HomeMy WebLinkAboutMattituck Creek Watershed Analysis 2001MATTITUCK CREEK WATERSHED ANALYSIS
Final Report
PrePared For:
Town of Southold Board of Trustees
Prepared By:
EEA, Inc.
55 Hilton Avenue
Garden City, New York 11530
(5~6) 74~ ~,~.oo
eeainc~earthlink.aet
In Conjunction with:
U.S.D.3~ Natural Resources Conservation Service
And
Suffolk County Soil and Water Conservation District
Apdl2001
This plan has been prepared for the New York State Department of State
with funds provided under Title 11 of the Environmental Protection Fund
Act
TABLE OF CONTENTS
IVe
Page
I troduction a d Project Background .... 1
Literature ............................................................................ 3
3
Project Location ....................................................................
B.
Physical Characteristics ................................................. 4
Natural Resources ............................... ~ ......................... 4
1. Wetlands ........................................................... 4
2. Significant Coastal Fish and Wildlife Habitats (SCFWH) 5
3. Shellfisheries of Mattituek Creek ............................. 6
Subwatershed Arcas ...................................................... 6
Mcthoiogies .......................................................................... 7
Land Use and Land Coverage .......................................... 7
Water Quality Sampling .................................................7
1. Water Quality Classifications and Use Standards ......... 8
2. Coliforms ........................................................... 9
3. Shellfish Closures ................................................. 9
Overview of Current and Previous Studies Completed on The
Mattituck Watershed ............................................................... 10
A.
B.
C.
D.
NYSDEC Priority Waterbodies List ................................... I0
Shoreline Pollution Source Survey ..................................... 11
Land Use Qualification ................................................... 12
Comparison to PEP Tidal Creek Study ............................... 13
Overview of Projects Completed on Mattituck Creek ...................... 14
Current Protection and Management Programs ............................ 14
Analysis of Water Quality Data for Mattituck Creek ...................... 14
Overview of Creek Impairments ....................... ~ ....................... 17
Possible Point Pollution Sources ....................................... 17
1. Hazardous Materials.... ................................... .... · . 17
2. Marinas and Boatyards ......................................... 18
Overview of Non-Point Pollution Sources ........................... 19
1. Agricultural ....................................................... 19
2. Urban ............................................................... 22
3. Septics ............................................................... 24
4. Boats ................................................................ 25
5. Out'fall Pipes Discharging Directly into the Creek ........ 26
6, Other ............................................................... 26
X. Addressing Water Quality Concerns .......................................... 28
XI. Estimated Loading Rates for Potential Contaminants ..................... 30
· A. Determination of Hydrologic Factors of Subwatersheds ......... 32
XH. Findings by Subwatershed ....................................................... 33
B.
C.
D.
Background ................................................................ 33
Prloritization List ........................................................
Project Practices by Subwatershed ...................................
Subwatershed Characteristics .............................. .... . .. ... .
2.
3.
4.
5.
6.
7.
8.
9.
10.
34
35
37
Subwatershed 01 ................................................ 37
Subwatershed 02 ................................................ 40
Subwatershed #3 ................................................ 44
Subwatershed 04 ................................................ 46
Subwatershed #5 ................................................ 49'
Subwatershed ~6 ................................................ 51
Subwatershed ~/ ................................................ 54
Subwatershed #8 ................................................ 56
Subwatershed #9 ................................................ 60
Subwatershed #10 ............................................... 61
XIH. Project Implementation ......................................................... 63
B.
C.
D.
E.
Introduction ............................................................... 63
Stormwater Quality Management .................................... 64
Overview of Mitigation Measures .................................... 65
Example Project .......................................................... 71
Projects to be Completed ............................................... 72
XIV. Conclusions ......................................................................... 74
XV. Recommendations ................................................................. 75
References
Engineering Design Specifications for Mitigation Projects
LIST OF TABLES AND PHOTOGRAPHS
Page
Table 1 "Subwatersheds and Corresponding Sampling Stations" ........................ 8
16
Table 2 "Fecal Coliform Levels". ............................................................
Table 3 "Total Coliform Levels" ............................................................. 16
Table 4 ''Fecal Coliform Loading Rates". ................................................... 31
PHOTOGRAPHS
I-Iashamomuck Project ........................................................................... 72
Each subwatershed secti6n also includes one photograph before the discussion.
I. Introduction and Project Background
The Mattituck Inlet and Creek watershed was investigated in order to identify the
acute and chronic pollution sources, and to assess various potential treatment alternatives
on a subwatershed basis. Mattituck Inlet has consistently appeared on the NYSDEC
Priority Water Problem List (PWL). This list identifies pathogens as the main type of
pollutant precluding shellfishing. The main source of pathogens noted in the PWL is
urban nm-off with on-site systems listed as a secondary source. Through this study, the
Town of Southold seeks to implement a stormwater management plan for Mattituck
Creek, with the objectives of reducing pollutant loads (e.g., pathogens, sediments,
nutrients and other pollutants transported by stormwater runoff to the Creek). The long-
term goal of the Town Trustees is to enable re-opening of the entire Mattituck Creek
system in the future for shellfish harvesting. This would greatly enhance the public and
recreational use of these waters as well as provide additional economic benefits to the
Town. The primary purpose of this investigation was to develop various treatment
scenarios that could be implemented in a phased approach aimed at raising the current
water quality of the Creek.
Though the NYSDEC PWL states that urban run-off is the primary source of
pathogens, with on-site systems listed as a secondary source, all land use practices that
potentially degrade water quality are discussed in this report. Though the land use within
Mattituck Creek watershed is predominately agricultural, the land use immediately
adjacent to the Creek is primarily residential. Because the overall land use within the
Mattituck Creek watershed is primarily agriculture, this report identifies many
agricultural remedies for the water quality problems. However, this study supports the
findings by the NYSDEC in the PWL in identifying urban nm-off and on-site systems as
two of the major contributors to the water quality degradation in the Creek.
The intent of this report is not a Creek Management Plan, and an extensive
evaluation of the septic systems for homes and businesses along the Creek was beyond
the scope of this report, but is recommended for future studies. In the following report,
identification of subwatersheds was conducted to coincide with outfall pipes that directly
discharged into the Creek. These pipes deliver stormwater that travels through both
agricultural and residential areas. Since there is no reliable laboratory test available to
differentiate between human and animal fecal constituents in fecal coliform data,
determination of the sources of these pollutants is a challenging, exhaustive task. It was
determined, through the studies and analysis conducted for this report, that retarding the
stormwater runoff from entering the Creek would increase the water quality. Analysis
was conducted to determine the subwatersheds with the greatest quantity of stormwater
entering the Creek, and also those with the greatest fecal coliform content.
The major pollutants that were evaluated for this project were Fecal and Total
Coliform. Mattituck Inlet has consistently appeared on the NYSDEC Priority Water
Problem List. In 1988, the Inlet was a high priority waterbody with a problem ranking of
"severe". The creek had been heavily utilized in the past for its shellfish production.
However, in 1984 the New York State Department of Environmental Conservation
(NYSDEC) closed the creek to all shellfish harvesting due to excessive levels of coliform
bacteria. There have been seasonal openings in the past (from 1985 to 1998) but this has
been discontinued due to the chronically high bacteria levels. It is important to note that
although the water samples from Mattituck Creek have only been analyzed for coliform
levels, the mitigation recommendations that are presented in this report would also
increase the water quality of Mattituck Creek by lowering sediment and nutrient levels
entering the Creek.
Field data collection included water samples taken at six stations along the creek,
often during storm events. The boundaries of the Mattituck Creek watershed and of the
ten subwatersheds are shown on Figure 1. The ten subwatersheds were identified within
the larger watershed, and land coverage was evaluated in the field utilizing soil,
topographic, and aerial maps. Land coverage data was then input into a stormwater runoff
computer model. This stormwater mnoffmodel was developed by the U.S.D.A. Natural
Resources Conservation Service (NRCS) entitled: Urban Hydrology for Small
Watersheds, Technical Release 55 (TR-55). Pollutant loading rates were then estimated
for each subwatershed, using the mean Fecal Coliform level and the amount of runoff
(obtained from the TR-55 model) for each subwatershed. The results of these field
investigations and modeling have enabled the determination of priority watershed areas
where mitigation efforts could be focused to achieve the maximum results based on the
level of effort expended. In other words, public expenditures could be directed to those
degraded water quality areas that are most easily rectified or show the greatest potential
improvement at the least cost. The locations of the waters sampling stations are shown
on Figure 2.
In November 1998, an initial watershed analysis and report of findings for
Mattituck Creek was conducted by the U.S.D.A. NRCS and the Suffolk County Soil and
Water Conservation District (SWCD). The water samples were collected by Southold
Town Trustee, Jimmy King, and laboratory analysis was conducted by the NYSDEC.
Final watershed analysis, mitigation recommendations and field investigations were
conducted by EEA. Invaluable assistance was provided by Mr. James McMahon, Mr.
Jimmy King, Ms. Valerie Scopaz, Mr. John Sepenowski, Mr. Emerson Hasbrouk, Mr.
Alan Connell, and Mr. Tom McMahon for providing necessary resources to complete the
study.
This project has been fimded by the New York State Department of State
(NYSDOS) through an Environmental Protection Ftmd (EPF) grant award. The project has
been broken into two phases; Planning and Design constitute Phase I, and Project
Implementation constitutes Phase II. Phase I is the subject of this grant. In this first Phase,
the Town shall assess the volume of water entering the watershed utilizing best available
data on loading rates. Estimates will then be derived of the total amotmts of sediments,
nutrients and pollutants that are contained in the runoff, and potential treatment options will
be discussed conceptually. The planning and design phase will enable the Town to
establish an implementation timetable and budget based on the design recommendations.
Phase II will be the subject of future grant applications. A portion of Phase II has recently
been funded by a grant award through the NYSDEC Nonpoint Source Implementation
2
Grants Program. The following sections of this watershed analysis report will discuss the
methodology, results and recommendations for mitigation efforts.
II. Literature Review
Literature pertaining to this project was obtained from EEA's in-house library.
Many reports pertaining to non-point source pollution, mitigation techniques, water
quality, watershed management, and watershed best management practices (BMP's) were
reviewed and utilized in the analysis for this project. Watershed recommendation guides
and manuals were reviewed, such as the Long Island Regional Planning Board (LIRPB)
Non-point Source Management Handbook (1983), the U.S. Environmental Protection
Agency (USEPA) Guidance Specifying Management Measures for Sources of Non-Point
Pollution in Coastal Waters (1993), the New York State Department of Environmental
Conservation (NYSDEC) Reducing the Impacts of Stormwater Runoff from New
Development (1992), among other guides and manuals. The Centerport Harbor Fecal
Coliform Study by Comell Cooperative Extension Marine Program (1995) was reviewed
and referred to for comparison and relevance to the Mattituck Creek report.
IlL Project Location
Mattituck Inlet is located in the Town of Southold, Suffolk County, New York on
the north side of the north fork of Long Island and drains into the Long Island Sound.
The total watershed for Mattituck Inlet and Creek encompasses approximately 1,687
acres. Figure 1 depicts the entire drainage area servicing Mattituck Creek and Inlet, as
well as the 10 subwatershed areas, which are the subject of this investigation. The
approximate boundaries of the Mattituck Creek/Inlet watershed are as follows: County
Road 48 to the south, the mouth of Mattituck Inlet to the north, extending west as far as
Bergen Avenue and extending east just beyond Elijah's Lane. The dominant land use is
agriculture followed by residential. Commercial land use is a distant third. The bulk of the
residential development found in the watershed is situated at the head of the Creek in the
Town of Mattituck. Residential development around the Creek and towards Long Island
Sound on either side of Inlet is generally of low to medium density, with lot sizes ranging
from less than 10,000 square feet to over two acres. Over the past several years, land
dedicated to agriculture has slowly been converted to other uses. In addition to being a
focal point for residential development, Mattituck Inlet and Creek is an important harbor
containing a large number of water-dependent and water-enhanced uses. Unfortunately,
there is a trend towards stripping native vegetation from homesites to "improve" the view
of the water. However, this activity has impacted the neighborhood's view of those sites
has heightened the potential for soil erosion. Land use practices that increase the
potential for soil erosion have potentially negative implications for the water quality
within the creek
A. Physical Characteristics
The water bodies of Mattituck Inlet and Creek encompass approximately 165 acres,
and stretch approximately 2.5 miles inland. The mouth of Mattituck Creek is armored by
two rock jetties that extend approximately 1000 linear feet into Long Island Sonnd.
Mattituck Creek is tidally connected to Long Island Sound and has a tidal fluctuation of
about five feet. The Creek is no more than 400 feet at its widest point. A naturally shallow
waterbody, Mattituck Creek has been dredged to a depth of 10 feet in the center channel.
The creek is the only safe harbor on Long Island Sound east of Mount Sinai Harbor, a
stretch of more than 40 miles. The creek has two long arms which extend outward; one to
the west (Howard's Creek), the other to the east (Long Creek). The former is navigable for
most of its entire length. The latter, however, is navigable only to the original Grand
Avenue bridge crossing, a few hundred feet northeast of the existing crossing. Only small
boats with shallow drat~ can be taken past this point. These particular physical
characteristics have limited commercial use of this port to boats of less than 60 feet in
length.
The Creek supports an active working harbor that has retained significant natural
resources in spite of the degree of residential and commercial development within its
watershed. The majority of the Creek shoreline remains natural, with fringing intertidal
marshes. The water-dependent uses include four marinas, a federal anchorage, numerous
moorings and private docks; four commercial fishing docks, fish packing facilities and two
public boat ramps at its head. On either side of the Inlet mouth, outside the rock jetties
guarding the channel are park district beaches. The two rock jetties, most particularly the
westerly one, are heavily utilized for recreational fishing. Most of the water-dependent
uses are concentrated on the west side of the Creek. Mattituck Inlet also supports a
significant commercial fishing industry.
B. Natural Resources
There are many important natural resources within the Mattituck Creek watershed
which are in need of protection or restoration. These natural resources support significant
finfish, shellfish and wildlife habitats. These natural resources include:
1. Wetlands
Extensive tidal marshes, upwards of 45 acres, fringe the shoreline of Mattituck Inlet
and Creek. The wetlands support both intertidal and high marsh vegetation, and the creek
itself is classified by NYSDEC as littoral zone. Smooth cordgrass (Spartina alterniflora)
dominates the marsh vegetation. There are also areas of dredge spoil located within this
wetland system.
These tidal wetlands are relatively undisturbed and highly productive, providing
habitat for a variety of wildlife, shellfish and marine finfish. The most extensive complex
of tidal wetlands is located on the east side of the mouth of the Inlet and is owned almost
entirely by the State of New York. This includes the open water and intertidal wetlands
north of Mill Road. This wetland is characterized by good flushing action and an estuary
community that supports juvenile marine finfish, clams, mussels, and osprey.
The remainder of the underwater lands and tidal wetlands in the Mattituck Creek
watershed are owned by either the Mattituck Park District, the Town of Southold or private
property owners. These wetlands are highly productive habitats that support a variety of
fish and wildlife, both within the Inlet and Creek and in Long Island Sound near the Inlet.
These undexwater lands support a substantial soft clam and oyster shellfishery, which is
dependent on high water quality and undisturbed wetlands.
2. Significant Coastal Fish and Wildlife Habitats (SCFWH)
There is one designated Significant Coastal Fish and Wildlife Habitat in the
Mattitack Creek watershed. This is the Mattituck Inlet Wetland SCFWH. The following
discussion is based on information contained in the Department of State's Coastal Fish and
Wildlife Habitat Rating Forms (NYSDOS, 1987) and follow up.
Location and description of habitat:
The Mattitack Inlet Wetland SCFWH consists of approximately 60 acres of
tidal wetland and open water within the inlet and the creek. It includes Mattitack
Inlet, a deepwater inlet with strong tidal flushing, which enters Long Island Sound
between two jetties. South of the inlet, Mattitack Creek is bordered by tidal
wetlands and moderate residential and marina development. The wetland habitat
itself is undisturbed and the majority of the wetland is owned by the NYSDEC.
Fish and wildlife values:
Small, undisturbed areas of tidal wetlands with good flushing are unusual in
northern Suffolk County. The Mattituck Inlet Wetland has a high primary
productivity that supports a large variety of fish and wildlife species, both in the
wetland itself and around the mouth of the inlet in Long Island Sound. Osprey
(New York State Special Concern species) nested on the state property in the
wetland in 1984 and 1985 and feed in the wetland and on the creek. That nest was
still active in 1999. (Within the past few years, ospreys have been observed nesting
on poles that were erected in an island in the center of the southern part of the
Creek, at its junction with Howard's Creek.) The wetland also serves as an
important habitat for a variety of other wildlife as well as marine finfish and
shellfish. Surf clams, hard clams and mussels have been harvested in or adjacent to
the habitat area, but there have been pollution problems due to marina development
within close proximity, thereby consequent shellfish closures. One pair of piping
plover (T) nested on the beach to the east of the inlet in 1984, but the extent of use
of this habitat by this species is not documented.
3. Shellfisheries of Mattituck Creek
The estuarine waters of Long Island historically supported a significant fishery for
numerous species, such as the hard clam (Mercenaria mercenaria), blue mussel (Mytilus
edulis), bay scallop (Aequipecten irradians), soft-shelled clam (Mya arenaria), and
common oyster (Crassostrea virginica). The change to water quality characteristics,
primarily increases to salinity, the introduction of predators (i.e., oyster drill [Urosalpinx
cinerea]), dredging of mudflats, decline of eelgrass (Zostera marina), and overharvesting,
have all contributed to the reduction of both diversity and abundances. Presently, only
the hard clam remains in harvestable numbers.
Hard clams are found in varying abundances from Bar Harbor, Maine and the
Gulf of St. Lawrence to the north, all the way south to the Gulf of Mexico. The species is
found fi.om the intertidal zone to subtidal depths down to 60 feet. Hard clams are
typically found in waters with a salinity of greater than 15 parts per thousands, and a
substrate ranging fi.om sand to muddy sand. Hard clams are typically harvested manually
by means of a clam rake with attached basket or tongs. In shallow water, the clams can
also be collected by hand.
Hard clams are filter feeders, meaning they strain large amounts of water to obtain
food which primarily consists of phytoplankton (microscopic free floating plants).
During the feeding process, additional materials are injected. These can include fine
grain sediments, chemical constituents, nutrients, and bacteria. In most cases, these
elements pass quickly through clams or become inactive. The bacteria which is not
typically found in clams remains inside the clams, but cannot sustain itself and dies off
within five days. If the clams were cooked, the bacteria would be killed before eating
them.
Since most hard clams are eaten raw, the bacteria would still be active and present
a hazard to the consumer. It is for this reason that the NYSDEC has established
guidelines on the amount of bacteria present in the water to avoid people from becoming
ill. Area closures occur once bacteria levels exceed a total coliform medium Most
Probable Number (MPN) of 70 per 100 milliliters of water, and not more than 10 percent
of the samples exceed an MPN of 330 per 100 milliliters for a three-tube, three-dilution
test. The coliform levels must remain below these standards for seven days prior to
harvesting.
