HomeMy WebLinkAboutFI Hydrogeologic Report 1990
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
HYDROGEOLOGIC REPORT
Conducted on Fisher's Island, New York
for
Fisher's Island Conservancy
Fisher's Island, New York
APRIL 1990
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I.
II.
III.
IV.
V.
VI.
Table
Table
Table
Table
Table
Table
Table
Table
TABLE OF CONTENTS
Abstract
INTRODUCTION
A. Purpose
B. Scope of Study
GEOLOGY
A. Introduction
B. Previous Work
C. Monitor Well Installation
D. Sub-Surface Materials
E. Environments of Deposition
F. Cross-sections
G. Discussion
HYDROGEOLOGY
A. Introduction
B. Hydraulic Conductivities
C. Water Level Data
D. Ground Water Flow
E. Ground Water Recharge
F. Salt/Fresh Water Interface
G. Water Use
CHEMICAL ANALYSIS AND WATER QUALITY PROBLEMS
A. Introduction
B. General Ground Water composition
C. Areas of Degraded Quality
CONCLUSIONS
RECOMMENDATIONS
A. Additional Assessment
B. Management Practices
TABLES
1 - Generalized Stratigraphy
2 - Hydraulic Conductivity Tests
3 - Water Level Data
4 - Average Precipitation
5 - Recharge Rates
6 - Ground Water Budget
7 - Ground Water Contaminant Summary
8 - Proposed Ground Water Monitoring Schedule
Paae
1
4
30
50
69
72
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
FIGURES
Figure 1 - Location of Ronkonkoma and Harbor Hill Moraines
Figure 2 - Idealized Distribution of proglacial Environments
Figure 3 - Exposure of Proximal Outwash
Figure 4 - Close-up of Proximal Outwash
Figure 5 - Exposure of Lacustrine Deposits
Figure 6 - Close-up of Rhythms
Figure 7 - Facies Map
Figure 8 - Piper Diagrams
PLATES
Plate 1 - Island Geology
Plate 2 - Geologic Cross sections
Plate 3 - Ground Water Contours
Plate 4 - Ground Water Chemistry - Stiff Diagrams
APPENDICES
Appendix A: Driller's logs for homeowners and monitor
wells; results from private well owner survey
are included.
Appendix B: Recovery Test Calculations used to determine
the hydraulic conductivity of various
sub-surface materials
Appendix C: Laboratory analysis sheets from ground water
and surface water samples across the island.
Appendix D: Kerfoot and Horsley Method for determining the
zone of influence for private wells.
1
1
1
1
I
1
I
I
I
I
I
I
I
I
I
I
I
I
'I
Abstract
The shallow ground water supplies on Fisher's Island
are relatively complex and fragile in comparison to ground
water supplies on Long Island and other glaciated areas. An
extensive hydrogeologic study on Fisher's Island has
concluded that permeable aquifer materials are restricted to
thin gravel lenses and sorted outwash sands stratified with
relatively impermeable silty clay and glacial till.
Hydraulic conductivities of these aquifer materials range
from 1 to 100 ft/day. The locations of the gravel lenses
are difficult to predict but appear to be related to
discrete discharge points of high velocity glacial meltwater
associated with the glacial front.
Ground water flow is defined by a series of marginally
interconnected ground water mounds with ground water flow
generally moving from recharge areas located in the center
of the mounds to discharge areas located at cell borders.
The exact location of recharge areas is difficult to
determine due to the abundance of impermeable layers
separating the gravel lenses. Average ground water recharge
is estimated to be approximately 709 million gallons per
year. Ground water withdrawals are difficult to estimate
because of the unknown quantities used for lawn irrigation,
but the range is estimated between 175 million and 300
million gallons per year (between 25% and 50% of average
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
annual recharge). Based on the irregular geometry of the
aquifers, it is unlikely that 100% of the annual recharge
will ever be safely available for use.
The shallow ground water should be adequate, however,
to provide potable fresh water supplies provided that proper
management programs are instituted. The potential for
significant additional sources from centralized water supply
systems and aquifers is not great. Individual private water
supply wells can and should provide most of the water for
future development on the island. It is crucial, however,
that an appropriate regulatory process be instituted for
these private wells to prevent local well interference and
water mining and the development of salt water intrusion.
Centralized aquifers such as the Middle Farms Aquifer should
be protected and used with caution. Monitoring wells in the
vicinity of the Middle Farms Aquifer should be tested on a
frequent schedule during pumping so that salt water
intrusion and aquifer dewatering can be quickly detected,
monitored and corrected. Additional recommendations include
further exploration for an alternative centralized supply,
further ground water monitoring at Picketts Landfill, the
Metal Dump and other possible sources of ground water
contamination and the institution of an island-wide ground
water protection and monitoring strategies stressing
conservation and land use policies that will preserve ground
water quality and insure that adequate fresh water supplies
will continue to be available in the future.
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I. INTRODUCTION
A. Purpose
Fisher's Island is one of four (4) small islands
located within the Town of Southold, Long Island. Like all
of these islands and much of the Town of Southold, the
available fresh water resources are limited and currently
under stress of ever increasing development. The
inhabitants of the island have used ponded fresh water as a
primary source for drinking and irrigation and though the
quality of the water has generally been good, future demands
will require further development of the island's aquifers.
The purpose of this study is to develop an
understanding of the aquifers on Fisher's Island and their
hydrogeology. Secondly, the study characterizes the nature
and present extent of man-induced alterations to the
quantity and quality of surface and fresh waters.
B. Scope of studv
The hydrogeologic investigation consisted generally
of the installation of eighteen monitoring wells between May
1988 and June 1989 in various parts of the island. During
well installation, the geology of the sub-surface materials
- 1 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
was described and carefully logged so that an overall view
of the island geology could be pieced together. The
hydrogeologic properties of the aquifers were determined by
repeated water level measurements and conductivity testing
of these wells. Finally, the water quality of the aquifers
was determined by laboratory analysis of samples obtained
from these wells.
The specific objectives of the study were as follows:
1. to determine the extent, thickness and geometry
of the important hydrologic features of
permeable sediments (aquifers) and impermeable
sediments (aquicludes);
2. to determine the hydrologic properties of all
the aquifers;
3. to determine the recharge to aquifers by
estimating the Island's water budget;
4. to determine the ambient water quality of the
aquifers and to locate any threats to aquifer
water quality;
5. to estimate the risk of salt water intrusion
and severe storm tidal surges on the aquifers;
- 2 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
II. GEOLOGY
A. Introduction
The first step in characterizing the aquifers on
Fisher's Island is to define the island's geology. By
obtaining information on the location and orientation of
coarse and fine grained deposits, the sizes of the aquifers
can be estimated and potential water supply well sites can
be identified.
B. Previous Work
1. Regional Setting:
The topography in this vicinity of Long Island
is related to the retreat of the Laurentide Ice
Sheet during the Wisconsin stage of the
Pleistocene (Flint, 1947). As the climate
became slightly warmer, the ice sheet reached
its maximum southern advance as marked by the
Ronkonkoma terminal moraine which stretches
across the middle of Long Island eventually
connecting up with similar deposits in Martha's
Vineyard and Nantucket. A second moraine
accumulated to the north of the Ronkonkoma that
can be traced from deposits along the north
- 4 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
shore of Long Island to the mainline of Rhode
Island. This second moraine, termed the Harbor
Hill, Charlestown, Buzzards Bay moraine
includes the deposits found on both Fisher's
and Plum Islands. The configuration of these
two moraines is shown on Figure 1. The details
concerning the exact origin of this moraine are
unclear. Some geologists believe that this
second moraine marks a readvance of the
Laurentide Ice Sheet (Soren, 1971) while others
believe the moraine formed as the ice sheet
remained stationary before a later advance
(Fleming 1935).
The Pliestocene deposits regionally overlie
semi-consolidated sand and clay units derived
from the north sometime during the Cretaceous
Period (Crandell 1962). The bedrock on the
Long Island and Southern Connecticut consists
of a complexly faulted and deformed sequence of
Pre-Cambrian Gniesses and Granites (Rodgers
1985) .
2. Previous work on Fisher's Island:
The geology at Fisher's Island was first
described by Fuller (1904) who used the
lithologic descriptions from a deep bedrock
- 5 -
-------------------
'"
~
"'
c
~
"
,
;r
.";',....
+~..,
J~' -
'Is';:):.
.,'
I:i':'--;:::-I End moqlne
""^"'- Pr...,med Int.,IOO.t. zonet
N
t
0 :;IDmiles
I , , , ,
0 50 km
73' 72'
71'
70'
~Ground Water, Inc.
FISHERS ISLAND LOCATION MAP
FIGURE ONE
_ SKETCH MAP SHOWING END MORAINES
FROM FLINT 1971
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
well on the island (the Ferguson well) and
various surface exposures to define the
island's stratigraphy. Bedrock was encountered
at 281 feet and the overlying Cretaceous and
Pleistocene deposits were differentiated into
various sand and gravel units. Fuller (1904)
attempted to correlate units discovered on
Fisher's Island with units previously described
on Long Island, Pennsylvania, Mississippi and
Canada. Most noteworthy of these units is the
Gardiner's Clay, the name given to the thick
clay deposits which are exposed in bluffs and
beach exposures around the island. Fuller
suggested that the clay is part of a thick clay
bed which is traceable through the Long Island
Sound area. More recent field work by Upson
(1970) has shown that lithologically similar
clay units in the Mattituck quadrangle on Long
Island pinch out laterally, putting Fuller's
correlations into questions. These
observations coupled with more recent
developments and understanding in glacial
geology, put many of Fuller's (1904)
interpretations into doubt. However, this
initial work provided a scale and starting
point for later description on the Island.
- 7 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
One significant observation by Fuller was the
recognition of deformation features in the
surficial deposits suggesting that deposits on
the island have been moved from their original
site of deposition. This has been
substantiated by later workers.
A more rigorous inventory of glacial sediments
on Fisher's Island was conducted by the united
states Geologic Survey in the quadrangle
reports of Goldsmith 1962 (New London Quad) and
Upson, 1971 (Mystic Quad). These geologists
found that the most of the island is covered by
end moraine deposits which are composed of both
till and stratified drift. Both reports
indicate that the end moraine deposits are
complex and no attempt is made by either to
differentiate till from stratified drift.
Goldsmith's mapping of the western part of the
island (New London Quadrangle) includes rough
stratigraphic descriptions of beach and inland
exposures and these descriptions suggest that
till generally overlies stratified drift.
Upson (1971) notes that the end moraine
deposits are underlain by thick clay to silt
and sand sub-units which Fuller (1904) deemed
- 8 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
the Gardiner's Clay. The clay/sand sub-units
reach a maximum of 60 feet thick in beach
exposures in the south central part of the
island. The lateral continuity of these
deposits is not known. Upson (1971) also maps
three broad sand-plain deposits which cross the
island from north to south. He reports that
these units are "predominantly sand". The
origin of the deposits is not clear and Upson
suggests that they may represent either
fillings of meltwater channels or large
collapse depressions in the moraine when the
retreating ice lay immediately north of the
island. Both authors show that the glacial
deposits are overlain in places by beach, salt
marsh, swamp and minor alluvial deposits of
Holocene (recent) age.
Goldsmith (1982) reevaluated his earlier
mapping to include significant areas of
stratified drift on the southwest end of the
island. He explained this outwash as glacial
stream deposits that extended away from a
stagnant ice margin.
- 9 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
3. Plum Island:
The work conducted by the USGS matches well
with Crandall's (1962) mapping on Plum Island
located just to the west of Fisher's Island.
Through the description of surface exposures
and the installation of monitoring wells,
Crandall noted that Plum Island consists
primarily of end moraine deposits. Like
Goldsmith's mapping on Fisher's Island,
Crandall noted that the end moraine's deposits
consisted primarily of stratified drift with an
upper veneer of unstratified till. Like
Upson's sand plains, Crandall noticed a roughly
north-south trending channel filled with
outwash sand interpreted as meltwater
deposition. Crandall also noticed that clay,
"tentatively assigned to the Gardiner's Clay"
underlies the end moraine deposits. His test
borings could not confirm that the clay
underlies the entire island, further
questioning Fuller's 1904 correlations.
4. Rhode Island:
The moraine continues to the east in Rhode
Island as the Charlestown Moraine. This
- 10 -
~"
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
section of the moraine was mapped by Kaye (1960)
who concluded that downwasting was the major
mechanism responsible for sediment deposition.
Ridges, mounds and hummocky terrain on the moraine
were attributed to ice fracture filling and ice
block casts. The resulting stratigraphy is a
highly chaotic assemblage of lacustrine, fluvial
and till materials deformed largely from the
downwasting of the glacier. Although specifics
concerning the internal fractures of the moraine
are not discussed, this model is still generally
accepted for much of the Charlestown section of the
moraine (Byron stone, U.S.G.S. personal
communication) .
C. Monitor Well Installations
Monitoring wells were installed to supplement
geologic interpretations made by these earlier workers and
to obtain hydrogeologic information from any encountered
aquifers. The location of these wells are shown on Plates
in the back of the report and driller's logs are attached in
Appendix A.
