The Lloyd aquifer contains about 9 percent of Long Island’s potable water and has been a source of public-water supply since the early part of the 20th century. Many studies during the 20th century have provided information on this confined 

aquifer and helped refine its representation in ground-water flow models.

The Lloyd is the lowermost aquifer on Long Island and has the lowest transmissivity (1,500 to 19,000 feet squared per day). 

The Lloyd receives 3.1 percent of Long Island’s total recharge through a narrow corridor along the island’s ground-water divide. 

Nearly all pumping from the Lloyd aquifer has been in the western part of Long Island; the maximum annual withdrawal was 

about 6.4 billion gallons in Nassau County in 1971. Excessive pumpage has led to saltwater intrusion in the Lloyd aquifer in 

coastal areas.

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2006–1341

December 2006

Hydrogeology of the Lloyd Aquifer on Long Island,

New York–A Brief Summary of USGS Investigations
Introduction

The four counties of Long Island (fig. 1) are underlain by 

a wedge-shaped sequence of unconsolidated deposits of Late 

Cretaceous and Pleistocene age that lie unconformably on 

crystalline bedrock (fig. 2). A saprolitic (weathered bedrock) 

zone 20 to 100 ft thick overlies the bedrock in most areas. The 

sequence of unconsolidated deposits thickens to the south and 

southeast by about 65 to 100 feet per mile and contains Long 

Island’s fresh ground water.

Long Island’s ground-water system consists of four main 

aquifers–the upper glacial, the Jameco, the Magothy, and the 

Lloyd. The Lloyd aquifer underlies nearly all of Long Island 

(fig. 3), but pumpage from the Lloyd has been limited to the 

northern and southern coastal areas of the island by the New 

York State Department of Environmental Conservation since 

about 1955 (Garber, 1986). Coastal areas are exempt where the 

Lloyd is the only source of potable water. The former Jamaica 

Water Supply Corporation (now owned by New York City) is a 

noted exception withdrawing as much as 6 million gallons per 

day (Mgal/d) since the mid-1930s from the Lloyd in central 

Queens County.

This paper: (1) provides a brief history of U.S. Geological 

Survey (USGS) studies that provided significant data on the 

Lloyd, (2) summarizes the hydraulic characteristics of the 

Lloyd as reported in those studies, and (3) describes present-day 

monitoring of the Lloyd by the USGS.

Previous Studies

The earliest comprehensive study of Long Island’s groundwater resources was done by Veatch and others (1906), who 

were the first to name a stratigraphic deposit from Lloyd Neck 

as the “Lloyd sand.” Suter (1937) estimated the potential 

ground water yield of the four aquifers, including the Lloyd 

sand, in each county. Suter and others (1949) mapped Long 

Island’s geologic units, at which time they named the Lloyd 

sand member and grouped it with the Raritan Formation. Cohen 

and others (1968) were the first to use the name Lloyd aquifer 

for the Lloyd Sand Member. McClymonds and Franke (1972) 

estimated hydraulic properties of the Lloyd and other aquifers 

on Long Island. Franke and Cohen (1972) estimated regional 

rates of ground-water movement and the age of ground water 

in the upper glacial, Magothy, and Lloyd aquifers on Long 

Island. Kimmel (1973) mapped the potentiometric surface of 

the Lloyd throughout Long Island and the changes in its altitude 

between 1900 and 1970. Sirkin (1974, 1986) used pollen data to 

revise the stratigraphy of the Cretaceous age sediments on Long 

Island and correlate them with stratigraphic units off of Long 

Island. Rich and others (1975) and Donaldson and Koszalka 

(1983) mapped the potentiometric surface of the Lloyd aquifer 

on Long Island in 1975 and 1979, respectively. Garber (1986) 

provided a compilation of previous hydrogeologic investigations 

of the Lloyd aquifer. Doriski (1986, 1987) mapped the watertable and potentiometric-surface altitudes of the upper glacial, 

Figure 1. Approximate location of ground-water divide, Kings, Queens, Nassau, and Suffolk 

Counties on Long Island, N.Y.