C Subwatershed Areas
The entire watershed of Mattituck Creek encompasses 1,687 acres. The total area
of the 9 subwatersheds (not including Subwatershed # 9, as it has been discovered not to
contribute to the Mattituck Creek watershed) encompass 1022.6 acres. The remaining
664.4 acres have not been included in this study. Since the subwatersheds were delineated
from water sampling stations identified by the NYSDEC as areas of highest pollutant
loadings (due to location near outfall pipes, etc.), it is believed that the analysis of these 10
6
subwatersheds will allow for the maximum amount of pollutant source identification with a
reasonable amount of effort (water sampling and analysis). After the NYSDEC identified
the areas of highest pollutant loading (due to outfall pipes, etc.), delineation of the
subwatersheds which contributed to these pipes or road-ends was conducted. This was
accomplished with the use of topographic maps, and verified in the field. Even though the
areas outside the delineated subwatershed areas did not have any correlating water quality
data, an analysis of the remaining land within the watershed has also been conducted for
this report. Though this analysis does not include any water quality sampling or analysis, it
does include analysis of literature, field observations, and maps (including soil, wetland,
topographic, etc.).
IV. Methodologies
A. Land Use and Land Coverage
The present land use and land cover has been determined using 1996 aerial
photography provided by the NRCS, field verification, and detailed land use maps in GIS
(Geographic Information Systems) format provided by the Town of Southold.
B. grater Quality Sampling
NYSDEC has established 15 water quality sampling stations in Mattituck Creek.
These are shown on Figure 2. Each station is sampled according to procedures described
in Recommended Procedures for the Examination of Sea grater and Shellfish, APHA,
1970. Stations were placed near potential pollution sources, such as drain pipes. Stations
were also located at readily identified landmarks. These stations have been deemed
adequate to evaluate the sanitary condition of the Creek by NYSDEC in the report,
"Evaluation of Bacteriological Water Quality for Conditional Certification" (December,
1998). The water quality samples were analyzed for coliform bacteria (both total and
fecal), that are used as indicators of human and animal waste contamination and possible
presence of pathogenic microorganisms. Since shellfish are harvested for consumption, it
is important to know the coliform levels in the waters from which the shellfish are being
harvested. The shellfish filter the water, and coliforms in the water are absorbed by the
shellfish. These coliforms can become harmful to humans when the shellfish are
ingested.
Water sampling was conducted by Shellfisheries staff members and the Town of
Southold Trustee, James King. The water samples were examined using a 3-tube 3-
dilution test by the NYSDEC microbiology laboratory following procedures described in
Standard Methods for the Examination of Water and Wastewater, (APHA, AW'WA, 1992).
Mattituck Creek was evaluated and classified based on the analysis of total coliform
bacteria data. The method to collect the water samples was taken fi-om recommendations
from the National Shellfish Sanitation Program (NSSP). The method involves the
collection of water samples under adverse pollution conditions, such as afier a rainfall and
during an ebbing tide. Since Mattituck Creek is a conditional area, water quality data were
collected following varying amounts of rainfall. This aids in determining the rainfall limits
within which the water quality remains acceptable. Sampling data used in the report were
collected during the ebbing tide, and rainfall was recorded at the Town of Southold police
station in Peconic. Sampling locations were identified by NYSDEC because of proximity
to either road ends or stormwater direct discharge pipes. After this, seven were chosen to
have a subwatershed analysis conducted for reasons described below.
TABLE 1: Subwatersheds and Corresponding Sampling Stations:
Corresponding
Subwatershed Sampling Station
1
2 6.2
3 6.1
4 6.3
5 7.1
6
7 4.1
8 8
9
10
Subwatershed # 9 has no corresponding sampling location listed, as it was discovered to
be disconnected fi.om the watershed of Mattituck Creek.
1. Water Quality Classifications and Use Standards
Water quality classifications in New York State are currently based primarily on
three indices: total coliform level, fecal coliform level, and dissolved oxygen
concentration. The primary objective of the on-going water quality monitoring program
in Mattituek is to prevent human health impacts from exposure to pathogenic bacteria and
viruses which can result from either direct contact with contaminated water or the
consumption of tainted shellfish. However, the detection of these pathogens is generally
a tedious undertaking. Consequently, water quality testing for Mattituck entails the
analysis of coliform bacteria, which are relatively easy to measure; these bacteria co-
occur with the pathogens of primary concern and serve as indicators of the possible
presence of those pathogens.
In order to be certified as a shellfish harvesting area, the median total coliform
level for any series of samples must be 70 MPN/100 ml or less (where MPN/100 ml is
the most probable number of organisms per 100 milliliters of sample). New York State
(2 NYCRR Part 701 20) classifies these certified shellfishing waters as "SA", which
designates the highest level of water quality. An "SB" classification is assigned where
the monthly median total coliform level is 70 to 2400 MPN/100 mi, where no more than
20 percent of the samples exceed 5000 MPN/100 ml, and where the monthly geometric
mean value is 200 MPN/100 ml or less.
2. Coil forms
Coliform bacteria are used as an indication of the possible presence of pathogenic
organisms. Since it is difficult, timely and expensive to test for specific pathogens, then in
order to insure that water quality is satisfactory for the protection of public health, simple,
reliable and rapid methods for detection and enumeration of micro-organisms are
necessary. Therefore, methods have been developed which determine the presence of other
fecal organisms. These are called indicator organism and are indicative of the possible
presence of pathogenic organisms.
Total coliforms can come from a variety of sources, including soils and
vegetation. Fecal coliforms, however, have their origins in the intestinal tracts of warm-
blooded animals. Since fecal coliforms are more indicative of a fecal origin, and are a
higher standard than total coliforms, fecal coliforms as an indicator were used in this
study (Comell Cooperative Extension, 1995).
A review of the literature on coliform removal, (EPA 1993, Jolly 1990, NYSDEC
1992, and Schueler 1992, 1987), all confirm that the removal of fecal coliforms is a
function of hold time. At a minimum, 72 hours is required to remove the bulk of the
coliforms. Optimally, six to seven days of detection time is required to maximize the
reduction. Anything longer can lead to stagnation, odors, and anaerobic conditions. The
removal of bacteria during the holding time is achieved through a variety of functions
that include: absorption, sedimentation, natural die-off and predation by zooplankton.
3. Shellfish Closures
As discussed previously, the waters of Mattituck Creek have historically provided a
rich shellfish harvest. The waters within Mattituck Inlet and Creek experience significant
fluctuations in water quality and thus are, with one exception, closed (uncertified) to
shellfish harvesting. The exception to this mle is during the winter (December 9th - April
30th) when water quality north of a line between landmarks at the south side of entrance to
Howard Creek and 1085 West View Drive improves adequately to permit a conditional
harvesting program. The conditional harvesting program allows shellfish to be taken
except following a 0.3 inch rainfall within a 24 hour period, when coliform levels are
unacceptable. The colder and dryer winter season is a time when there is little stormwater
runoff entering the inlet and there are lesser levels of boating activity. The Creek has been
uncertified since 1984. The conditional shellfish harvesting programs have been operating
in Mattituck Creek annually since 1985. These programs have been operated with the joint
cooperation of the NYSDEC Shellfisheries Section and the Town of Southold.
During the preparation of this report, the conditional harvest of Mattituck Creek has
been eliminated. This was not due primarily to further water quality impairments, rather,
an administration action by NYSDEC in response to fiscal and personnel constraints. As of
9
the submission of this report, shellfish harvesting is currently prohibited throughout the
Creek. However, NYSDEC staff are presently analyzing the water quality of the Creek to
determine whether a possible seasonal shellfish harvesting program can be supported. The
Town of Southold has an ultimate goal of re-opening the shellfish beds without a
conditional restriction.
V. Overview of Current and Previous Studies Completed on the Mattituck
Watershed
There have been several studies conducted conceming the Mattituck Creek
watershed. These include studies conducted by NYSDEC and other agencies reporting the
pollutant levels and the shellfish closures for the Creek. Other studies include the Local
Waterfront Revitalization Program, currently being proposed by the Town of Southold. In
1986, the Southold Conservation Advisory Council identified and mapped all known sites
where stormwater nm-off was discharged directly into the creek. This map, updated in
1994, shows the location of completed improvement projects (filtration of stormwater
runofo.
A. NYSDEC Priority Waterbodies List
Periodically, the NYSDEC Division of Water publishes a list of surface waters
that either cannot be fully used as a resource, or have problems that can damage their
environmental integrity. The NYSDEC Priority Waterbodies List (PWL) includes
individual waterbody data sheets describing the conditions, causes, and sources of water
quality problems. Since 1984, Mattituck Inlet has remained on the PWL, despite
attempts to improve water quality.
The "Problem Information" description for Mattituck Inlet in the 1996 Priority
Waterbodies List" states:
"Use Impairment: Shellfishing
Type of Pollutant: Pathogens
Sources of Pollutant: Urban Runoff, On-site Systems, Other (Boat/Marinas)
Severity: Precluded
Documentation: Good
Resolvability: Strategy Exists; Funds Needed"
The "Further Details" description of this document states:
"Use impairment: Year-round shellfish closures-conditional shellfish harvesting
in the northern 2/3 each year.
Cause: Stormwater nmoff, failing septic systems, boat discharges-heavy boat
population in summer
10
The Inlet has poor flushing characteristics. This area is part of the Long Island
Sound Study and the Long Island Coastal Management Plan. A local stormwater
management plan is being developed and implemented.
Source of Information: Region, Marine Resoumes and Regional Water"
Tidal waters at the mouth of Mattituck Inlet have been designated by NYSDEC as
high-quality SA waters. The tributaries of Mattituck Creek (Howard's and Long creeks)
are designated as SC waters. According to NYSDEC Water Quality Regulations, the best
usages of Class SA saline surface waters are shellfishing for market purposes, primary
and secondary contact recreation and fishing. These waters shall be suitable for fish
propagation and survival. The best usage of Class SC waters is fishing. These waters
shall be suitable for fish propagation and survival. The water quality shall be primary
and secondary contact recreation, although other factors may limit the use for these
purposes. Mattituck Inlet has consistently appeared on the NYSDEC Priority Water
Problem List and the Priority Waterbodies List. In 1988, the Inlet was a high priority
waterbody with a problem ranking of "severe". This indicated that the designated use of
the waterbody, shellfishing, was precluded by the poor water quality. The 1996
NYSDEC PWL identified the primary pollutant in Mattituck Creek to be of pathogens.
The primary source pathogen indicating organisms was identified as urban rtmoff. Other
sources identified are boat/marinas, and on-site wastewater treatment systems located
close to the shoreline. Pathogens can also come from illegal discharges from holding
tanks of boats, and high concentrations of waterfowl, especially in the sheltered portions
of the Creek during the winter months. The use impairment for the creek is year-round
shellfish closures with conditional shellfish harvesting in the northern 2/3 each year. The
cause of this use impairment is the presence of pathogen indicating organisms from
stormwater runoff, failing septic systems, and boat and marina discharges, due to the
heavy boat population in the summer. The correlation between rain events, particularly
during fall, winter, and spring seasons, would indicate that urban runoff and failing septic
systems are more important than the marina discharges. Water quality problems in
Mattituck Inlet have been identified as having a high resolution potential in the 1996
Priority Waterbodies List.
The NYSDEC PWL also states that the lower (southern) part of Mattituck Creek
has poor flushing characteristics. While water quality within Mattituck Creek fails to meet
SA water quality standards most of the year, it may be possible to improve water quality
and reopen areas within this otherwise productive water body for shellfishing on a more
regular basis. On land, this will require a concerted effort to collect and detain the flow of
stormwater long enough to remove pollutants.
B. Shoreline Pollution Source Survey
In December 1989, the NYSDEC Bureau of Shellfisheries completed the Mattituck
Inlet/Mattituck Creek Shoreline Pollution Source Survey. This report describes the
pollution sources that are contributing to Mattituck Creek. This survey is implemented in
response to a closure of a waterbody for shellfish harvesting. Findings of this survey stated
11
that although there are approximately 140 houses on the shore of this creek, and all have in-
ground sewage treatment systems, according to NYSDEC, there was no evidence of any
system malfunctioning. One of the main sources of pollution identified by this report was
storm drains found on many streets, which border the shoreline of Mattituck Creek. In
many cases, these storm drains discharged directly into the Creek.
Another source of pollution identified by this survey was streets that end on the
shoreline of Mattituck Creek. These include Jackson Landing, Westphalia Avenue, South
Drive, and Bayview Avenue. In these situations, rainfall runoff and runoff from nearby
houses (lawn watering, car washing) can flow directly into the creek. This survey
identifies waterfowl as another possible pollution source. Waterfowl (i.e., ducks, geese and
swans), gulls, cormorants and herons have been observed in great numbers on the Creek.
Finally, the survey mentions abandoned oil storage and asphalt tanks located on the
western shore just inside Mattituck Inlet.
C. Land Use Qualification
A review of the land use maps produced for the Town of Southold LWRP,
indicates that the vast majority of the land associated with the land adjacent to Mattituck
Creek is classified as low density residential(A/AA). The shoreline adjacent to the creek
is nearly entirely residential, with the exception of four small marinas, a restaurant, and a
boat mooring area (27 moorings) at the head of the creek. Agricultural lands dominate
the land use in the western and eastern margins of the watersheds.
Based on these land uses, the primary chemical constituent of concern would be
petroleum hydrocarbons that could leak from residential heating oil tanks. Marinas have
also been documented as introducing the following pollutants into the environment:
petroleum products, paint, solvents, and anti-fouling paints utilized on boat bottoms. The
usage of such materials is highly regulated by NYSDEC pursuant to NYCRR Part 325 Fi
Fra 3 (D)(1)(C), as well as the United States Environmental Protection Agency (USEPA).
However, current water quality monitoring programs do not routinely sample for such
constituents; therefore, data are restricted to spills and/or violations.
Since agricultural and residential land uses pre-dominate within the creek
watershed, bacteria and nutrient loads present the greatest concern. Nutrient loading is
associated with both residential areas (lawn fertilizers, wastewaters) and agricultural
areas (plant fertilizers and animal wastes). Nutrients typically show up in the following
analyses: Total Kjeldahl Nitrogen (TKN), nitrogen-ammonia (NH3)), nitrite (NO2), nitrate
(NO3), total phosphorus (TPO4), ortho-phosphorus, and total organic carbon. The
elements above are by-products transported to the creek either via stormwater runoff or
grotmdwater flow. Nutrients present in the groundwater may take decades to reach the
creek. Excess nutrient loading often results in an increase of chlorophyll-a (plankton
blooms) which will reduce light transparency that could ultimately result in a decrease in
dissolved oxygen levels as the phytoplankton die off and begin to decay.
12
The potential discharge of chemical pollutants and effects of nutrient loading are
all detrimental to the productivity of any water body and should not be overlooked. The
data presented by the NYSDEC in the "Evaluation of Bacteriological Water Quality for
Conditional Certification" (1998) indicates that the level of coliforms within the Creek
typically exceed the State standard for total coliforms of 70 MPN per 100 milliliters of
water. The correlation of exceedance with high rainfall events (0.60 inches of ran/hour)
indicates that bacterial loading is pr/madly stormwater driven (NYSDEC 1998).
There are several sources of pathogens identified in the literature referenced.
These sources include septic (sanitary) systems, marina and boat waste/discharge,
domestic pet waste, and livestock waste, among others. It has been identified in the
NYSDEC PWL that septic systems and urban runoff are the two main contributors to the
pathogens entering the Creek. For this reason, an analysis of the loading rates for each
subwatershed has been conducted. Through this analysis, conclusions can be drawn
concerning the highest priority projects that will have the greatest positive effect on the
water quality of the Creek. The projects suggested in this report include berms,
detention/retention areas, wetlands, and other methods of retarding the stormwater runoff
from directly discharging into the Creek from outfall pipes. Though this does not address
the possibility of failed septic systems directly discharging into the Creek, it is believed
that the suggested projects will have a significant positive impact on the water quality of
the Creek. Further studies (Creek Management Plans, etc.) can be conducted to
determine the impacts of individual sources, such as failing septic systems or marinas, to
the water quality of the Creek. These studies can be conducted through the use of dye-
testing or other methods.
D. Comparison to PEP Tidal Creek Study
In October 1999, EEA concluded a study for the Peconic Estuary Program on ten
tidal creeks in the Peconic Estumy. As part of this study, EEA analyzed a wide range of
water quality data, including fecal and total coliform levels. The coliform levels obtained
from Mattituck Creek were compared to the values for the other 10 creeks studied, to gain
an understanding of the water quality in Mattituck Creek relative to other creeks within the
same region. Though water quality samples were taken at different times for both of these
studies, and there was much more data for Mattituck Creek than any of the ten tidal creeks,
this comparison is still informative and useful.
A mean fecal coliform level for subwatersheds 2,3,4,5,7, and 8 was determined to
be 42 MPN/100 ml. A mean total coliform level for the same subwatersheds, under dry
conditions (since this was similar to the Tidal Creeks study) was determined to be 210
MPN/100 ml. The levels determined for Mattituck Creek are negatively biased, as the
sampling stations were located in close proximity to known pollutant sources. Comparing
the fecal coliform data from the 10 other creeks to the levels detected in Mattituck Creek,
the following is apparent: five creeks had higher levels of fecal coliform, and five creeks
had lower levels. Comparing the total coliform data to the other 10 creeks; four creeks had
higher levels of total coliform, while six creeks had lower levels of total coliform. This
13
rough comparison shows that both the total and fecal coliform levels in Mattituck Creek are
within the mid-range of readings for other tidal creeks within the same region.
VI. Overview of Projects Completed on Mattituck Creek
The Town of Southold has implemented two storm drainage improvement on the Mattituck
watershed in response to some of the studies that have been conducted. One was
conducted on Bayview Avenue, on the western shore of Mattituck Creek. Here, nine catch
basins and leaching pools were installed in gravel trenches at the road end. A series of
catch basins were also installed along either side of Bayview Avenue. Two catch basins
were also installed at the foot of Knollwood Lane on the east side of Mattituck Creek.
Even though the overall goal of this plan is to identify impairments to and
mitigation alternatives for the entire Mattituck watershed, ten subwatersheds were
identified. These subwatersheds were identified based on available water sampling data
and by attempting to choose subwatersheds which may have greater impacts than others
(due to a heavy influence of aghculmral, stormwater, or other mnoffinputs.)
VII. Current Protection and Management Programs
The Town of Southold has several programs through the Peconic Estuary Program
that have been designed to protect and manage the resources and water quality of the area
(PEP Nonpoint Source Management Plan - Inventory, June 1995). The "Base Programs"
that pertain to Southold have been included in Appendix D of this report.
VIII. Analysis of Water Quality Data for Mattituck Creek
Under adverse pollution conditions, many sampling stations in Mattituck Creek fail
the water quality standards set by NYSDEC for certified shellfish areas. Bacteriological
data at Mattituck Creek show that rainfalls in excess of 0.20 inches have an adverse impact
on water quality. However, Mattituck Creek does satisfy the criteria for a conditionally
certified area under specific rainfall conditions. Under dry weather conditions (less than
0.10 inch) all stations meet the water quality criteria. Under moderate weather conditions
(rainfall between 0.10 and 0.40 inch) only Station 3 fails to meet the criteria. Close
examination of the water quality and rainfall data shows that this station exceeded the
acceptable total coliform levels only twice. These two instances also occurred early during
the conditional evaluation period of Mattituck Creek.
