Development of sewer cost function

Abstract

This article compares the ability of nine different cost functions to model a set of 88 sewer cost data. The empirical constants associated with the cost models are estimated by using a commercially available software package. The results of this study indicate that those cost functions using the depth of excavation as their sole independent variable gave a much poorer fit to the data than those using the diameter alone. However, better results are obtained when both the depth of excavation and the diameter are used as the independent variables. This study also indicates that the use of common statistical criterion like sum of square errors around the fitted curve, correlation coefficient and root‐mean‐square error are insufficient for evaluating the sewer cost functions objectively. It is shown that the use of basic economic concept will greatly help to ease the difficult task of evaluating sewer cost functions.