The source of the Locust Valley Water District’s groundwater is the Upper Glacial, North Shore, and Lloyd Aquifers, which are situated deep beneath the earth’s surface. Approximately 90 percent of what is pumped by the Locust Valley Water District to meet consumer demand is drawn from the Lloyd/North Shore Aquifer, with the remaining coming from the Upper Glacial layer.
The Locust Valley Water District currently obtains its entire potable water supply from the North Shore, Lloyd and Upper Glacial formations through six supply wells drilled at six individual plant sites throughout its service area.
The middle layer and largest of all the formations is the Magothy Aquifer: Running from 200 to 1,000 feet deep, this layer of sand, gravel and silt was deposited about 60 million years ago. The majority of Nassau-Suffolk’s public drinking water, which can be as much as 1,000 years old, is drawn from here.
Between the Magothy Aquifer and the third, deepest layer is a Raritan clay layer. Most scientists believe that gaps in this section allow some exchange of water between the two aquifers.
The deepest and least-used layer is the Lloyd/North Shore Aquifer. Beginning 600 feet below the surface, this 200-foot layer is more than 1,800 feet deep at points and holds the oldest groundwater water, some of it precipitated more than 5,000 years ago!