AQUIFERS
General
Early settlers obtained their potable water supply from springs or shallow dug wells - the latter usually less than 30 feet deep. Agricultural irrigation water came from streams or ponds. Water for these shallow wells comes directly from the surface; hence, as development continued, this water was subject to pollution from septic disposal, animals, chemicals and pesticides. Colts Neck laws now ban wells supplied by surface water. The deeper, "artesian" wells are much less likely to be polluted. (See the chapter on Water Quality)
Ponds, both natural and man-made, and streams are still used for irrigation. A few large scale farmers use deep (600-700 ft.) wells. Most, if not all, of the springs are dry now because of cyclic low rainfall and interruption of water flow by development.
Porous and permeable rocks containing water are called aquifers and are classified as "water table" or "artesian." The former are charged directly from the surface (precipitation, ponds, streams, etc.), while the latter are charged by the same method, but only at the outcrops. The water then moves downdip, being filtered in the process. If the aquifer is separated from the surface by a formation which does not readily transmit water (an "aquiclude"), the increase in pressure with depth causes water to rise in the hole when the aquifer is penetrated, and even to flow to the surface if the elevation differential is great enough; hence, the term "artesian".
Occurrence and Movement of Ground Water in Monmouth County [Reference: "Geology of Monmouth County in Brief," Bureau of Geology and Topography, NJ Department of Environmental Protection, August 1977. ]:
The Local Water Budget
Ground water, like surface water, originates from precipitation and is in transit from the land to the oceans, or back into the atmosphere. It is not a static resource, but flows from higher areas, where it has soaked into the ground, to low areas, where it is naturally discharged through springs, lake bottoms, or marshes. A small portion is recovered through wells.
Ground water is thus part of a finite water budget which can be expressed by:
P = E + T + R + I
Precipitation in Monmouth County averages about 44 inches per year (which, on average, is about 2,000,000 gallons per day per square mile). The range is from 34 inches in the driest recorded year to 63 inches in the wettest year.
Evaporation and transpiration are difficult to measure separately and are usually combined as a single term, "evapotranspiration". Evapotranspiration is relatively constant from year to year with an estimated average loss of 1,000,000 gallons per square mile per day, half of the water supplied by precipitation. The rate of loss varies through the year from over 2,000,000 gallons per square mile per day in the summer, to less than 50,000 gallons per square mile per day in the wintertime. During extreme drought, plant activity will decrease and evapotranspiration losses will be somewhat reduced.
Runoff and infiltration are variable from place to place depending upon soil, slope, vegetation, freezing of the ground, and other factors. Where the ground is frozen, or where slopes are steep and soil is clayey and impermeable, little water will be able to soak into the soil and runoff will be great. Conversely, runoff is negligible on flat areas with sandy soils. Rainfall instead soaks into the ground and flows through pore spaces between grains to become ground water. This process is known as recharge, and balances water losses through natural discharge and wells.
Ground water can be removed from wells faster than it is replaced by infiltration only for a limited period of time. Removal of water faster than it can be replaced by recharge is known as ground water mining and will eventually lead to well failure.
Ground water occurs in two zones, an upper "unsaturated zone," or "zone of aeration", in which pore spaces in sediment or rock contain both air and water; and a deeper "saturated" "zone", in which pore spaces are completely filled with water. The top of the zone of saturation is known as the "ground water level" or "water table". Water will fill an open hole to the elevation of the water table. The water table is not flat but forms a modified reflection of the surface contours. Where the water table interse cts the surface, it forms springs, marshes, lakes, and streams.
"Water table" conditions exist where the water surface at the top of the zone of saturation is exposed to the atmosphere. At this point the ground water level is free to rise or fall as water enters or leaves the ground water system. This is the case when permeable materials extend upward from the zone of saturation towards the land surface.
"Artesian" conditions exist when ground water is confined by impermeable materials so that water level is not free to rise and fall. Pressure in an artesian well is due to the height difference between the ground water level at the recharge area and at the well site. In many cases confining materials are not totally impermeable, but allow water to seep slowly into or out of "leaky aquifers". In Monmouth County confined conditions are the result of water being trapped in sandy formations lying between clayey formations.
