1996 overview
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Massachusetts
Water Resources Authority
MWRA Environmental Quality Department Technical Report
Series 97-8
Outfall Monitoring
- Overview Report: 1996
November 199
Prepared Under the Direction of:
Douglas B. MacDonald, Executive Director
John F. Fitzgerald, Director, Sewerage Division
Board of Directors:
Trudy Coxe, Chair
\ John J. Carroll, Vice Chair
SN Lorraine M. Downey, Secretary
Norman P. Jacques
a Joseph A. MacRitchie
Vincent G. Mannering
Donald A. Mitchell
Samuel G. Mygatt
Andrew Pappastergion
Robert Spinney
Marie T. Turner
OUTFALL MONITORING OVERVIEW REPORT: 1996 - MWRA
Outfall Monitoring Overview Report: 1996
November, 1997
Technical Report No. 97-8
Environmental Quality Department
Massachusetts Water Resources Authority
Report Contributors:
Donald P. Galya — ENSR
Rebecca Zavistoski ~ ENSR
Nancy Maciolek — ENSR
Windsor Sung — ENSR
Stephen Cibik — ENSR
David Mitchell — ENSR
Michael S. Connor — MWRA
Michael Mickelson — MWRA
Kenneth Keay — MWRA
Maury Hall — MWRA
James Blake — ENSR
Kelly Sullivan — ENSR
Kenneth Hickey — ENSR
Report Layout and Graphics by:
Kim Loosen -- ENSR
Ilse Stryjewski — ENSR
Citation:
Galya, D.P., et al. 1997. Outfall Monitoring Overview
Report: 1996. MWRA Enviro. Quality Dept. Tech. Rpt. Series No. 97-8.
Massachusetts Water Resources Authority, Boston MA. 57 pp.
MWRA - OUTFALL MONITORING OVERVIEW REPORT: 1996 /1
Table of Contents
Executive Summary
1.0 Introduction ........ 0... cece ccc ccc cc ce ete eee eee eee need 01
11 Report objectives and content............ 0... eee 01
1.2 Background .. 0.2.0.0... cece tet e eect eee eee eee 02
13 Trigger parameters and thresholds............... 0000s ee ee eee 03
14 Monitoring program summary .......... 0.00.00. 0S
1S Data management and analysis.................000 00 eeeeeee 05
2.0 Effluent Monitoring Program. ...........0.. 0.02. c eee e eee ee eee eee 09
2.1 Effluent issues... 0.0.0... 0.0.00. c cece ee eect eee eens 09
2.2 Monitoring program design... ........... 000 c cece cence eens 10
2.3 Monitoring Results Compared to Thresholds.................005 n
3.0 Water Column Monitoring Program ........ 0.06 s ees eee cece rere eee aaee 19
3.1 Water column issues... 0... 2... cece etc e ee eee eee eee 19
3.1.1 Organic material....... eee eee eens 19
3.1.2 Nutrients...... 2... ee eee eee te eee 19
3.1.3 Toxic contaminants...... 0.0... 0. cee eee ee eee ee 20
3.2 Monitoring program design ....... 20.2000 e eee ee eee eee 20
3.3 Threshold comparison... 2.0.0... cece cece cence eee eens 22
3.4 Monitoring results...... 0.0... eee eee eee eee eee 28
4.0 Benthic studies ......... 00... c cece cece eee eee eee eee e eee eeeee 37
4.1 Benthic issues... 0.0.6.0 c cece eee 37
4.1.1 Community Structure... 0... eee 37
4.1.2 Sediment Grain Size Composition .................... 37
4.1.3 Nutrients/Oxygen...............000..02.-.0.000008 37
4.14 Toxic Contaminants .......... 0.0... cece eee eae 38
4.1.5 Solids and Organic Material....... 202... cece cece eee 38
42 Monitoring program design .... 0.0... 0.00. eee c cece 38
4.2.1 Soft-bottom Benthic Surveys ............. 0c. eee eee 39
4.2.2 Hard-bottom Surveys ........ 0... ec eee cece eee 40
4.2.3. Nutrient Flux Surveys... 2.0... 2k eee eee 42
4.3 Threshold comparison... 6... 6.00. c cece cece eee eee 42
44 Monitoring results... 00... cece eee eens 45
Il / OUTFALL MONITORING OVERVIEW REPORT: 1995 - MWRA
4.4.1 Biological community results.............00. 000-00 45
4.4.1.1 Boston Harbor.......... 2... c ee eee ee eee 45
4.4.1.2 Massachusetts Bay/Cape Cod Bay............-. 46
4.4.2 Nutrient Flux Results ......... 2.0.60. cee eee eee 47
4.4.2.1 Boston Harbor.............. 00 cece eee eee 47
4.4.2.2. Massachusetts Bay.... 02... eee eee eee 48
5.0 Fishand shellfish 0... eee center teen ee enneee 49
5.1 Fish and shellfish issues... 0... cece eee 49
5.2 Monitoring program design ......... 0.0 c cece eee ee ee eee 49
5.3 Threshold comparisons ..... 0... cece cee eee ee eee 51
5.4 Monitoring results... 0... eee eee 52
5.4.1 Flounder...... 0... 0c cece eee eects 52
5.4.2 Lobster... ee eee 54
5.4.3 Bluemussel........... 00sec cece eee eee eee 56
References
Glossary of Terms
Acronyms
List of Tables
1-1 Summary of available reports related to the outfall monitoring program 01
1-2 Summary of trigger parameters... 2.6... eee eee eee 03
1-3 Summary of MWRA outfall monitoring program................. 06
21 Effluent thresholds compared to 1996 monitoring results........... 12
2-2 Maximum 1996 primary effluent contaminant concentrations
compared to dilution adjusted water quality criteria.............. 16
3-1 Water column thresholds compared to 1996 results .............. 23
3-2 Minimum DO concentration and percent saturation:
1996 and baseline period... 1... 6 ee eee eee 24
3-3 DO saturation thresholds violations..............0 00-0 e eee eee 25
3-4 Plankton thresholds comparison... .. 2... 66. e eee eee eee eee 26
3-5 Shellfish monitoring stations for PSP... 22... eee eee eee 27
4-1 Benthic thresholds compared to 1996 monitoring results........... 4]
4-2 1996 diversity data for the midfield stations.................... 41
4-3 Comparison of mean regional diversity values ............-.---. 42
4-4 Toxic contaminant thresholds and 1995 data
for eight nearfield stations... 0... 6... 44
5-1 Fish and shellfish thresholds compared to 1996 monitoring results. . . . 50
5-2 Comparison of average body burdens of deployed mussels
for selected organic compounds and metals..........--..20.005 54
MWRA : OUTFALL MONITORING OVERVIEW REPORT: 1995 / III
List of Figures
1-1 Distances of the new outfall from selected sensitive areas
in MA and Cape Cod Bays... 0... eee teen nee 02
2-1 Total Nitrogen load discharged from the Deer Island and Nut Island......... 13
2-2 Monthly average BODS in the Deer Island Treatment Plant effluent.......... 13
23 Daily average fecal coliform in effluent.... 0.0.0... 0... cece ee ee eee 15
2-4 Monthly average TSS in the Deer Island Treatment Plant effluent ........... 15
3-1 Nearfield and farfield water column sampling locations.................- 19
3-2 Water quality modeling results near future outfall... 2.0.0... eee 24
3-3 Annual Water Column Cycle of Massachusetts Bay ......... 0.0000 e eee 28
3-4 1996 daily precipitation and river discharge data.... 0.2.2.0... . eee eae 29
3-5 1996 moored salinity sensor data... .... cece cee ees 30
3-6 1996 moored temperature sensor data 11... eee cece eee 30
3-7 1996 seasonal density cycle in the nearfield.. 2.2.2.0 6. 31
3-8 1992-1996 chlorophyll a averages in the nearfield.....................0, 31
3-9 Nearfield DIN concentrations for 1992-1996 2.2... ccc eee cee eee eee 32
3-10 1992-1996 dissolved oxygen cycle in surface
and bottom waters in the nearfield...... 0.0... cece eee eee ee 32
3-11 1992-1996 dissolved oxygen cycle in surface and bottom waters
in Stellwagen Basin. 0... 2... cece etree 34
3-12 Rate of decline of dissolved oxygen concentrations
in bottom waters in the nearfield.. 0.2... eee eee es 34
4-1 Soft-bottom benthic stations in the Bays... 6.1... 0... eee eee ee eee 37
4-2 Nearfield and midfield soft-bottom stations......... 0.0... sce e eee eee 38
43 Boston Harbor benthic sampling stations ....... 0.0.0... eee eee 39
44 Transect locations for nearfield hard-bottom video survey...............-- 40
45 Benthic nutrient flux sampling locations... 2... 2... 42
4-6 Distribution of amphipod tube mats in Boston Harbor................... 45
4-7 Soft-bottom benthic community diversities at nearfield
and midfield stations ©... 6... ees 46
5-1 Sampling stations for winter flounder, lobster and mussels during 1996. ...... 49
5-2 Prevalence of CHV near the future outfall site: 1991-1996 ................ 51
5-3 Mercury, PCB, DDT and PAH concentrations in flounder 1992-1996 ......... 53
5-4 Mercury, PCB, DDT and PAH concentrations in lobster 1992-1996........... 53
5-5 Comparison of PCB body burdens reported as dry weight or lipid-normalized
concentrations for flounder, lobster and mussel...............-.0.00 00s 55
5-6 Indicator LMW PAH Bioaccumulation in mussels near
Deer Island Discharge 1987-1996 0.6... eee 56
Executive Summary
The people of the metropolitan Boston area, through the MWRA, are in the midst of an
ambitious program to upgrade their sewage treatment facilities and improve the quality of MWRA’s baseline outfall
Boston Harbor. This program includes the elimination of sludge discharges to the harbor, monitoring program has
construction of new primary and secondary sewage treatment plants, and relocation of the gathered considerable
current Boston Harbor effluent discharge points to a new location in Massachusetts Bay.
Sludge discharge ceased in 1991 and the new Deer Island primary treatment facility went
on-line in January 1995. In August 1997, the first part of secondary treatment began opera-
tion. The second phase of secondary treatment (adequate for 90% of the effluent flow) will Harbor, Massachusetts Bay,
information documenting
existing conditions in Boston
begin operation in early 1998, and in late 1998 the new effluent discharge outfall to and Cape Cod Bay. Post-dis-
Massachusetts Bay is expected to be operational. This report presents data from 1996 and charge monitoring will be
reflects the primary treatment system operating during that period. used to evaluate conditions
after the new outfall is
A number of concerns have been raised regarding potential environmental impacts associat- operational.
ed with the relocation of the wastewater discharge to Massachusetts Bay. In order to assure
that these concerns are addressed, MWRA developed a Contingency Plan and an outfall
monitoring program, and documented these in a series of reports. The Contingency Plan
(MWRA 1997) develops expectations for environmental quality in Massachusetts Bay and
Cape Cod Bay. The expectations are expressed as Caution and Warning Levels that would
trigger action if they are exceeded. Those trigger levels are compared to environmental
monitoring results in this report, the annual Outfall Monitoring Overview, which will also
describe any actions taken in response to an exceedance of a caution or warning level when
the outfall is operational. The monitoring results are obtained following the procedures
detailed in a report called the Outfall Monitoring Plan (MWRA 1991, 1995). The effluent monitoring
The outfall monitoring program consists of two main phases. Baseline studies which com- program characterizes ;
MWRA wastewater quality.
menced in 1992 are currently underway to document conditions before outfall relocation.
Post-discharge monitoring will commence in late 1998; these studies will evaluate condi-
tions after the new outfall is operational. This report describes the baseline monitoring pro-
gram, summarizes and discusses the 1996 baseline program results, and summarizes post-
discharge monitoring Caution and Warning Levels. The 1999 report will be the first Outfall
Monitoring Overview report that discusses formal actions under the Contingency Plan.
Both phases of monitoring evaluate six categories of wastewater constituents: nutrients,
organic material, toxic contaminants, pathogens, solids, and floatables. These six parame-
ters were evaluated as they apply to four different environmental measurement areas: efflu-
ent, water column, benthic environment, and fish and shellfish.
Wastewater Effluent Monitoring
The baseline effluent program monitors for nutrients, organic material, toxic contaminants,
pathogens, solids, and oil and grease. The primary goal of this program is to ensure that
discharged effluent meets required permit limitations. Effluent monitoring is also used to
evaluate the future effectiveness of the secondary treatment plant by analysis of the effluent
of a pilot secondary treatment plant.
Trigger parameters, thresholds, and 1996 monitoring results for the effluent monitoring pro-
gram are summarized on Table ES-1. The listed warning levels for cBOD, PCB, toxicity,
ii / OUTFALL MONITORING REPORT: 1996 - MWRA
The water column monitoring
program measures marine
water quality and ecological
conditions in Massachusetts
and Cape Cod Bays.
bacteria, and solids are taken from the expected future permit for the fully operational
secondary treatment plant {year 2000). The present plant is operating under an interim
permit and those limits are shown in italics in the last two columns.
In 1996, the total nitrogen Caution Level was exceeded. This exceedance is not a cause for
concern as the Caution Level is set at 90% of the Warning Level, and this exceedance
occurred prior to the implementation of secondary treatment. The 1995 pilot study showed
that secondary treatment can remove an average of 10% of total nitrogen. Therefore, it is
expected that future effluent levels will be less than the thresholds. BOD, acute toxicity,
suspended solids, and plant performance exceeded the warning levels derived from
the expected future permit. Only acute toxicity and plant performance exceeded the interim
permit limits. Each of these parameters should also reduced by secondary treatment.
Effluent monitoring results indicate that improvements made to the MWRA system during
the last few years have generally resulted in improvements in wastewater effluent quality.
Pilot treatment plant results indicate that secondary treatment will significantly reduce the
effluent levels of organic material, suspended solids, and many toxic parameters. As addi-
tional phases of secondary treatment are implemented and toxic source control measures
continue, effluent quality will continue to improve and will result in compliance with feder-
al secondary treatment standards and Massachusetts water quality standards.
Water Column Monitoring Program
The water column monitoring program is designed to measure marine water quality and
ecological conditions in Massachusetts and Cape Cod Bays. Based on extensive predictive
modeling studies, changes in water quality due to outfall relocation are expected to be mini-
mal in Massachusetts and Cape Cod Bays. Detectable changes in water quality are expected
to occur only in the immediate vicinity of the outfall. The water column monitoring pro-
gram provides a basis for detecting changes in water quality and plankton resulting from
the relocation of the effluent outfall. It also provides a basis for monitoring potential food
chain effects on endangered species, such as humpback and right whales.
A number of different parameters are evaluated in the baseline water column monitoring
program. Studies are underway to gather baseline information on nutrient levels, tempera-
ture, salinity, algae, and dissolved oxygen in the marine system. Interpretation of the base-
line data requires an understanding of the seasonal cycle. As with other water bodies, the
Massachusetts and Cape Cod Bay system follows an expected regular seasonal pattern but
with considerable spatial and temporal variability of complicated interrelated processes.
Starting with the cold well-mixed nutrient-rich waters of winter, the brightening sun of
spring provides the light needed for algae (phytoplankton) to grow. Their abundant growth
forms a spring algae bloom which begins to deplete nutrients, especially nitrogen. Spring
also brings stratification of the water column due to increased sunshine and freshwater
runoff that result in warmer and slightly fresher surface waters. The spring bloom ends as
algae deplete the nutrients in surface waters and are blocked from nutrient-rich bottom
waters by stratification. During summer, the algal biomass is less overall with the highest
biomass located at the boundary between surface and bottom waters (thermocline) where
there is a balance between the algal requirement for both light and nutrients. This contin-
ues until the fall, when stratification begins to weaken, so that storms are able to mix the
water column, bringing nutrients to surface waters and resulting in a fall algal bloom.
MWRA + OUTFALL MONITORING REPORT: 1996 / iii
Parameter
Total Nitrogen
TABLE ES-1
Effluent Thresholds Compared to 1996 Monitoring Results
Caution Level
Total nitrogen annual
Warning Level
Total nitrogen annual loading > 14,000
1996 Results
Annual loading = 12,692 metric tons, slightly
(nutrients) loading > 12,500 mtons/year | mtons/year. exceeded the Caution Level.
cBOD None. Expected levels: 40 mg/L weekly, Daily Deer Island BODS5 range from 33 to 129 mg/L
(organic material) 25 mg/L monthly. with an average of 73 mg/L. Monthly Deer Island
Current interim permit limit = BODS range from 38 to 67 mg/L with an average of
140 mg/L monthly. 52 mg/L. Pilot secondary effluent monthly average
= 10 mg/L. cBOD is typically less than BODS.
Toxics None. PCB (as Arochlors) limit = PCBs as Arochlors were all below detection limits.
(toxic contaminants) 0.045 ng/L monthly. Monthly total PCB concentrations: from 0 to 35.9
ng/L with an average of 8.4 ng/L.
Toxicity None. Acute: effluent LC50 for shrimp <50% Acute: 11 of 12 shrimp tests had LC50 < 50%
(toxic contaminants) effluent. Chronic: effluent NOEC for fish —_| effluent. Chronic: No fish growth tests had NOEC
(silverside) growth and sea urchin < 1.5% effluent; sea urchin tests are not yet
fertilization <t.5% effluent. implemented.
Interim acute limit: shrimp NOEC < 20% | Acute: 6 of 12 tests violated interim shrimp 20%
effluent Current chronic limits: minnow NOEC limit. Chronic: no violations of current minnow
and red algae NOEC < 10% effluent 10% NOEC limit; All tests failed
current red algae 10% NOEC limit.
Pilot secondary effluent > 50% for chronic NOEC for
silverside and sea urchin. Five pilot plant acute tests
had LC50 = 100%
Bacteria None. Expected level: 14,000 fecal current No exceedances of expected level or the current
(pathogens) coliform/100 mL at point of dechlort- monthly limit of 200 fecal coliform/100mL.
nation (weekly mean, monthly 90th
percentile, and 24 consecutive hours).
Current interim permit limit = 200 fecal
coliform/100 mL monthly average.
Suspended None. Expected levels: 45 mg/L weekly, Range at Deer Island from 24 to 133 mg/L, with an
Solids 30 mg/L monthly. average of 52 mg/L. Pilot secondary effluent
Current interim permit limit = monthly average = 9 mg/L.
110 mg/L monthly.
Floatables None. Floatables less than 5 gal/day. Not measured until secondary treatment
plant is on line.
Oil and Grease None. 15 mg/L weekly. Maximum weekly = 6.5 mg/L.
(floatables)
Plant Performance | More than 5 violations of Operating in violation of the expected Violation of nearly all the expected limits on BOD,
expected permit
requirements per year.
permit requirements more than 5% of
the time over a year.
solids, and acute toxicity, most of the time.
Violation of interim permit limits for acute toxicity, and
on one occasion for removal efficiency of BOD.
The reader is directed to the glossary and acronym summary at the end of the report.
Current interim permit limits are presented in the Warning Level column in italics.
iv / OUTFALL MONITORING OVERVIEW REPORT: 1996 * MWRA
Trigger parameters, thresholds, and 1996 monitoring results for the water column program
Benthic studies measure are summarized on Table ES-2. Monitoring results show that 1996 was similar to other
bottom-dwelling ecological years with some notable differences. The stratification period was relatively short because
communities and sediment of a hurricane in early September that resulted in much earlier mixing of the water column
quality characteristics. than in previous years. The 1996 spring bloom was the largest but the fall bloom was the
smallest during the baseline period. On average, chlorophyll concentrations during 1996
were relatively low compared to other baseline years. The phytoplankton species composi-
tion during spring and fall blooms was similar to previous years, with centric diatoms dom-
inating the spring bloom and pennate diatoms dominating the fall bloom. The zooplankton
community in the outfall nearfield in 1996 consisted of an assemblage of offshore and
nearshore species, similar to previous years. No shellfish toxicity or significant numbers of
toxic or nuisance algae were observed in 1996. Minimum dissolved oxygen concentrations
in bottom waters in 1996 were higher than in 1994 and 1995 because initial dissolved oxy-
gen concentrations were higher (greater than 12 ppm), bottom water temperatures were
generally lower, and fall overturn occurred earlier. As in previous years, monthly average
dissolved oxygen saturation levels declined below the Warning Level in the nearfield, and
below the Caution Level in Stellwagen Basin. These low saturation levels were due more to
higher water temperatures, as the concentrations and decline rates were fairly average.
These findings suggest that the OMTF needs to re-evaluate the applicability of the current
dissolved oxygen threshold levels.
A total of six whales were sighted during the 1996 nearfield surveys: one right, one fin, one
unidentified and three minke whales.
Benthic Studies
Benthic Studies are designed to evaluate the sea floor environment in Boston Harbor and
Massachusetts and Cape Cod Bays. These studies are designed to assess potential impacts
to the Massachusetts and Cape Cod Bays sea floor resulting from relocation of the outfall.
Benthic studies also provide a means to document recovery of Boston Harbor following
improvements to the MWRA system.
Trigger parameters, thresholds, and 1996 monitoring results for the benthic program are
summarized on Table ES-3. In Massachusetts Bay, the benthic sedimentary environment,
or habitat, is highly diverse, with large variability in sediment type over relatively short dis-
tances. The benthic biological communities also vary spatially, reflecting a strong influence
of sediment type on the benthic community characteristics. In addition, the benthic envi-
ronment in the nearfield is highly changeable, with dramatic shifts in both sediment type
and benthic organisms occurring after storm events. The dominant benthic species in 1996
and 1995 was also abundant in 1987, but not in 1992 through 1994. Benthic organism den-
sities in Massachusetts Bay are moderately high and the community structure does not
reflect stressed conditions. The numbers of species in the benthic community are similar in
the nearfield and farfield, but the types of species are different. Sediment sampling for con-
taminant analysis was not performed in 1996. The most recent results, from 1995, showed
contaminant concentrations that were generally below environmental criteria.
In Boston Harbor, the benthic ecosystem has improved dramatically in the past few years.
This improvement is associated with an increase in abundance of a pollution sensitive
amphipod, likely related to sediment quality improvement. Increased amphipod coloniza-
tion, in turn, appears to be increasing the rate of sediment quality improvement.
MWRA + OUTFALL MONITORING OVERVIEW REPORT: 1996 /v
Parameter
Dissolved oxygen
concentration in
TABLE ES-2
Water Column Thresholds Compared to 1996 Monitoring Results
Caution Level
Monthly mean DO is less than 6.5 ppm or 80% of
saturation levels for any one month during stratifica-
Warning Level
Monthly mean DO is less than 6 ppm
or 75% of saturation levels for any one
1996 Resulis
DO saturation above
Caution Level in September
Nearfield region | tion (June-Oct.) month during stratification (June-Oct.} (87.2%).
bottom waters (See Table 3-2)
Dissolved oxygen | Monthly mean DO is less than 6.5 ppm or 80% of Monthly mean DO is less than 6 ppm DO saturation below
concentration in
saturation levels for any one month during stratifica-
or 75% of saturation levels for any one
Caution Level in October
Stellwagen Basin | tion (June-Oct.) month during stratification (June-Oct.) (79.2%).
bottom waters (See Table 3-2)
Dissolved oxygen | DO depletion rate is greater than 1.5 times DO depletion rate is greater than 2 1992-96 Average Baseline
depletion rate in
Nearfield region
the baseline rate during stratification
(June-Oct.), -0.040 mg/Liday.
times the baseline rate during stratifi-
cation (June-Oct.), -0.053 mg/L/day.
