The problem of sewage overflow continues to threaten waterways in New York City and across the nation, according to a recent New York Times article.  Over the past three years, 9,400 of the nation's 25,000 sewer systems have violated the Clean Water Act of 1972, dumping untreated human waste and other hazardous materials. 

Combined sewer systems, which collect sewage and rainwater together, are the primary culprit behind overflows.  Systems can be overwhelmed by a sufficient rainfall, as the rain leads to more wastewater than the treatment plant can handle.  Paved and other nonporous surfaces add to the problem by increasing the amount of stormwater runoff that enters the sewer system.

In New York City, half of all rainstorms results in sewage overflows.   City officials estimate that it would cost $58 billion to make the improvements to prevent all sewage spills.  One quarter of the state's water treatment plants are using inadequate technology, according to he New York State Department of Environmental Conservation.

Untreated sewage results in millions of reported illnesses nationwide each year.  As many as 20 million people become sick from drinking water containing with bacteria associated with untreated sewage. In California alone, 4 million people are made ill by swimming in contaminated waters.