The Mamaroneck wastewater plant pumped 13.8 million gallons of partially treated sewage into Long Island Sound on Sunday, Sept. 13.

That figure, from an updated NY Alert sent Monday afternoon, nearly tripled the 5 million gallons first reported Sunday morning.

The initial alert went out around 9:30 a.m. Sunday. The revised estimate arrived around 1 p.m. Monday, Sept. 14, as The Rye Record reported. The discharge was disinfected but bypassed the plant's full secondary treatment process.

The revised total makes the Sept. 13 event the largest of four partial-treatment discharges from the plant this summer, based on the reported figures for each incident.

The three earlier releases were an estimated 536,000 gallons on July 21, an estimated 4 million gallons on Aug. 3 and an estimated 5 million gallons on Aug. 20, according to prior Rye Record reporting.

Combined, the plant has sent more than 23 million gallons of partially treated sewage into the Sound since late July.

The plant matters to Rye residents because it handles sewage from many Rye homes, according to Patch.

Elevated bacteria levels from discharges can trigger closures at Rye's public and private beaches along the Sound Shore. The Westchester County Health Department closed Coveleigh Club beach in Rye after rainfall events on July 7, July 22 and Sept. 2 this summer, attributing those closures to bacteria from road runoff.

No beach closure tied specifically to the Sept. 13 discharge had been posted as of Monday afternoon.

The Mamaroneck Water Resource Recovery Facility is undergoing a construction project with about five years remaining. Westchester County's Department of Environmental Facilities (DEF) previously told The Rye Record that when plant flow exceeds 28 million gallons per day, portions bypass secondary treatment.

During construction, the county agreed to issue a NY Alert and a noncompliance report each time wastewater receives only partial treatment.

Westchester County DEF had not publicly addressed the revised 13.8 million gallon figure as of Monday afternoon.