1、Designation: C1131 101Standard Practice forLeast Cost (Life Cycle) Analysis of Concrete Culvert, StormSewer, and Sanitary Sewer Systems1This standard is issued under the fixed designation C1131; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorial changes were made throughout in April 2011.1. Scope1.1 This practice covers procedures for
3、least cost (life cycle)analysis (LCA) of materials, systems, or structures proposedfor use in the construction of concrete culvert, storm sewer, andsanitary sewer systems.NOTE 1As intended in this practice, examples of analyses include, butare not limited to the following: (1) materials-pipe linings
4、 and coatings,concrete wall thicknesses, cements, additives, etc.; (2) systems-circularpipe, box sections, multiple lines, force mains, etc.; and (3) structures-wetand dry wells, pump and lift stations, etc.1.2 The LCA method includes costs associated with plan-ning, engineering, construction (bid p
5、rice), maintenance, reha-bilitation, replacement, and cost deductions for any residualvalue at the end of the proposed project design life.1.3 For each material, system, or structure, the LCA methoddetermines in present value constant dollars, the total of allinitial and future costs over the projec
6、t design life, and deductsany residual value.1.4 Major factors in the LCA method include project designlife, service life, and relevant interest and inflation rates.2. Terminology2.1 Definitions:2.1.1 constant dollarsdollars of uniform purchasingpower exclusive of inflation or deflation.2.1.1.1 Disc
7、ussionConstant dollars are costs stated atprice levels for a specific reference year, usually the particulartime that the LCA is being conducted.2.1.2 current dollarsdollars of purchasing power in whichactual prices are stated, including inflation or deflation.2.1.2.1 DiscussionCurrent dollars are c
8、osts stated at pricelevels in effect whenever the costs are incurred. In the absenceof inflation or deflation, current dollars are equal to constantdollars.2.1.3 direct coststhe costs of excavation, removal, anddisposal of existing materials, systems, or structures; installa-tion and testing of repl
9、acements materials, systems, or struc-tures; backfill; surface restoration, traffic rerouting, safety,utility relocations; and additional future costs required by newland uses, population growth.2.1.4 discount rateaccounts for the time value of moneyand reflects the impartiality of paying or receivi
10、ng a dollar nowor at a future time.2.1.4.1 DiscussionThe discount rate is used to convertcosts occurring at different times to equivalent costs at acommon time. Discount rates may be expressed in nominal orreal terms.2.1.5 future costscosts incurred after a project has beenconstructed and operating,
11、 such as maintenance, rehabilitation,and replacement costs.2.1.6 indirect coststhe costs to the owner that users pay interms of delayed time.2.1.7 inflation ratean increase in the volume of moneyand credit relative to available goods and services resulting ina continuing rise in the general price le
12、vel.2.1.7.1 DiscussionIn this practice, inflation refers toyearly change in the Producer Price Index (1).22.1.8 interest ratethe cost of borrowed money.2.1.9 maintenance coststhe annual or periodic direct andindirect costs of keeping a material, system, or structurefunctioning for the project design
13、 life; such maintenance doesnot extend the service life of the material, system, or structure.2.1.10 nominal discount ratea discount rate that takesinto account both the effects of inflation and the real earningpotential of money invested over time.2.1.10.1 DiscussionWhen future costs and values are
14、expressed in current dollars, after having been adjusted forinflation, a nominal discount rate is used to convert the futurecosts and values to present value constant dollars. Users of thispractice should consult with their accountant or client todetermine the appropriate discount rate for a given p
15、roject.2.1.11 original costscosts incurred in planning, design-ing, and constructing a project.2.1.12 project design lifethe number of years of usefullife the material, system, or structure must provide.1This practice is under the jurisdiction of ASTM Committee C13 on ConcretePipe and is the direct
16、responsibility of Subcommittee C13.05 on Special Projects.Current edition approved Dec. 1, 2010. Published January 2011. Originallyapproved in 1995. Last previous edition approved in 2007 as C1131 95 (2007).DOI: 10.1520/C113110E01.2The boldface numbers refer to the list of references at the end of t
17、he standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.1.13 real discount ratea discount rate that takes intoaccount only the real earning potential of money over time andis the differential between the interest and inflation