Rate: -0.026 mg/L/day
bottom waters 1996 Rate:
-0.025 mg/Liday
Chlorophyll in Annual mean concentration greater than 1.5 times Annual mean concentration greater 1992-96 Baseline:
Nearfield region the baseline annual mean, 2.80 jug/L. than 2 times the baseline annual 1.87 pg/L
mean, 3.74 pg/L. 1996: 1.54 pg/L
Chlorophyll in Season mean concentration exceeds 95th percentile | None. Spring: 2.43 mug/L.
Nearfield region —_| of the baseline seasonal distribution. Summer: 0.78 pg/L
Spring: 2.71 pg/L Fall: 1.47 pg/L
Summer: 2.27 pg/L
Fall: 4.44 wo/L
Nuisance algae in | Alexandrium tamarense None. Alexandrium tamarense
Nearfield region Season mean population densities exceed 95th per- Spring: 0 cells/L
centile of the baseline seasonal mean. Summer: 0 cells/L.
Spring: 2.34 cells/L Fall: 0 cells/L
Summer: 26.1 cells/L (See Table 3-3)
Fall: 7.57 cells/L
PSP extent in New occurrence. PSP has never been observed None. No occurrences.
Farfield region at 3 of the 18 monitoring stations (see Table 3-4).
Zooplankton Nearfield assemblage shifts from a transitional None. Transitional assemblage in
assemblage in community towards an inshore community. nearfield region.
Nearfield region Inshore: Acartia, Eurytemora, Centropages hamatus
Offshore: Calanus, Pseudcalanus, Centropages typi-
cus, Oithona
Nearfield: Transitional between two regions.
Initial effluent dilu-
tion at new outfall
location
None.
Effluent dilution less than that set by
the NPDES permit.
No data until outfall is
online.
vi/ OUTFALL MONITORING OVERVIEW REPORT: 1996 - MWRA
Fish and Shellfish Monitoring Program
The fish and shellfish
. The fish and shellfish monitoring program samples and evaluates key natural resources in
program measures toxic . : . .
; the marine environment, focusing on flounder, lobster, and mussels. This program evalu-
contaminant effects on ates potential risks to human health and the environment from toxics contamination in fish
flounder, lobster, and and shellfish. Fish and shellfish studies also provide a basis for evaluating the recovery of
mussels, Boston Harbor biota following MWRA upgrades.
Trigger parameters, thresholds, and 1996 monitoring results for fish and shellfish are sum-
marized on Table ES-4. In 1996, as in previous years, the contaminant concentrations in
fish and shellfish at all sites have consistently been well below levels that might cause any
concern through human consumption. Nevertheless, the pattern of contamination provides
evidence of the degree of exposure of the fish. In general, contaminant concentrations in
flounder meat decline progressively from Boston Harbor to the future outfall site to Cape
Cod Bay. However, mercury concentrations did not follow any specific spatial pattern, indi-
cating that the most significant mercury sources may be more regional (e.g. atmospheric
deposition) rather than local (e.g. point source discharges) in nature. Liver lesions in floun-
der continue to be present at all sites. The number of lesions in 1996 were slightly
increased over the 1995 levels, but are still much less than 1992 levels.
Contaminant concentrations in lobster meat generally followed the same spatial pattern as
contaminants in flounder meat, with the highest organic concentrations in Boston Harbor
and the lowest in Cape Cod Bay, and no definite pattern in mercury concentrations. Metal
concentrations in lobster hepatopancreas showed no overall trend, with some metal concen-
TABLE ES-3
Benthic Thresholds Compared to 1996 Monitoring Results
Parameter Caution Level Warning Level 1996 Results
Community Structure | Species diversity, composition, None. Shannon-Wiener Diversity Index
(Diversity, Species and relative abundance patterns Midfield mean = 2.8
Composition, and measured in the midfield appre- (Range 1.95 - 3.30)
Species Abundance) | ciably depart from those mea-
in outfall midfield area | sured during the baseline moni- (See also Table 4-2)
toring period, after factoring out
the effect of storms on sediment Results in similar range to
texture. Specific diversity thresh- previous years.
‘ old values are being developed.
Depth of Oxygenated | RPD depth declines by half. None. No 1996 data available;
Sediments [Redox The threshold value is under 1995 results: Nearfield
Potential development. mean = 3.5 cm
Discontinuity (RPD) {Range 1.8 - >6.2 cm)
Depth] in outfall
nearfield area.
Toxic Contaminant
Concentrations in
outfall nearfield area.
Nearfield mean toxic contami-
nant concentrations greater than
90% of EPA sediment criteria.
Nearfield mean toxic contaminant concentra-
tions greater than EPA sediment criteria or the
NOAA Effects Range Median (ER-M) value.
Examples: NOAA ER-M values:
PCBs = 180 ng/g
Mercury = 0.71 ug/g
No 1996 data available;
1995 example results:
PCBs: Geometric Mean = 4 ng/g
Range = 1.1 - 53 ng/g
Mercury:
Geometric mean = 0.16 g/g
(See also Table 4-4)
FALL MONITORING OVERVIEW REPO
TABLE ES-4
Fish and Shellfish Thresholds Compared to 1996 Monitoring Results
Parameter Caution Level Warning Level 1996 Results
Mercury in fish Annual mean mercury concentration in flounder, lob- | Annual mean mercury concentration in } Flounder: 0.1 g/g
and shellfish ster, and caged mussel meat greater than 0.5 ug/g | flounder, lobster, and caged mussel Lobster: 0.18 g/g
from Outiall site | wet weight (50% of the US FDA action level). meat is greater than 0.8 j19/g wet Mussel: 0.03 ug/g
weight (80% of the US FDA action
level).
PCBs in fish and J Annual mean PCB concentration in flounder, lobster, | Annual mean PCB concentration in Flounder: 0.04 ya/g
shellfish from and caged mussel meat greater than 1 ug/g wet flounder, lobster, and caged mussel Lobster: 0.02 pg/g
Outfall site weight (50% of the US FDA action level). meat is greater than 1.6 jig/g wet Mussel: 0.02 g/g
weight (80% of the US FDA action
level).
Lead in mussels | Annual mean lead concentration in caged mussel Annual mean lead concentration in Mussels: 0.3 pg/g
at Outfall site meat greater than 2 g/g wet weight. caged mussel meat is greater than
3 19/9 wet weight.
Lipid-normalized | Lipid-normalized toxic concentrations in flounder, None. Concentrations in wg
toxics in fish and | lobster, and caged mussel meat greater than two toxic per gm lipid
shellfish from times the interim baseline concentrations (i.¢., aver- Flounder DDT: 1.02
Outtall site age value from 1992-1996 data). The final baseline Flounder PCB: 10.19
concentration will be based on 1992-1998 data. Lobster DDT: 0.56
Interim baseline (1992-1996) concentrations in Lobster PCB: 4.44
Hg toxic per gm lipid. Mussel DDT: 0.28
Flounder DDT: 1.62 Mussel PAH: 1.35
Flounder PCB: 14.94 Mussel PCB; 0.94
Lobster DDT: 0.56
Lobster PCB: 4.46
Mussel DDT: 0.66
Mussel PAH: 6.22
Mussel PCB: 2.58
Liver disease Flounder liver disease (CHV) incidence greater None. Flounder CHV prevalence:
incidence in fish | than interim harbor prevalence (1991-1996): 48% 22%
from outfall site The final baseline prevalence will be based on
1991-1998 data.
trations higher in Boston Harbor, others higher in Cape Cod Bay, and others similar at all
stations. All levels are below those of concern, and are expected to improve as secondary
treatment leads to improved effluent and water quality in Boston Harbor.
Summary of Exceedances
In 1996, four parameters exceeded Warning Level thresholds, and another two exceeded
Caution Level thresholds. Five effluent parameters were among these exceedances; BOD,
TSS, toxicity, and plant peformance exceeded the Warning Levels and total nitrogen exceed-
ed the Caution Level. Secondary treatment has been shown to reduce all of these parame-
ters, and therefore it is expected that there will be no exceedances once secondary treat-
ment is on-line. The Caution Level for Stellwagen Basin DO saturation was also exceeded.
This exceedance, along with DO concentrations and DO saturation exceedances from previ-
ous monitoring years, strongly suggest that the OMTF needs to re-evaluate the applicability
of the current DO threshold levels.
MWRA : OUTFALL MONITORING OVERVIEW REPORT: 1996 / 01
1.0 INTRODUCTION
1.1 Report Objectives and Content
The outfall monitoring program is an important component of the Massachusetts Water
Resources Authority's (MWRA’s) overall program to improve the quality of Boston Harbor.
The outfall monitoring program provides the means to identify, measure and respond to any
impacts associated with the relocated outfall, as described in the Outfall Monitoring Plan
(MWRA 1991, 1997). The Contingency Plan (MWRA 1997) outlines the MWRA’s response
program in case any unexpected impacts occur. The Outfall Monitoring Overview Report is
intended to serve as an annual companion document to the Contingency Plan.
The objective of the Outfall Monitoring Overview Report is to describe the monitoring
program results on an annual basis and compare those results to established environmental
benchmarks or threshold levels for trigger parameters (described below). In addition, the
report will summarize any actions taken pursuant to the Contingency Plan during the year.
Monitoring program results and threshold comparisons for field data collected through 1996
are presented in this report. Since data collection started in 1992 and the future outfall is
not yet operational, the data in this report represent the fifth year of the baseline collection
period. As such, comparisons of data to thresholds are used to test the validity of the
threshold values. Also, the report provides interim threshold values for those parameters
for which thresholds will be determined from a full set of baseline data. Finally, since the
outfall is not operational, actions pursuant to the Contingency Plan are not addressed in this
1996 report, but will be in future reports.
A number of related reports have been, and will continue to be, produced by MWRA.
These reports provide substantially more detailed information on the monitoring program
and results than the summary provided in this report. Related program reports are
summarized on Table 1-1.
TABLE 1-1
The outfall monitoring
program was developed to
measure baseline conditions,
changes from baseline,
and potential impacts
to Massachusetts and
Cape Cod Bays.
The Outfall Monitoring
Overview Reports serve
as annual companion
documents to the
Contingency Plan, reporting
monitoring results and
comparison to threshold
values.
Summary of Available Reports Related to the Outfall Monitoring Program
Report |
Outfall Monitoring Plan
Phase | — Baseline Studies (MWRA 1991)
Phase Il — Post-Discharge Monitoring (MWRA 1997)
monitoring programs,
Description/Objectives
Discusses goals, strategy, and design of baseline and post-discharge
Contingency Plan (MWRA 1997)
MWRA’s planned contingency measures.
Describes development of trigger parameters and threshold values, and
Program Area Synthesis Reports (Annual)
Summarize, interpret, and explain annuat results for effluent, water column,
benthos, and fish and shellfish monitoring areas.
Toxics and Nutrients Issues Reports (Annual)
in Massachusetts and Cape Cod Bays.
Discuss, analyze, and cross-synthesize data related to toxic and nutrient issues
The State of Boston Harbor Reports (Annual)
monitoring results.
Discuss a range of topics related to Boston Harbor and recent harbor
A current listing of the technical reports can be found on the internet at http/www.mwra.state.ma.us
02 / OUTFALL ORING REPORT: 1996 - MWRA
This report is organized into the following sections: (1) this introduction that discusses the
overall background and components of the monitoring program; (2) four sections that dis-
cuss the issues, design, comparison to thresholds, and recent results for each area of the
monitoring program: effluent, water column, benthic studies, and fish and shellfish; and
(3) a glossary and summary of acronyms.
1.2 Background
The outfall monitoring In 1986 the MWRA initiated a program to end longstanding violations of the Clean Water
Act associated with the discharge of sewage sludge and effluent in Boston Harbor. This
program includes the relocation of the treated effluent discharge point to a location in
Massachusetts Bay (Figure 1-1) approximately 9.5 miles from the present Deer Island
program was developed
to resolve concerns about
outfall relocation. outfall. Discharge of effluent through the new outfall is expected to begin in 1998.
The U.S. Environmental Protection Agency (EPA) and the National Marine Fisheries Service
(NMFS) assessed the potential impacts associated with the discharge of MWRA’s waste-
water effluent into Massachusetts Bay. Both the EPA and NMFS determined that there
would not be significant water quality or biological impacts associated with the project.
This conclusion was documented in the EPA’s Supplemental Environmental Impact
Statement (SEIS) and Biological Assessment and the NMFS’s Biological Opinion.
Even though minimal impacts were predicted from the relocated, cleaner discharge,
concerns remained with respect to the potential environmental effects associated with the
relocation of the wastewater discharge to Massachusetts Bay. General concerns identified
\ |
— 42°30"
X New Outfall
X Existing Outfalls
— 42°15"
FIGURE 1-1 a0
Distances of the new outfall
from selected sensitive areas
in Massachusetts and a
Cape Cod Bays. The existing
outfalls are near Deer Island
and the more southerly Nut
Island. The new outfall is 9.5
miles from Deer Island.
41°45"
71°00" 70°45" 70°30" 11s 70°00"
MWRA + OUTFALL MONITORING REPORT: 1996 / 03
with respect to the relocated discharge were potential aquatic life, human health, and aes-
thetic impacts in Massachusetts and Cape Cod Bays.
An Outfall Monitoring Task
Force provides MWRA with
Suidance and recommenda-
tions on the outfall monitor-
In order to assure that discharge from the new outfall does not result in adverse impacts to
human health or the environment, the EPA and the Massachusetts Executive Office of
Environmental Affairs (EOEA) required the development of an outfall monitoring program.
The objective of the monitoring program was to establish baseline conditions of the
Massachusetts and Cape Cod Bay ecosystem and measure any future impacts on the system
due to outfall relocation. At the direction of the EOEA, an Outfall Monitoring Task Force
ing program.
(OMTF) was formed to provide MWRA with guidance and recommendations on the devel-
opment of a monitoring plan. The OMTF is composed of a science council of academic sci-
entists, with participation by representatives from federal and state regulatory agencies and
citizens’ groups.
Numerous scientific studies performed as part of the outfall
siting process in 1986 and 1987 were used as the basis by
MWRA and the OMTF for the development of the Outfall
Monitoring Plan in 1991. Baseline studies, dedicated to deter-
mining background conditions in the Bays, began in 1992 (except
for flounder studies which began in 1991) and will continue until
the new outfall becomes operational in late 1998. Then, similar
post-discharge studies, dedicated to determining the effects of the
discharge, will begin.
The OMTF reviews the monitoring results on an ongoing basis
and works with MWRA to implement cost-effective modifica-
tions that better address public and technical concerns. In May
1996, a technical workshop with MWRA scientists, OMTF
members, and nationally recognized scientists was held to eval-
uate the outfall monitoring program. The workshop included a
review of monitoring methods and results, trigger parameters
and threshold values, and an evaluation of changes that would
improve the effectiveness of the program. Some of the program
changes implemented in 1996, with OMTF concurrence, includ-
ed: (1) the temporary suspension of some portions of the ben-
thic program (sediment toxics chemistry and sediment profile
image studies), and, (2) the performance of pilot video plank-
ton recorder studies.
1.3 Trigger Parameters and
Thresholds
The outfall monitoring program provides the basis for evaluating
potential impacts associated with the relocated outfall and the
need for action under the Contingency Plan. This report evalu-
ates monitoring program results based on specific measurement
indicators of changes from benchmark environmental conditions.
These measurement indicators were designated as trigger para-
TABLE 1-2
Summary of Trigger Parameters
Monitoring Trigger
Area Parameter
Effluent
Total Suspended Solids
Biochemical Oxygen Demand
Pathogenic Indicator Bacteria
Nitrogen Loading
Toxic Metals and Organic Chemicals
Toxicity Testing
Floatables
Oil and Grease
Plant Compliance with Permit Limits
Water Column
Dissolved Oxygen Concentration
Dissolved Oxygen Respiration Rate
Chlorophyll
Nuisance and Noxious Algae
Zooplankton
Diffuser Mixing
Benthos
Benthic Community Structure
Sediment Oxygen
Sediment Toxic Metal and Organic
Chemicals
Fish and Shellfish
Mercury and PCBs in Flounder, Lobster,
and Mussels
Lead in Mussels
Lipophilic Toxic Contaminants
Liver Disease in Flounder
04/ OUTFALL MONITORING REPORT: 1996 - MWRA
MWRA uses two levels of
threshold values to evaluate
the need for action under the
Contingency Plan:
m Caution Level exceedances
indicate the need for
increased study or attention.
a Warning Level exceedances
indicate the need for action to
avoid potential environmental
impact, triggering the devel-
opment and implementation
of a response plan.
meters in the Contingency Plan. A summary of the current trigger parameters is presented
in Table 1-2. Each trigger parameter has a quantitative, or in some cases a qualitative,
threshold that indicates the potential for impacts. Once discharge begins, the exceedance of
trigger parameter threshold values will automatically trigger MWRA action.
There are two types of thresholds under development that will be used to alert MWRA and
others to different degrees of potential environmental risk. Caution Level exceedances
would indicate the need for more intensive study or increased attention. Warning Level
exceedances would indicate the need for a response to avoid a potential environmental
impact. The trigger parameters and thresholds for each of the measurement areas are dis-
cussed in detail in the corresponding report section below.
The definition of a threshold exceedance depends on the trigger parameter. It is desirable
for most of the measured parameters (e.g. contaminant concentrations, treatment plant
violations, algae and liver disease) to remain below the threshold. Other parameters
(e.g. dissolved oxygen level, dilution, dissolved oxygen penetration into sediments, percent
effluent with specified toxicity level, and diversity) should remain above the threshold.
The OMTF has used the following sources to establish threshold values for the trigger
parameters:
m Limits expected in the forthcoming EPA/MADEP NPDES permit
m= State water quality standards
m Predictions and assumptions made about the impacts of the discharge during the
preparation of the EPA’s SEIS
m Expert guidance and opinion
Expert guidance has helped refine trigger parameters and associated threshold
values. The technical workshops held in May 1996 resulted in a recommendation that
MWRA should revise the proposed Caution and Warning Levels. Specifically, it was recom-
mended that MWRA focus on a reduced set of critical trigger parameters, define the trigger
parameters more precisely, allow for seasonality of the natural baseline in the definition of
thresholds, and choose threshold levels which are more protective of the environment.
In addition, in the case where the NPDES permit limits serve to define the Warning Levels,
it was determined that it would not be useful to try to define a corresponding Caution
Level. This report, the 1996 Outfall Monitoring Overview Report, reflects those recommen-
dations and decisions.
Several of the trigger parameters are expressed as change relative to baseline values.
Because the baseline period is ongoing, interim thresholds are calculated as an exercise in
this report based on the existing five years of monitoring data. The thresholds will be
updated each year until just before the outfall begins discharging, when the final threshold
values will be calculated.
MWRA : OUTFALL MONITORING REPORT: 1996 / 05
1.4 Monitoring Program Summary
_ ; ; The outfall monitoring
The outfall monitoring program was developed and has evolved with continuous atten- program is designed to
tion to a number of specific goals and objectives. The Outfall Monitoring Program is .
. provide measurements of
intended to: _, ;
m Develop baseline data from which future changes can be evaluated, six primary constituents of
m Test whether the impact of the discharge is within the bounds predicted concern within the context
in the SEIS, of four program areas:
m= Evaluate compliance with threshold values for trigger parameters, and ae water column,
enthic environment,
@ Measure and evaluate potential impacts to Massachusetts and Cape Cod Bays ’
associated with outfall relocation. and fish and shellfish.
The monitoring program has focused on the following six wastewater constituents for
determining the environmental impact of coastal discharges of treated sewage, as
recommended by the National Research Council (NRC, 1993):
= = Nutrients
Organic material
Toxic contaminants
Pathogens
Suspended solids
m@ Floatables
The outfall monitoring program is designed to obtain data that will allow an assessment
of the water quality and ecological impacts of these constituents within the context of four
monitoring program areas: effluent, water column, benthos, and fish and shellfish.
A summary of the monitoring program is presented in Table 1-3.
Environmental data generally demonstrate considerable variability in both space and time
due to the inherent behavior of natural systems. The outfall monitoring program is designed
to provide data with sufficient temporal and spatial detail to characterize the variability of
the Massachusetts and Cape Cod Bays system. Each of the different program areas has
different requirements in this regard and the monitoring program design reflects these
differences. For example, the water column in Massachusetts and Cape Cod Bay experi-
ences considerable temporal variability and spatial patchiness. The combination of frequent
boat-based surveys, continuous monitoring at a mooring, and satellite imagery in the water
column program is designed to resolve this variability and provide detailed characterization
of the water column system. The benthic environment displays at least as much
spatial patchiness as the water column but much less temporal variability. Correspondingly,
benthic monitoring is much less frequent than water column monitoring but provides
spatial coverage that is similar. The outfall monitoring
program’s data management
15 Data Management and Analysis system allows interactive
Since the beginning of the outfall monitoring program in 1992, more than 200 million use, as well as permanent
pieces of data have been generated and compiled. As the program continues, the amount archiving of monitoring data.
of compiled data will grow even larger. In order to meaningfully use this large mass of
data, a coupled computerized database system and Geographical Information System (GIS)
06 /
OUTFALL MONITORING REPORT: 1996 - MWRA
Effluent Sampling
Objective
Characterize wastewater
discharged from Deer Island
Treatment Plant and pilot
secondary treatment plant
TABLE 1-3
Summary of MWRA Outfall Monitoring Program
EFFLUENT MONITORING
« Weekly
© Dail
* Weekly (metals); 3 times/Month (organics)
* 3Times/Day
* Daily
* Weekly
* Weekly
WATER COLUMN MONITORING
Sampling Locations and Schedule
Analyses
* Nutrients
* Organic material (cBOD)
* Toxic contaminants
* Pathogens
* Solids
© Oil & Grease
« Floatables (starting in 1998)
on a regional scale
through satellite imagery
Nearfield Surveys Collect water quality data * 17 surveys/year * Temperature * Nutrients
near future outfall location * 21 locations (See Figure 3-1) * Salinity * Solids
* Dissolved oxygen * Chlorophyll
* Plankton + Water clarity
* Marine mammal’ * Photosynthesis
sea turtle * Respiration
observations
Farfield Surveys Collect water quality data * 6 surveys/year Same as Nearfield Surveys except no
throughout Massachusetts * 26 locations (See Figure 3-1) mammaliturtle observations
and Cape Cod Bays
Plume Track Surveys } Track location and * 4surveys/year in 1999 © Salinity »* Nutrients
characteristics of © Temperature * Metals
discharge plume * Rhodamine dye + Solids
Mooring Provides continuous * Continuous monitoring * Temperature * Chlorophyll
oceanographic data * Single station * Salinity
near outfall * 3 depths © Water clarity
Remote Sensing Provides oceanographic data} * Available daily (cloud cover permitting) * Surface Temperature
BENTHIC MONITORING
© Chlorophyll (not available in 1996)
in Boston Harbor
and Massachusetts Bay
Nutrient Flux Surveys | Evaluate nutrient interactions | * 5 surveys/year * Oxygen demand
between the sediment * 8 locations (See Figure 4-1) * Nutrient flux
and water column * Porewater nutrients
Soft Bottom Surveys Evaluate sediment quality * 60 Boston Harbor stations © Sediment chemistry
(See Figure 4-2)
* 20 nearfield stations (See Figure 4-3)
* 11 farfield stations (See Figure 4-4)
* Benthic community composition
* Sediment profile imaging
Hard Bottom Surveys
Characterize marine
communities in rock
and cobble areas
* 1 survey/year
* 6 transects (See Figure 4-5)
SH AND SHELLFISH MONITORING
* Topography
¢ Substrate
* Benthic community composition
body burden
Flounder Studies Determine contaminant * 1 survey/year * Tissue contaminant concentrations
body burden and * 5 locations (See Figure 5-1) * Physical abnormalities
population health (including histopathology)
Lobster Studies Determine contaminant * 1 survey/year * Tissue contaminant concentrations
* 3 locations (See Figure 5-1)
* Physical abnormalities
Mussel Studies
Evaluate biological
condition and short-term
contaminant bioaccumulation
* 1 survey/year
3 locations (See Figure 5-1)
* Tissue contaminant concentrations
© Physical abnormalities
MWRA + OUTFALL MONITORING OVERVIEW REPORT: 1996 / 07
has been developed. The coupled database/GIS system allows MWRA to store, retrieve,
analyze, and display data from the monitoring program. Arc/Info is used as the GIS
platform. The database management system is an Oracle 7 server networked to PC work-
stations running MS Access. This system allows monitoring data to be entered, analyzed,
and viewed simultaneously by several researchers working at their own computers. The
database is the source of the multi-year data analyzed by researchers in the preparation of
synthesis reports.