Production From Water Table Aquifers
Water table portions of aquifers are locally important in supplying water to farms and individual homeowners in areas of low density development.
Optimum water budgets in gallons per day per square mile for water table portions of sandy Coastal Plain formations are listed in the New Jersey Land Oriented Reference Data System as:
| Formation | Optimum Water Budget |
| Magothy-Raritan | 1,000,000 |
| Englishtown | 750,000 |
| Mt. Laurel-Wenonah | 750,000 |
| Vincentown | 750,000 |
| Kirkwood | 900,000 |
| Cohansey | 1,000,000 |
These values can vary greatly with local conditions, and are, therefore, of dubious value - see discussion below.
Clay and marl formations have little permeability and yield little water to wells.
While it would theoretically be possible to draw substantial quantities of water from water table portions of sandy aquifers, these supplies would be potentially vulnerable to pollution, and would in many cases, require installation and maintenance of well fields or infiltration galleries. Larger supplies in Monmouth County are therefore drawn from deeper, more easily developed, and less easily contaminated artesian portions of aquifers.
With increasing development has come extensive reliance on artesian aquifers. Increase in demand was gradual from 1900 until the mid-1950's, and more rapid from the mid-1950s to the present.
Demand has been most severe in the Englishtown and Mount Laurel-Wenonah Formations. The impact is most pronounced near heavily suburbanized pumping centers along the shore and in southern Monmouth County, near Lakewood. Water levels in observation wells in these areas dropped as much as 100 feet between 1959 and 1970; and were dropping at rates of 8 to 12 feet per year during the 1970's
Optimum water budget for water table portions of formations are based on their abilities to accept, store, and release precipitation locally. Withdrawals from artesian portions of aquifers are replaced by flow from outcrop areas as much as 25 miles from withdrawal sites, and by slow leakage from underlying and overlying formations. Decrease in artesian pressure due to pumpage can be felt across broad areas, and is transmitted vertically upward and downward to adjacent aquifers. Water budgets, therefore, cannot be assigned on a per square mile basis, nor can they be restricted to a single aquifer. They must be regional and account for effects on other aquifers.
Evaluation of water budget is further complicated by lack of precise knowledge of water-bearing formations, and variation in these properties from place to place. Although an optimum water budget cannot be calculated, it is clear that that over-pumping has occurred in certain formations at population centers. Unchecked further development will lead to more extensive over-pumping and eventually require development of new, potentially expensive sources of supply.
Computer modeling provides a tool for simulating the complex interactions among water-bearing formations. This enables the evaluation of magnitudes of available supplies, and the merits of alternative schemes of development. A preliminary model has been developed on the basis of estimated abilities of aquifers and confining beds to store and transmit water.
Although the model has serious shortcomings, as a planning tool, it has proven its ability to simulate historical water-level fluctuations and to indicate magnitudes of leakage between formations.
The Red Bank - Tinton, Vincentown, Kirkwood and Cohansey sands are classified as water table aquifers within the Township. Farther downdip they may be artesian. In 1968, Jablonski [Geological. Survey & N.J. Dept. Conserv., Special Report 23] strongly suggested that formations lying between the Mt. Laurel-Wenonah and the Englishtown sands were not true aquicludes - that they "leaked" water between the two aquifers. This appears to be confirmed by two recent studies, by Nemikas [Digital Simulation Model of the Wenonah-Mt. Laurel Aquifer in the Coastal Plain of N.J., U.S. Geological. Survey - 1976.] and Nichols. [Digital Computer Simulation Model of the Englishtown Aquifer in the Northern Plain of N.J., U.S. Geological Survey, 1976.]
In the Point Pleasant area where municipal water supplies are obtained from the Englishtown and Mt. Laurel-Wenonah sands, the water table dropped about 100 feet in the period 1959 to 1970. The later study by Nichols showed a static water table drop of 100 feet in the Englishtown for the period 1900 to 1959, and an additional drop of 120 feet in the period 1959 to 1970; ostensibly from overproduction. The authors concluded that because of limited withdrawal in that area from Mt. Laurel-Wenonah, the static water table drop in that formation substantially reflected downward migration into the Englishtown.
