1992

Massachusetts Water Resources Authority · from the MWRA · 55 pages · 6.8 MB
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THE STATE OF BOSTON HARBOR 1992

Massachusetts Water Resources Authority
Douglas B. MacDonald |
Executive Director

Second printing, May 1993

Technical Report No. 93-6
Environmental Quality Department

Merryl Alber
John Hallam
Michael S. Connor

Prepared under the direction of
Douglas.B. MacDonald, Executive Director .
John F. Fitzgerald, Director, Sewerage Division

MWRA Board of Directors
Trudy Coxe, Chair

John J. Carroll, Vice-Chair
~~ Robert J. Ciolek
Patricia A. Crutchfield
Lorraine M. Downey, Secretary
Norman P. Jacques
- Charles Lyons
Joseph A. MacRitchie
Samuel G. Mygatt
Thomas E. Reilly
Walter J. Ryan, Jr.

fi

EXECUTIVE SUMMARY

Each year, the MWRA produces a State of Boston Harbor Report that describes the
environmental health of Boston Harbor. As we are now nearing the half-way point in the
multi-billion dollar Boston Harbor Project to upgrade the region’s sewerage system, this
year’s report examines the Harbor’s health in the context of that project. The 1992 State of
Boston Harbor Report therefore covers four main areas: :

1) the relationships between the region’s sewerage system and the.pollution problems
in Boston Harbor and its tributaries;

2) recent improvements in the existing sewerage system;

3) the effects of those improvements on Harbor water quality; and
4) the progress made on new treatment facilities and what can be expected in the way
of further improvements in environmental quality as the Boston Harbor Project

continues.
Three themes emerge from the data discussed in the report:

First, the sewerage collection system now has more capacity and is more
efficient.

Pipes are being systematically inspected.
- Over the last four years, 116 miles of the MWRA’s 230 miles of interceptor pipes
have been internally inspected with closed-circuit TV.

Pumping facilities have been upgraded or replaced.
- The new $35.7 million Charlestown Pump Station is the most visible example of
necessary reinvestment in pumping system infrastructure.

Headworks have been overhauled.
- A $25.2 million overhaul has led to an increase in the amount of grit and screenings
taken out of the sewage flow from 104,000 cubic feet in 1987 to 165,000 cubic feet in
1992,

The Deer Island Power and Pump Station has been upgraded.
- A $33.2 million upgrade has led to an average of 7 pumps being operational at any
one time in 1992, versus 5 in 1988.

Increased capacity has resulted in improved system performance.

Headworks now need to hold back (or “choke”) less flow, i.e. the collection system is better
able to transport, store, and regulate the flow.
- Choking time decreased from 5,395 hours in 1987 to 584 in 1992.

Combined sewer overflows (CSOs), which occur when the system’s capacity is exceeded,
have decreased.
- There were no dry weather overflows in 1992.
- Wet weather CSO flow in 1992 was approximately 45% less than that measured in
1990.

iii

Second, the treatment system is also much improved, with measurable effects on
environmental quality.

The sewage flow now contains less of the substances that are particularly difficult to treat.
This is in large part the result of an aggressive toxic reduction program, which helps
industries and homes minimize the amount of toxic contaminants in their discharges into
the sewerage system. ; :
- Zinc and copper loadings to the treatment plants have decreased by at
least 75% since the early 1980s, which is reflected in decreased
concentrations measured in the Harbor.
- Discharges of EPA-designated “priority pollutants” have decreased by
about 33% since 1990.
- Pesticides measured in mussels at Deer Island in 1992 were only 25% to
50% of what they were in 1987.
- Instances of liver diseases in winter flounder caught off Deer Island have
decreased dramatically since the early 1980s.

While still severely undersized, the treatment plants themselves are more effective following
more than $100 million of improvements affecting every part of the treatment process.

The most dramatic advances involve the way in which the plants deal with scum and sludge.

New scum removal systems now skim grease and floatable trash off the top of the sedimenta-
tion tanks. This material used to be discharged into the Harbor and float back onto area
beaches.

The new way in which the MWRA deals with sludge, the solid material that settles out from
the liquid effluent, represents a major environmental advance. Until December 1991,
sludge was discharged into the Harbor. Since that time, sludge has been shipped to the
MWRA’s new sludge-to-fertilizer plant. -
- Dry-weather fecal coliform counts at the Nut Island sludge dumping site decreased
from 2,364 per 100 ml in 1990 while sludge was still being discharged, to 4 in 1992.

Treatment plant performance has consequently improved.

- The number of Deer Island NPDES violations in Fiscal Year 1992 was 7, as compared :
to 35 in Fiscal Year 1987. The number at Nut Island was 0 in 1992, 1 in 1987.

More CSO flow is now treated.

Improved CSO treatment has also improved the quality of the flow that still gets diverted
away from the treatment plants due to temporary system overload. Since 1987, MWRA has
built three new CSO treatment facilities at a combined cost of approximately $13 million.
About half of the total CSO flow is now chlorinated and screened.
- Fecal coliform counts in the waters close to new CSO treatment facilities at
Fox Point have decreased from 749 per 100 mi to 79, and at Commercial
Point from 175 to 49. (State swimming standard is 200 per 100 ml.)
- Water samples at Malibu and Tenean beaches, close to new CSO facilities,
always met swimming standards in 1992. In contrast, these beaches did
not meet standards 15% and 17% of the time in 1987.

iv

Third, there is nevertheless a limit to how much more environmental improvement
can be made before completion of new court-ordered secondary treatment facilities
and the associated effluent outfall tunnel.

The requirements of the Clean Water Act are not going to be met, however, by massaging
the current treatment system. Primary treatment does not remove enough solids (TSS) and
organic material (BOD), and the Harbor is too small a body of water to absorb the amount
of oxygen-consuming material that is currently being discharged into it.
- In 1992, 22% of dissolved oxygen measurements taken in bottom waters
at dawn were below water quality standards.

Consequently, MWRA is engaged in a multi-billion dollar construction project. New:
facilities will come on-line in stages. More sophisticated primary treatment will begin
operation in 1994, and partial secondary in 1996. .
- By the end of the century, when the secondary facilities will be fully operational,
BOD and TSS loading are predicted to decrease by 90% from 1990 levels.

The 1992 State of Boston Harbor Report therefore conveys a dual message. On the one
hand, rehabilitation of the sewerage system has already made a measurable difference to
the state of the Harbor. On the other hand, the limited nature of the environmental
benefit that can be gained from this rehabilitation underlines the need to press on with
new secondary facilities and a new effluent outfall tunnel into Massachusetts Bay.

TABLE OF CONTENTS.

1.Boston Harbor and the Region’s Wastewater

A. Understanding the Problem
B. Crafting a Solution

2. Overhauling the Existing System

A. Introduction

B. Pipes

C. Pumping Facilities

D. Headworks and Deer Island Power and Pump Station

E. Combined Sewer Overflows :

F. Improvements at Treatment Plants (Deer Island/Nut Island)
G. Pollutant Source Reduction

3. Effects on Harbor Water Quality to date

A. Effluent Quality

B. Harbor Water Quality
C. Sediment Quality

D. Marine Life

E. Remaining Problems

4. Continuing System Improvements

A. The new Secondary Treatment Plant
B. The new Outfall Tunnel

C. Siting the new Outfall

D. Outfall Monitoring

Bibliography

vi

Centerfold
Figure 2-1
Figure 2-2
Figure 2-3
Figure 2-4
Figure 2-5
Figure 2-6
Figure 2-7
Figure 2-8
Figure 2-9
Figure 2-10
Figure 2-11
Figure 2-12
Figure 2-13
Figure 2-14
Figure 2-15
Figure 3-1
Figure 3-2

_ Figure 3-3
Figure 3-4
Figure 3-5
Figure 4-1
Figure 4-2
Figure 4-3
Figure 4-4
Figure 4-5
Figure 4-6
Figure 4-7
Figure 4-8

LIST OF FIGURES

MWRA sewerage system.

MWRA interceptors

Meter record of tidal inflow

MWRA pumping facilities

MWRA headworks

Choking time at Deer Island headworks

Combined sewer overflow outlets and treatment facilities
Fecal coliform counts in Fort Point Channel

Wet weather flow through CSOs

Fecal coliform counts in water near CSO treatment facilities
Fecal coliform counts at beaches near CSO treatment facilities
Fecal coliform counts at Constitution Beach

Fecal coliform counts in Charles River

The primary treatment process

Fecal coliform counts near sludge discharge site

Treatment plant loadings of zinc and copper

Priority pollutants released from the treatment plants

Zinc and copper concentrations in the Harbor

Organic contaminants measured in mussels at Deer Island

Organic contaminants measured in mussels sampled in various urban harbors

Liver diseases in winter flounder caught off Deer Island

The secondary treatment process

Anticipated pollutant loadings as different stages of the project are completed

Court schedule
Deer Island, 1990 and 1992

The new outfall tunnel
Dilution of sewage from present and future outfalls

Nitrogen in Boston Harbor

Outfall monitoring in Massachusetts Bay

vii

18

10
11
12
13
14
14
15
16
17
22
23
26
28
29
30
30
32

35
36

37
38

39
41

Table 1-1

Table 2-1

Table 2-2
Table 2-3
Table 2-4
Table 2-5
Table 2-6
Table 2-7
Table 2-8
Table 3-1
Table 32
Table 3-3
Table 4-1
Table 4-2

Table 4-3

LIST OF TABLES

Key environmental dates in court schedule

Components, anticipated cost and completion dates of major
interceptor projects

Miles of MWRA pipe inspected with closed-circuit TV
Pumping capacity at Deer Island Power and Pump Station
Dry weather combined sewer overflows

CSO treatment facilities

Sewage indicators per mile of Boston Harbor beaches
Levels of contaminants in MWRA sludge .
TRAC enforcement actions 1990-92

Violations of interim discharge limits at treatment plants
Priority pollutant concentrations near Deer Island outfall
Dissolved oxygen measurements in the Inner Harbor
Percent removal from primary and secondary treatment
Effectiveness of Clinton plant’s secondary treatment

Organizations involved in the Outfall Monitoring Task Force

viii

10

12

13

20

21

23

26

27

31

33

34

40

BOSTON HARBOR
AND THE REGION’S WASTEWATER

A. Understanding the Problem

Most of us take for granted the availability of water entering our homes
and businesses. Flushing a toilet, taking a shower, using a washing machine,
hosing down a dirty factory floor—for all these activities we demand, and are
used to getting an instant stream of clean, fresh water. We also tend to take
for granted that we do not have to worry about the subsequent stream of
wastewater leaving our homes and businesses. We assume that the combina-
tion of water, industrial cleaner, and dirt from the factory floor, the soapy
water from the shower or washing machine, and whatever is flushed down
the toilet will all be transported far away and somehow “dealt with.”

However, the safe management of our domestic and industrial wastewater
(sewage) cannot be taken for granted; it is one of the key issues facing the
region. Specifically, our wastewater must be treated and then disposed of in
a way that does not harm human health or marine life.

Management of the metropolitan region’s wastewater is the responsibility
of the MWRA. Homes and businesses in 43 Boston-area communities
generate and discharge wastewater into an intricate network of local pipes.
These pipes lead to the Authority’s much larger “interceptor” pipes, which
carry the flow through a variety of pump stations and other facilities until it
reaches one of two treatment plants on the edge of Boston Harbor (see
centerfold). This means that wastewater from locations as close to the
Harbor as Rowes Wharf, and from as far away as Ashland some 30 miles west
of Boston, is channeled into these plants. The plants treat the flow to
remove as many contaminants as possible, and the resultant “effluent,” or
cleaned wastewater, is discharged into the Harbor.

