Environmentalists raise concerns after wastewater plant spill near Riverdale

A sewage spill sent millions of gallons of partially treated wastewater into the Hudson River over the Fourth of July weekend, according to Westchester County. The Yonkers Joint Wastewater Treatment Plant sits less than a mile from Riverdale, where experts say water and any contaminants it carries moves beyond municipal boundaries.

The county-owned facility at 1 Fernbrook St. is just north of the intersection of Riverdale Avenue and West 261st Street at the Bronx-Westchester border. Westchester County warned residents to avoid contact with the Hudson River, and New York City issued an advisory due to the plant’s close proximity to the Bronx.

The Riverdale Press asked the New York City Department of Environmental Protection whether the city conducted water quality testing. The department referred questions to the city’s department of health and mental hygiene, which did not respond before press time.

Riverkeeper, a nonprofit organization that advocates for the protection of the Hudson River and monitors water quality, said the river’s tidal nature means pollution is not confined to one location.

“The Hudson River is an estuary,” said Dan Shapely, senior director of advocacy, policy and planning at Riverkeeper. “It flows north with the tides, it flows south with the tides. A discharge like this is going to affect both upstream and downstream because of the tidal nature of the river.”

Westchester County spokesperson Catherine Cioffi said the spill began shortly after midnight July 4, after Con Edison implemented a system-wide voltage reduction because of high electricity demand in a heatwave, causing the treatment plant to lose power. The lower voltage placed significant strain on critical treatment equipment, causing the backup system to fail, according to Cioffi. 

“The on-site generators require a 30-second power outage before they engage and power the plant,” Cioffi said. “As the power was reduced and not terminated, the generators did not engage. “

Cioffi also said operators first tried switching to the plant’s second utility feeder — one of two separate power lines serving the facility — but the ongoing voltage issues prevented that fix from working. Power was eventually restored to the plant’s primary treatment system, but attempting to bring secondary treatment equipment online triggered another outage.

Crews ultimately restored operations by dividing the electrical load between utility power and three mobile generators already on site for a construction project. Primary and secondary treatment returned to service by approximately 1:45 p.m., while full utility power from both Con Edison feeders was not restored until July 6, according to Cioffi.

“The reason this work took the time required to complete it was that this is the first time this type of event occurred at our facility and it had to be thoroughly investigated before bringing back our equipment on-line,” Cioffi said, adding it required hazardous work with high voltage equipment.

A spokesperson for Con Edison said there had been an 8 percent voltage reduction in the area because of increased power use.

Electricians have since reconfigured the plant’s power supply to better handle voltage fluctuations and are reviewing the incident with Con Edison. Cioffi also noted the county is moving forward with a long-planned overhaul of the plant’s electrical system, much of which dates to 1972.

For Robert Fanuzzi, president of the Bronx Council for Environmental Quality, the spill exposed a different consequence of increasingly frequent extreme heat.

“This is a wake-up call for one of the unexpected impacts of climate change. It’s the failure of critical infrastructure,” Fanuzzi said. “This was a case in which our energy resources met the increased temperatures caused by climate change, and we didn’t make the grade. We weren’t ready, and the water suffered.”

He said the nearly 14-hour disruption raised questions about whether the plant was adequately prepared for a prolonged electrical emergency.

The Center for the Urban River at Beczak, an environmental research center operated by Sarah Lawrence College in Yonkers, said the incident highlighted the need for greater transparency about water quality in the Hudson.

Researchers at the organization began sampling the river July 6 at several locations, including near the former Domino Sugar property, located less than a mile north of the wastewater treatment plant.

Ryan Palmer, the center’s director, said the sample collected near that site measured 183 colony-forming units of bacteria per 100 milliliters of water. The Environmental Protection Agency recommends levels remain below 60 colony-forming units per 100 milliliters for a single recreational water sample. By later in the week, however, all of the group’s sampling sites had fallen below that threshold.

“The Hudson is a super dynamic system,” Palmer said. “The tides, the wind and the sunlight all affect how long bacteria persist and how far they travel.”

Although Westchester County described the release as “partially treated” wastewater, Palmer said that does not eliminate the health risks. Contact with contaminated water can expose swimmers to disease-causing bacteria and other pathogens, particularly if water is swallowed or enters cuts or the eyes, he said.

Riverkeeper did not collect samples during the spill itself, but Shapley said years of monitoring combined sewer overflows have shown bacteria levels typically spike after sewage discharges before declining within several days.

To Fanuzzi, the July 4 failure serves as a prompt for agencies to look beyond repairing the plant itself and consider how extreme heat from climate change is testing infrastructure across the region.

“We absolutely need to think about creating reliable and overly-redundant energy sources for critical infrastructure, especially those that are on the waterfront,” he said. “We can’t allow the water to become the dumping ground for failures on land.”