Aquifer-test analysis of the upper aquifer of the Potomac-Raritan-Magothy aquifer system, Union Beach Borough, Monmouth County, New Jersey

Abstract

The hydraulic properties of the upper aquifer of the Potomac-RaritanMagothy aquifer system and of the overlying and underlying confining units were determined by an aquifer test in the vicinity of Union Beach Borough, New Jersey. The April 1986 test included the pumping of 2 test wells for 72 hours at a combined discharge rate of 1,375 gallons per minute, and the measurement of water levels in wells. No single, lateral recharge boundary affected the observed water-level changes. Assuming leaky artesian conditions, the average transmissivity and storage coefficient of the upper aquifer are 7,754 square feet per day and 4.4 x 4 , respectively. The leakance of the combined confining units ranges from 3.0 x 5 to 7.6 x 10 5 feet per day per foot. On the basis of lithologic samples from a recently drilled nearby well, the overlying and underlying confining units were assumed to have similar hydraulic properties. By using this assumption, the vertical hydraulic conductivity of the confining units ranges from 0.010 to 0.027 feet per day. INTRODUCTION Background Because of increasing population and development within the study area (fig. 1), the regional demand for water for public supply, industrial, and agricultural use has increased greatly in recent years. Because of these large withdrawals, ground-water levels throughout the study area have declined considerably, causing significant changes in the regional groundwater flow system. In some areas, water-level declines have caused large cones of depression, the reversal of natural ground-water flow directions, and localized flow of saltwater into freshwater aquifers (Leahy and others, 1987, p. 42). Protection of the ground-water resources of the upper aquifer of the Potomac-Raritan-Magothy aquifer system is a primary concern in the northern Coastal Plain of New Jersey. Saltwater intrusion has caused the closing of five public-supply wells screened in the upper aquifer--three wells in the Borough of Keyport and two wells in the Borough of Union Beach, New Jersey (fig. 1) (Schaefer and Walker, 1981). Additional knowledge of the hydrogeologic conditions in the area is needed to improve understanding of the nature of the intrusion problem. An aquifer test, conducted near Keyport and Union Beach, New Jersey, from April 22 to 28, 1986, was used to estimate (1) the transmissivity, hydraulic conductivity, and storage coefficient for the upper aquifer of the Potomac-Raritan-Magothy aquifer system; (2) the leakance of the confining units; and (3) the location of any aquifer recharge boundaries in the area. 7 4 °1 2 7 4 ° 1 0 ' 7 4 °0 9 ' E X P L A N A T IO N A T ra c e o f h y d ro g e o lo g ic s e c ti o n sh o w n in fi g u re 2.