usin+ linear interpolation of the standard data2

TA!E 5-1" Cost *ata for Equipment and %nillar# $tems

Equipmentt#pe

Equipment Cost (9===)Cost of anillar# items

as I of equipment ost (9===)

9==,=== bbl 4==,=== bbl 9==,=== bbl 4==,=== bbl

"urnae A,=== 9=,=== 4=I A=I

To&er @,=== 6,=== 4>I A>I

*rum 9,>== >,=== >=I 4=I

1ump, et2 9,=== 4,=== 6=I >=I

% ne& hemial proessin+ plant &ith a dail# prodution apait# of @==,=== bbl is tobe onstruted in Memphis, T in four #ears2 *etermine the total preliminar# ost

estimate of the plant inludin+ the buildin+ and the equipment on the follo&in+ basis5

92 The installation ost for equipment &as based on linear interpolation fromTable >9@, and ad3usted for inflation for the inter!enin+ four #ears2 e

epet inflation in the four #ears to be similar to the period 9;;=9;;4 and &e&ill use the G1 *eflator inde2


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@2 The loation inde for equipment installation is =2;> for Memphis, T, inomparison &ith the standard ost2

A2 %n additional ost of >==,=== &as required for the loal onditions inMemphis, T2

The solution of this problem an be arried out aordin+ to the steps as outlined inthe problem statement5

92 The osts of the equipment and anillar# items for a plant &ith a apait# of@==,=== bbl an be estimated b# linear interpolation of the data in Table >9@,

and the results are sho&n in Table >9A2

TA!E 5-1( 0esults of Linear $nterpolation for an Estimation Eample

Equipmentt#pe

Equipment Cost(in 9,===)

1erenta+e foranillar# items

"urnaeA,=== O (9BA)(9=,===A,===) H

>,AAA

4=I (9BA)(4=IA=I) H

AI (9BA)(4>IA>I) H4@I

*rum9,>== O (9BA)(>,===9,>==) H@,66=I (9BA)(>=I4=I) H4=I) H>2D) as5

A2 (>,AAA)(92A

>2 The total ost of the pro3et after ad3ustment for loation is

(=2;>)(@9,AA>,===) O >==,=== @=,D==,===

a7 to top

5.19 Estimate ased on Engineer+s !ist o$ uantities

The en+ineer-s estimate is based on a list of items and the assoiated quantities from&hih the total onstrution ost is deri!ed2 This same list is also made a!ailable tothe bidders if unit pries of the items on the list are also soliited from the bidders2Thus, the itemized osts submitted b# the &innin+ ontrator ma# be used as the

startin+ point for bud+et ontrol2

$n +eneral, the pro+ress pa#ments to the ontrator are based on the units of &or7ompleted and the orrespondin+ unit pries of the &or7 items on the list2 ene, the


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estimate based on the en+ineers- list of quanitities for !arious &or7 items essentiall#defines the le!el of detail to &hih subsequent measures of pro+ress for the pro3et

&ill be made2

Example 5-15: id estimate &ased on engineer+s list o$ 'uantities

Usin+ the unit pries in the bid of ontrator 9 for the quantitites speified b# theen+ineer in Table >@ (Eample >A), &e an ompute the total bid prie of ontrator

9 for the road&a# pro3et2 The itemized osts for !arious &or7 items as &ell as thetotal bid prie are sho&n in Table >942

TA!E 5-1,:id 1rie of Contrator 9 in a i+h&a# 1ro3et

$tems Unit .uantit# Unit prie $tem ost

Mobilization ls 9 99>,=== 99>,===

0emo!al, berm lf D,=@= 92== D2=@=

"inish sub+rade s# 9,@=== =2>= 6=A,=

'urfae dithes lf >@> @2== 9,=>=

Ea!ation strutures # = 9,6@;,;==

Lean onrete, 4-- thi7 s# D@=,A9= A29= @,>4@,;69

1CC, pa!ement, 9=-- thi7 s# =;

Conrete, i %% (%E) ls 9 @==,=== @==,===

'mall struture # >= >== @>,===

arrier, preast lf 2== 99D,D==

"lat&or7, 4-- thi7 s# 2== D,4==

Loose riprap # A@ 4=2== 9,@D=

raed posts ea >4 9== >,4==

*elineators, t#pe $ lb 9,AA= 9@2== 9>,;6=

t#pe $$ ea 94= 9>2== @,9==

Construti!e si+ns fied sf >@,6== =29= >,@6=

arriades, t#pe $$$ lf @;,>== =2@= >,;==

arnin+ li+hts da# 6,A== =29= 6A=

1a!ement mar7in+, epo# material


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la7 +al 4 ;=2== 4@,= ello& +al ;=2== DD,6>=