For the goals of the program to be met, all of the data must be of known, high quality.
Data quality is maintained through the program-wide use of rigorous Quality
Assurance/Quality Control procedures. Data from field surveys and laboratory analyses
are exhaustively checked and validated to ensure that field equipment was working
properly during surveys and that the analyses met the program’s Quality Control objectives.
Only validated data are loaded onto the centralized database.
MWRA + OUTFALL MONITORING OVERVIEW REPORT: 1996 / 08
2.0 Effluent Monitoring Program
2.1 Effluent Issues
The National Research Council (1993) has recommended consideration of the following six
wastewater constituents in determining the environmental impact of coastal discharges of The constituents of concern
treated sewage: nutrients, organic material, toxic contaminants, pathogens, solids, and in wastewater effluent
floatables. The issues associated with each of these constituents are described below. include:
. a Nutrients
Nutrients a Organic Material
Nutrients are essential for the growth of algae and other aquatic plants. However, excessive = Toxic Contaminants
concentrations of nutrients in the water can be detrimental, and may lead to low dissolved
oxygen levels and eutrophication. For marine and coastal environments, such as the = Pathogens
Massachusetts and Cape Cod Bays system, nitrogen is the most important nutrient, and is = Solids
the focus of effluent monitoring. However, measurements are also made regularly of phos- a Floatables
phorous, and occasionally silica.
Organic Material
Organic material is a concern because as it decays it consumes dissolved oxygen (DO), ,
which is critical to aquatic life. Low levels of DO may have serious effects on fish and other
marine animals. The amount of DO consumed by decomposing organic material in effluent
is the biochemical oxygen demand (BOD) which consists of the nitrogenous biochemical
demand (nBOD) plus carbonaceous biochemical oxygen demand (cBOD). The standard
measurement for BOD is the 5-day BOD test, or BOD5. The BODS measures both the car-
bonaceous and nitrogenous BOD. Because nitrogen is considered under measurements of
total nitrogen in effluent, and because the ratio of oxidized/reduced forms of nitrogen vary
with a number of factors including temperature, future measurements of organic material
will focus on cBOD.
Toxic Contaminants
Toxic contaminants are substances that can cause diseases such as cancer in humans or
organisms through direct contact with or accumulation in living tissue. Toxic contaminants
include trace metals (such as lead, mercury, chromium, and cadmium); volatile organic
compounds (such as benzene, toluene, and chlorinated solvents); semi-volatile organic com-
pounds (including polyaromatic hydrocarbons [PAHs]); polychlorinated biphenyls PCBs;
pesticides (such as DDT); ammonia; and chlorine. To evaluate levels of trace metals and
organic contaminants in the effluent, the MWRA collects and analyzes effluent samples
from the treatment plants at Deer Island and Nut Island. In addition, bioassay tests, which
measure the response of indicator species to treated effluent, are being used to evaluate tox-
icity to various life stages of marine organisms such as shrimp, finfish, red macroalgae, and
sea urchins.
Pathogens
Human pathogens are bacteria, viruses, and protozoa from human and animal waste that
cause disease in humans. Although human pathogens are not known to harm marine life,
they may concentrate in filter feeding shellfish, such as mussels and clams. Human expo-
10 / OUTFALL MONITORING REPORT: 1996 - MWRA
The effluent monitoring
includes NPDES sampling
detailed effluent studies, and
pilot secondary treatment
plant sampling.
sure to pathogens may occur primarily from the consumption of contaminated shellfish and
from incidental ingestion of water while swimming. Fecal coliform bacteria are often used
as an indicator of the presence of human pathogens and to evaluate the effectiveness of
chlorine addition at the treatment plant. MWRA regularly measures the levels of fecal and
total coliform bacteria. Any health effect of pathogens which escape chlorination and are
discharged in marine waters would not extend far from the outfall due to dilution and nat-
ural death of the microorganisms.
Suspended Solids
Suspended solids are small particles of matter, such as mud, sand, or organic debris, sus-
pended in the water column. Solids influence the behavior of toxic contaminants and other
water quality parameters but the primary concern associated with solids is deposition and
the resulting potential for smothering of the bottom habitat and benthic (bottom dwelling)
organisms, Another issue of some concern is the aesthetic effect of loss of clarity of waters
with high suspended solids levels.
Floatables
Floatables are pollutants that sit on the water surface, as opposed to being in the water col-
umn. Typical floatables are plastic tampon applicators, oil and grease. Floatables are pri-
marily an aesthetic problem, although some floatables, such as oil, can be harmful to
marine life.
2.2 Monitoring Program Design
The primary objective of the effluent monitoring program is to characterize waters dis-
charged from the Deer Island treatment plant. Concentrations and variability of chemical
and biological constituents in the treatment plant effluent are measured. These data will
allow comparison to NPDES permit limitations and evaluation of loadings and potential
impacts on Massachusetts Bay.
Under the NPDES program the samples of the Deer Island treatment plant effluent were
collected and analyzed as outlined below. Composite samples are taken over a 24-hour
period, usually at weekly intervals (weekly composite). Compositing provides the best
estimate of the average concentration of contaminants provided that they do not degrade
in the storage unit; those that degrade are collected as a grab sample.
The following samples are collected under the NPDES program:
H Nutrients. A weekly composite sample is analyzed for total Kjeldahl nitrogen,
ammonia, nitrate, nitrite, total phosphorus, and phosphate.
HM Organic material. A daily composite sample is analyzed for 5-day Biochemical
Oxygen Demand. In the future the carbonaceous BOD will be analyzed.
Toxic contaminants. A weekly composite sample is analyzed for trace metals of
concern: silver, cadmium, copper, chromium, mercury, lead, molybdenum, nickel,
and zinc. The analyses incidentally yield data on arsenic, selenium, thallium,
boron, beryllium, iron, antimony, but these are of little concern for this outfall.
MWRA + OUTFALL MONITORING REPORT: 1996 / 11
Three composite samples per month are analyzed for organic contaminants: petro-
leum hydrocarbons, pesticides, PAH, PCB, phenols, and phthalates. Volatile organ-
ic compounds (VOA) are analyzed in three grab samples per month.
—™ Toxicity testing. Three daily composites are currently used in the monthly bioas-
say toxicity tests. The three toxicity tests are: 1) acute mortality in marine mysid
shrimp; 2) chronic survival and growth in sheepshead minnow and 3) chronic
" reproduction in red algae. In the future it is likely that the fish used for testing
will be changed to a more sensitive species, and the red algae be replaced by a
more reliable test organism, the sea urchin.
M Pathogens. Three grab samples per day are analyzed for fecal and total coliform.
Ml Suspended solids. A daily composite sample is analyzed for total suspended
solids.
™ Floatables. A weekly grab sample is analyzed for oil and grease. Beginning
in 1998 the amount of floating material in the final skimmer will be visually
estimated.
In addition to samples collected and analyzed under the NPDES program, other samples
may be collected occasionally to provide more sensitive and detailed information about the
effluent. Those measurements are called the detailed effluent characterization study
(DECS). In 1996 the DECS measurements were made at Deer Island only; every month from
January to June and again in August, two composite samples were taken a few days apart
and analyzed for toxic contaminants. Trace metals analyzed were: silver, cadmium, copper,
chromium, mercury, lead, molybdenum, nickel, and zinc. Organic contaminants analyzed
consisted of 17 persistent chlorinated pesticides, an extended list of PAHs, 20 PCB con-
geners, and C10 to C14 linear alkyl benzenes.
A pilot plant has been in operation since 1994 to estimate removal efficiencies of the full
scale secondary treatment plant. Removal of toxic compounds and nutrients were studied
in 1994 and 1995. In 1996 TSS and BOD removal was monitored, although the results are
not representative of the expected operational efficiency of the future full scale secondary
treatment plant.
Most effluent threshold
values were developed
2.5 Monitoring Results Compared to Thresholds from expected NPDES
permit limits.
Thresholds for nine parameters are established for the effluent. The thresholds for organic
material (BOD), toxic contaminants (toxics and toxicity), pathogens (bacteria), solids (TSS),
and oil and grease will be based on the NPDES permit to be issued by the EPA and DEP to
MWRA for the Deer Island Treatment Plant and outfall. Three other thresholds, for nutrients
(total nitrogen), floatables (other than oil and grease), and plant performance, have already
been specified. A summary of the expected effluent thresholds and comparison of 1996
monitoring results to thresholds are given in Table 2-1. It should be noted that the thresh-
olds are for the future Deer Island Treatment Plant, with secondary treatment being phased
in from 1997 to 2000. The 1996 monitoring results are for the Deer Island Plant with new
primary treatment but no secondary treatment.
XING REPORT: 1996 - MWRA
Parameter
Total Nitrogen
Effluent Thresholds Compared to 1996 Monitoring Results
Caution Level
Total nitrogen annual
TABLE 2-1
Warning Level
Total nitrogen annual loading > 14,000
1996 Results
Annual loading = 12,692 metric tons, slightly
(nutrients) loading > 12,500 mtons/year | mtons/year. exceeded the Caution Level.
cBOD None. Expected levels: 40 mg/L. weekly, Daily Deer Island BODS range from 33 to 129 mg/L
(organic material) 25 mg/L monthly. with an average of 73 mg/L. Monthly Deer Island
Current interim permit limit = BODS range from 38 to 67 mg/L with an average of
140 mg/L monthly. 52 mg/L. Pilot secondary effluent monthly average
= 10 mg/L. cBOD is typically less than BODS.
Toxics None. PCB (as Arochlors) limit = PCBs as Arochlors were all below detection limits.
(toxic contaminants) 0.045 ng/L monthly. Monthly total PCB concentrations: from 0 to 35.9
ng/L with an average of 8.4 ngiL.
Toxicity None. Acute: effluent LC50 for shrimp <50% Acute: 11 of 12 shrimp tests had LC50 < 50%
{toxic contaminants) effluent. Chronic: effluent NOEC for fisn —_| effluent. Chronic: No fish growth tests had NOEC
(silverside) growth and sea urchin < 1.5% effluent; sea urchin tests are not yet
fertilization <1.5% effluent. implemented.
Interim acute limit: shrimp NOEC < 20% _ | Acute: 6 of 12 tests violated interim shrimp 20%
effiuent Current chronic limits: minnow NOEC limit. Chronic: no violations of current minnow
and red algae NOEC < 10% effluent 10% NOEC limit; All tests failed
current red algae 10% NOEC limit.
Pilot secondary effluent > 50% for chronic NOEC for
silverside and sea urchin. Five pilot plant acute tests
had LC50 = 100%
Bacteria None. Expected level: 14,000 fecal current No exceedances of expected level or the current
(pathogens) coliform/100 mL at point of dechlori- monthly limit of 200 fecal coliform/100mL.
nation (weekly mean, monthly 90th
percentile, and 24 consecutive hours).
Current interim permit limit = 200 fecal
coliform/100 mL monthly average.
Suspended None. Expected levels: 45 mg/L weekly, Range at Deer Island from 24 to 133 mg/L, with an
Solids 30 mg/L monthly. average of 52 mg/L. Pilot secondary effluent
Current interim permit limit = monthly average = 9 mg/L.
110 mg/L monthly.
Floatables None. Floatables less than 5 gal/day. Not measured until secondary treatment
plant is on line.
Oil and Grease None. 15 mg/L weekly. Maximum weekly = 6.5 mg/L.
(floatables)
Plant Performance More than 5 violations of Operating in violation of the expected Violation of nearly all the expected limits on BOD,
expected permit permit requirements more than 5% of solids, and acute toxicity, most of the time.
requirements per year. the time over a year. Violation of interim permit limits for acute toxicity, and
on one occasion for removal efficiency of BOD.
The reader is directed to the glossary and acronym summary at the end of the report.
Current interim permit limits are presented in the Warning Level column in italics.
Most of the threshold levels are expressed as a number in relation to a certain interval of
time and space. For example, the daily bacteria limit is compared to the pooled measure-
ments in a day. There are three measurements of bacteria in a day, and pooling is calculat-
ed in this case as a geometric mean. Likewise, the monthly limit is compared to the pooled
measurements taken over a month. The concept of a spatial interval is more relevant to the
other monitoring areas and is discussed in Section 3.3.
MWRA « OUTFALL MONITORING REPORT: 1996 / 13
Nutrients
Because nitrogen is the most important nutrient to moni-
tor when discharging effluent to marine waters, MWRA
tests treatment plant effluent for the concentration of total
nitrogen. The SEIS and later modellng studies predicted
little or no impact from the outfall discharge assuming a
nitrogen loading of 14,000 mtons/year. The Warning
Level was established to verify that the load assumed in
those predictions is not exceeded. The Caution Level was
set at approximately 90% of the Warning Level, or 12,500
Warning Level
mtons/year.
In the 1996 DECS sampling program, nutrients were not
measured. MWRA measured total nitrogen load at both
the Deer Island and Nut Island treatment plants, using composite samples of primary efflu-
ent. The total annual nitrogen load in 1996 was 12,692 metric tons, which slightly exceeds
the Caution Level. The total annual nitrogen load increased from 1994 to 1996, possibly
reflecting increased efficiency in the sludge dewatering process (the effluent from the sludge
14000
Caution Level
12000
10000
= 8000
5 .
= 0 Z
4000
2000
°
1990 1991 1992 1993 1994 1995 1996
Year
FIGURE 2-1
Total nitrogen load discharged
from the Deer Island and Nut
Island treatment plants from
1990 to 1996.
dewatering process is recycled back to Deer Island). Figure 2-1 shows the total nitrogen
load discharged from the Deer Island and Nut Island treatment plants from 1990 to 1996.
The 1995 pilot study showed that secondary treatment can remove an average of 10% for
total nitrogen and it is expected that the 1997 total nitrogen load will show a decrease from
the 1996 load.
Organic Material
Although the NPDES permit has not been issued, the expected Warning Level thresholds
for effluent organic materials are 40 mg/L on a weekly average, and 25 mg/L on a month-
Effluent BOD and solids
levels are expected to drop
below Warning Levels after
the new secondary treatment
system is fully operational.
ly average. These levels are based on carbonaceous BOD. Typically, cBOD will be lower
than BODS.
In 1996, daily BODS in the primary effluent ranged from 33 to 129 mg/L with an average
of 73 mg/L. This showed the improved performance, after the start-up period, of the new
primary treatment plant that became operational in 1995. In 1995 the BODS range was
50 to 179 mg/L, with an average of
102 mg/L. The thresholds being
developed apply to cBOD for the
new secondary treatment system,
but the 1996 results are for BODS
from the primary treatment system.
BOD levels are expected to drop to
below the Warning Level when the
new system is fully operational and
cBOD measurements are used. The
1996 average BODS in the effluent
BODS5 (mg/l)
160
140
120
100
Figure 2-2
Monthly average BODS in the
Deer Island Treatment Plant
effluent from 1994 to 1996.
Expected future warning level
threshold of 25 mg/L shown for
comparison.
interim permit limit
of the pilot secondary treatment 40 }----------------------------------------- core
plant was 10 mg/L. Figure 2-2 0 Warning Level
shows the monthly average BODS in J ne
the Deer Island Treatment Plant 0 _ a_i _. : ee .
tr Tt t t+ wo w wo wo o © oO oO
2 SF FS SF SG SG FB FB SF FB GF &
§ 23 8 § $3 8 § & 3 8B
14/ OUTFALL MONITORING REPORT: 1996 - MWRA
effluent from 1994 to 1996.
Maximum 1996 toxic
concentrations for all para- Toxic Contaminants
meters, except DDT, were NPDES toxic contaminant limits are based on water quality standards and very conservative
below dilution-adjusted assumptions about water conditions within the effluent/sea water mixing zone (i.e. strati-
fied conditions and conservative estimates of available dilution). If limits for toxics are
included in the new NPDES permit, they will serve as the Warning Levels for effluent toxic
contaminant concentrations. If not, the thresholds will be revised to reflect water quality
standards. Presently, the only toxic parameter expected in the permit is PCBs.
water quality criteria,
Maximum toxic analyte concentrations from DECS and MWRA sampling for the Deer Island
Treatment Plant primary effluent from January to December 1996 (only seven months were
actually sampled) compared to dilution-adjusted water quality criteria (WQC) are presented
in Table 2-2. None of the maximum concentrations of analytes listed in the table exceed
the dilution-adjusted WQC except DDT. This exceedance was for the human heath criterion
which assumes long term exposure. The average DDT measured in the 1996 Deer Island
primary effluent was 0.003 pg/L, which is below the dilution-adjusted WQC. The 1995
pilot secondary treatment results showed a high removal efficiency of DDT by secondary
treatment. The 1996 mean effluent concentrations of these contaminants were all lower
than the corresponding 1995 results except for acenaphthene (0.107 g/L in 1996 versus
0.093 ug/L in 1995). PCBs as Arochlors will be limited in the new NPDES permit with no
allowance for dilution. All samples in 1996 were below PCB Arochlor detection limits. The
OMTF also requires MWRA to measure the 20 individual PCB congeners listed in NOAA's
National Status and Tends protocol; total PCB is calculated in this report as the sum of
those congeners. In 1996, primary effluent concentrations averaged 8.4 ng/L.
Toxicity (Bioassay Results)
In addition to concentration-based limits for toxic parameters, the NPDES permit will
require the use of laboratory-based bioassays to assess acute and chronic toxicity. The
Warning Level for acute toxicity is expected to be an effluent LC50 of less than 50% efflu-
ent for shrimp. The Warning Level for chronic toxicity is expected to be effluent NOEC for
fish growth and sea urchin fertilization that is less than 1.5% effluent. The expected permit
limits that form the basis for these thresholds differ from the present toxicity permit limits.
In 1996, 11 of 12 Deer Island Treatment Plant primary effluent acute toxicity tests for
shrimp had an LCS0 of less than the Warning Level of 50% effluent. Acute tests also had a
NOEC range of 10 to 50% effluent, with an average of 18%. Six of the twelve tests violated
the 20% interim acute NOEC limit. Chronic NOEC values from minnow tests averaged
43% effluent with a range of 20 to 60%. There were no exceedances of the thresholds or
the 10% NOEC interim limit. In contrast, all of the red algae tests failed. The chronic
interim NOEC limit is 10%, while the test results were between 0.2 and 7%, with an aver-
age of 2%. These results, as well as those from other treatment plants, and other practical
test considerations have prompted the EPA to revisit the test species, and it is expected that
sheepshead minnow and red algae will be replaced in the permit. Exploratory toxicity test-
ing was conducted in 1996 using silversides and sea urchin. Three tests using silversides
and sea urchin in pilot secondary effluent showed a 50% NOEC. These results are well
above the 1.5% NOEC being considered for permit limits, i.e. the effluent is not expected to
violate the toxicity limits of the new permit.
MWRA : OUTFALL MONITORING REPORT: 1996 / 15
1000000 =-—
Pathogens
The Warning Level
threshold is based on
the expected NPDES
permit level of 14,000
fecal coliform/100mL
at the treatment plant.
Because of the
increased contact time
that will be provided
by the outfall tunnel 10 |
and the dilution that
will be achieved at the : |
100000
10000
1000
T
|
i
|
|
|
i
I
i
I
i}
|
I
I
I
q
T
i
i
i
|
|
|
|
|
t
t
|
|
i
|
|
|
100 1
i}
Fecal Coliforms per 100 mL
point of discharge, it is
nearly inconceivable
that any bacterial water quality standards for shellfishing or swimming would be exceeded
(except in the immediate vicinity of the outfall, where the Division of Marine Fisheries pro-
hibits fishing and shellfishing) if effluent bacteria concentrations were below the NPDES
permit limits.
Fecal coliform levels in Deer Island effluent vary widely (Figure 2-3). In 1996, there were
no exceedances of the Warning Level or the interim monthly limit of 200 fecal coliform/100
mL. This level of performance is expected to be continued when the new treatment plant is
on-line. The new treatment plant will have a longer chlorine contact time, resulting in
increased pathogen destruction.
1992 1993 1994
Solids
The current interim permit limit for TSS is 110 mg/L as a monthly average. The expected
NPDES permit limits for total suspended solids (TSS) are used as the MWRA Warning Level
thresholds. These limits are 45 mg/L of TSS weekly, and 30 mg/L of TSS monthly. In
1996, TSS concentrations in Deer Island Treatment Plant effluent averaged 52 mg/L with a
range between 24 and 133 mg/L. Although the TSS appears to be lower in the new prima-
ty plant effluent than in previous years, these values are still substantially higher than the
established threshold values. MWRA anticipates that completion of the new secondary
treatment facility will further
12345678 90121234567 890NIZ12 345678910121 2345678 9100121234567 89 101112
1995 1996
FIGURE 2-3
Daily Average Fecal Coliform in
Effluent
FIGURE 2-4
Monthly average TSS in the Deer
Island Treatment Plant effluent
from 1994 to 1996. Future
Warning Level threshold of 30
mg/L shown for comparison.
