Performance Comparison of Alternative Delivery Methods in Water and Wastewater Projects Based on Project Size

Across the United States, growing reinvestment needs, aging assets, and rising service expectations are placing increasing pressure on how water and wastewater projects are delivered. Traditional Design–Bid–Build (DBB) has been widely used, but alternative delivery methods such as Design–Build (DB) and Construction Management-at-Risk (CMAR) are being adopted with the expectation of better cost and schedule performance. Their increased use has created a need to assess their performance and compare these delivery methods in terms of cost and time. Performance comparisons of this nature have been conducted in the highway and building sectors; however, there has been limited research in the water and wastewater sectors. In addition, a performance comparison including construction intensity with a large sample size across all three delivery methods has not been conducted in water and wastewater projects. Hence, this study conducts a statistical comparison of DBB, DB, and CMAR using three project performance indicators: cost growth, schedule growth, and construction intensity, with costs normalized to 2025 for inflation and durations measured in working days. The analysis compares outcomes across delivery methods for both the full project sample and a consistent project-size range. Results indicate that cost growth is generally low and does not differ significantly between methods irrespective of project size. However, schedule performance and construction intensity vary by delivery approach and project size. The study found that DB and DBB schedule growth is better than CMAR when considering all samples. With samples of projects costing $10 million to $110 million, only DB schedule growth was found to be better than DBB and CMAR. Considering the entire sample, the construction intensity of DB was found to be superior to DBB and CMAR, and CMAR was superior to DBB. When the data are separated between $10 million and $110 million, only DB construction intensity was found to be superior to DBB and CMAR water and wastewater projects. The outcomes of the cost and schedule comparison among the three delivery methods can assist water and wastewater project owners in making well-informed decisions regarding the selection of the delivery method based on their project scope, time, and budget.