HomeMy WebLinkAboutGeology & Ground Water Resources of the Town of Southold.Geology and Ground-Water
Resources of the Town of
[..Southold, Suffolk County
New York
GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1619-GO
Prepared in cooperation with the Suffolk
County Board of Supervisors, ttie Suffolk
County li~ater ~luthority, and tke New
York State Ifrater Resources Commission
Geology and Ground-Water
Resources of the Town of
Southold, Suffolk County
New York
By H. C. CRANDELL
CONTRIBUTIONS TO THE HYDROLOGY OF Tile UNITED STATES
GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1619 G~'('
Prepared in cooperation with the Suffolk~"
County Board of Supervisors, the Suffolk [e'[~-2
County llfater .quthority, and the New ((~.((~q~
York State l~ater Resources Commission
UNITED STATES GOVERNMENT PRINTING OFFICE, W~,SHINGTON : 1963
UNITED STATES DEPARTMENT OF THE INTERIOR
STEWART L. UDALL, Secretary
GEOLOGICAL SURVEY
Thomas B. Nolan, Director
CONTENTS
Abstract ...............................
Introduction .......................... 1
Purpose and scope of the investigation ........ l
Location of the area
Previous investigations ............. 4
Methods of investigation ...... 5
Well-numbering system_
Acknowledgments .............. 5
Geography ........................ 6
Topography and drainage ........ 6
Climate_ _
History of development ............. 9
Geology _
Ground water - - .... 11
Hydrology_ ............... 19
Water-level fluctuations
Withdrawal__ - - - ....... 24
........... 24
Sea-watcr encroachinent ......... 28
Chemical quality _ ............. 31
Conclusions
References cited _ - ......... 33
......... 3,5
ILLUSTRATIONS
PLATE l. Surficial geologic map. '2. Geohydrologic sections.
3. Water-table mai).
FIGURE 1. Map showing location of the towll of Southold GG3
2. Photograph showing stratified drift, thin till cap, and large
erratics, north shore 15
CONTENTS
TABLES
TABLE 1. Precipitation, i~inches, dnring 1958 and 1959 at 1 I stations in tile
town of Southold and at 2 nearby stations GG10
2. (]cneralizcd stratigraphic section ill the town of Southold 12
~ t
3. Logs of selected wells in the town of Southok _ 16
4. Physical characteristics of upper Pleistocene water-bearing
deposits in the tow~ of Southold _ 18
5. Chemical analyses, i~ parts per miliio~a, of water from public-
supply wells in thc villages of Gree~port and Southold 32
CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES
GEOLOGY AND GROUND-WATER RESOURCES OF THE
TOWN OF $OUTHOLD, SUFFOLK COUNTY, NEW YORK
By H. C. Ca.',XVELL
PURPOSE AND SCOPE OF THE INVESTIGATION
In 193° tile [~.S. Geological Stn",-i,y hog'an :ul orel'al] and conl hming
appraisal of ground-water conditions on Lon~z Island. This report
GG2 CONTRIBUTIONS TO TI-IE HYDROLOGY OF THE I~ITED STATES
presents the results of au investigatiou undertaken as a part of that
program in cooperation with the Suffolk Couuty Board of Supervi-
sors, the Suffolk ('ouuty Water Autbority. and the New York State
Water Resoarces Commissiou (formerly /lie New York State Water
Power and Coutrol Commisslou). Fieldwork by the writer begau
in September 1957 aud ended in 1)ecember 1959. The present report
is based on data available prior 1o ,lanuary 1960.
The town of Southold is 1 of 10 major political subdivisions of
Suffolk County. In this report the names "towR of Soutbold" and
"Southold" are used interchaugeably. Because the town of Southold
is almost entirely surrounded by salt water and has a relatively small
area for recharde to the ground-water reservoir, development and ys.e
of fresh ground water must be such as to prevent or keep to a m~m-
mmn the encroachment of sea water into deposits now contaiuing fresh
water. Two public water-supply iustallations aud many domestic
and crop-irrigation systems are totally dependent on the continued
availability of groRud water of good quality. This investigation,
therefore, has included study of (1) the areal extent, thickness, and
physical properties of the water-bearing deposits: (2) the hydrologic
characteristics of the ground-water reservoir; (3) the conditions un-
der which sea-water eRcroachmeut may take place; and (4) the estab-
lishment of a monitoriug program to observe any futnre sea-water
encroachment resulting from depletiou of the ground-water supply.
The report includes pertiuent conculsions from previous investiga-
tions of the geology and hydrology of Southold as well as data ob-
t ained during this investigation.
LOCATION OF THE AI%EA
The eastern third of Long Island is made up of two narrow penin-
sulas septtrated hy Peconic Bay, Gardiners Bay, and contiguous
inlets. The town of Southold occupies the easteru 9q0 miles of the
northern peninsula and also iucludes Robins, Plum. Great Gull, Little
Gull, and Fishers Islands (fig. 1). Robins Island is in Peconic Bay,
whereas the other islands form a broken chain in Long Island Sound
that is a continuatfon of the Rortheastward-trending peninsula.
Plum Island is about 1 nfile from Orient Point, Great Gull aud Little
Gull Islands are about 7 miles from Orieut Point, aRd Fishers Islaud
is about 13 miles from Orient Point and about 7 miles southeast of
New London, Conn. The total area of Southold is about 54 square
miles, distributed as showR in the following table:
41°
__ 74°
NEW
JERSE
London ~ro~n
.' ers Island,'
Great Gull I¢Little Gull I , I
YORK',
AT ANTIC
CONTi~IBL*TIONS TO THE HYDROLOGY OF Tk~IE ITNITED STATES
42.90
5.20
Plum Island
.03
Gull Islands
Fishers Ishtnd .................... 4.22
The whole of Southold lies almost e~tirely between lat 40°57%0''
and 41°17'30'' N. and hmg l l°;m and ~12 ,,o B~. This i~vestigation
included the peni~sular part of the town only.
The following topographic quadrangle maps of the I:.S. Geological
Survey include all parts of Southold:
Greenport. . I New York I 1:24, 000 I 1956
Mattituek i New York 1:24, 009 1956
Mat~tituck IIills _ I New York 1:24, 000 ! 1956
3dx tic Conn. ~.Y. lg.I 1:31,680 1951
Soathold I New 5ork i /:24.000 195(5
pI~EVIOUS INVESTIGATIONS
P~eferences to parts of Southold apl)ear frequently in early works
on the geology of Long lsland. Mather (1843) described in some
detail the bluffs and boul(ler strewn beaches of the 1)eni~sula's north
shore, as well as the ('lay deposits between the x illages of Greenport
and Southold. These deposits were again discussed hy Merrill (1886)
and by Ries (U}0o). Veaich (l~)O~;) prepared a detailed report on
I,ong ~sland's water resources, which ineluded the logs of eight wells
h~ Sonthold. The most comprehensh-e report of Long Island geolo~'
was prep:trod by Fuller (1~14). This report contains many specific
:~bservari¢nls lnafle ill $outhohl alld evaluates them in their relation
, o the geologic history of the Long Island area. An earlier paper by
~uller (1905) deseribes lhe geology of Fishers Island.
Very Utile has been written since Fuller's lime dml ntentiol/S
Sou~hold. Logs of many wells in Suffolk Comity, imluding some in
Southold, were compiled by Leggette (D~3S), Roberts a~d Brashears
(1945), and Johnson (1052). Surer, deLaguna, and Perhnutter
(19~9) summarized the geology of Long Island and correlated the
logs of several deep wells in Somhold with logs of wells elsewhere on
;he island. Data on the temperature and chloride concentration of
GEOLOGY AND GROUND WATER, SOUTI~OLD~ NEV, r YORK GG5
water from wells in Soffolk Courtly were presented and interpreted
by Hoffman and Spiegel (1958).
Mm'e recent work oo Southo]d was done by Hoffman (1961)~ who
described tho hydrolo~, of the shallow grou;~d-water re~rvoir, with
particular referenre to sea water encroachment, and by Crandell
(1962)~ who investigated the geo]o~' and ~romid-water ~:esources of
Plum Island.
METHODS OF INVESTIGATION
In earc:ing ont the purposes of this investigation the author exam-
fined outcrops of glacial outwash and tilI ~n Sontho]d and prepared a
generalized nmp of tho deposits. Tbil~v-five test holes, ranging in
depth from about 50 to 100 feet~ were a~gered to obtab; samples ot
outwash for perme,bili~y and si)celtic?icld determinations. ]Veil
points and pipe were instal]ed in 32 of the test holes to establish control
for a contour map of the water table. Eleven rain ga~es were estab-
lished ht different parts of the area to comp, re differences in precipita.
tion. I)ata on evaporation uere obtained from the U.S. ]Veather
Buremh which operated an eraporation pan at Greenport. Eighty
wells were measured momhly to delermine lbe ahitude and trend
water levels, and 100 wells and 5 ponds were sampled to determine !he
chloride content of the water.