(Current interim permit limit of
0m/L not shown)
improve effluent water quality, 100
and that TSS levels will drop
substantially once secondary
treatment commences. The TSS
a a A
\
level for the secondary treatment
plant is expected to be approxi-
[Xi Nf
Vand |
mately 15 mg/L. The average
aa
TSS (mg/l)
pilot secondary treatment plant
ve
effluent TSS concentration in
8 6 86 8 8 8 8
Warning Level
1996 was 9 mg/L. Figure 2-4
shows the average monthly TSS 20
in Deer Island Treatment Plant 40
primary effluent from 1994 to
1996.
Jan-94
Mar-94
May-94
Jul-94
Sep-94
Nov-94
Jan-95
Mar-95
May-95
Jul-95
Sep-95
Jul-96
Nov-95
Jan-96
Mar-96
May-96
Sep-96
Nov-96
16 / OUTFALL MONITORING OVERVIEW REPORT: 1996 - MWRA
TABLE 2-2
Maximum 1996 Primary Effluent Contaminant Concentrations
Compared to Dilution Adjusted Water Quality Criteria
1996 Maximum Human Health Chronic Acute
Parameter Effluent Concentration’ WQC x 364 WQC x 60.8 WOQC x 48.3
(mg/L) ents (ug/L) (ug/L) (ug/l)
Pesticides
Aldrin ND 0.027 NA 62.8
4, 4-DDT 0.025 0.0087 0.061 6.3
Dieldrin ND 0.026 0.116 34.3
Endrin ND 364 0.14 1.8
Heptachior ND 0.102 0.22 2.6
Heptachlor
Epoxide ND 0.036 0.22 2.6
Lindane 0.028 6.8 NA 77
|_PAH
Acenaphthene 0.180 NA 43,200* 46,800*
Fluoranthene 0.300 15,300 975* 1,900*
Naphthalene 1.20 NA NA 113,000*
PAH 14.4 NA NA NA
PCB {as Arochtors) ND 0.000045? NA NA
Metals 18,200 NA NA
Silver 5.1 3,600 322 110
Cadmium <2.0 18,200 3,040 2,000
Chromium (VI) 12.5 NA 176 53,000
Copper 105 52.4 1.5 140
Mercury 0.62 4,880 500 100
Nickel 8.3 18,200 340 3,600
Lead 24.2 NA 5,200 6,800
Zinc 128 4,500
* Maximum concentration in samples
in which contaminant was detected.
*The Human Health Criteria for PCB
as Arochlors is reported as an undiluted value, as
the NPDES permit
* Insufficient information for development of WQC.
NOEC used instead.
ND = Not detected.
NA = Not Available
will not allow for dilution.
Floatables
The Warning Level for oil and grease is the same as the expected NPDES permit limits, 15
mg/L in weekly grab samples. One anomalously high result in January of 1996 exceeded
the level but was rejected as a laboratory error. For the remaining data, the maximum
weekly value was 6.5 mg/L which occurred in September.
A separate threshold is being established for floatables (visible floating debris) which are
assessed by a different method from oil and grease. Floatables cause aesthetic problems.
Current sewage treatment operation includes regular and efficient removal of floatable
materials early in the treatment process. As a result, substantial levels of floatables have
not been detected in the effluent. A more comprehensive procedure for assessing visible
floatables will be instituted when the secondary plant is on line. The floatables Warning
Level was set in relation to the performance of the future secondary treatment plant, which
has a series of floatables-removing skimmers. The expectation is that the final skimmer is
redundant. If as much as 5 gallons of floating matter accumulates in that final skimmer
MWRA : OUTFALL MONITORING OVERVIEW REPORT: 1996 / 17
over the course of a day, that would indicate that it is not redundant and the upstream
skimmers may be overloaded or inefficient. The visual inspections will begin in 1998 and
be conducted weekly. The design of the present primary plant does not allow for any such
quantification of floatables now, and so the 1996 floatables results portion of Table 2-1 is
blank.
Plant Performance
The MWRA Caution Level for plant performance is the Association of Metropolitan
Sewerage Agencies’ (AMSA) standard of 5 violations/year, while the Warning Level is the
EPA standard of noncompliance 5% of the time. The expected future permit for the fully
operational secondary treatment plant (year 2000) lists limits for cBOD, PCB, toxicity, bacte-
ia, and solids. BOD, acute toxicity, and suspended solids exceeded those limits most of the
time and thus exceeded the Warning Level for plant performance. Expressed in relation to
the interim permit the plant exceeded acute toxicity half the time, plus one occurrence
when BOD removal efficiency was slightly less than required by the interim permit. Thus
plant performance violated the Warning Level in relation to the expected permit as well as
the interim permit. Results of the pilot secondary treatment plant shows that once the new
treatment system is on line, TSS and BOD will be effectively removed and the frequency of
violations is expected to drop below the threshold.
18 / OUTFALL MONITORING OVERVIEW REPORT: 1995 - MWRA
MWRA : OUTFALL MONITORING OVERVIEW REPORT: 1996 / 19
5.0 Water Column Monitoring
Program
3.1 Water Column Issues
Potential water column issues due to the relocation of the out-
fall are associated with the effects of the effluent organic mate-
tial, nutrients, and toxic contaminants. Of these, changes in
the nutrient balance in Massachusetts and Cape Cod Bays
have the most potential for significant effects on the health of
marine life in the Bays.
3.1.1 Organic Material
Organic material occurs naturally in water bodies and may
also be introduced by wastewater effluents. Decomposition of
organic material consumes dissolved oxygen (DO). DO is oxy-
gen dissolved in water and available to marine mammals for
respiration. If DO concentrations are low, a condition known
as hypoxia, sensitive animals may suffocate. Hypoxia can
occur when the DO demand of decomposition is greater than
the natural resupply. The oxygen depletion rate is a measure
aw
Nearfiald Water
Column Locations
@ Fattield Water
Column Locations
aoe
ants
of this difference between DO supply and demand, and
describes how quickly DO concentration decreases.
3.1.2 Nutrients
Nutrients are necessary for the growth of all plants, aquatic and terrestrial. The amount of
nutrients in the water, along with several other factors, controls the growth of aquatic
plants, including algae. Since algae are the foundation of the aquatic food web, nutrients
have a great effect on how much life a marine ecosystem can support. In particular, there
are two basic ways in which nutrients from wastewater effluent could have a negative
effect on marine environments: through the effects of algae on dissolved oxygen concen-
tration and through changes in algal community structure. Nitrogen is the nutrient of
greatest concern.
Low Dissolved Oxygen (Hypoxia)
An algal bloom is a burst of algal growth, which occurs when a variety of conditions come
together. A sufficiently high nutrient level is one of the requirements, but other factors such
as sunlight and temperature are also important. Algal blooms are the base of the food web,
without which fish, whales, and most other marine life would not survive. Algal blooms
are necessary, common occurrences in the marine environment, but they can be a cause for
concern, depending on the intensity and frequency of the bloom, and the types of algae
that bloom.
If a body of water receives too great a nutrient load, it may become subject to eutrophica-
tion: over-stimulation of algal growth and excessive algal blooms. When algae grow faster
than they are consumed, the excess algae die, sink to the bottom, and decompose.
Decomposition of the algae consumes DO, just as with the decomposition of organic
rose most 00"
FIGURE 3-1
Nearfield and Farfield water
column sampling locations
Water column issues
primarily consist of potential
hypoxia effects associated
with organic matter and
nutrients, and shifts in the
algae community assemblage.
20 / OUTFALL MONITORING REPORT: 1996 - MWRA
material, as discussed above. This DO consumption can contribute to the creation of
hypoxic conditions.
Algal Community Structure (Growth of Undesirable Algae)
Adding effluent to the marine environment may change the relative levels of different nutri-
ents so that undesirable algae dominate or are present along with useful algae. The nutri-
ent composition of effluent is different from that in Massachusetts Bay, and there is public
concern that undesirable algae may be better able to take advantage of this difference than
desirable algae. Two types of undesirable algae can have direct effects on the marine envi-
ronment: 1) nuisance algae, such as brown and red tides, which affect the appearance of
the water; and 2) noxious algae, such as some red tides, which are toxic to marine mam-
mals, some fish, and, if concentrated in shellfish, to humans. Undesirable algae can also
have an indirect effect on the marine environment by out-competing another algal species.
If the out-competed species is a primary food source for a marine mammal, that animal
may suffer. For instance, it has been suggested that right whales in Cape Cod Bay are
linked through the food chain to a kind of algae that might be affected by effluent-induced
changes in nutrient concentrations.
3.1.3 Toxic Contaminants
Toxic contaminants are not always toxic. They are harmful at and above certain concentra-
tions, but at lower levels they may be harmless. Some even may be essential to life (e.g.,
copper and zinc, whereas mercury and lead are not). The timing of exposure is also an
important factor: temporary exposures are less harmful than constant ones. This is reflect-
ed in higher water quality criteria for acute exposure than for chronic exposure. Animals
passing briefly by the outfall would be only temporarily exposed. Because the harmful
effect of contaminants decreases with decreasing concentration, the dilution of the effluent
is key to minimizing the impact of the outfall.
The potential for increased levels of toxic contaminants in the vicinity of the new outfall is
generally low. The new outfall will minimize the environmental impact of effluent by maxi-
mizing dilution. Because outfall relocation is unlikely to have a significant effect on the
concentrations of toxic contaminants in waters of Massachusetts Bay, toxic contaminant
concentrations are monitored in the other three program areas but not in the water column
program. Because adequate dilution is central to the expectation of no impact, the effluent
dilution achieved by the diffuser will be evaluated using data obtained from the plume
tracking surveys (described below).
6.4 Monitoring Program Design
The water column monitoring program is designed to provide measurement of water quality
and plankton data in Massachusetts Bay and Cape Cod Bays. The data will help detect
changes in the water column of the Bays resulting from the relocation of the effluent outfall.
The monitoring program, which began in 1992, is designed to characterize background
water column conditions before completion of the outfall. Once the outfall is on line, water
column monitoring data will be compared to background data and any impacts to
MWRA + OUTFALL MONITORING REPORT: 1996 / 21
Massachusetts and Cape Cod Bays will be assessed.
The water column monitoring
The five major components of the water column monitoring program, nearfield surveys, program includes nearfield
farfield surveys, plume track surveys, moorings, and remote sensing, are outlined below. and farfield surveys, plume
These components are designed to provide comprehensive coverage of water quality condi- tracking surveys, mooring
tions in Massachusetts and Cape Cod Bays. measurements, and remote
Nearfield Surveys : sensing Imagery.
Nearfield water column surveys are designed to collect frequent intensive sets of water
quality and plankton data near the outfall location. Impacts are most likely to be measur-
able near the outfall site, and are likely to be confined to the nearfield area. The
nearfield area is defined by a rectangle surrounding the 1.2 mile outfall diffuser line at a
distance of 3 miles. The stations are spatially intensive to document the decrease of
impacts with distance from the outfall in the region where the decrease is expected to be
strongest and most detectable. Data are collected at 17 locations (Figure 3-1) in 17 annual
surveys. These surveys provide vertical profiles of physical, chemical, and biological
water column characteristics throughout each year, identifying seasonal cycles and events
of interest (e.g., algal blooms).
During each nearfield survey, temperature, salinity, dissolved oxygen, chlorophyll fluores-
cence, light transmission, and photosynthetically available light are electronically measured
in situ throughout the depth of the water column. Water samples are collected at selected
stations and depths in the water column for laboratory analysis of constituents including
nutrients, chlorophyll, suspended solids, dissolved oxygen, phytoplankton, zooplankton,
primary productivity, and respiration. Primary productivity (i.e., photosynthesis, the algal
growth rate) measurements are performed to evaluate how the algae are responding to
ambient nutrients and light. Respiration measurements evaluate the rate of oxygen con-
sumption due to metabolic activity including degradation of algal biomass and other organ-
ic matter. Observations of whales, other marine mammals, and sea turtles are also per-
formed during the nearfield surveys.
Farfield Surveys
Farfield water quality surveys are designed to collect intensive sets of water quality, plank-
ton, and primary productivity data over a broad spatial scale, and to cover Massachusetts
and Cape Cod Bays. Stations are not spatially intensive as they are in the nearfield, but are
spread out over the Bays with adjustments to cover special resource areas and to detect the
influence of coastal and offshore sources of nutrients to the Bays. The main purpose of the
farfield surveys is to determine differences across the bays and assess seasonal changes over
a large area, (e.g., relating trends observed in the nearfield area to the surrounding region).
Six farfield surveys are conducted each year collecting water quality at 26 stations through-
out Massachusetts and Cape Cod Bays (Figure 3-1). Plankton and primary productivity
data are collected at selected stations. Farfield and nearfield methods are comparable.
Plume Tracking Surveys
Plume tracking surveys are performed to determine the location of and physical, chemical
and biological characteristics of the effluent discharge plume leaving the outfall and mixing
with ambient waters. Sampling will include measurement of salinity, temperature, rho-
22 / OUTFALL MONITORING REPORT: 1996 - MWRA
Trigger parameters
associated with DO include
the DO concentration
in the outfall nearfield and
Stellwagen Basin, and DO
depletion rate in the
nearfield.
damine dye and suspended solids. The dilution and transformation of components charac-
teristic of the effluent will be tracked using salinity, nutrients, and metals as well as other
chemical, isotopic, and microbial constituents. Intensive studies will begin when the outfall
is on line.
Moorings
A mooring is maintained by the US Geological Survey near the future outfall site to measure
currents, temperature, salinity, light transmission, chlorophyll, and sediment processes. In
addition to a mooring, which physically consists of instruments suspended from a float and
anchored by a weight, the USGS also deploys tripods mounted on the sea floor. The pur-
pose of moorings and tripods is to obtain continuous data at a location. The outfall moni-
toring program uses the data to capture temporal (i.e., time-dependent) variations in water
quality between nearfield surveys.
Remote Sensing
Satellites provide remote sensing imagery which the outfall monitoring program uses to cap-
ture spatial variations in water quality on a regional scale. The images provide a snapshot
of sea surface temperature over the Bays at one time. Sometime after 1996, chlorophyll
data will also become available. Remote sensing fills in the information between survey
sample locations. Data from remote sensing complements the data from the ship surveys
and moorings.
8.6 Threshold Comparison
Several thresholds for water column monitoring parameters have been developed in order to
assess the potential impacts of the new outfall. The trigger parameters, threshold levels,
and 1996 monitoring results for the water column are summarized on Table 3-1. A detailed
discussion of the thresholds and current status of compliance with thresholds is provided
below.
Most of the threshold levels are expressed as a number in relation to a certain interval of
time and space. The relevant data are pooled over those intervals and then compared to
the threshold number. The pooling may be done by calculating an average, a geometric
mean (bacteria) or other statistic (benthic diversity). Pooling yields a number which is less
extreme than that of the worst-case individual reading, and so the spatial and temporal
intervals have to be chosen carefully: large enough to reflect the ecological response scale of
the resource to be protected but small enough to not mask transient problems that occur.
The thresholds are designed to be compared to pooled rather than individual data because
the latter are dependent on the sampling effort. An example of how the pooling is done is
that the “monthly mean DO in nearfield bottom waters” is calculated by averaging the
deepest DO measurements from all the nearfield stations during one survey that result is
averaged over all the surveys {there are up to two) within a calendar month to give the
nearfield monthly mean.
MWRA * OUTFALL MONITORING REPORT: 1996 / 23
Parameter
Dissolved oxygen
concentration in
Nearfield region
bottom waters
TABLE 3-1
Water Column Thresholds Compared to 1996 Monitoring Results
Caution Level
Monthly mean DO is less than 6.5 ppm or 80% of
saturation levels for any one month during stratifica-
tion (June-Oct.)
Warning Level
Monthly mean DO is less than 6 ppm
or 75% of saturation levels for any one
month during stratification (June-Oct.)
1996 Results
DO saturation above
Caution Level in September
(87.2%).
(See Table 3-2)
Dissolved oxygen
concentration in
Monthly mean DO is less than 6.5 ppm or 80% of
saturation levels for any one month during stratifica-
Monthly mean DO is less than 6 ppm
or 75% of saturation levels for any one
DO saturation below
Caution Level in October
Stellwagen Basin | tion (June-Oct.) month during stratification (June-Oct.) (79.2%).
bottom waters {See Table 3-2)
Dissolved oxygen | DO depletion rate is greater than 1.5 times DO depletion rate is greater than 2 1992-96 Average Baseline
depletion rate in
Nearfield region
bottom waters
the baseline rate during stratification
(June-Oct.), -0.040 mg/Liday.
times the baseline rate during stratifi-
cation (June-Oct.), -0.053 mg/L/day.
Rate: -0.026 mg/L/day
1996 Rate:
~0.025 mg/Liday
Chlorophyil in
Nearfield region
Annual mean concentration greater than 1.5 times
the baseline annual mean, 2.80 jig/L.
Annual mean concentration greater
than 2 times the baseline annual
mean, 3.74 ug/L.
1992-96 Baseline:
1.87 pg/L
1996: 1.54 pg/L
Chlorophyll in Season mean concentration exceeds 95th percentile } None. Spring: 2.43 mug/L
Nearfield region of the baseline seasonal distribution. Summer: 0.78 pg/L
Spring: 2.71 pg/L Fall: 1.47 pg/L
Summer: 2.27 ug/L
Fall: 4.44 po/L
Nuisance algae in | Alexandrium tamarense None. Alexandrium tamarense
Neartield region Season mean population densities exceed 95th per- Spring: 0 cells/L
centile of the baseline seasonal mean. Summer: 0 cells/L
Spring: 2.34 cells/L Fall: 0 cells/L
Summer: 26.1 cells/L (See Table 3-3)
Fall: 7.57 cells/L
PSP extent in New occurrence. PSP has never been observed None. No occurrences.
Fartield region at 3 of the 18 monitoring stations (see Table 3-4).
Zooplankton Nearfield assemblage shifts from a transitional None. Transitional assemblage in
assemblage in community towards an inshore community. nearfield region.
Nearfield region | Inshore: Acartia, Eurytemora, Centropages hamatus
Offshore: Calanus, Pseudcalanus, Centropages typi-
cus, Oithona
Nearfield: Transitional between two regions.
Initial effluent dilu-
tion at new outfall
location
None.
Effluent dilution less than that set by
the NPDES permit.
No data until outfall is
online.
24 / OUTFALL MONITORING REPORT: 1996 » MWRA
Dissolved Oxygen Concentration and
DO [mg/L]
Saturation
Aquatic animals are sensitive to the concentration of
DO in the water column. Low levels of DO can have
negative impacts on marine life. Because of the
importance of DO, the state has set a water quality
JF MAM J J AS ON OD
-——— Present Outfalls with Primary
Treatment
serene Future Outfall with Secondary
Treatment
Figure 3-2
Water quality modeling results
near future outfall: Existing
(1992) conditions and post out-
fall relocation/secondary treat-
ment (Source: HydroQual. and
Normandeau 1995)
standard that a discharge should not cause DO to fall
below 6 mg/L nor below 75% of saturation in
Massachusetts Bay.
The DO percent saturation threshold is unique in that, even with pooling, it has already
been exceeded in the baseline period before the future outfall is operational. The issue of
causality implied in the state standard is pivotal in such a case and will be decided on by
the OMTF. Water quality modeling studies have indicated that dissolved oxygen levels
will improve at the future outfall site as a result of outfall relocation and secondary treat-
ment (Figure 3-2). In the post-discharge period, when the Contingency Plan becomes
active, action will be taken in response to an exceedance. (It should be noted that for DO
an “exceedance” is less than the threshold value.) The first action to be taken is to notify
the OMTF. Even if low DO is determined to be unrelated to the MWRA discharge, it is
appropriate to have in place such a mechanism for keeping the OMTF immediately
informed of episodes of low DO, given the ecological importance of that parameter.
Actions could also include water quality modeling studies to evaluate the cause of the
violation.
In 1996 the lowest nearfield monthly mean DO concentration, 7.7 mg/L in September, was
above the Caution Level of 6.5 mg/L (Table 3-2). The lowest individual measurement was
7.2 mg/L in October. During the entire baseline period to date (1992-96), the lowest
nearfield monthly mean was 6.5 mg/L in September 1994, and the lowest individual mea-
surement was 4.8 mg/L in October 1994.
In Stellwagen Basin in 1996, the lowest nearfield monthly mean DO concentration, 7.7
mg/L in October, was also above the Caution Level of 6.5 mg/L (Table 3-2). The lowest
individual measurement was 7.6 mg/L in October. During the entire baseline period to date
(1992-96), the lowest nearfield monthly mean was 6.6 mg/L in October 1994, and the low-
est individual measurement was 6.3 mg/L, also in October 1994.
TABLE 3-2
Minimum DO Concentration and Percent Saturation:
1996 and Baseline Period
1996 Baseline (1992 — 1996)
Minimum Individual Minimum Monti Minimum Individual
Sept.96 j 4-8mg/L } Oct. 94 6.5 mg/L | Sept. 94
Location & Trigger
Parameter
Nearfield Concentration 7.2 mg/L | Oct. 96 7.7 mg/L
Stellwagen Concentration | 7.6 mg/L | Oct. 96 7.7 mg/L }oct.96 | 6.3mo/L | Oct. 94 6.6 mg/L | Oct. 94
Nearfield % Saturation 77.1% Sept.96 | 87.2% Sept.96 | 55.6% Oct. 94 74.0% Oct. 94
Stellwagen % Saturation | 75.0% Aug.96 | 79.2% Aug. 96 | 68.2% Oct. 94 71.0% Oct. 95
MWRA - OUTFALL MONITORING REPORT: 1996 / 25
In 1996 the lowest nearfield monthly mean DO percent saturation, 87.2% saturation in There are several trigger
September, was above the Caution Level of 80% saturation (Table 3-2). The lowest individ- parameters for algae, includ-
ual measurement was 77.1% saturation in September. During the entire baseline period to
date (1992-96), the lowest nearfield monthly mean was 74.0% saturation in October 1994,
and the lowest individual measurement was 55.6% saturation, also in October 1994.
ing seasonal and annual
chlorophyll concentration,
the presence of nuisance
In Stellwagen Basin in 1996, the lowest nearfield monthly mean DO, 79.2% saturation in algae, and occurence of
August, was between the Caution (80%) and Warning (75%) Levels (Table 3-2). The low- Paralytie Shellfish Poisoning.
est individual measurement was 75.0% saturation in August. During the entire baseline
period to date (1992-96), the lowest nearfield monthly mean was 71.0% saturation in
October 1995, and the lowest individual measurement was 68.2% saturation, also in
October 1994.
