Background, 2008
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O utfall monitoring overview
BACKGROUND
Massachusetts Water Resources Authority
Environmental Quality Department
Report 2008-18
Citation:
Werme C, Hunt CD. 2008. O utfall monitoring overview BACKGROUND . Boston:
Massachusetts Water Resources Authority. Report 2008-18. 54p.
Outfall Monitoring Overview
BACKGROUND
prepared for
Massachusetts Water Resources Authority
Environmental Quality Department
100 First Avenue
Charlestown Navy Yard
Boston, MA 02129
prepared by
Christine Werme
Berkeley, CA 94705
and
Carlton D. Hunt
Battelle
397 Washington Street
Duxbury, MA 02332
November 4, 2008
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OUTFALL MONITORING OVERVIEW BACKGROUND I
Table of Contents
Summary ............................................................................................................................ iii
1. Introduction..................................................................................................................... 1
Background ..................................................................................................................... 1
Outfall Permit.................................................................................................................. 4
Monitoring Program........................................................................................................ 5
Contingency Plan ............................................................................................................ 9
Data Management ......................................................................................................... 11
Reporting....................................................................................................................... 11
Outfall Monitoring Overview ....................................................................................... 12
2. Effluent ......................................................................................................................... 14
Background ................................................................................................................... 14
Pollution Prevention and Wastewater Treatment ..................................................... 14
Environmental Concerns........................................................................................... 15
Monitoring Design ........................................................................................................ 17
Contingency Plan Thresholds ....................................................................................... 20
3. Water Column............................................................................................................... 21
Background ................................................................................................................... 21
Circulation and Water Properties.............................................................................. 21
Environmental Concerns........................................................................................... 23
Monitoring Design ........................................................................................................ 25
Contingency Plan Thresholds ....................................................................................... 31
4. Sea Floor ....................................................................................................................... 32
Background ................................................................................................................... 32
Bottom Characteristics and Sediment Transport ...................................................... 32
Environmental Concerns........................................................................................... 32
Monitoring Design ........................................................................................................ 33
Contingency Plan Thresholds ....................................................................................... 38
5. Fish and Shellfish.......................................................................................................... 40
Background ................................................................................................................... 40
Monitoring Design ........................................................................................................ 41
Winter Flounder ........................................................................................................ 41
Lobster ...................................................................................................................... 41
Blue Mussel .............................................................................................................. 43
Contingency Plan Thresholds ....................................................................................... 44
6. Special Studies .............................................................................................................. 45
Background ................................................................................................................... 45
7. Stellwagen Bank National Marine Sanctuary ............................................................... 46
Background ................................................................................................................... 46
Monitoring Design ........................................................................................................ 47
References......................................................................................................................... 50
List of Acronyms .............................................................................................................. 54
OUTFALL MONITORING OVERVIEW BACKGROUND II
List of Figures
Figure 1-1. Massachusetts and Cape Cod bays, including the location of the MWRA
outfall and other factors that were important to the siting process. .................................... 3
Figure 3-1. (a) General circulation within Massachusetts Bay. (b) General circulation
within the Gulf of Maine................................................................................................... 22
Figure 3-2. MWRA Bay Water Quality Monitoring stations and regional groupings
included in the program .................................................................................................... 27
Figure 3-3. MWRA plankton stations included in water-column monitoring.................. 28
Figure 3-4. MWRA Boston Harbor Water Quality Monitoring stations ......................... 29
Figure 4-1. Locations of nearfield soft-bottom stations.................................................... 34
Figure 4-2. Locations of farfield soft-bottom stations. ..................................................... 35
Figure 4-3. Locations of hard-bottom stations.................................................................. 36
Figure 5-1. Sampling areas and reference sites for fish-and-shellfish monitoring ........... 42
Figure 7-1. MWRA and supplemental water-column stations in and near the Stellwagen
Bank National Marine Sanctuary...................................................................................... 48
Figure 7-2. Farfield benthic stations ................................................................................. 49
List of Tables
Table 1-1. List of panel and committee organizations........................................................ 5
Table 1-2. Public concerns and environmental responses presented in the monitoring plan
............................................................................................................................................. 7
Table 1-3. Monitoring program objectives and analyses.................................................... 8
Table 1-4. Contingency Plan threshold parameters. ......................................................... 10
Table 1-5. Monitoring reports submitted to OMSAP. ...................................................... 12
Table 2-1. Monitoring questions developed by OTMF related to the effluent................. 15
Table 2-2. Reporting requirements of the outfall permit. ................................................. 18
Table 2-3. Monitoring plan parameters for effluent. ........................................................ 19
Table 2-4. Contingency Plan threshold values for effluent monitoring............................ 20
Table 3-1. Monitoring questions developed by OTMF related to the water column. ...... 24
Table 3-2. Components of water-column monitoring....................................................... 26
Table 3-3. Nearfield water-column monitoring parameters. ............................................ 30
Table 3-4. Farfield water-column monitoring parameters................................................ 30
Table 3-5. Contingency Plan threshold values for water-column monitoring.................. 31
Table 4-1. Monitoring questions developed by OTMF related to the sea floor. .............. 33
Table 4-2. Contingency Plan threshold values for sea-floor monitoring.......................... 39
Table 5-1. Monitoring questions developed by OTMF related to fish and shellfish........ 40
Table 5-2. Chemical analyses of fish and shellfish........................................................... 43
Table 5-3. Contingency Plan threshold values for fish-and-shellfish monitoring. ........... 44
OUTFALL MONITORING OVERVIEW BACKGROUND III
Summary
Since its creation by an act of state legislature in 1984, the Massachusetts Water
Resources Authority (MWRA) has worked to minimize the effects of wastewater
discharge on the marine environment. The MWRA program has taken steps to reduce the
amount of pollutants entering the waste stream, improve treatment before discharge, and
provide for better dilution upon discharge of treated effluent into marine waters. In
September 2000, MWRA ended discharge into the more confined waters of Boston
Harbor and began to discharge at a deeper site in the more open waters of Massachusetts
Bay. Subsequent years are referred to as being “post-diversion.”
One condition of the National Pollutant Discharge Elimination System (NPDES) permit
for the Massachusetts Bay discharge is that MWRA prepare an annual document
summarizing the year’s monitoring results. Outfall monitoring overview documents were
prepared for most years prior to the permit being in place and for each post-diversion
discharge year. Overviews prepared for the years through 2006 included the background
information that is the basis for this document.
With the 2007 monitoring year, it had become apparent that most or all of the questions
developed prior to the discharge diversion had been answered. As had been anticipated,
it was possible to detect minimal effects in the immediate vicinity of the outfall, but there
has been no indication of unexpected or broad-range changes. As part of a new focus on
verification of continued protection and anticipation of new challenges, MWRA has
decided to focus the annual overviews on new and interesting results. The background
information, which does not change from year-to-year, has been placed into this separate
document.
This document presents background information on environmental concerns, monitoring
design, and Contingency Plan thresholds for effluent, water-column, sea-floor, and fish-
and-shellfish monitoring. Also described are MWRA’s special studies and its
commitment to reporting data relevant to the Stellwagen Bank National Marine
Sanctuary.
OUTFALL MONITORING OVERVIEW BACKGROUND IV
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OUTFALL MONITORING OVERVIEW BACKGROUND 1
1. Introduction
Background
For more than two decades, the Massachusetts Water Resources Authority
(MWRA) has worked to minimize the effects of wastewater discharge on
the marine environment. MWRA was created by an act of the
Massachusetts state legislature in December 1984 and in 1985 embarked
upon what has become known as the Boston Harbor Project. Before then,
the Boston metropolitan area discharged both sewage biosolids and
inadequately treated sewage effluent into the confined waters of Boston
Harbor from outfalls located at Deer Island in the northern part of the
harbor and at Nut Island in Quincy Bay, in the southern part of the harbor.
MWRA ended discharge of municipal biosolids into Boston Harbor in
1991, when biosolids from both treatment plants began to be barged to a
processing plant in Quincy and made into fertilizer pellets. Steps to
minimize effects of effluent discharge have included:
• Source reduction to prevent pollutants from entering the waste
stream.
• Improved treatment before discharge.
• Better dilution once the effluent enters the marine environment.
Source reduction has included projects to lessen household hazardous-
waste disposal and minimize mercury discharges from hospitals and
dentists. An industrial pretreatment/pollution-prevention program ensures
that toxic contaminants are removed before they reach the sewer system.
In addition, best management practices are employed at sewer facilities to
mitigate accidental discharge of pollutants.
Improved treatment has been implemented in a series of steps. In 1995,
a new primary treatment plant was brought on-line at Deer Island
Treatment Plant (DITP), and disinfection facilities were completed.
(Primary treatment is a physical treatment process, which involves
removal of solids through settling, followed by disinfection.) Batteries of
secondary treatment (which includes bacterial decomposition as well as
settling and disinfection) went on-line in 1997, 1998, and 2001. Also
during 1998, discharge from the Nut Island Treatment Plant into Quincy
Bay ceased, and all wastewater was conveyed to the Deer Island
Treatment Plant (DITP) for treatment, ending effluent discharge to the
southern part of the harbor.
OUTFALL MONITORING OVERVIEW BACKGROUND 2
Efforts to improve treatment continued in 2005, when MWRA initiated
studies aimed at maximizing flow through the secondary treatment system.
These studies built on several capital projects, including improvements to
the secondary treatment facilities and upgrades to the oxygen-generation
plant. In 2005, the final piece of the cross-harbor tunnel, which connected
DITP to the Fore River biosolids pelletizing plant was completed. Pipes
within the tunnel now transport digested biosolids from DITP to the
pelletizing plant; the liquid waste from biosolids thickening at Fore River
is piped back to DITP. Before the tunnel was completed, liquid (rich in
nutrients) was removed from the biosolids at DITP in batches, in
preparation for barging to the pelletizing plant, and was added in batches
to the influent stream at the beginning of the effluent treatment process.
This sporadic addition of nutrients made it more difficult to maintain a
stable microbial secondary process. Now, the liquid is removed at the
pelletizing plant and piped back to DITP in a relatively steady stream,
facilitating a more stable process.
Better dilution was achieved in 2000, by diverting the effluent discharge
from Boston Harbor to a 9.5-mile-long outfall and diffuser system, located
offshore in Massachusetts Bay (Figure 1-1).
The Massachusetts Bay site was selected because it had a water depth and
current patterns that would promote effective dilution, it was the least
likely of the alternative sites to affect sensitive resources, and it was
feasible to construct an outfall tunnel to the location.
The outfall tunnel is bored through bedrock and has a diffuser system
made up of 53 risers, each with five or six open ports, along its final 1.25
miles. Discharge from the diffuser heads is at the sea floor, at water
depths of about 100 feet. Initial dilution at the outfall is about five times
that of the Boston Harbor outfall that it replaced, which was located in
shallower water, at a depth of 50 feet. The offshore location of the outfall
ensures that effluent will not reach beaches or shellfish beds within a tidal
cycle, even if currents are shoreward.
