The Sewer in a Suitcase, an educational tool developed by the Center for Urban Pedagogy, explains how untreated wastewater gets dumped into rivers and bays during heavy rainstorms.

Educators can take it around to classrooms and community workshops and set it up. Inside the wooden box, is a model city, with a street grid and buildings.  And underneath teh strreets lies a sewer system that, when it rains, gets backed up and, instead of sending water into treatment plants, releases the untreated effluent directly into wateways. 

In this video, Shino Tanikawa, the executive director of the New York City Soil and Water Conservation District and a member of the S.W.I.M. Coalition, explains how it works.