![Figure 1: U.S. Combined-Sewer Systems Serving Populations of 50,000 or More](https://www.infrastructureusa.org/wp-content/uploads/2016/02/sewers-1.jpg)
MANHATTAN INSTITUTE
The biggest capital project, by far, in many American cities is one that few of their citizens even know about and that almost none has ever seen: the legally mandated retrofitting of “combined sewers,” sewers in which storm-water runoff and sanitary waste from buildings are channeled into the same pipes to reduce or eliminate overflows of untreated wastewater into local waterways.