In summary for 1996, both the nearfield and Stellwagen Basin monthly mean DO concen-
tration values were above the Caution Level and monthly mean DO saturation levels were
above the Warning Level. However, the Stellwagen Basin minimum monthly mean DO
saturation was below the Caution Level. The nearfield region experienced a minimum
monthly mean DO saturation of 87.2% in
Y TABLE 3-3
September, while Stellwagen Basin . a ae
experienced a minimum monthly mean DO Saturation Threshold Violations
of 79.2% in August. Nearfield |___Stellwagen |
During the five year baseline period, the Concentration | Saturation Concentration | saturation |
nearfield and Stellwagen monthly mean DO Oct. 92 7.6 mg/L 79.5% 7.6 mg/L 76.7%
saturation Caution Levels have been violated Sep. 94 6.5 mg/L 75.9%
four and five times respectively (Table 3-3). Oct. 94 6.6 mg/L 74.0% 6.6mg/L 72.6%
Two of the four nearfield, and three of the Nov. 94 7.0 mg/L 79.4%
five Stellwagen low monthly means also vio- Aug. 95 ; 7.5 mg/L 73.9%
lated the DO saturation Warning Levels. No Sep. 95 6.9 mg/l 74.8% -
DO concentration thresholds have been vio- Oct, 95 6.7 mg/L 71.0%
Aug. 96 8.1 mg/L 79.2%
lated, although the nearfield Caution Level
was equaled in both September and October,
1994. The frequency and degree of DO saturation threshold violations during the baseline
period strongly suggest that the OMTF needs to re-evaluate the applicability of the current
DO threshold levels.
Dissolved Oxygen Depletion Rate
The DO depletion rate thresholds are based on the calculated average rate from the baseline
period. The rates over the four years of baseline to date vary from a low of -0.024
mg/L/day in 1992 to a high of -0.031 mg/L/day in 1994. Both 1994 and 1995, which
experienced low DO concentrations and saturation levels, had higher rates of DO decline
than 1992, 1993 and 1996. Based on the data collected to date, the interim threshold for
the average baseline DO depletion rate is -0.026 mg/L/day (Table 3-1}. As additional
baseline data are collected, this value will be updated. Based on this average value, the DO
depletion rate thresholds would be -0.040 mg/L/day for the Caution Level and -0.053
mg/L/day for the Warning Level. The 1996 DO depletion rate was -0.025 mg/L/day, which
26 / OUTFALL MONITORING OVERVIEW REPORT: 1996 - MWRA
TABLE 3-4 is below the Caution and Warning
Plankton Thresholds Comparison Levels.
; : ; Chlorophyll and Nuisance
Trigger Caution Warning 1996 Algae
Location Paramater Level Level Results
Adding effluent to the marine
Nearfield Annual Mean Year 2.80 pg/L 3.74 pg/L 1.54 pg/L environment could change the
Chlorophyll . A
Concentration amount of nutrients or the relative
- levels of different nutrients so that
Nearfield | Seasonal Mean | SPring 2.71 yg none 2.43 yg excessive or prolonged algal bloom
Chlorophyll Summer] 2.27 pg/L none 0.78 ug/L could occur, As discussed earlier,
Concentration | Fall 4.44 pg/L none 1.47 pg/L the settling and decomposition of
Nearfield | Seasonal Density | Pring 2.34 cells/L none 0 cells/L algal biomass in the bottom water
of Alexandrium | Summer| 26.1 cells/L none 0 cells/L can lead to low DO conditions. Algal
famarense | Fall 7.57 cells/L none O cells/L biomass is most commonly mea-
i sured as chlorophyll, a ph -
Nearfied | Seasonal Density | SPring_| 1,050 cells/L none 1,000 cells/L , ‘ * c ea y! ; ap. ane
of Nitzschia | Summer] 17,600 cells/L none 5,000 celis/L thetic chemical in all green plants.
pungens [Fal 15,600 cells/L none 1,000 cells/L reel a : te Oe chloro- ;
- . phyll measured in the approve
Nearfield Seasonal Density Spring | 2.46 x 10° cells/L none 5,000 cells/L standard test for chlorophyll and
of Phaeocystis | Summer 0 none 0 cells/L adopted by MWRA, and is the form
jouchetii ”
p Fall 48,700 celis/L none Ocells/L implied when the “a” is omitted.
As there are no state or federal regu-
lations for chlorophyll, the Warning Level was developed based on expert peer review com-
ments to the OMTF. The commentators agreed with the rule of a thumb that appeared in
1993 in the National Oceanographic and Atmospheric Administration’s Estuarine
Eutrophication Survey: “normal blooms become problematic when chlorophyll values reach
20 ug/L.” The commentators wanted a greater level of protection for Massachusetts Bay,
however, because present levels are so much lower (2-3 ug/L} and deleterious changes
would be apparent long before chlorophyll reached the NOAA level of 20 ug/L. Therefore
the Warning Level was set at twice the baseline value of the annual mean nearfield chloro-
phyll concentration, or well before there is a likelihood of biologically significant change.
In addition to the trigger parameter above which focuses on the annual average, another
was established which recognizes the inherent seasonality of chlorophyll over the year and
is designed to protect against unusually high algal biomass in any one season. By allowing
for seasonality the new trigger parameter would be more sensitive to meaningful change.
The statistic chosen to reflect the meaning of “unusual” in this case was chosen to be the
95th percentile. A measurement would be deemed to be unusually high if it were to exceed
95 percent of the baseline values. There is a 5 percent chance of a false alarm with this
approach but it is appropriate nevertheless to notify the OMTF immediately of such an
occurrence.
The interim chlorophyll thresholds (shown on Table 3-4) were developed from the existing
five years of baseline monitoring data. The chlorophyll concentrations for 1996 were below
the existing threshold values.
Nuisance and noxious algae naturally occur in Massachusetts and Cape Cod Bays in small
numbers annually. There is public concern that effluent nutrients could stimulate a red tide
MWRA : OUTFALL MONITORING REPORT: 1996 / 27
or similar noxious algae bloom in TABLE 3-5
the vicinity of the new outfall. At Shellfish Monitoring Stations for PSP
the 1996 peer review workshop, it
was recommended that the Primary Stations Secondary Stations
Massachusetts shellfish toxicity Gloucester-Annisquam Yacht Club Rockport-Granite Street
monitoring program be used to set Hull-Pt. Allerton (not sampled each week) Cohasset-Border Street
red tide Caution Levels. The state Cohasset-Little Harbor Scituate/Marshfield-South River Humarock
program monitors the toxicity of Scituate-Scituate Harbor Marshfield-Green Harbor
Paralytic Shellfish Poisoning (PSP) Marshfield-Damon’s Point Duxbury-Eaglenest Creek
at shellfish beds along the edge of Plymouth-Manomet Point Plymouth-Plymouth Harbor
Massachusetts and Cape Cod Bays. Sandwich-Cape Cod Canal (east entrance) Plymouth-Ellisville Harbor
A list of Department of Marine Dennis-Sesuit Harbor Sandwich-Sandwich Harbor
Fisheries (DMF) shellfish monitoring Barnstable-Marispan Creek
stations is provided in Table 3-5. Provincetown-The Dike
To date, no shellfish toxicity has
been observed at the monitoring sta-
tions in Dennis, Barnstable, or Provincetown. Prior to the large Alexandrium bloom which
occurred in 1993, toxicity had not been observed beyond the Cape Cod Canal. However,
toxicity was observed for the first time in Sandwich as a result of the 1993 bloom. Such an
occurrence will be viewed as a trigger parameter for contingency planning in order to fully
evaluate its origin.
The nuisance algae thresholds are being developed from the baseline conditions. The
Caution Levels will be set as the 95th percentile of seasonal mean concentrations of the
three target species of nuisance algae (Table 3-4). In 1996, only Alexandrium tamarense
was undetected in the monitoring samples. Other studies in Massachusetts Bay confirmed
that 1996 was uneventful for Alexandrium throughout Massachusetts Bay and much of the
New England coastal waters. All nuisance algae were below threshold values in 1996.
Zooplankton
Zooplankton assemblages vary with location in Massachusetts Bay. The species composi-
tion of inshore communities is dominated by Acartia, Eurytemora, and Centropages hama-
tus, while the species composition of offshore communities is dominated by Calanus,
Pseudocalanus, Centropages typicus, and Oithona. The nearfield region represents a transi-
tion between the two communities.
The zooplankton species in inshore communities are known to require the high concentra-
tions of nutrients and algae that are found in Boston Harbor for maximal growth and repro-
duction. Once the new outfall is online, the nutrient concentrations in both the Boston
Harbor and the nearfield region may change. The zooplankton community in Boston
Harbor may change to resemble that presently in Massachusetts Bay. The Caution Level
seeks to protect the zooplankton community in the nearfield of Massachusetts Bay from
changing to one similar to an inshore community.
Dilution
Since all evaluations of toxic impacts depend on concentrations after initial mixing, the
MWRA will measure the actual dilution of effluent by seawater around the new outfall to
test predictions of effluent dilution. Testing will focus on measurements of tracers to deter-
28 / OUTFALL MONITORING OVERVIEW REPORT: 1996 : MWRA
mine dilution in the immediate discharge mixing zone of the diffuser. The results will be
compared with predictions of contaminant concentrations. Because EPA dilution estimates
are very conservative, it is extremely unlikely that actual dilution will be less than the EPA
predicted dilution. However, if the study showed that real dilutions were less than antici-
pated and did not reduce toxic contaminant concentrations enough to protect the environ-
ment, the EPA and the state could revise MWRA’s NPDES permit by lowering the allowable
discharge concentrations. Thus, effluent dilution tests provide a Caution Level which would
lead to revision of Caution and Warning Levels for toxic contaminants if it were exceeded.
As the new outfall is not on-line, no data is available to evaluate this trigger parameter.
3.4 Monitoring Results
The behavior of the Massachusetts Bay system is primarily controlled by the annual weath-
er patterns and cycle, although the individual system components (physical, chemical, and
biological) are also largely influenced by complex system interactions (Figure 3-3).
The monitoring program measures the annual behavior of the Bay system and provides data
sufficient to quantify the annual variability of each parameter. In 1996 the behavior of the
Bay system was similar to that observed in previous years. The following sections present
the components of the annual Bay cycle as they were measured in 1996.
Physical Characterization of the Water Column
The annual cycle of the Massachusetts Bay system begins in late winter when the Bay is
unstratified. Water temperature and salinity are vertically uniform throughout the water
Figure 3-3 . . . .
. A , th
‘Annual Water Column Cycle column. As the snow melts in the spring, the runoff increases freshwater input to the Bay
of Massachusetts Bay
Late Fall— Spring Summer Fall
Late Winter im shorter
0; jonger. cooler days
UNSTRATIFIED days DEVELOPING STRATIFICATION STRATIFIED STRATIFICATION BREAKDOWN
Physical | Tuniform \ TT at surface TT, Tsurf > Tbottom Tsutt 1
Temperature § uniform V4 SJ at surface Ssust < Sbottom = mixing
snow melt/runoff \
river discharge
i limited late winter/
Biology | rankton activity) | spring blooms fll bloom
generally increasing { densities generally decreasing densities
Nutrients | uniform | | decreasing surface surface T
qu concentrations depletion > uniform
Dissolved bottom bottom T
Oxygen uniform depletion = uniform
MWRA + OUTFALL MONITORING OVERVIEW REPORT: 1996 / 29
(a) Charles River Discharge
3000 3000
Source: USGS
2500 2500
2000 2000
q
&
°
B® 1500 1500
A
: \
3
3 1000 \ iN WA, 4000
500 \ IN Zn. f iw fl \ f 500
a WPL ™“
ci) s ~ oO
Jan Feb Mar Apr May Jun Jul ‘Aug Sep Oct Nov Dec
{b) Merrimack River Discharge
60000 60000
Source: USGS
§0000 50000
_~ 40000 40000
q
: |
& 30000 f 30000
i A | \
2
5
a |
5 20000 \ \ \ \ | \ vy 20000
10000 NN 10000
v al WA
0 . . : 2 ‘ : °
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Figure 3-4
. . . . 1996 Daily Precipitation and
from the Merrimack, Charles and other rivers (Figure 3-4). This fresh water runoff enters River Discharge Data. Merrimack
the Bay at the surface, and because it is less dense than the salty water in the Bay, it stays and Charles Rivers,
on the surface. As a result, a vertical salinity gradient develops (Figure 3-5).
Simultaneously, as the days get longer, the sun heats the surface water and a vertical tem-
perature gradient begins to develop (Figure 3-6). By the end of the spring (late May) the
water column is stratified (Figure 3-7), with fresher, warmer water in a surface layer and
saltier, colder, denser water in a bottom layer. During the summer, the water column
becomes more stratified due to continued solar heating at the surface.
Storms and upwelling events can temporarily break down stratification and mix the water
column. No large scale upwelling events occurred during 1996; however, one nearshore
mixing event occurred in August. Upwelling is characterized by a drop in surface water
temperature as substantially cooler bottom waters are brought to the surface.
In the fall, the water column completely re-mixes in a process known as overturn.
Overturn occurs because as the days get shorter and cooler, the surface water cools. When
the density of the surface water becomes greater than that of deeper waters, it sinks. This
process generally takes place in October, after which time the water column gradually and
uniformly cools throughout the winter. The overturn process during this time of year is
enhanced by increased mixing energy from storms which erode the stratification. In 1996,
Sallnity (PSU)
30 / OUTFALL MONITORING REPORT: 1996 - MWRA
32.5
the fall overturn began in early
September (Figure 3-6) with mix-
ing caused by the passing of
Hurricane Eduoard. Subsequently,
a strong northeaster during mid-
September produced a second mix-
32.0
315
Temperature (°C)
20
sre ing event where surface and bot-
tom temperatures almost con-
$08 verged. Complete turnover
occurred by mid-October (Figures
30.0 3-6 and 3-7).
205 Plankton and Chlorophyll
ee Typically there are two major
29.0 aeons (--; plankton blooms each year. The
\ a — increasing sunlight and water tem-
ann Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dee Peratures in spring trigger the first
phytoplankton bloom, and
Figure 3-5 _ turnover with its inherent mixing drives another phytoplankton bloom in the fall. An
on6 Moorea Salinity increase in the zooplankton population follows each phytoplankton bloom, as phytoplank-
ton are the main food source for zooplankton. Grazing of phytoplankton by zooplankton
controls the size and duration of phytoplankton blooms and can often end them.
In 1996, the largest spring bloom (as measured by average nearfield chlorophyll concentra-
tions) during the MWRA baseline record (1992-1996) occurred (Figure 3-8). The 1996
bloom was 40 percent larger than any previous baseline year. In contrast, the 1996 fall
bloom was the smallest during the baseline period, and summertime blooms ranked fourth
in intensity among the five baseline years. Conditions were apparently favorable for a large
and prolonged spring bloom, yet the sequence of events around the time of the fall turnover
FIGURE 3-6 resulted in an uneventful fall bloom. The species composition of these bloom events (cen-
1996 Moored Temperature ro . . .
Sensor Data tric diatoms in spring, pennate diatoms
20 in fall) was similar to that of other
years.
18
1s There was no evidence in 1996 of any
significant occurrence of the three toxic
‘* or nuisance plankton species moni-
2 tored by the MWRA monitoring pro-
: gram. There were also no occurrences
M 10 of shellfish toxicity reported by the
NY Massachusetts DMF in 1996. The zoo-
nh ° plankton community measured in the
I nearfield in 1996 was similar to that of
a i previous years, consisting of a transi-
“UE “| ~ ———— ‘ tional community between nearshore
* ares USGS Mooring (22m) 7
© Niscz-10m) Lt, and offshore species.
. A N16 (20-25)
ee ee
Jul ‘Aug Sep Oct Nov Dec
MWRA - OUTFALL MONITORING REPORT: 1996 / 31
Density (g/L)
248 22.0 22.5 23.0 23.5 24.0 24.5 25.0
“4: Early August 3: Early Seplgmbar 2: Mi Apr
—_— oc
—
6 \w hs
\
XN
SK
AN N
. SAN \\
at
ti Late February
7:Mid-December
on
Depth (m)
B
6 6 FIGURE 3-7
3 1996 Annual Mean = 1.54 mg/L. 1996 Seasonal Density Cycle
20 1o in the Nearfield
2
&
3 Too 7 5
i ee
2
i, a oe ae ae > a °
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
a 15
3 1995 Annual Mean = 1,39 mg/L
£0 10
2
Ea
g 8 yaw 3
2
2 Ee. _ 1 ee ee tte il Ne ;
Jan Feb Mar Apr May Jun Jul ‘Aug Sep Oct Nov Dec
a 15
3 71996 Annual Mean = 1.54 mg/L.
20 10
2
3
S 5 rT rr T 5
j AE,
2
i eh 4 ee
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
a 15 15
3 1995 Annual Mean = 1.39 mgf.
g 10
: 0
25 LN 5
i == Ne
2
3 L
£0 t+ °
Jan Feb Mar Apr May Jun Jul Aug Sep ‘Oct Nov Dec
15 5
3 1992 Annual Mean = 2.08 FIGURE 3-8
210 wo 1992-1996 Chlorophyll a
3 Averages in the Nearfield
8
Bs r 5 (Error bars represent
ee a So eee ee
é oe
~ 0 a ° deviation.)
§
g
E
Apr May Jun Jul ‘Aug Sop Oct Nov Dec
32 / OUTFALL MONITORING REPORT: 1996 - MWRA
Nearfleld (N04, NO7, N16, N20)
DIN Witrate + Nitrite + Ammonium) (uM)
FIGURE 3-9
Nearfield DIN
Concentrations
for 1992-1996
Nutrient Cycle
The nutrient cycle in Massachusetts Bay is closely
linked to the physical and biological changes that take
place through the year. Nutrients, like the physical
parameters, become vertically mixed during the winter,
and begin the year at their highest levels (Figure 3-9).
The spring plankton bloom partially depletes nutrients
throughout the water column, as phytoplankton growth
consumes nutrients. As spring and summer progress,
continued plankton growth and stratification cause
nutrient depletion in the surface layer. Lack of algal
growth prevents nutrient depletion in the bottom layer.
In fact, plankton death and subsequent settling to and
decomposition in the bottom layer cause nutrient con-
centrations to increase somewhat in the bottom waters.
Stratification prevents the nutrients in the
bottom layer from vertically mixing into the surface
layer. Overturn releases the nutrients trapped in the
bottom waters to mix throughout the water column
(Figure 3-9).
FIGURE 3-10
1992-1996 Dissolved Oxygen Cycle in Surface and Bottom Waters in the Nearfield
13
(Error bars represent +/- one standard deviation.)
13
ji.
|
iw”
a
a
a
rope
Ww
2 ra
Eo Tf — Le NE | lg
2 { THY,
° [
4 4 i
. ‘of if
L i
7 yi 7
6 6
a
i—e— Surface
—®— Bottom |
5 on | 5
¢ 8 8s 8 8 8 8 8 &$§ $€$ &€$ $$ 8 8 8 8 8 8 8B 8
s &@ 3 8 § &€ 3 8 &§ #2 3 8 § #2 3 8 § € 3 6
MWRA + OUTFALL MONITORING REPORT: 1996 / 33
Upwelling events during the summer can release some of the nutrients trapped in the bot-
tom layer into the surface layer. Nutrient releases into the surface layer can result in
increased phytoplankton growth. In 1996, the mid-August upwelling event described earli-
er, resulted in a localized increase in phytoplankton density (as measured by chlorophyll a)
in the inner nearfield region. This increase is not seen in Figure 3-8 because values in that
figure represent an average over all 17 nearfield stations.
Dissolved Oxygen
As with nutrients, dissolved oxygen (DO) is closely linked to the physical and biological
changes in the Bay. Water column DO concentrations are the highest during the winter and
early spring (Figures 3-10 and 3-11) and are well mixed throughout the water column. The
highest DO concentration measured in bottom waters (12 ppm) in 1996 occurred in mid-
March in the nearfield and early-April in the Harbor.
Once the water column is stratified, the bottom waters are effectively cut off from the
atmosphere (the source of DO). However, consumption of DO via respiration continues.
As a result, bottom water DO concentrations decline continuously throughout the stratified
period. In addition, the saturation level of oxygen varies with temperature. Cooler water
can hold more DO than can warmer water. Therefore, DO concentrations will decrease nat-
urally as the water column warms during the spring and summer. The fall water column
overturn ends the isolation of the bottom layer and results in increased DO concentrations
in the bottom waters.
Minimum DO concentrations in the bottom layer are reached just before overturn, and in
1996 equaled 5.5 mg/L in Cape Cod Bay, 7.2 in the nearfield region and 7.6 mg/L in
Stellwagen Basin (Figure 3-11). The survey-average minimum DO concentrations in the
nearfield were higher in 1996 than in either 1994 or 1995, although the 1996 concentrations
were still significantly lower than in 1992 and 1993. The lower minimum concentrations in
1994 and 1995 were caused by lower pre-stratification DO concentrations in late spring,
faster rates of DO decline during stratification (Figure 3-12) and the length of the stratifica-
tion period. The faster rates of DO decline in 1994 and 1995 were driven by warmer bot-
tom water temperatures. In 1996, DO concentrations in early spring were higher, bottom
temperatures in summer were generally lower, and stratification breakdown began earlier,
all resulting in higher minimum DO concentrations.
Productivity and Respiration
Productivity measurements during 1996 showed that peak production in the more offshore
areas of the nearfield occurred during the late winter bloom in February. Smaller peaks
occurred in early July when a bloom developed offshore, and in late September with the
overturn of nutrients. The more inshore areas of the nearfield and Boston Harbor experi-
enced peak production in early summer (June), with smaller peaks in the late spring and
August. Surface respiration was highest during the late spring and early summer as the
winter/spring bloom decayed. Bottom water respiration was highest during the late sum-
mer and early fall.
34 / OUTFALL MONITORING OVERVIEW REPORT: 1996 - MWRA
\cnae
aie |
wa
°
\ \ f ; N f,
4 { Ni x /
8 \ ‘ \/ D 4
6
—e— Surface
—®— Bottom
5
S 3 § $ 8 8 & 8 3 3 3 BS 3 3 8 3 3 8 8 3
58 $8 § 3 8 § & § 8 F FS 8 FES
FIGURE 3-11
1992-1996 Dissolved Oxygen
Cycle in Surface and Bottom
Waters in Stellwagen Basin
(Error bars represent +/- one standard
deviation.)
"1
SS | 1992
> 41993
T I mi994
10 oo € 1995 |
= ae 1996
9 Tt {
z L TS
3 1992
&
5
= 8 T 1993,
fo} lL ry
3 1998 i
[-3
a
a 7. _Year Slope 1995
(mg/L /day)
FIGURE 3-12 1992 70.024
Rate of Decline of 1995 2088 wes
Dissolved Oxygen ae oe
1880} 2xY§E 6 fomme———] 1995 -0.027
Concentrations in Bottom 1996 70.025 [
Waters in the Nearfield. Average -0.026
(Error bars represent +/- one
standard deviation.) 5
Jun Jul Aug Sep Oct
13
12
abl
10
W
10
MWRA + OUTFALL MONITORING OVERVIEW REPORT: 1996 / 35
Marine Mammal/Sea Turtle Observations
A number of whales, harbor porpoises, and harbor seals were sighted during the nearfield
surveys. A right whale was observed during the early April survey. An unidentified whale
was observed during the mid-June survey. During the early August survey, a fin whale and
three minke whales were sighted. A total of 16 harbor porpoises were observed during sur-
veys in February, April, and November, with the majority of observations during the early
April survey. A total of seven harbor seals were sighted during surveys in February, April,
and September. No sea turtles were sighted during the surveys.