This system is best understood in the context of the history of the region’s
attempts to deal with its sewage.

Boston Harbor has long been the location of choice for the disposal of the
region’s sewage. Attracted by the ability of the water and the tides to dilute
sewage and move it offshore, early residents built pipes to transport waste
using the shortest line to the water. Later they combined these pipes with
the storm drains that they had built to carry storm run-off into the Harbor,
but the sewage remained untreated.

The human health risks associated with this convenient method of sewage
disposal soon became evident. Outbreaks of disease were attributed to poor
sanitary conditions. Periodic modifications to improve the system, however,
were aimed only at pushing sewage further offshore into slightly deeper
waters. In the 1870s, for instance, a brick sewer line was constructed under
Dorchester Bay to Moon Island, where sewage was held in vast storage tanks
before being released on the outgoing tide. The Harbor still had to absorb
untreated sewage.

It was not until 1952 that a primary treatment plant was built on Nut
Island to treat at least a portion of the sewage that had previously been
discharged untreated into the Harbor. And it was not until 16 years later
that a much larger primary treatment plant was built on Deer Island to treat
most of the rest of the region’s sewage. These plants marked the end of the
wholesale dumping of untreated sewage into the Harbor.

The most important advance provided by the two primary treatment
plants was that sewage was disinfected to kill most of the disease-causing
pathogens, or germs. The effluent discharged from the plants therefore
posed much less risk to human health.

1

Wastewater is
generated by every
home and industry
in the Boston
region.

The MWRA now
manages the
collection,
treatment, and
disposal of the
region's
wastewater.

Historically, the
region's sewage has
been channeled into
Boston Harbor.

The system's primary
treatment plants
came on line in 1952
and 1968.

Even treated effluent However, small amounts of untreated or partially treated sewage were still
discharged either into the Harbor or into tributary rivers through some of
from primary plants the relief outlets associated with the old pipes that combined sewage with

can have a major storm water.

environmental Unfortunately, although primary treatment deals well with pathogens, it
imp act is less effective with other materials contained in sewage. Some of these,

° such as solids and oxygen-consuming organic matter, would be relatively
harmless in the Harbor at low concentrations. By the late 1960s, however,
they had become a genuine problem: while the Harbor’s small size remained
constant, the amount of sewage (and therefore the amount of solids and
organics) flowing through the system had increased dramatically as a conse-
quence of population growth.

Types of Pollutants in Boston Harbor

1, Pathogens

High levels of pathogens, or disease-causing organisms, are a risk to human health. Since most patho-
gens are difficult to measure directly, the presence of fecal coliform bacteria, a group of bacteria typically
found in human waste, is used as an indication of the potential presence of disease-causing organisms.
When fecal coliform levels in the water exceed state standards, beaches and shellfish beds are closed.
Chlorination during the sewage treatment process serves to kill most bacteria; a major source of pathogens
to Boston Harbor is therefore untreated sewage that discharges during heavy rains when stormwater over-
loads combined sewer systems.

2. Toxic materials
The toxic materials of most concern are metals and organic compounds. In addition to harming marine

life directly, many of these materials can accumulate in living tissue; they can therefore harm organisms
further up the food chain.

Metals—All metals occur naturally in seawater in trace amounts, but higher concentrations can be
harmful. Metals of concern include arsenic, cadmium, chromium, copper, lead, mercury, molybdenum,
nickel, silver, and zinc.

Organic compounds—These include chemicals such as acetone, benzene, naphthalene, petroleum
hydrocarbons, pesticides (e.g. DDT), and polychlorinated biphenyls (PCBs).

Toxic contaminants enter Boston Harbor from industrial, commercial and residential discharges to the
MWRA sewerage system. Non-sewage sources of toxic materials include stormwater, rivers, and groundwa-
ter. The contribution of sewage effluent to the overall load of toxic materials to the Harbor varies. For
example, effluent accounts for approximately 70% of the copper and 16% of the lead finding its way into
the Harbor.

3. Suspended solids

An important reason for concern about suspended solids (particles suspended in the water) is that toxic
materials in the effluent stream tend to be concentrated on them. In addition, water containing suspended
solids is murky, which is not only unattractive but also reduces the amount of light available for photosyn-
thesis by marine plants. ;

Sludge and sewage effluent both contributed solids to Boston Harbor in the 1980s. The cessation of
sludge discharges decreased this amount, but effluent is still a major contributor of suspended solids.

4, Oxygen-consuming organic matter .

As organic material in the water decomposes, oxygen dissolved in the water is consumed. In an area
that contains a great deal of decomposing organic matter, the water can therefore be depleted of the
oxygen necessary to support most marine life. The amount of oxygen-consuming material is measured as
BOD (biochemical oxygen demand). Effluent is the leading source of BOD in Boston Harbor.

5. Nutrients

Nitrogen is an important nutrient for algae, the marine plants at the base of the food chain. In exces-
sive amounts, however, nitrogen can stimulate growth until excessive quantities of algae accumulate.
Oxygen is consumed when these algae die and decompose, and oxygen levels can become depleted. Sew-
age effluent accounts for more than 90% of the nitrogen entering Boston Harbor:

|

2° MWRA

Moreover, the flow of sewage now contained many toxic contaminants
such as pesticides and metals. These contaminants tend to adhere to the
solids in the flow. Although some of the solids are separated out during
primary treatment, the potential environmental benefit to be gained was
negated by the practice at the Deer Island and Nut Island treatment plants of
discharging removed solids into Harbor waters as “sludge.”

B. Crafting a Solution

Growing awareness of the threat to the environment caused by disposing
of inadequately treated sewage effluent led to the enactment by Congress of
the Clean Water Act in 1972. The Act, passed only four years after the Deer
Island primary treatment plant opened, mandated secondary treatment for
publicly owned treatmenit plants. Secondary treatment is more sophisticated
than primary and greatly increases the amount of solids and other materials
removed from sewage before treated effluent is discharged.

Over the next decade, the Metropolitan District Commission (the agency
then responsible for the sewerage system) made several failed attempts to
obtain a waiver from the secondary treatment requirement. Meanwhile,
conditions worsened in the Harbor. By the early 1980s, beaches were often
closed to swimmers and shellfishing was prohibited. Pollution was also
taking its toll on marine life: flounder exposed to high concentrations of
contaminants developed liver tumors and fin rot; areas of the Harbor be-
came inhospitable to sensitive bottom-dwelling organisms.

Eventually, a series of lawsuits in the early 1980s led to the creation of the
MWRA and the establishment by a federal court of a mandatory schedule for
meeting the secondary treatment standards of the Clean Water Act and
hence improving the water quality of Boston Harbor.

This court schedule governs the MWRA’s ongoing program to (i) upgrade
existing treatment facilities, (ii) stop dumping sludge into the Harbor, (iii)
build new primary and secondary treatment facilities on Deer Island and a
new outfall tunnel to carry the treated effluent out into the deeper waters of
Massachusetts Bay, and (iv) control overflows from those sections of the
system where sewers are combined with storm drains (combined sewer
overflows).

There are several dates in the schedule that are of particular importance in
terms of the quality of the material released from the treatment plants. As
Table 1-1 shows, the MWRA has already stopped discharging both scum and
sludge. Scum, the grease and trash skimmed off from wastewater, used to
form noticeable slicks in the Harbor; sludge added solids, toxic contami-
nants, and pathogens to the Harbor.

Key environmental dates in court schedule.

Date Environmental Milestone

2/89 | Scum no longer discharged into Harbor.

12/91 | Sludge no longer discharged into Harbor.

7/95 | Full operation of new primary treatment plant,
with discharge through effluent outfall tunnel.

10/96 | Operation of first battery of secondary treatment.

12/99 | Full operation of new secondary treatment plant.

Tablel-1

The 1972 Clean
Water Act
mandated changes
in sewage
treatment.

MWRA’s program to
renovate the’
sewerage system is
subject to a court
schedule.

MWRA ¢ 3

New treatment
facilities are at the
heart of the MWRA

program.

The MWRA is
undertaking the
court-ordered
program in the
context of an
overhaul of the
entire system.

4°MWRA

At the heart of the program lie the new treatment facilities, without
which compliance with the Clean Water Act would clearly be impossible.
With the addition of the new effiuent outfall tunnel, these facilities account
for approximately $3.5 billion of the $4.3 billion that the Authority expects
to have spent by the end of Fiscal Year 1999 on court-ordered projects
mandated by the Clean Water Act. This figure represents over 65% of the
funds allocated to overhauling the entire wastewater system between 1986
and the end of the century.

Improving the region’s entire sewerage infrastructure is an integral
component of the Boston Harbor environmental protection program. Since
the various parts of the system are interconnected, a failure in one area
usually has consequences in another. A new plant, however sophisticated,
cannot function independently of the community pipes, MWRA intercep-
tors, and pumps that deliver the region’s sewage for treatment. Moreover,
the existing treatment plants must be made to operate as efficiently as
possible until the new facilities come on line. The Authority is therefore
engaged in an ambitious system-wide overhaul. Aithough the cost of this
overhaul, approximately $500 million, is only a fraction of the cost of the
new facilities, it still represents a major and long overdue investment in the
region’s infrastructure.

OVERHAULING THE EXISTING
SYSTEM
A. Introduction

Each of the 43 communities in the MWRA service area owns and main-
tains its own sewage pipes. There are some 5,400 miles of these local pipes,
which are typically between 8 inches and 2 feet in diameter. In most
communities, sewage and stormwater runoff are carried in separate pipes.
However, several communities in the MWRA service area have combined
systems, where sewage and stormwater runoff are carried in the same pipe.

The communities’ pipes feed into the Authority's 230 miles of “intercep-
tor” sewers, which at some places may be 12 feet but are more typically
about 5 feet in diameter. The sewage is transported through these intercep-
tors until it eventually reaches the treatment plants on Deer Island or Nut
Island. It moves through the system in large part by force of gravity; the
system was designed so that the pipes follow the contours of the land and
run parailel to stream and river beds. However, at some places the sewage
has to be pumped uphill, at one of the Authority’s pumping stations.

By the early 1980s, many sections of pipe were too small to handle the
amount of flow generated by a population much larger than they were
designed to serve. Some sections were over 100 years old. Other sections
needed to be cleaned or repaired or had deteriorated so much that they
needed to be replaced. The pumping system also contained archaic ele-
ments: the Smithsonian was interested in acquiring one steam pump which
was still in use in the 1980s at the East Boston pump station. Understaffed
and underfunded, the MDC Sewerage Division was forced to be reactive,
making repairs as accidents occurred but unable to do much more than
apply the engineering equivalents of Band-Aids to the larger needs of the
system. :

The capacity of the collection system was often exceeded. A problem at
one of the treatment plants would create a domino effect back through the
system, with bottlenecks and backups exacerbated by lack of pumping
power and inadequate storage capacity within the pipes. This was most
common during heavy rain, when the volume of flow was much increased.
In some cases, untreated sewage would overflow into private dwellings,
backyards, and streets, and into local streams and rivers.

Today, the MWRA is working both to rebuild the collection system at its
weakest points and to maintain it by cleaning pipes and managing sewage
flows with modern metering technology and communications systems.
New computer programs wiil soon allow MWRA not only to generate
detailed maps of any given section of pipe but to simulate any number of
operational scenarios affecting that pipe and hence promote proactive flow
management.