Through December 1998, Mattituck Creek was sampled 41 times: 15 times under
dry weather conditions (0.00 - 0.10 inch rainfall), 18 times following moderate rainfall
(0.10 - 0.60 inch), and 8 times following rainfalls greater than 0.60 inch. Stations 1,1.1,
2,3,4,4.1,5,7,7.1, and 9 satisfy the water quality criteria for a certified shellfish land under
dry weather conditions and following moderate rainfall. These stations lie within the
portion of Mattituck Creek that have been designated as conditionally certified. Stations
6,6.1,6.2,6.3,8, and 8.1 do not satisfy the water quality criteria. These stations lie within
the portion of Mattituck Creek that have remained uncertified and closed to shellfish
14
harvesting (located at the southem end of Mattituck Creek and along Long Creek). The
NYSDEC recommends that Mattituck Creek should be closed to harvesting for seven days
following rainfalls greater than 0.30 inch. It does not appear that the bacteria spreads
throughout the creek during a typical tidal cycle, but remains within the headwaters,
perhaps dying off before it can spread. This would support the theo~ of low flushing rate
of the headwaters. It is also possible that some other unknown factors are controlling the
spread of bacteria.
The vast majority of the water sampling conducted for the 1998 NYSDEC report
took place in November through May. During this seasonal time period, there is typically
reduced level of activity at each of the four identified marinas and many of the homes
which may be used by summertime residents only. Review of this data indicates that the
strongest correlation with bacterial levels is with both rainfall and seasonal events.
Whenever rainfall exceeds 0.20 inches, bacteria levels increase particularly at the station
found at the southern terminus of Mattituck and Long Creeks. The NYSDEC
bacteriological data indicate that the southern portion of the creek receives the highest
concentration, with levels dropping as one proceeds north to the inlet. Stations situated
north of Howard's Creek are typically below NYSDEC standards, but can exceed the
standards after a heavy rain. This would suggest that the probability of keeping the creek
open to shell fishing increases significantly towards the northern portion of the Creek.
It would appear that the greatest concentration of bacteria would occur on a
regular basis from June through August. This is due, in part, to the following:
· the large concentration of recreational vessels
· apparent lack of adequate pump-out facilities
· increased summertime population exerting pressure on the aging septic system
· the increased volume of patrons to the waterside restaurants.
Most of this heightened creek-side activity diminishes after Labor Day, and is
nearly gone by the end of October. The wintertime loading rates would thus be greatly
reduced and confined to periods of heavy rain (0.20 inches) when deposits of bacteria are
washed into the creek.
It is anticipated that the majority of the stormwater discharge points should be
identifiable and associated pollutants treatable. The potential for non-point source
discharges is also probable, but it is anticipated they contribute only a small percentage of
the bacteria. This would indicate that the fall through spring period would offer the
lowest potential for high bacteria levels offering the least impact to the shellfish industry.
Upon analysis of the available water quality for the Creek, it appears that water
quality is most conducive to shellfish harvesting during seasonal periods, from fall through
late spring period optimal. Additionally, since bacteria levels drop towards the northern
end of the Creek, this section is more likely to support a certified shellfish area. The
addition of some form of stormwater treatment at key locations is also likely to reduce the
15
likelihood of the water quality at the Creek to exceed NYSDEC guidelines during heavy
rainfall events. This may permit the harvesting of shellfish without conditional closures.
Additional Water Ouality Sampling
In addition to the 15 regularly sampled stations, three additional rounds of water
quality sampling were conducted during July, August, and September of 1997, during
periods of heavy rainfall. These samples were collected by Southold Town Trustee Jimmy
King. The samples were collected at the road ends (or pipes) to obtain estimated values of
total and fecal coliforms that are being directly introduced into the Creek. Samples were
collected at subwatersheds 1 through 8 at the discharge points (identified by NYSDEC and
verified in the field).
Although this data is limited to only three sampling days, analysis of the data
provides useful insight as to the source of the coliform levels that are being monitored near
the center of the Creek. Both the July and August sampling periods contained data fxom
three different sampling events, while the samples for September was collected during just
one sampling event. Both fecal and total coliform levels were analyzed, and the arithmetic
means of these numbers appear in the tables below.
TABLE 2: Fecal Coliform Levels
Additonal Water Quality Samplin.q (at Road Ends)
Fecal Coliform Levels (in MPN/100 mi)
Date Corresoondino Subwatershed Number
1 2 3 4 5 6 7 8
7/24/97 4.783 40.533 18.200 2.053 28.333 28,333 4,655 5,850
8/18/97 8.867 941 32.100 2.450 31.333 26,433 5,900 4,900
9/11/97 93.000 43.000 9.300 15.000 75.000 240,001 46,000 3,900
TABLE 3: Total Coliform Levels
Additonal Water Quality Samplin.q {at Road Ends)
Total Coliform Levels (in MPN/100 mi)
Date Corres~ondino Subwatershed Number
I 2 3 4 5 6 7 8
7/24/97 24.767 55.100 196.667 40.533 240.001 124.667 230.047 240,001
8/18/97 196.667 81,500 196.667 198.867, 196,667 153,334 78,000 30,500
9/11/97 230.000 39.000 230.000 93.000 93.000 ,240,001 240,001 110,000
Mean 110,717 68,300 196,667 119,700 218,334'139~001 154,024 135,251
16
IX. Overview of Creek Impairments
The general focus of this study is to improve the water quality of Mattituck Creek.
Stormwater runoff from the roads and the developed properties has been identified by
NYDEC as the primary adverse impact on the water quality of the Creek. This water may
contain various kinds of organic and inorganic pollutants related to homeowner land use
and landscaping practices, highway maintenance, fanning practices, marinas and
recreational boat activity, and other practices. With residential development, the volume of
runoff discharging directly into surface waters may increase due to the introduction of
impermeable surfaces and the channeling of water onto those surfaces into the Creek. The
obliteration of natural drainage swales through thoughtless building practices and site
design can result in a change in the normal water recharge pattern within the watershed of
the Creek. In addition, the location of subsurface wastewater leaching pools between
shorefront homes and the water's edge means that high tides and storm tides can result in a
temporary influx of salt-water into the leaching systems with a subsequent outflow of
pollutants into the Creek waters.
There are two ways to classify impairment sources to any water body. One is point
source pollution, where the pollutant source can be directly identified. The other is non-
point source, where the pollution does not come from an easily identifiable source or
location. In order to discuss any mitigation measures for Mattituck Creek, further
discussion and understanding of these impairments must be defined and discussed. These
pollutant sources are discussed in detail below:
A. Possible Point Pollution Sources
As discussed above, point source pollution refers to water pollution that comes
from an identifiable source or location. Point source discharges are subject to the permit
requirements of the Clean Water Act. For the purposes of this study, point sources include:
land uses along the shorefront which potentially generate surface water contaminants (e.g.,
marinas, gas stations, etc.), processed wastewater discharges, or piped stormwater outfalls.
Road ends are discussed separately, and are not considered point sources in this report.
The following point pollution sources may be contributing to the degraded water quality at
Mattituck Creek:
1. Hazardous Materials
Historically, there were gasoline storage tanks just inside the mouth of the Inlet on
the west side of the Creek. These storage tanks have been removed and the soil has been
cleaned. Also, there are asphalt tanks that are situated directly across from the mouth of the
Inlet. These tanks contain a small amount of asphalt, but are no longer in operation. No
other hazardous materials information was gathered for this report, as it was out of scope
for the goals of the project.
17
2. Marinas and Boatyards
Mattituck Inlet and Creek supports four marinas. These provide a total of just
under 300 slips. The facilities and services that these marinas and boatyards provide are
discussed below:
Peterson's Dock
Located just inside the mouth of the inlet on the west side on a 3.4 acre parcel,
Peterson's Dock has about 30 slips, which are used by commercial and recreational
craft. The commercial boats include a trawler and half-a-dozen lobster boats. In
addition to the in-water slips, Peterson's has the only outside dry rack storage
facility on the Inlet. The dry rack capacity is about 60 craft. Upland uses on the site
include winter storage, staging areas for commercial operations and lobster trap
storage. Amenities provided include travel lift, electricity, water, ice, and basic
repair and fueling services. A launching ramp is available for public use for a fee.
Mattituck Inlet Fishing Station
Just south of Peterson's is the Mattituck Fishing Station, a 3 acre parcel with about
50 slips. This marina provides rental boats along with a bait and tackle shop, a
launching ramp available for a fee, gasoline fuel and rest rooms. This marina caters
to smaller craft in the under-20 to 30 foot range. There also is a residence on the
property.
Mattituck Inlet Marina and Shipyard
Mattituck Inlet Marina is a large full-service marina, located just south of the Old
Mill Road on the west side of Mattimck. Although it provides slips for seasonal
rental and limited transient use, one of its principal functions is full-service boat
maintenance and repair. There are seven large sheds on the upland portion of the
site, which are used for hull and engine repair, maintenance, paintIng, drying and
refinishing as well as winter storage. Outdoor winter and wet storage are also
provided. There are three travel lift stations with the capacity to handle boats of 30,
50, and 80 tons, and lengths up to 110 feet. The in-water docking capacity is about
78 slips. Amenities include showers and restrooms. Gasoline and diesel fuel also
is available. A pump-out station is proposed for this marina. This marina has also
installed a contalument with a drywell to retain waters, which are used in the
washing of the boats at the haul-out stations.
Matt-A-Mar Marina
Located at the eastern bank of the head of the creek, Matt-a-Mar marina is one of
the larger recreational marinas in the Town. It has about 90 to 100 slips, of which
close to 50 percent are used by transient croft. In conjunction with the federal
anchorage located nearby, this marina provides one of the main concentrations of
18
transient use within the inlet. Matt-a-Mar provides many recreational boating
amenities, with showers and restrooms, ice, and full-service repair. Matt-A-Mar is
reported to have a pumpout facility, however, it has not been available for use
according to a local fisherman. Also provided are a restaurant, an outdoor pool
with a cabana, and a kayak launching dock. In addition to outdoor winter storage,
the marina has the ability to store about 100 boats in its sheds. In-water wet storage
is available for about 25 craft.
B. Overview of Non-Point Pollution Sources
Non-point source pollution refers to water pollution that does not come from an
easily identifiable source or location. Non-point sources of pollution are more diffuse
and difficult to define than traditional point sources, which originate from "any
discemable, confined, and discrete conveyance, including but not limited to any pipe,
ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock,
concentrated animal feeding operation, or vessel or other floating craft, from which
pollutants are or may be discharged" (Section 502 (14) of the Clean Water Act). Non-
point sources are not subject to Federal permit requirements. Control of non-point
sources is a process that requires action by several agencies and individuals.
Non-point sources of water pollution contribute contaminants that seep, leak,
runoff, and rain into surface waters and groundwater. The complex runoff process
includes both the detachment and transport of soil particles and leaching and transport of
chemical pollutants. Chemicals can be bound to soil particles and/or be soluble in
rainwater. As the runoff moves, it picks up and can'ies away natural pollutants and
pollutants resulting from human activity, finally depositing them into lakes, rivers,
wetlands, coastal waters, and ground waters.
1. Agricultural
Historically, land use in areas such as Mattituck has been predominately
agricultural. Residential development has increased in this area, however, Mattituck
remains largely agricultural with a mixture of newer uses (i.e.: vineyards). The use of
fertilizers and pesticides has caused groundwater contamination in portions of the North
Fork where agricultural uses are prevalent. Excessive pumpage from irrigation has
resulted in the accelerated movement of pesticide and fertilizer contaminated
groundwater.
Pesticides/Herbicides
Pesticides and their degradation products may enter grotmd and surface water in
solution, in emulsion, or bound to soil colloids. Some types of pesticides are resistant to
degradation and may persist and accumulate in aquatic ecosystems. Certain pesticides
have been found to inhibit bone development in young fish or to affect reproduction by
inducing abortion. Herbicides in the aquatic environment can destroy the food source for
higher organisms, which may then starve. Herbicides can also reduce the amount of
19
vegetation for protective cover and the laying of eggs by aquatic species. Also, the decay
of plant matter exposed to herbicide-containing water can cause reductions in dissolved
oxygen concentrations (North Carolina State University, 1984).
The Suffolk County Department of Health Services (SCDHS) has conducted an
eighteen-month study (October 1997 through March 1999) to provide a comprehensive
examination of pesticide impacts on Long Island groundwaters. This study was analyzed
because of the significant amount of groundwater input feeding into Mattituck. Of all the
Suffolk and Nassau townships, the Town of Southold was found to have the greatest
pementage of pesticide-impacted wells (51%). Forty-eight wells in the community of
Mattituck had detectable levels of pesticides, metabolites, or nitrates (greater than the
MCL). Most of these 48 well samples had detectable levels of aldicarb (aldicarb
sulfoxide+sulfone, trade name Temik). The other pesticides within detectable levels
included nitrite (NO3), dieldrin, Edb (ethylene dibromide), TCPA (tetrachloroterephthalic
acid), metalaxyl, metolachlor, Simazine (herbicide), and 1,2-dichloropropane. Other
chemicals that were discovered during this study in wells at Mattituck included MTBE and
metribuzin.
Animal Waste
Animal waste, which contains nutrients and bacteria, including fecal coliform,
fecal streptococci bacteria and other pathogens, can be either a point or non-point source
of pollution. The more dispersed wastes of dogs, horses, and wildlife (including
waterfowl) are considered non-point sources because they originate in many dispersed
locations and are transported by stormwater runoff to surface waters and to groundwater.
Waterfowl are a significant source of coliform bacteria into numerous bay and other tidal
areas within Suffolk County. Non-point source pollution problems caused by waterfowl
are attributable to domestic White Peking Ducks that have been released, abandoned or
have escaped to coastal or inland ponds; semi-wild ducks, and the increasing populations
of Canada geese, mallard, and seagulls in certain areas. Migrating Canada geese utilize
agricultural fields as feeding and resting areas in the spring and fall. Runoff from these
fields can carry large amounts of fecal coliform and pathogens deposited by geese and
other migratory waterfowl. Runoff from fields receiving manure will contain extremely
high numbers of bacteria if the manure has not been incorporated or if the bacteria have
not been subjected to stress. Shellfish closure and beach closure can result from high
fecal coliform counts. Although not the only source of pathogens, animal waste has been
responsible for shellfish contamination in some coastal waters. The method, timing and
rate of application are significant factors in determining the likelihood that water quality
contamination will result. Manure is generally more likely to be transported in nmoff
when applied to the soil surface than when incorporated into the soil.
The presence of large, open, manicured grassy areas (i.e., golf courses, ballfields,
schools, etc.) can also indirectly contribute to pathogen levels, in addition to nutrient
loading (fertilizer) and pesticide and herbicide pollution of the receiving waterbody.
Presently, only the presence of pathogens has been identified. The greatest potential
source of pathogens associated with these areas would be those derived from Canada
20
goose droppings. In recent history, Canada geese have become less migratory, spending
entire winters in the northeast United States. These birds feed in large numbers on the
grasses associated with golf courses, ballfields, etc. During the grazing process, large
amounts of bird wastes are left behind which have the potential to be washed into the
estuary. Additionally, farm fields with unharvested or lost grain can also support large
populations of geese. In either case, it does not appear that adequate habitat exists to
support a large number of geese adjacent to Mattituck Creek.
Certain parts of Mattituck Creek, particularly Long Creek and Howard's Creek,
have been observed to be heavily utilized by waterfowl. Fecal wastes from these birds can
contribute significantly to the overall pathogen levels in the receiving waters. Recreational
feeding of waterfowl exacerbates the problem of fecal contamination by causing species
that would normally migrate northward during the spring to remain in the area year-round,
and by allowing populations to expand above normal levels due to easily obtainable food
supplies. Although no study has been undertaken in Mattituck Creek which assesses the
impact that waterfowl can have on water quality conditions, it is likely that waterfowl make
a significant contribution to coliform concentrations in this waterbody.
The control of waterfowl waste as a source of surface water contamination is a
particularly difficult problem to address. Signs can be posted at key locations to discourage
the introduction of artificial food supplies to waterfowl habitats. However, feeding
waterfowl is perceived as an acceptable form of recreation and interaction with wildlife by
humans. Furthermore, any future effort to moderate waterfowl populations in Mattituck
Creek must be undertaken in a manner that is consistent with the somewhat conflicting goal
of protecting the Creek's important natural resources, which includes those same
waterfowl. Waste composition varies with animal age, breed, sex, and feed. For example,
ducks produce about twice the daily volume of waste of humans, but more than five times
the fecal coliform bacteria.
Fertilizers
The three primary macronuthents used in fertilizers are nitrogen, phosphorus, and
potassium. Of the three primary macronutrients, nitrogen appears to be the major
groundwater contaminant. Often because of the complexities of varying soil
characteristics and plant requirements, more fertilizer is applied than the plant can use.
Since nitrate-nitrogen is highly soluble, the nitrogen that is not taken up by plants and
bacteria leaches out of the root zone and eventually reaches ground or surface waters.
Nitrate-nitrogen is highly mobile and can move readily below the crop root zone,
especially in the sandy soil characteristics of the North Fork.
The topsoil of a field is usually richer in nutrients and other chemicals because of
past fertilizer and pesticide applications, as well as nutrient cycling and biological
activity. Topsoil is also more likely to have a greater percentage of organic matter. Soil
eroded and delivered from cropland as sediment usually contains a higher percentage of
finer and less dense particles than the parent soil on the cropland. This change in
composition of eroded soil is due to the selective nature of the erosion process. This
21
selective erosion can increase overall pollutant delivery per ton of sediment delivered
because small particles have a much greater adsorption capacity than larger particles. As
a result, eroding sediments usually contain higher concentrations of phosphorus, nitrogen,
and pesticides than the parent soil.
In aquatic environments, nutrient availability usually limits plant growth. When
nitrogen and phosphorus are introduced into a stream, lake, or estuary at rates higher than
normal background or natural levels, aquatic plant productivity may increase
dramatically. This process, referred to as cultural eutrophication, may adversely affect the
suitability of the water for other uses. Increased aquatic plant productivity results in the
addition to the system of more organic material, which eventually dies and decays. The
decaying organic matter produces unpleasant odors and depletes the oxygen supply
required by aquatic organisms. Excess plant growth may also interfere with recreational
activities such as swimming and boating. Depleted oxygen levels, especially in colder
bottom waters where dead organic matter tends to accumulate, can reduce the quality of
fish habitat and encourage the propagation of fish that are adapted to less oxygen or to
wanner surface waters. Highly enriched waters will stimulate algae production, with
consequent increased turbidity and color. The increased turbidity results in less sunlight
penetration and availability to submerged aquatic vegetation (SAV). Since SAV provides
habitat for small or juvenile fish, the loss of SAV has severe consequences for the food
chain.
2. Urban
As urbanization occurs, changes to the natural hydrology of an area are inevitable.