Three methods were used for monitor well
installation: 1. Drive and Wash Method; 2. Auger Method;
and 3. Air Rotary Method.
- 11 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Monitoring wells 1 through 9 were installed between
May 5th and May 19th, 1988 by the Stephen B. Church Company
using the drive and wash method. This method involves
driving lengths of casing to the desired depths while
washing the casing out after each additional casing length
had been driven in. At the desired depth, 1-1/4" diameter
well screen was set within the casing and the casing was
withdrawn to expose the desired length of screen. Sediment
samples were described from the casing wash. The wells were
developed using either a pump or an air compressor.
Monitoring wells 10 through 16 were installed
between October 10, 1988 and April 21, 1989 by Clarence
Welti and Associates, Inc. of Glastonbury, CT using the
hollow stem auger method. This method involves using a
hollow stem auger to bore to the desired depth and
installing a 2-inch PVC well with slotted screen through the
hollow stem. Samples were obtained by hammering split
spoons at 10 foot intervals. These samples were described
on-site and saved for future analysis.
One additional monitoring well (4A) was installed using
the air rotary method. This method involves drilling with a
rotating bit with cuttings being removed by constant
circulation with air. Samples were described from cuttings
that were flushed to the surface. A finished four inch PVC
casing well was installed into the boring.
- 12 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
D. SUb-surface materials
A summary of the geologic materials on Fisher's
Island is presented on Table 1. Description of deeper
deposits was taken from Fuller (1904), Crandall (1972) and
Upson (1971). Shallow material descriptions are summarized
from boring logs from monitor wells installed as a part of
this project. Alongside such material description is an
interpretation of the environment of deposition and unit
thickness. Also described in the table are the water
bearing characteristics of the sediments determined either
by inference to similarly described materials or by on-site
hydraulic conductivity testing. Details concerning the
hydraulic conductivity testing are given in chapter III.
1. Pre-Cambrian Basement:
Pre-Cambrian basement and Cretaceous deposits
were not encountered during drilling and are generally not
pertinent to this aquifer study. It should be noted that
the Ferguson well drilled into bedrock and mentioned by
Fuller (1904) functioned as an effective water well and the
granitic basement mav contain potential water supplies. The
Ferguson well log shows the bedrock was encountered at 281
feet. Assessing the exact nature and yield of the bedrock
supply would require additional work beyond the scope of
this study. From work conducted at Orient Point, bedrock
- 13 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
slopes to the southwest reaching depths of between 500 and
1000 feet.
2. Cretaceous Deposits:
Similarly, the Cretaceous sediments may contain
abundant supplies of water. Much of Long Island relies on
water from these sediments for its water supply. However,
Crandall (1962) theorized that the Cretaceous deposits are
too deep on Plum Island and probably saline because they lie
beneath the thin fresh water lens (the fresh water lens will
also be discussed in greater detail in chapter 3). Since
bedrock is shallower on Fishers Island, fresh water may
extend down to any Cretaceous deposits above the bedrock.
This is not based on any hard evidence and, like potential
bedrock water supplies, assessing the water supply potential
in the Cretaceous sediments would require additional work
beyond the scope of this study.
3. Pliestocene Deposits:
The potential for high yield aquifers within
the Pliestocene deposits or "Glacial Aquifer" varies widely
from region to region. Generally, deposits associated with
the Ronkonkoma and Harbor Hill Moraines are relatively
impermeable in comparison to glacial outwash found between
the moraines (Hauptmann, et al., 1989).
- 14 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
This study concentrates on potential water
supplies in the shallow Pliestocene deposits that can be
most easily tapped. Drilling and monitor well installation
encountered four (4) general types of material:
a. fine to medium sand, moderately sorted with
varying degrees of sand and gravel. Roughly encountered in
thick layers (over 10 feet thick);
b. graded, rhythmic coarse to fine sand and
gravel occurring in lenses varying from less than one foot
to several feet in thickness;
c. grey silt and clay stratified with the
thinly bedded coarse sand;
d. poorly sorted sand silt and clay with
varying degrees of cobbles (glacial till).
The distribution of the Pliestocene and recent
deposits is mapped on Plate 1. This map is primarily a
compilation of the Upson and Goldsmith Reports with some
revisions based on field observations.
E. Environments of Deoosition
Glacial sediments deposited in association with
- 15 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Discharge Point
Glacial Till
Marginal Outwash Facies
Distal Outwash Facies
Proximal Outwash Facies
Medial Outwash Facies
i\GroundWater, Inc.
FISHER'S ISLAND
FACIES MODEL FOR
PROGlACIAl ENVIRONMENTS
-BASED ON BROZIKOWSKI AND LOON (1987),
FRASIER AND COBB (1982),
ANDERSON (1982)
- 16 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
recessional moraines can most conveniently be subdivided
into glacial till, marginal and proximal outwash deposited
close to the glacial front and medial (Edwards, 1978 and
Anderson, 1989) and distal outwash deposited further away
from the glacier (Anderson 1989, Brozicowski and van Loon,
1987, Frasier and Cobb, 1982). Figure 2 shows the
distribution of sedimentary facies encountered in morainal
or "proglacial" environments.
Proglacial environments are dominated by high
competence and capacity streams exiting the glacier. At the
discharge points these streams deposit very coarse and
laterally discontinuous gravel deposits. On either side of
the discharge points are thick deposits of glacial till. As
the streams flow away from the glacial front they lose
velocity and finer materials are deposited. This sorting
results in more laterally continuous and finer grained
materials moving away from the moraine. Ice damming and
damming related to previous moraines can cause ponded water
to be located adjacent to the glacial front. This may cause
coarse materials to be interstratified with fine grained
lacustrine deposits.
The poorly sorted sand, silt and clay with abundant
cobbles is interpreted as glacial till deposited directly
from glacial ice with no meltwater involved. This till
forms the core of the moraine that accumulated as the ice
front remained stationary.
- 17 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
The coarse to fine sand and gravel deposited in
lenses is intimately associated with grey silt and clay and
together these deposits represent the "marginal" deposits.
The sorting and abrupt grain size changes are caused by
rapid variations in water flow from the glacier and by
direct deposition of gravels into lacustrine environments.
The fine to medium sand, moderately sorted with
varying degrees of gravel represents proximal outwash
deposited a larger distance away from the glacier. These
sediments were more likely deposited by braided streams
which deposited thicker and more consistent layers of coarse
sand.
F. Cross-Sections
Four cross-sections have been constructed
connecting the borings from this study of these materials
(Plate II). The lines of cross-section are shown on the
maps enclosed as plates in the back of the report.
section A-A' is drawn roughly west to east across
the spine of the island and three shorter cross-section
trending roughly north-south cross the island as follows:
in the North Hill/West End of the island (B-B'), central
Middle Farms area (C-C') and the east end (D-D').
Lithologic descriptions from test wells drilled for the
- 18 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Fisher's Island Country Club by S. B. Church were used in
constructing 0-0' and the eastern section of A-A'.
The western end of the island is made up of till
and brown sorted sand deposits overlying the interbedded
silts and gravels of marginal outwash materials. The brown
fine to medium sand of the marginal outwash makes up a large
thickness of the western part of the island with glacial
till interfingering in places. The uppermost deposits
contain glacial till, as noted in the upper parts of the
Lamborne and Nitze wells. This overlying till was also
observed by earlier USGS Mapping and by Crandall on Plum
Island. Deeper till zones were encountered in MW-ll, MW-6
and MW-7.
The proximal outwash materials are best exposed in
the south shore face to the east of the Hay Harbor Golf
Course. See Figures 3 and 4. Here the outwash shows
classical glacial delta features including a general
coarsening upward grain-size trend. Outwash at the base of
this exposure is stratified with silt and clay suggesting
deposition into ponded water. The upper, coarser part of
the delta is capped by a thin till zone noticed on much of
the Island's western end.
- 20 -
--- -:.-- ,.~,-~,
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
The marginal outwash below the till contains some
thick gravel zones as noted in MW-6 and 11. These gravels
may not be laterally continuous as suggested by the
interfingering of thin gravel lenses in the Nitze well with
the thicker gravel deposit of MW-ll.
Moving eastward, the thickness of till increases
while the overlying thickness of medium to fine sand
decreases. Much of the island between Barlow Pond and Mt.
Prospect appears to be underlain by a thick sequence of
till. A small thickness of marginal outwash appears in MW-4
as grey silt to clay at thirty and forty feet below land
surface. A thick section of gray lacustrine clay (first
described by Fuller 1904 as the Gardiners clay) underlies
the till. Exposures of this clay can be found at Isabella
beach (se Figures 5 and 6). Cuts into this clay show vary
fine laminations and gradings from brown dense clay laminate
to grey green fine silt and sand. These features are
typical of lacustrine sedimentation. Some exposures show
highly chaotic deformation of the clay from either slumping
or ice tectonism. Generally, no thick gravel zones were
encountered in this area.
The overlying till pinches out moving into the
Middle Farms Pond area. The brown silty sand thins slightly
in comparison to wells drilled west of Barlow pond. More
importantly, a thick sand and gravel layer, approximately
- 21 -
. ~:.1,~"i'!
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
forty feet thick was found in the center of the Middle
Farms flats. This aquifer was the subject of intense study
by Ground Water, Inc. during the installation and permitting
of 2 public drinking water supply wells. The aquifer is
confined by silts above and below, and is interpreted to
represent a large channel in the marginal outwash materials.
The channel could be traced laterally to monitor wells lA
and to other monitoring wells installed for the pumping
tests. However, the channel could not be traced to MW-2A,
20 and 9, suggesting that the channel is of limited extent
in a north/south direction in the Middle Farms area.
The Chocomont area is mantled with a thick layer of
till as noted in the Schmidt well and MW-l6. MW-l6 did not
completely penetrate the till but the log of the Schmidt
well suggests that the area is underlain by gravels and
silts of the marginal outwash.
A thin outwash channel has been carved in the till
in the vicinity of MW-8 in the vicinity of East Harbor and
shallow ground water is confined to the brown proximal
outwash sands. However, unlike the Middle Farms outwash
channel, no gravels from the marginal outwash facies were
encountered.
The till reaches its greatest thickness in test
wells drilled by S. B. Church in the eastern end of the
- 23 -
C7----~:':c:::;;-
',,;'
~~--c--.C7--~",~~---~~'-~:-~C~"-
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
island. A thick mantle of brown outwash sands overlies the
till, and stratified ice contact drift was encountered at
depths between 20 and 40 feet below mean sea level. Also,
some minor sand lenses were encountered within the till as
noted in test wells 4, 5 and 7.
G. Discussion
From reviewing the cross-sections, some underlying
facts can be deduced. The majority of the island's
topographic highs (the North Hill/West Harbor area, the
Chocomont area and East Harbor areas) consist primarily of
till with minor amounts of proximal outwash sands. Much
greater amounts of proximal outwash sands are encountered in
the southwestern part of the island (see MW-12 and 13)
forming a possible aquifer. The proximal outwash sands also
could provide aquifer materials in the vicinity of East
Harbor (see MW-S) but the lateral and vertical extent of
these deposits is much more confined.
The major aquifer materials on Fisher's Island are
the gravels associated with the marginal outwash and
lacustrine deposits which underlie a majority of the
island. The relationships between the till and the outwash
are complex and remain equivocal. Two till events are
suggested: An older till was encountered below the marginal
outwash in the area east of Barlow Pond. A younger till was
- 24 -
- -,-----7".'=:~:--~7-
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
encountered mantling the marginal outwash and proximal
outwash sands on the western end of the island. with
marginal outwash encountered at depth in test holes drilled
on the east end of the island, till in this area may
represent the younger till.
Aquifer materials tapped in the marginal outwash
and lacustrine materials (MW-11, MW-6 and MW-1) should be
considered as vertically and laterally confined. These
gravels were deposited in association with large fluxes of
meltwater directly into a meltwater lake at the glaciers
edge. These fluxes waned during cold periods allowing finer
materials such as clay/silt rhythms to settle out. Also,
the axis of the meltwater fluxes migrated significantly in
much the same ways that rivers migrate causing abundant
lateral pinchouts of the gravels within the silts and
clays. These processes created deposits which are
discontinuous and very heterogeneous. This geologic origin
must be considered when interpreting the volumes and yields
of the ice contact stratified drift aquifers.
Figure 7 shows the estimated distribution of
facies. The marginal facies with thick gravels and silt is
associated with two glacial stream discharge points in the
central and western end of the island. The outwash channel
mapped in the eastern end of the island by Upson (1971) and
Goldsmith (1962) could be related to another discharge
- 25 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
l'
GLACIER
\ \
\ \ \
II I I \ \ \
- 26 -
-------------------
TABLE 1
GENERALIZED STRATIGRAPHY
Thickness
Aqe (ft.)
Interpretation
Holocene 0-20+
Beach Deposits
Pliestocene 100-
200=
Proximal Outwash
Marginal Outwash
sand channels
'"
....,
Marginal Outwash:
lacustrine deposits
Non-stratified
Ice Contact Drift
(Glacial Till)
1
Crandall 1962
2
Upson 1971
3
Description
Coarse sand and
gravel marshy
areas with sand,
silt and or~anic
matter. 1,
Fine to medium sand
with varying
degrees of silt.
possibl~ some
gravel.