OUTFALL MONITORING OVERVIEW BACKGROUND 3
Figure 1-1. Massachusetts and Cape Cod bays, including the location of the MWRA outfall and
other factors that were important to the siting process.
OUTFALL MONITORING OVERVIEW BACKGROUND 4
For many of the components of MWRA’s work, there was little or no
argument that the project benefited the marine environment and the people
of the region. Moving the effluent outfall from the harbor to
Massachusetts Bay did raise some concerns, which were expressed as
general, continuing questions:
• Is it safe to eat fish and shellfish?
• Are natural/living resources protected?
• Is it safe to swim?
• Are aesthetics being maintained?
These concerns were recognized by MWRA and by the permit for the
outfall issued jointly by the U.S. Environmental Protection Agency (EPA)
and the Massachusetts Department of Environmental Protection
(MADEP). An outfall monitoring program, which had already been
initiated, was formally established in MWRA’s National Pollutant
Discharge Elimination System (NPDES) permit.
Outfall Permit
The permit issued by EPA and MADEP under NPDES became effective
on August 9, 2000 and continues to be in effect, although it formally
expired on August 9, 2005. The permit limits discharges of pollutants and
requires reporting on the treatment plant operation and maintenance. The
permit requires MWRA to continue its ongoing pollution prevention
program and to employ best management practices aimed at preventing
accidental discharge of pollutants to the sewer system.
The permit requires MWRA to monitor the effluent and the ambient
receiving waters for compliance with permit limits and in accordance with
monitoring plans (MWRA 1991, 1997a, 2004) developed in response to
the EPA Supplemental Environmental Impact Statement (SEIS) prepared
as part of the outfall-siting process (EPA 1988). It requires that MWRA
implement a Contingency Plan (MWRA 1997b, 2001), which identifies
relevant environmental quality parameters and thresholds that, if
exceeded, would require a response.
In 1998, in anticipation of the permit, EPA and MADEP established an
independent panel of scientists to review monitoring data and provide
advice on key scientific issues related to the permit. This panel, the
Outfall Monitoring Science Advisory Panel (OMSAP, Table 1-1),
conducts peer reviews of monitoring reports, evaluates the data, and
advises EPA and MADEP on scientific implications. OMSAP also
provides advice concerning any proposed modifications to the monitoring
or contingency plans.
OUTFALL MONITORING OVERVIEW BACKGROUND 5
OMSAP may form specialized focus groups when specific technical issues
require expanded depth or breadth of expertise. One long-standing
OMSAP focus is the Model Evaluation Group, which has met periodically
since 1992 to evaluate the Bays Eutrophication Model. Two standing sub-
committees also advise OMSAP. The Public Interest Advisory Committee
(PIAC) represents local, non-governmental organizations and
environmental groups and advises OMSAP on values and uses of the
harbor and the bays. The Inter-agency Advisory Committee (IAAC)
represents state and federal agencies and provides OMSAP with advice
concerning environmental regulations.
Table 1-1. List of panel and committee organizations.
Outfall Monitoring Science Advisory Panel (OMSAP)
Woods Hole Oceanographic Institution
University of Rhode Island
Massachusetts Institute of Technology Sea Grant
University of Massachusetts at Boston
Harvard School of Public Health
Inter-agency
Advisory Committee (IAAC)
US Geological Survey
MA Coastal Zone Management
US Army Corps of Engineers
Stellwagen Bank National Marine
Sanctuary
MA Department of Environmental
Protection
MA Division of Marine Fisheries
US Environmental Protection Agency
National Marine Fisheries Service
Public Interest
Advisory Committee (PIAC)
Save the Harbor/Save the Bay
Center for Coastal Studies
Wastewater Advisory Committee
Conservation Law Foundation
Massachusetts Audubon Society
New England Aquarium
MWRA Advisory Board
Association for the Preservation of Cape
Cod
Safer Waters in Massachusetts
The Boston Harbor Association
Cape Cod Commission
Monitoring Program
EPA and MADEP require monitoring to ensure compliance with the
permit, to assess whether the outfall has effects beyond the area identified
in the SEIS as acceptable, and to collect data useful for outfall
management. In anticipation of these requirements, MWRA began some
studies during 1989–1991 and implemented a broad baseline-monitoring
program in 1992. Outfall ambient monitoring plans were originally
developed and refined under the direction of an Outfall Monitoring Task
Force (OTMF), made up of scientists, regulators, and environmental
advocacy groups (MWRA 1991, 1997a). (The OMTF was disbanded
upon creation of OMSAP.) Because the first years of monitoring
following diversion of effluent to the bay found no unexpected changes to
OUTFALL MONITORING OVERVIEW BACKGROUND 6
the system, changes to the monitoring program were approved by EPA
and MADEP, and a new plan (MWRA 2004) was implemented in the
2004 monitoring year.
The outfall ambient monitoring plan expands the general questions of
public concern by translating them into possible “environmental
responses,” which are more specific questions directly related to the
outfall (Table 1-2). To answer those questions, the monitoring program
focuses on critical constituents of treatment plant effluent, such as
nutrients, organic material, toxic contaminants, pathogens, and solids.
Presence and potential effects of these constituents are evaluated within
the context of four environmental measurement areas: effluent, water
column, sea floor, and fish and shellfish (Table 1-3).
The basic program is augmented by special studies, which are conducted
in response to specific permit requirements, scientific questions, and
environmental concerns. The monitoring program is designed to compare
environmental quality of the Massachusetts Bay system, including Boston
Harbor and Cape Cod Bay, before and after the outfall location moved
from the harbor to the bay.
OUTFALL MONITORING OVERVIEW BACKGROUND 7
Table 1-2. Public concerns and environmental responses developed by the
OTMF and presented in the monitoring plan (MWRA 1991).
Public Concern: Is it safe to eat fish and shellfish?
Will toxic chemicals accumulate in the edible tissues of fish and
shellfish, and thereby contribute to human health problems?
Will pathogens in the effluent be transported to shellfishing areas
where they could accumulate in the edible tissues of shellfish and
contribute to human health problems?
Public Concern: Are natural/living resources protected?
Will nutrient enrichment in the water column contribute to an
increase in primary production?
Will enrichment of organic matter contribute to an increase in
benthic respiration and nutrient flux to the water column?
Will increased water-column and benthic respiration contribute to
depressed oxygen levels in the water?
Will increased water-column and benthic respiration contribute to
depressed oxygen levels in the sediment?
Will nutrient enrichment in the water column contribute to changes
in plankton community structure? (Such changes could include
stimulation of nuisance or noxious algal blooms and could affect
fisheries.)
Will benthic enrichment contribute to changes in community
structure of soft-bottom and hard-bottom macrofauna, possibly
also affecting fisheries?
Will the water column near the diffuser mixing zone have elevated
levels of some contaminants?
Will contaminants affect some size classes or species of plankton
and thereby contribute to changes in community structure and/or
the marine food web?
Will finfish and shellfish that live near or migrate by the diffuser be
exposed to elevated levels of some contaminants, potentially
contributing to adverse health in some populations?
Will the benthos near the outfall mixing zone and in depositional
areas farther away accumulate some contaminants?
Will benthic macrofauna near the outfall mixing zone be exposed
to some contaminants, potentially contributing to changes in
community structure?
Public Concern: Is it safe to swim?
Will pathogens in the effluent be transported to waters near
swimming beaches, contributing to human health problems?
Public Concern: Are aesthetics being maintained?
Will changes in water clarity and/or color result from the direct
input of effluent particles or other colored constituents, or indirectly
through nutrient stimulation of nuisance plankton species?
Will the loading of floatable debris increase, contributing to visible
degradation?
OUTFALL MONITORING OVERVIEW BACKGROUND 8
Table 1-3. Monitoring program objectives and analyses.
Task Objective Analyses
Effluent
Effluent sampling
Characterize wastewater
discharge from Deer Island
Treatment Plant
Flow
Organic material (cBOD)
Solids
pH
Bacterial indicators
Total residual chlorine
Toxicity
Nutrients
Toxic contaminants
Floatables
Water Column
Nearfield surveys Collect water quality data
near outfall location
Farfield surveys
Collect water quality data
throughout Massachusetts
and Cape Cod bays
Temperature
Salinity
Dissolved oxygen
Nutrients
Solids
Chlorophyll
Water clarity
Photosynthesis
Respiration
Phytoplankton
Zooplankton
Moorings
(GoMOOS and
USGS)
GoMOOS mooring is near
Cape Ann. USGS mooring
was near outfall and
provided continuous
oceanographic data until
February 2006.
Currents
Temperature
Salinity
Water clarity
Chlorophyll
Remote sensing
Provides oceanographic
data on a regional scale
through satellite imagery
Surface temperature
Chlorophyll
Sea Floor
Soft-bottom studies
Evaluate sediment quality
and benthos in Boston
Harbor and Massachusetts
Bay
Sediment chemistry
Sediment profile imagery
Community composition
Hard-bottom
studies
Characterize marine
benthic communities in
rock and cobble areas
Topography
Substrate
Community composition
Fish and Shellfish
Winter flounder
Determine contaminant
body burden and
population health
Tissue contaminant
concentrations
Physical abnormalities,
including liver
histopathology
American lobster Determine contaminant
body burden
Tissue contaminant
concentrations
Physical abnormalities
Blue mussel
Evaluate biological
condition and potential
contaminant
bioaccumulation
Tissue contaminant
concentrations
OUTFALL MONITORING OVERVIEW BACKGROUND 9
Baseline monitoring was initially planned to last for a minimum of three
years, as the outfall was originally planned for completion in 1995.
Delays in construction allowed a relatively long period for baseline
studies. Consequently, MWRA’s nine years of baseline monitoring were
able to document greater natural variability and develop a better
understanding of the system than would have been possible in a briefer
baseline period. MWRA was also able to evaluate the environmental
responses in Boston Harbor to other facilities improvements ( e.g. , Leo et
al. 1995; Pawlowski et al. 1996; Rex and Connor 1997; Rex 2000; Rex et
al. 2002; Taylor 2002, 2003, 2004, 2005a, 2005b, 2006). The extended
period also meant that the discharge to Massachusetts Bay, when it did
begin, had the benefit of nearly complete implementation of secondary
treatment.
The monitoring plan is a “living document.” That is, every effort is made
to incorporate new scientific information and improved understanding
resulting from the monitoring program into appropriate continued
measurements. MWRA’s NPDES permit allows an annual list of
proposed changes to the monitoring plan.
