&EPA
United States
Environmental Protection
Agency
Office of Water
(WH-556F)
EPA 842-S-9 2-006
June 1992
Determination of Sludge
Dumping Rates for the
106-Mile Site
Recycled/Recyclable
Printed with Soy/Caoola Ink on paper thai
contains at least 5O% recydad fiber
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FINAL REPORT
DETERMINATION OF SLUDGE DUMPING RATES
FOR THE 106-MILE SITE
March 15, 1989
U.S. ENVIRONMENTAL PROTECTION AGENCY
Region II
New York, New York
and
Office of Marine and Estuarine Protection
Washington, DC
Prepared Under Contract No. 68-03-3319
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FINAL REPORT
DETERMINATION OF SLUDGE DUMPING RATES
FOR THE 106 MILE SITE
June 1992
U.S. ENVIRONMENTAL PROTECTION AGENCY
Region II
New York, New York
and
Office of Wetlands, Oceans
and Watersheds
Washington, D.C.
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TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY i
1. INTRODUCTION . . 1-1
2. BACKGROUND INFORMATION 2-1
2.1 REVIEW OF EXISTING DILUTION MODELS ... . . 2-1
2.2 CHARACTERIZATION OF SLUDGE TRANSPORT BARGES ....... 2-4
2.2.1 Barge Characteristics . » ....... 2-4
2.2.2 Dumping Methods 2-7
2.3 NEARFIELD STUDIES OF SLUDGE PLUME BEHAVIOR 2-13
3. DEVELOPMENT OF DUMPING RATE EQUATION 3-1
3.1 SLUDGE PLUME DILUTION . 3-2
3.1.1 Hake-Induced Initial Mixing 3-3
3.1.2 Oceanic Mixing. .................. 3-7
3.2 DUMPING RATE EQUATION 3-9
3.3 SPEED CONSIDERATIONS 3-14
4. DUMPING RATES 4-1
4.1 DUMPING RATES FOR INDIVIDUAL PERMIT APPLICANTS ...... 4-1
4.2 NOMOGRAPH OF DUMPING RATES FOR SPECIFIC DILUTION
REQUIREMENTS 4-6
1. STRATEGIES FOR MULTIPLE DUMPING 5-1
5.1 BULK LOADING CONSIDERATIONS 5-1
5.2 DUMPING STRATEGIES AT COURT-ORDERED RATE OF 15,500 gpm . . 5-3
5.3 DUMPING STRATEGIES AT RATES 5-6
6. RECOMMENDATIONS ..... 6-1
7. REFERENCES 7-1
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LIST OF TABLES
Page
TABLE 2.1 ASSESSMENT OF MODELS FOR PREDICTION OF INITIAL
MIXING OF SLUDGE DUMPED AT THE 106-MILE SITE 2-3
TABLE 2.2 SUMMARY OF VESSELS THAT TRANSPORT SEWAGE SLUDGE
TO THE 106-MILE SITE 2-6
TABLE 2.3 SLUDGE CAPACITY OF VESSELS THAT TRANSPORT
SEWAGE SLUDGE TO THE 106-MILE SITE 2-8
TABLE 2.4 PHYSICAL DIMENSIONS OF VESSELS THAT TRANSPORT
SEWAGE SLUDGE TO THE 106-MILE SITE 2-9
TABLE 2.5 SLUDGE DISCHARGE METHODS AND MAXIMUM RATES FOR
VESSELS THAT TRANSPORT SEWAGE SLUDGE TO THE
106-MILE SITE. 2-11
TABLE 2.6 OBSERVED DILUTIONS AND RATES OF DILUTION FOR SLUDGE
PLUMES SURVEYED IN SEPTEMBER 1987 AND 1988 2-22
TABLE 4.1 WHOLE SLUDGE METAL CHARACTERIZATION RESULTS FROM
THE NINE NEW YORK-NEW JERSEY SEWERAGE AUTHORITIES. ... 4-3
TABLE 4.2 WHOLE SLUDGE TOXICITY RESULTS FROM THE NINE
NEW YORK-NEW JERSEY SEWERAGE AUTHORITIES 4-4
TABLE 4.3 COMPARISON OF SLUDGE DUMPING RATES BASED ON
TOXICITY AND TRACE METAL RESULTS . . 4-5
TABLE 4.4 RECOMMENDED SLUDGE RATES VERSUS REQUIRED
DILUTION 4-9
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LIST OF FIGURES
Page
FIGURE 1.1 SCHEMATIC DIAGRAM OF ACTIVITIES ASSOCIATED WITH THE
REGULATIOH AND MONITORING OF SLUDGE DUMPING RATES FOR
THE 106-MILE SITE 1-3
FIGURE 2.1 DIAGRAM OF SLUDGE COMPARTMENTS WITHIN BARGES OPERATED
BY THE NEW YORK CITY DEPARTMENT OF ENVIRONMENTAL
PROTECTION 2-10
FIGURE 2.2 TIME HISTORY OF SLUDGE DILUTION WITHIN PLUME EVENT
DB-3 AT THE 106-MILE SITE DURING SEPTEMBER 1987 2-16
FIGURE 2.3 CONCEPTUAL DIAGRAM OF THE DILUTION OF SLUDGE PARCELS
WITHIN PLUMES FOR TWO CASES OF MIXING CONDITIONS 2-18
FIGURE 2.4 TIME HISTORY OF SLUDGE DILUTION WITHIN THE CORE OF
SLUDGE PLUMES SURVEYED IN SEPTEMBER 1987 AND 1988 2-20
FIGURE 3.1 CONCEPTUAL MODEL OF SLUDGE PLUME DILUTION FROM
OBSERVATIONS DURING PLUME EVENT DB-3 3-11
FIGURE 3.2 PLOT OF VOLUME DUMPING RATE (gal/min) VERSUS BARGE
SPEED. THE SHADED REGION REPRESENTS EPA DUMPING
REGULATIONS 3-15
FIGURE 3.3 PLOT OF VOLUME DUMPING RATE (gal/min) VERSUS BARGE
SPEED. BARGE DUMPING CHARACTERISTICS FROM SEPTEMBER
1987 AND 1988 ARE REPRESENTED BY INDIVIDUAL POINTS 3-17
FIGURE 4.1 NOMOGRAPH OF SLUDGE DUMPING RATES (in gal/min) VERSUS
REQUIRED SLUDGE DILUTION 4-h AFTER DUMPING AT THE
106-MILE SITE 4-7
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EXECUTIVE SUMMARY
The U.S. Environmental Protection Agency (EPA), under the Marine
Protection, Research, and Sanctuaries Act of 1972, is responsible for
regulating the disposal of sludge at the 106-Mile Deepwater Municipal Sludge
Site (106-Mile Site) located approximately 100 nrai offshore New York and New
Jersey. EPA has developed a monitoring plan ( EPA f 1992a) for the 106-
Mile Site which ensures that regulatory requirements are net, and that field
measurements are made to support site management decisions. As part of the
monitoring plan, a series of field measurement surveys has been conducted to
monitor the nearfield behavior and fate of sludge dumped at the 106-Mile
Site. These measurements represent a high-quality data set from which to
base analyses of nearfield, short-term sludge plume dilution and compliance
with marine water quality criteria.
EPA received sludge dumping permit applications for continued use of the
106-Mile Site from nine sewerage authorities in New York and New Jersey, and
is in the process of reviewing the applications to determine whether the
proposed dumping operations will comply with water quality criteria. As part
of this review process, EPA must determine whether the court-ordered dumping
rate of 15,500 gal/n'n is suitable for the 106-Mile Site, or whether dumping
rates and strategies must be altered. This report presents analyses that
wiVl aid EPA in making sound management decisions'concerning the dumping of
sewage sludge at the 106-Mile Site. The study focuses on three major
objectives.*
* Development of an empirical equation for calculating optimum
sludge dumping rates, based upon field observations of sludge plume
behavior at the 106-Mile Site.
* Calculation of sludge dumping rates for individual permit
applicants, based upon sludge characteristics.
* Development of candidate strategies for multiple dumping at the
106-Mile Site.
The following activities were conducted as secondary objectives}
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An assessment of whether the existing models of waste plume
dilution are suitable for prediction of sludge plume dispersion at
the 106-Mile Site,
A preliminary survey of the physical characteristics and dumping
procedures for the barges that dump sludge at the 106-Mile Site.
Analyses of the physical and chemical measurements obtained during the
nearfield monitoring surveys in September 1987 and 1988 indicate that sludge
plumes are not dispersed rapidly during summer conditions; plumes are
generally confined to the upper 25 m of the water column during the first 4 h
after dumping. Dilutions of sludge parcels within the core of the plumes
were on the order of 4,000:1 4 h after dumping at rates between 12,000 and
15,000 gal/rain.
Analyses of trace metals and toxicity data provided in the dumping
permit applications and obtained from analyses of whole sludge samples
obtained in August 1988 indicate that sludge dilutions at 4 h must be much
greater than 10,000:1 for many of the sewerage authorities* These dilution
requirements are based upon compliance with specific water quality criteria
for metals and toxicity 4 h after sludge is dumped. Metal-based and
toxicity-based dilution requirements differ significantly for each sewerage
authority, and large differences are observed among the nine authorities in
New York and New Jersey. To achieve these high dilutions, sludge dumping
rates must be reduced greatly because oceanic mixing processes, at least
during summer, are not sufficient for attaining this degree of dilution over
a period of 4 h; winter monitoring surveys will be necessary to determine
whether oceanographic mixing processes are significantly more intense during
winter.
An empirical equation has been developed for calculating the optimum
sludge dumping rate for each permit applicant, based upon the field data from
the September 1987 and 1988 monitoring surveys. The results indicate that
dumping rates should be less than 1,000 gal/min for three of the permit
applicants and less than 5,000 gal/min for the remaining six applicants to
ensure compliance with water quality criteria 4 h after dumping. It is
recommended that additional nearfield data be acquired during plume
monitoring surveys in order to validate the coefficients in the empirical
ii
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dumping rate formula: however, the results from the Septeiber 1987 and 1988
surveys are viewed as an excellent data set from which to base a conservative
model of sludge plume dilution at the 106-Mile Site.
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1. INTRODUCTION
The U.S. Environmental Protection Agency (EPA), under the Marine
Protection, Research, and Sanctuaries Act of 1972 (MPRSA, PL 92-532) is
responsible for regulating the disposal of municipal sewage sludge in ocean
waters. As a result of an April 11, 1985, decision to deny petitions to
redesignate the 12-Mile Sludge Site offshore New York, EPA Region II halted
all sludge disposal in New York Bight. Effective January 1, 1988, all
municipalities in the New York and New Jersey have shifted sewage sludge
disposal operations to the 106-Mile Deepwater Municipal Sludge Site (106-Mile
Site).
EPA has developed a monitoring plan ( EPA , 1992a) for the 106-Mile
Site which ensures that regulatory requirements are met, and that field
measurements are made to support management decisions concerning (l) site
redesignation or dedesignation, (2) issuance, continuation, or revocation of
sludge dumping permits, and (3) continuation, modification, or termination of
the monitoring program itself. The overall strategy of the monitoring plan,
and its companion implementation plan ( EPA , 1992b), focuses on two areas
of concern; assessment of compliance with permit conditions and assessment of
potential impacts of sludge disposal on resources and other aspects of the
marine environment.
As part of the 106-Mile Site monitoring plan, EPA has conducted a series
of field measurement surveys to monitor the nearfitld behavior and fate of
sewage sludge dumped at the 106-Mile Site ( EPA , 1992c; 1988a; 1988b).
These surveys (in September 1987 and March and September 1988) provided
accurate, high-resolution measurements of physical and chemical properties
within sludge plumes immediately after dumping. The physical measurements
were used to determine the physical characteristics of the sludge plumes and
the effects of oceanographic processes on sludge plume dilution and
advection. The chemical measurements were used to determine rates of sludge
dilution and to test compliance with marine water quality criteria.
EPA received dumping permit applications for continued use of the 106-
Mile Site from nine sewerage authorities in New York and New Jersey, and is
in the process of reviewing the applications to determine whether the
proposed sludge dumping operations will comply with marine water quality
1-1
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criteria. As part of this review process, EPA must determine whether the
court-mandated sludge dumping rate of 15,500 gal/min is suitable for the 106-
Mile Site, or whether dumping rates and strategies must be altered to ensure
compliance with water quality criteria (WQC) and toxicity-based limiting
permissible concentrations (LPCs). These management decisions will require
analyses of monitoring studies followed by regulatory decisions as
illustrated in Figure 1.1; the four major components of this
regulation/monitoring scheme are described below.