B. Pipes

Major new pipe construction projects are targeted to those areas where
backups and overflows cause the most severe customer service and environ-
mental problems. Currently, most of these areas are located in the southern
part of the MWRA’s region (see Fig. 2-1 and Table 2-1).

The new interceptors will not only improve the delivery of sewage to the
treatment plant, they will also protect environmentally sensitive rivers,
wetlands, and drinking water supplies by dramatically reducing backups and
overflows.

These projects typically take many years to complete because of the
complexities of the planning and permitting process. Moreover, they often
involve several communities, requiring MWRA to ensure that local concerns
are addressed both before and during construction.

2

The sewage
collection system is
made up of pipes
and pumps.

By the early 1980s,
the collection system
was in decline.

New pipes with
adequate capacity
are now being built.

MWRA ¢ 5

6 ¢ MWRA

MWRA Interceptors

io

“4

a

Framingham
». Extensign

Fig. 2-1
Components, anticipated cost and completion
dates of major interceptor projects
Project New Repaired Other Components Cost Year
Pipe Pipe (millions)
(miles) (miles)
Wellesley 7A 7.0 7 $72 | 1995
Extension
New 8.7 _ New 46-million-gallons- $40 1995
Neponset per-day (mgd) pump
Valley Relief station
Framingham 6.8 43 New 22-mgd pump station $46 1997
Extension :
Braintree 13 2.2 New 60-mgd pump station $136 2000
Weymouth New 13-mgd pump station
Relief 2.9-mile deep-rock tunnel
Table 2-1

The MWRA is also engaged in aggressive upkeep of existing sewer pipes.
Regular inspections (See Table 2-2) ensure that the pipes do not fall back
into disrepair once they have been upgraded. Pipeline repair and rehabilita-
tion was allocated $2.2 million in Fiscal Year 1993.

Miles of MWRA pipe internally inspected
with closed-circuit TV.

Fiscal Miles
Year inspected
89 15
90 23
91 35
Table 2-2 : 92 43

Closed-circuit TV cameras are attached to small “boats,” which
are pulled through the pipes by electric winches.

The Authority’s maintenance work helps identify the cracks in pipes and
pipe joints that lead to infiltration of groundwater, and the illegally con-
nected sump pumps, improperly connected catch basins and defective
tidegates that lead to inflow of stormwater runoff and surface water.

Infiltration/Inflow (1/1) unnecessarily increases the amount of flow in the
system, which results in the treatment plants treating a greater volume of
flow than should be necessary. Approximately 60% of the average daily
flow reaching the plants is actually I/I. This is a difficult problem for
MWRA to solve because so much i/] originates in local systems’ pipes. The
MWRA has therefore recently established a $25 million I/I Local Financial
Assistance Program to assist communities in the funding of I/I reduction
and sewer system rehabilitation projects. This program will provide 25%
grants and 75% interest-free loans as an incentive for communities to
reduce extraneous flow.

It is already possible to see reductions in the amount of inflow. Inflow
accounts for only 10% of the flow overall, but it has a dramatic time-specific
impact, particularly during storms. It creates sudden peaks of flow that can
overwhelm system capacity.

MWRA’s newly installed wastewater meters record flow at 170 points in
the system and are useful in the identification and quantification of inflow.
As Fig. 2-2 shows, flow meter data from a site in Everett near the Mystic
River identified a twice-daily influx of water coincident with the time of
high tide. Subsequent investigations by MWRA and the City of Everett led
to the discovery and repair of an old overflow pipe that was allowing water
from the Mystic River to enter the sewer system at a peak rate of 4 million
gallons per day (mgd). The meter record shows that the inflow was elimi-
nated once the end of the pipe was sealed shut.

Existing pipes are
now being
systematically
maintained.

Maintenance work is
helping control
infiltration/inflow.

MWRA ¢ 7

Outdated pumping
facilities are being
replaced.

8 * MWRA

Tidal inflow was reduced following repair
of an old overflow pipe.

Flow (mgd)
;

0

March 26,1991 27 28 29 30
Fig. 2-2
Readings from meter EV-3C in Everett for the period March 26 to 30, 1991.

C. Pumping Facilities
Pumping in the sewage collection system is handled by 9 major pumping

stations (see Fig. 2-3). Two CSO treatment facilities, Prison Point and
Cottage Farm, can also function as pump:stations.

Before the creation of the MWRA, unreliable old or obsolete equipment
often forced the pumping system into crisis mode. Today the MWRA is able
to repair.equipment when it breaks down and to practice cost-effective
preventive maintenance. In Fiscal Year 1993, pump maintenance was
allocated $500,000 in operating funds.

Spending on new pumping facilities and equipment has been focused on
the system’s most vulnerable points, such as the antiquated Charlestown
Pump Station or the underpowered Hingham Pump Station. Some of the
large southern system interceptor pipe projects also include construction of
new pumping stations (see Table 2-1).

The Charlestown Pump Station receives flow from Charlestown, parts of
Cambridge, Somerville, and Medford, via a tunnel under the Mystic River.
Flow is lifted and pumped to an interceptor leading to the Chelsea
Headworks and ultimately the Deer Island treatment plant. Originally built
in 1895, the station was converted to diesel power in 1950. By the early
1980s, its pumps had become inefficient and often broke down. Mainte-
nance was expensive because replacement parts for the outmoded engines
had to be custom-made. Limitations of space made rehabilitation of the
station impractical and total replacement the only sensible option.

The new 93-mgd Charlestown facility, which will soon come on-line at a ~
cost of $35.7 million, features electric rather than diesel power to operate
new screens and pumps. It also includes flow meters, a stand-by generator,
and a wet well to hold incoming flow and facilitate automatic regulation of
the volume going to the pumps. The environmental benefit gained from
the construction of a new pump station is the reduction of the risk of
catastrophic breakdown, with all the attendant backups and overflows.

Rehabilitation rather than replacement was possible at the Hingham
Pump Station, where the Authority has spent approximately $3.1 million
over the last few years with dramatic environmental effect. The station used
to overflow periodically into the Weymouth Back River because its pumps’
capacity was only 3 mgd, whereas incoming flow from the town could reach
5 mgd. These overflows were of particular significance because the river is a
state-designated Area of Critical Environmental Concern.

The installation of larger, more powerful, variable-speed pumps have
given the station a capacity of 7 mgd. Two new “comminutors” grind up
solids and protect the pumps from excessive wear and tear, and an emer-
gency stand-by generator gives the station operational independence in the
event of power failures. These improvements have allowed the Authority to
permanently close off the bypass pipe that used to discharge the station’s
excess flow out to the river, thereby eliminating pollution from this source.

Pump Stations Headworks

ad

Allison Hayes

el Quincys
ad
7’ Braintree / Weymot

Fig 23
D. Headworks and Deer Island Power
and Pump Station

Rags, grit, and large objects are screened out of sewage flows at the
system’s headworks facilities, shortly before the sewage enters the MWRA’s
treatment plants. This represents the first stage of primary treatment, and is
sometimes referred to as “preliminary treatment.” As Fig. 2-4 shows, three
of the headworks serving the Deer Island plant are actually located off-
island. These are called the “remote” headworks.

By the early 1980s, obsolete and inefficient equipment at the remote
headworks was causing problems further back in the collection system and
at the treatment plant itself. When intake channels had to be closed off for
equipment repair, flow backed up to pumping stations and made it impos-
sible for the stations to pump any more flow. Moreover, inefficient grit
removal at the headworks increased the wear and tear on equipment at the
treatment plant.

Completed in 1990, the $25.4 million upgrade to the three remote
headworks included replacement or rehabilitation of sluice gates, grit
collectors, and screening equipment. The upgrade increased the amount of
grit and screenings collected from 104,000 cubic feet in 1987 to 165,000
cubic feet in 1992. Moreover, in 1992 all four intake channels at each of
these headworks were available 98% of the time.

There was no more dramatic example of the sewerage system’s vulnerabil-
ity in the early 1980s than the “Mother’s Day ’83" disaster at the Deer Island
Power and Pump station. For 48 straight hours, heroic MDC divers felt their
way around in the pitch darkness of a three-story building flooded with raw
sewage, trying to locate and close a malfunctioning valve. The incident
brought a good portion of the region’s sewerage system to a standstill: the

Headworks screen
the wastewater flow
before it enters the
treatment facilities.

Headworks have
been upgraded.

MWRA * 9

The Power and
Pump Station has
been overhauled.

Choking time has
decreased
dramatically.

10 © MWRA

Deer Island plant closed down, upstream pump stations had to stop operat-
ing, and the entire northern part of the system backed up.

A $33.3 million upgrade, completed in 1990, included replacement of
five pumps, new electric pump motors, and back-up diesel generators. As
Table 2-3 shows, pumping capacity and reliability is consequently much
improved.

Pumping capacity has increased at
Deer Island Power and Pump.

Fiscal |’ # Pumps High Peak Flow

Year | Operated (mgd)
88 4.9 480 _|
89 5.9 600
90 6.7 623
91 83 677

[ 92 72 746
Table 2-3

Regulating the amount of flow going through the headworks and on to
the Deer Island plant wili always be necessary, particularly during heavy
storms. However, the Deer Island Power and Pump upgrade and improve-
ments at the headworks and throughout the collections system have led to a
decrease in the amount of time that the headworks have to regulate or
“choke back” flow (see Fig. 2-5). This is an excellent indicator of overall
system improvement.

Choking time at Deer Island headworks has decreased.

6,000

5,000-4
4,000

3,000-

Hours choked

2,000 -

1,000-4

O77
‘8990 ‘92
Fiscal Year

The total number of hours the headworks at Ward Street, Chelsea Creek and Columbus Park
choked back flow between 1987 and 1992.

1987 ‘88 ‘91

Fig. 2-5

E. Combined Sewer Overflows

Parts of six communities—Boston, Cambridge, Somerville, Chelsea,
Brookline, and Everett—have combined systems, with pipes that carry both
sewage and rainwater. These systems, which are still common in many
urban areas across America, date from the late 1800s when combined sewers
were accepted practice. Of the six MWRA communities with combined
sewers, all but Brookline and Everett have combined sewer overflow struc-
tures (CSOs) that divert excess flow into Boston Harbor or its tributaries
during heavy rains. There are more than 80 CSO outfalls that can discharge
combined rainwater and sewage (see Fig. 2-6).

Under normal circumstances, all the flow in combined systems is carried
to a treatment plant. However, CSO activations can occur when pipe
capacity in the combined systems is exceeded. This happens most often
during storms. Not only does stormwater enter the combined systems
directly, it also enters indirectly, through inflow into the pipes of adjacent
communities. This inflow uses up pipe capacity that would otherwise be
available for combined sewage. :

Until recent years, the problem of combined sewer overflows was exacer-
bated by mechanical breakdowns that limited the collection system’s
capacity to transport, store, and regulate the flow. This used to lead to
overflows even during dry weather. Moreover, only a small Proportion of
the combined sewer overflows received any sort of screening or disinfection.
Beaches near the overflow points were closed regularly because of violations
of bacterial water quality standards.