Contingency Plan
The MWRA Contingency Plan (MWRA 1997b, 2001) describes how, if
monitoring results indicate a possible environmental problem, MWRA and
the regulatory agencies will respond to determine the cause of the problem
and to specify the corrective actions that should be taken if the problem
appears to be related to the discharge. The Contingency Plan identifies
parameters that represent environmentally significant components of the
effluent or the ecosystem and that, if specific threshold levels are
exceeded, indicate a potential for environmental risk (Table 1-4). The
plan provides a process for evaluating parameters that exceed thresholds
and formulating appropriate responses.
OUTFALL MONITORING OVERVIEW BACKGROUND 10
Table 1-4. Contingency Plan threshold parameters.
Measurement
Area Parameter
pH
Fecal coliform bacteria
Residual chlorine
Total suspended solids
Biochemical oxygen demand
Toxicity
PCBs
Plant performance
Flow
Effluent
Total nitrogen load
Floatables
Oil and grease
Dissolved oxygen concentration and
saturation
Dissolved oxygen depletion rate
Chlorophyll
Nuisance and noxious algae
Water Column
Effluent dilution
Sea Floor
Sediment contaminants
Redox potential discontinuity (RPD) depth
Benthic community structure
PCBs, mercury, chlordanes, dieldrin, and
DDTs in mussels and in flounder and lobster
tissue
Lead in mussels
Fish and
Shellfish
Liver disease in flounder
Threshold values, the measurements selected as indicators of the need for
action, are based on permit limits, state water quality standards, and expert
opinion. To alert MWRA to any changes, some parameters have more
conservative “caution” as well as more serious “warning” thresholds.
Exceeding either caution or warning thresholds could indicate a need for
increased attention or study. If a caution threshold is exceeded, MWRA,
with guidance from OMSAP and the regulatory agencies, may expand the
monitoring to track effluent quality and environmental conditions. The
data are examined to determine whether it is likely that an unacceptable
effect resulting from the outfall has occurred.
Exceeding warning levels could, in some circumstances, indicate a need
for a response to avoid potential adverse environmental effects. If a
threshold is exceeded at a warning level, the response includes early
notification of EPA and MADEP and, if it appears that the outfall has
contributed to adverse environmental effects, the quick development of a
response plan. Response plans are to include a schedule for implementing
actions, such as making adjustments in plant operations or undertaking an
engineering study regarding specific potential corrective activities.
OUTFALL MONITORING OVERVIEW BACKGROUND 11
Every effort is made to incorporate new scientific information and
improved understanding resulting from the monitoring program into
appropriate thresholds. A process for modifying the Contingency Plan is
set forth in MWRA’s NPDES permit, and Revision 1 was approved during
2001.
Data Management
The monitoring program has generated extensive data sets. Data quality is
maintained through program-wide quality assurance and quality control
procedures. After validation, data from field surveys and laboratory
analyses are loaded into a centralized project database. Data handling
procedures are automated to the maximum extent possible to reduce
errors, ensure comparability, and minimize reporting time. Data that are
outside the expected ranges are flagged for review. Data reported by the
laboratory as suspect (for example, because the sample bottle was cracked
in transit) are marked as such and not used in interpretation or threshold
calculations, although they are retained in the database and included in
raw data reports. Any corrections are documented. Each data report notes
any special data quality considerations associated with the data set.
As monitoring results become available, they are compared with
Contingency Plan thresholds. Computer programs calculate each
threshold parameter value from the data, compare it to the threshold, and
notify the project staff if caution or warning levels are exceeded.
Reporting
MWRA’s NPDES permit requires regular reports on effluent quality and
extensive reporting on the monitoring program. A variety of reports are
submitted to OMSAP for review (Table 1-5). Changes to the monitoring
program or the Contingency Plan must be reviewed by regulators and
published in the Environmental Monitor . Data that exceed Contingency
Plan thresholds and corrective actions must also be reported. Data that
exceed thresholds must be reported within five days after the results
become available, and MWRA must make all reasonable efforts to report
all data on thresholds within 90 days of each sampling event.
Reports are posted on MWRA’s web site (www.mwra.com/harbor/
html/npdes.htm), and copies are placed in repository libraries in Boston
and on Cape Cod. OMSAP also holds public workshops at which outfall
monitoring results are presented.
OUTFALL MONITORING OVERVIEW BACKGROUND 12
Table 1-5. Monitoring reports submitted to OMSAP.
Reports Description/Objectives
Outfall Monitoring Plans
Phase I—Baseline Studies
(MWRA 1991)
Phase II—Discharge Ambient
Monitoring (MWRA 1997a,
2004)
Discuss goals, strategy, and design
of baseline and discharge monitoring
programs.
Contingency Plan (MWRA
1997b, 2001)
Describes development of threshold
parameters and values and MWRA’s
planned contingency measures.
Program Area Synthesis
Reports
Summarize, interpret, and explain
annual results for effluent, water
column, benthos, and fish and
shellfish monitoring areas.
Special Studies Reports
Discuss, analyze, and cross-
synthesize data related to specific
issues in Massachusetts and Cape
Cod bays.
Outfall Monitoring
Overviews
Summarize monitoring data and
include information relevant to the
Contingency Plan.
Outfall Monitoring Overview
Among the many reports that MWRA completes, the outfall monitoring
overview has been prepared for most baseline-monitoring years and for
each year that the permit has been in place (Galya et al. 1996, 1997a,
1997b; Werme and Hunt 2000a, 2000b, 2001, 2002, 2003, 2004, 2005,
2006, 2007). The reports include scientific summaries for the year of
monitoring. Overviews for 1994 through 1999 included only baseline
information. With the Massachusetts Bay outfall discharging, subsequent
reports have included information relevant to the Contingency Plan,
including threshold exceedances, responses, and corrective actions. When
data suggest that monitoring activities, parameters, or thresholds should be
changed, the report summarizes those recommendations.
Overviews prepared through the 2006 monitoring year included the
background information that is the basis for this document, the Outfall
Monitoring Overview Background. After nine years of baseline
monitoring and six years of post-diversion monitoring, however, it became
clear that most or all of the monitoring questions that had been developed
by the OTMF had been answered. As had been expected, monitoring has
been able to detect minimal effects in the immediate vicinity of the outfall,
but there has been no indication of unexpected or broad-range changes.
OUTFALL MONITORING OVERVIEW BACKGROUND 13
As MWRA began to focus monitoring on verification of continued
protection of the environment and anticipation of potential new
challenges, it became clear that the annual overviews should focus on new
and interesting results rather than on the background. Overviews for 2007
and subsequent years focus on those results and on comparison of results
to the Contingency Plan thresholds.
This background document presents information that does not change
from year-to-year—the environmental concerns that have driven the
monitoring program, monitoring designs, and Contingency Plan thresholds
for effluent, water-column, sea-floor, and fish-and-shellfish monitoring. It
also describes MWRA special studies and its commitment to reporting of
data relevant to the Stellwagen Bank National Marine Sanctuary.
OUTFALL MONITORING OVERVIEW BACKGROUND 14
2. Effluent
Background
Pollution Prevention and Wastewater Treatment
Ensuring that the final effluent is clean is the most important element in
MWRA’s strategy to improve the environmental quality of Boston Harbor
without degrading Massachusetts and Cape Cod bays. MWRA ensures
clean effluent through its vigorous pretreatment program and by proper
maintenance and operation of DITP.
The MWRA Toxic Reduction and Control (TRAC) program sets and
enforces limits on the types and amounts of pollutants that industries can
discharge into the sewer system and works with industries to encourage
voluntary reductions in their use of toxic chemicals. TRAC has also
implemented programs to reduce mercury from dental facilities and to
educate the public about proper disposal of hazardous wastes. A booklet,
A Healthy Environment Starts at Home (available at www.mwra.com),
identifies household products that could be hazardous and recommends
alternatives.
Secondary treatment further reduces the concentrations of contaminants of
concern, except for nutrients. DITP removes approximately 85–90% of
the suspended solids and biochemical oxygen demand (BOD), 50–90% of
the toxic chemicals, and about 15% of the nitrogen from the influent.
To prevent accidental discharge of pollutants and mitigate effects should
an accident occur, MWRA has implemented best management practice
plans at the treatment plant, headworks facilities, combined sewer
overflow facilities, pumping stations, and biosolids-to-fertilizer plant. The
plans include daily visual inspections and immediate corrective actions.
Effectiveness of best management practices is assessed by non-facility
staff.
OUTFALL MONITORING OVERVIEW BACKGROUND 15
Environmental Concerns
Sewage contains a variety of contaminants that could, at too high levels,
affect the marine environment, public health, and aesthetics. The MWRA
permit sets limits on these contaminants so as to ensure that these
attributes will be protected. Several specific questions in the MWRA
ambient monitoring plan respond to public concerns and possible
environmental responses by addressing whether the effluent is meeting
permit limits (Table 2-1). Other questions require the use of effluent data
in conjunction with plume-dilution studies, which were completed in
2001, and water-column monitoring (see Section 3, Water Column).
Table 2-1. Monitoring questions developed by OTMF related to the effluent.
Is it safe to eat fish and shellfish?
Will pathogens in the effluent be transported to shellfishing areas where they
could accumulate in the edible tissues of shellfish and contribute to human health
problems?
Do effluent pathogens exceed the permit limit?
Are pathogens transported to shellfish beds at levels that might affect
shellfish consumer health?
Are natural/living resources protected?
Will the water column near the diffuser-mixing zone have elevated levels of some
contaminants?
Do effluent contaminant concentrations exceed permit limits?
What are the concentrations of contaminants and characteristic tracers
of sewage in the influent and effluent and their associated variability?
Will finfish and shellfish that live near or migrate by the diffuser be exposed to
elevated levels of some contaminants, potentially contributing to adverse health
in some populations?
Does acute or chronic toxicity of effluent exceed permit limits?
Do levels of contaminants in water outside the mixing zone exceed state
water quality standards?
Is it safe to swim?
Will pathogens in the effluent be transported to waters near swimming beaches,
contributing to human health problems?
Do effluent pathogens exceed the permit limit?
Are pathogens transported to beaches at levels that might affect
swimmer health?
Are aesthetics being maintained?
Will changes in water clarity and/or color result from the direct input of effluent
particles or other colored constituents, or indirectly through nutrient stimulation of
nuisance plankton species?
Will the loading of floatable debris increase, contributing to visible degradation?
Do conventional pollutants in the effluent exceed permit limits?
Has the clarity and/or color of the water around the outfall changed?
Has the amount of floatable debris around the outfall changed?
OUTFALL MONITORING OVERVIEW BACKGROUND 16
The effluent constituents of greatest concern include pathogens, toxic
contaminants, organic material, solid material, nutrients, oil and grease,
and “floatables,” such as plastic and other debris. The MWRA permit also
sets limits for chlorine and pH:
• Pathogens , including bacteria, viruses, and protozoa, are found in
human and animal waste and can cause disease. Human exposure
to water-borne pathogens can occur through consumption of
contaminated shellfish or through ingestion or physical contact
while swimming.