Regulation, whereby sludge dumping rates are established and
routinely monitored for compliance with water quality criteria.
pumping Operations, wherein the effective rate of sludge disposal
is based upon volume dumping rates and barge speed.
Sludge Dispersion, which is governed by dumping rates, barge
characteristics, and oceanographic dispersion processes.
Monitoring, whereby field measurements and water samples are used
to test compliance with water quality criteria and recommend
changes to, or maintenance of, sludge dumping rates.
Work Assignment 1-111 of Contract No. 68-03-3319 was initiated to
provide EPA with technical assistance on various operational aspects of the
106-Mile Site sludge dumping program, including the evaluation of appropriate
sludge dumping rates. This report presents the results of Task 1 of Work
Assignment l-lll. The major objectives of this task include
An assessment of whether the existing models of waste plume
dilution are suitable for prediction of sludge plume dispersion at
the 106-Mile Site.
A survey of physical characteristics and dumping procedures for the
barges that dump sludge at the 106-Mile Site.
Development of an empirical formula for calculating optimum sludge
dumping rates, based upon field measurements of sludge plumes at
the 106-Mile Site.
Calculation of sludge dumping rates for individual permit
applicants, based upon sludge characteristics.
Development of candidate strategies for multiple dumping at the
106-Mile Site.
1-2
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DUMPING OPERATIONS
Barge
Configuration
Oceanographic
Conditions
REGULATION
DUMPING RATE
(gal/min)
BARGE SPEED
(kn)
EFFECTIVE
DUMPING RATE
(gal/ft)
WAKE DILUTION
(0-5 min)
OCEANIC DILUTION
(0-4 h )
WATER QUALITY
TESTS
WATER SAMPLE
COLLECTION
OCEANOGRAPHIC
MEASUREMENTS
SLUDGE DISPERSION
MONITORING
FIGURE 1.1 SCHEMATIC DIAGRAM OF ACTIVITIES ASSOCIATED WITH THE
REGULATION AND MONITORING OF SLUDGE DUMPING RATES FOR THE
106-MILE SITE.
1-3
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This report is structured in sections that address the specific
objectives given above. Section 2 presents information on existing models of
waste plume dilution, barge characteristics, and field observations of sludge
plyme behavior at the 106-Mile Site. The derivation of an empirical formula
for calculating optimum sludge dumping rates is given in Section 3. Section
4 presents recommended dumping rates for individual permit applicants, in
addition to a nomograph for quick determination of optimum dumping rates for
a wide variety of sludge dilutions in receiving water. Section 5 presents a
number of operational strategies for dumping sludge at the 106-Mile Site.
Recommendations for additional analyses and field studies are given in
Section 6. References are listed in Section 7.
1-4
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2. BACKGROUND INFORMATION
This section presents background information on three topics that
pertain to ocean disposal of sewage sludge. Subsection 2.1 provides a brief
review of existing models of waste plume dispersion! rationale is given for
the use of field data over existing models when estimating sludge dilution.
Subsection 2,2 describes the physical dimensions, sludge capacity, and
dumping procedures of the barges that transport sludge to the 106-Mile Site.
Field observations of sludge plume dilution from a recent EPA cruise to the
106-Mile Site are discussed in Subsection 2.3.
2.1 REVIEW OF EXISTING DILUTION MODELS
The ocean dumping regulations require calculation of the limiting
permissible concentration (LPC) for wastes that are to be dumped in the
ocean. The LPC is the concentration of a constituent, after allowance for
initial mixing, that does not exceed (1) applicable marine WQC and (2) a
toxicity threshold, defined as 0.01 of a concentration shown to be acutely
toxic to appropriate, sensitive marine organisms. The LPC is used to
calculate the maximum allowable dumping rate based on the initial mixing of
the waste. Initial mixing is defined as the mixing that occurs within 4
hours of dumping.
The ocean dumping regulations allow for several methods of calculating
initial mixing. These methods, in order of preference, are as follows:
1. When field data on the proposed dumping activities are adequate for
prediction of initial dispersion and dilution of the waste, these
data shall be used. If necessary, the field data should be used in
conjunction with an appropriate mathematical model of waste mixing
and dilution.
2. When field data on the dispersion and dilution of a waste similar
in characteristics to that proposed for discharge are available,
these data shall be used in conjunction with an appropriate
mathematical model.
3. When no field data are available, theoretical oceanic turbulent
diffusion relationships may be applied to known characteristics of
the waste and the disposal site.
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4. When no other means of estimation are feasible, a procedure for
calculating initial mixing is presented in the regulations.
The regulations thus emphasize that when field data are available, these
data should be used in the estimation of initial mixing. As a result of the
recent nearfield monitoring studies at the 106-Mile Site ( EPA , 1992c;
1988a; 1988b), high-quality field data are now available for estimating the
initial mixing of sludge dumped at the 106-Mile Site. The question that
remains Is what model, if any, should be used with these data to estimate the
amount of initial mixing, and hence, the optimum rate for dumping sludge at
the 106-Mile Site.
Because the regulations state that the procedure for calculating initial
mixing which is specified in Part 227 of the Code of Federal Regulations
(CFR) should be used only "when no other means of estimation are feasible,"
this "model" is not appropriate for estimating the initial mixing of sewage
sludge dumped at the 106-Mile Site.
Since the mid-1970s, ten "state of-the-art" models have been used to
predict Initial mixing of dumped wastes (see Table 2.1). These models have
been reviewed ( EPA , 1986) to determine the extent to which they had
been validated with field data, and to ascertain the types of materials for
which they are appropriate. The following statements are based upon the
above-mentioned review of mixing models.
Of all the models presented in Table 2.1, none are presently capable of
predicting maximum concentrations of isolated parcels of sludge in ocean
water. These models predict either average or Gaussian-distributed
concentrations of disposed material in receiving waters. With the exception
of the Walker et al. (1987) sewage sludge model and the Offshore Operators
Committee (OOC) Mud Discharge Model (Brandsma et al., 1983), all of the
models are inappropriate for, or would require major revisions before use in,
estimating initial mixing of sewage sludge in oceanic waters.
The Walker et al. model was developed specifically for analyses of
sewage sludge disposal at the 106-Mile Site. Its major application is
predicting farfield dispersion characteristics of sewage sludge. The model
predicts average, steady-state concentrations of sludge constituents over the
farfield, but the results are based upon an empirical algorithm (with
inherent, non-conservative assumptions) rather than a deterministic solution.
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TABLE 2.1 ASSESSMENT OF MODELS FOR PREDICTION OF INITIAL MIXING OF SLUDGE DUMPED AT THE 106-MILE SITE.
Authors
Year
Material
Validation
Appropriate for
Initial Mixing
Brandsma and Divoky 1976
Brandsma, Sauer, and Ayers 1983a
Christodoulou et al. 1974
Economic Analysis and ASA 1986
Goldenblatt and Bowers 1978
Koh and Chang 1973
Krishnappen 1983
Lavelle et al. 1981
Walker, Paul, and Bierman 1987
Wu and Leung 1983
Dredged material
Drilling muds and
produced water
Suspended sediments
Spilled oil
Dredged material
Dredged material
Dredged material
Suspended sediments
Sewage sludge
Drilling muds
Field and lab
Field and lab
Some
None
Lab
Field and lab
Lab and other models
Field
None
Other models
No
Potentially
No
No
No
No
No
No
Doubtful
No
versions of produced water and drilling mud models will be available in February 1989.
The drilling mud model was field validated for the important convective descent phase (O'Reilly et.al, 1988),
and laboratory validated for convective descent and dynamic collapse phases (Brandsma and Sauer, 1983).
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Although the model cannot be validated by field measurements, the general
concensus is that it overestimates long-term dilutions*
The OOC Mud Discharge Model, which is being expanded to include fluids
without particles, can predict the nearfleld and farfield dispersion of
almost any type of discharged fluid, including sewage sludge, for most
current regimes. The model contains the appropriate phases of dispersion
dynamics to predict dilution of dumped material; convective descent, dynamic
collapse, and passive diffusion. The first two phases that are important to
initial mixing have been laboratory and field validated for drilling fluid
discharges. Although this model only considers discharges from a fixed
point, it can easily be modified to predict dilutions from a moving barge.
It also has the capability to consider wake effects and particle
flocculation.
Presently, the computer models that are available for use in modeling
dispersion and initial mixing of sewage sludge dumped in the 106-Mile Site
are inapplicable. There are, however, candidate models as noted above that
have the potential of being used for sewage sludge dispersion determinations
after modification and/or verification. At this time, the recent nearfield
monitoring surveys at the 106-Mile Site provide the best alternative for
evaluating initial mixing.
2.2 CHARACTERIZATION OF SLUDGE TRANSPORT BARGES
This subsection presents a preliminary survey of the characteristics of
barges that are used to transport sewage sludge from New York and New Jersey
to the 106-Mile Site. Information on these barges was obtained from files
maintained by EPA Region II, and by contacting the New York City Department
of Environmental Protection and the various transportation companies
identified below.
2.2.1 Barge Characteristics
Sludge transport vessels are operated by the New York City Department of
Environmental Protection (NYCDEP) and four private transport companies.
Together, these transport companies and NYCDEP have permits to use 23 barges
2-4
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and nwstor vessels for the transport of sewage sludge to the 106-Mile Site.
Individual sludge dumping permits are issued for each transport vessel by EPA
Region II. Table 2.2 lists the 23 vessels, their ownership, and the
sewerage authorities serviced by each vessel.
Of thi 23 sludge vessels, only 14 travel to the 106-Mile Site on a
regular basis; the remaining 9 are primarily used for sludge transport and
transfer within the various New York and New Jersey harbors. The 14 barges
that dump regularly have a collective carrying capacity of nearly 46 million
gallons of sludge; the total capacity of the 9 standby barges is i.5 million
gallons. Santoro and Fikslin (1987) indicate that the 9 New York and New
Jersey sewerage authorities produced 1.5 billion gallons of sludge in 1985.
If this volume of sludge were dumped at the 106-Mile Site by the 14 regular
carriers, on average, each would be required to make 32 trips to the site.
NYCDEP owns and operates a fleet of four identical barges that have a
collective carrying capacity of 14 million gallons of sludge, which is
roughly one-third of the total carrying capacity of the 14 barges that
regularly transport sludge to the 106-Milt Site.
106-Mile Transport Associates is a consortium of three transportation
companies that carry sludge to the 106-Mile Site: Weeks Stevedorings Co.,
A & S Transportation Co., and General Transport/Standard Marine. Together,
these three companies own and operate 15 sludge barges. Nine of these barges
are regular dumpers at the 106-Mile Site, with a total carrying capacity of
22.5 million gallons of sludge, and roughly half the carrying capacity of the
entire 23-barge fleet.
National Seatrade Inc. owns one large sludge barge and three smaller
vessels. Only the large barge, the Seatrader I, regularly transports sludge
to the 106-Mile Site. The other vessels are primarily used for sludge
transport within harbors, but in rare cases, these small vessels do transport
sludge to the 106-Mile Site. The Seatrader I is the largest barge that
transports sludge to the 106-Mile Site; its carrying capacity is 9.3 million
gallons of sludge, which is approximately 20 percent of the carrying capacity
of the entire 14-vessel fleet that regularly dumps sludge at the 106-Mile
Site.
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TABLE 2.2 SUMMARY OF VESSELS THAT TRANSPORT SEWAGE SLUDGE TO THE
106-MILE SITE. SEWERAGE AUTHORITIES SERVICED BY EACH
BARGE OPERATOR ARE INDICATED.
Barge Operator
Vessel
Sewerage
Authority
New York City
Department of
Environmental
Protection
Weeks Stevedoring Co.l
A & S Transportation Co.*
General Transport/Standard
Marinel
National Seatrade Inc.
Lemon Creek
Springs Creek
Tibbetts Brook
tidal Is Cove
Weeks 701
Weeks 702
Weeks 703
Weeks 704
Dina Marie
Eileen
Kimberley Ann
Lisa
Maria
Veronica Evelyn
Leo Frank
Morris J. Herman
Princess B.
Rebecca K.