Work done on pumping stations and headworks over the last few years
has increased overall system capacity, which means that more of the flow
can get to the treatment plants. Even routine maintenance work has
reduced CSO activations: regular cleaning of the interceptor pipes creates
more space to store wastewater in the event that the treatment plants are
temporarily overloaded. ;

Combined sewer overflow outlets
and treatment facilities

Fig. 2-6

Maintenance work on CSO structures has had a similar impact.
Tidegates, which permit the discharge of wastewater but prevent river or
Harbor water from flowing into the sewer system, can wear out or get locked
in place. Regulators, the devices that direct most flow in a combined sewer
to the treatment facility and divert excess flow to an outfall, can get blocked
or otherwise malfunction, as can the outfalls themselves. Regular mainte-
nance of these structures reduces inflow and increases the amount of sewage
that reaches the treatment plants.

Combined storm
drains and sanitary
sewers can overflow.

CSOs were largely
untreated.

MWRA ® 11

Improved
maintenance
provides more
capacity to
transport combined
sewer flow.

In the winter of 1989-90, a malfunctioning regulator in the CSO pipe at
the head of the Fort Point Channel was unnecessarily diverting flow to a
nearby CSO outfall rather than to the treatment plants. As Fig. 2-7 shows,
after the discovery and repair of this faulty equipment, wet weather fecal
coliform counts in the Channel decreased by approximately half.

Fecal coliform counts in Fort Point Channel decreased
once a malfunctioning CSO regulator was repaired.

2000
=
S
iva) 4
—
§ : . .
= . CSO regulator
& 1000 repaired
8 .
mS
S ,
iS ;
>
=x

0 ;

8/89 10/90 8/91
Fig. 2-7

Each bar represents the average (geometric mean) fecal coliform count of approximately 20
samples. There was about a quarter-inch of rain during each sampling period.

Today, dry weather CSO activity has been eliminated, and wet weather
activity is far less common than even a few years ago (see Table 2-4 and Fig.
2-8). ;

. : The number of dry weather
Fiscal | Cottage | Prison | Somer- || combined sewer overflows.
Year | Farm | Point ville

Marginal

87 10 1 na.

88 12 na 0

89 3 | 0 0

90 3 0 0

91 1 0 0

* - n.a. - not available
Overt designated “dry weather”
2] 0 | 0 | 0 ee EO ts nous
Table 2-4

12 ¢ MWRA

Wet weather flow through CSOs has decreased.

30005

Treated Flow
Hl Constitution
Py
< EB Fox Point
&
& EQ Commercial Point
5 [J Somerville Marginal
= Prison Point
=
=
2 Untreated Flow
I Other
Ed Fort Point Channel
A Carson Beach Area

oO al
Fig. 2-8

MWRA meter records were used to determine flow through the six CSO treatment-facilities.
Flow through Commercial Point in 1990 was untreated.

Boston Water and Sewer Commission model data were used to estimate untreated flow.
Although BWSC’s model does not include discharges of untreated CSO flow into the Charles or
other discharges by Cambridge, Chelsea, and Somerville, it nevertheless indicates the
downward trend in wet weather CSO activity. 0

1990 1991 1992.

Some of this decrease in wet weather CSO flow is due to the increased
capability of the Deer Island Power and Pump station to pump more flow
through the plant. This permits flow that used to back up and discharge
through CSO outlets to be treated at Deer Island. It is then discharged
through the relief outfall close to the mouth of the Harbor, where there is
better flushing than at CSO discharge’sites such as the Inner Harbor and the
Charles River. ;

MWRA has spent millions of dollars to build or upgrade the six CSO More of the cso
treatment facilities (see Table 2-5). These screen and chlorinate CSO flow flow now receives
before it is discharged. Approximately 50% of the total CSO volume is now Sonal
treated in this manner. P relimi mary

treatment.
The six CSO treatment facilities
Facility Improvements - Date Cost
Completed
Prison Point Built in 1981 under the MDC
Cottage Farm Upgrade oe 1987 $ 452,000
Constitution New Construction 1987 $1,264,746
Somerville Marginal | Upgrade 1989 $1,696,931
Fox Point New Construction 1989 $4,164,000
Commercial Point New Construction 1991 $7,140,000
Table 2-5 fa.- not available

MWRA ° 13

CSO facilities
measurably
improved
environmental
quality.

14 ¢ MWRA

Average fecal
coliform/100ml

Screening and chlorination at the MWRA’s six CSO treatment facilities
make CSOs in these areas far less likely to degrade bacterial water quality,
and cause beach closings. The improvements in water quality can be seen
by comparing fecal coliform counts measured near the CSO outlet before
and after the construction of treatment facilities (see Fig. 2-9).

CSO treatment facilities resulted in decreased fecal
coliform concentrations in nearby water.
Fox Point ; Commercial Point

1000 200

100

Before After Before After

(1989) (1990-91) (1989-90) (1991)

Fig. 2-9

Average (geometric mean) fecal coliform counts measured at CSO facilities.

As Fig. 2-10 demonstrates, water quality at beaches also shows i improve-
ment near new CSO facilities

CSO facilities have benefited nearby beaches.

70:
Tenean North Beach

604
504 .
Commercial Point
404 Sed on-line

304°
204
104

04

Malibu Beach

% Weekly samples greater than standard

Fox Point on-line

Source: Metropolitan District Commission

Fig. 2-10

The percentage of routine bacterial samples that exceeded the state water quality standard for
swimming (geometric mean of no more than 200 fecal coliform per 100 ml of water) over the
past four years. Total rainfall for the months of June, July, and August was 6.4" in 1987 (dry),
13.8" in 1989 (wet), and ranged from 10.0" to 11.3" in the remaining years (normal).

Constitution Beach: More than a cso Problem

Before a CSO screening and disinfection facility began operation in March 1987, untreated sewage that
discharged near Constitution Beach during rainstorms caused high bacteria counts in the water and conse-
quent beach closures. However, even after the CSO treatment facility began operating in 1987, problems
with beach contamination remained (see Fig. 2-11, left).

Sampling in 1987 indicated that a large storm drain emptying at the beach was a significant source of
bacteria. The Boston Water and Sewer Commission found that the sanitary sewers from many neighbor-
hood residences were connected to the storm drain rather than to the sewer system. In 1990, 26 of these
improper connections were repaired, and the counts of coliform in the immediate vicinity of the storm
drain decreased (see Fig. 2-11, right). Although water quality at the beach remains a problem; the average
fecal coliform count decreased from 60 in 1990 to 17 in 1992. Continued inspection of the storm drains has
revealed more illegal sewer connections; water quality at the beach should steadily improve as these are
repaired. :

Constitution Beach is slowly improving.

Constitution Beach South

B 607

8 Summer Rainfall Wet weather fecal coliform
§ 504 LJ] Dry counts are decreasing as

“ . .
sg the storm drains are repaired.
s 407 ae

5 §

s 30 S 200

8 304 S

> E 150

Lv &

a 2074 =

iS S 100

S =~

i iS}

= 105 & 50

g %

= )tt_| i! “8

RS 1987 8 1987 1991/92
Fig. 2-11

Left: The percentage of routine bacterial samples that exceeded the state water quality standard for swimming (geometric mean of no
more than 200 fecal coliform per 100 ml of water) over the past four years. Source: Metropolitan District Commission. Rainfall as for
Fig. 2-10. :
Right: Average (geometric mean) fecal coliform counts from samples taken during wet weather.

MWRA e 15

However, CSO
discharges still
present problems.

CSO discharges
exacerbate pollution
of the Charles River.

Approximately half of the CSO volume now passes through one of the
six CSO treatment facilities, where it is screened to remove trash and chlori-
nated to kill bacteria. Although solids and organic materials are not re-
moved, chlorination decreases the likelihood of adverse impacts on human
health. However, the remaining half of the flow is discharged untreated
through other CSO outfalls, particularly in the Inner Harbor and along the
Charles River.

As Fig. 2-12 demonstrates, water quality in the Charles River is already
severely degraded at a station near the Newton Yacht Club, which is up- -
stream of any CSOs. CSOs, therefore, are not the only source of sewage
pollution in the Charles but do contribute significantly to wet-weather
water quality problems. Fecal coliform counts along most of the lower
Charles are particularly high close to CSO outlets (see Fig. 2-12), ‘In addi- ©
tion, dissolved oxygen levels in the river are exceedingly low and often
violate standards, at least in part because CSO discharges contain so much
organic matter. Aesthetically, too, CSOs create problems, causing unattrac-
tive, oily slicks of debris to accumulate, particularly close to the Charles
River Dam.

The dam itself is part of the reason for poor water quality in the Charles,
for it limits the exchange of water with the Harbor. The Charles is therefore
poorly flushed, and cannot absorb high loads of pollutants without environ-
mental deterioration.

Fecal coliform counts along the Charles River are much
higher than the State standard.

State standard = 200

® Combined sewer outlets
Fecal coliform counts

Fig. 2-12

The CSO
management
planning process is
ongoing.

16 *MWRA

Average (geometric mean) fecal coliform counts taken during the summer of 1991.
Source: Rex 1993. .

- Two major components of CSO control are ongoing. First, the Authority
is working with the CSO communities to develop low-cost, easily imple-
mented structural or operational modifications that maximize the storage,
transport, and treatment capabilities of the existing system, thereby further
reducing overflows. The second, longer-term project involves evaluating a
set of CSO control strategies which include different combinations of new
construction, optimization of interceptor capacity, reduction of infiltration
and inflow, and a variety of treatment options. The goal is to develop a

system-wide, integrated plan that ensures CSO control requirements are met
in a cost-effective manner.

F. Improvements at Treatment Plants
(Deer Island/Nut Island)

The Deer Island and Nut Island primary treatment plants were built in
1968 and 1952 respectively. Outdated almost as soon as they were built, by
the early 1980s they were inefficient and occasionally subject to dramatic
breakdowns.

The long-term solution for the region’s sewage treatment involves the
building of a new secondary plant on Deer Island and the decommissioning
of the two old plants. However, in the interim, the old plants must be made
to operate as effectively as possible.

Since it took over the operation of the plants, the MWRA has spent over
$100 million on intermediate upgrades or “fast-track” improvements to
virtually every stage of the primary treatment process (see Fig. 2-13). Some
of these improvements, such as odor and noise control systems mitigate
impacts on adjacent communities, but most increase the plants’ reliability
and efficiency.

Primary Wastewater Treatment

Fast-track upgrades
have improved the
treatment plants.

1
Preliminary I Primary

treatment ' treatment
I
| Sedimentation
' tank
1
a

Screens
tank"

Chlorination

Effluent to
Boston Harbor

Fertilizer
pellet plant

Fig. 2-13

Primary treatment at the plants begins with the separation of the solid
material from the liquid flow in sedimentation tanks. A rehabilitation
project at Deer Island has increased the amount of time the wastewater
remains in these tanks, so that more solids can settle to the bottom. This
reduces the amount of solids and BOD in the effluent eventually discharged
into the Harbor.

Scum removal systems at both plants have made a dramatic difference to

More solids settle
out in sedimentation
tanks.

MWRA ¢ 17

Interceptors Wilmingto

A Pump Station
Bo Headworks .
6 Power and Pump Station
© C50 Outlet | Bedford Burlington :
@ 50 Treatment Facility
§ Wobu

Wastewater Treatment Plant
“e & Winchester

“wey
s

as Adington
% ig

%
Se
& se

Belmont® ——

Framingham

a=

?

