Boston Harbor
Wastewater
Conveyance System
Volume I
Draft Supplemental Environmental Impact Statement
United States Enyironmental Protection Agency
Region I
J.F.K. Federal Building
Boston, Massachusetts 02203
1988

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Cover photograph taken by Kathleen Kirkpatrick Hull.

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Boston Harbor
Wastewater
Conveyance System
Volume I
Draft Supplemental Environmental Impact Statement
Prepared by:
United Slates Environmental Protection Agency
J.F.K. Federal Building
Boston, Massachusetts 02203
1988
Technical Assistance by:
Metcalf & Eddg
10 Harvard MU Sguare
Wakel eId, Massachusetts
/1 4 / ? O- c - /‘ z
ICHAEL R. DELA.ND Date
Regional Administrator,
U.S. EPA, Region I
This Draft Supplemental Environmental Impact Statement (SEIS)
has been prepared by the U.S. Environmental Protection Agency
(EPA) with assistance from the U.S. Army Corps of Engineers.
This Draft SEIS identifies and evaluates the environmental
impacts of the wastewater conveyance system for Greater
Boston’s wastewater treatment facility in compliance with
Federal and State water pollution control laws.

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DRA?P SUPPLF NTAL TIEC*IMENTAL Ir4PAC m STATEMENT
PROPOSED ACTION: SITING AND F VALUATION OF CONSTRUCTION T’FI 1S
FOR ASTEWATER CONVEYANCE SYSTEM FOR SFC0NDARY
TPFATMENT PLANT, B0S )N HARBOR
LOCATION: BOS9 N, MASSA HHSE PS
DATE: APRIL 1988
sur’ 4ARY OP AcTION: Draft SEIS considers the environmental accepta-
bility of alternative locations for the wastewater
conveyance and outfall systems of the new waste—
water treatment facilities for Boston Harbor. The
Draft SETS recon ends deep rock tunnels for the
inter—island and outfall conduits and a diffuser
located at least seven miles east of Deer Island.
‘7OLUMES: I. SUPPLEMENTAL EflVI1 DNME AL WPACT STATEMENT
II. APPENDICES
LEAD AGENCY: U.S. ENVI1 NMEflTAL PROTEC’IION AGENCY, PEGION I
JFK Federal Building, Boston, Massachusetts 02203
COOPERATING AGENCY: U . S. ARMY ODRPS OF ENGINS
TECHNICAL CONSULTANT: ME I ALF & EDDY, INC.
Wakefield, Massachusetts
FOR ENT THER T ’FOEMATION: Mr. David Thmey
Water Management Division
U.S. A, Reqion I
JFK Federal Building
Boston, MA 02203
l7—565—442 )
FINAL DATE BY W IICH
CC MHNTS TIUST BE RECEIVED: May 16, 1988

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TABLE OF CONTENTS
Page
LIST OF TABLES viii
LIST OF FIGURES xii
CHAPTER 1 INTRODUCTION
1.1 Background 1-1
1.2 History of the Project 1—2
1.3 Draft SEIS Format 1—5
CHAPTER 2 PURPOSE AND NEED FOR ACTION
2.1 Existing Conditions 2-1
2.2 ProposedAction 2—2
CHAPTER 3 PRINCIPLE ALTERNATIVES: SCREENING AND DESIGN
3.1 Definition of No Action 3—1
3.2 Diffuser Location Alternatives 3—1
3.2.1 Screening Process 3-3
3.2.1.1 Landward Boundary: Identification of
Screening Criteria 3—3
3.2.1.2 Landward Boundary: Application of
Criteria 3—3
3.2.1.3 Eastern Boundary: Identification of
Screening Criteria 3-3
3.2.1) Eastern Boundary: Application of
Screening Criteria 3—5
3.2.1.5 Final Site Screening Step: Alternative
Discharge Location 3—7
3.2.1.6 Interim Discharge Location:
Identification of Criteria 3-7
3.2.1.7 Interim Discharge Screening:
Application of Criteria 3-7
3.2.2 Description of Discharge Location Alternatives
for Detailed Evaluation 3-9
3.2.3 Criteria for Detailed Evaluation 3-9
3.3 Effluent Conveyance Mode 3-9
3.3.1 Screening Process 3—9
3.3.1.1 Identification of Screening Criteria 3—9
3.3.1.2 Application of Screening Criteria 3-9
3.3.2 Description of Outfall Conduit Alternative
for Detailed Evaluation 3—16
3.3.3 Criteria for Detailed Evaluation 3-16
1

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TABLE OF CONTENTS (Continued)
3.14 Diffuser Types 3-16
3.4.1 Screening Process 3-16
3.4.1.1 Identification of Screening Criteria 3-22
3.4.1.2 Application of Screening Criteria 3-22
3.14.2 Description of Diffuser Alternatives for
Detailed Evaluation 3-22
3.4.3 Criteria for Detailed Evaluation 3-22
3.5 Inter-Island Conveyance Mode 3-22
3.5.1 Screening Process 3-22
3.5.1.1 Identification of Screening Criteria 3-26
3.5.1.2 Application of Screening Criteria 3-26
3.5.2 Description of Inter-Island Conduit Alternative
for Detailed Evaluation 3-26
3.5.3 Criteria for Detailed Evaluation 3-26
CHAPTER 11 AFFECTED ENVIRONMENT
14.1 Introduction 14-1
4.1.1 ProJect Setting
4.1.2 Service Area 14_i
14.2 Summary of Environmental Conditions 14-1
4.2.1 Physical Oceanography 14-1
4.2.1.1 Processes and Controlling Parameters 14_3
14.2.1.1.1 Nearfield 14-3
14.2.1.1.2 Farfield 4-3
4.2.1.1.3 Shoreline Impacts 14-3
4.2.1.1.14 Sedimentation and Resuspension 14-5
4.2.1.1.5 Sirnmt ry 14_5
4.2.1.2 Data Sources 4-5
4.2.1.2.1 MWRA Field Data 14 6
4.2.1.3 Tides 4-7
4.2.1.14 Currents 4 . . .i0
14.2.1.4.1 Instantaneous Currents 4-10
4.2.1.4.2 Tidal Currents 14 10
4.2.1.14.3 Net Drifts 14 -114
14.2.1.5 Stratification 14 1 14
14.2.2 Water Quality 14-15
14.2.2.1 Constituents and Criteria 14-15
4.2.2.2 Dissolved Oxygen 14-20
4.2.2.3 pH 4-21
4.2.2.4 Suspended Solids 14_21
4.2.2.5 Toxic Chemicals 14-21
4.2.3 Marine Geology
4.2.3.1 Overview 1 4 2 14
4.2.3.2 Geological Setting 14-214
14.2.3.3 Bottom Sediment Distribution 14-214
14.2.3.44 Sedimentation Rates 14-27
11

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TABLE OF CONTENTS (Continued)
14.2.3.5 Sediment Chemistry . 4-28
4.2.3.6 Bioturbation Mixing Depth 4-30
14.2.14 Marine Ecosystems 4-32
14.2.14.1 Macrobenthos J4-32
4.2.44.1.1 Benthic Epifauna 4—32
1 L2.4.1.2 Benthic Infauna 14-36
14.2.J4.1.3 Benthic Communities in
Boston Harbor 14 . .38
14 2. 1 L2 Plankton 14-38
4.2.14.2.1 Phytoplankton 14 38
14.2.14.2.2 Zooplankton 4—140
14.2.14.2.3 Plankton Communities
in Boston Harbor 14 40
14.2.14.3 Fish 14 1 40
14.2.14.3.1 General 4—140
14.2.14.3.2 Massachusetts Bay 1 4 i ll
4.2.4.3.3 Fish Con!nunities in Boston Harbor
14.2)4.3.4 Demersal Fish and Epibenthic
Shellfish Contamination
14.2.4.4 Marine Man nals 4—45
14.2.4.4.1 Whales 4—45
14.2.4.4.2 Seals ‘4—45
14.2.4.5 Marine Turtles 14_ 145
14.2.14.6 Seabirds
14.2.5 Harbor Resources 14.. .145
14.2.5.1 Navigation 14—146
14.2.5.2 Commercial Shipping 4 146
14.2.5.3 Commercial Fishing 14 _146
14.2.5.14 Recreation 4—49
11.2.5.5 Sensitive Resources 14—52
11.2.5.6 Marine Archaeology 14—52
14.3 Inter—Island Conduit Area 14—57
4.3.1 Introduction 14-57
4.3.2 Summary of Conditions 14-57
4 14 Disposal Areas 4-57
4.4.1 Identification of Available Disposal Areas 4-57
14.4.2 Summary of Existing Disposal Site Conditions -58
CHAPTER 5 CONSEQUENCES OF ALTERNATIVES
5.1 Operation of Effluent Discharge at Alternative Locations 5-1
5.1.1 Water Quality 5—1
5.1.1.1 Constituents 5—1
5.1.1.2 Loadings 5...1
5.1.1.3 Fate Processes 5-3
iii

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TABLE OF CCWTENTS (Continued)
Page
5.1.1.4 Nearfield Dilution Modeling . 5-6
5.1.1.5 Farfield Modeling 5—7
5.1.1.6 Shoreline Impact Analyses 5-18
5.1.1.7 Criteria Compliance Evaluation 5—18
5.1.1.7.1 Dissolved Oxygen 5-18
5.1.1.7.2 pH 5-23
5.1.1.7.3 Mixing Zone Criteria 5—23
5.1.2 Sediment Quality 5—25
5.1.2.1 Sediment Chemistry Simulation Methods 5-25
5.1.2.2 Susw ary of Sediment Simulation Results 5-27
5.1.3 Marine Ecosystems 5_314
5.1.3.1 Operation Consequences Outside the
Mixing Zone 5_3Ls
5.1.3.1.1 Sediment Organic Enrichment 5_314
5.1.3.1.2 Sediment Toxicity 5 142
5.1.3.1.3 Nutrient Enrichment 5— 45
5.1.3.1.14 Water Column Toxicity 5 _ . 149
5.1.3.1.5 Dissolved Oxygen Deficits 5—51
5.1.3.1.6 Impacts to Protected Species 5—51
5.1.3.2 Operation Consequences Inside the Mixing Zone... 5—52
5.1. 4 Public Health 5—53
5.1)4.1 Pathogens 5—53
5.1.4.2 Chemical Contaminants 5-53
5.1.5 Harbor Resources 5-55
5.1.5.1 Navigation, Shipping and Water
Transportation 5—56
5.1.5.2 Coninercial Fishing 5-56
5.1.5.3 Recreation 5—56
5.1.5.4 Sensitive and Protected Areas 5-57
5.1.5.5 Cultural and Archaeological Resources 5-57
5.1.6 Regulatory and Institutional Considerations 5-57
5.1.7 Boston Harbor Consequences 5-57
5.2 Outfall Tunnel Construction 5—58
5.2.1 Environmental 5—58
5.2.2 Engineering Feasibility 5—59
5.2.3 Cost 5-59
5.2.Li Materials Disposal 5-60
5.2.5 Institutional 5—61
5.2.6 Harbor Resources 5-61
5.3 Diffuser 5—61
5.3.1 Drilled Riser Diffuser 5-61
5.3.1.1 Environmental 5-61
5.3.1.2 Engineering Feasibility 5-62
iv

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TABLE Cf CCWTENTS (Continued)
P e
5.3.1.3 Materials Disposed . 562
5.3.1.4 Institutional 5—62
5.3.1.5 Marine Ecosystem 5.63
5.3.1.6 Harbor Resources 5-63
5.3.2 Pipe Diffuser 5—6k
5.3.2.1 Environmental 5—6’4
5.3.2.2 Engineering Feasibility 5 6 14
5.3.2.3 Materials Disposal 5—64
5.3.2.14 Institutional 5—64
5.3.2.5 Marine Ecosystem 5—65
5.3.2.6 Harbor Resources 5-65
5.14 Inter—Island Conduit 5—66
5.4.1 EnvIronmental 5—66
5.14.2 Engineering Feasibility 5—67
5.14.3 Cost 5—67
5.4.4 Materials Disposal 5—67
5,145 Institutional 5—67
5.4.6 Harbor Resources 5-68
5.5 Sun n ry of Economic Impacts 5—68
5.5.1 Boston 5—68
5.5.2 Needham 5-69
CHAPTER 6 - CUMULATIVE IMPACTS AND OPERATIONAL RELIABILITY
6.1 Overview 6-1
6.2 Cumulative Impact Scenario 6-2
6.2.2 Water Quality, Sediment Quality and
Marine Ecosystems 6—2
6.2.3 Disposal of Excavated and Dredged Material 6-2
6.2.14 Traffic and Transportation 6-2
6.2.5 Socioeconomic Considerations 6-5
6.3 Prediction of Cumulative Impacts 6-5
6.3.1 Water Quality, Sediment Quality and Marine
Ecosystems 6-5
6.3.2 Disposal of Excavated and Dredged Material 6-6
6.3.3 Traffic and Transportation 6-6
6.3.4 Socioeconomic Considerations 6-6
6. 4 Operational Reliability 6-7
6.4.1 Treatment Plant Overview 6-7
6.14.2 Redundancy 6-9
6.14.3 Power 6—9
6.14.4 Operating Scenarios Considered 6-9
CHAPTER 7 SELECTION AND EVALUATION OF THE RECOMMENDED PLAN
7.1 Alternative Comparison arid Recommendation 7_i
7.1.1 Comparison and Recou nendatiofl for Discharge 7-1
Location 7- i
V

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TABLE OF COWTENTS (Continued)
7.1.2.1 Comparison of Long Term Impacts from
Secondary Effluent Discharge 7-4
7.1.1.2 Evaluation of Interim Impacts from Primary
Effluent Discharge 7-9
7.1.1.3 Recommended Discharge Location 7-12
7.1.2 Reconunended Plan for Outfall Conduit Construction 7—13
7.1.3 Recommended Plan for Diffuser Construction 7-13
7.1.4 Recommended Plan for Inter-Island Conduit
Construction 7—13
7.2 Mitigation 7—13
CHAPTER 8 LIST OF PREPARERS
CHAPTER 9 PUBLIC PARTICIPATION
9.1 Introduction 91
9.2 Public Participation Activities 9—2
9.2.1 Scoping 9-2
9.2.2 Workplan and Coordination 9-2
9.2.3 Formation of the Citizen’s Advisory Committee 9—3
9.2.4 Citizen’s Advisory Committee Meetings:
Participation and Presentations 9-3
9.2.5 Technical Advisory Group: Facilities Plan
TAG and EOEA TAG 9 114
9.2.6 Public Meetings 9—14
9.2.6.1 Information Meetings 9 1 14
9.2.6.2 Public Hearing 9—15
9.2.7 Informational Activities 9-15
9.2.7.1 Fact Sheets 9—15
9.3 Other Services 9—15
9.3.1 Mailing List 9—15
9.3.2 Information Repositories 9—15
9.3.3 Announcements 9—15
9.14 Public Issues 9—17
9.4.1 Discharge of Interim Primary 9—17
9.4.2 Alternatives Evaluated 9—17
9.44.3 Effluent Quality 9-17
9.14.4 Fate and Effect of Solids Deposition 9—17
9.4.5 Dissolved Oxygen (DO) Concentrations During
Stratified Conditions 9—’8
9.4.6 Nutrient Enrichment 9_18
9.14.7 Assessment Using Limited Data 9...18
9.14.8 Cumulative Impacts 9—18
vi

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TABLE OF CONTENTS (Continued)
9.14.9 Toxic Compounds 9 -18
9.14.10 Construction Schedule 9-19
9.14.11 Quantitative Evaluation of’ Boating Schedules 9-19
9.14.12 Evaluation of Compounds Without Criteria 9-19
9.14.13 Size of the Mixing Zone 9-19
9.14.114 Freshwater Discharged to Massachusetts Bay 9-19
ATTACHMENT 1 Boston Harbor Marine Wastewater Conveyance 9-20
Systems Supplemental Environmental Impact
Statement Notice of Intent
REFERENCES
GLOSSARY
INDEX
vii

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LIST OF TABLES
Table
CHAPTER 3 - PRINCIPLE ALTERNATIVES: SCREENING AND DESIGN
3.2.2.a Descriptions of the Alternative Discharge Locations 3-10
3.2.3a Criteria for the Evaluation of Alternative
DischargeSites 3—11
3.3.1.a Stinin ry of Effluent Conveyance Mode Screening 3-15
3.3.2.a Criteria for the Evaluation of the Effluent
Conveyance Alternative 3—17
3.lI.1.a Sun’n ry of Diffuser Type Screening 3-23
3.L$.3.a Criteria for the Evaluation of the Diffuser Type
Alternatives 3.214
3.5.1.a Snnin ry of Inter-Island Conveyance Mode Screening 3-27
3.5.3.a Criteria for the Evaluation of Inter-Island
Conveyance Alternative 3-30
CHAPTER 11 - AFFECTED ENVIRONMENT
Table
1 4.2.1.a Statistics of 1987 MWRA Current Meter Measurements 14-13
i4.2.2.a Coixinonwealth of Massachusetts Surface Water Quality
Standards Minimum Criteria Applicable to all Waters 14-16
1 L2.2.b Con!nonwealth of Massachusetts Surface Water Quality
Standards Additional Criteria for Marine Class SA Waters.. 14-17
1 4.2.2.c Saltwater Aquatic Life and Human Health Water Quality
Criteria Ugh) 14. .18
1 4.2.2.d Metal Concentrations in Water Column at Two Stations
in Massachusetts Bay 14 . 23
14.2.2.e Concentrations of PCB in Seawater Collected at Two
Stations in Massachusetts Bay in April 1987 14—25
viii

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LIST OF TABLES
Table Page
1 1.2.3.a Si’nrt ry of Reported Massachusetts Bay and Boston
Harbor Sedimentation Rates 3—28
4.2.3.b Contaminants for Assessment of Sediment Deposition
Impacts Ls...29
4.2.3.c Si’vmn ry of Sediment PCB Measurements
S rna ” ry of Sediment Metals Measurements 14 _31
JL2.LLa SI1w!nary of General Bottom Types and Associated
Epifaunal Assemblages 14_3i4
1 L2. 1 Lb General Characterization of Nearshore and Far
Shore Parameters in Massachusetts Bay 4—37
Seasonal Migration Characteristics of Some
Important Fish Species
CHAPTER 5 - COIJSEQUENCES OF ALTERNATIVES
5.1.1.a Constituents Loadings 5—2
5.1.1.b Distribution of Discharged Solids Fall Velocities 5—5
5.1.1.c Nearfield Dilution 5—7
5.1.1.d Background Buildup for Base Loading 5-1k
5.1.1.e Maximum Dissolved Oxygen Deficits 5-17
5.1.1.f Maximum Shoreline Concentrations Predicted with
Spring and Sunm er 1987 Current Data 5—21
5.1.1.g Minimum Dissolved Oxygen Concentrations in the
Water Column 5—22
5.1.1.h Minimum Water Column Dissolved Oxygen Concentrations
During Resuspension Event 5-22
5.1.1.i Summary of Predicted Water Quality Criteria Exceedance.... 5-26
5.1.2.a Comparison of Simulated Maximum Sediment Pollutant
Concentrations, Primary Effluent, 5 Years Duration,
Non—stratified Conditions 5—28
5.1.2.b Comparison of Simulated Maximum Sediment Pollutant
Concentrations, Primary Effluent, 6 Months Duration
Stratified Conditions 5—29
ix

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LIST OF TABLES
Table Page
5.1.2.c Comparison of Simulated Maximum Sediment Pollutant
Concentrations, Secondary Effluent, 5 Years Duration,
Non—stratified Conditions 5—30
5.1.2.d S’rn n ry of Site to Site Comparison of Sediment Pollutant
Concentrations 5—31
5.1.3.a Sirn n ry of Areal Extent of Predicted Sediment Organic
Organic Enrichment 5—36
5.1.3.b Sirnv ry of Evaluation of Constituents of Concern 5_143
5.1.3.c Sirnin ry of Sediment Toxics Information 5_L 4
5.1.3.d Aeral Extent Sediment Toxicity at Alternate Outfall
Sites Under Primary and Secondary Treatment 5— 46
5.1.3.e Sunr’ ry of Aeral Extent of Predicted Average and Worst-
Case Nutrient Enrichment in the Water Column 5 _148
5.1.3.f St1w!n&ry of Predicted Aquatic Life Water Quality
Criteria Exceedance 5—50
5.1.3.g Predicted Minimum Water Column Dissolved Oxygen
Concentration Under Resuspension Events for
Primary and Secondary Treatment 5-52
5.2.3.a Costs of the Tunnelled Outfall System Alternatives 5-60
5.5.1.a Simmi ry of Sewer Use Charges for the Outfall Alternatives,
Boston 5—70
5.5.2.a SiiiTvn ry of Sewer Charges for the Outfall Alternatives,
Needh 5—71
CHAPTER 6 - CUMULATIVE IMPACTS AND OPERATIOWAL RELIABILITY
Effluent Concentrations After Primary Treatment,
Year 1999, Average Flow Conditions 6-10
6 . 1 4. 1 4.b Non—Conventional Pollutant Effluent Concentrations
After Primary Treatment, Year 1999, Maximum Loading
Conditions on Storm Day 6-11
6. 4.LLc Effluent Concentrations After Secondary Treatment,
rear 2020 6—12
6.Lt.4.d Effluent Concentrations After Secondary Treatment,
year 2020 6—13
x

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LIST OF TABLES
Table Page
6.lL 4.e Effluent Concentrations P tter Secondary Treatment,
Year 2020, Maximum Loading Conditions 6 114
6.LLI4.f Mixed Primary-Secondary Effluent, Year 2020 6-15
CHAPTER 7 - SELECTION AND EVALUATION OF THE REC0 Q1ENDED PLAN
7.1.1.a Comparison of Site Determinative Criteria for
Outfall Site Selection 7—2
7.1.1.b Comparison of Nonsite Determinative Criteria for
Outfall Site Selection 7—3
7.1.2.a Costs of the Tunnelled Outfall System Alternatives 7-8
CHAPTER 9 - PUBLIC PARTICIPATION
Table
9.2.a Coordination List 9—
9.3.a List of Repositories 9—16
xi

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LIST OF FIGURES
3 - PRINCIPLE ALTERNATIVES: SCREENING AND DESIGN
Existing Effluent and Sludge Discharge Locations
of Deer and Nut Island Wastewater Treatment Plants
Landward Boundary of Secondary Effluent Discharge in
Relation to All Discharge Site Options
Area of Potentially Acceptable Secondary Effluent
Discharge Locations
Alternative Discharge Locations
Profile View of Pipeline Diffuser with One Riser
Profile View of Pipeline Diffuser with Eight
to Ten Risers
Plan and Profile Views of Tunnelled Diffuser with
Multiple Risers
Plan View of Inter-Island Conveyance System
Alternative
Profile View of Inter-Island Conveyance System
Alternative
- AFFECTED ENVIRONMENT
MWRA Sewerage Service Area
Schen tic Effluent Plume in the Nearfield
Location of MWRA Current Water Meter Stations in
Relation to Alternative Diffuser Sites
Locations of MWRA Survey Transects
Filtered Water Levels at Provincetown (Top) Gloucester
(Middle) and Their Difference (Bottom)
Magnitude-Direction Scatler Plot for Station 4,
August 1987
Locations of the Suspended Solids, Metals, and PCB
Sampling Stations
Figure
CHAPTER
3.1.a
3.2.1.a
3.2.1.b
3.2.1.c
3. 1 1.1.a
3)4.1.b
3. 1 4.1.c
3.5.2.a
3.5.2.b
CHAPTER II
1 4.1.2.a
1 L2.1.a
4.2. 1.b
.2.1.c
.2.1.d
U.2.1.e
4 .2.2.a
P e
3-2
3-4
3—6
3-8
3—19
3-20
3-21
3-28
3-29
14 8
4—9
14 ...1 1
14 _ 12
14_22
xii

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LIST OF FIGURES (Continued)
Figure
1 4.2.3.a General Station Locations for Sediment Sampling 4-26
4.2. La Location of MWRA Sampling Stations 44_33
4.2.LLb Bottom Types of the Study Area L4_3 5
i4.2.1 .c General Movement of Migratory Fish Species in the
Northwest Atlantic Ocean 14 .142
Conmiercial Navigational Resources 1 4 . 147
11.2.5.b Typical Conunercial and Passenger Ship Routes 4— 48
1 L2.5.c Conmiercial Fishing Resources 4-5O
14.2.5.d Beaches and Shoreline and Island Parks 4-51
1 4.2.5.e Major Boating Public Access Point 14_53
4.2.5.f Sensitive Harbor Resources 14_514
Shipwrecks Within 1.5 Miles of the Candidate
Outfall Sites 14 —56
CHAPTER 5 - COWSEQUENCES OF ALTERNATIVES
5.1.1.a Model Grid for Unstratified Conditions 5—9
5.1.1.b Model Grid for Stratified Conditions 5-10
5.1.1.c Calculated Farfield Concentrations for Base Loading 5—12
5.1.1.d Calculated Farfield Concentrations for Base Loading 5-13
5.1.1.e Dissolved Oxygen Deficit for Primary Discharge at
Site 2 Under Stratified Conditions, Average Net Drift 5-15
5.1.1.f Dissolved Oxygen Deficit for Primary Discharge at
Site 5 Under Stratified Conditions, Averge Net Drift 5-16
5.1.1.g ELA Predicted Sedimentation Rates, Site 5, Secondary
Treatment, Stratified Conditions 5-19
5.1.1.h ELA Predicted Sedimentation Rates, Site 5, Primary
Treatment, Stratified Conditions 5-20
xiii

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LIST OF FIGURES (Continued)
Figure
5 1.2.a Sediment PCB Concentrations vs. Area; Primary Effluent,
Non-stratified Conditions, 5 Year Duration 5-33
5.1.3.a Areas of Predicted, Changed and Degraded Benthic
Communities Due to Organic Enrichment Under
Non-Stratified Conditions with Primary Treatment
for All Sites 5-37
5.1.3.b Areas of Predicted, Changed and Degraded Benthic
Communities Due to Organic Enrichment Under
Non-Stratified Conditions with Secondary Treatment
for All Sites 5—38
5.1.3.c Areas of Predicted, Changed and Degraded Benthic
Co unities Due to Organic Enrichment Under
Stratified Conditions with Primary Treatment
for All Sites 5—39
5.1.3.d Areas of Predicted, Changed and Degraded Benthic
Communities Due to Organic Enrichment Under
Stratified Conditions with Secondary Treatment
for All Sites 5—40
5.1.3.e Areas of Predicted, Changed and Degraded Water
Column Conditions Due to Nutrient Enrichment Under
Conditions of No Net Drift (Predictions are the Same
for Both Primary and Secondary Treatment) 5-42
CHAPTER 6 - CU?WLATIVE IMPACTS AND OPERATIONAL RELIABILITY
6.1.a Project Timeframe 6-3
6.1.b Discharge Locations 6—4
6.4.1.a Recommended MWRA Treatment Facilities 6-8
CHAPTER 7 - SELECTION AND EVALUATION OF THE RECOMMENDED PLAN
7.1.3.a Recommended Location of the Deer Island WWTP Discharge.... 7- 14
xiv

