Some Sewage Is More Expensive Than Other Sewage

All you really have to know is contained here:

Citing the city's history of diverting 6.4 million gallons of untreated sewage and storm water into local waterways during rain events, the EPA has ordered the city to make improvements by 2016 or face penalties.

Six point four million gallons.

Or, as MMSD would put it, "A drop in the bucket."

MMSD's bucket is Lake Michigan.