Sole Source Aquifers: A Lifeline for Many New Yorkers

Long Island may be surrounded by water, but would it surprise you to know that our drinking water only comes from beneath the surface? Specifically, there are only three geologic regions on Long Island from which we obtain our water, and over 2.8 million people rely on them for daily use. These regions are known as aquifers.

What Is an Aquifer?

An aquifer is a natural storage area for water composed of porous rock and/or sediment like sand and gravel. Aquifers are naturally sealed by impermeable rock layers, making them suitable sources of clean, usable water. Aquifers are vital for human survival in many places, which is why sole source aquifers exist.

What Is a Sole Source Aquifer?

Sole source aquifers (SSAs), as defined by the Environmental Protection Agency (EPA), exist when there are no alternatives for drinking water should an aquifer be contaminated. A SSA also provides at least 50% of an area’s drinking water.

The importance of SSAs cannot be understated, which is why the EPA created the SSA Program, a program designed to keep these aquifers clean. The program establishes which aquifers are considered sole source, limiting the types of projects that can be undertaken if in proximity of a SSA so as to prevent contamination.

About Long Island’s Aquifers

Long Island’s geology is naturally suited for the creation and preservation of aquifers, a unique and important geological feature of the region. As mentioned previously, there are three aquifers Long Islanders utilize:

1. Upper Glacial Aquifer

The Upper Glacial Aquifer (UGA) is the youngest and closest to the surface of the three. It derives from the Pleistocene age (2 million–12,000 years ago).

With the island’s geological structures sloping southwards, the depth of the UGA ranges from the surface on the north shore to around several hundred feet below grade on the south shore of the island. As its name suggests, this aquifer originated when the glaciers covering Long Island retreated, and subsequently deposited the sediments that would comprise the UGA.

2. Magothy Aquifer

Long Island’s other two aquifers are much older, with their origins dating back to the Cretaceous period (135–66 million years ago).

The Magothy Aquifer is situated below the UGA, and its depth ranges from several feet below the surface in the north to over 1,000 feet in the south.

3. Lloyd Aquifer

The Magothy Aquifer is underlain by the Lloyd Aquifer. The Lloyd Aquifer is the oldest of the three, and has a depth ranging from 400 feet in the north to over 2,000 feet in the south.

Thanks to a crystalline basement underlying the Lloyd Aquifer, all three aquifers are enclosed and hold an enviable amount of fresh water.

Protecting Our Aquifers

Since so many rely on Long Island aquifers, the aquifer system is labeled a sole source aquifer. As the area is becoming more and more developed, heightened caution around overuse and extra concern about what contaminants are making their way into our groundwater is warranted.

Roughly 20% of water pumped from the aquifers is pumped back down to ensure the water source does not run dry.

Precipitation helps to return water to the aquifers, but increased development on the island leads to an increase of impermeable surfaces, meaning more water runs off to surface water like rivers and streams, and less water is returning to the ground.

When more than 375 million gallons are used daily, and the number is only increasing, it is imperative that we protect Long Island aquifers from contamination. Walden’s experienced staff of engineers, geologists, and scientists are well versed in groundwater investigations and remediation. Call our water quality experts today at 516-559-6976 to learn more.