• Toxic contaminants include heavy metals, such as copper and
lead, polychlorinated biphenyls (PCBs), pesticides, polycyclic
aromatic hydrocarbons (PAHs), and petroleum hydrocarbons.
Toxic contaminants can lower survival and reproduction rates of
marine organisms. Some toxic contaminants can accumulate in
marine life, potentially affecting human health through seafood
consumption.
• Organic material , a major constituent of untreated sewage,
consumes oxygen as it decays. Even under natural conditions,
oxygen levels decline in bottom waters during the late summer, so
any effluent component that might further decrease oxygen levels
is a concern. Too much organic material could also disrupt animal
communities on the sea floor.
• Suspended solids , small particles in the water column, decrease
water clarity and consequently affect growth and productivity of
algae and other marine plants. Excess suspended solids also
detract from people’s aesthetic perception of the environment.
• In marine waters, nitrogen is the limiting nutrient that controls
growth of algae and other aquatic plants. Excess nitrogen can be
detrimental, leading to eutrophication and low levels of dissolved
oxygen, excess turbidity, and nuisance algal blooms. Nutrients,
particularly dissolved forms, are the only components of sewage
entering the treatment plant that are not substantially reduced by
secondary treatment.
• Oil and grease slicks and floating debris known as floatables pose
aesthetic concerns. Plastic debris can be harmful to marine life, as
plastic bags are sometimes mistaken for food and clog the
digestive systems of turtles and marine mammals. Plastic and
other debris can also entangle animals and cause them to drown.
• Sewage effluent is disinfected by addition of a form of chlorine ,
sodium hypochlorite, which is the active ingredient in bleach.
While sodium hypochlorite is effective in destroying pathogens, at
high enough concentrations, it is harmful to marine life.
Consequently, MWRA dechlorinates the effluent with sodium
bisulfite before discharge.
OUTFALL MONITORING OVERVIEW BACKGROUND 17
• Seawater is noted for its buffering capacity, that is, its ability to
neutralize acids and bases. However, state water quality standards
dictate that effluent discharges not change the pH of the ambient
seawater more than 0.5 standard units on a scale of 1 to 14.
Consequently, the outfall permit sets both upper and lower values
for pH of the effluent.
Monitoring Design
Effluent monitoring measures the concentrations of constituents of the
effluent and variability in those concentrations to assess compliance with
NPDES permit limits, which are based on state and federal water quality
standards and criteria and on ambient conditions. Effluent monitoring also
provides measurements of mass loads of effluent constituents, so that fate,
transport, and risk of contaminants can be assessed.
The permit includes numeric limits (Table 2-2) for suspended solids, fecal
coliform bacteria, pH, chlorine, PCBs, and carbonaceous biochemical
oxygen demand (cBOD). In addition, state water quality standards
establish limits for 158 pollutants, and the permit prohibits any discharge
that would cause or contribute to exceeding any of those limits.
Allowable concentrations of contaminants were based on the predicted
dilution at the outfall and verified by field studies of outfall plumes in
2001. The permit also prohibits discharge of nutrients in amounts that
would cause eutrophication, and it requires MWRA to test the toxicity of
the effluent as a whole on sensitive organisms and establishes limits based
on the tests.
Most parameters are measured in 24-hour composite samples, and some
must meet daily, weekly, or monthly limits. Flow is measured
continuously. Nutrient measurements include total nitrogen, ammonium,
nitrate, and nitrite. Organic material is monitored by measuring the
cBOD. Monitoring for toxic contaminants includes analyses for heavy
metals of concern, chlorinated pesticides, PCBs, volatile organic
compounds, PAHs, total residual chlorine, and cyanide. Toxicity is tested
using whole effluent samples. Tests for acute toxicity include 48-hour
survival of mysid shrimp ( Americamysis bahia , formerly known as
Mysidopsis bahia ) and inland silverside fish ( Menidia beryllina ). Chronic
toxicity is assessed through inland silverside growth-and-survival and sea
urchin ( Arbacia punctulata ) one-hour-fertilization tests. Pathogen
monitoring consists of enumeration of fecal coliform bacteria. Total
suspended solids (TSS) and settleable solids are also measured.
The Contingency Plan also sets limits for overall plant performance,
annual nitrogen load, floatables, and oil and grease. Floatables are
measured as part of a special study.
OUTFALL MONITORING OVERVIEW BACKGROUND 18
Table 2-2. Reporting requirements of the outfall permit.
Parameter Sample Type Frequency Limit
Permit-required monitoring
Flow Flow meter Continuous Report only
Flow dry day Flow meter Continuous 436 MGD annual
average
cBOD 24-hr composite 1/day 40 mg/L weekly
25 mg/L monthly
TSS 24-hr composite 1/day 45 mg/L weekly
30 mg/L monthly
pH Grab 1/day Not <6 or >9
Fecal coliform bacteria Grab 3/day 14,000 col/100ml
Total residual chlorine Grab 3/day 631 μg/L daily
456 μg/L monthly
PCB, Aroclors 24-hr composite 1/month 0.045 ng/L
Toxicity LC50 24-hr composite 2/month 50%
Toxicity C-NOEC 24-hr composite 2/month 1.5%
Settleable solids Grab 1/day
Chlorides (influent only) Grab 1/day
Mercury 24-hr composite 1/month
Chlordane 24-hr composite 1/month
4,4’–DDT 24-hr composite 1/month
Dieldrin 24-hr composite 1/month
Heptachlor 24-hr composite 1/month
Ammonium-nitrogen 24-hr composite 1/month
Total Kjeldahl nitrogen 24-hr composite 1/month
Total nitrate 24-hr composite 1/month
Total nitrite 24-hr composite 1/month
Cyanide, total Grab 1/month
Copper, total 24-hr composite 1/month
Total arsenic 24-hr composite 1/month
Hexachlorobenzene 24-hr composite 1/month
Aldrin 24-hr composite 1/month
Heptachlor epoxide 24-hr composite 1/month
Total PCBs 24-hr composite 1/month
Volatile organic
compounds Grab 1/month
Report only
Contingency Plan-required monitoring
Oil and grease, as
petroleum hydrocarbons Grab Weekly
Warning
threshold/ 15
mg/L
Floatables Continuous
Plant performance Ongoing 5 violations/year
OUTFALL MONITORING OVERVIEW BACKGROUND 19
Beyond the requirements of ordinary post-diversion monitoring, the
MWRA monitoring plan requires additional nutrient measurements and
non-standard, low-detection methods to measure toxic contaminants
(Table 2-3). These measurements are made to better interpret field-
monitoring results.
The monitoring plan also calls for an evaluation of indicators of human
pathogens. To date, MWRA has collected data on anthropogenic viruses,
viral indicators, and Enterococcus bacteria in the influent and effluent.
Table 2-3. Monitoring plan parameters for effluent.
Parameter Sample Type Frequency
Total Kjeldahl nitrogen Composite Weekly
Ammonium Composite Weekly
Nitrate Composite Weekly
Nitrite Composite Weekly
Total phosphorus Composite Weekly
Total phosphate Composite Weekly
Acid base neutrals Composite Bimonthly
Volatile organic compounds Grab Bimonthly
Cadmium 24-hour composite Weekly
Copper 24-hour composite Weekly
Chromium 24-hour composite Weekly
Mercury 24-hour composite Weekly
Lead 24-hour composite Weekly
Molybdenum 24-hour composite Weekly
Nickel 24-hour composite Weekly
Silver 24-hour composite Weekly
Zinc 24-hour composite Weekly
17 chlorinated pesticides 24-hour composite Weekly
Extended list of PAHs 24-hour composite Weekly
20 PCB congeners 24-hour composite Weekly
OUTFALL MONITORING OVERVIEW BACKGROUND 20
Contingency Plan Thresholds
Contingency Plan thresholds for effluent monitoring include warning
levels for all parameters and caution levels for PCBs, plant performance,
and nitrogen loads (Table 2-4). Floatable debris is present in low amounts
in the effluent, and appropriate methods for assessing it before discharge
have remained in development. Meanwhile, presence of debris is assessed
by net tows in the vicinity of the outfall site during water-column surveys.
Table 2-4. Contingency Plan threshold values for effluent monitoring.
Parameter Caution Level Warning Level
pH None <6 or >9
Fecal coliform
bacteria None
14,000 fecal coliforms/100 ml
(monthly 90 th percentile, weekly
geometric mean, maximum daily
geometric mean, and minimum of 3
consecutive samples)
Chlorine, residual None 631 μg/L daily,
456 μg/L monthly
Total suspended
solids None 45 mg/L weekly
30 mg/L monthly
cBOD None 40 mg/L weekly,
25 mg/L monthly
Toxicity None
Acute: effluent LC50 <50% for
shrimp and fish
Chronic: effluent NOEC for fish
survival and growth and sea urchin
fertilization <1.5% effluent
PCBs Aroclor=0.045
ng/L
Plant performance 5 violations/year Noncompliance >5% of the time
Flow None Flow >436 for annual average of dry
days
Total nitrogen load 12,500 mtons/year 14,000 mtons/year
Floatables Thresholds remain under development
Oil and grease None 15 mg/L weekly
OUTFALL MONITORING OVERVIEW BACKGROUND 21
3. Water Column
Background
Circulation and Water Properties
Circulation, water properties, and consequently, the biology of
Massachusetts and Cape Cod bays are driven by the larger pattern of water
flow in the Gulf of Maine (Figure 3-1) and by regional and local winds. A
coastal current flows southwestward along the Maine and New Hampshire
coasts; it may enter Massachusetts Bay to the north of Boston at Cape
Ann. This current drives an average counterclockwise circulation in
Massachusetts Bay and (sometimes) Cape Cod Bay. Water flows back out
of the bays at Race Point, located at the tip of Cape Cod. Whether the
coastal current enters Massachusetts Bay and whether it continues south
into Cape Cod Bay depends on the strength of the current and the
direction, duration, and speed of the wind. Because the coastal current is
strongest during the spring period of high runoff from rivers and streams,
the spring circulation pattern is more consistent than that of the summer
and fall (Geyer et al. 1992, Jiang et al. 2006).
During the summer and fall, freshwater inflow is lower, and so the wind
and water density interact in a different, more complex way, with
alternating periods of upwelling and downwelling in various locations,
depending primarily on the wind direction and strength (Lermusiaux
2001). Water flow varies with week-to-week changes in weather patterns.
Flow at any particular time depends on the wind speed and direction
relative to the topography of the sea floor. At times, flow can “reverse,”
with flow northward along the coast. Transient gyres in Massachusetts
and Cape Cod bays spin in either direction.
