Evaluation and Management of Nitrate in Ground Water in Suffolk County, New York

Suffolk County, NY contains over 1.4 million people that rely entirely upon ground water as their source of drinking water. Currently, Suffolk County has over 650 active community public supply wells. Since most of Suffolk County (70%) is unsewered, contamination of the underlying aquifers from sanitary wastewater discharged from septic systems and onsite wastewater systems is of concern. Because the aquifer is a sole source aquifer, several planning studies have been conducted since the 1950s to manage and protect the ground water resources of the county. The protection of water supply recharge areas began on a local level in Suffolk County in the late 1970s, and included the establishment of ground water management zones throughout the county. In an effort to protect the aquifer from excess nitrate/nitrogen contamination, Suffolk County regulations were established on January 1, 1981 that restrict density and lot sizes for single family homes (and equivalent commercial densities) in the absence of a community sewage system.

 

Currently, the Suffolk County Department of Health Services (SCDHS) and the Suffolk County Water Authority are developing a Comprehensive Water Resources Management Plan to effectively manage and protect ground water resources. This management plan utilizes numerous tools that the county has developed over the last several years including complex three-dimensional ground water models, GIS-based applications and water quality databases that contain ground water nitrate/nitrogen data that have been collected since the 1950s.

 

Water quality analyses suggest that ground water nitrate/nitrogen concentrations are directly correlated to land use and more specifically, development density. Areas of increased development density have shown increased nitrate concentrations in ground water, supporting the residential and commercial density restrictions in unsewered areas. A case study is presented for the Forge River watershed that documents the correlation of nitrate/nitrogen concentrations in ground water to various land uses.