Climate impact on combined sewage overflows (CSOs) in New York City (NYC)

Keywords: hurricane, sewage outflows, CSOs, water pollution
Abstract Type: Paper Abstract

Abstract

Hurricanes and tropical storms have occurred more often in NYC in recent years. In the summer of 2021, Hurricanes Elsa, Henry, and Ida hit NYC and the surrounding area. These hurricanes caused sewage outflows, increasing nutrient and bacteria levels in rivers, and the flooding of subways. Hurricane Ida hit NYC in July 2021. The swim portion in NYC Triathlon had to be cancelled, and was substituted with a one mile run instead, due to the high bacteria levels in the Hudson River. Hurricane Ida hit NYC on September 1, 2021. New Yorkers were blindsided by the storm. There was no accurate weather forecast or warning/evacuation in advance. Seventeen people died in basement apartments in Queens and Brooklyn, and at least 43 people died in NY, NJ, CT, and PA.

In NYC, most (60%) of the sewage system is combined sewage, a single pipe that carries both stormwater and sewage from buildings. The mixture is usually sent to wastewater treatment plants (WWTP). However during rainstorms, hurricanes, and tropical storms, the mixture volume exceeds WWTP capacity, and the excess volume of untreated sewage mixed with stormwater runoff, called combined sewage overflows (CSOs), discharges directly into NYC’s waterways. It causes water pollution and increased nutrients and pathogen levels. This makes the river unsafe for swimming and boating, and threatens fish consumption safety. Frequent hurricanes and heavy rainstorms resulted in a large volume of CSOs. How to reduce sewage outflows and upgrade the infrastructure of the sewage system is a major concern in NYC.