1lo&able, one&a# &hite ea A4@ >=2== 9,=== >,===

'i+n, o!erin+ sf 96 9=2== 96=

t#pe C@ &ood post sf ;D 9>2== 9,42== ;9>

'teel post, 4D--6=-- ea 99 >== >,>==

t#pe A, &ood post sf 66; 9>2== 9=,=A>

@4-- ea @A 9== @,A==

A=-- ea 9 9== 9==

A6-- ea 9@ 9>= 9,D==

4@--6=-- ea D 9>= 9,@==

4D-- ea < @== 9,4== %uiliar# sf 9A> 9>2== @,=@>


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'teel post sf 9,69= 4=2== 64,4== 9@--A6-- ea @D 9== @,D==

"oundation, onrete ea 6= A== 9D,===

arriade, 4D--4@-- ea 4= 9== 4,===

ood post, road losed lf 9== A=2== A,===

Total ;1,31"73474.55

a7 to top

5.11 Allocation o$ Construction Costs


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reahin+ 9@2>I of pro3et ost at t H A &hile be+innin+ to derease from 9@2>I at t H; to =I at t H 9=2

Figure 5-7: 0ate of or7 1ro+ress o!er 1ro3et Time

The !alue of &or7 ompleted at a +i!en time (epressed as a umulati!e perenta+e ofpro3et ost) is sho&n shematiall# in "i+ure >9=2 $n eah ase (%, or C), the!alue of &or7 ompleted an be represented b# an N'shapedN ur!e2 The effets ofrapid mobilization and slo& mobilization are indiated b# the positions of ur!es

and C relati!e to ur!e %, respeti!el#2

Figure 5-19: Falue of or7 Completed o!er 1ro3et Time


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hile the ur!es sho&n in "i+ures >; and >9= represent hi+hl# idealized ases, the#do su++est the latitude for ad3ustin+ the shedules for !arious ati!ities in a pro3et2

hile the rate of &or7 pro+ress ma# be han+ed quite drastiall# &ithin a sin+le

period, suh as the han+e from rapid mobilization to a slo& mobilization in periods9, @ and A in "i+ure >;, the effet on the !alue of &or7 ompleted o!er time &ill

diminish in si+nifiane as indiated b# the umulati!e perenta+es for later periodsin "i+ure >9=2 Thus, ad3ustment of the shedulin+ of some ati!ities ma# impro!e the

utilization of labor, material and equipment, and an# dela# aused b# suhad3ustments for indi!idual ati!ities is not li7el# to ause problems for the e!entual

pro+ress to&ard the ompletion of a pro3et2

$n addition to the speed of resoure mobilization, another important onsideration isthe o!erall duration of a pro3et and the amount of resoures applied2 Fariousstrate+ies ma# be applied to shorten the o!erall duration of a pro3et suh as

o!erlappin+ desi+n and onstrution ati!ities (as desribed in Chapter @) orinreasin+ the pea7 amounts of labor and equipment &or7in+ on a site2 o&e!er,

spatial, mana+erial and tehnial fators &ill t#piall# plae a minimum limit on thepro3et duration or ause osts to esalate &ith shorter durations2

Example 5-1: Calculation o$ =alue o$ >or2 Completed

"rom the area of &or7 pro+ress in "i+ure >;, the !alue of &or7 ompleted at an#point in "i+ure >9= an be deri!ed b# notin+ the area under the ur!e up to that pointin "i+ure >;2 The result for t H = throu+h t H 9= is sho&n in Table >9> and plotted in

"i+ure >9=2

TA!E 5-15 Calulation of Falue of or7 Completed

Time Case % Case Case C

= = = =

9 A29I 62@I @29I

@ 9@2> 9D2< D2A

A @>2= A92@ 9D2D

4 A 4A2< A92A

> >=2= >62@ 4A2D6 6@2> 6D2< >62A

< 2= D92@ 6D2D

D D ;92< D92;

; ;62; ;