On Long Island the Geological Sm'rev uses a well-unmbering sys
tern eslablisbed by the New York Water Resources (e mnissio..
~rells in eaeb eOUllt~, are nmnbered serially as drilling reports are
re~ived by the Commission. The well nmnber is prefixed by the
initial letter of ~he cmmlv in which it is ]oeated. rl'h.s a well
Suffolk County is desitin'ted by the lelter 'S- followed by the
signed number (for example, S1036I).
The author wishes to acknowledge the aasisl ante of lhe staff mere
bern of lhe Long lshmd ofllee of the Xew York State ~Valer Resoui'ees
('omnlission for providing most of 1he ~sell ',. n'ds used in the in,epa-
in the compilation of precipitation data. and the author is esl)eeitdlv
grateful to Mr. l[Nl'r¥ Monsell, SUl)erh~ endent of Public Works.
village of Greenport, f}n' generously lU,ovidinE the Geological Survey
with additional manpower and equipmel~ to instnll wells, to measme
determhmtions.
GG6 CONTRIBUTIONS TO THE t-IYDROLOG¥ OF THE UNITED STATES
GEOGRAPHY
Much of Southold, particularly the eastern part, may ~ conside~
· s virtually a chain of small islands along an axis trending no~h-
e~stward. Even the peninsular part is naturally subdivided by sMt-
water ponds, ma~h~, and inlets into six separate morphologic and
hydrologic areas~ four of which are desi~ated by the lette~ A, B,
C, and D for pur~ses of reference in this repoR (pls. 2 and 3). The
other two a~as are Little Hog Neck and Great Hog Neck, which jut
south f~m the peninsul~ but are largely detached from it by salt-
water mashes and inlets. Plum~ Great Gull, Little Gull, and Fishers
Islands are separa~d by o~n salt-water p~ssages and lie in ~ chain
extending no~heastward from the peninsula. Robins Island l~ in
Peconic Bay between the northern and southex~ peninsulas of I~ng
Island.
Are~ A (about 7 ~ua~ miles) extends from a sho~ distance west
of the weste~x boundaw of the town of Soutbold to Matt~tuck C~ek,
is ~bout 3 miles wide, and ~ntains most of the village of Mattituck.
Are~ B (abut 25 ~uare miles) ~s bounded on the west by Mattituck
Cr~k and on the east by Hashamomuck Pond. This area constitutes
the largest p~rt of Southold. It ~nges in width fl~m about 1~/2 to
4 miles. The villages of Cutcho~e, Pecon~c, and Southold are ha this
area. Are~ C (a~ut 7 square miles) extends eastward from Hash~-
momuck Pond to Dam Pond. It is about I to 1Ve miles wide. Green-
port, which is Southold~s largest village~ and East Marion are in this
a~a. Are~ D (about 5 squ~ miles) is bounded on the west by
Dam Pond and te~inates to the east at Orient Point. The a~a has
a width of about I to 1~/~ miles. Little Hog Neck (about 0.75
mile) and Great Hog Neck (about 2.3 square miles) extend ~uthe~t-
w~rd from the south shore of area B.
The southern shoreline of the peninsula is very irre~lar as it is
m~rk~ by numerous salt-water emb~yments ~nd marshes. Attractive
beaches~ which are made up of well-sorted clean quartz sand, form the
rest of the southe~ shm~llne. In many places they form bayhead
beaches and spits. The most prominent spit~ Long Beach (pl. 3) ex-
tends southwestward almost 4 miles from Orient Point and is occupied
by Orient Beach State Park. The combination of pleasant beaches
~nd embayments, which provide good swimming conditions and boat
anchorage, has attracted many summer-home builders.
The north shore of peninsular Soutbold is relatively rugged. A
prominent ridge lies near the shore except where inlets and ponds
m~rk the boundaries between areas A, B~ C~ and D. In the eastern
pa~ of area D, however, erosion has removed most of this ridge. The
GEOLOGY AND GROUND VgATER, SOUTHOLD, NEW YORK GG7
shoreline is generally regular and smooth, but two small headlands
in area B, two in area C, and one in area D extend into Long Island
Sound. Most parts of the ridge are more than 50 feet above sea
]eve]. The ridge has a maximum altitude of slightly more than 160
feet in area A. Erosion by storm waves and high tides has removed
much of the ridge material and has left steep bluffs which are from
about ~0 to more than 50 feet high at the shore, and narrow beaches
strewn with cobbles and boulders. Very large boulders are clustered
at the headlands and at some places on the southern slope of the ridge.
Mather (1543, p. 169) described their size in the following quotation:
Some of the erratic blocks of Long Island are of great size. One on Mr.
Latham's farm at Oysterpond Point (Orient) was mostly blasted to pieces, and
made into a stone fence. He stated that the fragments made eighty rods (one-
fourth of a mile) of stone feuce, four feet high. A portion still remains in the
ground. The portion used must have weighod more than nine hundred tons.
A gently rolling outwash plain with numerous shallow depressions
extends from the ridge along the north shore to the south shore. The
plain slopes southeastward at about 20 to 30 feet per mile.
Great Hog Neck and Little Hog Neck extend southeastward from
area B. Little Hog Neck is roughly trlangu]ar, about ~ miles long
and about half a mile wide at the base, which is joined to area B by a
very narrow sand bar. Much of the ]and surface has an altitude of
more than 50 feet and is extremely hilly. Great Hog Neck is almost
a rectangle, about 1~ miles wide by 2 miles long. It is joined to area
B by a small marshy area about a quarter of a mile wide. l~Iost of the
land surface is similar to the gently rolling plain in the central parts
of areas A, B, C, and I), although it has somewhat greater relief.
Two prominent hills more than 70 feet high lle in the northwestern part
o f the neck.
:Robins Island has very much the same shape and appearance as
Little Hog Neck and is only slightly smaller. It is very hilly; the
altitude of most of the land surface.is more than 50 feet and exceeds
80 feet in the north-centra] part. Bluffs that rise 20 to 50 feet above
sea level mark the island's western shore]ine.
Plum Island also has a triangular outline and ranges in width from
about 300 feet near the eastern end to a]most I mile at the southwestern
end. The island is about 3 miles long. A lowland in the central part
of Plum Island slopes gently to the northeast and thence southeast
and separates two low ridges. The northeastern ridge is the more
extensive and rises to an altitude of more than 100 feet, whereas the
southeastern ridge ranges in a]titude from 40 to 75 feet. Both ridges
are marked at the shoreline by steep b]uffs~ and the beaches are strewn
with many large boulders.
GG8 CONTRIBUTIONS TO THE HYDROLOGY OF TIlE U'NITED STATES
Great Gull Island is about one-teuth mile wide by about one half
mile long and is only about 30 feet above sea level at its h~gbest point.
Little Gull Island is about 400 feet wide by about 800 feet long and is
only slightly above sea level.
The ontline and topography of Fishers Island are very irregular.
The island is ahnost 7 miles long and ranges in width from 500 feet
near the northeastern end to 1~/2 miles Dear the southwestern end.
The principal ridge of hills, which lies along the south-central shore-
line~ bas a maximum altitude of about 70 feet, which is about the
average elevation of the many knoblike hills that cover most of the
remaining parts of the island. Some individual knobs however, rise
to 100 feet above sea level. Shoreline bluffs are m)t well formed and
are less than ~0 feet high in most places. Numerous shallow un-
drained depressions are scattered over tim ishtnd, and some of these in
the central part contain fresh-water ponds.
Most of peninsular Soutbold is cropland. Vegatation in the
maining parts of Southold consists maiDly of marsh grasses, beach
and dune grasses, and wild shrubs and bushes. Stauds of mixed
deciduous forest and stone conifers are in the billy areas and where
land has not been cleared for farming.
None of the islands iu Southnld have streams, and the peninsula
has relatively few. Ground water discharge ipso lbese streams is
uegligible, and virtually all lhe streams are ephemeral. Surface run-
off during and after heavy storms provides the only observable flow in
the stream channels. Generally the streams are no more than a mile
long and discharge into the marshes aloDg ~ he south shore.
Owing to its virtually insnlar nature, its latitude, and the proxin?y
of the Atlantic Ocean~ Southo]d has a prednminantly temperate marine
climate. Tenq)eratures are moderate, and preeipitation is abundant
during the fall, winter, add spring. A brief dry spell commonly
occurs during the summer. The following table compiled from infor-
mation collectedbv Mordoff (1949) and periodic climatic sumnmries of
the U.S. Weathe~~ Bureau sumarizes available temperature and pre-
cipitation data. All stations are in Southold except Bridgebampton
and New London-Groton (fig. 1 ).
GEOLOGY AND GROUND WATER~ SOUTHOLD, NEW YORK GG9
Mean annual temperature and precipitation at stations in and near the ~own of
Southold
I Distance
I (miles and
Bridgeharnpton, N.Y _
Cutchogue, N.Y_ _
Greenport, N.Y _ _ .
