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Brooklyn - Queens Aquifer System Brooklyn - Queens Aquifer System

Support Document

  Kings and Queens Counties New York 
December 1983

I. Introduction

A. Statement of Section 1424 (e)

The Safe Drinking Water Act (SDWA), Public Law 93-523, of December 16, 1974 contains a provision in Section 1424(e), which states that:

"If the Administrator determines, on his own initiative or upon petition, that an area has an aquifer which is the sole or principal drinking water source for the area and which, if contaminated, would create significant hazard to public health, he shall publish notice of that determination in the Federal Register. After the publication of any such notice, no commitment for Federal financial assistance (through a grant, contract, loan guarantee, or otherwise) may be entered into for any project which the Administrator determines may contaminate such aquifer through a recharge zone so as to create a significant hazard to public health, but a commitment for Federal financial assistance may, if authorized under another provision of law, be entered into to plan or design the project to assure that it will not so contaminate the aquifer."

This section allows for the specific designation of areas which are dependent upon ground water supplies. Following designation, the review will ensure that federal agencies will not commit funds toward projects which may contaminate these ground water supplies.

B. Receipt of Petition

The Jamaica Water Supply Company supplies water from sixty-five (65) wells located in or near the water supply franchise area to approximately 650,000 people in the southern portion of Queens County, a borough of New York City. In total about eighty percent (80%) of the water used by the Jamaica Water Supply Company is derived from ground water in that area.

On June 18, 1979, the Jamaica Water Supply Company petitioned the EPA Administrator to declare the portion of the Long Island Aquifer defined in the petition and occurring in the service area as a sole source aquifer under the provisions of the Act.

C. Area of Consideration

The Long Island aquifer system underlies all of Nassau, Suffolk, Kings, and Queens Counties. While the Kings and Queens Aquifers are not utilized as the sole or principal source of drinking water for the Borough of Kings or for any other portion of Queens County, the geographic boundaries of Kings and Queens Counties are the recharge zone for the aquifers underlying the southeastern portion of Queens County. The Administrator has determined that the recharge zone and streamflow source zone for the aquifers underlying southeastern Queens County are defined by the outside boundary of Kings County (Borough of brooklyn) and Queens County (Borough of Queens) in the city of New York and parts of Nassau County. Since parts of Nassau County within the recharge and streamflow source zones of the aquifers are already under sole source protection as the result of the Agency's prior designation of aquifers underlying Nassau-Suffolk Counties, this designation extends the area for project review to encompass projec ts undertaken in the Boroughs of brooklyn and Queens of New York City, New York.

II. Hydrogeology

A. Geologic Framework

That part of the Long Island Aquifer System supplying water to the area is in Queens is located at the western end of Long Island, New York, and lies within the Atlantic Coastal Plain Physiographic province of the United States. This part of the aquifer system is bounded on the north by the ground water divide of the water table in the northern Queens-central Kings County, on the east by Nassau County (already under sole protection), on the south it extends into the Atlantic Ocean and on the west by New York Bay and the East River. In many other ground situations streams must be considered for their effect on the aquifer, but in the case of this part of Long Island, there is no streamflow that affect the aquifer.

Long Island's present configuration is primarily the result of the glaciation which occurred during the Pleistocene Era, predominantly that of the last ice age, the Wisconsin which ended about ten thousand (10,000) years ago.

Long Island's present configuration is primarily the result of glaciation which during the Pleistocene Era, predominately that of the last ice age,the Wisconsin, which ended about ten thousand years ago. Two advances of the Wisconsin ice sheet during the Upper Pleistocene of the Quaternary Period caused the island to be blanketed with till, icecontact stratified drift, outwash deposits and deposits composed of clay, silt, sand, gravel and boulders. The terminal moraines and the north shore are composed primarily of stratified drift with some till. The area between the moraines and south of them are mostly the outwash deposits. Central and South Long are of the glaciofluvial origin. The Pleistocene deposits lie atop the gentlydipping Cretaceous rocks.

