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Geohydrology of the Englishtown Formation in the northern Coastal Plain of New Jersey

Water-Resources Investigations Report 76-123

Prepared in cooperation with the New Jersey Department of Environmental Protection, Division of Water Resources
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Abstract

The Englishtown Formation of the Matawan Group of Late Cretaceous age is exposed in the western part of the New Jeresy Coastal Plain along a northeast-southwest trending zone extending from Raritan Bay to Delaware Bay. In outcrop, in the northern part of the Coastal Plain, the Englishtown typically consists of a series of thin, cross-stratified, fine- to medium-grained lignitic quartz sand beds intercalated with thin beds of sandy silty clay and clayey silt, ranging in total thickness from about 140 feet (43 meters) near Raritan Bay to about 50 feet (15 meters) near Trenton. In the subsurface of the northern part of the Coastal Plain, the formation retains most of the lithologic characteristics displayed in outcrop. In northern and eastern Ocean County the Englishtown can be subdivided into three distinct lithologic units; upper and lower units of quartz sand with thin interbeds of dark sandy silt, separated by a thick sequence of sandy and clayey lignitic silt. The confined part of the aquifer in the Englishtown Formation is utilized as a source of water over an area of about 1,100 square miles (2,849 square kilometers) of the New Jersey Coastal Plain and is an important source of supply in Monmouth and northern Ocean Counties. The annual average rate of withdrawal from the aquifer in the two-county area increased from 5.5 million gallons per day (0.24 cubic meters per second) in 1959 to 9.5 million gallons per day (0.4 cubic meters per second) in 1970. Water levels in parts of this area were declining 8 to 12 feet (2.4 to 3.6 meters) per year as of 1970 and they declined as much as 140 feet (43 meters) between 1959 and 1970 near pumping centers. The aquifer transmissivity ranges from 2,400 square feet per day to 650 square feet per day (223 square meters per day to 60 square meters per day); the estimated hydraulic conductivity ranges from about 11 feet per day to 20 feet per day (3.3 meters per day to 6.1 meters per day); and the storage coefficient ranges from 8 x 10-5 to 3 x 10-4. The underlying and overlying confining beds, which have an average thickness of 200 feet (61 meters) and 40 feet (12 meters), respectively, have vertical hydraulic conductivities on the order of 1 x 10-5 feet per day (3 x 10-6 meters per day) and specific storage on the order of 8 x 10-5 ft-1 (2.4 x 10-5 m-1). The Englishtown aquifer is an integral part of the complex multi- aquifer system of the New Jersey Coastal Plain. The withdrawal of water from the Englishtown aquifer has had a marked effect on the water level in the overlying Moutn Laurel aquifer, and these effects will continue so long as the water level in the Englishtown continues to decline. Any increase in the development of the Mount Laurel aquifer that reduces the volume of leakage to the Englishtown will cause an increase in the rate of water-level decline in the Englishtown even with no increase in direct withdrawals. The interrelationship and interdependency between pumping stresses in individual aquifers within the complex Coastal Plain aquifer sytem must be recognized and appreciated, and the hydrodynamics of all parts of the system must be considered if reliable predictions of aquifer response to these stresses are to be made. Such predictions generally require a simulation model analysis of the system.

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Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Geohydrology of the Englishtown Formation in the northern Coastal Plain of New Jersey
Series title:
Water-Resources Investigations Report
Series number:
76-123
Year Published:
1977
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Trenton, NJ
Contributing office(s):
New Jersey Water Science Center
Description:
vi, 62 p.
Country:
United States
State:
New Jersey
Online Only (Y/N):
Y