New London-Groton, Conn_
Orient Point, N.Y_ _
Temperature Precipitation
12 SE 44. 85
5 SW 44. 93
4 NW_ __ 37. 80
26 NW_ 44. 36
10 NW. ~ [ 41. 47
The amount of catch in the 8-inch rain gages at Cutcho~m, Green-
port, and Orient differs pereeptihly. This difference may be at-
tributed to the local topography, the exposm'e aud location of the
gage, and the spotty distribution of local storms. In order to obtaiu
more accnrate data on precipitation in the mauy parts of Southold,
additional 3-inch rain-gaging stations were e~tab]ished as follows:
East Marion, Greenport Nm-th, Mattituck Inlet, Mattituek West,
village of Orient, Peconic, Southold (pl. 3), aud P/mn Island (fig. 1).
Data for 1958 aud 1959 from these statmns toget mr with those for the
th~ee earlier long-term stations iu Southold add the two nearby long-
term stations are compiled in table 1. '
HISTORY 0~7 DEVELOPMENT
Southold was founded in tlhe early ]7th century. Colonists, p~ob-
ably EnglisbmeD, settled at Yeuuicott (town of Southold) as early
as 1638 (Wood, 1949). Southold was part of a large land graDt nmde
by Charles I of Enghmd to Sir William Alexander, Earl f Snrhng.
Fishers Island, bowever, was discovered iu 1614 by Adrian Block and
grtm(ed in 1640 to Johu Winthrop, in whose family it remained
until 1869.
The first settlement in Southold was just west of G~eeDport. This
was follox~ed by settlements at the village of Southo]d and then hy
settlements at other locations; Gresnport was the last village to be
founded. Some of the early settlers had come from Southwold,
England, and ~l~e Indian name Yemficott, which had beeu apl)lied to
the area, was soon changed to Southold.
The early inhabitants cleared ]and and established crops, which were
mostly ~'aiD, fodder, and pasture. In the early 19th century, shipping
and whaling became important aspects of Southold's economy. The
need for a fast combined railroad and steamer route from New York
to Boston b~'ought about the extension of the Long Island Railroad
to Greenport in 1848. Fishing and oyster fanning have always been
TAB~m l.--Precipitation, in inches, during 1958 and 1959 at 11 stations in the town of Southold and at 2 nearby station~
IAI1 statioos except for Plum Island, Bridgehampton, and New LonOon-Groton ar~ shown on pL 3]
1958
Area C stations
Area I) stations
Nearby stations
GEOLOGY AND GROUND WATER, $OUTHOLD, NEW YORK GGll
important industries, but agriculturs has been the nlain snpport of
the area's inhabitants.
With the invention of the mechanical potato digger in 1888, potatoes
became the most important crop and remain so today. Southold farms
a/so produce cauliflower, brussels sprouts~ peas, beans, and other
vegetables. In 1948, vegetables were planted in 13,61-I acres, and
more than three-quarters of this acreage was used for the cultivation
of potatoes (U.S. Depart~nent of Agriculture, 1948). The area under
cultivation has renlained relatively constant since 1899 (Itoffman,
1961, p. 5).
The following table shows the population trend in the lqllage of
Greenport and the town of Southold:
Population o! town of Southold and village of Greenport
Village of Town of
Year O~enport Southold~
1920 ....................... 3,122 10,147
1930 ........
1940 ........ ~~~ 3,062 11,669
3,259 12,046
1950 3,028 11, 484
1957_- ....................
Jan. l~b; ................... 2, 646 12, 608
.................. 2,653 13,388
GEOLOGY
No geologic formatious older than the Pleistocene crop out in
Southold; however, older formatlons are present at depth. A gen-
eralized stratigraphlc section of the formations in the Southo]d area,
together wifl~ their water-bearing characteristics, is shown in table 9.
The estlm~ted thickness and ]ithologlc descriptions are based largely
on the log of well S189 (Leggette, 1938), drilled in 1935 at Orient
Beach State Park, and on the general stratigrapbic studies of Long
Island by Suter and others (1949). Logs of the following wells col-
lected by Veatch (1906), which penetraie Cretaceous deposits and in
places Precambrlan(?) bedrock, also were used to compile the strati-
graphic section.
S490 (892)~ .................................. Greenport
S507 (909)x .................................. Long Beach
S5~2 (914): ................................. GreatGull Island
S517 (919)~ .................................. Fishers Island
Generalized strati#raphic section in the town of Southold
· I ] (Ieet/
(Qg)
Precambrian (?) Crystalline rocks
fresh ground water in Southohl. l,ower
part probably contains salt water.
GEOLOGY AzN~D GROUND WATER, SOUTI-~OLD, 1VEW YORK GG13
The bedrock basement in the Southo]d arsa is made up of crystalline
rocks of probable Precambrian age. On Long Island the basement
surface generally slopes to the southeast st about. 80 feet per mile as
determined frmn many well logs. Semiconsolidated and tmcensoli-
dated deposits of Cretaceous and Quaternary age rest on this surface.
The materials coustltuting these deposits were probably eroded from
the elevated parts of the bedrock surface north of Southold.
The Lloyd sand member of the Raritan formation of Late Creta-
ceous age was deposited directly on the Precambrian bedrock. It
consists of beds of coarse quartz sand aud gravel, fine sandy clay,
clayey sand, and some very thin laye~ of clay. In much of western
and central Long Is]~nd, the Lloyd sand member is an excellent aquifer
and in most places yields moderate to large supplies of fresh water to
wells. In SouthoId at well S490 (No. 89'2 in Veatch, ] 906, p. 331-332),
however~ only a small amount of fresh water was found in the Lloyd;
and at well S189 (Leggette, 1938, p. 93 97) on Long Beach (Orient
Beach State Park) salty water was found. The Lloyd grades upward
into the clay member of the Raritan formation. The clay member
contains some sandy layers, but it is predominantly gray day and
silt:}, clay. Its permeability geuera]ly ]s very low; therefore, it com-
monly acts as a confining bed or aquidnde and retards the movement
of water between the Lloyd sand member and the overlying beds.
An unconformity separates the Raritan formation from the over-
lying post-Raritan beds of Late Cretaceous age. These beds consist
of fine sand, silt, layers of clay, and scattered beds of coarse sand and
gravel. Beds equivalent in age to the Mmgothy formation of New
Jersey are preseuj in the post-Raritan depesits of Long Island, but
their upper and lower boundaries are not distinct ]n the logs of wells
that penetrate tbese deposits (Perhnutter and Crande]l, 1959). Al-
though the post-Raritan beds coutain several excellent water-bearing
zones that yield large snpp]les of fresh water to wells in most of Long
Island, in SouthoId they probebly conta n mostly brackish or salty
water.
During Tertiary and possibly during early Quaternary time, the
post-Raritan deposits were dissected bv streams and po~ib]y by ice
into a hilly terraiu of moderate relief.~ Pleistocene glacial deposi(s,
eonsistlng largely of saud and gravel but with local ]euses of clay~
were then laid down on this irregular snrface. Southold~s reservoir
of fresh ground xvatcr is contained in the upper part of these permeable
glacial deposits.
Several geologists, including Veatch (1906). Fuller (1905 and
1914), Fleming (1935), MacCliatock and Richards (1936), Thomp-
son and others (1937), and Suter and others (1949), have studied the
GG14 CONTRIBUTIOXS TO T}IE HYDROLOGY 0r T~{E UNITED STATES
comp]ex Pleistocene glacial history of Long Ishmd and vicinity and
reeo~ize two or more major glacial advances. This report, however.
is concerned with only the most recent, or Wisconsin glaciation of the
Pleistocene Epoch. The following discussion is based, iu part., on their
findings, and, in part, on tield observations. Much data have been
obtained from logs of wells drilled in Sonthold and published in
Veatch (1906), Leggette (1938). Ilobems and Brashears (lf)45). and
Johnson (1952), as well as from unpublished well logs on file in the
Mineola, 5L¥., office of the U.S. Geological Survey, and the Westbnry.
N.Y., office of the New York State Water Resources Comndssion.
The presen[ topographic features and surficlal deposits of Long
Island are rdated largely to the advance of a part of the Huron-
Ontario lobe of the great Lam'entide ice sheet during the Wisconsin
glaciation (Flint, 1947). The ice in its southward movement accumu-
lated rock debris from the brad over which it. passed and shoved addi-
tional material ahead of it in the manner of a bulldozer. After
pa~ing over most of the northern half of Long Island and the deposits
of earlier ice advances, as well as the beds of sand and gravel laid
down by its own melt water, the ice was checked by increased melting
at its termim~s and by decreased nourishment in its region of accomu-
lation. The accumulation of rock debris held in the ice was released by
the melting and, together with the material previously pushed ahead,
was partly reworked by the melt ~ aler ~o form a ridge of poorly strati-
fied sand and gravel r~loeg the ice front. This ridge at the southern
terminus of the ice sheet is known on Long Island as the Ronkonkoma
tern-final moraine. Continned melting and htck of nonrishment in the
region of ice accumulation caused the ice front to recede northward.