NEW YORK

NEW

Base from U.S. Geological Survey digital data, 1:100,000, 1979,

Universal Transverse Mercator projection, NAD 27, Zone 18

74° 73° 72°

40°30'

41°

41°30'

SUFFOLK

CONNECTICUT

KINGS

QUEENS

NASSAU

JERSEY

ATLANTIC OCEAN

LONG ISLAND SOUND

0 10 20 40 KILOMETERS

0 10 20 40 MILES

NEW YORK

LONG ISLAND

EXPLANATION

LOCATION OF LLOYD WELL

GROUND-WATER DIVIDE
Figure 2. Cross section showing lithology of major hydrogeologic units 

along a generalized north-south section through the ground-water system 

of Long Island, N.Y. (Section represents an area near the Nassau-Suffolk 

County border.) (Modified from McClymonds and Franke, 1972, fig. 3)

EXPLANATION

GLACIAL DEPOSITS

DELTAIC AND MARINE DEPOSITS

Atlantic Ocean

Long Island

Sound

Bedrock

VERTICAL SCALE IS GREATLY EXAGGERATED

400

FEET

-400

-800

-1,200

-1,600

-2,000

-2,400

0

NORTH SOUTH

Brown, fine to coarse sand and

gravel with some interbedded silt

and clay

Gray, fine to coarse sand with

interbedded silt, clay and lignite.

Monmouth Greensand contains

glauconite

Gray or white, fine to coarse sand

and gravel with some interbedded

silt and clay 

Gray clay with silt and fine sand.

Gardiners Clay contains glauconite

and some interbedded gravel

0

0

5 MILES

5 KILOMETERS

Gardiners Clay

Magothy aquifer

Raritan confining unit

Lloyd aquifer

Jameco Gravel

Upper glacial aquifer

Figure 3. Extent and elevation of the upper surface of the Lloyd aquifer on Long Island, N.Y. (Modified 

from Smolensky and others, 1989)

-500

-1000

-1500

74° 73° 72°

40°30'

41°

41°30'

EXPLANATION

-500

EXTENT LIMIT of continuous Lloyd aquifer

0 10 20 40 KILOMETERS

0 10 20 40 MILES

STRUCTURE CONTOUR--Shows elevation of the upper

surface of the Lloyd aquifer. Dashed where approximately

located. Contour interval 100 feet. National Geodetic

Vertical Datum of 1929

Base from U.S. Geological Survey digital data, 1:100,000, 1979,

Universal Transverse Mercator projection, NAD 27, Zone 18
Magothy, and Lloyd aquifers on Long Island in 1983 and 

1984, respectively. Soren and Simmons (1987) mapped the 

thickness of each aquifer and confining unit below the upper 

glacial aquifer throughout Long Island. Smolensky and others 

(1989) incorporated data from previous studies to map the 

hydrogeologic framework of Long Island. Buxton and others 

(1991) and Buxton and Smolensky (1999) used a threedimensional numerical model and particle-tracking analysis of 

Long Island’s ground-water flow system to estimate the rates 

of recharge to the Magothy and Lloyd aquifers and to delineate 

their recharge areas. Buxton and Modica (1992) simulated 

patterns and rates of ground-water flow to analyze recharge 

along a cross-section at the Nassau-Suffolk County border. 

Busciolano and others (1998) mapped the water-table and 

potentiometric-surface altitudes of the upper glacial, Magothy, 

and Lloyd aquifers on Long Island.

Kilburn (1982), Buxton and others (1981), Snavely and 

Williams (1984), and Chu and others (1997) reported pumpage 

from the Lloyd in western Long Island. They, however, did 

not report pumpage values from the Lloyd aquifer in Suffolk 

County, but included pumpage from the Lloyd in Nassau 

County, which has the largest consumptive use of water from 

the Lloyd. Buxton and others (1981) and Chu and others (1997) 

reported pumpage from the Lloyd aquifer in Kings, Queens and 

Nassau Counties.

Perlmutter and Geraghty (1963) studied the geology and 

ground-water conditions in southern Nassau and southeastern 

Queens and demonstrated that the Lloyd aquifer is hydraulically 

separated from the overlying units and contains freshwater.

Many local studies that provided information on the 

hydrogeologic framework of Long Island’s ground-water system 

are not mentioned here because their focus was beyond the 

scope of this report. A few are mentioned further on, however, 

that are focused on quantifying pumpage from the Lloyd and 

mapping and modeling saltwater intrusion.

