To protect its reservoirs from contamination, and prevent degradation of its water supply, New York City, through the Department of Environmental Protection (NYCDEP) has promulgated revised watershed protection regulations. These regulations strictly control construction, operation and maintenance of wastewater treatment plants (WWTPs) which discharge into city reservoir drainage basins. NYCDEP and Westchester County agreed to undertake a study to determine whether it is feasible to divert wastewater from WWTPs in the County, which currently discharge into the city watershed, to WWTP outside the watershed. The Study Area includes twelve towns in Northern Westchester County.

The study developed seven alternatives for diversion. Four of the alternatives involve in-basin treatment of sewage at new, centrally located WWTPs and discharge of the effluent to the Hudson River. Three involved out-of-basin treatment of sewage at the three Hudson River WWTPs owned by Westchester County - Peekskill, Ossining and Yonkers Joint Treatment.