Susan Frank
OBI IV
Seatrader I
Sotoco II
E-57
New York City
Department of
Environmental
Protection
New Jersey:
Passaic Valley,
Middlesex County,
Bergen County,
Linden-Roselle,
Rahway Valley,
Essex and Union
Counties.
New York:
Westchester
County
same as Weeks
same as Weeks
Nassau County
Department of
Public Works
iThese owners serve six New Jersey sewerage authorities and Westchester
County under a joint venture called 106 Mile Transport Associates.
2-6
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Table 2.3 presents the sludge carrying capacity for each of the 23
vessels; the 14 vessels that are regular carriers to the 106-Mile Site are
listed separately from those that are standby carriers. The standby
carriers are much smaller than the regular carriers. Table 2.4 presents the
physical dimensions of each of the 23 vessels in the fleet.
Sludge transport vessels have two general hull categories: unpowered
barges or motor vessels. Unpowered barges are typically constructed with a
pointed bow, a rectangular cross-section, and a flat bottom. Some
(including the NYCOEP barges) have a notch in the stern for use by tugs when
pushing is necessary in harbors and alongside piers. All unpowered barges
are constructed of welded steel and are towed, using a long (wl/4 mile)
towing cable, to the 106-Mile Site. Motor vessels are basically self-powered
sludge tankers. These diesel-powered vessels operate under their own
control, with nothing in tow.
Typical construction for any vessel transporting liquid includes
internal compartmentalization, primarily to prevent instability and
capsizing. A cross-section and compartment plan for the New York City barges
is shown in Figure 2.1.
2.2.2 Dumping Methods
The vessels that dump sludge at the 106-Mile Site use three different
methods of dumping: gravity-induced bottom dumping; pumping; or an.eductor
system. Regardless of the dumping method, the individual sludge compartments
on a vessel are equipped with separate discharge lines, valves, or pumps so
that dumping rates can be controlled, either by on-board personnel or, in the
case of unmanned barges such as those operated by NYCDEP, by personnel on the
towing vessel (tug).
Table 2.5 lists the 14 vessels that regularly transport sludge to the
106-Mile Site and their individual dumping procedures. Bottom dumping is the
most common method (11 barges), compared to 2 vessels that pump sludge, arid
1 vessel (the SeatraderI) that uses an eductor. A brief description of
each dumping method is given below.
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TABLE 2.3 SLUDGE CAPACITY OF VESSELS THAT TRANSPORT SEWAGE SLUDGE TO THE
106-HILE SITE.
Barge
Operator
New York City
Department of
Environmental
Protection
Weeks
Stevedorings Co.
ASS Transpor-
tation Co.
General
Transport/
Standard'Marine
National
Seatrade Inc.
Regular Carriers
Capacity
Vessel (Short Tons)
Lemon Creek
Spring Creek
Tibbetts Brook
Udalls Cove
Weeks 701
Weeks 702
Eileen
Kimberlty Ann
Lisa
Maria
Leo Frank
Morris J. Herman
Princess B.
Seatrader I
IS ,000
15,000
15,000
15,000
6,400
17,832
18,132
8,000
8,000
7,900
5,500
12,000
12,000
38,528
Standby Carriers
Capacity
Vessel (Short Tons)
Weeks 703
Weeks 704
Dina Marie
Veronica Evelyn
Rebecca K.
Susan Frank
OBI IV
Sotoco II
E-57
4,000
3,000
2,900
2,900
1,620
996
954.5
6,200
2-8
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TABLE 2.4
PHYSICAL DIMENSIONS OF VESSELS THAT TRANSPORT SEWAGE SLUDGE TO THE 106-HILE SITE.
ro
i
Barge Operator
New York City Department
of Environmental Protection
Weeks Stevedoring Co.
A&S Transportation Co.
General Transport/Standard
Marine
National Seatrade Inc.
Vessel Type
Lemon Creek
Spring Creek
Tibbetts Brook
Udalls Cove
Weeks 701
Weeks 702
Weeks 703
Weeks 704
Dina Marie
Eileen
Kimberly Ann
Lisa
Mari a
Veronica Evelyn
Leo Frank
Morris J. Berman
Princess B.
Rebecca K.
Susan Frank
OBI IV
Seatrader I
Sotoco II
E-57
Barge
H
ii
ii
H
ii
it
H
ii
ii
ii
11
11
il
II
II
M/V
Barge
M/V
M/V
Barge
M/V
Barge
Dimensions
Length Width
380'
380'
380'
380'
266'
400'
290'
78'
211'
390'
272'
272'
300'
211'
298'
303'
303'
260'
260'
180'
430'
180'
300'
84'
84'
84'
84'
56'
80'
53'
43'
42 '-9"
78'
68'
68'
64'
42 '-9"
50'
90'
90'
46 '-6"
46 '-6'
38 '
105'
38'
50'
Loaded Sludge
Draft Compartments
21' -6"
21 '-6"
21 '-6"
21' -6"
11'
25'
16 '-8"
13'. 7»
12 '-6"
27'
18 '-4"
14'-11"
18' -4"
12 '-6"
15'
15 '-10"
15 '-10"
11'
11'
12 '-6"
35 '-6"
13 '-6"
13'
10
10
10
10
8
10
8
8
2
10
6
6
12
2
8
9
9
6
6
16
6
14
10
-------
I
t1
o
JD- StUDSE DISCHARGE VALV6
FOREPEAK BALLAST
BOW
THRUSTiR
FIGURE 2.1 DIAGRAM OF SLUDGE COMPARTMENTS WITHIN BARGES OPERATED BY THE
NEW YORK CITY DEPARTMENT OF ENVIRONMENTAL PROTECTION: REAR
VIEW OF PORT SIDE OF BARGE (UPPER); PLAN VIEW (LOWER).
-------
TABLE 2.5 SLUDGE DISCHARGE HETHODS AND MAXIMUM RATES FOR VESSELS THAT TRANSPORT SEWAGE SLUDGE TO
THE 106-MILE SITE.
Barge Operator
New York City
Department of
Environmental
Protection
Weeks Stevedoring Co.
A&S Transportation Co.
General Transport/
Standard Marine
National Seatrade Inc.
Average Estimated
Capacity Discharge Discharge Maximum
Vessel (Million Gallons) Method Duration (h) Discharge Rate
At 15,500 gal /mi n (gal /mi n)
Lemon Creek
Spring Creek
Tibbetts Brook
Udalls Cove
Weeks 701
Weeks 702
Eileen
Kimberly Ann
Lisa
Maria
Leo Frank
Morris J. Berman
Princess B.
Seatrader I
3.513
3.513
3.513
3.513
1.504
4.190
4.200
2.000
2.000
1.850
1.290
2.820
2.820
9.290
Bottom Dump
Bottom Dump
Bottom Dump
Bottom Dump
Bottom Dump
Bottom Dump
Bottom Dump
Bottom Dump
Bottom Dump
Bottom Dump
Bottom Dump
Pump Out
Pump Out
Eductor System
4
4
4
4
1.5
4.5
4.5
2
2
2
1.5
3
3
12.5
150,0001
150,0001
150,0001
150,0001
46,0002
139,5002
31,0003
31,0003
31 ,0003
31,0003
31,0003
31,0003
31,0003
13,500
1Attained if all 20 valves were opened at once.
2Capable of discharging full load in 30 minutes.
3Rates with valves fully opened.
-------
Bottom Dumping
In bottom-dumping operations, sludge exits the bottom of the barge via
dump valve openings that are installed in the bottom of each sludge
compartment. Dump valves are hydraulically operated and may be throttled to
vary sludge levels in each tank compartment. The sludge dump valves are
approved by the U.S. Coast Guard for the sptcific category of service in
which they are utilized. Although the valves can be closed somewhat more
than the position used to achieve dumping rates of 15,500 gal/min, extremely
low dumping rates would most likely lead to clogging of the valves.
For bottom-dumping barges, the maximum attainable discharge rate is a
function of the available pressure head, the viscosities of sludge and
seawater, and the configuration and diameter of the dump valve. The rate of
discharge varies with the square root of the pressure head, according to the
following expression:
Q - C A ( 2g Ah )i
where: Q = flow (ft3/sec)
C = a constant
A « discharge area (ft2)
g * gravity; 32 ft/sec2
Ah= pressure head differential (ft)
Pumping
Sludge is pumped out of the Morris J. Serman and the Princess B. using
variable speed, submersible slurry pumps. Discharge rates can be controlled
by varying the speed of the pumps. Pump discharge rates are affected by the
pressure head in the individual sludge compartment, but the effect of head on
discharge rates is much less for pumpers than bottom-dumping barges.
Eductor System
The eductor system used on the Seatrader I is unique. It operates on
the principle of aspiration caused by a pressure differential between two
fluids. Seawater, serving as the motivating fluid, is pumped into the sludge
compartment against the low head of the sludge. Seawater and sludge are
2-12
-------
consequently mixed to achieve a 1:1 dilution as the mixture is expelled into
the receiving water beneath the barge. This process does not require a
slurry pump because only clean seawater is pumped into the barge; the sludge
mixture exits the barge due to the pressure within the compartment.
The eductor system on the Seatrader I was installed less than 2 years
ago, and consequently, its effectiveness and maintenance requirements have
yet to be evaluated. It is expected that the eductor system will require
less maintenance than standard sludge pumping systems, which use slurry pumps
that are prone to mechanical failure.
Table 2.5 also presents the average time for each barge to discharge a
full load of sludge, assuming a constant rate of 15,500 gpm. With the
exception of the Seatrader I, which requires 12.5 h to dump its load of 9
million gallons, the remaining barges require between 1 and 5 h for dumping.
The maximum attainable discharge rates presented in Table 2.5 are
estimates based on information obtained from individual barge operators.
Although the individual barge representatives stated that the barges
discharge at a maximum rate of 15,500 gpm, they indicated that the barges are
capable of discharging at much higher rates. For instance, if the valves
were opened for all 10 sludge compartments of a New York City barge, then the
discharge rate could reach 150,000 gpm. Only the Seatrader I, which has an
eductor system, has a maximum discharge rate that is below the permissible
dumping rate of 15,500 gpm.
If dumping rates are to be lowered by factors of 10 or more (see Section
4), representatives from 106-Mile Transport Associates indicate (C. Hunt
personal communication) that severe engineering problems will arise. One
result is that only one sludge compartment will be dumped at a time, which
would pose serious vessel stability problems. Other considerations are given
in subsection 5.3.
2.3 NEARFIELD STUDIES OF SLUDGE PLUHE BEHAVIOR
This subsection presents a summary of recent field observations within
sludge plumes that were dumped at the 106-Mile Site. These observations
represent a high-resolution data set for analyses of the nearfield, short-
term behavior of sludge plumes. The results were obtained during EPA surveys
2-13
-------
to the 106-Mile Site in September of 1987 and 1988 ( EPA , 1992c; 1988b).
Although information was acquired on the physical behavior and transport of
sludge plumes during the nearfield survey in March 1988, the chemical data
from the survey were insufficient for accurate determinations of sludge
dilution versus time*
The primary scientific objectives of the two September surveys were to
* Track a specific portion of a sludge plume to monitor its movement
within and outside of the 106-Mile Site.
* Remain with the plume for at least 4 h for collection of water
samples for analyses of chemical and biological tracers and total
suspended solids.
* Conduct in situ measurements of near-surface currents and water
properties to identify physical features and processes that may
affect sludge plume behavior and transport.
* Acquire water samples for analysis to determine actual
concentrations of sludge components in a plume. Results are to be
used for testing compliance with marine water quality criteria and
calculating rates of sludge dilution.
* Perform all sampling activities for a number of sludge plumes to
acquire statistics on plume behavior for different barges under
various oceanographic conditions.
* Evaluate shipboard instrumentation and sampling procedures for
their suitability in monitoring of sludge plumes.
A major factor that contributed to the success of these surveys was the
instrumentation used for in situ sampling within the sludge plumes. In order
to achieve rapid, high-resolution measurements of physical water properties
concurrently with the collection of water samples for chemical analyses, a
seawater pumping system was integrated with a CTD (conductivity-
temperature-depth) profiling system. With the real-time sampling and display
capabilities of this system, it was possible to locate the most concentrated
parcels of sludge within the plume and position the underwater unit at the
depth of the turbidity maximum, which was indicative of the highest
concentrations of sludge. Thus, the profiling activities yielded accurate
measurements of
2-14
-------
Plume depth and thickness as a function of time, from which
plume cross-sectional area, and plume-averaged dilution can be
estimated.
