New Jersey Water Science Center
This publication is downloadable in PDF format.
To view or print PDF files, the freely downloadable Adobe Acrobat Reader® may be used.
Cape May County is investigating the feasibility of restoring the lowermost reach of Cox Hall Creek to its former state as a tidal saltwater wetland; however, the potential for contamination of the shallow ground-water system, which provides water to hundreds of nearby privately owned domestic wells, with saltwater from the restored wetland is of particular concern. To evaluate the potential effectiveness and risks of restoring the saltwater wetlands, the County needs information about the hydrogeologic framework in the area, and about the potential vulnerability of the domestic wells to contamination.
The shallow ground-water system in the Cox Hall Creek area consists of unconsolidated Holocene and Pleistocene deposits. The Holly Beach water-bearing zone, the unconfined (water-table) aquifer, is about 35 feet thick and contains a 2- to 4-foot-thick clay lens about 10 feet below land surface; a lower, more discontinuous clay lens about 30 to 35 feet below land surface ranges up to 5 feet in thickness. A 75-foot-thick confining unit separates the Holly Beach water-bearing zone from the underlying estuarine sand aquifer. The clay lenses in the Holly Beach water-bearing zone likely retard the movement of contaminants from septic tanks, lawns, and other surficial sources, protecting wells that tap the lower, sandy part of the aquifer.
The clay lenses also may protect these wells from salty surface water if withdrawals from the Holly Beach water-bearing zone are not increased substantially. Deeper wells that tap the estuarine sand aquifer are more effectively protected from saltwater from surface sources because of the presence of the overlying confining unit.
Abstract
Introduction
Purpose and Scope
Previous Investigations
Methods of Investigation
Ground-Penetrating-Radar Surveys
Interpretation of Natural Gamma-Ray Geophysical Well Log
Review of Well Drillers’ Logs
Hydrogeologic Framework
Holly Beach Water-Bearing Zone
Confining Unit Overlying the Estuarine Sand Aquifer
Estuarine Sand Aquifer
Effect of Clay Lenses and the Confining Layer on Potential Vulnerability of Wells to Contamination
Summary
Acknowledgments
References Cited
Download: PDF of OFR2006-1044 (1.4Mb).
U.S. Department of the Interior | U.S. Geological Survey
Persistent URL: http://pubs.water.usgs.gov/ofr20061044
Page Contact Information: USGS Publishing Network
Page Last Modified: Saturday, 12-Jan-2013 22:05:12 EST