Hydrogeology

The Lloyd aquifer (Lloyd Sand Member of the Raritan 

Formation), is the oldest of the Cretaceous age formations 

on Long Island. It extends from central Kings, northwestern 

Queens and Nassau, and northeastern Suffolk Counties to 

the east and south (fig. 3). It lies unconformably upon the 

bedrock surface and is bounded conformably above by the 

Raritan confining unit (unnamed clay member of the Raritan 

Formation), or Raritan clay (fig. 2). The Raritan clay has a very 

low vertical hydraulic conductivity of .001 feet per day (ft/d) 

and is areally extensive, making the Lloyd aquifer the only fully 

confined aquifer on Long Island. The Lloyd thickens to the 

southeast on the western portion of Long Island and to the south 

on the eastern portion. The thickness of the Lloyd aquifer varies 

from zero in northern Kings, northwest Queens and Nassau, 

and northeast Suffolk Counties—to over 500 ft in south central 

Suffolk County.

Lloyd aquifer deposits generally consist of fine to coarse, 

quartz-rich sand and gravel, commonly within a clayey matrix 

(see photos, p. 5). The coarse sand particles are subangular 

to rounded, and thin lenses of clay are common, as are lenses 

of fine sandy clay and clayey sand. Some clay lenses are as 

thick as 40 ft and may extend more than one mile locally. 

However, these clay units do not seem to affect the hydraulic 

interconnectivity of the Lloyd. Lloyd deposits are generally 

clear or white, but may also be yellow or gray.

The clayey matrix of the Lloyd aquifer gives it moderate to 

low permeability. The average horizontal hydraulic conductivity 

ranges from 40 ft/d (McClymonds and Franke, 1972) to 67 ft/d 

(Soren, 1971), and its horizontal to vertical anisotropy is about 

10:1 (Smolensky and others, 1989). The average transmissivity 

of the Lloyd is about one-third that of the Magothy aquifer, and 

ranges from about 1,500 to 19,000 ft2/d (Garber, 1986). Average 

transmissivity varies locally from about 4,700 ft2/d in Kings 

County, 8,000 ft2/d in Queens County, 12,000 ft2/d in northern 

Nassau County, 16,000 ft2/d in southern Nassau County, and 

10,000 to 12,000 ft2/d in Suffolk County (McClymonds and 

Franke, 1972).

The general configuration of the potentiometric-surface 

altitude of the Lloyd aquifer (fig. 4) is similar to that of the 

upper glacial and Magothy aquifers. It gradually rises from 

the western part of Long Island to form an east-west-trending 

mound in eastern Nassau County that continues eastward into 

central Suffolk County and then generally declines toward the 

eastern end of Long Island.

The quality of water in the Lloyd aquifer is generally good; 

although high iron content and salinity have been noted locally. 

Several local studies mapped the extent of saltwater intrusion in 

several coastal areas of Long Island. Stumm (2001), and Stumm 

and others (2002, 2004) delineated areas of saltwater intrusion 

in the Lloyd aquifer on the north shore of Nassau County. Misut 

and others (2002) used a three-dimensional finite-element 

model to simulate saltwater intrusion in the four major aquifers 

in Kings, Queens, and western Nassau Counties. Terracciano 

(1997) updated previous studies of saltwater intrusion in 

southeastern Queens and southwestern Nassau Counties. 

Soren (1971) mapped the northern extent of saltwater intrusion 

into the Lloyd aquifer in Queens County. Lusczynski and 

Swarzenski (1966) studied the saltwater intrusion and mapped 

landward extent of saltwater in the Lloyd and the other aquifers 

in southern Nassau and southeastern Queens Counties; they also 

estimated the rates of landward movement of saltwater, by depth 

and area.

A Geographic Information System links spatially referenced databases, and 

facilitates refinement of the regional hydrogeologic framework and analysis 

of changes over time to Lloyd aquifer potentiometric-surface altitude and 

water-quality conditions.
	 