Hydrologic and hydraulic changes occur in response to site clearing, grading, and the
addition of impervious surfaces and maintained landscapes (Schueler, 1987). Most
problematic are the greatly increased runoff volumes and the ensuing erosion and
sediment loadings to surface water that accompany these changes to the landscape.
Hydrological changes to the watershed are magnified after construction is completed.
Impervious surfaces, such as rooftops, roads, parking lots, and sidewalks decrease the
infiltrative capacity of the ground and result in greatly increased volumes of runoff.
Urban stormwater runoff is rainwater that collects on hard surfaces (i.e., roads,
parking lots, roofs, etc.) that is unable to leach back into the groundwater through the soil
and is therefore transported to the creek via a network of storm drains and culverts under
the roads. The runoff has the potential to collect pathogens fi.om several sources. One
contributor is the waste fi'om private pets. People fail to curb (pick-up) their pet's waste
(which is against the law) while walking the animal. This waste is eventually transported
to the creeks. Other sources of waste include animals (e.g., raccoons) which live in storm
drains and rock doves (pigeons) which roost under bridge overpasses. Another potential
source would be materials that leaked onto the road fi.om household refuse during the
collection process and is eventually transported to the creek by stormwater runoff. These
scenarios would appear to be the most likely in regard to the coliform loading of
Mattituck Creek. This is supported by data collected by the NYSDEC and reported in
their 1998 water quality sampling report.
22
Samples routinely failed the shellfishing standards at stations located at the
southern terminus of the creek. These stations are primarily located in the portion of the
creek with the greatest concentration of developed land. Additionally, some of the oldest
homes in the area and the greatest concentration of permanent residents are located at the
southern terminus of the Creek. Due to the lack of freshwater influx as a result of the
replacement of natural landscapes with impervious surfaces associated with development,
the headwaters of the creek have the potential to become stagnant. If this were the case,
the head waters would show a greater trend towards eutrophication which would be
evident by poor water quality (i.e., lower dissolved oxygen, turbid water, high nutrient
level, periodic plankton bloom, etc.). The episodic occurrence of high coliform counts
and the rapid drop off would also support the stormwater transport of pathogens. As
indicated by the relatively short temporary closures (i.e., seven days) mandated by the
NYSDEC, the presence of coliform bacteria is of a short-term nature.
Urban development also causes an increase in pollutants. As population density
increases, there generally is a corresponding increase in pollutant loadings generated
from human activities. These pollutants typically enter surface waters via runoff without
undergoing treatment. The major pollutants found in runoff from urban areas include
sediment, nutrients, oxygen-demanding substances, heavy metals, road salts, petroleum
hydrocarbons, pathogenic bacteria, and viruses.
Auto and track engines that drip oil are the source of most of the petroleum
hydrocarbon pollution found in urban runoff. Some polynuclear aromatic hydrocarbons
(PAHs) are known to be toxic to aquatic life at low concentrations. Hydrocarbons have a
high affinity for sediment, and they collect in bottom sediments where they may persist
for long periods of time and result in adverse impacts on benthic communities. Lakes and
estuaries are especially prone to this phenomenon.
A large portion of the developed residential acreage is in turf or other plantings
that require the use of fertilizers, pesticides, and herbicides that release nitrogen and
organic chemicals. Lawns are a major source of nitrates. Lawn irrigation may also impact
aquifers through the over-pumpage of the water supply.
Other impacts not related to a specific pollutant can also occur as a result of
urbanization. Temperature changes result from removal of vegetative cover, and increase
runoff across impervious surfaces. Impervious surfaces act as heat collectors, heating
urban runoff as it passes over impervious surfaces. Thermal loading disrupts aquatic
organisms that have finely tuned temperature limits. Salinity can also be affected by
urbanization. Freshwater inflows due to increased runoff can impact estuaries, especially
if they occur in pulses, disrupting the natural salinity of the area and leading to a decrease
in the number of aquatic organisms living in the receiving waters in some areas.
All aquatic organisms, from algae to the most complex plants or animals, respond
to changes in the environment. Responses may be due to either particular, non-recurring
stimuli, or rhythmic changes, which are usually related to recurring factors (such as tide
23
or day length) in the environment. Certain factors have especially pronounced effects;
light, temperature, dissolved oxygen, hydrogen ion concentration (pH), nutrient
availability, and solute concentration. An organism's response to one factor, such as
temperature, may alter its response to another, such as the presence of a solute in the
water making difficult to predict the results of a particular set of changes in the
environment. Tolerance to features of the environment varies widely among aquatic
organisms.
Such as often occurs with stormwater collected from urbanized areas, large inputs
of freshwater into a marine estuary resulting from storm events have the ability to disrupt
the natural salinity of an area and can lead to a decrease in the number of aquatic
organisms living in the receiving waters in certain areas. Changes in salinity can also
disrupt metabolic activity in animals. The salt concentration in the body fluids of most
marine invertebrates is nearly the same as that of the environment. These forms of
animals have a narrow salt tolerance and are restricted to regions of relatively stable,
near-seawater salinities.
The alteration of natural hydrology due to urbanization and the accompanying
runoff diversion, channelization, and destruction of natural drainage systems have
resulted in riparian and tidal wetland degradation or destruction.
3. Septics
Septic systems and cesspools are the most commonly used on-site sewage
treatment systems on Long Island. Pollutants from on-site systems include: nitrogen,
organic chemicals, metals, bacteria, and viruses. The nitrate found in the effluent from
on-site systems is highly soluble and moves easily through the soil to groundwater.
Nitrates discharged in shallow recharge areas can contaminate shallow aquifers and
surface waters.
Nitrogen from on-site systems can pose a threat to groundwater if housing
densities exceed one house per acre. On-site systems generally produce low pollution
loadings to groundwater in low-density residential areas such as the North Fork. In the
past, septic systems and cesspools were sometimes poorly sited, but now revised health
department regulations tend to eliminate this problem. Many septic systems or cesspools
were installed during the drought of the 1960's when the depth to grotmdwater was much
greater than it is now. With the recurrence of normal rainfall in the 1970's, the water
table rose and many leaching systems were flooded by groundwater and ceased to
fimction.
Many owners of on-site systems do not follow a preventative maintenance
program. More often than not, homeowner's do not have the septic tanks pumped out as
frequently as needed, thus allowing the sludge to flow to the leaching pool where it clogs
the infiltrative surface of the leaching pool and field. Unnecessary or toxic chemicals may
be poured into the system in an effort to avoid a pump out. Tree roots may also enter the
piping and leaching pool and eventually prevent proper functioning.
24
Septic systems can be a source of viruses and other pathogens to groundwater and
water supply wells. Bacteria, on the other hand, from septic systems do not appear to be a
significant problem because most bacteria are trapped in the soil or material within the
leaching field area. However, falling systems may contribute to high total coliform counts,
especially older systems located near coastal areas. The location of subsurface wastewater
leaching pools between shorefront homes and the water's edge means that high tides and
storm tides can result in a temporary influx of saltwater into the leaching systems with a
subsequent outflow of pollutants into the Creek waters.
4. Boats
Marinas and recreational boating are increasingly popular uses of coastal areas.
On Long Island, boating activities are an integral part of both an extensive marine-
commercial industry and a large recreational pastime. Boating activity brings with it a
potential for the discharge of human wastes and other pollutants into waters that are
utilized for recreational activities and shellfish harvesting. The most significant impact
from boating activities is the discharge of untreated and partially treated sanitary wastes
into Long Island waters. The discharge of boat wastes can result in elevated fecal
coliform counts, and nutrient and Biochemical Oxygen Demand (BOD) loadings.
Another important impact of boating activities is the contamination of benthic organisms,
finfish, and wetlands from oil products.
Sanitary boat wastes contain ammonia, nitrates, phosphorus, BOD, total solids,
suspended solids, and other pollutants similar to those generated by a household on land.
Untreated sanitary waste may also contain large numbers of fecal coliform and a number
of other types of bacteria and viruses. Shellfish that ingest the microorganisms discharged
from boat sanitary waste can become vectors for the transmission of diseases if the
concentration of pathogenic organisms in shellfish meats is substantial.
In addition to the health related problems, the introduction of sanitary waste into a
body of water can increase the concentration of oxygen-demanding substances, which
consequently reduce the amount of available oxygen for the metabolic needs of aquatic
organisms. The effect of boat sewage on dissolved oxygen (DO) can be intensified in
temperate regions because the peak boating season coincides with the highest water
temperatures and thus the lowest solubilities of oxygen in the water and the highest
metabolism rates of aquatic organisms.
The majority of the registered boats on Long Island are under 25 feet in length.
According to Coast Guard regulations they are not required to have sanitary facilities and
most do not. These boats tend to be used on a dally basis and those without sanitary
facilities discharge untreated wastes directly into coastal waters. The larger boats, 25 feet
in length or more, are required to have Marine Sanitation Devices (MSD's) and holding
tanks. Boats with holding tanks are required to discharge the wastes at approved pump-
out stations. There is one such pump-out facility in Mattituck Creek that accepts wastes
from boats during the boating season.
25
Hydrocarbon pollution from boating activities can also cause localized problems
in marinas and embayments. Careless or improper fueling practices and leaking fuel
tanks at marina fuel docks result in a large number of small spills that can severely affect
the aquatic environment in the immediate vicinity. Petroleum hydrocarbons tend to
adsorb to particulate matter and become incorporated into sediments. They may persist
for years, resulting in exposure to benthic organisms. The soluble fractions of oil can be
toxic, inhibitory, and, in some cases, stimulatory to marine phytoplankton; and have the
capacity to alter phytoplankton population structures.
Boat maintenance, and repair operations can also be sources of metals and
compounds that may be toxic to marine organisms.
5. Ou{fall Pipes Discharging Directly into the Creek
There are at least ten storm drainage outfall pipes emptying directly into Mattituck
Creek. The drains originate from County and Town roads as well as from private property.
The size of the outfall pipes range from 4 to 36 inches in diameter. These pipes are
believed to be a significant contributor to water quality impairments in the Creek. In
addition, several local streets terminate at the creek shorehne, allowing rainfall runoff to
enter directly into the creek. These roads include: Bayview Avenue, West Mill Road,
Knollwood Lane, The Anchorage, and Wickham Avenue. These pipes are considered non-
point source pollution because, according to the NYSDEC Water Resources Department,
there are no formal outfall pipes discharging into Mattituck Creek under SPDES (State
Pollutant Discharge Elimination System) permits.
6. Other
Highway Deicing
Highway deicing materials include salts, gravel, sandy soils, and other materials.
Sodium chloride is the most extensively used salt on Long Island. Improper storage and
highway application can cause a significant impact on the environment when salts
percolate through the soils and subsurface materials to the water table. Once in the
groundwater, both sodium and chloride ions are non-reactive and can persist for
centuries. They move with the general groundwater flow and can be carded down to
deeper aquifers that are used for public water supply. Runoff from roads can carry excess
salt into creeks and embayments leading to a temporary increase in the salinity and a
subsequent change in the physical character of the water body.
Sediments
Although not directly investigated as part of this project, sediments in Mattituck
Creek are strongly suspected to be an additional source of fecal coliforms, especially during
the summer. Other investigators have observed the accumulation of fecal coliform in
marine sediments (Rittenburg, et. al. 1958; Sayer, et.al. 1975; Von Donsel and Geldreich
26
1971, Volterra, et.al. 1985, all cited in Heufelder 1988). Heufelder (1988) found that
Buttermilk Bay, Massachusetts conta'ms sediments with the capacity to accumulate fecal
coliforms and that these bacteria can return to the water column by physically disrupting
the sediments. Heufelder (1988) further found that the accumulation of fecal coliforms in
the sediments was related to the organic content of the sediment and the proximity of the
area to a contamination source. Fine-grained highly organic sediment contained higher
fecal coliform concentrations.
Heufelder (1988) further found, based on his own work and the work of others,
that not only do sediments have the potential for protecting and accumulating fecal
coliforms, but they may also support their growth in proportion to the available nutrients.
He further concludes that this gives added implication to the input of nutrients from on-
site septic systems even if those systems are not directly contributing live bacteria to
surface waters.
Valiela, et.al. (1991) expanded on Heufelder's sediment work. They evaluated
the size of stocks of fecal coliforms in the water column, sediment and sea wreck in
Buttermilk Bay, and concluded that sediments contained most of the fecal coliforms.
They found that fecal coliforms in the sediments were as much as one order of magnitude
greater than in the water column or sea wrack and further that bacteria were so abundant
that re-suspension of fecal coliforms from just the top two centimeters of muddy
sediments could add sufficient bacteria to the water column to have the bay exceed the
shellfish standard.
These studies have applicability to Mattituck Creek. Buttermilk Bay, part of
Buzzards Bay in Massachusetts, is relatively similar to Mattituck Creek. Both water
bodies are geographically close to each other, support similar flora and fauna, areas
surrounded by similar development, experience similar climate and are geographically
somewhat similar. It is not unreasonable, then, to consider sediments as part of the
problem causing high non-rainfall bacteria levels in Mattituck Creek in the summer. The
increased survivability and growth of fecal coliforms in warm temperatures, and the
likelihood of increased re-suspension of sediments in the summer by increased boating
traffic (prop churn as well as wake), increased swimming and other anthropogenic
activity in and on the water, as well as scouring by tides, currents and waves can all
combine to produce the increased levels of coliforms.
However, there must be a source of fecal coliforms to the sediments to initiate this
process. Stormwater runoff in the watershed supplies a constant (storm-driven) source of
high numbers of fecal coliforms to colonize and grow in the sediments. Additionally,
stormwater is most likely a major source of fine-grained organic sediments to Mattituck
Creek. Stormwater runoff tan'les a large sediment load, much of it fine-grained and high
in organic content (from agricultural fields in the Mattituck watershed), to surface waters.
Also, stormwater runoff is a major source of nutrients which, according to the above
authors, contributes to the survival and growth of fecal coliforms in sediments.
Therefore, any measures which reduce stormwater runoff to Mattituck Creek will also act
to reduce the accumulation of fine-grained organic sediments, reduce the nutrient
27
loading, reduce the replenishing supply of fecal coliforms to the sediments and, therefore,
help to reduce fecal coliform levels in Mattituck Creek (Comell Cooperative Extension,
1995).
X. Addressing Water Quality Concerns
Pathogen loadings fi'om natural wildlife populations can be a substantial source of
water quality degradation in an area such as Mattituck Creek. However, human activities
in the coastal zone, especially land development, generally have an overriding effect on
natural contaminant inputs to stormwater discharges. Depending on the type of
development present, stormwater runoff can be a source of metals, organic compounds,
nutrients, or other contaminants, in addition to pathogens.
The water quality impairments in Mattituck Creek due to stormwater runoff that
have been discussed above can generally be addressed in two ways:
1)
Measures can be implemented to reduce contaminant loadings in the effluent
carded by individual stormwater discharges (e.g., outfalls, streams, etc.). This
approach treats stormwater runoff as a "point source", and typically involves
structural devices that address a relatively small portion of the entire
contributing watershed area, but which can be very effective in mitigating
acute, localized water quality problems.
2)
The rate of contaminant generation and transport in the upland areas can be
controlled through the use of "best management practices", public education
initiatives, and other non-structural means. This "watershed-wide" approach
treats stormwater runoff as a "non-point source", and typically involves
relatively inexpensive implementation measures.
The implementation of structural control measures (e.g., catch basins, leaching pool
systems, retention basins, etc.) can serve the multiple purposes of storing a specific volume
of stormwater, allowing the stored water to be recharged to groundwater, and creating
conditions by which sediment particles can settle out of suspension. The sedimentation
fimction of stormwater management structures is particularly important, since most
contaminants (including coliform bacteria and other pathogens) associate with fine-grained
sediment particles. As sediment is removed fi'om the stormwater, therefore, so too is a
large fi'action of the contaminants.
Conservation Choices
The key to successful conservation practices that lead to increased water quality in
a watershed is careful, complete planning. Several different conservation and
environmental farming practices have been identified by the U.S. Department of
Agriculture Natural Resources Conservation Service and are apphcable to the Mattituck
Creek watershed. Each practice will work most effectively in combination with others as
part of a total resource management system. These practices include:
28
Pasture Planting: This conservation practice entails planting grass and legumes to
reduce soil erosion and improve production. To accomplish this, one must drill or
broadcast adapted grass or legumes into a low-producing pasture or a steep, eroding
cropland field. This practice results in the heavy grass cover slowing the water flow, which
reduces soil erosion. Good pastures protect water quality by filtering nmoff water and
increasing infiltration.
Stream Protection: This conservation practice entails protecting a stream by
excluding livestock and by establishing buffer zones of vegetation to filter runoff. To
accomplish this, grass, riprap, gabious, catchment basins, and/or infiltration chambers are
installed along the edges of a stream to buffer the banks from heavy stream flow and
reduce erosion. A buffer zone of vegetation along the streambank filters runoff and may
also absorb excess nutrients and chemicals.
Crop Residue Management: Leaving last year's crop residue on the surface before
and during planting operations provides cover for the soil at a critical time of the year. The
residue is left on the surface by reducing tillage operations and turning the soil less. Pieces
of crop residue shield soil particles from rain and wind until plants can produce a protective
canopy. Ground cover prevents soil erosion and protects water quality.
Wetland Enhancement: Most wetland enhancement work includes small structures
built to add water or regulate waters in an existing wetland. Subsurface and surface drains
and tiles ar~ plugged. Concrete and earthen structures - usually dikes or embankments -
are built to trap water. These practices maintain a predetermined water level in an existing
wetland. Adjustable outlets allow the landowner to fluctuate the water level during
different seasons. Enhancement also includes planting native wetland vegetation if plant
populations need to be supplemented.
Crop Rotation: Crops are changed year by year in a planned sequence. Crop
rotation is a common practice on sloping soils because of its potential for soil saving.
Rotation also reduces fertilizer needs, because alfalfa and other legumes replace some of
the nitrogen that eom and other grain crops remove.
Nutrient management: After taking a soil test, setting realistic yield goals, and
taking credit for contributions fi-om previous years' crops and manure applications, crop
nutrient needs are determined. Nutrients are then applied at the proper time by the proper
application method. Nutrient sources include animal manure, sludge, and commercial
fertilizers. These steps reduce the potential for nutrients to go unused and wash or infiltrate
into water supplies.
Pest Management: Crops are scouted to determine type of pests - insects, weeds,
and diseases - and the stage of development. The potential damage of the pest is then
weighed against the cost of control. Finally, if pest control is economical, all alternatives
are evaluated based on cost, results, and environmental impact. Precaution is taken to keep
any chemicals from leaving the field by leaching, runoff or drift.
29
Water and Sediment Control Basin: An embankment is built across a depressional
area of concentrated water runoff to act similar to a terrace. It traps sediment and water
running off farmland above the structure, preventing it fi.om reaching farmland below.
Cover Crop: Crops including cereal rye, oats and winter wheat are planted to
temporarily protect the ground f~om wind and water erosion during times when cropland is
not adequately protected against soil erosion.
XI. Estimated Loading Rates for Potential Contaminants
To determine the adverse impacts that each subwatershed is contributing to
Mattituck Creek, coliform loading rates were quantified by multiplying total runoff by
mean fecal coliform level. These loading rates will aid in the determination of the priority
of each subwatershed and the subsequent conservation and mitigation choices that are
proposed for the subwatershed.
