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Daryll A. Pope

Publications and source records attributed to Daryll A. Pope.

13 recordsLinked to original sources
USGS2023

Hydrologic effects of possible changes in water-supply withdrawals from, and effluent recharge to, the Kirkwood-Cohansey aquifer system, Winslow Township, Camden County, New Jersey

Winslow Township and the Camden County Municipal Utility Authority (CCMUA) developed a plan to shut down the Winslow sewage-treatment facility and associated effluent infiltration facility and transfer the effluent to the CCMUA sewage-treatment facility on the Delaware River in Camden, New Jersey. Winslow Township reduced groundwater withdrawals from the Kirkwood-Cohansey aquifer system to offset groundwater recharge lost with the cessation of effluent infiltration. The U.S. Geological Survey, in cooperation with Winslow Township and the CCMUA, collected data to evaluate conditions prior to cessation of effluent infiltration and installed two continuous-record streamflow-gaging stations. Streamflow measurements also were made at two low-flow partial-record sites, and groundwater levels were measured in 17 wells at high and low water-level periods (May and September 2010). A groundwater-flow model provides estimated changes in base flow of the Great Egg Harbor River under several groundwater-withdrawal and effluent infiltration scenarios. Water levels were measured in an observation well 480 feet (ft) from the infiltration lagoons during 1971–2010. A downward trend in water levels in the well prior to 1985 is attributed in part to increased impervious surfaces and groundwater withdrawals associated with development in the area that began in the early 1970s. From late 1985 to 2010, there was an upward trend in water levels in the well that is attributed to the construction of nearby effluent infiltration lagoons in 1985 and the increasing rate of effluent infiltration during the period. Recent and historical measurements made at the four surface-water sites were correlated with same-day discharges measured at three nearby index stations to estimate continuous low-flow record at the sites. Effects on base flow caused by reductions in groundwater withdrawals or the cessation of effluent infiltration in Winslow Township could not be ascertained from the available data with the statistical and analysis methods used. Groundwater discharge to streams (base flow) was simulated with a groundwater-flow model of the Great Egg Harbor and Mullica River Basins. Simulated monthly base flows using 2008–10 withdrawal rates and effluent recharge (Scenario 1) are generally about 1.5 million gallons per day (Mgal/d) greater than simulated base flows using 2003–07 withdrawal rates (Baseline Scenario) because of the 1.57 Mgal/d reduction in average withdrawals by Winslow Township from the Kirkwood-Cohansey aquifer system from 2003–07 to 2008–10. Simulated monthly base flows using 2008–10 withdrawals but without effluent infiltration (Scenario 2) are very similar to, but typically slightly lower than, Baseline Scenario base flows. Three hypothetical future distributions of groundwater withdrawals from existing Winslow Township wells are simulated, each without effluent infiltration and using the same groundwater withdrawal rate as Scenario 2, but with different hypothetical distributions of withdrawals among existing Winslow Township wells. The Scenario 3 and 4 base flows are greater than the Baseline Scenario base flows in all months, and the Scenario 5 base flows are less than the Baseline Scenario base flows in all months. The simulation results indicate that a reduction in average withdrawals from the Kirkwood-Cohansey aquifer system by 1.57 Mgal/d offsets the reduction of effluent infiltration by about the same rate, resulting in nearly unchanged base flows in the Great Egg Harbor River near Blue Anchor (01410820).

New Jersey↗
USGS2012

Simulated effects of alternative withdrawal strategies on groundwater flow in the unconfined Kirkwood-Cohansey aquifer system, the Rio Grande water-bearing zone, and the Atlantic City 800-foot sand in the Great Egg Harbor and Mullica River Basins, New Jersey