Prior to results of the latter two reports and a later lithologic study of the Mt. Laurel-Wenonah [L.C. Lamar, Cert. Prof. Geologist, Colts Neck Environmental. Commission.] formation, there was concern that downdip withdrawal might have a serious effect on aquifer water supplies available within the Township. It would now appear that static water table drop within the Township amounts to no more than 15 to 20 feet; based on limited control points. It also appears that local drops in withdrawal capacity from the Mt. Laurel-Wenonah of as much as 50% over a 10 year period is due to poor and irregular recharge rates vs. usage, and that the Englishtown still has an adequate supply.
Salt water intrusion has been noted in the Englishtown sand in the Raritan Bay area (Keyport) and in the Raritan-Magothy in the Atlantic City area. These encroachments are being monitored by the NJ Department of Environmental Protection, and remedial action is planned.
Depending on the surface elevation, depths to the principal artesian aquifers within the Township vary in depth, north to south, as follows: Mt. Laurel - 25 to 250 feet; Englishtown 125 to 300 feet; and Raritan-Magothy, 500 to 725 feet.
In summary, it appears that adequate domestic water will continue to be available in the Mt. Laurel-Wenonah formation except in the central densely developed area of Colts Neck. Initially adequate wells (10 gallons per minute minimum) may be subject to future supply drop because of slow recharge. Use of Englishtown water is now limited. Some Mt. Laurel-Wenonah wells have ceased to supply adequate water and new wells to the Englishtown have had to be drilled. Township sanitary regulations require Englishtown wells in the northernmost portion of the Township where the out-cropping Mt. Laurel-Wenonah may make it subject to pollution.
In conclusion, there appears to be no serious problem with underground water supplies so long as present development spacing, and limitation to only light industry are enforced. Any concentration of water use, however, such as community water supply for planned unit development, golf course, extensive agricultural irrigation, or unusually large use for light industry or professional offices, could cause an eventual drop even in the Englishtown sand. Unusually large potable or irrigation needs should be supplied from the Magothy-Raritan sands.
The lithology ["Lithology" in geology means the physical characteristics of a rock or stratigraphic unit.] and consequent hydrologic characteristics of the principal aquifers in Colts Neck Township [See Fig. 2 for Columnar Section thickness and general lithology.], from the geologically youngest and shallowest to the oldest and deepest, is as follows:
The Cohansey is a fine-grained, poorly cemented, porous and permeable quartz sand. It is an excellent water table aquifer present only in the south central portion of the Township and only within the confines of Naval Weapons Station Earle. Little of its local characteristics are known, but to the south it is used as a potable water supply.
The Kirkwood is divided into an upper and lower sand unit. It, like the Cohansey, is fine-grained and poorly cemented quartz sand, but clay inclusions in the upper portion and silt in the lower portion limits its value as an aquifer in local areas. It, too, is present in the Township only in the confines of NWS Earle and is a water table aquifer.
The Vincentown is also divided into an upper and lower unit. In a well immediately north of NWS Earle (Municipal garage) it is 70 feet thick. The uppermost 20 feet is poorly cemented, yellow quartz sand. The next 40 feet is gray silty clay with quartz grains increasing in the lower portion as gray sand and silt. The lower 10 feet is mostly sandy, calcareous clay with mica. Prior to being depleted by a cut on Highway 18, the Vincentown was a water table aquifer for a number of residents in the Stout Hill-Five Points Road area. It appears to be of better quality in that area where it is in excess of 80 feet thick. Further south, where the entire section is complete, it may be in excess of 100 feet thick.
The Red Bank-Tinton is a course-grained, poorly cemented,silty sand. The upper member is red to brown course-grained quartz sand, predominantly cemented with iron oxide, and becomes gray toward the base. The lower member grades downward from gray, limey sand and silt to dark gray, glauconitic, lignitic, sandy shale. It is also a water table aquifer within the Township and was used for water supply in early dug wells. Sand development is erratic and generally poor.
The Mt. Laurel-Wenonah formation consists of the upper Mt. Laurel, a light, fine-grained, micaceous quartz sand and the lower Wenonah, which is siltier, more glauconitic, and darker. The contact is gradational and difficult to pick, even under a microscope.