The bedrock was eroded to a peneplain before the overlying Cretaceous sediments were deposited; its surface shows signs of later erosion by Pleistocene glaciation in the north. Bedrock crops out in northwestern Queens County near the East River and slopes southward at about eighty (80) feet per mile. Consequently, the overlying formations form a southward-dipping wedge that attains a maximum thickness of one-thousand fifty (1,050) feet in the southeast corner of Queens County. The maximum thickness of unconsolidated deposits in Kings County is about eight-hundred (800) feet in southeast Kings.

Overlying bedrock is the Raritan Formation of Late Cretaceous age, consisting of the Lloyd Sand Member and an upper, unnamed clay member. Overlying the Raritan Formation is the Magothy Formation and Matawan Group, undifferentiated, also of Late Cretaceous age, the Jameco Gravel of Pleistocene age, the Gardiners Clay of Pleistocene age, upper Pleistocene deposits of Wisconsin age, and a generally thin soil mantle of Holocene age. Holocene beach deposits make up most of the Rockaway Peninsula and Coney Island in the south, and Holocene salt-marsh deposits underlie and fringe the south-shore bay areas. Artificial filling has been done in low and swampy shoreline areas. Because Holocene deposits occur in relative small areas of Kings and Queens and are not significant water bearers, they are not included in the geologic descriptions that follow. The four distinct formations on Long Island: The Upper Glacial, the Jameco, the Magothy and the Lloyd aquifers. They all occur in the unconsolidated materials overlyin g the bedrock (Figure 2).

1. Upper Glacial Aquifer

The Upper Glacial aquifer, overlie all underlying units and are found at the surface in nearly all of Kings and Queens Counties. The surficial geologyof this area was mapped and contain the following glacial deposits: (1) terminal moraine deposits emplaced by an ice front of Harbor Hill age; and (2) ground-moraine deposits north of the terminal moraine; and (3) glacial outwash south of the terminal moraine. Thickness of the Upper Glacial range from zero in small areas of northwestern Queens, where bedrock crops out, to as much as three-hundred (300) feet in the terminal moraine and near the buried valley. The terminal moraine is an unsorted and unstratified mixture of clay, sand, gravel, and boulders that were accumulated at the front of a continental glacier.

The ground moraine is similar in character to the terminal moraine but was formed at the base of the ice sheet during periods of ablation. Meltwater from the ice front flowed southward and carried sand and gravel in broad coalescing sheets to form an outwash plain that extends from the terminal moraine south to the coast. Pre-Harbor Hill deposits are present at depth in the sequence of Upper Glacial deposits. The twenty foot (20') clay in eastern Queens and Nassau Counties is a marine clay deposited during the Ronkonkoma-Harbor Hill interstade (Soren, 1978). This unit locally separates the Harbor Hill drift from the underlying Ronkonkoma Drift and earlier deposits.

2. Jameco Aquifer

The Jameco Gravel is the earliest Pleistocene deposit in the area. It is considered to be a channel filling associated with ancestral pre-Sangamon diversion of the Hudson River (Soren, 1978). The Jameco is present in most of Kings County and southern Queens County. It reaches greatest thickness in the deep channels eroded in the underlying unit and thins severely over the higher areas. For example, a small area in southeast Queens in which the Jameco Gravel has not been found coincides with a high point on the surface of the underlying Magothy Formation. Thickness of the Jameco ranges from a knife edge at its northern limit to more than two-hundred feet (200') in the main buried valley in central Queens County. Jameco deposits consist mainly of a heterogeneous suite of igneous, metamorphic, and sedimentary rock types that are typically dark brown. The deposits grade from coarse sand and gravel with many cobbles and some boulders in the northern part of Kings County to finer particles southward. Many diab ase fragments indicate transport by meltwater fro a glacial terminus northwest of New York City. The surface altitude is generally highest along the units north edge, as shallow as one hundred-ten feet (110') below sea level in northern Kings County, and ninety feet (90') below sea level in Queens County. It is generally deeper to the south and over the deep channels eroded in the Late Cretaceous surface, where it is more than two-hundred feet (200') below sea level. The surface of the Jameco was probably shaped by stream erosion and by glaciation.

