Assessing the impact of rightsizing drinking water infrastructure system in Flint, Michigan

For sustainable urban systems, appropriately sized infrastructure is essential. When cities face long-term population decline, however, downsizing rigid infrastructure built to last decades is challenging and costly. Some of the challenges include significant upfront costs to remove or modify infrastructure, weighing future expansion burdens, and prioritizing which portion of the infrastructure modify. This study examines engineering challenges associated with rightsizing water infrastructure in a shrinking city. In this paper, utilizing on a full-scale model of Flint’s drinking water distribution system, we evaluate scenarios which include abandoning and resizing of pipes based on block-level population and economic decline. We also quantify the cost of property acquisition and construction for these changes. The impact of these changes on water pressure and quality (i.e., water age) as well as on different racial and socioeconomic groups are also analyzed. Based on the results of this analysis, we present six major findings broadly applicable to shrinking cities: (1) local modification to drinking water pipe networks impacts surrounding areas, (2) decommissioning pipes can negatively impact water system performance, (3) shrinking pipes generally improves water quality, (4) resizing pipes is expensive, (5) housing-related costs are significant, and (6) shrinkage can disproportionately impact groups of people. This study highlights the complexities involved when attempting to shrink infrastructure and supplies valuable information for practitioners, planners, and decision-makers about the engineering challenges and upfront costs of rightsizing infrastructure for sustainable redevelopment.