Coarse to fine ~rey
sand and gravel
Grey silt and clay
with varying rhythms
degree~ of fine
sand
Poorly sorted sand,
silt and clay wi
varying djgrees of
cobbles.
Determined from on-site inspection or testing
4
Fuller 1904
Conductivity K
or Water Bearing
Properties (ft/dav)
Probably water
conductive but
vertically shallow
and latertlly
confined
K = 0.8 3
(from one well)
K = 46 to 0.04 to
K = 0.2 to 0.09
K = 0.1 to 0.007
-------------------
GENERALIZED STRATIGRAPHY (continued)
Aqe
Thickness
(ft.)
Interpretation
Description
Conductivity K
or Water Bearing
Properties
Gardiners Clay
Clay, fine sand and
silt in guadational
sub-units wjclays
grading (possibly
deformed)
Low permeability
possible con-
fining unit.2
Cretaceous 100'I
Unconsolidated
Clastics
stratified sands,
~~l~S and clays.
Sands are probably
permeable and water
bearing but most
likely saline.
Low permeability
porosity - However,
fresh water was
encountered at >300. 4
Pre-Cambrian
Intrusive Granite
No descript!ons
available.
'oJ
:.0
1
Crandall 1962
2
Upson 1971
3
Determined from on-site inspection or testing
4
Fuller 1904
I
I
I
I
I
I
I
I
I
I -
I
I
I
I
I
I
I
I
I
point. Proximal outwash is thickest in the western end of
the island where the island is widest. Glacial readvance
and the affects of downwasting and ice tectonisms have
greatly complicated this general scheme. Obviously more
work is needed, specifically through the careful analysis of
surface exposures to refine this model.
- 29 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
III. HYDROGEOLOGY
A. Introduction
Pumping and periodic gauging of the monitoring
wells was conducted to determine the hydrologic
characteristics of the aquifers on Fisher's Island. This
section describes the nature of ground water flow on the
island and develops a rough ground water budget based on
anticipated recharge and withdrawal.
B. Hvdraulic Conductivities
The ability of aquifer materials to transmit water
is proportional to the material's hydraulic conductivity,
(K) and hydraulic conductivity is proportional to the median
grain size and degree of sorting of the material. Once the
conductivity of the materials are known, estimates
concerning aquifer yield and flow rates can be made.
Conductivities were determined using the recovery
test method which involves measuring the static water level
in a well, pumping out a volume of water and monitoring the
rate rise of the water in the well. Conductivity K, is
given by K = r2 In (LjR),
- 30 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
where
r = radius of well
R = radius of screen
L = Length of screen
Calculations are enclosed in Appendix B.
A summary of the conductivity results for each well
is given in Table 2.
Hydraulic conductivity was also determined in the
Middle Farms Aquifer using pump test data from the two
public drinking water supply wells. Pumping data were
analyzed using two separate methods and derived conductivity
values ranging from 61 to 160 ft/day for the Proximal
outwash gravel aquifer.
Using these data, coupled with an understanding of the
geology of the island, the vertical and lateral arrangements
of aquifers can be roughly outlined. The term "aquifer"
means a saturated unit which is capable of transmitting
usable quantities of water. This is, of course, a relative
term, but for this overview, an aquifer will be considered
as a saturated material with conductivities greater than 1
ft/d.
- 31-
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
TABLE 2
Hydraulic Conductivity Testing
K
Well # Screened Material (in ft/davl Test Date
2D sil t and Clay 0.094 5/88
3 Glacial Till 0.087 5/88
3 Glacial Till 0.26 7/88
4 Glacial Till 0.087 5/88
4 Glacial Till 0.10 7/88
5 Glacial Till 0.066 5/88
6 Sand and silt 0.14 5/88
6 Sand and silt 0.17 7/88
8 Glacial Till 0.088 5/88
9 silt 0.22 7/88
13 Sand 0.80 11/88
- 32 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
The geologic materials can now be evaluated as to their
water bearing properties (conductivity ranges are tabulated
next to geologic descriptions in Table 1 - Generalized
Stratigraphy):
1. Beach Deoosits - these materials were not
encountered during drilling but their well sorted,
sandy nature suggests that they would be water
conductive. However, their laterally limited
extent and proximity to salt water suggests that
they would not make productive aquifers.
2. Proximal Outwash Deoosits: - only one well was
screened in the outwash deposits, GWI-12. The
limiting factor with the outwash is the limited
extent to which these deposits are saturated. The
cross-sections show that most of the outwash exists
above the average water table surface and this
material, although porous, may not be available as
an aquifer. This could be verified through
additional well installations.
J. Marainal Outwash Deoosits - this material contains
abundant saturated coarse gravel deposits as noted
by the high conductivities derived through the pump
testing of the Middle Farms supply wells. The
problem with this material is that it is complexly
- JJ -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
stratified with lacustrine clays. Coarse sands
may be thick in places but may pinch out in
others and stratify with fine grained silty
clays. The laterally and vertically confined
nature of this material may seriously restrict
ground water yields.
4. Glacial Till - glacial till has generally lower
conductivities because it is usually very
poorly sorted and contains a high degree of
silt/clay sized particles. Some minor water
bearing lenses have been identified in some
wells (see Well GWI-4A) but the significant
lateral confinement of these zones precludes
their use as major water supplies. Low volume
homeowner wells may tap usable supplies of
water from these deposits.
C. Water Level Data
Water level readings were determined for the wells
on several occasions from 6/14/88 to 7/25/89. These
readings were subtracted from surveyed well elevations to
determine the water table elevations relative to mean sea
level. These data, coupled with the elevations of surface
water expression of the water table (ponds), allows for a
determination of the ground water surface across the island.
- 34 -
I
I
TABLE 3 - WATER LEVEL DATA
I
WATER TABLE DATA
DEPTH TO WATER
I
WEll
DATE: ELEVATION 06/14/88 07/21/88 10/12/88 11/14/88 04/20/89 07/25/89
==============================================================================
I
WEll:
HW-l 15.33 9.80 10.50 NOT GAUGED 21.67 9.75 OESTROYED
HW-1A 24.37 NO WEll NO WEll NO WEll 24.65 NOT GAUGED DESTROYED
HW.2S 11.72 4.65 6.90 7.40 6.67 4.10 4.40
HW-2D 12.14 7.45 7.75 8.28 7.95 6.05 6.00
HW'3 19.14 11.30 12.90 14.15 13.90 10.35 10.52
HW.4 20.54 6.55 8.90 10.50 10.42 6.75 5.70
MW-4A 21.93 NO WEll NO WEll NO WEll 12.18 8.75 7.40
MW-5 15.40 10.70 11.90 12.25 12.07 10.15 10.10
MW-6 22.68 12.25 13.80 13.60 14.10 11.35 10.60
MW-7 67.01 DRY DRY DRY DRY DRY DRY
MW-8 10.36 8.25 8.80 8.80 8.52 7.15 7.15
MW-9 17.75 13.40 13.30 14.10 14.34 12.20 DESTROYED
MW-l0 9.25 NO WEll NO WEll NO WEll 7.10 6.15 6.25
MW-l1 21.97 NO WEll NO WEll NO WEll 18.15 16.00 14.80
MW-12 54.10 NO WEll NO WEll NO WEll 42.60 41.50 38.90
HW-13 17.93 NO WEll NO WEll NO WEll 10.53 8.35 8.90
MW-14 UNSURVEYED NO WEll NO WEll NO WEll NO WEll NO WEll 13_50
MW-15 UNSURVEYED NO WEll NO WEll NO WEll NO WEll NO WEll 22.60
MW-16 UNSURVEYED NO WEll NO WEll NO WEll DRY 21. 05 22.60
I
I
I
I
I
WATER TABLE ELEVATION
WEll ELEVATION 06/14/88 07/21/88 10/12/88 11/14/88 04/20/89 07/25/89
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
MW-l 15.33 5.13 4.83 NOT GAUGED -6.34 5.58 DESTROYED
MW-1A 24.37 NO WEll NO WEll NO WEll -0.28 NOT GAUGED DESTROYED
MW-2S 12.14 5.37 4.82 4.32 5.05 7.32 7.32
MW-2D 11. 72 5.59 4.39 3.87 4.19 6.09 6.14
MW-3 19.14 8.34 6.24 4.99 5.24 8.79 8.62
MW-4 21. 93 12.99 11.64 10.04 10.12 13.79 14.84
MW-4A 20_54 NO WEll NO WEll NO WEll 9.75 13_18 14.53
MW-5 15.40 4.20 3.50 3.15 3.33 5.25 5.30
MW-6 22.68 10.33 8.88 9.08 8.58 11.33 12.08
MW-7 67.01 DRY DRY DRY DRY DRY DRY
MW-8 10.36 2.01 1.56 1.56 1.84 3.21 3.21
MW-9 17.75 4.85 4.45 3.65 3.41 5.55 DESTROYED
MW.10 9.25 NO \JEll NO \JElL NO WEll 2.15 3.10 3.00
MW-ll 21.97 NO WEll NO WEll NO WEll 3.82 5.97 7.17
MW-12 54.10 NO WEll NO WEll NO WEll 11.50 12.60 15.20
MW-13 17.93 NO WEll NO WEll NO WEll 7.40 9.58 9.03
MW-14 UNSURVEYED NO WEll NO WEll NO WEll NO WEll NO WEll .
MW.15 UNSURVEYED NO WEll NO WEll NO WEll NO UEll NO WEll .
MW.16 UNSURVEYED NO WEll NO WEll NO WEll . . .
MEAN 6.53 5.57 5.08 5.87 7.85 8.87
I
I
I
I
I
I
I
I
I
- 35 -
~
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
The water elevation data is compiled in Table 3.
The mean water table surface averaged between 6 and 9 feet
above sea level for the period of measurement with a low
water level at 5.08 AMSL during October of 1988 and a high
water level of 8.87 feet on 7/25/89. Water level readings
from 11/14/88 at MW-1 and MW-1A show effects of pumping from
the Middle Farms Aquifer and these readings do not represent
static conditions. Water table values for 4/20/89 are
plotted on Plate III to show the orientation of the water
table during an intermediate water level position.
The highest water level elevations are located in the
central parts of the island specifically MW-12 and MW-4.
The highest water elevations can be found just north of
Isabella beach where pond elevations reach up to 24.5 feet
above mean sea level as shown in large scale topographic
maps provided by the Suffolk County. It is debatable as to
whether these ponds represent the true water surface or a
perched water table; perched water tables are saturated
materials that are separated from the major or regional
water table by unsaturated materials. It is likely that the
thick lacustrine clays underlie these surface water bodies,
preventing water infiltration.
Drillers log available for a homeowner's well (the
Gaston's well) near these ponds record over fifty feet of
clay with occasional fine to coarse sand lenses.
- 36 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
The water table intersected at MW-16, Chocomont East,
may also represent a perched water condition. This well was
dry when first gauged in November of 1988. However, the
following two rounds encountered over seven feet of water.
This increase is over twice as great as any other water
level increase noticed in this time period. MW-16 is
screened in relatively impermeable till and water level
fluctuations are probably caused by the low hydraulic
conductivity of the impermeable layers.
D. Ground Water Flow
Ground water elevation contour lines on Plate III
roughly define four ground water mounds with each mound
sharing common discharge areas. Ground water flow is
oriented perpendicular to contour lines, radiating in all
directions away from ground water highs or recharge areas
towards the discharge area which ultimately would be the
Long Island or Block Island Sound.
The western flow mound has a primary recharge area
somewhere between monitor well 6 and monitor well 12 with a
maximum water table elevation of approximately 12 feet above
MSL. Some constriction of this flow cell is noted between
Goose Island and Hay Harbor and it may be possible to define
a fifth flow mound within the northeastern end of the
island.
- 37 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
A second mound parallels Isabella beach with
highest ground water levels occurring in the clay pit ponds
adjacent to Isabella Beach and in Brickyard and Barlow
Ponds. The northern extent of this mound is not known but
an additional flow mound may be located in the hummocky
terrain located between West Harbor and Chocomont Cove.
Ground water flow is skewed somewhat to the north with the
axis of the flow mound paralleling Isabella Beach.
The Middle Farms aquifer area is a discharge point
between the mound just described and a large mound
recharging at Middle Farms Pond and the highlands around the
Chocomont Reservoir. Not much detail can be defined in this
ground water mound because of the sparsity of monitoring
data.
The eastern most mound can be defined east of East
Harbor with recharge occurring at the high points defined
south of Ice Pond. Ground water elevations and ground water
flow are not well defined. Monitor well 8 is located
between the Chocomont and East Harbor mounds.
vertical flow has been described by two well pairs,
MW-2S and MW-2D, MW-4A and 4. Both pairs show a head loss
with depth indicating a downward vertical flow. This
condition is to be expected in areas with high infiltration
and little runoff. However, it should be noted that
- 38 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
stratification of coarse and fine sediments typical of the
proximal outwash are bound to create confined water tables
that would show localized areas of upward vertical flow.