Groundwater is essential for water supply and plays a critical role in maintaining the environmental health of freshwater and estuarine ecosystems in the Atlantic Coastal basins of New Jersey. The unconfined Kirkwood-Cohansey aquifer system and the confined Atlantic City 800-foot sand are major sources of groundwater in the area, and each faces different water-supply concerns. The U.S. Geological Survey (USGS), in cooperation with the New Jersey Department of Environmental Protection (NJDEP), conducted a study to simulate the effects of withdrawals in the Kirkwood-Cohansey aquifer system, the Atlantic City 800-foot sand, and the Rio Grande water-bearing zone and to evaluate potential scenarios. The study area encompasses Atlantic County and parts of Burlington, Camden, Gloucester, Ocean, Cape May, and Cumberland Counties. The major hydrogeologic units affecting water supply in the study area are the surficial Kirkwood-Cohansey aquifer system, a thick diatomaceous clay confining unit in the upper part of Kirkwood Formation; the Rio Grande water-bearing zone; and the Atlantic City 800-foot sand of the Kirkwood Formation. Hydrogeologic data from 18 aquifer tests and specific capacity data from 230 wells were analyzed to provide horizontal hydraulic conductivity of the aquifers. Groundwater withdrawals are greatest from the Kirkwood-Cohansey aquifer system, and 65 percent of the water is used for public supply. Groundwater withdrawals from the Atlantic City 800-foot sand are about half those from the Kirkwood-Cohansey aquifer system. Ninety-five percent of the withdrawals from the Atlantic City 800-foot sand is used for public supply. Data from six streamgaging stations and 51 low-flow partial record sites were used to estimate base flow in the area. Base flow ranges from 60 to 92 percent of streamflow. A groundwater flow model of the Kirkwood-Cohansey aquifer system, the Rio Grande water-bearing zone, and the Atlantic City 800-foot sand was developed and calibrated using water-level data from 148 wells and base-flow data from 22 gaging or low-flow partial record stations. The Kirkwood-Cohansey aquifer system within the Great Egg Harbor River and the Mullica River Basins was simulated on a monthly basis from 1998 through 2006. An existing regional model of the New Jersey Coastal Plain was revised to provide boundary conditions for the Great Egg Harbor and Mullica River Basin model (referred to as the Great Egg-Mullica model). In the Great Egg-Mullica model, monthly groundwater recharge rates used in the model ranged from 10-15 inches per year in 2001 to 20-25 inches per year in 2005. The mean-absolute error for 10 of the 14 long-term hydrographs used in model calibration was less than 5 ft. Groundwater flow budgets for the Great Egg-Mullica model calibration periods, May 2005 and September 2006, and for the entire model calibration period 1998 to 2006, showed that nearly 70 percent of the water entering the Atlantic City 800-foot sand came from the horizontal connection with the Kirkwood-Cohansey aquifer system in updip areas. The groundwater flow model was used to simulate scenarios under three possible conditions: average 1998 to 2006 withdrawals (Average scenario), full-allocation withdrawals (Full Allocation scenario), and projected 2050-demand withdrawals (2050 Demand scenario). Withdrawals in the Full Allocation scenario are nearly twice the withdrawals from the Average scenario, primarily because of the potential for large agricultural withdrawals if all allocations are used. Withdrawals for the 2050 Demand scenario are about 50 percent greater than those for the Average scenario, primarily due to expected increases in withdrawals for public supply. Monthly base-flow depletion criteria were determined using the Low-Flow Margin method, currently under consideration by NJDEP, to estimate available water on an annual basis at the Hydrologic Unit Code 11 (HUC11) level and to determine whether a water-supply deficit exists. Simulations of various groundwater-withdrawal scenarios were made using the calibrated model, and results were compared with baseline conditions (no withdrawals) to determine where and when base-flow deficits may be occurring and may be expected to occur in the future. Scenarios were simulated to assess base-flow depletion that could occur from different groundwater-withdrawal situations. In the Average scenario, deficits occurred in 7 of the 14 subbasins. In the Full Allocation scenario, deficits occurred in 11 of the subbasins. In the 2050 Demand scenario, deficits occurred in 9 of the 14 subbasins. The largest deficits occurred in the Absecon Creek subbasin because the base-flow depletion criteria for this subbasin is small due to the surface-water diversions that are already occurring there and because existing groundwater withdrawals in the subbasin have resulted in base-flow depletion under current (1998-2006) conditions. Three adjusted scenarios, variations of the Average, Full Allocation, and 2050 Demand scenarios, were simulated; for the adjusted scenarios, the withdrawals were modified in stages with the intent to successively eliminate or minimize the base-flow deficits. Modifications included shifting withdrawals to a deeper part of the Kirkwood-Cohansey aquifer system, implementing seasonal conjunctive use of shallow and deep aquifers, and specifying reductions in withdrawals within a HUC11 subbasin in deficit. The adjusted scenarios are intended to show the relative effectiveness of each of the three approaches in reducing the deficits. Most of the deficits under the Average, Full Allocation, and 2050 Demand scenarios were eliminated by reductions in withdrawals or allocations. Shifting withdrawals to a deeper part of the Kirkwood-Cohansey aquifer system or seasonal conjunctive use did not eliminate deficits for any subbasin. Reductions in withdrawals accounted for more than 95 percent of the total reduction of deficits in all but one subbasin.

