Drinking Water

We all know that our drinking water comes out of the faucet, and is supplied by pipes, usually in the basement of a house or business. Depending on where you are in Gloucester County, these pipes are either hooked into a public water supply system – pipes running under the streets – or they come directly from an individual pump and well on the property itself.

Both the public-supply system and private wells draw water from the ground. When it rains, water percolates, or seeps, down through the topsoil into the underlying layers of soil, gravel and sand, filling (saturating) the spaces, or pores, between the sediment particles. This water is called groundwater. There is a vast amount of groundwater found in these underlying layers.

The geology of Gloucester County is that of a tilted “layer cake” or strata of gravels, sands, silts, and clays. The saturated gravel and sand layers, with their large pore spaces, are the aquifers, from which water is drawn through wells. The silt and clay layers, which impede the movement of water, are called confining beds.

Three major aquifers exist beneath Gloucester County. They are the Potomac–Raritan–Magothy (called the PRM), the Wenonah–Mount Laurel, and the Kirkwood–Cohansey. The first two are confined aquifers, meaning that there are layers of less permeable material (silt and clay), which generally isolate the water-bearing layers from each other. These confining layers also protect the aquifer from contamination that might seep down into the groundwater from the land surface. The Kirkwood–Cohansey is close to the surface in eastern Gloucester County. Because it is unconfined, rainwater can get into it easily and re-supply (recharge) the aquifer. This also makes it more vulnerable to surface contamination.

The Coastal Plain Aquifers are not horizontal but tilt to the southeast, getting deeper as they cross Southern New Jersey toward the Atlantic Ocean. Because of this tilting, each aquifer emerges on the land surface in a sequential manner. Water enters (recharges) each aquifer from rainfall directly on its outcrop.1

The PRM yields the most water of the three aquifers and is the primary water supply in the western half of Gloucester County, as well as in Burlington and Camden Counties and across the river in the heavily developed northern part of the state of Delaware. Because it supplies drinking water to so many people, there has been a significant decline in its water levels. This became so serious that the New Jersey Department of Environmental Protection established Water Supply Critical Area #2 in 1986. All water supply companies (companies and municipal utilities) within Critical Area #2 were given annual limits on water withdrawals in the PRM. Usage from the PRM was cut back by over 20 percent and no increases in pumping were allowed.

1. "Information on Gloucester County aquifers comes from an article by Anthony S. Navoy, PhD., U.S. Geological Survey, “Gloucester County Ground-Water Resources and Issues” in the early spring Issue 2001 of Watershed Newsletter; issued by the Federation of Gloucester County Watersheds and the South Jersey Land Trust.

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