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At least 235 records · Page 13Linked to original sources
USGS2002

Hydrogeologic framework, availability of water supplies, and saltwater intrusion, Cape May County, New Jersey

During 1960-90, saltwater intrusion forced the abandonment of at least 10 public-supply wells, 3 industrial-supply wells, and more than 100 domestic-supply wells in Cape May County, N.J. Actual or imminent ground-water contamination caused by land-use practices and human activities has forced the closure of at least six shallow public-supply wells and many domestic-supply wells. Freshwater in Cape May County flows in many small streams and is held in wetlands and natural and artificial ponds. More importantly, freshwater from precipitation passes through and is stored in five aquifers-- Holly Beach water-bearing zone, estuarine sand aquifer, Cohansey aquifer, Rio Grande water-bearing zone, and Atlantic City 800-foot sand. Surface-water discharges were measured at 14 stream sites. The Tuckahoe River is the largest stream in Cape May County. The mean annual discharge for the Tuckahoe River at Head of River was 43.8 ft 3 /s (cubic feet per second) or 10,800 Mgal/yr (million gallons per year) during the period of record (1969-93). Mean daily discharge ranged from 25 ft 3 /s or 16 Mgal/d in September to 73 ft 3 /s or 47 Mgal/d in April. Mean daily discharge at the eight largest streams wholly within the county ranged from 15.9 to 3.05 ft 3 /s (3,750 to 720 Mgal/yr). Total water use in the county was about 8,600 Mgal/yr in 1990, including about 25 Mgal/yr of surface water, 3,000 Mgal/yr from the Holly Beach water-bearing zone, 1,000 Mgal/yr from the estuarine sand aquifer, 2,200 Mgal/yr from the Cohansey aquifer, 200 Mgal/yr from the Rio Grande water-bearing zone, and 2,200 Mgal/yr from the Atlantic City 800-foot sand. Water-level data collected during April 1991 for more than 200 wells show that in some locations ground-water flow directions and rates have changed when compared with those shown on historical potentiometric-surface maps. In 1991, water levels in the Holly Beach water-bearing zone were nearly identical to levels prior to development. A cone of depression has developed in the estuarine sand aquifer; the water-level altitude near the center of the cone was about -5 ft in 1991. An extensive cone of depression has developed in the Cohansey aquifer; the water-level altitude near the center of the cone was about -20 ft. A small cone of depression has developed in the Rio Grande water-bearing zone; the altitude near the center was -5 ft. An elongated cone of depression has developed in the Atlantic City 800-foot sand; the water-level altitude was about -70 ft in Ocean City and -20 ft in Stone Harbor. Waterlevel maps from predevelopment, 1958, 1978, 1983, and 1988 show that the cones of depression are getting deeper and are expanding in the Atlantic City 800-foot sand. The 250-mg/L (milligram per liter) line of equal chloride concentration and 50 mg/L line of equal sodium concentration have moved inland, possibly since the early 1900's. Chloride concentrations have increased in many wells in the confined aquifers along the coastline in the southern part of the county. Nitrate concentrations greater than 1 mg/L were present in water samples collected from 10 wells that tap the Holly Beach water-bearing zone. Concentrations of nitrate greater than 10 mg/L in samples collected in Lower, Middle, Upper, and Dennis Townships may result from effluent from septic systems or from agricultural activities. A water budget shows that the mean annual precipitation is about 42 in., and about 119,000 Mgal falls each year on uplands and freshwater wetlands in the county. About 63,600 Mgal/yr is evapotranspired, 8,200 Mgal/yr becomes overland flow, and 47,200 Mgal/yr recharges the Holly Beach water-bearing zone. In northern Cape MayCounty, most recharge ultimately is discharged to streams. In southern Cape May County, about 20 percent of recharge is diverted to withdrawal wells. Because saltwater intrusion has occurred in the confined aquifers along the Atlantic and Delaware Bay coastlines, new supply wells placed along the axis of the peninsula would likely provide freshwater for the longest period of time. The supply wells could be coupled with observation wells placed at or near the saltwater front in the aquifers. The observation wells could be used to obtain water-quality samples and waterlevel measurements to observe any changes in the location of the saltwater front that might result from withdrawals.