The Harbor Hill end moraine, part of which is in ~ontho]d, was formed
when the ice front readranced to the position shown by the end-
moraine deposits on plate 1. The moraine cousists of large coalescing
outwash fans of stratified saed and gravel and associa~edt~ll. Tbetill
ranges in thickness from about 5 to ahnost 50 feet and is cbara('terized
by many large bouhlers (fig. 2). Gaps m' depressions in the ridge
formed by the Ilarbor Ilill end moraine are probably the sites of large
blocks office that were wholly or partly buried and then melted after
the retreat of the main ice front. These gaps provided passageways
across the ridge for melt-war er flo~. which, in i)laces, Imrtly refilled the
gaps with stratified sand and gravel. However. Ihe marked depres
sions now occupied hv Mattituck ('reek. Ilasbamomuck Pond. and
Dam Pond, which are ~ide-water inlets separating areas A, B, C, and D.
and Plum Gat, which separates area D frnm Plmu Island, were never
completely filled. Fuller (191& p. 40) considered Maltiluck Creek.
which is now a tidal embaymenl leading to the northwest, to be a
GEOLOGY AND GROUND WRATER, SOUTHOLD, NEW YORK GGi5
ket[le valley. Reference to plate :l shows that the creek's tributaries
enter it at such an augle as to suggest that its flow was ouee south
eastward. Recent deposition of sand [mrs and beaches, largely by
longshore currents, bare closed paris of these gaps and thus tied
together areas A, B, C, and I) and l,ittle and Great Itog Necks; ali
exc~pt for area A, were once separate islands.
At several points along the north shore of area l) discontinuous
bodies of gray to grayish-brown clay are expend (pl. 1 ) at lhe shore-
line. Because of the appearance aud stratigraphic position of this
clay, it is teutatively assigned lo the Gardiners clay in this report.
although no substantiating fossil evidence has been found. The clay
~curs in irregular~ highly contorted mas~s and was probably moved
to its present position by ice-shove. Clay with shnilar characteristics
is also found on the western shore (pi. 1} of Robius Island aud on the
southeasten~ shore of Plmn Island. Well logs do not iudicate that
the clay underlies Soutbo]d except ,t the few localities previously
mentioued. Appareutly, it occurs only in isolated masses or dis-
contiuuous lenses at ]east m~der the maiu parl of the Southo]d
peniusula.
Another clay, probably of late Pleistocene age, occurs iu several
places along the south shore of peninsular Southold. No exposures
have beeu found, but it lies m~der several feet of soil and, in some
places, under stratified sand and gravel. This clay underlies most
of the south shore, where well logs imlicate that it'rauges in thick-
GG16 CONTRIBUTIONS TO THE [IYDROLOGY OF TIlE UNITED STATES
l~ess from 5 t. (;0 feet. (~ee l,~s .f wells $4(;77 ,,~nd ~ [7g¢ 5~ table
except in tbat part of ar~a (' we~t of Greenport. where it extends
nearly to the nm'th shore. Tho clay was once quarried in this area
for use in the produetiol~ of brick.
On Robbh~ l~land, at l,~tile II.~- Xeck. and at the western end of
Great Hog Xeck mm~erous bills flint eonsi<t .f stratified sand and
gravel range in :tJlitude fi'om about 30 to T0 feet. The bigbin' bills
:~re capped with till, which is generally about 5 feel thick.
of the morMne along the north shot'e of the l~eninsubt, as shown by
many large lag b(mlders on the botlom of Long Island Sound as far
as a quarter of a mile offshore. Also. thin swamI) and marsh deposils
have accumub~ted in kettle ponds and depressions, partieuhtr]y around
drowned kettle valleys on the south shore (pl. 1). Wave action and
tidal cnrrm~ts have constructed several bay-head beaebes and spits.
especially along the south slm]'e of the peninsula, lVind-bhm-n beach
sand has also accmmdated as dunes on top of the Harbor Hill end
moraine in the central part of area B.
The physical properties of the uPI>er Pleisio('e~e outwash and strat-
ified drift are described in logs in table g. ~t~([ mechanical analyses
of samples from ES ob~evvation wells are givet~ in table t. The~e
samples are probably representative of the bulk of the upper Pleis
tocene deposits underlying Somhold. The deposits consist mainly of
angular to subangular quartz grains and rock particles and of sma]]er
amounts of biotite, feldspar, ma~'netite, garnet, and hornb]eDde.
Particle diameters are commm~lv greater than 0.95 mm (medimn
sand) and most are about 0.5 mm ('coarse sand).
Sand, rcry eoarsc; ow gr s 17 74
GEOLOGY AND GROUND WATER, SOUTHOLD! NEW YORK
(feet)
GGI,~ CONTRIBUTIONS TO THE I~YDROLOGY OF T~E L~fglTED STATES
TABL~' 4 Physical chara eristics of ~pper Pleislocene water-bear ~ng deposits in
' the town of So~thold
67 72
27-32
87 92
34.5
31.2
Sections ,1 A' through E 5" (pl. '2) show the subsurface geologic
relations and the inferred depth to salt water in ea(h of the areas of
theSouthohlpeninsula. SectionA A' (pl.2) sbows unstratified drift
(till) uot more thau 35 feet thick exposed iu the bluff at the northwest-
ern cud of the sect]ou. The log of well S4081 shows about 8 feet of
clay at sea level that may be a local body of ice shoved or reworked
G~rdiners(?) clay. The logs of the rennduing wells indicate only
outwash deposits. Sectiou B-l~' (pl. 2) is very much the same except
for a smaller amount of till exposed iu the uorthwestern bluffs. Sec
tion C-U' (pl. 2) indicates a till body about 40 feet thick exposed in dm
bluff above Long Island Sound aud a ~d (ff clay of htie Pleistocene
age about 18 feet thick in well S12151. Section 1) O' (pl. 2) shows
till about 35 feet thick exposed in the b nfl, and sectmn ~ ~ (pl.
shows about 20 feet of till iu the bluff, whielh according to the log of
well S7171, thickens southeastward to almost 35 feet before thbm]ug
out or gradiu~ iuto the outwash deposits. Each of these sections
indicates that the anmunt of unstratified drift is negligible in com-
parison to the great Ihickness of stratified and scm}stratified outwash
deposits.
Section F-F' (pl. 2) trends approximately alon~ the axis of the
peninsula from west to eas~. ttere as in the other seefious~ consider-
GEOLOGY AND GROUND x~YATER, SOUTtIOLD, NEW YORK GG19
able thickness of outwas]l deposits are iRdicated at most wells.
area (~ the log's of wells 88(;08 and 811748 indicate the presence of
abou~ (;0 feet of clay of late Pleistocene age; and in area D the log
of well S7171, also shown in section A'-]~" (pl. 2), indicates the pres
once of till.
GROUND ;VATER
HYDROLOGY
The following discussion of groined-water hydrology refers only
to the Soutbold peninsula (areas A, B, C, and D, Little Itog Neck, and
Great Hog Neck). Available ground water data for Robins Island
are very meager, but a small body of fresh ground water occurs on
the ishmd. Only one family resides on the island at present (1960).
(-~round-water conditions on Plmn Ishmd have been described in some
detail by Crandell (19{;2). The (}till Islands are nninhabited.
Pouded fresh water is the principal soarce for public and domestic
supplies on Fishers lshmd, which was not included in this
investigation.
Precipitation, which averages about 45 inches each year, provides
the only natural sour, e of replenishment to the ground-water res-
ervoir in $outhold. A part of this precipitation flows overland to
tile surrounding bodies of salt water, a paL~ is returned to the atmos-
phere by evapm-ation and by transpiration of plants, and a part seeps
into the ground. Some of the seepage into the ground eventually
reaches the ground-water re.servoir and becomes available for with-
drawal by wells.
Because of the low moisture-retention capacity of the prevailing
silty-loam ~il, the excellent subsoil drainage, thc flatness of most
of the terrain, and the ahsence of visible runoff during most storms,
Hoffman (1961~ p. 17) suggest that possibly as little as 10 percenf
of the annual precipitation iu Soutbold enters the streams as direct
runoff. Hoffman's estimate is accepted foL' use in this report.
3,fuch of the precipitation is returned ~o the atmosphere by evapo-
ration and by the transpiration of plants, collectively termed "crape-
transpiration." Using a ~nethod developed by Meyer (1944, p. 457),
Itoffman (1961, p. 16) estitnated evaporation in Southold to be 12
inches for the year of least annual precipitation (1908), 17 inches
for the year of greatest, annual precipitation (1948), and 14 inches
for the year in which annual precipitation closely approached the
long-term average (1949). tloffman's estimates were based on the
long-term precipitation records of the Cutchogme gage. However,
the U.S. Weather Bureau evaporation pan at the Greenport power
house recorded about 23 inches of water evaporated in 1959, a year
GG20 CONTRIBUTIONS TO THE HYDROLOGY OF THE L~NITED STATES
in which precipitation closely approached the long term average.
