The Combined Sewer System: New York’s Double-Edged Sword

Approximately 60% of New York City is serviced by a combined sewer system, where stormwater runoff and sewage share the same pipes. This system, designed in the 19th century, was meant to efficiently handle both types of water but has become a significant issue during heavy rainfall.

When it rains, these combined sewers can become overwhelmed, leading to combined sewer overflows (CSOs) where untreated sewage and stormwater are released into local waterways like the Hudson River and New York Harbor. This not only pollutes the water but also poses health risks and environmental damage.

The city has been working on mitigation strategies, including green infrastructure projects like rain gardens and permeable pavements to reduce runoff. There are also plans for upgrading treatment plants and constructing storage tunnels to hold excess flow until it can be treated.

However, the cost and complexity of overhauling such an extensive system are immense, leading to debates over funding, the pace of change, and the balance between modern solutions and the historical infrastructure.