Watersheds and Water Supply

The Town’s major streams and trib­u­taries include the Saw Mill Riv­er and Kisco Riv­er. The Town is locat­ed with­in four major water­sheds: the Pocantico/​Saw Mill Riv­er Water­shed, the Bronx Riv­er Water­shed, the Long Island Sound Water­shed and the Cro­ton (Riv­er) Water­shed as well as many small­er water­sheds includ­ing the Indi­an Brook Basin, the Cor­nell Brook Basin and the Ged­ney Brook Basin, among oth­ers. The Cro­ton Water­shed, which encom­pass­es 63% (9,413 acres) of the Town’s land area, sup­plies a por­tion of New York City’s drink­ing water, and as such, the area of New Cas­tle that falls with­in in it is sub­ject to height­ened NYS­DEC Munic­i­pal Sep­a­rate Storm Sew­er Sys­tem (MS4) Per­mit require­ments and oth­er reg­u­la­tions as dic­tat­ed by the New York City Depart­ment of Envi­ron­men­tal Pro­tec­tion (NYCDEP). Much of the devel­op­ment with­in this water­shed is also sub­ject to review and per­mit­ting by the NYCDEP through author­i­ty grant­ed to them in the 1997 New York City Water­shed Agree­ment. This agree­ment was estab­lished to pro­tect New York City’s drink­ing water while bal­anc­ing local gov­ern­ments’ abil­i­ty to con­trol land use. 

In 1993, New Castle’s water fil­tra­tion plant was put online and the Town’s water dis­tri­b­u­tion net­work was sig­nif­i­cant­ly expand­ed. Today, there are few­er house­holds that rely on ground­wa­ter wells for drink­ing water than there were at the writ­ing of the TDP. How­ev­er, for those house­holds that rely on ground­wa­ter, and for the envi­ron­men­tal health of the region at large, mea­sures tak­en in the Town to address ground­wa­ter pol­lu­tion and to mit­i­gate the effects of stormwa­ter runoff on water qual­i­ty con­tin­ue to pro­mote sig­nif­i­cant envi­ron­men­tal ben­e­fits. New Castle’s ground­wa­ter is sup­plied large­ly by aquifers and aquifer recharge areas under­neath the sur­face of the earth. The soils that cov­er these aquifers have a high per­co­la­tion rate and are recharged by rain­wa­ter and stormwa­ter. As such, these soils can eas­i­ly trans­mit water con­tain­ing pol­lu­tants to the aquifers and into the ground­wa­ter. Ground­wa­ter pol­lu­tants often go unde­tect­ed, and even after they have been dis­cov­ered, can be hard to remove. The TDP rec­om­mend­ed that aquifers be pro­tect­ed and reg­u­lat­ed in the Town the same way streams and wet­lands were, but con­ced­ed that a detailed hydro­ge­o­log­i­cal study (includ­ing the map­ping of pri­vate wells) would be need­ed to iden­ti­fy and delin­eate major aquifers. This Plan rec­om­mends con­duct­ing such a study as part of mit­i­gat­ing the neg­a­tive impacts of stormwa­ter runoff and pol­lu­tants, plan­ning for a last­ing potable water supply.