SUSTAINABILITY OF POTABLE AND ECOLOGICAL WATER SUPPLIES, CAPE MAY COUNTY, NEW JERSEY

The potable and ecological water supplies of Cape May County, New Jersey are threatened by excessive withdrawals from public-supply wells in shallow aquifers that are both too close to each other and to the 250 milligrams per liter (mg/L) chloride isochlor. Water supply withdrawal in the County is about 8.2 billion gallons per year (Bgal/yr) and is expected to be about 11.7 Bgal/yr at full build out, about 2050. Cape May County communities have individually dealt with potable water-supply sustainability problems since 1910 by abandoning salt water intruded supply wells; drilling wells inland of the shore; drilling deeper wells; building dams to cause fresh water spreading and to prevent salt water tidal flooding ; employing aquifer storage and recovery via well injection; and building New Jersey's first desalination plant. Today, salt-water intrusion within the Cohansey aquifer is threatening the public-supply well fields for Wildwood and Lower Township. Selected monitoring wells in the Cohansey Aquifer on the Delaware Bay side of Cape May County show chloride concentrations that increase about 100 mg/L each year. The ecological water supply is sustained by government and ecological organizations that preserve land in refuges and promote regulations to protect the supply. The US Geological Survey in cooperation with the County and New Jersey Department of Environmental Protection (NJDEP) is investigating potable water-supply alternatives that include: well relocation to the interior of the county, well nests with wells in different aquifers, wells nest that are separated from one another, locating more wells in deep aquifers, expand the use of desalination, and injection of highly purified waste-water into shallow aquifers to create a barrier to saltwater intrusion. The USGS will simulate six local and three regional ground-water withdrawal options using density dependent solute transport techniques (SEAWAT) for the shallow aquifers and particle tracking techniques (MODFLOW) for the deep aquifers. The simulations will determine rates of saltwater intrusion and fresh surface-water depletion. The NJDEP will evaluate the rates of intrusion and depletion and determine if such rates are sustainable for future potable and ecological water supplies needs.