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CHAPTER 1
INTRODUCTION
1.1 BACKGROUND
Boston Harbor, a valuable regional resource, is being degraded by the discharge of
wastewater from 143 cities and towns served by the Massachusetts Water Resources
Authority (MWRA) sewerage system. During an average day of operation, MWRA’s two
existing wastewater treatment plants discharge 1450 million gallons of inadequately
treated wastewater and 70 dry tons of’ digested sewage sludge into the harbor
(USEPA, 1985b). To remedy this problem, a new wastewater treatment facility is
being constructed on Deer Island. This Draft Supplemental Environmental Impact
Statement (SEIS) describes the effects construction and operation of an inter-island
wastewater conduit and an effluent outfall will have on the environment of Boston
Harbor and Massachusetts Bay. The conduit and outfall are critical components of
the treatment facilities needed to clean up Boston Harbor.
The rich natural resources of Boston Harbor attracted the attention of man more than
8,000 years ago. Early inhabitants of’ the area fished, hunted, and gathered
shellfish and plants from the harbor and its rivers and estuaries (tJSEPA Vol. 2,
19814). These same resources, along with sheltered anchorages, attracted Europeans
who sailed to the area to begin establishing permanent settlements around the harbor
in 1625. Boston grew to become a major port city, trading and exporting fish and
shellfish from the harbor and importing commercial goods from around the world.
Today, Boston Harbor covers roughly fifty square miles and supports a wide variety
of commercial, recreational, and aesthetic resources. Shellfish and lobster are
harvested in the harbor, shoreline parks and beaches provide recreation, commercial
shipping facilities handle thousands of vessels per year, and the harbor provides
opportunities for boating and panoramic views from downtown Boston and shoreline
communities. The Boston Harbor Islands are easily accessible from the city and
offer uncrowded parks, historic sites, and natural areas.
The resources of the harbor are seriously endangered by pollution. The wastewater
treatment plants, more than 100 combined sewer overflows (CSOs), direct runoff and
river discharges from over 322 square miles of urban and suburban lands, discharges
from commercial and pleasure boats, oil terminals, and contaminated sediments all
pollute Boston Harbor (USEPA Vol. 1, 19814). Pollution results in beach closings
when bacteria levels in the water threaten the health of bathers. Flounder and
shellfish are contaminated. Excrement and plastic objects from the sewerage system
wash up at beaches and parks. Odors and floating wastes detract from the beauty and
health of the harbor.
The construction of a new secondary wastewater treatment plant on Deer Island is a
critical step in cleaning up Boston Harbor. The new treatment facilities will
alleviate a considerable amount of harbor pollution by replacing the two existing,
outdated treatment plants, by providing adequate treatment of wastewater, and by
eliminating the discharge of sewage sludge into Boston Harbor and Massachusetts Bay
(USEPA, Vol. 1 and 2, 19814).
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Two key components of the treatment facilities which must be constructed are an
inter—island conduit to carry sewage to the new treatment facility, and an outfall
to carry treated effluent from the facility for discharge. The inter-island
conduit, which will run from the site of the existing Nut Island treatment plant to
Deer Island, must be constructed to convey wastewater from the southern portion of
the sewerage district to the new treatment plant. The effluent outfall will be
constructed from the new treatment plant to a location in Broad Sound east of Deer
Island where a diffuser system will disperse treated wastewater into the ocean.
This Draft SEIS evaluates the effects of constructing and operating the proposed
inter-island conduit and effluent outfall. It is termed supplemental because it
supplements an earlier EIS which focused on treatment plant siting (USEPA 1985).
The evaluation described in this document considers various conduit and outfall
locations and construction methods, and evaluates the impacts of transporting
construction materials and personnel, disposal or reuse of excavated materials from
construction, and discharge of effluent to the marine environment.
1.2 HISTORY OF THE PROJECT
Boston’s wastewater has been collected and discharged into the harbor since 1885
when the construction of the Main Drainage Works was completed. Construction of the
works was undertaken because sewage was being discharged through privately owned
drain pipes to shallow areas of the harbor and rivers, causing serious health
problems (Sundstrom, 1983). The original system drained wastewater and stormwater
from Boston to holding tanks on Moon Island and discharged untreated wastes to the
harbor on the outgoing tide.
The Main Drainage Works was expanded over time to eventually provide service to what
is now the MWRA Service Area. Discharge of untreated wastewater to the harbor
continued until the construction of the primary sewage treatment plants on Nut
Island in 1952 and Deer Island in 1968 (MDC, 1976). These treatment plants provide
primary wastewater treatment and discharge disinfected effluent and digested sewage
sludge to Boston Harbor. The Federal Clean Water Act, passed in 1972, requires
secondary sewage treatment and bans most ocean dumping of sewage sludge.
Studies considering the construction of new secondary wastewater treatment
facilities began in 1973 when the Metropolitan District Commission (MDC), the agency
charged with responsibility for sewage disposal before the creation of MWRA,
commissioned the Wastewater Engineering and Management Plan for Boston
Harbor/Eastern Massachusetts Metropolitan Area (EMMA Study) (MDC, 1976). The
principal recommendations of the EMMA Study were to upgrade the Nut Island and Deer
Island treatment plants to secondary treatment, to dispose of sludge by
incineration, to eliminate CSOs, to build additional advanced treatment plants on
the Charles and Neponset Rivers and to extend and improve the interceptor system.
None of these recommendations were implemented by MDC.
EPA issued a Draft Environmental Impact Statement (DEIS) in 1978 which concluded
that some of the EMMA Study recommendations were not suitable (USEPA, 1978). The
DEIS recommended that al]. wastewater be treated at a new secondary treatment
facility at Deer Island and discharged to Boston Harbor. Sludge disposal through a
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combination of incineration and landfilling was also recommended, and construction
of any other treatment plants was not recommended.
The recommendations of the DEIS caused controversy and negative public comment. At
the same time, changes to the Federal Clean Water Act in 1977 included provisions
for a waiver of the requirement for secondary wastewater treatment (IJSEPA Vol 2.
19814). If deemed acceptable by EPA, waivers of secondary treatment requirements
were granted for five year periods, and were potentially renewable. The law
required that planning for upgrading to secondary treatment had to proceed or be in
place if a waiver was not renewed for any five year period.
The controversy surrounding the DEIS and the changes to the Clean Water Act prompted
EPA and MDC to reach an agreement that planning for new treatment facilities should
proceed in a flexible, segmented fashion to accelerate harbor cleanup by allowing
immediate upgrading actions while providing sequential decision-making on an overall
harbor clean-up program (USEPA Vol 2. 19814).
MDC filed an application for a waiver of secondary treatment in 1979 (MDC, 1979) and
submitted additional application information in 1982. This waiver was tentatively
denied by EPA in 1983. An amended waiver application was filed by MDC in 19814 and
was denied by EPA in March 1985.
While the initial waiver application was being prepared, planning for wastewater
treatment facility upgrading proceeded simultaneously. The first result of this
planning was a site options study published by MDC in 1982 (MDC, 1982). The study
found that primary treatment at both Nut Island and Deer Island could be an
environmentally sound and economically preferable option. Denials of waiver
applications by EPA countermanded this finding.
In 1983, EPA and the Commonwealth of Massachusetts began working jointly on an SDEIS
to further evaluate and site new treatment facilities on Boston Harbor. The SDEIS
(USEPA Vol.l&2, 19814) also served as an Environmental Impact Report to satisfy the
requirements of the Massachusetts Environmental Policy Act (MEPA). The SDEIS
considered twenty—two treatment site alternatives and selected seven for final
evaluation. All of the seven final siting alternatives involved Deer Island, Long
Island, and Nut Island, either separately or in combination.
On July 1, 1985, the Massachusetts Water Resources Authority (MWRA) was created by
an act of the Massachusetts legislature to take over the sewer and water operations
of the MDC. Following extensive public review and comment on the SDEIS, EPA produced
a final environmental impact statement (FEIS) (US EPA, l985b). The FEIS recommended
that a secondary treatment facility be constructed on Deer Island and also found
that a secondary treatment facility on Long Island or a facility split between Deer
and Long Islands would be environmentally acceptable. The FEIS also outlined
mandatory mitigation actions required for construction and operation of the
treatment facilities.
At the same time, the newly-created MWRA reviewed the SDEIS and produced a final
environmental impact report (FEIR) (MWRA, 1985). The FEIR selected Deer Island as
the tentative preferred alternative site for a treatment plant. The FEIR and the
EElS had been prepared through cooperative efforts between EPA and MWRA, and both
benefitted from a high degree of public and agency input. A number of factors,
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including outfall location and residuals management, were regarded to not be
determinative to treatment plant siting.
Following joint public hearings on the FEIS and FEIR, MWRA made a final selection of
Deer Island as the treatment plant site on February 3, 1986 and EPA issued a Record
of Decision (ROD) supporting that selection on February 28, 1986. The ROD states
that the siting of a treatment facility on Deer Island is EPA’s preferred
alternative, provided that the mitigation measures outlined in the FEIS are
followed. MWRA has formally committed to enacting a series of mitigation measures.
The ROD also concluded that a number of project components, including the water
quality and construction impacts of an effluent discharge outfall, and the
construction of an under-harbor conduit to convey sewage to the new treatment plant
would require additional environmental review. This Draft SEIS performs the
required additional review for the inter-island conduit and the effluent outfall.
Two sets of MWRA planning documents also deal with these topics. The Deer Island
Secondary Treatment Facilities Plan (7 volumes plus appendices) details the
alternative designs, construction methods, locations, and impacts of the treatment
plant, inter-island conduit, and effluent outfall. The Water Transportation
Facilities Plan (10 volumes) deals with the transportation of workers and materials
for construction and operation of the treatment plant, inter-island conduit, and
outfall, and the impacts of these activities (see references for complete volume and
appendix titles).
This Draft SEIS and the MWRA facilities plans were produced through a cooperative
effort of EPA and MWRA, sharing common data. The MWRA facilities plans fulfill the
requirements for an Environmental Impact Report (EIR) under the Massachusetts
Environmental Policy Act (MEPA). This Draft SEIS fulfills Federal environmental
review requirements under the National Environmental Policy Act (NEPA) and the
Federal Water Pollution Control Act Construction Grants Program. Both documents use
as their basis data from the MWRA facilities planning efforts. While avoiding
duplication of effort in data gathering, the independent analysis and public review
of the Facilities Plan/EIR and the Draft SEIS provides exhaustive review of impacts,
and an opportunity to tailor each document to precisely fit the regulatory
requirements it seeks to fulfill (MEPA or NEPA).
The ROD also required additional environmental review of residuals (sludge)
management and disposal, the construction of piers and staging areas for materials
and workers needed to build the treatment plant, the disposal of earthen or dredged
materials from construction, the transport and storage of chlorine, and projects to
upgrade CSOs, all of which were not considered determinative for treatment plant
location. These issues are the specific subjects of separate studies by MWRA and
EPA. Since these issues, to a varying degree, are related to the construction and
operation of the inter-island conduit and the effluent outfall, they are generally
considered where applicable in this EIS.
Since 1982, when the City of Quincy filed suit against MDC charging negligence in
operating its treatment plants, litigation has been a part of the effort to halt
harbor pollution. Additional lawsuits by citizen groups, cities and towns, and EPA
resulted in an aggressive schedule for construction of new treatment facilities
being mandated by the Federal District Court. Actions to construct the facilities
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necessary for harbor cleanup are driven by this schedule, and the Court regularly
reviews progress. Major deadlines of this schedule are:
• Initiate construction of new primary treatment facilities 12/90
• Complete construction and commence operation of new 7/95
primary treatment facilities
• Initiate construction of outfall 7/91
• Complete construction of outfall 7/914
• Initiate construction of inter-island wastewater 14/91
conveyance system
• Complete construction of inter-island wastewater 4/914
conveyance system
• Initiate construction of secondary treatment facilities during 1995
• Complete construction of secondary treatment facilities during 1999
1.3 DRAFT SEIS FORMAT
Scoping is normally the first step in preparing an EIS or SEIS. Scoping identifies
the issues of importance regarding the proposed action. In the case of this Draft
SEIS, extensive prior knowledge of the issues surrounding the construction and
operation of the inter—island conduit and the effluent outfall was gained through
the preparation of the draft and final EISs on treatment plant siting. The siting
EIS process generally considered the impacts of conduit and outfall construction,
and public comment on these impacts was sought as part of that process (USEP .
Vol.l&2, 19814; USEPA, 1985b). Formal scoping sessions for this Draft SEIS were held
in December 1986 (Chapter 9). This Draft SEIS, using the issues identified during
the siting process and scoping sessions, develops, analyzes, and evaluates conduit
and outfall alternatives.
This Draft SEIS consists of:
• An Executive Summary.
• Chapter 1 providing an introduction, background, and project history.
• Chapter 2 outlining the need for the project and describes the planned
actions.
• Chapter 3 explaining outfall siting alternatives, outfall and inter-island
conduit construction method options and the screening process used to
narrow the field of siting alternatives and construction method options.
• Chapter 14 describing the natural and man-made environment affected by the
project.
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• Chapter 5 describing the environmental consequences of each option
surviving screening.
• Chapter 6 providing a description of the cumulative impacts for this and
other projects occurring in the project area.
• Chapter 7 comparing the alternatives surviving screening and recommending
an effluent outfall site, diffuser design, and effluent and inter-island
conveyance construction methods.
• Chapter 8 listing preparers of this document.
• Chapter 9 siini rizing public participation.
• References, and an Index, Glossary, and a list of acronyms follow the text.
• The following technical appendices are published in a separate volume:
A. Physical Oceanography and Water Quality
B. Marine Geology and Sediment Deposition
C. Marine Ecosystems
D. Harbor Resources
E. Economic Impacts
F. Screening and Development of Alternatives
G. Regulatory Conditions
H. Operational Reliability
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CHAPTER 2
PURPOSE AND NEED FOR ACTION
2.1 EXISTING CONDITIONS
Boston Harbor is about 50 square miles in area, the largest harbor serving a major
east coast metropolitan area. Its significant national historical prominence,
natural resources, and recreational opportunities are threatened by pollution from
malfunctioning and overloaded wastewater treatment plants serving eastern
Massachusetts at Deer Island and Nut Island.
A detailed description of pollution associated with the Boston Harbor region’s
wastewater treatment can be found in EPA’s treatment plant siting SDEIS (USEPA, Vol.
1, 198)4). Effluent and sludge discharges from Deer and Nut Island treatment plants
represent over half of the suspended solids and oxygen-consuming matter entering
Boston Harbor (USEP , Vol. 1, 19814). In absolute terms, 135 tons of effluent solids
and approximately 70 tons of digested sludge solids are discharged to the harbor
daily. Raw wastewater bypassing the harbor treatment facilities in violation of
federal and state water pollution control laws puts additional stress on marine life
and results in closed beaches and shellfish beds close to the outfall discharges.
Therefore, not only has inadequate treatment polluted the harbor but the locations
of the Deer and Nut Island outfalls, several of which were built at the turn of the
century, have exacerbated the problem.
The siting EIS Record of Decision (ROD) is EPA’s final decision on the preferred
location of Secondary Wastewater Treatment facilities for Boston Harbor. The ROD
responds to MWRA’s siting decision and comments on the FEIS. The ROD (USEPA 1986c),
in addition to determining that the cleanup of Boston Harbor is best served by
consolidation of influent flows to a new secondary wastewater treatment plant at
Deer Island, also directed additional environmental review on two necessary elements
of a this plan: “the construction of an under-harbor tunnel or pipeline to
transport wastewater to the treatment plant” and the construction of “an outfall
pipe or pipes through which effluent will be discharged”.
This Draft SEIS provides the environmental review for these elements. The under-
harbor wastewater conduit is needed to connect Nut Island to Deer Island so that all
MWRA sewage will flow to Deer Island and receive secondary treatment. The new
outfall is needed to replace the existing outfalls previously discussed to increase
capacity and provide a new route to transport and disperse the treated effluent out
of Boston Harbor to Massachusetts Bay.
These improvements are part of the overall system improvements which will provide a
two-thirds reduction in sewerage solids discharged to Boston Harbor when the entire
new treatment system is operational in the year 2000 (USEPPL, Vol. 1, 198)4). Public
benefits include improvements in aesthetics, recreation, public health, and commerce
to all those who use the harbor and its shoreline.
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Reductions in pollution loadings and cessation of sewage sludge discharge will
result in substantial improvements in water quality in the harbor. Immediate
effects of improved water quality would improve the recreational value of the harbor
by reducing beach closings due to pollution and improving aesthetics throughout the
harbor. Over the long term, the biota of the harbor will respond to improved water
quality. Fthfish and shellfish resources will likely improve in quality, producing
greater opportunities for commercial and recreational fishing and reducing the
potential for public health risk through ingestion. Such sensitive resources as
saltmarsh areas, submerged vegetation, and protected areas will benefit when
improved water quality reduces stress on these sensitive systems. Economic benefits
derived from water quality improvement include increased value of commercial
fisheries, and increased value of’ recreational activities and such associated
services as sightseeing and whale watch cruises, and recreational fishing charters
and party fishing boats.
2 • 2 PROP ED ACTION
The Proposed Action consists of the following three elements:
• Construction and operation of an effluent diffuser in Massachusetts Bay which
provides dispersion of the effluent into the marine environment outside of
Boston Harbor;
• Construction and operation of an outfall conduit to transport treated
effluent from Deer Island to the diffuser site; and
• Construction and operation of a conduit delivering South System flows from
Nut Island to the Deer Island Wastewater Treatment Plant to effect
consolidation of wastewater treatment for the entire MWRA service area.
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CHAPTER 3
PRINCIPAL ALTERNATIVES: SCREENING AND DESIGN
The purpose of this chapter is to present the selection of the discharge location,
outfall and inter-island conduit construction and diffuser configuration
alternatives to be evaluated in detail in Chapter 5 of this Draft SEIS. To narrow
the alternatives, screening criteria were identified and applied to a full range of’
options. Following this screening process, options still acceptable were selected
as alternatives for detailed evaluation. This chapter summarizes the screening
process while Appendix F of this Draft SEIS presents it in detail.
Analyses conducted by MWRA (MWRA, STPF I V and V, 1987) were considered adequate for
the screening level analyses of this process. Separate analyses were conducted in
Chapter 5 of this Draft SEIS for alternatives selected for detailed evaluation.
3.1 DEFINITION OF “NO ACTION”
Consideration of the “No Action” alternative is required of EPA by National
Environmental Policy Act regulations. In the case of this Draft SEIS, “No Action”
refers to the continued discharge of’ effluent to Boston Harbor through the existing
Deer and Nut Island outfalls (Figure 3.1.a).
The Record of Decision (U.S. EPA, 1986) for the siting of MWRA’s secondary
wastewater treatment plant determined that all treatment of wastewater will be
conducted on Deer Island, and that the Nut Island wastewater treatment plant (WWTP)
will be removed. “No Action” implies that there would be no method of conveying
wastewater from Nut Island to the Deer Island WWTP, however, an inter-island conduit
is a necessary feature of MWRA’s Secondary Wastewater Facilities Plan. Therefore,
“No Action” concerning the inter-island conduit would be unacceptable.
“No Action” related to a new effluent outfall system implies that all of the
wastewater which is currently treated by the Deer and Nut Island WWTPs would
continue to be discharged to President Roads and Nantasket Roads. The numerous
pollution sources to Boston Harbor have produced a highly stressed ecosystem and
accumulation of bottom sediments with high toxic concentrations and oxygen demand.
The “No Action” alternative of continued discharge to the harbor would further
degrade the quality of Boston Harbor. In addition, the WWTP siting FEIS (EPA, 1985)
stated that the Deer Island WWTP outfall is to be located outside of Boston Harbor,
east of Deer Island. For these reasons, “No Action”, related to the effluent
outfall system is also an unacceptable alternative.
3.2 DIFFUSER LOCATION ALTERNATIVES
Completion of the EIS for siting of wastewater treatment facilities for Boston
Harbor resulted in a decision to build a secondary facility at Deer Island and
discharge the effluent east of Deer Island (EPA, 1985). It was concluded that
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0.5
0.5
SLUDGE
DISCHARGE LINES
OS
05
STATUTE MILES
0
NAUTICAL MILES
SOURCE: MWRA STFP 1987
FIGURE 3.1.a. EXISTING EFFLUENT AND SLUDGE DISCHARGE LOCATIONS
OF THE DEER AND NUT ISLAND WASTEWATER TREATMENT PLANTS
0.5
DISC)4A E LIII
ç\LOVELL
ç AND
11 SLAND
,0*05
NT*S
“A
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actual designation of the discharge site was not necessary for the determination of
the plant location. The EIS did not consider alternative discharge locations but
concluded that an acceptable site for discharge of secondary effluent could be
designated. The development of alternative locations, evaluation of the
alternatives and designation of’ a recommended discharge site was to be part of the
continued NEPPL process represented by this Draft SEIS.
3.2.1 SCREENING PROCESS
The screening process began with the entire study area of the marine environment
east of Deer Island as defined in the siting FEIS (EPA, 1985). The ability to
receive secondary effluent was used to establish the potentially acceptable
discharge sites for detailed evaluation since, with the exception of approximately
the first five years of operation, the diffuser will discharge secondary effluent.
Sites selected for detailed evaluation were analyzed for both primary and secondary
effluent discharges in Chapter 5 and Appendices A, B, C and D of this Draft SEIS.
This analysis was conducted to determine whether the five-year interim primary
effluent discharge should continue at the existing location in Presidents Roads
(Site PR) or be relocated to one of the alternative discharge sites (Site 2, L or
5). Every step in the screening process had the potential for being iterative. If
analyses at any step during screening or detailed evaluation (Chapter 5)
contradicted conclusions made during this screening process, then the process would
have been repeated.
3.2.1.1 Landward Boundary: Identification of Screening Criteria
The first step in the selection of an area encompassing potentially acceptable
secondary effluent discharge sites is to define the landward boundary of the area.
Screening criteria were selected to eliminate areas which clearly could not: (1)
provide a minimum specified initial dilution, (2) protect public health and aquatic
life, or (3) avoid sensitive or unique resources. Appendix F of this Draft SEIS
presents a detailed discussion of these criteria and how they were applied.
3.2.1.2 Landward Boundary: Application of Criteria
The landward boundary was determined by combining the 70-foot contour line, within
which effluent will receive an initial dilution of 50:1, with predictions of
particle transport analyses. Figure 3.2.1.a presents the landward boundary along
with potential discharge Sites PR through 5 (MWRA, STFP V, 1987) and Site 6 (SWIM,
1987). This boundary represents the northern, western and southern limits of the
area in Massachusetts Bay which contains potentially suitable discharge locations.
This first screening step eliminated MWRA’s Sites PR, 1 and 3 from further
consideration due to poor dilution characteristics and proximity to shore.
3.2.1.3 Eastern Boundary: Identification of Screening Criteria
The objective of the second secondary effluent site screening step is to define the
eastern or offshore boundary of the area encompassing potentially suitable discharge
locations. Once established, the eastern boundary can be used with the landward
boundary to define the entire area containing potential discharge locations.
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DISTANCE IN STATUTE MILES TO:
MANC ESTER
/
STATUTE MILES
FIGURE 3.2.1.a. LANDWARD BOUNDARY OF SECONDARY EFFLUENT DISCHARGE
IN RELATION TO ALL DISCHARGE SITE OPTIONS
DEER EAST POINT
ISLAND POINT ALLERTON
BEVERI.Y
PR
SITE 1
SITE 2
SITE 2.5
SITE 3
SITE 3.5
SITE 4
SITE4.5
SITE 5
SITE 6
0.1
3.2
4.0
4.8
5.6
7.0
6.6
8.0
9.4
11.5
52 2.3
4.0 4.3
2.4 52
2.5 5.5
6.5 2.6
5.9 4.9
3.5 6.1
5.4 7.0
6.0 8.1
9.0 9.0
‘I
/
/
SALEM
LANDWARD
BOUNDARY
2.5
0
4.5
0
4
0
5
0
06
3.5
0
3
2.0
2.0
15
0
15
NAUTICAL MILES
Co i.
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For screening purposes, conditions along a line extending seaward from Sites 2 to 6
were compared and contrasted to determine the eastern boundary of the study area.
Sites 2, 4 and 5 were analyzed by MWRA (MWRA, STFP V,A, 1987). Site 6 was analyzed
in this Draft SEIS using the actual depth at Site 6, distance from Deer Island to
Site 6 and the farthest offshore current and density data available (Site 5).
Sites 2, 4, 5, and 6 represent a wide range of potentially acceptable conditions and
are located at sufficient distance from one another so that distinctions can be
made.
The screening criteria used to establish the eastern boundary were: 1) nearfield
dilution, 2) background buildup concentrations of contaminants, 3) achievement of
U.S. EPA Water Quality Criteria and 4) outfall length. The rate of nearfield
dilution increase is greater beyond Site 4 than between Sites 2 and 4. Under
stratified and average conditions, predicted background build-up of contaminants
remains fairly constant and relatively high from Site 2 to 4. East of Site 14, there
is a relatively large decrease in predicted background build-up of contaminants.
Based on these criteria, the eastern boundary should be east of Site 14. For the
discharge of secondary effluent, predicted EPA Water Quality Criteria exceedanees
are reduced by one from Site 2 to Site 14 and by one from Site 14 to Site 5. Mo
reduction in exceedances is predicted from Site 5 to Site 6.
3.2.1k Eastern Boundary: Application of Screening Criteria
Based on the application of the above criteria, there is sufficient justification
for extending the eastern boundary past Site i4 Of all the discharge site options,
outfall construction to Site 6 would involve the highest cost and the largest amount
of material disposal. An operational scheme involving pumping would be required at
Site 6 versus gravity flow outfall operation at Sites 2, 4, and 5. The number of
U.S. EPA Water Quality Criteria exceedances predicted for Sites 5 and 6 are
identical. Thus, the increased dilution does not produce significantly improved
water quality, practical difference in public health risk, or decreased impact on
the marine ecosystem. The only justification for extending the boundary past Site 5
is to increase initial and farfield dilutions. Even east of Site 6 there would
still likely be predicted exceedances of the U.S. EPA Water Quality Criteria.
Therefore predicted exceedances and their impacts at Sites 5 or 6 would have to be
addressed by a method other than increasing the outfall length, such as source
control or pretreatment, which is a preferable means of controlling pollution.
Based on both the screening analysis of this Draft SEIS and !4WRA’s analysis, there
are few predicted impacts at Site 5 and none which would be eliminated at a more
offshore site. An acceptable discharge location can be identified between the
landward boundary and an eastern boundary established at Site 5 (Figure 3.2.1.b).
Therefore, Site 6 was eliminated during this screening analysis. A more detailed
presentation of this analysis is included in Appendix F.
If the discharge site was based exclusively on achieving U.S. EPA Water Quality
Criteria, the discharge site could be identified much farther from Deer Island than
the sites investigated. Since east of Site 6 there would still likely be predicted
exceedances of the U.S. EPA Water Quality Criteria, then predicted exceedances will
have to be addressed by a method other than increasing the outfall length, such as
source control or pretreatment, where are preferable means of controlling pollution.
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STATUTE MI LES
FIGURE 3.2.1.b. AREA OF POTENTIALLY ACCEPTABLE SECONDARY
EFFLUENT DISCHARGE LOCATIONS
DISTANCE IN STATUTE MILES TO
DEER EAST POINT
ISLAND POINT AIIERTON
\ j\
•1
MANCHESTER
BEVERLY
PR
SITE 1
SITE 2
SITE 2.5
SITE 3
SITE 3.5
SITE 4
SITE4.5
SITE 5
SITE 6
0.1
3.2
4.0
4.8
5.6
7.0
6.6
8.0
9.4
11.5
. 5.,. /
5.2 2.3
4.0 4.3
2.4 5.2
2.5 5.5
6.5 2.6
5.9 4.9
3.5 6.1
5.4 7.0
6.0 8.1
9.0 9.0
/
/
S*1 .EM
• L O
,c “
I
vt
I
EASTERN
BOUNDARY
LANDWARD
BOUNDARY
(
2.5
0
4
0
4.5
0
5
0
1
0
6
I
I
I
/
0 1 w
3.5
0
G A .
3
/
/
2.0
2.0
1.5
0
1 5
NAUTICAL MILES
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3.2.1.5 Final Site Screening Step: Alternative Discharge Locations
The goal of the final site screening step is to identify locations within the area
defined during the previous steps for detailed evaluation and comparison. One
objective is to ensure that the range of physical oceanographic, geologic, biologic
and water quality conditions are represented by the alternative locations. Another
important objective is to establish alternative discharge locations which differ
enough to permit meaningful comparisons. Sites which were investigated by MWRA
(MWRA, STFP V,A, 1987) and which also passed the first screening steps were
reviewed. If discharge locations met the two objectives discussed above, they was
selected for detailed evaluation.
Sites investigated by MWRA within the area of potential suitability outfall
locations include Sites 2, 2.5, 3.5, 14, 14.5 and 5. The extremes in range of
conditions within the area are represented at Sites 2 and 5. Therefore, these two
sites will be among those evaluated in detail. There is no large change in
predicted dilution or water quality conditions between Sites 2 and 2.5. Since
expected differences between these two stations are less acute than the sensitivity
of the analytical tools, Site 2.5 was eliminated. Site 14 represents a distinct
change in depth dilution and potentially other characteristics from both Sites 2
and 5. Therefore, it was chosen for detailed evaluation. Sites 3.5 and 14,5 fall
within the range of oceanographic conditions represented by Sites 2,4 and 5. They
provide no unique characteristics such as increased depth, distance from a resource,
current regime or reduced construction costs. Therefore, they were not evaluated in
detail.
Based on the three step screening process, the sites chosen for detailed evaluation
were Sites 2, 14 and 5 (Figure 3.2.1.c) which represent a reasonable range of
alternatives.
3.2.1.6 Interim Discharge Screening Location: Identification of Criteria
A necessary step in implementing the required Deer Island secondary wastewater
treatment plant is to discharge primary effluent during the construction period of
approximately five years. The goal of this screening is to determine the
potentially acceptable locations of the five-year interim discharge of primary
effluent. The existing Deer Island discharge site in President Roads (Site PR) was
compared to the sites selected for detailed analysis in this Draft SEIS (Sites 2, 14
and 5) to determine if the primary effluent discharge at Site PR should continue or
occur only at one of the three selected alternative discharge locations. The
criteria used in this screening included: 1) achievement of U.S. EPA Water Quality
Criteria, 2) compliance with Massachusetts Surface Water Quality Standards, 3)
shoreline impacts of pollutants and 14) cumulative impacts.
3.2.1.7 Interim Discharge Screening: Application of Criteria
It is clear that discharge of effluent at President Roads should be discontinued
once the new effluent outfall system is constructed (Appendix F). Discharging
primary effluent at Sites 2, !I or 5 rather than at Site PR would offer the benefits
of increased achievement of water quality criteria at the edge of the mixing zone;
decreased percentages of effluent at the shorelines of Winthrop, Hull and Nahant;
3—7

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FIGURE 3.2.1.c. ALTERNATIVE DISCHARGE LOCATIONS
2.0 0 2.0
STATUTE MILES
1.5 0 1.5
I- ‘
NAUTICAL MILES
,
,
SALEM
EAST POINT
2
0
4
0
5
0
-I,
ThsGmvs
POINT ALLERTON
3-8

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increased compliance with the state dissolved oxygen concentration standard; and
less chance of further stressing the Boston Harbor ecosystem. Therefore, discharge
of primary effluent to President Roads during the five—year interim period is
eliminated from further consideration. Discharge of primary effluent for the five-
year interim period is evaluated for Sites 2, 1 and 5 in this Draft SETS.
3.2.2 DESCRIPTION OF DISCHARGE LOCATION ALTERNATIVES FOR DETAILED EVALUATION
Sites chosen for further evaluation are Sites 2, and 5 (Table 3.2.2.a). Although
the alternative discharge locations are called “sites”, they also represent regions
within Massachusetts Bay in which an outfall could be located. Since these sites
are already known to the public and agencies by these names, this Draft SETS retains
these names.
3.2.3 CRITERIA FOR DETAILED EVALUATION
Alternative discharge sites were evaluated in detail in Chapter 5 and Appendices A,
B, C and D using the criteria in Table 3.2.3.a. These criteria are discussed in
further detail in Appendix F.
3.3 EFFLUENT CONVEYANCE MODE
3.3.1 SCREENING PROCESS
Effluent from the new Deer Island wastewater treatment plant will be transported by
a submarine ocean outfall and discharged to a site in Massachusetts Bay. Three
potential outfall systems were screened using a set of relevant criteria. The
alternative(s) with the least predicted impacts was selected for detailed
evaluation.
The three construction technologies for the effluent outfall conveyance systems
proposed and evaluated by MWRA were marine pipeline, sunken tube and deep rock
tunnel. These outfall construction technologies represent a reasonable range of
alternatives and were screened in this Draft SETS.
3.3.1.1 Identification of Screening Criteria
The criteria developed for screening the effluent outfall system include:
1) impacts on the marine ecosystem, 2) impacts on commercial and recreational
resources, 3) disposal of dredged or tunnelled material, 4) constructability
5) institutional constraints and 6) cost.
3.3.1.2 Application of’ Screening Criteria
Based on the application of the above criteria (Appendix F), the deep rock tunnel
construction alternative would have least impact on environmental quality and harbor
resources, be most adaptable to future uses of the harbor, be easiest to construct,
have the least institutional constraints, and be the least costly of the three
effluent outfall alternatives (Table 3.3.1.a). Therefore, tunnel construction was
the only alternative selected for further evaluation.
3—9

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TABLE 3.2.2.a CESCR1PTI0I O ThE ALTEATIVE DISCHAIIGE LOCATT( 4S
Site
Description
Water
Depth
(ft. MLW)
Distance
From
Deer island
(miles)
Distance
From
Nahant
(miles)
Distance
From
Hull
(tiles)
Average
Depth of
Diffuser
(feet)
Total
Tunnel
Length
(feet)
Tunnel
Inside
Diameter
(feet)
Total
Construction
Time
(months)
($
Project
Cost
Million)
2
Broad Sound
75
J4.0
2.Il
5.2
75
28,000
22
1 7
276
1s
Broad Sound
90
6.6
3.6
6.1
90
3,000
2
51
389
5
Massachusetts
Bay
100
9 .i
6.0
8.1
100
5 ,000
25
56
‘ 68
Source: MWRA STFP V, 1987
-a
0

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TABLE 3.2.3.a CRITERIA FOR THE EVALUATION 0 ALTERNATIVE DISCHARGE SITFS
Criteria Description Measure
WATER JALITY
Ability to Meet EPA Aquatic Water Each alternative discharge site was evaluated Exceedances of EPA Aquatic Life Water
Life Quality Criteria to determine its ability to achieve EPA Aquatic Quality Criteria
Life Water Quality Criteria goals as defined
in Quality Criteria for Water, U.S. Environmental
Protection Agency, May 1, 1986, EPA J O/5-86—0O1.
Conformance with Mass Water Alternative discharge locations were assessed Violations of Massachusetts Surface
Quality Standards based on the ability of both primary and Water Quality Standards
secondary effluents to comply with Massachusetts expected at each site
Surface Water Quality Standards with emphasis
on dissolved oxygen concentration.
Impacts of Pollutants at Shoreline Percentage of effluent pollutant concentrations Predicted percentages at shoreline
at the shoreline were calculated for discharge
at Sites 2, 14, and 5.
SEDIMENT QUALITY
Sediment Toxicity The potential impacts on marine biota due to the Toxic concentrations were assessed
the accumulation of toxics in sediment were based on values found in literature
assessed.
Sediment Enrichment Impacts on benthic organisms due to organic <0.1 gC/m 2 /day “No Noticeable Effect”;
loadings from the discharge were examined. 0.1 to 1.5 gC/rn /day “Changed Benthic
Communities”;
>1.5 gC/m 2 /day “Degraded Benthic
Communities”
MARINE ECOSYSTEMS
Adverse Effects Due to Water Column Impacts due to nutrient enrichment of the water <0.114 mg/l “No Effect”;
Enrichment column will be assessed. 0.114 to 0.5 mg/l “Changed”;
>0.5 mg/l “Degraded”

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TABLE 3.2.3.a (Continued) CRITERIA FOR T1€ EVALUATIOW OF ALTERNATIVE DISCHAR(Z SITRB
Criteria Description Measure
Safeguarding Protected Species from The potential for adverse impacts on habitats Relative ratings of
Habitat Modifications of protected species was assessed. “Minor”, “Moderate”, “Extensive”
Avoidance of Sensitive and/or The potential for affecting areas which would be Relative ratings of
Important Habitat highly susceptible to impacts of sewage “Minor ”, “Moderate”, “Extensive”
discharge, including submerged vegetation and
shellfish areas, was assessed.
HARBOR R OURCRB
Protection of Offshore Recreation The potential to protect recreation and aesthetics Relative ratings of
and Aesthetics in the open waters and along the shorelines of “Minor”, “Moderate”, “Extensive”
Massachusetts Bay and to protect and restore
recreation and aesthetics of the open waters and
along the shoreline of Boston Harbor was assessed.
Protection of Cultural and The potential to protect areas of cultural or Relative ratings of
Historical Resources historical value was assessed for each “Minor”, “Moderate”, “Extensive”
alternative discharge location. Included in
this assessment are potential impacts on
archaeology and historic resources such as
shipwrecks.
Protection of Commercial Fishing Potential interference with commercial fishing Relative ratings of
Activities activities such as dragging, trawling, “Minor”, “Moderate”, “Extensive”
gilinetting and lobstering and preemption of
fishing areas in Massachusetts Bay was examined
Protection of Commercial and The potential for maintenance of potentially Relative ratings of
Recreational Species harvestable stocks of commercially and “Minor”, “Moderate”, “Extensive”
recreational aquatic species was examined.
Water Traffic Interference with coninercial and recreational Relative ratings of
marine traffic as a result of construction at “Minor”, “Moderate”, “Extensive”
each of the alternative discharge sites was
examined.

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TABLE 3.2.3.a (Continued) CRITERIA FOR THE EVALUATION OF ALTERNATIVE DISCHARGE SITES
Criteria Description Measure
PUBLIC HEALTH
Ability to Meet EPA Public Health The ability of discharge sites to insure the Exceedances of EPA Public Health
Water Quality Criteria protection of public health was evaluated. Water Quality Criteria
This criterion involves examining data on
existing and projected levels of pathogens and
carcinogens in water, sediment and seafood.
ENGINEERING FEASIBILITY
Constructibility The difficulty and risk associated with locating Relative ratings of
the diffuser at each of the alternative “Minor”, “Moderate”, “Extensive”
discharge sites were assessed. Included
LA ) in this criterion are adverse impacts of
weather and construction technologies required
to reach a specific site.
cosr
Capital Cost Capital cost represents the sum of the Millions of Dollars
costs required to construct and operate the
project and is presented as a single
investment. Capital cost includes
construction and operation and maintenance costs
of the práject through the year 2020.
MATERIALS DiSPOSAL
Disposal of Excavated Material Both quantity and quality of excavated or Volume of material to be disposed;
tunnelled material were estimated to degree of difficulty associated with
determine the potential difficulties associated disposal
with disposal of the material.

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TABLE 3.2.3.a (Conti ved) CRITERIA FOR TIE EVALUATION OF ALTERNATIVE DISCBAE(Z SITES
Criteria Description Measure
INSTITUTIONAL
Construction Duration The relative dirficulty which a specific Time required for completion
discharge location is expected to have, based
on the expected time required to complete
outfall construction, was estimated.
Permitting The number of permits required and the relative Relative ratings of
difficulty in obtaining these permits for “Moderate”, “Extensive”
each alternative was assessed.
Demand for Unique or Scarce The relative demand that an alternative may Relative ratings of
Construction Resources put on scarce resources or resources not “Moderate’ t , “Difficult”
available in the local area was assessed.
These resources include labor and construction
materials which may be in heavy demand due
to other major local construction projects.

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TABLE 3.3.1 .a SUMMARY OF EFFLUENT CONVEYANCE MODE SCREENING
Screening Criteria Tunnel Sunken Tube Pipeline
Marine Ecosystem No Impact Negative Impact Negative Impact
(0) (-) (-)
Resources No Impact Negative Impact Negative Impact
(0) (—) (—)
Disposal of Excavated Material Difficult Difficult Difficult
Constructibility Difficult Difficult Difficult
(—.) (.—) (—)
Institutional Constraints Possible Definite Definite
(0/—) (-..) (—)
Cost Expensive More Expensive More Expensive
(0) (-) (-)

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3.3.2 DESCRIPTION OF OUTFALL CONDUIT ALTERNATIVE FOR DETAILED EVALUATION
A single effluent conveyance mode has been selected for detailed evaluation in this
Draft SEIS. This outfall alternative involves deep rock tunnelling from Deer Islanc
to the discharge location. It includes a 30-foot by 15-foot rectangular vertical
access shaft on Deer Island and a 25-foot finished inside diameter concrete-linec
tunnel connected to the access shaft (MWRA, STFP V,E, 1987). The tunnel could
either end below the beginning of a pipeline diffuser or below the last diffuser
riser of a tunnelled diffuser. The length of the tunnel would be between 28,000 anc
5U,000 ft., depending upon the diffuser design and discharge location. A vertical
shaft will be excavated on Deer Island from grade to the tunnel. The vertical shaft
will be excavated deep enough to allow for a 0.25 percent (or less) positive slopin
tunnel and to assure a minimum of 60 feet of bedrock overlying the outfall tunnel.
The outfall conduit would be mined using a tunnel boring machine (TBM) and, wherE
necessary, drill and blast techniques (MWRA, STFP V,E, 1987). Tunnel spoils will bE
removed through the access shaft. A medium—hard rock, Cambridge argillite, is thE
most common rock type in Boston Harbor/Massachusetts Bay. It is anticipated that
the TBM will progress an average of’ 50 to 70 feet/day in the tunnel construction and
that approximately 15 percent of the tunnel will require rock bolting and
grouting. These estimates are based upon the available data and may be revised
pending MWRA’s detailed geologic investigations planned for spring 1988. The tunnel
system would be lined with reinforced concrete to provide a smooth conduit wall and
thus, minimize friction head loss.
3.3.3 CRITERIA FOR DETAILED EVALUATION
The tunnelled outfall alternative is evaluated in detail in Chapter 5 using thE
selection criteria discussed in Appendix F and presented in Table 3.3.2.a.
3.14 DIFFUSER TYPES
3 14 1 SCREENING PROCESS
MWRA proposed and evaluated three diffuser alternatives (MWRA, STFP V,D, 1987)
representing a range of diffuser construction technologies. This Draft SEI
examines the diffuser alternatives discussed by MWRA, combining two of MWRA’a
diffuser options into one option for the screening analysis.
The first of the two diffuser options to be screened in this Draft SEIS is a
pipeline situated within an excavated trench connected to the deep rock tunnel
outfall by one (Figure 3.’Ll.a) to ten (Figure 3. 1 .1.b) risers. Ports or nozzlea
would either be cast into or attached to the pipe. Each individual riser would
connect the tunnel to a diffuser pipe extending in the direction of the outfall (for
a one riser system) or extending about 100 meters in opposing directions (for a
multiple riser system). The second diffuser option involves many risers
(approximately 80) with each riser fitted with a multi-port cap (between 8 and 1(
ports) (Figure 3)4.1.c).
3-16

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TABLE 3.3.2.a CRITERIA FOR THE EVALUATION OF THE EFFW T CONVEYANCE ALTERNATIVE
Criteria Description Measure
D VI ROWMENTAL
Air Emissions Control
Noise Control
The potential for generating air emissions and
odor during conduit construction was
qualitatively addressed.
The noise due to construction of the shaft on
Deer Island was assessed.
Relative ratings of
“Mitigable”, “Not Mitigable”
Quantitative prediction of noise;
relative ratings of “Minor”, “Moderate”,
“Extensive” based on those predictions
ENGINEERING FEASIBILITY
Reliability
Constructibility
COST
The ability of the conduit system to continuously
operate over the expected range of conditions
during the life of the design was examined.
The difficulty and risk associated with
constructing the conduit system was assessed.
Included in this criterion are adverse impacts
of weather and construction technology involved.
Relative ratings of
“Reliable”, “Not Reliable”
Relative ratings of
“Minor”, “Moderate”, “Extensive”
Capital Cost
Capital cost presents the sum of costs
required to construct and operate the project
through the year 2020 as a single investment.
Millions of Dollars
MATERIALS DISPOSAL
Disposal of Tunnelled Material
Both quantity and quality of tunnelled material
were be estimated to determine potential
difficulties associated with this plan for
disposal.
Volume of material to be disposed;
degree of difficulty associated with
disposal

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TABLE 3.3.2 .a (Continued) CRITERIA FOR THE EVALUATION O THE EPFUJERT CONVEYANCE ALTERNATIVE
Criteria Description Measure
• INSTITrrIONAL
Construation Duration The relative difficulty which a specific Time required for completion
construction technology is expected to have
based on the expected time required to complete
outfall construction was examined.
Permitting The number of permits required and the relative Relative ratings of
difficulty in obtaining these permits for the “Moderate”, “Extensive”
alternative was assessed.
Demand for Unique or Scarce The relative demand that the alternative may put Relative ratings of
— Construction Resources on scarce resources or resources not available “Moderate”,”Difficult”
in the local area was assessed. These
resources include labor and construction
materials which may be in heavy demand due to
other major local construction projects.
HARBOR RRBCIJRCRB
Protection of Cultural and The potential to protect areas of cultural or Relative ratings of
Historical Resources historical value was assessed for each “Minor”, “Moderate”, “Extensive”
alternative discharge location. Included in
this assessment will be potential impacts on
archaeology and historic resources such as
shipwrecks.
Water Traffic Interference with marine traffic as a result Relative ratings of
of construction was examined. “Minor”, “Moderate”, “Extensive”

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fill] I ITI1lT1TflTrrrrrrrr 1 - 1111 ii iii iiiii IIiii
PIPELINE
w
(NOT TO SCALE)
FIGURE 3.4.1.a. PROFILE VIEW OF PIPELINE DIFFUSER WITH ONE RISER

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SOURCE: MWRA, STFP V, 1987
(NOT TO SCALE)
FIGURE 3.4.1.b. PROFILE VIEW OF PIPELINE DIFFUSER WITH EIGHT TO TEN RISERS
I ’ )
0
TUNNEL

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SEA LEVEL EL. 105 FT
PLAN OF RISER CAP
NT. S.
6600 FT. DIFFUSER
80 EQUALLY SPACED RISERS
0 10 120
I a I
SOURCE: MWRA STFP V, 1987
DETAIL A
SECTION
N.TS.
L
RISER CAP
(TIP 80 PLACES
SCALE- FEET
FIGURE 3.4.1.c. PLAN AND PROFILE VIEWS OF TUNNELLED DIFFUSER WITH MULTIPLE RISERS

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3.14.1.1 Identification of Screening Criteria
Operation of the two diffuser options would be identical (MWRA, STFP V, , 1987),
thus, only construction impacts were addressed by the diffuser system soreenin
criteria. Costs for alternative diffuser systems cannot be determined without site.
specific geotechnical information. Therefore, costs are not used to comparE
alternatives in this Draft SEIS. The screening criteria are: 1) operational
complexity, 2) impacts on marine ecosystems, 3) impacts on commercial arid
recreational resources, L ) disposal of dredged material, 5) constructability and
6) institutional constraints.
3.14.1.2 Application of Screening Criteria
The diffuser construction alternative involving 80 risers drilled through bedrock
and connected to the tunnelled outfall would have the least marine ecosystem anc
harbor resources impacts of the alternatives (Table 3.4.1.a). However, based on thE
application of the other screening criteria (Appendix F), it is difficult to choosE
only one preferred option. Both diffuser construction options are expected to bE
difficult to construct, costly, and require permitting through various agencies,
Therefore, neither diffuser construction technologies was eliminated durin
screening.
3.14.2 DESCRIPTION OF DIFFUSER ALTERNATIVES FOR DETAILED EVALUATION
Two general diffuser construction alternatives are evaluated in detail in this Draft
SEIS. The first alternative is a tunnelled diffuser with 80 risers drilled througt
the overlying sediment and bedrock and attached to the tunnelled outfall. ThE
second diffuser alternative is a tunnelled outfall connected to a pipeline diffuse!
by one to ten risers.
3.11.3 CRITERIA FOR DETAILED EVALUATION
Selection criteria are discussed in Appendix F and listed in Table 3. 1 .3.a au
applied in the detailed evaluations of the diffuser alternatives presented lu
Chapter 5.
3.5 INTER-ISLAND CONVEYANCE MODE
3.5.1 SCREENING PROCESS
Wastewater entering the South System of the MWRA collection and treatment systel
will receive some initial treatment for removal of grit and bulk solids at thE
proposed headworks on Nut Island. From Nut Island, the wastewater will be conveyel
to Deer Island, the location of the new wastewater treatment plant, via an inter•
island conveyance system.
Three potential inter—island conveyance systems were screened using a set ol
criteria identical to those used to screen potential outfall construction options
The screening ratings of the three possible systems were compared. These potential
conveyance systems of pipeline, sunken tube and deep rock tunnel were proposed and
3-22

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TABLE 3. $.1.a SU)IIABY OF DIFFUSER TYPE SCREENING
Alternative 1: Tunnel with
One Riser to Pipeline Alternative 2: Tunnel with Alternative 3: Tunnel with
Diffuser with Multiple Ten Risers To Ten 80 Risers Through Bedrock
Screening Criteria Ports or Nozzles Pipe Diffusers Multi—Port Riser Caps (8 Ports)
Marine Ecosystem Negative Impact Negative Impact Less Negative Impact
(—) (—) (0)
Resources Negative Impact Negative Impact Less Negative Impact
(-) (—) (0)
Constructibility Difficult Difficult Difficult
(—) (—) (—)
Operational Complexity Minimal Purging Required! Purging Required/ Purging Required/
(Purging!External Damage) External Damage Possible External Damage Possible Least External Damage
(+1-) (—I-) (-1+)
Institutional Constraints Probable Probable Probable
(—) (—) (—)

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TABLE 3 .i .3 .a. CRITERI A FOR TEE EVALUATICII OF TEE DIFFUSER TYPE ALTEmIATIVES
Criteria Description Measure
(VI ROSI4 ITAL
Noise Control Noise impacts due to excavation and drilling Quantitative predictions of noise;
during diffuser construction were assessed. ratings of “Minor”, “Moderate”,
“Extensive” based on those predictions
IGINEERING FEASIBILITY
Reliability The ability of the diffuser system to Relative ratings of
continuously operate over the expected range “Reliable”, “Not Reliable”
of conditions during the life of the design
was assessed.
‘t’ Constructibility The difficulty and risk associated with Relative ratings of
constructing the diffuser system was assessed. “Minor”, “Moderate”, “Extensive”
MATERIALS DISP AL
Disposal of Excavated Material Both quantity and quality of tunnelled material Volume of material to be disposed;
were estimated to determine potential degree of difficulty associated with
methods of and difficulties associated with disposal
this plan for disposal.
IWSTITUTIOIAL CRITERIA
Construction Duration The relative difficulty which a specific diffuser Time required for completion
construction technology is expected to have
in maintaining the court ordered schedule was
examined.
Permitting The number of permits required and the relative Relative ratings of
difficulty in obtaining these permits for each “Moderate”, “Extensive”
alternative was assessed.

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TABLE 3)L3.a. (Continued) CRITERIA FOR THE EVALUATION OF THE DIFFUSER TYPE ALTERNATIVES
Criteria Description Measure
Demand for Unique or Scarce The relative demand that an alternative may Relative ratings of
Construction Resources put on scarce resources or resources not “Moderate”, “Difficult”
available in the local area was assessed.
These resources include labor and construction
materials which may be in heavy demand due
to other major local construction projects.
MARINE ECOSYSTEM
Protection of Water Quality Since construction of the diffuser has the Relative ratings of’
potential to disturb bottom sediments, causing “Minor”, “Moderate”, “Extensive”
them to resuspend and to increase turbidity,
the relative impact which the diffuser options
have on water quality was assessed.
F .)
‘- Protection of Sensitive Biota The extent to which, sensitive biota and habitat Relative ratings of
and Habitat will be affected by resuspension of’ bottom “Minor”, “Moderate”, “Extensive”
sediments and loss of habitat due to construction
of the diffuser was assessed.
HARBOR RESOURCES
Protection of Cultural and The potential to protect areas of cultural Relative ratings of
Historical Resources or historical value was assessed for each diffuser “Minor”, “Moderate”, “Extensive”
alternative. Included in this assessment are
potential impacts on archaeology and historic
resources such as shipwrecks.
Water Traffic Interference with marine traffic as a result Relative ratings of
of construction was examined. “Minor”, “Moderate”, “Extensive”
Protection of Commercial Fishing Potential Interference with commercial fishing Relative ratings of
P.ctivlties activities such as dragging, travelling, “Minor”, “Moderate”, “Extensive”
gillnetting and lobstering and preemption of
fishing areas was examined.