3. Magothy Aquifer

The Magothy aquifer, which underlies both of Kings and Queens Counties, are of continental origin and are mostly deltaic quartzose very fine to coarse sand and silty sand with lesser amounts of interbedded clay and silt. The unit commonly has a coarse quartzose sand and in many places a gravel basal zone twenty-five to fifty feet (25 - 50') thick. The units thickness ranges from zero at its limits to more than two-hundred feet (200') in southeast Kings and five-hundred feet (500') in southeast Queens. Altitudes of the Magothy surface range from a few feet above sea level in northeast Queens to more than four-hundred feet (400') below sea level in the buried valley to the south.

4. Lloyd Aquifer

The Lloyd aquifer, which lies unconformably on bedrock. It is absent in northwestern Kings and Queens Counties. The limit generally follows a line from southwest Kings County through central Kings northward to near LaGuardia Airport. The Lloyd Sand Member consists mainly of deltaic deposits of fine to coarse quartzose sand interbedded with sand and small to large pebble quartzose gravel. Interbeds of silt and clay and silty and clayey sand are common throughout the unit. The extend of the Lloyd are largely coincident where eroded in the buried valley system in northern Queens. Thickness of the Lloyd ranges from zero at its northern extent to about two-hundred feet (200') at Kings County's southeast edge and three-hundred feet (300') in southeast Queens County. The units surface is as shallow as ninety feet (90') below sea level in northern Queens County and as deep as eight hundred twenty-five feet (825') below sea level in the southeast.

B. Geologic Setting

The Long Island aquifer system is located in Long Island, New York, and lies within the Atlantic Coastal Plain physiographic province of the United States. Long Island is bounded on the north by Long Island Sound, on the east and south by the Atlantic Ocean and on the west by New York Bay and the East River (Figure 1). The island is one hundred twenty (120) miles (193 kms) wide. Including the barrier beach and other outlying islands, its area is approximately one thousand four hundred (1,400) square miles (3,600 square kilometers).

C. Ground Water Hydrology

The entire ground water reservoir may be regarded as a single hydraulic system in which the more permeable zones, which yield useable amounts of water to wells, are termed aquifers, and the less permeable, which retard the movement of ground water, are termed confining beds.

Where present, the Gardiners Clay restricts vertical flow between the Upper Glacial and the deeper aquifers, and the Raritan confining unit restricts vertical flow between the upper aquifers and the Lloyd Aquifer. Both clay units are significant confining beds and have been estimated to have a vertical hydraulic conductivity of 0.001 foot per day (Franke and Cohen, 1972), much lower than that of the aquifers. Large hydraulic gradients are developed across these units, and flow patterns in aquifers are affected. Where the confining units are absent, ground water flow between aquifer units is uninhibited. Thus special attention should be paid to the exact extent of the confining units when defining ground water flow patterns.

The bedrock underlying these unconsolidated deposits has a low hydraulic conductivity and does not yield more than a few gallons per minute to wells. The quantify of water that can flow across this boundary is insignificant compared with the quantities that flow in the overlying unconsolidated units. Therefore, the bedrock surface is considered to be the bottom hydrologic boundary of the ground water flow systems.

1. Recharge

Data from central and eastern Long Island indicate that, approximately fifty percent (50%) of annual precipitation infiltrates to the water table and recharges the ground water system (Cohen, 1968); the remainder is lost to evapotranspiration and direct runoff. Although precipitation fluctuates on both seasonal and longer term cycles, the addition of fresh water is adequate to maintain a large reservoir of fresh water stored in the unconsolidated deposits beneath Long Island.

