Change Orders and Schedule Performance of Design-Build Infrastructure Projects: Comparison between Highway and Water and Wastewater Projects

Abstract

According to previous studies, change orders in general lead to delays in design-bid-build (DBB) projects. However, none of the studies have determined such a relationship in design-build (DB) projects. To address this issue, the current paper focuses on change-order- and schedule-related performance differences in highway and water and wastewater projects built using the DB method. To do so, this study collected data from 53 DB highway and 44 DB water and wastewater projects and compared change orders and schedule performance. The average project cost of highway and water and wastewater projects were $128 million and $58 million, respectively, converted to base costs of 2018. In addition, 98% of the highway and 68% of water and wastewater projects used a best value procurement method to select a design-builder and 93% of the projects used a lump sum contract. The t-test results showed that change orders, which are the percentage of extra costs added to the original contract amounts, were significantly higher in DB highway projects (4.5%) than those in DB water and wastewater projects (0.43%). In contrast to this, the construction intensity of DB highway projects was found to be significantly higher than that of water and wastewater projects. The results also showed that the percentage of DB highway projects having positive change orders (76%) was higher than the percentage of DB water and wastewater projects with positive change orders (41%). When the total cost of change orders was calculated, it was found that $123 million of change orders were added in highway projects, whereas in water and wastewater projects only $0.94 million of change orders were added. These findings indicate that DB water and wastewater projects received greater benefits in terms of change orders compared to highway projects. In contrast, DB highway projects were designed and built faster than DB water and wastewater projects. The primary contribution of this study is that in comparison to DB highway projects, DB water and wastewater projects had fewer change orders but lower construction intensity. This finding is opposite to that of DBB projects in the sense that the projects that had fewer change orders had better schedule performance. The authors would recommend conducting similar types of studies with larger sample sizes and with other types of projects, such as residential buildings, commercial buildings, and railroad projects.