Photographs of Lloyd core samples collected from northern Nassau County, N.Y., show the upward fining sequence of the Lloyd 

aquifer. (Units are in inches.)
Figure 4. Potentiometric-surface altitude of the Lloyd aquifer in March-April 1997 on Long Island, 

N.Y. (Modified from Busciolano and others, 1998 )

10

EXPLANATION

20 LINE OF EQUAL POTENTIOMETRIC-SURFACE ALTITUDE--Shows 

 altitude at which the water level would have stood in tightly cased 

 Lloyd wells. Solid where approximately known; dashed where 

 inferred. Contour interval 5 feet. National Geodetic Vertical 

 Datum of 1929

74° 73° 72°

40°30'

41°

41°30'

0 10 20 40 KILOMETERS

0 10 20 40 MILES

Base from U.S. Geological Survey State base map, 1:100,000, 1979,

Universal Transverse Mercator projection, NAD 27, Zone 18

15

20

25

35

30

40

10

15

50

30

5

5

0

The Lloyd aquifer is the sole source of public water-supply for Long Beach Island, Nassau County, N.Y. (Composite aerial photo of Long Beach from New York State Statewide D
	 

Pumpage

Public-supply pumping from the Lloyd aquifer (fig. 5) has 

been limited to the north and south shores of Nassau County, 

except for the former Jamaica Water Supply Corporation in 

central Queens County. Pumping from the Lloyd aquifer in 

Suffolk County is limited to a few wells on the barrier islands 

on the south shore and is not considered to be significant. 

Industrial-supply withdrawals from the Lloyd have been 

estimated to represent less than 20 percent of total islandwide 

pumpage from the Lloyd.

Kings County—Public-supply pumpage from the Lloyd 

aquifer in Kings County consisted of a single well that supplied 

an average of 270 million gallons per year (Mgal/yr) between 

1929 and 1946. The annual maximum was 1.1 billion gallons 

(Bgal) in 1931, and the minimum 11 Mgal in 1946 (Chu and 

others, 1997).

Queens County—Public-supply pumpage from the Lloyd 

aquifer in Queens County began in 1928 and continues today. 

Annual maximum and minimum pumpage during 1920–95 was 

3 Bgal from five wells in 1944, and 6 Mgal from one well in 

1992, respectively (no water was withdrawn from the Lloyd 

aquifer in Queens County in 1993). The mean annual pumpage 

for the same period (excluding 1993) was 1.5 Bgal (Chu and 

others, 1997).

Nassau County—Pumpage records in Nassau County 

began in 1920. The annual maximum and minimum publicsupply withdrawals from the Lloyd during 1920–95 were about 

6.4 Bgal from 33 wells in 1971, and 250 Mgal from two wells 

in 1920. The mean annual pumpage was 3.3 Bgal (Chu and 

others, 1997).

igital Ortho-Imagery program, 2001.)

Figure 5. Annual pumpage from Lloyd aquifer in Kings, Queens, 

and Nassau Counties, N.Y., 1920 –95. (From Chu and others, 1997)

KINGS COUNTY

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

PUMPAGE, IN MILLIONS OF GALLONS

1920 1930 1940 1950 1960 1970 1980 1990 1996

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

PUMPAGE, IN MILLIONS OF GALLONS

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

PUMPAGE, IN MILLIONS OF GALLONS

QUEENS COUNTY

NASSAU COUNTY

YEAR


Recharge

The Raritan clay protects the Lloyd aquifer from 

contamination from the overlying aquifers, but also inhibits 

recharge to the Lloyd. The Lloyd aquifer has been estimated to 

contain about 9 percent of Long Island’s freshwater (Garber, 

1985), but receives only 3.1 percent of the recharge that enters 

the Long Island aquifer system (Buxton and others, 1991; 

Buxton and Modica, 1992). The Lloyd aquifer receives this 

recharge through a corridor generally less than 0.5 miles wide 

that lies approximately along the ground-water divide (fig. 1). 

Traveltime from the water table to the top of the Lloyd aquifer 

has been estimated to be on the order of several hundred years 

(Buxton and others, 1991). The age of water in the Lloyd 

aquifer is oldest at the southern coast of Long Island, where 

it is more than 8,000 years old; and is more than 2,000 years 

old at the northern coast (Buxton and Modica, 1992). This 

difference in age is attributed mainly to the proximity of the 

recharge area to the north shore.