2. Discharge

Much of the water that enters the ground water system remains in the Upper Glacial aquifer, moves laterally, and discharges to surrounding salt-water bodies. Ground water seepage to streams and springs causes some vertical gradients in the shallow water aquifer. The rest of the water entering the system flows downward to the deeper aquifers, that discharges to surrounding salt-water bodies.

D. Ground Water Quality

In addition to lowering ground water levels, urbanization and development of the ground water system in Kings and Queens Counties have caused serious deterioration of ground water quality. The most striking example was the encroachment of salt water from surrounding tidewater in response to excessive drawdown. Other sources of contamination, some of which were present from the early stages of development, include road salts, leaking sewers, and toxic spills at land surface. Historical water quality data are sparse; however, chloride and nitrate data were collected as far back as 1900 and are used here to give an indication of the response of ground water quality during this century.

Water fro much of the Upper Glacial aquifer in Queens County had a chloride concentration greater than forty (40) milligram per liter. Chloride contamination appears primarily in shore areas and is largely the result of salt water encroachment. Landward migration of salty ground water is evident in two tongues that originate where drawdown of water levels to near or below sea level reached shore areas. A part of the chloride contamination in Queens County is undoubtedly from inland surface sources, especially in northwest Queens County, which has been extensively developed since the 19th century and where apparent water table gradients suggest that saltwater intrusion is unlikely.

High concentrations of nitrate in ground water indicate contamination from surface sources, such as fertilizers, landfills, leachate from cesspools and septic tanks, and leaky sewer lines. Data on nitrate contamination of the deeper aquifers in Kings County are scarce. Nitrate data in Queens County, was sampled from thirty-eight (38) wells (10 in the Lloyd, 15 in Magothy-Jameco, and 13 in the Upper Glacial). Nitrate concentrations were above ten milligrams per liter in water from only four wells. Nitrate contamination in Queens County is not as extensive as that in KingsCounty.

E. Designated Areas

The area designated as the Sole Source Aquifer is the recharge zone and streamflow source zone for the aquifers underlying southeastern Queens County and defined by the outside boundary of Kings County (Borough of brooklyn) and Queens County (Borough of Queens) in the city of New York and parts of Nassau County. Since the parts of Nassau County with the recharge and streamflow source zones of the aquifers underlying southeastern Queens County are already under sole or principal source protection as the result of the Agency's prior designation of the aquifers underlying Nassau-Suffolk Counties, designation will extend the area to encompass the Boroughs of brooklyn and Queens in the city of New York.

III. Susceptibility to Contamination

The brooklynQueens Aquifer System is highly vulnerable to contamination. With the exception of the water derived from the Lloyd aquifer, about ten percent (10%) of the ground water withdrawals, the quality of ground water has declined from that of pristine conditions. Nitrate exceeds 10 mg/l at some well locations in the Upper Glacial aquifer. The source of this nitrogen is probably leaking sewer pipes, though other sources such past farming practices and present fertilization of lawns and gardens may be significant. Further and continued withdrawal of water at the current rate also threatens water quality if the saltfresh water interface enters the area. This phenomena is highly likely, if the present rate of withdrawal is maintained or increased, since the loss of fresh water will no longer prevent salt water encroachment. Currently a mound of fresh water separates the depressed water table from salt water but unless measures are taken to maintain this feature the supply will, in time, become salty. Care ful management of this resource is needed if the resource is to be available continuously.

IV. Alternative Sources

Under current conditions New York City has supplied up to thirty percent (30%) of the water demand for the franchise area of Jamaica Water Supply Company. This source is the only possible alternative at similar cost.Whether or not the City could meet the demand of the Jamaica area could not be verified with city officials. New York City would not reply to the question of sufficient supply. It is known however, that City water main connections with the Jamaica franchise area are reported to be too small to maintain sufficient pressure in the Jamaica area.