E. Ground Water Recharae
Recharge on Fisher's Island comes exclusively from
direct precipitation on the island and of this
precipitation, significant amounts of water are lost to
runoff, evaporation and transpiration (uptake by
vegetation). Values for precipitation were determined from
data collected by the Water Works at Barlow Pond and
estimates for runoff, evaporation and transpiration are
based on data from similar areas in this region.
1. precioitation - average rainfall on Fisher's
Island is tabulated below (from Fisher Island Water Works).
Average annual rainfall on the island is approximately 53
inches per year. Average rainfall is higher than the mean
annual rainfall noted on Long Island or Plum Island.
Proximity to the mainland and exposure to mainland generated
thunderstorms may cause this greater precipitation on
Fishers Island compared to the other nearby islands.
Probable precipitation data from drought and
periods of excessive rainfall are also tabulated on Table
- 39 -
-.-
- - - - - - - - - - - - - - - - - - -
TABLE 4 - AVERAGE PRECIPITATION
FISHERS ISLAND PRECIPITATION DATA
AVERAGE MONTHLY AND YEARLY RAINFAll
JAN FEB MARCN APRIL MAY JUNE JULY AUGUST SEPT OCT NOV DEC
1970 2.20 5.65 4.15 3.10 3.45 1.95 3.12 2.22 4.21 6.1B 3.40
1971 2.79 5.18 2.93 2.32 4.42 0.54 3.41 1.75 1.25 4.73 6.37 6.00
1972 2.21 5.48 6.05 5.87 4.22 9.25 1.83 1.90 3.93 4.70 8.93 8.47
1973 3.30 3.14 4.12 7.31 4.90 2.51 6.25 3.66 2.55 3.40 2.40 7.95
1974 4.27 2.39 4.99 3.45 2.80 2.70 1.53 2.21 4.99 2.70 1.30 7.33
1975 7.87 4.90 3.69 4.50 3.20 5.57 4.09 4.38 6.68 7.78 6.81 5.44
1976 6.11 2.95 3.42 1.68 3.03 1.50 2.95 8.09 2.21 6.12 0.47 3.09
1977 3.55 2.57 6.22 4.97 2.93 5.00 1.68 6.50 6.02 9.19 5.73 6.19
1978 7.72 1.00 3.33 1.94 7.91 0.79 5.93 7.75 4.60 2.20 3.73 7.51
1979 13.39 6.02 3.10 5.52 7.60 2.60 1.92 6.35 4.71 5.71 4.85 2.71
1980 1.96 0.70 10.10 6.25 2.63 2.55 3.21 3.34 0.97 5.77 4.72 1.47
1981 0.43 6.24 0.20 5.59 1.73 7.88 4.50 1.80 4.60 4.20 3.10 6.60
1982 4.55 4.00 5.10 4.80 2.70 17.40 2.20 3.70 3.90 4.10 5.10 2.60
1983 5.62 4.60 9.25 12.20 5.60 3.10 2.30 6.30 1.40 6.00 11.70 6.50
1984 2.00 8.30 6.40 6.10 8.50 9.60 9.50 0.10 2.30 4.50 3.30 3.60
1985 1. 10 2.10 4.00 0.50 7.00 7.30 2.80 9.80 3.50 3.30 9.20 1.80
1986 5.78 4.50 3.80 2.60 1.10 4.80 5.70 4.90 1.20 3.75 8.30 11.90
1987 5.75 0.75 7.00 7.60 2.35 0.68 1.50 4.45 5.15 3.09 3.00 3.00
Average 4.61 3.72 4.96 4.85 4.21 4.85 3.51 4.45 3.45 4.75 5.29 5.31
...
C>
PRECIPITATION DATA FROM OTHER NEARBY STATIONS
GROTON FROM 1951-80, ORIENT FROM 1941-50, GREENSPORT FROM 1941-50
JAN FEB MARCH APR MAY JUNE JULY AUG SEPT OCT NOV DEC ANNUAL
GROTON 4.41 3.96 4.76 4.17 3.84 2.69 3.20 4.01 3.95 3.93 4.62 5.01 48.55
GREENPORT 2.80 2.03 3.06 2.89 3.20 2.09 2.51 3.72 1.78 2.17 3.90 3.23 33.38
ORIENT 3.52 2.75 3.60 3.08 3.54 2.09 2.46 3.84 2.06 2.19 4.59 3.58 37.30
PROBA8lE PRECIPITATION AT GROTON STATION DURING DROUGHT
JAN FE8 MAR APR MAY
90X 1.70 2.17 2.87 1.94 1.54
10X 8.47 6.01 7.57 7.30 6.63
(90X) AND
JUN
1.16
5.06
FLOOD (lOX) PERIODS (FROM HUNTER AND MEADE,
JUl AUG SEPT OCT NOV
1.35 1.39 1.46 1.90 1.99
6.10 9.76 8.23 7.35 6.92
1983)'
DEC
2.13
8.68
ANNUAL
38.10
60.05
'EACH PRECIPITATION VALUE IS THE AMOUNT OF PRECIPITATION THAT Will 8E EQUALED OR EXCEEDED BY A CERTAIN PERCENTAGE OF EVENTS
PROBABLE PRECIPITATION FOR FISHER'S ISLAND DURING FLOOD AND DROUGHT PERIODS"
JAN FEB MAR APR MAY JUN JUl AUG
90X 1.75 2.01 2.98 2.23 1.68 2.08 1.47 1.51
10X 8.85 5.61 7.89 8.49 7.07 9.12 5.16 6.71
SEPT
1.46
5.04
OCT
1.88
8.93
NOV
1.98
7.88
DEC
2.10
11.15
ANNUAL
41.58
65.57
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
4. Drought and above normal precipitation statistics were
calculated for Groton, Connecticut by Hunter and Meade,
(1983). The Groton precipitation data is obtained from the
Groton-New London Airport, located approximately 3 miles
north of Fishers Island. Drought period rainfall values are
exceeded 90% of the time while wet period rainfall values
are exceeded only 10% of the time. The differences between
these extremes and the average Groton values are
extrapolated to the Fisher's Island data to estimate above
and below normal precipitation frequency and magnitude.
Based on these data, drought years occurring every lout of
10 years will have approximately 41 inches of annual
precipitation, while wet years (wettest year out of 10) have
as much as 65 inches.
2. Runoff - Values of runoff have not been
measured or calculated for the island and estimates are here
derived from Hoffman for Northfork, Southhold (1959) and
Crandall for Plum Island (1962). Hoffman uses 10% as a
runoff figure since most of the rainfall is expected to
infiltrate through the silty loam soil on Southhold. Plum
Island, like much of Fishers Island, is covered by a
relatively impermeable till and displays considerably
steeper topography relative to North Fork, Southhold. These
factors lead Crandall to suggest runoff of around 15% of
mean annual precipitation on Plum Island. Therefore, the
same percentage is thought to be applicable to Fishers
Island.
- 41 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
3. Evapotranspiration - Potential ground water
recharge is also lost not only to runoff, but also to
evaporation and to transpiration by plants. Hoffman
estimates that evaporation ranges from 12 to 17 inches per
year and transpiration is approximately 9 inches. Crandall
(1962) notes that the transpiration noted on North Fork may
be higher than Plum Island because of extensive cultivation
on the former. This elevated rate of transpiration on the
North Fork is balanced against an interpreted higher
evaporation rate on Plum Island because of the large bodies
of ponded water on the island. Plum Island is similar to
Fishers Island in that there is very little cultivation
(with the exception of lawn watering) and an abundance of
fresh water ponds. Therefore, Crandall's (1962) estimate of
21 to 26 inches per year evapotranspiration rate is used in
the Fishers Island water budget calculation.
4. Recharqe Rate - The total area of the island is
4.25 square miles, but many of the thinner parts of the
island and areas close to the shorelines probably do not
provide significant recharge to the island's aquifers.
Recharge occurs primarily in the center of the flow mounds
defined on Plate 3. Areas on the outside of these flow
mounds that discharge into the Sound probably provide very
little water by way of recharge to the island's aquifers.
For recharge calculations, the recharge areas for the island
are defined by the 5 foot contour line on Plate 3. Ground
- 42 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
water below this contour begins to show signs of quality
degradation and pumping in this area can quickly cause sea
water intrusion problems. Using the five foot contour line
describes two separate recharge zones: a large zone
incorporating the western, Isabella/Barlow Pond, and
Chocomont Flow Mounds and a much smaller, separate zone for
the eastern flow mound. The area of these recharge zones
was determined by planimetry with the larger western
recharge area at 1.95 square miles and the smaller eastern
recharge area at 0.202 square miles. Totalling these two
areas produces a sum of 2.15 square miles for the island or
roughly 1/2 the total island area. This matches Crandall's
(1962) determination of recharge area for Plum Island which
was taken as 50% of the total island area.
subtracting runoff and evapotranspiration from the
total average precipitation yields an annual recharge of
roughly 19 inches per year. Totalling this across the
effective recharge area yields a volume of 93,000,000 cubic
feet per year or 709 million gallons per year. These
recharge rates match interpreted rates on North Fork and
Southhold fairly well (see Table 5).
- 43 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Plum Island
West Orient,
LI
Area
1.3 miles2
2.3 Miles2
Fishers Island 4.25 miles
TABLE 5
RECHARGE RATES
Estimated
Annual Recharqe
164 million gals.
Annual
Recharqe Rate
126 million qals.
square mile
350 million gals. 152 million qals.
square mile
709 million gals. 167 million qals.
square mile
- 44 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Using extrapolations from the Groton Precipitation
data, recharge for very wet and drought years, ranges from a
low of 79 million gallons per square mile and 251 million
gallons per square mile, respectively. These estimates
assume that evapotranspiration and runoff remain constant.
F. Salt/Fresh Water Interface
The quantity of fresh water stored on Fisher's
Island is primarily dependent on the depth to salt water.
Fresh water occupies a relatively thin lens overlying salt
water throughout the island. For isotropic and
heterogeneous aquifers (ideal conditions) the depth to salt
water is described by the Ghyben-Herzberg equation:
h = t where
g-l
h = depth of water below sea level
t = height of fresh water above sea level
g = specific gravity of sea water, taken as 1.025
Using this equation, one foot of fresh water
elevation or head above sea level equates to a fresh water
lens approximately 40 ft. thick. Water level data from
monitoring wells show that the depth to salt water or the
salt/fresh water interface varies from greater than 600 feet
below sea level inland to less than 80 feet near the
shoreline. Water elevation readings can be used to
determine the depth of the salt/fresh water interface,
because each foot of elevation, multiplied by 40,
approximates the depth to the salt/fresh interface.
- 45 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
This relationship does not necessarily apply within
heterogeneous aquifers and geologic analysis has shown that
all aquifer materials on Fisher's Island are essentially
heterogeneous. Heath (1970) notes that crossing from
conductive to relatively non-conductive boundaries produces
losses in head which reduce the thickness of the fresh water
lens. Therefore, estimates of depth to the salt/fresh water
interface derived from the Gyben-Herzberg relationship must
be viewed as maximum depths of fresh water on Fishers
Island.
G. Water Use
Information on total water use is based on data
from the Fisher's Island Water Works and on estimates of
water use and irrigation from private wells.
1. Water Works: The status of the current Water
Works was defined in a report by Buck and Buck in January of
1988. Records in that report show that annual water
production varied from between 54 to 67 million gallons.
The projected annual demand is anticipated to be 87 million
gallons by the year 2010. The report does not include
withdrawals from private wells but notes that the number of
private wells on the island has risen and most of these
wells are used for irrigation. Another disturbing trend
recognized by Buck and Buck is the increasing use of large
automated irrigation systems for large lawns.
- 46 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
2. Private water use: Hoffman (1959) estimates
100 gallon/per day/per capita domestic water use. Using
population records, domestic water usage would be 73 million
gallons to 95 million gallons in the year 2010. This seems
to match the magnitude of withdrawals expected by the water
company.
3. Irriaation: the amount of water used for
watering lawns is difficult to determine using the limited
amount of available data. The estimates presented here must
be viewed only as estimates and starting points for further
work.
A generally accepted rate of water use for
vegetative growth is one inch per week. Taking the growing
or landscaping season to be 18 weeks results in 18 inches of
required precipitation plus irrigation.
50% of this water is estimated to come from
precipitation requiring the remainder to come from ground
water via irrigation. The area of application on the island
has not been determined but is estimated to be 10 to 20% of
the total land area or approximately 0.84 square miles.
Nine (9) inches of water over 0.84 square miles yields an
estimate of 131 million gallons per year. Over 80% of this
water is probably lost to evapotranspiration leading to a
net annual loss of approximately 100 million gallons.
However, a study on Long Island by Hauptmann, et al., 1989
- 47 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
has determined that water use by lawn sprinkling during the
summer months is about ten times normal residential use.
For Fisher's Island this would mean that over 300 million
aallons could be potentiallv lost annual Iv throuah lawn
irriaation.
Total water usage is tabulated against derived
recharge calculations for very wet flood and drought years
in Table 6. Using irrigation maximums of 300 million
gallons/year, maximum annual water usage is estimated at 373
million gallons/year and this water usage is expected to
rise to 395 million gallons per year by 2010. Using the
water budget derived in previous sections, the recharge rate
varies from 336 million gallons per year during drought
years to 1,083 million gallons per year during wet years.