Concentrations of chemical and biological tracers within
samples of plume water, from which sludge dilution can be
estimated for the most concentrated parcels of sludge within a
plume.
Figure 2.2 presents a time series plot of sludge dilution derived from
data collected during plume event DB-3 on September 3, 1987. Note that
dilution is plotted on a logarithmic scale to accommodate the wide range of
dilutions observed during the 9-h survey. This figure presents information
on the plume-averaged dilution (solid circles) as well as the dilution of
discrete parcels of plume water (open symbols), derived from analyses of
trace metals.
Plume-averaged dilutions, derived from the cross-sectional area of the
plume and the average dumping rate per unit of plume length, suggest a high
rate of dilution during the first 2 h after dumping. Initial dilutions
(within 5 min after dumping) were approximately 2,500:1; dilutions 30 min and
2 h after dumping were on the order of 10,000:1 and 80,000:1, respectively.
As indicated in Figure 2.2, the plume-averaged dilutions were much
greater than dilutions derived from chemical analyses of water samples
collected within the core of the plume. One may suspect that the high plume-
averaged dilutions were a result of overestimating the width of the plume,
but the error associated with this estimate is less than 10 percent. During
the first 2 h after disposal, the plumes spread laterally, but they remained
intact, such that horizontal turbidity profiles along the plume transects
exhibited no significant patches of "clean" receiving water inside the
distinct outer edges of the plume. Thus, these high plume-averaged
dilutions were not a consequence of "streaking" of the plume and
overestimation of plume width.
Detailed analyses of turbidity data within the individual plume
transects have revealed that the highest sludge concentrations are maintained
within a concentrated core which, on a volume basis, represents a small
percentage of the plume. As illustrated by the open symbols in Figure 2.2,
discrete parcels of sludge from the core of the plume were much less dilute
than the "average plume" derived from the plume dimensions. At the various
2-15
-------
100,000
^ 10,000--
Q
Ld
Ld
CO
QQ
O
1,000
100
PLUME EVENT OB-3
SEPTEMBER 1987
4 5
TIME (hours)
FIGURE 2.2 TIME HISTORY OF SLUDGE DILUTION WITHIN PLUME EVENT DB-3 AT THE
106-MILE SITE DURING SEPTEMBER 1987. SOLID CIRCLES REPRESENT
AVERAGE DILUTION OF ENTIRE PLUME; OPEN SYMBOLS REPRESENT TRACE
METALS RESULTS FROM DISCRETE WATER PARCELS WITHIN THE CORE OF THE
PLUME.
-------
sampling times indicated, separate analyses of copper, lead, and zinc were
performed on the samples collected within the most concentrated portion of
the plume. Dilutions were calculated by dividing the measured concentrations
of a trace metal by the mean concentration of that specific trace metal
within sludge generated by the Port Richmond treatment facility (Santoro and
Fikslin, 1987), which was the source of the sludge dumped during event DB-3.
The final report for the September 1987 survey ( EPA , 1992c) provides
detailed information on sludge dilution calculations.
The solid lines connecting the trace metal results in Figure 2.2
illustrate that (1) parcel dilutions were much lower than plume-averaged
dilutions, (2) the rate of dilution of concentrated parcels was much less
than the rate of plume-averaged dilution during the first 4 h after the dump,
and (3) the results from three trace metals were very similar. Within 5 min
after dumping, parcel dilutions were roughly i,000;lj at 4.4 h, parcel
dilutions were on the order of 4,500:1. The higher sludge dilutions
indicated at 3.4 and 4.3 h were obtained from water parcels situated outside
the most concentrated portion of the sludge plume, and consequently, they
are not appropriate in estimating minimum dilution.
Beyond 5 h after dumping for event DB-3, the sludge plume was broken
into patches of undetermined sizes. Using the real-time sampling system, it
was possible to locate relatively concentrated parcels of sludge water
between 5 and 9 h after dumping, but there was no way to ensure that a single
parcel was being surveyed repeatedly. Chemical analyses of the most
concentrated portion of sludge water located 8.5 h after the dump
demonstrated a parcel dilution of 77,000:1 (Figure 2.2). Attainment of these
dilutions required an increase in the rate of dilution over the rate that is
demonstrated between 1 and 4 h. This accelerated dilution was most likely
attributed to the break-up of the plume,* with the directed sampling
capability during the survey, we are relatively confident that this sample
was taken from the most concentrated portion of the plume that existed at the
time of the observation.
Figure 2.3 presents a conceptual diagram (with linear dilution axis) of
the three phases of plume dilution that may have occurred during event DB-3:
initial, wake-induced mixing, gradual oceanic mixing, and accelerated mixing
after plume break-up. The solid line in this figure represents a
2-17
-------
10,000
ro
t
03
g
i
ID
_j
o
_j
O 5,000 -f
C£
<
Q.
bJ
O
Q
MIXING AFTER
PLUME BREAK-UP
INITIAL WAKE MIXING
OCEANIC MIXING (D J
WEAK MIXING CONDITIONS
> ACTIVE MIXING CONDITIONS
0
8
TIME (hours)
FIGURE 2.3 CONCEPTUAL DIA6RAN OF THE DILUTION OF SLUDGE PARCELS WITHIN PLUMES FOR TWO
CASES OF MIXING CONDITIONS.
-------
hypothetical case of weak mixing conditions (e.g., low winds, calm seas)
such as those encountered during plume event DB-3. Plume break-up and
accelerated dilution apparently occurred after 4 h. The broken line in
Figure 2.3 represents a case of active mixing, whereby the rate of oceanic
mixing would be greater than the rate during weak mixing conditions. During
active mixing, plume break-up may occur well before 4 h.
All four of the plumes monitored during the September 1987 survey
exhibited dilution characteristics similar to those representing weak mixing
conditions in Figure 2.3. Although the linear plumes began to break up 2 or
3 h after dumping, concentrated patches of plume water remained relatively
intact for periods longer than 4 h. For example, Figure 2.4 presents minimum
dilutions of plume DB-3, based upon field-measured copper concentrations and
mean copper values of sludge described by Santoro and Fikslin (1987). With
dilutions presented on a linear axis, it is evident that the rate of parcel
dilution from initial mixing (5 win after dumping) to 4 h was quite constant
(«900 per h).
The dilution estimates given in Figures 2.2 and 2.4 provide a realistic
representation of the short-term behavior of plume event DB-3, but three
factors contribute errors to these minimum dilution estimates; (1) spatial
sampling problems; uncertainties in having sampled the maximum concentration
within the plume at a given time, (2) laboratory/analytical errors during
processing and analysis of trace metal samples, and (3) uncertainties in the
actual metals concentration in the sludge that was dumped. Positioning
errors cannot be quantified, but missing the maximum concentration will
result in higher apparent dilutions than actually exist within the core of
the plume. Laboratory errors are small (<10%), but uncertainties in sludge
constituent concentrations are large. Constituent concentrations of the
dumped sludge were not measured; dilutions were calculated from published
values of constituent concentrations in sludge. Santoro and Fikslin (1987)
estimate that mean copper concentrations in Port Richmond sludge are SO.9
mg/L with a standard deviation of 36% of the mean. Thus, with *1 standard
deviation about the mean, copper concentrations could range from 32.6 to 69.2
mg/L for the Port Richmond facility. This variation in copper concentration
may also result in a *36 percent uncertainty in the rate of dilution after
initial wake mixing (e.g., 900 *324 per hour).
2-19
-------
i
rvj
o
20.000
15,000 +
O
Q
bJ
on
i_y
c/)
m
10,000
5,000 +
o
0
O DB-3 SEPTEMBER 1987
A DB-21 SEPTEMBER 1988
DB-23 SEPTEMBER 1988
456
TIME (hours)
8
10
FIGURE 2.4 TIME HISTORY OF OBSERVED SLUDGE DILUTION WITHIN THE CORE OF
SLUDGE PLUMES SURVEYED IN SEPTEMBER 198? AND 1988. DILUTIONS ARE
BASED UPON COPPER CONCENTRATIONS WITHIN WATER SAMPLES.
-------
To reduce these errors during the September 1988 survey, sludge samples
were obtained from the individual barges that transported sludge to the site
during the survey. Trace metals analyses of (1) the barge (sludge) samples
and (2) water samples collected from the core of the plumes during the
nearfield survey yielded direct estimates of the time rate of dilution of the
sludge plumes.
In addition to the dilution results from September 1987, Figure 2.4
presents dilution information from plume events DB-21 and DB-23 monitored
during the September 1988 nearfield survey ( EPA , 1988b). As discussed
above, the 1988 results were derived from the ratio of copper concentrations
in plume water samples to those determined from analyses of 100% sludge.
This figure illustrates that both the range and the rate of change of
dilution were very similar for plume events DB-3 and DB-21. Table 2.6
indicates that initial dilutions («5 min after dumping) were 1,018:1 and
1,724:1 for plume events DB-3 and OB-21 respectively; dilutions for both were
near 4,000:1 4h after dumping. The results from plume event DB-21 also
illustrate that the rate of core dilution remained relatively constant for
more than 8h,
The dilution results from plume event DB-23 exhibited a similar rate of
dilution during the period from 1 to 4h after dumping, but the extent of the
dilution was roughly twice that of plume events DB-3 and DB-21. We suspect
this offset was due to uncertainties in the copper concentration of the
sludge that was dumped in the portion of the plume surveyed (the barge
samples were collected prior to transit to the 106-Mile Site and various
compartments of sludge could have had different chemical characteristics).
2-21
-------
TABLE 2.6 OBSERVED DILUTIONS AND RATES OF DILUTION FOR SLUDGE PLUMES SURVEYED IN SEPTEMBER 1987 AND 1988.
Plume
Survey
DB-3
DB-21
DB-23
Observed Dilutions Rate of Dilution (1/h)
Date Sain Ih 4h 7h t*lh to 4h t-5«in to 4h
9-87 1,018 2,055 4,258 - 734 827
9-88 1,724 2,629 3,717 5,303 363 508
9-88 - 5,200 6,664 10,887 488 610*
^Estimated value.
-------
3. DEVELOPMENT OF DUMPING RATE EQUATION
One of the primary objectives of this work assignment is to use existing
information (in this case, field dati rather than predictive models) to
determine the rate at which sludge plumes are diluted at the 106-Mile Site.
Field measurements of short-term sludge dilution are necessary in order to
determine whether dumping operations are in compliance with EPA water quality
criteria, but the results can also be used to develop a conceptual dilution
model that will allow prediction of optimum sludge dumping rates which, in
turn, will achieve the dilutions required by the water quality criteria. The
process of developing a realistic model of sludge dilution entails a number
of steps:
1. Utilization of the field results from the nearfield studies at the
106-Mile Site to determine the rate of change of sludge
concentration within the plumes, and hence, the rates of sludge
dilution.
2. Identification of the major physical processes responsible for
sludge plume dilution, followed by formulation of an empirical
model for dilution of sludge parcels based upon the existing field
observations.
3. Application of the empirical model of sludge dilution for
prediction of the rate at which sludge should be dumped in order
to achieve dilutions that satisfy EPA water quality criteria.
4, Identification of the major sources of variability (e.g.,
- oceanographic conditions, barge dumping characteristics, and sludge
characteristics) that will affect sludge dilution yet cannot, at
the present time, be quantified, given the limited set of field
observations.
5. Recommendation of additional field measurements that will
facilitate better predictions of sludge dilution, and consequently,
more defensible rates for dumping of sewage sludge at the 106-Mile
Site.
The following discussion addresses the formulation of the empirical model of
sludge dilution and the assumptions made during its development.
3-1
-------
3 a SLUDGE PLUME DILUTION
The field observations of sludge parcel dilution, which were presented
in Subsection 2.3, indicate three phases of mixing during the first 8 h
after dumping: (1) an initial period (from 0 to w5 minutes after dumping) of
turbulent, wake-induced mixing, (2) a gradual phase of relatively slow
mixing primarily due to oceanographic processes, and (3) an accelerated
mixing phase when the sludge plume is broken up and sludge parcels from the
interior of the plume are actively mixed with clean receiving water.
