Groundwater Supply System

Groundwater service area map

Between 1887 and 1996, the privately owned Jamaica Water Supply Company (JWS) operated a group of wells that served the communities of southeastern Queens and portions of Nassau County. In 1996, New York City purchased the Queens portion of the JWS and took responsibility for the delivery of drinking water to those communities served by the groundwater wells. After acquiring the JWS wells, the Department of Environmental Protection (DEP) renamed the group of wells the groundwater supply system.

Located in southeastern Queens, the groundwater supply system consists of 67 supply wells at 43 well stations and several water storage tanks. Most of the system has not operated in more than 14 years, but the groundwater system did provide water to a limited portion of the city’s distribution system in Queens until 2007. When online, residents within the service area received groundwater or a mix of ground and surface waters depending on demand and supply availability.

For more information about New York City’s Drinking Water Supply, visit Drinking Water.

Wells in Operation

There were no wells in operation in 2019. Download the List of Wells.


An aquifer is a natural underground layer of porous, water-bearing materials (sand, gravel) usually capable of yielding a large supply of water. Three aquifers run the length of Long Island, which includes Brooklyn and Queens Counties: the Upper Glacial, which is the shallowest; the Magothy, which is the middle layer; and the Lloyd, which is the deepest. Formed approximately 60 million years ago, the three aquifers are separated by layers of clay.

Download the Cross-Section of Brooklyn and Queens Aquifer Diagram

Treatment Information

All groundwater entering New York City’s distribution system is treated with chlorine, fluoride, food grade phosphoric acid, and, in some cases, sodium hydroxide. New York City uses chlorine to meet the New York State Sanitary Code and federal Safe Drinking Water Act disinfection requirements. Fluoride, at a concentration of approximately 0.7 part per million, is added to help prevent tooth decay and has been added since 1966 in accordance with the New York City Health Code. Phosphoric acid is added to create a protective film on pipes that reduces the release of metals such as lead and copper from household plumbing. Additionally, a sequestering phosphate is applied at several wells to prevent the precipitation of naturally occurring minerals, mostly iron and manganese, in the distribution mains and customers’ household piping. Air stripper facilities can be operated at several wells to remove volatile organic compounds (VOCs).

Operational Information for 2019

Water Quality Data

Index Numbers

DEP assigns index numbers to sampling locations throughout the distribution system. The nomenclature of the index for a well sample location signifies the status of the water at a specific tap. An index number followed by the letters E, F or T denotes sampling sites that are treated, or finished groundwater. Well index numbers that have no letter after the number, or are followed only by the letters A, B, C, D, I or S are considered untreated, or raw water. Examples of untreated water IDs are W5 and W23A.  Examples of treated water are W5E and W23AT. The following table illustrates this in greater detail:

Index Numbers Description
W##, W##A-D, I, S Groundwater wells sampling points prior to final treatment
W##E Effluent finished groundwater from wells with air-stripping
W##F Finished groundwater effluent from wells without any special treatment
W##T Treated finished groundwater effluent from sequestering/iron treatment wells

Data Tables and Graphs

There were no wells in operation in 2019; therefore there are no 2019 Groundwater Supplemental data available.