This ewtporation was measured from a free-water surface without
plant growth and open to wind from all directions. The author sng-
gests that evaporation may possibly range from Hoffman% low est]-
mate of 19 inches to as much as ~0 inches and nmy average about 17
inches. This suggestion is in close agreemen~ with the observations
of Spear (1912). Meyer (1944) suggests that the average annmfl
rate of transpiration for agricultural crops in the North Central
States is from 9 to 10 inches. The nature of the crop and natural
vegetative cover in Southold would favor an avera,o'e rate of aboui
10 inches. Thus, the annual evapotranspiration rate for peninsular
Southold probably ranges from 2.2 to 30 inches (about 16.000 to
million gallons per year).
Recharge to the ground-water reservoir iD Southold is the difference
between the amount of precipitation and the sum of direct runoff and
evapotransplration. This stun may range from abont 75 percent of
the annual precipitation in very dry years to about 65 percent in
~ery wet years. Thus, '25 to 35 percent of the total annual precipi-
tation would be available for recharging the ground-water reserv.oi[.
Recharge in the Southold peninsnla during a year of average precqn
ration (assuming 13.5 inches of recharge) would be about 9,400 million
gallops. This recharge is summarized for the individual areas as
follows:
Area i~ million gallo~s
A .................................................. 1,500
B ..................................... 5,300
C ............................................. 8~0
~) ..................................... 1, 10~
IAttle Hog Neck ............................. lO0
Great Flog N'eck ........................ 500
Total ................. 9, 410
The effective recharge a~a of area C was first reduced by about
square miles to allow for an area west of Greenport underlain near
the surface by clay of late PleistoceDe age and Wisconsin till that
would inhibit recharge. The remainder of area C was then rednced
by 25 percent because of paving, storm and sanitary sewers, and bnild
ings in GreeDport aud vicinity. All other areas were reduced by 10
percent to allow for local near-surface till and clay deposits, paviDg,
and built-up areas.
Most if not all the fresh ground water available for use in Southold
is contained under water-table (unconfined) conditions iD upper
PleistoceDe deposits. The fresh water occurs in a series, or chain,
GEOLOGY AND GROUND V;rATER, SOUTHOLD, NEW YORK
of irreg'ularly shaped lenses that are heralded hath laterally and at
(lei)th hy ~la{'ial deposhs saturated with sally gte.nd wate~y (l)]. 2).
Areas A, B, (, and D. Little IIo~ Neek. and Great tiaa' Neck are
virtually separated from one another by salt-water marshes aud by
iulets that also are uuderlah~ by salty grouud water. ('onseqaently,
these areas are treated as individual "islands of ~'rouud water," as
each has a discrete fresh-water lens. Because the specific gravity of
the fresh water is less thau that of the underlying salt water, the
fresh water tends to "float" on the salt water within the boundaries
of the island ~enerally according- to the Ghyben-Herzberg priuciple.
Fig'urc 3 shows the contact betweeR f~,sh water and salt water
Well
Land
~~~ Wrater table surface
Fresh water
pl. 8).
schematically. Fresh water fills the deposits to the depth at which
its head is halanced by the head of the salt water. At equilibrium,
the depth of fresh water below sea level at any point on the island
is proportional to the fresh-water head above sea level and dependent
on the relatiou of the specific gravities of fresh and salt water. This
GG'22 CONTi/IBUTIONS TO T[IE HYDI/OLOGY OF THE UNITED STATES
relationship is summarized in the following' equation, which is often
referred to as the Ghyhen Herzber~ principle:
t
where
~ depth of fresh water below sea level,
~ beight of fresh water abm'e sea level, and
9--specific gravity of salt water as compared to the assumed
specific gravity of 1 e~ fresh water.
The specific gravity of sea water x aries somewhat from place to place,
bn~ the average of 1.0P5, if used in this equation, sbows lhat ~resh
water would extend 40 feet helow sea level for each foot it extends
above sea level.
The zone of diffusion, or zone of mixed water between nornml fresh
ground water and salty greuml water baring' ll~e dens~ty of sea water,
is assumed to be of negli~'ible thickness in the general application
of the Ghvbe~-Herzberg formula. Also, Hubbe~ (]940) has shown
that the ~hyben Herzberg formula is theoretically correct only under
conditions of bydrostatic equilibrium. Although neither of these
assumptions are e~ntirely valid for the Southold area, a brief study
in Greenport (tloffman, 1961, p. ~3) suggests that the 40:1 ratio
may be approximately correct in some parts of the area. Therefore.
owing to scantiness of data, the 40: 1 relationship is used in this report
to define the approximate bottom of the fresh water lenses (pl. ~)
under the Sonthold peDinsula.
The upper surfaces of the fresh-water lenses in Southold are defined
by the water table, whose configuration is shown in plate 8 by contour
lines referred to mean sea level. The contours are based on water
levd measurements made at the end of July 1~}59 iD 89 obserwtion
wells.
The upper surfaces of the fresh-water lenses are marked by a chain
of ~-ound-water ramrods alined along the axis of the S¢mthold penin
sula. These mounds are defined by closed contours on the water lable
(pl. 3). Area B apparently contains only one large and eloDgated
mound, whose crest is at an altitude of 7 to 8 feet, about a mile north
of Cutchogue. Little ttog Neck and Great Hog Neck each centains
a monnd with a crest altitmle of slightly more than ] and P feet,
respectively. Area C contains three mounds represented hy closed
P-foot contours. Also, a shallow cone of depression in the water
table is indicated by the 1-foot contour around well S3078 in Green
port. Prior to 1950 substantial withdrawals were made from wells
in this vicinity, and the cone of depression was deeper. For example,
the water table contour map of April 1050 (ttoffman. 1961. pl. 1)
GEOLOGY AND GROUND ~VATER, SOUTYIOLD~ NEW YORK GG23
shows the cone of depression extending below an altitude of 0.5 foot.
Since I950 the rate of pumping has decreased; consequently, by
July ~959, the cone of depression had shrunk to a volume of less than
one-third that of 1950.
The movement of ground water in each of the areas of the Southold
peninsula is radially outward from the crests of the ground-water
mounds on the water table, he ~'ound-water dlv de passes through
these crests and, in general, follows the northeast trend of the penin-
sula. From the vicinity of this divide, ground water moves toward
tl~e surrounding salt-water ~)dies along- flow lines whose Qirection
is normal to the water-table contours. The local direction of move-
ment in the horizontal plane is indicated hy arrows on the contour
lines. Section B-B' (pl. 2) shows this movement in the vertical
pbme also hy means of arrows indicaling the dh'ection of flow. The
direction and rate of flow are largely flmctions of the permeability
of the deposits throngh which the water moves and of the hydrauliC.
gradient. The net natnral grom~d-warer discharge from the penin
sula by lateral ontflow inte lite sea, which lakes 1)lace mostly at or
below sea level, and by evapotranspiratlon in nmrshv tracts near the
shore is unknown. Ifoffman (19{ 1, p 33) estimates ghat it may range
from ~,500 to 6,000 million gallons ammally. No data were collected
during this investigation to substantiate/here estimates
Saturated upper Pleistocene dcposils, whose volume is estimated
to total 126,500 million cubic feet, contain the fresh ground water
in storage under Southohl. The estimates for the individual areas
are given as follows:
IAttle Hog Neck _
Great Hog Neck ................. 2, 9~)
................ 126, 500
The estimate for each area has })cell redllced by 10 ])el'cenf (25 per-
cent for area C) to allow for il)e x'o]nme of till and clay, which con-
rain {itt]e available water. Not all the water fil]m~ the {nferstices of
even the coarse texim-ed deposits is avai{ab{% however. The vohnne
of ~vailab]c water is rou~h{y equivalent to the specific yield of thc
deposits. Ten determ ~ ttions of ~pecific > iehl made on s}~mi)les from
wells in upper Pleistocene deposits on Plum Ishtnd ( ~andelL 1962)
(
l'an~e from 18 to Q8 l)ercent and avel'a~e about 22 percent. Mechani-
GG24 CONTRIBUTIONS TO T}IE HYDROLOGY OF THE UNITED STATES
cai analy~s of samples of upper Pleistocene deposits froni wells on
the Southold peninsula (table 4) show tha~ they have v rtn dlv the
same physical character as those of Plnm island deposits. For this
reason a specific yield of 22 percent was applied in esthnating the
volmne of fresh ground water in storage in Southold. This volume
in ,July 1959 was computed m be a out 20(~,50(I million gMlons. The
volmne eontained in each area is as follows:
Owing to lack of data, the zone of diffusion was considered to be
of negligible thickness, and the est n ~tes should be therefore regarded
as approximate.