As in many coastal waters, during the winter the water is well-mixed from
top to bottom and nutrient levels are high. As light levels increase in the
early spring, phytoplankton populations often begin a period of rapid
growth known as a spring bloom. Contrary to popular wisdom, however,
strong spring blooms do not occur every year. During the years in which
they occur, spring blooms begin in the shallowest waters of Cape Cod
Bay. Blooms in the deeper Massachusetts Bay waters follow two to three
weeks later. Spring phytoplankton blooms are typically followed by an
increase in zooplankton abundance. These zooplankton populations are
food for many animals, including the endangered right whale.
OUTFALL MONITORING OVERVIEW BACKGROUND 22
(b)
Figure 3-1. (a) General circulation within Massachusetts Bay. Reprinted from
Journal of Marine Systems, Vol. 29, Author: PFJ Lermusiaux, "Evolving the
subspace of the three-dimensional multiscale ocean variability: Massachusetts
Bay," pp 385-422 © 2001 with permission from Elsevier. (b) General circulation
within the Gulf of Maine (from Beardsley et al. 1997).
OUTFALL MONITORING OVERVIEW BACKGROUND 23
Later in the spring, the surface waters warm, and the water column
stratifies. Inputs of freshwater from rivers contribute to the stratification,
with lighter, less saline water remaining at the surface. Stratification
effectively separates the surface and bottom waters, preventing
replenishment of nutrients to the surface and oxygen to the bottom.
Phytoplankton in the surface waters deplete the available nutrients and
then undergo senescence, sinking through the pycnocline to the bottom.
While oxygen levels remain high in the surface waters throughout the
year, levels fall in the bottom waters, as bottom-dwelling animals respire,
and bacteria use up oxygen as the phytoplankton decompose. Bottom-
water oxygen levels are typically lowest during the late summer or early
fall.
Cooling surface waters and strong winds during the autumn months
promote mixing of the water column. Oxygen is replenished in the bottom
waters, and nutrients brought to the surface can stimulate a fall
phytoplankton bloom. Similar to the spring, varying meteorological and
oceanographic conditions greatly influence the timing, magnitude, and
spatial extents of the blooms, and fall blooms do not always occur. When
they do occur, the fall blooms typically end in the early winter, when
declining light levels limit photosynthesis. Plankton die and decay,
replenishing nutrients in the water column.
Environmental Concerns
Water-column monitoring questions focus on the possible effects of
nutrients, organic matter, pathogens, and floatable debris from wastewater
on the water quality of Massachusetts Bay (MWRA 1991, Table 3-1).
Due to source reduction and treatment, concentrations of toxic
contaminants discharged in the MWRA effluent are so low that it is
impractical to measure them in the water column. Because organic
material, pathogens, and floatables are effectively removed by treatment at
DITP, but nutrients are not, nutrient issues caused the greatest concern
during development of the monitoring program.
The monitoring program looks extensively at possible effects of
discharging nutrient-rich effluent into Massachusetts Bay. One concern
was that excess nutrients, particularly nitrogen, could over-stimulate algal
blooms, which would be followed by low levels of dissolved oxygen in
the bottom waters when the phytoplankton organisms die, sink, and
decompose. Another concern was that changes in the relative levels of
nutrients could stimulate growth of undesirable algae. Three nuisance or
noxious species or species groups were of particular concern: the
dinoflagellate Alexandrium fundyense ( A. fundyense and A. tamarense ,
which are varieties of the same species), the diatom Pseudo-nitzschia
multiseries , and the colonial flagellate Phaeocystis pouchetii .
OUTFALL MONITORING OVERVIEW BACKGROUND 24
Table 3-1. Monitoring questions developed by OTMF related to the water column.
Is it safe to eat fish and shellfish?
Will pathogens in the effluent be transported to shellfishing areas where they could
accumulate in the edible tissues of shellfish and contribute to human health problems?
Are pathogens transported to shellfish beds at levels that might affect shellfish
consumer health?
Are natural/living resources protected?
Will nutrient enrichment in the water column contribute to an increase in primary production?
Will nutrient enrichment in the water column contribute to changes in plankton community
structure?
Have nutrient concentrations changed in the water near the outfall; have they
changed at farfield stations in Massachusetts Bay or Cape Cod Bay, and, if so, are
they correlated with changes in the nearfield?
Has the phytoplankton biomass changed in the vicinity of the outfall or at selected
farfield stations in Massachusetts Bay or Cape Cod Bay, and, if so, can changes be
correlated with effluent or ambient water nutrient concentrations, or can farfield
changes be correlated with nearfield changes?
Have the phytoplankton production rates changed in the vicinity of the outfall or at
selected farfield stations, and, if so, can these changes be correlated with effluent or
ambient water nutrient concentrations, or can farfield changes be correlated with
nearfield changes?
Has the abundance of nuisance or noxious phytoplankton species changed in the
vicinity of the outfall?
Has the species composition of phytoplankton or zooplankton changed in the vicinity
of the outfall or at selected farfield stations in Massachusetts Bay or Cape Cod Bay?
If so, can these changes be correlated with effluent or ambient water nutrient
concentrations, or can farfield changes be correlated with nearfield changes?
Will increased water-column and benthic respiration contribute to depressed oxygen levels in
the water?
Do the concentrations (or percent saturation) of dissolved oxygen in the vicinity of the
outfall and at selected farfield stations meet the state water quality standard?
Have the concentrations (or percent saturation) of dissolved oxygen in the vicinity of
the outfall or at selected farfield stations in Massachusetts Bay or Cape Cod Bay
changed relative to pre-discharge baseline or a reference area? If so, can changes
correlated with effluent or ambient water nutrient concentrations, or can farfield
changes be correlated with nearfield changes?
Is it safe to swim?
Will pathogens in the effluent be transported to waters near swimming beaches, contributing
to human health problems?
Are pathogens transported to beaches at levels that might affect swimmer health?
Are aesthetics being maintained?
Will changes in water clarity and/or color result from the direct input of effluent particles or
other colored constituents, or indirectly through nutrient stimulation of nuisance plankton
species?
Will the loading of floatable debris increase, contributing to visible degradation?
Has the clarity and/or color of the water around the outfall changed?
Has the amount of floatable debris around the outfall changed?
Information on transport and fate necessary to answer all the questions
Are model estimates of short-term (less than 1 day) effluent dilution and transport
accurate?
What are the nearfield and farfield water circulation patterns?
What is the farfield fate of dissolved, conservative, or long-lived effluent constituents?
OUTFALL MONITORING OVERVIEW BACKGROUND 25
Alexandrium fundyense blooms are known in New England as red tides.
They produce a toxin, which when sufficiently concentrated by shellfish
that take up the algae, causes paralytic shellfish poisoning (PSP), a
condition that can be fatal to marine mammals, fish, and humans. At high
concentrations (more than 1 million cells per liter), some diatoms in the
genus Pseudo-nitzschia may produce sufficient quantities of toxic domoic
acid to cause a condition known as amnesic shellfish poisoning, which is
marked by gastrointestinal and neurological symptoms, including
dementia. Phaeocystis pouchetii is not toxic, but individual cells can
aggregate in gelatinous colonies that may be aesthetically displeasing or
provide poor food for zooplankton.
Dissolved oxygen concentrations in bottom waters naturally decrease
during the stratified period as part of the natural seasonal pattern. If
discharged nutrients were to stimulate large phytoplankton blooms, the
conditions could lead to lower levels of dissolved oxygen when the cells
sink to the bottom and decay.
Because of the concern that lowered levels of dissolved oxygen could
affect animals in the vicinity of the outfall, it was important during the
baseline-monitoring period to develop an understanding of the natural
fluctuations of oxygen levels within the system. Modeling and
measurements showed that the typical periods of low oxygen
concentrations in bottom waters correlate with warmer and saltier bottom
waters. Ongoing monitoring assesses potential departures from the natural
conditions.
Monitoring Design
Water-column monitoring includes assessments of water quality,
phytoplankton, and zooplankton in Massachusetts and Cape Cod bays.
Regular monitoring includes four components: nearfield surveys, farfield
surveys, continuous recording, and remote sensing (Table 3-2). Plume-
tracking studies, conducted in 2001, qualitatively verified the expected
dilution at the outfall and confirmed predictions that bacteria and toxic
contaminant concentrations in the discharged effluent are very low.
OUTFALL MONITORING OVERVIEW BACKGROUND 26
Table 3-2. Components of water-column monitoring.
Task Objective
Nearfield surveys Collect water quality data near the outfall
Farfield surveys Collect water quality data throughout
Massachusetts and Cape Cod bays
Moorings Provide continuous oceanographic data
near outfall location
Remote sensing Provides oceanographic data on a regional
scale through satellite imagery
Nearfield surveys provide vertical and horizontal profiles of physical,
chemical, and biological characteristics of the water column in the area
around the outfall, where some effects of the effluent were expected and
have been observed. Farfield surveys assess differences across the bays
and seasonal changes over a large area. Several farfield stations mark the
boundary of the monitoring area and are in or near the Stellwagen Bank
National Marine Sanctuary. Two of those stations denote the “northern
boundary,” representing water entering Massachusetts Bay from the Gulf
of Maine. Other stations are in Boston Harbor, coastal and offshore
regions, and in Cape Cod Bay (Figures 3-2, 3-3, and 3-4). Since 2004,
typically, twelve surveys of seven nearfield stations and six surveys of 25
farfield stations are conducted each year.
Parameters measured in the water column include dissolved inorganic and
organic nutrients, particulate forms of nutrients, chlorophyll, total
suspended solids, dissolved oxygen, productivity, respiration,
phytoplankton abundance and species composition, and zooplankton
abundance and species composition (Tables 3-3 and 3-4). Nutrients
measured include the major forms of nitrogen, phosphorus, and silica.
The measurements focus on the dissolved inorganic forms, which are most
readily used by phytoplankton. The surveys also include observations and
net tows in the outfall area to assess the presence of floatable debris.
The continuous recording components of the program capture temporal
variations in water quality between nearfield surveys. Remote sensing by
satellite captures spatial variations in water quality on a larger, regional
scale.
OUTFALL MONITORING OVERVIEW BACKGROUND 27
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0 10 20 30 40 50 5
Kilometers
boundary region
northern
boundary
region
offshore
region
coastal region
nearfield region
z MWRA stations (BWQM)
GoMOOS Buoy A
NOAA Buoy 44013
MWRA outfall diffuser
Regions
Stellwagen Bank Sanctuary
High : 0
Low : -125
Figure 3-2. MWRA Bay Water Quality Monitoring (BWQM) stations and regional groupings
included in the program. “Farfield” stations include all stations in Boston Harbor; the coastal,
offshore, and northern boundary regions; and Cape Cod Bay. Also shown are the MWRA outfall;
two instrumented buoys, one operated by the Gulf of Maine Ocean Observing System (GoMOOS)
and the other by the National Oceanic and Atmospheric Administration (NOAA) National Data
Buoy Center (NDBC); and the Stellwagen Bank Marine Sanctuary.
