MR87-1_REDUCED.pdf

The costs of the pipe are discussed here on a sizebasis even though they are not hydraulically equivalent.As expected, the initial installed cost of CSP was lessthan Class III RCP in all sizes. In the sizes 12 through 36inch diameter,the initial installed cost of CSP was 60 to82 percent of the RCP with an average of 69 ' percent . Asimilar calculation of all Class III RCP and CSP placedbycontract in 1986 showed a weighted average initial installed,cost of CSP to be 78 percent of RCP .Standard economic formulas may be used to attempt toequate the present worth of RCP and CSP . However, theseformulas require bidding of both types of pipes for the sameinstallation, hydraulically sizing each type of pipe,assuming a service life for each type of culvert for thatlocation, and assuming an inflation factor and rate ofreturn on money for the analysis period . This type ofeconomic analysis could not be performed on the Department ' sculverts because 1) the life of CSP is too variableand would require a different analysis period for eachinstallation , 2) where pipe are bid as alternates, theDepartment sizes the pipe on the basis of CSP whichgenerally oversizes the Rep, and 3) selecting an inflationfactor or interest rate is beyond the scope of this study .Another problem with any economic prediction attemptingto equate the two types. of pipe is , it has to be assumed theDepartment would have the money and manpower to replacethe- 18 -