Nitrogen and phosphorus are indicators of pollution fi.om human activity. It is
impossible to quantify all system inputs such as concentrated effluent plumes due to non-
uniform subsurface flow, failing septic systems, large heavily used systems, underground
storage tanks or surface runoff into wells. However, since the water quality data in this
analysis focuses on coliform levels, these pollutant loadings will be more directly analyzed
and quantified.
The pollutant loading rates of each subwatershed were calculated using the
mathematical equations and conversions shown below:
Total volume of runoff:
43560 square feet/acre x 1 foot/12 inches = 3630 cubic feet/acreage in inches
Watershed acreage x Runoff depth x 3630 cubic feet/acreage in inches = X cubic feet
X cubic feet x 7.48 gallons/cubic feet = X gallons
Fecal Coliform Loading:
1 ounce = 29.57 ml
1 ounce/29.57 mL x 100 ml x 1 gallon/128 ounces = 0.02642 gallons
X gallons of runoff/0.02642 gallons per 100 ml x mean fecal coliform level (MPN)/100 ml
= MPN
MPN = Most Probable Number
The table below identifies the fecal coliform loading rates for each subwatershed.
The loading rates are calculated with the equation described above. The loading rate is a
30
useful indicator of the potential impact that each subwatershed has to Mattituck Creek (in
terms of feacl coliform input). The priority rankings (the column on the fight) were
determined by using an average of the three rainfall rates (1.0, 2.7, and 3.5 inches per day).
Once these numbers were averaged, a priority ranking was determined in descending order
(fi:om highest loading rates to lowest). This priority ranking is an important factor in
determining the overall ranking of the potential for mitigation projects in each
subwatershed. These loading rates allow the determination of the greatest amount of fecal
coliform reduction potential by subwatershed.
TABLE 4: Fecal Coliform Loading Rates
Fecal Coliform Loading Rates by Subwatersheds
Mean
Fecal
Coliform Total Vol. Fecal Coliform
Subwatershed Acres Level Rainfall Of Runoff Loading Rate PrioriW
Inches/24
MPN/100ml hrs. Gallons MPN
1 5.3
2 123.2 24 1.0 33452 3.03 * 10^7 1
2.7 2140912 1.94 * 10^9
3.5 3746597 3.4 * 10^9
3 69.4 34 1.0 0 0 3
2.7 716063 9.21 * 10^8
3.5 1413282 1.82 * 10^9
4 76.8 12 1.0 0 0 6
2.7 0 0
3.5 145971 66.3 * 10^6
5 23.8 14 1.0 0 0 5
2.7 32311 1.71 * 10^6
3.5 129245 6.85 '10^7
6 19.6
7 21.4 10 1.0 0 4
2.7 151076 5.72 * 10^7
3.5 331205 1.25 * 10^8
8 663.9 13 1.0 0 0 2
2.7 7390856 3.63 * 10^9
3.5 14421183 7.09 * 10^9
MPN = Most Probable Number
Fecal coliform loading rates were not determined for Subwatershed # 9 or # 10. There was
no corresponding water quality sampling location for Subwatershed # 10, so there was no
available data on fecal coliform levels. As discussed previously (and below), it was
determined that Subwatershed # 9 was isolated fi:om the Mattituck Creek watershed.
31
Determination of Hydrologic Factors of Subwatersheds
NRCS Technical Release 55 (TR~55) was used to estimate the hydrological
factors necessary for determining the amount of stormwater each subwatershed is
contributing to the entire Creek under separate storm events. TR-55 presents simplified
procedures to calculate storm runoff volume, peak rate of discharge, hydrographs, and
storage volumes required for floodwater reservoirs. These procedures are applicable in
small watersheds, especially urbanizing watersheds. The TR-55 model begins with a
rainfall amount uniformly imposed on the watershed over a specified time distribution.
Mass rainfall is converted to mass runoff by using a runoff curve number (CN). CN is
based on soils, plant cover, amount of impervious areas, interception, and surface storage.
Runoff is then transformed into a hydrograph by using unit hydrograph theory and
routing procedures that depend on runoff travel time through segments of the watershed.
Rainfall: A regional rainfall time distribution for a 24-hour period is included in
the TR-55 model. One critical parameter in the model is time of concentration, which is
the time it takes for runoff to travel to a point of interest from the hydraulically most distant
point.
Hydrologic Soil Groups: Soils are classified into four Hydrologic Soil Groups
(HSG's) (A,B,C, and D) according to their minimum infiltration rate, which is obtained for
bare soil after prolonged wetting. The HSG's are as follows:
A = Sand, loamy sand, or sandy loam - low runoffpotential and high infiltration rates even
when thoroughly wetted. Deep, well to excessively drained sands or gravels.
B = Silt loam or loam - moderate infiltration rates when thoroughly wetted and consist
chiefly of moderately deep to deep, moderately well to well drained soils.
C = Sandy clay loam - low infiltration rotes when thoroughly wetted and consist of soils
with a layer that impedes downward movement of water.
D = Clay loam, silty clay loam, sandy clay, silty clay, or clay - high runoff potential, very
low infiltration rates when thoroughly wetted.
Estimating Runoff: By increasing runoff and decreasing travel times, urbanization
can be expected to increase downstream peak discharges.
XII. Findings by Subwatershed
A. Background
As discussed previously, in 1986, the Southold Conservation Advisory Council
identified and mapped all known stormwater runoff sites in the Mattituck Creek area. This
map was updated in 1994, with completed drainage projects noted on the map. From these
identified stormwater rtmoff sites, water samples were collected at 16 locations within
32
Mattituck Creek. From these 16 sampling stations, eight were chosen that had the highest
coliform levels. The NRCS identified the 9 subwatersheds with identifiable outlets. These
subwatersheds coincided with eight of the sampling stations with one exception; there is a
substantial contributing area located west of Cox Neck Road south of sampling station # 5
referred to as Subwatershed # 9. Runoff from this watershed is reaching Cox Neck Road,
and flows over the road during severe storms, according to a local source. There is no
culvert pipe under the road at this location. A final subwatershed (Subwatershed # 10) was
identified and studied by EEA. However, since there was no corresponding water quality
sampling station, no pollutant loading rates were estimated. The boundaries of each
subwatershed were determined by using topographic surveys (Two-foot interval contour
maps), and by ground-trothing to distinguish the contributing drainage area of each
subwatershed. There are additional land areas within Mattituck watershed that contribute
to the Creek that are not addressed in this report. The reason these areas are not addressed
in the following part of this report is that these areas did not correspond to discrete outfall
locations identified by the NYSDEC. The Town may address these in a more generic
fashion by Best Management Practices or land use recommendations.
B. Prioritization List
Each of the ten subwatersheds were evaluated and given a priority ranking with
regard to the other subwatersheds. The major attributes that were considered were the
amount of contributing water to the entire Mattituck Creek watershed (using TR-55), the
interpretation of all available water quality data, the fecal coliform pollutant loading
rates, and an overall evaluation of the positive impacts that mitigation measures could
have on the subwatersheds. Priority was given to subwatersheds where a combination of
high pollutant loading rates, and the opportunity for a highly beneficial mitigation
measure existed.
33
Rank (According
Rank to Availability and
(according to Degree of
Average Beneficial
Pollutant Loading Rates for the Pollutant Mitigation
Subwatershed Following Storm Events (in inches) Loading Rates) Measures
1.0 2.7 3.5
1 8
2 3.03' 10^7 1.94' 10^9 3.4' 10^9 2 1
3 0 9.21 * 10^8 1.82' 10^9 3 5
4 0 0 66.3 * 10~ 6 4
5 0 1.71 * 10~6 6.85' 10^7 5 3
6 9
7 5.72' 10^7 1.25' 10^8 4 6
8 0 3.63' 10~ 7.09' 10^9 1 2
9 7 N/A
10 7
C. Project Practices by Subwatershed
Subwatershed 1
Practice Components Estimated Cost Timeline
Maintenance of Street cleaning and $185,000 Completed
existing structures catch basin
maintenance(AirVac
Truck)
Subwatershed 2
Practice Components Estimated Cost Timeline
Retention basins Raise inlet N/A Suffolk County
elevations of drop Dept. of Public
structure in swales Works to complete
within median of this project.
CR 48
34
Subwatershed 3
Practice Components Estimated Cost Timeline
Wet pond/retention Utilize large natural N/A Suffolk County
basin depression on the Dept. of Public
south side of CR 48 Works to complete
to accept runoff this project.
from CR 48
Subwatershed 4.
Practice Components Estimated Cost Timeline
Wetland Filtration Install a water $50,000 Not yet determined,
control structure on since this mitigation
the outlet culverts project was not
on Westphalia ranked highly
Avenue to divert
water into existing
wetland area
Subwatershed 5
Practice Components Estimated Cost Timeline
Storm Water Installation of new $50,000 Summer 2001
Drainage Facilities storm water
drainage facilities
underneath Cox
Neck Road
Subwatershed 6
Practice Components Estimated Cost Timeline
Maintenance of Street cleaning and $185,000 Completed
existing structures catch basin
maintenance
(AirVac Track)
35
Subwatershed 7
Practice Components Estimated Cost Timeline
Install catch Install catch $50,000 Not yet determined,
basins/infiltration basins/infiltration since this mitigation
chambers chambers along Mill project was not
Road ranked highly
Subwatershed 8
Practice Components Estimated Cost Timeline
Earth Berm Construct a berm at $50,000 To be completed in
the intersection of the Fall of 2001
Oregon and Mill
Road
Road run-off Replace the road-end $50,000 To be completed in
drainage project at the Old Grand the Fall of 2001
Ave. Bridge with
vegetation and catch
basins/infiltration
chambers
Subwatershed 9
This subwatershed does not contribute runoff to Mattituck Creek (as discussed in
the report).
Subwatershed 10
Practice Components Estimated Cost Timeline
Earth Berm Creating a berm at $25,000 To be completed in
Mill Road the Fall of 2001
D. Subwatershed Characteristics
Subwatersheds 1 through 10 are presented graphically in Figure 1, and the
corresponding areas of each are listed in the table below. This table also shows the fecal
coliform levels of the surface water samples fi.om 1998, as described previously. These
levels are important indicators for ranking the priority of each subwatershed for mitigation
projects. The mean slope was obtained using topographic maps. The major soil types were
obtained using Suffolk County Soil Conservation Service Soil maps. The depth to
groundwater was obtained using the Suffolk County Groundwater Contour Map.
36
Depth toiMajor Mean Fecal
Subwatershed Ground Soil Drainage Mean Coliform
Number Acreage water Type Class Slope Levels
(feet) 'Percent)MPN/I OOml
1 5.3 -5 Pi/Rd A/B 7 N/A
2 123.2 -5 Ha B >1 24
3 69.4 -5 C A >1 34
4 76.8 -5 C A 1.8 12
5 23.8 -5 Rd A 4.8 14
6 19.6 ~5 C/Rd A/B 8 N/A
7 21.4 ~5 C/Rd A/B/C 8 10
8 663.9 ~5 Ha B 3 13
9 N/A -5 Ha B 1.7 N/A
10 19,2 -5 C/PI/Rd A/B 3,4 N/A
1. Subwatershed #1
37
Photo Description
The photo above shows the discharge pipe that formerly extended directly off of
Knollwood Lane. This pipe has been removed and a series of catch basins have been
installed in the area where the road end used to exist.
Extent/Location
Subwatershed # 1 extends just north and south along Knollwood Lane and east
almost to Grand Avenue.
Topography and Depth to Groundwater
Based on interpretations made from the Suffolk County Department of Public
Works Topographic Maps (March, 1974), and the Suffolk County Department of Health
Services "Water Table Contours and Locations of Observation Wells in Suffolk County,
NY" map (March, 1997), the depth to groundwater was determined to be approximately
within five feet of the ground surface for this subwatershed.
The average slope within Subwatershed # 1 is approximately 7%. The overall pitch
in this subwatershed is from northeast to southwest, and the topography is fairly uniform.
The elevation of the high point is approximately 40 feet above mean sea level (MSL),
occurring near Grand Ave at the northeastern part of the subwatershed.
Land Uses and Land Coverage
Subwatershed #I consists of 5.3 acres. The land use within this subwatershed is
entirely residential.
Soil Types and Relationship to Runoff Generation
The soils within Subwatershed #1 are a mix of soils within the hydrologic zones A
and B. There are similar amounts of Plymouth and Riverhead soils within this
subwatershed. These soils indicate both sandy and sandy loam soils, which are both
relatively well-dralned soils. Therefore, the infiltration rotes within this watershed would
be a mix of infiltration versus nmoff compared to the entire watershed.
Documented and Identified Potential Contaminant Sources
There are no known documented or identified potential contaminant sources within
this subwatershed. However, this subwatershed is entirely residential, and formerly
Knollwood Lane was collecting the nmoff fi'om these house lots and directly discharging
this nmoff into the Creek via the discharge pipe in the above photo. The potential
contaminant sources include typical urban sources (e.g., pet wastes, auto wastes, lawn
fertilizers, etc.) as discussed earlier in the Non Point Source Pollution section.
38
Ouantitativel¥ Estimated Non-point Pollution Loads
The pollutant loading levels for Subwatershed # 1 were not calculated as there was
no corresponding sampling station.
PropertF Ownership
All of the property within Subwatershed #1 is privately owned, as of the printing of
this report.
Applicable Treatment Strategies
An additional pair of leaching pools may be installed in this subwatershed to handle
additional flows. However, the infiltration chambers described earlier would be an
excellent alternative. A major advantage to these units is that they can be installed in high
water table conditions and is applicable to this subwatershed. With as little as 12 to 18
inches of properly compacted backfill, the chambers are designed to withstand loads of up
to 32,000 pounds per axle.
Proiects Completed and Tentative Results
The road-end at Knollwood Lane was removed and replaced with vegetation. Two
catch basins were installed at this road-end also. Though there is no water quality data to
support the assumption that this project has been successful, anecdotal information
suggests that much of the stormwater that in the past had gone directly into the Creek is
now being infiltrated. The vegetation in this area has reached almost full cover, and local
residents who have witnessed heavy rainfall events say that the catch basins rarely
overflow. This indicates that a majority of the stormwater is being infiltrated.
2. Subwatershed #2
39
Photo Description
The photo above shows the culvert that extends beneath Wickham Avenue (looking
west). Matt-a-Mar Marina is on the right in the photo.
Extent/Location
The southern end of Subwatershed # 2 extends east and west along County Road
48. The subwatershed extends northward to just below Tuthill Road, and follows
Wickham Avenue north and south.
Topography and Depth to Groundwater
Based on interpretations made from the Suffolk County Department of Public
Works Topographic maps (March, 1974), and the Suffolk County Department of Health
Services "Water Table Contours and Locations of Observation Wells in Suffolk County,
NY" map (March, 1997), the depth to groundwater was determined to be approximately
within five feet of the ground surface for this subwatershed.
The topography within Subwatershed # 2 was uniform. The high point in elevation
was approximately 32 feet. The overall slope for this subwatershed is >l%.
4o
Land Uses and Land Coverage
Subwatershed #2 is the second largest watershed, consisting of 123.2 acres. The
predominant landuse is cultivated agricultural land (67 acres). These agricultural lands are
situated at the far end of the subwatershed. The outlet of this subwatershed into the creek is
intercepted by a small tidal marsh. There is also a significant amount of residences in this
subwatershed, in close proximity to the Creek. There is also a cow pasture and barnyard
north of CR 48. Stormwater drains via a swale across the cow pasture, into a Phragmities-
dominated wetland that is ditched, and into the Creek.
Soil Types and Relationship to Runoff Generation
The soils within subwatershed #2 are predominately within the hydrologic zone B.
There are substantial amounts of Haven soils within this subwatershed. These soils
indicate sandy loam soils, which are relatively less well-drained soils. Therefore, the
generation of runoff within this subwatershed would be relatively more, due to the low
amount of infiltration.
Documented and Identified Potential Contaminant Sources
The contributing runoff area includes a significant portion of County Road 48 (6.3
acres). Runoff generated from CR 48 is conveyed through storm drains and culverts, and
collects in a deep swale between CR 48 and the raikoad tracks, and a swale within the
median of the eastbound and westbound lanes of CR 48. These two swales are connected
via a culvert pipe and drop structure located in the median, which outlets into a cow pasture
on the north side of the road. There did not appear to be any vegetated filter strips between
the barnyard and the drainage swale. Livestock and/or their waste products may enter
surface runoff that enters the wetlands. According to the NRCS, the receiving wetland is
bisected by a surface ditch, which reduces the efficiency of this marsh in filtration of
stormwater and removal of dissolved or transported pollutants/wastes.
A significant agricultural area is located further upgradient in this subwatershed on
the east side of Mary's Road. This farmed parcel has the potential to contribute significant
sediment, nutrient and chemical loads to the receiving waters. This is exacerbated by the
fact that a natural drainage swale is located through the center of this farmland that is not
currently protected by permanent vegetation. Gullies develop annually in this swale,
indicating delivery of topsoil and sediment to downstream areas.
There are also a lot of waterfowl that have been observed along Long Creek, which is in
Subwatershed # 2. This subwatershed is situated at a point in Long Creek which has
relatively little flushing, compared to the rest of the watershed of Mattituck Creek.
Ouantitativel¥ Estimated Non-point Pollution Loads
41
The mean fecal coliform level for Subwatershed # 2 was calculated as 24 MPN/100
ml. These calculations were made from water quality data taken at sampling station 6.2.
The following pollutant loading calculations were estimated:
For a 1.0 inch rainfall:
Total volume of runoff: 33,452 gallons
Fecal coliform loading: 30,387,888 MPN
For a 2.7 inch rainfall:
Total volume of runoff: 2,140,912 gallons
Fecal coliform loading: 1.94 x 109 MPN
For a 3.5 inch rainfall:
Total volume of runoff: 3,746,597 gallons
Fecal coliform loading: 3.40 x 109 MPN
Subwatershed # 2 is the only subwatershed where there was substantial runoff
generated by a 1 inch rainfall in 24 hours. Although the fecal coliform loading rates are
higher in subwatershed # 8 for a 2.7 inch and 3.5 inch storm, subwatershed # 2 is having a
significant impact on bacteria loading trader all storm conditions.
Property Ownership
The County of Suffolk controls a drainage easement in this area located at section
107 block 19 lot 2.1. The rest of the subwatershed is privately owned, as of the printing of
this report. The NYSDOT is currently proposing the construction of a recharge basin on
the lots located north of CR 48.
Applicable Treatment Strategies
Subwatershed # 2 is the number one priority area and is where mitigation efforts
should concentrate. Mitigation efforts within this subwatershed should include measures to
reduce runoff and control erosion on cropland. Conservation management plans should be
developed with the landowners to address gully prevention, soil erosion control, nutrient
management, pest management and nmoff reduction. Farm conservation practices such as
crop rotations, contour farming, and cover and green manure crops will help to increase
crop residue in the soil, and reduce erosion and runoff. Field borders and filter strips will
filter runoff before it reaches the Creek. The construction of a sod waterway to convey
surface runoff through the natnral drainage swale would slow the stormwater to a non-
erosive velocity. This sod waterway would substantially reduce soil erosion and sediment
transport to the wetlands and Creek. Improved bamyard drainage, routing stormwater
around the barnyard, and maintaining/improving livestock fencing to keep animals from
entering drainage swales will also reduce the potential for livestock wastes to enter the
Creek. Pest management practices could be used to apply pesticides according to insect
thresholds determined through field scouting. Fertilizers should be applied according to
42
soil test results. Many of these practices are already being implemented, others are not.