Needham’ }
a Hts oa Fe ay bag esa BP
&

Sen
Dedham

Westwood a
%

Se cal

tm eg

Norwood a

55S cog

os a

[ogg
y vhs
of ir

Walpole

Pump Station

) MWRA
= sewerage System

&? Wakefiely

4
/
4

+7 Stoneham
t

Medford

Se en

a ay ~

SANT, Excrett

WW ! elsea'

7 ~
< ‘

Somervill€ Poe
ef
4 Cambrifige
s\%

a A,

Randolph

Stoughton

Headworks

New scum removal
systems have visible
impact on the
Harbor.

Deer Island has a
new chlorination
system.

Sludge is no longer
discharged into
Boston Harbor.

Sludge is now
turned into fertilizer
pellets.

20 * MWRA

the aesthetics of the Harbor. Grease and floatable trash such as rags and
plastics are now skimmed off the top of the sedimentation tanks. This scum
is then crushed and bound with inert material that turns it into a soil-like
substance that is transported to landfills. Previously the scum was dis-
charged into the Harbor and eventually floated back onto area beaches.

There was a slight decrease in the number of plastic tampon applicators
collected on Boston Harbor beaches in the 1991 annual beach cleanup
conducted by Massachusetts Coastal Zone Management (see Table 2-6).
Since tampon applicators are sewage-related wastes, the decrease indicates
the effectiveness of the improvements in the sedimentation tanks and scum
removal systems. Some sewage-related debris may still escape these pro-
cesses to be discharged with the effluent, or it may enter the Harbor through
CSO discharges.

Scum removal resultsin | ; 1
fewer “sewage indicators” Year | # tampon
per mile of beach on. applicators
Boston Harbor. per mile of
beach

1989 208

1990 213
Average number of plastic . 4991 170
tampon applicators collected per mile of

beach on Boston Harbor.
Source: Massachusetts Coastal Zone Management. Table 2-6

From the sedimentation tanks, the wastewater passes into the chlorina-
tion system where it is disinfected before being discharged into the Harbor.
Liquid chlorine provided the disinfection at Deer Island until 1991, when
the Authority completed a new disinfection facility that uses sodium hy-
pochlorite. The new facility is much more reliable than its predecessor. The
old gas diffusers, in particular, were subject to breakdown. Moreover,
sodium hypochlorite is safer to store and handle than liquid chlorine.

Solids that settle out in the sedimentation tanks are thickened and
transferred to digesters. At this stage, the solids are called sludge. In the
digesters, bacteria break down sludge, reducing its volume by about 50
percent.

Until 1991, approximately 40 dry tons of sludge from the digesters were
discharged daily into the Harbor on the outgoing tide. About one-third of
the sludge would return to the Harbor on the following incoming tide.

In December 1991, MWRA opened its $90 million sludge pelletizing plant
at the former Fore River Shipyard. Since that time, digested sludge has been
barged from both treatment plants to the facility on the Quincy-Braintree
border, where it is dewatered and heat-dried into fertilizer pellets. The
cessation of sludge dumping represents the major environmental advance
for the Harbor since the creation of the MWRA.

Sludge pellets cannot be sold in Massachusetts for use as fertilizer unless
both federal and state standards are met. Fortunately, due to aggressive
source reduction programs, the concentration of toxic chemicals and heavy
metals in sludge from the MWRA’s treatment plants is below the limits set
by federal and Massachusetts regulations. The Authority has applied for a
Massachusetts certification to classify its pellets as “Type I” fertilizer, which
meets the strictest criteria for toxic metals and can be sold in-state with no
restrictions. As Table 2-7 shows, metal concentrations in MWRA pellets
compare favorably with the concentrations found in sludge pellets gener-
ated by other municipal treatment plants for agricultural land application.

Comparison of levels of contaminants measured in sludge
with state and federal standards and with sludge
produced by other plants.

Table 2-7

ppm - parts per million
n.a. - not available

“Average concentration measured in sludge pellets during calendar year

1992,

Metal Federal | Renton/ | Blue Plains/ | South Shore/
(ppm) sludge | limit? | limit® | Seattle’ | Washington | Milwaukee®
pellets* D.c!
Arsenic 2.5 la. 41 na. na. na.
Boron 13.4 300 na. m.a. na. na.
Cadmium 6.3 14 39 6.3 6.7 11
| Chromium 64.0 1000 1200 83 180 3100
|| Copper 745:7 1000 1500 730 526 700
Lead 227.5 300 300 100 140 230 .
Mercury 5.7 10 17 0.7 18 0.7
Molybdenum 12.8 25° 18 11 60 32
Nickel 36.0 200 420 23 50 150
Selenium 2.5 na. 36 n.a. na. n.a.
Zinc 982.3 2500 | 2800 850 750 1900

'Type I standards, Mass. Dept. of Environmental Protection Reg. 310 CMR
32.

‘High quality sewage sludge designation, Clean Water Act Part 503.
“MWRA 1991 survey of plants/cities that produce sludge for land application.
‘In Massachusetts, pellets with molybdenum concentrations greater than

10 ppm cannot be used on crops that are used to feed grazing animals,

like cows. At these levels molybdenum is not of concern to humans, but
it can interfere with a cow’s ability to absorb copper, an essential nutrient

for the cow.

MWRA ¢ 21

As a result of
cessation of sludge
dumping, Harbor
water quality
immediately
improved.

Discharge of toxic
contaminants into
the sewerage system
must be controlled.

22 © MWRA

There has been a dramatic reduction in the concentration of sewage-
associated bacteria in the vicinity of the sludge outfall as a result of sludge
abatement (see Fig. 2-14).

Fecal coliform counts decreased dramatically
once sludge discharge stopped.

N
4
3

ut]

HE During sludge discharge

100 BI Post-discharge

Average fecal coliform/1 00m!
wn
o

Fig. 2-14
The first series of samples was collected in October 1991; the second in
November 1992. Samples were all collected during dry weather at low tide.

G. Pollutant Source Reduction

Three factors make it essential to control the amounts of toxic organic
chemicals (such as 1,1,1-trichloroethane, a cleaner used by circuit board
manufacturers) and toxic metals (such as the chromium used by metal
finishers) that go into the sewerage system.

First, a considerable percentage of these pollutants does not get removed
in the present primary treatment process but remains in the effluent
discharged into Boston Harbor.

Second, some hazardous pollutants settle out in the sludge that is now
turned into fertilizer. Contaminants therefore affect the marketability of
the fertilizer made from the sludge: the fewer pollutants in the sludge,
the more uses for the fertilizer.

Third, some of these pollutants could be hazardous to people exposed to
sewerage system fumes, including MWRA’s own maintenance and treat-
ment plant personnel. They could also harm the sewerage infrastructure
and treatment plant equipment.

The Authority’s Toxic Reduction and Control Department (TRAC) has

had considerable success in reducing the concentration of these pollutants
in the flow that goes to the treatment plants. TRAC issues sewer use permits
to industries, inspects their facilities, monitors their discharges, and enforces
federal, state, and local discharge regulations. Enforcement can take several

forms (see Table 2-8), from informal notices of violation, to financial penal-
ties, to referrals for criminal prosecution. This table demonstrates TRAC’s

MWRA enforces

commitment to help companies achieve compliance before financial penal- discharge
ties must be imposed. regulations.
TRAC enforcement actions 1990-92
Fiscal Violation Non- Penalty
Year Notices* | Compliance | Assessments®
Notices?
90 0 23 2
91 16 99 1S
92 127 171 11
Table 2-8

* Letter describing violation, asking user to identify reason for the viola-
tion and what steps will be taken to ensure it will not recur.

» Formal notice of violation specifying requirements the user has violated
and a schedule by which user must return to compliance.
* Formal, written notice to user assessing civil monetary penalties.

Although TRAC permits and regulates over 1,300 local industrial sewer
users, it pays particular attention to the nearly 250 that are designated
Significant Industrial Users (SIUs). Defined by federal law, SIUs are compa-
nies that because of their size or the types of chemicals used to make their
product are the most likely to violate local discharge limits or cause harm to
the collection system or the treatment plants.

TRAC work over the last few years shows that households are also a
source of toxic pollutants in the waste stream. Public outreach campaigns
encourage people to use products that are environmentally safer and to take
precautions when disposing of potentially hazardous materials such as
pesticides and used motor oil. TRAC has also worked with communities to
collect and dispose of household hazardous waste.

Toxic contaminant

loadings in the
_ waste stream have

declined.
There is evidence that the amounts of the pollutants in the waste stream
are declining. For example, total metal loadings in the influent have
dropped considerably. Fig.-2-15 shows the decreased loadings of zinc and
copper to the plants over the past decade.
Influent loadings of 25
zinc and copper to the . MM Zinc
treatment plants have S 20-4 Copper
decreased. g
3S 154
s
>
i=)
Qa
zg 1.04
Combined loading of zinc and copper 5
based on average monthly concentrations a
(data missing for 11% of the months) and € 0.54
average monthly flows through both Deer h
Island and Nut Island. fs eed |

Fiscal Year
Fig. 2-15

1981 '82 '83 '84 '85.'86 '87 '88 '89 '90 '91 '92

MWRA ¢ 23

24 © MWRA

Aside from the efforts of TRAC, several factors have contributed to the
decline in the amount of toxic materials in the waste stream. First, the
federal government has taken action on a national level. Manufacture of
many of the most toxic pesticides and other hazardous materials has been
banned. In addition, EPA continues to refine the standards for its pretreat-
ment program, which regulates the amounts of toxic materials that indus-
tries can discharge into a sewerage system. Moreover, educational efforts
such as Earth Day have increased public awareness of the problem.

Helping Business Achieve Compliance

Emtex Inc., located in Chelsea, dyes and laminates fabric for footwear.

Until recently, Emtex had recurring violations for pH, copper, zinc, mercury, and silver.
in its wastewater discharges. To comply with MWRA regulations, Emtex cooperated with
the Toxic Reduction and Control Department to (i) review possible source reduction
options, (ii) modify those processes that were contributing to its non-compliance, and (iii)
focus particular attention on the dye house operation, which had a history of heavy metal
discharges. : . :

In October 1992, Emtex and MWRA signed a Consent Agreement whereby Emtex would
undertake source reduction and pretreatment activities to assure compliance with MWRA
regulations. Soon after this, the company stopped its industrial process discharges except
those from its dye house. It also agreed to comply with a series of sampling and reporting
deadlines, in an effort to isolate the problem.

The subsequent sampling and analysis identified that one of the company’s imported
fabrics contained zinc. The copper was traced to an additive in the dyes. Emtex has
stopped processing the problem fabric and discontinued its use of the additive. Further-
more, it now tests all fabric shipments for zinc, copper, lead, and chromium before pro-
cessing begins. The company has also installed a pH neutralization system at its final
discharge point.

Since implementing the above recommendations, Emtex has been in compliance with
MWRA regulations.

EFFECTS ON HARBOR WATER
QUALITY TO DATE

MWRA conducts scientific studies designed to characterize pollutants
entering the Harbor,.identify their consequent effects on environmental
quality, and study their movement. These studies are often carried out in
partnership with universities, private research laboratories, environmental
agencies, and other government agencies.

The results of these studies are used to monitor compliance with dis-
charge permits and to assess current environmental conditions in the
Harbor. They are also used to track changes in conditions as improvements
are made to the sewerage system.

MWRA monitors

pollutants in Boston
Harbor.