Seasonal wtriations in precipitation, pumpage for irrigation nsc,
and elmnges in the rate of natural discharge are the main fa(ttors
affecting fluctuations of the water table in the Southold peninsula.
lVater levels have been measured periodically in some observalion
wells in Sonthold for 10 years or more. The hydrographs of wells
in fignre 4 illustrate the trend and fluctuations of the waler table
Sonthold fl'em 1949 to 1959. Below normal precipitation and
charge and COhere'rent ~ewy withdrawal for irrigatiou aecount for
the low stages of the water table in late 1949, early 1950, and the
summer and autamn of 1957. Heavv precipitation and recharge
and light withdrawal for irrigation ,~esulted in exceptionally high
stages of the ware{' table in the springs of 1953 and 1958.
lVithdrawal from Sonlhold's fresh OToHnd-water reservob' in 1957
for public-supply, irrigation, and domestic use was esl imated to be
2~400 million gallons. Of the total withdraw:t] about T percent was
used for public supply, 79 l)erce~t for irrigation~ aml 14 percel~t for
domestic supply. Withdrawal foc publ SUpl)lV decreased somewha~
in 1958 and 1959~ but Ihe gross withdrawal for all lmrposes was nbout
GEOLOGY AND GROUND %~ATER, SOUTI{OLD, NEW YORK GG25
Precipitation,
in inches, at
LCutchogue,N. y
GG26 CONTRIBUTIONS TO THE IIYDROLOGY OF TIlE UNITED STATES
Before 1957 there were two public-supply systems in the town of
? O
Southold; the privately owned North Fork IR ater C . at the village
of Soutbold and the mnnlcipally owned village of Greenport Water
Supply. The village of Greenport~ however purchased the ~orth
Fork Water Co. in 1957 and now operates both systems. In 1959 the
Greenport system, which withdrew water frown two well fields h~
Greenport and one in East Marion, served 1,006 consmners. The
North Fork system served 281 consumers from a well field in the
village o~ Southold. Both systems supply water for domestic, eom-
mercial~ and fire-protection needs. The Greenport system also sup-
plied about 5.2 m~lfion gallons in 1957 and about 4.6 million gallons
in 1958 for irrigation use. Although pumpage from the Greenport
system increased somewhat from 1947 to 1959, the annual withdrawal
from year to year has varied markedly, owing largely to seasonal de-
mands for irrigation and lawn sprinkling, which are greater in dry
than in west summers. Pumpage from the North Fork system im
creased steadily from 1950 through 1959. Annual withdrawals from
the two systems are shown in the ~ollowing table. The demand on
Year
1947 ..........................
1948 .........................
1949 ........................
1950
1951
1952
1953
1954 ......................
1955
1056 ......................
1957
1958 ........................
1959
Pumpage (million gallons)
Village of North Fork
Water Co.
Oreenport
Water Suppl]
113. 5
131.3
153. 6
114. 2 3. 3
114. 2 4. 1
123. 6 4. 1
148. 5 4. 6
161.4 4. 9
166. 1 5. 0
133. 5 / 17. 0
159. 6 20. 0
130. 0 90. 0
122.7 22. 8
both systems is greatest during the tourist season--June, July, August,
and September. The sewer system of the village of Greenport dis-
charges directly into Long Island Sound, but elsewhere in Southold
the water pumped for public supply and from privately owned domes-
tie wells returns to the ground through cesspools and septic tanks.
Sprinkler irrigation of crops, particularly potatoes, accounted for
a withdrawal of about 1,900 million gallons of ground water in 1957,
or about 79 percent of the total ground-water withdrawal in the town
of Southhold for that year. Hoffnmn (1961, p. 7) estimates that as
much as 4,600 million' gallons may have been withdrawn in 1949,
GEOLOGY AND GROUND WATER, SOUTHOLD, NEW YORK GG27
a year of below-normal precipitation. Some farmers irrigate when
the soil no longer cakes on being squeezed or supplement precipitation
by an amount that will provide I inch of water each week during the
growing eeason. Others adjust irrigation to the ]imitations of equip-
ment and manpower. Correspondingly, the amount of water used
.and the frequency of application varies wlde]y. 5Iost irrigatlon water
is withdrawn from wells, 4 to 1'2 inches in diameter. However~ in
areas with shallow water tabIes--nearshore in areas A, B~ and C, am]
in most of area D--water is pumped from gangs of 4 to 10 shallow
small-diameter wells or from artificially excavated ponds. -5{cst oscl]-
lating springier heads in use in Southold distribute about 15 gpm (gal-
lons per minute), although a few larger ones may distribute as much
as 250 gpm. A substantial part of the water distributed by sprinkling
systems is transpired by plants or is evaporated, and this represents
a net loss from the grouud-water reservoir.
Between 9,000 and 10,000 persons are not served by public-supply
systems aud use privately owned domestic wells. ]Vithdrawa]s from
these wells totaled about 3'25 million gallons in 1957.
Ground-water withdrawal in Southold is mostly from driven and
drl]led wells, which range from lx~ to 12 inches in diameter. The
smaller diameter driven wells are used mainIy for domestic supply,
whereas the larger diameter drl]]ed wells are used for irrigation and
public supply. The fo]lowing table summarizes well-screen data for
Area
A
~ ..... Z: iiZiiiZZZiiZZZiZiZiZZZZiZZZZZZ
~l:~f~ii~-:~iii-ZZi'Z:iiZZ_'iZZ :-111'-: ....
Great YIog Neck '-- -
Approximate depth
of bottom of Length ofI screen
Median
(feet)
3
243 wells. Most htrge-diameter irrigation and public-supply wells are
equipped with deep-well turbb~e or snb~nersible pumps, whereas the
smaller diameter domestic wells are equipped with jet pumps. Where
the depth to water does not exceed suctiou lift, gasoline, diesel, or
electrically operated centrifugal pumps are used. Dug wells no longer
are constructed in Southold, but many old ones remain in use. Some
artifically excavated ponds are used in area D to supply water for
irrigation. These are usually constructed where the water table is
less than 8 feet below the land surface.
GG2$ CONTRIBL'TIONS TO THE I~IYDROLOGY OF TYIE I~ITED STATES
In an ideal hydrologic system discharge equals recharge p]us or
minus changes in ground-water storage. The system is unbahmced
when natural discharge is augmented by artificial di~harge from
wells. Balance is reestablished when recharge replaces the water
artificially withdrawn from storage. Recharge to the ground-water
reservoir in Southold during a year of average precipitation totals
about 9,400 million gallons aud avdrages about. '26 mgd (million gallons
per day). Ideally', pumpage could be allowed to approach this
amount. For practical purposes, however, withdrawal must be kept
well bdow Otis amount to minimize demand on storage and thus pre-
vent sea-water encroachment. If recharge in 1959 (a year of average
precipitation) was about 9,400 milliongallons and pmnpage was ap-
proximately ~,400 nfl]lion gallons, then pumpage amounted to about
'25 percent of the recharge on the Southold peninsula. On the basis
of known geologic and hydrologic conditions, withdrawal generally
should not exceed 30 percent of the anmml recharge. Larger with-
drawals could be made probably in areas A and B, at least, inter-
mittently, where points of withdrawal are widely spaced and the vol-
ume of fresh ground-water storage is relatively large. In areas C
aud D, however, where the total recharge and the vohmm of fresh-
water storage are relatively small and present (1959) heavy with-
drawals are concentrated at a few points, continuous pumping in
excess of preseut rates may induce sea-water encroachment.
SEA-WATEI~ ENCi~OACHM~NT
The fresh ground-wa~er supply of the Southold peninsula is po-
tentially subject, to sea-water encroachment because the fresh-water
lenses that underlie the peninsula are bounded laterally and below
by a zone of diffusion and an underlying body of salt water. The
fresh water generally has a chloride concentration of less tban 40
ppm (parts per ~nillion). The chloride cmmentration of water in the
zone of diffusion increases from abont 40 ppm on the fresh water side
to about 18~000 ppm on Ihe salt water side. The thickness of the
zone of diffusion varies widely, depending ou such factors as lithology,
changes in fresh-wat,er head~ pm tern of movement of fresh water, and
tidal fluctuations, which affect heads in the fresh aud salt water. No
data on the thickness of the zone of diffusion in Soulhold were col-
lected for this report. For the sake of si~nplicity of }malysis and
representation~ the zone of diffusion was assumed to be of negligible
thickness ou plate 2. The underlying hndy of sahy ground water
probably has a eholnride coutent of 16,000 18,000 ppm, as in sea water.
J~3ncroachment may occur where wells that are screened close to the
boundary between fresh and salt water are pumped heavily and cause
GEOLOGY AND GROUND WATER, SOUTttOLD, NEW YORK GG29
an upward or laudward migration of the sal~y water. Where the land
surface is low and relatively unprotected, as along the sooth shore,
sal't water from high tides or storm waves also may inundate the vi-
cinity of wells and coDtaminate the fresh ground water by direct
downward seepage. Figure 5 illustrates schematically the manner
Well being
pumped\
Lan
Water
level
Sand and gravel contain-\ ~,
ing fresh water (chloride\ u /Sand and gravel cam-
content generallyl~.- r.~/ raining salt water
than 4-0 ppm) .~ o
,~ ~,/ ( chloride content
~ ~ ~, ,~?/ 16,000-18,000 ppm)
cone o~ salt-water intrusion ~.. ~b¢/
in which a cone of salt water may be drawn up toward a pumping well.