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umerous omputer aided ost estimation soft&are s#stems are no& a!ailable2 Theseran+e in sophistiation from simple spreadsheet alulation soft&are to inte+rated

s#stems in!ol!in+ desi+n and prie ne+otiation o!er the $nternet2 hile this soft&arein!ol!es osts for purhase, maintenane, trainin+ and omputer hard&are, some

si+nifiant effiienies often result2 $n partiular, ost estimates ma# be prepared more

rapidl# and &ith less effort2

'ome of the ommon features of omputer aided ost estimation soft&are inlude5

*atabases for unit ost items suh as &or7er &a+e rates, equipment rental or

material pries2 These databases an be used for an# ost estimate required2 $fthese rates han+e, ost estimates an be rapidl# reomputed after the

databases are updated2 *atabases of epeted produti!it# for different omponents t#pes,

equiptment and onstrution proesses2 $mport utilities from omputer aided desi+n soft&are for automati quantit#

ta7eoff of omponents2 %lternati!el#, speial user interfaes ma# eist toenter +eometri desriptions of omponents to allo& automati quantit#ta7e

off2 Eport utilities to send estimates to ost ontrol and shedulin+ soft&are2 This

is !er# helpful to be+in the mana+ement of osts durin+ onstrution2 Fersion ontrol to allo& simulation of different onstrution proesses or

desi+n han+es for the purpose of tra7in+ han+es in epeted osts2 1ro!isions for manual re!ie&, o!erride and editin+ of an# ost element

resultin+ from the ost estimation s#stem "leible reportin+ formats, inludin+ pro!isions for eletroni reportin+ rather

than simpl# printin+ ost estimates on paper2 %rhi!es of past pro3ets to allo& rapid ostestimate updatin+ or modifiation

for similar desi+ns2

% t#pial proess for de!elopin+ a ost estimate usin+ one of these s#stems &ouldinlude5

92 $f a similar desi+n has alread# been estimated or eists in the ompan#arhi!e, the old pro3et information is retrei!ed2

@2 % ost en+ineer modifies, add or deletes omponents in the pro3etinformation set2 $f a similar pro3et eists, man# of the omponents ma# ha!e

fe& or no updates, thereb# sa!in+ time2

A2 % ost estimate is alulated usin+ the unit ost method of estimation21roduti!ities and unit pries are retrie!ed from the s#stem databases2 Thus,

the latest prie information is used for the ost estimate242 The ost estimation is summarized and re!ie&ed for an# errors2

a7 to top

5.1( Estimation o$


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subsequent maintenane poliies and failit# use2 $n partiular, the ma+nitude ofroutine maintenane osts &ill be redued if the failit# under+oes periodi repairs

and rehabilitation at periodi inter!als2

'ine the tradeoff bet&een the apital ost and the operatin+ ost is an essential part

of the eonomi e!aluation of a failit#, the operatin+ ost is !ie&ed not as a separateentit#, but as a part of the lar+er parel of life #le ost at the plannin+ and desi+n

sta+e2 The tehniques of estimatin+ life #le osts are similar to those used forestimatin+ apital osts, inludin+ empirial ost funtions and the unit ost method

of estimatin+ the labor, material and equipment osts2 o&e!er, it is the interation ofthe operatin+ and apital osts &hih deser!e speial attention2

%s su++ested earlier in the disussion of the eponential rule for estimatin+, the !alueof the ost eponent ma# influene the deision &hether etra apait# should be built

to aommodate future +ro&th2 'imilarl#, the eonom# of sale ma# also influenethe deision on rehabilitation at a +i!en time2 %s the rehabilitation &or7 beomes

etensi!e, it beomes a apital pro3et &ith all the impliations of its o&n life #le2ene, the ost estimation of a rehabilitation pro3et ma# also in!ol!e apital and

operatin+ osts2

hile deferrin+ the disussion of the eonomi e!aluation of onstruted failities toChapter 6, it is suffiient to point out that the stream of operatin+ osts o!er time

represents a series of osts at different time periods &hih ha!e different !alues &ithrespet to the present2 Consequentl#, the ost data at different time periods must be

on!erted to a ommon base line if meanin+ful omparison is desired2

Example 5-14: 0aintenance cost on a roadway86:

Maintenane osts for onstruted road&a#s tend to inrease &ith both a+e and use ofthe failit#2 %s an eample, the follo&in+ empirial model &as estimated for

maintenane ependitures on setions of the /hio Turnpi7e5

C H >;6 O =2==9; F O @92< %&here C is the annual ost of routine maintenane per lanemile (in 9;6< dollars), F is

the !olume of traffi on the road&a# (measured in equi!alent standard ale loads,E'%L, so that a hea!# tru7 is represented as equi!alent to man# automobiles), and %is the a+e of the pa!ement in #ears sine the last resurfain+2 %ordin+ to this model,

routine maintenane osts &ill inrease eah #ear as the pa!ement ser!iedeteriorates2 $n addition, maintenane osts inrease &ith additional pa!ement stress

due to inreased traffi or to hea!ier ale loads, as refleted in the !ariable F2

"or eample, for F H >==,A== E'%L and % H > #ears, the annual ost of routinemaintenane per lanemile is estimated to be5

