1、Designation: C 1131 95 (Reapproved 2007)Standard Practice forLeast Cost (Life Cycle) Analysis of Concrete Culvert, StormSewer, and Sanitary Sewer Systems1This standard is issued under the fixed designation C 1131; the number immediately following the designation indicates the year oforiginal adoptio
2、n or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers procedures for least cost (life cycle)analysis (LCA)
3、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 and coatings,concrete wall thicknesse
4、s, 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 price), maintenance, reha-bilitation an
5、d 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 LCAmethoddetermines in present value constant dollars, the total of allinitial and future costs over the project design life, and deductsany residu
6、al value.1.4 Major factors in the LCA method include project designlife, service life, and relevant interest and inflation rates.2. Referenced Documents2.1 ASTM Standards:2E 833 Terminology of Building Economics3. Terminology3.1 Definitions:3.1.1 constant dollarsdollars of uniform purchasingpower ex
7、clusive of inflation or deflation.3.1.1.1 DiscussionConstant dollars are costs stated atprice levels for a specific reference year, usually the particulartime that the LCA is being conducted.3.1.2 current dollarsdollars of purchasing power in whichactual prices are stated, including inflation or def
8、lation.3.1.2.1 DiscussionCurrent dollars are costs stated at pricelevels in effect whenever the costs are incurred. In the absenceof inflation or deflation, current dollars are equal to constantdollars.3.1.3 direct coststhe direct costs of excavation, removal,and disposal of existing materials, syst
9、ems, or structures;installation and testing of replacements materials, systems orstructures; backfill; and surface restoration.3.1.4 discount rateaccounts for the time value of moneyand reflects the impartiality of paying or receiving a dollar nowor at a future time.3.1.4.1 DiscussionThe discount ra
10、te is used to convertcosts occurring at different times to equivalent costs at acommon time. Discount rates may be expressed in nominal orreal terms.3.1.5 future costscosts incurred after a project has beenconstructed and operating, such as maintenance, rehabilitation,and replacement costs.3.1.6 ind
11、irect coststhe costs of traffic rerouting, safety,utility relocations, etc., and additional future costs required bynew land uses, population growth, etc.3.1.7 inflation ratean increase in the volume of moneyand credit relative to available goods and services resulting ina continuing rise in the gen
12、eral price level.3.1.7.1 DiscussionIn this practice, inflation refers toyearly change in the Producer Price Index (1).33.1.8 interest ratethe cost of borrowed money.3.1.9 maintenance coststhe annual or periodic direct andindirect costs of keeping a material, system, or structurefunctioning for the p
13、roject design life; such maintenance doesnot extend the service life of the material, system, or structure.3.1.10 nominal discount ratea discount rate that takesinto account both the effects of inflation and the real earningpotential of money invested over time.3.1.10.1 DiscussionWhen future costs a
14、nd values areexpressed 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
15、for a given project.1This practice is under the jurisdiction of ASTM Committee C13 on ConcretePipe and is the direct responsibility of Subcommittee C13.05 on Special Projects.Current edition approved May 1, 2007. Published May 2007. Originallyapproved in 1995. Last previous edition approved in 2000
16、as C 1131 95 (2000).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers refer to the list o
17、f references at the end of the standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.11 original costscosts incurred in planning, design-ing, and constructing a project.3.1.12 project design lifethe number of years of usefulli
18、fe the material, system, or structure must provide.3.1.13 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 rates.3.1.13.1 DiscussionWhen future costs and values areexpressed in future
19、 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 conductedin current dollars using nominal discount rates because noforecast o
20、f the inflation rate is required.3.1.14 rehabilitation coststhe direct and indirect costs ofrehabilitating a material, system, or structure to extend theservice life of the material, system, or structure.3.1.15 replacement coststhe direct and indirect costs ofreplacing a material, system, or structu
21、re before the end of theproject design life, so it will again function as originallyintended.3.1.16 residual valuethe remaining value of the material,system, or structure at the end of the project design life.3.1.17 service lifethe number of years of service a mate-rial, system, or structure will pr
22、ovide before rehabilitation orreplacement is required.3.1.17.1 DiscussionProject design life and service life areusually established by the owner or controlling agency.4. Significance and Use4.1 The significance of the LCA method is that it is acomprehensive technique for taking into account all rel
23、evantmonetary values over the project design life and provides ameasure of the total cost of the material, system, or structure.4.2 The LCA method can be effectively applied in both thepreconstruction and bid stages of projects.After bids are taken,real costs can be used instead of estimates.5. Proc
24、edures5.1 The procedures for determining the LCA of a material,system, or structure can be summarized in five basic steps.5.1.1 Identify Objective, Alternatives, and Constraints.5.1.2 Establish Basic Criteria.5.1.3 Compile Data.5.1.4 Compute LCA for Each Material, System, or Struc-ture.5.1.5 Evaluat
25、e Results.5.2 Objectives, Alternatives, and ConstraintsEstablish thespecific objectives of the project and identify alternative waysof accomplishing the objectives. For example, alternatives fora sanitary sewer system may include a gravity flow systemversus a gravity flow system with life stations v
26、ersus a singleforce main. Identify constraints, such as maximum culvert heador tail water, maximum and minimum slopes and depths ofburial, installation methods, etc.5.3 CriteriaEstablish basic criteria that should be fol-lowed in applying the LCA method, including project designlife; the material, s
27、ystem, 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.5.4 Compile DataCompile basic data required to computethe LCA of potential alternatives, including cost
28、s of planning,design, engineering and construction; maintenance costs; reha-bilitation costs; replacement costs; residual values; and thetime periods for all future costs.5.5 Compute LCAThe LCA of a material, system, orstructure can be formulated in simple terms with all costs andvalues in present v
29、alue 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 = replacement cost.5.5.1 Original CostOriginal cost is defined in Section 3and is normally developed from the engineers estimate or isthe actual bid price.