Figure 6 shows bow it nmy migrate laterally and vertically loward a
pumping well, where the cone of depression has exten(]ed to the
shoreline.
Available data iudicate that clay and other deposits of low perme-
ability m~derlie some parts of the Soutbold peninsula. If these de-
posits were extensive, they would provide some degree of protection
against the migratioD of salt water toward pumpiag wells. Data
from well logs~ bowever~ suggest that these deposits are probably local
and diseontinous and, therefore, would have little if any effect in
retarding sea-water encroachmeDt.
Hoffinan and Spiegel (1958) recorded several instances of salt-water
contamination of the fresh ground water of Soutbold. In area B
(pl. $) and on Liltle Itog Xeck, four wells (S4091, Sf;059, S547b, add
S5476) yielded water having cldoride concentrations ranging from
103 to 1,600 ppm helween 1950 and 1952. Each well was drilled withiD
about 500 feet of the souil~ shore and probably penetrated the zone
of diffusion or was contaminated by lateral migration of the zone
of diffusion.
GG30 CONTRIBUTIONS TO TYIE t~YDROLOGY OF TI-rE UNITED STATES
Well
being pumped
/~ surface
.Sea. / ,~,,,or tabte__J L~prior t.o .pumping__
', I'~1
Salt water ~ ~ ~ , Fresh water
In area C (pl. 3) several wells (S1678-S1678; S1668~ and S1669)
ia the village of Gz~enport yielded water having chloride concen-
twfions ranging from 76 to 4'24 ppm between 1949 and 1951. As
GEOLOGY AND GROUND WATER, SOUTHOLD, I~rE~r YORK GG3,1
these wells are 0.5 mile from any shoreline, contamination probably
took place by migration of the zone of diffusion.
In area D (pl. 3) two wells (S7176 and S14597) yielded water hav-
ing chloride concentrations ranging from ~96 to 1~000 ppm, and two
irrigation ponds near the south shore had water ranging from 100
to 5,810 ppm of chloride. The determinations of chloride concen-
trations were made between 1948 and 1952, which was a period when
precipitation was generally less than normal, the water table was at
below normM stage, and withdrawal of water for irrigation was above
normal LaterM migration of the zone of diffusion probably caused
the high chloride concentration.
In recent years chloride determinations made on water from some of
these wells and ponds indicate a substantial decrease in chloride con-
centration. For example, in area C, wells S1673-S1678 had chloride
coucentratlous averaging about 70 ppm in the summer of 1959 as
compared with about 1~5 ppm in May 195~ (table 4). Also chloride
concentrations in artificial ponds in area D ranged from 15 to 450
ppm in September 1957 but ranged ~rom 100 to 5~810 ppm in 1948-5~.
CI-I~MICAL ~UAL?T¥
The natural chemical quality of most of the fresh ground water of
Southold is good to excellent (table 5), except in a few places where
sea-water contamination has caused some increase in chloride content
(P. GG28-GG31). The fresh water generally meets U.S. Public
Health Service limits, which were suggested for interstate carriers in
1946 as follows:
(ppm)
Iron (Fe) and manganese (/~n) combined ................ 0. 3
Magnesium (Ma) ..................................... 125
Chloride (Cl) ......................................... 250
Sulfate (SO~) ......................
Total solids (desirable) ....... }----22_~222~}2}~-~ 250
50O
Total solids (permitted) ........................... 1, 000
Hardness of water from wells of the North ork ~ ater Co. and
F
from the village of Greenport system (table 4) ranges from 44 to
200 ppm. Although no official classification for hardness of water
is available, Lamar (194~) cites the following classification as being
generally acceptable:
1-60 ............................... Soft
61-120 ......................... Moderate y hard
121-200 ........................ Hard
~ 20I ........................... Hard to very hard
T ^BLr: 5. Chemica anal~/ses, in parts per .lillion, of water,from public-supply wells in the villages of Greenport and Sol~thold
manga Calcium na e Sul[~te Oh~o~i ~ (F)
GEOLOGY AND GROUND WATER, SOUTHOLD~ NEW YORK GG33
Thus, most of the water sampled can be classed :is moderately hard
or hard. The iron conteut of the water is less than 0.3 ppm for all
samples, except two ihat contaiu 0.5 ppm and 1.5 ppm. The pH of
water sampled ranges from 5.5 to 7.5, but most of the water is aeldic
(plI less than 7.0).
The chloride content of water from public-supply wells, which
were uncontaminated or moderately tout aIninated by sea water, ranged
from S6 to 270 ppm. In other wells used for domestic, irrigation, or
fire-protection purposes--the chloride content of tbe water ranged as
follows:
CT~loride concentration of water in private wells screened in upper Pleistocene deposits,
%uthold, N.Y., 19,58 1959
CONCLUSIONS
Wader-bearing deposits of Late Cretaceous and late Pleistocene age
nnder]ie the Southold peninsula. The known £resh ground-water
snpply, however, is contained only in the upper Pleistocene deposits
under water-table eouditions. The peniDsu]a is naturally divided
into six islandlike areas, each having a fresh ground-wrtter lens that
is in dynamic balance laterally and at depth with salty ground water
in probable accordance with ~l~e Gbyben Herzberg principle. The
deposits eoutaining fresh ground-water have relatively uniform hy-
draulic characteristics and are moderately to highly permeable. De-
posits of Iow perlneability occur only l~cal]y. Fresh water can be
drawu from wells or ponds ahnost everywhere ou the peninsula pro-
vided that (l) they are not too close to }he shoreline, (~)) the screens
of wells are not set too deeply below the water table, or (3) heavy
withdrawals are not concentrated in small areas. Sea-water en-
croachmeut is likely where these conditions are not fulfilled.
Fresh gronnd water iu storag'c probably exceeds 207,000 million
gallons, and average recharge is suffi(ient to balance losses due to
wilhdrawals from wells and to natural discharge to the sea.
IIoffman and Spiegel (1958) reported some salt-water contanfina
tion of wells and ponds during the period 1948-52, when precipitation
was below normal and withdrawals for irrigation and public supply
GG34 CONTmBU~O~'~S TO TYIE I~IYDROLOG¥ OF T}IE I~ITED STATES
were high. The current (1960) degree of contain]nation ]s uot
critical.
With the exception of locally lfigh concentrations of iron and
manganese, tbe chemical quality o~ the fresh ground water ]s good and
is satisfactory for most uses.
A water-level and chloride-monitoring program, which would be
intensified during periods of below-normal prec]Ifitatlon and increased
withdrawal~ should be mMnta~ned on a continuing basis h, Southo]d.
Definite evidence o~ sea-water encroachment or overdevelopment of
the grouud-water reservoir can be established only by the accumula-
tlon o~ such data over a considerable period of time.
Chemical analyses of water ~rom representative wells should be
made at periodic intervals to determine changes {n iron content, hard-
ness~ and otber constituents important to consumers. Also, water
samples fi'mn wells in relatively densely populated areas should ~
analyzed periodically for syuthetic-detergent content.
The contact between ~resh and salt water shown on plate 2 is ~heo-
retica] and assumes a sharp boundary that does not exist in nature.
For simplicity o~ ana]ysis~ the zone o~ diffusion is assmned to be of
negligible thickness. In each o~ the hydrologic areas of Southold,
the depth and thickness o~ the zone o~ diffusiou and movement of the
sMty water need to be determined with nmch more precls~on than
available data allow. The construction of "outpost" wells in the
central part of each area and at selected poh~ts on the periphery
would give the required data. The wells should terminate in or near
the top of the zone of diffus]ou between ~resh water and salt water.
Periodic deternfinat]ons o~ the chloride concentration of the water
from the wells and measurement of water levels would indicate
whether salty water is moving upward or inland. "Outpost" wells
drilled to a depth of 250-300 {eet below the land surface in the central
pat~ of areas A and B and 100~00 ~eet below the land surface in the
central part of areas C and D would provide lhe required information.
In general, new production wells probably should not be located
within 1~000 feet o~ salty surface wa~er or wit]fin 300 feet o~ each
other. The~ spacings may be adjusted somewhat for shallow snmll-
diameter wel]s that are pumped by suction li~t and that bare a low
rato of withdrawal, but large-d~ameter wells used for large with-
drawM would require greater spaciug. The hazard of salt-water con-
tamination can be markedly reduced by appropriate well spacing and
construction. Greater use of field tensiometers to measure soil mois-
ture should prove helpful in conserving water pumped for irrigatiou.
