Exploring Unit Cost Performance for Water Infrastructure Delivery

Abstract

Various delivery methods are used in the water industry for delivering treatment plant projects, which include the traditional design-bid-build (DBB) method as well as alternative project delivery methods (APDM), such as construction manager at risk (CMAR) and design-build (DB). Research has shown that APDM may improve water infrastructure project delivery performance when compared to DBB. However, utilizing an APDM does not guarantee a project’s successful delivery; other project variables also influence project delivery performance. The objective of this study is to develop exploratory mathematical models to investigate the impact of project-specific delivery factors and attributes on a water project’s success. The authors assess unit cost performance, which is a measure of a water treatment plant’s capacity in million gallons per day, over a project’s total cost. This study consisted of holding an industry expert workshop to review and develop a data collection questionnaire. Information on a total of 15 water treatment plant projects delivered in the US was collected and used to develop multiple linear regression models that explored project-specific key factors and attributes that impact unit cost performance. Results of the regression models revealed four critical variables: (1) use of GMP; (2) project team experience; (3) level of design completed before constructor engagement; and (4) project complexity, to have a statistically significant impact on the unit cost performance of water projects. The findings and contributions of this study can aid water stakeholders in understanding the unit cost performance impact of key project variables on their projects and support them in their project delivery method decisions.