New Jersey↗
USGS2002

Comparisons of water quality during various streamflow conditions in five streams in northern New Jersey, 1982-97

Relations between water-quality and flow characteristics and the relative importance of constant (point sources and ground-water discharge) and intermittent (nonpoint storm runoff) sources were determined for eight water-quality stations located on the Flat Brook and the Delaware, Musconetcong, Whippany, and Saddle Rivers. Water-quality and streamflow data were categorized on the basis of streamflow at the time of sample collection. Differences in concentrations and yields of selected water-quality constituents, including nutrients and bacteria, (1) among the stations during eight streamflow conditions and (2) at each station (a) between base flow and stormflow; (b) among before, during, and after a storm; and (c) among low, medium, and high flows were determined and related to the predominant type(s) of land development in the areas contributing drainage. At the station on the Delaware River, yields of fecal-coliform bacteria were affected more by contributions from storm runoff than by contributions from point sources and ground-water discharges; yields during a storm [7.0 x 108 (MPN/d)mi2 (most probable number per day per square mile)] were greater than yields during base flow (3.7 x 108 (MPN/d)mi2). Yields of nitrate plus nitrite, alkalinity, and chloride were affected more by contributions from point sources and ground-water discharges than by contributions from storm runoff; yields of these constituents were not significantly different during base flows and stormflows. At the Flat Brook and Whippany River stations, yields of most water-quality constituents were affected more by contributions from storm runoff than by contributions from point sources and ground-water discharge. For example, yields of nitrate plus nitrite were greater during stormflow (1.20 (lb/d)/mi2 (pounds per day per square mile) and 15.88 (lb/d)/mi2, respectively) than during base flow (0.26 (lb/d)/mi2 and 8.20 (lb/d)/mi2, respectively). At the Musconetcong River station, yields of total nitrogen, alkalinity, and chloride were affected more by contributions from storm runoff than by contributions from point sources and ground-water discharge. At three of the four water-quality stations on the Musconetcong River, yields of total phosphorus and bacteria were affected less by contributions from storm runoff than by contributions from point sources and ground-water discharge. At the Saddle River station, yields of alkalinity and chloride were affected more by contributions from storm runoff than by contributions from point sources and ground-water discharge; for example, yields of chloride during stormflows (707 (lb/d)/mi2) were greater than during base flows (401 (lb/d)/mi2). Yields of total phosphorus were affected less by contributions from storm runoff than by contributions from point sources and ground-water discharge; yields during base flows (4.00 (lb/d)/mi2) and stormflows (4.67 (lb/d)/mi2) were similar. Concentrations and yields of total phosphorus and nitrogen, and nitrate plus nitrite were strongly related to the amount of development in each drainage basin. At stations on the Saddle and Whippany Rivers, which drain areas with substantial development, concentrations and yields for all streamflow categories were higher than at stations on the Flat Brook and Delaware River, which drain areas with little development. Results of the Tukey test indicate that there are significant differences in total phosphorus concentrations at Saddle River and Flat Brook during base flows (0.77 mg/L (milligrams per liter) and 0.02 mg/L, respectively) and stormflows (0.42 mg/L and 0.02 mg/L, respectively).

New Jersey↗
USGS2002

Relation of Environmental characteristics to the composition of aquatic assemblages along a gradient of urban land use in New Jersey, 1996-98