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examined by MWRA (MWRA, STFP IV, 1987). These alternatives use the same
construction technologies as were presented for the effluent outfall system. These
inter-island construction modes represent a reasonable range of alternatives and
were used in this Draft SEIS.
Since President Roads (between Long Island and Deer Island) is a major shipping lane
of Boston Harbor, construction of either a pipeline or a sunken tube across
Presjd nt Roads would have to be coordinated with the U.S. Coast Guard to prevent
unsafe conditions in the harbor. In addition, construction involving a pipeline or
sunken tube may impact the harbor’s islands and therefore, may require coordination
with various agencies. For these reasons, only tunnelled conveyance construction is
considered for the President Roads portion of the inter-island conduit.
3.5.1.1 Identification of Screening Criteria
Criteria developed for screening the inter—island conduit construction options for
the remainder of the conduit (Nut Island to Long Island) are identical to those used I
screen potential effluent outfall construction options (Section 3.3 and Appendix F).
3.5.1.2 Application of Screening Criteria
Based on the application of the criteria, the deep rock tunnel construction
alternative would least Impact environmental quality and harbor resources, be most
adaptable to future uses of the harbor, be easiest to construct, have the least
institutional constraints, and be the least costly of the three inter-island conduit
alternatives (Table 3.5.1.a). Therefore, tunnel construction from Nut Island to
Deer Island was the only alternative selected for further evaluation.
3.5.2 DESCRIPTION OF INTER-ISLAND CONDUIT ALTERNATIVE FOR DETAILED EVALUATION
The single inter-island conveyance alternative selected for detailed evaluation is
an li-ft finished inside diameter deep-rock tunnel from Nut Island to Deer Island
(Figures 3.5..2.a and 3.5.2.b) (MWRA, STFP IV, 1987). This alternative would involve
similar tunnelling methods to those described for the tunnelled outfall system
alternative (Section 3.3.2). Vertical access shafts would be excavated on Deer
Island and Nut Island. Excavation of the 2Zt,800-ft-long tunnel would begin at the
Deer Island shaft and eventually connect to the Nut Island shaft. The tunnel would
have a positive slope towards Nut Island. Tunnel spoils would be removed through
the Deer Island access shaft. The tunnel would be lined with reinforced precast
concrete sections.
3.5.3 CRITERIA FOR DETAILED EVALUATION
The tunnelled inter—island conveyance system alternative was evaluated in detail in
Chapter 5 using the selection criteria in Table 3.5.3.a and described in detail in
Appendix F.
3—26

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TABLE 3.5.1.a SUMMARY OF INTER-ISLAND CONVEYANCE MODE SCREENING
Tunnel • Sunken Tube Pipeline
No Impact Negative Impact Negative Impact
(0) (-) (-)
No Impact Negative Impact Negative Impact
(0) (-) (-)
Not Difficult Difficult Difficult
(+) C-) (-)
Difficult Difficult. Difficult
(—) (—) C—)
Possible Definite Definite
(0/—) (—) C—)
Expensive More Expensive More Expensive
(0) (-) C-)
Screening Criteria
Marine Ecosystem
Resources
Disposal of Excavated Material
Constructibility
Institutional Constraints
Cost

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0.5
0.5
STATUTE MILES
0 0.5
I
NAUTICAL MILES
SOURCE: MWRA STFP IV, 1987
QUINCY
B 4 V
NUT
SUNKEN
LEDGE
ISLAND
LONG
ISLAND
TUNNEL
It.)
DEER
ISLAND
TUNNEL
RAINSFORD
ISLAND
NIXES
MATE
PEDDOCKS
ISLAND
SOUTH
SYSTEM
PUM PING
0
LOVE LL
GEORGES ISLAND
ISLAND
STATION
C
FIGURE 3.5.2.a. PLAN VIEW OF INTER-ISLAND CONVEYANCE SYSTEM ALTERNATIVE

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DEER ISL.
—REINFORCED CONCRETE LINER
‘ROCK
2000 1000 0 1000 2000
TYPICAL TUNNEL
CROSS SECTION
*METROPOLITAN DISTRICT COMMISSION STANDARD ADDS 105 FEET TO ACTUAL ELEVATION.
SOURCE: MWRA STFP IV, 1987
HORIZ SCAL(-F(CT
NEW
HEADWORKS
NUT ISLAND SEA BOTTOM
‘30
p 1 00
I ii
SO
50
-j
I SO
20 0
I’ -)
RAINSFORD ISLAND
•SOUTH SYSTEM
PUMP
ROCK
AJ
GROUT HOLES (TYP)
12(MIN)
ISO
100 p
o
S0
A-A
1-ISO
J- 0
INV
FIGURE 3.52.b. PROFILE VIEW OF INTER-ISLAND CONVEYANCE SYSTEM ALTERNATIVE

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TABLE 3.5.3.a CRITERIA FO THE EVAWATIOW CF INTER-iSLAND CONVEYANCE ALTERNATIVE
Criteria Description Measure
JVIHOSIERTAL
Air Emissions Control The potential for generating air emissions and Relative ratings of
odor during conduit construction was qualitatively “Mitigable”,”NOt Mitigable”
addressed.
Noise Control The noise due to conduit construction was Quantitative prediction of
assessed, noise; ratings of “Minor”, “Moderate”,
“Extensive” based on those predictions
ERGIWEERING FEASIBILITY
Reliability The ability of the conduit system to continuously Relative ratings of
operate over the expected range of conditions “Reliable”, “Not Reliable”
during the life of the design was examined.
Constructibility The difficulty and risk associated with Relative ratings of
constructing the conduit system was assessed. “Minor”, “Moderate”, “Extensive”
Included in this criterion are adverse impacts
of weather and construction technology involved.
ST
Present Worth Cost Present worth cost presents the sum of the Millions of Dollars
costs required to construct and operate the
project, through the year 2020, as a single
investment.
Project Cost Project cost includes the capital cost of Millions of Dollars
constructing facilities, equipment replacement
costs during the planning period plus 35 perbent
to cover construction contingencies and
administrative, engineering and legal costs.

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TABLE 3.5.3.a (Continued) CRITERIA FOR THE EVALUATION OF INTER—ISLAND CONVEYANCE ALTERNATIVE
Criteria Description Measure
MATERIALS DISP AL
Disposal of Tunnelled Material Both quantity and quality of tunnelled material Volume of material to be disposed;
were estimated to determine potential degree of difficulty associated
difficulties associated with this plan for with disposal
disposal.
INSTITUTIONAL
Construction Duration The relative difficulty a specific construction Time required for completion
technology is expected to have based on the
expected time required for completion of
construction was examined
Permitting The number of permits required and the relative Relative ratings of
difficulty in obtaining these permits for the “Moderate”, “Extensive”
alternative was assessed.
Demand for Unique or Scarce The relative demand that the alternative may put Relative ratings of
Construction Resources on scarce resources or resources not available “Moderate”, “Difficult”
in the local area was assessed. These
resources include labor and construction
materials which may be in heavy demand due to
other major local construction projects.
HARBOR RESWRCES
Protection of’ Cultural and The potential to protect areas of cultural or Relative ratings of
Historical Resources historical value was assessed for each “Minor”, “Moderate”, “Extensive”
alternative discharge location. Included in
this assessment will be potential impacts on
archaeology and historic resources such as
shipwrecks.
Water Traffic Interference with marine traffic as a result Relative ratings of
of construction was examined. “ Minor”, “Moderate”, “Extensive ”

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CHAPTER 4
AFFECTED ENVIRONMENT
11.1 INTRODUCTION
4.1.1 PROJECT SETTING
This chapter presents an overview of environmental conditions and marine resources
in the area that will potentially be affected by the construction and operation of
the effluent conveyance and diffuser system and the, inter-island conduit
structure. The effluent conveyance structure alignment will approximate a straight
line from Deer Island to the diffuser location while the inter—island conduit
structure will approximate a straight line between Nut Island and Deer Island. In
general, the affected environment includes the area of Massachusetts Bay within
approximately 10 miles of Boston Harbor, portions of Boston Harbor itself, and in
the case of affected marine resources, the associated shoreline as well.
Specific technical disciplines discussed in this chapter include physical
oceanography, water quality, marine geology and marine biology. Harbor resources
such as shipping, fisheries and recreation are also discussed. Information
presented include data collected by MWRA in support of the outfall siting decision
(MWRA, STFP V, 1987) as well as data from previous studies.
4.1.2 SERVICE AREA
Since 1847, Boston Harbor has been receiving all domestic, commercial and industrial
wastewater and stormwater from the Boston metropolitan area. At present, the area’s
two wastewater treatment plants at Nut Island and Deer Island treat wastewater
collected from a network of almost 5,000 miles of sewers, conduits and pipes
servicing 1.9 million people in 1 13 metropolitan cities and towns (Figure 1 4.1.2.a).
The Deer Island and Nut Island plants provide primary treatment to the North and
South Metropolitan Sewer Service Areas respectively. Some communities are serviced
by both plants (MWRA, STFP I, 1987).
4.2 SUMMARY OF ENVIRONMENTAL CONDITIONS
4.2.1 PHYSICAL OCEANOGRAPHY
The water quality analyses conducted to evaluate the alternative discharge sites
require as input physical oceanography parameters describing the currents and
vertical stratification in the affected area of Massachusetts Bay. Although the
effluent discharge flow rate will be large, its impact on these parameters will be
only local and existing physical oceanography conditions can be used for the
predictive water quality analyses. The specific parameters of importance are first
discussed, as well as their role in the processes which control the fate of the
effluent. The data sources and the information which they can provide relative to
these needs are then reviewed, followed by analyses of the data to provide the
specific information which will be used in the water quality predictions.
1_i

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SOURCE: MDC, 1979
FIGURE 4.1.2a. MWRA SEWERAGE SERVICE AREA
HARBOR
4-2

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11.2.1.1 Processes and Controlling Parameters
11.2.1.1.1 Nearfield. Immediately following its discharge through the nultiport
diffuser, in a region called the discharge nearfield, the effluent will undergo
rapid initial dilution with ambient water. The essentially freshwater effluent will
form a buoyant plume rising through the water column (Figure 1 L2.1.a). Both the
initial dilution and final height of rise depend on the current speed, direction
relative to the diffuser and water column stratification.
11.2.1.1.2 Farfield. Following initial dilution, the effluent will be carried
somewhat passively by the ambient current, undergoing slower dispersion by ambient
turbulence. In tidal situations, the effluent plume may return over the diffuser,
resulting in the development of a background build—up in the discharge area. The
magnitude of this background build-up is dependent on the tidal current patterns and
the net drift. Tidal current patterns control the trajectory and short-term
dispersion of the effluent; tidal currents, however, do not result in any net
transport away from the discharge area. Net transport is provided by the net drift,
which may result from a number of factors, including large-scale weather patterns,
freshwater discharges, local topography and wind. Net drifts are therefore variable
in time and intensity. As the background build-up develops only slowly, the
persistence of net drifts is important. The background build-up is also dependent
on the stratification which can trap the effluent in the lower layer and, by
limiting its vertical and horizontal extent, can cause higher concentrations of
pollutants.
In the water quality analyses conducted to evaluate the impacts of the discharge,
horizontally, two-dimensional models were used to calculate background build-ups.
This type of model relies on the fact that concentrations are approximately uniform
over the water depth (or in the upper and lower layers when the water is stratified)
and only horizontal variations are resolved. The models calculate vertical averages
of the currents and concentrations. Two models were in olved: a hydrodynamic
model, TEA, to calculate the current speeds and directions as a function of time,
and a transport model, ELA, to calculate constituent concentrations. Calibration of
the hydrodynaniic model requires measured tidal currents and net drifts. The
transport model, ELA, requires the specification of a dispersion coefficient. This
parameter can be specified based in the literature, but preferably should be
calibrated by comparison with field measurements. The measurements needed are
concentrations of a tracer corresponding to a known source (Appendix A).
In the long term, the effluent will disperse over much of Massachusetts Bay and
eventually leave it for the open ocean. These processes are controlled by large-
scale circulation patterns in Massachusetts Bay, including the exchange of waters
between the Bay and the Gulf of Maine.
14.2.1.1.3 Shoreline Impacts. Superimposed upon the general flow patterns are local
and generally transient current events which are primarily driven by winds.
Depending on the location of the discharge in relation to shoreline resources, these
events may occasionally transport effluent to the shoreline in relatively short
times, resulting in elevated concentrations there.

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— Y WATER SURFACE -
AMBIENT
CURRENT
ENTRAINED
AMBIENT
WATER
PORT
FIGURE 4.2.1.a SCHEMATIC EFFLUENT PLUME IN THE NEARFIELD
PLUME
MAXIMUM HEIGHT
OF RISE
ENTRAINED
BOTTOM
4-4

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14.2.1.1.11 Sedimentation and Resuspension. Sedimentation is controlled by the size
of the particles, their concentration in the water column (which affects
flocculation) and the level of ambient turbulence. Resuspension is dependent on the
bottom currents, and turbulence. In coastal situations, high bottom currents likely
to produce resuspension are generated by waves. For this Draft SEIS, no correlation
between waves and resuspension was attempted. Rather, resuspension was assessed
from direct measurements and sediment thickness analyses.
14.2.1.1.5 Sunmc ry. This brief review of effluent fate processes pointed to the
following controlling parameters, which are required for direct input into the water
quality analyses and for calibration of elements thereof.
• Tides
• Instantaneous currents, magnitude and direction
• Tidal current patterns
• Net drift magnitude, direction and persistence
• Sustained shoreward currents
• Stratification profiles
11.2.1.2 Data Sources
Massachusetts Bay has been the subject of numerous physical oceanography studies,
each with a rather narrow focus, however. These studies include Bigelow (1927),
Bumpus (19714), Manohar -Maharaj and Beardsley (1973), NOAA (19714), Butman (1977),
EG&G (1976), Mayer (1975), NEA (1975), Fitzgerald (1980), Metropolitan District
Commission (1978, 1979, 1982, 19814), Butman (1987) and MWRA (1986, 1987). A review
of these studies relative to the water quality prediction needs of this project was
conducted by MWRA (MWRA, STFP V,A, 1987). Salient features are summarized below.
The combined Massachusetts and Cape Cod Bays form a body of water enclosed by land
along 75 percent of its perimeter. It is bounded on the north by Cape Ann and on
the south by Cape Cod. It has an area of approximately 3600 square kilometers with
depths of up to 90 m. A characteristic feature is the submarine ridge called
Stellwagen Bank which lies in the middle of the Cape Ann-to—Provincetown line. The
average depth of Stellwagen Bank is about 30 m with depths as low as 20 m. On
either side, between the bank and the tips of Cape Ann and Cape Cod are deeper
channels.
Currents in Massachusetts Bay, and particularly in the proposed discharge sites
area, are in a large part tidally driven. The tides are primarily semi-diurnal (two
high water tides in one day). Different semi—diurnal tides exist, depending on
their origin. The dominant tide in Massachusetts Bay has a period of 12.142 hours.
Diurnal variations are also observed but with a much lower amplitude. The tidal
range (difference between high and low water levels) varies during the lunar month
(27.3 days), with two spring tides (higher range) and two neap tides (lower
range). The average tidal range is on the order of 2.6 meters along the Gloucester-
Provincetown line which separates Massachusetts Bay from the Gulf of Maine. The
14-5

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tidal range in Boston Harbor is 2.7 meters, with a lag of approximately 1 minute
compared to Provincetown (NOAA, 1987). The volume of water flowing in and out of
the Bay during each tide cycle (tidal prism) is therefore on the order of
9.5 billion cubic meters, approximately 6 percent of the mean volume of the Bay. In
the proposed discharge sites area, the tidal currents are predominantly east-west
with a maximum speed on the order of 10 cm/s. Much higher velocities occur in some
constricted passages such as President Roads and Nantasket Roads, with speeds of up
to 60 cm/sec.
Non—tidal currents in Massachusetts Bay have been the subject of several studies.
Bigelow (1927) first proposed the existence of a cyclonic gyre (counterclockwise
circulation) in Massachusetts Bay, as an extension to the Gulf of Maine eddy. More
recent studies by Butman (1977) indicate a more complicated situation. Winds and
freshwater inflows, particularly from the Merrimack River also affect large—scale
flow patterns in Massachusetts Bay. And indeed, available data indicate net drifts
of varying direction and amplitude.
The exchange of water between Massachusetts Bay and the Gulf of Maine controls the
rate at which dissolved constituents discharged through the diffuser are removed
from the Bay. It was noted above that the tidal prism represents approximately 6%
of the volume of the Bay. The corresponding flushing time scale is 8.5 days. This
time scale is a measure of the time needed for the Bay to adapt to changes of
loading. Some of the water leaving the Bay during ebb, however, returns during the
following flood and the actual flushing time scale is larger. Values from 9 days to
2 months were estimated by Butman (1971).
Most of Massachusetts Bay stratifies during the summer months. Starting in June,
surface waters warm up due to surface heating. In July, a stable stratification has
developed with two distinct layers separated by a pycnocline at a depth on the order
of 10 m. The upper layer is warmer than the lower layer and little exchange occurs
between the layers. In July, the temperature difference between the layers is on
the order of 10°C. In August, the pycnocline deepens to 15 to 25 m. The
temperature difference, however, remains on the order of 10°C. During September,
the upper waters start to cool and the pycnoeline becomes more diffuse. The fall
overturn occurs during November. These thermal effects are strengthened by the
freshwater discharges into the upper layer, which also decrease surface water
density. Large freshwater inflows during the spring can cause transient
stratification periods.
Several of the physical oceanography data needed for the water quality analyses must
be specific to the proposed discharge sites. Data are also needed for parameters
which are not directly measured but must be extracted from the measurements. For
these, it is important to have the data in a form which allows easy input into a
computer. The MWRA data meet this requirement and, therefore, form much of the
specific basis of the present analyses. The data from previous studies was used to
provide a framework of interpretation of the MWRA data and to complement it where
needed.
11.2.1.2.1 I4WRA Field Data. A preliminary Phase I survey was conducted in 1986 to
guide in the selection of sites and in the specification of the Phase II program
conducted in 1987.

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The Phase I data collection consisted of:
• Drogue tracking of’ short duration (U.5 to 8.5 hours),
• Vertical density profiling,
• Dissolved oxygen profiling and Secchi disk measurements of turbidity,
• Surface and sea bed drifter recovery tracking.
The Phase II data gathering was a more detailed study lasting from mid-March to
September 1987 and including the following measurements:
• Tidal elevations at Gloucester, on Cape Ann and Provincetown, on Cape Cod,
to provide boundary conditions to the farfield hydrodynamic model TEA,
• Continuous current speeds and directions at 10 different stations shown in
Figure 1 t.2.1.b. Some of these stations included two current meters,
designated U and L for upper and lower, designed to be above and below the
pycnocline in the summer. Details of the current meter coverage are given
in Figure 1 4.2.1.b. These data were used for the nearfield modeling and to
calibrate the farfield hydrodynamic model TEA,
• Continuous CTDO (Conductivity, Temperature and Dissolved Oxygen) at some
of the current meter stations, with the coverage also indicated in
Figure 1 t.2.1.b. These data were used to characterize the ambient water
quality in Massachusetts Bay,
• Vertical CTDO profiles along two transects shown in Figure 1 L2.1.c, to
characterize the vertical stratification cycle in Massachusetts Bay,
• Long—term drogue tracking (1 days), to provide data on large-scale
transport patterns from the proposed discharge sites,
• Wind speeds, to provide input to shoreline impact assessments,
• Chemical tracer concentrations, to validate the farfield water quality
model.
All the data gathered during these programs were plotted and analyzed by MWRA (MWRA,
STFP V,A and G, 1987). The data were also transcribed to magnetic tapes and made
available for the present analyses. These analyses are described in the following
sections and further details are provided in Appendix A. Their objectives were to
refine the understanding of local and global processes in Massachusetts Bay and to
fulfill the specific data needs of the water quality analyses.
k.2.1.3 Tides
Water surface elevations along the Gloucester-Provincetown line are needed to drive
the hydrodynamic model, TEA. Continuous measurements at 10 to 15 minute intervals
were conducted at Gloucester and Provincetown and referenced to the National
Geodetic Vertical Datum (NGVD).

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MANcHESIER
BOSTON
LEGEND
— SIMULATED DIFFUSER
• SUMMER AND WINTER
• WINTER ONLY
12
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FIGURE 4.2.1.b. LOCATION OF MWRA CURRENT METER STATIONS IN RELATION TO
ALTERNATIVE DIFFUSER SITES
2
STATUTE MILES
14 —8

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MANcHESTER
T NORTHERN TRANSECTS
S SOUTHERN TRANSECTS
17
9 ,
S3
T13
S4
STATUTE MILES
FIGURE 4.2.1.c. LOCATIONS OF MWRA SURVEY TRANSECTS
BEVERLY
I
SITE 4
I
SITE
.
SITE 5
.
2
T9
111
T14
115
15
BOSTON
Im.
57
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LEGEND
2 0
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4-9

-------
It can be hypothesized that net drifts in Massachusetts Bay are due to a difference
in mean water levels (i.e., exclusive of tidal variations) between Gloucester and
Provincetown. This water level difference is referred to as the boundary “tilt”.
The water surface elevation records at Provincetown and Gloucester filtered to
remove tidal variations show fluctuations with a time scale on the order of 7 to
10 days, which is the period of sub-tropical storms (Figure 1 4.2.1.d). The
difference in filtered water levels, or tilt, however, varies with a much slower
time scale, on the order of several months. In general, the tilt varies between
+10 cm and -10 cm, with extremes on the order of 15 cm.
1l.2.1.k Currents
Extensive current measurements in Massachusetts Bay were conducted by MDC (1979,
198 1 4a and b), Butman (1987) and MWRA (1987). The latter were analyzed and presented
in a variety of ways, (MWRA, STFP V,G, 1987). As discussed earlier, important
features of the current relative to water quality analyses are i) instantaneous
values, ii) tidal components and iii) net drifts.
11.2.1.14.1 Instantaneous Currents. These are current speeds and directions at any
instant, regardless of their origin (tidal, wind, weather system). They are
important for the initial dilution calculations, and cumulative exceedence
frequencies of current speeds will allow a statistical analysis of the mixing zone
water quality criteria concentrations. These data are summarized in
Table 1 4.2.1.a. A slight increase of current velocities is apparent as one goes from
Site 2 to 24 to 5. Note that lower meter velocities are often higher than those at
the corresponding upper current meters.
Instantaneous current directions also affect initial dilution, and can be seen in
the magnitude-direction scatter plots (an example of which is reproduced in
Figures 2 L2.1.e for Station 14 for the month of August 1987). Results are also
available for other time periods and stations, with similar trends. The plots
clearly show a preferred east-west current directionality due to the tides. This
factor is important for the orientation of the diffuser, as increased nearfield
dilutions can be obtained when the diffuser is oriented perpendicular to the current
direction.
4.2.1.14.2 Tidal Currents. The tidal component of currents in Massachusetts Bay can
be studied using tidal ellipse plots. These represent the locus of the end of the
velocity vector at one point during the tide cycle. Tidal ellipses are presented in
Appendix A, Attachment A.b, based on the MWRA data for the months of March to May
1987 and August 1987. These plots show that the amplitude of the tidal currents in
the upper waters is approximately the same at Sites 2 and 14 (15 cm/see) and slightly
lower at Site 5 (12 em/see). Comparison of these speeds with the cumulative
exceedence frequency plots (MWRA, STFP V,G, 1987), shows that in the upper waters,.
the relative influence of tides on currents decreases as one moves in the offshore
direction. At the lower current meters, the tidal current amplitudes are again
approximately equal at Sites 2 and 24 (12 cm/see), but slightly higher at Site 5
(15 cm/sec). These tidal current magnitudes show no clear trend of the relative
tidal influence with distance offshore.
L4_10

-------
C
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ft
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I.
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TC
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SOURCE: MWRA STFP, VOL V. APP A, 1987
FIGURE 4.2.Ld. FILTERED WATER LEVELS AT PROVINCETOWN (TOP)
GLOUCESTER (MIDDLE) AND THEIR DIFFERENCE (BOTTOM)
4.
IS
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STATION 4, AUGUST 1987
a
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SOURCE: MWRA STFP, VOL V. APP G, 1987
14_ 12

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TABLE 1 4.2.1.a STATISTICS OF 1987 MWRA CURRENT
Vector Mean
(a) These figures represent the percent of time during which measured current
speeds are lower than the indicated values: eg. for Station 1 currents are
lower than 1.9 cm/s for 10% of the time; lower than 6.2 cm/s for 50% of the
time; and lower than 11.9 cm/s for 90% of the time.
METER MEASUREMENTS
Speeds (cm/s)
Meter
Station
Maximum
10 %(a)
50 %(a)
90 %(a)
Speed
(cm/sec)
Direction
(degrees true)
1
1.12
2 J 4 O
23.3
1.9
6.2
11.9
2u
2.05
209
33.3
3.6
10.2
18.5
21
2.65
160
31.6
3.0
9.5
15.8
3u
1.68
180
56.3
1 L2
11.5
20.1
31
2.05
256
47.6
14 4
11.6
22.0
4u
1.07
99
31.6
3.6
9.6
18.5
41
3.9i
336
38.7
14•4
12.8
23.2
5u
1.39
252
35.0
5.1
11.5
19.7
51
1. 148
29
145.5
14.14
11.9
21.3
6u
2.90
260
140.0
3. 14
9.2
17.5
61
1.50
300
30.8
2.3
7.1
13.6
7u
3.13
131
40.7
14.5
11.0
20.5
71
1.73
50
83.5
3.1
10.0
21.0
9
5.146
34
105.0
2.4
21.0
50.9
10
1.15
303
101.0
5.2
28.6
52.5
Source: MWRA
STFP, Vol.
V, App. A,
1987
‘4- 13

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The tidal ellipse plots also were used for the calibration of the two-dimensional
hydrodynainic mathematical model of Massachusetts Bay, (TEA).
14.2.1.14.3 Net Drifts. Progressive vector plots based on current measurements show
that net drifts are highly variable in time, with periods of practically no net
drift and periods of sustained high net drift (MDC 198 1 4a and b; Butman 1987; MWRA,
STFP V, 1987). Spacially, net drifts are also very variable, as can be seen on maps
of monthly averaged current speeds shown in Appendix A, Attachment A.a. The plots
show that there is no coherence between the different current meter locations, and
upper and lower current meters often give significantly different net drifts. This
display of the data does not support the gyre model discussed earlier and would tend
to indicate that net drifts are largely due to localized wind events and perhaps to
density effects resulting from freshwater inflows.
In order to gain additional perspective on net drifts and their persistence, net
drifts over 10 complete tidal cycles were computed and plotted versus time,
representing, in a sense, a vector running average of the currents. These plots are
presented in Appendix A, Attachment A.c. They clearly show a periodicity of high
net drifts with a period on the order of 7 to 10 days.
During the stratified summer months, the net drifts are often significantly
different at the upper and lower current meters. In general, the upper meters gave
larger net drifts, except at Station L4, where the lower net drifts were larger. The
directions of the upper and lower layer net drifts are also often different.
11.2. 1 .5 Stratification
As discussed earlier, Massachusetts Bay stratifies in the summer due to surface
heating. The MWRA field program included measurements of temperature and salinity,
from which density is determined, along two transects at several times during the
spring, and summer of 1987. The resulting vertical density contours are provided in
Appendix A, Attachment A.d. These show a pycnocline during the summer months at a
depth of 10 to 15m, with large variations during the tide cycle. Vertical density
profiles based on these measurements were used for the initial dilution analyses.
The continuous density records produced by MWRA clearly show the tidal variations,
particularly in the bottom-to—top meter density differences, which are a measure of
the stratification. The average bottom to top density difference varies during the
summer due to the surface heating/cooling cycles and wind mixing, but never
vanishes. This indicates that effectively distinct top and bottom layers exist,
with significantly reduced interchange. Relative to water quality analyses, this
suggests that models recognizing the existence of these layers are desirable. This
was done in this Draft SEIS by simulating the lower layer separately during
stratified months.
During the spring, the continuous density measurements indicate that strong
stratification can develop following major runoff events. This stratification,
however, is not uniform and is of relatively short duration so that prolonged
blockage of the effluent plume in a lower layer would not be expected.
LI—i )4

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11.2.2 WATER QUALITY
11.2.2.1 Constituents and Criteria
Water quality is measured by the concentrations of dissolved and suspended
constituents in the water column, as well as other more subjective measures such as
aesthetics or odor. The list of constituents and factors to be considered can be
established based on applicable water quality standards and criteria. Those
standards are the Massachusetts Surface Water Quality Standards and the U.S. EPA
Water Quality Criteria for Aquatic Life and Human Health. These standards and
criteria are reviewed below, with the objective of determining the constituents
which should be considered as measures of water quality and to characterize present
conditions and impacts due to the discharge alternatives.
The Massachusetts Surface Water Quality Standards are defined in the Code of
Massachusetts Regulations, Title 3114. They involve minimum criteria applicable to
all waters, listed in Table 1 4.2.2.a, and additional criteria for specific classes of’
waters, defined on the basis of their use. The waters of the Outer Boston Harbor
are classified as SA, consistent with the following uses: protection and
propagation of fish, other aquatic life and wildlife; primary and secondary contact
recreation such as swimming and boating; and shellfish harvesting without depuration
in approved areas. The additional criteria pertaining to SA class waters are listed
in Table lt.2.2.b.
Many of the minimum criteria are based on avoidance of objectionable effects and are
therefore qualitative. Quantitative criteria corresponding to these effects, such
as aquatic toxicity, are provided by the EPA criteria discussed below. Quantitative
criteria are provided for SA Class waters for Oxygen, pH, and Coliform bacteria.
The EPA Water Quality Criteria are provided in the so—called “Gold Book” (USEPA
1986a). These criteria include aquatic life and human health criteria, the latter
including toxicity, carcinogenicity (from fish consumption) and taste and odor
criteria.
Aquatic life criteria are further discussed in the “Technical Support Document for
Water Quality-Based Toxics Control” (USEPA, 1985c). Two approaches are proposed to
assess and control toxicity to organisms, the chemical-specific approach, which is
used here, and the whole effluent approach which will be considered when the
necessary data become available.
The chemical-specific approach is based on published laboratory bioassay test
results involving each chemical independently. This approach has the advantage of
requiring no effluent-specific bioassay, but it assumes that the composition of the
effluent is known (so that the concentrations of chemicals can be determined), that
the toxicity of separate toxicants is not additive, and that those toxicants are
bioavailable in the effluent.
Acute and chronic concentration levels are determined. The acute (short-term)
concentration, called the Criterion Maximum Concentration, or CMC, is the
concentration which must not be exceeded at a specified point with a frequency of
more than 1 hour every 3 years. However, it is recognized that this is
unenforceable and, therefore, the frequency of occurrence, for enforcement purposes,
LI... 15

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TABLE 1$ .2.2. a COMMONWEALTH OF MASSACHUSETTS SURFACE
WATER QUALITY STANDARDS’ MINIMUM CRITERIA
APPLICABLE TO ALL WATERS
Parameter Criteria
1. Aesthetics All waters shall be free from pollutants in
concentrations or combinations that:
a) Settle to form objectionable deposits;
b) Float as debris, scum, or other matter to form
nuisances;
c) Produce objectionable odor, color, taste, or
turbidity; or
d) Result in the dominance of nuisance species
2. Radioactive Shall not exceed the recommended limits of the United
Substances States Environmental Protection Agency’s National
Drinking Water Regulations.
3. Tainting Shall not be in concentrations or combinations that
Substances produce undesirable flavors in the edible portions of
aquatic organisms.
Z • Color, Turbidity, Shall not be in concentrations or combinations
Total Suspended that produce undesirable flavors in the edible
Solids portions of aquatic organisms.
5. Oil and Grease The water surface shall be free from floating oils,
grease and petrochemicals; and any concentrations or
combinations in the water column or sediments that are
aesthetically objectionable or deleterious to the biota
are prohibited. For oil and grease of petroleum origin
the maximum allowable discharge concentration is
15 mg/l.
6. Nutrients Shall not exceed the site—specific limits necessary to
control accelerated or cultural eutrophication.
7. Other Waters shall be free from pollutants alone or in
Constituents combinations that:
a) Exceed the recommended limits on the most sensitive
receiving water use;
b) Injure, are toxic to, or produce adverse
physiological or behavioral responses in humans or
aquatic life; or
c) Exceed site-specific safe exposure levels determined
by bioassay using sensitive resident species.
*310 CMR 14.03.
14—16

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TABLE k .2.2. b COMMONWEALTH OF MASSACHUSETTS SURFACE
WATER QUALITY STANDARDS*
ADDITIONAL CRITERIA FOR MARINE CLASS SA WATERS
Parameter Criteria
1. Dissolved Oxygen Shall be a minimum of 6.0 mg/i
2. Temperature None except where the increase will not exceed the
recommended limits on the most sensitive water use.
3. pH Shall be in the range of 6.5—8.5 standard units and not
more than 0.2 units outside of the naturally occurring
range.
14. Total Coliform Shall not exceed a median value of 70 MPN per 100 ml,
Bacteria and not more than 10% of the samples shall exceed
230 MPN per 100 ml in any monthly sampling period.
*310 CMR 14.03
is increased to 1 day every 3 years. The chronic (long-term) concentration,
called the Criterion Continuous Concentration, or CCC, is the concentration
which must not be exceeded with a frequency of more than 14 consecutive days in
3 years. CMC’s and CCC’s are provided for a range of chemicals in the “Gold
Book”. These values are provided in Table LL2.2.c for the chemicals of
concern. These are the same as were considered by MWBA in their analyses.
The process by which this list of chemicals was established included the
following steps, starting from the list of chemicals detected in the influent
to the plant:
1. Remove those chemicals for which no water quality criterion exists,
2. Remove those constituents that already meet the criteria in the
influent,
3. Remove those chemicals detected in the influent infrequently,
14. Add chemicals for which the detection limit is greater than the
criteria.
Human health criteria include human toxicity criteria, carcinogenicity
criteria and taste and odor criteria. The carcinogenic ty criteria are based
on risks of 1 in 100,000 (10 ), 1 in 1,000,000, (10 ) or 1 in 10,000,000
(10 ) chances of contracting cancer or suffering genetic mutation in a
lifetime given assumed intakes of contaminated fish. The Division of Water
Pollution Control of the Massachusetts Department of En vironmental Quality
Engineering (DEQE) typically utilize a risk factor of 1O ’ or lower, which it
believes allows for acceptable protection of the public’s health and is
4-1 7

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ACID BASE NEUTRALS & PANS
anthracene 300
benz [ a] anthracene 300
benz [ b] fluoranthene 300
benz [ k] fluoranthene 300
benz [ g, h, i ] fluoranthene 300
benz0 [ a] pyrene 300
bis( 2—ethyihexyl )phthalate2 , 91 114
butylbenzyl phthalate 2,91411
chrysene 300
d ibenz [ a, h ] anthracene 300
3, 3-dichlorobenzidine -—
2, 4-dichiorophenol --
di-n-octyl phthalate 2,91411
fluorene 300
hexachlorobenzene 160
indeno(1 ,2,3-cd)pyrene 300
naphthalene 2,350
phenanthrene 300
pyrene 300
METALS
arsenic
beryllium
cadmium
chromium
copper
TABLE 1 4.2.2.c SALTWATER AQUATIC LIFE AND HUMAN HEALTH
WATER QUALITY CRITERIA (ugh)
VOLATILES
Toxicity to
Aquatic
(Acu
Chemical CMC
Saltwater
Life
(Chro ç)
CCC “
Toxicity o
Humans
Carcinogenicity
Taste
i0 10 and Odor
benzene
5,100
700
brornomethane
12,000
6,1400
chloroform
--
--
ethylbenzene
1430
-—
methyl chloride
12,000
6,1400
styrene
1430
-
tetrachloroethylene
10,200
1450
- - 400.
- — 157.
- — 157.
3,280 --
-- 157
3,280 --
- - 88.5
—— 0.311
—— 0.311
—— 0.311
-— 0.311
-— 0.311
—— 0.311
-- 500,000.
—— 0.311
—— 0.311
- - 0.2
3,090 —-
— — 0.311
-- 0.00714
- — 0.311
—— 0.311
—— 0.311
-— 0.175
-— 1.17
40.
15.7
15.7
15.7
8.85
0.0311
0.0311
0.0311
0.0311
0 .0311
0.0311
50,000.
0 .0311
0 .0311
0.02
0.0311
0.00074
0 .0311
0 .0311
0.0311
0.0175
0.117
3. 14
3. 1$
3.4
129
36
9.3
50
Continued
69
143
1,100
2.9
0.3
1,000
1 1 18

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TABLE lj .2.2. c SALTWATER AQUATIC LIFE AND HUMAN HEALTH
WATER QUALITY CRITERIA (j ig/i) (Continued)
Chemical
Toxicity to
Aquatic
(Acu
CMC “ ‘
Saltwater
Life
(Chroçi ç)
CCC ‘
Carcinogenicity
Toxicity o 6
Humans ‘ i0 10-
(
Taste
and Odor
METALS (continued)
lead
mercury
nickel
selenium
silver
zinc
1140
2.1
75
760
2.3
170
5.6
0.025
8.3
-—
-—
58
-- --
0.1146 --
- — --
-— --
-— --
- — - -
--

--
——
-—
-—
--

-—
——
——
5,000
PESTICIDES
aidrin
chlordane
dieldrin
heptachior
toxaphene
1.3
0.18
0.141
0.053
0.21
--
0.0014
0.0019
0.0036
0.0OO2
-— 0.00079
-- 0.00148
-— 0.00076
-- 0.0029
-- --
0.000079
0.000148
0.000076
0.00029
--
——
--
-—
--
--
OTHER CHEMICALS
PCBs
. .—
0.03
-— 0.00079
0.000079
--
Source:
May, 1986, and
updated
in
1986 and
From the EPA Gold Book as published in
again in May, 1987.
1. Criterion Maximum Concentration (CMC) = one—hour average not to be exceeded more
than once in three years.
2. Criterion Continuous Conentration (CCC) four-day average not to be exceeded
more than once in three years.
3. Human Health Toxicity Ambient water criterion not to be exceeded to protect
humans from the toxic properties of a chemical ingested via consumption of
contaminated aquatic organisms.
14. Carcinogenicity = 10 and io 6 risk levels which may result in an incremental
increase in cancer from lifetime consumption of aquatic organisms contaminated
with the given concentration of a chemical.
5. Taste and odor Maximum level not to be exceeded to avoid undesirable taste and
odor.
4-19

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attainable and enforpeable. For this project, the Division recommended that the
MWR utilize the 10° risk factor but that it may consider use of a risk factor of
10 in certain situations. Those situations must be reviewed with the Division
prior to utilization (May 15, 1987 letter of T.C. MacMahon to M. Gritzuk). Criteria
concentrations corresponding to both risk factors are listed in Table 11.2.2.c.
Additional discussion of the water quality criteria, focused on their interpretation
relative to the water quality analyses, is provided in Section 5.1.1.
11.2.2.2 Dissolved Oxygen
Numerous and extensive dissolved oxygen (DO) measurements have been conducted in
Boston Harbor and Massachusetts Bay. Review of those prior to 19811 indicated that
in Boston Harbor, and even in the vicinity of the existing discharges, DO levels
rarely go below 6 mg/i (MDC, 19811). The data from 1978 and 1979 MDC surveys at
multiple depths indicated that in the vicinity of the Deer Island discharge, 90
percent of the measurements exceeded 7 mg/l and the lowest DO recorded was 6.2
mg/i. In the vicinity of the Nut Island discharge 80 percent of the measurements
exceeded 7 mg/i and the lowest DO recorded was 5.9 mg/i. Of the 11100 measurements
obtained at stations surrounding the discharges, only one was less than 6 mg/i.
Extensive discrete DO measurements were also gathered by MDC in the Site 5 area in
July and August, 1978 and 1979. Summer represents worst case conditions relative to
DO since the saturation DO concentration is lower and bottom waters are isolated
from the water surface by the pycnocline. Indeed, strong vertical variations of DO
were observed, with supersaturation (indicating photosynthetic activity) in the top
waters and below saturation concentrations in the bottom waters. Out of all the
measurements, approximately 83 percent exceeded 7 mg/i and 1 percent were below
6 mg/i. The average DO in the bottom 10 meters was 7.6 mg/i.
The MWRA field program included continuous measurements of dissolved oxygen at
several stations and depths. Because these measurements were continuous, they had
the potential for detecting unusual events which may have been missed by the earlier
shorter-term surveys. Such an event was recorded on June 6, 1987, when DO levels
dropped to 5 mg/i at Station 3. Unfortunately, meters at other nearby stations were
not operative at this time and the validity of these measurements cannot be
corroborated. The wind and current records indicate nothing unusual on that date,
and, therefore, the origin of these measurements remains unclear. Other than this
event, the MWRA data tends to confirm the earlier surveys, with high dissolved
oxygen values in the upper waters, up to 12.5 mg/i, and somewhat lower values in the
bottom waters. Out of the 11,056 DO measurements in the lower layer during June-.
August 1987, the lowest value was 7.8 mg/i and only 11 measurements were below
8 mg/i.
Water quality data collected in September 1986, however, indicated DO concentrations
in the lower layer ranging from 5.9 mg/i to 6.8 mg/i. Similarly, in October 1987,
MWRA measurements indicated low dissolved oxygen values for a period of about two
weeks at the lower meters. At Station 11, the lower meter DO concentrations showed
high semi-diurnal fluctuations (on the order of 3 mg/i) with an average of
approximately 6.5 mg/i (Kolb, personal communication). The lower meter depth was
17m (MLW) and the water depth was 2Om. The large semi—diurnal fluctuation indicates
that the meter was alternatively in the upper layer and lower layer during tidal
variations. This is confirmed by strong temperature variations at the same
frequency. Vertical density profiles are not available to locate the pycnociine,