C H >;6 O (=2==9;)(>==,A==) O (@92)H >;6 O ;>=2> O 9=D2> H 9,6>> (in 9;6< dollars)

Example 5-1: Time stream o$ costs o8er the li$e o$ a roadway8


37/86


38/86

42 *ie7mann, 202, N1robabilisti Estimatin+5 Mathematis and %ppliations,N!CE +ournal of Construction Engineering and Management, Fol2 9=;, 9;DA,

pp2 @;2 umphre#s, K2K2 (ed2),ro-ect and Cost Engineers' .andbook(sponsored b#

%merian %ssoiation of Cost En+ineers), @nd Ed2, Marel *e77er, $n2, e&

or7, 9;D4262 Mae!is, %2C2, NConstrution Cost Control b# the /&ners,N!CE +ournal of

the Construction %ivision, Fol2 9=6, 9;D=, pp2 4A>4462@ is used to pro!idea +routin+ seal beneath another landfill of 9@ ares2 The +rout line is epeted

to be bet&een 42> and >2> feet thi7ness2 The !oids in the soil la#er arebet&een @>I to A>I2 Usin+ the same unit ost data (in 9;,>4>2 The bids &ere submitted on

ul# @9, 9;D< and the ompletion date of the pro3et under the ontrat &as%u+ust 9>, 9;D;2 ('eeE#R, /tober D, 9;D=,===)9B@

&here . is the dail# prodution apait# of batteries and C is the ost of thebuildin+ in 9;D< dollars2 $f a similar plant is planned for a dail# produtionapait# of @==,=== batteries, find the sreenin+ estimate of the buildin+ in

9;D< dollars2

>2 "or the ost fator K H 46,=== (in 9;6D dollars) and m H =26< for an aeratedla+oon basin of a &ater treatment plant in Table >4 (Eample >6), find the

estimated ost of a proposed ne& plant &ith a similar treatment proess ha!in+a apait# of 4D= million +allons (in 9;6D dollars)2 $f another ne& plant &as


39/86

estimated to ost 96=,=== b# usin+ the same eponential rule, &hat &ould bethe proposed apait# of that plantP

62 Usin+ the ost data in "i+ure >> (Eample >99), find the total ost inludin+o!erhead and profit of ea!atin+ ;=,=== u2#d2 of bul7 material usin+ a

ba7hoe of 92> u2#d2 apait# for a detailed estimate2 %ssume that theea!ated material &ill be loaded onto tru7s for disposal2


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additional information +i!en belo&, ma7e a sreenin+ estimate of the ost ofthe proposed plant2

92 $n the total onstrution ost for the Caraus, Fenezuela plant, there&as an item of @ million for site preparation and tra!el &hih is not

t#pial for similar plants2

@2 The !ariation of sizes of the refineries an be approimated b# theeponential la& &ith m H =262

A2 The inflation rate in U2'2 dollars &as approimatel# ;I per #ear from9;2 e& air pollution equipment for the e& /rleans, L% plant ost 4

million in 9;D= dollars (not required for the Caraas plant)262 The site ondition at e& /rleans required speial pilin+ foundation

&hih ost @ million in 9;D= dollars2

992 The total ost of a se&a+e treatment plant &ith a apait# of >= million +allonsper da# ompleted 9;D9 for a ne& to&n in Colorado &as 42> million2 $t &asproposed that a similar treatment plant &ith a apait# of D= million +allonsper da# be built in another to&n in e& erse# for ompletion in 9;D>2 "oradditional information +i!en belo&, ma7e a sreenin+ estimate of the ost of

the proposed plant292 $n the total onstrution ost in Colorado, an item of A==,=== for site

preparation is not t#pial for similar plants2@2 The !ariation of sizes for this t#pe of treatment plants an be

approimated b# the eponential la& &ith m H =2>2A2 The inflation rate &as approimatel# >I per #ear from 9;D9 to 9;D>242 The loational indies of Colorado and e& erse# areas are =2;> and

