[s]ix months after Sandy, data from the eight hardest hit states shows that 11 billion gallons of untreated and partially treated sewage flowed into rivers, bays, canals, and in some cases, city streets, largely as a result of record storm-surge flooding that swamped the region’s major sewage treatment facilities. To put that in perspective, 11 billion gallons is equal to New York’s Central Park stacked 41 feet high with sewage, or more than 50 times the BP Deepwater Horizon oil spill. The vast majority of that sewage flowed into the waters of New York City and northern New Jersey in the days and weeks during and after the storm.
Our analysis of sewage-spill data provided by state agencies and individual treatment plant operators shows that:
- One third of the overflow (3.45 billion gallons) was essentially untreated raw sewage. The remainder (7.45 billon gallons) was partially treated, meaning that it received at least some level of filtration and, perhaps, chlorination.
- 94 percent of the spilled sewage, well over 10 billion gallons, was the result of some form of damage caused by coastal flooding. In some cases, Sandy’s storm surge simply flooded treatment plants and pumping stations, while in other cases a combination of power outages and flood conditions shuttered facilities or caused major diversions of sewage into receiving waters.
- 93 percent of the volume of sewage overflows took place in New York (47 percent) and New Jersey (46 percent). Eighteen of the 20 largest spills ended up in New York and New Jersey waters, as did the four individual sewage overflows of more than 1 billion gallons each; two each from New York and New Jersey.
- The notable exception to storm-surge related sewage discharges was in Washington D.C., where instead, rainfall was the main culprit. Sandy produced 5.1 inches of rain in 24 hours, leading to the sixth-largest Sandy-related sewage overflow at 475 million gallons of untreated sewage and contaminated runoff. That was the only rain-related sewage spill in the top 30 overflows. Overall, heavy rainfall caused a reported 776 million gallons of sewage spills to waters in Mid-Atlantic States.