Community data from 36 watersheds were used to evaluate the response of fish, invertebrate, and algal assemblages in New Jersey streams to environmental characteristics along a gradient of urban land use that ranged from 3 to 96 percent. Aquatic assemblages were sampled at 36 sites during 1996-98, and more than 400 environmental attributes at multiple spatial scales were summarized. Data matrices were reduced to 43, 170, and 103 species of fish, invertebrates, and algae, respectively, by means of a predetermined joint frequency and relative abundance approach. White sucker ( Catostomus commersoni ) and Tessellated darter ( Etheostoma olmstedi ) were the most abundant fishes, accounting for more than 20 and 17 percent, respectively, of the mean abundance. Net-spinning caddisflies ( Hydropsychidae ) were the most commonly occurring benthic invertebrates and were found at all but one of the 36 sampling sites. Blue-green (for example, Calothrix sp. and Oscillatoria sp.) and green (for example, Protoderma viride ) algae were the most widely distributed algae; however, more than 81 percent of the algal taxa collected were diatoms. Principal-component and correlation analyses were used to reduce the dimensionality of the environmental data. Multiple linear regression analysis of extracted ordination axes then was used to develop models that expressed effects of increasing urban land use on the structure of aquatic assemblages. Significant environmental variables identified by using multiple linear regression analysis then were included in a direct gradient analysis. Partial canonical correspondence analysis of relativized abundance data was used to restrict further the effects of residual natural variability, and to identify relations among the environmental variables and the structure of fish, invertebrate, and algal assemblages along an urban land-use gradient. Results of this approach, combined with the results of the multiple linear regression analyses, were used to identify human population density (311-37,594 persons/km 2 ), amount and type of impervious surface cover (0.12-1,350 km 2 ), nutrient concentrations (for example, 0.01-0.29 mg/L of phosphorus), hydrologic instability (for example, 100-8,955 ft 3 /s for 2-year peak flow), the amount of forest and wetlands in a basin (0.01-6.25 km 2 ), and substrate quality (0-87 percent cobble substrate) as variables that are highly correlated with aquatic-assemblage structure. Species distributions in ordination space clearly indicate that tolerant species are more abundant in the streams impaired by urbanization and sensitive taxa are more closely associated with the least impaired basins. The distinct differences in aquatic assemblages along the urban land-use gradient demonstrate the deleterious effects of urbanization on assemblage structure and indicate that conserving landscape attributes that mitigate anthropogenic influences (for example, stormwater-management practices emphasizing infiltration and preservation of existing forests, wetlands, and riparian corridors) will help to maintain the relative abundance of sensitive taxa. Complementary multiple linear regression models indicate that aquatic community indices were correlated with many of the anthropogenic factors that were found to be significant along the urban land-use gradient. These indices appear to be effective in differentiating the moderately and severely impaired streams from the minimally impaired streams. Evaluation of disturbance thresholds for aquatic assemblages indicates that moderate to severe impairment is detectable in New Jersey streams when impervious surface cover in the drainage basin reaches approximately 18 percent.

New Jersey↗
USGS2001

Frequently co‐occurring pesticides and volatile organic compounds in public supply and monitoring wells, southern New Jersey, USA

One or more pesticides were detected with one or more volatile organic compounds (VOCs) in more than 95% of samples collected from 30 public supply and 95 monitoring wells screened in the unconsolidated surficial aquifer system of southern New Jersey, USA. Overall, more than 140,000 and more than 3,000 unique combinations of pesticides with VOCs were detected in two or more samples from the supply and monitoring wells, respectively. More than 400 of these combinations were detected in 20% or more of the samples from the supply wells, whereas only 17 were detected in 20% or more of the samples from the monitoring wells. Although many constituent combinations detected in water from the supply and monitoring wells are similar, differences in constituent combinations also were found and can be attributed, in part, to differences in the characteristics of these two well types. The monitoring wells sampled during this study yield water that typically was recharged beneath a single land‐use setting during a recent, discrete time interval and that flowed along relatively short paths to the wells. Public supply wells, in contrast, yield large volumes of water and typically have contributing areas that are orders of magnitude larger than those of the monitoring wells. These large contributing areas generally encompass multiple land uses; moreover, because flow paths that originate in these areas vary in length, these wells typically yield water that was recharged over a large temporal interval. Water withdrawn from public supply wells, therefore, contains a mixture of waters of different ages that were recharged beneath various land‐use settings. Because public supply wells intercept water flowing along longer paths with longer residence times and integrate waters from a larger source area than those associated with monitoring wells, they are more likely to yield water that contains constituents that were used in greater quantities in the past, that were introduced from point sources, and/or that are derived from the degradation of parent compounds along extended flow paths.