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but the foregoing observations indicate that it was at a depth comparable to that of
the lower meter, i.e. 17m. The lower layer depth would then become very small (3m
or less) and it is possible that the low DO concentrations recorded were due to
resuspension oxygen demand caused by breaking internal waves at the pycnociine.
This aspect is important because it affects the selection of ambient DO
concentrations for the impact analyses (Appendix A , Section A.3.8.1).
11.2.2.3 pH
The pH is a measure of the acidity or alkalinity of water and is determined from the
concentration of hydrogen ions in the water. A pH of 7.0 corresponds to neutral
conditions; acidic conditions have a pH below 7.0 and basic conditions have a pH
above 7.0. In the ocean, pH is controlled primarily by carbonate and bicarbonate
(bases) and carbonic acid.
Measurements of pH conducted by MDC in summer 1979 in the Site 5 area ranged from
7.9 to 8.1, with an average of 8.0. Harbor values were similar but with greater
variability, especially due to freshwater inputs. The pH was sometimes noticeably
lower in the inner harbor and nearshore areas than in the outer harbor, but on other
days, there was little variation among stations (MDC, 198 a and b).
As part of its field program, MWRA conducted pH measurements in April 1987 in Broad
Sound. The measured pH values ranged from 8.1 at the surface to 7.9 at a depth of
30m (MWRA, STFE’ V,A 1987). These measurements confirm the earlier data.
14.2.2.11 Suspended Solids
Extensive measurements of suspended solids were conducted during the MDC secondary
treatment waiver applications process in Boston Harbor and in the general area of
the proposed discharge sites (MDC, 198 1 4a and b). In the harbor, great variability
was encountered, in particular in response to runoff events. In the proposed
discharge sites area, total suspended solids ranged from 1 mg/i to 12 mg/i, with an
average concentration of k.5 mg/i. These measurements were conducted in the summer
and reflect high primary productivity.
Suspended solids concentrations were also measured during the MWRA field program, at
two stations shown in Figure 4.2.2.a. These measurements, which were made in
April 1987, gave total suspended solids concentrations on the order of 2.5 mg/i at
Station B2, which is between Sites 2 and , and 1.5 mg/i at Station Hi, located at
the edge of Stellwagen Bank (MWRA, STFP V,M, 1987).
4.2.2.5 Toxic Chemicals
Much of the existing data on toxic chemical concentrations in Massachusetts Bay were
collected in Boston Harbor. Those are therefore largely influenced by the present
discharges from Deer Island and Nut Island Treatment Plants and the CSO’s.
Concentrations of dissolved and particulate metals in the water column have been
measured at two stations in Massachusetts Bay (Figure LL2.2.a), as part of the MWRA
field program (MWRA, STFP V,B, 1987) and are summarized in Table t .2.2.d. These
concentrations are generally low, and well below the CMC and CCC values, except for
copper (average concentration of 0.11 pg/i) which is on the same order of magnitude
as the CMC (2.9 pg/l).
U—2 1

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MANcHESTER
0
STATUTE MILES
FIGURE 4.2.2.a. LOCATIONS OF THE SUSPENDED
STATIONS
SOLIDS, METALS, AND PCB SAMPLING
aE LY
I
SITE 2
S
SITE 5
SITE 4
S
S
(TA. 0VW
‘p
I
2
2
14 -22

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TABLE 1 1..2.2.d METAL CONCENTRATION IN WATER COLUMN AT TWO STATIONS
IN MASSACHUSETTS BAY
Depth
Station (m) Phase
As
pg/i
Cd
pg/i
Cr
pg/i
Cu
pg/i
Hg 1
ng/1
Ni
pg/i
Pb
pg/i
V
pg/i
Zn
pg/i
Ml 11.8 Diss.
Part.
Tot.
0.142
0.01)4
0.143
0.023
0.001
0.02)4
0.26
0.055
0.31
0.37
0.039
0. 11
1.97
1.63
3.61
0.22
0.127
0.35
0.0145
0.050
0.096
1.11
<0.0)45
1.11
0.6)4
0.086
0.73
22.2 Diss.
Part.
Tot.
0.50
0.013
0.51
0.025
0.001
0.026
0.26
0.056
0.32
0.30
0.027
0.33
2.07
0.97
3.11
0.57
0.376
0.95
0.056
0.0)43
0.099
1.30
<0.0145
1.30
0.72
0.072
0.79
148.7 Diss.
Part.
Tot.
0.53
0.012
0.55
0.026
0.001
0.027
0.27
0.051
0.32
0.36
0.026
0.38
2.01
2.10
14.11
0.38
0.081
0.147
0.0)48
0.032
0.078
1.33
<0.0)43
1.33
0.85
0.069
0.92
B2 8.6 Diss.
Part.
Tot.
0.014
0.010
0. 4i
0.030
0.002
0.031
0.19
0.075
0.26
0.46
0.060
0.52
1.6)4
0.50
2.13
0.53
0.153
0.68
0.069
0.058
0.128
1.25
<0.0)414
1.25
1.16
0.262
1.60
19.4 Diss.
Part.
Tot.
0.50
0.013
0.51
0.027
0.001
0.028
0.19
0.093
0.29
0.36
0.035
0.39
1.3
0.148
1.8
0.45
0.051
0.50
0.031
0.067
0.098
1.25
0.032
1.27
0.91
0.156
1.06
214.14 Diss.
Part.
Tot.
0.149
0.022
0.051
0.025
0.001
0.026
0.25
0.167
0.42
0.146
0.063
0.45
2.12
1.53
3.65
0.65
0.504
1.1
0.106
0.083
0.189
1.39
0.055
1.2414
1.02
0.1514
1.17
CCC Concentration
36
43
1100
0.025
7.1
5.6
58
CMC Concentration
69
9.3
50
2.9
2.1
1140
1110
170
Source: MWRA, STFP V,B, 1987
(1) Note different unit.
14-23

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Concentrations of’ dissolved and particulate PCB’s were measured at the same stations
for samples collected in April, 1987 (Battelle, 1987). These measurements indicate
detectable dissolved and particulate PCB concentrations (calculated as Aroclor 1251 )
with a maximum value of 0.0073 ig/l for dissolved PCB (Table LL2.2.e).
lt.2.3 MARINE GEOLOGY
4.2.3.1 Overview
The assessment of’ existing conditions in the vicinity of the proposed diffuser sites
is based on available information on the geology and bottom sediments in the
Massachusetts Bay region. No field data collection program was conducted as part of
this Draft SEIS project; however, extensive data are available from previous
investigations. The most recent bottom sediment data were collected in conjunction
with the Deer Island Secondary Treatment Facilities Plan (MWRA, STFP V, 1987).
These and other data presented herein have been used to establish existing
conditions. Appendix B of this Draft SEIS provides more detailed information on
existing marine bottom conditions. This information is used as the basis for
projecting sediment deposition impacts due to the proposed discharge (Section
5.1.2).
4.2.3.2 Geological Setting
The inner Massachusetts Bay region is at the margin of the Boston Basin, a
structural and topographic feature. Structurally, it consists of folded and faulted
sedimentary and volcanic rooks. There are several east-northeast trending folds
that project seaward from Boston Harbor, plunging at less than 20 degrees in the
same direction. The bedrock is dominated by slightly metamorphosed agrillite
(Cambridge Formation), which is commonly thinly bedded and fine grained. Many dikes
and sills of trap rock (basalt or diabase) intrude into the agrillite in the Harbor
area. The bedrock surface is highly irregular in the area east-northeast of Deer
Island, varying from bottom outcrops to 250-foot (MSL) depths.
4.2.3.3 Bottom Sediment Distribution
There is little consistency in the available data on existing sediment conditions.
This is the result of extreme variability in bottom sediment types on several
scales. This conclusion was reached by Tetra-Tech (198L ) in a technical review of
sediment data from the 198!I MDC waiver of’ secondary treatment. MWRA (STFP V,N,
1987) concluded that the area consisted of “very patchy. . .benthic environments.”
MWRA (STFP V,R, 1987) sampled sediments at 15 sites on three separate cruises,
taking three replicates at each site (Figure 4.2.3.a). An analysis of’ variation
between replicates and cruises showed that there is often more variation in sediment
types between replicates than over time or area. Bottom types were described in
MWRA (STFP V N and 0 1987) based on imaging from a remotely operated vehicle. These
transects are useful in that they describe changing bottom conditions over a small
area.
The available data indicate that bottom sediment types in the study area include
silt, clay, mud, sand, gravel and rock. The bottom sediment types can vary ona
scale of tens of meters; therefore, it is difficult to generalize bottom
characteristics. The available data do, however, define the types and ranges of
sediments encountered. In general, nearshore (Sites 2 and 2.5), have predominantly
4-2 4

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TABLE 4.2.2. e CONCENTRATIONS OF PCB IN SEAWATER COLLECTED AT
NO STATIONS IN MASSACHUSETTS BAY IN APRIL, 1987
Station
Depth
(m)
PCB Concentrations
(pg/l)
Dissolved
Particulate
B2
B2
B2
ii
11
11
0.0005
0.0020
0.00i t
<0.0005
0.0006
0.0005
B2
B2
B2
20
20
20
0.0022
<0.0025
<0.0005
<0.0005
<0.0005
Hi
Hi
114
0.0073
<0.0005
<0.0005
Hi
Hi
ItO
ItO
0.0062
0.0033
<0.0005
<0.0005
Field Blank
Field Blank
0.00075
0.0015
Laboratory
Blank
Process
0.0018
1. Calculated as Aroclor 12514.
Adapted from Battelle, 1987.
14 25

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.
SOURCE: ADAPTED FROM MWRA STFP VS. 1987
AND MDC WAIVER VOL.1.
FIGURE 4.2.3.a.
GENERAL STATION LOCATIONS FOR SEDIMENT SAMPLING
)
%• __ ,,
--4---
‘0
\0
MALODI
1 0 1
NAUTICAL MILES
7
TRANSECT D
SITE 4.5
TRANSECT A
SITE 2
S
TRANSECT C
SITE 4
.
. .
® PDA •
SITE 5
.
ØOSTON
MASSACHUSETTS BAY
‘I
P1
(I.
C
LEGEND
a
1979 MDC WAIVER STATION
1982 MDC WAIVER STATION
Qu .4Cy
1987 MWRA STFP STATIONS
0
SEIS ALTERNATIVE SITES
A
4-26

-------
silty sediments. Farther offshore (Sites U and 5), rocky bottom is more common than
nearshore. Results of 1987 ROV surveys (MWRA, STFP V,0, 1987) show that areas at
Sites U and 5 are generally covered with nearly equal areas of rocky and silty
sediments with Site 5 having slightly more rocky area than Site U. Table 4.2.l4.b in
section 14.2.14.1.1 of this Draft SEIS shows in greater detail the variability in
sediment types between and within sites.
Several factors indicate that much of the bottom in the area of’ the alternative
discharge sites can be characterized as non-depositional. This includes areas where
no deposition is taking place, and areas where there is scour, or net removal of
pre-existing bottom sediments. These areas of nondeposition may include a veneer of
underlying sediments that have been reworked by recent marine processes.
A seasonal depositional cycle has been suggested by MWRA (STFP V,P, 1987) in
locations where biogenically-bound mud covering exposed rock surfaces was observed
in the summer. The same surfaces were free of mud in the winter. The death of
tubiculous species that bound the mud, as well as increased turbulence, was cited as
responsible for the loss of material. The same process was identified by Butman
(1978; 1987) through bottom photographs and turbidity measurements. It was shown
that the resuspension was a short-term, storm-related process in the winter
months. Butman’s data demonstrated that bottom velocities associated with winter
storms ranged from 5 cm/sec in Stellwagen Basin to 40 cm/sec in inshore areas.
1 23L Sedimentation Rates
Existing sedimentation rates have been estimated in a number of past studies which
have examined bottom sediments at various locations. The broad areas of clean
gravel which cover much of Massachusetts Bay suggested to Fitzgerald (1980) that
sediment accumulation has been negligible since glacial times. The rise in sea
level has transferred the shoreline over the present inner shelf area. This has
resulted in a reworking of glacial deposits, distributing a “skin” of marine sand
and gravel over much of the area (Fitzgerald, 1980).
In the deeper water east of the Graves, Fitzgerald used the thickness of marine
sediments and an average submergence time of 10,000 years to estimate that the
average sedimentation rate was on the order of 0.006 cm/year. This rate accounted
for all material overlying a Blue Clay deposit. Bothner (1987) estimated modern
sedimentation rates to be 0.2 to 0.6 cm/year in Massachusetts Bay at a location 7
nautical miles east of Deer Island (Appendix B). This large range of accumulation
rates in Massachusetts Bay is attributed to factors such as bioturbation and lateral
sediment transport (Appendix B).
The larger topographic basins in deeper water, such as Stellwagen Basin, are
dominated by relatively smooth surfaces and fine sediments (Schlee et al., 1973;
MWRA, STFP V F and Q, 1987). These areas are likely areas for deposition of
suspended sediments. Tucholke and Hollister (1973; in Butman, 1978) suggested that
most of this deposition occurred just after the glacial retreat, and that the
sedimentation rate has steadily decreased since then, with the current deposition
rate in Stellwagen Basin estimated to be 0.001 to 0.002 cm/year.
Using the thickness of sediments inside Boston Harbor, Fitzgerald (1980) estimated
sedimentation rates to be 0.0114 and 0.016 cm/year, which probably represent a
minimum Holocene sedimentation rate in the Harbor. A maximum rate was estimated to
be 0.1 cm/year. This was based on an assumed 10,000 year period of deposition,
4-27

-------
which may render these estimates low. Pb-210 sedimentation rates were calculated by
Fitzgerald (1980) at the entrance to Boston Inner Harbor (0.27 cm/year) and at the
Inner Harbor in the vicinity of Fort Point Channel (0.14 cm/year). This approach was
compared to a Corps of Engineers estimate of accumulation of 0.2 cm/year based on
the volume of material collected between successive dredging operations in the Inner
Harbor. Fitzgerald (1980) concluded that modern sedimentation rates were 0.2 to
0.3 cm/year in Boston Harbor. Using Pb-210 methods, one site in the Harbor showed a
modern accumulation rate of 2 cm/year (Bothner, 1987).
In summary, available data indicate a wide variation in background sedimentation
rates, although there is a general trend of higher sedimentation in Boston Harbor
and lower sedimentation in deeper offshore basins (Table 1 L2.3.a). In the area of
the alternative discharge sites, the available data indicate deposition rates of 0.2
to 0.6 cm/yr (Bothner, 1987) and 0.006 cm/yr (Fitzgerald, 1980). As discussed in
Appendix B, this is a wide range of values and it is possible that the higher rates
are artificially high due to factors such as Pb-210 methods, bioturbation and
lateral deposition. For this Draft SEIS a background sedimentation rate of 0.05
cm/yr was used since it is approximately one order of magnitude above and below the
lowest and highest measurements, respectively. MWRA assumed that the background
deposition rate was 0.1 cm/year (MRWA, STFP V,C, 1987). This higher background
sedimentation rate would have the effect of diluting the concentration of any
contaminants in the effluent particulates which reach the bottom. The lower rate
used for this Draft SEIS (0.05 cm/year) is more conservative (i.e., provides less
dilution of toxic compounds from the effluent).
TABLE lê .2.3. a SUMMARY OF REPORTED MASSACHUSETTS BAY AND BOSTON HARBOR
SEDIMENTATION RATES
Rate
Location
Est. Method
Source
(cm/yr)
Boston Harbor
Sediment Thickness
Fitzgerald, 1980
0.0114—0.1
Boston Harbor
Pb—210
Fitzgerald, 1980
0.12-0.50
Boston Harbor
Dredging
USACE
0.2
Boston Harbor
Pb-210
Bothner 1987
2.0
Boston Harbor
Carbon Dates
Rosen, in progress
1.0
Mass Bay
10,000 yr cores
Fitzgerald, 1980
0.006
Mass Bay
Pb—210 and Artifact
Bothner, 1987
0.2-0.6
Steliwagen Basin
Various
Tucholke and Hollister,
1973
0.001-0.002
Mass Bay
-
MWRA, STFP V,C, 1987
0.1
Mass Bay
Lit. Rev.
This Draft SEIS
0.05
4.2.3.5 Sediment Chemistry
The contaminants for which effluent deposition impacts were assessed are summarized
in Table 14.2.3.b. This list was developed using the effluent contaminant screening
process developed in MWRA’s STFP (MWRA, STFP V,A, 1987) and further screening as
presented in Section 5.1.3 of this Draft SEIS.
14. .28

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TABLE 1 L2.3.b CONTAMINANTS FOR ASSESSMENT OF SEDIMENT DEPOSITION IMPACTS
Class I Sedimen
Compound threshold (ppmY’
PCB Compounds (total) 0.5
Metals
Arsenic 10
Copper 200
Mercury 0.5
Nickel 50
Seleniu!n — -
Silver --
Zinc 200
Pesticides
Aidrin
1 4,14 - DDT ( 1 )
Dieldrin” 1)
Heptachior
Acid, Base Neutrals
Butylbenzyl phthalate
Di-n-octyl phthalate
1. Analyzed for
2. Barr (1987)
publ
TABLE
ic health
4.2.3. c
impacts
SUMMARY
only
OF SEDIMENT PCB MEASUREMENTS
Total PCB Concentration (ppm
Range
dry weight)
Average
Transect
A (Site
2)
0.001-0.033
0.012
Transect
C (Site
14)
<0.001-0.0142
0.018
Transect
D (Site
14.5)
<0.001-0.0 17
0.011
a. MWRA, STFP V,S, 1987.
4-29

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Available data from MWRA (STFP V,S, 1987) and MDC (19814a and b) were used to assess
background chemical concentrations in the existing bottom sediment. This
information is summarized in Tables 14.2.3.c and 1 L2.3.d for PCB’s and metals. In
general, little variation in PCB concentrations occurred between and within sites.
All measured PCB concentrations are below the threshold of 0.5 ppm for Class I
sediments using Massachusetts Division of Water Pollution Control (DWPC) dredged
material classification (Barr, 1987). Class I sediments have the lowest chemical
dredged material disposal restrictions (Appendix B). The highest concentrations for
all metals generally occurred at Site 14. Concentrations of metals measured at all
Sites fall below the DWPC Class I threshold for dredged materials and therefore are
relatively clean by this standard (Appendix B). Appendix B provides additional
information on these data.
The pesticides aidrin, 1 4,4—DDT, dieldrin and heptachlor were not analyzed by the
MWRA. However, pesticide samples were collected at Station PD (Table 4.2.3.a) in
1982 (MDC, 198 1 4a). Additional pesticide samples were collected in 19814; however, no
sampling stations were located in the present study area (MDC, 19814a). For the 1982
data, no pesticides were detected using a detection limit of 0.0140 ppm. Therefore,
for this Draft SEIS analysis, background bottom sediment concentrations of 0.0140 ppm
were used for aidrin, 14,4—DDT, dieldrin and heptachior.
Bis (2-ethyihexyl) phthalate, butylbenzyl phthalate and di-n—octyl phthalate were
not measured in the STFP or by MDC (198 1 4a). Thus for these compounds the effect of
bioturbation mixing of effluent particulate cannot be fully evaluated. For the
Draft SEIS a background concentration of zero in the existing sediments for these
compounds was used to assess bioturbation mixing effects and to make relative
comparisons among sites. The actual bottom sediment concentration after mixing will
be higher if acid-base neutral compounds are present in the existing bottom
sediments.
14.2.3.6 Bioturbation Mixing Depth
One of the processes which influences the impact of effluent suspended solids
deposition is the mixing of bottom sediments by benthic organisms known as
bioturbation. By this process the effluent particulates are incorporated and
dispersed into the existing bottom sediments. As part of the MWRA, STFP (MWRA, STFP
V P and Q, 1987) sediment profiling was used to measure the depth to which the fine
grained bottom sediments are oxidized. This depth can be interpreted as a
conservative indicator of biological mixing depth. In general, this depth varied
from 2 to 14 cm, with occasional deeper measurements and frequent zero measurements
due to rocky bottom. This range is consistent with measured values in similar
temperate marine systems (Appendix B). For the purpose of assessing the impact of
biological bottom mixing on the concentration of settled effluent particulates, a
bioturbation mixing depth of 3 cm was used in this Draft SEIS. This value is
reasonable and generally conservative based on the available data (Appendix B).
Available data also indicate that the background bottom sediments are of lower
chemical concentration than the effluent particulate, therefore, the greater the
mixing depth, the greater the dilution of effluent particulate chemicals.
As an alternative, more conservative case, the impact of a zero mixing depth was
also assessed. This situation might occur in a rocky bottom area where there is
minimal soft bottom sediment but where periods of deposition may occur between
resuspension events.

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TABLE 11.2.3. d SUMMARY OF SEDIMENT METALS MEASUREMENTS
Transect A (Site 2)
Arsenic
Copper
Mercury
Nickel
Selenium
Silver
Zinc
Transect C (Site 4)
Arsenic
Copper
Mercury
Nickel
Selenium
Silver
Zinc
Arsenic
Copper
Mercury
Nickel
Selenium
Silver
Zinc
0.41
1 .73
0.02
1 .87
NA
9.70
4.30
9.15
0.0 4
5.27
NA
NA
30.03
3.89
63.28
0.38
7.88
6.76
44.62
0. 1414
13.97
152.51
2.87
12.56
0.15
14.66
NA

26.12
5.53
17.88
0.17
9.24
NA
NA
147.55
14.62
6.71
0.11
4.88
<0. 1 (c)
25.03
MWRA, STFP V,S, 1987, unless otherwise noted
1979 MDC Waiver Data, Station 9 (MDC, 19814).
1982 MDC Waiver Data, Station PD (MDC, 198 1 4a).
NA - not analyzed
Total Metal Concentration (ppm dry weight)
Range Average
47.32
Transect D (Site 4.5)
3.17
1 .09
0.19
2.30
- 7.214
— 16.814
- 1.014
- 8.85
(a)
(b)
(c)
(d)
11. 145 — 107.6
4—31

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14.2.1; MARINE ECOSYSTEM
This section presents information on baseline biological conditions in the area
potentially affected by the operation of the effluent conveyance and dispersion
structures. Biological communities described include infaunal and epifaunal benthic
communities, phytoplankton, zooplankton, fish, marine mammals, turtles and
seabirds. These communities are described in detail in Appendix C. Data used to
describe these communities include data collected by MWRA (STFP V and Appendices,
1987) as well as historical data. Fig. 4.2.LLa presents the locations of the MWRA
1987 survey stations. The area under most intense evaluation in this section is the
general transect starting nearshore at MWRA Site 2 and extending to MWRA Site 5.
14.2.14.1 Macrobenthos
The marine macrobenthic community is likely to be one of the better indicators of’
long-term environmental conditions of a marine or estuaririe ecosystem because the
adult stages of this community are relatively non-motile and long-lived. The
benthos, therefore, can reflect the more long-term environmental conditions of the
water and sediments prior to the time of sampling while planktonic organisms often
reflect more short-term conditions indicative of the time of sampling. Although
fish have a relatively long life span, they are mobile and often migratory and
seasonal and can avoid an area which may be less suitable due to a transient
condition such as lack of food. This section on macrobenthos presents a general
description of benthic epifaunal species composition in the study area followed by a
description of infaunal species composition.
14.2.11.1.1 Benthic Epifauna. The seafloor of Massachusetts Bay is very
heterogeneous due to irregular changes in sediment ranging from patches of mud to
areas of cobbles and boulders (Appendix B). Mobile and sessile epifauna generally
exist where pebbles, cobbles and boulders are most prevalent (hard bottom areas),
while infaunal communities generally exist in the soft bottom mud patches. Hard
bottom areas are generally more prevalent at MWRA Sites 5 and 3.5 while soft bottom
areas are generally more common nearshore at MWRA Sites 2 and 2.5. Typical
epifaunal species in Massachusetts Bay include sessile species such as sponges,
hydroids and bryozoans as well as several motile species Including seastars, lobster
and fish, such as cunner and ocean pout. A more complete description of epifauna in
the study area is found in MWRA, (STFP V T, N and 0 1987).
Extensive epifaunal surveys were conducted by MWRA in 1987 (MWRA, STEP V N,O,P,Q,
and T, 1987). These surveys indicate that variations in epifaunal community
structures between different sites relate to differences In bottom types in the
study area. The heterogenous seafloor in Massachusetts Bay ranges from mud to sand
to cobble to boulders. Different epifaunal assemblages are associated with these
different bottom types. At least six different bottom types and associated
epifaunal assemblages can be characterized from review of the MWRA 1987 Remotely
Operated Vehicle (ROV) surveys. Table 1 .2.1;.a presents a summary of this
information. Fig. LL2.1;.b shows where in the study area these bottom types are
known to occur. In general, soft bottom areas (categories I and II; Table 4.2. 1 4.a)
have very few sessile epifaunal species with some motile species. Sessile epifauna
are generally associated with rocks. Motile epifauna also tend to be more abundant
in areas where rocks are present since the rocks provide shelter.
‘4-32

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o PRIMARY PRODUCTIVITY
o FISH AND EPIBENTHIC
— — REMOTS STATIONS—FIRST SURVEY
— REMOTS STATIONS—SECOND SURVEY
• NUTRIENTS SAMPLING
S
ROV
A
a
SECOND ROV
SOFT—BOTTOM TRANSECS
HARD—BOTTOM TRANSECTS
0
STATUTE MILES
0 1
f
w
tJJ
NAUTICAL MILES
.1
/
/
BOSTON
/
n ‘
II
0
0
AUerton
ADAPTED FROM: MWRA,
STFF, V. B, 1987
FIGURE 4.2.4.a. LOCATION OF MWRA SAMPLING LOCATIONS

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TABLE 1 4.2. i.a SUMMARY OF GENERAL BOTTOM TYPES AND ASSOCIATED EPIFAUNAL ASSEMBLAGES
Heterogeneous flat
areas with sandy
sediment interspersed
with areas of pebbles,
cobbles and some
boulders
flat areas with worm or
ainphipod tubes and excava-
tion pits interspersed with
rocky areas
restricted rocky
areas; colonial and
sessile hydroids,
finger sponges
anemones
winter flounder,
lobster, crabs,
scallops, seastars,
cunner, sculpin
Sediment
Characteristics
Bottom
Topography
Sessile
Epifauna
Motile
Epifauna
I. Homogeneous soft
flat with worm or
very sparse;
occasslonal winter
bottom with high
silt/clay content
amphipod tubes and
excavation pits
occasional solitary
hydroid
flounder, Jonah crab,
scallop
II. Homogeneous soft
bottom with low
Mostly flat, occasional
ripple; worm or amphipod
extremely sparse
occasional to abundant
winter flounder, Jonah
silt/clay content
tubes and excavation pits
crab
III. Homogeneous pebbles
flat; worm or amphipod
coninon to abundant
seastars, sculpin,
and cobbles covered
tubes and excavation pits
solitary and
Ocean Pout, cunner,
with sandy sediment;
colonial hydroids,
occasional lobster,
occasional exposed
finger sponges,
crabs and scallops
rooks
anemones, cerianthids
IV. Homogeneous pebbles,
rocky
sparse to coninon
abundant winter
cobbles some boulders
finger sponges,
flounder, crabs,
covered with sediment
anemones, tunicates,
scallops. Lobsters,
high silt/clay content
some solitary and
colonial hydroids
seastars, sculpin,
cunner
V. Heterogeneous muddy
flat areas with worm or
restricted to rocks;
winter flounder,
patches with high silt!
amphipod tubes and
finger sponges,
lobster, crabs,
clay content inter-
excavation pits inter-
colonial hydroids,
scallops
spersed with areas of
spersed with rocky areas
tunicates
cobbles, pebbles and
some boulders
VI.

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1 0
NAUTICAL MILES
LEGEND
A I HOMOGENEOUSSOFT BOTTOM
WITH HIGH SILT/CLAY
CONTENT
A HOMOGENEOUSSOFT BOTTOM
WITH LOW SILT/CLAY CONTENT
• 111 HOMOGENEOUS PEBBLES AND
COBBLES COVERED WITH
SANDY SEDIMENT
O IV HOMOGENEOUS PEBBLES AND
COBBLES COVERED WITH
SILTY SEDIMENT
• V HETEROGENEOUS WITH AREAS OF
OF HIGH SILT/CLAY CONTENT
INTERSPERSED WITH AREAS OF
COBBLES AND PEBBLES
o VI HETEROGENEOUS WITH AREAS OF
SAND INTERSPERSED WITH AREAS
OF COBBLES AND PEBBLES
DATA SOURCE: MWRA, STFP, V.0, 1987
)
MALDEN
- 1’
/
/
EVERETT
0
1=
Lfl
7
Deer
Island
I s 4 ,
•.
The Graves
Green Is.
LovII
Island
“-I
S
.
Georges
Island
0
Bumkjn
Island (. ,
FIGURE 4.2.4.b. BOTTOM TYPES IN THE STUDY AREA

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The epifauna biomass in the study area and Massachusetts Bay in general appears to
increase between winter and summer. This increase in biomass is due to build-up of
dense aggregations of tubiculous species on rock surfaces during periods of low
energy. During these periods, almost all hard surfaces are covered with
biologically-bound, silt-clay size material. This biogenically-bound mud contains
some species that are otherwise typically infaunal. This phenomenon has been
observed in several surveys (MWRA, STFP V 0, P, Q, and S, 1987). It is likely that
this animal sediment complex builds up in the low-energy summer months and is
periodically removed during periods of high wave energy (Appendix B).
14.2.11.1.2 Benthic Infauna. The benthic infauna generally inhabit the mud or soft
bottom patches in the study area. This community is generally dominated by
polychaete worms capable of’ consuming particulate organic materials that have
accumulated in the bottom sediments.
Evaluation of the most comprehensive data set (soft bottom sampling at Sites 2, 2.5,
3, 3.5 and 14; Fig. 1 4.2.itt.a) for the study area (MWRA, STFP V,T, 1987) shows two
distinct infaunal communities within the study area One community appears to be
indicative of nearshore conditions (Sites 2 and 2.5) while the other type is more
indicative of farshore conditions (Sites 14 and 14.5). This change in infaunal
communities is due to differences in physical and chemical parameters as well as
depth from nearshore to farshore along the transect. This distinction may not occur
throughout Massachusetts Bay, but it has been shown to occur in the study area.
This could be due to the deposit of fine material at the Harbor mouth.
Table 1 4.2.14.b summarizes general trends at nearshore and farshore areas in
Massachusetts Bay. The following is a discussion of these trends.
Infaunal Species Composition. Spionid polychaetes are the dominant infaunal taxon
throughout the study area (Appendix C; Table C.1.d). This taxori is abundant in a
range of sediment types and depths in Massachusetts Bay. The spionids are sedentary
worms generally characterized by a pair of elongate palpi used to sweep the surface
of the substratum and bottom waters for food (Gosner, 1971; Levin, 1981; Dauer et
al., 1981).
While spionids occur throughout the study area, some differences do exist between
other taxa in nearshore areas (Sites 2 and 2.5) and farshore areas (Sites 14 and
4.5). This was especially evident in the extensive 1987 survey (Appendix C;
Table C.1.d). Cirratulid, capitellid, and aricidiad polychaete worms and
oligochaete worms are relatively abundant nearshore while offshore these taxon
represent only a very small portion of the community. Maldanid and syllid
polychaetes, amphipods and bivalves occur in relatively high numbers offshore and in
very low numbers nearshore (MWRA, STFP V,T, 1987). Both species diversity and total
number of species appear to increase from nearshore to farshore areas (Appendix C;
Table C.1.e).
Species Densities. Total densities of infaunal organisms are statistically similar
throughout the study area (Appendix C; Table C.1.f). Although total densities are
spatially consistent throughout the study area, densities of individual species
differ significantly spatially from nearshore to farshore as indicated in the 1987
survey. Density of the polychaete, Aricidea catherinae, is significantly higher
nearshore (Sites 2 and 2.5) than offshore (Sites 14 and 14.5) while densities of’ the
polychaete worms, Exogene verugera and Euclymene sp. are generally significantly
higher offshore than nearshore (Appendix C; Table C.1.g).

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TABLE 14.2.1!. b GilIERAL CHARACTERIZATION OF NEAR SHORE AND FAR SHORE PARAMETERS IN I4ASSACHUSEflS BAY
Bottom
Depth
Water
Column
Density
of
Dominant
Infaunal
Temporal
Evidence
Type
(m)
Nutrients
Organisms
Taxa
Patterns
of
Stress
Nearshore Sand and silt Shallower Higher Not significantly Aricidiad, Total densities decline Elevated metal and PAH
(Sites 2, 2.5) prevalent (22—26) different from Cirratulids, by end of suniner concentrations; higher
W far shore Splonids abundance of oppor-
tunistic species
Farshore Cobbles and Deeper Lower Not significantly Spionids, Total densities decline None
(Sites LI, 4.5) pebbles (28—32) different from Syilids, by end of sununer
prevalent near shore Amphipods

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Temporal Patterns. The information on infaunal benthic communities in the study
area and Massachusetts Bay in general is only available from spring and summer.
Although no real changes in sediment type or species composition appear to occur
throughout the spring and summer, densities of organisms apparently decline between
spring and summer. This decline appears to be the result of changes in densities of
dominant species. Nearshore (Sites 2 and 2.5), the densities of the dominant
species Aricidea catherinae, Prionospio steenstrupi, and Tharyx acutus declined
gradually throughout the summer in 1987. Offshore (Sites L and 14.5), the dominant
species Prionospio steenstrupi and Exo gone verugera also declined in density fro n
spring to summer (MWRA, STFP V,T, 1987). The decline in densities of these dominant
species is likely the results of two factors: one is reduced recruitment as
evidenced by large declines in smaller animals (MWRA, STFP V,T, 1987), the other
factor appears to be mortality of all size classes, perhaps due to predation.
Evidence of Stress. The relatively high levels of PAH’s and certain metals in
nearshore areas (MWRA, STFP V,S 1987; Appendix B) may be indicative of a somewhat
stressed benthic environment in this area. Species known to be opportunistic or
pollution-tolerant (Pearson and Rosenberg, 1978) are not highly dominant in the
study area as a whole; however, two pollution tolerant taxa, the polychaete,
Mediomastus californiensis and oligochaete worms are relatively common nearshore,
(MWRA, STFP V,T, 1987). This may indicate that the nearshore area may be somewhat
stressed. Also, pollution sensitive species such as amphipods (Maughan, 1986;
Pearce, 1972; Bottom, 1979; Steimle, 1982) are more abundant offshore than
nearshore, indicating that conditions offshore may be relatively less stressed than
nearshore.
.2)4.1.3 Benthic Communities in Boston Harbor. The benthic communities in Boston
Harbor generally consist of two distinct communities. One type of community:
inhabits the southern portion of the harbor while the other occurs in the northern
portion. The community in the southern part of the Harbor (near Nut Island) is
generally characterized by moderately dense communities with a high number of taxa,
high evenness and diversity and with relatively high numbers of pollution sensitive
amphipods (MDC, 198 1 4a and b).
The northern part of the Harbor, in the vicinity of Deer Island and west of
Deer Island, is characterized by a benthic community that appears to be more:
impacted by pollution than the southern community. The benthic community at Deer
Island Flats (west of Deer Island) and the mouth of the Inner Harbor exhibits
several ecological community indices which are indicative of a stressed macrobenthie
community, including low species diversity, dominance by a few opportunistic species
and few amphipods (MDC, 19814a and b; MDC, 1979; Rowe et al., 1972).
Lt.2.1t.2 Plankton
14.2. 1.2.1 Phytoplankton. : Several studies on phytoplankton and primary productivity
have been conducted in the Gulf of Maine and its coastal embayment, Massachusetts
Bay. The following is a description of’ general phytoplanLcton distribution in the
Gulf of Maine and Massachusetts Bay.
General. Marshall and Cohn (19814) summarized several years of National Marine
Fisheries Service (NMFS) Marine Monitoring Assessment Program (MARMAP) phytoplankton
cruises in the northeastern continential shelf. Phytoplarikton populations over the
‘4—38

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northeastern shelf where found to consist of a diverse assemblage of species that
differ seasonally in composition across the shelf. The most abundant phytoplankters
can be divided into three major groups: the small-sized diatoms, the
phytoflagellates, and the nannoplankton (mainly 2 to 10 p size range). The small
diatoms were seasonally associated with the spring and fall bloom periods, with
highest concentrations close to large estuary systems. According to Marshall and
Cohn (19814), lower diatom densities generally occurred seaward with patches of high
densities associated with Georges Bank. The phytoflagellates occurred in high
numbers in late spring and summer. The nannoplankton component of the phytoplankton
was generally non-flagellate. This community is generally abundant and widespread
over the continential shelf, (Marshall and Cohn, 19814).
Phytoplankton communities of low densities (approximately 50,000 cells per liter)
generally dominated by dinoflagellates or diatoms, occur from November to February
in the Gulf of Maine and Massachusetts Bay (TRIGOM, 19714). From February to June
various diatoms bloom. Spring blooms in Massachusetts Bay generally occur by
April. These blooms result in densities of over a million cells per liter. Summer
blooms of small-sized coccolithophores are common in open basins of the Gulf of
Maine while certain diatoms may bloom in early fall in the more coastal areas.
Secondary late summer and fall blooms of some diatoms occur in Massachusetts Bay
(TRIGOM, 197J4).
Massachusetts Bay Studies. Similar to the general pattern described above, maximum
phytoplankton densities in Massachusetts Bay occur during spring (March to May) and
fall (September to October) diatom bloom periods (MWRA, STFP V,Z, 1987; Parker,
19714). Primary productivity is generally highest during the spring bloom period in
March (Parker, 19714). There appears to be a marked offshore trend of decreasing
primary productivity and phytoplankton bioniass associated with a parallel decline in
nutrient concentration (Appendix C).
Parker found that variation in specific productivity rates and variation in
chlorophyll content were directly related to observations made on nitrogen-deficient
cultures of marine phytoplankton, suggesting that nutrient availability
(specifically nitrogen) had a strong influence on the initiation and duration of the
major bloom periods. According to Parker (19714), nutrient addition from land
drainage into the inner harbor area is transported into Massachusetts Bay and
appears to be the most significant variable that contributes to spatial differences
in primary productivity. The 1987 survey confirmed that nitrogen is the limiting
nutrient in these waters, based on production levels and nitrogen-to-phosphorus
ratios.
Significant chlorophyll a concentrations (indicating the presence of phytoplankton)
occurred in deep water and the stratified surface layer during the 1987 survey.
Nannoplankton (the <10 p size fraction) accounted generally for more than 70 percent
of the total chlorophyll concentration. During the 1987 survey, “surges” of
nitrogen and phosphorus which coincided with incursions of colder water occurred
twice (MWRA, STFP V Y and Z, 1987). The origins of these surges are unknown.
The mean carbon growth rates during the 1987 survey were similar at all stations,
approximately 0.5 g C/day, corresponding to a mean population carbon doubling time
of <18 hours. This indicates that the phytoplankton communities at all the sites
were in a similar physiological state suggesting that nearshore Sites (P1 and P3;
14...39