Comparing these figures quickly shows that water demand can
outweigh recharge during drought years and water demand can
make up approximately 50% of average annual recharge. When
comparing these figures it is important to remember that the
island's coarse aquifer deposits are laterally discontinuous
and irregular and whether or not 50% of the annual recharge
can actually be withdrawn from these aquifer materials must
remain a point of debate and concern.
In conclusion, these data show that ground water is
limited in three ways: 1. the quantity of precipitation
and resulting recharge to the ground water supply; 2. the
- 48 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
ability of the glacial sediments to yield water and 3. the
position of freshwater/salt water interface. All three
factors have to be considered on Fisher's Island when making
water supply and usage decisions.
TABLE 6 - WATER BUDGET *
WATER RECHARGE P90 E.2Q PIO
Precipitation 41" 53" 65"
Runoff 15% (6") 15% (8") 15%
(lO")
Evapotranspiration 26" 26" 26"
Recharge Rate 336 mgy 709 mgy 1,083 mgy
Recharge Rate/sq mi 79.1 mgy 167 may 251 mgy
Todav 2010
WATER USAGE
Water Works 60 mgy 90 mgy
Domestic Use 73 mgy 95 mgy
IRRIGATION 100 mgy - 300 mgy
MAXIMUM POSSIBLE USE 373 mgy 394
P90 = drought conditions; annual rainfall exceeded 90% of
the time
P50 = average rainfall
P10 = very wet conditions; annual rainfall exceeded 10%
of the time.
* refer to text for derivation of these figures.
(1) Based on recharge area of 2.15 mi2
- 49 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
IV. CHEMICAL ANALYSIS AND WATER OUALITY PROBLEMS
A. Introduction
Ground water samples were obtained from monitoring
wells to assess ground water quality. Water samples were
taken in cooperation with the NY DEC following protocols for
ground water monitoring. Each sampling event involved well
gauging and purging of three well volumes to replace any
stagnant water with formation water. Well purging was
accomplished with either a hand pump or electric pump.
Water samples were obtained with cleaned and rinsed
stainless steel bailers. Water samples were analyzed in the
field for temperature, pH, and specific conductivity by
members of the DEC. Water samples were taken from each well
were analyzed at DEC labs for metals, inorganics,
herbicides, pesticides and volatile organic compounds. Data
sheets for these analyses are included in Appendix C.
Results from these analyses are used to make conclusions
concerning ground water quality across the island. Water
quality data was also obtained from homeowner wells to help
identify water quality trends. All data are tabulated in a
ground water quality summary Table 7. Ground water quality
across the island is summarized on Plate IV. Ground water
analyses are plotted on a modified stiff diagram for each
sample point which allows a rapid overview of ground water
quality. For monitor wells, the last sampling event is
- 50 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
TABLE 7 - GROUND WATER CONTAMINANT SUMMARY
--------------.-......-----------------------------------------------.----------------------------------------
06/13/88 06/13/88 11/14/88 06/14/88 11/14/88 06/14/88
PARAMETERS MIl-I MW-2S MW-2S M11-2D MII.2D MW.3
--------------------------------------------------------------------------------------------------------------
METALS (mg/L):
CALCIUM 3.10 2.00 3.90 20.00 31.00 6.50
IRON 0.90 0.50 1.20 1.00 9.00 3.80
MAGNESIUM 1.70 1.10 2.00 9.00 15.00 2.60
MANGANESE 0.14 0.15 0.22 0.61 1.40 0.36
POTASSIUM 1.80 0.90 1.70 3.60 6.80 2.00
SOl) IUM 7.80 6.60 10.00 22.00 29.00 17.00
INORGANICS (mg/L):
AMMONIA-N NO<0.02 NO<0.02 NO<O.02 NO<0.02 0.08 (0.03) 0.03
CHLORIDE 14.00 16.00 12.00 76.00 91.0 (92.0) 30.00
NITRATE-N 0.16 NO<0.05 ND<0.05 NO<0.05 ND<0.05 (ND<0.05) NO<0.05
NITRITE 0.01 0.00 0.00 0.003 0.001 (0.003) 0.00
PNOSPHATE NT NT ND<0.005 NT ND<0.005 NT
SULfATE 6.40 7.00 6.40 4.90 1.4 (1.4) 14.00
flELO MEASUREMENTS:
TEMPERATURE (C) 15 14.00 16.00 14.00 14.00 14.00
pH 6.3 5.70 6.20 6.80 6.70 6.20
SPECifiC CONDUCTIVITY (ur/los) 80 76.00 105.00 338.00 222.00 146.00
SDWA HERBICIDES (ppb):
2,4-D ND<1 NT NT NT NT NT
2,4,5-TP NO<1 NT NT NT NT NT
PESTICIDES (ppb):
ALDICARB ND<1 ND<l NT NO<l NT ND<l
ALDICARB SULfOXIDE ND<l NO<l NT NO<1 NT ND<l
ALDICARB SULfONE ND<l NO<l NT ND<1 NT NO<l
CARBOfURAN ND<l ND<l NT ND<l NT ND<l
3'HYDROXYCARBOfURAN ND<1 ND<1 NT ND<1 NT ND<l
OXAMYL ND<1 ND<1 NT ND<1 NT ND<l
CARBARYL ND<1 ND<1 NT ND<1 NT NO<l
l-NAPHTHOL NO<l ND<l NT NO<l NT ND<l
METHOMYL NO<l ND<l NT NO<l NT ND<l
VOLATILE ORGANICS (ppb):
CHLOROfORM ND<0.5 ND<O.S NO<O.5 ND<0.5 NO<O.S ND<D.5
METHYLENE CHLORIDE ND<O.S ND<D.5 NO<O.S ND<0.5 ND<0.5 ND<0.5
1,1,1 TRICHLOROETHANE ND<0.5 ND<O.5 ND<0.5 ND<O.5 ND<0.5 NO<O.S
CIS OICHlOROETHYlENE ND<O.5 ND<O.5 ND<D.5 ND<D.5 ND<O.5 ND<O.5
BENZENE ND<0.5 ND<O.5 NO<D.5 ND<0.5 NO<0.5 NO<O.5
TOLUENE NO<0.5 ND<O.S ND<0.5 2.00 1.00 2.00
ETHYLBENZENE NO<0.5 NO<O.S NO<O.S 1.00 1.00 ND<O.S
TOTAL XYLENES NO<O.S 2.00 3.00 9.00 11.00 2.00
1,2,4 TRIHETHYLBENZENE NO<O.S NO<O.S 0.60 S.OO 1.00 1.00
p.OIETHYLBENZENE ND<O.S NO<O.S ND<O.S 2.00 ND<O.S 1.00
1,2,4,S TETRAMETHYLBENZENE NO<O.S ND<O.S ND<O.S 2.00 ND<O.S ND<O.S
ISOPROPYLTOLUENE (P-CYMENE) ND<O.S ND<O.5 ND<O.5 NO<O.5 ND<O.5 ND<O.5
-------------.----.......-........---.-------.-------------------------_.._-----_.._-------.----_._-----------
NOTE: NO - Not detected < detection limit.
ppb - parts per bill ion.
mg/l - milligrams/liter.
NT - Not Tested
- 51 -
I
I
TABLE 7 CONT'O
.-.-.----...---------------------------------------------.--------------------------------------------------------------------
I 11/16/88 06/15/88 11/15/88 11/16/88 06/14/88 11/16/88 06/15/88 11/15/88
RAMETERS M~'3 M~'4 M~'4 M~-4A M~'5 M~.5 M~'6 M~'6
_._____________________.________________._.________________w________________________________________________-------------___
METALS (mg/L):
ELCIUM
RON
GNESIUH
MANGANESE
fTASSIUH
OOIUM
INORGANICS (mg/L):
_HMONIA-N
MLORIOE
ITRATE-N
NITRITE
PHOSPHATE
fuLFATE
~ELO MEASUREMENTS:
TEMPERATURE (C)
IIJ:ECIFIC CONOUCTIVITY (umhos)
SO~A HERBICIOES (ppb):
I:~:~-TP
PESTICIDES (ppb):
ILO I CARB
LOICARB SULFOXIDE
LOICARB SULFONE
CARBOFURAN
.'HYOROXYCARBOFURAN
XAMYL
ARBARYL
I-NAPHTHOL
METHQMYL
~LATILE ORGANICS (ppb):
CHLOROFORM NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5
METHYLENE CHLORIDE NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5
_.1.1 TRICHLOROETHANE NO<0.5 NO<0.5 NO<0.5 NO<O.5 NO<0.5 NO<0.5 1.00 0.70
IS DICHLOROETHYlENE ~D<O.5 ND<O.5 NQ<O.5 NO<O.5 ND<O.5 ND<O.5 NO<O.S NO<O.5
ENZENE ND<O.5 ND<O.5 NO<O.5 0.70 ND<O.5 ND<O.5 2.00 ND<O.5
TOLUENE 4.00 NO<0.5 1.00 NO<0.5 4.00 2.00 2.00 1.00
ITHYLBENZENE 1.00 NO<0.5 NO<0.5 NO<0.5 3.00 1.00 NO<0.5 NO<0.5
OTAL XYLENES 16.00 2.00 2.00 NO<0.5 19.00 11.00 3.00 1.00
,2.4 TRIMETHYLBEN2ENE 7.00 1.00 1.00 NO<0.5 3.00 4.00 NO<0.5 NO<0.5
p'OIETHYLBENZENE 2.00 NO<O.~ 1.00 NO<0.5 0.80 1.00 NO<0.5 NO<0.5
1.2.4,5 TETRAHETHYLBENZENE NO<0.5 0.80 NO<0.5 ND<0.5 0.90 NO<0.5 NO<0.5 NO<0.5
SOPROPYLTOLUENE (P-CYMENE) NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5 2.00 NO<0.5 NO<0.5
____OP__O_______________._._________________________________0_______._._______________________________________~~~~_________.
NOTE; NO - Not detected < detect;on limit.
ppb - perts per billion.
ov/L - .illigrons/liter.
NT - Not Tested
I
I
I
I
9.90
12.00
5.00
0.80
4.00
21.00
0.13
28.00
0.14
0.09
0.14
7.50
14.00
6.60
81.00
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
6.50
0.60
2.80
0.25
2.30
14.00
51.00
25.00
4.60
3.80
17.00
19.00
0.02 0.14 (0.13)
22.00 18.00
NO<0.05 0.05
0.01 0.05
NT 0.19
13.00 12.00
14.00
6.40
118.00
NT
NT
NO<l
NO<l
NO<l
NO<l
NO<l
NO<l
NO<l
NO<l
NO<l
14.00
7.40
71.00
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
7.6IJ
4.6IJ
2.00
0.33
4.40
40.00
0.92
18.00
0.08
0.03
0.100
9.80
13.00
7.40
125.00
NT
NT
ND<1
NO<l
NO<l
NO<l
NO<l
NO<l
NO<1
NO<l
ND<1
- 52 -
14.00
1.50
5.00
0.50
2.80
15.00
0.03
25.00
NO<0.05
0.00
NT
2.60
17.00
7.00
158.00
NT
NT
NO<l
NO<l
NO<l
NO<l
NO<l
NO<l
NO<l
NO<l
NO<l
30.00
28.00
13.00
2.50
13.00
14.00
0.13
20.00
NO<0.05
0.03
0.05
0.80
16.00
8.70
115.00
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
12.00
1.40
4.30
0.16
3.00
35.00
0.10
27.00
0.48
0.143
NT
37.00
14.00
6.50
240.00
NO<l
NO<l
NO<'
NO<'
NO<l
NO<l
NO<l
NO<l
NO<l
NO<l
NO<l
28.00
26.00
11.00
1.60
13.00
38.00
0.07
23.00
0.37
0.11
0.12
33.00
14.00
6.50
140.00
NT
NT
NT
NT
NT
NT
N1
NT
NT
NT
NT
I
TABLE 7 CONT'O
I
.....__...~.._____________..___..._____....._________.____.pe.______________________________________________---------------------
I 06/13/88 11/14/88 06113188 11/14/88 11/16/88 7125189 11/15/88 7125189
AMETERS M11-8 M11-8 MW-9 M11-9 MII-l0 MII-l0 MW-l1 I"J-11
__________________________________.________________________________________________.____________________________0._------------
METALS (mg/l):
flClUM
RON
GNESlUM
MANGANESE
fTASSIUM
00 lUM
INORGANICS (mg/L):
~HMONIA-N
NLORIOE
ITRATE-N
NITRI TE
PNOSPHATE
IUlFATE
ElD MEASUREMENTS:
TEMPERATURE (C)
II~ECIFIC CONDUCTIVITY (umhos)
SDWA HER81CIDES (ppb):
I:~:~-TP
PESTICIDES (ppb):
ILOICARB
LDICARB SULFOXIDE
LDICARB SULFONE
CARBOFURAN
i-HYDROXYCARBOFURAN
XAMYl
ARBARYL
I-NAPHTHOL
METHQHYL
ILATILE ORGANICS (ppb):
CHLOROFORM ND<0.5 ND<0.5 ND<0.5 ND<0.5 ND<0.5
METHYLENE CHLORIDE ND<0.5 ND<0.5 ND<0.5 ND<0.5 ND<0.5
_,1,1 TRICHLOROETHANE ND<0.5 ND<0.5 ND<0.5 ND<0.5 ND<D.5
IS DICHlOROETHYLENE ND<O.5 NO<O.5 NO<O.5 NO<O.5 NO<O.5
ENZENE ND<0.5 ND<0.5 ND<0.5 ND<0.5 ND<0.5
TDLUENE 3.00 3.00 I.DO 1.00 ND<0.5
ITHYlBENZENE ND<0.5 2.00 ND<0.5 1.00 ND<0.5
DTAl XYLENES 4.00 24.00 2.00 10.00 ND<0.5
,2,4 TRIMETHYLBENZENE 4.00 5.00 2.00 3.00 ND<0.5
p-DIETHYLBENZENE 2.00 2.00 2.00 2.00 ND<0.5
1#2,4,5 TETRAHETHYlBENZENE NO<O.5 NO<O.5 NO<O.5 ND<O.5 ND<O.5
SOPROPYlTOLUENE (P-CYMENE) ND<0.5 ND<0.5 NO<0.5 ND<0.5 ND<0.5
--______0______---------_.------------------------.---____0__________________________.____._
NOTE: NO - Not detected < detection limit.
ppb - parts per billi on.
mg/L - milligrams/liter.