OUTFALL MONITORING OVERVIEW BACKGROUND 28
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70°15'W
70°15'W
70°30'W
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42°30'N
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42°0'N
42°0 'N
41°4 5'N
41°45'N
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70°15'W
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42°30'N
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42°0'N
42°0 'N
41°4 5'N
northern
boundary
region
41°45'N
Cape Cod Bay
Boston
Harbor Massachusetts Bay
coastal region
offshore
region
nearfield region
z z Phytoplankton and zooplankton station
z Zooplankton-only station
GoMOOS Buoy A
NOAA Buoy 44013
MWRA outfall diffuser
Regions
High : 0
0 10 20 30 40 50 5
Kilometers
Low : -125
Figure 3-3. MWRA plankton stations included in water-column monitoring. The stations are a
subset of those monitored for water quality. Regional groupings, the instrumented buoys, and the
MWRA outfall are also shown.
OUTFALL MONITORING OVERVIEW BACKGROUND 29
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42°1 5'N
Boston
Harbor
Massachusetts
Bay
0 10 20 5
Kilometers
{ Harbor station (BHWQM)
z z Plankton station
NOAA Buoy 44013
MWRA outfall diffuser
High : 0
Low : -50
Figure 3-4. MWRA Boston Harbor Water Quality Monitoring (BHWQM)
stations and nearby BWQM plankton stations. Primary productivity is measured
at Stations F23, N18, and N04.
OUTFALL MONITORING OVERVIEW BACKGROUND 30
Table 3-3. Nearfield water-column monitoring parameters.
Parameter Measurement Details
Temperature
Salinity
Dissolved oxygen
Chlorophyll fluorescence
Transmissometry
Irradiance
Depth of sensors
In-situ sensor measurements
Boat surveys of seven stations
Every half meter depth
Ammonium
Nitrate
Nitrite
Phosphate
Silicate
Inorganic nutrients sampling
Seven stations
Five depths
Dissolved inorganic carbon
Dissolved nitrogen
Dissolved phosphorus
Particulate carbon
Particulate nitrogen
Particulate phosphorus
Particulate biogenic silica
Total suspended solids
Additional nutrients sampling
Seven stations
Three depths
Primary productivity
Respiration
Phytoplankton
Zooplankton
Rates and plankton sampling
Two stations
Variable depths
Floatables Net tows
Table 3-4. Farfield water-column monitoring parameters.
Parameter Measurement Details
Temperature
Salinity
Dissolved oxygen
Chlorophyll fluorescence
Transmissometry
Irradiance
Depth of sensors
In-situ sensor measurements
Boat surveys of 25 stations
Every half meter depth
Ammonium
Nitrate
Nitrite
Phosphate
Silicate
Inorganic nutrients sampling
23 stations at five depths
Two shallow stations at three depths
Dissolved inorganic carbon
Dissolved nitrogen
Dissolved phosphorus
Particulate carbon
Particulate nitrogen
Particulate phosphorus
Particulate biogenic silica
Total suspended solids
Phytoplankton
Zooplankton
Additional nutrients and plankton sampling
Ten stations
Variable depths
Primary productivity Rates sampling
One station
Five depths
Respiration
Rates sampling
Two stations
Three depths
OUTFALL MONITORING OVERVIEW BACKGROUND 31
Contingency Plan Thresholds
Threshold parameters for water-column monitoring include minimum
dissolved oxygen concentrations and percent saturation in nearfield and
Stellwagen Bank bottom waters, dissolved oxygen depletion rate in
nearfield bottom waters, chlorophyll levels, abundance of nuisance algal
species, geographic extent of PSP toxin, and initial dilution (Table 3-5).
Oxygen concentrations and percent saturation are compared to background
levels rather than to the caution and warning levels.
Table 3-5. Contingency Plan threshold values for water-column monitoring.
Location/
Parameter
Specific
Parameter Baseline Caution Level Warning Level
Dissolved oxygen
concentration
Background 5 th
percentile
5.75 mg/L
Lower than 6.5
mg/L for any
survey (June-
October) unless
background
conditions are
lower
Lower than 6.0
mg/L for any
survey (June-
October) unless
background
conditions are
lower
Bottom water
nearfield
Dissolved oxygen
percent saturation
Background 5 th
percentile
64.3%
Lower than 80%
for any survey
(June-October)
unless background
conditions are
lower
Lower than 75%
for any survey
(June-October)
unless background
conditions are
lower
Dissolved oxygen
concentration
Background 5 th
percentile
6.2 mg/L
6.5 mg/L for any
survey (June-
October) unless
background
conditions lower
Lower than 6.0
mg/L for any
survey (June-
October) unless
background
conditions are
lower
Bottom water
Stellwagen Basin
Dissolved oxygen
percent saturation
Background 5 th
percentile
66.3%
Lower than 80%
for any survey
(June-October)
unless background
conditions
Lower than 75%
for any survey
(June-October)
unless background
conditions are
lower
Bottom water
nearfield
DO depletion rate
(June-October) 0.024 mg/L/day 0.037 mg/L/day 0.049 mg/L/day
Annual 79 mg/m 2 118 mg/m 2 158 mg/m 2
Winter/spring 62 mgml 2 238 mg/m 2 None
Summer 51 mg/m 2 93 mg/m 2 None
Chlorophyll
nearfield
Autumn 97 mg/m 2 212 mg/m 2 None
Winter/spring 468,000 cells/L 2,020,000 cells/L None
Summer 72 cells/L 357 cells/L None
Nuisance algae
nearfield
Phaeocystis
pouchetii Autumn 317 cells/L 2,540 cells/L None
Winter/spring 6,200 cells/L 21,000 cells/L None
Summer 14,600 cells/L 43,100 cells/L None
Nuisance algae
nearfield Pseudo-
nitzschia Autumn 9,940 cells/L 24,700 cells/L None
Nuisance algae
nearfield
Alexandrium
fundyense
Any nearfield
sample
Baseline maximum
= 163 cells/L 100 cells/L None
Farfield PSP toxin extent Not applicable New incidence None
OUTFALL MONITORING OVERVIEW BACKGROUND 32
4. Sea Floor
Background
Bottom Characteristics and Sediment Transport
The sea floor of Massachusetts and Cape Cod bays was originally shaped
by the glaciers, which sculpted the bottom and deposited debris, forming
knolls, banks, and other features. Within Massachusetts Bay, the sea floor
ranges from mud in depositional basins to coarse sand, gravel, and
bedrock on topographic highs. The area around the outfall is marked by
underwater drumlins, which are elongated hills about 10 meters high, with
crests covered by gravel and boulders. Long-term sinks for fine-grained
sediments include Boston Harbor, Cape Cod Bay, and Stellwagen Basin.
Modeling and long-term monitoring have confirmed that sediment
transport in the region occurs primarily during storms (Butman et al.
2005). Typically, waves during storms with winds from the northeast
resuspend sediments, which are transported by shallow currents from
western Massachusetts Bay toward Cape Cod Bay and by deeper currents
to Stellwagen Basin. Cape Cod Bay is partially sheltered from large
waves by the arm of Cape Cod, and storm waves are rarely large enough
to resuspend sediments in Stellwagen Basin, which is the deepest feature
in the region. Tidal currents, wind-driven currents, and currents
associated with spring runoff are too weak or too shallow to resuspend
sediments.
Environmental Concerns
Within Boston Harbor, studies of the sediments have documented the
recovery that had been expected after the end of biosolids and effluent
discharges and other improvements. Conversely, relocating the outfall
raised concerns about potential effects on the offshore sea floor. Concern
focused on three mechanisms of potential disruption to the animal
communities living on the sea floor: eutrophication and related low levels
of dissolved oxygen, accumulation of toxic contaminants in depositional
areas, and smothering (Table 4-1).
OUTFALL MONITORING OVERVIEW BACKGROUND 33
Table 4-1. Monitoring questions developed by OTMF related to the sea floor.
Are natural/living resources protected?
Will benthic enrichment contribute to changes in community structure of soft-
bottom and hard-bottom macrofauna, possibly affecting fisheries?
Will benthic macrofauna near the outfall mixing zone be exposed to some
contaminants, potentially contributing to changes in the community?
Will the benthos near the outfall mixing zone and in depositional areas farther
away accumulate some contaminants?
What is the level of sewage contamination and its spatial distribution
in Massachusetts and Cape Cod bays sediments before discharge
through the new outfall?
Has the level of sewage contamination or its spatial distribution in
Massachusetts or Cape Cod bays sediments changed after
discharge through the new outfall?
Have the concentrations of contaminants in sediments changed?
Has the soft-bottom community changed?
Are any benthic community changes correlated with changes in
levels of toxic contaminants (or sewage tracers) in sediments?
Has the hard-bottomed community changed?
Will increased water-column and benthic respiration contribute to depressed
oxygen levels in the sediment?
Have the sediments become more anoxic; that is, has the thickness
of the sediment oxic layer decreased?
If diversion of the nutrient loads to offshore were to cause eutrophication,
the depressed levels of dissolved oxygen that were also a concern in
water-column monitoring could adversely affect bottom-dwelling animals.
An increase in the amounts of particles and organic matter to the bottom
could disrupt normal benthic community structure in the vicinity of the
discharge. Although source control and treatment plant performance are
designed to keep effluent contaminant concentrations too low to affect the
sediments, the location of the outfall in an area of sediment transport
caused concern about increased accumulation of toxic contaminants in
Cape Cod Bay and Stellwagen Basin. Similarly, concentrations of
particulate matter were expected to be low, but there remained some
concern that bottom communities near the outfall could be affected by
deposition.
Monitoring Design
Sea-floor monitoring includes several components: measurements of
sediment characteristics, sewage effluent tracers, and contaminant
concentrations in sediments; sediment-profile imaging to provide a rapid
assessment of benthic communities and sediment quality; studies of
nearfield and farfield soft-bottom communities (sampling sites in Figures
4-1 and 4-2); and study of hard-bottom communities (sampling sites in
Figure 4-3).
OUTFALL MONITORING OVERVIEW BACKGROUND 34
Figure 4-1. Locations of nearfield soft-bottom stations.
OUTFALL MONITORING OVERVIEW BACKGROUND 35
Figure 4-2. Locations of farfield soft-bottom stations.
OUTFALL MONITORING OVERVIEW BACKGROUND 36
Figure 4-3. Locations of hard-bottom stations.
OUTFALL MONITORING OVERVIEW BACKGROUND 37
Measurements of sediment characteristics, tracers, and contaminants
include analyses of grain size, total organic carbon (TOC), Clostridium
perfringens spores, PAHs, PCBs, chlorinated pesticides, and metals.