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Fig. Lt.2. )4.a) were under no more stress than offshore sites (P2; Fig. U.2. 1 4.a).
These phytoplankton communities appear to have similar species composition at all
sites but with higher densities and production rates near the harbor.
In summary, the principal components of the phytoplankton communities in the
Massachusetts Bay surveys reflect normal occurrence of the summer flora of New
England temperature coastal waters with flagellates being abundant throughout the
summer and diatom blooms occurring in spring and fall (Marshal and Cohn, 198 4; and
Marshal, 198 )4a; Marshall, 198 1 4b, Marshall, 198)4; NMFS, MARMAP 1978-1985). Trends of
decreasing productivity, chlorophyll a concentration and phytoplankton density with
increasing distance from shore occur in Massachusetts Bay. The limiting nutrient in
phytoplankton production in the study area is nitrogen.
14.2.11.2.2 Zooplankton. Zooplankton comprise the animal component of the plankton
and may be divided into two major groups, the neritic and oceanic zooplankton. The
neritic zooplankton exist along the coast and seaward to about 100 meters in
depth. The zooplankton occurring in the study area are generally neritic (TRIGOM,
197 ) 4).Although no specific data is available on trends in zooplankton densities, it
is likely that the relative density of zooplankton reflect the relative densities of
their food source, the phytoplankton. Hence, zooplankton densities likely decrease
with increasing distance from shore in Massachusetts Bay.
Ichthyoplankton are the component of the zooplankton that consist of fish larvae and
eggs. Lux and Kelly (1978) summarized NMFS ichthyoplankton data collected in
Massachusetts Bay from 1976 to 1977. Their results show that the abundance of fish
eggs and larvae in Massachusetts Bay was low in late winter, increased to a peak in
June and declined considerably by August (Appendix C). This appears to be the
typical seasonal pattern for ichthyoplankton in Massachusetts and Cape Cod Bays
(Anderson and McGrath, 1976).
14.2.11.2.3 Plankton Communities in Boston Harbor. In general, based on a review of
several plankton studies in Boston Harbor, both the phytoplankton and zooplankton
communities appear to be uniform throughout Boston Harbor. The plankton community
composition appears generally similar to that of Massachusetts Bay (MDC,1979;
198’4a).
14.2.11.3 Fish
Quantitative information on fish communities in Massachusetts Bay is somewhat
limited and not site specific; however, a wide variety of fish investigations have
been conducted in the Gulf of Maine and Massachusetts Bay. Most work has been
conducted by NMFS and Massachusetts Division of Marine Fisheries (DMF). NMFS is
involved, in such programs as groundfish surveys, MARMAP, and population dynamics
studies of commercially important species (TRIGOM, 197)4). Understanding the
population dynamics of fish in the Gulf of Maine as well as Massachusetts Bay is
important because of the cosmopolitan and migratory nature of fish. The
distribution of fish in Massachusetts Bay is highly influenced by the Gulf of
Maine. The following is a general description of fish populations in the Gulf of
Maine and Massachusetts Bay.
14.2.11.3.1 General. Fish species generally migrate in response to seasonal and
local variations in temperature. Seasonal temperature variations therefore have the

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greatest influence on the seasonal abundance, distribution and species composition
of the fish fauna in the study area. Seasonal temperature conditions that influence
the fish populations in the study area include the cold water barrier at Cape Cod,
which separates the Gulf of Maine from the Mid-Atlantic Bight from June to September
by means of a sharp temperature differential. During the rest of the year, a
temperature continuity exists between the areas. Temperatures in the Gulf of Maine
waters are generally similar throughout the Gulf seasonally while the temperature of
Mid—Atlantic Bight waters varies spatially (TRIGOM, 1974).
The Mid—Atlantic Bight contains very few permanent residents and is composed of
continuously shifting populations, while the Gulf of Maine contains mostly endemic
species with some seasonal change in species composition. In the Mid-Atlantic
Bight, a population of southern migratory fishes follows a northern dispersal to
Cape Cod (Fig. 1 4.2. 1 4.c; Table 1 L2.LLc; TRIGOM, 19714; Bigelow and Shroeder, 1953).
Many of these species including spiny dogfish, American shad, hakes and mackerel
enter the Gulf of Maine and Massachusetts Bay and remain there throughout the
summer. In winter, they migrate either south or to the warmer continental slope
waters in the Gulf of Maine. The Mid-Atlantic Bight populations are “replaced” by a
limited seasonal diffusion of a few species that are endemic to the Gulf of Maine,
but which “spill over” to the Mid-Atlantic Bight in winter (TRIGOM, 1974).
During winter, many summer migratory species move to the warm slope water off
southern New England. These species include red hake, silver hake, scup,
butterfish, summer flounder and goosefish, as well as some less common species
(Table 1 L2.4.c). The winter component of fishes migrating from the north and east
consist of Atlantic cod, yellowtail flounder, and longhorn sculpin, (TRIGOM,
1974). Generally, the fishes of the summer component are most abundant on inshore
grounds, when the water temperature is the same as that in which they were most
abundant offshore.
Generally, almost all non-migratory species exhibit some seasonal movement. Fish
are generally scarce along nearshore areas in the Gulf of’ Maine in winter. Only sea
raven, or longhorn sculpin occur in shallow waters in winter. In March, winter
flounder, ocean pout, sculpin and little skate appear nearshore. Later in the
summer, cunners, alewife and luxnpfish occur. In the fall the process is reversed
(TRIGOM, 1974).
Appendix C presents information on the life histories of several species occurring
in Massachusetts Bay.
14.2)4.3.2 Massachusetts Bay. Information on fish in Massachusetts Bay is available
from the NMFS biome program, semi-annual trawl surveys of demersal fish, by
Massachusetts Division of Marine Fisheries (MDMF) as well as a limited 1987 MWRA
survey (Appendix C; Table C.1.k and C.1.l).
MDMF surveys of May and September bottom trawls from 1978 to 1986 show that winter
flounder is the most abundant species in all depth intervals sampled in May and
remains the most abundant species in September although actual abundance decreased
at all depths from May to September. Winter flounder in Massachusetts Bay are known
to disperse to deeper water throughout the summer after spawning in Boston Harbor in
spring; however, they generally do not migrate a great distance (Howe and Coates,
1975). Atlantic cod and ocean pout are also abundant in May but declined
14...14 1

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TABLE 14.2.14. c SEASONAL MIGRATION CHARACTERISTICS
OF SOME IMPORTANT FISH SPECIES
Common Name Species Name
I. Southern summer migrants (north to Cape Cod)
Sununer flounder Paralichthys dentatus
Soup Stenotomus chrysops
Weakfish Cynoscion regalis
Kingfish Menticirrhus saxatilis
Mullets Mugil sp
Black seabass Centropristes striata
Filefishes Aluterus sp., Monacanthus sp.
Fompanos Caxanx hippos and other species
Northern puffer Sphaeroides aaculatus
II. Northern summer migrants (north into the Gulf of Maine)
Spiny dogfish Squalus acanthias
Silver hake Merluccius bilinearis
Red hake Urophgcis chuss
White hake Urophycis tenuis
American shad Alosa sapidissiiaa
Striped bass Morone saxatilis
Menhaden Srevoortia tyrannus
Bluefish Pomatoaius saltatrix
Atlantic mackerel Scomber scombrus
Butterfish Peprilus triacanthus
Bluefin tuna Thunnus thynnus
III. Southern winter dispersal
Atlantic herring Clupea harengus
Atlantic cod Gadus morhua
Pollocic Pollachius virens
Source: TRIGOM, 1971$.

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68°
66
O s
..i •-7 A
t. .-. : k /
- .,“
- .
0
t,..
/ ‘
0 , - •
70°
SUMMER TEMPERATURE
BARRI ER
68
HGURE4.2.4.c ENERAL MOVEMENT OF MIGRATORY FISH SPECIES IN THE
NORTHWESTERN ATLANTIC OCEAN.
74.
72
70°
1 =
w
74°
72°

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substantially in September. These two species are relatively less abundant in the
shallower waters in both May and September. Cod are known to migrate south to spawn
in warmer waters during fall and winter. Ocean pout spawn in southern New England
waters (including the present study area) in fall (Grosslein and Azarovitz, 1982),
A total of 142 species have been collected in these DMF surveys over the sampling
period. Total abundance of all species combined tends to decrease from May to
September at all depths.
The data on the abundance of shellfish collected in the same DMF trawls from 1978
through 1986 indicate that American lobster (Hornarus americanus) is the most
abundant epifaunal shellfish species in May for all depths. Its numbers tend to
increase in deeper offshore water in September as does the rock: crab (Cancer
irroratus).
14.2)1.3.3 Fish Communities in Boston Harbor. Winter flounder are abundant
throughout Boston Harbor. This species appears to dominate in the northern part of
the Harbor (west of Deer Island). Demersal fish density is high in the northern
part of Boston Harbor but species diversity is low (MDC, 19814). In the southern
part of Boston Harbor (in the vicinity of Nut Island), density of fish is lower than
the northern harbor but diversity is higher. Pollock, cod, skate, and cunner were
also relatively abundant in the southern portion of Boston Harbor (MDC 1984; MDC ,
1979; DMF, 1979). Haedrich and Haedrich (19714) found winter flounder dominating the
fish population within the upper reaches of the inner harbor at the mouth of the
Mystic River. In spring and early summer smelt and alewife were also abundant in
this area.
11.2.11.3.11 Demersal Fish and Epibenthic Shellfish Contamination. Several studies
have been conducted documenting detnersal fish and epibenthic shellfish tissue
contamination in Boston Harbor and Massachusetts Bay (Boehm et al., 19814; Capuzzo et
al., 1986; MDC, 198 1 4a; 1979; Schwartz, 1987). Boehm et al. (19814) made a comparison
of tissue concentrations of pollutants in organisms from Boston Harbor to those in
organisms in Massachusetts Bay, revealing a trend of increased contamination with
increased proximity to Boston Harbor.
The presenäe of elevated tissue concentration of PCB’s and PAH’s in the demersal
species in Boston Harbor and vicinity may be the result of the current wastewater
discharges in Boston Harbor. PCB’s and PAH’s from the present discharges may
accumulate in the sediments and be transferred to these demersal organisms as they
feed and as they otherwise contact the sediment.
Boehm et al. (19811) also evaluated coprostanol, considered a sewage tracer, and its
relationship with PCB levels. Coprostanol/PCB ratios have been used to relate the
presence of PCB with sewage-ralated material. The ratios range from zero (no
sewage) to approximately 200 (Boehin et al., 19811). The highest coprostanol/PCB
values were found in Boston Harbor with intermediate values occurring offshore,
indicating significant sewage-related PCB transport offshore (Boehm et al., 19814).
MWRA is conducting bloaccuinulation studies in support of the Secondary Treatment
Facilities Plan; however, this data is not yet available.
14

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142k1$ Marine M nmi ls
4.2.’L4.1 Whales. Finwhales, humpback whales, minke whales, right whales and sei
whales have been known to occur in Massachusetts Bay. All of these species with the
exception of the sei whale are listed on the federally endangered species list.
Table C.1.p in Appendix C summarizes the ranges of these species. These species
primarily occur offshore of the study area (NMFS, 1988; Kenney and Winn, 1987). The
highest use areas by whales in the vicinity of the study area is Steliwagen Bank and
basin (Kenney and Winn, 1987).
k.2.1L1t.2 Seals. Two species of pinipeds, harbor seals (Phoca vitulina) and the
gray seal (Halichoerus grypus) are known to occur in Massachusetts Bay and the Gulf
of Maine. The harbor seal is found year-round in inshore waters basking on
nearshore half-tide ledges and islands. The gray seal is found among the harbor
seals only during the warmer summer months. Gray seals are capable of long periods
of pelagic existence. Table C.1.q of Appendix C summarizes the distribution and
abundance of these two seals (TRIGOM, 197L ).
112k5 Marine Turtles
Three species of marine turtles are known to occur in Massachusetts Bay, the
leatherback turtle (Demochelys coriacea), Kemp’s Ridley turtle (Lepidochelys Kempi)
and the loggerhead turtle (Caretta caretta). Loggerheads are listed as
threatened. Leatherbacks and loggerheads are listed as endangered and threatened
respectively by NMFS. Leatherback turtles are highly pelagic. Sitings off
Massachusetts are most common from July to September (CeTAP, 1982). Ridley’s
turtles occur off southern New England in summer. This species uses inshore
embayments, estuaries and harbors to feed (ISJMFS, 1988). Loggerhead turtles are rare
north of Cape Cod. Generally, Massachusetts is the northern range limit for
loggerheads, therefore these waters are marginal habitat (Payne and Ross, 1986).
14.2.14.6 Seabirds
Manomet Bird Observatory (MBO) has conducted standardized bird surveys east of the
present study area in Stellwagen Basin from 1980 to 1985. The species observed in
these surveys are typical of the Gulf of Maine and are generally the same species
that would occur in the present study area. Dominant taxa include alcids, gulls and
shearwaters. Of the species occurring in the study area, Leach’s storm—petrel is
listed as threatened by the state of Massachusetts. Table C.1.r of Appendix C
summarizes the feeding behavior of the dominant species. Some coastal species
including seaducks, grebes, loons, petrals and terns may also occur in the study
area.
14.2.5 HARBOR RESOURCES
Harbor resources discussed in this section include the natural, commercial, and
recreational resources of Boston Harbor and adjacent Massachusetts Bay that could
potentially impacted by the construction and operation of the effluent outfall and
dispersion structure. Harbor resources and impacts are described in detail in
Appendix D, with emphasis on the marine transportation aspects of this and related
projects which could impact existing harbor resources. MWRA also presents a
description of some harbor resources (MWRA, STFP V,L, 1987). The affected harbor
!4

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resources environment is summarized below. Potentially affected harbor resources
are navigation, commercial shipping, commercial fishing, recreation, and marine
archaeology.
11.2.5.1 Navigation
Navigation channels and anchorages provide commercial and recreational boating
routes from Massachusetts Bay to the marinas and commercial port facilities of
Boston Harbor. These channels and anchorages support shipping, commercial and
recreational fishing, and pleasure boating and will be used by project-related
marine traffic. Two major channels serve Boston Harbor, passing through President
Roads and Nantasket Roads (Fig. 1 1.2.5.a). The President Roads Channel serves port
and pier facilities in Boston, Charlestown, East Boston, South Boston, Everett,
Chelsea, and Revere (Boston Shipping Assn., 1986). The channel passing through
Nantasket Roads serves the industrial waterfront of Quincy including the former
General Dynamics Shipyard now owned by MWRA. A single designated anchorage area for
large vessels, located west of Deer Island, is used by 95 percent of commercial
shipping traffic which needs to anchor due to delays in loading or unloading (USACE,
1 9 8Z ). Channels and anchorages are periodically maintained by the U.S. Army Corps
of Engineers. Improvement dredging will likely occur within the inner harbor on the
Mystic and Chelsea Rivers and the Reserved Channel in South Boston during the
project construction period, as will dredging for the Third Harbor Tunnel/Central
Artery highway project (Appendix D). Navigation resources are shown in
Fig. 1 1.2.5.a.
11.2.5.2 Commercial Shipping
Commercial shipping contributes significantly to local and regional economies
surrounding Boston Harbor (Appendix D). The inner Boston Harbor waterfront supports
roughly two dozen public and private port facilities. Nearly 7,000 commercial
vessel round trips occur yearly. Most of the commercial vessel traffic enters and
leaves the harbor via the President Roads channel traveling to and from port
facilities on the Boston, Chelsea River, and Mystic River waterfronts with the
remaining traffic traveling through Nantasicet Roads to the Quincy waterfront on the
Weymouth Fore River. In 1985, 6,266 vessels traveled through President Roads and
633 through Nantasket Roads (USP 1 CE, 1986).
Commercial shipping traffic is expected to remain stable or increase slightly during
the next decade (Habel, 1987). In addition to commercial shipping activity,
sightseeing and whale watching cruises and passenger ferry services operate from
piers at Logan Airport, Hull, Hinghain, the Boston Harbor Islands State Parks
(seasonal), and downtown Boston wharves (Fig. 1 L2.5.b). Commuter ferries carried an
average of 931 passengers per day in 1985 (MWRA, WTFP 7, 1987). Most ferry vessels
operating in Boston Harbor have the capacity for approximately 150 passengers.
11.2.5.3 Commercial Fishing
Commercial fishing in the Boston Harbor vicinity consists largely of lobster
fishing, shellfish (clam and mussel) harvesting, and f’infishing by draggers and
gilinetters. Shellfish and lobster harvest is allowed and takes place inside and
outside the harbor, while commercial finfishing is prohibited within the harbor, but
‘ J4 6

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.......... Third Harbor Tunnel Dredging 1991 — 1992
Sources: NOAA Nautical Charts, USACOE, 1987
USACOE Project Maps, 1986
Federal Highway Admin., 1985
MWRA STFP VL, 1987
—. . — U.S. Army Corps of Engineers
Improvement Dredging 1988— 1995
F— - -
/
SITE 5
.
Potential
Diffuser
Sites
I I t
4
.
SITE
2
.
(The Graves
Green Is.
LEGEND
Navigation Channels
________ Anchorage #2
coHAssEl
FIGURE 4.2.5.a. COMMERCIAL NAVIGATIONAL RESOURCES

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— — Commercial Vessels
Green Is.
Source: Boston Harbor Islands State Park 1986
Master Plan, Mass Dept. of Environmental Management
Massport, 1987 B, Boston Shipping Association, 1986
—. —. — Boston Harbor Island State Park Ferries (Projected and Existing)
Commuter Service and Logan Shuttle
FIGURE 4.2.5.b. TYPICAL COMMERCIAL AND PASSENGER SHIP ROUTES
—. .— I,
/
5
SITE
.
Potential
Diffuser
Sites
SITE
4
.
SITE
2
Deer /
Island
The Graves
/
Calf
Is.

I?
j ç ’
ç land
Georges
LEGEND
Cohasset
‘1
COHASSEr

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does occur in Massachusetts Bay. Boston commercial fishing landings for 1986, which
include fish harvested outside the study area, included 14 million pounds of lobster
and 17.5 million pounds of finfish (MDMF 1987; MWRA, STFP V,L, 1987). More than
5,000 acres of shellfish beds exist in Boston Harbor, but at present, unacceptable
levels of coliform bacteria have caused more than half of the existing shellfish bed
acreage to be closed. Harvest of the remaining shellfish beds is limited to
licensed Master Diggers whose harvest is processed at the Newburyport depuration
plant before being consumed (MWRA, STFP V, 1987; MDC, 198 L I). Lobster fishing is
generally concentrated inside the harbor in summer and outside the harbor in fall
and winter (MDC, 198LIa).
Herring (Clupea herangus herangus) winter flounder (Pseudopleuronectes americanus),
yellowtail flounder (Limanda ferruginea) and cod (Gadhus morhua) are major finfish
commercially harvested in the project area. Virtually the entire study areaeast of
a line from Deer Island to Hull is utilized by commercial fishermen (MDMF, 1988).
Site 2 is in a restricted area inshore of the spawning closure and the trawl closure
line (Fig. LI.2.5.c) and so is intensively fished during January but closed to
trawling for the rest of the year. Sites LI and 5 are fished less intensively than
Site 2, but are open to fishing more of the year.
1 L2.5.1I Recreation
Recreation areas and facilities are located along the shoreline of Boston Harbor and
the harbor islands and on the coast along Massachusetts Bay north and south of the
harbor. Recreational resources include parks, beaches (Fig. 1 L2.5.d), boating
facilities, fishing facilities, and sightseeing and whale watching vessel
services. More than 100 recreational beaches and parks and 150 facilities for
recreational boating are present in Boston Harbor and Massachusetts Bay from Lynn to
Scituate (MWRA, STFP V,L, 1987). Boston Harbor Islands State Park encompasses
9 major islands, each with various recreational facilities available and serviced by
seasonal passenger ferries (Appendix D).
Recreational fishing takes place in the harbor and throughout the Massachusetts Bay
area. Most anglers utilize their own boats, lease boats, or use the available party
boats and charters based in the area. The recreational fishing industry in the
Boston area once thrived but has been depressed in recent years because of the
negative publicity on harbor pollution and contaminated or cancerous fish.
Recreational fishing activity generally occurs from spring through fall with peaks
during the summer vacation months. The Massachusetts Division of Marine Fisheries
(MDMF, 1988) has indicated that this activity occurs at all candidate outfall
sites. However, the most popular areas are located inshore of Site 2 and the “B”
buoy located about one mile south of Site 5. Other popular areas include the Harbor
Islands, Graves Light, Boston Light, and the Three and One-Half Fathom Ledge.
The most popular target species include winter flounder, cod, mackerel, and
bluefish.

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LEGEND
98 ] Approximate Number of Lobster Buoys 7/27/79
Shellfish Beds Closed to All Diggers
(Closure Varies w/Conditions)
Shellfish Beds Restricted to Master Diggers
Sources: Metcalf & Eddy, 1984
MWRA Vol. V App. L, 1987
MWRA Vol. V App. B, 1987
MDMF, 1988
FIGURE 4.2.5.c. COMMERCIAL FISHING RESOURCES
L 5O

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LEGEND
Recreational Beaches
Boston Harbor Island State Park
• Other Parks
Source: Boston Harbor Islands State Park
1986 Master Plan—Mass. Dem
MDC, 1984
MWRA, VOL. V, App. L, 1987
— Harbor Islands Ferries (Proposed)
FIGURE 4.2.5.d. BEACHES, SHORELINE PARKS, AND ISLAND PARKS
)
. ‘
,
SITE 5
.
SITE
4
.
Potential
Diffuser
Sites
SITE
2
The Graves
QUINCY
NAUTICAL MILES
1

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14.2.5.5 Sensitive Resources
Sensitive resources are natural resources which merit special consideration due to
their fragility and potential for significant irreparable damage or immediate danger
to public health. Resources considered sensitive in this Draft SEIS will be given
particular attention in Chapter 5. Sensitive resources are: bathing beaches,
shellfish beds, marine research facilities, estuarine wetlands and areas of’
significant submerged aquatic vegetation, and sanctuaries (Fig. LL2.5.e to 14.2.5.1).
Bathing Beaches are deemed sensitive because contamination from effluent or spills
from vessels could have immediate adverse effects on public health and recreation.
Shellfish Beds , like bathing beaches, are deemed sensitive because contamination
could adversely affect public health if contaminated shellfish are harvested and
consumed. Contamination could also cause economic and environmental impacts if the
vigor and reproductive capabilities of shellfish populations were affected or if
additional shellfish beds had to be closed.
Marine Research Facilities are considered sensitive resources because ongoing
research could be adversely affected if in-site experimental areas or seawater
supply to laboratories or aquaria became contaminated. Two facilities exist in the
study area, the New England Aquarium in Boston and the Northeastern University
Marine Lab in Nahant. Estuarine Wetlands and Areas of Signficant and Submerged
Vegetation are included as sensitive resources because contamination or physical
disruption could cause long term adverse impacts on the Boston Harbor ecosystem by
diminishing areas of primary productivity and reproductive or breeding habitat.
Wetland and submerged vegetation areas have already been greatly reduced by
development along the shore of Boston Harbor, increasing the relative importance of
remaining areas. Sanctuaries and Areas of Critical Environmental Concern are areas
which have been protected by the Commonwealth of Massachusetts because of their
unique ecological values. The areas within the study area are protected because of
their ecological and aesthetic value as saltmarsh and shoreline environments. The
state designated South Essex Ocean Sanctuary and Areas of Critical Environmental
Concern on the Back River and Weir River lie within the project study area.
4.2.5.6 Marine Archaeology
Cultural and archaeological resource sites are located throughout Boston Harbor,
Massachusetts Bay, and the surrounding shoreline. Only those resources potentially
affected by the outfall and inter-island conduit construction and operation are
described.
Cultural and archaeological resources potentially impacted by outfall and diffuser
construction consist of shipwrecks in the vicinity of the diffuser sites. Neither
the outfall tunnel nor the inter-island conduit would impact any cultural or
archaeological resources because they will pass through rock below the ocean floor,
but drilling or trenching for the diffuser could cause obvious disruption of
wrecksites. A recent review of’ cultural and archaelogical resources performed for
MWRA (MWRA, STFP V,FF, 1987) indicated potential shipwreck sites in the vicinity of’
diffuser alternative locations. Shipwreck locations were developed from historic
records and have not been field verified. The recorded locations of shipwrecks
indicate a greater occurrence of wrecks closer to shore. However, historic records
of shipwrecks are thought to be incomplete and locations reported are not thought to
14—52

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• Marinas w/more than 50 Slips or Moorings
Source: Boating Almanac 1986
* Boat Ramps
o Facilities w/more than 50 Slips or Moorings
and Boat Ramps
FIGURE 4.2.5.e. MAJOR BOATING PUBLIC ACCESS POINTS
- - -- -I
SITE 5
i1E
Potential
.
Diffuser
Sites
4
.
SITE
2
.
De
Island
The Graves
Green Is.
Call
IL

a
Lovell
lsand
Gallops Georges
Island Island
LEGEND
)4_53

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LEGEND
Saltmarsh
- Signthcant Identifiea areas of
L -: 1 - Submerged Vegetation
Areas of Critical
L Environmental Concern
_______ South Essex Ocean Sanctuary
ROADS
Sources: MWRA Vol. V. APP.L, 1987
BARR, 1987
(Shellfish Beds Shown on Figure D.3.c)
(Bathing Beaches Shown on Figure D.3.d.)
• Marine Research Facilities
FIGURE 4.2.5.f. SENSITIVE HARBOR RESOURCES
I
r
‘
0
0
LROSE
\ ,•\
MALDEN
)
/
/
- --1
I
/
EVERETT I
5
SITE
.
SITE
4
SITE
2
.
Potential
Diffuser
Sites
Ds
Island
car.
Is O

Island Island
0
PIAUIJCAL PiLES
L _54

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beprecise. About one third of’ the known shipwrecks identified in the diffuser area
date from 1919 to 1950. Wrecks predating World War I are possible but are not
recorded. The general locations of recorded wrecks are shown by Fig. 4.2.5 .g.
Historical and archaeological resources on land (Deer Island and Nut Island) have
been evaluated by earlier studies (USEPA, 19814; USEPA, 1985; MWRA, STFP IV, 1987).
No potential marine archaeological impacts will occur from construction of the
inter -island conduit or the effluent outfall tunnel because both will be deep rock
tunnels originating onshore.

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UNIDENT IFIED
UNIDENTIFIED
WINIFRED SHERIDAN
(PRE-WW II)
Y. MS. 14 (1945)
ROMANCE
(1936)
UNIDENT IF ED
UNIDENTIF ED
CITY OF SALISBURY
(1938)
NUMBER IS (1927)
gOADS
sP
LOVEL.L.
ISLAND
c: GEORGES
ISLAND
27
PT ALLERTON
LEGEND
• CANDIDATE OUTFALL SITES
SOURCE: MWRA VOL. V APP. FF 1987
FIGURE 4.2.5.g.
SHIPWRECKS WITHIN 1.5 MILES OF CANDIDATE OUTFALL SITES
(SHIP NAMES INDICATE APPROXIMATE LOCATIONS)
BEACH
ARCO #8(1950)
BROAD SOUND
LEIGH # 3(1919)
DEER
ISL AND
\ SOUTH
BOSTON
UNIDENTIFIED
LONG
ISLAND

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1 .3 INTER-ISLAND CONDUIT AREA
14.3.1 INTRODUCTION
Wastewater from the Nut Island collection system will be conveyed to Deer Island via
an inter-island conduit system. The deep rock tunnel alternative was selected for
detailed evaluation since it would incur fewer impacts on the environment and harbor
resources and be less costly than the other potential alternatives (Chapter 3). This
inter-island conduit system involves the construction of access shafts on Nut and
Deer Islands connected by a 25,000 foot long, 11 foot diameter deep rock tunnel
between Nut Island and Deer Island.
14.3.2 SUPO(ARY OF CONDITIONS
Only the subsurface geology between Nut and Deer Islands and the island shaft
locations would be affected by construction of a deep rock tunnel.
The dominant bedrock in Boston Harbor is the Cambridge Formation. This rock is
somewhat metamorphosed, and extremely folded and faulted. The Cambridge Formation
is generally thinly bedded, laminated to occasionally nonbedded, fine grained, well
indurated and moderately hard to hard. Within the Cambridge Formation, there are
documented areas of kaolinized bedrock which is assumed to be randomly distributed
along the inter—island conduit route (MWRA, STFP IV 1987).
Along the inter—island conduit route, the bedrock, which is predominantly argillite
with intrusion by igneous dikes or sills, has a very irregular surface
configuration. Some areas of bedrock are exposed as harbor islands while other
areas occur 150 to 175 feet below mean sea level. The presence of igneous bedrock
along the inter-island conduit route increases the likelihood that tillite or
conglomerate would also be encountered. In the vicinity of the conduit route,
argillite bedding occurs at angles varying from 145 degrees to vertical. These
formations show evidence of complex folding and shearing. Several major
irregularities are anticipated along the conduit route.
Bedrock formations in the vicinities of the access shafts on Nut and Deer Islands
are similar. The argillite bedrock generally dips at an angle of 145 to 50 degrees
from horizontal and has closely spaced parallel-to-subparallel jointing. Fractures
in the bedding have often been healed by calcite. Exposed joint surfaces show
little indication of weathering. At Nut Island, the top of the bedrock is at
elevation 143 feet while at Deer Island, the bedrock is located at elevation 33 feet.
11.11 DISPOSAL AREAS
14.14.1 IDENTIFICATION OF AVAILABLE DISPOSAL AREAS
Excavated materials from the construction of the inter-island conduit and effluent
tunnel will, for the most part, be utilized as construction materials for project—
related construction or for such other projects as the Third Harbor Tunnel/Central
Artery highway project (MWRA, STFP III, 1987; MWRA, STFP V, 1987). If any excavated
14_57

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materials remain unutilized, upland disposal is likely. Since the materials consi
of crushed rock, they are presumed to be relatively uncontaminated “clean fill”.
Upland disposal should not be constrained, and disposal should not affect selection
of conduit or outfall alternatives. No specific upland disposal sites have been
identified or evaluated for these materials. However, disposal operations will
follow all state requirements for disposal on upland areas.
14.11.2 SU) 4ARY OF EXISTING CONDITIONS AT THE FOUL AREA DISPOSAL SITE
Dredged materials will result from the construction of the diffuser, and are likely
to be disposed of at sea at the nearest federally designated dredged material
disposal site. The federally designated disposal site nearest the project is the
Foul Area Disposal Site located approximately 22 miles east of Boston, centered at
latitude 142° 25” N and longitude 700 35” west (USACE, 198J4). Disposal is
administered by the U.S. Army Corps of Engineers (USACE) and subject to EPA
approval. To gain USACOE acceptance for disposal, the quality of the dredged
material (as sampled and tested) must be compatible with the ocean dumping criteria
stipulated in the Marine Research, Protection, and Sanctuaries Act (Appendix G).
The Foul Area Disposal Site is topographically within the Steliwagen Basin in a
300 foot-deep depression separated from Stellwagen Bank on the east by a 200 foot
high slope (USACOE, 19811). The site has historically been used for the disposal of
dredged materials and industrial wastes and has received approximately 3 million
cubic yards of dredged material per decade (USACOE, 1988). Sediments at the site
are largely sandy silts, reflecting the nature of past deposition. Mean bottom
currents at the site are generally less than 5 centimeters per second with a maximum
bottom current of about 35 centimeters per second (SAIC, 19814).
Recent sampling for USACOE indicates that the western portion of the site where
disposal occurs is dominated by spionid, cirratulid, and capitellid polychaete and
oligochaete worms which typically inhabit clayey silts (SAIC, 198k). Continued
disturbance due to disposal activities keeps the conununity in a pioneering state. A
1985 sampling of the area indicates that the dominant fish species include dogfish
(squalus ananthias) in the late spring/summer season and witch flounder
(Glyptocephalus cynoglossus) and American plaice (Hippoglossoides platessoides)
during the rest of the year. Less dominant species include red hake (Urophycis
chuss), white hake (Urophycis tenuis) and deepwater redfish (Sebastes mentella)
(SAIC 1987). Most fisherman avoid the Foul Area because of the debris from previous
disposal operations.
Humpback, finback and right whales and leatherback and loggerhead turtles, currently
on the endangered species list, use the nearby Steliwagen Bank area (NMFS, 1988).
Kenny and Winn (1988) indicated a high habitat use in the region based on a three
year study performed by the University of Rhode Island (CETAP, 1982).
4-58

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CHAPTER 5
CONSEQUENCES OF ALTERNATIVES
5.1 OPERATION OF EFFLUENT DISCHARGE AT ALTERNATIVE LOCATIONS
5.1.1 WATER QUALITY
5.1.1.1 Constituents
The water quality impact analyses furnish the basis for the evaluation of’ compiianc
with water quality standards and criteria (Section 14.2.2.1) and the assessment o:
impacts to water column and benthic ecosystems. For these analyses, the parameters
and constituents which must be evaluated are:
• Dissolved Oxygen (DO), which is consumed by the biochemical oxygen deman i
(BOD) of’ the effluent, sediment oxygen demand (SOD), and resuspension
oxygen demand (RDOD);
• Suspended Solids and Sedimentation , resulting from the discharge of solids
with the effluent;
• , which is affected primarily by the alkalinity of the effluent;
• Nutrients , including nitrogen, phosphorus and silica, which support primary
productivity and the development of objectionable algal blooms; and
• Toxic Chemicals , including volatile organic compounds (VOCs), acid/base
neutrals, metals, pesticides and other chemicals. A list of toxic
chemicals to be considered has been developed by MWRA based on measurements
of influent quality, the applicable water quality standards and criteria
and specific toxicity concerns (MWRA, STFP V,A, 1987).
These water quality parameters are measured in terms of water column
concentrations. Sediment deposition rates, in turn, are directly dependent on
suspended solids concentrations. These concentrations are the result of a balance
between loadings and removal or fate processes. The loadings of interest are from
the proposed MWRA discharge; loadings from other sources, however, are also
considered to evaluate cumulative impacts. The fate processes include transport
processes, which are the same for all the constituents, and physico-bio-chemical
processes which are constituent specific. These elements are briefly described
below and are covered in further detail in Appendix A.
5.1.1.2 Loadings
The discharge rates or loadings of the constituents identified above are provided in
Table 5.1.1.a for primary and secondary effluent (MWRA, STFP III and V,A, 1987).
The carbonaceous BOD loadings for primary and secondary effluent are based on the
MWRA estimates (MWRA, STFP III, 1987). Separate values are provided for low and
5—1

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TABLE 5.1.1.a. CONSTITUENTS LOADINGS
Constituents
Primary Effluent
Secondary Effluent
Low High
Low
High
Conventional
Ground-
Ground-
Ground- Ground-
Pollutants (g/sec)
water
water
water water
Carbonaceous BOD
Nitrogenous BOD
DO Deficit
2,915
1,785
139
3,1145
1,785
278
3714 858
1,785 1,785
139 278
Total Suspended Solids
1,150
363
Nitrogen
390
390
390 390
Flows mgd
m /s
377
16.5
657
28.8
390 670
17.1 29.3
Toxic Chemicals (mg/see)
Primary
Effluent
Secondary Effluent
Mean Standard High ’: 2 )
Deviation
Mean
Standard
Deviation
benzene
86.8
16.0
14.3 0.8 26.0
bromomethane
327.6
116.8
16.14 5.8 81.9
chloroform
117.1
514.0
11.7 5 . 14 58.5
ethylbenzene
methylene chloride
styrene
175.8
632.3
197.2
79.1 1
14514.6
147.7
8.8 14.0 52.7
31.6 22.7 279.14
19.7 14.8 59.2
tetrachloroethylene
trichloroethylene
bis(2—ethylhexyl)phthalate
butylbenzyl phthalate
di—n—octyl phthalate
fluorene
3214.2
183.3
1411.3
3314.7
3145.7
86.14
189.9
97.14
121.1
1149.3
129.7
27.2
32.14 19.0 97.3
11.5 6.1 68.7
141.1 12.1 205.6
16.7 7.5 100.14
314.6 13.0 103.7
8.6 2.7 25.9
arsenic
30.0
9.3
20.0 6.2 214.0
cadmium
37.6
114.14
22.2 8.5 26.6
chromium
279.1
108.7
111.6 143.5 186.0
copper
lead
1365.14
197.2
1409.1
86.2
378.1 113.3 630.2
157.0 68.6 109.6
mercury
20.14
25.7
6.5 8.2 7.8
nickel
353.1
157.9
282.5 126.3 290.8
selenium
251.9
237.9
139.9 132.1 167.9
silver
66.0
16.14
9. 14 2.3 18.9
zinc
2731.0
3111.5
1092.14 121414.6 1365.5
aidrin
3.5
1.5
0.3 0.1 1.0
14,14’.. .DDT
0.85
0.29
0.09 0.03 0.252
dieldrin
0.37
0.15
0.014 0.02 0.11
heptachlor
14.0
0.03
0.1414 0.003 1.32
polychiorinated biphenyls (PCBs)
16.7
143
1.3 0.3 14.7
(1) Average day, year 1999 for primary, 2020 for secondary.
(2) Reduced removal during storms.
Source: MWRA STFP III and V,A 1987.
5-2

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high groundwater conditions, reflecting the fact that increased infiltration during
high groundwater produces additional flows and loads. The nitrogenous BOD loadings
were calculated based on the nitrogen loadings, which are practically the same for
primary and secondary effluent.
The nitrogen loading was computed based on the measured influent Total Kjeldahl
Nitrogen (TKN) concentration of 23 mg/l (MWRA Memo FB2OC attachment to MWRA, STFP
III, 1987), which was assumed to be essentially uncha ged during treatment. The
average day, low groundwater flowrate of 390 mgd (17 mi/sec) was used to calculate
the loading, recognizing that high groundwater conditions provide additional flow
without additional significant nitrogen load. The NBOD loading was calculated as
the nitrogen loading multiplied by 14.57, which is the theoretical ratio of NBOD to
TKN.
The dissolved oxygen deficit (DOD) is the amount by which dissolved oxygen (DO) is
reduced due to the discharge. The DO in the effluent was assumed to be zero,
leading to a DOD loading equal to the ambient DO concentration multiplied by the
discharge flow rate. Average day flows were used, since the development of DO
deficits occurs on a time scale of one to two weeks and short duration events would
not significantly affect DO levels.
The toxics loadings are highly variable and the corresponding water quality criteria
are based on exceedance frequencies (Section 4.2.2.1). To allow determination of
these frequencies, both the mean and standard deviation of the toxics loadings are
provided based on measured influent concentrations and estimated removal
efficiencies. Except for PCBs, these loadings are the same as those used by MWRA in
their analyses (MWRA, STFP, V,A, 1987). Lower removal efficiencies were, however,
assumed to prevail during periods of very high flows. Further discussion of this
factor is provided in Appendix H of this Draft SEIS.
The PCB loading used by MWRA corresponded to the 1 iig/l concentration of
Aroclor 1242, which was the only PCB mixture detected in the 198)4 surveys (MDC,
1984). In 1986-87, influent surveys conducted by MWRA could not detect any PCBs.
The detection limit for Aroclor 12)42 was 0.5 pg/i and this value was therefore used
conservatively here to compute a loading. This reduced PCB level is consistent with
observed trends towards decreasing PCB levels in wastewaters and in the environment.
5.1.1.3 Fate Processes
The fate processes include transport processes, which affect all the constituents
comparably, and physico-bio-chemical processes which are constituent specific.
Transport Processes. These processes are advection (the transport of dissolved or
suspended matter due to the movement of the carrier fluid), and diffusion (the
transport from high to lOW concentration areas due to turbulence). These processes
assume very different characters in the immediate vicinity of the outfall structure
(discharge nearfield) and farther away from it (farfield) and different models are
used to analyze these two regions.
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In the discharge nearfield, the effluent undergoes rapid dilution with ambient water
because of turbulent entrainment. This dilution is enhanced by discharge through
the multiport diffuser, which distributes the effluent over a number of individual
jets eventually merging into a single line plume. In the nearfield, the main
driving forces are buoyancy and, to a lesser degree, the discharge momentum of the
effluent. Because of buoyancy, the effluent plume rises through the water column
while entraining ambient water (Figure ‘L2.1.a). When the water column is
stratified, the density of the plume may reach that of the ambient because of
previous entrainment of deep, dense ambient waters. In this case, the plume reaches
a maximum height of rise. For unstratified conditions, the plume rises all the way
to the water surface and typically achieves greater dilution. The dynamics of the
nearfield plume are controlled by the diffuser characteristics (primarily its
length), the ambient current speed and direction relative to the diffuser axis, and
the ambient density stratification profile. The time that the effluent spends in
the nearfield is relatively short (on the order of a few minutes) and, therefore,
the effects of the constituent-specific physical, chemical or biochemical reactions
is negligible.
The multiport diffuser is made up of a line of individual or multiport risers
(Chapter 3). In order to achieve maximum dilution for a given diffuser length, the
port spacing must be sufficiently small to insure that all the ambient crossflow is
intercepted and optimum dilution of the effluent is achieved by orienting the
diffuser perpendicularly to the ambient current direction. Hydraulically, the
diffuser must be designed to insure seawater purging, uniform flow distribution
among ports and sufficient velocities in the conduit to avoid settling (Fischer et
al., 1979).
In the farfield, the diluted effluent is carried by ambient currents, undergoing
additional mixing by large scale turbulent diffusion. This mixing is largely
controlled by the large scale circulation patterns in Massachusetts Bay. The
effluent becomes mixed vertically over the water depth. During stratified
conditions, the effluent may remain trapped under the pycnocline and, in these
critical conditions, become mixed in the lower layer only. This represents the most
critical condition in terms of constituent concentrations and settling, since the
water depth is effectively reduced. On the other hand, the surface waters remain
relatively unaffected, with associated benefits such as reduced shoreline impacts.
The constituent—specific physical, chemical or biochemical fate processes play an
important role in the farfield, where residence times are longer. These processes
are reviewed below.
Dissolved Oxygen Exertion. Dissolved oxygen (DO) is consumed by carbonaceous and
nitrogenous biochemical oxygen demand (CBOD and NBOD), sediment oxygen demand (SOD),
and resuspension oxygen demand (RDOD). The latter occurs during storms or other
resuspension events, when organic sediments are put back in suspension and exert
additional DO demand. DO is replenished by surface reaeration (or diffusion through
the interface for effluent trapped in the lower layer), and photosynthetic
activity. These processes and their kinetics are further described in Appendix A.
Photosynthesis is only active during the day and, for conservativeness, its effect
were not taken into account in this analysis.
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Suspended Solids Deposition. Suspended solids (SS) remain in suspension because of
turbulence and their deposition is controlled by their fall velocity. The fall
velocity is a function of the particle sizes, ambient turbulence and suspended
solids concentration, which controls flocculation (Farley, 19814). For a given range
of suspended solids concentrations and ambient turbulence levels, experiments have
been conducted to determine the distribution of particles fall velocities (Cardoni
et al., 1986). For this SEIS, three fall velocities were used: 0.1, 0.01 and
0.001 cm/sec. Solids with a fall velocity lower than 0.001 cm/sec effectively do
not settle. The fraction of solids in each fall velocity range is given in
Table 5.1.1.b based on EPA, 1982b; Cardoni et al., 1986; and MWRA, STFP V,A, 1987.
TABLE 5.1.1. b. DISTRIBUTION OF DISCHARGED SOLIDS FALL VELOCITIES
Fall Velocity
(cm/see)
Primary
Secondary
0.1
5%
0%
0.01
20%
16%
0.001
35%
3k%
Does
not settle
140%
50%
itrients Cycling. The most important nutrient is nitrogen, since it tends to be
the limiting growth factor in estuarine and coastal areas (Appendix C). Nitrogen is
supplied by the effluent primarily in the form of ammonia and, following discharge,
undergoes a number of bio-chemical reactions and transformations within the nitrogen
cycle. During the summer, nitrogen is recycled very rapidly and it can be assumed
that nitrogen is a conservative substance.
ieal Decay Processes. Organic chemicals discharged in the effluent will be
subject to the following removal processes in the water column: vaporization,
hydrolysis, photolysis, biodegradation and adsorption onto suspended solids followed
by settling. Each of these processes approximately follows a first order decay
(decay rate proportional to the constituent concentration), with a rate constant
dependent on the chemical and other ambient. For each organic chemical and each
process, MWRA estimated a rate constant, from which combined rate constants were
calculated. Based on these, three classes were identified, characterized by half
lives (time required for one half of the concentration to decay) of 20 days, 60 days
and no decay, in to which the organic chemicals were placed (MWRA, STFP V,A,
1987). These estimates of half lives were reviewed and found to provide an adequate
characterization of the decay processes. This classification was therefore used for
the Draft SEIS analyses.
Inorganic chemicals, primarily metals, can exist many different forms, depending on
ambient factors such as pH and ligand concentrations, with different bioavailability
and toxicity. The primary physico-chemical fate process undergone by these
chemicals is adsorption to suspended solids followed by settling. The degree of
adsorption and settling, however, is difficult to predict and, therefore, these
chemicals were treated as conservative (no decay) for water column concentration
5—5