929=, respeti!el#, a+ainst the national a!era+e of 92==2>2 The installation of a speial equipment to satisf# the ne&

en!ironmental standard ost an etra @==,=== in 9;D> dollar for thee& erse# plant2

62 The site ondition in e& erse# required speial foundation &hihost >==,== in 9;D> dollars2

9@2 Usin+ theE#Rbuildin+ ost inde, estimate the 9;D> ost of the +routin+ sealon a landfill desribed in Eample >@, inludin+ the most li7el# estimate and

the ran+e of possible ost2

9A2 Usin+ the unit pries in the bid of ontrator @ for the quantitites speified b#the en+ineer in Table >@ (Eample >A), ompute the total bid prie of

ontrator @ for the road&a# pro3et inludin+ the ependiture on eah item of&or72

942 The rate of &or7 pro+ress in perent of ompletion per period of aonstrution pro3et is sho&n in "i+ure >9@ in &hih 9A time periods ha!e


41/86

been assumed2 The ases %, and C represent the normal mobilization time,rapid mobilization and slo& mobilization for the pro3et, respeti!el#2

Calulate the !alue of &or7 ompleted in umulati!e perenta+e for periods 9throu+h 9A for eah of the ases %, and C2 %lso plot the !olume of &or7

ompleted !ersus time for these ases2

Figure 5-1"

9>2 The rate of &or7 pro+ress in perent of ompletion per period of aonstrution pro3et is sho&n in "i+ure >9A in &hih 9= time periods ha!e

been assumed2 The ases %, and C represent the rapid mobilization time,normal mobilization and slo& mobilization for the pro3et, respeti!el#2

Calulate the !alue of &or7 ompleted in umulati!e perenta+e for periods 9throu+h 9= for eah of the ases %, and C2 %lso plot the !olume of &or7

ompleted !ersus time for these ases2

Figure 5-1(


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962 'uppose that the empirial model for estimatin+ annual ost of routinemaintenane in Eample >9< is appliable to setions of the 1enns#l!ania

Turnpi7e in 9;D> if theE#Rbuildin+ ost inde is applied to inflate the 9;6=,===barrelsBda#)

Coal +asifiation

(A@= billionsTUBda#)

Tar 'ands

(9>=,===barrelsBda#)

Cost ( billion)

@2> 4 D to 9=

asi desi+n (Thousands ofhours)

D= @== 9==

*etaileden+ineerin+ (Millions ofhours)

A to 4 4 to > 6 to D

Constrution (Millions ofhours)

@= A= 4=

Materials ( billion)

9 @ @2>

'oure5 Eon 0esearh and En+ineerin+ Compan#, "lorham 1ar7,

a7 to top

5." Approaches to Cost Estimation

Cost estimatin+ is one of the most important steps in pro3et mana+ement2 % ostestimate establishes the base line of the pro3et ost at different sta+es of de!elopmentof the pro3et2 % ost estimate at a +i!en sta+e of pro3et de!elopment represents a

predition pro!ided b# the ost en+ineer or estimator on the basis of a!ailable data2%ordin+ to the %merian %ssoiation of Cost En+ineers, ost en+ineerin+ is definedas that area of en+ineerin+ pratie &here en+ineerin+ 3ud+ment and eperiene areutilized in the appliation of sientifi priniples and tehniques to the problem ofost estimation, ost ontrol and profitabilit#2


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Firtuall# all ost estimation is performed aordin+ to one or some ombination ofthe follo&in+ basi approahes5

#roduction $unction.$n miroeonomis, the relationship bet&een the output of aproess and the neessar# resoures is referred to as the prodution funtion2 $n

onstrution, the prodution funtion ma# be epressed b# the relationship bet&eenthe !olume of onstrution and a fator of prodution suh as labor or apital2 %

prodution funtion relates the amount or !olume of output to the !arious inputs oflabor, material and equipment2 "or eample, the amount of output . ma# be deri!edas a funtion of !arious input fators 9, @, 222, nb# means of mathematial andBorstatistial methods2 Thus, for a speified le!el of output, &e ma# attempt to find a setof !alues for the input fators so as to minimize the prodution ost2 The relationship

bet&een the size of a buildin+ pro3et (epressed in square feet) to the input labor(epressed in labor hours per square foot) is an eample of a prodution funtion foronstrution2 'e!eral suh prodution funtions are sho&n in "i+ure AA of Chapter A2