18、rates.2.1.13.1 DiscussionWhen future costs and values areexpressed in future constant dollars, a real discount rate is usedto convert constant dollars to present value dollars. Life cycleeconomic analyses conducted in constant dollars and a realdiscount rate are often preferred to similar analyses c
19、onductedin current dollars using nominal discount rates because noforecast of the inflation rate is required.2.1.14 rehabilitation coststhe direct and indirect costs ofrehabilitating a material, system, or structure to extend theservice life of the material, system, or structure.2.1.15 replacement c
20、oststhe direct and indirect costs ofreplacing a material, system, or structure before the end of theproject design life, so it will again function as originallyintended.2.1.16 residual valuethe remaining value of the material,system, or structure at the end of the project design life.2.1.17 service
21、lifethe number of years of service a mate-rial, system, or structure will provide before rehabilitation orreplacement is required.2.1.17.1 DiscussionProject design life and service life areusually established by the owner or controlling agency.3. Significance and Use3.1 The significance of the LCA m
22、ethod is that it is acomprehensive technique for taking into account all relevantmonetary values over the project design life and provides ameasure of the total cost of the material, system, or structure.3.2 The LCA method can be effectively applied in both thepreconstruction and bid stages of proje
23、cts.After bids are taken,real costs can be used instead of estimates.4. Procedures4.1 The procedures for determining the LCA of a material,system, or structure can be summarized in five basic steps.4.1.1 Identify Objective, Alternatives, and Constraints.4.1.2 Establish Basic Criteria.4.1.3 Compile D
24、ata.4.1.4 Compute LCA for Each Material, System, or Struc-ture.4.1.5 Evaluate Results.4.2 Objectives, Alternatives, and ConstraintsEstablish thespecific objectives of the project and identify alternative waysof accomplishing the objectives. For example, alternatives fora sanitary sewer system may in
25、clude a gravity flow systemversus a gravity flow system with life stations versus a singleforce main. Identify constraints, such as maximum culvert heador tail water, maximum and minimum slopes and depths ofburial, installation methods, etc.4.3 CriteriaEstablish basic criteria that should be fol-low
26、ed in applying the LCA method, including project designlife; the material, system, or structure service life; direct andindirect costs and timing of maintenance, rehabilitation andreplacement; real or nominal discount rate; and the compre-hensiveness of the LCA evaluation.4.4 Compile DataCompile bas
27、ic data required to computethe LCA of potential alternatives, including costs of planning,design, engineering and construction; maintenance costs; reha-bilitation costs; replacement costs; residual values; and thetime periods for all future costs.4.5 Compute LCAThe LCA of a material, system, orstruc
28、ture can be formulated in simple terms with all costs andvalues in present value constant dollars:LCA 5 C 2 S 1 (M 1 N 1 R! (1)where:C = original cost,S = residual value,M = maintenance cost,N = rehabilitation cost, andR = direct and indirect replacement cost.4.5.1 Original CostOriginal cost is defi
29、ned in Section 2and is normally developed from the engineers estimate or isthe actual bid price. A material, system, or structure may havea service life longer than the project design life and, conse-quently, would have a residual future current dollar value,which must be discounted back to a presen
30、t constant dollarvalue, and subtracted from the original cost. Since mainte-nance, rehabilitation, and replacement costs may be incurredseveral times during the life of the project, the future currentdollar value of each occurrence must be discounted back to apresent constant dollar value and the va
31、lues summed.4.5.2 Future CostsFuture costs are normally estimated inconstant dollar values, which are then converted to futurecurrent dollar values by an inflation factor and then discountedback to present constant dollar values by an interest factor:FV 5 A 1 1 I!n(2)where:FV = future current dollar
32、 value,A = constant dollar value,I = inflation rate, andn = number of years in the future at which costs areincurred.PV 5FV1 1 i!n(3)where:PV = present constant dollar value, andi = interest or nominal discount rate.Combining Eq 2 and Eq 3:PV 5 AS1 1 I1 1 iDn(4)Eq 4 is usable, but requires assumptio
33、ns of both interest andinflation rates. Although interest and inflation rates can varywidely, historical records indicate that the differential betweeninterest and inflation rates has been relatively stable over thelong term. Therefore, by defining an inflation/interest factor, F,as:F 5S1 1 I1 1 iD(
34、5)where:F = inflation/interest factor.C1131 1012Restating Eq 4:PV 5 A F!n(6)The inflation/interest factor is virtually constant for specificdifferentials between interest and inflation rates. Therefore,utilizing the inflation/interest factor in present value calcula-tions eliminates the uncertaintie