New Jersey↗
USGS2001

Variation in aluminum, iron, and particle concentrations in oxic ground-water samples collected by use of tangential-flow ultrafiltration with low-flow sampling

Particulates that move with ground water and those that are artificially mobilized during well purging could be incorporated into water samples during collection and could cause trace-element concentrations to vary in unfiltered samples, and possibly in filtered samples (typically 0.45-um (micron) pore size) as well, depending on the particle-size fractions present. Therefore, measured concentrations may not be representative of those in the aquifer. Ground water may contain particles of various sizes and shapes that are broadly classified as colloids, which do not settle from water, and particulates, which do. In order to investigate variations in trace-element concentrations in ground-water samples as a function of particle concentrations and particle-size fractions, the U.S. Geological Survey, in cooperation with the U.S. Air Force, collected samples from five wells completed in the unconfined, oxic Kirkwood-Cohansey aquifer system of the New Jersey Coastal Plain. Samples were collected by purging with a portable pump at low flow (0.2-0.5 liters per minute and minimal drawdown, ideally less than 0.5 foot). Unfiltered samples were collected in the following sequence: (1) within the first few minutes of pumping, (2) after initial turbidity declined and about one to two casing volumes of water had been purged, and (3) after turbidity values had stabilized at less than 1 to 5 Nephelometric Turbidity Units. Filtered samples were split concurrently through (1) a 0.45-um pore size capsule filter, (2) a 0.45-um pore size capsule filter and a 0.0029-um pore size tangential-flow filter in sequence, and (3), in selected cases, a 0.45-um and a 0.05-um pore size capsule filter in sequence. Filtered samples were collected concurrently with the unfiltered sample that was collected when turbidity values stabilized. Quality-assurance samples consisted of sequential duplicates (about 25 percent) and equipment blanks. Concentrations of particles were determined by light scattering.

New Jersey↗
USGS2001

Water quality of the Delaware and Raritan Canal, New Jersey, 1998-99

Since 1934, the Delaware and Raritan Canal has been used to transfer water from the Delaware River Basin to the Raritan River Basin. The water transported by the Delaware and Raritan Canal in New Jersey is used primarily for public supply after it has been treated at drinking-water treatment plants located in the Raritan River Basin. Recently (1999), the raw water taken from the canal during storms has required increased amounts of chemical treatments for removal of suspended solids, and the costs of removing the additional sludge or residuals generated during water treatment have increased. At present, action to control algae is unnecessary. The water quality of the Delaware and Raritan Canal was studied for approximately 16.5 months from mid-January 1998 through May 1999 to determine whether changes in water quality along the length of the canal are associated with storms. Nine water-quality constituents, and field measured specific conductance and turbidity were statistically tested. Instantaneous or grab samples of water were collected from the Delaware and Raritan Canal after five storms and during four nonstorm events. Median values of water-quality constituents in samples collected immediately after storms and during nonstorm conditions when statistically compared by sampling location were not significantly different. Therefore, the data were combined or aggregated to eliminate one of the two explanatory variables, either individual sampling sites or the two types of sampling events, in order to generate a sample population large enough to show statistically significant differences. After combining sampling events, only the median concentration of suspended organic carbon, and field measured specific conductance and turbidity, were significantly different among sampling sites. Median concentrations of total and filtered ammonia plus organic nitrogen, total phosphorous, turbidity, ultraviolet absorbance at 254 nanometers, and dissolved organic carbon in samples collected after storms were significantly greater than in samples collected during nonstorm conditions, when the sampling locations were aggregated in the statistical analysis. Methyl tert-butyl ether, the most frequently detected volatile organic compound (VOC), was detected in 55 of 80 samples. The highest concentration of methyl tert-butyl ether, 3.2 micrograms per liter, was measured in a sample collected during nonstorm conditions. The median of the continuously monitored specific conductance during nonstorm conditions at Port Mercer, N.J., increased by approximately 3 to 4 ?S/cm (microsiemens per centimeter) (1.5 to 2 percent of the median specific conductance) relative to that at the nearest upstream site, at Lower Ferry Road. The land use in the influent basins for this reach of the Delaware and Raritan Canal is primarily urban. One possible source of water with high specific conductance is either domestic or industrial wastewater that continuously discharges into pipes, then empties into the canal. Another possible source is ground water from an area within this reach where the elevation of the water table is higher than that of the water surface of the Delaware and Raritan Canal. The median continuously monitored specific conductance measured during nonstorm conditions at the Route 18 Spillway site increased relative to that of the nearest upstream site, Ten Mile Lock, by approximately 3 to 4 ?S/cm. The mean net change in continuously monitored specific conductance for this reach during storms also increased. Land use in the two largest influent basins within this reach, the Borough of South Bound Brook and Als Brook, is predominantly urban. The mean and median of continuously monitored turbidity varied along the length of the canal. In the reach between Raven Rock and Lower Ferry Road, the mean and median for continuously monitored turbidity during the study period increased by 7.2 and 6.2 NTU (nephelometric turbidity units), respectively. The mean of continuously monitored turbidity decreased downstream from Lower Ferry Road to Ten Mile Lock. Turbidity could increase locally downstream from influent streams or outfalls, but because the average velocity of water in the canal is low, particles that cause turbidity are not transported appreciable distances. In the reach between Ten Mile Lock and the Route 18 Spillway, the mean and median of the continuously monitored turbidity changed less than 0.5 NTU during the period of record. The small change in turbidity in this reach is not consistent with an average velocity for the reach; the average velocity in this reach was the lowest in all of the reaches studied. The expected decrease in turbidity due to settling of suspended solids is likely offset by turbid water entering the canal from influent streams or discharges from storm drains. Field observation of a sand bar immediately downstream from the confluence of Als Brook and the canal confirmed that the Als Brook drainage basin has contributed stormwatergenerated sediment to the canal that could reach the monitor located at the Route 18 Spillway and the raw water intakes for two drinking-water treatment plants.