Boston Harbor Monitoring Projects

1. Pollutant characterization:

-studies of sources of pollutants into the Harbor, including sources other
than sewage

-monthly measurements of toxic contaminants in MWRA discharges to
assess the effectiveness of pollution prevention and treatment programs

2. Pollutant effects:

-extensive monitoring of the concentrations of sewage-related bacteria,
which are used to assess both water and sediment quality and potential
health hazards

-studies of the distribution of sea floor animals as an indication of the
extent and severity of pollution in the Harbor

-studies of the health of the winter flounder in Boston Harbor, because
abnormalities in these fish can be strongly linked with a degraded
environment

-studies of the amount of toxic contaminants accumulated in mussels
near treatment plant discharges

-studies of the concentration of nutrients released from sediments as well
as oxygen consumption by bottom-dwelling organisms

3. Pollutant movement:

-tracking of discharge plumes from sewage treatment plants and com
bined sewer overflows

-studies on the fate of contaminated sediments in the Harbor

-modeling studies to predict water circulation and pollutant transport
within the Harbor and near-shore waters

MWRA ¢ 25

Discharge
monitoring reveals
that effluent quality
is better.

A. Effluent Quality

Treatment plants are expected to meet discharge standards that limit the
concentrations of pollutants that can be released in the effluent. In the case
of MWRA discharges, interim standards were set with the understanding
that the region’s outdated system is in the process of being comprehensively
upgraded. These interim limits are therefore not as stringent as those that
will be required of the new plant.

Each month, the number of violations of the standards must be reported
to the court. As Table 3-1 shows, the Deer and Nut Island plants violated
standards on only a few occasions in Fiscal Year 1992.

Violations of interim discharge limits.

Deer Island — Nut Island
Fiscal | BOD | TSS | Coliform | pH Fiscal |} BOD | TSS | Coliform | pH
Year ] .
87 31 | 2] 2 0 0 0 0 1
88 32 10 | il 0 88 0 0 0 0
89 32 5 8 1 89 Tt 0 0 0
90 14 2 1 0 | 90 2 0 1 0
91 17 1 0 3 91 0 0 2 2
92 7 0 0 0 92 0 0} 0 0
Table 3-1 — ,

26 © MWRA

Additional monthly monitoring of the effluent involves “priority pollut-
ants,” a group of 125 metals and organic pollutants designated of prime
concern by EPA. As Fig. 3-1 shows, there has been a decrease in the amount
of priority pollutants released from the plants.

There has been a decrease in the amount of priority
pollutants released from the treatment plants.

1500
Volatile organics
Other Organics
1250 4 Cyanide
J Metals
> 1000 4
RSJ 4
3
= 7507
3
& 4
500 5
2504
0
1990 1994 1992
Fig. 3-1 Fiscal Year

The combined loadings of volatile organic compounds,
other organic compounds, cyanide and metals were
calculated from monthly concentrations and flows
measured at the Deer Island and Nut Island plants.

The MWRA also runs monthly analyses of the toxicity of treatment plant
effluent. These test the survival of several species of marine organisms
exposed to varying concentrations of effluent. Very high mortality rates
occurred in these tests during Fiscal Year 1992. Subsequent investigations
by the EPA concluded that the mortality was probably caused by the pres-
ence of both surfactants (e.g. laundry detergents and soaps) and chlorine in
the waste stream. The new treatment plant should greatly reduce these
problems, since surfactants will be biodegraded by secondary treatment and
chlorine will be removed from new plant effluent before it is discharged.

B. Harbor Water Quality

People who spend time on and in the Harbor say that the water is cleaner
than it used to be. This is probably based on the perception that floatable
trash and grease slicks are no longer common eyesores: sludge abatement
and the new scum removal system have had a major impact. Local swim-
mers participating in a September 1992 race at Carson Beach, sponsored by
Save the Harbor/Save the Bay, spoke of the improved color and feel of the
water. Regular boaters also comment on the improved visibility in the
water. :

Several lines of scientifically verifiable evidence also suggest that the
decreased loading of toxic contaminants from the treatment plants is
improving the environmental quality of the Harbor. The concentrations of
several priority pollutants measured in water near the current Deer Island
effluent discharges do not violate EPA water quality criteria (see Table 3-2).

Priority pollutant concentrations near Deer Island outfall.

Contaminant Observed EPA marine | EPA marine Coastal
concentration acute chronic water
near DL? criteria® criteria
(ppt) (ppt) (ppt) (ppt)
Arsenic 498 ILS. ILS. 1500
Copper 1567 2900 ILS. 130
Mercury 5 2100 25 1
Heptachlor 0.089 53 3.6 0.01
Aldrin 0.05 13 ns. 0.01
Dieldrin 0.62 710 19 0.01
DDT 0.064 - 130 ¢ 1.0 0.01
PCBs 7 10000 30 1
Table 3-2

ppt - parts per trillion.

ns. - no standard

? Observed concentrations at two stations located near Deer Island.

Source: MWRA 1988, Secondary Treatment Facilities Plan, Appendix X.

® Source: EPA Quality Criteria for Water, EPA 1992.

© Data from typical coastal Atlantic waters. Source: Furness and Rainbow 1990.

The most complete water quality data sets for Harbor metal concentra-
tions are measurements of zinc and copper (see Fig. 3-2). These show
improvement in water quality since the early 1980s. The decrease in copper
and zinc concentrations in the water correlates specifically with the decrease
in effluent metal loadings into the Harbor, suggesting that the improvement
in water quality is associated with the decrease in effluent loadings.

Harbor water
quality is better.

MWRA °¢ 27

Concentrations of
contaminants in
sediments

have decreased.

Toxic contaminants
measured in fish and
shellfish have also
decreased.

28 e MWRA

Zinc and copper concentrations
in the Harbor have declined.

18
16
~ 14 MB Zinc
32 MI Copper
~
S 10
§
=
g
§
Ee | i.
1972 1983 1988 1989
Source: Sung 1991 Year

Fig. 3-2

The concentrations of zinc and copper measured in water samples taken in the inner and
northwest portions of the Harbor. Concentrations reported here are averaged based on the
volumes of the inner and northwest portions of the Harbor.

C. Sediment Quality

Water in Boston Harbor should recover from the effects of pollution
much faster than bottom sediments. This is because water in the Harbor is
flushed regularly by the tides and is therefore renewed over a period of days
to weeks. In contrast, sediments remain in place, so natural cleansing
processes take years to decades. In fact, once a contaminant is no longer
entering the water, the sediments can themselves become a source of toxic
materials as the contaminants leach out into the overlying water. Research-
ers at the Massachusetts Institute of Technology, Woods Hole Oceano-
graphic Institution, and University of Massachusetts/Boston have shown
that organic contaminants such as petroleum hydrocarbons are already
being released from the sediments into the water. The rate of this release is
still under investigation, but it will probably be slow enough to pose no
threat to water quality while gradually decreasing the levels of contami-
nants in the sediments.

D. Marine Life

Since they process large volumes of water through their feeding struc-
tures, filter-feeding animals like mussels often concentrate toxic metal and
organic compounds in their tissues in a process called bioaccumulation.
Because mussels stay attached in one place, they are useful for comparing
conditions in different areas. How much of a toxic contaminant accumu-
lates in the tissues of a mussel indicates the relative level of the contami-
nant in that particular area of the water.

Since 1987, the MWRA has measured the accumulation of contaminants
in mussels placed in various regions of the Harbor. Mussels set out near
Deer Island in 1991 and 1992 had lower levels of most organic compounds
than those tested in 1987 (see Fig. 3-3). For example, there was a marked
decrease in low molecular weight PAHs over time. Low molecular weight
PAHs are organic chemicals predominantly found in petroleum-based
products.

There has been a decrease in the concentration of organic
contaminants measured in mussels at Deer Island.

Pesticides

70

60 WE Dieldrin
Gy DDT

50 BRB Alpha-chlordane
Trans-nonachlor

40

30

Concentration (ug)/mussel dry weight (kg)

300:

- 200:
100:

"987 1991 1992 1987 1991 1992

Fig. 3-3
Concentrations of pesticides, polychlorinated biphenyls (PCBs) and polycyclic aromatic
hydrocarbons (PAHs) measured in mussels set out at Deer Island in 1987 (for 30 days) and in
1991 and 1992 (for 60 days). Only shallow water samples are included for 1991.. In samples
where an individual PAH was not detected, it was assumed. present at the method detection
limit.

The results of MWRA’s bioaccumulation studies are supported by similar
results reported by the National Oceanic and Atmospheric Administration
(NOAA). In its Mussel Watch program, NOAA compiles data on concentra-
tions of contaminants in mussels collected from different coastal locations
throughout the Unites States. At Deer Island, one of Boston Harbor’s mussel
watch sites, there has been a statistically significant decrease in PAHs
measured in mussels over the past six years. Low molecular weight PAHs
have decreased by 30%, and total PAHs by 18%.

As shown in Fig. 3-4, mussels measured in Boston Harbor have levels of
organic contaminants similar to those in other estuaries on the East Coast.

Because of their living and feeding habits, winter flounder are particularly
susceptible to a contaminated environment. Théy live on the bottom of the
Harbor, feeding on small animals found on or in the sediments. Flounder
are therefore exposed to contaminants directly (from the environment) and
indirectly (from their prey). They have been shown to undergo a progres-
sive liver disease whose extent is closely correlated with levels of exposure to
chemical contaminants. This species is therefore an important bellwether
for the biological effects of coastal contaminants on bottom-feeding fish.
For the past three years, the Authority has sponsored research at Woods
Hole Oceanographic Institution into the prevalence of disease in winter
flounder collected in Boston Harbor. Tumors in Harbor flounder appear to
be less frequent now than they were in the early 1980s, as are other indica-
tors of liver disease caused by pollution (see Fig. 3-5).

MWRA ® 29

Organic contaminant concentrations are similar in
mussels sampled in various urban harbors.

3.54 3.45
» ll Boston Harbor
1.04 i Hudson-Raritan Estuary
i Long Island Sound
0.9- Mf Delaware Bay
Buzzards Bay
3 08-4 Narragansett Bay
= C1 Penobscot Bay
=
= 07-4
=
3 0.644
=
Bz 054
—
s
B04
s
vs
g 0.34
ro)
0.24
014
0.04 : :
PAH PCB DDT
Source: NOAA Mussel Watch 1997

Fig. 3-4
Average concentration of PAHs, PCBs, and DDT and its breakdown products measured
in mussels collected for Mussel Watch in 1991.

Liver diseases have declined since 1984 in winter flounder

caught off Deer Island.
100
80 - MMM Early liver disease
HB Liver tumors
u
u
S
£
3
iS)
[s)
&
on 1984 ‘87 ‘88 ‘89 90 ‘91 92
f.
Fig. 3-5 Source: Moore et al. 1993

No tumors were detected in flounder collected at Deer Island Flats in 1992. However, these
results must be interpreted with caution. The fish sampled in 1992 were younger than those
sampled in previous years and a substantial percentage of them exhibited early liver disease.
Young fish may well develop tumors as they age.

30 © MWRA

E. Remaining Problems

There is, however, a limit to the environmental benefits that can be :
achieved without new facilities that have both the capacity and technology
to handle the region’s sewage adequately. One way to look at this is
through measurements of dissolved oxygen.

Marine organisms breathe oxygen that is dissolved in seawater. Deple-
tion of dissolved oxygen in the water or in sediments can cause loss of
habitat, or induce stress and the eventual death of marine organisms.
Oxygen is also used during the decomposition of the organic material
released into the water from sewage treatment plants. Dissolved oxygen
problems are therefore aggravated by sewage discharges, particularly in
shallow estuaries such as the Harbor.

