When it rains in NJ cities, raw sewage flows into your rivers — legally

Published by NJ Clean Stream  |  Combined Sewer Overflows Series, Article 1 of 3

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What is a combined sewer system?

Most modern sewer systems have two completely separate pipe networks: one for sanitary sewage (wastewater from toilets and sinks) and one for stormwater (rain and snowmelt). Sanitary sewage flows to a wastewater treatment plant. Stormwater flows separately to streams and rivers.

Older cities — including most of New Jersey’s historically dense urban centers — were built with combined sewer systems. A single network of pipes carries both. Under dry-weather conditions, the combined flow travels to a wastewater treatment plant. But during rainfall, stormwater enters the pipes and rapidly overwhelms their capacity. The overflow goes somewhere — and that somewhere, by design, is the nearest river or stream. This discharge is called a combined sewer overflow, or CSO.

A CSO discharge consists of a mixture that is primarily stormwater but that contains raw, untreated sewage — human fecal matter, bacteria, viruses, pharmaceuticals, and every other contaminant that entered the sewer system before the overflow occurred.

New Jersey’s 191 CSO outfalls

New Jersey has 191 permitted CSO outfall locations — discharge points that have been identified, mapped, and permitted under the federal Clean Water Act. Each outfall is a pipe that, under wet weather conditions, discharges a mixture of stormwater and raw sewage into a New Jersey waterway.

The heaviest concentrations are in Newark and Essex/Hudson counties, Paterson and the Passaic River valley, Trenton and the Delaware River communities, New Brunswick and the Raritan watershed, and Camden and southwestern New Jersey. These are the communities built in the era of combined sewers. The affected waterways include the Passaic River, the Raritan River, the Delaware River, the Hackensack River, and the Rahway River. Some outfalls overflow only during heavy storms; others overflow during any rainfall exceeding a quarter inch.

What happens to the rivers

Pathogen contamination. Raw sewage contains high concentrations of bacteria, viruses, and parasites. After a significant CSO event, fecal indicator bacteria in the receiving waterway can remain elevated for 24 to 72 hours or longer. Rivers and streams receiving regular CSO discharges are frequently unsafe for swimming, kayaking, or wading for days after rainstorms — during the same warm-weather months when residents most want to use them.

Nutrient loading. Sewage is rich in nitrogen and phosphorus, which drive algal blooms in receiving waters. Algal blooms deplete dissolved oxygen, killing fish and other aquatic life. In slow-moving or impounded waters, nutrient loading from CSOs can drive persistent eutrophication that fundamentally alters the ecology of the receiving water body.

Oxygen depletion. Organic matter in sewage consumes dissolved oxygen as it decomposes. During and after a CSO event, dissolved oxygen levels can drop sharply, driving fish from the area or causing die-offs. Sensitive aquatic invertebrates that serve as food sources for fish are particularly vulnerable.

Toxic contaminants. CSO discharges contain whatever has entered the combined sewer from the urban catchment — motor oil, heavy metals, pesticides, pharmaceuticals, industrial discharges. In industrial watersheds, CSO discharges carry significant toxic loads that accumulate in sediments.

Beach and shellfish bed closures. CSO discharges ultimately reach New Jersey’s coastal waters through the estuaries and bays connecting the state’s rivers to the ocean. Raritan Bay, Sandy Hook Bay, and southern Jersey Shore bays receive CSO-contaminated water. Fecal indicator bacteria from CSO events contribute to the beach closures and shellfish harvesting prohibitions that affect the Jersey Shore coastal economy each summer.

Why CSOs are legal

The federal Clean Water Act’s CSO Control Policy, adopted in 1994, recognized that completely eliminating CSO discharges would require infrastructure investments that could not be accomplished overnight. It required communities to implement nine minimum operational controls and develop Long-Term Control Plans (LTCPs) charting a path to water quality standard compliance. The key phrase is “long-term” — LTCPs are allowed to span 20 years or more. Many communities have been revising and extending their plans for decades while CSO discharges continue.

New Jersey’s regulatory framework is administered through the NJ DEP’s NJPDES permit program, which issues permits for each of the state’s 191 outfalls. But enforcement has been limited, LTCP timelines have been extended repeatedly, and the fundamental infrastructure problem remains largely unaddressed in most communities.

Why fixing it is so expensive and so slow

The fundamental solution to combined sewer overflows is separating the combined sewer system — installing separate pipe networks so stormwater no longer enters the wastewater system. In an older urban environment, complete sewer separation requires excavating the streets of the entire combined sewer service area, installing new pipe networks in parallel with existing infrastructure, reconnecting every building, and restoring disrupted streets. In a large city, this work can cost hundreds of millions to billions of dollars and take decades to complete.

Green infrastructure — rain gardens, green roofs, permeable pavement, and bioswales — offers a potentially faster and more cost-effective complement by reducing stormwater volume before it reaches the drain. But even green infrastructure at scale requires significant investment that the most burdened communities — Newark, Trenton, Camden, Paterson — cannot finance independently. State and federal assistance is essential and has been chronically insufficient.