Dilution, D, at any time, T, after dumping can therefore be estimated from an
expression which contains the three observed phases of mixing:
dD0 x T
it
bu
0
it
x T
t
bu
(1)
where
dDo
if
3t
* the dilution of sludge parcels at any time, T,
after initial wake-induced mixing
= the dilution achieved (at T«5 rain) from initial,
wake- induced mixing
= the time rate of change of sludge parcel dilution
during the time from dumping (T=0) to the time
at which the plume breaks up (T=bu)
* time after dumping
= the time rate of change of sludge parcel dilution
during the period after plume break-up (T*bu)
The time at which a sludge plume starts to physically break up is highly
dependent upon oceanographic conditions, sludge characteristics, barge
dumping characteristics, and other physical, chemical, and engineering
factors. Under extreme conditions of high waves and current shear, plumes
may break up within 1 to 2 h after dumping, but during weak mixing
conditions, plumes may remain relatively intact for periods of 4 h or
longer.
3-2
-------
The field observations of plumes during September 1987 and 1988 were
made during relatively calm sea and mixing conditions, and consequently, the
effect of plume break-up on parcel dilution was not substantial until many
hours (» 4 h) after dumping. Additional surveys of sludge plume behavior
will be required to develop a statistical estimate of the time at which
plumes break up, but based upon the limited field data, we can assume that a
significant number of sludge plumes will remain relatively intact for at
least 4 h. This type of plume behavior would be appropriate for development
of a model that predicts the minimum dilution of sludge parcels at any time
after dumping.
If we are concerned about the conservative behavior of sludge plumes and
dilution only up to 4 h after dumping, then Eq.(l) reduces to
dD0 x T
4h
0
(2)
This simplified expression represents the two-phase behavior of sludge parcel
dilution prior to plume break-up: dilution at 4 h is achieved by an initial
phase of rapid dilution (to achieve dilution Di), followed by a slower phase
of oceanographic mixing and dilution,
3.1.1 Wake-Induced Initial Mixing
Mixing of sludge within the wake of the barge is extensive during the
first few minutes after dumping. Much of this mixing (and sludge dilution)
is attributed to the turbulence of the receiving water immediately behind the
barge, but within 5 to 10 minutes after dumping, the momentum of the wake
diminishes and other factors govern plume mixing and dilution.
During the period of initial (0 to B§ min) mixing, wake momentum may be
the most important factor, but there are additional parameters/processes
that affect mixing and dilution. Initial, wake-induced dilution, Dj, is
expected to be a function of the following parameters:
3-3
-------
f [ R, B, S, Z, MW ] (3)
where R - the effective dumping rate: the amount of
sludge dumped per unit of track (pluwe) length,
expressed in units of gal/ft
B = the effect of barge characteristics (size, speed,
draft, depth of discharge port) and dumping method
(bottom dump, pump, or eductor)
S = sludge characteristics (specific gravity, solids
content, ability to flocculate, density relative to
receiving water)
Z pycnocllne depth
MW - mixing (dispersion) due to winds and waves
Determination of the relative effects of these parameters on initial (0
to «5 min) sludge dilution would require rapid, intensive field measurements
of plume mixing over a wide range of dumping rates, barge types, dumping
methods, sludge types, stratification regimes, and oceanographic mixing
regimes. Because this research activity is well beyond the scope of the EPA
Ocean Dumping program, we will represent initial (0 to «5 min), wake-induced
dilution as a single parameter, Df, in the reduced equation for sludge
dilution (see Eq. 2). With the field results from the past nearfield
monitoring surveys, it is possible to estimate initial dilution, Of, 5 min
after dumping, but we cannot determine the relative importance of the
individual parameters in Eq. (3).
To facilitate future comparisons between initial dilution rates from
other monitoring surveys, the various engineering and environmental
conditions encountered during plume event DB-21 (September 1988) are
summarized below.
R effective dumping rate was 22.85 gal/ft, based upon an average
dumping rate of 10,855 gal/min at a barge speed of 4.7 kn.
B barge configuration was that of the Princess B, which pumps
sludge out of its side; this barge has a maximum draft
of 15 ft and a beam of 90 ft.
3-4
-------
S the sludge within the barge was from Passaic Valley,* the
specific gravity of the sludge (»1.QQ4) was less than that
of the receiving water (»1.Q23), which had water properties
of »22°C and «33 ppt.
Z the seasonal pycnocline at the 106-Mile Site was strong and
shallow, situated between roughly 25 and 40 m.
MK surface mixing conditions were mild, due to calm (<3 ft) seas
and winds less than 15 kn.
As indicated in subsection 2.3, the initial dilution of sludge parcels 5 min
after dumping for plume event DB-21 was estimated at 1,724:1 from analyses of
trace metals data. Because the relative effects of the various parameters in
the initial dilution equation (Eq. 3) are unknown, we can only speculate on
how the rate of initial dilution would change under different dumping and
environmental conditions?
MW Had the sea and wind conditions been more severe (i.e., during
winter storm events) initial dilution might have been significantly
greater due to increased dispersion.
Z The observed sludge plume might have settled somewhat deeper, and
dilutions might have been greater had there been no seasonal
pycnocline. Preliminary results of the winter survey indicate,
however, that sludge dumped at rates near 15,000 gal/min does not
settle deeper than about 30 m in the first 8 h following dumping.
S Other than from laboratory studies, little is known about the
settling characteristics of the various sludges dumped at the
site. Nevertheless, the saline receiving water will, during all
seasons, be much more dense than the sludge dumped at the site,
such that all plumes will be relatively buoyant and variations in
sludge settling characteristics may have a second-order effect upon
initial dilution.
B The Princess B, which pumps sludge out of one side of the vessel,
may have somewhat different initial mixing characteristics than
barges which are bottom dumpers, but the available field results
from barges of different configurations suggest that initial
dilution may be relatively insensitive to dumping method.
In summary, the environmental conditions (parameters MW and Z) during
plume event DB-21 represent mild conditions for sludge dilutions (conditions
that produce low dilutions). Because the object of the present analysis is
3-5
-------
to derive a model for prediction of worst-case (lowest) dilutions, the field
data from event DB-21 are appropriate for development of the model.
For the purpose of developing a conservative model, we will assume that
(1) all sludges will behave similarly during the first few minutes after
dumping, and (2) the rate of initial mixing is generally the same for all
barge configurations. With these assumptions, the only parameter remaining
that will appreciably affect the wake-induced dilution, Dj, is the effective
dumping rate, R. We expect that dilution is inversely proportional to
effective dumping rate, such that we obtain the following expression for
initial dilution:
Di * f (1/R)
The recent field observations of plume width within the waks of barges
indicate that, during the initial period of wake-induced mixing, the sludge
plume is confined within the turbulent mixing volume created by the barge
wake. For the New York barges, the initial plume is as wide as the barge
wake, but for other barges such as the Princess B, the plume is a fraction of
the wake width. Therefore, we may assume that the initial (t=0) mixing
volume behind a barge has an upper limit equal to the volume of the barge
wake (roughly the barge width times the draft), and to a first-order
approximation, the average dilution would be inversely proportional to the
volume of material dumped in the wake (the effective dumping rate, R). In
the absence of short-term (0 to 5-iin) measurements behind the various
barges, we will consider the initial mixing regime as a linear system such
that
Di = A/R
where A » a constant relating dilution
to effective dumping rate
This linear expression can then be used to predict effective dumping rates
from observed dilutions and known dumping rates:
3-6
-------
[ R x Of ] obs - A = [ R x Di ] req
or R req s [ R x Di ] obs (4)
[ Di ] req
where R req = the effective dumping rate that will be
required to achieve a specific dilution
DI req = the required initial dilution (at
t*5 min) based upon compliance with water
quality criteria at 4 h
and 'obs' refers to observed initial dilutions and
average effective dumping rates from plume
event DB-21
This expression will be used later, in conjunction with Eq. (2), to obtain an
empirical equation for determining dumping rates which are based upon (1)
dilutions required to prevent selected sludge constituents from exceeding
water quality criteria at 4 h, (2) observations of initial dilution, and (3)
observed rates of oceanic mixing and sludge dilution.
3.1.2 Oceanic Mixing
After the initial (0 to «5 min) period of wake-induced turbulent mixing,
sludge plumes are diluted at slower rates as a result of buoyancy effects,
sludge flocculation and settling, and oceanic dispersion processes. Under
extreme wind and wave conditions, near-surface plumes may be dispersed at
rates that approach the rates achieved during wake-mixing, but most of the
time, oceanic dispersion is relatively slow. For the period following wake-
induced mixing, the factors expected to control the rate of sludge dilution,
dD0, are given below:
3t
dD0 = f [ Di, S, 2, Mw, Mc ] (5)
dt
3-7
-------
whert Dj * the extent of wake-induced initial dilution
S = sludge characteristics ( e.g., flocculation and
settling)
Z « pycnocline depth
HW » dispersion due to winds and waves
MC « dispersion due to current shear
Di, the initial dilution 5 minutes after dumping, Is an important
factor in the longer-term (5 min to 4 h) dilution phase because, if the
effective dumping rate is high and the dilution is low, the core of the plume
will be more concentrated and achievement of a specified (high) dilution will
require a longer period of time.
Sludge characteristics, pycnocline depth, and surface mixing due to
winds and waves will affect sludge dilution as described during the phase of
initial mixing* Dispersion due to current shear was not expected to have a
major effect upon dilution during the first few minutes after dumping,
because the turbulence due to barge momentum is much greater than the
effective mixing due to current shear. However, after the wake has lost its
momentum, current shear, if present, can effectively increase dilution by
lateral displacement of portions of the plume.
During plume event DB-3 (September 1987), strong current shear at the
base of the surface mixed layer effectively increased the rate of dilution
within the plume. Had the current shear been weak or nonexistent (which may
be the typical case except during the passage of warm-core eddies), the rate
of plume dilution might have been less. During the September 1988 survey
(plume events DB-21 and DB-23), there was no significant current shear at the
base of the mixed layer. As indicated in Table 2.6, the rate of dilution
from 0 to 4 h for DB-21 and DB-23 was significantly less than observed for
DB-3, but we cannot be sure this difference was mainly attributed to the lack
of current shear.
To summarize, although we can identify the physical factors/processes
that affect the rate of sludge plume dilution, dDo, after the period of
Bt
3-8
-------
Initial, wake-induced mixing, we do not have sufficient field data to
quantify the effects of each process in Eq. (5). He will therefore estimate
the rate of dilution, dD0, from specific field data of representative
3t
sludge plumes. As discussed in subsection 2.3, the results from plume event
DB-21 provide the most conservative (lowest) rate of dilution during the
first 4 h following dumping: a 500:l/h« This rate will be used in the
following section.
3.2 DUMPING RATE EQUATION
Derivation of an empirical equation for prediction of optimum dumping
rates requires combination of Eqs. (2) and (4):
or
D
wqc
req
req
Wqc
dDo x T
dD0 x T
"St
t-4
t=0
t=4
t=0
(2)
and
req
R obs
i obs
Combining Eqs. (2') and (4') yields
req
(4')
R req
R obs
D wqc
x Di obs
- dD0 x T
at
t-A
t=0
(6)
3-9
-------
where R feq - the required effective dumping rate to
achieve a specified 4 h dilution, D wqc*
that is based upon water quality criteria
D wqc = the dilution at 4 h that is required by
the water quality criteria
obs» Di obs = field observations of plume event DB-21 during
September 1988
The underlying concepts and assumptions inherent in this empirical
dumping rate equation (Eq. 6) are illustrated in Figure 3.1* This figure
schematically represents the observed time series of sludge parcel dilution
from plume event DB-21 (lower line), as well as the required dilution (upper
line) that would be necessary to achieve a 4 h dilution, 0 wqci of 20,000:1.
Note that this dilution of 20,000:1 is merely an example; actual dilution
requirements for each permit applicant are given in subsection 4.1.
This conceptual dilution model (Eq. 6) is based on two assumptions:
* The rate of oceanic dilution from 0 to 4 h, dDo,
if
is equivalent for the observed and required dilution cases.
The required initial dilution (at Tw5 min), Di feq» can be
- achieved by a linear reduction in the effective dumping rate, R.
Thus, if D Wqc (at 4 h) can be specified by water quality criteria, then Eq.
(6) can be used to predict the effective dumping rate, R req> that would
achieve the required dilution at 4 h. A sample calculation is provided
below.