MWRA routinely measures dissolved oxygen in the Harbor. Beginning in
late summer 1991, the program was expanded to include measurements
made at dawn, when oxygen levels are expected to be lowest. This is
because aquatic plants produce oxygen in daylight (photosynthesis), and
consume it at night (respiration), so dissolved oxygen levels are lowest after
a whole night of oxygen consumption with no production. Measurements
made at mid-day therefore tend to be higher than those made at dawn, and
may underestimate the extent of dissolved oxygen problems. Similarly,
dissolved oxygen tends to be lower near the bottom of the water column.
than near the surface, both because sea-floor organisms use oxygen from the
water and because the bottom of the water column is some distance away
from the atmospheric source of oxygen. .

As Table 3-3 shows, DO measurements less than the State Class SB stan-
dard (S mg/l) were most frequent in bottom samples taken at dawn.

Dissolved oxygen measurements in the Inner Harbor.

Percent of D.O.
measurements Dawn Mid-Day
below standard | -

Surface 16.3 4.8
Bottom 22.4 12.4
Table 3-3

Samples from the summers of 1991 and 1992,

Surveys in all parts of the Harbor show that dissolved oxygen averaged
about 1 milligram per liter lower during the early morning hours than
during mid-day. This result suggests that most surveys carried out in the
past have substantially underestimated the severity of dissolved oxygen
problems in Boston Harbor. .

Secondary treatment will remove substantially more oxygen-consuming
materials from the sewage than the present level of treatment. A really
dramatic improvement, however, cannot be expected until the discharge is
moved offshore where it can receive sufficient dilution.

Nevertheless, water
quality problems
continue.

Since oxygen plays a.
role in so many
biological processes,
it can be used as an
integrated measure
of the health of a
water body.

MWRA ¢ 31

4 . CONTINUING SYSTEM
IMPROVEMENTS

In order to meet the requirements of the Clean Water Act, the MWRA is
In Boston Harbor, building a secondary treatment plant on Deer Island. However, the Harbor
both seconda will not dilute even secondary effluent to the point where state and federal
te lity standard. et Thi tfall th fore has to be relocated
water quality s ards are met. The out erefore has to be relocate:
treatment and an from its present position at the mouth of Boston Harbor to deeper water

outfall are required where more seawater will be available to dilute it.
to meet discharge
standards. A. The new Secondary Treatment Plant

Construction of the new Deer Island treatment facilities (including the
outfall tunnel) will cost approximately $3.5 billion. The new facilities will
replace the old Deer Island and Nut Island plants. Some elements of the old
Deer Island plant will be incorporated into the new plant, while others will
be torn down; the Nut Island plant will be replaced by a headworks to
screen sewage flow from the southern part of the system. This flow will
then be transported 5 miles across the Harbor to Deer Island via an 11-foot
diameter tunnel now being constructed beneath the Harbor floor.

The centerpiece of the system, the new Deer Island plant will be the

The new pi lant will second largest in the nation and have sufficient capacity. to handle the
be large and region’s sewage flow for the foreseeable future. It will have a capacity of
or 1,270 mgd for primary treatment and 1,080 mgd for secondary. The current
technologi cally daily average flow reaching the Deer and Nut Island plants combined is
sophisticated. approximately 400 mgd, though flow can exceed 700 mgd during wet
weather.

The new plant will also provide more sophisticated treatment. Primary
treatment relies mainly on physical processes such as screening and sedi-
mentation (the process by which heavier particles settle to the bottom of a
column of water) to remove solids. The effluent is then disinfected with
chlorine to kill disease-causing pathogens before being discharged into a
body of receiving water.

Secondary Wastewater Treatment

Fig.4-1
: [ A :
Preliminary t Primary Secondary
treatment t treatment treatment

' .
Sedimentation coer
! tank tank
i
i

Dechlorination
: es
Effluent to

hlorination
tank Massachusetts Bay

Activated sludge

Fertilizer
pellet plant

32 © MWRA

Secondary treatment at the new plant will use biological processes to
increase the amount of solids removed from wastewater (see Fig. 4-1). After
primary treatment, the wastewater will be oxygenated in the aeration tank
to promote the growth of naturally occurring microorganisms that consume
organic material. The wastewater will then flow into secondary sedimenta-
tion tanks where the solids settle. Some of this secondary sludge will be
returned to the aeration tank to maintain the level of bacterial activity and
thereby optimize the consumption of organic matter. The remainder will be
added to the primary sludge before being further broken down in digesters.
The treated sludge will be shipped off-island and turned into fertilizer
pellets. Following treatment, the remaining effluent will first be disinfected
with chlorine and then dechlorinated before being discharged into the
ocean.

‘More solids and BOD are removed by secondary treatment than by
primary treatment (see Table 4-1). The improved solid removal will also
serve to slightly decrease the amount of nitrogen in the effluent, as some
nitrogen is removed as solids.

Percent removal from primary and . :

secondary treatment. Type of Material Primary _| Secondary
Solids 60 85
Toxic 10-46 32-95
Contaminants*

* Varies with contaminant. BOD 35 * 85

Data from MWRA 1988, Secondary Treatment

Facilities Plan, Appendix A. Nitrog en 5 10-15

Table 4-1

Effluent quality will improve dramatically when two batteries of second-
ary treatment are on-line (see Fig. 4-2).

Anticipated pollutants loadings as different
stages of the project are completed.

During sludge discharge - 1990

0 50 1 oo 1 50 200 250
. Tons/day
Fig. 4-2 f@tss sop
Data from combined Deer and Nut Island effluent and sludge loadings were used for 1990;

combined effluent data were used for 1992; future loadings are
based on projections by Metcalf and Eddy, Inc.

MWRA ¢ 33

Secondary Treatment at Clinton

Located 50 miles west of Boston, the MWRA’s secondary treatment plant in Clinton—which serves the
communities of Clinton and Lancaster—is quite separate from the rest of the Authority’s sewerage operation
and has no direct connection to the water quality in Boston Harbor. Moreover, with an average daily flow
of 3 mgd, the plant is clearly on a much'smaller scale than its counterparts on Deer Island and Nut Island.
Clinton’s secondary treatment, however, provides excellent evidence of what can be expected from the new
Deer Island plant once it moves to full secondary treatment in 1999. .

The effluent from the Clinton plant is discharged into the South Branch of the Nashua River, a small
body of water that could easily suffer intense degradation from sewage contaminants. Since the completion
of a recent upgrade in June 1992, the plant provides treatment that meets discharge limits on all criteria (see
Table 4-2). At points close to the outfall, the river water is now cleaner than it is several miles upstream.

Effectiveness of Clinton plant’s secondary treatment

| Characteristic ; Effluent j Interim | Effluent | NPDES
before limit after limit*
upgrade? j upgrade?

Biological oxygen demand (mg/l) 52 50 48 20
Suspended solids (mg/I) 28 35 - 5.9 20
Settleable solids (ml/1) 0.1 0.1 0 0.1
Fecal coliform (#/100 ml) 270 200 10 200

| Residual chlorine (mg/l) 1.1 4 02-15 0 0.03

Table 4-2 * Average concentration, June - December 1990

> Average concentration, June - December 1992
© National Pollution Discharge Elimination System

The large reduction in the fecal coliform count is due to improvements in the plant’s chlorination sys-
tem. More relevant for analysis of what can be expected from the introduction of secondary treatment at
the new Deer Island plant are the results for biological oxygen demand removal. Primary treatment will
never have this sort of dramatic impact on oxygen-consuming material.

34° MWRA

Construction of the new plant follows the schedule laid out by the The new Deer Island
federal court (see Fig. 4-3). ; plant is being built

in accordance with
the court schedule.
Court Schedule

1990 ‘91 ‘92 93 ‘94 ‘95 ‘98 ‘99.2000

Build new primary facilities at Deer Island
Complete batteries: A & B

Build inter-island tunnel between
Nut and Deer Islands

Build effluent outfall tunnel into
Massachusetts Bay

Build new secondary facilities at Deer Island
Complete batteries: A :

1990 =’9] ‘92 93, ‘94 95 ’96 '97 ‘98 ‘99 2000
Fig. 4-3

MWRA ® 35

Deer Island, 1990 and 1992

Fig. 4-4 Top photo taken January 1990. Bottom photo taken October 1992.
36 * MWRA

B. The new Outfall Tunnel

The new outfall tunnel will cost approximately $380 million and be the
largest of its kind ever built. As shown in Fig. 4-5, the tunnel begins with a
30-foot diameter vertical access shaft at Deer Island. This shaft extends 420
feet below sea level. The effluent will flow down this shaft and then enter
the 24-foot diameter tunnel, which runs under the ocean floor 9.5 miles out
into Massachusetts Bay. Along the last 1.25 miles, effluent will travel up
through 55 vertical riser pipes, bored 240 feet down through the ocean floor
and connected to the tunnel. The risers will disperse the effluent into the
ocean, which in this area is over 100 feet deep.

Extensive exploratory borings were taken to gather information about the
type of rock and soil along the proposed route. The excavation is being
done by a 3,000-hp tunnel boring machine (TBM) made by the same com-
pany that is supplying the boring machines for the “Chunnel” currently
being constructed between England and France beneath the English Chan-
nel. Over 26 feet wide and 40 feet long, the TBM weighs about 600 tons.

The TBM was fully assembled and tested at the manufacturer’s Wisconsin
plant, and then disassembled and shipped to Boston through the Great

Lakes to the Erie Canal, down the Hudson River and up the coast to Boston. ~

Once at Deer Island, the machine was lowered down the access shaft in
sections and reassembled at the rock face.

The new outfall tunnel discharges
into the deeper waters of Massachusetts Bay.

Deer Island

Massachusetts Bay

Fig.4-5

C. Siting the new Outfall

Effluent from Deer Island is currently discharged within Boston Harbor,
at a site approximately half a mile offshore, where the water is 30 feet deep.
In contrast, the new effluent outfall will be 9.5 miles offshore, at a point
where Massachusetts Bay is 100 feet deep. As part of the new outfall siting
process, existing data on the oceanographic conditions of Massachusetts Bay
were compiled, field studies were conducted to collect new data, and com-
puter models were used to predict pollutant concentrations in Massachu-
setts Bay from different outfall sites. Chosen out of seven candidate sites,
the new outfall is located where it will provide sufficient dilution of the
effluent to protect public health and aquatic life. It is also far enough from
shore to keep effluent away from beaches and shellfish beds.

The new outfall
tunnel

will discharge
cleaner

effluent into deeper
waters.

The new outfall was
sited on the basis of
environmental and

engineering criteria.

MWRA ¢ 37

The computer model used in the outfall siting process predicted that
Boston Harbor and nearby shorelines to the north and south are more
affected by the present discharge than they will be by the new outfall. The
modeling effort is ongoing: the U.S. Geological Survey (USGS) and
HydroQual Inc. are working on a more sophisticated model of water motion
in Boston Harbor, Massachusetts and Cape Cod Bays. So far, predictions
from the new model confirm those made earlier, and suggest that more of
the shoreline is impacted by the present near-shore outfall than will be by
the future off-shore outfall.

As Fig. 4-6 shows, when effluent is released from the new outfall rather
than at the existing outfall site, (1) the area of. concentrated wastewater is
only 0.5 square miles versus 77 square miles, (2) the predicted concentra-
tions of effluent in Boston Harbor and along the north and south shores are
considerably lower, and (3) the predicted concentration of wastewater in.
most of Massachusetts Bay and Cape Cod Bay does not change.