The amouut of available ground water in Southold is comparatively
small, and all reasouable measures should be taken to conserve the
GEOLOGY AND GROUND WATER, SOUTHOLD, NEW YORK GG35
supply and to control withdrawal, especially (luring periods of below-
p~orma] precipitation. A small increase in withdrawal over the
amotmt withdrawn in 1957 59 probably is permissible in areas A and
B, provided that withdrawal is not concentrated locally or centered
[oo closely to salt-water bodies. Ilydrologic data indicate that the
available ground-water supply in areas C and D (pl. 3) has ahnost
reached full deve]opmeut; eonsequently~ sustained withdrawal sub
stantially exceeding that prevailing in 1957-59 would probably induce
sea-water encroachment in these areas.
REFERENCES CITED
CrandalI, H. C., 1962, Geology and ground-water resources of Plmn Island, Suffolk
Co ntv N.Y.: U.S. Geol. Survey Water-Supply Paper 1539-X, 35 p.
v. 30, p. 216-238.
Flint, R. F., 1947, Glacial geology and the Pleistocene epoch: New York, John
Wiley & Sons, 589 p.
Fuller, M. L., 1,005. Geology of Fishers Island. New York: Geol. Soc. America
Bull., v. 16. no. 6. p. 367~q90.
---, 1914, The geology of Long Island, New York: l!.S. Geoh Survey Prof.
Paper 82, 231 p. ·
tfoffman, J. F. 196I. Hydro ogv cfi lbo shallow ground water reservoir of the
GG36 CO~'TRIBUTIONS TO T;rtE YIYDROLOGY OF TIlE UNITED STATES
Contributions to the
Hydrology of thc
United States, 1961
GEOLOGICAL SURVEY WATER-SUPPLy
This water-supply paper was printed
as separate chapters ~I-GG
PAPER 1619
UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1963
UNITED STATES DEPARTMENT OF THE INTERIOR
STEWART L. UDALL, Secretary
GEOLOGICAL SURVEY
Thomas B. Nolan, Director
CONTENTS
(A) Hydrogeology of a spring in a glacial terranc near Ashland. Ohio, by
Stanley E. Norris.
(B) Ground-water geology and hydrology of Bunker Hill Air Force Basc
and vicinity, Peru, Indiana, by F. A. YVatkins and J. S. Rosenshein
(C) Subsidence in the Santa Clara Valley California--A progress report.
by J. F. Poland and J. H. Green.~
(D) Ground-water resources of thc coastal sand-dune area north of Coos
Bay, Oregon, by S. G. Brown and R. C. Newcon~b.
(E) Ground-water resources of thc Alma area, Michigan, by t(enneth
E. Vanlier.
(F) Geology and ground-water features of Point Argucllo Naval Missile
F~cility, Santa Barbara County, California, by R. E. Evenson
and G. A. Miller.
(G) Causes of depletion of the Pecos River in New Mexico, by H. E.
Thomas.
(H) Reconnaissance of headwater springs in the Gila River drainage
basin, Arizona, by d. H. Feth and J. D. Hem.
(I) Pumping tests in the Los Alamos Canyon well field near Los Alamos,
New Mexico, by C. V. Theis and C. S. Conover.
(J) Ground-;vater geology of Edwards County, Texas, by A. T. Long.
(K) Hydrogeology of Middle Canyon, Oquirrh Mountains, Tooele
County, Utah, by d. S. Gates.
(L) Ground water in the alluvium of Kings River Valley, Humboldt
County, Nevada, by C. P. Zones.
(M) Ground-water resources of Cow Valley, Malheur Countv, Oregon~
by S. G. Brown and R. C. Newcomb.
(N) Geology and occurrence of ground water in Lyon County, Minne-
sota, by Harry G. Rodis.
(0) Problems of utilizing ground water in the west-side business distric~
of Portland, Oregon, by S. G. Brown.
(P) Ground water in the Prineville area, Crook County, Oregon, bv
J. W. Robinson and Don Price.
(Q) Reconnaissance study of the chemical quality of surface watcrs
thc Sacramento River basbh California~ by Robert Brennan.
(R) Flow of springs and small streams in the Tccolotc Tunnel arca of
Santa Barbara County, California, by S. E. Rantz.
(S) Geology and ground-water appraisal of the Naval Air Missile Test
Center area, Point Mugu, California, by R. W. Page.
(T) Beach-area water supplies between Ocean City, Maryland, and
Rehoboth Beach, Delaware, by Turbit H. Slaughter.
(U) Methods of mcasuring soil moisture in thc field, by A. I. Johnsom
CONTENTS
tV) Alluvial aquifer in northcast~!rn Louisiana A large source of water,
by A. N. Turcan, ,Ir., and R. R Me?r.
(W) Chemical quality of surface waters ill Pennsylvania, hy C. N. Durfor
and P. W. Anderson.
tX) Geology and ground-water resources of Rock County, Wisconsin, by
E. F. LeRoux.
(5') Geology and hydrology of Valle Grande anti Valle Toledo, Sandoval
County, New Mexico, by C. V. Theis, C. S. Conover, and R. L.
Griggs.
(Z) Water-resources reconnaissance in southeastern part of ltoney Lake
Va ley, Lasse Connt~, California, by George S. Hilton.
(AA) Ground-wat(r conditions in the Fernley-Wadsworth area, Churchill,
Lyon, Storey, and Washoe Counties, Nevada, hy W. C. ~4inclair
and O. J. Loeltz.
(BB) (iround-watcr exploration and test pumping in the Halma-Lakc
Bronson area, Kittson County, Mimmsota, by G. R. Schiner.
(CC) Ground-water in the P, aft River basin, Idaho, with special reference
to irrigation use, 1956 1960, hy M. J. Mundorff and H. G. Sisco.
(DI)) Analysis and evahmtion of availat)le hydrologic data for San Simon
basin, Cochise and Graham Counties, Arizona, by Natalie D.
White.
tEE) Sedimentation of Lake Pillsbury, Lake County, California, hy G.
Porterfield and C. A. I)unnam.
(FF) Geology and ground-water resources of Barrow County, Georgia,
by M. G. Croft.
(GG) Geology and ground~water resources of thc town of Southold,
Suffolk County, N.'i'., by H. C. Crandell.
UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
A
/ 0 N G
Duck Pond
Qhm
Qhm
L
N
D
,Qsh
HE TE
SL AND
SOUND
F'
Osh
G HAr~
0 U N D
E
T
Qsl
WATER-SUPPLy ~APER
PLAT£ 1
1619-GG
LONG
BEA C
BAY
Qsh
Qhm
Qsh
Qsh
G R E A T P E C O N / C
EXPLANATION
Qsh
Y
Qo
LITTLE
PECONIC
BAY
ARDINERS
BAY
boulde~ gravel deposited by
Oo
Outwash
Gardlners(?) clay
Marsh deposits
Harbor Hill end moraine
deposits
ROSINS
ISLAND
Qsh
Base from U,S Ge0loglcal Survey
topograph}c maps
A A'
SURFICIAL GEOLOGIC MAP OF THE TOWN OF SOUTHOLD, LONG ISLAND, NEW YORK
I 2 3
Geology largely adapted from M · Fuller (1914)
-50
EXPLANATION
SECTION A-A' FROM LONG ISLAND SOUND TO GREAT PECONIC BAY (AREA A)
SECTION B-B' FROM LONG It;LAND SOUND TO LITTLE PECONIC BAY (AREA B)
75
50
-25
Chloride 20 ppm
SECTION C-C' FROM LONG ISLAND SOUND TO SHELTER ISLAND SOUND
(AREA B)
25
25
-25 depth ~ -85
x / M ' I
..,,-.X
SECTION D-D' FROM LONG ISLAND SOUND TO FIREENPORT HARBOR
(AREA C)
25
5O
-5O
-300
-350
--400
AREA A
I
I
I
/
/
/
?/
/
SECTION F-F* FROM HERRICKS LANE TO PLUM GUT
C-EOHYDROLOG[C SECTIONS IN TI-II~, 'I'OW~ OF 5;O[TT~IOLD, SUFFOLI~ COUNTY, ~EW
5O
UNITED
STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
WATER-SUPPLY PAPER
PLATE [ 5
REA 8 AREA C
~REA A-
1676E
E OSt
1619-GG
016 756
8,52
5.27
H E L 'T E /? HA~
ISLAND
SOUND
L
BEACH
BAY
O ri
G R E A T
EXPLANATION
Ob~rvation well
E C 0 N / C B A Y
/LITTLE
HOG
6
LITTLE
PEGONIC
BAY
ARDINERS
BAY
Well for which hydrograph
is given in figure
~5475
Well which yielded water of high
chlorldeconeentration
Well for which log is given in table 3, or log
is shown graphically on geohydrologie
+
Preelpitation station
[3
Approximate center of populated
MAP OF THE TOWN OF SOUTHOLD, LONG ISLAND, NEW YORK, SHOWING LOCATION OF WELLS
.~ ,/AND POSITIONal - - ~- = ~' ,,~OF o THE WATERi, TABI,E21 IN~i MiLEsJULY~ 1959 /
A A'
Line of geohydrologie section
See report for description of hydrologic areas A-D
tY by H C Crandell, 1959