NT - Not Tested
1.80
1.20
2.10
0.28
.2.80
110.00
0.03
82.00
1.20
0.81
NT
87.00
14.00
7.00
575.00
ND<1
ND<1
ND<1
ND<1
ND<1
ND<1
ND<1
ND<1
NO<1
ND<1
NO<1
I
I
I
I
11.00
24.00
12.00
4.7D
9.00
120.00
12
4.8
5.5
0.43
4.5
16
37.00
28.00
28.00
4.80
17.00
42.00
7.50
0.50
2.80
0.25
1.90
13.00
0.12
83.00
0.18
0.22
0.21
61.00
0.02
22.00
0.51
0.02
NT
9.30
NOT
TEST EO
DUE
TO
COLLOIDAL
SUSPENSION
0.07
17.00
0.05 (0.05)
0.03
0.030
6.20
18.00
7.40
474.00
15.00
6.50
128.00
14.00
6.80
118.00
14.00
7.10
65.00
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NO<1
ND<1
ND<1
ND<1
NO<1
ND<1
ND<1
ND<1
NO<1
ND<1
ND<1
NO<1
ND<1
ND<1
ND<1
ND<1
ND<1
NO<1
NT
NT
NT
NT
NT
NT
NT
NT
NT
- 53 -
6.50
0.04
3.70
<.02
1.30
14.0
<.02
28.0
0.36
0.001
NT
10.0
18.00
4.80
6.80
1.90
4.70
41.00
0.23
25.00
0.99
0.04
0.03
43.00
13.00
5.90
134.0D
ND<1
ND<1
ND<1
ND<1
ND<1
ND<1
ND<1
NO<1
NO<1
3.00
ND<O.S
NO<O.S
ND<0.5
0.70
0.60
NO<O.5
NO<O.5
ND<0.5
ND<0.5
ND<O.5
NO<0.5
15.0
4.8
5.8
0.49
3.70
27.00
0.39
2S.00
1.50
C.029
NT
21.00
NT
;.90
,~6.0
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
N:<0.5
w:"o.s
~:<O.5
N:<O.5
0.7
N!:<0.5
N:..:;O.5
2.00
2.0
1.0
0.7
w:..:;O.S
I
I
TABLE 7 CONT'D
....----------------------------------------------------------------------------------------
JIl~~:~:~~____________.._________.::~~~~___~~~~!~__..::~~~!;---~~~~~--~~~~!;--~~~~~!~
METALS (mg/L):
ILCIUH
ON
GNESIUM
MANGANESE
FASSIUH
IUM
INORGANICS (mg/L):
IMONIA'N
LORloE
TRATE'N
NITRITE
fOSPHATE
LFATE
FIELO MEASUREMENTS:
TEMPERATURE (C)
~ECIFIC CONDUCTIVITY
PESTICIOES (ppb):
10leARB
oleARB SULFOXIDE
olCARB SULFONE
CARBOFURAN
IHYOROXYCARBOFURAN
AMYL
RBARYL
I-NAPHTHOL
(T HOHYL
ATllE ORGANICS (ppb):
CNLOROFORM No<0.5 No<0.5 No<0.5 No<0.5 1.00 No<0.5
'THYLENE CHLORIDE No<0.5 No<0.5 1.00 No<0.5 NO<0.5 No<0.5
,1,1 TRICHLOROETHANE NO<0.5 NO<0.5 NO<0.5 NO<0.5 0.90 NO<0.5
15 DICHlOROETHYlENE ND<O.5 ND<D.5 0.80 NO<D.5 ND<O.5 ND<D.5
BENZENE 8.00 NO<0.5 0.80 4.00 No<0.5 3.00
TOLUENE 0.70 NO<0.5 1.00 1.00 NO<0.5 NO<0.5
~HYLBENZENE NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5 NO<0.5
TAL XYLENES No<0.5 2.00 NO<0.5 1.00 NT NT
,2,4 TRIMETHYLBENZENE NO<0.5 1.00 NO<0.5 NO<O.5 NO<0.5 NO<O.5
p,oIETHYLBENZENE NO<0.5 0.70 NO<0.5 7.00 NO<0.5 NO<0.5
1,2,4,5 TETRAHETHYLBENZENE NO<0.5 0.05 NO<0.5 2.00 NO<0.5 No<0.5
SQPROPYLTOLUENE (P-CYMENE) NO<0.5 ND<0.5 No<0.5 NO<0.5 NO<0.5 No<0.5
.-.----------------------------------------.-----------------------------------------------
NOTE: NO - Not detected < detection limit.
I ppb - parts per billion.
mg/l - .illigrams/liter.
NT - Not Tested
6.60
5.10
3.0
0.40
.3.40
12.00
0.11
9.90
0.98
0.02
0.04
13.00
(...mos)
13.00
7.10
54.00
SO~A HERBICIDES (ppb):
14,0
4,5-TP
NO<l
ND<l
ND<l
ND<l
ND<l
ND<l
NO<l
ND<l
NO<l
I
I
I
6.80
0.31
2.70
0.08
1.90
12.0
0.05
16.0
1.BO
0.017
NT
9.50
NT
6.90
69.0
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
10.00
21.00
6.70
15.00
11.00
44.00
0.07
55.00
No<0.05
0.00
0.01
61.00
13.00
6.50
281.0
ND<l
NO<1
NO<l
ND<l
ND<l
ND<l
NO<1
NO<l
ND<l
23.0
0.26
14.0
3.50
3.80
50.0
0.03
31.0
0.70
0.021
NT
51.0
NT
6.50
412.0
NT
NT
23.0
10.0
9.60
1.50
3.40
22.0
0.03
30.0
1.00
0.068
NT
11.0
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
-54 -
2.80
0.06
1.10
0.06
1.00
8.20
0.03
14.0
NO<0.5
0.005
NT
6.70
NT
NT
NT
NT
5.80
58.0
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
plotted. Other sampling locations such as homeowner wells
and monitoring wells from other projects are also included.
B. General Ground Water Composition
As noted in the hydrogeology section, ground water
recharge comes exclusively from rainfall and is eventually
discharged into the sea. Accordingly, the major ion
chemistry of ground water varies from the composition of
rain water close to the recharge areas to sea water close to
the areas of discharge. To determine how ground water
chemistry varies from place to place across the island,
ground water samples were plotted on Piper diagrams along
with water samples from Barlow and Middle Farms Pond and
samples of precipitation and sea water. Data for
precipitation and sea water are taken from Thomas et al.,
1968. In preparing piper diagrams raw data for anions
(chloride, sulfate and bicarbonate) and cations (calcium,
magnesium, sodium and potassium) are first reduced to
milliequivalents per liter. These values are totalled and %
meqjl are calculated for each anion and cation for each
ground water sample. This information is then transferred
to the Piper diagram. Samples from each flow mound are
grouped together on a single Piper diagram to help identify
chemical trends in the flow mound.
- 55 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
1. Precipitation: Data concerning precipitation
was taken from the Noank area (Thomas et aI, 1968). These
authors show that precipitation is affected by industry in
the Thames River area. When air flow is from west, the
industrial influence is seen in low pH readings between 3.9
and 4.5 and relatively high sulfate readings. However, when
air flow is from the ocean (from the south) pH readings are
higher, around 6, and bicarbonate levels are increased over
sulfate levels. precipitation on Fisher's Island most
likely shows a more continuous oceanic influence over the
Noank data with data somewhere between oceanic and westerly
air mass data from Noank.
2. Sea Water: Sea water data from Hem (1959) show
that sea water differs from precipitation primarily in
percentages of chloride and sulfate; sea water is higher in
chloride while precipitation is higher in sulfate.
Percentages of cations between precipitation and sea water
do not vary significantly and reflect changes in air mass
flow direction rather than inherent differences.
3. Ground Water: trends in ground water flow are
most dramatically shown by differences in pH. Mean pH for
the island is 6.7. Water samples from wells located in the
center of the recharge area from wells are significantly
below this value while discharge area wells (such as well 8)
are above this value. pH changes with respect to depth also
- 56 -
I
I
I
I
I
I
I
I · MIDDLE FARMS POND
o BARLOW POND
Ha ~ HANCOCK
E - EVANS
I Z = ZANGETTI
NUMBERS. "\ MONITOR WELLS
I 0 HI pH > 6.7 ..
O (no'~ymbol represents an Intermediate pH)
LO pH < 6.7
I ... PRECIPITATION
+SEA WATER
cJ'
":Jo~"/
o
\~
'<
Ca
:>
CATIONS
CI
ANIONS
EXPLANTION
!GroundWater, InC.
FISHER'S ISLAND
PIPER DIAGRAM
MOUND 1
WE.STERN
GROUND WATER MOUND FLOW
I
I
I
I
I
I
I
I
I
I
I
I
I
0-
",0'11-"'/
Oti ~~
\!?)@
09~
@
ill
~
o
~@
<
Ca
CATIONS
>
CI
ANIONS
EXPLANATION
. MIDDLE FARMS POND
o BARLOW ROND
C - CALHOUN
H - HALL
NUMBERS = MONITOR WELLS
o HI pH > 6.7
O (no symbol represents an Intermediate pH)
LO pH < 6.7
... PRECIPITATION
+SEA WATER
!GroundWater, InC.
I
FISHER'S ISLAND
PIPER DIAGRAM"
MOUND 2
ISABELLA BEACH/BARLOW POND
GROuND WATER MOUND FLOW
0-
,,0'\1.""/
o
S
I
I
I
I
I
I
I
I
I
I
I
I
..:
Ca
CATIONS
EXPLANATION
· MIDDLE FARMS POND
o BARLOW POND
NUMBERS = MONITOR WELLS
OHI pH <"6.7
O (no symbol represents an Intermediate pH)
LO pH > 6.7
. PRECIPITATION
+ SEA WATER
o
\~
@
[!]
1/
O~I /
(j
5
~
@
S
;>
CI
ANIONS
i\GroundWater,lne.
FISHER'S ISLAND
PIPER DIAGRAM
MOUND 3
MIDDLE FARMS/CHOc:oMONT
GROUND WATER MOUND FLOW
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
as shown in the well pairs 2S, 2D and 4, 4A. In each case,
the deeper well is higher in pH indicating that the deeper
ground waters are closer to the salt or brackish water
interface zone and are zones of ground water discharge.
An increase in sodium and chloride and a decrease
in calcium with increased flow is typical of most ground
water flow systems (Freeze and Cherry, 1979). This basic
trend can help further delineate discharge and recharge
areas. Piper diagrams for each flow mound shows a general
enrichment in sodium, potassium and chloride. within each
flow mound, wells located near discharge areas and at the
borders of the mounds are characterized by sodium, chloride
enrichment zones. Generally, low pH wells near recharge
areas have major ion chemistries that cluster very close to
percentages shown in Middle Farms and Barlow Pond. High pH
wells plot further away from the pond plots suggesting
further travel within the ground water system. Further
travel does not automatically mean increased chloride and
sodium concentrations. Intermediate ion chemistries are
sometimes displayed showing enrichment in sulfate (see wells
MW-2 and MW-14 in Mound 1 and MW-4A, MW-2S and MW-5 in Mound
2). Sulfate enrichment is sporadic due to the uneven
distribution of sulfur related compounds such as anhydrite
or gypsum in the soil. Discharge areas are defined by high
pH wells with either high chloride (Well 2D in Mound 2 or)
high sodium (Well 4A in Mound 2 and Well 8 in Mound 3).
- 60 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
C. Areas of Dearaded Qualitv
Water quality as assessed by the wells is generally
excellent across the island. However, several threats to
water quality have been identified including: 1) salt water
intrusion; 2) elevated levels of iron and manganese; and 3)
trace hydrocarbon contamination.