Empirical cost in$erence.Empirial estimation of ost funtions requires statistialtehniques &hih relate the ost of onstrutin+ or operatin+ a failit# to a fe&important harateristis or attributes of the s#stem2 The role of statistial inferene isto estimate the best parameter !alues or onstants in an assumed ost funtion2Usuall#, this is aomplished b# means of re+ression anal#sis tehniques2

%nit costs $or &ill o$ 'uantities.% unit ost is assi+ned to eah of the failit#omponents or tas7s as represented b# the bill of quantities2 The total ost is thesummation of the produts of the quantities multiplied b# the orrespondin+ unitosts2 The unit ost method is strai+htfor&ard in priniple but quite laborious inappliation2 The initial step is to brea7 do&n or disa++re+ate a proess into a numberof tas7s2 Colleti!el#, these tas7s must be ompleted for the onstrution of a failit#2/ne these tas7s are defined and quantities representin+ these tas7s are assessed, aunit ost is assi+ned to eah and then the total ost is determined b# summin+ theosts inurred in eah tas72 The le!el of detail in deomposin+ into tas7s &ill !ar#onsiderabl# from one estimate to another2

Allocation o$ joint costs.%lloations of ost from eistin+ aounts ma# be used tode!elop a ost funtion of an operation2 The basi idea in this method is that eahependiture item an be assi+ned to partiular harateristis of the operation2 $deall#,the alloation of 3oint osts should be ausall# related to the ate+or# of basi osts in

an alloation proess2 $n man# instanes, ho&e!er, a ausal relationship bet&een thealloation fator and the ost item annot be identified or ma# not eist2 "or eample,in onstrution pro3ets, the aounts for basi osts ma# be lassified aordin+ to(9) labor, (@) material, (A) onstrution equipment, (4) onstrution super!ision, and(>) +eneral offie o!erhead2 These basi osts ma# then be alloated proportionall# to!arious tas7s &hih are subdi!isions of a pro3et2

a7 to top

5.( Types o$ Construction Cost Estimates


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Constrution ost onstitutes onl# a fration, thou+h a substantial fration, of the totalpro3et ost2 o&e!er, it is the part of the ost under the ontrol of the onstrutionpro3et mana+er2 The required le!els of aura# of onstrution ost estimates !ar#at different sta+es of pro3et de!elopment, ran+in+ from ball par7 fi+ures in the earl#sta+e to fairl# reliable fi+ures for bud+et ontrol prior to onstrution2 'ine desi+n

deisions made at the be+innin+ sta+e of a pro3et life #le are more tentati!e thanthose made at a later sta+e, the ost estimates made at the earlier sta+e are epeted to

be less aurate2 Generall#, the aura# of a ost estimate &ill reflet the informationa!ailable at the time of estimation2

Constrution ost estimates ma# be !ie&ed from different perspeti!es beause ofdifferent institutional requirements2 $n spite of the man# t#pes of ost estimates usedat different sta+es of a pro3et, ost estimates an best be lassified into three ma3orate+ories aordin+ to their funtions2 % onstrution ost estimate ser!es one of thethree basi funtions5 desi+n, bid and ontrol2 "or establishin+ the finanin+ of a

pro3et, either a desi+n estimate or a bid estimate is used2

92 )esign Estimates."or the o&ner or its desi+nated desi+n professionals, thet#pes of ost estimates enountered run parallel &ith the plannin+ and desi+nas follo&s5

o 'reenin+ estimates (or order of ma+nitude estimates)

o 1reliminar# estimates (or oneptual estimates)

o *etailed estimates (or definiti!e estimates)

o En+ineer-s estimates based on plans and speifiations

"or eah of these different estimates, the amount of desi+n information

a!ailable t#piall# inreases2

@2 id Estimates."or the ontrator, a bid estimate submitted to the o&ner eitherfor ompetiti!e biddin+ or ne+otiation onsists of diret onstrution ostinludin+ field super!ision, plus a mar7up to o!er +eneral o!erhead and

profits2 The diret ost of onstrution for bid estimates is usuall# deri!edfrom a ombination of the follo&in+ approahes2

o 'ubontrator quotations

o .uantit# ta7eoffs

o Constrution proedures2

A2 (. Control Estimates."or monitorin+ the pro3et durin+ onstrution, a

ontrol estimate is deri!ed from a!ailable information to establish5o ud+et estimate for finanin+

o ud+eted ost after ontratin+ but prior to onstrution

o Estimated ost to ompletion durin+ the pro+ress of onstrution2

)esign Estimates

$n the plannin+ and desi+n sta+es of a pro3et, !arious desi+n estimates reflet thepro+ress of the desi+n2 %t the !er# earl# sta+e, thescreening estimateor order ofmagnitudeestimate is usuall# made before the failit# is desi+ned, and must thereforerel# on the ost data of similar failities built in the past2 %preliminary estimateorconceptual estimateis based on the oneptual desi+n of the failit# at the state &henthe basi tehnolo+ies for the desi+n are 7no&n2 The detailed estimateor definitive