Providing cost sharing assistance to implement these conservation measures will provide an
added incentive for participation. Grants may be applied for through the Environmental
Protection Fund with sponsorship from the Suffolk County Soil and Water Conservation
District.
A portion of County Road 48 falls within this subwatershed. It is conveyed through
storm drains and culverts and collects in a deep swale on the south side of CR 48, north of
the railroad tracks and a swale within the median of the east and west lanes. The two
swales could be used as additional stormwater detention areas simply by raising the inlet
elevations of the drop structure in the median and the culvert pipe connecting the two
swales. The feasibility of using these swales for ponding water, however, must be
approved by NYSDOT and the Long Island Rail Road.
For a 2-year storm, or a 3.5 inch rainfall event, the implementation of this project
would result in an approximate 0.4184 acre/feet of gained storage area. Using the pollutant
loading rates described earlier in this report (in "Estimated Loading Rates for Potential
Contaminants" section), this would be an approximate fecal coliform loading reduction of
1.2 x 108 MPN.
43
3. Subwatershed # 3
Photo Description
The photo above shows the discharge pipe that extends off of the comer of CR 48
and Westphalia Avenue, at the head of Mattituck Creek.
Extent/Locatio~
Subwatershed # 3 is 69 acres in size. This subwatershed consists mostly of County
Road 48, and portions of Youngs' Avenue and surrounding properties.
Topography and Depth to Groundwater
Based on interpretations made from the Suffolk County Department of Public
Works Topographic Maps (March, 1974), and the Suffolk County Depamnent of Health
Services "Water Table Contours and Locations of Observation Wells in Suffolk County,
NY" map (March, 1997), the depth to groundwater was determined to be approximately
within five feet of the ground surface for this subwatershed.
The stormwater converges from the east and west along CR 48 in Subwatershed #
3. The highest elevation in this subwatershed is approximately 46 feet above sea level,
which occurs along CR 48, at the western-most part of this subwatershed. The lowest
44
elevation of 3 feet above MSL occurs near the intersection of CR 48 and Westphalia
Avenue. The median watershed slope is very gentle, less than 1%.
Land Uses andLandCoverage
This subwatershed includes a significant drainage area (approximately 5 acres)
fi.om County Road 48. There are 16.5 acres of impervious areas in this watershed.
Soil Types and Relationship to Runq_ff Generation
The majority of soils within Subwatershed//3 are within hydrologic soil group A.
There are substantial amounts of Carver soils within this subwatershed. These are
relatively well-drained sandy soils. The generation of runoff within this subwatershed
would be relatively less than in Subwatersheds gl and #2, due to the high amount of
infiltration. However, County Road 48 also constitutes a significant portion of this
subwatershed. Much of the runoff fi.om this subwatershed comes fi.om pipes and storm
drains along this road. Therefore, the impelMous surfaces associated with CR 48and the
presence of the stormwater piping system would have a more significant impact in this
portion of the watershed than the soil types.
Documented and Identified Potential Contaminant Sources
Several outfall pipes were observed discharging directly to Mattituck Creek within
Subwatershed # 3. The origin of many of these pipe outfalls are not known, and thereby
are suspect. A high concentration of waterfowl was also observed in Subwatershed # 3.
Additionally, numerous smaller homes are concentrated at the head of the Creek. It is
unknown whether all subsurface septic systems are fully functional. Due to the shallow
groundwater conditions and proximity to the water's edge, it is likely that several of these
systems may be failing, thereby contributing to the nutrient and pathogen loads in the
Creek.
Ouantitativel¥ Estimated Non-point Pollution Load~
The mean fecal coliform level for Subwatershed # 3 was calculated as 34 MPN/100
mi. These calculations were made fi'om water quality data taken at sampling station 6.1.
The following pollutant loading calculations were estimated:
For a 1.0 inch rainfall:
Total volume of runoff.' 0.0 gallons
Fecal coliform loading: MPN
For a 2.7 inch rainfall:
Total volume of runoff.' 716,063 ~gallons
Fecal coliform loading: 9.21 * 10°MPN
For a 3.5 inch rainfall:
45
Total volume of runoff: 1,413,282 gallons
Fecal coliform loading: 1.82 * l09 MPN
Property Ownership
A portion of this watershed is Town (Trustee's) property and currently constitutes
the parking lot area adjacent to the boat ramp. This area is immediately south of the Creek.
The rest of the subwatershed is privately owned, as of the printing of this report.
Applicable Treatment Strategies
A large natural depression exists on the south side of Route 48 directly south of
Shirley Road, section 122 block I lot 2.2. If an easement could be obtained, this depression
could accept a significant amount of the runoff generated and conveyed by County Road
48. The depression would require alteration/engineering to handle the runoff.
It is also recommended that dye-testing be conducted for two outfall pipes which
flow directly into the Creek. The original design plans for the pipes cannot be located, so it
would be very important to know where the water is originating that is directly entering the
Creek.
4. Subwatershed # 4
46
Photo Description
The photo above shows the culverts extending directly into Mattituck Creek,
carrying nmoff from Westphalia Avenue. A natural wetland area exists on the opposite
(west) side of Westphalia Avenue (upper left on the photo above). This wetland is a
brackish marsh, and there is a significant amount of Phragmities australis growth
throughout the marsh. The lower corrugated metal pipe seen in this photo provides the
hydraulic connection between the wetland opposite Westphalia Avenue and the creek.
Extent/Location
Subwatershed # 4 encompasses 76.8 acres. The northerly and easterly boundaries
of this subwatershed coincide, for the most part, with Westphalia Avenue. This
subwatershed extends south along Cox Neck Road, and through the residential area,
through Cindy and Pat Lanes.
Topography and Depth to Groundwater
Based on interpretations made from the Suffolk County Department of Public
Works Topographic Maps (March, 1974), and the Suffolk County Department of Health
Services "Water Table Contours and Locations of Observation Wells in Suffolk County,
NY" map (March, 1997), the depth to groundwater was determined to be approximately
within five feet of the ground surface for this subwatershed.
The topography is uniform in Subwatershed # 4. The high point in the elevation is
approximately 51 feet above sea level. There are no noticeably steep slopes, and the
overall slope is approximately 1.8%.
Land Uses and Land Coverage
Subwatershed # 4 cOnsists primarily of woodlands. There is also a significant
amount of residential areas within this subwatershed.
Soil Types and Relationship to Runoff Generation
The soils within Subwatershed #4 are predominately within the hydrologic zone A.
There are substantial amounts of Carver soils within this subwatershed. These soils are
relatively well-drained. Similar to Subwatershed #3, the generation of nmoff within this
subwatershed would be relatively less than in Subwatersheds #1 and #2, due to the high
amount of infiltration.
Documented and Identified Potential Contaminant Source.*
Besides the typical contaminant sources that are associated with a relatively large
amount of residential area, there are no known documented or identified potential
contaminant sources in this subwatershed.
47
Ouantitativel¥ Estimated Non-point Pollution Loads
The mean fecal coliform level for Subwatershed # 4 was calculated as 12 MPN/100
ml. These calculations were made from water quality data taken at sampling station 6.3.
The following pollutant loading calculations were estimated:
For a 1.0 inch rainfall:
Total volume of runoff.' 0.0 gallons
Fecal coliform loading: MPN
For a 2.7 inch rainfall:
Total volume of runoff.' 0.0 gallons
Fecal coliform loading: MPN
For a 3.5 inch rainfall:
Total volume of runoff.' 145,971 ~gallons
Fecal coliform loading: 66.3 * 10v MPN
Property Ownership
All of the property within Subwatershed g4 is privately owned, as of the printing of
this report.
Applicable Treatment Strategies
The two culverts, which currently discharge road runoff directly into Mattituck
Creek, should be removed/replaced with a catch basin inlet structure fitted with a
sediment trap (either in a series or at the base of the structure) to provide some
stormwater pre-treatment prior to discharge. These catch basins should also be connected
to a conveyance system which re-routes the stormwater to the in wetland area on the west
side of Westphalia Avenue, thereby providing additional filtration prior to ultimate
discharge into Mattituck Creek. The wetland area located on the west side of Westphalia
Avenue could also be used to increase stormwater detention time and provide natural
filtration. This could be accomplished by installing a water control structure on the outlet
culvert, which would raise the outlet elevation several inches. This treatment would
require a detailed engineering survey and design to ensure that adjacent properties are not
flooded and that the character of the natural wetland is not significantly impacted. The
necessary easements would have to be obtained. There are a series of catch basins
collecting stormwater runoff off Bennets Pond Lane, which presumably discharge into
this wetland area. These systems should be examined further to determine whether
improved sediment control is needed. Restoration of the upper marsh utilizing plants
such as smooth cordgrass (Spartina alterniflora), which filter and cleanse stormwater
rtmoff, would be ideal for this subwatershed.
48
5. Subwatershed # 5
Photo Description
The photo above shows the culvert that directly discharges the stormwater runoff
from Cox Neck Lane (just west of Breakwater Road) into Howard's Creek (a tributary of
Mattituck Creek).
Extent/Location
Subwatershed # 5 encompasses 23.8 acres. This subwatershed extends north and
south along Cox Neck Road (which tums into Mill Road) as far south as Bergen Avenue,
and north along Luthers Road almost as far as Stanley Road.
Topograph¥ and Depth to Groundwater
Based on interpretations made from the Suffolk County Department of Pubhc
Works Topographic Maps (March, 1974), and the Suffolk County Department of Health
Services "Water Table Contours and Locations of Observation Wells in Suffolk County,
NY" map (March, 1997), the depth to groundwater was determined to be approximately
within five feet of the ground surface for this subwatershed.
49
The topography in Subwatershed # 5 is relatively moderate, with an approximate
slope of 4.8%. The high point in elevation for this subwatershed is approximately 47.5 feet
above mean sea level.
Land Uses and Land Coverage
The land use within this subwatershed is entirely residential.
Soil Types and Relationship to Runoff Generation
The soils within Subwatershed #5 are predominately within the hydrologic zone A.
There are substantial amounts of Riverhead soils within this subwatershed. These soils are
sandy and relatively well-drained. Therefore, the generation of runoff within this
subwatershed would be relatively low, due to the high amount of infiltration.
Documented and Identified Potential Contaminant Sources
Besides the contaminant sources that are typically associated with relatively large
residential areas, there are no known documented or identified potential contaminant
sources in this subwatershed.
During one site inspection, however, "grey" water was observed at the outlet end of
the culvert from Cox Neck Lane. The water also had a noticeable rancid odor, and suds or
flocculent was observed floating in Howards Creek towards the direction of Mattituck
Creek. This may represent an isolated incident or be indicative of a chronic pollution
problem, and should be investigated further.
Ouantitativelv Estimated Non-point Pollution Loadv
The mean fecal coliform level for Subwatershed # 5 was calculated as 14 MPN/100
ml. These calculations were made from water quality data taken at sampling station 7.1.
The following pollutant loading calculations were estimated:
For a 2.7 inch rainfall:
Total volume of runoff: 32,311 gallons
Fecal coliform loading: 1.71 * 106 MPN
For a 3.5 inch rainfall:
Total volume of runoff: 129,245 .gallons
Fecal coliform loading: 6.85 * 10'MPN
It should be noted that the loading rates presented above reflect long-term readings
taken at the NYSDEC sampling stations shown in Figure ~ and do not account for the
coliform loads sampled at the pipe outfalls as presented in Tables 2 and 3 (Part 1 of this
report). Isolated releases of "grey" water or suspect wastewater, such as described above,
may also not be reflected in these mean bacterial loading estimates.
50
Propert~ Ownership
All the property within Subwatershed #5 is privately owned, as of the printing of
this report.
Applicable Treatment Strategies
Stormwater from Cox Neck Road could be diverted into the existing wetland area
with the installation of curb inlet catch basins with sediment pits and manholes for clean-
out (at the terminus of Howard's Creek) northwest of Cox Neck Road. This wetland is
primarily freshwater, and supports a significant stand ofPhragmities australis.
Currently, the culvert that runs underneath Cox Neck Road is acting as a water control
device due to the accumulation of leaf litter and sediments in the culvert. The litter and
sediments should be removed and replaced with an engineered water control structure, so
that a desired water level and release rate can be achieved. Thus, the wetland can serve
an additional function as a stormwater detention pond. An altemative treatment strategy
would include the installation of two sets of curb inlet catch basins containing sediment
pits along Cox Neck Road, to the east and west of the existing inlet structure. Manholes
should be provided for maintenance access to the sediment pits for the grit removal.
These structures would then drain to a series of infiltration basins located below the
grassy area between the existing inlet and the creek. These infiltrations will provide pre-
treatment to road runoffprior to discharge to the creek. The installation ora series of
catch basins and leaching pools to intercept roadway runoff fi-om Rosewood Drive and
Luther's Road will help to reduce the total capacity needed in the infiltrators at Cox Neck
Road.
51
6. Subwatershed # 6
Photo Description
The photo above shows the end of Bayview Ave., where one of the mitigation
projects, funded by NYSDEC was implemented. This photo was taken during a rain
event, where the runoff can be observed being delivered into the catch basins, as opposed
to running directly into the Creek. This treatment has been observed to be successful in
catching most of the runoff for the majority of the rain events.
Extent/Location
Subwatershed # 6 surrounds Bayview Ave. on the west side of the Creek. This
subwatershed extends to Cedar Drive to the west, and just into the Shore Acres
development.
Topography and Depth to Groundwater
Based on interpretations made from the Suffolk County Department of Public
Works Topographic Maps (March, 1974), and the Suffolk County Department of Health
Services "Water Table Contours and Locations of Observation Wells in Suffolk County,
NY" map (March, 1997), the depth to groundwater was determined to be approximately
within five feet of the ground surface for this subwatershed.
52
The approximate slope in Subwatershed #6 is 8%. The highest point in elevation is
approximately 5 l0 feet above sea level.
Land Uses and Land Coverage
The land use within Subwatershed # 6 is residential adjacent to the Creek, and
agriculture further away from the Creek.
Soil Types and Relationship to Runqff Generation
The soils within Subwatershed #6 are a mix of soils within the hydrologic zones A
and B. There are similar amounts of Carver and Riverhead soils within this subwatershed.
These include both sandy and sandy loam soils, which are both relatively well-drained
soils. Therefore, the runoff generation rates within this watershed would be relatively low,
due to the high degree of infiltration.
Documented and Idento~ed Potential Contaminant Sources
Besides the typical contaminant sources that are associated with relatively large
residential areas (i.e., cesspool overflow, lawn chemicals), there are no known documented
or identified potential contaminant sources in this subwatershed.
Quantitatively Estimated Non-point Pollution Loads
The pollutant loading levels for Subwatershed # 6 were not calculated, as there was
no corresponding NYSDEC sampling station in Mattituck Creek.
Propert~ Ownership
All of the property within Subwatershed #6 is privately owned, as of the printing of
this report.
Applicable Treatment Strategies
If the mitigation measure discussed above is not adequate to handle the average
storm flow conditions, a series of infiltration chambers could be added to increase the
capacity. However, local residents have observed that the catch basin system that has been
installed appears to accept the runoff fi'om all but the heaviest storm events.
Projects Completed and Tentative Results
The road-end at Bayview Ave. was removed and replaced with vegetation. Two
catch basins were installed at this road-end also. Though there is no water quality data to
support the assumption that this project has been successful, anecdotal information
suggests that much of the stormwater that in the past had gone directly into the Creek is
53
now being infiltrated. Local residents who have wimessed heavy ra'mfall events say that
the catch basins rarely overflow. This indicates that a majority of the stormwater is being
infiltrated.
7. Subwatershed # 7
Photo Description
The photo above shows sheet flow runoff during a rain event traversing across
West Mill looking west. Note the berm on the right of the photo that was built to
discourage flooding of the property at right, but which results in increased volume and
velocity of runoff.
Extent/Location
Subwatershed #7 is only 21 acres in size. This subwatershed extends southward
from West Mill and Naugles Roads.
Topography and Depth to Groundwater
Based on interpretations made from the Suffolk County Department of Public
Works Topographic Maps (March, 1974), and the Suffolk County Department of Health
Services "Water Table Contours and Locations of Observation Wells in Suffolk County,
54
NY" map (March, 1997), the depth to groundwater was determined to be approximately
within five feet of the ground surface for this subwatershed.
The slopes in subwatershed # 7 are relatively moderate to steep, averaging 6
percent or more along the flow path of West Mill Road. The highest point in elevation is
approximately 64.5 feet above sea level. The overall slope throughout this subwatershed is
approximately 8%; however, there are steep slope sections characterized by a 25-foot drop
in elevation with a 100-foot linear distance adjacent to the Creek.
Land Uses and Land Coverage
A portion of this subwatershed is residential; however, the predominant land use is
pasture/grassland (13.8 acres). Also included within this subwatershed are two marinas;
Captain Bob's Fishing Station and Mattituck Inlet and Marina.
Soil Types and Relationship to Runoff Generation
Soils within Subwatershed # 7 vary between hydrologic zones A and C. A
significant portion of this subwatershed is classified as "C"; while there is also a large
amount of Riverhead (Zone B) and Carver (Zone A). Such a mix of soil types makes it
difficult to determine the relationship to runoff generation, as part of this watershed would
be well-drained, and an approximately equal part would be more susceptible to runoff.
Documented and Identified Potential Contaminant Sources
Besides the contaminant sources that are typically associated with residential areas
and marinas, there are no known documented or identified potential contaminant sources in
this subwatershed.
Quantitatively Estimated Non-point Pollution Loads
The mean fecal coliform level for Subwatershed # 7 was calculated as 10 MPN/100
ml. These calculations were made fi.om water quality data taken at sampling station 4.1.
The following pollutant loading calculations were estimated:
For a 2.7 inch rainfall:
Total volume of runoff.' 151,076 ~[allons
Fecal coliform loading: 5.72 * 10' MPN
For a 3.5 inch rainfall:
Total volume of runoff.' 331,205 gallons
Fecal coliform loading: 1.25 * 10~MPN
Propert~ Ownership
55
All the property within Subwatershed #7 is privately owned, as of the printing of
this report.
Applicable Treatment Strategies
The installation of a series of catch basins and drywells along West Mill Road
would help reduce roadway runoff from directly entering Mattituck Creek by intemepting
and percolating it into the ground higher up in the watershed. Such engineered systems
should replace all existing culverts and road edge drainage systems along West Mill Road
which currently discharge road runoff overland directly into the creek. A more cost
effective method would be to install infiltration chambers to act as storage and infiltration
sites. These units consist of high density polyethylene chambers designed to store rtmoff
underground. The chambers have an open bottom and permeable sides to promote
infiltration. They can be linked together to increase capacity and are designed to replace
traditional catch basins. They are cost effective, easy to install and provide effective
treatment where pollutants are removed by adsorption, straining or decomposition by
bacteria in the soil.