36 / OUTFALL MONITORING OVERVIEW REPORT: 1996 - MWRA
MWRA -
4.0 Benthic Studies
4.1 Benthic Issues
One of the concerns about relocating the sewage outfall to a relatively unpolluted area of
Massachusetts Bay is that the discharge might result in unexpected impacts to the bottom-
dwelling organisms in the vicinity of the outfall. In a healthy environment, both the infau-
na (organisms living in ‘the bottom sediments) and epifauna (organisms living on the sedi-
ment surface or attached to large rocks or surface features) will be diverse and indicative of
clean environmental conditions. In addition to studying the biological composition of the
communities in the vicinity of the new outfall, several additional parameters which might
also influence the distribution of species are also measured either annually or at longer
intervals. Such parameters include sediment grain size composition, amounts of total
organic carbon and toxic contaminants present in the sediments, and depth of oxygen pene-
tration.
4.1.1 Community Structure
In general, a healthy benthic community comprises many different species with a balanced
distribution of individuals among species. Several statistical measures can be used to
determine the diversity of these communities. Healthy, well-established communities will
have high diversity values. Communities in areas that have been adversely impacted and
are environmentally degraded will have low diversities and will be dominated by one or a
few pollution-tolerant species.
4.1.2 Sediment Grain Size Composition
Studies of animal-sediment relationships have shown that
many benthic species have definite associations with par-
OUTFALL MONITORING OVERVIEW REPORT: 1996/ 37
Benthic issues include
potential hypoxia effects of
nutrients and organic matter,
accumulation of toxics, and
smothering caused by solids
deposition.
FIGURE 4-1
Soft-Bottom Benthic
Stations in the Bays
ticular sediment types. For example, some polychaete
worms are found only in areas of very coarse-grained sed-
iments, while other species are associated with muddy
(fine-grained) sediments. Information on the pre-dis-
charge pattern of sediment types in the Bays and the nat-
ural faunal changes associated with storm-induced or
other natural shifts in sediment composition is necessary
to help distinguish potential impacts of the outfall dis-
charge from natural cycles of a healthy environment.
4.1.3 Nutrients/Oxygen
The concern regarding the potential impact of nutrients is
that eutrophication {as discussed in the Water Column
Monitoring section) might lead to low levels of oxygen
(hypoxia) in bottom waters overlying the seafloor and,
consequently, decreased oxygen within the sediments. A
healthy benthic community depends on well-oxygenated
overlying water to deliver the oxygen necessary for benth-
ic respiration and metabolism. Generally, the healthier
I I I
+ Near/midficld Stations
© Farficld Stations
— avast
38 / OUTFALL MONITORING REPORT: 1996 - MWRA
and better established the community, with larger and
more active animals present, the deeper the penetration
2 of oxygen into the sediment. Therefore, the depth of
MILES
FFIO
FB cy)
It FFI2
+
MF20
. MFO /
oxygen penetration in soft sediments is monitored by the
MWRA as a measure of environmental health with
. respect to sediment oxygen supply and demand.
MF21
ane
y
+
/ NB NF23
Future Outfall,
7
7
-
4.1.4 Toxic Contaminants
Metals or other toxic substances in the wastewater dis-
charge could potentially accumulate in the sediments
fart near the outfall. Metals may precipitate directly out of
\ the water column, whereas other toxic substances may
SN wrta attach directly to solids which then settle to the bottom.
il In areas where sediment depositional rates are high,
these contaminants could concentrate and adversely
impact the health of the bottom communities.
Therefore, toxic contaminant concentrations in sedi-
ments are monitored periodically by the MWRA to
assess the validity of the prediction that discharge of
wastewater from the outfall will not lead to toxic conta-
mination of the sea floor.
mriz7 | *NFIS
+
NFI4
+
a
_
— a ae
+
MF22 \
+ FFIS
+ MF2
rst
FIGURE 4-2
Nearfield and Midfield Soft
Bottom Stations
The benthic program includes
soft-bottom surveys, a hard-
bottom survey, and nutrient
flux surveys.
Tso
4.1.5 Solids and Organic Material
Suspended solids are tiny particles (mud, organic debris)
that are present in the water column and in the effluent discharged at the outfall. A poten-
tial impact of solid particles on the habitat is smothering of the benthic organisms.
Smothering would occur if the rate of particulate deposition became so great that the organ-
isms could not maintain contact with oxygenated water at the sediment/water interface.
The problem would be even greater if the settling solids consisted of organic material that
consumes oxygen. Sediment grain size composition and total organic carbon content of the
sediments are measured as part of the soft-bottom benthic program.
4.2 Monitoring Program Design
The benthic monitoring program is designed to provide qualitative and quantitative descrip-
tions of the benthic environments of Boston Harbor and Massachusetts and Cape Cod Bays.
The goals of the benthic program are twofold. The first objective is to document the recov-
ery of benthic conditions in Boston Harbor following the cessation of sludge discharge and
improvements in Combined Sewer Overflow (CSO) treatment and discharge. Comparison of
benthic parameters measured before and after termination of sludge disposal into the
Harbor has provided valuable information on bottom sediment response and benthic
ecosystem recovery. Further improvements in sediment quality in Boston Harbor should be
seen after the transfer of sewage discharge from the existing Deer Island outfall to the new
Massachusetts Bay outfall in 1998.
The second objective of the benthic program is to collect background data on physical,
MWRA : OUTFALL MONITORING REPORT: 1996 / 39
chemical, and biological processes in the benthic environment near the outfall location in
Massachusetts Bay. These data are essential to assessing potential impacts of the dis-
charged effluent on the surrounding benthic ecosystem.
Three types of benthic surveys are performed: soft-bottom infauna surveys, hard-bottom
video surveys, and nutrient flux surveys. Each of the three survey types is described below.
4.2.1 Soft-Bottom Benthic Surveys
The soft-bottom benthic surveys are designed to assess sediment quality and the status of
the infaunal benthic communities. Sediment grab samples taken at each station are
processed to determine the number of species and individuals present in each sample.
Replicate samples are taken at selected stations. Previously, sediment samples were ana-
lyzed for toxic contaminants and sediment profile images were taken at selected locations to
determine the apparent redox potential discontinuity (RPD) depth and other sediment prop-
erties. Toxic contaminant analyses and sediment profile image studies were not performed
in 1996. Having collected baseline data in several previous years, OMTF allowed MWRA to
suspend these portions of the monitoring pro-
gram in 1996. Sediment profile image studies
will be performed again in 1997 and sediment
toxic contaminant analysis will resume in 1998.
Key: IN | 42°22"
+ Traditional Stations
Sediment Profile
Imaging Stations .
The soft-bottom sampling regions are
Massachusetts and Cape Cod Bays and Boston
Harbor. Sampling stations in Massachusetts
and Cape Cod Bays are shown on Figure 4-1;
stations in the vicinity of the new outfall are
shown on Figure 4-2. The soft-bottom surveys
around the new outfall location in
Massachusetts Bay are designed to provide
baseline data on the sedimentary environment,
including concentrations of contaminants and
benthic infaunal communities. These data will
be used as a benchmark to evaluate the effects
of sewage disposal from the outfall when it
becomes operational in 1998.
42°20"
42°18"
Rige R27, @
ae pg
R4ége RSO
= 42°16
The benthic monitoring program uses a differ-
ent definition of nearfield from that used by the
water column monitoring program. For the
; FIGURE 4-3
water quality program, the nearfield is a rectangle with sides five kilometers (three miles) Boston Harbor Benthic
from the outfall and farfield stations are those outside the rectangle. The benthic program Sampling Stations
originally followed a similar convention, but greater sophistication of spatial analyses has
allowed discrimination among three subareas of the study area: the nearfield is 0-2 kilome-
ters, the midfield is 2-7 kilometers, and the farfield is greater than seven kilometers from the
new outfall. The nearfield coincides with the area that is most likely to be impacted
according to the SEIS. The midfield and farfield are farther from the outfall and should not
show impacts. Three stations originally designated as farfield stations are now considered
to lie within the midfield area. The original designations for these stations (FF10, FF12,
RING REPORT: 1996: MWRA
FF13) have been retained because there already are
midfield stations MF10, MF12, and MF13. The reas-
signment of these three farfield stations was imple-
mented in the 1996 program.
7049" 700048" 70247" 70046!
42<04 Farfield soft-bottom sediments are also sampled once
per year at eight locations throughout Massachusetts
and Cape Cod Bays (Figure 4-1). The farfield stations
are used as a reference for the nearfield and midfield
stations and as true monitoring stations in the unlikely
event that the effects of the sewage discharge extend
42g farther than expected.
420024
42023
The sampling design for the soft-bottom benthic pro-
gram provides at least the minimum number of sam-
ples (12) necessary to detect change in each area
(Coats, 1995). There are eight stations (two with trip-
42-22 licate samples = 12 samples) in the nearfield, 15 sta-
tions {four with triplicate samples = 23 samples) in
the midfield, and eight stations (all with triplicate
samples = 24 samples) in the farfield.
420022"
The soft-bottom surveys in Boston Harbor are
designed to measure the long-term recovery of benthic
communities and sedimentary conditions as sewage
discharge has been phased out of this area. These
FIGURE 4-4 surveys are performed twice each year. Replicate grab
Transect locations for nearfield samples are collected at eight stations (Figure 4-3) during each survey. Sediment profile
hard-bottom video survey. Open images are taken during the summer survey at the same eight stations, as well as an addi-
circles are 1995 stations; filled tional 52 stations.
circles are 1996 stations.
4.2.2 Hard-Bottom Surveys
A video survey of the nearfield hard bottom is performed annually to supplement the
nearfield soft-bottom surveys. A considerable part of the area closest to the new outfall is
hard bottom, consisting of drumlins that shoal to about 25 meters. Grab samples for
quantitative faunal analyses cannot be obtained in these areas. The hard-bottom survey
provides semi-quantitative visual information on the benthic habitat and the organisms
occupying these rock and cobble areas. Both video and still photographs are taken dur-
ing this survey: the video survey provides greater areal coverage and the still pho-
tographs provide fine detail and more accurate assessments of the benthic communities
inhabiting these areas.
A Remotely Operated Vehicle (ROV) equipped with both a color video camera and a 35-mm
still camera is used in these surveys. The ROV travels along established transects in order
to permit detection of year-to-year changes In 1996, 20 stations along six transects were
surveyed (Figure 4-4).
MWRA « OUTFALL MONITORING REPORT: 1996 / 41
Parameter
Community Structure
(Diversity, Species
Composition, and
Species Abundance)
in outfall midfield area
TABLE 4-1
Benthic Thresholds Compared to 1996 Monitoring Results
Caution Level
Species diversity, composition,
and relative abundance patterns
measured in the midfield appre-
ciably depart from those mea-
sured during the baseline moni-
toring period, after factoring out
the effect of storms on sediment
texture. Specific diversity thresh-
old vatues are being developed.
Warning Level
None.
1996 Results
Shannon-Wiener Diversity Index
Midfield mean = 2.8
(Range 1.95 - 3.30)
(See also Table 4-2)
Results in similar range to
previous years.
Depth of Oxygenated
Sediments [Redox
Potential
RPD depth declines by half.
The threshold value is under
development.
None.
No 1996 data available;
1995 results: Nearfield
mean = 3.5 cm
outfall nearfield area.
90% of EPA sediment criteria.
NOAA Effects Range Median (ER-M) value.
Examples: NOAA ER-M values:
PCBs = 180 ng/g
Mercury = 0.71 g/g
Discontinuity (RPD) (Range 1.8 - >6.2 cm)
Depth] in outfall
nearfield area.
Toxic Contaminant Nearfield mean toxic contami- Nearfield mean toxic contaminant concentra- No 1996 data available;
Concentrations in nant concentrations greater than | tions greater than EPA sediment criteria or the 1995 example results:
PCBs: Geometric Mean = 4 ng/g
Range = 1.1 - 53 ng/g
Mercury:
Geometric mean = 0.16 Ltg/g
(See also Table 4-4)
Trigger Parameter
TABLE 42
1996 Diversity Data for the Midfield Stations (2-7 km from the outfall)
Caution Level
Warning Level
Range and Mean ( x )
Shannon-Wiener H' Appreciable change No criteria 1.95 (MF4) - 3.30 (FF10)
x =2.80
Evenness J’ Appreciable change No criteria 0.48 (MF4) - 0.72 (MF9, MF16)
x = 0.65
Hurlbert Rarefaction Appreciable change No criteria 11.21 (MF4) - 21.87 (FF10)
# species./50 ind. x= 17.09
Hurlbert Rarefaction Appreciable change No criteria 15.65 (MF4) - 31.01 (FF10)
# species./100 ind. x= 23.71
Hurlbert Rarefaction Appreciable change No criteria 34.47 (MP4) - 65.38 (FF10}
# species./500 ind. x= 45.74
42 / OUTFALL MONITORING REPORT: 1996 - MWRA
I I
4.2.5 Nutrient Flux Surveys
Nutrient flux surveys are designed to measure nutrient
interactions between sediments and the water column in
Boston Harbor and Massachusetts Bay. The nutrient flux
e —| ane surveys take place five times per year at seven sampling
" locations (Figure 4-5). An eighth station (Quincy Bay)
\ was added during the last three surveys in 1995; data
collection at this station has continued in 1996. Using a
| aoe sediment coring technique, vertical columns of sediment
are removed and brought to the surface intact. For each
sediment core, measurements are made of sediment oxy-
gen demand and oxygenation, sediment nutrient flux,
and nutrients in the sediment pore water (water con-
tained between sediment particles). Analysis of these
parameters provides information necessary to assess
nutrient and oxygen exchanges between the sediments
and the water column, as well as the potential for
impacts on sediment and water column oxygen.
FIGURE 4-5
Benthic Nutrient Flux
Sampling Locations 4.3 Threshold Comparison
Trigger parameters and their thresholds for the benthic sediments and 1995 monitoring
results are summarized in Table 4-1. The basis of the trigger parameters and threshold
values, as well as progress in comparing monitoring results to threshold values are dis-
cussed below.
Benthic Community Structure
Benthic community thresholds are intended to verify the prediction in the SEIS that there
will not be appreciable change in the benthos outside the 2 kilometer nearfield boundary.
The trigger level to describe community change is under development, and MWRA has
been considering the utility of various measures of benthic species composition, diversity,
and relative abundance. The trigger level developed will involve comparison of a measure
of the community in the midfield area against baseline values.
Diversity values measured in 1996 at the midfield stations are given in Table 4-2. Three
measures of species diversity, Shannon-Wiener diversity (H’), evenness (J’), and Hurlbert
rarefaction are given. The station east of Nahant (FF10) continues to be the most diverse,
with H’ and Hurlbert # species/50 individuals and # species/100 individuals slightly high-
er than measured in 1995. Station MF4, north of the new outfall and east of FF10, was
the least diverse.
TABLE 4-3 Mean diversity values in Boston Harbor, the
Comparison of Mean Regional Diversity Values outfall mid-field, and the farfield are shown
4-3, hat diver-
SN TS: These values show that Giver
sity is generally | in Boston Harbor
Shannon-Wiener H’ 1.94 2.80 271 y 8 ora’ ower ty ge gs
than in the mid-field or farfield, indicating
Evenness J’ 0.53 0.65 0.61
that diversity may be a useful measure of
Hurlbert Rarefaction 13.89 23.71 25.20 ery my wt
. . benthic communicity degradation.
# species/100 ind.
MWRA : OUTFALL MONITORING REPORT: 1996 / 43
Nevertheless, establishment of the final threshold values and comparison of threshold val-
ues to post-discharge monitoring results will need careful consideration. A decrease in
species diversity or a change in species composition is not necessarily reflective of envi-
ronmental degradation. While a moderate organic enrichment of the sediment may cause
the disappearance of some sensitive species, the overall effect may not be detrimental if
increased biomass is available as a food source for bottom fishes. Also, the existing data
from previous years show that year-to-year changes in diversity or other community para-
meters can occur naturally.
Redox Potential Discontinuity
The Redox Potential Discontinuity (RPD) depth is the location where the sediment changes
from oxic, or oxygenated, to anoxic, or depleted of oxygen. The RPD depth provides an
important measure of the overall health of the benthic infauna habitat. In the absence of a
state standard for the RPD depth, a threshold was developed to measure and evaluate sig-
nificant changes in RPD depth which could provide an indication of adverse impacts from
the deposition of discharged organic material. The RPD depth threshold is applicable to the
nearfield area.
Since sediment profile image studies were not performed in 1996, the most recent RPD
depth data is from 1995. The 1995 RPD depth results indicated that, in general, sediments
appear to be well-oxygenated and are healthy with respect to the depth of oxygenated sedi-
ments. The 1995 RPD depth data showed a range of 1.8 cm to greater than 6.2 cm (sedi-
ments oxygenated at maximum depth reached), with a mean value of 3.5 cm. Comparison
of the results from 1995 and previous years indicates that RPD depth values are similar and
have not changed significantly.
Toxic Contaminants
Thresholds for toxic contaminants in sediments are established to be protective of benthic
organisms. Monitoring results from the post-discharge operation period will be compared to
sediment threshold values to verify predictions of potential toxic contaminant concentration
in sediments and to assure that adverse toxic effects to benthic organisms do not occur.
Specific threshold values are based on EPA sediment criteria and NOAA ER-M values. Draft
EPA sediment criteria exist for five organic contaminants: acenaphthene, fluoranthene,
phenanthrene, dieldrin, and endrin. NOAA ER-M values are available for a variety of organ-
ic and metal contaminants.
No sediment samples were obtained for toxic contaminant analysis in 1996. Comparison of
1995 sediment concentration data to relevant thresholds is provided on Table 4-4. The trig-
ger parameter is expressed as a sediment concentration averaged over the nearfield stations.
As in previous years, organic contaminant concentrations were generally low and did not
exceed any of the thresholds; even stations with relatively high organic content had contam-
inant concentrations well under EPA sediment criteria. Metal concentrations were similar to
those measured in previous years. The nearfield mean concentrations for all heavy metals
were below the warning level. One individual nearfield station (NF24), however, had a
mercury concentration of 1.69 pg/g, exceeding the warning level of 0.71 g/g. Elevated
mercury was also apparent in the 1994 data and reflects the very highly depositional nature
of those sites.
44 / OUTFALL MONITORING OVERVIEW REPORT: 1996 - MWRA
TABLE 4-4
Toxic Contaminant Thresholds and 1995! Data for the Eight Nearfield Stations (0-2 km from the outfall)
Trigger Parameter Caution Level: Warning Level: Range and Mean (x), and
(units) 90% EPA criterion” EPA criterion’ or (Geometrical Mean)
(NOAA ER-M) * level
Organic Contaminants
Total PAH - (44,792) 78 (NF17) - 10,903 (NF24)
(ng/g) X = 2,380; (870)
Acenaphthene 1170 1300 ND (2 stations) - 41(NF24)
(ng/g) (600) % = 11; (NAF
Fluoranthene 5580 6200 8.8 (NF17) - 1050 (NF24)
(ng/g) (5100) X = 245; (96)
Phenanthrene 1620 1800 4 (NF17) - 570 (NF24)
(ng/g) (1500) XK = 132; (49)
Total PCB a (180) 1.4 (NF13, NF17, NF23) - 53 (NF24)
(ra/a) XK = 10; (4)
Total Chlordane - (6) ND (7 stations) - 1.09 (NF24)
(ng/g) X = 0.136; (NA)
Total Dieldrin 99 110 ND®(8 stations)
(ng/g) (8) X = 0; (NAY
Endrin 37.8 42 ND* (8 stations)
(ng/g) x = 0; (NA
Total DDT - (46.1) ND (8 stations) - 11.21 (NF24)
(ng/g) % = 2.2; (NA)®
Trace Metal Contaminants
Cadmium - (9.6) 0.05 (NF13) - 0.46 (NF24)
(ug/g) X = 0.12; (0.09)
Chromium - (370) 23.2 (NF23) - 177.0 (NF24)
(ug/g) & = 53.5; (41.7)
Copper - (270) 3.41 (NF23) - 54.25 (NF24)
(ug/g) X = 16.60; (11.22)
Lead _ (218) 25.8 (NF23) - 92.9 (NF24)
(ug/g) X = 44.9; (41.3)
Mercury _ (0.71) 0.029 (NF23) - 1.69 (NF24)
(9/9) X = 0.36; (0.16)
Nickel - (51.6) 7.2 (NF17) - 31.8 (NF24)
(ug/g) X = 13.8; (12.3)
Silver _ (3.70) 0.08 (NF17) - 1.4 (NF24)
(19/9) X =0.3; (0.2)
Zinc - (410) 25.2 (NF17) - 131.5 (NF24)
(ug/g) XK = 49.5; (42.7)
‘ No sediment samples were obtained for toxics analysis in 1996.
? Values for EPA sediment quality criteria assume 1% organic carbon. Hull and Suter (1995)
2? NOAA ER-M levels taken from Long ef af. (1995)
* From Long and Morgan (1992)
5 NA = Not Available. Geometric means cannot be calculated for data sets that include zeroes.
® Detection levels: Dieldrin = 0.022 ng/g; Endrin = 0.0061 ng/g.
MWRA : OUTFALL MONITORING REPORT: 1996 / 45
4.4 Monitoring Results
4.4.1 Biological
Community Results
Surveys of benthic biological communities are
used by the MWRA to evaluate the overall
ecological health and environmental quality of
Boston Harbor and the Massachusetts
Bay/Cape Cod Bay ecosystems. In addition to
species composition and density, sediment
grain size distribution and total organic car-
bon, which may influence species distribution
patterns, are measured.
700255"
I
KEY
+ Traditional Stations
‘© Sediment Profile Imaging
ns
=] Full Mat (Tubes present in 2or
of 3 replicates)
Fe Patchy Mat Tubes presentin
TTearrx Suecossional stages given
Teteptit Ora stellons ocieide tre
indeerrine’’ mat area. Number in
parentheses ls number of
UV
f}- 420020"
o
°
4.4.1.1 Boston Harbor
Prior to the abatement of sludge discharge in
December 1991, some stations in the northern
portion of Boston Harbor were generally char-
acterized by the presence of a few, pollution-
tolerant species, Stations in the northern part
420015"
of the Harbor (i.e., closest to the outfalls)
were characterized by opportunistic, highly FIGURE 46 ;
variable assemblages able to tolerate high levels of organic material in the sediments. Distribution of Amphipod Tabe
toe A , Mats in Boston Harbor.