New Jersey↗
USGS2009

Future water-supply scenarios, Cape May County, New Jersey, 2003-2050

Stewards of the water supply in New Jersey are interested in developing a plan to supply potable and non-potable water to residents and businesses of Cape May County until at least 2050. The ideal plan would meet projected demands and minimize adverse effects on currently used sources of potable, non-potable, and ecological water supplies. This report documents past and projected potable, non-potable, and ecological water-supply demands. Past and ongoing adverse effects to production and domestic wells caused by withdrawals include saltwater intrusion and water-level declines in the freshwater aquifers. Adverse effects on the ecological water supplies caused by groundwater withdrawals include premature drying of seasonal wetlands, delayed recovery of water levels in the water-table aquifer, and reduced streamflow. To predict the effects of future actions on the water supplies, three baseline and six future scenarios were created and simulated. Baseline Scenarios 1, 2, and 3 represent withdrawals using existing wells projected until 2050. Baseline Scenario 1 represents average 1998-2003 withdrawals, and Scenario 2 represents New Jersey Department of Environmental Protection (NJDEP) full allocation withdrawals. These withdrawals do not meet projected future water demands. Baseline Scenario 3 represents the estimated full build-out water demands. Results of simulations of the three baseline scenarios indicate that saltwater would intrude into the Cohansey aquifer as much as 7,100 feet (ft) to adversely affect production wells used by Lower Township and the Wildwoods, as well as some other near-shore domestic wells; water-level altitudes in the Atlantic City 800-foot sand would decline to -156 ft; base flow in streams would be depleted by 0 to 26 percent; and water levels in the water-table aquifer would decline as much as 0.7ft. [Specific water-level altitudes, land-surface altitudes, and present sea level when used in this report are referenced to the North American Vertical Datum of 1988 (NAVD 88).] Future scenarios 4 to 9 represent withdrawals and the effects on the water supply while using estimated full build-out water demands. In most townships, existing wells would be used for withdrawals in the simulation. However, in Lower and Middle Townships, the Wildwoods, and the Cape Mays, withdrawals from some wells would be terminated, reduced, or increased. Depending on the scenario, proposed production wells would be installed in locations far from the saltwater fronts, in deep freshwater aquifers, in deeper saltwater aquifers, or proposed injection wells would be installed to inject reused water to create a freshwater barrier to saltwater intrusion. Simulations indicate that future Scenarios 4 to 9 would reduce many of the adverse effects of Scenarios 1, 2, and 3. No future scenario will minimize all adverse impacts. In Scenario 4, Lower Township would drill two production wells in the Cohansey aquifer farther from the Delaware shoreline than existing wells and reduce withdrawals from wells near the shoreline. Wildwood Water Utility (WWU) would reduce withdrawals from existing wells in the Cohansey aquifer and increase withdrawals from wells in the Rio Grande water-bearing zone. Results of the simulation indicate that saltwater intrusion and ecological-water supply problems would be reduced but not as much as in Scenarios 5, 7, 8, and 9. In Scenario 5, the Wildwoods and Lower Township each would install a desalination plant and drill two wells to withdraw saltwater from the Atlantic City 800-foot sand. Saltwater intrusion problems would be reduced to the greatest extent with this scenario. Ecological water supplies remain constant or decline from 2003 baseline values. Water-level altitudes would decline to -193 ft in the Atlantic City 800-foot sand, the deepest potentiometric level for all scenarios. In Scenario 6, Lower Township would build a tertiary treatment system and drill three wells open to the Cohanse

New Jersey↗
USGS2006

Simulation of proposed increases in ground-water withdrawals on the Atlantic City 800-foot sand, New Jersey Coastal Plain