Present-Day Monitoring

The Long Island branch of the USGS New York Water 

Science Center, located in Coram, New York, (in 2006) 

monitors water levels at about 63 Lloyd wells on Long Island; 

two in Kings, six in Queens, 17 in Nassau, and five in Suffolk 

Counties. Island-wide, nine of the 63 wells are continuous 

record sites, 30 are measured monthly, and 45 are measured 

annually. The number of wells in the network varies annually as 

wells are destroyed, replaced, or access to wells changes. 

Water-quality samples are collected at about three Lloyd 

wells annually on Long Island. Borehole geophysical logs are 

collected to delineate geology at all new Lloyd wells that are 

drilled, and induction logs are collected to delineate and monitor 

the extent of saltwater intrusion. Borehole-geophysical logs 

(including gamma, electrical resistivity, and electromagneticinduction (EM) logs) are collected at about four Lloyd 

wells annually. 

Open-hole borehole-geophysical logging at 

a 1,700 foot-deep Lloyd well on Jones Beach 

Island, Nassau County, N.Y.

Geophysical wireline

Open borehole
	 

Summary

The Lloyd aquifer, the deepest of the four main aquifers on 

Long Island, has supplied as much as 1.1 Bgal of public-supply 

water per year from Kings County, 3 Bgal from central Queens 

County, and 6.4 Bgal from shoreline communities in Nassau 

County. Many hydrogeologic studies since 1903 have provided 

the data needed to describe the hydrogeologic framework of the 

Lloyd. Several local studies have made significant contributions 

to the refinement of the regional hydrogeologic framework.

The Lloyd aquifer has the lowest average horizontal 

hydraulic conductivity and transmissivity of the four main 

aquifers on Long Island. Average horizontal hydraulic 

conductivity ranges from 40 to 67 ft/d, and transmissivity 

ranges from 1,500 to 19,000 ft2/d. Average transmissivity varies 

locally; from about 4,700 ft2/d in Kings County, to 8,000 ft2/d 

in Queens County, 12,000 ft2/d in northern Nassau County, 

16,000 ft2/d in southern Nassau County, and 10,000 to 12,000 

ft2/d in Suffolk County. Several saltwater wedges in the Lloyd 

that were induced by over-pumping on western Long Island 

have been mapped in local studies. Pumpage from the Lloyd 

in Kings County ceased in 1946 but continues today in Queens 

and Nassau Counties along with a handful of sole source water 

supply wells on the barrier beaches of Suffolk County.

Only 3.1 percent of recharge on Long Island enters the 

Lloyd aquifer through a corridor that is generally less than 0.5 

mi. wide, and located approximately along the ground-water 

divide. Traveltime from the water table to the top of the Lloyd 

aquifer is several hundred years. The age of water in the Lloyd 

aquifer ranges from 2,000 years at the northern shore to 8,000 

years at the southern shore.

The USGS New York Water Science office in Coram, New 

York, (in 2006) monitors water levels at a network of about 63 

Lloyd wells on Long Island, and samples about three Lloyd 

wells annually for water quality. Gamma and electric logs are 

collected to help delineate geology at all new Lloyd wells that 

are drilled, and EM logs are collected to delineate and monitor 

saltwater intrusion. 

By Anthony Chu, U.S. Geological Survey, Coram, NY

References

Busciolano, Ronald, Monti, Jack, Jr., and Chu, Anthony, 

1998, Water-table and potentiometric-surface altitudes of 

the upper glacial, Magothy, and Lloyd aquifers on Long 

Island, New York, in March-April, 1997, with a summary of 

hydrogeologic conditions: U.S. Geological Survey WaterResources Investigations Report 98–4019, 17 p., 6 pls.

Buxton, H.T. and Smolensky, D.A., 1999, Simulation of the 

effects of development of the ground-water flow system of 

Long Island, New York: U.S. Geological Survey WaterResources Investigations Report 98–4069, 57 p.

Buxton, H.T. and Modica, Edward, 1992, Patterns and rates 

of ground-water flow on Long Island, New York: Ground 

Water, v. 30, no. 6, p. 857–866.