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estimateis made &hen the sope of &or7 is learl# defined and the detailed desi+n isin pro+ress so that the essential features of the failit# are identifiable2 The engineer'sestimateis based on the ompleted plans and speifiations &hen the# are read# forthe o&ner to soliit bids from onstrution ontrators2 $n preparin+ these estimates,the desi+n professional &ill inlude epeted amounts for ontrators- o!erhead and

profits2

The osts assoiated &ith a failit# ma# be deomposed into a hierarh# of le!els thatare appropriate for the purpose of ost estimation2 The le!el of detail in deomposin+the failit# into tas7s depends on the t#pe of ost estimate to be prepared2 "oroneptual estimates, for eample, the le!el of detail in definin+ tas7s is quite oarse?for detailed estimates, the le!el of detail an be quite fine2

%s an eample, onsider the ost estimates for a proposed brid+e aross a ri!er2 %sreenin+ estimate is made for eah of the potential alternati!es, suh as a tied arh

brid+e or a antile!er truss brid+e2 %s the brid+e t#pe is seleted, e2+2 the tehnolo+#

is hosen to be a tied arh brid+e instead of some ne& brid+e form, a preliminar#estimate is made on the basis of the la#out of the seleted brid+e form on the basis ofthe preliminar# or oneptual desi+n2 hen the detailed desi+n has pro+ressed to a

point &hen the essential details are 7no&n, a detailed estimate is made on the basis ofthe &ell defined sope of the pro3et2 hen the detailed plans and speifiations areompleted, an en+ineer-s estimate an be made on the basis of items and quantities of&or72

id Estimates

The ontrator-s bid estimates often reflet the desire of the ontrator to seure the3ob as &ell as the estimatin+ tools at its disposal2 'ome ontrators ha!e &ellestablished ost estimatin+ proedures &hile others do not2 'ine onl# the lo&est

bidder &ill be the &inner of the ontrat in most biddin+ ontests, an# effort de!otedto ost estimatin+ is a loss to the ontrator &ho is not a suessful bidder2Consequentl#, the ontrator ma# put in the least amount of possible effort for ma7in+a ost estimate if it belie!es that its hane of suess is not hi+h2

$f a +eneral ontrator intends to use subontrators in the onstrution of a failit#, itma# soliit prie quotations for !arious tas7s to be subontrated to speialt#subontrators2 Thus, the +eneral subontrator &ill shift the burden of ost

estimatin+ to subontrators2 $f all or part of the onstrution is to be underta7en b#the +eneral ontrator, a bid estimate ma# be prepared on the basis of the quantit#ta7eoffs from the plans pro!ided b# the o&ner or on the basis of the onstrution

proedures de!ised b# the ontrator for implementin+ the pro3et2 "or eample, theost of a footin+ of a ertain t#pe and size ma# be found in ommerial publiationson ost data &hih an be used to failitate ost estimates from quantit# ta7eoffs2o&e!er, the ontrator ma# &ant to assess the atual ost of onstrution b#onsiderin+ the atual onstrution proedures to be used and the assoiated osts ifthe pro3et is deemed to be different from t#pial desi+ns2 ene, items suh as labor,material and equipment needed to perform !arious tas7s ma# be used as parametersfor the ost estimates2

Control Estimates


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oth the o&ner and the ontrator must adopt some base line for ost ontrol durin+the onstrution2 "or the o&ner, a budget estimatemust be adopted earl# enou+h for

plannin+ lon+ term finanin+ of the failit#2 Consequentl#, the detailed estimate isoften used as the bud+et estimate sine it is suffiient definiti!e to reflet the pro3etsope and is a!ailable lon+ before the en+ineer-s estimate2 %s the &or7 pro+resses, the

bud+eted ost must be re!ised periodiall# to reflet the estimated ost to ompletion2% re!ised estimated ost is neessar# either beause of han+e orders initiated b# theo&ner or due to unepeted ost o!erruns or sa!in+s2