The confined Atlantic City 800-foot sand and the unconfined Kirkwood-Cohansey aquifer system (surficial aquifer) are major sources of water for southeastern New Jersey. Because of recent concerns about streamflow depletion resulting from ground-water withdrawals and the potential ecological effects on stream habitat in the area, the focus on future withdrawals has been shifted away from the surficial aquifer to the confined Atlantic City 800-foot sand until the effects of increased withdrawals from the surficial aquifer can be investigated. A study was conducted to evaluate the effects of seven proposed increases in ground-water withdrawals from the Atlantic City 800-foot sand and the Kirkwood-Cohansey aquifer system on the Atlantic City 800-foot sand. The proposed withdrawals are increases above the 2004 allocated rates (full allocation). The effects of full-allocation ground-water withdrawals and the cumulative effect of withdrawals for each of seven proposed increases in withdrawals were simulated using three previously published ground-water flow models: the New Jersey Coastal Plain Regional Aquifer System Analysis model, the Coastal Plain Optimization model, and a model of the Atlantic City 800-foot sand in Atlantic County, New Jersey. These models were used to simulate changes in water levels, the source supplying the increased ground-water flow, and the effects on saltwater movement towards production wells in Cape May County as a result of the proposed increased withdrawals at proposed or existing wells. The results of the simulations represent the effects of the proposed increase from full-allocation withdrawals to an additional 1,825 Mgal/yr (million gallons per year) from the Atlantic City 800-foot sand and an additional 1,045 Mgal/yr from the deep part of the Kirkwood-Cohansey aquifer system near the updip limit of the Atlantic City 800-foot sand. Most of the simulated decline in water levels in Atlantic County occurred as the result of the proposed increased withdrawals simulated for the New Jersey American Water Company wells. Simulated declines in water levels in Cape May were caused mainly by the simulated increased withdrawals for the Cape May City Desalination Plant wells. The additional water to supply the proposed increases in the scenarios was primarily horizontal flow from the unconfined updip part of the Kirkwood-Cohansey aquifer system, which accounted for 63 percent of the inflow, and flow from the overlying Kirkwood-Cohansey aquifer system into the Atlantic City 800-foot sand, which supplied 27 percent of the additional water. Because the withdrawals were made from the confined aquifer and the deeper part of the unconfined aquifer, the effect on streamflow was substantially less than would have occurred had the withdrawals been made directly from the shallower parts of the unconfined aquifer. The travel times from the 250-mg/L isochlor to production wells in Stone Harbor were longer as a result of all the additional withdrawals. For some scenarios, withdrawals in Atlantic County caused the saltwater to move slightly faster towards the production wells. These effects were offset by the increase in travel time caused by the potential increased withdrawals simulated for the Cape May City desalination wells, which either diverted water towards the desalination wells or increased the travel time towards production wells.

New Jersey↗
USGS2005

Use of a ground-water flow model to delineate contributing areas to the Puchack Well Field, Pennsauken township and vicinity, Camden county, New Jersey

The New Jersey Department of Environmental Protection (NJDEP) Well Head Protection Program, developed in response to the 1986 Federal Safe Drinking Water Act Amendments, requires delineation of Well Head Protection Areas (WHPA's), commonly called contributing areas, for all public and non-community water-supply wells in New Jersey. Typically, WHPA's for public community water-supply wells in New Jersey are delineated using a two-dimensional ground-water flow model incorporating the regional hydraulic gradient; however, NJDEP guidelines allow for the use of a three-dimensional flow model to delineate contributing areas to wells in complex hydrogeologic settings. The Puchack well field in Pennsauken Township, Camden County, N.J., is an area of strong hydraulic connection between the Lower aquifer of the Potomac-Raritan-Magothy aquifer system and the Delaware River. Interactions among and within the public-supply well fields in the area are complex. To delineate the contributing area to the Puchack well field, the U.S. Geological Survey, in cooperation with the NJDEP, developed an 11-layer ground-water flow model of the Potomac-Raritan-Magothy aquifer system in the Pennsauken Township area to simulate flow in the vicinity of the well field. The model incorporates the interaction between the aquifer system and the Delaware River, and includes boundary flows from an existing regional model of the Camden area. Recharge used in the model ranged from 4.5 to 14 inches per year, and horizontal hydraulic conductivity ranged from 50 to 250 feet per day. Values of vertical hydraulic conductivity ranging from 0.001 to 0.5 feet per day were assigned to zones created on the basis of variations in hydrogeologic conditions observed in geophysical logs from wells. A steady-state simulation was used to calibrate the model to synoptic water-level data collected in March 1998. Near the Puchack well field, simulated heads generally were within 1 foot of the measured heads in both the Middle and Lower aquifers. Simulated water-level differences across the confining units at most of the nested wells were within ? 0.5 feet of the differences calculated from measured water levels. The existing flow model was modified to meet NJDEP guidelines for delineating contributing areas in complex hydrogeologic settings. These modifications included rediscretizing the model grid to a finer grid and preparing the water-use data set for use in the rediscretized model. The contributing area to the Puchack well field was delineated by means of particle tracking. An uncertainty analysis was conducted in which 36 model-input parameters were both increased and decreased until the resulting change in simulated heads exceeded the model-calibration criterion of ? 5 feet at any model cell. Porosity most affected the size and shape of the contributing area. The distribution of withdrawals at the Morris/Delair well field and variations in recharge affected both the size and shape of contributing area to the Puchack well field and the source of water to the Puchack wells. The results of the uncertainty analysis were combined to determine the 'aggregate' contributing area to the Puchack well field--a composite of areas on the land surface that contributed flow to the Puchack well field in less than 12 years in any uncertainty simulation. The shape of the aggregate contributing area was most similar to that associated with a reduction in porosity, which indirectly affected the size and shape of the contributing areas by changing travel time.