In general the upper member has a maximum thickness of 30 feet and is best developed in the western portion of the Township, while the lower member appears best developed on the eastern side. A central north-south area has poor or no sand development in general, though some good wells have been reported. Water productivity in this area is generally at, or below, 10 gallons per minute - considered minimal for domestic needs. The development of the lower member, in general, is siltier and darker than the upper member.
The depositional history of the Mt. Laurel-Wenonah is considered near shore marine. Microscopic studies of both surface and well samples indicates the aquifers to be buried sand bars. [Ron Martino, Masters Thesis, Rutgers Univ. ] Based on a regional study [L.C. Lamar, private study for the Environmental Commission. ] of both sample and drillers' logs, the area of poor or no sand development is indicated to be a high energy zone - possibly near the mouth of a stream or a tidal outwash zone.
The Englishtown formation is composed of medium-to-course-grained sand interlayed, in some areas, by clay or silt layers. The entire formation may exceed 100 feet in thickness and is developed as an excellent aquifer over the entire Township. Most wells to this aquifer produce in excess of 25 gallons per minute and may exceed 100 gallons per minute. More and more residents are drilling to the Englishtown sand, particularly in the central part of the Township where the Mt. Laurel-Wenonah is poorly developed.
The Raritan-Magothy formation consists of massive quartz sands interstratified with dark silty clays and dark and light fine sands. Although the Raritan and Magothy are separated by a disconformity, they may be considered as a single aquifer. In Colts Neck Township, only a few wells have been drilled to this aquifer and these used for farm irrigation and to furnish water for a golf course. Production may exceed several hundred gallons per minute.
Miscellaneous aquifers, generally of low productivity and spotty development, include glauconitic and/or silty sands in the Navesink formation, particularly in the lower portion.
Chemical & Bacteriological Character
All well water contains dissolved minerals. These minerals are derived from the sediments, rocks and soil particles with which the ground water has been in contact. The chemical composition of ground water varies from aquifer to aquifer. Because of changes in rock composition and in the direction and rate of movement of ground water, the composition can vary from point to point, even within the same aquifer.
The chemical constituents which may occur in objectionable concentrations in Colts Neck are iron, calcium, magnesium, hydrogen sulfide, carbon dioxide, and silica. Water treatment methods are available for correcting the problems caused by these substances.
Iron is objectionable because when its concentration exceeds 0.3 parts per million (as it does in most Colts Neck wells), it leaves a reddish-brown stain on plumbing fixtures, laundered clothes, dishes, etc. The calcium and magnesium salts cause a scale to form in pipes, particularly in the hot water system, and it also decreases the amount of lather produced by soaps. A "rotten egg" odor in the water indicates the presence of hydrogen sulfide. When carbon dioxide is present in the water, it makes the water corrosive. Silica in the water can contribute to scale formation.
Other chemicals which are usually present in small concentrations are manganese, sodium, potassium, carbonates, bicarbonates, sulfates, chlorides, fluorides and nitrates.
The degree of acidity or alkalinity of water is measured by the pH values which, for well waters, generally range from 4.5 to about 9.0. A pH of 7.0 indicates neutral water. Values below 7 indicate increasing acidity, and values above 7 increasing alkalinity. A knowledge of the pH assists in the control of corrosion and in the determination of the proper water treatment methods to use.
Because of the general presence of iron in Colts Neck well waters, contamination of well water by "iron bacteria" has occasionally been a problem. Iron bacteria are nuisance organisms which are not harmful to humans or animals drinking the water. They feed on the iron and have the ability to oxidize and precipitate it. These bacteria can clog water treatment equipment and can also reduce the carrying capacity of water pipes. A slimy, rust-colored coating on the interior surfaces of toilet flush tanks indicates the presence of these bacteria.
The temperature of ground water is nearly constant throughout the year. This temperature is near the average annual temperature at the surface, about 53 F in Colts Neck. Water from sources less than 50 feet deep may vary slightly from one season to another. Beyond 100 feet of depth, the temperature increases steadily at the rate of about 1 F for each 100 feet of depth.