The existing curb inlet at the base of West Mill Road is partially located below a
retaining wall, and difficult to mainta'm properly. There did not appear to be any
manhole in line with the drainage system to enable sediment cleanout. The installation of
a sediment trap or grit chamber that can be cleaned out periodically would improve the
effectiveness of stormwater pretreatment. Also, the bulkhead along Mattituck Creek
appears to be threatened by uncontrolled stormwater, which has washed out soil behind
the bulkhead. This will threaten the longevity of the bulkhead and connective measures
should be taken promptly.
In line with the Board of Trustees' Policy of Pump-Out Stations, Mattituck Inlet
and Marina is scheduled to install a pump-out facility per the considerations of their
bulkhead repair program. Additional stormwater controls and BMP's could be
implemented at Captain Bob's Fishing Station to further improve Creek water quality.
The Town Trustees may seek to develop a cooperative drainage improvement project
with this facility.
8. Subwatershed # 8
56
Photo Description
The photo above depicts a water control structure that was installed in a natural
drainage swale located south of Wickham Avenue. Tlfis structure was designed by the
USDA NRCS and installed with the cooperation of the Suffolk County Soil and Water
Conservation Service. This water control structure is at the northern part of a drainage-way
easement owned by the Town.
Extent/Location
Subwatershed # 8 is by far the largest of the subwatersheds, totaling 667 acres.
This subwatershed includes all areas north of Wolf Pit Lake (including the Long Creek
tributary), east to Elijah's Lane, and west to approximately Reeve Avenue. The
northernmost boundary of this subwatershed is approximately Sound View Avenue.
Topography and Depth to Groundwater
Based on interpretations made from the Suffolk County Department of Public
Works Topographic Maps (March, 1974), and the Suffolk County Department of Health
Services "Water Table Contours and Locations of Observation Wells in Suffolk County,
NY" map (March, 1997), the depth to groundwater was detemfined to be approximately
within five feet of the ground surface for this subwatershed.
57
The topography in Subwatershed # 8 is relatively uniform, except for a large natural
drainage swale occurring south of East Mill/Oregon Road. Much of this swale is wooded
and leads to a marsh area. There is channelized flow within this swale. The swale has
slopes of approximately 5%. The highest point in the subwatershed is approximately 105
feet above sea level.
Land Uses and Land Coverage
The predominant land use is intensive agricultural production including potatoes,
com, and other mixed vegetables.
Sod Types and Relationship to Runoff Generation
The soils within Subwatershed #8 are predominately within the hydrologic zone B.
There are substantial amounts of Haven sandy loam soils within this subwatershed, which
are relatively less well-drained soils. Therefore, the mnoff generation within this
subwatershed would be relatively higher than in subwatersheds #3 and g4, due to the low
amount of infiltration.
Documented and Identified Potential Contaminant Sources
Waterfowl f~equent Long Creek, which is where this sampling station is located.
Also, there is a concentration of residential properties adjacent to the Creek within this
subwatershed. The large agricultural area within this subwatershed also potentially
provides a significant source of pesticides, fungicides, sediment, and possibly coliforms
(t~om soil, live stock, etc.)
Ouantitativel¥ Estimated Non-point Pollution Loads
The mean fecal coliform level for Subwatershed # 8 was calculated as 13 MPN/100
ml. These calculations were made fi.om water quality data taken at sampling station 8. The
following pollutant loading calculations were estimated:
For a 2.7 inch rainfall:
Total volume ofnmoff: 7,390,856 gallons
Fecal coliform loading: 3.63 * 109 MPN
For a 3.5 inch rainfall:
Total volume of runoff.' 14,421,183 gallons
Fecal coliform loading: 7.09 * 109 MPN
Property Ownership
Most of Subwatershed #8 is privately-owned property. There are also some large
parcels on the western part of the subwatershed that are designated as "County
58
Development Rights". In the southeast of the subwatershed, there are two large parcels of
"Town Development Rights". A relatively small portion of property designated as
"Subdivision Open Space" exists at the western part of the subwatershed. Finally, there are
two relatively small parcels of property designated as "Town Owned" in the southwest
portion of Subwatershed #8. The Town also has a drainageway easement south of Mill
Road.
Applicable Treatment Strategies
There are several areas within this subwatershed where conservation practices
might be installed to reduce the volume and rate of runoff entering Long Creek. The first
location falls within the existing drainage easement area between Lots 1 and 2 of Section
100, Block 5. A dam could be constructed across the drainageway with a water control
structure to detain and slowly release the accumulated nmoff at a rate that will allow for
sediment settling and bacteria reduction.
The second site is located within the triangular piece of property botmded by East
Mill Road/Oregon Road and Mill Lane (Section 100, Block 5, Lot 1). This small area
could be used for sediment retention and as a recharge basin. Due to the relatively small
size of this area, the basin would have to be designed to allow runoff to pass through
during intense storms. Its major function would be to reduce sediment and runoff during
low flow storm conditions. The Town may wish to consider closing the southerly road
on this triangle, to gain additional area for construction of such a basin.
The third site is located within the drainageway of Section 100, Block 2, Lot 4.
This field has already been laid fallow due to the high erosion potential when actively
farmed. A dam similar to site 1 could be constructed to detain and treat runoff. Since
sites 2 and 3 are on private property, easements would have to be obtained before
proceeding with any of this work. The fourth area where measures could be implemented
is within the cropland. These fields could be treated in much the same way as in
Subwatershed # 8. If cost share assistance is provided, there is a much greater chance of
obtaining farmer participation.
There are two road ends of Grand Avenue that currently deliver roadway runoff
directly into Long Creek. The Town is currently considering closing the southerly road
and just below the existing residential driveways in order to provide enough area to
accommodate installation of a series of leaching pools, similar to the treatment utilized at
the end of Bayview Avenue in Subwatershed #6. The grade above these structures could
be restored with plantings of native groundcovers to provide an enhanced vegetative
buffer. The northerly road end of old Grand Avenue could receive a similar treatment,
with leaching pools installed to the west side of the existing road end. A low-profile
bulkhead could be considered seaward of the infiltration area, to create a perched beach
for intertidal marsh restoration. This combined treatment would not only provide needed
stormwater control; it would also increase marine aquatic habitat, reduce shoreline
erosion and improve water quality in Long Creek.
59
9. Subwatershed # 9
Extent/Location
Subwatershed # 9 encompasses 118 acres, and extends westerly fi.om Cox Neck
Road along Bergen Avenue.
Topography and Depth to Groundwater
Based on interpretations made from the Suffolk County Department of Public
Works Topographic Maps (March, 1974), and the Suffolk County Department of Health
Services "Water Table Contours and Locations of Observation Wells in Suffolk County,
NY" map (March, 1997), the depth to groundwater was determined to be approximately
within five feet of the ground surface for this subwatershed.
The topography in Subwatershed # 9 is fairly uniform. The overall slope is
approximately 1.7%. The high point in elevation in this subwatershed is approximately 53
feet above sea level.
Land Uses and Land Coverage
The land use within this subwatershed is predominately agricultural.
Soil Types and Relationship to Runoff Generation
The soils within Subwatershed #9 are predominately within hydrologic zone B.
There are substantial amounts of Haven sandy loam soils within this subwatershed, which
are relatively less well-drained than the soils occupying other subwatersheds in this study.
Therefore, the runoff generation would be slightly higher, due to the reduced permeability
of the surface soils.
Documented and Identified Potential Contaminant Sources
There are no known documented or identified potential contaminant sources in
Subwatershed # 9.
Quantitatively Estimated Non-point Pollution Loads
Pollutant loads were not quantitatively estimated for this subwatershed, since rtmoff
seldom hms over Cox Neck Road, and does not discharge directly into Mattituck Creek.
PropertF Ownership
A little more than half of Subwatershed #9 is privately-owned property. A
relatively large portion (encompassing just under one-half the subwatershed) is designated
as "Town Development Rights (Partial)" property.
60
Applicable Treatment Strategies
Subwatershed # 9 has been given the lowest priority for mitigation measures.
There is a relatively large natural drainage basin located on the west side of Cox Neck
Road, which seldom, if ever, flows over Cox Neck Road. There is no culvert under the
road and there is a 7.9 fl. elevation difference between the road shoulder and the lowest
point in the drainage basin. There is a house located directly north of the basin that
would receive two feet of water in the basement if the runoff topped Cox Neck Road.
There is no indication that the house is flooded on a regular basis. Cox Neck Road
appears to be acting as a dam for this subwatershed.
10. Subwatershed # 10
Photo Description
The photo above shows the runoff (containing a significant amount of silt)
emanating from the farmland located north of East Mill Road. This photo was taken on
East Mill Road, looking west and downhill towards Mattituck Creek. This runoff collects
into a pipe on the southerly road bank, and flow is channelized down a natural swale
which discharges directly into the Creek.
61
Extent/Location
Subwatershed # 10 extends eastward to Reeve Avenue, and extends north and south
of East Mill Lane. This subwatershed encompasses 19.2 acres.
Topography and Depth to Groundwater
Based on interpretations made from the Suffolk County Department of Public
Works Topographic Maps (March, 1974), and the Suffolk County Department of Health
Services "Water Table Contours and Locations of Observation Wells in Suffolk County,
NY" map (March, 1997), the depth to groundwater was determined to be approximately
within five feet of the ground surface for this subwatershed.
The topography within Subwatershed #10 is fairly uniform, except for a drainage
swale that hms along East Mill Road and extends southwest to the Creek. The highest
point in elevation is approximately 67 feet above sea level. The average slope in this
subwatershed is approximately 3.4%.
Land Uses and Land Coverage
The predominant land use within Subwatershed # 10 is row crops (9.2 acres).
There is also a significant amount of woods in this subwatershed (7.79 acres). A portion of
this watershed is also occupied by a nursery operation which grows stock primarily in
covered hoop houses and greenhouses.
Soil Types and Relationship to Runqff Generation
The soils within Subwatershed #10 are a mix of soils within hydrologic zones A
and B. There are similar amounts of Carver and Plymouth Sands, and there is a large
portion of Haven sandy loam soils within this subwatershed. These soils are relatively
well-drained. Therefore, the runoff generation rates within this watershed reflect a mix of
infiltration and runoff.
Documented and Identified Potential Contaminant Sources
A significant area of row crops occupies the head of Subwatershed #10. Silt-laden
stormwater runoff fxom the farmland runs down East Mill Road, is discharged into a
woody swale, and then channelized and discharged into the Creek. There is a small marsh
area, which may filter some of this water on the fringe of the Creek.
Quantitatively Estimated Non-point Pollution Loads
Pollution loading rates were not estimated, as there was no corresponding water
quality sampling station for Subwatershed # 10.
62
Property Ownership
The majority of this subwatershed is privately owned property. A small portion of
Subwatershed # 10 is classified as "Subdivision Open Space". This area is south of Mill
Road.
Applicable Treatment Strategies
The implementation of BMP's on the farmland at the head of Subwatershed #10 is
essential to improving water quality in this reach of Mattituck Creek. Though there is no
fecal coliform data to determine the pathogen loads in this area, but sediments can be
observed entering the Creek in this area. These sediments, originating on farmland have
the potential to carry fertilizers and pesticides. Currently, the crops are planted parallel to
the flow of nmoff, which increases the flow and velocity. Crops could be planted
perpendicular to the flow, which would slow the runoff. Also, a grass filter strip could be
planted between East Mill Road and the tillable farm area. Financing could be obtained
from the Conservation Reserve Program if this grass filter strip is declared a
Conservation Reserve Area. Finally, if an agreement could be made with the property
owner(s), a small retention basin could be built on the farmland north of East Mill Road,
which could reduce the volume of runoff and associated off-site sediment delivery. This,
again, would require developing cooperative agreement with the property owner(s).
Another complex treatment strategy would entail damming up the existing natural
channel and installing a water control structure to create a wet pond or retention basin for
the stormwater runoff water that is discharged directly into the Creek via the open
channel. The existing woody swale is a deep depression that appears to comprise
relatively un-developable land. The creation of such a wet pond in this woodland setting
would provide additional wildlife habitat potential as well. This swale occupies private
land and agreement must be sough with the property owner to facilitate such a treatment.
.The Town may also wish to consider acquisition of the portion of this property necessary
to accommodate such a detention pond system. Suffolk County is currently offering
bond funds up to a 4020 match under their Land Preservation Partnership Program, to be
used for acquisition of properties for estuary protection and open space preservation.
XIII. Project Implementation
A. Introduction
One of the next steps for this project will be for the Town to select one of the high
priority subwatersheds where best management practices are needed and feasible. The
USDA Natural Resources Conservation Service and Suffolk County Soil and Water
Conservation District staffs are committed to completing the necessary engineering
survey and project design, and supervise the installation of best management practices
within the subwatershed selected. Other practices will be designed and installed by the
Town on a priority basis as available funding permits. Further discussions with the Town
of Southold Trustees and Engineering Department will determine where the most feasible
63
project possibilities exist of the ones outlined in this report. Non-scientific factors, such
as land ownership and easements were not addressed in this report, and must be
considered before these projects can commence.
B. Stormwater Quality Management
There are many approaches that can be utilized to manage the water quality
problems at Mattituck Creek. The more traditional type of program has reacted to
existing water quality problems by constructing facilities to ameliorate them. Less
traditional approaches tend to guide growth and develop various types of programs,
which prevent water quantity or quality problems from occurring in the first place, or
develops solutions, which do not include siting facilities.
The following strategies can aid in minimizing problems attributable to stormwater
pollution soumes:
Require the immediate recharge or on-site detention of stormwater, where feasible, in
order to reduces the volume ofnmoff;
· Promote the use of storage areas - either specifically constructed detention basins,
multi-purpose paved areas, natural ponds or other existing or altered landforms - to
reduce sediment transport and coliform contamination from nmoff;
· Limit, regulate and, where necessary and practicable, prohibit new shoreline
development in order to protect the quality of adjacent surface waters;
· Provide adequate buffer zones surrounding tidal and freshwater wetlands;
· Promote or require the institution of municipal street cleaning programs to help
minimize the pollution effects of stormwater nmoff; and
· Require strict control over the disposal of collected materials in sanitary landfills.
The following stormwater management systems, sununarized in descending order
of preference, should be used to capture and treat the "first flush" when designing
stormwater facilities. (First flush refers to the delivery of a disproportionately large load
of accumulated pollutants that are washed from the surface of the land during the early
part of storms and transported in runoff). The systems are: (a) infiltration, (b) retention,
and (e) extended detention.
(a) Infiltration
Infiltration of runoff on-site by use of vegetated depressions and buffer areas,
pervious surfaces, drywells, infiltration basins and trenches permits immediate recharge
to groundwater reserves. Studies of the effect of stormwater recharge on groundwater
conducted as part of the Nationwide Urban Runoff Program (NURP) on Long Island
indicate that, while chlorides and nitrates in infiltrated stormwater reach groundwater,
lead and other heavy metals and most organic compounds are absorbed by the soil and do
not enter groundwater. Thus, potential chloride and nitrate loading must be minimized
by instituting appropriate management practices within the watershed.
64
(b) Retention
Retention by use of wet ponds or constructed wetlands provides for the storage of
collected runoff in a permanent pool. True retention allows for storage of stormwater
runoff with release via evaporation or infiltration only. Pollutant removal efficiency is
related to the duration over which stormwater runoff is detained in the wet pond and is
subject to physical settling of sediment and biological uptake.
(c) Detention
There are two approaches to stormwater detention: d~ detention and extended
detention. The primary function of dry detention is to store and gradually release or
attenuate stormwater runoff in order to control peak discharges and minimize flooding.
Dry detention provides few, if any, water quality benefits and, therefore, this practice
may not be used as a substitute for water quality treatment practices such as infiltration,
retention or extended detention. Nevertheless, dry detention can be used in combination
with measures (such as infiltration or retention) so that both the quality of stormwater
runoff can be enhanced and peak discharges attenuated.
Extended detention provides for a longer storage time than a dry detention pond.
Sediment is the primary pollutant removed from stormwater runoff prior to its release
into a waterbody. As such, the degree of removal is likely to be quite high if the pollutant
is a particulate, but very limited removal can be expected for dissolved pollutants.
C. Overview of Mitigation Measures
A number of factors are considered in formulating and applying control methods
to non-point sources. Structural methods (e.g., retention/settling basins) can be used
where stormwater is conveyed to the receiving water by a stream or large storm sewer. If
the greater portion of flow reaches the water at many diffuse locations, Best Management
Practices (usually including street cleaning) are appropriate, if cost-effective.
An overview of the different methods to accomplish the three stormwater
management systems discussed above (infiltration, extended detention, and retention) are
discussed below in greater detail:
Catch basins
A catch basin is a stormwater runoff inlet equipped with a small sedimentation
sump or gdt chamber. A catch basin provides for the capture and subsequent removal
through regular maintenance of sediment and debris from stormwater runoff before it
enters a subsurface stormwater conveyance system. They are designed to handle
contributing watersheds of lA acre or less. Catch basins are effective in removing
coarse-grained sediment and debris in stormwater runoff, but only if they are maintained
and cleaned out after storm events. Fine-grained particles and dissolved pollutants are
65
not effectively trapped in catch basins. The estimated capital costs for material and labor
range from $2,000 to $4,000 per basin.
Constructed Wetlands
Constructed wetlands consist of a constructed, shallow water area, usually a
marsh, dominated by cattail, bulrush, rashes or reeds, designed to simulate the water
quality improvement function of natural wetlands. Constructed wetlands are usually a
component practice in a total system approach to stormwater treatment. The wetlands
are constructed downstream from stormwater management structures (e.g., infiltration,
retention and detention practices.) Constructed wetlands can be designed as either "free
water surface systems" or "subsurface flow systems". Free water surface systems
consist of basins or channels with a natural or constructed subsurface barrier to prevent
seepage. Soil or another suitable medium supports emergent vegetation. Subsurface
flow systems, on the other hand, consist of trenches or beds underlain with a natural or
constructed impermeable subsurface barrier. Soil or gravel are used in the trench or bed
to support emergent vegetation. Stormwater nmoff to be treated is introduced into the
wetland via drainage pipe and a stone-filled trench.
The performance of any constructed wetland system is dependent upon the system
hydrology, precipitation, infiltration, evapotransportation, hydraulic loading rate, water
depth and pH. All these factors can effect the removal of organics, nutrients, and trace
elements not only by altering retention time, but also by either concentrating or diluting
the stormwater. The cost of constructed wetlands varies depending upon the size
needed. Along with the design and construction of this wetland, there are also costs for
environmental analysis (and permitting), complex grading and hydrophytic vegetation
plant materials. Also, watertight membrane liners are very expensive.
Based on the available literature, it is apparent that the use of wetlands as a
pollutant treatment system is a viable option. Many states, including Alabama, Arkansas,
Florida, Minnesota, Mississippi, North Dakota, Texas, Virginia, and Washington are
currently utilizing aquatic plant systems. In general, the efficiency rates for these
wetlands has been approximately 65 to 99 percent for various parameters (i.e., total
suspended solids, total phosphorus, TKN, trace metals, and bacteria). Efficiency will
vary by climate and season. Regarding fecal coliforms, some systems function at nearly
100 pement. At the Phillips High School in Bear Creek, Alabama, fecal coliform levels
dropped from 1,560,000/100 mg to <10/100 ml (TVA 1990).