Scientific Investigations Report↗
USGS2004

Simulation of ground-water flow in the Potomac-Raritan-Magothy aquifer system, Pennsauken Township and vicinity, New Jersey

The Potomac-Raritan-Magothy aquifer system is one of the primary sources of potable water in the Coastal Plain of New Jersey, particularly in heavily developed areas along the Delaware River. In Pennsauken Township, Camden County, local drinking-water supplies from this aquifer system have been contaminated by hexavalent chromium at concentrations that exceed the New Jersey maximum contaminant level. In particular, ground water at the Puchack well field has been adversely affected to the point where, since 1984, water is no longer withdrawn from this well field for public supply. The area that contains the Puchack well field was added to the National Priorities List in 1998 as a Superfund site. The U.S. Geological Survey (USGS) conducted a reconnaissance study from 1996 to 1998 during which hydrogeologic and water-quality data were collected and a ground-water-flow model was developed to describe the conditions in the aquifer system in the Pennsauken Township area. The current investigation by the USGS, in cooperation with the U.S. Environmental Protection Agency (USEPA), is an extension of the previous study. Results of the current study can be applied to a Remedial Investigation and Feasibility Study conducted at the Puchack well field Superfund site. The USGS study collected additional data on the hydrogeology and water-quality in the area. These data were incorporated into a refined model of the ground-water-flow system in the Potomac-Raritan-Magothy aquifer system. A finite-difference model was developed to simulate ground-water flow and the advective transport of chromium-contaminated ground water in the aquifers of the Potomac-Raritan-Magothy aquifer system in the Pennsauken Township area. An 11-layer model was used to represent the complex hydrogeologic framework. The model was calibrated using steady-state water-level data from March 1998, April 1998, and April 2001. Water-level recovery during the shutdown of Puchack 1 during March to April 1998 was simulated to evaluate model performance in relation to changing stresses. The Delaware River contributes appreciable-flow to the ground-water system from areas where the Middle and Lower aquifers crop out beneath the river. A transient simulation of an aquifer test near the Delaware River was run to help characterize the hydraulic conductivity of the riverbed sediments represented in the model. Vertical flow across confining units between the aquifers is highly variable and is important in the movement of water and associated contaminants through the flow system. The model was imbedded within a regional model of the Potomac-Raritan-Magothy aquifer system in Camden County. In general, a simulation of baseline conditions, which can provide a representation on which simulations of various alternatives can be based for the feasibility study, incorporated average conditions from 1998 to 2000. Ground-water withdrawals within the model area during this period averaged about 14 Mgal/d. Regional ground-water flow is from recharge areas and from the Delaware River to downgradient pumped wells located just east of the model area in central Camden County. Simulation results show an important connection between the Intermediate sand and the Lower aquifer of the Potomac-Raritan-Magothy aquifer system in the vicinity of the chromium-contaminated area. The Delaware River contributes nearly 10 Mgal/d to the flow system, whereas recharge contributes about 6 Mgal/d. Ground-water withdrawals within the model area account for nearly 14 Mgal/d (mostly from the Lower aquifer of the Potomac-Raritan-Magothy aquifer system).

Scientific Investigations Report↗
USGS2003

Real-time ground-water-level monitoring in New Jersey, 2002

This network was created to provide data to indicate water-level trends in shallow ground-water systems within the State of New Jersey and to make the data available in the shortest time possible. The wells in this network are located throughout New Jersey (fig. 1) and were chosen because they are completed in shallow aquifers (table 1). The monitoring of shallow aquifers is important because these aquifers are relied on for water supply and irrigation. Additionally, the natural discharge from shallow aquifers provides base flow to streams. Water levels in these aquifers respond relatively quickly to precipitation and dry periods, so the rapid reporting of water-level data is necessary to follow trends. This network, for example, provides data that allow observation of the onset of drought conditions in ground water. Also, the data from this network can be used to estimate the most recent water-level trend in surficial-aquifer wells not outfitted with satellite telemetry.

New Jersey↗
USGS2002

Real-time ground-water-level monitoring in New Jersey

A network of seven observation wells that transmit ground-water-level data on a real-time basis through satellite telemetry is operating (started May 2001) in New Jersey through a cooperative effort of the U.S. Geological Survey (USGS) and the New Jersey Department of Environmental Protection (NJDEP). The water-level data from these observation wells are transmitted every 4 hours and then are immediately posted for viewing on the Internet. This fact sheet describes the rationale for real-time monitoring of ground-water levels, the design of the network, and the equipment used to measure water levels and transmit the data to the Internet. Instructions for viewing the data are included.