1. Salt water intrusion: As noted in the hydrogeology
section, the fresh water lens is relatively thin. Ground
water contamination by salt water is most easily identified
by high levels of chloride but sodium, calcium, magnesium
and specific conductivity levels may also be influenced.
Chloride levels naturally range between 5 and 25 ppm and
levels above 25 ppm may be related to salt water intrusion.
Concentrations above 250 to 300 ppm give water a salty taste
and concentrations above 500 ppm make water unusable for
most purposes.
Salt water can be introduced into the fresh water lens
either through upconing or through lateral encroachment.
Upconing is the drawing of salt water from directly under a
pumping well. Lateral encroachment is the lateral movement
of salty water into the fresh water lens along highly
conductive deposits. Given that the geology of the island
is highly heterogeneous, it is more likely that salt water
intrusion/contamination will arise from lateral encroachment
rather than from upconing.
- 61 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Several areas of concern have been identified.
Information from the Fisher's Island Country Club on the
eastern end of the island identified a salt water
contamination problem in association with the pumping of
water for golf course irrigation. During the pumping of the
production well in association with this irrigation system,
an increase in chloride content was noted and chloride
levels reached 169 ppm after 24 hours of pumping.
Monitoring well 8 located on the Country Club Golf Course
detected over 80 ppm chloride during two sample rounds
indicating that salt water intrusion is a very real problem
on the east end of the island.
Elevated levels of chloride were also detected in
MW-2D located in the Middle Farms area. Salt water may
migrate along in a more permeable layer at depth extending
into the Middle Farms aquifer area.
Several other smaller areas of salt water
contamination are visible on the map including MW-13 and the
Evans well. Both of these wells are located relatively
close to sea water on the island's edge.
These data suggest that future ground water
pumping, particularly heavy pumping such as for irrigation
or centralized water production, could create additional
salt water problems. Pumping of ground water should be
- 62 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
carefully monitored to insure that drawdowns are maintained
above MSL. Drawdowns to MSL or below may cause eventual
upconing of salt water and salt water contamination of the
aquifer. If ground water quality is degraded by pumping,
the pumping rate should be decreased to resist or reverse
further intrusion. Thomas, et al. (1968) gives several case
studies involving reversibility from salt water
contamination. Norwich Hospital (Connecticut) noted an
increase of 6 ppm chloride to 695 ppm chloride after an
increased pump rate from 500 gpm to 1000 gpm. When the
chloride concentrations were noticed, pumping was halted
for a period of about a year. During this period, the
natural ground water gradients were re-established and salt
water was flushed out of the aquifer. Pumping was then
resumed at 500 gpm and intrusion problems were not
encountered. A similar case was noted for Dow Chemical
(Ledyard, CT) in 1968 when pumping caused salt water
intrusion from a nearby estuary. After reducing the pumping
rate, withdrawals continued without a problem. Thomas, et
al. (1968) concluded that stratified drift is generally
permeable enough so that intrusion can be reversed if a
satisfactory hydraulic gradient is re-established.
Salt water contamination from hurricane storm
surge and spray may cause longer term contamination of the
aquifer. Crandall (1962) suggests that increases in
chloride content from supply wells may have resulted from
- 63 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
hurricanes in 1954 and 1955, and elevated chloride levels
continued until 1959. This contamination is more persistent
than salt water encroachment or intrusion problems because
chlorides were introduced at the well source and the entire
aquifer had to be flushed out before normal chloride
concentrations could be obtained. Supply wells at Middle
Farms are approximately 10 feet above MSL and wash and spray
from a major hurricane could significantly affect the ground
water quality for an extended period.
2. Recharqe from ponds: The ponds on Fisher's
Island serve as an important reservoir for stored fresh
water with Barlow Pond being presently used as the island's
water supply source. Also, the ponds serve as important
recharge areas for ground water. Plum Island and Northfork
do not have as many ponds per unit area which may be one
reason for the decreased thickness of their fresh water
lenses in comparison to Fisher's Island. However, storage
and recharge in fresh water ponds may produce some
undesirable effects on ground water quality. None of these
ponds have any source of recharge other than precipitation
and this may lead to decreased oxygen content, increased
manganese and iron content and bacteria counts.
a. Iron and Manqanese: Plate IV shows that
many of the elevated iron concentrations (in excess of 20
ppm iron) are noted downgradient from fresh water ponds.
- 64 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
This connection of increased iron and manganese content and
ground water recharge through organic rich sediments has
also been noted by Silvey and Johnson (1977) in wells from
Rhode Island.
Suffolk County Health Department has a health
standard of 0.3 ppm for drinking water supplies but they
note that iron is a common problem and more than half of the
wells in Suffolk County would be above this limit if they
were all tested. This standard of 0.3 ppm is mostly based
on aesthetic qualities such as taste and iron staining of
clothing, cookware and glassware. However, increased iron
content may result in precipitation of iron in piping and
pumps, shortening their life spans, causing substantial and
increasing supply costs and problems. Therefore, while iron
is more of an inconvenience with homeowner wells, pump
burn-out on a public supply well could be a major problem.
b. Bacteria: Very limited bacterial sampling from
the Island Pond and neighboring wetlands area showed some
elevated levels of fecal coliform and fecal streptocci.
Much of this fecal material may be related to bird life on
the island rather than septic contamination but this has not
been determined. In one case, bacteria from adjacent
wetlands migrated through a coarse gravel zone and were
detected in a homeowner well. This shows that where soil
conditions are not sufficient for bacteria removal,
- 65 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
ponds and swamps can serve as sources of bacterial
contamination of ground water. Unfortunately, not enough
data is available from the monitoring wells to address
widespread trends in bacterial levels on the island.
3. Landfills and Orqanic Contaminants: Considering
the finite nature of the water supply on the island, all
man-induced pollution should be precluded or minimized. The
impact of two dump areas, the Pickett Landfill and the
Airport Metal dump are addressed in this study. A third
disposal area, the wood and brush dump, located near the
airport, was not studied.
Pickett's landfill, located on the south side of
the island, east of the military reserve, currently accepts
garbage, trash and sept age from the island's population.
MW-13 was placed in a location thought to be downgradient of
the landfill area to identify leachate discharged from the
landfill on ground waters. Landfill leachate typically
contains high levels of nitrogen, iron, manganese,
chlorides, oxygen demanding organics, alkalinity and
possibly volatile organic compounds from industrial,
commercial, or domestically used fuels or solvents.
A second dump (known as the Metal Dump) is
located on the west side of the island just east of the
airport. The dump developed in an old army bunker that was
used for the disposal of 55-gallon drums, electrical
- 66 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
transformers, oil tanks and other materials according to the
fire department. MW-10 was installed to assess this
contamination.
Both of the monitoring wells, 13 and 10,
encountered high concentrations of iron and chlorides and it
is uncertain whether these contaminants are related to the
landfill or to natural occurrences. Nitrate and ammonia
concentrations, at levels likely due to landfill leachate,
were not encountered at elevated concentrations. However,
low levels of volatile organic compounds have been detected
at MW-13 possibly related to disposal of chemicals at
pickett's landfill.
Unfortunately, conclusions regarding the status
of these two dump sites must remain equivocal. Much
additional study is needed to assess these dump areas in
more detail to adequately determine the presence, extent and
degree of ground water degradation originating from these
sources. MW-lO and MW-13 may simply be located outside of
leachate plumes. Further study would expand the monitoring
network in the vicinity of the dumps to answer site specific
questions such as local gradients, flow directions and
contaminant plume identification.
4. Other sources of contamination: More
widespread sources of contamination may include septic
- 67 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
fields, improper and/or widespread use of fertilizers and
pesticides, underground storage tanks and improper chemical
use and disposal. The ground water analyses produced no
data suggesting that septic fields or fertilizers/pesticides
are a widespread problem. However, trace levels of a
variety of volatile organic substances were detected in some
of the monitoring wells. Volatile organics discovered in
the wells installed by S. B. Church (MW-1-9) have been
attributed to grease used on the well casing threads. All
well casings have been removed to remove any unnecessary
"noise" from future sampling rounds. Trace levels were also
encountered in wells installed by C. Welti and two separate
rounds of water sampling produced problematical results.
Different contaminants were detected in the same well during
different sample rounds and concentrations increased and
decreased between the two rounds depending on the well. The
exact origin of detected hydrocarbons is unknown. Volatile
organics have been detected before on the island in
monitoring wells installed ~s part of the proposed trash
incinerator. Levels of less than 10 ppb total volatile
organics were encountered, generally matching the levels of
organics detected in the wells tested as part of this study.
- 68 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
V. CONCLUSIONS
1. Three geologic materials have been defined in the
shallow subsurface of Fisher's Island: 1. Glacial till
consisting of poorly sorted sand, silt and clay with
abundant cobbles; 2. Marginal outwash consisting of coarse
gravel to cobble lenses in a finer grained silt to clay
matrix accumulating directly adjacent to the recessional
moraine; and 3. Proximal outwash consisting of coarse to
medium moderately sorted sand deposited from braided streams
some distance from moraine margins.
2. The gravels associated with the proximal outwash
and the distill outwash sands form the most accessible and
viable aquifers with relatively high conductivity values
ranging from 1 to 100 ft/day. Highest conductivities were
observed in the proximal gravels but the yield from these
gravels is highly unpredictable because of their variable
extent. Proximal outwash sands may present more reliable
yields because of their more extensive continuity. Only one
proximal outwash sand aquifer was encountered (in MW-12) and
its characteristics are not well defined.
3. Ground water flow is defined by at least four
ground water mounds cells on the island. Two other flow
mounds are possible but are not currently well defined.
Ground water flows from recharge areas located in the center
- 69 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
of the mounds to discharge areas located at the mound
borders. Ponds serve as the major recharge areas and ground
water discharges to the sea and shared cell boundaries.
Average annual ground water recharge is estimated as 167
million gallons per square mile.
4. Recharge to the aquifers is provided solely by
precipitation and recharge averages 709 million gallons
annually, island-wide. Estimates of drought precipitation
produce aquifer recharge rates at 336 million gallons
annually. Considering that water usage on the island is
estimated at 373 million gallons (largely depending on the
amount of irrigation) and considering the irregular
geometries of the aquifer materials, periods of ground water
mining will occur during years with below normal
precipitation. This may lead to salt water intrusion
through lateral migration, up-coning or both.
5. Salt water intrusion has been identified in the
eastern flow mound due to pumping of irrigation water for
the country club golf course. Aquifer materials are
primarily composed of till and salt water has encroached
laterally along slightly more permeable lenses. Several
other places on the island, including deeper zones in the
Middle Farms aquifer, show evidence of salt water
intrusion. Effects of salt water intrusion can be retarded
by reducing or
- 70 -
.'>>-:
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
curtailing pumping until chloride concentrations can be
flushed out of the aquifer materials by recharging fresh
water.
6. Iron and manganese appear to be persistent and
common problems in the ground water because of recharge
through oxygen depleted swamps and ponds.
7. Ground water degradation from dump sources on the
Island (Pickett's Landfill and the Metal Dump) was not
conclusively shown. Volatiles detected in Monitor well 13
(near the pickett Landfill) may be related to fuels or
chemicals disposed of at the landfill. It is highly
suspected that contaminant plumes exist at both sites.
- 71 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
v. RECOMMENDATIONS
The conclusions from this study show that the shallow
ground water resources on Fisher's Island can provide a
finite and limited supply of fresh water to the island's
population. Over-use combined with drought conditions will
likely result in depletion of the fresh water aquifer and
potentially serious salt water intrusion effects.
Therefore, it is imperative that proper management programs
be instituted as soon as possible. Ground water management
should focus on two major goals: 1. the collection and
assessment of additional ground water information required
to adequately describe ground water quality and quantity; 2)
the establishment of island wide policies and/or regulations
to promote ground water protection and encourage
conservation.
A. Additional Assessment: Information collected up to
this point in time suggests that the aquifers on Fisher's
Island are relatively complicated and restricted. Efforts
should be made to refine estimates of aquifer yield and
location. Also, contamination sources identified in this
study should be properly assessed. The following steps are
recommended:
1. The monitoring network around the Middle Farms
aquifer should be expanded to include several additional
wells. These wells should be placed to replace destroyed
- 72 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
monitoring wells (MW-9), and supplement the current network
of monitor wells and to further delineate the lateral extent
of the gravel. Once these wells have been installed, a
program of water level measurement and conductivity
monitoring should be instituted so that the influences of
pumping can be monitored. Monitoring and assessment should
be conducted monthly from May to September and twice during
the winter months.
2. All the other monitoring wells installed as
part of this study should be gauged and sampled on a
quarterly basis. Ground water level data should be
correlated with precipitation data so that hydrologic trends
in recharge can be identified. Well sampling for basic
ground water constituents plus nitrate and a Flame
Ionization Detection (FID) screen for organic constituents
should be sufficient to detect ground water quality trends.
Steps one and two are combined on a proposed ground water
monitoring schedule (Table 7).
