Facing a chronic problem of raw sewage emptying into city waterways during rainfalls, and struggling to meet health regulations, New York City environmental officials are turning to a new method of treating bacteria in sewage: dumping chlorine into sewer pipes leading to the waterways.

The city’s Department of Environmental Protection has long tried to mitigate the pollution and health risks from the estimated 20 billion gallons per year of untreated sewage that flow into city waterways when treatment systems are overwhelmed during a rainfall.

In recent years, the city has promoted projects like new retention tanks and has planted patches of greenery to lessen the runoff during rainstorms.

But some environmental advocates claim that details have been scant on the city’s plan to disinfect wastewater by chlorinating it inside pipes just before the waste discharges into three bodies of water in Queens and the Bronx.