New Jersey↗
USGS2001

Effects of land use and travel time on the distribution of nitrate in the Kirkwood-Cohansey aquifer system in southern New Jersey

Residents of the southern New Jersey Coastal Plain are increasingly reliant on the unconfined Kirkwood-Cohansey aquifer system for public water supply as a result of increasing population and restrictions on withdrawals from the deeper, confined aquifers. Elevated nitrate concentrations above background levels have been found in wells in the surficial aquifer system in agricultural and urban parts of this area. A three-dimensional steady-state ground-water-flow model of a 400-square-mile study area near Glassboro, New Jersey, was used in conjunction with particle tracking to examine the effects of land use and travel time on the distribution of nitrate in ground and surface water in southern New Jersey. Contributing areas and ground-water ages, or travel times, of water at ground-water discharge points (streams and wells) in the study area were simulated. Concentrations of nitrate were computed by linking land use and age-dependent nitrate concentrations in recharge to the discharge points. Median concentrations of nitrate in water samples collected during 1996 from shallow monitoring wells in different land-use areas were used to represent the concentration of nitrate in aquifer recharge since 1990. On the basis of upward trends in the use of nitrogen fertilizer, the concentrations of nitrate in aquifer recharge in agricultural and urban areas were assumed to have increased linearly from the background value in 1940 (0.07 mg/L as N) to the 1990 (2.5-14 mg/L as N) concentrations. Model performance was evaluated by comparing the simulation results to measured nitrate concentrations and apparent ground-water ages. Apparent ground-water ages at 32 monitoring wells in the study area determined from tritium/helium-3 ratios and sulfur hexafluoride concentrations favorably matched simulated travel times to these wells. Simulated nitrate concentrations were comparable to concentrations measured in 27 water-supply wells in the study area. A time series (1987-98) of nitrate concentrations at base-flow conditions in three streams that drain basins of various sizes and with various land uses was compared to simulated concentrations in these streams. In all three of the streams, a reasonable fit to the measured concentrations was achieved by multiplying the simulated concentration by 0.6. Because nitrate appeared to move conservatively (not degraded or adsorbed) in ground water to wells, the apparent non-conservative behavior in streams indicates that about 40 percent of the nitrate in aquifer recharge is removed by denitrification in the aquifer near the streams and (or) by in-stream processes. The model was used to evaluate the effects of various nitrate management options on the concentration of nitrate in streams and water-supply wells. Nitrate concentrations were simulated under the following management alternatives: an immediate ban on nitrate input, reduction of input at a constant rate, and fixed input at the current (2000) level. The time required for water to move through the aquifer results in a time lag between the reduction of nitrate input in recharge and the reduction of nitrate concentration in streams and wells. In the gradual-reduction alternative, nitrate concentrations in streams and wells continued to increase for several years after the reduction was enacted. In both the immediate-ban and gradual-reduction alternatives, nitrate concentrations remained elevated above background concentrations long after nitrate input ceased. In the fixed-use alternative, concentrations in streams and wells continued to increase for 30 to 40 years before reaching a constant level. The spatial distributions of simulated nitrate concentrations in streams in 2000 and 2050 were examined with the assumption of no change in land use, nitrate concentration in recharge, or ground-water withdrawals. As expected, nitrate concentrations were highest in agricultural areas and lowest in largely undeveloped areas.