3. Additional assessment is required to identify
.
and delineate the extent and degree of possible ground water
contamination at Picketts Landfill and at the metal dump.
At least three additional monitoring wells should be
installed at each site so that a more detailed view of
ground water flow, geology and contamination can be
determined. If no contamination is detected at the metal
- 73 -
-------------------
TABLE 8 - PROPOSED GROUND WATER MONITORING SCHEDULE
MONITOR WELLS 2S 2D 3 4 5 6 8 9* 10** 11 12 13** 14 15 16
=============================================================================================
WATER LEVEL*** M M Q Q Q Q Q A Q Q Q Q Q Q Q
CONDUCTIVITY*** M M Q Q 8 Q Q A Q Q Q 8 Q Q 8
SODIUM Q Q Q Q Q Q Q Q Q Q Q Q
POTASSIUM 8 Q Q Q Q Q Q 8 Q Q Q 8 8 Q 8
CALCIUM Q Q Q Q Q Q Q Q Q Q
MAGNESIUM Q 8 Q Q Q 8 Q Q 8 Q 8 Q 8 Q 8
IRON Q Q Q Q Q Q Q Q Q
MANGANESE Q 8 Q 8 Q 8 8 Q 8 Q Q 8 8 8 8
CHLORIDE Q Q Q Q Q Q
BICARBONATE Q Q Q Q Q 8 8 Q Q 8 Q Q 8 8 Q
SULFATE Q Q Q Q Q Q Q Q Q ~
FID SCREEN A A A A A A A A A A A A A A
pH*** M M Q Q Q Q Q M Q Q Q Q Q Q Q
..... * WELL 9 IS DESTROYED - RE~UIRES REPLACEMENT - OTHER MONITOR WELLS NEEDED
... ** PICKETTS LANDFILL AND ME AL DUMP - OTHER MONITOR WELLS REQUIRED TO ASSESS LEACHATE
***PARAMETER ASSESSED IN THE FIELD
M= MONTHLY DURING SUMMER TWICE IN THE WINTER
Q= QUARTERLY - FOUR TIMES A YEAR
A= ANNUALLY
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
dump, monitoring for this site can be discontinued.
However, ground water monitoring at Picketts landfill should
be continued so that landfill leachate can be characterized
and controlled. This monitoring should be considered
standard procedure accompanying landfilling of solid wastes.
4. An additional source of ground water should be
sought. The present information suggest that the North Hill
area contains good aquifer materials. The installation of 2
more monitoring wells with appropriate water quality and
pump testing is suggested to further assess the water supply
potential and water quality character of this aquifer. The
proximal outwash underlying the Hay Harbor golf course may
also provide additional supplies, and additional monitoring
will be required to assess the feasibility of a public water
supply in this area. The hydrogeology of the area between
East Harbor and Chocomont Cove is relatively unknown and the
potential for water supplies in this ground water mound have
not been fully addressed. An additional monitoring well in
this vicinity would be helpful.
B. Management Policies
In addition to additional assessment work, island
wide policies and/or regulations should be established as a
part of an island-wide ground water protection plan. The
- 75 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
goal of this plan and these policies is to draw attention to
the limited nature of ground water resources inspiring
conservation efforts and to develop and enforce land-use
policies that will preserve the ground water resources. The
following essential steps should be taken:
1. The withdrawal rate, frequency and purpose for
all existing private wells should be determined through an
island-wide survey. A major conclusion of this study is
that aquifer materials are relatively thin and
discontinuous. Given this geometry, the identification and
development of additional aquifers capable of providing a
centralized source of water for the entire island may not be
successful. Therefore, the continued use of private wells
is necessary. If properly managed, they may balance ground
water withdrawals across the island preventing significant
localized aquifer depletion. Therefore, care should be
taken in locating and utilizing these private wells.
2. The proper governing body (probably the Town of
Southold), should adopt regulations requiring each new
building and/or well permit to provide the following
information:
a. a map with a scale and north arrow showing
the location of the well in relation to nearby structures
and roads;
- 76 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
b. a geologic log showing all strata changes
and the location of pump intake;
c. well yield and drawdown based upon an
8-hour pump test;
d. the location of any nearby wells;
e. the projected withdrawal rate based on
proposed water use (domestic use, irrigation, swimming
pools, etc.).
If the projected withdrawal rate is to be greater
than 5,000 gallons per day, a more detailed study should be
conducted to determine the wells zone of contribution. The
method outlined by Kerfoot and Horsley (1988) may be
appropriate for this purpose (refer to Appendix for the
methodology).
3. Regulations concerning periodic inspection and
testing of private supplies should be adopted. This would
provide safeguards over public health that are routinely
conducted on larger public supplies. Regulations should
include an annual inspection of the well to assure that the
casing is intact, the cap is tight and no subsidence has
taken place around the well. Secondly, a water sample should
be taken annually for potability analysis including pH,
- 77 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Alkalinity, Hardness, Chloride, Color, Odor, Turbidity,
Nitrates, Nitrites, Ammonia, Detergents, Iron, Total
Coliform, Manganese and Sodium. Optional testing for
pesticides should also be made available for residences
close to golf courses. This testing will not only protect
public health but will also provide useful information on
regional water quality trends.
4. The Town of Southold may consider adopting
special regulatory controls in the two most sensitive areas
on the island: the watershed area tributary to Barlow and
Middle Farms Ponds and within the island's delineated
recharge areas especially Middle Farms. Suggested actions
are:
1. Zonina Considerations
a. Overlay Aquifer Recharge Protection
districts and Watershed Areas;
b. Prohibition of Selected Land Uses;
c. Special Permitting (could be used to
regulate lawn care activities in a. above, such as
fertilizer use, pesticide use and irrigation);
- 78 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
d. Large Lot Zoning or re-zoning;
e. Transfer of Development Rights (to the
Town or FIDCO, for example, in especially sensitive areas);
f. Growth Controls (either a moratorium or
limitation on numbers of building permits issued in a
specified time period, to allow for better planning of
anticipated growth).
2. Additional Health Requlations
a. Underground Fuel storage
* prohibit new residential
underground fuel storage tanks;
* remove existing residential
underground fuel storage tanks;
* prohibit all new underground tank
installations (except for replacements) within aquifer
recharge or watershed areas.
b. Develop a Phosphorous Buffer Zone
around fresh water lakes and ponds, particularly water
supply sources. A 300 foot setback for septic systems is
recommended.
- 79 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
c. Ban all Septic Tank Cleaning Agents
(those containing synthetic organic chemicals) - this law is
in place in Connecticut and on Cape Cod.
d. Require mandatory septic system
maintenance. An important issue related to this is the
proper disposal of septic tank pumpings. The current
practice of disposal at the Pickett Landfill is
unacceptable. A permanent, appropriate disposal alternative
is needed, either on or off Fishers Island.
e. Develop a systematic and periodic
septic system inspection program. This can also be a
condition of a property sale or issuance of a building
permit to expand or change an existing structure.
3. Non-Requlatorv Protective Measures
a. Donations of land to the Town or local land
trusts;
b. outright purchase of lands in sensitive
water resource areas;
c. Conservation easements, or the voluntary
relinquishment of certain development rights on the land.
- 80 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
d. Public education of the critical nature of
water supplies on Fishers Island; develop and carry out a
specific public education program.
e. Voluntary and involuntary water
conservation measures such as:
* 100% metering of all users on public
water;
* a pricing schedule designed to discourage
large water consumption; additional revenues from increased
rates should go toward more leak detection surveillance,
repair and metering, as necessary, and public education.
f. The Town and the Water Works should develop
a Drought/Water Supply Emergency Plan and Procedures to deal
with chronic and acute water supply shortages, to manage the
island's limited resources in a water supply emergency.
g. Amend building and plumbing codes to
require the use of water saving devices on all new
construction. Encourage the use and retrofitting of water
saving devices through public education.
h. The Town of Southold should fund and hire a
full-time professional to oversee the implementation,
- 81 -
.
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
adoption and enforcement of the various regulatory tools
needed to insure the on-going and future protection of water
supplies on Fishers Island.
i. Develop an official "Water Supply Watershed
and Aquifer Recharge Areas" map for Fishers Island which can
be used as a regulatory reference with respect to whatever
controls are adopted.
5. All underground storage tanks, hazardous waste
generators and septic field locations should be identified
and inventoried. This may be the responsibility of the
local health department through the use of mailed
questionnaires followed by field checks. All information
should be compiled on the Watershed/Recharge Area Map and
held at a central location on the island. The success of
this inventory hinges on a simple, clear form for inventory
purposes and easy access to the information for
decision-making purposes.
- 82 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
REFERENCES
Anderson, Mary P., 1989 Hydrogeologic facies models to
delineate large scale special trends in glacial and
glacial fluvial sediments: Geologic Society of
America, Bulletin V. 101, P. 501-511.
Brodzikowski, K., and van Loon, A. J., 1987. A systematic
classification of glacial and periglacial environments,
facies and deposits: Earth Science Reviews, V. 24 (5),
p. 297-381.
Crandell, H. C., 1962, Geology of Groundwater
of Plum Island Suffolk County New York:
Survey Water-Supply Paper 1539X.
Resources
Geological
Edwards, M., 1986, Glacial Environments in Reading H.G. ed.
Sedimentary Environments and Facies: Oxford, England,
Blackwell Scientific Publishing, p. 445-470.
Fleming, W. L. S., 1985, Glacial Geology of Central Long
Island: Am. Jour. Sci. V. 30, p. 216-238
Flint, R. F., 1947, Glacial Geology and the
Epoch: John Wiley and Sons, New York,
1971, Glacial and Quaternary Geology:
and Sons, Inc. 892 p.
Flint, R.F., 1971, Glacial and Quaternary Geology: John
wiley and Sons, Inc.: New York, 589 p.
Pleistocene
589 p.
John Wiley
Fraser, Gordon S., and Cobb, James C., 1982, Late
Wisconsinan proglacial sedimentation along the West
Chicago Moraine in Northeastern Illinois: Journal of
Sedimentary Petrology Vol. S2, No.2 June 1982.
Freeze, R. Allan, and Cherry, John A., 1979, Groundwater,
Prentice Hall, Inc., Englewood Cliffs, New Jersey.
Fuller, Myron L., 1904, Geology of Fishers Island, New York:
Geologic Society of America Bull. Vol. 16, p. 367-390.
GOldsmith, Richard, 1962, Surficial Geology of the New
London Quadrangle, Connecticut-New York: U.S.
Geological Survey, Washington, D. C.
, 1982, Recessional Moraines and Ice Retreat
in Southeastern Connecticut in Larson, G. J. and Stone,
B. D. eds., Large Wisconsinan Glaciation of New
England: Dubuque, Iowa, Kendall/Hunt Publishing Co. pg
61-76.
Ground Water, Inc., 1989, Danbury, CT Watershed Protection
Plan prepared for the Housatonic Valley Council of
Elected Officials, Brookfield Center, CT.
- 83 -
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Hauptmann, M. G., van der Leeden, and Ross, L.C., 1989,
Management of Regional Ground Water Issues: Town of
Oyster Bay, Long Island in Recent Advances in
Ground-Water Hydrology John E. Moore, Alexander A.
Zaporozec, Sandor C. Lsallany, and Timothy C. Varney
eds. American Institute of Hydrology, Minneapolis,
Minnesota.
Heath, Ralph C., 1971, Basic Ground-Water Hydrology:
U.S. Geological Survey Water-Supply Paper 2220,
Denver, CO.
Hem, J. D., 1959, U.S. Geol. Survey - Water Supply
paper, 1473, p. 10.
Hoffman, John F., 1959, Hydrology of the shallow
Ground-Water Reservoir of the Town of Southhold,
Suffolk County, L.I., N.Y: U.S. Geological Survey
open-file report.
Hunter, Bruce W., and Meade, Daniel B., 1983, Precipitation
in Connecticut, Department of Environmental Protection
Bulletin No.6.
Kay, Clifford A., 1960, Surficial Geology of the Kingston
Quadrangle. Geological Survey Bulletin 1071-1.
Kerfoot, William B., and Horsley, Scott W., Private Well
Protection, 1988, Information Bulletin No. 10,
Association for the Preservation of Cape Cod, Orleans,
Mass.
Rodgers, John, 1985, Bedrock Geological Map of Connecticut:
Connecticut Geological and Natural History Survey and
the U.S. Geological Survey.
Silvey, W.D., and Johnson, H.E., 1977, Preliminary Study of
Sources and Processes of Enrichment of Manganese in
Water from University of Rhode Island supply wells:
U.S. Geological Survey Open-File Report 77-561, 33 p.
Thomas, Chester E., Jr., Cervione, Michael A., Jr. and
Grossman, I.G., 1968, Water Resources Inventory of
Connecticut Part 3 Lower Thames and Southeastern
Coastal River Basins: Connecticut Water Resources
Bulletin No. 15.
Upson, Joseph E., 1971, Surficial Geological Map of the
Mystic Quadrangle, Connecticut, New York and Rhode
Island: U.S. Geological Survey 1970, The Gardiners
Clay of Eastern Long Island: A Re-examination U.S.
Geol.. Survey Prof. Paper 700-B p. 157-160.
- 84 -