35、s and distortions due to selec-tion of possibly incompatible individual interest and inflationrates (2).NOTE 2Table X1.1 presents the inflation/interest factor for a range ofinflation rates from 4 through 18 % and differentials between interest andinflation rates of 1 through 5 %. For different sour
36、ces of financing, thedifferential between interest and inflation rates significant in constructionover a 30-year period is presented in Table X1.2.4.5.3 Residual ValueIf a material, system, or structure hasa service life greater than the project design life, it would havea residual future current do
37、llar value, which should be dis-counted back to a present constant dollar value and subtractedfrom the original cost. Using a straight-line depreciation, thepresent value of the residual value is:S 5 CF!np SnsnD(7)where:S = residual value,C = present constant dollar cost,ns= number of years the mate
38、rial, system, or structureservice life exceeds the project design life,n = service life, andnp= project design life.With a lack of data to determine the residual value, a salvagevalue or cash value may be substituted or the term neglected.If accounting practices dictate, another depreciation method,
39、other than straight-line, may be used.4.5.4 Maintenance CostsThe present value of mainte-nance costs is calculated by determining the future value ofeach cost occurrence, discounting each to a present value, andsumming all the values. Maintenance costs may be on anannual basis or estimated as a tota
40、l for a periodic cycle orcovering a certain number of years, which reduces the numberof computations. The total present value of all maintenancecosts is:M 5 CM( Fn 1 F2n. 1 Fmn! (8)where:M = total present value of all maintenance costs,CM= constant dollar cost of a maintenance cycle,n = number of ye
41、ars in maintenance cycle, andm = number of maintenance cycles in project design life.If a maintenance cycle ends in a year in which rehabilitationor replacement work is scheduled, then the total present valueof maintenance costs should be refined by omitting the costs ofthat maintenance cycle. Where
42、 future maintenance costs are onan annual basis, the total present value of all maintenance costscan be determined by:M 5 CMF1F!mn1/F 1G (9)4.5.5 Rehabilitation CostsIf a material, system, or struc-ture has durability or structural problems before the end of theproject design life, it may be possibl
43、e to extend its service lifeby rehabilitation repairs. If the extended service life does notequal or exceed the project design life, the material, system, orstructure would probably require replacement at the end of theextended service life. A material, system, or structure mayrequire rehabilitation
44、 or replacement several times during theproject design life. The present value of rehabilitation costs iscalculated by determining the future value of each costoccurrence, discounting each to a present value and summingall values:N 5 (CNFn(10)where:N = present value of rehabilitation costs,CN= const
45、ant dollar cost estimated for a rehabilitationproject,n = number of years after the project is completed thatrehabilitation costs will be incurred.4.5.6 Replacement Costs:4.5.6.1 The present value of replacement costs is zero for amaterial, system, or structure with a service life equal to orgreater
46、 than the project design life.4.5.6.2 The present value of replacement costs for a mate-rial, system, or structure with a service life less than the projectdesign life is calculated by determining the future value of eachreplacement, discounting each to a present value, and summingall values:R 5 (CR
47、Fn(11)where:R = present value of replacement costs,CR= constant dollar cost of direct and indirect replace-ment, andn = number of years after the project is completed thatreplacement costs are estimated to occur.C1131 10134.5.6.3 The future value of indirect replacement costs for amaterial, system,
48、or structure with a service life less than theproject design life is calculated by determining user delaysduring construction (3):CRi5 AADT 3 t 3 d cp3 vp3 vof1 cf3 vf! (12)where:AADT = Annual Average Daily Traffic of the roadwaywhich the culvert is being installed,t = the average increase in delay
49、to each vehicle perday, in hours,d = the number of days the project will take,cp= the average rate of person-delay, in dollars perhour (4),vp= the percentage of passenger vehicle traffic,vof= the vehicle occupancy factor,cf= the average rate of freight-delay, in dollars perhour (5), andvf= the percentage of truck traffic.5. Keywords5.1 acceptance criteria; concrete; costs; culvert; inflationrate; interest rate; least cost analysis; life cycle analysis; pipe;procedures; project design life; sanitary sewer; service life;storm sewerAP