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predictions. This is a conservative approach because a significant portion of the
metals were also assumed to be deposited in the sediments (Appendix B and
Section 5.2).
5.1.1.5 Nearfield Dilution Modeling
The EPA nearfield dilution model ULINE was used for these analyses (Pluellenhoff et
al., 1985). Based on diffuser characteristics, effluent flowrate and density,
ambient current, and stratification, this model calculates the nearfield dilution
and maximum height of rise of the effluent plume. Recent studies have shown that
this model consistently underpredicts nearfield dilution (Appendix A
Section A.3.5.1); it was nevertheless used here because other available model
sometimes overpredict dilution and might thus not provide a conservative assessment
of impacts.
For each alternate diffuser site, a range of effluent flow, ambient current and
stratification conditions were considered. A probability of occurrence was
attributed to each of these parameters, to allow subsequent evaluation of compliance
with toxicity criteria, which involve a frequency of exceedance limit. The effluent
flowrates were the same for all the sites, based on MWRA estimates (MWRA, STFP V,A,
1987). For each site, the current speeds used in the simulations were the 10, 50
and 90 percentile speeds (Table 1 L2.1.a) measured at the lower current meters (since
the plume first experiences these currents and may stabilize below the upper current
meter in the summer). The density profiles used in the simulations were based on
site—specific temperature and salinity measurements. These profiles and their
probabilities are the same as those used by MWRA (MWRA, STFP V,A, 1987). Further
details on the nearf’ield modeling conditions are provided in Appendix A
(Section A.3.3.2).
The discharge depth used at each site was the depth below mean low water minus 1 .5 m
to account for riser height. The proposed diffusers have a length of 2000 m and
were assumed to be oriented at 115 degrees to the current, (MWRA, STFP V,A, 1987).
This intermediate value between 90°, which gives the highest dilution, and 0°, which
gives the lowest, was used by MWRA because current directions at the discharge sites
are variable. The current scatter plots at the proposed diffuser sites, however,
exhibit a strong biomodality (approximately east-west), suggesting that the
diffusers could be oriented perpendicular to the ambient current for a preponderence
of the time. Another consideration in the selection of a diffuser orientation is to
have the ports at the same elevation, to insure a uniform flow distribution among
all the ports. This would suggest that a preferred orientation is along the depth
contours, which tend to be north—south in the diffuser site areas. An average
orientation close to 90 degrees therefore appears desirable and achievable. This
orientation was therefore also considered in the analyses. A critical design
parameter for the diffuser is its length and sensitivity to this parameter was
investigated by also running the analyses for a 3000 m long diffuser.
For each diffuser site and design, between 120 and 135 sets of ambient conditions
were considered, as described above. The results are summarized in terms of 10, 50
and 90 percentile nearfield dilutions (Table 5.1.1.c), which are minimum dilutions
obtained 10, 50 and 90 percent of the time.
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TABLE 5. 1.1.c. NEARFIELD DILUTIONS
Diffuser
Configuration
Percentjle 2
SITE
2
SITE
14
SITE
5
Length(m)
0rientation
2000
145°
10
50
90
57
98
163
75
128
259
92
150
272
2000
90°
61
50
90
79
1114
222
105
150
369
190
388
3000
145°
10
50
90
72
120
232
91
159
385
122
196
14014
(1) Angle between diffuser and ambient current.
(2) Percent of the time that the dilution is less
For the 2000 m long diffuser oriented at 145 degrees to the currents (base case),
nearfield dilutions increase from Site 2 to Site 5, as expected. The increase of
50 percentile (median) dilution is 31 percent from Site 2 to 14 and 17 percent from
Site 14 to 5. The 10 percentile dilutions increase slightly more.
Orienting the diffuser at 90 degrees to the currents increases dilutions by an
average of about 23 percent, with larger increases for the larger dilutions
(90 percentile). This increase can be put in perspective by noting that the Site 14
diffuser at 90 degrees to the current provides essentially the same dilutions as the
Site 5 diffuser at 145 degrees.
The 3000 m long diffuser at 145 degrees to the currents provides an average increase
of’ dilution of 33 percent compared to the base case. This option should be
considered as it can potentially be achieved at minimal extra cost by increasing the
prn’t spacing and keeping the same number of ports.
5.1.1.5 Farfield Modeling
Farfield modeling simulates the transport and physio-bio—chemical processes which
take place over large distances and time scales (hours to weeks) after the nearfield
dilution. The results of the farf’ield modeling are i) constituent background build-
ups, ii) depletion of dissolved oxygen and iii) rates of effluent solids deposition
due to discharge at the alternative diffuser sites.
than the value indicated.
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Background concentration build-up develops in the discharge area as a result of the
returning ebb and flood of the tide, which bring previously discharged effluent back
in to the diffuser area. The magnitude of the background build-up is determined by
a balance of the input from the effluent discharge and removal rates of individual
constituents. The removal mechanisms are: i) transport by net drift
(Section 14.2.1.14), ii) horizontal dispersion and iii) natural decay phenomena
(Section 5.1.1.14). Perfectly symmetrical tidal currents do not provide any net
transport removal since their average velocity (net drift) is zero. The net drift
is the result of tidal asymmetries, winds, fresh water discharges and large scale
weather patterns and, as such, is variable in space and time (Section 14.2.1.4).
Periods of low net drifts result in temporarily higher background build-ups and the
duration of low net drift periods is therefore an important factor. The background
build—up represents the ambient water which is used for initial dilution of the
effluent in the nearfield.
Models and Methodologies. The hydrodynamic model TEA and companion water quality
transport model ELA were selected for the farfield modeling of this study. These
two-dimensional (vertically-averaged) finite element models account for the
location, magnitude and configuration of alternative effluent discharges, as well as
the effects of spacial and temporal variations in tidal and residual circulation,
turbulent diffusion and effluent constituent decay and sedimentation. These models
permit detailed resolution of complex coastal geometries as well as refined grid
resolution in areas of special interest. Further description of these models is
provided in Appendix A (Section A.3.6..2).
The finite element grid used for farfield modeling during unstratified conditions is
the same as that used by MWRA (Figure 5.1.1.a). The model grid is highly resolved
in Boston Harbor and in the vicinity of the alternative discharge sites where
concentration gradients are likely to be large. Lower resolution is used in
portions of Massachusetts Bay removed from the alternative discharge sites. This
grid is more resolved than in any previous numerical models of Boston Harbor and/or
Massachusetts Bay.
TEA and ELA were also used to simulate discharge under vertically stratified
conditions, during which the effluent plume would be trapped below the pycnocline.
For this purpose, the grid was modified by decreasing nodal depths to include only
those below a 15 meter—deep pycnocline, which corresponds to observed summer
stratified conditions. As a result, most of’ the shallow nodes within Boston Harbor
and numerous nodes along the land boundaries of the original grid were eliminated
(Figure 5.1.1.b).
The TEA model of Boston Harbor and Massachusetts Bay used to simulate circulation in
non-stratified conditions was recalibrated during preparation of this Draft SEIS to
more accurately simulate the semi-diurnal tidal circulation observed at the current
meters during the Spring of 1987. The tidal forcing specified at the ocean boundary
of TEA was recalculated based on a harmonic analysis of the tide gauge data and the
bottom friction coefficient was readjusted. A similar calibration was performed for
stratified conditions.
Net drifts are produced in the model by specifying a slope (tilt) at the ocean
boundary. Results of the net drift analysis of the 1987 current meter data indicate
that net drifts can be either towards the south or north in the vicinity of the
5-8

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GLOUcESTER
FIGURE 5.1.1.a MODEL GRID FOR UNSTRATIFIED CONDITIONS
BOSTON
OCEAN BOUNDARY
PLYMOUTh
5-9

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FIGURE 5.1.1.b MODEL GRID FOR STRATIFIED CONDITIONS
GLOUCESTER
BOSTON
HARBOR
OCEAN BOUNDARY
PROV1NCETOWN
PLYMOUTH
HARBOR
5-10

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alternative discharge sites (Section Zt.2.1.k). Therefore, TEA was run with both
steady north-to—south and south-to-north boundary tilts. Tilts of 10 cm between
Gloucester and Provincetown were found to provide net drifts similar to those
measured. The net drift analysis also indicated that periods of low net drift
occurred and, accordingly, TEA was also run with no boundary tilt.
The water quality model, ELA, was used to simulate both stratified and
non-stratified conditions with discharge of conservative and first-order decaying
constituents (20 and 60—day half lives) at the alternative sites. A base
constituent mass loading of 200 mg/sec was simulated at each diffuser site. Because
of linearity, concentrations are proportional to the loading and these base
simulations can be used for any constituent. Results can be converted to individual
constituents by multiplying the computed concentrations by the ratio of the actual
loading to the simulated loading of 200 mg/sec.
The modeling approach was to compute “average” concentrations corresponding to
average net drift conditions and “worst case” concentrations corresponding to zero
net drift for a period of time. The “average” simulations were continued until
steady state (tidally repeating concentrations) was reached. The net drift analyses
showed that relatively stagnant periods of low drift can persist in Western
Massachusetts Bay for up to approximately 10 days (Section LL2.1.14). Accordingly,
worst-case ELA simulations were conducted for that duration.
Contour plots of concentration for all the ELA runs are given in Appendix A.e. Plots
of the results for a conservative tracer under average net drift, vertically
unstratified conditions for Sites 2 and 5 are shown in Figure 5.1.1.c and 5.1.1.d
respectively. It is seen that the constituent concentrations are higher at Site 2
than at Site 5.
Background build—ups were determined using concentrations computed with the
discharge stopped for one tide cycle before the display time. Background build-ups
with the north-south and south-north boundary tilts were found to be closely equal
and only north-south tilts were considered for the majority of the simulations.
Background build-up results are given in Table 5.1.1.d. It is seen that sensitivity
to constituent decay rate is generally small, being greatest at Site 2 and least at
Site 5. Differences between build-up during average and worst-case stagnant
conditions is greatest at Site 5 and least at Site 2 because net drift currents at
Site 2 are lower, and thus closer to non-net-drift conditions, than at Site 5.
Dissolved Oxygen. For dissolved oxygen simulations, ELA was modified to include the
processes of carbonaceous and nitrogenous BOD decay, reaeration and sediment oxygen
demand. Predicted contour plots of dissolved oxygen deficit for primary treated
effluent discharged at Sites 2 and 5, under average net drift, stratified
conditions, are shown in Figures 5.1.1.e and 5.1.1.f, respectively. DO deficits are
the amounts by which DO is lowered below the ambient by the discharge. Contour
plots for all DO deficit simulations are given in Appendix A.g. Maximum DO deficits
averaged over an area of approximately 1.5 2 representative of the mixing zone are
listed in Table 5.1.1.e.
5—11

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FIGURE 5.1.1.c
CALCULATED FARFIELD CONCENTRATIONS (mg/i)
FOR BASE LOADING (200mg/eec)
DIFFUSER SITE 2
UNSTRATIFIED WATER
AVERAGE NET DRIFT
CONSERVATIVE CONSTITUENT
HIGH WATER
OWN
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FIGURE 5.1.ld
CALCULATED FARFIELD CONCENTRATIONS (mg/i)
FOR BASE LOADING (200mg/sec)
DIFFUSER SITE 5
UNSTRATIFIED WATER
AVERAGE NET DRIFT
CONSERVATIVE CONSTITUENT
HIGH WATER
p
QUINCY
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TABLE 5.1.1 .d BACKGROUND BUILDUP (ng/l) FOR BASE LOADING (200 nig/sec)
Stratification Net Drift Half Life Site 2 Site 14 Site 5
Unstratified Average 20 days 125 75 38
60 days 1414 81 140
Conservative 158 86 41
Worst 20 days 127 81 68
60 days 150 101 73
Conservative 166 108 75
Stratified Average 20 days 4143 178 78
60 days 507 196 81
Conservative 550 208 83
Worst 20 days 1451 205 123
60 days 5214 230 132
Conservative 576 2148 137
5_ill

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FIGURE 5.1.1.e DISSOLVED OXYGEN DEFICIT (mg/i) FOR PRIMARY DISCHARGE
AT SITE 2 UNDER STRATIFIED CONDITIONS, AVERAGE NET DRIFT.
1.0
5-15

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FIGURE 5.l.1.f DISSOLVED OXYGEN DEFICIT (mg/I) FOR PRIMARY DISCHARGE
AT SITE 5 UNDER STRATIFIED CONDITIONS, AVERAGE NET DRIFT.
0.06
\
0.1
\
‘1
2
5-16

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TABLE 5.1.1.e MAXIMIJII DISSOLVED OXYGEN DEFICITS (mg/1)( 1
itment Stratification Net Drift Site 2 Site 14 Site 5
Primary Unstratified Average 0.91 0.63 0.21
Worst 0.92 0.80 0.58
Stratified Average 14.15 1.56 0.39
Worst 14.22 1.91 1.03
Secondary Unstratified Average 0.53 0.38 0.114
Worst 0.514 0.148 0.35
Stratified Average 1.76 0.69 0.19
Worst 1.81 0.87 0.146
(1) Averaged over area of approximately 1.5 km 2 , representative of the mixing
zone.
5—17

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Sedimentation. Sediment deposition rates were determined for primary and secondary
treated effluent discharges at the alternative sites, under both stratified and
unstratified average net drift conditions. Simulations were carried out for fafl
velocities of 0.1, 0.01 and 0.001 cm/sec until steady-state results were achieved
and total sediment accumulation rates were determined by suimning the accumulation
rates for each fall velocity prorated by the appropriate percentage (Table 5.1.1.b).
Contour plots of the resultant total sediment accumulation rates for primary and
secondary discharges at Site 5 under stratified conditions are given in
Figures 5.1.1.g and 5.1.1.h. At Sites 2 and k, the deposition was found to be more
concentrated spacially, with higher deposition rates over smaller areas. These
predicted sedimentation rates were used in Appendix B to determine sediment
concentrations of effluent constituents. The sedimentation rates were also used in
Appendix C to determine benthic enrichment.
5.1.1. 6 SHORELDIE IMPACT ANALYSES
Shoreline concentrations of discharged constituents were determined as part of the
farfield modeling. However, the fart ield analyses considered average and zero net
drift conditions, and the highest shoreline concentrations can be expected as a
result of sustained net drifts towards shore, most likely due to critical wind
events. A different model was therefore used for the shoreline impact analyses.
The worst shoreline impacts will occur when the plume surfaces and is driven to the
shore by ambient current. However, it is conceivable that upwelling of lower layer
waters at the shoreline, due to a combination of events, could bring a submerged
plume to the shoreline. Therefore, the protecting influence of stratification was
neglected and the same analyses were conducted for stratified and non-stratified
conditions.
The quasi-analytical MIT Transient Plume Model (TPM) was used for the shoreline
impact analyses (Adams et al., 1975). This model simulates a discharge as a
succession of puffs (or short duration releases of effluent) which are individually
transported by the current and superimposed for continuous discharge simulations.
An advantage of this approach is that it allows realistic three-dimensional
diffusion of the effluent plume. The currents used to drive the model are assumed
to be spacially uniform, which is an obvious limitation, but also permits measured
currents to be used, representing actual events.
Analyses were conducted with the Transient Plume Model using MWRA current meter data
for spring and sumer 1987 (MWRA, STFP V,G, 1987). Simulations of discharges at
each of the three alternative diffuser sites used current records from the nearest
current meter station. Maximum shoreline concentrations at Swampscott, Mahant, Deer
Island and Hull are listed in Table 5.1.1.f in percent of the discharge
concentration.
5.1.1.7. Criteria Co 1iance Evaluation
5.1.1 7.1 Dissolved Oxygen. The dissolved oxygen criterion of the applicable
Massachusetts Surface Water Quality Standards is a minimum value of 6 mg/i anywhere
in the water column after hydraulic mixing and consideration of natural background
conditions (3111 CMR 11.02) (Table k.2.2.1.b).
5-18

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MARBLEHEAD
FIGURE 5.1.1.g ELA PREDICTED SEDIMENTATION RATES SITE 5,
SECONDARY TREATMENT, STRATIFIED CONDITIONS (g/m 2 lday)
O.6O
p
HARBOR
NANTA ET
DUXBURY
5-. 19

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MARBLEHEAD
FIGURE 5.l.l.h ELA PREDICTED SEDIMENTATION RATES, SITE 5,
PRIMARY TREATMENT, STRATIFIED CONDITIONS (g/m 2 /day)
2.23:
0.6
0.3
BOSTON
HARBOR
NANTASKET
DUXBURY
5-20

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TABLE 5.1.1. f MAXIMUM SHORELINE CONCENTRATIONS (IN PERCENT OF THE
DISCHARGE CONCENTRATION) PREDICTED WITH SPRING AND SUMMER 1987 CURRENT DATA
Site 2
Site 14
Site 5
swampscott
0.65
0.58
0.57
tiahant
1.01
0.55
0.58
Deer Island
1.27
0.19
0.2 4
Hull
0.56
0.32
0.141
Dissolved oxygen deficits have been predicted in the farfield analyses
(Section 5.1.1.6). Contrary to individual constituents discharged in the effluent,
dissolved oxygen deficits develop over a time scale of several days as a result of
the BOD exertion. Therefore, the largest DO deficits are obtained in the farfield
modeling and those were listed in Table 5.1.1.e for the different sites and
operating conditions. Actual DO levels will be equal to the ambient value minus the
DO deficit.
The ambient DO Is almost always above 8 mg/i (Section 14.2.2.2) both in the upper and
lower water column. During the fail, however, the ambient DO can drop to 6.5 mg/i
or less in the lower layer (Section 14.2.2.2). At that time, however, the pycnocline
is very deep and weak and would not be able to trap the effluent plume in the lower
layer. The thickness of the lower layer would be about 3 m at Site 2 to 13 m at
Site 5, with strong tidal variations, and these depths are not sufficient to contain
the effluent plume. Therefore, DO values in-the lower layer would not be reduced by
DOD exertion from the effluent. The low ambient DO values, however, would be
reduced by resuspension of sediment deposited during the summer and this aspect is
considered separately below.
.itside of resuspension events, therefore, and in areas affected by the effluent, a
low estimate of the ambient DO concentration is 8 mg/i and minimum DO levels due to
the effluent are listed in Table 5.1.1.g.
Resuspension Oxygen D and. Further dissolved oxygen exertion can occur as a result
of sediment resuspension during storms or other events. The dissolved oxygen demand
resulting from a resuspension event, RDOD, can be estimated based on the sediment
deposition rates (EPA, 1982b) and is fully discussed in Appendix A (Section P.3.8).
For spring and summer conditions, 8 mg/i represents a low estimate of the ambient
DO; and the minimum DO concentration, during a resuspension event, is equal to the
ambient DO minus the farfield DO deficit (Table 5.1.1.f) minus the resuspension DOD’
demand. During the fall, lower layer ambient DO concentrations drop to about
6.5 mg/l. However, the effluent does not remain trapped in the lower layer and the
minimum DO concentration, during a resuspension event, is therefore equal to the
ambient DO minus the resuspension DO demand only. The corresponding minimum DOs are
listed in Table 5.1.1.h.
5—21

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IN THE WATER COLUMN 1
Site 14 Site 5
7.14 7.8
7.2 7 14
6.14 7.6
6.1 7.0
7.6 7.9
7.5 7.7
7.3 7.8
7.1 7.5
TABLE 5.1.1.g
Treatment
Primary
Secondary
MINIMUM DISSOLVED OXYGEN CONCENTRATIONS
Stratification Net Drift Site 2
Unstratified Average 7.1
Worst 7.1
Stratified Average 3.9
Worst 3.8
Unstratified Average 7.5
Worst 7.5
Stratified Average 6.2
Worst 6.2
(1) Equal to ambient DO (8 mg/i) minus maximum DO deficient (Table 5.1.1.e).
TABLE 5.1.1 .h MINI4JM WATER COLU)SI DISSOLVED OXYGEN CONCENTRATIONS
DURING RESUSPENSION EVENT (ugh)
Treatment Stratification Net Drift Site 2 Site 14 Site 5
Primary Unstratified Average 6.5 6.7 7.2
Worst 6.5 6.5 6.8
Stratified 1 Average 2.3 5.3 6.8
Worst 2.2 5.0 6.2
Fall 2 5.0 5.14 5.7
Secondary UnstratifiedW Average 7.3 7.5 7.8
Worst 7.4 7.4 7.6
Stratified Average 5.9 7.1 7.7
Worst 5.9 7.0 7.14
Fail 2 6.2 6.3 6.14
(1) Equal to ambient DO (8 mg/i) minus maximum f’arfield DO Deficit (Table 5.1.1.e)
minus resuspension oxygen demand.
(2) Equal to ambient DO (6.5 mg/i) minus resuspension oxygen demand.
5—22

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The smallest minimum DO concentration is generally obtained for primary effluent, in
stratified, worst net drift conditions, after a resuspension event. These values
can be obtained only once per year, at the end of the summer and assume the
following combination of events: no resuspension event during 90 days in the
summer, followed by a 10 day period of zero net drift, followed by a resuspension
event. Given the limited expected duration of primary discharge, it is likely that
such an event will never be experienced.
For secondary discharge, the results show that the 6 mg/l standard would not be
violated at any site, except by 0.1 mg/i at Site 2 during stratified conditions.
For primary discharge, the standard would be violated at Site 2 during resuspension
events for both stratified and non—stratified conditions. At Site 14, the standard
would be violated during resuspension events occurring while the water column is
stratified. The violations during resuspension events would be over a depth of
approximately 10 m from the bottom. Unfortunately, data are not available to
indicate how frequently resuspension events can occur at the various sites during
stratified summer conditions. The large storms leading to resuspension occur most
often in the winter when DO levels are usually higher.
5.1.1.7 2 pH
Changes in pH in the ambient water will arise due to the pH of the effluent and its
alkalinity. Using a range of ambient water temperatures, carbon dioxide content and
pH, with an effluent alkalinity of 0.5 to 1.0 meq/l and pH of 6.5 to 7.0, MWRA
estimated a range of pH values of 7.6 to 8.3 at the edge of the mixing zone for
secondary effluent discharge. These estimates are based on a minimum nearfield
dilution of 10:1 and are therefore applicable to all sites (MWRA, STFP V,A, 1987).
For primary effluent discharge, changes in ambient water pH were estimated
experimentally by MDC by diluting a mixture of Deer Island and Nut Island effluents
with Massachusetts Bay water in ratios of 20:1, 140:1, 500:1, and 1600:1 (MDC,
19814). The initial pH of the seawater was 8.1 and the measurements indicated that
no significant change occurred for the duration of the tests (19.5 hours). The
minimum pH of any mixture was 7.8.
The Massachusetts Water Quality Standards require the pH to be in the range of 6.5
to 8.5, with a maximum change of 0.2. The analyses and tests described above
Indicated that pH values for primary and secondary discharges will be within the
required range at all the alternative diffuser sites. Additional testing is
proposed by MWRA to show that the change will not exceed 0.2. (HWRA, STFP V,A,
1987).
5.1.1.7 3 Mixing Zone Criteria. The EPA water quality criteria (14.2.2.1) apply at
the edge of the mixing zone, which is defined as the end of the zone of initial
dilution, when the plume either reaches the surface or its final intermediate height
of rise.
Concentrations at the edge of the mixing zone are made up of the following
components: i) nearfield concentration, ii) background build-up concentration,
iii) concentration due to other discharges into Massachusetts Bay and iv) ambient
concentration. Because the dilutions are large, these concentrations are additive.
5—23

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Nearfield Concentrations are equal to the effluent concentrations divided by
the riearfield dilution; the effluent concentration being equal to the
constituent loading divided by the flowrate. The nearfield dilution depends on
the flowrate, among other parameters, but it can be assumed that the loadings
are independent of the flowrate, even though at first, high flows during storms
carry higher loads. The probability of any nearfield concentration occurring
is then equal to the product of the probabilities of the flowrate, current
speed, stratification profile and constituent loading.
Background Build-up Concentrations were calculated in the farfield modeling
for stratified arid non-stratified water columns under average and worst net
drift conditions. Based on a review of the net drift persistence plots
(Appendix A.c), a probability of occurrence of 90 percent was attributed to the
average background build-ups and 10 percent to the worst case build-ups.
Concentrations from Other Sources were calculated by MWRA, accounting for
discharges from Lyrin/Saugus, Swampscott, South Essex Sewerage District (SESD)
and the inner harbor combined sewer overflows (CSOs). Since these discharges
are far from the alternative diffuser sites, their contribution is the result
of long term processes and-, therefore , average net drift conditions can be
used. These concentrations were obtained through the TEA/ELA farfield models
with loading estimates for each constituent of interest (Appendix A,
Table A.3.12). Values were not available for some constituents, such as
pesticides, and therefore, their loadings were taken equal to zero.
Ambient Concentrations represent concentrations present in Massachusetts Bay
due to previous discharges and other inputs. These are assumed to be uniform
over the Bay and were estimated from measurements far from known sources
(Section 1t.2.2.3). Measurements were not available for all constituents and
zero ambient concentrations were assumed in case of lack of data.
The EPA Water Quality Criteria for aquatic life toxicity involve concentrations not
to be exceeded with a frequency greater than a specified value. For acute toxicity,
the limiting concentrations are the Criteria Maximum Concentrations (CMC) which must
not be exceeded with a frequency of more than 1 day in 3 years. For chronic
toxicity, the limiting concentrations are the Criteria Continuous Concentrations
(CCC), which must not be exceeded for more than k consecutive days every 3 years.
The CMC and CCC concentrations are listed in Table 1 4.2.2.c. In order to evaluate
compliance with the aquatic life toxicity criteria, a joint probability analysis was
conducted (Appendix A, Section A.3.8.7).
The EPA Water Quality Criteria human toxicity and carcinogenicity are based on long
term, (lifetime) exposure and fish consumption and, therefore, their compliance was
addressed by comparing the average expected edge of mixing zone concentrations
(statistical expected values) to the criteria concentrations.
All chemicals on EPA’s Priority Pollutant and Hazardous Substances lists were
orginally included in this analysis. MWRA conducted a screening analysis which
identified the constituents of concern. Many constituents were present at levels
below the Water Quality Criteria In the effluent and thus also at all sites. The
constituents which did exceed either aquatic life or public health criteria at the
5—2 4

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edge of the mixing zone are summarized in Table 5.1.1.i in terms of the ratios of
calculated concentrations to criteria concentrations. Thj table shows that some of
the exceedances are by a small amount and others by several orders of magnitude.
Exceedances by ambient waters for the arsenic and PCBs carcinogenicity criteria
occur at all sites. For PCBs, but not for arsenic, the criterion would be exceeded
because of the discharge, even in the absence of any ambient concentration.
For secondary treatment, Table 5.1.1.1 shows that Site 5 does pot exceed any aquatic
lif criterion and exceeds 5 human health criteria at the 10—0 risk factor. At the
1O ’ risk factor, Site 5 exceeds only two human health criteria (arsenic and PCBs),
which are already exceeded by the ambient. Site 14 exceeds one more criterion than
Site 5 (CCC Mercury).
For primary treatment, a larger number of criteria exceedances at the io 6 risk
level occurs: 12 for Sites 2 and 14 and 11 for Site 5. For the 10 risk level,
11 criteria are exceeded at Site 2, 10 at Site 14 and 8 at Site 5.
5.1.2 SEDIMENT QUALITY
A simulation of the composition of bottom sediment in Massachusetts Bay was
conducted to assess changes that will take place following initiation of primary and
secondary effluent discharges at the alternative diffuser locations. The wastewater
discharge will cause increased sediment accumulation due to deposition of effluent
solids. The chemical constituents contained in the effluent solids will result in a
change in the concentration of these chemicals in the bottom sediments. In general,
greater deposition of effluent solids results in greater increase in bottom sediment
chemical content. A summary of the methods used to assess these increases and the
resulting concentration changes is presented in this section. A full description of
the simulation process and results is provided in Appendix B, Marine Geology and
Sediment Deposition. The marine biological impacts associated with the change in
bottom sediment chemical content are presented in Section 5.1.3.2, Sediment
Toxicity.
5.1.2.1 SEDIMENT CHEMISTRY SIMULATION METHODS
Effluent suspended solids deposition was evaluated at the alternative discharge
sites for both primary and secondary treatment using the models TEA-NL and ELA
(Appendix A). The deposition contours from this analysis are important to the
simulation of bottom sediment chemical concentrations. An effluent solids chemical
concentration was estimated for each constituent of concern (Appendix B). In
addition, the concentration of chemicals associated with the background water column
sediments and the background sediments were estimated. These values were used in
the simulation to account for settling of background solids and distribution mixing
of settled solids with existing bottom sediments. The effluent solids deposition
pattern and background bottom sediment chemical content varies for each discharge
site based on predicted effluent solids deposition and measured values in
sediments. The background water column solids deposition is assumed the same at all
sites. The simulation of sediment chemistry impacts therefore varies for each of
the discharge sites. The three discharge sites under consideration were evaluated
for the following conditions:
5-25

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TABLE 5.1.1.1 SUMMARY OF PREDICTED WATER QUALITY CRITERIA EXCEEDAJICES
Criterion
Constituent Ambient
CONCENTRATION/CRITERION
Primary
Site 2 Site 14 Site 5 Site
RAT
os 1)
Secondary
2
Site
14 Site 5
CMC
copper 2.1 1.26
CCC
heptachior 3.149 2.11 1.51 1.01
1 4, 4’—DDT 3.55 1.99 1.311
mercury 4.96 3.14 2.18 1.90 1.26
PCBs 2.37 1.116 1.09
Carcinogenicity
(10 risk factor)
aidrin 13.30 6.02 3.26 1.111
l4, 1 1’-DDT 11.140 5.014 2.65 1.21
heptachior 3.66 1.73
dieldrin 1.57
arsenic 2.85 3.51 3.17 3.014 3.32 3.09 2.99
PCBs 9.214 72.75 38.00 214.80 14.69 1.70 10.57
(10-6 risk factor)
aidrin 133.1 60.23 32.11 114.08 6.35 3.113
4, 1 4’—DDT 1114.1 50.38 26.146 12.08 5.33 2.79
heptachior 36.614 17.30 9.81 11.30 2.03 1.15
dieldrin 15.68 6.02 3.26 1.66
fluorene 7.50 3.56 2.014
arsenic 28.145 35.07 31.75 30.37 33.25 30.95 30.814
PCBs 92.140 727.50 379.78 2147.96 146.86 117.00 105.70
(1) ConcentratIon 4 Criterion (e.g. at Site 2, for primary, the predicted
concentration is 2.1 times the CMC criterion).
5—26

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• Nonstratified conditions for five years duration, primary and secondary
effluent;
• Nonstratified conditions for one year duration, primary and secondary
effluent;
• Stratified conditions for six months duration, primary and secondary
effluent; and
• Stratified conditions for six months duration, no bioturbation mixing
(rocky bottom), primary and secondary effluent at Site 5 only.
Under stratified conditions, sediment concentrations will be higher but over a
smaller area because the effluent is trapped at a lower depth and settles at greater
concentrations near the diffuser. Stratified conditions were evaluated for six
months duration, since this condition would not be maintained over the full year.
tjonstratified conditions were evaluated for six months, one year and five years
duration to evaluate the change in impacts with time.
The case of no bioturbation mixing under stratified conditions was evaluated to
assess the potential worst—case impacts at a site where there is minimal existing
bottom sediment accumulation due to seasonal resuspension (such as hard rock
surfaces), but where periods of sediment accumulation occur between resuspension
events. This is a worst-case condition because there is no dilution of effluent
solid chemicals with background solids. This condition would occur only within the
portion of the predicted deposition area with no previously accumulated sediments.
This is presumed to be a relatively small area and thus does not represent the
general case.
The chemicals which are a potential problem under primary effluent conditions were
evaluated for secondary effluent conditions (bis(2—ethylhexyl)phthalate, DDT, PCB,
Zn). The background bottom sediment concentrations used in the secondary effluent
simulations are the results of the primary effluent simulations under nonstratified
conditions after five years duration. This is based on the assumption that
secondary treatment will begin approximately five years after the primary
discharge. The modified background bottom sediment concentration for secondary
treatment is the weighted average of five years primary effluent simulation
concentration over the entire deposition area.
5.1.2.2 SU44ARY OF SEDIMENT SIMULATION RESULTS
For nearly all compounds, the highest simulated pollutant sediment concentrations
occur at Site 2 and the lowest concentrations at Site 5 (Tables 5.1.2.a, b, c and
d). For several metals, the highest background bottom sediment concentrations occur
at Site 1 , and therefore, in some cases, high simulated concentrations also occur at
Site IL
The worst case simulation is the case of primary effluent with no bioturbation for
six months duration. In this case, it is assumed that effluent and background water
column solids are deposited on a rocky bottom with no dilution with existing bottom
sediments. This case could occur at any location where sediment resuspension has
exposed a rocky bottom substrate. ROV Studies (MWRA, STFP V,O, 1987) indicate that
5-27

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TABLE 5.1.2 .a. COMPARISON OF SIMULATED MAXIMUM SEDIMENT POLLUTANT CONCENTRATIONS,
PRIMARY EFFLUENT, 5 YEARS DURATION, NONSTRATIFIED CONDITIONS
Background Concentration (ug/g) Maximum
Simulated
Concentration (ug/g)
Site 5 Site 2 Site 14 Site 5
Chemical
Site
2
Site
It
PCBs 0.01 0.02 0.01 1.38 1.03 0.77
Metals
Arsenic 2.87 5.53 14.62 3.79 5.78 4.97
Copper 12.56 17.88 6.71 130.63 1014.02 72.30
Mercury 0.15 0.17 0.11 1.82 1.141 1.014
Nickel 4.66 9.214 4.88 29.67 28.72 21.00
U, Selenium 2.00 2.00 2.00 11.12 8.65 6.92
Silver 2.44 0.10 0.10 7.88 4.140 3.28
Zinc 26.12 47.514 25.03 283.20 233.63 166.69
Pesticides
Aidrin 0.014 0.014 0.04 0.30 0.23 0.18
4,4-DDT 2 0.014 0.014 0.04 0.114 0.11 0.09
Dieldrin 2 0.014 0.04 0.014 0.014 0.014 0.014
Heptachlor 0.04 0.014 0.04 0.13 0.10 0.09
Acid Base Neutrals
Bis(2—ethylhexyl)phthalate NA 1 NA NA 20.21 14.89 11.02
Butylbenzyl phthalate NA NA NA 114.19 10.146 7.74
Di—n—octylphthalate NA NA NA 22.71 16.714 12.39
1. NA No data available - zero background concentration assumed.
2. Analyzed for public health impacts only.

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TABLE 5 • 1 • 2 • b • C 1PAEISON CF SIMULATED MAX IMW4 SEDIMENT POLLUTANT CONCENTRATIONS,
PRIMARY EFFLUENT, 6 MONTHS DURATION, STRATIFIED CONDITIONS
Background Concentration (ug/g) Maximum
Simulated
Concentration
(ug/g)
Site 2 Site 14 Site 5 Site 5(3)
Chemical
Site
2
Site
11
Site
5
¼
PCBs
Me ta is
Arsenic
Copper
Mercury
Nickel
Selenium
Silver
Zinc
Pesticides
Aidrin
l ,14_DDT’: )
Dieldrin’ 2)
Heptachior
Acid Base Neutrals
Bis(2-ethyihexyl)phthalate
Butylbenzyl phthalate
D i-n-octy lphthalate
2.87
12.56
0.15
14.66
2.00
2. 1j14
26. 12
0.014
0.0k
0.011
0.0k
0.01
0.02
0.01
0.141
0.22
0.15
5.57
5.53
4.62
3.10
5.58
14.68
6.82
17.88
6.71
117.211
35.51
18.8k
1490.85
0.17
0.11
0.614
0.142
0.28
6.914
9.2k
11.88
10.98
12.71
7.56
112.02
2.00
2.00
11.65
3.36
2.92
38.50
0.10
0.10
14.011
0.98
0.69
23.69
117.514
25.03
101.39
85.56
51.19
1068.814
0.011
0.011
0.12
0.08
0.07
1.08
0.04
0.011
0.07
0.05
0.05
0.113
0.011
0.014
0.011
0.011
0.014
0.03
0.011
0.014
0.07
0.05
0.05
0.39
NA 1
NA
NA
5.95
3.05
2.05
81.78
NA
NA
NA
14.18
2.14
1. 14 1 4
57.115
1. NA No data available - zero background concentration assumed.
2. Analyzed for public health impacts only.
3. No bioturbation mixing analyzed on Site 5 only.