New Jersey↗
USGS1999

Simulation of ground-water flow and movement of the freshwater-saltwater interface in the New Jersey coastal plain

The confined aquifers of the New Jersey Coastal Plain are sands that range in thickness from 50 to 600 feet and are separated by confining units. The confining units are composed of silts and clays that range in thickness from 500 to 1,000 feet. The aquifers are recharged by precipitation on their outcrop areas. This water then flows laterally downdip and vertically to the deeper confined aquifers. The confined aquifers ultimately discharge to the Raritan and Delaware Bays and to the Atlantic Ocean. In 1988, ground-water withdrawals from confined and unconfined New Jersey Coastal Plain aquifers were approximately 345 million gallons per day, more than 75 percent of which was pumped from the confined aquifers. These withdrawals have created large cones of depression in several Coastal Plain aquifers near populated areas, particularly in Camden and Monmouth Counties. The continued decline of water levels in confined aquifers can cause saltwater intrusion, reduce stream discharge near the outcrop areas, and threaten the quality of the ground-water supply. SHARP, a quasi-three-dimensional finite-difference computer model that can simulate freshwater and saltwater flow, was used to simulate the ground-water flow system in the New Jersey Coastal Plain, including the location and movement of the freshwater-saltwater interface in nine aquifers and eight intervening confining units. The freshwater-saltwater interface is defined as the hypothetical line seaward of which the chloride concentration is equal to or greater than 10,000 milligrams per liter. Model simulations were used to estimate the location and movement of the freshwater-saltwater interface resulting from (1) eustatic sea-level changes over the past 84,000 years, (2) ground-water withdrawals from 1896 through 1988, (3) and future ground-water withdrawals from 1988 to 2040 from Coastal Plain aquifers. Simultion results showed that the location and movement of the freshwater-saltwater interface are more dependent on the historical sea level than on the stresses imposed on the flow system by ground-water withdrawals from the Coastal Plain aquifers from 1896 to 1988. Results of a predictive simulation in which pumpage from existing wells was increased by 30 percent indicate that additional withdrawals from each of the eight confined aquifers in the Coastal Plain would broaden and deepen the existing cones of depression and result in significant drawdowns from the 1988 potentiometric surfaces. Drawdowns of 30 feet were simulated at the center of the cone of depression in the Upper, Middle, and Lower Potomac-Raritan-Magothy aquifers in Camden and Ocean Counties. Simulated drawdowns exceeded 80 feet at the center of the cone of depression in the Wenonah-Mount Laurel and Englishtown aquifers in Monmouth County. Drawdowns of 30 feet were simulated in the lower Kirkwood-Cohansey and confined Kirkwood aquifers in Cape May County. Simulation results showed that the increase in ground-water withdrawals would result in only minimal movement of the freshwater-saltwater interface by 2040, despite large drawdowns.

New Jersey↗
USGS1995

Occurrence of the gasoline additive MTBE in shallow ground water in urban and agricultural areas

Methyl tert -butyl ether (MTBE) is a volatile organic compound (VOC) derived from natural gas that is added to gasoline either seasonally or year round in many parts of the United States to increase the octane level and to reduce carbon monoxide and ozone levels in the air. In 1993, production of MTBE ranked second among all organic chemicals manufactured in the United States. Currently, the U.S. Environmental Protection Agency (EPA) tentatively classifies MTBE as a possible human carcinogen. Health complaints related to MTBE in the air were first reported in Fairbanks, Alaska in November 1992 when about 200 residents reported problems such as headaches, dizziness, eye irritation, burning of the nose and throat, disorientation, and nausea. Similar health complaints have been registered in Anchorage, Alaska; Missoula, Montana; Milwaukee, Wisconsin; and New Jersey. As part of the U.S. Geological Survey’s National Water-Quality Assessment (NAWQA) Program, concentrations of 60 VOCs were measured in samples from 211 shallow wells in 8 urban areas and 524 shallow wells in 20 agricultural areas. Chloroform and MTBE were the two most frequently detected VOCs. MTBE was detected in 27 percent of the urban wells and 1.3 percent of the agricultural wells. Concentrations ranged from less than the detection level of 0.2 μg/L (micrograms per liter) to as high as 23,000 μg/L. When detected, the median concentration of MTBE was 0.6 μg/L. MTBE was most frequently detected in shallow ground water in Denver, Colorado and urban areas in New England. In Denver, 79 percent of the samples from shallow urban wells had detectable concentrations of MTBE and in New England, 37 percent of the samples from urban wells had detectable concentrations. Only 3 percent of the wells sampled in urban areas had concentrations of MTBE that exceeded 20 μg/L, which is the estimated lower limit of the EPA draft drinking water health advisory level. Contaminant concentrations below the health advisory are not expected to cause any adverse effects over a lifetime of exposure. MTBE is on the EPA’s Drinking Water Priority List, which means it is a possible candidate for future regulation.