New Jersey↗
USGS2001

Water quality and occurrence of methyl-tert butyl ether (MTBE) and other fuel related compounds in lakes and ground water at lakeside communities in Sussex and Morris Counties, New Jersey, 1998-1999

Densely populated communities surround many of the larger lakes in northwestern New Jersey. These communities derive most of their water supply from wells. The lakes can be navigated by gasoline-powered watercraft, can be in various stages of eutrophication, may contain pathogens associated with bathing and waterfowl, and are periodically subjected to chemical applications to control aquatic plant growth. Another feature that contributes to water-quality concerns in lakeside communities is the widespread use of septic tanks. Concentrations of methyl tert-butyl ether (MTBE), a gasoline oxygenate, in samples from Cranberry Lake and Lake Lackawanna ranged from 20 to 30 ug/L (micrograms per liter) and 5 to 14 ug/L during the summers of 1998 and 1999, respectively. These levels were persistent throughout the depth of the lakes when mixing conditions were present. MTBE concentrations in samples from the top 20 feet of Lake Hopatcong during summer 1999 were about 10 ug/L and about 2 to 3 ug/L in samples below 20 feet. The source of the MTBE in the lakes was determined to be gasoline-powered watercraft. Other constituents of gasoline--tertiary amyl methyl ether (TAME) and benzene, toluene, ethylbenzene, and xylenes (BTEX)--were detected in the lakes but at much lower concentrations than MTBE. Ambient ground-water quality at Cranberry Lake and Lake Lackawanna appears to be affected by the use of gasoline-powered watercraft. MTBE was detected in water samples from 13 of the 14 wells sampled at Cranberry Lake in fall 1998 and summer 1999. The wells were selected to monitor ambient ground-water quality and had no history of contamination. In ground-water samples collected during fall 1998, MTBE concentrations ranged from 0.12 to 19.8 ug/L, and the median concentration was 0.43 ug/L. In samples from summer 1999, MTBE concentrations ranged from 0.14 to 13.2 ug/L, and the median concentration was 0.38 ug/L. MTBE was detected in samples from four of the five wells at Lake Lackawanna in summer 1999;concentrations ranged from 0.05 to 0.19 ug/L. Lake/ground water interaction is a feasible explanation for the nearly ubiquitous presence of MTBE in ground water. The movement of water from lakes to wells is feasible because many static water levels and essentially all pumped water levels in the wells were below lake levels. Furthermore, diatom fragments were present in samples from the wells. Ambient ground water at Cranberry Lake also may be affected by septic-tank effluent, as indicated by the relation among concentrations of nitrate, boron, and chloroform. This result indicates potential vulnerability of the water supply to contamination by other chemicals and pathogens. Radon in ambient ground water is a concern throughout northern New Jersey. In particular, the median radon concentrations in ground-water samples collected from 14 wells at Cranberry Lake in 1998 and 1999 were 1,282 and 1,046 pCi/L, respectively. The median radon concentration in five ground-water samples collected at Lake Lackawanna in 1999 was 340 pCi/L. Although these values exceed regulatory levels, they are not high relative to radon concentrations measured in northwestern New Jersey. Eight wells in a neighborhood of Cranberry Lake with known MTBE contamination were sampled by the U.S. Geological Survey in summer 1998. MTBE was detected at concentrations greater than or equal to 40 ug/L in five of the wells. Concentrations of TAME, another gasoline oxygenate, were highly correlated with concentrations of MTBE; MTBE concentrations were about 10 times the TAME concentrations. In all samples, however, the concentrations of the BTEX compounds were less than 0.05 ug/L, and the sample from the most highly contaminated well, where the MTBE concentration was 900 ug/L, had no detectable BTEX.

