New tool can help determine most cost effective material for water pipelines

Kansas City, Mo. — A tool developed by a team of researchers at the University of Michigan can be used by utility decision-makers to evaluate multiple factors affecting pipes, allowing them to determine cost-effectiveness beyond initial expense, including costs associated with environmental impacts. The Ductile Iron Pipe Research Association (DIPRA) sponsored the research.

"It is important to consider more than one factor in selecting a pipeline material," said Carol C. Menassa, PhD, of the University of Michigan Civil and Environmental Engineering Department, and lead researcher of the project. "With this new tool, the true value of the pipe, as an asset, can be understood, allowing for investment to be made in a good way."

She noted that the life cycle cost assessment (LCCA) tool allows for different pipe sizes, flows and locations, providing a framework for analyzing various operations and actual service life scenarios.

Developing the LCCA model was a primary objective of the University of Michigan research paper published by the American Society of Civil Engineers (ASCE), and presented by Menassa at the ASCE 2016 Pipelines Conference on July 18. Titled, "A Framework to Evaluate Life Cycle Costs and Environmental Impacts of Water Pipelines," the paper compares two of the most common pipe materials used in water systems, Ductile Iron Pipe and polyvinyl chloride (PVC) pipe.

Research results

Results of the research show that while PVC pipe may have initial cost benefits, Ductile Iron Pipe is the more cost-effective material over the pipeline's service life.  Of note, there is a sharp rise in a cost break-even graph analysis of the two pipe materials due to the shorter service life of PVC pipe, which then requires replacement.

Because PVC pipe has a limited performance history, the University of Michigan research team conducted an extensive literature review on reported service lives of both PVC and Ductile Iron Pipe. From the studies, the research team set service lives for PVC pipe at 50 years, and Ductile Iron Pipe at 100 years. Users of the LCCA model, however, can make adjustments to test any service life option.

Other findings of the University of Michigan study showed that Ductile Iron Pipe has a lower environmental impact, based both on the production and operation phases of the alternatives, and the rate of pumping across all pipe diameters has the highest impact on cost.

The University of Michigan study on both economic and environmental impacts is important for utility decision-makers as they seek to balance fiscal concerns over immediate and long-term needs as well as the environmental impact of pipeline materials across production, design, installation, operations and maintenance, and planned end of life. For local government leaders, utility officials and engineers designing pipeline systems, the LCCA model serves as a tool to test various scenarios to determine the right solution for site-specific conditions and community values, as well as provide the necessary defensible data to support those decisions.

In addition to Menassa, the research team included Albert Thomas and Bharadwaj R.K. Mantha. Data for the LCCA model was obtained from various participating U.S. utilities, and the literature review from associations including, but not limited to, the American Water Works Association (AWWA), American Society of Civil Engineers (ASCE), Ductile Iron Pipe Research Association (DIPRA), Plastics Pipe Institute, U.S International Trade Commission, U.S. Environmental Protection Agency and the Water Research Foundation. DIPRA sponsored the research project.

A copy of the University of Michigan paper, "A Framework to Evaluate the Life Cycle Costs and Environmental Impacts of Water Pipelines," can be obtained at https://ascelibrary.org/doi/pdf/10.1061/9780784479957.107 from the ASCE library under Conference Proceedings for Pipelines 2016: Out of Sight, Out of Mind, Not Out of Risk.

About the research team

Carol C. Menassa, PhD, A.M., ASCE, is an Associate Professor and John L. Tishman Faculty Scholar in the Department of Civil and Environmental Engineering at the University of Michigan. She received her PhD in Civil and Environmental Engineering from the University of Illinois at Urbana-Champaign (UIUC). Menassa directs the Sustainable and Intelligent Civil Infrastructure Systems Laboratory at the University of Michigan. Her current research focuses on sustainability of buildings and infrastructure systems. Her research is funded by the National Science Foundation, the Construction Industry Institute, the Ductile Iron Pipe Research Association, the Wisconsin Alumni Research Foundation and the Wisconsin Energy Research Consortium. Menassa is the recipient of the 2015 CII Distinguished Professor Award and 2014 NSF Career award. She also received the 2013 Best Paper Award from the ASCE International Conference on Computing in Civil and Building Engineer, and the Distinguished Young Alumni Award from the American University of Beirut. Menassa is an Associate Editor for the ASCE Journal of Computing in Civil Engineering and Assistant Specialty Editor for the ASCE Journal of Construction Engineering and Management.