Buxton, H.T., Reilly, T.E., Pollock, D.W., and Smolensky, D.A., 

1991, Particle tracking analysis of recharge areas on Long 

Island, New York: Ground Water, v. 29, no. 1, p. 63–71.

The USGS measures water levels (above left) at about 63 Lloyd wells, and collects water-quality samples (above right) from about three Lloyd wells 

on Long Island, N.Y. annually.
10

Buxton, H.T., Smolensky, D.A., and Shernoff, P.K., 1989, 

Hydrogeologic correlations for selected wells on Long 

Island, New York—A data base with retrieval program: U.S. 

Geological Survey Water-Resources Investigations Report 

86–4318, 107 p.

Buxton, H.T., Soren, Julian, Posner, Alex, and Shernoff, P.K., 

1981, Reconnaissance of the ground-water resources of Kings 

and Queens Counties, New York: U.S. Geological Survey 

Open-File Report 81–1186, 64 p.

Chu, Anthony, Monti, Jack, Jr., and Bellitto, A.J., Jr., 1997, 

Public-supply pumpage in Kings, Queens, and Nassau 

Counties, New York, 1880–1995: U.S. Geological Survey 

Open-File Report 97–567, 61 p.

Cohen, Philip, Franke, O.L., and Foxworthy, B.L., 1968, An 

atlas of Long Island’s water resources: New York State Water 

Resources Commission Bulletin 62, 117 p.

Donaldson, C.D. and Koszalka, E.J., 1983, Potentiometric 

surface of the Lloyd aquifer, Long Island, in January 1979: 

U.S. Geological Survey Open-File Report 82–162, 2 sheets, 

scale 1:250,000.

Doriski, T.P., 1986, Potentiometric-surface altitude of major 

aquifers on Long Island, New York, in 1983: U.S. Geological 

Survey Water-Resources Investigations Report 85–4321, 

4 pls., scale 1:125,000.

Doriski, T.P., 1987, Potentiometric surface of the watertable, Magothy, and Lloyd aquifers on Long Island, New 

York, in 1984: U.S. Geological Survey Water-Resources 

Investigations Report 86–4189, 4 pls., scale 1:125,000.

Franke, O.L., and Cohen, Philip, 1972, Regional rates of 

ground-water movement on Long Island, New York in 

Geological Survey Research, 1972: U.S. Geological Survey 

Professional Paper 800–C, p. C271–277.

Garber, M.S., 1986, Geohydrology of the Lloyd aquifer, Long 

Island, New York: U.S. Geological Survey Water-Resources 

Investigations Report 85–4159, 36 p.

Kilburn, Chabot, 1982, Ground-water pumpage in Nassau 

County, Long Island, New York, 1920–77— Introduction and 

user’s guide to the data compilation: U.S. Geological Survey 

Open-File Report 81–499, 67 p.

Kimmel, G.E., 1973, Change in potentiometric head in the 

Lloyd aquifer, Long Island, New York: U.S. Geological 

Survey Journal of Research, v. 1, no. 3, p. 345–350.

Lusczynski, N.J. and Swarzenski, 1966, Salt-water 

encroachment in southern Nassau and southeastern Queens 

Counties, Long Island, New York: U.S. Geological Survey 

Water-Supply Paper 1613–F, 76 p.

McClymonds, N.E. and Franke, O.L., 1972, Water-transmitting 

properties of aquifers on Long Island, New York: U.S. 

Geological Survey Professional Paper 627–E, 24 p.

Misut, P.E., Monti, Jack, Jr., and Voss, C.I., 2002, A ThreeDimensional Finite-Element Model of Seawater intrusion 

in Western Long Island, New York (abst.), in ASCE 

Engineering Mechanics Conference, June 2–5, 2002, 

Columbia University, New York, N.Y., 8 p.

Perlmutter, N.M. and Geraghty, J.J., 1963, Geology and groundwater conditions in southern Nassau and southeastern Queens 

Counties, Long Island, N.Y.: U.S. Geological Survey WaterSupply Paper 1613–A, 205 p.

Rich, C.A., Prince, K.R., and Spinello, A.G., 1975, 

Potentiometric surface of the Lloyd aquifer on Long Island, 

New York, in January 1975: U.S. Geological Survey OpenFile Report, 12 p.