Sediment-contaminant monitoring has been complemented by special
studies, primarily in association with USGS (for example, Bothner and
Butman 2007).
Sediment-profile-image monitoring is conducted each August and results
in area-wide assessments of sediment quality and benthic community
status. A sharp-edged prism is used to cut into sediment surfaces at each
station; a camera mounted to the prism records images of the sediment-
water interface and the surface-sediment profiles. At each station, the
camera is lowered to the sea floor three or four times, and a series of two
to four replicate images is taken, generally within the first 12 seconds after
bottom contact. A video feed allows real-time monitoring and ensures that
adequate still photographs are obtained. The sediment-profile images
provide more rapid assessments of benthic habitat conditions than is
possible from traditional faunal analyses. The images are used to measure
a number of parameters, including the apparent reduction-oxidation
(redox) potential discontinuity (RPD) depth, apparent successional stage
of the community, and an organism sediment index which is derived from
the RPD depth and the succession stage.
Monitoring the soft-bottom benthic infauna also includes annual sampling
surveys conducted in August. Samples are collected with a 0.04-m 2
Young-Van Veen benthic grab, sieved on 300- μ m mesh, and fixed in
formalin in the field, then transferred to alcohol and stained with Rose
Bengal in the laboratory. Animals are sorted, identified, and counted.
Most pollutant-effect monitoring studies of benthic communities,
including the MWRA monitoring program, focus on the soft-bottom areas
with finer-grained sediments, but such depositional areas are few in the
vicinity of the outfall. Therefore, MWRA also conducts video and
photographic surveys of the hard-bottom habitats found on the tops and
flanks of drumlins in western Massachusetts Bay. Video and still
photographs are taken at a series of stations or waypoints, including
diffuser head #44 of the outfall (which was not opened) and diffuser head
#2 (which is active). These annual surveys are conducted in June.
Photographs are examined for substrate type (top or flank of the drumlin,
with relief defined by presence of boulders and cobbles), amount of
sediment drape (the degree to which a layer of fine material covers the
hard surface), and biota (taxa identified to species or species groups and
counted).
OUTFALL MONITORING OVERVIEW BACKGROUND 38
Beginning in 2003 and 2004, the existing 23 nearfield and 8 farfield soft-
bottom stations were split into two subgroups. This division was made
randomly after accounting for regional representation and level of
replication, with two stations (NF12 and NF17, which are also sampled by
USGS) being included in both groups. The program includes the
following:
• Sediment characteristics and tracers, such as TOC, sediment grain
size, and Clostridium perfringens spore counts, are measured in
samples from one subset in alternate years, such that each station is
sampled at least once every two years.
• Chemical constituents, including PAHs, PCBs, pesticides, and
metals, are measured annually in samples from the two stations
included in both groups and once every three years in samples
from stations being sampled for other parameters, with those
measurements most recently occurring in 2005.
• Sediment-profile images continue to be taken at all 23 nearfield
soft-bottom stations each year.
• Benthic infauna is studied at the same stations as are sampled for
sediment characteristics. Species composition and abundance are
assessed for all stations sampled.
• Hard-bottom monitoring continues to be conducted annually,
except that two stations were discontinued and two stations were
added in 2003.
Contingency Plan Thresholds
The Contingency Plan sets caution levels for RPD depth and benthic
community parameters and warning levels for toxic contaminants in
sediments (Figure 4-2). Because different stations are sampled in even
and odd years, benthic-diversity parameters have separate Contingency
Plan caution levels for those subsets of stations. Caution and warning
levels exist for benthic opportunists, which are species that could be
indicative of pollution.
OUTFALL MONITORING OVERVIEW BACKGROUND 39
Table 4-2. Contingency Plan threshold values for sea-floor monitoring.
Location Parameter Caution Level Warning Level
Sediments,
nearfield RPD depth 1.18 cm None
Acenaphthene None 500 ppb dry
Acenaphylene None 640 ppb dry
Anthracene None 1100 ppb dry
Benzo(a)anthracene None 1600 ppb dry
Benzo(a)pyrene None 1600 ppb dry
Cadmium None 9.6 ppm dry
Chromium None 370 ppm dry
Chrysene None 2800 ppb dry
Copper None 270 ppm dry
Dibenzo(a,h)anthracene None 260 ppb dry
Fluoranthene None 5100 ppb dry
Fluorene None 540 ppb dry
Lead None 218 ppm dry
Mercury None 0.71 ppm dry
Naphthalene None 2100 ppb dry
Nickel None 51.6 ppb dry
p,p’-DDE None 27 ppm dry
Phenanthrene None 1500 ppb dry
Pyrene None 2600 ppb dry
Silver None 3.7 ppm dry
Total DDTs None 46.1 ppb dry
Total HMW PAH None 9600 ppb dry
Total LMW PAH None 3160 ppb dry
Total PAHs None 44792 ppb dry
Total PCBs None 180 ppb dry
Sediment toxic
contaminants,
nearfield
Zinc None 410 ppm dry
Species per sample <48.41 or >82.00 None
Fisher’s log-series alpha <9.99 or >16.47 None
Shannon diversity <3.37 or >4.14 None
Even years:
benthic
diversity,
nearfield Pielou’s evenness <0.58 or >0.68 None
Species per sample <46.52 or >79.95 None
Fisher’s log-series alpha <9.95 or >15.17 None
Shannon diversity <3.30 or >3.91 None
Odd years:
benthic
diversity,
nearfield Pielou’s evenness <0.56 or >0.66 None
Benthic
opportunists Percent opportunists >10% >25%
OUTFALL MONITORING OVERVIEW BACKGROUND 40
5. Fish and Shellfish
Background
MWRA monitors fish and shellfish because of concerns for public health
and because some fish and shellfish species are good indicators of effects
of pollutants on overall marine health (Table 5-1). The fish and shellfish
industry is an important part of the regional identity and economy of
Massachusetts.
Table 5-1. Monitoring questions developed by OTMF related to fish and
shellfish.
Is it safe to eat fish and shellfish?
Will toxic chemicals accumulate in the edible tissues of fish and shellfish, and
thereby contribute to human health problems?
Has the level of contaminants in the tissues of fish and shellfish
around the outfall changed since discharge began?
Do the levels of contaminants in the edible tissue of fish and shellfish
around the outfall represent a risk to human health?
Are the contaminant levels in fish and shellfish different between
outfall, Boston Harbor, and a reference site?
Are natural/living resources protected?
Will fish and shellfish that live near or migrate by the diffuser be exposed to
elevated levels of some contaminants, potentially contributing to adverse
health in some populations?
Has the level of contaminants in the tissues of fish and shellfish
around the outfall changed since discharge began?
Are the contaminant levels in fish and shellfish different between the
outfall, Boston Harbor, and a reference site?
Are the contaminant levels in fish and shellfish different between
outfall, Boston Harbor, and a reference site?
Has the incidence of disease and/or abnormalities in fish or shellfish
changed?
The two main concerns for fish and shellfish were that the discharge of
sewage effluent into the relatively clean waters of Massachusetts Bay
could result in chemical contamination of the fisheries and that
contaminants in the effluent could cause direct damage to health of the
fishery stocks. Because many toxic contaminants adhere to particles,
which settle, animals that live on the bottom, in contact with sediments
and those that eat bottom-dwelling organisms were considered to be the
most likely species to be affected. Exposure to contaminated sediments
could result in fin erosion, disease, or other, subtler, abnormalities in
flounder, lobster, or other bottom-dwelling animals. Shellfish that feed by
filtering suspended matter from large volumes of water are also potential
bioaccumulators of toxic contaminants. Consumption of filter-feeding
OUTFALL MONITORING OVERVIEW BACKGROUND 41
animals by predators could result in transferring contaminants up the food
chain and ultimately to humans.
Monitoring Design
The monitoring program focuses on three indicator species: winter
flounder ( Pseudopleuronectes americanus ), lobster ( Homarus
americanus ), and blue mussel ( Mytilus edulis ). Winter flounder and
lobster are important resource species in the region. Like all flatfish,
winter flounder live and feed on the bottom, often lying partially buried in
the sediments. Lobsters live on a variety of surfaces within the region,
including mud, sand, gravel, and rock outcrops. Blue mussels are also
resource species. Like other filter feeders, mussels process large volumes
of water and can concentrate toxic metals and organic compounds in their
tissues. They can be readily maintained in fixed cages, so they are
convenient monitoring tools.
Flounder and lobster are sampled from Deer Island Flats, near the outfall
site, and Cape Cod Bay (Figure 5-1). Flounder are also taken near
Nantasket Beach and until 2005, at Broad Sound, just off the coast to the
north of Deer Island. Mussels are deployed at the edge of the mixing
zone, one kilometer south of the diffuser line, in Cape Cod Bay, at Deer
Island Light, and in the Inner Harbor.
Winter Flounder
Flounder are collected annually. Whole fish are examined for external
lesions or other abnormalities, and flounder livers are examined to
quantify disease, including three types of vacuolation (centrotubular
(CHV), tubular, and focal, representing increasing severity), microphage
aggregation, biliary-duct proliferation, and neoplasia or tumors.
Vacuolation and neoplasia have been associated with chronic exposure to
contaminants.
Since 2004, chemical analyses for flounder are completed every third year,
including 2006, to determine tissue burdens and to evaluate whether
contaminant burdens approach human health consumption limits.
Chemical analyses (Table 5-2) of composite samples of fillets and livers
include PCBs, pesticides, mercury, and lipids. Liver samples are also
analyzed for PAHs, lead, silver, cadmium, chromium, copper, nickel, and
zinc.
Lobster
Commercial lobstermen collect lobsters for the monitoring program.
Since 2004, lobsters have been studied every third year, including 2006.
All lobsters are examined for external conditions, and chemical analyses
are performed on composite samples. Meat (from the tail and claw) and
hepatopancreas are analyzed for lipids, PCBs, pesticides, and mercury.
OUTFALL MONITORING OVERVIEW BACKGROUND 42
Hepatopancreas samples are also analyzed for PAHs, lead, silver,
cadmium, chromium, copper, nickel, and zinc.
Figure 5-1. Sampling areas and reference sites for fish-and-shellfish monitoring.
OUTFALL MONITORING OVERVIEW BACKGROUND 43
Blue Mussel
Mussels are collected from clean reference sites (which have included
Rockport, Gloucester, and Sandwich, Massachusetts, and Stover’s Point,
Maine; see Figure 5-1). They are placed in cages and deployed in
replicate arrays. Since 2004, mussel deployments and analyses have been
carried out every third year, including 2006.
After a minimum deployment of 40 days or a preferred deployment of 60
days, chemical analyses are performed on composite samples of mussel
tissue. Tissues are analyzed for PCBs, pesticides, PAHs, lipids, mercury,
and lead.