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TABLE 5.1 .2.c. COMPARISON OF SIMULATED MAXIMUM SEDIMENT POLLUTANT CONCENTRATIONS,
SECONDARY EFFLUENT, 5 YEARS DURATION, NONSTRATIFIED CONDITIONS
Background Concentration ( g/g) Maximum Simulated Concentration ( g/g )
Chemical Site 2 Site it Site 5
Site 2
Site it
Site 5
PCBs
0.10
0.10
0.11
0.33
0.27
0.21
Zinc
i t2.50
61.81$
‘$3.06
85.53
91.10
62.98
‘ $,14-DDT
0.0 ’ $5
0.0 t5
o. O’t6
006
0.06
0.05
Bis(2-.ethylhexyl)phthalate
1.08
1.06
1.21
1t.28
3.3L 1
2.5 4
in
0

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TABLE 5.1.2.d.
SLJ)I4ARY OF SITE- -SITE COMPARISON OF SEDII€NT POLLUTANT CONCENTRATIONS
PCB Background
0.5 Y ars Stratified
Kin’ >0.1 ug/g
5 Yea s Unstratified
Km >0.1 ug/g
Bis phthalate Background
0.5 y ars stratified
Km >7.2 ug/g
5 yea s unstratified
Kin >7.2 ug/g
DDT Background
0.5 y ars stratified
Kin >0.07 ug/g
5 yea s unstratified
Km >0.1 uglg
0.01 0.02
3.5 2.14
17.7 13.6
NA NA
0 0
2.8 2. l
0.0 11 0.014
0 0
1.4 0.9
0.01 0.01
1.3 ,50.1
10.14
NA
0 35.6
1.6
0.014
0 50.1
0
0.1 0.1
16.9 9.8
6.2 5.2
1.1 1.1
0 0
0 0
0.05 0.05
0 0
0 0
0.1 0
7.5 >7.5
14.5
1.2 0
0 5.7
0
0.05 0
0 7.5
0
ZN Background
0.5 y ars stratified
Km >709 ug/g
5 yea s unstratified
Km >709 ug/g
26.1 147.5
0 0
0 0
25.0
0 3. 1 1
0
112.5 61.8
0 0
0 0
143.1 0
0 0
0
(a) Hard Bottom area; only hard rock surfaces within the area would be at the concentration.
Primary
Site 2 Site 14 Site 5 5HB
Secondary
Site 2 Site 14 Site 5 5HB
U i
-a
(b) For PCB at Site
somewhat higher
area was used at
actually smaller
5, for secondary effluent, the predicted depositions in Table B.3.e (Appendix B) are
than for Site 14. This is an artifact of the prediction method because a much smaller
Site 5 to estimate weighted average after 5 years of primary. Since the rates are
at site 5 than at site it, rates have been used in this calculation.

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rocky substrate is more prevalent in the immediate vicinity of Site 5 than Site ) ,
and minimal at Site 2. Therefore, the analysis was done only for Site 5
(Table 5.1.2d). These concentrations would only occur in the limited portion of
the depositional area where horizontal hard rock surfaces occur.
The results presented herein are most useful in comparing relative impacts between
sites. Figure 5.1.2.a presents a comparison of the PCB simulations for primary
effluent, 5 years duration, with similar trends occurring for the other compounds
analyzed. The projected PCB levels represent a range associated with PCB
contamination elsewhere in New England. These concentrations would be 10 (soft
bottom) to 100 (rock surface) times higher than concentrations presently
characteristic of Sites 2, 14, and 5. The maximum values fall within the range of
0.3—78 ug/g reported for the New Bedford Outer Harbor (Boehm et al., 198)4 and
Hillman et al., 1987). They also overlap the upper end of the range of PCB
concentrations of the more contaminated sediments in Boston Inner Harbor
(0.1-O.k ug/g; Boehm et al., 1984). While the projected soft-bottom sediment values
are less than those projected for hard bottoms, they still overlap the ranges of
potential concern cited above within the immediate vicinity of the outfall, even at
Site 5.
The existing background concentration at the alternative outfall sites is
approximately 0.01 ug/g. This level is representative of areas where little to no
PCB effects are reported. Areas where potentially adverse bioaccurnulation is
occurring include Quincy Bay arid New Bedford Harbor. Maximum sediment levels in
Quincy Bay are about 1.0 ug/g and levels generally range from 0.5 to 0.9 ug/g (EPA,
1987). High levels of PCBs in the tissues of bottom dwelling organisms have been
found in the same areas in the Bay. Similarly, sediment PCB levels in ew Bedford
Harbor range from 0.3 to 78 ug/g are reported for areas closed to fishing due to
high PCB levels in fish and shellfish tissue (Boehm, 19814).
The level of of 0.1 ug/g chosen for this analysis represents a conservative estimate
of sediment PCBs which could result in bioaccumulation. This level has no
established regulatory or accepted scientific basis, but is used to differentiate
sediment PCB impacts between sites for this analysis.
PCB concentrations are predicted to build up during discharge of primary effluent.
With the cessation of primary discharge and the initation of secondary treatment the
amount of both PCBs and solids discharged will be greatly reduced (Table 5.1.2.d).
Also, constant addition of relatively uncontaminated background sediment will dilute
the PCB concentration built up during the primary discharge. Finally, over the 5
years of primary discharge, sediment resuspension and resettlement are predicted to
redistribute the sediment PCBs. The result of these processes is that after 5 years
of secondary discharge, the area of sediment with a PCB concentration greater than
the comparison level of 0.01 ug/g will be largely confined to the mixing zone and
similar for all sites. Consequently, long term build up of PCB in the sediment iS
similar arid of minimal impact for all sites.
These projections indicate that the build-up of potential sediment contaminants iS
greatest at Site 2 and generally intermediate at Site 14 The resulting
concentrations are not expected to produce significant adverse impacts at any of th
sites (Section 5.1.3). However, sediment pollutant concentrations are predicted tO
build—up during primary discharge and then decrease during secondary discharge.
5—32

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.J
3
0.4—
(
z
uJ
0.3—
0 10
I
AREA (KM 2 )
20
FIGURE 5.1.2.a. SEDIMENT PCB CONCENTRATIONS VS. AREA; PRIMARY EFFLUENT,
NONSTRATIFIED CONDITIONS, 5 YEAR DURATION
0.6
0.5-
0.2 ’-
SITE 2
I
30
5—33

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This reduction is predicted based on dilution with cleaner background sedimentation,
natural redistribution of in—place sediments and less deposition of PCB in secondary
effluent. Assessment of present pollutant concentrations (MWRA, STFP V,S, 1987)
indicate that there is an area of relatively high sediment concentrations in the
area between Sites 2 and 14 Neither the source of this material nor the mechanisms
which produce the concentrations are known. However, no matter what the cause, the
data indicate that there could be less reduction during secondary discharge in
concentrations built up during primary discharge in this area. This would make any
discharge in the area between Sites 2 and 1 less desirable.
5.1.3 MARINE ECOSYSTEMS
This section presents an analysis of the operation impacts of the effluent
outfall. Operation impacts are discussed for the three alternative outfall
locations (Sites 2, and 5). Operational impacts both outside the mixing zone and
inside the mixing zone are considered.
5.1.3.1 Operation Consequences (kits ide the Mixing Zone
Impacts outside the mixing zone due to the discharge of both primary and secondary
effluent are evaluated in terms of predicted changes in sediment and water quality
and resultant impact on the biota. The parameters that are examined in detail
include organic enrichment, sediment toxicity and accumulation of toxic compounds,
while for the water column the parameters analyzed In detail include nutrient
enrichment, exceedance of U.S. EPA (1986a) water quality criteria for aquatic life
and periodic low dissolved oxygen concentrations.
5.1.3.1.1 SedIment Organic Enric ent. Historically, organic enrichment from
wastewater discharges has been observed to have the greatest impact on benthic
communities (Swartz et al., 1986; Pearson and Rosenberg, 1978; Mearns and Word,
1982; Bascom et al., 1978; Maughan, 1986; Pearson, 1982; Oviatt et al., 1987; Poore
and Kudenov, 1978). Pearson and Rosenberg (1978) found macrobenthic infaunal
communities to respond in a consistent pattern to changes in the level of sediment
organic enrichment. In general, benthic communities in the immediate vicinity of a
source of major organic enrichment contain either no macrofauna or are dominated by
only a few pollution-tolerant, opportunistic species (such as capitellids) that
occur In high numbers. These types of conmiunities are considered to be degraded.
With increasing distance from the source of enrichment this degraded community is
replaced by a community with higher species richness and biomass that gradually
changes to a community characteristic of unpolluted environment. These communities
with higher species richness and biomass are considered to be changed communities.
Unpolluted communities generally have lower species densities and often higher
diversity than the impacted areas (Pearson and Rosenberg, 1978; Swartz et al.,
1986). In general, these changes in benthic community structure reflect the changes
in the level of organic enrichment with increasing distance from the source.
In order to assess impacts (changes in community structure) due to organic
enrichment from the future MWRA wastewater, discharge rates of organic sediment
enrichment have been predicted at the alternative outfall locations. These rates
have been predicted from modeled sediment deposition rates (Section 5.1.1) assuming
organic carbon comprises 40 percent of the effluent particulates (Metcalf & Eddy,
1979). The rate of organic enrichment above in situ production in which benthic
5—34

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ci ninity degradation would occur (1.5 g CIm 2 Iday) an the rate below which no
change in conununity structure would occur (0.1 g C/me/day) were estimated from
literature values. Between these two values, it is expected that species densities
will increase over unaffected areas; however, the relative abundance of species will
remain fairly constant. These types of communities are considered changed
co imiunities.
The rates used in this analysis were estimated from both field and experimental
studies. Depos 2 ition rates causing no benthic change have been estimated between 0
and 0.13 g C/rn /day while areas of degraded benthos have organic deposition rates
estimated from 1.5 g C/m 2 /day to approximately 5.0 g C/m’ /day (Maughan, 1986).
These rates were estimated from studies in the New York Bight (O’Conner et al.,
1983; Gunnerson et al., 1982) and southern California (Herring and Abati, 1979;
Mearns and Word, 1982 as well as mesocosm experiments (Maughan, 1986). Enrichment
rates above 1.5 g C/rn /day generally result in benthic communities characterized by
densities 3 to 14 times background densities, numerical domination by a few species,
domination by species with a different feeding type and potential mass mortality
produced by anoxia (Maughan, 1986).
A maximum sedimentation value of 25 g/m 2 (as defined by the sediment deposition rate
divided by the sediment decay rate of 0.01 /day) was used by MWRA (STFP V,H, 1987)
to present an “area of impact.” This has also been used by U.S. EPA (1982b) to
evaluate other discharges. Assuming effluent so] ids are 140% organic ca bon, the
Mxlmum sedimentation value would be: (25 glni * 0.140) = 10 C/rn’. This
interprets to a deposition rate of: 10 C/rn 2 * 0.1 /d 0.1 g C/m’/day. This is
nsistent with literature values discussed above.
In order to compare alternative outfall sites, the areal extent of predicted
degraded benthic communities and changed benthic communities have been determined.
Table 5.1.3..a presents a comparison of predicted organic enrichment between Sites
for both primary and secondary treatment under stratified and nonstratified
nditions.
lanstratified condition . No areas of degraded benthic conditions (organic loading
greater than 1.5 g C/m’/day) are predicted for any site under secondary treatment
during nonstratified conditions. Under grimary treatment, during nonstratified
nditions, degraded areas (less than 1 kin’) are expected to occur at Sites 2 and
4. changed benthic conditions are predicted to occur at all sites under both types
of treatment during nonstratified conditions with the area of impact being greatest
at Site 2 and lowest at Site 5 (Figures 5.1.3.a and 5.1.3.b). Under primary
treatment with nonstratified conditions, the area of changed conditions is
approximately 140 percent less at Site 5 than Site 2. Under secondary treatment
(nonstratified), this area is approximately 80 percent less at Site 5 than Site 2.
Stratified Conditions. Organic enrichment has also been predicted for the
stratified summer conditions, from approximately late-June to mid-September. During
these months, impacts to the benthos due to organic enrichment will be most
Severe. This is because the solids are deposited over a smaller area since they
have a shorter distance to fall before currents disperse them. Degraded communities
are predicted to occur under primary treatment at all three sites over small areas
during this period (Figure 5.1.3.c to 5.1.3.d). The area of predicted degradation
at Site 5 is only 2 percent of that predicted for Site 2 under primary treatment.
5-35

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TABLE 5.1. 3.a SUMMARY OF AREAL EXTENT OF PREDICTED SEDIMENT ORGANIC ENRICHMENT
Primary Treatment Secondary Treatment
AREA AREA AREA AREA
DEGRADES ()( 2) CHANGED DEGRADED t 2) CHANGED ( 2)
(>l.5gC/m Id) (0.l-1.5gCIm /d) (>1.5gC/m /day) (0.l—1.5gC/m /day)
Non-Stratified Conditions
SITE 2 0.8 16.9 0 3.0
Lfl +
SITE 14 0.02 13.7 0 1.9
0 ’
SITE 5 0 10.14 0 0.6
Stratified Conditions
SITE 2 2.2 32.7 0 14.9
SITE 14 1.2 18.9 0 3.2
SITE 5 0.05 12.2 0 3.1

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2 0 2
I- I I
KILOMETERS
LEGEND
CHANGED AREA
DEGRADED AREA
FIGURE 5.1.3.a. AREAS OF PREDICTED CHANGED AND DEGRADED BENTHIC COMMUNITIES
DUE TO ORGANIC ENRICHMENT UNDER STRATIFIED CONDITIONS WITH
PRIMARY TREATMENT FOR ALL SITES
SITE 4
SITE 5
1 0 1
I I I
NAUTICAL MILES
5-37

-------
I I I
NAUTICAL MILES
2 0 2
KILOMETERS
3END
CHANGED AREA
DEGRADED AREA
FIGURE 5.1.3.b. AREAS OF PREDICTED CHANGED AND DEGRADED BENTHIC COMMUNITIES
DUE TO ORGANIC ENRICHMENT UNDER STRATIFIED CONDITIONS WITH
SECONDARY TREATMENT FOR ALL SITES
0
SITE 2
SITE4 SITE 5
p
0 1
NOTE: NO DEGRADED AREAS
5-38

-------
2 0 2
I_ I
KILOMETERS
I.cGEND
CHANGED AREA
DEGRADED AREA
FIGURE 5.1.3.c.
AREAS OF PREDICTED CHANGED AND DEGRADED BENTHIC COMMUNITIES
DUE TO ORGANIC ENRICHMENT UNDER NON-STRATIFIED
CONDITIONS WITH PRIMARY TREATMENT FOR ALL SITES
SITE 4
SITE 5
1 0 1
— I I
NAUTICAL MILES
5-39

-------
I I I
NAUTICAL MILES
2 0. 2
I — I
KILOMETERS
LEGEND
CHANGED AREA
DEGRADED AREA
p
FIGURE 5.1.34. AREAS OF PREDICTED CHANGED AND DEGRADED BENTHIC COMMUNITIES
DUE TO ORGANIC ENRICHMENT UNDER NON-STRATIFIED CONDITIONS
WITH SECONDARY TREATMENT FOR ALL SITES
SITE 2
SITE 4
SITE 5
1 0 1
NOTE: NO DEGRADED AREAS
5- 4O

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Areas of changed benthic communities are expected to occur at all sites under both
primary and secondary treatment during periods of stratification. The greatest area
of changed communities with stratified conditions is expected to occur at Site 2
while the lowest area of change is expected at Site 5 under both primary and
secondary treatment. Under primary treatment, the area of change at Site 5 is
predicted to be approximately 37 percent of that at Site 2. Under secondary
treatment, areas of change at Site S is predicted to be 60 percent of that area at
Site 2.
The surface deposit feeding polychaetes, spionids, are the most abundant infaunal
taxa throughout the study area (Appendix C). This taxon has been reported to
increase in numbers with organic enrichment (Bottom, 1979; Dauer and Conner, 1980;
Pearson and Rosenberg 1978; Oviatt et al, 1987). Two taxa common at Site 2, Tharyx
spp. and Oligachaeta are also known to respond positively to organic enrichment
(Thompson, 1982; Pearson and Rosenberg, 1978; Swartz et al., 1986). Under changed
conditions, these species will increase in densities along with most other taxa;
however, under degraded conditions these taxa will likely dominate. At Site 14, the
relatively common pollution-sensitive ainphipods will likely decrease in numbers in
response to maximum organic enrichment with the exception of Corophium spp. (Pearce,
1972; Bottom, 1979; Steimle et al., 1982; Pearson and Rosenberg, 1978; Oviatt et al;
1987).
In general it would appear that within the changed or degraded area the nearshore
site would undergo less of’ a shift in infaunal species composition than the more
offshore sites since there is already some evidence of stress nearshore
(Appendix C). Several infaunal taxa that are known to respond positively to nrganic
enrichment are already abundant at Site 2. The relatively unstressed offshore sites
y undergo a greater shift in infaunal species composition and relative abundance
than nearshore; however, the area impacted will be considerably smaller Offshore
than nearshore (Figure C.1.3.a to C.1.3.d). No species changes are anticipated at
any site areas of enrichment less than 0.1 g C/m 2 /d.
The increased abundance and biomass of the benthic infaunal community will also
likely result in an increase in abundance in demersal species such as winter
flounder that feed on these organisms or organic matter directly. Pelagic fish
co miunities will not necessarily be as directly affected by sediment organic
enrichment since these species are highly mobile and have broad ranges (Section
C.1.5, Appendix C).
Little information is available on impacts to epibenthic organisms; however,
epibenthic organisms living in these areas will potentially be subjected to the same
types of impacts as infaunal benthic communities. Therefore, the degree of impact
and the relative differences of impacts between sites will be similar to that
described above for infaunal communities. Based on the characteristics of the
epibenthic species present, a qualitative assessment of likely impacts is presented.
There are two basic types of epibenthos. One group consists of sessile organisms
which predominantly feed in the water column (such as sponges, anemones and
hydroids). The other group contains organisms which are motile and feed mostly on
01’ in the sediments (such as crabs, lobsters and crangon shrimp). These two groups
have different susceptibility to organic enrichment and are discussed separately.
5.1 11

-------
The sessile group is highly dependent on particulate matter in the water column. If
the particulates are at suitable density and have a usable nutritional value, the
organisms would respond with increased consumption and thus possible increased
growth and reproduction. There is evidence that benthic animals can assimilate
sewage solids (Maughan, 1986), so epibenthic populations could be expected to
increase in areas of moderate deposition. However, if deposition is too high,
dominance by tolerant species and high sediment oxygen demand could inhibit the
epibenthic populations. There is no quantitative documentation of the deposition
rate that would produce these adverse affects, however the rates used above for
degraded infauna could also be expected to adversely affect the epifauna.
The motile epifauna are expected to respond differently to organic sediment
deposition. They do not rely directly on particulate matter as food so a simple
response to enrichment is not anticipated. They could be expected to increase
somewhat in density as overall system secondary production increased due to their
general scavenging and carnivorous feeding behavior.
5.1.3.1.2 Sediment Toxicity. Toxic substances associated with effluent
particulates can accumulate in bottom sediments and may have adverse effects on the
associated blota. Toxic substances may not only cause mortality but at sublethal
concentrations may limit the reproductive potential of sensitive populations,
thereby causing a shift in coninunity composition (Wolfe et al., 1982).
Very little quantitative information is available on concentrations of toxics in the
sediments and the associated effects on the benthos and higher trophic levels.
There is also no established criteria to evaluate sediment chronic and acute
toxicity. Even at a given concentration, toxicity of a given constituent may vary
between different sediment types due to differences in bioavailability of the
constituent (Windom et al., 1982). Realizing these limitations, an attempt has been
made to predict and quantify impacts associated with toxics accumulation in the
sediments in order to compare relative impacts among sites.
An approach has been developed to predict concentrations of various effluent toxics
in the sediments (Appendix B). The list of constituents was developed from a list
of detectable influent constituents of concern (MWRA, STFP V,A, 1987). This
original list was reduced by eliminating all constituents that were not predicted to
occur in effluent suspended solids and all constituents whose predicted
concentration in effluent (MWRA, STFP V,A, 1987) was known from literature to be
non—toxic in sediments. Also eliminated from this list were volatiles with low
associations with sediment particulates. Table 5.1.3.b siinr rizes this elimination
procedure and presents a list of the remaining constituents.
The sediment concentrations and the areal extent of these remaining constituents
were then predicted for the remaining 15 constituents for each site for durations of
six months, one year, and five years under both stratified and non-stratified
conditions (Appendix B). The sediment concentrations of these constituents for each
site were compared to available literature concentrations where possible to
determine potential impacts to benthic organisms. Studies found to be useful for
these comparisons include Swartz et al., 1986; Perez et al., 1983; Reed et al.,
1984; Peddicord, 1980; Rubenstein et al., 1984; Calabrese, et al. 1982; and Oviatt
et al., 1982. Values for selenium, aldrin, butylbenzyl phthalate, di-n—octYl
phthai.ate and heptachior were not found in the available sources. Table 5.1.3.C
siniin rizes the available sediment toxics concentrations information.
5-42

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TABLE 5.1 .3.b SUP 4ARY OF EVALUATION OF CONSTI11JFiITS OF CONCERN
Eliminated Because
Not Projected in
Eliminated Because
Eliminated Because
Remaining
Influent
Constituent
Effluent Suspended
of Low Association
Effluent Concentration
Sediment
Constituents
01 ’ Concern
Solids
With Particulates
Not Toxic
of
Concern
VOLATI LES
benzene X
bromomethane X
chloroform X
ethylbensene X
methylene chloride X
styrene X
tetrachioroethylene X
trichioroethylene X
ACID, BASE NEUTRALS ACID, BASE NEUTRALS
bis (2-ethylhexyl)phthalate bis (2—ethylhexyl)phthalate
butylbenzyl phthalate butylbenzyl phthalate
di—n—octyl phthalate di—n-octyl phthalate
flourene X
METALS METALS
arsenic arsenic
cadmium X
chromium X
copper copper
lead X
mercury mercury
nickel X nickel
selenium selenium
silver silver
zinc zinc
PESTICIDES PESTICIDES
aidrin aidrin
LI,LIDDT 14,ZI DDT
dieldrirt dleldrin
heptachior heptachior
OTHER CHEMiCALS OTHER CHEMICALS
PCBs PCBs

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TABLE 5.1.3.c SWISABY OF SEDINaIT fOXICS IIiFOHWITION
NA = Not available
*Concentratjon of effluent particulates
predicted.
a. Under primary treatment for 5 years, nonstratified.
in
Constituent
Maximum
in
Concentration (ppm)
Predicted
Sediment (a)
Concentration (ppm)
below which
toxic effects Literature
do not occur source
Comments
Site 2
Site ZI
Site 5
bis (2—ethylhexyl)phthalate
20.2
1ZI.9
11.0
7.2
Perez et al., 1983;
butylbenzyl phthalate
di—n—octyl phthalate
flourene
arsenic
11 1.2
22.7
0
3.8
10.14
16.7
*
5.8
7.7
12.14

5.0
NA
NA
129
128
Swartz et al., 1986.
Oviatt et al., 1982
Peddicord, 1980
Toxic concentration given is
Not accumulated by juvenile
for total PAUs
crab, Cancer
cadmium
chromium
copper
lead
mercury
C
•
130.6
0
1.8
0
0
10 4.0
0
1.11
0
72.3
0
1.01
22
720
51 17
252
1. 1 17;6
Swartz et al., 1986
Swartz et al., 1986
Swartz et al., 1986
Swartz et al., 1986
Peddicord, 1980;
Calabrese et al, 1982
magister
Not accumulated by shrimp,
(crangon migromaculata); no
effect on
nickel
selenium
29.7
11.0
28.7
8.6
21.8
6.9
85
NA
Swartz et al., 1986
lobster (Hoaxarus americanus)
silver
zinc
aldrin
7.9
283.2
0.3
11.11
233.6
0.2
3.3
166.7
0.2
6—10
>709
NA
Calabrese et al, 1982
Swartz et al., 1986
L4,’4-DDT
0.13
0.1
0.1
>0.07
Swartz et al., 1986
U.S. EPA, 1986
Toxic concentration for
1 4,1l_DDE was given in Swartz
is 108 times more toxic than
water column. Therefore DDE
et al.; 14,4_DDT
4,ll-DDE in
concentration
dleldrln
0.014
0.011
0.014
was divided by 108.
heptachior
0.1
0.1
0.08
NA
PCB
1.14
1.03
0.8
>20
5.2
Reed et al., 1982
Rubenstein et al., 19811
is less than concentration known to cause effects; therefore, concentration in sediments not

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As shown in Appendix B, maximum concentrations of all constituents at each
alternative outfall site occurred over the five-year interim primary discharge
period. Maximum predicted sediment concentrations of all constituents were
consistently highest at Site 2 and lowest at Site 5 with the exception of arsenic
which was highest at Site 4. The high arsenic concentration at Site 4 is due to the
high background concentration in the existing sediment (MWRA, STFP V,S, 1987).
Of the constituents for which toxic information exists, only two (DDT and bis(ethyl-
hexyl phthalate) are predicted to occur in concentrations that will directly effect
the benthic species (Table 5.1.3.c), The maximum areal extent of impacts due to
sediment toxicity ranges from 2.8 km at Site 2 to 1.6 2 at Site 5 during primary
treatment (Table 5.1.3.d). These areas are within the mixing zone area. No
sediment toxicity impacts are predicted under secondary treatment.
A possible sublethal effect of sediment toxicants includes the potential for
organisms to concentrate toxicants in their tissues (bioaccumulation). The
concentrated toxicant may then be transferred through the food web and be
biomagnified. It is difficult to predict the effects of biomagnification on
carnivores at the top of the food chain including sea birds and marine mammals
because the rate of accumulation and body turnover time is poorly understood and
varies among toxicants (U.S. EPA, 1980a).
Perez et al. (1983) found bis(ethyl—hexyl) pthalate to accumulate in mollusc and
polychaete tissue in a controlled mesocosm experiment. Kay (19814) reviewed the
available literature on biomagnification of heavy metals, organic compounds
(including PCB and DDT) and PAH’s. In general, he found PCB’s to have the potential
for biomagnification in the food web while information on heavy metal
biomagnification was frequently contradictory.
Although top predatory fishes sometimes contained higher levels of specific
contaminants than other members of the food web, the relationship between
contaminant levels in the tissues and an organism’s position in the food web was
not clear. The apparent inconsistency in the data may reflect a number of
factors including the mobility of the top predators, age and size differences,
inadequate understanding of the feeding habits of different species
(particularly with respect to the changing of feeding habits at different stages
of the life cycle), in precision in the assignment of trophic levels, and
inadequate sampling and analytical procedures. (Kay, 1984).
Compounds which likely do not biomagnify include DDT and most PAUs (Kay, 1984).
Although it may not be possible to quantify impacts at each alternative outfall site
for each constituent in terms of toxicity and biomagnification, it may be assumed
that these affects, if any, would be greatest where toxic sediment concentration is
predicted to be the highest (Site 2) and least where the concentration is predicted
to be the lowest (Site 5).
5.1.3.1.3 Nutrient Enrichment. Wastewater discharges have been shown to cause
nutrient enrichment in marine waters (Mearns et al., 1982; Malone, 1982; Oviatt et
al., 1986). Moderate increases in nutrients may result in stimulation of the entire
marine community by increasing phytoplankton growth, respiration, secondary
production and eventually density of predators such as fish. However, above certain

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Lfl
0 ’
Site 2
TABLE 5.1. 3.d AREAL EXTDIT ( 1 C M 2 ) SEDIMEV TOXICITY AT ALTERNATE O ?TFALL SITES UNDER PRIMARY AND SECONDARY TREATMEWI
Primary Treatment Secondary Tr jnPnt
Site 4 Site 4
Site5 Site2
Site 5
Bis(
ethyl—hexyl) phthalate
0
0
0
0
0
0
After 6 months stratified
After 5 years non-stratified
2.8
2.4
1.6
0
0
0
DDT
After 6 months stratified
0
0
0
0
0
0
After 5 years non-stratified
1.4
0.9
0
0
0
0

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nutrient levels the stimulation cannot be assimilated by the marine systems. Above
this critical level, significant shifts in species composition or even excessive
oxygen demand and anoxia may occur (Mearns et al., 1982).
For the purpose of this analysis of nutrient enrichment, increases in nitrogen
concentrations have been predicted for each alternative outfall location (Appendix
A). Nitrogen was used in the analysis because it appears to be the limiting
nutrient in the study area (Section C.1.1.3 of Appendix C). Also, increases in
concentrations of other nutrients would be proportional to those of nitrogen.
Nitrogen additions greater than 0.5 mg/l are expected to cause excessive oxygen
demand leading to degraded conditions in the summer months, while additions of less
than O.1 I mg/l are expected to have no impact. The estimates were derived from
long—term marine system nutrient addition studies with multiple dose levels (Oviatt
et. al, 1986). These values have been calculated based on estimated steady-state
concentrations. Between these two values, increased production is expected but with
no excessive oxygen demand resulting in changed conditions. Generally consistent
with these levels, forty—eight hour nutrient spike experiments conducted by MWRA
with water samples collected within the study area(MWRA, STFP V,Z, 1987) indicated
that nitrogen addition of up to 0.35 mg/l stimulated carbon production rates,
chlorophyll biomass yield and species growth rates, but did not cause algal blooms
within the experimental time period.
In this analysis, the enrichment effects were assumed to be similar for primary and
secondary treatment. This is because neither treatment process will remove
significant amounts of nitrogen, therefore the influent nitrogen concentrations were
used. The form of nitrogen will initially be different for these two levels of
treatment with more amonia present in the secondary effluent. However, nitrogen has
been treated as a conservative substance for this analysis; therefore, for the
steady-state projections most, of the nitrogen is in the system long enough to be
initially consumed and then remineralized. Consequently, its original form is the
major concern.
The areas within which degraded and changed water column conditions may occur were
predicted for each site under average conditions (Table 5.1.3.e). The area in which
degraded conditions are predicted as a result of increased nutrients in the water
column is greatest at Site 2. The area in which these conditions are predicted to
exist is 75 percent smaller at Site 14 than Site 2 during average conditions. High
oxygen demand resulting in degraded conditions, is not expected to occur at all at
Site 5. The area of increased primary production (changed conditions) is also
greatest at Site 2 (Table 5.1.3.e). The area affected by increased production
resulting from a discharge at Site 2 would include most of’ Boston Harbor.
Nutrient enrichment predictions were also made for worst-case conditions with no net
drift for a period of ten days (Figure 5.1.3.e). These conditions are expected to
occur approximately ten percent of the time. The area of degraded conditions is
96 percent smaller at Site 2 than Site during no net drift conditions. No
degradation due to water column nutrient enrichment is predicted at Site 5.
Since ambient nutrient concentrations are generally higher in the vicinity of site 2
than site 5 (MWRA, STFP V,Z, 1987), it is likely that nutrient enrichment would have
a greater impact at site 2 than site 14 even over equal areas, since the higher ambient
nutrient concentrations occur at site 2; therefore the water column at site 2 would
require less additional nutrient loading to reach potential algal bloom conditions.
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TABLE 5.1 .3.e. SWI4ARY OF AREAL EXT iT OF PREDICTED AVERAGE AND WORSI-CASE NUTRIENT ENRICI 4 IT IN THE WATER COLUMN
(VALUES ARE T1 SAME FOR BOTH PRIMARY AND S IDARY TREAT*NT)
Avara e ‘ ‘ I
Worst-Case
Conditions
Increased Primary
Production”
Area
(Km 2 ) of degraded
conditions’
In c ampl i ry
Production 0 ’
Area
(1Cju2) of degraded
conditions’
SITE 2
130.0
0.5
159.0
0.5
SITE 14
6.6
0.1
6.8
0.2
SITE 5
0.14
0
11.25
0
‘ Nitrogen
“ Nitrogen
addition > 0.57 t.g/i
addition 0.111 to 0.57 mg/i

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LEGEND
DEGRADED AREA
L774 AREAOF INCREASED
ILL! PRODUCTIVITY
FIGURE 5.1.3.e AREAS OF PREDICTED CHANGED AND DEGRADED WATER COLUMN
CONDITIONS DUE TO NUTRIENT ENRICHMENT UNDER CONDITIONS OF
NO NET DRIFT (PREDICTIONS ARE THE SAME FOR BOTH PRIMARY AND
SECONDARY TREATMENT
SITE 5
SITE 4
1 0 1
I- I ___ I
NAUTICAL MILES
2 0 2
KILOMETERS

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Under both average and no net drift conditions, discharge from site 2 would entrain
and trap nitrogen in Boston Harbor. This, along with the other sources of nutrients
in the Harbor (such as CSOs and urban runoff) could add to the already stressed
Harbor ecosystem. This in turn could have implications on all Harbor uses and
reduce the benefits of the Boston Harbor clean-up. In contrast, discharges at Sites
14 and 5 are not expected to impact the Harbor.
In general, areas of increased primary production with no associated excessive
oxygen demand have little negative impact (Oviatt et al., 1986; Oviatt et al.,
1987). Increased phytoplankton growth will likely result in increased zooplankton
densities and eventual increase in production up the food web. Local fish
populations such as sculpin, sand lance and Atlantic herring may increase in
abundance and provide increased food source for their predators such as marine
m nvn ls and sea birds in the area of the increased production.
In summary, areas of excessive production leading to depressed oxygen levels and
degraded conditions are predicted at Sites 2 and 14 under both primary and secondary
treatment. The areas in which these conditio 9 are expected to occur are within the
area of the mixing zone (approximately 1.5 km ) and therefore increased production
is not expected to have significant impact on the ecosystem outside the mixing zone.
5.1.3.1.k Water Column Toxicity. Toxic constituents (priority pollutants) will
occur in the water column as a result of the wastewater discharge. Depending on the
concentrations of these constituents, chronic or acute mortality could result in
more sensitive species such as ainphipods. Also, zooplankton may uptake toxic
constituents directly from the water column, consequently a concentrated source of
toxicants may be available to higher trophic levels including seabirds and marine
m nmtils (U.S. EPA, 1980a).
Toxicity in the water column is assessed by comparing predicted concentrations of
priority pollutants to U.S. EPA (1986a) water quality criteria for aquatic life.
Specifically, criteria used in this analysis are the Criteria Maximum Concentration
(CMC) for evaluation of acute effects and the Criteria Continuous Concentration
(CCC) for evaluating chronic effects on marine organisms. These are described in
Section 5.1.1.
Under primary treatment conditions, heptachior, 4,14’ —DDT, mercury and PCB are
expected to exceed U.S. EPA CCC criteria at the edge of the mixing zone at all three
alternative outfall locations, while copper is expected to exceed CMC criteria at
Sites 2 and 14. Under secondary treatment, only mercury at Sites 2 and 14 and
heptachior at Site 2 exceed CCC criteria at the edge of the mixing zone.
Heptachior is an organochlorine pesticide which is very persistent in the
environment. At all sites under primary treatment, heptachlor is expected to be
less than 2.5 times greater than the criteria (Table 5.1.3.f). Under secondary
treatment, heptachior will exceed criteria by only one percent only at Site 2. The
CCC criterion for heptachlor is 0.0036 i.ig/l for a 214—hour average concentration.
The likelihood of an organism being exposed to chronic affects from heptachlor is
minimal because of the small areal extent in which this exceedance would occur. It
is unhikley that an organism would remain in that small area long enough for chronic
effects to occur. Also, a chronic value of 1.58 ugh has been reported for
sheepshead minnow (U.S. EPA, 1985c). This value is two orders of magnitude higher
than the conservative criteria.
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TABLE 5.1.3. f SUMMARY OF PREDICTED AQUATIC LIFE WATER
QUALITY CRITERIA EXCEEDANCES
CONCENTRATION/CRITERION
RATI
os( 1)
Constituent
Primary
Secondary
Site 2
Site 14
Site
5
Site
2
Site
14
Site
5
cMC
copper
2.10
1.26
Ccc
heptach lor
3.149
2.11
1.51
1.01
14, 14’—DDT
3.55
1.99
1.314
mercury
4.96
3.14
2.18
1.90
1.26
PCBs
2.37
1.46
1.09
(1) Concentration 4 Criterion
DDT is another organochlorine pesticide that is very persistent in the
environment. The CCC value for DDT is 0.0010 iig/l as a 214-hour average. This value
is expected to be exceeded at all three alternative outfall sites under primary
treatment only. The predicted CCC exceedence for DDT is 1.34 times greater than the
criteria at Site 5 and over 2 times greater at Sites 2 and 14. As discussed
previously with heptachior, the area in which this exceedance will occur will be
very small and therefore will have minimal impact, especially at Site 5.
For a primary discharge the predicted concentration of the trace metal mercury at
the edge of the mixing zone will be almost four times greater than CCC criteria at
Sites 2 and 14 and two times greater at Site 5. Under secondary treatment the level
of exceedance is much lower at Sites 2 and it, with no exceedance at Site 5. The CCC
for mercury states that the 14-day average concentration of mercury should not exceed
0.025 mg/l more than once every three years. A life-cycle experiment with a mysid
shrimp indicated that inorganic mercury significantly affected the time of first
spawn and productivity at a concentration of 1.6 mg/i (U.S. EPA, 1986a). This
concentration is an order of magnitude higher than that predicted at the edge of the
*ixing zone. Also, mysid shrimp are known to be very sensitive to stressed
conditions and are not abundant in the study area. It is likely that organisms in
the study area will be more tolerant than the mysids.
PCB is predicted to exceed CCC criteria by relatively small amounts (Table 5.1.3.f)
at all three sites at the edge of the mixing zone under primary treatment only. The
CCC for PCB is 0.03 ugh. PCBs are bioaccumulated and can be biomagnified.
Therefore, their toxicity increases with length of exposure and position of the
exposed species on the food web.
Under primary treatment, copper is predicted to be 2.1 and 1.3 times greater than
MC at Sites 2 and Lt respectively. Copper is not expected to exceed criteria under
secondary treatment. The CMC value for copper is 2.9 mg/liter. According to U.S.
EPA (1986) acute sensitivities of saltwater animals to copper range from 5.8 mg/i
5-50