Critical Area Protection (Permanent Vegetative Cover)
Another critical area protection technique is to establish or maintain permanent
vegetation to stabilize these areas, discourage conversion of environmentally sensitive
areas, and prevent sediment and nutrients from entering waterbodies. The practice also
includes stabilizing eroding areas using biotechnology, hydoseeding and mulching,
sodding, and the use of container-grown plants. This practice includes seeding cool
season grasses and legumes, warm season grasses, placing sod, planting trees and shrubs,
66
and utilizing existing perennial vegetation. Permanent vegetative cover controls surface
runoff, sediment and solid phase nutrients by providing long-term perennial cover for
critical areas. The cost varies from "no-cost", when existing vegetation is used, up to
$1,500 (or more) per acre for hydroseeding critically eroding areas.
Critical Area Protection (Streambank and Shoreline Protection)
This practice entails the use of vegetation, structures, biotechnology, or
management techniques to stabilize and protect streambanks and shorelines. Streambank
and shoreline protection involves the following components: (1) vegetation (rushes,
sedges, grasses, legumes, shrubs or trees), (2) structural improvements (slope
stabilization, filter fabric, riprap, deflectors, fencing, bulkheads, or groin systems), (3)
management techniques (removing debris, fallen trees, or gravel bars in the flood plain
on the inside curves of the stream), and (4) biotechnical altematives (the use of willow
wattles or direct seeding). In general, this practice will decrease the bed load of the
stream (or creek), reduce soil erosion, decrease sediment and nutrient delivery to
waterbodies, and lower stream temperature by shading streams. The cost of this practice
ranges from low cost for biotechnical components to very expensive for structural
designs.
Diversions
A diversion consists of an earthen drainage-way of parabolic or trapezoidal cross-
section with a supporting ridge on the lower side. Diversions are constructed across the
slope and are stabilized using grasses and legumes. This technique intercepts and re-
routes runoff away from areas of high pollution potential, and reduces erosion.
Diversions redirect stormwater runoff to safe outlets and only indirectly control the
release of sediment, pesticides, pathogens, organics and nutrients. The costs of this
technique varies according to design requirements, though the costs are generally low.
Dry Detention Basin
A dry detention basin is designed to collect and store stormwater runoff in a
temporary pool of water for less than 24 hours. This technique provides for the gradual
(attenuated) release of stormwater runoff, and permits settling of coarse-grained sediment
found in it. As previously stated, pollutant removal effectiveness is very limited for dry
detention basins. Dry detention basins are generally not effective for water quality
control. Dry detention basins cannot be designed to handle the "first flush" of runoff.
These basins are expensive to construct, but cost less than extended detention basins.
Extended Detention Basin
Extended detention basins are designed to collect and store stormwater runoff in a
temporary pool of water for 24 hours or greater. This allows for complete settling and
removal of most particulate pollutants found in urban stormwater runoff. Indirectly,
extended detention basins control the release of sediment (coarse and some soluble
67
nutrients, organic matter, trace metals, pathogens, hydrocarbons, and thermal
modifications). Extended detention basins typically consist of an excavated area with an
embankment dam, a principal spillway (riser) with an extended detention control device
at the riser outlet. These basins have been designed to capture, detain and treat urban
stormwater nmoff from the first ½ inch of runoff ("first flush"), or runoff from a 1-year,
24-hour storm event, for a minimum of 24 hours, prior to gradual release through the
riser. Ideal detention time is 40 hours or longer. The longer the detention time, the
greater the pollutant removal. Typical removal rates for pollutants after 48 hours are: 80-
90% for sediment, 40-50% for total phosphorus, 40% for nitrogen, 50% for organic
matter, and more than 90% for trace metals. Significant reductions in pathogen counts
and hydrocarbons were reported after 32 hours. Extended detention basins are expensive
and require maintenance.
Implementation q£Land Use Planning
Implementation of land use planning entails the adoption and implementation of
comprehensive environmental regulations to govern the development process for the
purpose of providing long-term watershed protection. This technique is used to guide
future development and land use activities so as to mitigate the effects of non-point
source pollution. The cost varies due to the varieties of components involved, including
the level of effort needed to complete and implement a program.
Infiltration Basins and Pits
Infiltration basins and pits consist of an excavated basin (or pit) constructed in
permeable soils, for the temporary collection and storage of stormwater runoff prior to
ex filtration. These basins and pits only indirectly control sediments, nutrients, trace
metals, organic matter and pathogens. After temporary stormwater detention, stormwater
runoff exfiltrates (percolates) through undisturbed subsoils in the basin (or pit) floor.
These basins (or pits) remove pollutants through sorption, precipitation, trapping,
straining and bacterial degradation or transformation. It is estimated that under ideal
exfiltration conditions, long-term pollutant removal rates for infiltration basins are from
75-100% for sediment, 50-75% for trace metals, 70-90% for organic matter and 75-100%
for pathogens. The cost of such structures varies depending upon basin (pit) design. This
alternative has relatively inexpensive construction costs.
Infiltration Trench
An infiltration trench is a blind sub-surface trench, 3 to 10 feet in depth,
backfilled with gravel for the temporary collection and storage of stormwater rnnoffprior
to exfiltration. Stormwater rtmoff exfiltrates (percolates) through undisturbed subsoils in
the trench floors, or is collected by perforated underdrain pipes and routed to an outflow
facility. These trenches effectively remove fine particulates and soluble pollutants
through sorption, precipitation, trapping, straining and bacterial degradation or
transformation. Stormwater runoff should be pretreated prior to reaching the trench.
Infiltration trenches are not intended to provide removal of coarse particulate pollutants.
68
When coarse particles are deposited, they can plug the infiltration trench and render it
useless. It is estimated that under full exfiltration conditions, infiltration trenches can
remove up to 100% of sediment, 65-75% of total phosphorus, 60-70% of total nitrogen,
up to 100% of trace metals, 90% of organic matter and 98% of pathogens. Most trench
systems are able to divert 60-90% of the annual nmoff fi.om impervious areas into the
soil. The cost varies depending upon infiltration trench design.
Integrated Pest Management
Integrated pest management (IPM) is an ecologically-based integrated pest
control strategy designed to keep pest populations below economically injurious levels
using a variety of control tactics. IPM uses monitoring, pest forecasting, scouting, and
"economic thresholds" to determine the appropriate use of pesticides, and altemate pest
control tactics. The management options include: use of biological control agents,
cultural practices, such as: rotation, the use of trap crops, destruction of pest breeding and
refuge sites, ecosystem diversification, scouting, resistant varieties, mechanical weed
control, timing of planting and harvesting, and the selection and use of pesticides,
pesticide formulations and alternatives, and timing of application. In most of these
management options, IPM reduces the availability of pesticides as a nonpoint source
pollutant. The cost is variable, depending upon the control tactic used.
Irrigation Water Management
Irrigation water management is a planned system that determines and controls the
rate, amount, and timing of irrigation water. This technique is used to reduce the
leaching of pollutants by applying irrigation water based upon waterholding capacity of
the soil and the needs of the plant material. This practice is accomplished by
"scheduling" the rate, amount, and timing of the application of irrigation water. The cost
may entail additional labor expenses to collect "scheduling" data. Software scheduling
programs are commercially available.
Nutrient Management
Nutrient management consists of integrating the availability of nutrients in the
soil (supplied fi.om organic matter and plant residues) with the nutrient requirement of
plants. Commercial fertilizer should be used to meet additional needs. A well-designed
nutrient management program controls nutrient loss by reducing excessive applications.
Component practices of a nutrient management program include soil testing,
development of a nutrient management plan, managing the rate, timing and placement of
nutrient applications, and soil management practices to control surface losses of nutrients.
There is no additional cost associated with this technique, except for soil tests or
consulting fees for services to prepare nutrient management plans.
69
Pathogen and Nutrient Control
This measure includes waterfowl waste management and control. This entails
adoption and enforcement of a "No Feeding Waterfowl" Ordinance, including a public
information/outreach program. Another measure is grass management, limiting lawn size
and extent. Physical barriers for geese~ swans and ducks can be installed between water
and feeding areas. Also, land use regulations and planning can be applied to discourage
developments and landscaping which would attract additional nuisance waterfowl to an
area plagued by nuisance waterfowl. Other, less passive forms of waterfowl waste
management can be explored if it is felt that this is a large source of pollutant loadings to
Mattituck Creek. The costs range from no cost (for homeowner-initiated auditory
harassment or feeding prohibition) to very costly (for intensive efforts to interfere with
reproduction over a large area).
Another measure of pathogen and nutrient control includes institutional control
measures employed by local governments and management measures employed by
individuals to prevent non-point source pollution by canines and felines. Expenses
involved are associated with municipal enforcement and personal responsibilities
connected to spaying, neutering and purchasing of "pooper scoopers".
Retention Pond (Wet Pond)
A retention pond (also known as wet ponds) are typically excavated ponds with a
dam and emergency spillway, designed to accept stormwater runoff from watersheds
greater than 10 acres in size. Ponds vary in size according to design; however, they
usually have a shallow inlet area 0.5 to 2 feet deep, and a permanent pool of 3 to 8 feet in
depth. Retention ponds maximize the hydraulic residence time of the detained
stormwater runoff, and allow pollutants to settle out from 2 to 14 days.
Retention ponds control post-development peak discharge rates to pre-
development levels, and can achieve a high removal rate of pollutants due to gravity
settling, chemical flocculation and biological uptake. Retention ponds generally cost less
than extended detention ponds. Routine maintenance of retention ponds includes
removing woody vegetation, mowing side-slopes, embankments and the emergency
spillway, inspections conducted annually and after design storms, debris and litter
removal, erosion control of vegetated areas and nuisance control of insects, weeds, odors,
and algae. Non-routine maintenance includes structural repairs and replacement, and
removal of accumulated sediment in the bottom of the pond (performed every 2 to 5
years).
Roof Runoff System
A roof runoff system handles roof runoff by directing it to down spouts and into
trenches prior to infiltration into permeable soil. Estimated costs are very low.
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Street and Pavement Sweeping
Street sweepers are designed to dislodge debris and dirt from the street surface,
transport it onto a moving conveyor, and deposit it into a storage hopper. The most
common types of street sweeper is a mechanical sweeper, which uses a rotating gutter
broom to transport particles from the gutter area into the path of a large cylindrical broom
which rotates to carry the material onto a conveyor belt. Water is sprayed on the
collected material to control resuspension of the fine particles. Intensive cleaning of
streets and pavements can result in up to 50% reduction of fecal coliform and a 15%
reduction of total coliform; however seasonal differences may occur. Overall, the
practice is limited in pollutant load reductions. Estimated costs of this measure are high.
In 1988, the City of Milwaukee swept 86,000 curb-miles for about $25 per curb mile
swept.
Peat/Sand Filter Systems
Peat/Sand filters are gravity-driven, constructed filtration systems designed to
reduce nonpoint source pollutant loadings from watersheds to receiving bodies. These
systems capture and treat the first ½-inch of runoff from impervious areas by temporary
detention and infiltration. Peat/sand filter systems consist of three basic concepts:
A small pre-treatment wet pond: for gravitational settling and temporary storage.
· A flow-splitting concrete weir and earth embankment (to control the depth of stored
stormwater runoff)
· An off-line grass/peat/sand filter bed basin area: for temporary surface ponding, rapid
infiltration and treatment of urban runoff.
An addition of a gate valve to the end of the peat bed underdrain system provides
greater flexibility in controlling the hydraulic residence time of stormwater runoff. Also,
reed canary grass is typically used in peat/sand filter bed basin to harvest nutrients from
the surface-ponded stormwater runoff. Based on experimental data, it is believed that
peat/sand filter systems can remove up to 90% of suspended solids, 70% of total
phosphorus, 50% of total nitrogen, 90% of biological oxygen demand (BOD), 80% of
trace metals, and greater than 90% of pathogenic bacteria found in stormwater nmoff.
The engineered designs of these systems are expensive.
D. Example Project
Hasharnomuck Pro/ect
The USDA, NRCS and the Suffolk Count Soil and Water Conservation District,
with funding and support from the Town of Southold and NYDEC, designed and
installed a stormwater retention and control structure in the Town of Southold. The water
control structure was designed to store an identified amount of water. This water is held
in the ponded area, as shown in the photo below. The water is then slowly released to a
stream that feeds Hashamomuck Pond. This structure replaced a culvert underneath the
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road that directly discharged all stom~water from the gully seen in the photo to the stream
that feeds Hashamomuck Pond. An easement was obtained by the property owner to the
west of this retention pond and an agreement was made as to the design levels of the
pond. This project was implemented to reduce the amount ofcoliforms in Hashamomuck
Pond. Though no water quality data directly supports the effectiveness of this structure,
the project has clearly been successful in holding water for a significant amount of time
before allowing it to flow into the Pond.
Photo Description: The water control structure can be seen in the center of the photo
(barrel riser covered by a gridded trash rack), and the water being retained is covered in
snow and surrounds the structure.
E. Projects to be Completed
#1) Location: Intersection of Mill Road and Oregon Road
Project Components:
· Easement or purchase of triangular parcel
· Installation of two catch basins
· Excavation
· Sand fill
· Installation of concrete weir with adjustable elevation
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· Rip-rap/headwall
· Topsoil and seed
· Re-alignment of Mill Road end
· Erosion control
Estimated Cost: -$50,000 (Plus easements/purchases)
#2) Location: Mill Road East
Project Components:
· Easements
· Installation of two catch basins
· Installation of culvert pipe
· Headwall and Rip-rap
· Asphalt Patch
· Erosion control
· Topsoil and seed
Estimated Cost: -$25,000 (Plus easements)
#3) Location: Cox Neck Lane
Project Components:
· Easements
· Raise road 300 linear feet (+/-)
· Installation of two catch basins
· Installation of culvert pipe with outfall headwall
· Installation of concrete weir structure
· Topsoil and seed
· Erosion control
Estimated Cost: -$50,000 (Plus easements)
#4) Location: Intersection of Grand Avenue and Wickham Avenue
Project Components:
· Demolition
· Installation of guard rail
· Erosion control
· Installation of two catch basins with inlet grate
· Installation of two leaching pools
· Installation of two manholes
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· Topsoil and seed
· Installation of drainage pipe
Estimated Cost: ~$50,000
XIV. Conclusions
Mattituck Creek suffers from the effects of fecal coliform pollution. Because of
fecal coliform contamination, water use impairments are experienced in the Creek. The
Creek is uncertified for shellfish harvest. Non-point source pollution is the primary cause
of fecal coliform contamination in Mattituck Creek. One of the major non-point sources
of fecal coliform bacteria to Mattituck Creek is stormwater runoff, especially on the
southern part of the Creek. Agricultural activities in the Mattituck Creek watershed area
also contribute to high fecal coliform levels. The open farm fields are habitat to many
waterfowl, which contribute to the fecal coliform production. Though farm animals are
minimal, there are still several farms that contain animals (dogs, cats, horses, chickens)
which can also contribute to high fecal coliform levels. These large agricultural fields are
barren for most of the winter, and offer minimal infiltration for stormwater.
The results of our investigation suggest that stormwater discharges are the most
important factor causing periodic and episodic increases in fecal coliform levels at
Mattituck Creek. Mattituck Creek shows an immediate and significant response of
increased fecal coliforms' levels linked to rainfall events. The increased levels of fecal
coliforms occur quickly after the onset of nmoff. Mitigation efforts need to be directed at
runoff, because of the high loadings associated with runoff events, and further because
NYSDEC sampling is always carried out trader rainfall conditions. If improvements in
water quality are to be made based on NYSDEC testing, then pollution loading of
Mattituck Creek by rainfall must be mitigated. Also, because of the stormwater
contribution of fine-grained sediments, nutrients and sources of fecal coliform bacteria to
the sediments, it is important to remediate stormwater runoff inputs in terms of how they
can also impact dry weather background fecal coliform levels.
High density development, a gridwork pattern of numerous streets, a high pement
of impervious surfaces and the sloping terrain all contribute to the volume of stormwater
runoff and the loading of fecal coliform bacteria. A total of 10 subwatersheds, each
relating to specific nmoff sites to the Creek, were delineated. Runoff volumes and fecal
coliform loadings were calculated for each.
All of these drainage areas were (and continue to be) sampled during rainfall
events. Data shows that runoff fecal coliform levels are very high for all drainage areas,
and that runoff for all areas leads to significantly increased fecal coliform levels in
adjacent harbor waters. Runoff volumes are also significant for these drainage areas. For
many of the discharge points, where stormwater enters the Creek, the fecal coliform
levels in the runoff are in the range of tens of thousands of fecal coliforms per 100 ml.
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During rainfall events the actual Creek waters adjacent to the discharge points are in the
tens of thousands of fecal coliform per 100 ml.
Additional Creek samples taken adjacent to stormwater outflow pipes are
extremely high (hundreds to tens of thousands/100 ml). These levels greatly exceed the
shellfish standard. Water quality is greatly reduced in the Creek waters in the vicinity of
outflow pipes in discharge areas.
Recommendations
A top-down approach is recommended for Mattituck Creek, whereby activities
should be initiated in the upper most sections of the watershed, and are then extended
downslide through the watershed to the Creek so that stormwater is collected and
infiltrated throughout the watershed. A further recommendation is to address the
pollutant loading caused by the "first flush" throughout the watershed.
Long-term impacts of improving structural and non-structural stormwater runoff
controls will result in an improvement in general water quality depending on the control
alternatives implemented at Mattituck Creek. The non-structural alternatives of detention
and retention of more diffuse sources of stormwater rtmoff will also improve long-term
water quality, by reducing turbidity. Peak flows will be modified, reducing suspended
sediment concentrations in watercourses. Retention of water will also enhance the
settling of suspended sediments.
Non-structural alternatives may not adequately control such sources of pollution
from stormwater runoff as coliform bacteria, pesticides, metals and hydrocarbons, since
they primarily address stormwater flows and suspended sediments. It is true, for
instance, that some phosphorus and heavy metals adsorb onto soil particles, which settle
and are thereby removed. However, nitrates are extremely soluble in water and are not
removed by alternatives that merely detain or retard flows. A non-structural alternative
that is an exception to this is street cleaning, which has been shown to reduce
contaminant concentrations.
A list of recommendations to help achieve the ultimate goal of improved water
quality in Mattituck Creek, are as follows:
System Maintenance - There already exists a system of storm drains, catch basins
and infiltration basins in the Mattituck Creek watershed. Although their number is
insufficient to address the entire runoff problem, they provide a base stormwater network.
Their effectiveness, however, has been nearly eliminated due to clogging. Throughout
the study period, most of the basins were filled with sediment, and the storm drains
clogged with debris. This has caused nearly a complete bypass of most of the system
during rainfall events. The problem is exacerbated during winier months when vast
quantities of sand is needed for street maintenance, since most of the streets are on the
slope of a hill. It is therefore recommended that a vigorous maintenance program be
established that keeps the storm drains cleared of debris, and the basins empty of
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