Fact Sheet↗
USGS1994

Hydrogeology, simulation of regional ground-water flow, and saltwater intrusion, Potomac-Raritan-Magothy Aquifer System, Northern Coastal Plain of New Jersey

The Potomac-Raritan-Magothy aquifer system in Middlesex and Monmouth Counties in the northern Coastal Plain of New Jersey consists primarily of unconsolidated Cretaceous sediments, which are divided into the upper and middle aquifers and confining units. These units, which strike northeastsouthwest along the Fall Line, dip and thicken to the southeast. The upper aquifer consists primarily of the Old Bridge Sand Member of the Magothy Formation, which is composed of coarse-grained sands, localized thin clay beds, and younger surficial sands and gravels in and near the outcrop. Transmissivity ranges from 1,760 to 19,400 ft 2 /d (feet squared per day) and tends to be higher in updip areas. Estimated withdrawals from the upper aquifer in the northern Coastal Plain were approximately 42 Mgal/d (million gallons per day) in 1986. Cones of depression whose centers range from 36 to 42 ft (feet) below sea level have developed as a result of these withdrawals. The upper aquifer is confined throughout most of the northern New Jersey Coastal Plain by clays and silts of the Cretaceous Woodbury Clay and Merchantville Formation and younger sediments of the Magothy Formation. This confining unit generally is greater than 200 ft thick. The simulated vertical hydraulic conductivity for the confining unit ranges from 8.4 x 10 -5 to 5.6 x 10 -3 feet per day; interpreted vertical hydraulic conductivities generally are lower except in southwestern Middlesex County, where the vertical hydraulic conductivities of the confining unit are higher. The middle aquifer consists primarily of the Farrington Sand Member of the Cretaceous Raritan Formation and surficial Holocene and Miocene sands and gravels in its outcrop area. It also can include the uppermost sands of the Cretaceous Potomac Group in parts of Monmouth County. The middle aquifer is composed of fine to coarse sand that contains some lignite and pyrite, and, locally, some clay beds. It pinches out in the northern part of Sayreville Township, near Raritan River. The transmissivity of the aquifer ranges from 2,140 to 13,800 ft 2/ d and tends to decrease in the northern part of the northern Coastal Plain of New Jersey where the aquifer thins. A poorly permeable confining unit composed mostly of clays and silts of the Woodbridge Clay Member of the Raritan Formation overlies the aquifer in most of this area. The confining unit generally is greater than 100 ft thick, although it thins and is sandy in the southwestern part of Middlesex County, where a good hydraulic connection exists between the middle and upper aquifers. Estimated withdrawals from the middle aquifer in the northern Coastal Plain were about 22 Mgal/d in 1986. These withdrawals have caused cones of depression whose centers range from 77 to 93 ft below sea level. A finite-difference, quasi-three-dimensional ground-water flow model was developed to simulate ground-water flow in the aquifer system. The confined and unconfined areas of the upper and middle aquifers were modeled as separate layers. The model was calibrated primarily by adjusting vertical hydraulic conductivity in the confining units and horizontal hydraulic conductivity in the aquifers, then matching simulated and measured groundwater levels for the period 1896-1986 and simulated and interpreted potentiometric surfaces under predevelopment conditions and in 1984. For the predevelopment period, the total flow into and out of the upper and middle aquifers is 35 and 21 Mgal/d, respectively. Recharge to the aquifer system is from direct recharge in the unconfined areas and from vertical leakage through overlying confining units. The main recharge areas are the topographically high areas in southwestern Middlesex County for both aquifers, in the eastern Sayreville area for the upper aquifer, and north of the Raritan River for the middle aquifer. Most ground water discharges to low-lying regional surface-water drains (streams), which flow into the South River. For 1984 transient conditions, the total ground-water flow into and out of the upper and middle aquifers is 61 and 34 Mgal/d, respectively. The largest amount of recharge is from direct recharge in the unconfined areas, but some recharge also is derived from vertical leakage through the Merchantville-Woodbury confining unit, captured ground-water discharge to streams, and induced inflow at artificial-recharge facilities. Regional flow is from recharge areas toward major cones of depression. Sensitivity analysis showed that the model was useful for representing flow in the system, especially in the confined-aquifer areas. Model representation of lateral and vertical boundary conditions was judged acceptable. Simulation results were less sensitive to changes in aquifer properties in the unconfined areas of the aquifers and to changes in storage in the confining units. Sensitivity analysis and calibration of hydraulic parameters and conditions showed that the distribution of hydraulic head was sensitive to changes in horizontal hydraulic conductivity in the aquifers, vertical hydraulic conductivity in the confining units, magnitudes of ground-water withdrawals, and initial hydraulic head in aquifer outcrop areas. Two scenarios were simulated to determine the effects of ground-water withdrawals from 1986 through 2019. For the scenario in which ground-water withdrawals increase to about 69 Mgal/d in the upper aquifer and 37 Mgal/d in the middle aquifer, centers of cones of depression are as deep as 100 ft below sea level in the upper aquifer and 170 ft below sea level in the middle aquifer. For this scenario, most of the additional water comes from captured surface-water discharge, induced cross-formational flow from overlying aquifers, and increases in induced flow from artificial-recharge areas. Induced flow from Raritan Bay also increases. For the scenario in which ground water withdrawals are reduced to 42.5 Mgal/d in the upper aquifer and 15 Mgal/d in the middle aquifer, water levels recover to above sea level nearly everywhere. In each aquifer, ground-water discharge to streams increases and induced flow through the confining units and from the overlying sediments decreases, and discharge of ground water to Raritan Bay in the upper aquifer exceeds the induced recharge from Raritan Bay. Reversal of ground-water gradients has caused saltwater intrusion in the two aquifers. Chloride concentrations in water from the upper aquifer in Keyport and Union Beach Boroughs were as high as 2,100 mg/L (milligrams per liter) in 1986. The intrusion has not increased significantly since well fields in the area were closed in the late 1970's. Elevated chloride concentrations also were measured in Keanesburg Borough in 1986. In both of these areas, saltwater has entered the upper aquifer from the Bay because of movement of the freshwater-saltwater interface in response to increasing ground-water withdrawals. Chloride concentrations in well-water samples from the middle aquifer were as high as 6,000 mg/L in Sayreville Borough in 1987; concentrations in samples from drive-point wells from the same aquifer near the Washington Canal, the main source of saltwater, were as high as 7,100 mg/L. The migration of the saltwater front at about 470 feet per year to the southeast is influenced mainly by a thinning of the middle aquifer, which constrains flow, and by the locations of regional cones of depression caused by groundwater withdrawals.