Stations in the southern part of the Harbor were generally more diverse, with somewhat s °
more stable assemblages of organisms that require better sediment quality. In the years
since sludge abatement, stations in the north have become progressively more similar to
stations in the south. This trend continued in 1996.
The most significant change in the benthos since sludge abatement has been the wide-
spread development of dense tube mats of the opportunistic, yet pollution-sensitive, amphi-
pod Ampelisca abdita. The powerful northeaster in October 1991 may have helped to set
the stage for the establishment of Ampelisca mats in the Harbor by causing a shift in bot-
tom sediments from mud to mostly fine sand, which is the substrate preferred by settling
larvae of this species. Prior to 1991, less than 20 percent of stations surveyed showed the
presence of amphipod tube mats; by 1995, more than 60 percent of the stations showed
well-developed mats. In 1996, tube mats were seen at all but a few of the southern inshore
stations (Figure 4-6).
Infaunal species richness has increased Harborwide since 1991, especially at the northern
stations. Several species that were previously rare or absent are now becoming dominants
(e.g., Chaetozone vivipara and amphipods belonging to the genus Corophium). Stations in
the north that were affected by the old Deer Island outfall were, prior to sludge abatement,
overwhelmingly dominated by one or a few pollution-tolerant species. These stations con-
tinued to show increasingly diverse assemblages.
46 / OUTFALL MONITORING REPORT: 1996 - MWRA
ra)
‘Symbol |Diversity
16 - 20 species/100 individuals
21 - 23 species/100 individuals
24 - 26 species/100 individuals
27 - 31 specias/100 individuals
©
4.4.1.2 Massachusetts
Bay/Cape Cod Bay
Benthic biology surveys in Massachusetts and
Cape Cod Bays provide baseline data that can
2 be used as a benchmark to evaluate the poten-
T
6:
e
16
9. tial effects of sewage disposal from the new out-
fall when it becomes operational in late 1998.
Future
Outta
vs A
a Nearfield and Midfield Soft-Bottom
“ Communities
e| \@ we e,, The nearfield and midfield stations are all in
2 a Massachusetts Bay. Unlike Boston Harbor,
NN @. L Massachusetts Bay is not a stressed environ-
nearitamitt ~~ a 4 «2 Ment, and the benthic community composition
is generally reflective of a clean offshore envi-
ronment. Statistical analysis of the 1996 data
indicates that the stations are roughly grouped
in bands or patches approximately parallel to
2 the mouth of the Harbor. This pattern may
reflect sediment distribution patterns, which are
e. influenced by water circulation patterns and
- occasional storm events.
e The species composition of the benthic commu-
22 nities is largely determined by sediment grain
size. In fine-grained sediments, some poly-
7054 70°52"
Figure 4-7
Soft-Bottom Benthic Community
Diversities at Nearfield and
Midfield Stations.
050" Toa" chaete species (spionids and capitellids) are
most abundant; whereas in sandier sediments
other polychaetes (syllids and paraonids), amphipod crustaceans, and certain oligochaetes
predominate. These basic community structures have been observed since the inception of
this program, with changes at individual stations reflecting changes in sediment composi-
tion, perhaps due to storm-generated currents. Results of the August 1996 benthic survey
were generally similar to those obtained in 1995 and previous years.
As in 1995, the most common dominant species in the nearfield were two spionid poly-
chaetes, Prionospio steenstrupi and Spio limicola, the capitellid Mediomastus californiensis,
and the lumbrinerid Ninoe nigripes. The last species has been relatively widespread
throughout the duration of this study, but was especially common in 1996, possibly because
sampling took place just as the postlarvae settled. As much as 80 percent of the individuals
in a single sample were tiny juveniles which may succumb to intense predation in the time
period following settlement.
Species diversity as measured by several statistical methods indicated that Station MF4
(north of the future outfall) had the lowest diversity and FF10 (east of Nahant) had the
highest diversity (Table 4-2). However, no particular geographical pattern in the distribution
of diversities could be identified (Figure 4-7). The number of species ranged from 19 to 29
species per 100 individuals in the nearfield, and from 15 to 31 species per 100 individuals in
the midfield.
MWRA + OUTFALL MONITORING REPORT: 1996 / 47
Farfield Soft-Bottom Communities
Benthic community structure at the farfield stations is influenced by water depth and loca-
tion (Massachusetts versus Cape Cod Bays). The two stations in Cape Cod Bay differ in
terms of dominant species, probably because of a different sedimentary environment. In
1996 as in 1995, cossurid polychaetes were dominant at the Cape Cod Bay stations, but the
spionid polychaete Prionospio steenstrupi ranked first at all Massachusetts Bay stations.
Diversities at the farfield stations were basically similar to those at the near- and midfield
stations, ranging from 18 to 31 species per 100 individuals. Species richness and diversity
was slightly higher in 1996 than in 1995, but was within the range of previous observa-
tions. Species diversity, species composition, and infaunal density all exhibit fluctuations
from year to year, as they do in the nearfield. These variations probably reflect changes in
area-wide environmental conditions that in turn influence the timing and success of larval
setilement of benthic organisms. However, faunal assemblage patterns in the farfield are
more consistent than those in the nearfield, indicating that monitoring the farfield stations
will help to distinguish changes due to natural processes from those caused by discharges
from the new outfall.
Nearfield and Midfield Hard-Bottom Communities
Only about one-third of the seafloor in the near-field consists of the sands and muds that
are the focus of the soft-bottom monitoring program. The remainder is made up of a variety
of gravel, cobble, and boulder fields covering the tops and sides of submerged drumlins
which shoal to about 25 meters. Because most potential impacts caused by sewage pollu-
tion are associated with suspended solids that do no permanently settle in hard-bottom
areas, there is little likelihood for adverse impacts. However, the OMTF required that
MWRA study rocky environments in the nearfield to ensure no dramatic impacts occur.
The complex topography in the hard-bottom areas in western Massachusetts Bay has a sub-
stantial influence on epibenthic communities. These communities are primarily determined
by depth, with red algae dominating the shallower drumlin tops (about 25 meters depth)
and macroinvertebrates dominating the deeper bottoms. Location on the drumlins (top ver-
sus flanks), depth, bottom type, and habitat relief all appear to play a role in determining
the structure of benthic communities inhabiting hard-bottom areas. Some species show
strong preferences for specific habitats, while others are broadly distributed. Some areas
are homogeneous in terms of bottom type and the fauna inhabiting them, while others
exhibit more patchiness. The communities of attached and encrusting animals and plants in
rocky bottom environments in the vicinity of the outfall are broadly similar to those found
throughout the Massachusetts Bay and the larger Gulf of Maine (the arm of the Atlantic
Ocean between Nova Scotia (Canada) and Cape Cod.
4.4.2 Nutrient Flux Results
4.4.2.1 Boston Harbor
Rates of total infaunal community respiration, while showing significant inter-annual vari-
ability, appear to be increasing in portions of Boston Harbor. While sludge was being dis-
charged in the Harbor, the benthic community was apparently overwhelmed by the amount
of settling organic material. When this practice ended, the benthic community began to
degrade the material that had accumulated over the years. Rates of the organic matter
breakdown process, or remineralization, were more than twice as high in 1995 than report-
ed in any previous monitoring period. Results from 1996 studies suggest that depuration of
48 / OUTFALL MONITORING OVERVIEW REPORT: 1996 - MWRA
sediment nutrients and organic matter is relatively rapid following infaunal recolonization.
Rates of denitrification and community metabolism declined and sediment oxidation began
to increase in 1996, suggesting that the labile organic matter present in the sediments may
be declining under continued bioturbation.
The colonization of Harbor sediments by infauna, particularly the development of dense
amphipod mats (Ampelisca and Leptocheirus), are likely responsible for the changes in
these rates. Both the degree of sediment oxidation and rates of sediment/water column
exchange has increased through bioturbation and burrow ventilation by these organisms.
Remineralization rates and denitrification were significantly enhanced in areas densely
colonized by amphipods (north of Long Island and Hull Bay) compared to areas with
lower total infaunal densities (Quincy Bay). Infauna affected carbon mineralization
directly through their metabolism and indirectly through irrigation of surficial sediments.
The result was increased oxidation of surficial sediments and higher rates of nitrifica-
tion/denitrification.
4.4.2.2 Massachusetts Bay
In contrast to Boston Harbor, where large and rapid changes are evident, the stations sam-
pled in Massachusetts Bay showed an inter-annual variability in respiration of less than 20
% (generally only 10%). Rates of biogeochemical cycling were similar in 1996 to those
measured in 1995 and previous years. The stability of these measurements indicates that
they will be sensitive tools for detecting relatively small changes in carbon enrichment.
The Massachusetts Bay benthic environment plays less of a role in contributing to nutrient
flux and DO depletion than it does in Boston Harbor. The greater water depth in the Bay
allows more remineralization to take place within the water column before particles reach
the benthos, and stratification tends to isolate the benthos from the upper water column.
Bottom waters may be affected by the benthos during periods of stratification.
5.0 Fish and Shellfish
5.1 Fish and Shellfish Issues
One of the recurrent public concerns regarding the relocation of the outfall is the potential
impacts to water chemistry and marine life. These concerns include potential impacts of Fish and shellfish issues are
the outfall to the health and well-being of local fishery stocks and, of perhaps greater public © mainly associated with the
interest, the potential effect on the quality and safety of fish and lobster caught in Boston potential effects of toxics
Harbor and Massachusetts. Toxic contaminants in the effluent have the potential to cause a bioaccumulation.
variety of problems throughout the food chain. Because many toxic contaminants adhere to
particles, toxic impacts on marine animals are likely to primarily affect bottom-dwelling
organisms and the animals that feed on them, such as flounder and lobster. Shellfish, such
as mussels and clams, that feed by filtering suspended matter from large quantities of water
are also potential bioaccumulators of toxic contaminants. Exposure of flounder or lobster to
toxic contaminants may result in fin rot, black gill disease, or other gross abnormalities.
Consumption of contaminated organisms results in exposure of predators through the food
chain including ultimately human consumers of fish and shelifish.
5.2 Monitoring Program Design
FIGURE 5-1
The fish and shellfish monitoring program addresses potential risks to human health and Sampling Stations for Winter
the environment arising from contamination of ecologically significant and economically Flounder, Lobster and Mussels
important fish and shellfish stocks. The primary goals of this monitoring program are (1) to during 1996.
evaluate the health of these marine resources
in terms of disease, and (2) to evaluate STATIONS: N
1 — Deer Island Outiall — flounder, lobster, mussels
2 — Nantasket Beach — flounder
3 — Broad Sound — flounder
4 — Future Outfall Site — flounder, lobster, mussels
5 — Cape Cod Bay Site — flounder, lobster
6 —N.E. Aquarium Discovery Site — mussels
organic and inorganic contaminant concen-
trations in the organs and edible tissues of
these organisms. Bioaccumulation data are
collected from flounder, lobster, and mussel
populations in Boston Harbor, Massachusetts
Bay, and Cape Cod Bay. Comparison of the
data between stations and between pre- and
post-discharge periods will allow evaluation
of spatial and temporal trends in the fish-
eries. In addition, the biomonitoring pro-
grams provide baseline data that may be
used to assess the potential environmental
impact of the effluent discharge on
Massachusetts Bay, and to evaluate the facili-
ty’s compliance with the NPDES effluent dis-
charge permit requirements. The three bio-
monitoring surveys are outlined below.
Massachusetts
Bay
The flounder survey is designed to collect Cape Cod Bay
sufficient mature winter flounder to perform
general and histopathological examinations
50 / OUTFALL MONITORING OVERVIEW REPORT: 1996 - MWRA
and determine bioaccumulation of priority pollutant organics, metals, and other con-
The fish and shellfish stituents. Flounder surveys began in 1991 and are performed annually at five locations:
program consists of the Deer Island outfall, future outfall site, Cape Cod Bay site, Broad Sound and Nantasket
monitoring of flounder, Beach (Figure 5-1). Fish are collected using a bottom trawl deployed by a commercial
lobsters, and mussels. dragger.
Similarly, the lobster survey is designed to collect sufficient mature lobster specimens to
provide data on gross abnormalities and provide sufficient tissue samples for determination
of physiological condition and body burden of contaminants. Once each year since 1992,
lobsters have been collected in 25 to 60 commercial lobster traps deployed at each of three
locations: the Deer Island outfall, future outfall site, and Cape Cod Bay site (Figure 5-1).
In the mussel bioaccumulation survey, blue mussels are obtained from a clean location,
deployed in floating cages or “arrays”, and recovered for determination of biological condi-
tion and short-term accumulation of contaminants in tissues. Mussels are used as test
organisms because of the extensive database available on the rate at which they bioaccu-
TABLE 5-1
Fish and Shellfish Thresholds Compared to 1996 Monitoring Results
1996 Results
Parameter Caution Level
Warning Level
Mercury in fish
and shellfish
from Outfall site
Annual mean mercury concentration in flounder, lob-
ster, and caged mussel meat greater than 0.5 p9/g
wet weight (50% of the US FDA action level).
Annual mean mercury concentration in
flounder, lobster, and caged mussel
meat is greater than 0.8 j1g/g wet
weight (80% of the US FDA action
level).
Flounder: 0.1 pg/g
Lobster: 0.18 Lg/g
Mussel: 0.03 g/g
PCBs in fish and
shellfish from
Outfall site
Annual mean PCB concentration in flounder, lobster,
and caged mussel meat greater than 1 i1.g/g wet
weight (50% of the US FDA action level).
Annual mean PCB concentration in
flounder, lobster, and caged mussel
meat is greater than 1.6 yig/g wet
weight (80% of the US FDA action
level).
Flounder: 0.04 ug/g
Lobster: 0.02 tug/g
Mussel: 0.02 yg/g
Lead in mussels
Annual mean lead concentration in caged mussel
Annual mean lead concentration in
Mussels: 0.3 g/g
incidence in fish
from outfall site
than interim harbor prevalence (1991-1996): 48%
The final baseline prevalence will be based on
1991-1998 data.
at Outfall site meat greater than 2 g/g wet weight. caged mussel meat is greater than
3 1.9/9 wet weight.
Lipid-normalized | Lipid-normatized toxic concentrations in flounder, None. Concentrations in tg
toxics in fish and | lobster, and caged mussel meat greater than two toxic per gm lipid
shellfish from times the interim baseline concentrations (i.¢., aver- Flounder DDT: 1.02
Outfall site age value from 1992-1996 data). The final baseline Flounder PCB: 10.19
concentration will be based on 1992-1998 data. Lobster DDT: 0.56
Interim baseline (1992-1996) concentrations in Lobster PCB: 4.44
Lag toxic per gm lipid. Mussel DDT: 0.28
Flounder DDT: 1.62 Mussel PAH: 1.35
Flounder PCB: 14.94 Mussel PCB: 0.94
Lobster DDT: 0.56
Lobster PCB: 4.46
Mussel DDT: 0.66
Mussel PAH: 6.22
Mussel PCB: 2.58
Liver disease Flounder liver disease (CHV) incidence greater None. Flounder CHV prevalence:
22%
MWRA + OUTFALL MONITORING REPORT: 1996 / 51
mulate contaminants and because they 100
provide good spatial and temporal exper- 90
imental control. Each year since 1987,
mussels have been deployed in replicate
arrays consisting of moored cages in 70
waters near Deer Island and in
Massachusetts Bay near the outfall loca-
CHV Prevalence (%)
8
tion (Figure 5-1). Mussel arrays are 1 ee ne Cation Level penne eee ween eee e ee werecee
deployed using a subsurface and surface 0
buoy system.
30
20
5.6 Threshold
Comparisons 0
To track the chronic environmental °
impact of the toxic contaminants, the 1091 1992 1993 1004 1995 1986
MWRA measures the concentrations of a variety of toxic contaminants in flounder, lobster,
and mussels from various locations in Boston Harbor and Massachusetts and Cape Cod FIGURE 5-2
Prevalence of CHV near the
Bays. Thresholds for fish and shellfish, summarized in Table 5-1, are designed to identify
any effects on marine life and potential effects on human consumers of fish and shellfish.
The thresholds apply to fish and shellfish caught or deployed at the new outfall site.
Of the five monitoring thresholds, three are associated with the potential for edible tissue
(flounder, lobster, mussel) to exceed warning levels for mercury, lead, or PCBs. Except for
lead, the Caution levels are 50% of the U.S. Food and Drug Administration (FDA) Action
Limits; the Warning levels are 80% of the FDA Action Limits. Lead thresholds are based
on an EPA risk assessment that determined the amount of lead that can be consumed with-
out adverse health effects. The flounder, lobster, and mussel data show that current tissue
concentrations are generally an order of magnitude or more below the Caution and
Warning levels (Table 5-1). Values approaching the Caution or Warning levels should be
readily detectable.
Because some toxics tend to concentrate in lipid-rich (fatty) tissues, a lipid-normalized
threshold was established to identify significant increases in these contaminants. This
threshold is exceeded if bioaccumulative lipophilic contaminants are twice the baseline
average at the outfall site. This baseline is the average of contaminant levels during the
years prior to the outfall relocation. Presently, the baseline data covers the years 1992-
1996, but will eventually include data from 1992-1998. The concentrations for 1996 are
shown in Table 5-1. Results from 1996 for the flounder liver and lobster hepatopancreas,
which are not considered edible tissue for any of the thresholds, indicate levels within the
range of values previously observed at the outfall site or (for lobster) slightly elevated from
last year.
In order to monitor and assess the potential impacts of toxic contaminants on flounder, a
threshold concerning the prevalence of flounder liver CHV was developed which compares
the postdischarge prevalence of CHV with the baseline average prevalence in the Harbor.
future outfall site, 1991-1996.
52 / OUTFALL MONITORING REPORT: 1996 - MWRA
The 1996 CHV prevalence at the future outfall site (22%) is below the interim threshold
value (Figure 5-2). The monitoring design will be able to detect changes approaching the
Caution Level.
5.4 Monitoring Results
The results of the fish and shellfish program have revealed temporal and areal patterns, and
illustrated the variability of the ecosystem. In general, levels of contaminants and the num-
ber of physical abnormalities in the fish and shellfish studied have decreased over the study
period. Boston Harbor organisms are the most affected by toxic contaminants, while those
in Cape Cod Bay are least affected. The following sections present the 1996 fish and shell-
fish monitoring results, along with comparisons to previous data.
5.4.1 Flounder
In 1996, winter flounder were collected at each of the five monitoring program sites: Deer
Island Flats, the future outfall site, Nantasket Beach, Broad Sound, and eastern Cape Cod
Bay (Figure 5-1). All flounder were examined for physical abnormalities and histopatholog-
ical liver lesions. In addition, the tissue from fifteen of the fifty flounder from all five loca-
tions was analyzed for concentrations of organic and inorganic contaminants.
Physical Condition and Histology
The external condition of the collected fish indicated few abnormalities, although fin ero-
sion was seen in fish from all stations. The flounder from the future outfall site showed sig-
nificantly lower levels of fin rot than fish caught at Deer Island or Nantasket Beach. The
overall levels of fin erosion observed throughout is considered low, and is well below that
observed in the late 1980s.
The flounder liver histology results indicated that flounder from all sampling locations expe-
rienced some degree of liver lesions. The flounder from Deer Island Flats and Broad Sound
exhibited the greatest prevalence of lesions (43-44%). The prevalence of one type of liver
lesion, centrotubular hydropic vacuolation (CHV), has been used by MWRA since 1991 as a
sensitive indicator of contaminant exposure in flounder from Boston Harbor and the bays.
Although there is significant regional variability, sampling results indicate that the incidence
of CHV in winter flounder has been generally decreasing since 1991. The presence of CHV
in fish from the future outfall site increased slightly in 1996 from 14% to 22%. The reasons
for this slight increase are not known, but may be due to the capture of older fish in 1996
(mean age = 4.5 years) as compared to 1995 (mean age = 4.1 years). This value still rep-
resents a decline from about 30% of the population in 1992. Meanwhile, the prevalence of
CHV in flounder from Broad Sound has dropped from more than 75% to about 44% over
the same period. In areas such as Cape Cod Bay, the prevalence of CHV has been relatively
low and constant (e.g., 1996 prevalence is 2%).
Bioaccumulation
In 1996, contaminant concentrations were measured in 15 flounder meat (e.g., fillet) sam-
ples, and 15 flounder liver samples from the Deer Island Flats, future outfall site, and Cape
Cod Bay sampling locations. All samples were analyzed for PCBs, chlorinated pesticides,
and mercury. The liver samples were also analyzed for a number of other organic and inor-
MWRA -
OUTFALL MONITORING REPORT: 1996 / 53
ganic contaminants. Annual
‘Mercury In Flounder Meat
trends for selected contami-
nants in flounder are shown in
Figure 5-3. Comparing 1996
data to last year’s results, it
can be seen that mercury and
gig wol WL
G7692 01905 wisss GIFS wi085]
ng/g wot wt
Total PCBs in Flounder Meat
hand
Note: Caution Level = 1000 ppb
i682 aes wines 1995 _a1958]
DDT In Flounder Meat
total PAH body burdens
increased, while total PCBs
and total DDT values —ere
decreased slightly. This
amount of variability in tissue ai
concentrations is not unusual
and supports the use of sever-
>
al years data to establish base- 3
line levels for contaminants.
{Note: flounder fillet results i
are reported on wet weight
basis, while flounder liver con-
PENAARAEN
[Bisse avers wise aes 01896]
‘99 lpls
oS ER EEE BE
‘Total Lipld Normalized PAH In Flounder Liver
all
ais aise “w1ess a isa0
al
centrations were normalized for lipid content.]
The 1996 monitoring results continue the general trend previously observed in the moni-
toring program (1992-1995) that contaminant concentrations in flounder meat and liver
are generally highest in Boston Harbor near the Deer Island outfall, intermediate at the
future outfall site, and lowest at the Cape Cod Bay site (Figure 5-3). Contaminant concen-
trations at the Broad Sound and Nantasket Beach stations are generally intermediate
between values at Deer Island and the future outfall site.
As shown in Figure 5-3, the levels of flounder fillet total DDT, total PCBs, and liver
hepatopancreas PAHs exhibit a spatial trend, with a gradient of decreasing contaminant lev-
els from Deer Island to the outfall site to Cape Cod Bay. The two other nearshore stations
(Nantasket Beach, Broad
FIGURE 5-3
Mercury, PCB, DDT and PAH
concentrations in flounder,
1992 - 1996.
FIGURE 5-4
Mercury, PCB, DDT and PAH
concentrations in lobster,
1992 - 1996.
Sound) are more variable
but appear to be compara-
ble to the outfall site lev-
els, In contrast, there is
little evidence of a similar
gradient in the flounder fil-
let mercury levels. Other
than generally lower levels
at Cape Cod, there is litile
Concentration (upig wot wt)
Note; Cautton Level = 0.5 ppm
[ar902 1909 w 1984 01955 mi998
Total PCBs In Lobstor Meat
Note: Caution Level = 1000 ppb
fove92 a 1900 isos G1905 1008
difference between sta-
DDT In Lobster Meat
tions. This suggests that
the distribution of mercury
in the environment may be
less localized than for the
organic contaminants and
subject to regional influ-
Concentration (ag'g wot wt)
ences (e.g., atmospheric ° E
deposition).