Sirkin, L.A., 1974, Palynology and stratigraphy of Cretaceous 

strata on Long Island, N.Y. and Block Island, Rhode Island: 

U.S. Geological Survey Journal of Research, v. 2, no. 4, p. 

431–440.

Sirkin, L.A., 1986, Palynology and stratigraphy of Cretaceous 

and Pleistocene sediments on Long Island, New York—A 

basis for correlation with New Jersey coastal plain sediments: 

U.S. Geological Survey Bulletin 1559, 44 p.

Smolensky, D.A., Buxton, H.T., and Shernoff, P.K., 1989, 

Hydrologic framework of Long Island, New York: U.S. 

Geological Survey Hydrologic Investigations Atlas HA–709, 

3 sheets, scale 1:250,000.

Snavely, D.S. and Williams, James, 1984, Estimated publicwater supply and industrial-commercial ground-water 

withdrawals and returns in Nassau County, New York, 

1973–79: U.S. Geological Survey Water-Resources 

Investigations Report 84–4246, 16 p.

Soren, Julian, 1971, Ground-water and geohydrologic 

conditions in Queens County, Long Island, N.Y.: U.S. 

Geological Survey Water-Supply Paper 2001–A, 39 p.

Soren, Julian, and Simmons, D.L., 1987, Thickness and 

hydrogeology of aquifers and confining units below the upper 

glacial aquifer on Long Island, New York: U.S. Geological 

Survey Water-Resources Investigations Report 86–4175, 

3 sheets, scale 1:125,000.

Stumm, Frederick, 2001, Hydrogeology and extent of saltwater 

intrusion of the Great Neck peninsula, Great Neck, Long 

Island, New York: U.S. Geological Survey Water-Resources 

Investigations Report 99–4280, 41 p.

Stumm, Frederick, Lange, A.D., and Candela, J.L., 2002, 

Hydrogeology and extent of saltwater intrusion on Manhasset 

Neck, Nassau County, New York: U.S. Geological Survey 

Water-Resources Investigations Report 00–4193, 42 p.

Stumm, Frederick, Lange, A.D., and Candela, J.L., 2004, 

Hydrogeology and extent of saltwater intrusion in the 

Northern Part of the Town of Oyster Bay, Nassau County, 

New York: U.S. Geological Survey Water-Resources 

Investigations Report 03–4288, 55 p.
11

Terracciano, S.A., 1997, Position of the freshwater/saltwater 

interface in southeastern Queens and southwestern Nassau 

Counties, Long Island, New York, 1987–88: U.S. Geological 

Survey Open-File Report 96–456, 17 p.

Veatch, A.C., Slichter, C.S., Bowman, Isaiah, Crosby, W.O., and 

Horton, R.E., 1906, Underground water resources of Long 

Island, New York: U.S. Geological Survey Professional 

Paper 44, 394 p. 

Suter, Russell, 1937, Engineering report on the water supplies 

of Long Island: New York State Water Power and Control 

Commission Bulletin GW–2, 64 p.

Suter, Russell, de Laguna, Wallace, and Perlmutter, N.M., 

1949, Mapping of geologic formations and aquifers of Long 

Island, New York: New York State Water Power and Control 

Commission Bulletin GW–18, 212 p.

The Lloyd aquifer continues to be an important source of water supply in the shoreline communities. 
12

0 200 0 1000

0 1000

0 1000 (Ohm-meters)

0

200

400

600

800

1,000

1,200

1,400

1,600

DEPTH BELOW LAND SURFACE, IN FEET

Single Point Resistance

Short Normal Resistivity

Long Normal Resistivity

(Ohm-meters)

Gamma (counts per second) (Ohms)

Lloyd

aquifer

(approx.)

The USGS utilizes geophysical methods to monitor saltwater intrusion.

For additional information write to: 

New York Water Science Center

U.S. Geological Survey

2045 Route 112, Bldg. 4

Coram, NY 11727

Information requests:

(518) 285-5602

or visit our Web site at:

http://ny.water.usgs.gov

For more information on the USGS--the Federal source for science 

about the Earth, its natural and living resources, natural hazards, 

and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

Geophysical logs of Lloyd well at west end of Jones Beach, N.Y.