New Jersey↗
USGS1989

Water-quality data for the Potomac-Raritan-Magothy aquifer system in the northern coast plain of New Jersey, 1923-86

Ground-water-quality data for the upper and middle aquifers of the Potomac-Raritan-Magothy aquifer system in Middlesex and Monmouth Counties are compiled for the period 1923-86. A total of 330 wells were sampled: 192 wells in the upper aquifer and 138 wells in the middle aquifer. Most of the complete water-quality analyses were collected after September 1984, as part of a regional ground-water assessment. Well-construction data for the sampled wells also are presented. Public-supply, domestic-supply, industrial, commercial, irrigation, and observation wells were sampled for the study. Field measurements made at the time of sample collection include water temperature, specific conductance , dissolved oxygen, pH, alkalinity, and bicarbonate concentration. Laboratory determinations include common ions, silica, dissolved solids, trace metals, volatile organic compounds, and pesticides. A quality-assurance program was followed to evaluate and assure the quality of the data. The report also contains a table of lithologic and hydrologic characteristics of the geologic units in the study area, a table of chloride concentrations and field measurements from 1923-86, and statistical summaries of selected water-quality data for the upper and middle aquifers. Many constituents were found in a wide range of concentrations. Water from more than 25 percent of the wells sampled contained lead concentrations above the detection limit of 10 ug/L (micrograms per liter). Included in this number are some wells that had lead concentrations greater than the U.S. Environmental Protection Agency (USEPA) primary drinking-water regulation of 50 ug/L. Cadmium concentrations, although lower than lead concentrations, followed a similar pattern. Water from approximately 25 percent of the wells in the upper aquifer, contain cadmium concentrations equal to or greater than the detection limit of 1 ug/L. Dissolved iron concentrations ranged from 5 ug/L to 480,000 ug/L. Water from more than 50 percent of the wells sampled contained iron concentrations in excess of the USEPA secondary drinking-water recommended limit of 300 ug/L. Chloride concentrations greater than the USEPA secondary drinking-water recommended limit of 250 milligrams per liter were found in samples from wells located in the cities of Perth Amboy and South Amboy; in the boroughs of Keansburg, Sayreville, Keyport, and Union Beach; and in the townships of Old Bridge and Woodbridge. Of 21 samples collected from wells screened in the upper aquifer and analyzed for 30 volatile organic compounds (VOCs), 5 samples contained at least 1 VOC at or above the detection limit. In the middle aquifer, 12 of the 21 samples collected and analyzed for VOCs contained at least 1 VOC greater than the detection limit. Concentrations of pesticides generally were low. Of the 43 samples collected from wells screened in the upper aquifer and analyzed for pesticides, 4 samples contained concentrations of pesticides at or greater than the detection limit. In the middle aquifer, 6 of 38 samples collected and analyzed for 32 pesticides had at least 1 pesticide with a concentration greater than the detection limit.

New Jersey↗