‘Total Lipld Normalized PAH In Lobster Hepatopancreae
Concaion oo oe
F
FA
Es
Deer Intend
outta site
[e192 a 1980 w y98s G 1995 © 1956
§4/ OUTFALL MONITORING REPORT: 1996 * MWRA
5.4.2 Lobster
Fifteen northern lobsters were collected from each of three sites (Deer Island Flats, future
outfall site, Cape Cod Bay; Figure 5-1) for the 1996 monitoring program. With the excep-
tion of two observations of shell erosion (one each at the future outfall site and Cape Cod
Bay), no deleterious external conditions were noted. Edible tissue (i.e., tail meat) and
hepatopancreas (a.k.a., “tomalley”) samples were taken from each lobster and analyzed for
PCBs, chlorinated pesticides, and mercury. The hepatopancreas samples were also ana-
lyzed for a number of other organic and inorganic contaminants. Annual trends for select-
ed contaminants in lobster are shown in Figure 5-4. The levels of most contaminants
increased from the 1995 levels, but do not suggest an increasing trend. Generally the 1996
values fall within the range of values observed during the previous 4 years. [Note: lobster
meat concentration are reported on wet weight basis, while lobster hepatopancreas concen-
trations were normalized for lipid content.]
Following a similar pattern to flounder tissue chemistry, mean concentrations of organic
compounds in edible tissue were generally highest at Deer Island Flats and lowest in Cape
Cod Bay (e.g., lobster meat total DDT, total PCBs, and PAHs in hepatopancreas).
Concentrations of mercury in lobster meat showed little spatial or temporal resolutions
between stations. Metals in lobster hepatopancreas (not shown) exhibited variable results
with lead, silver, and chromium showing a decrease between Deer Island to the outfall site
and Cape Cod Bay, while nickel showed the reverse trend, and zinc was similar throughout
the stations.
In 1996, tissue body burdens of selected organic contaminants were reported as lipid-nor-
malized concentrations (i.e., ng/g lipid) in addition to dry and wet weight concentrations.
Lipid-normalized concentrations were compared to dry weight concentrations to examine
how reporting results in different units potentially affect interannual trends. As Figure 5-5
TABLE 5-2
Comparison of Average Body Burdens of Deployed Mussels
for Selected Organic Compounds and Metals
Predeployment
Discovery Gloucester
Predeployment Future
Parameters Gloucester/Sandwich Outfall Site Discovery
PAH (ppb wet weight)
LMW PAH 28.00 161.76 139.16 53,65 28.55 253,04 | 355.24
HMW PAH 21.24 83.08 267.03 37.18 19.61 144.18 | 498.46
Total PAH 49,22 244.84 406.19 90.83 48.16 398.22 | 853.70
Pesticides (ppb wet wt)
Total Chlordane 0.46 1.53 2.87 1.60 1.66 5.20 472
Total DDT 3.33 5.35 12.11 TAT 4.91 10.24 16.59
Polychlorinated
Biphenyls (ppb wet wt)
Total PCB 10.84 20.16 57.78 20.58 16.83 32.67 75.00
Metals (ppb wet wt)
Mercury 0.01 0.01 0.01 0.02 0.03 0.02 0.02
Lead 0.70 . 0.99 1.12 0.51 0.30 0.89 1.53
MWRA : OUTFALL MONITORING OVERVIEW REPORT: 1996 / 55
FLOUNDER PCB
PPB DRY
PPB DRY
12000
10000
PPB DRY
8000
Q
a
6000 4
oO
a
4000 a
2000
o4 |
1992 1993 1994 1995 1996
—@—DRY ——LIPID
LOBSTER PCB
a
=
a
o
a
a
[ —@—DRY LIPID
MUSSEL PCB
400 6000
350
300
250
PPB LIPID
50
0) 0
1992 1993 1994 1995 1996
—@—DRY —=—LIPID
FIGURE 5-5
Comparison of PCB body
burdens reported as dry weight
or lipid-normalized concentra-
tions (note different scales)
for flounder, lobster and mussel
(1992-1996).
56 / OUTFALL MONITORING OVERVIEW REPORT: 1996 * MWRA
07
3 e \@ MWRAData
= 06 I@ NOAA Status and Trends Data
=
5 05@
2
zpos
52
oe
xz 203
Fy
z 02 ° .
5 o
Bo ° e °
2 3 e
; t
1987 1988 1989 1990 1991 1992 1993 1994 1995 1996
Year
FIGURE 5-6 « -
Indicator LMW PAH indicates (using PCBs as an exemplary organic contaminant), there was little difference
Bioaccumulation in Mussels between trends reported in different units. This figure is consistent with the small differ-
Near Deer Island Discharge, ences observed between coefficients of variation (CV) for PCBs in these three organisms
1987-1996. (during the reporting period 1992-1996). For example, the mean CVs in lobster were 27%
* Set of 12 Low Molecular
Weight (LMW) PAHs (i.e. total
of 2&3 ring groups) used by
NOAA for Status and Trends
monitoring.
with a range of 16-52% for dry weight concentrations, and 31% with a range of 16-64% for
lipid-normalized concentrations. Similar results were observed for flounder (mean 30%,
range 16-43% for dry weight; mean 30%, range 5-59% for lipid-normalized) and mussel
(mean 10%, range 6-14% for dry weight; mean 11%, range 5-16% for lipid normalized—
1995-1996 data only) PCB concentrations. These results indicate that the trends observed
are largely independent of the various reporting units.
5.4.3 Blue Mussel
A series of mussel bioaccumulation studies have been conducted since 1987 to determine
whether selected contaminants (PCBs, pesticides, PAHs, and metals) bioaccumulate in shell-
fish. Mussels were collected from two relatively clean locations: Gloucester and Sandwich,
Massachusetts and deployed in cages in three locations (Figure 5-1): near the present outfall
location at Deer Island Flats; at the future outfall site; and in the inner Harbor (hanging off
the New England Aquariums barge, the Discovery). After 60 days, mussels were harvested
for biological and chemical analyses. In 1996, the arrays were successfully retrieved at all
sites due to an improved mooring system and increased redundancy in mussel cage arrays.
Predeployment organic contaminant levels at Gloucester were higher than previous years
(Table 5-2). Also, lipid levels in mussels were higher than in previous years.
Some study contaminant levels, particulary low molecular weight PAHs, at the Boston
Harbor station at Deer Island, have generally decreased since 1987. As shown in Figure
5-6, indicator low molecular weight PAH (i.e., a set of 12 low molecular weight PAHs select-
ed to allow direct comparison between NOAA Status and Trends and MWRA data) levels
near the Deer Island outfall decreased by over a factor of five between 1987 and 1996. The
spatial distribution of contaminant concentrations shows higher levels of most contaminants
at the Discovery site, with lower levels at the Deer Island Flats sampling location and signifi-
cantly lower concentrations at the outfall site (Table 5-2).
MWRA +: OUTFALL MONITORING OVERVIEW REPORT
Mussel PAH, PCB, and pesticide (DDT, chlordane, dieldrin) body burdens for the Deer
Island and Discovery sites in 1996 were higher than those seen in 1995 (Table 5-2).
In particular, the PAH fractions (i-e., low and high molecular weight fractions) were about
twice the levels seen in 1995 at all stations. [Note: the 1995 and 1996 PAH fractions report-
ed in Table 5-2 include an extended PAH analyte list not analyzed prior to 1995 and not
directly comparable to the NOAA Status and Trends PAHs. Thus, these PAH fractions are
not directly comparable to those depicted in Figure 5-6]. Also, DDT and chlordane concen-
trations were anomalously high compared to previous years. A potential explanation of the
high concentrations is the relatively high lipid content of the mussels in 1996. It is possible
that the organic parameters were concentrated in the mussel lipids. As shown in Figure 5-
5, the 1996 dry-weight PCB concentration was substantially higher than the 1995 level,
while the lipid-normalized concentrations were similar. Levels of lead and mercury in 1996
were similar to 1995 levels.
: 1996 / 87
MWRA + OUTFALL MONITORING OVERVIEW REPORT: 1996 / References
References
Butler, E., M. Higgins, J. Chiapella, and W. Sung. 1997. Deer Island Effluent
Characterization Studies: January 1995 — December 1995. MWRA Environmental
Quality Department Technical Report Series. No. 97-3. Massachusetts Water Resources
Authority, Boston, MA. 91 pp.
Cibik, S.J., B.L. Howes, C.D. Taylor, D.M. Anderson, C.S. Davis, and T.C. Loder III. 1996.
1995 Annual water column monitoring report. MWRA Environmental Quality
Department Technical Report Series No. 96-7. Massachusetts Water Resources Authority,
Boston, MA. 241 pp.
Coats, D.A. 1995. 1994 annual soft-bottom benthic monitoring: Massachusetts Bay out-
fall studies. MWRA Environmental Quality Department Technical Report Series No. 95-20.
Massachusetts Water Resources Authority, Boston, MA. 184 pp.
Galya, D.P, J. Bleiler, and K. Hickey. 1996. Outfall monitoring overview report: 1994.
MWRA Environmental Quality Department Technical Report Series No. 96-4.
Massachusetts Water Resources Authority, Boston, MA. 50 pp.
Hilbig, B., J.A. Blake, E. Butler, B. Hecker, D.C. Rhoads, G. Wallace, and I.P. Williams. 1997.
Benthic Biology and Sedimentology: 1995 Baseline Conditions in Massachusetts and
Cape Cod Bays. MWRA Environmental Quality Department Technical Report Series
No. 96-5. Massachusetts Water Resources Authority, Boston, MA. 230 pp.
Hilbig, B., J.A. Blake, D.C. Rhoads, and LP. Williams. 1997. Boston Harbor Soft-Bottom
Benthic Monitoring Program: 1995 Results, MWRA Environmental Quality Department
Technical Report No. 96-8. Massachusetts Water Resources Authority, Boston, MA. 94 pp.
Hull, R.N. and G.W. Suter. 1995. Toxicological benchmarks for screening contaminants
of potential concern for effects on sediment-associated biota:1994 revision.
Oak Ridge National Laboratory Report ES/ER/TM-95/R1. 28 pp.
Hydroqual and Normandeau Assoc. 1995. A Water Quality Model for Massachusetts and
Cape Cod Bays: Calibration of the Bays Entrophication Model (BEM). MWRA
Environmental Quality Department Technical Report Series No. 95-8. Massachusetts Water
Resources Authority, Boston, MA. 402 pp.
Long, E.R. and L.G. Morgan. 1990. The potential for biological effects of sediment-
absorbed contaminants tested in the National Status and Trends Program. NOAA
Technical Memorandum NOS OMA 52. U.S. National Oceanic and Atmospheric
Administration, Seattle, Washington, 175 pp.
Long, E.R., D.D. MacDonald, $.L. Smith, FD. Calder. 1995S. Incidence of adverse biological
effects within ranges of chemical concentrations in marine and estuarine sediments.
Environmental Management. 19(1):81-97.
References / OUTFALL MONITORING OVERVIEW REPORT: 1996 + MWRA
Mitchell, D.F., T. Mounce, J. Morton, K. Sullivan, M. Moore, and P. Downey. 1996. 1995
Annual fish and shellfish report. MWRA Environmental Quality Department Technical
Report Series No. 96-3. Massachusetts Water Resources Authority, Boston, MA. 112 pp.
Mitchell, D.F., M. Wade, W. Sung, and M. Moore. 1997.
1996 Toxics Issues Review Report. Draft.
MWRA. 1991. Massachusetts Water Resources Authority - Effluent Outfall Monitoring
Plan Phase I: Baseline Studies. MWRA Environmental Quality Department Misc. Report
No. ms-2. Massachusetts Water Resources Authority, Boston, MA. 95 pp.
MWRA. 1997. Massachusetts Water Resources Authority - Effluent Outfall Monitoring
Plan Phase II: Post Discharge Monitoring (Draft). Massachusetts Water Resources
Authority, Boston, MA.
MWRA. 1997. Contingency Plan. Massachusetts Water Resources Authority. 41 pp.
MWRA Web Site. http:\www.mwra.com
National Research Council. 1993. Managing Wastewater in Coastal Urban Areas. National
Academy of Sciences, National Academy Press, Washington, D.C.
MWRA - OUTFALL MONITORING OVERVIEW REPORT: 1996 / Glossary
Glossary
The following descriptions are not formal definitions but convey the sense of usage in this
report.
Algae - phytoplankton, the microscopic plants that drift with the currents. They are usual-
ly single celled but may form colonies. There are many species that form the community
assemblage in a sample of seawater. Phytoplankton are eaten (grazed on) by zooplankton,
larger but still very small animals which also drift with the currents. Zooplankton, in turn,
are eaten by animals higher up the food chain. Large multicellular algae are called
macroalgae and are usually attached to the sea floor. Although plants are an essential part
of the food chain, excess nutrients may make them too numerous or favor undesirable
forms.
Algal community assemblage — the composition of the algal community, or the relative
numbers of various algae species. Approximately 30 to 50 algae species typically are
observed in the Massachusetts Bay community assemblage . These include species co
monly known as diatoms, blue-green algae, and flagellates. Flagellates are planktonic algae
that have self- propelled mobility, albiet limited. Red tides are a specific kind of dinoflagel-
late bloom that may produce toxic chemicals. Some red tides can result in mortality of fish
and other marine organisms and toxicity of seafood.
Amphipod - benthic crustaceans commonly found in the Boston Harbor ecosystem.
Examples are the deposit-feeding Ampelisca abdita and A. vadorum, which build extensive
tube mat systems. Tube mats are often several centimeters thick, and may reach densities of
more than 100,000 individuals per square meter. The widespread colonization of Boston
Harbor sediments by this infaunal complex has increased both the degree of sediment oxi-
dation and rates of sediment/water column exchange through bioturbation and burrow ven-
tilation.
Apparent redox potential discontinuity depth - RPD. The visually measured thickness of
upper light-colored, and thus apparently well-oxygenated, layer in bottom sediments.
Bioassays - laboratory tests that measure the response of indicator species such as shrimp
to toxics in the effluent under specified conditions. Bioassays designed to assess acute toxi-
city are expressed in measurement units known as “LC50s.” An LCS0 is the concentration
at which 50% of test organism survive. For example, an LCSO of 60 means that half of the
organisms survived a mixture that was 60% effluent and 40% dilution water. To assess
chronic toxicity, the effluent “No Observed Effects Concentration (NOEC)” is generally used.
The NOEC is the highest concentration of effluent at which there is no statistical difference
in test organism response when compared against a control with no effluent.
Biomass — the total amount of a biological material. For example, algal biomass is a mea-
sure of the total amount of algae present in the water.
Glossary / OUTFALL MONITORING OVERVIEW REPORT: 1996 + MWRA
Bioturbation — mixing of the sediment strata by animals, which bring deeper sediment to
the surface as they burrow, and flush aerated bottom water into the mud by way of their
burrows and feeding activity.
Chlorophyll — the green pigment in plants that supports photosynthesis in the presence of
adequate light. Chlorophyll a is commonly used as a measure of algal biomass.
Community diversity - relative abundance and types of various species that live in a partic-
ular habitat. Measures of diversity are often used to evaluate environmental change and
health; typically, the more diverse the assemblage (i.e., the more species present, taking
into account the number of animals collected) the healthier the community.
Denitrification - the reduction of nitrate to nitrite and then to nitrogen gas.
Dissolved oxygen saturation level - the amount of dissolved oxygen (DO) that can be held,
or dissolved in water. The DO saturation level varies with temperature. Cooler water can
hold more DO. Therefore, DO concentrations will decrease naturally as the water column
warms during the spring and summer.
Drumlin - elongated piles of glacial debris left behind after the glacier recedes.
Epibenthic organisms - bottom-dwelling animals that live upon, rather than within, a sub-
strate such as impenetrable rock.
Eutrophication — a process of excessive algal growth that may result in dissolved oxygen
depletion (hypoxia).
FDA Action Levels — limits established by the U.S. Food and Drug Administration (FDA)
for toxic or deleterious substances in human food and animal feed. Action levels represent
limits at or above which FDA may take action to remove products from the market. For
example, the FDA legal limit for contaminants in fish and shellfish is 2.0 ppm for total PCBs
and 1.0 ppm for mercury.
Histopathology - the study of adverse changes in animal tissue structures, such as liver
lesions, often used as a sensitive indicator of contaminant exposure.
Hypoxia - a state of low dissolved oxygen in which sensitive animals may suffocate.
Infauna - bottom-dwelling animals that live within the sediments.
Mixing zone — region in the immediate vicinity of the diffuser where initial mixing and
dilution occurs. The defined size of the mixing zone reflects the designed dilution proper-
ties of the diffusers. An outfall would violate expectations if dilution is not sufficient to
meet water quality criteria at the edge of the mixing zone.
MWRA + OUTFALL MONITORING OVERVIEW REPORT: 1996 / Glossary
Nearfield or near field - a region near the new outfall which receives more intensive sam-
pling due to the expectation that effects are most likely to be manifest there. The definition
of the nearfield varies with the study type, reflecting the mobility of water as compared to
sediments. Water column monitoring defines the nearfield as the area within a rectangle
with sides 5 km from the outfall. Beyond that is the farfield, which includes the rest of
Massachusetts Bay, Cape Cod Bays, and Boston Harbor. Benthic monitoring defines the
nearfield as the area within 2 km of the new outfall. Beyond that is the midfield (2-7 km
away) and the farfield (greater than 7 km).
Primary production — the process by which algae produce organic carbon from carbon
dioxide through photosynthesis. Growth requires this carbon as well as nitrogen for protein ©
and phosphorus for nucleic acids. In addition, silica is required by diatoms for their outer
cell walls.
Primary treatment - wastewater treatment process involving solids removal via settlement
and effluent chlorination prior to discharge. Primary treatment removes 30 to 35% of
organic matter and 20 to 40% of toxic pollutants.
Priority pollutants - substances that the EPA has determined to be of national concern
because of their toxicity at certain concentrations.
Redox potential discontinuity (RPD) — depth of oxygen penetration, or location where the
sediments change from oxic (having oxygen) to anoxic. The RPD depth can be accurately
measured using a microelectrode, but more readily can be estimated (apparent RPD) by
visual examination of sediment cores or, more reliably, sediment profile images. The
appearance of the oxygenated (aerobic) near-surface layer is light-colored; the deeper anaer-
obic (having no oxygen) layer is generally full of sulphides and looks dark blue or black.
Remineralization - Degradation of algal biomass into soluble components which are then
available again for uptake and growth by other algae. The carbon, nitrogen, and phospho-
Tus in particulate organic matter are decomposed to carbon dioxide, urea, nitrate, ammonia,
and phosphate. Remineralization is the reverse of growth.
Replicates - multiple samples that are used to increase the reliability and accuracy, and
reduce the uncertainty of experimental data.
Respiration - the process of dissolved oxygen consumption by living organisms. It is the
reverse of photosynthesis.
Secondary treatment - wastewater treatment consisting of a combination of bacterial
decomposition and a physical settling process. Secondary treatment results in removal of
more than 75 to 90% of organic matter and most toxic pollutants prior to effluent discharge.
Glossary / OUTFALL MONITORING OVERVIEW REPORT: 1996 - MWRA
Sediment quality criteria/guidelines - sediment quality values established by EPA as guide-
lines to evaluate potential impacts to benthic organisms. Draft EPA sediment criteria exist
for five organic contaminants: acenaphthene, fluoranthene, phenanthrene,
dieldrin, and endrin. In addition, NOAA has developed effects- based sediment quality
guidelines based on a weight of evidence from many studies. Chemical concentrations
below the NOAA “Effects Range-Low” (ER-L) values are rarely associated with toxic effects,
whereas chemical concentrations above the NOAA “Effects Range Median” (ER-M) values
often are associated with toxic effects.
Stratification — the process of developing water column layers. Stratification is caused by
differences in water density. Water density increases with decreasing temperature and
increasing salinity. When the water column is unstratified, the density of the water is simi-
lar from top to bottom, and mixing of the entire water column can occur. When the water
column is stratified, two distinct layers exist in the water column: the surface layer which is
in contact with the atmosphere and the oxygen it contains, and the bottom layer which is
isolated from sources of oxygen. These two layers are separated by strong differences in
density.
Upwelling - a nearshore process involving the displacement of warm surface waters with
colder, deeper waters. Upwelling is caused by westerly and southwesterly winds which
blow surface waters away from the coast. Colder bottom waters move in toward shore, and
then upwards to replace the warmer outgoing surface waters.
. Water quality criteria - ambient concentration values that were established to protect
aquatic life. Acute criteria values were developed to be protective of relatively short-term
(generally less than 96 hours as measured in the laboratory) exposure to pollutants.
Chronic criteria are values that provide protection from relatively long-term pollutant expo-
sure.
MWRA - OUTFALL MONITORING OVERVIEW REPORT: 1996 / Acronyms
Acronym Summary
BOD
cBOD
CHV
DECS
DIN
DBO
EPA
ER-M
FDA
LABs
LCso
biochemical oxygen demand
carbonaceous biochemical oxygen
demand
centrotubular hydropic vacuola-
tion, a fish liver lesion
Detailed Effluent Characterization
Study
dissolved inorganic nitrogen
dissolved oxygen
U.S. Environmental Protection
Agency .
NOAA low effects range values for
sediment, rarely associated with
toxic effects
NOAA median effects range values,
often associated with toxic effects
U.S. Food and Drug Administration
linear alkyl benzenes
concentration for 50% lethality of
bioassay test organisms
MADEP Massachusetts Dept. of
nBOD
NMFS
NOAA
NOEC
NPDES
PAHs
PCBs
ppb
ppm
RPD
SEIS
TSS
USGS
WwaQc
Environmental Protection
nitrogenous biochemical
oxygen demand
National Marine Fisheries Service
National Oceanographic and
Atmospheric Administration
no observable effect concentration
National Pollutant Discharge
Elimination System
polyaromatic hydrocarbons
polychlorinated biphenyls
parts per billion
parts per million
redox potential discontinuity
Supplemental Environmental
Impact Statement
total suspended solids
U.S. Geological Survey
Water Quality Criteriarelated records
Records whose documents say similar things, nearest first.
- Water & harborMassachusetts Water Resources AuthorityDeer Island outfall monitoring overview, 1999
- Environmental permitU.S. Environmental Protection AgencyDeer Island treatment plant discharge permit (MA0103284), 2023 draft
- Water & harborMassachusetts Water Resources AuthorityDeer Island outfall monitoring overview, 2020
- Water & harborMassachusetts Water Resources AuthorityDeer Island outfall monitoring overview, 2000
- Water & harborMassachusetts Water Resources AuthorityDeer Island outfall monitoring overview, 2003