"or the ontrator, the bid estimate is usuall# re+arded as the bud+et estimate, &hih&ill be used for ontrol purposes as &ell as for plannin+ onstrution finanin+2 The

bud+eted ost should also be updated periodiall# to reflet the estimated ost toompletion as &ell as to insure adequate ash flo&s for the ompletion of the pro3et2

Example 5-": *creening estimate o$ a grouting seal &eneath a land$ill 8@:

/ne of the methods of isolatin+ a landfill from +round&ater is to reate a bo&lshapedbottom seal beneath the site as sho&n in "i+ure >=2 The seal is onstruted b#pumpin+ or pressurein3etin+ +rout under the eistin+ landfill2 oles are bored atre+ular inter!als throu+hout the landfill for this purpose and the +rout tubes areetended from the surfae to the bottom of the landfill2 % la#er of soil at a minimumof > ft2 thi7 is left bet&een the +routed material and the landfill ontents to allo& forirre+ularities in the bottom of the landfill2 The +rout liner an be bet&een 4 and 6 feetthi72 % t#pial material &ould be 1ortland ement +rout pumped under pressurethrou+h tubes to fill !oids in the soil2 This +rout &ould then harden into a permanent,impermeable liner2
http://www.ce.cmu.edu/pmbook/05_Cost_Estimation.html#fn2http://www.ce.cmu.edu/pmbook/05_Cost_Estimation.html#fn2http://www.ce.cmu.edu/pmbook/05_Cost_Estimation.html#fn2


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Figure 5-1:Grout ottom 'eal Liner at a Landfill

The &or7 items in this pro3et inlude (9) drillin+ eplorator# bore holes at >= ftinter!als for +rout tubes, and (@) pumpin+ +rout into the !oids of a soil la#er bet&een4 and 6 ft thi72 The quantities for these t&o items are estimated on the basis of the

landfill area5

D ares H (D)(4A,>6= ft@Bare) H A4D,4D= ft@

(%s an approimation, use A6=,=== ft@to aount for the bo&l shape)

The number of bore holes in a >= ft b# >= ft +rid pattern o!erin+ A6=,=== ft@is +i!enb#5

The a!era+e depth of the bore holes is estimated to be @= ft2 ene, the total amountof drillin+ is (944)(@=) H @,DD= ft2

The !olume of the soil la#er for +routin+ is estimated to be5

for a 4 ft la#er, !olume H (4 ft)(A6=,=== ft@) H 9,44=,=== ftAfor a 6 ft la#er, !olume H (6 ft)(A6=,=== ft@) H @,96=,=== ftA

$t is estimated from soil tests that the !oids in the soil la#er are bet&een @=I and A=Iof the total !olume2 Thus, for a 4 ft soil la#er5+routin+ in @=I !oids H (@=I)(9,44=,===) H @DD,=== ftA+routin+ in A= I !oids H (A=I)(9,44=,===) H 4A@,=== ftA

and for a 6 ft soil la#er5+routin+ in @=I !oids H (@=I)(@,96=,===) H 4A@,=== ftA+routin+ in A=I !oids H (A=I)(@,96=,===) H 64D,=== ftA

The unit ost for drillin+ eplorator# bore holes is estimated to be bet&een A and 9=per foot (in 9;@,=== to @,DD=,===for a 4 ft la#er &ith A=I !oids, +routin+ ost H 9,


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< per ubi foot of 1ortland ement +routin+2 $n this ase, the total pro3et ost isestimated to be5(> ft)(A6=,=== ft@)(@>I)(=,===%n important point to note is that this sreenin+ estimate is based to a lar+e de+ree onen+ineerin+ 3ud+ment of the soil harateristis, and the ran+e of the atual ost ma#

!ar# from 9,9>@,=== to 6,4D=,=== e!en thou+h the probabilities of ha!in+ atualosts at the etremes are not !er# hi+h2Example 5-(: Example o$ engineer+s estimate and contractors+ &ids8A:The en+ineer-s estimate for a pro3et in!ol!in+ 94 miles of $nterstate =,D>;2 ids &ere submitted on Marh 9=, 9;D= =2A='urfae dithes lf >@> @2== 92==

Ea!ation strutures # 2==

ase ourse, untreated, AB4-- ton A6@,@== 42>= >2==

Lean onrete, 4-- thi7 s# D@=,A9= A29= A2==

1CC, pa!ement, 9=-- thi7 s#


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9=-- thi7 s# 4,@49 @=2== @2== 9@2==

Loose riprap # A@ 4=2== A=2==

estimation techniq

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