Using the results of plume event DB-21:
R obs * 22.8 gal/ft (10,855 gal/min ^ 4.7 kn * 101.3
ft-h/min-nmi)
3-10
-------
25,000
Ul
I
20.000 - -
./ Dj woe
Required Dilution jf
Observed Dilution
2 3
TIME (hours)
FIGURE 3.1 CONCEPTUAL MODEL OF SLUDGE PLUME DILUTION FROM OBSERVATIONS
(LOWER LINE) DURING PLUME EVENT DB-21. IF A DILUTION OF 20,000
IS REQUIRED BY HATER QUALITY CRITERIA AT 4 ht THEN THE REQUIRED
DILUTION IS REPRESENTED BY THE UPPER LINE.
-------
Oi obs * 1,724
dDo « 500 per hour
ar
t=4
x T
= 500 x 4 h = 2,000
and, if the water quality criteria (e.g., for copper), require a dilution of
20,000:1 at 4 h:
D Wqc " 20,000
then, using Eq. (6) we obtain
R req = 22.8 x 1.724
20,000 - 2,000
req
* 2.2 gal/ft
for the effective dumping rate that would be required to meet water quality
criteria, based upon the field observations from plume event D8-21.
To determine the volume dumping rate, in units of gallons per minute,
requires multiplication of the effective dumping rate by the average barge
speed during the dumping operation?
VDR = R req x K x 101.3 ft-h (7)
min-nmi
where VDR = the volume dumping rate
R req = tne required effective dumping rate (gal/ft)
K - barge speed (kn)
During plume event DB-21, the barge Princess B was traveling at 4,7 kn such
that the volume dumping rate should have been
VDR = 2.2 gal/ft x 4.7 kn x 101.3
« 1,047 gal/rain
3-12
-------
to achieve a dilution of 20,000:1 at 4 h after dumping. Note that if the
barge speed had been 3 kn, the volume dumping rate would have to be lowered
to 668 gal/min (3/4.7 x 1,047).
Combination of Eqs. (6) and (7) yields the complete expression for
determination of volume dumping rates from field observations of event DB-21
in September 1988.
VDR * 101.3 x K x R obs x Di Obs
D wqc - ||o x T
It
and since V obs - R obs x K * 101.3
then
t=4
t*0
VDR " V obs x Di obs
0 wqc - dDo x T
dt
t-4
t=0
(8)
Substitution of results from plume event DB-21 yields
VDR * 10,855 x 1,724 1.8714 x 10?
D Wqc - 500 x 4
0 wqc - 2,000
(gal/min)
Section 4 presents sludge dumping rates that are based upon various values of
0 wqs in tne above expression. Note that this equation assumes a barge speed
of 4.7 kn (equivalent to that during plume event DB-21). To determine the
volume dumping rate, VQRS at any barge speed, S, the rate for 4.7 kn (for
VDR) can simply be multiplied by the ratio of speeds*.
3-13
-------
VDRS * VDR x s
477
The following subsection demonstrates the importance of barge speed to the
volume dumping rate (in gal/rain),
3.3 BARGE SPEEP CONSIDERATIONS
When considering sludge dumping rates, the most important point to
remember is that plume dilution and compliance with water quality criteria
are more dependent upon the effective dumping rate (in gal/ft) than the
volume dumping rate (in gal/min). For a given volume dumping rate, barges
that travel relatively fast (5 to 8 kn) tffectively dump much less sludge
per unit track length than do barges that travel slower.
Present EPA regulations for dumping of sewage sludge at the 106-Mile
Site specify (I) a maximum volume dumping rate, VDR, of 15,500 gal/min, and
(2) a minimum barge speed of 3 kn. Compliance with these regulations is
represented by the shaded region in Figure 3.2,
Under specific dumping conditions of 15,500 gal/min and 3 knf the
effective dumping rate, R( is 51 gal/ft. Also shown in Figure 3.2 is a line
indicating the set of barge speeds and volume dumping rates (in gal/min)
that satisfy the case of R » 51 gal/ft. The shaded region illustrates that
compliance with EPA dumping regulations (which are based upon volume dumping
rates and barge speeds) will normally result in effective dumping rates that
are well below the implied maximum rate of 51 gal/ft. For instance, if
barges dump at 15,500 gal/min while traveling at speeds >3 kn, the following
effective dumping rates, R, results
At 6 kn and 15,500 gal/min, R = 25.5 gal/ft
At 9 kn and 15,500 gal/min, R = 17.0 gal/ft
Thus, if the requirement were to achieve an effective dumping rate of 51
gal/ft, the volume dumping rates, V, could be increased as follows:
3-14
-------
20,000
tn
~ 15,000--
D
en
Ld
O
z
Q_
10,000--
5.000--
BARGE SPEED (knots)
FIGURE 3.2 PLOT OF VOLUME DUMPING RATE (6AL/MIN) VERSUS BARGE SPEED. THE
SHADED REGION REPRESENTS EPA DUMPING REGULATIONS. SOLID LINES
REPRESENT TWO VALUES OF THE EFFECTIVE DUMPING RATE IH UNITS OF
GAL/FT.
-------
To achieve R <= 51 gal/ft at 6 kn, V = 31,000 gal/mi n
To achieve R = 51 gal/ft at 9 kn, V - 46,500 gal/min
If EPA continues to regulate ocean dumping by specifying an upper limit
on the volume dumping rate, regardless of barge speed (so long as it exceeds
3 knots), the effective dumping rate should at least be considered when
setting criteria for ocean dumping violations. For instances, Figure 3.3
illustrates the volume dumping rates and barge speeds for the barges surveyed
during the September 1987 and 1988 surveys at the 106-Mile Site. Barges
(events) DZ-1, DB-2, DB-3, DB-4, DB-21 and DB-23 were all dumping at rates
below 15,500 gal/min, and at barge speeds greater than 3 kn, in accordance
with permit requirements. Their effective dumping rates differed greatly,
however, on account of large differences in barge speed. Event DB-3 had the
lowest effective dumping rate (R a 16 gal/ft) because it had the highest
barge speed; event DB-2 had the highest effective dumping rate (R « 29
gal/ft) of the four events, with volume dumping rates less than 15,500
gal/min. Nevertheless, the volume dumping rates for all of these barge
events could have been increased substantially beyond 15,500 gal/min while
maintaining an effective dumping rate less than 51 gal/ft (the EPA
requirement based upon 15,500 gal/min and 3 kn).
Figure 3.3 also illustrates that although plume event DB-1 had a volume
dumping rate in excess of 15,500 gal/min, its effective dumping rate (R«33
gal/ft) was still less than the implied EPA rate of 51 gal/ft. These
examples illustrate that, if sludge dumping rates are to be based upon water
quality criteria, then dumping rates should be based upon the effective
dumping rate; volume dumping rates could then be specified for a given barge
speed, or range of speeds (e.g., 4-6 kn).
3-16
-------
20,000
CO
I
15.000
o
0>
UJ
^
or
o
£=
Q_
10.000
5,000 --
BARGE SPEED (knots)
FISURE 3.3 PLOT OF VOLUME DUMPING RATE (§al/«in) VERSUS BARGE SPEED.
VARIOUS CASES ARE GIVEN FOR THE EFFECTIVE DUMPING RATE.R.
(gal/ft). BARGE DUMPING CHARACTERISTICS FROM SEPTEMBER 1987 AND
1988 ARE REPRESENTED BY INDIVIDUAL POINTS.
-------
4. RECOMMENDED DUMPING RATES
The previous section presented an empirical equation (Eq. 8) for
estimating the rate at which sewage sludge should be dumped in order to meet
toxicity requirements and water quality criteria at the 106-Mile Site.
Although additional field measurements will be necessary to validate this
formula under a variety of oceanographic conditions, dumping rates, and barge
configurations, EPA is currently faced with tirae constraints for sludge
dumping permits, and consequently, this preliminary formula will be used to
set initial sludge dumping rates for the 106-Mile Site. As additional field
data become available from subsequent monitoring studies at the 106-Mile
Site, modifications to the various coefficients in the dumping rate equation
should be considered.
In the following subsections we use the empirical dumping rate equation
to develop
* Specific dumping rates for each permit applicant.
* A nomograph for selection of dumping rates according to specific
dilution requirements that may be specified at a later date.
4.1 DUMPING RATES FOR INDIVIDUAL PERMIT APPLICANTS
EPA Region II has received applications for permits to dump municipal
sewage sludge at the 106-Mile Site from nine wastewater treatment authorities
in New York and New Jersey:
Permit App 1icants Abbreviation
Passaic Valley Sewerage Commissioners PVSC
Middlesex County Utilities Authority MCUA
Bergen County Utilities Authority BCUA
Linden-Roselle Sewerage Authority LRSA
Rahway Valley Sewerage Authority RVSA
Joint Meeting of Essex and Union Counties JMEUC
New York City Department of Environmental Protection NYCDEP
Nassau County Department of Public Works NCDPW
VJestchester County Department of Environment Facilities WCDEF
4-1
-------
Each permit application includes information on (1) the concentrations of
chemical constituents within the whole sludge, and (2) results of whole
sludge toxicity tests. With the exception of the NYCDEP, each permit
application provides information on the sludge from a single treatment
facility. In the case of NYCDEP, however, the permit application provides
data on the maximum chemical concentration or most toxic toxicity test
results obtained from any one of twelve treatment facilities. Thus, high
chemical concentrations from a single New York City plant apply to all plants
designated in the NYCDEP permit application.
Tables 4.1 and 4.2 present metal and toxicity characterization data,
respectively, from analyses that were conducted on whole sludge samples
obtained in August 1988 from the nine sewerage authorities in New York and
New Jersey. Analytical methods and a comparison of results with data
provided in the permit applications are provided in a separate report
(Battelle, Ii88f). The two tables also present estimates of the dilution
that would be required to meet the applicable metal-based or toxicity-based
water quality criteria.
As indicated in Table 4.1, the highest metal-based dilutions are
governed by copper for eight of the nine sewerage authorities,* mercury-based
dilutions exceed those of copper only for the Bergen County Utilities
Authority (8CUA). The metal-based dilutions range from 4,140 for Nassau
County to 80,000 for BCUA. The toxicity-based dilutions also have a wide
range of valuesi from 4,740 for Middlesex County to 166,700 for Linden-
Roselle. Comparison of Tables 4.1 and 4.2 illustrates that metal-based
dilutions exceed toxicity-based dilutions for five of the nine sewage
authorities studied.
To relate the required dilutions presented in Tables 4.1 and 4.2 to
actual sludge dumping rates, we have used the empirical dumping rate equation
(Eq. 8) given in the previous section to calculate the volume dumping rate
(in gal/min) that would be required to achieve the specified dilutions 4 h
after dumping and thus meet water quality criteria.
Table 4.3 presents volume dumping rates for each sewerage authority
based upon the required dilutions given in Tables 4.1 and 4.2,- dumping rates
are also given as a function of barge speed (e.g., 3, 6, and 9 kn)» These
4-2
-------
TABLE 4.1 WHOLE SLUDGE METAL CHARACTERIZATION RESULTS FROM THE NINE NEW
YORK-NEW JERSEY SEWERAGE AUTHORITIES APPLYING FOR PERMITS TO
DISCHARGE SEWAGE SLUDGE AT THE 106-HILE SITE. SAMPLES WERE
COLLECTED IN AUGUST 1988.
Metal (ng/L whole sludge)
Authority Cu Hg Dilution*
PVSC 42.0 14,500
MCUA 68.0 23,450
BCUA 2.00 80,000
LRSA 80.0 27,590
RVSA, 16.0 5,520
JMEUC 36 12,410
NYCDEP 38.0 13,100
NCDPW 12.0 4,140
WCDEF 56.0 19,310
PVSC - Passaic Valley Sewerage Commissioners.
MCUA = Middlesex County Utilities Authority.
BCUA = Bergen County Utilities Authority.
LRSA = Linden-Roselle Sewerage Authority.
RVSA = Rahway Valley Sewerage Authority.
JMEUC = Joint Meeting of Essex and Union Counties.
Metal
Cu
Cu
Hg
Cu
Cu
Cu
Cu
Cu
Cu
NYCDEP = Composite of the Mew York City Department of Environmental
Protection facilities.
NCDPW = Nassau County Department of Public Works.
WCDEF = Westchester County Department of Environmental Faci
lities.
aoilution based on the metal requiring the greatest amount of dilution to
meet water quality.
