At a Glance

A stormwater retrofit plan informs and empowers 12 New York municipalities to begin implementing measures to reduce phosphorus in drinking water sources.

Project Description

The Croton and Kensico Reservoirs are significant sources of unfiltered drinking water for New York City. Because phosphorus is a primary pollutant of concern in both reservoirs, the Municipal Separate Storm Sewer System (MS4) General Permit for Stormwater Discharges within the drainage basin requires municipalities to develop and implement stormwater retrofit programs.that will meet annual phosphorous reduction targets set in the Croton Watershed Phase II Phosphorus Total Maximum Daily Load (TMDL) Implementation Plan.

Biohabitats, in association with O’Brien & Gere, Hahn Engineering, and Insite, developed a regional stormwater retrofit program, with a five-year implementation schedule and budget, for the 12 municipalities within the Westchester County portion of the reservoir drainage basins.

Biohabitats developed desktop analysis and field evaluation plans that were utilized to identify and assess over 250 stormwater retrofit opportunities across the 12 municipalities. Biohabitats also developed and applied a total phosphorus accounting methodology to determine the potential reduction associated with the suite of stormwater retrofit opportunities. These opportunities included structural stormwater practices, non-structural stormwater practices, and stabilization of drainage channels. Biohabitats then ranked and prioritized the stormwater retrofits based on total phosphorus reduction, cost effectiveness and feasibility. The results of this prioritization were used to develop the five-year implementation plan, which was accepted by New York State Department of Environmental Conservation as meeting MS4 permit requirements.



Hudson River

Physiographic Province

New England


Croton-Kensico Reservoirs

Expertise Areas

Ecological Restoration, Infrastructure, Water


Town of Somers


Westchester County, New York, United States