Water from the Raritan formation is generally of excellent chemical quality, except for high concentrations of iron and corrosives (low pH). Iron concentrations in excess of 6 ppm are common. The pH values range from 4.6 to 7.4, with most of the samples tested falling within range of 5.6 to 6.6. The concentrations of other chemicals are low enough not to be a problem for most purposes.
Water from the Wenonah-Mt. Laurel sand formation is moderately hard and is generally of excellent quality. The hardness ranges up to about 100 ppm. Low pH and high iron content are occasionally a problem.
The water from the Englishtown formation is also of generally excellent chemical quality. The water is usually medium-hard (about 100 ppm) and the iron concentration may occasionally exceed 0.3 ppm.
Pollution
Sources of ground water pollution in other communities in the past have been:
1. Seepage of contaminants into wells due to improper construction of the well.
2. Too many septic fields or cesspools in an area producing more effluent than can be naturally filtered and degraded, so that contaminated water reaches the water table.
3. Leachate from improperly located, mismanaged dumps, or sanitary landfill sites.
4. Excess pumping permitting salt water to enter the aquifer.
5. Heavy use of chemicals, such as fertilizers, herbicides and pesticides.
Overall, the possibility of ground water pollution in our Township from these or any other sources appears remote for the foreseeable future. All new wells are tested for bacterial contamination prior to the issuance of a Certificate of Occupancy. Because water is filtered naturally as it flows below the surface, if a well is properly constructed, contamination by harmful bacteria should not become a problem. For example, in soils having the permeability of fine sand, bacterial contamination from the surface extends only about 20 feet down. The bacterial quality of water also improves during storage in the aquifer because storage conditions there are generally unfavorable for bacterial survival. Chemical pollutants, however, are usually not removed by natural filtration.
In 1982, the Colts Neck Board of Health initiated a program to test selected Colts Neck wells for toxic chemicals(the testing has been limited mostly to volatile organic compounds.) No significant problems have been uncovered by these tests as of mid-1983.
During 1977-1978 the New Jersey Department of Environmental Protection Program on Environmental Cancer and Toxic Substances sampled Monmouth County surface and ground waters for toxic and carcinogenic chemicals, such as organic chemicals, pesticides and heavy metals. Highly sensitive analytical techniques, capable of detecting parts per trillion of concentration, were used. Very low levels of pollutants were detected in some of the samples; however, "none of the wells sampled had any organic chemical or PCB, and pesticide concentrations above or near current and suggested water quality standards. However, standards have not been set for a number of these substances because of insufficient research on their health effects."
In the surface water sampling program for the Swimming River Reservoir watershed, "a total of nine different organic compounds were observed...the most frequently observed of these compounds was l,l,l-Trichloroethane, which was observed at eleven sampling sites out of a possible fifteen... the watershed with the greatest number of organics (7) was Big Brook...both phosphate and fecal coliform were above State standards at most sampling stations within the Swimming River watershed...three pesticides, Lindane, Heptachlor and -Chlordane, as well as PCB's were observed within this watershed...although the presence of these substances locally, at the concentration reported, presents no immediate danger to health, information and data relative to long-term effects at low level exposure on human health are lacking. In light of this lack of knowledge, it would be prudent to eliminate these substances entirely, or at least to minimize their presence in drinking water..."
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References:
1. L.A. Jablonski, "Ground Water Resources of Monmouth County, New Jersey" - USGS Special Report No. 23, 1968.
2. P.R. Seaber, "Variations in Chemical Character of Water in the Englishtown Formation, N.J." - USGS Professional Paper 498-B, 1965.
3. W. Black, "Hydrochemical Facies and Ground Water Flow Patterns in Northern Part of Atlantic Coastal Plain" - USGS PAPER 498-a, 1966.
4. G.M. Banino, F.J. Markewicz, J.W. Miller,Jr., "Geologic Hydrologic and Well Drilling Characteristics of the Rocks of Northern and Central New Jersey", - N.J. Dept. of Environmental Protection, Bureau of Geology and Topography, 1970.
5. Manual of Individual Water Supply Systems, U.S. Environmental Protection Agency, EPA 430-9-73-003, 1973.
6. Water Quality Management Plan - Monmouth County, N.J., New Jersey Dept. of Environmental Protection, 1979 .