New Jersey↗
USGS2001

Ground-water flow and quality in the Atlantic City 800-foot sand, New Jersey

The regional, confined Atlantic City 800-foot sand is the principal source of water supply for coastal communities of southern New Jersey. In response to extensive use of the aquifer--nearly 21 million gallons per day in 1986--water levels have declined to about 100 feet below sea level near Atlantic City and remain below sea level throughout the coastal areas of southern New Jersey, raising concerns about the potential for saltwater intrusion into well fields. Water levels in the Atlantic City 800-foot sand have declined in response to pumping from the aquifer since the 1890's. Water levels in the first wells drilled into the Atlantic City 800-foot sand were above land surface, and water flowed continuously from the wells. By 1986, water levels were below sea level throughout most of the coastal areas. Under current conditions, wells near the coast derive most of their supply from lateral flow contributed from the unconfined part of the aquifer northwest of the updip limit of the confining unit that overlies the Atlantic City 800- foot sand. Ground water also flows laterally from offshore areas and leaks vertically through the overlying and underlying confining units into the Atlantic City 800-foot sand. The decline in water levels upsets the historical equilibrium between freshwater and ancient saltwater in offshore parts of the aquifer and permits the lateral movement of saltwater toward pumping centers. The rate of movement is accelerated as the decline in water levels increases. The chloride concentration of aquifer water 5.3 miles offshore of Atlantic City was measured as 77 mg/L (milligrams per liter) in 1985 at a U.S. Geological Survey observation well. Salty water has also moved toward wells in Cape May County. The confined, regional nature of the Atlantic City 800-foot sand permits water levels in Cape May County to decline in response to pumping in Atlantic County and vice versa. Historically, chloride concentrations as great as 1 ,510 mg/L have been reported for water in a former supply well in southern Cape May County. These data indicate that salty water has moved inland in Cape May County. Analysis of the chloride-concentration data indicates that ground water with a chloride concentration of 250 mg/L is within 4 miles of supply wells in Stone Harbor, Cape May County, and is about 10 miles offshore of supply wells near Atlantic City. Results of numerical simulations of ground-water flow were analyzed to determine the effects of four water-supply alternatives on water levels, the flow budget, and potential saltwater movement toward pumping centers during 1986-2040. In the supply alternatives, pumpage is (1) held constant at 1986 rates of pumpage; (2) increased by 35 percent at 1986 locations; (3) increased by 35 percent, but with relocation of some supply wells further inland; and (4) increased by 35 percent but with some of the increase derived from inland wells tapping the Kirkwood-Cohansey aquifer system rather than the Atlantic City 800-foot sand. Inland relocation of supply wells closer to the updip limit of the overlying confining unit results in the smallest decline in water levels and the smallest rate of ground-water flow between the offshore location of salty water and coastal supply wells. Increased pumpage from coastal supply wells results in the greatest water-level declines and the greatest increase in the rate of ground-water flow from offshore to coastal wells. Flow of undesirable salty ground water from offshore locations remains nearly the same as for current (1986) conditions when pumping rates do not change, and the flow-rate increase is smallest for the relocated pumpage (fourth) alternative. In comparing the two conditions of a 35-percent increase in pumpage, the flow from undesirable salty water positions is lessened and flow from the unconfined aquifer is increased when some of the pumping centers are relocated farther inland. Ground water from the 250-mg/L isochlor position does not reach supply wells during any simulated conditions predicted for 1986-2040. The analysis of the simulation, however, includes only advective freshwater flow from an estimated 250-mg/L isochlor position and does not include density effects. A chloride concentration data-collection network could be designed to monitor for saltwater intrusion and serve as an early warning system for the communities of southern Cape May County and the coastal communities near Atlantic City. Data from existing offshore wells could continue to serve as an early warning system for the Atlantic City area; however, observation wells south of Stone Harbor, in the Wildwood area, would be useful as an early warning system for southern Cape May County.