30、 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 present constant dollarvalue, and subtracted from the original cost. Since mainte-nance, rehabilitatio
31、n, 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 values summed.5.5.2 Future CostsFuture costs are normally estimated inconstant dollar values, whic
32、h 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 A1 1 I!n(2)where:FV = future current dollar value,A = constant dollar value,I = inflation rate, andn = number of years in the future at whic
33、h 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 assumptions of both interest andinflation rates. Although interest and inflation rates can varywidely, his
34、torical 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(5)C 1131 95 (2007)2where:F = inflation/interest factor.Restating Eq 4:PV 5 A F!n(6)The inflation/
35、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 uncertainties and distortions due to selec-tion of possibly incompatible individual interest and infla
36、tionrates (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 sources of financing, thedifferential between interest and inflation rates significant in cons
37、tructionover a 30-year period is presented in Table X1.2.5.5.3 Residual ValueIf a material, system, or structure hasa service life greater than the project design life, it would havea residual future current dollar value, which should be dis-counted back to a present constant dollar value and subtra
38、ctedfrom the original cost. Using a straight-line depreciation, thepresent value of the residual value is:S 5 C F!np SnsnD(7)where:S = residual value,C = present constant dollar cost,ns= number of years the material, system, or structureservice life exceeds the project design life,n = service life,
39、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,other than straight-line, may be used.5.5.4 Maintenance CostsThe present value of mainte-
40、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 total for a periodic cycle orcovering a certain number of years, which reduces the numberof c
41、omputations. 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 years in maintenance cycle, andm = number of maintenance cycles in project design life.If a
42、 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 future maintenance costs are onan annual basis, the total present value of all maintenan
43、ce costscan be determined by:M 5 CMF1F!MN1/F 1G (9)5.5.5 Rehabilitation CostsIf a material, system, or struc-ture has durability or structural problems before the end of theproject design life, it may be possible to extend its service lifeby rehabilitation repairs. If the extended service life does
44、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 or replacement several times during theproject design life. The present value of rehabil
45、itation 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= constant dollar cost estimated for a rehabilitationproject,n = number of years after the proje
46、ct is completed thatrehabilitation costs will be incurred.5.5.6 Replacement Costs:5.5.6.1 The present value of replacement costs is zero for amaterial, system, or structure with a service life equal to orgreater than the project design life.5.5.6.2 The present value of replacement costs for a mate-r
47、ial, 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 (CRFn(11)where:R = present value of replacement costs,CR= constant dollar cost of replacemen
48、t, andn = number of years after the project is completed thatreplacement costs are estimated to occur.6. Keywords6.1 acceptance criteria; concrete; costs; culvert; inflationrate; interest rate; least cost analysis; life cycle analysis; pipe;procedures; project design life; sanitary sewer; service li
49、fe;storm sewerC 1131 95 (2007)3APPENDIX(Nonmandatory Information)X1. INFLATION/INTEREST FACTORX1.1 HistoryThe use of the inflation/interest factor tosimplify life-cycle cost estimation was first proposed by the JetPropulsion Laboratory of California Institute of Technologyunder a contract with the National Aeronautics and SpaceAdministration (2). Kerr/Ryan proposed the concept for pipe-line installations (3, 4), and developed the concept that thedifferential between interest and inflation rates for projectsinvolving state or local fundi