4-3
-------
TABLE 4.2 WHOLE SLUDGE TOXICITY RESULTS FROM THE KIHE NEW YORK-HEW JERSEY
SEWERAGE AUTHORITIES APPLYING FOR PERMITS TO DISCHARGE SEWAGE
SLUDGE AT THE 106-MILE SITE. SAMPLES WERE COLLECTED IN AUGUST
1988. THE MAXIMUM TOXICITY BASED SLUDGE DILUTION REQUIRED FOR EACH
MUNICIPALITY ARE LISTED.
LC50 (% whole sludge)
Authority*!
PVSC
MCUA
BCUA
LRSA
RVSA
JMEUC
NYCDEP
NCDPW
WCDEFW
Menidia
beryl Una
0.49
5.95
1.55
0.53
1.49
1.92
1.59
2.33
0.91
Mvsidopsis
bah la
0.17
2.11
2.10
0.06
0.88
1.68
2.25
0.92
1.17
Toxicity
Based
Required
Dilutionb
58,800
4.740
6,450
166,700
11,360
5,950
6,290
10,870
10,990
aAbbreviations are defined in Table 4,1.
bThe species with the lowest LC50 and an application factor of 0.01 were used
to determine the required dilution.
4-4
-------
TABLE 4.3 COMPARISON OF SLUDGE DUMPING RATES BASED ON TOXICITY AND TRACE
METAL RESULTS. REQUIRED DILUTION DATA WERE DERIVED FROM THE
AUGUST 1988 SLUDGE CHARACTERIZATION STUDY. DUMPING RATES WERE
BASED ON OBSERVED DILUTION RATES FROM THE SEPTEMBER 1988 SURVEY AT
THE 106-MILE SITE.
Authority*
PVSC
MCUA
BCUA
LRSA
RVSA
JMEUC
NYCDEP
NCDPW
WCDEF
PVSC
MCUA
BCUA
LRSA
RVSA
JMEUC
NYCDEP
NCDPW
WCDEF
Required
Dilution
58,800
4,740
6(450
166,700
11,360
5,950
6,290
10,870
10,990
14,500
23,450
80,000
27,590
5,520
12,410
13,100
4,140
19,310
Recommended
3 kn
Toxlclty Basis
210
4,359
2,684
85
1,276
3,024
2,784
1,347
1,329
Metal Basis
955
556
153
466
3,393
1,147
1,076
5,582
690
Dump i no Rate
6 kn
420
8,719
5,368
171
2,552
6,048
5,568
2,694
2,658
1,911
1,113
306
933
6,786
2,295
2,152
11,164
1,380
(aal/min)
9 kn
630
13,078
8,052
256
3,828
9,072
8,352
4,041
3,987
2,866
1,669
459
1,399
10,179
3,442
3,228
16,746
2,070
aAbbDeviations are defined in Table 4.1.
4-5
-------
results indicate that sludge dumping rates must be reduced greatly from the
court-mandated rate of 15,500 gal/min in order that sludge concentrations 4 h
after dumping are sufficiently low to meet EPA water quality criteria. At a
barge speed of 6 kn, recommended dumping rates for the nine permit
applicants vary from 171 to 8,719 gal/min based upon toxicity requirements;
306 to 11,164 gal/min based upon metals.
The recommended dumping rate for each permit applicant is, therefore,
dependent upon the speed of the barge (Table 4.3). As demonstrated in
Section 3, dilution requirements dictate an effective dumping rate, but
volume dumping rates are based upon the effective dumping rate and the barge
speed. Accordingly, volume dumping rates are directly proportional to barge
speed, such that barges traveling at 3 kn must dump at one-half the rate of a
barge with a speed of 6 kn, and one-third the rate of a barge with a speed of
9 kn. Thus, barges that travel relatively fast (7 to 9 kn) could dump at 2
to 3 times the dumping rate of slow (3 kn) barges, and meet water quality
criteria. The effect of barge speed on dumping rate is, however, a lesser
issue than the actual range of recommended dumping rates that are given in
Table 4.3. A major reduction in dumping rates from 15,500 gal/min to near
1,000 gal/min would represent more than a 15-fold decrease in rates, and
consequently, more than a 15-fold increase in the time for a barge to dump
its load at the 106-Mile Site. The logistical repercussions of this long
dumping time are discussed in Section 5.
4.2 NOMOGRAPH OF DUMPING RATES FOR SPECIFIC DILUTION REQUIREMENTS
The previous subsection presented specific dumping rates for each of the
nine permit applicants. These rates were based upon whole sludge data that
were determined from the characterization study conducted in August 1988
( EPA , 1992d)« We anticipate that additional chemical constituent and
toxicity data will be acquired over the next few years for the various
sludges dumped at the 106-Mile Site, and for this reason, a simplified
algorithm or nomograph will be needed to determine optimum dumping rates as a
function of the required dilution. For this purpose, Figure 4.1 illustrates
the relationship between the required dilution and the sludge dumping rate,
expressed in units of gal/min. The data are presented on logarithmic scales
4-6
-------
1,000,000 -r
i£ 100,000
Z>
_J
Q
Q
LJ
g 10,000
cr
1,000
10
3 kt 6 kt 9 kt /366 GPM
122 GPM
4479 GPM
1493 GPM
_, ,
> I I t-t
100 1,000 10,000
SLUDGE DUMPING RATE (gal/mm)
100.000
FIGURE 4.1 NOMOGRAPH OF SLUDGE DUMPING RATES (in gal/win) VERSUS REQUIRED
SLUDGE DILUTIONS 4-h AFTER DUMPING AT THE 106-MILE SITE.
SEPARATE CURVES ARE GIVEN FOR BARGE SPEEDS OF 3, 6, AND 9 kn.
CALCULATIONS BASED UPON FIELD OBSERVATIONS OF SLUDGE DILUTION
DURING SEPTEMBER 1988.
-------
to accommodate the wide ranges of dilution and dumping rates that may be
encountered. In accordance with Eq. (8), dumping rates are inversely
proportional to required dilution, and increases in barge speed can
effectively raise the permissible dumping rate for a given dilution
requirement. Because it is difficult to extract values from this graphic
presentation, the same data are presented in Table 4.4 for dilutions ranging
from 5,000 to 150,000, and barge speeds of 3, 6 and 9 kn.
4-8
-------
TABLE 4.4 RECOMMENDED SLUDGE DUMPING RATES VERSUS REQUIRED DILUTION.
VOLUME DUMPING RATES (gal/nin) ARE GIVEN FOR THREE BARGE
SPEEDS.
Required
Dilution
Effective
Dumping Rate
(gal/ft)
Barge Speed:
Volume Dumping Rate
3 kn 6 krt
(jal/minl
9 kn
5,000 11.4 3,982 7,963 11,945
10,000 2.5 1,493 2,985 4,479
15,000 1.4 919 1,838 2,757
20,000 0.98 664 1,328 1,992
25,000 0.75 520 1,039 1,559
30,000 0.61 426 853 1,279
40,000 0.44 314 628 942
50,000 0.34 249 498 747
75,000 0.22 163 327 490
100,000 0.17 122 244 366
125,000 0.13 97 194 291
150,000 0.11 80 161 241
Note: The effective dumping rate (gal/ft) to achieve the required dilution
is independent of barge speed.
4-9
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5. STRATEGIES FOR MULTIPLE DUMPING
The previous sections addressed the Initial (4-h) dilution of discrete
parcels of sewage sludge dumped at the 106-Mile Site. Dilution calculations
and, therefore, dumping rate formulas were based upon discrete parcels,
rather than plume-average sludge concentrations, because the EPA regulations
for ocean dumping of municipal wastes are directed at waste parcels rather
than spatial averages of entire waste plumes. Consideration of dumping
strategies and waste loading at the site does, however, require analyses of
whole plumes and calculations on spatial scales that include the entire
dumpsite.
In this section, we raise a number of practical issues and
considerations concerning the present and future dumping of sludge at the
106-Mile Site. The following subsections address the topics listed below:
Bulk loading of sludge at the 106-Mile Site
* Strategies for dumping at present rates of 15,500 gpm
* Considerations for dumping at greatly reduced rates.
5.1 BULK LOADING CONSIDERATIONS
The volume (load) of sludge dumped at the 106-Mile Site is estimated to
be roughly 7.2 million wet metric tons (1.7 billion gallons) annually, or
20,000 m3 per day (Walker et aU, 1987). The magnitude of this dumping
activity, coupled with the presumed ecological effects of sludge on the
marine life of the U.S. east coast, has fueled great concern for sludge
dumping at the 106-Mile Site. To determine the true fate and effects of
sludge dumping at the 106-Mile Site will require an extensive monitoring
activity as outlined in the 106-Mile Site monitoring plan ( EPA , 1988a).
This monitoring activity is under way, but information on the farfield fate
and long-term effects of sludge dumping will not be available for another
year or two.
Prior to implementation of the 106-Mile Site monitoring plan, Walker et
al. (1987) developed a model of the farfield transport and fate of sewage
sludge dumped at the 106-Mile Site. Their transport model was based upon (1)
5-1
-------
observations of mean southwestward currents at the site, and (2) estimates of
sludge loading at the site, rates of turbulent mixing within the barge wake,
and sludge diffusion rates over time scales of days to months. This model
provides estimates of the mean transport of sludge-derived pollutants dumped
at the 106-Mile Site. In addition, maps are provided to illustrate the two-
dimensional distribution of sludge concentration (dilution) along the U.S.
east coast. These steady-state model results, which were based upon a
dumping rate of 20,000 m3 of sludge per day, indicate that minimum dilutions
(highest sludge concentrations) within 50 km of the site would be on the
order of 1,000,000:1. Clearly, these dilutions are 2 or 3 orders of
magnitude greater than the dilutions that were observed during the nearfield
surveys of sludge plumes within the 106-Mile Site. Although the Walker et
al. model may represent the farfield, long-term fate of sludge dumped at the
106-Mile Site, it does not represent actual nearfield dilutions.
As a first step toward analyses of sludge loading within the 106-Mile
Site and on times scales of the dumping operations (hours to days), Table
5.1 presents basic calculations of the site receiving volume and the amount
of sludge that is now being dumped at the site. If the depth of the
receiving volume during summer is taken as the depth of the seasonal
pycnocline (20 m), and the dimensions of the site are 7.2 km by 37.0 km, then
the receiving volume in summer is approximately 10.7 x 1Q9 m3. Thus, one
MYCQEP barge load of sludge (12,500 m3) mixed evenly throughout the dumpsite
in summer would result in an average sludge dilution of w426,000:1.
likewise, if 10 barges dumped sludge at the site during a week-long period
without circulation (zero net current), the resulting site-averaged dilution
would be «42,600:1 in summer. These dilution estimates will certainly vary
with the number and size (sludge capacity) of the barges that would be
dumping during a period of no circulation, but this simple calculation leads
to the following conclusion:
* If no circulation were to persist for a week or so during summer
months, and dumping activities consisted of at least 1 barge per
day, then site-averaged sludge dilutions may be as low as
50,000:1. This condition represents the worst-case for sludge
loading because these site-averaged dilutions are less than the
minimum required dilutions for some of the sludges being dumped at
the 106-Mile Site (see Tables 4.1 and 4.2).
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The nearfield results from the winter 1988 survey at the 106-Mile Site
( EPA , 1988a) indicated that, on time scales of less than one day, sludge
may not settle in significant quantities beyond a depth of roughly 30 m.
Although sludge may penetrate deeper during periods of active mixing (e.g.,
storm events), the data suggest that the depth of the permanent pycnocline
{wlOO m) is an overestimate of the actual depth of the mixing (receiving)
volume during the first few days following dumping. Therefore, on time
scales of a few days, the receiving volume in winter may not be significantly
greater than during summer (thus contrary to earlier theories based simply
upon pycnocline depth).
We suspect that, due to significant currents that flush the site on
times scales of 2 to 20 hours, site-averaged sludge loading at the 106-Mile
Site is not a problem for most days of the year. Additional site-specific
field data are needed for meaningful statistics on the frequency of week-long
stagnant flow periods, but we estimate that such events would not occur more
than one or two times during the 5-month "summer" season,
5.2 DUMPING STRATEGIES AT COURT-ORDERED RATE OF 15.500 gpm
The present court order for dumping of municipal sludge at the 106-Mile
Site contains the following specifications!
* Dumping rates must not exceed 15,500 gpm.
Barges must maintain speeds of at least 3 kn.
Sludge must be dumped within the 106-Mile Site boundaries.
* An individual plume must not cross nor come within 1/2 mile of
itself at any point.