V. Summary

Based upon the information presented, the brooklyn-Queens Aquifer System meets the technical requirements for SSA designation. More than fifty percent (50%) of the drinking water for the aquifer service area is supplied by the brooklyn-Queens Aquifer System. It is therefore recommended that the brooklyn-Queens Aquifer System be designated a SSA. Designation will provide an additional review of those projects for which Federal financial assistance is requested, and will ensure ground water protection measures, incorporating state and local measures whenever possible, are built into the projects.

VI. Selected References

1. Philip Cohen and G.E. Kimmel, Status of Salt Water Encroachment in 1969 in Southern Nassau and Southeastern Queens Counties, Long Island, New York: U.S. Geological Survey Professional Paper 700-D. U.S. Geological Survey, 1970. pp. D281-286.

2. O.L. Franke and Philip Cohen, Regional Rates of Ground Water Movement on Long Island, New York: U.S. Geological Survey Professional Paper 800-C. U.S. Geological Survey, 1972. pp. C271-277.

3. O.L. Franke and N.E. McClymonds, Summary of the Hydrologic Situation on Long Island, New York, as a Guide to Water Management Alternatives: U.S. Geological Survey Professional Paper 627-F. U.S. Geological Survey, 1972. pp. 59.

4. Grant E. Kimmel, The Water Table on Long Island, New York, in March 1970: Long Island Water Resources Bulletin Number 2. U.S. Geological Survey. pp. 8.

5. Henry F.H. Ku, John Vecchioli, and Stephen E. Ragone, Changes in Concentration of Certain Constituents of the Treated Waste Water During Movement Through the Magothy Aquifer, Bay Park, New York: U.S. Geological Survey Journal Research, Vol. 3, No. 1, Jan-Feb 1975. U.S. Geological Survey. pp. 89-92.

6. N.E. McClymonds and O.L. Franke, Water Transmitting Properties of Aquifers on Long Island, New York; U.S. Geological Survey Professional Paper 627-E. U.S. Geological Survey, 1972. pp. 24.

7. J.F. Miller and R.H. Frederick, The Precipitation Regime of Long Island, New York: Hydrology and Some Effects on Urbanization on Long Island, New York, Geological Survey Professional Paper 627-A. U.S. Geological Survey, 1969. 21 pp.

8. N.M. Perlmutter, F.J. Pearson, and G.D. Bennett, Deep-Well Injection of Treated Waste Water--An Experiment in Re-Use of Ground Water in Western Long Island, New York: Repeat from New York State Geological Association Guidebook, 40th Annual Meeting, 1968. pp. 221-231.

9. Nathaniel M. Perlmutter and Theodore Arnow, Ground Water in Bronx, New York, Richmond Counties with Summary Data on Kings and Queens Counties, New York City, New York: Bulletin GW-32. Water Power and Control Commission, U.S. Geological Survey in Cooperation with New York State Department of Conservation, 1953. 86 pp.

10. Julian Soren, Ground Water and Geohydrologic Conditions in Queens County, Long Island, New York; U.S. Geological Survey Water-Supply Paper 2001-A. U.S. Geological Survey, 1971. pp. 39.

11. Julian Soren, Basement Flooding and Foundation Damage from Water-Table Rise in East New York Section of brooklyn, Long Island, New York; U.S. Geological Survey Water Resource Investigation 76-95. U.S. Geological Survey, 1976. pp. 14.

12. Julian Soren, Subsurface Geology and Paleogeology of Queens County, Long Island, New York; U.S. Geological Survey Water-Resources Investigations Open-File Report 77-95. U.S. Geological Survey, 1978. pp.17.

13. Joseph E. Upon, The Gardiners Clay of Eastern Long Island, New York--A Reexamination; U.S. Geological Survey Professional Paper 700-B. U.S. Geological Survey, 1970. pp. 157-160.

VII. Figures

Brooklyn - Queens Figures

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