Predicted dilution of effluent.

Existing Outtfall New Outfall

00 1,600 1,800

0 200 400 600 800 1,000 1,2!

The USGS model was used to simulate winter conditions in Massachusetts Bay.
This shows the predicted dilution of current effluent loads released from either
the existing or the new outfall site.

38 © MWRA

Outfall Siting and Massachusetts Bay

It is important to realize that most of the material released in the effluent stream is already transported
out into Massachusetts Bay. This is because Boston Harbor is effectively flushed by the tides. However,
since Boston Harbor is much smaller than Massachusetts Bay and dilution is therefore much less, contami-
nants are more concentrated in the Harbor than in the Bay. .

Only about one third of the particles currently released by the treatment plants actually settle in the
Harbor. For example, sewage-associated bacterial spores have been fourid distributed in the sediments of
Massachusetts and Capé Cod Bays, indicating that a considerable amount of material currently leaves the
Harbor.

The quick flushing of the Harbor can also be seen by the movement of nitrogen out of the Harbor into
Massachusetts Bay. More than 85% of the nitrogen that now enters the Harbor is flushed out into Massa-
chusetts and Cape Cod Bays (see Fig. 4-7). This means that changing the point of effluent release to the
new outfall site will not have a significant effect on the concentration of nitrogen in the Bays.

Most of the nitrogen that enters the Harbor is flushed out .

Denitrification

_potainesarmn Dredg ing

| 8-12%
° (<2%)
. : Flushing to
Boston. : Massachusetts
: : Bay
Harbor | (64-88%)

(100%) Burial (2%)

Source: Kelly and Nowicki 1992

Fig.4-7

Several studies conducted by researchers from Battelle Ocean Sciences, the University of
Rhode Island, and the Marine Biological Laboratory have shown that approximately 10%
of the nitrogen input is released as nitrogen gas into the atmosphere through a microbial
process called denitrification. However, the bulk of the nitrogen is exported to
Massachusetts Bay.

MWRA ° 39

A comprehensive
outfall monitoring
project ensures early
response to changes
in marine
conditions.

40 e MWRA

D. Outfall Monitoring

The MWRA monitoring program is designed to detect and evaluate the
environmental effects of the new effluent outfall. The program serves to
check that the new outfall’s benefits are as great or greater than those
predicted in outfall siting studies. A feature is considered appropriate for
tracking if it is an important technical or public concern or is specifically
covered by government regulations. The monitoring strategy provides for
the detection of meaningful changes in biological, chemical, and physical
measurements at levels far below, and thus in advance of, those that could
be of great concern.

The monitoring program began in February 1992 with studies designed to
measure environmental conditions during the three years before the new
outfall begins discharging effluent into Massachusetts Bay. The information
collected during pre-discharge monitoring will serve as the point of com-
parison for determining whether any changes occur once discharge begins.

Measurements are concentrated in the area immediately around the
diffusers, where changes are predicted to be most likely. Sampling is not
limited, however, to the immediate area: measurements extend into distant
areas of Massachusetts and Cape Cod Bays. The further away from the
outfall, the less likely changes will occur, both because the effluent becomes
progressively more diluted and because solid-associated contaminants either
break down or settle out.

To ensure a scientifically valid and environmentally sound foundation
for the monitoring program, the MWRA Outfall Monitoring Task Force
consists of scientists, staff of State and Federal agencies, and representatives
of universities and environmental interest groups (see Table 4-3).

Organizations involved in the Outfall
Monitoring Task Force

Association for the Preservation of Cape Cod
Cape Cod Commission

Center for Coastal Studies

Environmental Protection Agency

Harvard University

Massachusetts Audubon Society

Massachusetts Bays Program

Massachusetts Coastal Zone Management
Massachusetts Department of Environmental Protection
Massachusetts Division of Marine Fisheries
Massachusetts Environmental Policy Act Office
Massachusetts Institute of Technology
National Marine Fisheries Service

Safer Water in Massachusetts

U.S. Army Corps of Engineers

U.S. Geological Survey

University of Massachusetts/Boston

Woods Hole Oceanographic Institution

Table 4-3

Scientific Studies in Massachusetts and Cape Cod Bays

Baseline monitoring
Water quality monitoring
- hydrographic conditions (e.g. temperature, salinity, dissolved oxygen, light) |
- nutrient concentration (e.g. nitrogen, phosphorus, carbon)
Sediment monitoring
- benthic organisms
~ sediment conditions
Marine life
- plankton populations and growth
- fish pathology
- lobster surveys
- mussel bioaccumulation
Special studies
- modeling :
- nutrient exchange with the water column
- red tide causative factors
- Cape Cod Bay phytoplankton
- seawater mixing
- sediment transport

Scientists retrieve water samples during an outfall monitoring survey.

Photo by: John Ryther/Battelle

Fig. 4-8
Long-term management of coastal resources is a complex task including The overall goal
much more than the regulation of discharges from a single sewage treat- must be

lant. The real challenge is to manage all discharges into the offshore
ecosystem and control the harmful effects of all human activities around
Massachusetts and Cape Cod Bays. Information from the monitoring _
program will be used in conjunction with the Massachusetts Bays Program. -

to help regulatory agencies serve the broader goal of the long-ter
tion of the marine environment. os

comprehensive
protection of the

BIBLIOGRAPHY

Furness, R.W., and P.S. Rainbow, eds. 1990. Heavy Metals in the Marine Environment. CRC
Press, Boca Raton.

Kelly, J.R., and B.L. Nowicki. 1992. Sediment Denitrification in Boston Harbor. MWRA
Environmental Quality Department Technical Report, 92-2.

Massachusetts Coastal Zone Management. 1990. Coastsweep ’89. Coastal Brief, No. 5.
Massachusetts Coastal Zone Management. 1991. Coastsweep ’90. Coastal Brief, No. 7.
Massachusetts Coastal Zone Management. 1992. Coastsweep 91. Coastal Brief, No. li.
Moore, MJ., andj.J. Stegeman. 1993. Liver pathology of winter flounder: Boston Harbor,
Massachusetts Bay, and Cape Cod Bay - 1992. Final Report to Massachusetts Water

Resources Authority.

MWRA. 1988. Secondary Treatment Facilities Plan, Volume V, Appendix X:
Bioaccumulation. Massachusetts Water Resources Authority.

NOAA. 1992. Year Six Final Report on National Status and Trends Mussel Watch Project. U.S.
Department of Commerce, National Oceanic and Atmospheric Administration, Office
of Ocean Resources Conservation and Assessment, Rockville, MD.

Rex, A.C. 1993. Combined sewer overflow receiving water monitoring, Boston Harbor and
its tributary rivers, October 1990 - September 1991. MWRA Environmental Quality
__ Department Technical Report, 93-4.

Sung, W. 1991. Observations.on the temporal variations of dissolved copper and zinc in
Boston Harbor. Civil Engineering Practice, 6(1): 99-110.

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TECHNICAL REPORT SERIES
- Environmental Quality Department

1991 Reports
Cura, J.J., Jr. Review of phytoplankton data: Massachusetts Bay.

MWRA. Combined sewer overflow receiving water monitoring: June 1989-October
1990.

MWRA. A spatial and temporal analysis of Boston Harbor microbiological data.

Menzie, C. A., J.J: Cura, J.S. Freshman, and B. Potocki. Boston Harbor: Estimates of
loadings.

Giblin, A.E., J. Tucker, and C. Hopkinson. Sediment oxygen demand and nitrogen
flux in Massachusetts Bay.

Shea, D., D. Lewis, B. Buxton, D. Rhoads, and J. Blake. The sedimentary environ-
ment of Massachusetts Bay: Physical, chemical and biological characteristics.

McDowell, S., J. Ryther, and C. Albro.. Field studies of Nut Island sewage plumes and
background water properties in Boston Harbor: October-November 1990.

MWRA. CSO effects on contamination of Boston Harbor sediment.

Adams, E.E. and X. Zhang. Impact o of CSOs on Boston Harbor: A new look based on
1990 data.

Kelly, J.R. Nutrients and Massachusetts Bay: A synthesis of eutrophication issues.
1992 Reports

Giblin, A.E., C. Hopkinson, and J. Tucker. Metabolism and nutrient cycling in
Boston Harbor sediments.

Kelly, J. R. and B. L. Nowicki. Sediment denitrification in Boston Harbor.

Rex, A., K. Keay, W. Smith, J. Cura, C. Menzie, M. Steinhauer, and M. Connor. The
state of Boston Harbor: 1991.

Shea, D. and J. Kelly. Transport and fate of toxic contaminants discharged by
MWRA into Massachusetts Bay.

Moore, J., B. Woodin, and J. Stegeman. Liver pathology of winter flounder: Boston
Harbor, Massachusetts Bay, and Cape Cod Bay - 1991.Quincy, Hingham, and Hull
Bays.

SAIC. REMOTS sediment-profile photography survey of Boston Harbor, Dorchester,

Kelly, J.R. and R.K. Kropp. Benthic recovery following sludge abatement in Boston
Harbor.

92-8 Kelly, J., C. Albro, J. Hennessy, and D. Shea. Water quality monitoring in Massa-
chusetts and Cape Cod Bays: February-March 1992.

92-9 Adams, E., K. Stolzenbach, J. Abbott, D. Agostini, A. Canaday, J. Caroli, M. Lawler, J.
Lee, D. Martin, K. Newman, and X. Zhang. Transport of contaminated sediments
in Boston Harbor: fluorescent tracer studies.

92-10 Downey, P.C. and K.F. Young. Bioaccumulation of selected metals and organic
compounds in mussels deployed near Deer Island discharge, 1991.

1993 Reports

93-1 Kelly, J., C. Albro, and J. Hennessy. Water quality monitoring in Massachusetts and
Cape Cod Bays: April-August 1992.

93-2 Giblin, A.E., C. Hopkinson, and J. Tucker. Metabolism, nutrient cycling, and
denitrification in Boston Harbor and Massachusetts Bay sediments.

93-3 Kelly, J.R. and B.L. Nowicki. Direct measurements of denitrification in Boston
Harbor and Massachusetts Bay sediments.

93-4 Rex, A. CSO receiving water monitoring, 1990-1991.

93-5 | HydroQual Inc. and Normandeau Inc. A water quality model for Massachusetts Bay
_and Cape Cod Bay.

Technical reports can be ordered by contacting MWRA Environmental Quality Depart-
ment, (617) 242-6000.

ACKNOWLEDGEMENTS

Many people throughout the MWRA provided data, made suggestions, and reviewed drafts
of this report. The authors would like to thank Nathan Bailey, Ed Caruso, Dan Cushing,

Ben Davis, Rich Davison, Susan Curran Ford, Maury Hall, Mike Hornbrook, Dave Kubiak,
Hayes Lamont, Carl Leone, Charlie Lombardi, Mike McGraw, Mike Mickelson, Lisa Ventry
Milenkovic, Marcia Molay, Lise Paul, John Riccio, Virginia Renick, Elisa Speranza, Bill
Thompson, and Nancy Weatley. We would like to acknowledge especially the help of Grace
Bigornia-Vitale, Jim Hansen, Ken Keay, Wendy Smith Leo, Andrea Rex, Mark Sullivan, Steve:
Weinstein, and Lisa Wong.

Cover design:
Rita Berkeley and Carolynn DeCillo

Graphics and layout:
E. Paul Oberlander and Jack Cook

Printing:
Town Printing Inc.

44 © M“WRA