Modifications to the dumping rates are being considered (e.g., this report),
and the effects of barge speed on sludge dilution may also be the topic of
future studies related to ocean dumping. One of the most basic questions,
"Along what track should sludge be dumped within the site?", has, however,
received little attention coipared with other issues. In this subsection we
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propose a few strategies that may help to ensure that sludge dumping at the
106-Mile Site will meet EPA water quality criteria.
In Section 3, an empirical equation (Eq. 8) was developed for prediction
of sludge dumping rates that will ensure that water quality criteria are met
4 h after dumping. If, however, sludge plumes cross the site boundaries in
less than 4 h, dilutions will be less than those predicted at 4 h and,
therefore, the dumping rates will be too high. Therefore, if the dumping
rates derived from Eq. (8) are to be used, then (1) plumes must not cross the
site boundaries within 4 h after dumping, and (2) a plume must not cross
another plume nor overlap itself within 4 h after dumping.
Ensuring that sludge plumes remain within the site for at least 4 h is a
difficult task, considering that near-surface currents often attain speeds of
1 kn or more during periods when eddies pass through the site. Present
dumping regulations permit dumping anywhere within the site or along its
boundaries, and consequently, sludge may be transported out of the site
within minutes or a few hours after dumping, depending upon the position of
dumping and the direction and speed of the currents.
Below, we present candidate strategies for sludge dumping during three
hypothetical flow regimes: weak flow, having current speeds <0.25 kn;
moderate flow, with speeds between 0.25 and 1.5 kn; and strong flow, with
speeds >1.5 kn. In reality, this range of current speeds can be obtained
from all current directions, but we have based the present analyses upon the
worst-case flow condition: east-west flow, directed across the narrow (4,5
nmi; 7.4 km) width of the dumpsite.
Weak Flow (<0.25 kn)
Dumping must be prohibited within 1 nmi of all site boundaries to
ensure that sludge does not cross site boundaries before 4 h after
dumping.
The track of a barge must not cross the track of a previous barge
within the site unless at least 4 h has elapsed between the two
dumping operations. If the start of dumping for individual barges
could be separated by 4 h, then barges could follow the same track
within the site.
If simultaneous dumping is permitted, then dumping should be
conducted along parallel, north-south lanes to ensure that plumes
do not cross within 4 h after dumping. Three lanes could be
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established} one along the center of the site (along 72°02.5'W);
and two situated 1 nmi from both the east and west boundaries of
the site (along 72°G1'W and 72°04'W).
Moderate Flow (0.25 to 1.5 kn)
If flow is easterly or westerly, then dumping must be directed
along a north-south track that coincides with the site boundary on
the upstream side of the site (e.g., east boundary for westward
flow). This will ensure that plumes do not leave the site within 4
h of dumping.
If flow is northerly or southerly, then dumping should be confined
to the upstream half of the site (e.g., south of 38°50IN for
northerly flow) to ensure that plumes do not leave the site within
4 h of dumping.
* If a single dumping track is established for periods of moderate
flow, then dumping operations must be separated by at least 4 h.
Strong Flow (>1«5 kn)
* During periods of strong east-west flow, dumping should be
prohibited because sludge plumes will cross the site boundaries in
less than 3 h no matter where the material is originally dumped.
During periods of strong north-south flow, dumping is permissible
but all dumping should be confined to the upstream half of the site
(e.g., south of 38°50'N for northerly flow) to ensure that plumes
do not leave the site within 4 h of dumping.
The" dumping strategies presented above would ensure proper management of
sludge dumping operations at the 106-Mile Site, but they will require (1)
near-real-time knowledge of surface currents at the site, and (2) close
coordination between EPA and the transport companies that tow sludge barges
to the 106-Mile Site. EPA currently plans to deploy a surface current
mooring at the site in January 1989 for telemetry of near-real-time current
data to EPA Region II. This mooring will provide continuous information on
the speed and direction of the currents, which can be used to determine the
optimum dumping strategy (see weak, moderate, or strong flow strategies given
above). EPA could then post a radio bulletin, via the U.S. Coast Guard, that
directs the transporters to dump according to a preceded strategy or lane
designation.
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It is important to note that failure to implement a dumping strategy
such as that given above will definitely result in sludge plumes crossing the
boundaries of the site within 4 h of a dumping operation.
The above strategies are well suited for dumping operations at roughly
15,500 gal/min and for all barges except the Seatrader I. To dump its load
of roughly 9 million gallons of sludge, the Seatrader I requires about 12 h,
and an in-site trackline of «50 nmi at a towing speed of 4 kn. A special
dumping plan would be required for this exceptionally large barge.
S.3 DUMPING STRATEGIES AT REDUCED RATES
The previous subsection presented candidate dumping strategies that
would be appropriate for sludge dumping rates of roughly 15,500 gpm (e.g.,
present rates). At this dumping rate, the New York barges take roughly 4 to
5 h to dump their entire load of 3.3 million gallons of sludge. At towing
speeds of 5 kn, sludge plumes of New York barges are roughly the length of
the dumpsite (20 nmi from 38°40'N to 39QQQ'N). Only the Seatrader I
generates a plume that is 2 to 3 times the north-south length of the site.
From an operational standpoint, major problems arise if dumping rates
are reduced by factors of 15 or more, as discussed in Section 4. For
instance, if a New York barge were to dump at 1,000 gal/min, it would require
about 60 h to dump its entire load. If the Seatrader I were to dump at
1,000 gal/min, it would require 6 days to dump its load of 9 million
gallons. These long dumping times are a problem for several reasons:
* Transport costs for each barge load would be extremely high due to
the extensive time away from port.
* The contracted tugs may not have the fuel or water capacity to
remain at sea for periods of weeks.
* If the barges had to remain at the dumpsite for long periods, then
additional barges (maybe 10 times as many as currently used) would
be required by the New York and New Jersey sewerage authorities to
dump the amount of sludge generated.
Low dumping rates would result in vessel traffic problems within
the site because 10 or more barges would be dumping simultaneously,-
this number of vessels steaming inside the relatively small
dumpsite would be represent a navigational safety problem.
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The issues presented above illustrate that sludge dumping at
significantly reduced rates (say, 1,000 gal/min) may be environmentally
acceptable, but they could be operationally unfeasible for the lOS-Mile Site.
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6. SUMMARY AND RECOMMEKDATIONS
This report briefly reviews our knowledge of the nearfield, short-terra
behavior of plumes of sewage sludge dumped at the 106-Mile Site. Field
observations of plume behavior and dilution during EPA surveys to the 106-
Mile Site in September 1987 and 1988 have been used to develop an empirical
equation for predicting the optimum rates of sludge dumping that satisfy EPA
water quality criteria. Although data from a single plume event have been
used to develop the dumping rate formula, the observed conditions and plume
behavior may represent worst-case conditions for plume dilution (minimum
dilution due to weak mixing conditions during a summer period with a shallow
seasonal pycnocline). As data become available from additional nearfield
monitoring surveys, the coefficients in the proposed dumping rate equation
can be modified.
From the limited amount of plume observations acquired during the recent
monitoring surveys, we can predict the following nearfield behavior of sludge
dumped at the 106-Mile Site:
During summer, sludge is primarily confined to the surface mixed
layer (upper 20 m) above the seasonal pycnocline during the first 4
h after dumping.
Parcels of concentrated sludge within the center of a plume are
diluted at much slower rates than the average dilution for the
entire plume.
The rate of sludge dilution during the first 5 min after dumping
within the barge wake is much greater than the rate of dilution
from oceanographic mixing processes after wake mixing has ceased.
Sludge dilutions 4 h after dumping may be as low as 5000:1 for
individual sludge parcels; plume-averaged dilutions at 4 h may be
100,000:1 or greater.
Plume break-up, which initiates rapid dilution of parcels, can
occur before or after 4 h depending upon initial plume
concentrations and oceanographic mixing conditions.
The results of this preliminary assessment of sludge plume behavior
indicate that sludge dumping rates of 15,500 gal/min are too high to achieve
the 4 h dilutions necessary to meet water quality criteria. Dumping rates
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should be less than 15,500 gal/rain for all the permit applicants, based upon
(1) sludge characteristics data and (2) observed mixing conditions at the
106-Mile Site. The results have also left a number of unanswered questions
that require further considerations before we fully understand the nearfield
fate of sludge dumped at the 106-Mile Site:
* How does the rate of sludge dilution vary with oceanographic
mixing conditions, pycnocline depth, initial plume concentrations
(dumping rate), and sludge characteristics? Were the environmental
conditions encountered during the September 1987 and 1988 surveys
representative for the site?
Is wake-induced dilution a linear function of the effective
dumping rate (the amount of sludge dumped per unit track length)?
Do the sludge concentrations of parcels within plumes 4 h after
dumping have a Gaussian distribution such that statistical
techniques can be used to estimate the percentage of a plume that
may violate water quality criteria?
* Can plume break-up be achieved earlier such that the rate of sludge
dilution is increased? If, after initial wake-induced mixing, a
plume is broader and/or more dilute, oceanic turbulent mixing will
disperse the concentrate parcels of sludge more quickly.
* Do barge configurations and discharge methods have a significant
effect on initial dilution?
* Are instantaneous dumping rates roughly equivalent to average
dumping rates over the length of the pluie? If not, water quality
criteria may be greatly exceeded along portions of the plume.
* Does sludge settling and/or flocculation within the barge during
transit create significant variations in sludge characteristics
between the top and bottom of the sludge compartments? If so,
large variations in sludge characteristics along the plume would
result.
These questions lead to recommendations for additional analyses of
existing data and additional measurements during future surveys to the 106-
Mile Sitei
A statistically valid study of toxicity tests and laboratory
analyses of chemical constituent concentrations should be conducted
on sludge samples from each of the sewage treatment facilities to
determine whether data from the permit applications and/or Santoro
and Fikslin (1987) are representative of mean sludge
characteristics and ranges of variability.
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Additional plume monitoring surveys should be conducted behind
barges dumping at 15,500 gal/miri to develop statistically
defensible estimates of the rates of sludge dilution during the
first 4 h after dumping. The effects of barge configuration,
dumping rate, sludge characteristics, pycnocline depth, and
oceanographic mixing conditions have yet to be quantified.
If EPA is considering reductions in sludge dumping rates to ensure
compliance with water quality criteria, then nearfield plume
monitoring studies should be conducted behind barges dumping at
reduced rated (e.g., 5,000 and 1,000 gal/min). Analyses will
indicate whether rates of plume dilution are highly dependent upon
dumping rates, such that 4-h dilutions, and hence permissible
dumping rates, may be higher than those predicted from nearfield
studies it dumping rates of 15,500 gal/min.
Pretreatment of sludge and modifications to barge dumping
procedures should be considered as alternatives to major reductions
in dumping rates, especially as greatly reduced dumping rates
would pose major operational problems to barge operators and permit
applicants.
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7. REFERENCES
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Evaluation of Effluent Dispersion and Fate Models for OCS
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Brandsma, M.S., and O.J. Divoky. 1976. Development of Models for
Prediction of Short-Term Fate of Dredged Material Discharged in
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Brandsma, M.S., T.C. Sauer, Jr., and R.C. Ayers. 1983. Mud Discharge
Model. Report and User's Guide Model Version 1.0. A Model for
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Christdoulou, 6.C., W.F. Leimkihler, and A.T. Ippen. 1974.
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Mathematical Model for Dispersion of Suspended Sediment in Coastal
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Economic Analysis and ASA. 1986. Measuring Damages to Coastal and
Marine Natural Resources: Concepts and Data Relevant for CERCLA
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EPA. 1988a. Nearfield Fate Monitoring at the 106-Wile Deepwiter
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EPA. 1992a. Final Draft Monitoring Plan for the 106-Mile Diepwater
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EPA. 1992b. Final Draft Implementation Plan for the 106-Mile Deepwater
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EPA. 1992c. Final Report for Nearfield Monitoring of Sludge Plumes at
the 106-Mile Deepwater Municipal Sludge Site: Results of a Survey
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Koh, R.C.Y., and Y.C. Chang. 1973. Mathematical Model for Barged Ocean
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Krishnappan, B.G. 1983. Dispersion of Dredged Spoil When Dumped as a
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Santoro, E.D. and J.J. Fikslin. 1987. Chemical and lexicological
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Marine Pollution Bulletin. 18(7):394-399.
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