New Jersey↗
USGS2001

Geochemical constraints on the origin of the Sterling Hill and Franklin zinc deposits, and the furnace magnetite bed, northwestern New Jersey

T he p urpose of this chapter is to review two aspects of the geochemistry of the Sterling Hill and Franklin zinc-ironmanganese deposits and the Furnace magnetite bed that underlies the Franklin deposit. These are (1) oxidation and sulfidation states determined from heterogeneous phase equilibria, and (2) stable isotopic compositions determined from analyses of carbonate, silicate, oxide, and sulfide minerals. The data place constraints on the genesis of the ores, which is the topic of the final section of the chapter. This review draws heavily from the results of my own dissertation research on Sterling Hill (Johnson, 1990; Johnson et al., 1990a) and from recent and continuing projects (Johnson et al., 1990b, Johnson, 1994, 1996, 1997; Volkert et al., 2000); it also includes the sulfur isotope results obtained by Ault (1957). For a complete review of the geology of the deposits, the reader is referred to the chapter by Metsger (2001), and to Metsger et al. (1958) and Frondel and Baum (1974). A complete catalog of the extensive literature on the deposits is given by Dunn (1995).

New Jersey↗
USGS2001

Field trip day four: Road log for the Sterling Hill and Franklin Zinc Mines, New Jersey

T his p ortion of the field trip features visits to the world famous Sterling Hill and Franklin mines, in northwestern New Jersey, and their respective mining museums. Although both mines are no longer in operation, important geologic features can still be observed. At the Sterling Hill mine, we will have the opportunity to see zinc ore in place, both in an underground drift and in the Passaic open pit; at Franklin the pit is filled with water and only disseminated mineralization is still visible. The Furnace magnetite bed will also be seen adjacent to the Franklin open pit, as well as a large postore minette dike. If time permits we will visit a surface exposure of the Zero Fault in Franklin, which is an important regional structure that cuts the Sterling Hill orebody.

New Jersey↗
USGS2000

Mesoproterozoic graphite deposits, New Jersey Highlands: Geologic and stable isotopic evidence for possible algal origins

Graphite deposits of Mesoproterozoic age are locally abundant in the eastern New Jersey Highlands, where they are hosted by sulphidic biotite–quartz–feldspar gneiss, metaquartzite, and anatectic pegmatite. Gneiss and metaquartzite represent a shallow marine shelf sequence of locally organic-rich sand and mud. Graphite from massive deposits within metaquartzite yielded δ13C values of –26 ± 2‰ (1σ), and graphite from massive deposits within biotite–quartz–feldspar gneiss yielded δ13C values of –23 ± 4‰. Disseminated graphite from biotite–quartz–feldspar gneiss country rock was –22 ± 3‰, indistinguishable from the massive deposits hosted by the same lithology. Anatectic pegmatite is graphitic only where generated from graphite-bearing host rocks; one sample gave a δ13C value of –15‰. The δ34S values of trace pyrrhotite are uniform within individual deposits, but vary from 0 to 9‰ from one deposit to another. Apart from pegmatitic occurrences, evidence is lacking for long-range mobilization of carbon during Grenvillian orogenesis or post-Grenvillian tectonism. The field, petrographic, and isotope data suggest that massive graphite was formed by granulite-facies metamorphism of Proterozoic accumulations of sedimentary organic matter, possibly algal mats. Preservation of these accumulations in the sedimentary environment requires anoxic basin waters or rapid burial. Anoxia would also favour the accumulation of dissolved ferrous iron in basin waters, which may explain some of the metasediment-hosted massive magnetite deposits in the New Jersey Highlands.

New Jersey↗