The Mamaroneck Sanitary Sewer District Wastewater Treatment Plant (MMWWTP) by Harbor Island Park on the Boston Post Road in Mamaroneck has released 10,000,000 gallons of partially treated wastewater into the Long Island Sound. The discharge took place on Monday, March 16, 2026 in the evening around 7:00pm. Sewage from Rye homes is handled by both the Mamaroneck plant and the Blind Brook treatment plant in Disbrow Park. The 10 million gallons is an estimate.
The reason given for the discharge was “weather conditions – short term partial blend wet weather event” and the discharge was partially treated with disinfection. The Mamaroneck plant is operated by Westchester County and typically discharges treated effluent through a 60-inch outfall pipe extending approximately half a mile into the Long Island Sound.
Less than two weeks ago, on Thursday March 5, the MMWWTP released over 18 million gallons of partially treated wastewater.
The disclosure was made under the 2013 Sewage Pollution Right to Know Act (SPRTK) rules administered by the New York State department of Environmental Conservation (NYDEC). Notifications of sewage discharges help the public avoid boating, fishing or swimming in waterbodies that may contain illness causing bacteria. Especially in the summertime, high bacteria counts will lead to beach closures for both public and private beaches in Rye and along the sound shore.
