The Mamaroneck wastewater plant pumped 5 million gallons of partially treated sewage into Long Island Sound on Aug. 20, marking the third and largest such discharge this summer from the facility that handles waste from Rye homes.
The release began around 8:20 p.m. during heavy rainfall, according to a NY Alert notification reported by MyRye.com. The plant, operated by Westchester County at 199 West Boston Post Road in Mamaroneck, cited "weather conditions – short term partial blend wet weather event" as the cause. The wastewater was disinfected but did not receive full secondary treatment before being pushed through a 60-inch outfall pipe extending roughly half a mile into the Sound.
Nearly 10 million gallons in August alone
The Aug. 20 event caps an escalating pattern. The Rye Record reported three discharges this summer: 536,000 gallons on July 21, 4 million gallons on Aug. 3 and now 5 million gallons on Aug. 20. The August total alone approaches 10 million gallons.
Westchester County's Department of Environmental Facilities told the Rye Record after the Aug. 3 discharge that when plant flow exceeds 28 million gallons per day, portions of the flow bypass secondary treatment. The facility is undergoing a construction project expected to last five years, and the county agreed to issue a NY Alert and file a noncompliance report each time wastewater receives only partial treatment.
Rye beach closures a recurring concern
Sewage from Rye homes flows to both the Mamaroneck plant and the Blind Brook treatment plant in Disbrow Park. When bacteria counts spike after discharges, the Westchester County Department of Health closes beaches along the Sound Shore.
Coveleigh Club Beach in Rye has already been shut down multiple times this summer. The county closed it July 7–8 after nearly two inches of rain, again July 19–20 after more than 1.8 inches and once more on July 22. After the July 21 discharge of 536,000 gallons, the Health Department also closed Coveleigh Club Beach, according to Patch.
The county's rainfall thresholds for closures are straightforward: more than half an inch triggers a one-day closure, more than one inch triggers two days and anything above two inches is evaluated case by case.
No closure announced yet
No beach closure announcement tied specifically to the Aug. 20 discharge had been posted as of Friday, Aug. 21. The disclosure was made under New York's 2013 Sewage Pollution Right to Know Act, which requires public notification so residents can avoid swimming, boating or fishing in affected waters.
No public meeting addressing the Mamaroneck plant's discharge pattern or construction timeline has been announced.
