The Mamaroneck Wastewater Treatment Plant pumped an estimated 4 million gallons of partially treated sewage into Long Island Sound over a 24-hour period ending Monday morning. The latest discharge comes less than two weeks after the plant pumped 536,000 gallons into the sound on July 21.
The overflow of sewage at 199 West Boston Post Road has been caused by the ongoing rainy conditions. The facility is undergoing construction, which is expected to continue for the next five years. Westchester County’s Department of Environmental Facilities (DEF) told The Record that when the plant flow exceeds 28 million gallons per day, portions of the flow bypass the facility’s secondary treatment process.
“These flows are blended with flow that receives full secondary treatment. All flow is fully disinfected prior to discharge,” County Deputy Communications Director Carolyn Fortino told The Record, relaying a message from the DEF. “The plant flow under these elevated flow conditions receives primary treatment and partial secondary treatment; it is fully disinfected, and the effluent released is treated.”
During this construction phase, the county agreed to issue a NY Alert and a report of noncompliance when wastewater receives only partial treatment.
“When the construction is completed, we will revert back to our permit requirements, which require us to bypass secondary treatment and provide Partial Secondary Blending when the secondary flow is above 40 MGD,” the DEF said.
In the event of partially treated discharge, like what occurred on July 21 and Aug. 3, samples are taken from the water and tested. Following the July 21 incident, the state’s Department of Environmental Conservation said impact to public areas was still unknown.
However, even mild rainfall has caused frequent closures to area beach clubs. About 1.75 inches of rain fell Sunday into Monday, leading the Westchester County Department of Health to close the Coveleigh Club beach Tuesday and Wednesday, along with other beach clubs in Mamaroneck and New Rochelle. The Coveleigh Club beach in Rye has now been closed five of the past 18 days.
On July 19, 20, and 22, the county health department also temporarily shut down Harbor Island Park, Beach Point Club, Orienta Beach Club, and Mamaroneck Beach and Yacht Club in Mamaroneck, citing “bacterial contamination from road runoff into drainage outfalls near these beaches.”
Under county health protocols, those clubs’ beaches must close for one day after half an inch of rain and for two days after one inch of rain. In the event of two or more inches of rain, the length of the closure is to be determined.
Wastewater pollution continues to be an issue on the sound shore particularly after heavy rainfall, which often causes sewer systems to overflow and run into the Long Island Sound.
When wastewater enters the sound it introduces heightened levels of nitrogen, which then causes algal blooms to grow and release toxins that are harmful to animals and people. Additionally, once the blooms die they remove oxygen from the water, which can kill aquatic life.
Earlier this year, the Rye City Council voted to join the Long Island Sound Watershed Intermunicipal Council in an effort to collaborate with neighboring communities, including Mamaroneck, on best practices to mitigate wastewater pollution.
The move came after the Mamaroneck plant released 28 million gallons of partially treated wastewater into the sound in two separate occasions in March.
Last year, the county completed a $7 million project to upgrade the Mamaroneck plant, which entailed restoring the corrosion sustained by the outfall pipe that extends a half mile out into the sound.