Table 5-2. Chemical analyses of fish and shellfish.
Parameter Measurement Details
Flounder fillet
Mercury
PCBs
Chlorinated pesticides
Lipids
Three composites of fillets from five
flounder
Flounder liver
Trace metals
PAHs
PCBs
Chlorinated pesticides
Lipids
Three composites of livers from five
flounder
Lobster meat
Mercury
PCBs
Chlorinated pesticides
Lipids
Three composites of meat from five
lobsters
Lobster hepatopancreas
Trace metals
PAHs
PCBs
Chlorinated pesticides
Lipids
Three composites of hepatopancreas
from five lobsters
Mussel
Mercury
Lead
PAHs
PCBs
Chlorinated pesticides
Lipids
Six composites of soft tissue from ten
mussels
OUTFALL MONITORING OVERVIEW BACKGROUND 44
Contingency Plan Thresholds
Threshold parameters for fish and shellfish include levels of toxic
contaminants in flounder, lobster, and mussels and liver disease (measured
as CHV) in flounder (Table 5-3). Some thresholds are based on U.S. Food
and Drug Administration limits for maximum concentrations of specific
contaminants in edible portions of food. Others are based on the baseline
monitoring.
Table 5-3. Contingency Plan threshold values for fish-and-shellfish monitoring.
Parameter
Type/
Location
Parameter Baseline Caution
Level
Warning
Level
PCB 0.033 ppm 1 ppm wet
weight
1.6 ppm wet
weight
Flounder
tissue
nearfield Mercury 0.074 ppm 0.5 ppm wet
weight
0.8 ppm wet
weight
Chlordane 242 ppb 484 ppb None
Dieldrin 63.7 ppb 127 ppb None
Flounder
tissue, lipid
normalized,
nearfield DDT 775.9 ppb 1552 ppb None
Flounder
nearfield
Liver disease
(CHV) 24.4% 44.9% None
PCB 0.015 ppm 1 ppm wet
weight
1.6 ppm wet
weight
Lobster
tissue
nearfield Mercury 0.148 ppm 0.5 ppm wet
weight
0.8 ppm wet
weight
Chlordane 75 ppb 150 ppb None
Dieldrin 161 ppb 322 ppb None
Lobster
tissue, lipid
normalized,
nearfield DDT 341.3 ppb 683 ppb None
PCB 0.011 ppm 1 ppm wet
weight
1.6 ppm wet
weight
Lead 0.415 ppm 2 ppm wet
weight
3 ppm wet
weight
Mussel tissue
nearfield
Mercury 0.019 ppm 0.5 ppm wet
weight
0.8 ppm wet
weight
Chlordane 102.3 ppb 205 ppb None
Dieldrin 25 ppb 50 ppb None
DDT 241.7 ppb 483 ppb None
Mussel
tissue, lipid
normalized,
nearfield PAH 1080 ppb 2160 ppb None
OUTFALL MONITORING OVERVIEW BACKGROUND 45
6. Special Studies
Background
Besides monitoring the effluent and the water column, sea floor, and fish
and shellfish in Massachusetts Bay and the surrounding area, MWRA
conducts special studies in response to specific permit requirements,
scientific questions, and public concerns.
Some studies have been reported during each year of the monitoring
program. For example, studies of nutrient flux at the sediment-water
interface have been conducted each year in response to a concern that
increased loads of organic matter might enhance benthic respiration and
nutrient fluxes between the sediments and the water column in the
nearfield. The resulting higher rates of benthic respiration or sediment
oxygen demand might lead to lower levels of oxygen in both the
sediments and the water column.
Since 1995, MWRA has included endangered species observers on
monitoring surveys. Besides providing observational data, the presence of
trained marine mammal observers addresses a request by the National
Marine Fisheries Service that MWRA take active steps to minimize the
chances of a collision of one of its survey vessels with a right whale.
A major special study carried out by the US Geological Survey began in
1989 and was completed in 2007. This cooperative research project
investigated processes influencing the transport and fate of contaminated
sediments in Boston Harbor and Massachusetts Bay (Bothner and Butman
2007).
Other special studies have included reviews of nutrient and toxic-
contaminant issues, additional analyses of the effluent, evaluations of the
Bays Eutrophication Model, floatables monitoring, and red-tide
monitoring and analyses.
OUTFALL MONITORING OVERVIEW BACKGROUND 46
7. Stellwagen Bank
National Marine Sanctuary
Background
The Gerry E. Studds Stellwagen Bank National Marine Sanctuary
comprises 842 square miles located at the boundary between
Massachusetts Bay and the rest of the Gulf of Maine. Its landward
boundaries lie approximately 25 miles east of Boston, three miles north of
Provincetown, and three miles south of Gloucester. Stellwagen Basin,
which is partially within the sanctuary, is the deepest part of
Massachusetts Bay and a long-term sink for fine-grained sediments.
Stellwagen Bank, a sand-and-gravel plateau, lies to the east of Stellwagen
Basin and has water depths of about 65 feet. Tidal mixing of nutrients
throughout the relatively shallow water column creates a rich habitat for
marine life on Stellwagen Bank.
The most prominent pressures on the sanctuary according to a condition
report released in 2007 (available at http://sanctuaries.noaa.gov), are
shipping; discharges from the MWRA outfall and dumping at the dredged
material disposal site located adjacent to the sanctuary boundary; a fiber-
optic cable laid across the sanctuary; the likelihood of development of a
deepwater port approximately two miles west of the sanctuary for off-
loading of liquefied natural gas; noise pollution that adversely affects
marine mammals; commercial fishing; commercial whale watching;
recreational fishing and boating; and climate change.
The National Centers for Coastal Ocean Science (NCCOS) has published
an ecological characterization report for the sanctuary (NCCOS 2006;
available at http://ccma.nos.noaa.gov/products/biogeography/stellwagen).
The report describes the physical and oceanographic setting, chemical
contaminants, fishes, seabirds, and mammals in the sanctuary and the Gulf
of Maine. The report finds that there has been no indication that the
relocation of the MWRA outfall to Massachusetts Bay has exerted any
effect on the magnitude of contaminants reaching the sanctuary.
Although these positive findings were anticipated, MWRA’s discharge
permit requires an annual assessment of possible outfall effects.
OUTFALL MONITORING OVERVIEW BACKGROUND 47
Monitoring Design
MWRA’s regular water-column and sea-floor monitoring efforts include
stations within and near the sanctuary. Five water-column stations,
including four within the sanctuary and one just outside its northern
border, are considered “northern boundary” or “boundary” stations,
because they mark the boundary between Massachusetts Bay and the rest
of the Gulf of Maine. These stations are important to MWRA, not just
because of their location within a marine sanctuary, but also because
water-column processes within Massachusetts Bay are largely driven by
the regional processes in the Gulf of Maine. Eight water-column stations
located between the sanctuary and the coast are considered “offshore”
stations by the MWRA program. The revisions to the water-column
portion of the monitoring program implemented in 2004 did not change
the stations sampled within and in the vicinity of the sanctuary.
During 2001–2006, the sanctuary managers, in conjunction with MWRA’s
contractor Battelle, conducted a supplemental water-quality monitoring
program which added four stations to the August and October MWRA
surveys (Figure 7-1). These sites were selected to provide a more
comprehensive evaluation of water quality across the sanctuary.
Two MWRA sea-floor stations are within the sanctuary, one at the
southern boundary and one within Stellwagen Basin (FF04 and FF05,
Figure 7-2). A third sea-floor station (FF11) is just north of the sanctuary
boundary and a fourth station (FF14) is located outside the sanctuary, but
within Stellwagen Basin. These four stations are the deepest of those
included in the MWRA monitoring program and have similar properties,
with muddy sediments and moderate concentrations of total organic
carbon. The stations are east or northeast of the outfall, outside the
general circulation pattern that transports diluted effluent south and
southeastward in Massachusetts Bay. During 1992–2003, these stations
were sampled annually in August. Changes to the benthic monitoring
program implemented in 2004 call for sampling approximately half the
stations each year.
OUTFALL MONITORING OVERVIEW BACKGROUND 48
Figure 7-1. MWRA and supplemental water-column stations in and near the Stellwagen
Bank National Marine Sanctuary. MWRA stations within the sanctuary are F27, F28,
F12. Supplemental stations are indicated by ∗ .
OUTFALL MONITORING OVERVIEW BACKGROUND 49
Figure 7-2. Farfield benthic stations.
OUTFALL MONITORING OVERVIEW BACKGROUND 50
References
Beardsley RC, Butman B, Geyer WR, Smith P. 1997. Physical
oceanography of the Gulf of Maine: an update. In: Wallace G, Braasch E,
editors. Proceedings of the Gulf of Maine ecosystem dynamics: a
scientific symposium and workshop. RARGOM. 352p.
Bothner MH, Butman B. (editors) 2007. Processes influencing the
transport and fate of contaminated sediments in the coastal ocean—Boston
Harbor and Massachusetts Bay. Woods Hole: U.S. Geological Survey
Open-File Report 2007-1302.
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List of Acronyms
BHWQM Boston Harbor Water Quality Monitoring
BOD Biochemical oxygen demand
BWQM Bay Water Quality Monitoring
cBOD Carbonaceous biochemical oxygen demand
CHV Centrotubular hydropic vacuolation
C-NOEC Chronic test, no observable effect concentration
DDT Dichlorodiphenyltrichloroethane
DITP Deer Island Treatment Plant
DO Dissolved oxygen
EPA U.S. Environmental Protection Agency
FA Foul Area
GoMOOS Gulf of Maine Ocean Observation System
HMW High molecular weight
IAAC Inter-agency Advisory Committee
IWS Industrial Waste Site
LC50 50% mortality concentration
LMW Low molecular weight
MADEP Massachusetts Department of Environmental Protection
MBDS Massachusetts Bay Disposal Site
MGD Million gallons per day
MWRA Massachusetts Water Resources Authority
NCCOS National Centers for Coastal Ocean Science
NDBC National Data Buoy Center
NOAA National Oceanic and Atmospheric Administration
NOEC No observable effect concentration
NPDES National Pollutant Discharge Elimination System
OMSAP Outfall Monitoring Science Advisory Panel
OMTF Outfall Monitoring Task Force
PAH Polycyclic aromatic hydrocarbon
PCB Polychlorinated biphenyl
PIAC Public Interest Advisory Committee
RPD Redox potential discontinuity
PSP Paralytic shellfish poisoning
SEIS Supplemental Environmental Impact Statement
TOC Total organic carbon
TRAC Toxic Reduction and Control Program
TSS Total suspended solids
USGS U.S. Geological Survey
Massachusetts Water Resources Authority
Charlestown Navy Yard
100 First Avenue
Boston, MA 02129
(617) 242-6000
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