Over 162 million gallons of untreated sewage overflowed from Portland’s sewer system on 37 distinct occasions in 2017. That’s roughly equivalent to the volume of 245 Olympic-sized swimming pools.

Portland’s sewers overflow during rainy weather, when runoff from gutters and storm drains overwhelms the city’s sewer system. The chart below illustrates how much sewage has spilled into Casco Bay for the year, through the end of November. Mouse over the bar chart to view more details about each event, and to see where the sewage went in the map below:

Note: During wet weather, the East End Wastewater Treatment Plant gives some sewage only partial treatment, plus chemical disinfection, due to capacity constraints. This partially-treated wastewater, reported in the map above in a lighter shade of red, is then released along with fully-treated wastewater in the treatment plant’s outfall pipe, located near Pomroy Rock about 500 yards from the East End Beach.