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for the blue mussel to 600 mg/i for the green crab. A chronic life-cycle experiment
conducted with a mysid produced adverse effects at 77 mg/i copper (U.S. EPA,
1986). These studies and the fact that the copper exceedance will only occur over a
relatively small area, indicate that copper in the water column will not have a
significant effect on the biota.
In general, Site 5 has the fewest predicted water quality criteria exceedance and
the lowest magnitude of exceedances of the three alternative outfall sites while
Site 2 has the most. Generally speaking, while actual criteria exceedances do exist
at all three alternative outfall locations, they are not expected to have a
significant impact on the ecosystem due to the small areal extent in which they are
predicted to occur and the conservativeness of the criteria.
5.1.3.1.5 Dissolved Oxygen Deficits. The State of Massachusetts Surface Water
Quality Standard for dissolved oxygen (DO) concentration is 6 mg/i anywhere in the
water column after hydaulic mixing. However, marine communities can be exposed to
lower concentrations for short periods without adverse effects. Short-term (less
than one week) DO concentrations from 14 5 to 6.0 have been shown to cause no adverse
effects to biota (in terms of increased mortality or decreased reproductive
potential) in experimental wastewater studies (Oviatt et al., 1987; Oviatt et al.,
1986; Maughan, 1986; Nixon et al., 19814; Frithsen et al., 1985; Keller et al.,
1987). In these experiments, DO levels below 6.0 mg/l occurred several times in
late summer in systems with moderate nutrient enrichment and to a lesser extent in
controls. The benthic and zooplankton assemblages showed no adverse effects in
these systems; in fact, several of the systems supported higher densities of
organisms. In contrast, systems with high enrichment experienced DO concentrations
well below 3 mg/i, and adverse effects, including mass mortality, were observed.
Two cases of decreases in DO were considered as described in Section 5.1.1 and
Appendix A. Table 5.1.3.g summarizes the minimum DO concentrations at each site.
For the stratified summer conditions, predicted DO levels are above 6 mg/i for all
sites for discharge of secondary effluent, therefore no marine ecosystem impacts are
anticipated. Similarly for Sites 14 and 5 under primary treatment values are above 6
mg/i. However, for a primary discharge at Site 2 predicted values are below 14.0
mg/i. As discussed above this could produce adverse marine ecosystem impacts
including potential mortality over the affected area.
The predicted resuspension events produce lower DO levels than average conditions.
As discussed in Section 5.1.1 above and in Appendix A, these events occur very
infrequently and only over a few hours to a day. None of the predicted values are
anticipated to produce concentrations below 6.0 mg/i for secondary effluent and thus
no adverse effects are anticipated.
For primary discharge at Site 2 the DO values could be very low, and because the
coimnunity could be stressed due to exposure to lower DO prior to a resuspension
event (as discussed above for summer stratified conditions) the impacts could be
severe. At the other sites, for primary discharge the predicted minimum DO from
resuspension is much higher (5.0 to 5.7 mg/i). As discussed above rare short-term
exposure to concentrations in the 5.0 to 6.0 mg/l range will not have adverse
effects on the marine community.
5.1.3.1.6 Impacts on Protected Species. The only protected species to potentially
occur in the study area are whales and sea turtles (Chapter 14). Since these species
are very mobile and are distributed seaward of the project area. It is unlikely
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TABLE 5.1.3.g. PREDICTED MINIMUM WATER COLUMN DISSOLVED OXYGEN
CONCENTRAT ION (mg/i) UNDER RESUSPENSION EVENTS FOR
PRIMARY AND SECONDARY TREATMENT
I
Primary Treatment Secondary Treatment
Site
2
2.2
5.9
Site
5.0
6.3
Site
5
5.7
6i
that they will be directly affected by the discharge of effluent. It is possible
that nutrient enrichment may cause an increase in zooplankton production and certain
fish species which are the primary food sources for right whales, fin whales, and
humpback whales. This increase in food supply in the vicinity of the outfall may
result in attraction of the marine mammals to these areas; however, this is not
expected to have a negative impact on these protected species since toxic effects
from the outfalls are expected to be minimal, especially at Site 5. Review by NKFS
has indicated that the project would not jeopardize these species or the occasional
turtles that may occur in the area (letter dated 1988, Appendix G).
5.1.3.2 Operation Consequences Inside the Mixing Zone
The mixing zone is the area in the immediate vicinity of the diffuser discharge in
which initial dilution of the effluent occurs. The areal extent of the mixing zone
is the same for all alternative discharge sites. Within the water column, the
mixing zone is predicted to be approximately 1.5 km 2 (Section 5.1.1). The areal
extent of impact on the bottom sediments will be greater than the water column since
the mixing zone is constantly moving. The predicted sediment area directly impacted
by the mixing zone is approximately 1 icm .
A significant amount of continuous jet turbulence will occur in the mixing zone as a
result of the discharge. This turbulence will prevent most mobile organisms from
passing through the zone. For those organisms that do enter the mixing zone, their
residence time will be very brief due to the turbulence. These organisms (mainly
plankton) will generally not be in the mixing zone long enough to experience acute
or chronic exposure to toxic constituents in the effluent. Ten constituents are
expected to exceed criteria U.S. EPA (1986a) water quality criteria at the point of
discharge under primary treatment while four constituents are expected to exceed
under secondary treatment (Appendix A). The ocean bottom in the mixing zone will be
exposed to a high rate of effluent particle deposition ranging from 2.6 to
12.6 g/m 2 /day with primary treatment and from 0.3 to 2.2 g/m 2 /day with secondary
treatment. These relatively high sedimentation rates will likely result in a
degraded benthic community structure in this zone where the community dominated by
pollution-tolerant organisms such as capittellids and oligochaet9f (Swartz et al.,
1986). These impacts are not projected to occur beyond the km area for primary
and not at all for secondary.
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5.1.11 PUBLIC HEALTH
Public health impacts were evaluated from each of two perspectives: (1) exposure of
human populations to potential bacterial and viral pathogens and (2) food-web
exposure of seafood consumers to chemical contaminants discharged from the proposed
outfall.
5.1.11.1 Pathogens
The potential for direct exposure of human populations to bacterial and viral
pathogens will be reduced over existing conditions by the overall wastewater
treatment facilities improvements in the Secondary Treatment Facilities Plan. These
include the proposed shift to an offshore discharge location and redundancy of the
plant which would prevent incomplete disinfection (Appendix H). Bacterial
contamination from various sources including sewage overflows continues to
contribute to periodic beach and sheilfishing closures in and around Boston
Harbor. As described in Section 5.1.1 and Appendix A, the wastewater flows which
will receive treatment at the future Deer Island facilities, upon discharge at any
of three sites considered in detail in this SEIS (Sites 2, 14 or 5), would no longer
c3ntribute to such closures or to any discharge—related exposure to bacterial or
viral pathogens.
5.1.11.2 Chemical Contaminants
Projections are less certain concerning potential impacts of chemical contaminants
on seafood consumers. At a minimum, it is expected that replacement of the present
Deer Island, Nut Island and related inner harbor wastewater and sludge discharges by
a discharge of treated wastewater to Massachusetts Bay will lead to significant net
reduction in the availability of contaminants to inner-harbor populations of edible
fish and shellfish. However, the rate and extent of reductions of problematic
chemicals in the fish/shellfish body-burdens in the harbor is uncertain. Similarly,
the extent to which a Massachusetts Bay discharge may or may not create an exposure
pathway for seafood contamination is not easily or accurately quantifiable. This
subject is discussed below.
EPA’s Quality Criteria for Water 1986 identifies water column concentrations for a
number of chemicals, which correspond to three levels of’ potential excess lifetime
cancer risk due to consumption of seafood containing these chemica s. The three
lifetime cancer pisk levels are one in one-hundred thousand (1x1O ’), one in one
million (1 x 10°) and one in ten million (1 x 1O— ). All of these levels are in
the generally acknowledged range of many voluntary and involuntary risks experienced
in everyday life (Wilson and Crouch, 1987) and not subject to regulatory response
within that range. For seafood consumption, these ‘carcinogenicity criteria’ (as
they are referred to in the water quality discussions throughout this Draft SEIS)
are based on an assumed bioconcentration factor in seafood and the assumed lifetime
consumption of an average of’ 6.5 g/day (about 5.2 ibs/yr) of seafood from the area
exposed to the water column concentration. It is possible, although unlikely, that
5.2 lbs/yr of seafood consumption over a long-term could occur during the time-frame
of the secondary discharge at any of the alternative outfall sites if commercial and
recreational fishing were allowed within and at the edge of the mixing zone Of
initial dilution. However, the expected duration of the primary discharge is too
short for those public health considerations to be realistic. The validity of
assumed bioaccumulation factors varies, as discussed below.
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Table 5.1.1.1 compares the projected secondary discharge quality at the edge of the
mixing zone at Sites 2, 14 and 5 with both the one-in-one million (1O ) and one-in-
one-hundred thousand (10 ) EPA carcinogen criteria, for those chemicals projected
in Section 5.1.1 to potentially exceed one or more such criteria.
It is important to note that two of the compounds (PCBs and arsenic) presently
exceed the criteria in the ambient waters by up to 100 times. Discharge at any of
the sites would increase the amount of the exceedance over a relatively small area;
however, the addition from the effluent is not expected to significantly increase
the public health risk.
It is expected that the modeled arsenic exceedences will be of no significance to
public health for the following reasons:
1. Arsenic has been shown not to bioaccumulate in at least some tissue of
resident demersal food fish around large municipal wastewater outfalls
from which arsenic is discharged (de Goeij et al., 19714); and
2. The carcinogen criterion for arsenic exposure from seafood consumption is
hypothetical, rather than emperical. Evidence for arsenic as a human
carcinogen water ingestion comes from epidemiological studies of drinking
water ingestion in Taiwan (EPA, 1980). Evidence is lacking for any
similar epidemiology of arsenic ingestion in the forms in which it is
present in seafood.
The alternative discharge locations can be compared by evaluating the potential 10
public health risk for the compounds not already exceeding criteria in the ambient
water. For the discharge of primary effluent there are four (aidrin, DDT,
heptachlor, dieldrin), three (aldrin, DDT, heptachior) and two (aldrin, DDT) such
exceedances at Sites 2, 11 and 5, respectively. The exceedances range from 0.5 to
12 times the criteria and could be cause for concern. At Sites 14 and 5 the
exceedances are less than 5 times the criteria and thus are of less concern. Since
the criteria are developed for lifetime exposure, the primary discharge is only for
about 5 years, and the magnitude of exceedance is much lower at Sites 14 and 5, the
public health impacts are substantially less at the two more offshore sites.
Discharge of secondary effluent is predicted to produce much less public health risk
compared to primary. Using a 10 risk factor and excluding the ambient
exceedances, there are only two exceedances (aldrin and DDT) predicted for Site 2
and none for the other sites. This implies no substantial increase in risk at Sites
and 5 and minor increased risk at Site 2.
There is also potential concern over sediment contamination, particularly for
PCB’s. However, there are many uncertainties. All of the water and effluent
projections in this Draft SEIS for PCBs are based on extrapolations from
i easurements made at or below analytical detection limits. Also, the projections of
the levels of PCBs on particles and build—up in the sediments are based on
conservative assumptions.
PCBs do accumulate and biomagnify relatively quickly in edible seafood in proportion
to their availability in sediments, food organisms and the water column (Rubenstein,
et al., 19814, Hillman et al., 1987, and Boehin, et al., 19814). Given the
uncertainties involved in the water column and sediment projections and the
complexities of the discharge environment, monitoring of PCB levels in plant

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influent and in ambient water, biota and sediment around the proposed and existing
outfall site is the only likely means of accurate representation of impacts and
possible mitigation needs. If’ the modeling projections for water column PCB levels
are verified, monitoring and mitigation needs would likely be more driven by PCB
accumulation in sediments and subsequent transfer to seafood, as discussed below.
The projected sediment concentrations of several contaminants around the proposed
wastewater outfall (Appendix B Section B.3. 1 4) could, if verified, be a basis for
potential concerns over seafood contamination. Specifically, the maximum range of
projected PCB concentrations are:
Site Primary Secondary
2 0.14 to 1.14 ug/g 0.2 to 0.3 ug/g
14 0.2 to 1.0 0.1 to 0.3
5 0.1 to 0.8 0.1 to 0.2
In addition, during the summer PCB concentrations could reach 5.6 ug/g for primary
and 1.9 ug/g for secondary on vertical hard rock surfaces for any of these sites.
These concentrations would be 140 (soft bottom) to 500 (hard bottom) times higher
than concentrations presently characteristic of the sites. They fall within the
range of 0.3—78 ug/g reported for the New Bedford Outer Harbor closure area where
edible tissues of flounder and lobster continue to exceed 2 ppm, a value used by the
FDA for regulating PCB content of seafood (Boehm, et al., 19814, and Hiliman, et al.,
1987). The soft bottom sediments are below the maximum concentrations found in
Quincy Bay (EPA, 1987). There is no documented relationship between the PCB
sediment and tissue concentrations in these areas, but the potential for a
relationship does give cause for concern over public health risk from sediment PCB.
Similar considerations may apply to the projected sediment concentrations of other
contaminants for which carcinogen criteria exist, including aidrin and heptachlor.
However, unlike PCB’s, there is insufficient evidence to Judge whether these
concentrations, if verified, would be expected to result in seafood contamination.
The issue of potential public health impacts from sediment-related seafood
contamination does not appear to differ among alternative outfall sites, as the
projected concentrations for all sites have some uncertainty and are within about a
factor of two.
Because of the variety of conservative assumptions (e.g., contaminants present at
fuJ i. value of detection limits and fully conserved in deposited sediment) and the
considerable uncertainty surrounding all of these projections, there does not appear
to be a basis for classifying the expected public health impacts at any of the three
sites as unacceptable. However, there does appear to be a need for a process of
monitoring and possible mitigation, if the latter is shown to be necessary by
monitoring results.
5.1.5 HARBOR RESOURCES
This section relates harbor resources described in Section 14.2.14 to the potential
environmental consequences resulting from the operation of the effluent outfall at
the alternative locations.
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5.1.5.1 Navigation, Shipping and Water Transportation
The operation of the effluent diffuser will not directly affect any form of marine
transportation. Even at Site 2 the diffuser will be well below any navigation
depth. During times when the effluent plume surfaces it will not interfere with
traffic moving through the area. Since all alternative locations are well removed
from any maintained channels, no interference with any potential dredging projects
is envisioned.
5.1.5.2 Ccmercial Fishing
Coninercial fishing could potentially be impacted at any of the alternative
locations. Disruption of habitat could reduce the stocks and thus affect fisheries
over a relatively large area. However, as discussed in Section 5.1.3, except for
primary discharge at Site 2, where water winter flounder spawning occurs, no marine
ecosystems impacts great enough to affect fisheries populations are predicted.
Therefore on this basis commercial fisheries impacts are expected to be minimal, but
largest at Site 2.
lapacts can also potentially occur from physical interference with fishing
activities. The magnitude of the imapct is dependent on the amount of commercial
fishing directly over the discharge site. As discussed in Appendix D, there is very
little documentation of commercial fishing activity at a scale sufficient to
differentiate alternative discharge locations. Although there is some indication
that fishing activity varies among sites, it is assumed that the potential for this
type of fisheries impact are equal at all sites. These impacts can be minimized by
proper diffuser design which would minimize potential interferences for the
fishermen. It is likely that commercial fishing in an area of Massachusetts Bay
along the length of the diffuser may have restrictions to certain types of gear.
5.1.5.3 Recreation
There are potential recreation impacts both at the discharge site and at the shore
line. The impacts at the site are largely related to aesthetics. At sites closer
to shore there is a greater potential for small boat activity (Appendix B), thus the
potential for recreation impact is greater. Also, the more frequently the effluent
plume rises to the surface, the greater the aesthetic impact. This occurs more
often at Site 2 (Section 5.1.1).
As demonstrated in the analysis of onshore transport of effluent during extreme wind
events, effluent concentrations on the shore are projected to be highest if the
discharge is at Site 2. Although the concentration expected for these short-term
events generally would not be expected to threaten recreation value, some perceived
effect could impact recreation. This would be greatest at Site 2 and likely minimal
at Site 5.
Adverse impacts on Boston Harbor recreational resources are not expected from a
discharge at any of the sites. As shown in Section 5.1.1 water quality will be
preserved in the Harbor. Similarly effluent discharged at any of’ the sites will not
be directly transported into the harbor. Therefore, the recreational value of the
Harbor should be generally the same or much improved over present conditions by
discharge from any of the sites.
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5.1.5.11 Sensitive and Protected Areas
No significant impacts on any of the sensitive resources described earlier are
expected. Since insufficiently diluted effluent reaching these resources would
cause impact, the measures of relative shoreline impacts are the time for effluent
to reach the shore under an extreme on-shore wind event and the concentration of
effluent at the shoreline under such an extreme event. The differences in travel
time to shore from the various sites is relatively small (6.6 to 15.5 hours).
However, the travel time from Site 2 to the shoreline (6.6 hours) is close to the
duration of a flood tide so effluent could travel to shore with minimal dilution
beyond the mixing zone. Travel time from the other sites exceeds a flood tide and
thus would not travel directly to shore but would oscillate back and forth before
reaching shore, causing additional mixing and dilution. Discharge from all the
sites is predicted to have minimal shoreline impacts and will represent a
significant improvement over existing conditions. Sites 4 and 5 provide even more
protection for important shoreline resources than does Site 2.
5.1.5.5 Cultural and Archaeological Resources
Impacts on cultural and archaeological resources are limited to the area around the
effluent outfall, where artifacts (shipwrecks) could be disturbed by dredging
trenches or drilling riser shafts. The density of potential wrecksites decrease
from southwest to northeast along the line formed by the alternative outfall sites
(MWRA, STFP V,L, 1987). Site 5 has the least chance of containing a wrecksite, Site
14 a moderate chance, and Site 2 a good chance (MWRA, STFP V,B, 1987). Site specific
investigations are required to define the exact location of wrecks, and to formulate
avoidance or mitigation plans. It is anticipated that wrecksites can be avoided by
adjusting diffuser riser locations or mitigated through recovery of artifacts.
5.1.6 REGULATORY AND INSTITUTIONAL CONSIDERATIONS
Permit requirements and laws applicable to the outfall location are described in
detail in Appendix G. The major regulatory and institutional considerations
affecting outfall location involve water quality and discharge permit laws. All of
the alternative outfall sites require the same permits. Conditions at the various
outfall sites may affect the likelihood of violation of Massachusetts Water Quality
Standards or Federal NPDES standards, but all the sites will be compared to the same
sets of standards. All sites are subject to the same MEPA and NEPA reviews,
navigation regulations, and endangered species laws.
Concerns regarding timely implementation, external coordination, internal
coordination, and demand for unique or scarce resources are equal for all sites.
5.1.7 BOSTON HARBOR CONSEQUENCES
The current wastewater discharges for Nut and Deer Island Wastewater Treatment Plant
discharges are the major source of pollution causing environmental stress in the
Harbor. As discussed in the above sections, removal of these discharges by
relocation of the discharge to Site 11 or beyond will result in removal of these
discharges to the Harbor.
Water and sediment quality will improve upon removal of the current discharges.
Water column nutrient enrichment and associated low DO levels will be reduced as
will concentrations of toxic compounds in the water. Sediment quality will improve
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due to reduction in organic and toxic loading associated with settling of effluent
particulates throughout the Harbor.
Corresponding to the predicted improved water and sediment quality in the harbor,
the ecology of the harbor will also change. Biological communities will become more
like those characteristic of naturally occurring populations under non-stressed
conditions. Decreases in nutrient and organic enrichment will likely result in more
diverse benthic communities with lower densities indicative of more naturally
occurring communities (Swartz et al,, 1986). This predicted increase in benthic
biomass may also result in a corresponding decrease in demersal species which feed
on these benthic organisms. Reduction of toxic constituents in the water column and
sediments will also likely result in reduced tissue contamination in demersal
species and reduction in biomagnification of toxic compounds in the food web.
The recreational value of the harbor will also improve as a result of water quality
Improvements by reducing beach closings and improving aethetics throughout the
Harbor especially in high use and high visibility areas of the shoreline and
islands. The quality of extensive water based recreation (including boating,
swinnning and site seeing) in the harbor will improve. Finfish and shellfish
resources will likely improve in quality producing greater opportunity for
comercial and recreational fishing and reducing the potential for public health
risk through ingestion.
5.2 OUTFALL TUNNEL CONSTRUCTION
& deep rock tunnel effluent conduit system is evaluated in detail in this Draft
SEIS. This outfall alternative includes a vertical access shaft on Deer Island
which would be connected to the tunnelled conduit. The vertical shaft would be
excavated deep enough to allow for a 0.25 percent (or less) positive tunnel slope to
assure a minimum of 60 feet of bedrock overlying the outfall tunnel. The outfall
conduit would be mined using a tunnel boring machine (TBM). In some areas, drill
and blast techniques may be needed. The times required to construct a tunnelled
effluent outfall to Sites 2, I and 5 are 117, 51 and 56 months, respectively.
Excavated tunnel material would be removed through the access shaft on Deer
island. The tunnel would be lined with reinforced concrete (MWRA, STFP V, 1987).
The selection criteria for the tunnel outfall are applied below. There would be no
impacts on the marine ecosystem as a result of the outfall tunnel construction since
all construction would occur within the bedrock beneath the sea floor.
5.2.1 ENVIRONMENTAL - (OUTFALL TUNNEL CONSTRUCTION)
&ir Fanissions Control. Ventilation of the outfall conduit would be required during
tunnel construction. Gases could be created during blasting or released from the
bedrock during tunnelling. Dust would be created during tunnelling. Air exchange
uld also be required to rid the system of carbon dioxide formed by worker
respiration.
loise Control. According to Massachusetts Department of Environmental Quality
Engineering guidelines, operation of a new facility may increase ambient noise a
ximum of 10 dBA above the existing L90 ambient noise (the noise level which is
exceeded 90 percent of the time). Thus, the L90 ambient noise level represents the
I ckground noise which occurs when temporary noise is not present.
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MWRA measured sound levels at Point Shirley and Nut Island (MWRA, STFP III, 1987).
The ambient sound levels (L90) at Point Shirley are 39 dBA for nighttime and 45 dBA
for daytime.
MWRA predicted noise impacts due to the 12—year period of all construction at Deer
Island. Included in this analysis are noise impacts due to the outfall tunnel
construction. It is estimated that the noise level at Point Shirley will range
between 50 and 514 dBA during 83 percent of the daytime hours. During the remaining
17 percent of the daytime hours, sound levels at Point Shirley are predicted to
range between 60 and 65 dBA. An agreement exists between MWRA and the Town of
Winthrop concerning mitigation of noise associated with construction on Deer Island
(MWRA, Winthrop, 1988). Construction noise between 7:00 pm and 7:00 ant will not
exceed 36 dBA such that when combined with the ambient noise level of 36 dBA, the
noise level will not exceed 39 dBA. Noise levels on weekdays between 7:00 am and
7:00 pm must conform with noise level predictions by MWRA (MWRA, STFP III,D,
1987). These noise levels apply unless otherwise arranged between the Court, MWRA
and the Town of Winthrop. The impacts of noise from the construction of the new
treatment facilities will be addressed further in a separate EPA environmental
review of these facilities.
Noise due to the construction of the tunnelled outfall will be a relatively minor
component of total construction-related noise impacts on Deer Island and will be at
or below the ambient sound levels of 145 dBA during the day and 39 dBA during the
night. If barging of excess tunnel spoils to the Foul Area Disposal Site is
required, noise at Deer Island would be 119 dBA due to barge operation (MWRA,
STFP III, 1987). Therefore, noise impacts on Point Shirley, due to outfall tunnel
construction alone, are expected to be insignificant. Barging of tunnelled material
would have only a minor noise impact on Point Shirley and would never be louder than
the expected noise levels caused by the entire Deer Island construction project.
MWRA plans to mitigate noise impacts at the Deer Island construction site by
constructing soundproofing berms which will act as a barrier between Deer Island and
Point Shirley.
5.2.2 ENGINEERING FEASIBILITY - (OUTFALL TUNNEL CONSTRUCTION)
Reliability. Tunnel construction has been successfully used throughout the world
for wastewater conduits. The tunnelled outfall system is expected to operate
reliably over the range of expected conditions for its design life.
Constructability. MWRA indicates that the longest tunnel constructed to date is
8.5 miles (MWRA, STFP V,E, 1987). Given the available tunnelling technology,
however, constructing a tunnelled outfall to Site 5 is considered feasible, although
it might push on the edge of technological limitations. The technological
uncertainties associated with tunnel construction to Site 5 would probably not be of
concern during tunnel construction to Site 2. Thus, tunnel construction to Site 2
is considered to be less risky than to Site 5. It is expected that the tunnel
boring machine will proceed at an average rate of 50 to 70 feet per day. Tunnel
construction would not be affected by weather and could proceed throughout the year.
5.2.3 COST - (OUTFALL TUNNEL CONSTRUCTION)
Capital Cost. The cost of the access shaft on Deer Island for a tunnel outfall
system to either Site 2, 11 or 5 is approximately $10 million (G. Sankey, 1988)
(Table 5.2.3.a). The total cost for Site 2 is $151 million. Therefore, the average
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TABLE 5.2.3.a. COSTS OF THE TUNNELLED OUTFALL SYSTEM ALTERNATIVES
Site
Tunnel
Length
(feet)
Cost
($
Shaft
million)
($
Tunnel
million)
($
Total
million)
2
28,000
10
1241
151
14
143,000
10
238
2148
5
5 4,000
10
313
323
iirces: MWRA STFP V, 1987 and
Sankey,
1988.
cost of tunnel construction to Site 2 is $5,036 per foot, (the quantity $151 million
sinus $10 million, divided by 28,000 feet). Similarly, the average cost of tunnel
construction to Site 14 is $5,535 per foot, and to Site 5, the average cost of tunnel
construction is $5,796 per foot. Cost of tunnel construction per linear foot
increases with distance. One reason for this trend is that as distance increases,
so does travel time for construction workers. Thus, while they would be paid for a
full day of work, the workers may only spend 5 to 6 hours on the actual construction
at some sites. In addition, with increased distance from Deer Island, the tunnel
boring machine will require increased maintenance. For Site 5, a one-month overhaul
period would be required for the tunnel boring machine, thus incurring costs for
overhauling and construction down-time. Construction to Site 14 would be 624 percent
aore costly than to Site 2, while to Site 5, construction would be 1124 percent more
expensive than to Site 2. In addition, construction cost per foot increases with
the distance of the tunnel. Tunnelling expenses to Site 14 would be 10 percent
greater per foot than to Site 2. The cost per foot for tunnel construction to
Site 5 would be 15 percent higher than to Site 2.
5.2.1 MATERIALS DISPOSAL - (OUTFALL TUNNEL CONSTRUCTION)
Disposal of Tunnelled Material. Some materials excavated from the shaft on Deer
Island and the outfall tunnel will be disposed at upland areas other than Deer
Island (MWRA, STFP V, 1987). Amounts of tunnelled materials for each of the outfall
locations are 770,000 cu yd for Site 2, 1.28 million cu yd for Site 14, and 1.86
pillion cu yd for Site 5. Difference in amounts of excavated materials for various
outfall lengths is not the major factor in outfall site selection, since the
terials are not expected to be contaminated and possibilities for disposal or
weneficial use of the materials exist. Possibilities for using the materials as
aggregate for low-strength concrete or as backfill in the Third Harbor
Tunnel/Central Artery highway project are being evaluated (MWRA, STFP V, 1987).
Materials will likely be shipped via roll-on/roll-off ferry or barge to onshore
facilities for final truck or rail transport for disposal (MWRA, WTFP 7, 1987).
When the disposal site for the tunnelled material has been designated (after
environmental impact analysis), all applicable permits will have to be applied for
and permits will have to be adhered to.
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5.2.5 INSTITUTIONAL - (OUTFALL TUNNEL CONSTRUCTION)
Construction Duration. MWRA predicted outfall tunnel construction to Site 2 would
be complete by August 19914 to Site 14 by December 19914, and to Site 5 by May 1995
(MWRA, STFP V,E, 1987). A tunnelled outfall at any site would not meet the court
schedule of July 19914 for completion of the outfall system. However, a tunnelled
outfall for any sites would be available by the court-ordered completion date of
July 1995 for the new primary treatment plant at Deer Island.
Permitting. Only U.S. ACOE Section 10 permitting for the construction of the
tunnelled outfall system is anticipated (Appendix G). Tunnelled materials could be
used in local construction projects such as construction of the Third Harbor
Tunnel. Unused material would be disposed at an on-land disposal site which would
require certain permits depending on the sites selected.
Demand for Unique or Scarce Construction Resources. There will be a major demand
for tunnel construction resources, equipment and workers during construction of the
tunnelled outfall system. This project will be in competition for construction
resources with the Massachusetts Department of Public Works (Mass DPW) Third Harbor
Tunnel project and MWRA’s inter-island conduit system. A shortage of these
resources could occur. Coordination within MWRA as well as between MWRA and MassDPW
for proper allocation of tunnel construction resources is necessary to prevent
project delays.
5.2.6 HARBOR RESOURCES - (OUTFALL TUNNEL CONSTRUCTION)
Protection of Cultural and Historical Resources. The average depth to the top of
the tunnelled outfall will be between 210 and 235 feet. This includes a minimum of
60 feet of bedrock which will overlie the tunnel. Therefore, no cultural or
historical resources will be affected by tunnel construction.
Water Traffic. Tunnelling of the effluent outfall system would be conducted below
the surface of the sea floor. Tunnel spoils would be removed through the Deer
Island access shaft. It is possible that tunnel spoils which are not used in the
site preparation of Deer Island could be barged through Quincy to upland disposal
sites or to construction sites for reuse. The equivalent of one 3,000-ton barge
trip per day would be required to keep pace with tunnel boring at all sites.
5.3 DIFFUSER
Two diffuser construction alternatives are evaluated in detail, using the criteria
presented in Chapter 3. The first diffuser alternative (drilled risers) is a
tunnelled diffuser with approximately 50 to 100 risers drilled through the overlying
sediment and bedrock and attached to the tunnel. Each drilled riser would be fitted
with a multi-port (8 to 10 ports) cap. The second alternative (pipeline) is a
tunnelled outfall connected to a pipeline diffuser system by one to ten risers.
5.3.1 DRIII F1) RISER DIFFUSER
5.3.1.1 ENVIRONMENTAL - (DRILLED RISER DIFFUSER)
Noise Control. MWRA estimated the noise levels on Point Shirley, Winthrop and in
Nahant due to construction of a drilled riser diffuser between Sites 14.5 and 5
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(MWRA, STFP V, 1987). During construction of the tunnelled diffuser with drilled
risers, sound levels in Winthrop would be 20 dBA or less during normal conditions
and 35 dBA during conditions of atmospheric thermal inversion. In Nahant, predicted
noise levels were 27 dBA or less during most atmospheric conditions and up to 1 dBP .
during inversion weather conditions. These estimates are based on . rate of 6
decibels per doubling of distance during usual hemispherical radiation and 3
decibels per doubling of distance during periods of thermal inversion.
5.3.1.2 ENGINEERING FEASIBILITY - (DRILLED RISER DIFFUSER)
Reliability. The riser caps of the drilled diffuser would not protrude much and
therefore, would not be susceptible to much damage. Purging of this system would be
an issue during diffuser operation and therefore must be considered in final design.
Constructibility. The drilling of risers is a proven technology and there are
relatively few unknowns which could cause difficulties during construction. It is
anticipated that weather-related down-time will occur during four months of each
year of diffuser construction. Each drilled riser is expected to require 1 to 1
weeks to drill (MWRA, STFP V, 1987).
5.3.1.3 MATERIALS DISPOSAL — (DRILLED RISER DIFFUSER)
Disposal of Excavated Material. Approximately 50 cu. yds of material every 1 to 2
weeks would be excavated during the four to five year drilled riser diffuser
construction period. A total of 12,000 cubic yards of material will result from
this excavation (MWRA, STFP V, 1987). Disposal of this material would be minor and
would likely occur at the Foul Area, as described in 5.3.2iL. Since the vast
majority of the material excavated from drilled risers would originate far below the
sea floor and thus be clean, acceptance of the material for disposal is not likely
to be a problem, so no major differences among the outfall site alternatives occur.
5.3.1.18 INSTITUTIONAL - (DRILLED RISER DIFFUSER)
Construction Duration. MWRA estimated that construction of an 80 drilled riser
diffuser would require up to 36 months. This estimate assumes a 1 to 1 week period
for the drilling of each riser, 6 months of initial mobilization and months down-
time each year during winter months. Diffuser construction would begin in July 1991
and be completed by the court—ordered deadline of July 199 4 for outfall construction
completion. Therefore, the tunnel construction, not the diffuser construction, will
be the critical factor in meeting the court’s deadline.
Disposal permitting would require time, in addition to external and internal
coordination, but should not cause project delay.
Permitting. Drilled riser construction and ocean disposal of dredged material would
require a permit from the U.S. Army Corps of Engineers (USACE) subject to approval
by EPA. In addition, material which is excavated during drilling could be barged
from the construction site to an onshore facility and trucked to upland disposal or
use as construction fill. It is possible that the material could also be ocean
dumped, which would require an ocean dumping permit from EPA (Appendix G).
Den nd for Unique or Scarce Construction Resources. No other major offshore
drilling projects are planned for the Boston area in the near future. Therefore,
competition with other projects for obtaining a semi-submersible drilling platform
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or a jack—up barge for drilled riser construction should not be a significant
problem. The construction of a drilled riser diffuser could be in competition for
skilled workers with other local projects, including some of MWRA’s projects.
However, this is not anticipated to be a significant problem since the increased
construction work in the Boston area is likely to attract workers from other regions
of the country.
5.3.1.5 MARINE ECOSYSTEM - (DRILLED RISER DIFFUSER)
Protection of Water Quality. The drilling of 80 risers is expected to result in
temporarily increased turbidity which would cause a reduction in available light
necessary for primary productivity. Drilled material would be disposed at the Foul
Area Disposal Site. Impacts due to drilling and disposal would be short-term, as
the disturbed sediments would settle rapidly, and minor since only 150 cu. yds of
material would be excavated and disposed of every one to two weeks.
Protection of Sensitive Biota and Habitat. Construction of the drilled riser
diffuser will result in some minimal temporary impacts to the benthic conununity.
Construction of the diffuser risers is expected to result in the permanent removal
of a total of 2,200 square feet of benthic habitat over a four to five year period
(MWRA, STFP V,B, 1987). Because of the length of the diffuser and the heterogeneity
of the sea floor, it is likely that both hard and soft bottom communities will be
removed. Because of the relatively small area of habitat removal, it is unlikely
that there will be any long term effect on local communities in the study area
(Appendix C). Due to the small volume of material to be disposed at the Foul Area
Disposal Site, adverse impacts on benthos in the vicinity of the disposal site are
expected to be minor and limited in range.
5.3.1.6 HARBOR RES(XJRCES - (DRILLED RISER DIFFUSER)
Protection of Cultural and Historical Resources. Impacts on cultural resources are
limited to the area disturbed by the actual drilling of riser shafts. Because this
area is small, impacts are anticipated to be minimal and could be mitigated. It is
anticipated that precise locations of resources (wrecksites) can be determined and
avoided by adjusting diffuser riser locations or mitigated through recovery
documentation of resources in accordance with State and Federal guidelines.
Water Traffic. The installation of a drilling platform is required for the
construction of the drilled riser diffuser. Potential adverse impacts on water
traffic will not be a factor in selecting the discharge location. Despite the
presence of the drilling platform, most of the construction-related traffic would
occur outside of the major shipping lanes. Minimal barging would be required for
transporting workers to the construction site and for removal of material from
drilling the risers.
Protection of Comimercial Fishing Activities. Anticipated impacts on commercial
fisheries at the outfall locations include a five year disruption of fishing in the
vicinity of construction when access to the area will be precluded by the presence
of drilling equipment. During diffuser operation, the riser structures will be
obstacles which may foul fishing nets. Minimal impacts are anticipated because only
a small portion of the sea floor is actually affected by drilled risers, and the
distance between the risers may be large enough for small nets to pass through.
Also, riser design is expected to minimize fouling of nets.
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5.3.2 PIPE DIFFUSER
5.3.2.1 ENVIRONMENTAL - (PIPE DIFFUSER)
Iloise Control. It is anticipated that the above ground construction of a pipeline
diffuser, involving trench and riser excavation, would create more noise than would
construction of a tunnelled diffuser with 50 to 100 risers. This assumption is
based on the fact that all of the construction of a pipeline diffuser will be
conducted above the earth’s surface as opposed to a tunnelled diffuser with drilled
risers which would mainly be constructed beneath the bedrock. Therefore, based on
MWRA’s estimate of noise levels due to the construction of a drilled riser diffuser
between Sites 1 L5 and 5, noise levels due to construction of the pipeline diffuser
could be higher than 20 dBA during normal weather conditions and 35 dBP during
thermal inversions at Point Shirley, and higher than 27 dBA during normal conditions
and 1 1 dBA during temperature inversions in Nahant.
5.3.2.2 ENGINEERING FEASIBILITY - (PIPE DIFFUSER)
Reliability. The dynamic head required to purge seawater from the diffuser and
prevent intrusion of seawater to the system would be minimal for the pipeline
diffuser (MWRA, STFP V,D, 1987). However, the risers of the pipeline diffuser would
be susceptible to damage due to wave action, anchors and dragger fishermen since its
risers will be exposed to such elements. In addition, the pipeline diffuser could
be at risk of damage by earthquakes since it could cross geological faults in the
bedrock.
Constructibility. Some difficulty could be expected with the construction of a
pipeline diffuser. This type of construction could be subject to weather delays
during winter months. In addition, dredging is not typically conducted in water
depths of approximately 100 feet. Therefore, a clamshell digger may have to be used
for excavation which would likely require more time than MWRA anticipated for
dredging.
5.3.2.3 MATERIALS DISPOSAL - (PIPE DIFFUSER)
Disposal of Excavated Material. Dredged material from the trench excavated for a
pipe diffuser would be the only material requiring disposal. To establish a
conservative estimate of the amount of dredged material to be disposed of, the
assumptions of a 6,600-foot-long diffuser pipe, an average of 35 feet for trench
depth, and 1 to 14 slope for trench sides have been made. This yields a conservative
total estimate of 1. 4 million cubic yards of dredged material which must be disposed.
Disposal would likely take place at the Foul Area Disposal Site (See Section 14.4).
Sediment quality at the proposed outfall sites has been sampled and analyzed
(Appendix B) (MWRA, STFP V,S, 1987) and compared to Foul Area sediments. Dredged
mterial from Sites 2, 4 and 5 would likely be approved for disposal at the Foul
Area by the U.S. Army COE.
5.3.2.14 INSTITUTIONAL - (PIPE DIFFUSER)
Construction Duration. it is anticipated that the pipeline diffuser construction
schedule will adhere to the court—ordered deadlines of July 1991 for initiation and
July 19914 for completion of construction. Therefore, the tunnel construction, not
the diffuser construction will be the critical factor in meeting the court’s
deadline.
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Disposal permitting would require time, in addition to internal and external
coordination, but should not cause project delay.
Permitting. Construction of a pipeline diffuser would require a permit for the
dredging and disposal. Dredging material will be disposed at the Foul Area Disposal
Site.
De nd for Unique or Scarce Construction Resources. While there could be other
major offshore dredging projects in the Boston area in the near future, it is
unlikely that dredging equipment would be difficult to obtain. The construction of
a pipeline diffuser could be in competition for skilled workers with other local
construction projects including some of MWRA’S projects. This is not anticipated to
be a significant problem, however, as the increased construction work in the Boston
area is likely to attract workers from other regions of the country.
5.3.2.5 MARINE ECOSYSTEM - (PIPE DIFFUSER)
Protection of Water Quality. Dredging activity may cause a temporary increase in
water column turbidity which may result in reduction of light available for primary
production. These impacts are expected to be minimal since sediments will settle
rapidly. Disposal of dredged material at the Foul Area could temporarily increase
turbidity and depress dissolved oxygen concentrations in the water column. Impacts
due to disposal are not expected to be significant since disposal will be conducted
over an extended period of time.
Protection of Sensitive Biota and Habitat. The construction of a pipe diffuser will
require the dredging of a maximum of approximately 1.11 million cubic yards of
sediment (based on assumed 35-foot-deep trench with 11:1 slope) resulting in the
alteration of approximately 175,000 square yards of benthic habitat. Blasting may
be required in some areas, this would kill or injure marine organisms around the
explosions. Theseimpacts are judged to be minor because of the relatively small
area. After the diffuser is placed in the dredged trench, the trench will be filled
and covered with armoring rocks and boulders. This armoring material will provide
new habitat on which hard bottom species (such as those described in Appendix C,
section C.1.2.2) will colonize. Disposal of 1.11 million cu. yds. of material at the
Foul Area Disposal Site would have a greater adverse impact on benthos and fish
habitat than would disposal of material from drilled riser diffuser construction
(12,000 cu. yds.). However, the material excavated for the pipeline diffuser would
be clean and therefore could be used to cap more contaminated projects if the timing
is appropriate.
Impacts on sensitive biota and habitat are expected to be minimal, but because
excavated trench construction disrupts a much greater area than drilled riser
construction, and changes soft bottom habitat to hard bottom, the dredged trench
construction is more likely to impact sensitive biota and habitat than drilled riser
construction.
5.3.2.6 HARBOR RESOURCES - (PIPE DIFFUSER)
Protection of Cultural and Historical Resources. The likelihood of impacting
cultural and archaeological resources is also greater for dredged trench
construction than for the drilled riser diffuser because of the large bottom area
which would be disturbed (Appendix D).
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Water Traffic. Traffic impacts due to construction of a pipeline diffuser are
expected to be moderate since pipeline diffuser construction would require barge.-
mounted equipment at the construction site. In addition, barges would be used to
transport workers to the site and to carry the excavated material from the
construction site to the shore. However, most of the construction related traffic
would occur outside of the major shipping lanes. Potential adverse impacts on water
traffic will not be a factor in selecting the discharge location.
Protection of Coninercial Fishing Activities. Dredged trench construction will
impact commercial fishing by changing the bottom character from soft to hard bottom,
creating more obstacles to commercial fishing than drilled risers (Appendix D).
In addition, the pipeline diffuser would have approximately 6140 risers extending
through the sea floor, as opposed to the drilled riser diffuser which would have
80. Therefore, interference with fishing activities, such as dragging, would be
more significant with the pipeline diffuser than with the drilled riser diffuser.
5.11 INTER-ISLAND CONDUIT
The inter-island conveyance alternative selected for detailed evaluation is an
11-ft. inside diameter deep rock tunnel from Nut Island to Deer Island. Vertical
access shafts would be excavated on both Nut and Deer Islands. The 214,800-ft. -long
tunnel would begin at Deer Island, sloping positively towards Nut Island. Tunnel
spoils would be removed through the Deer Island access shaft. The tunnel would be
lined with reinforced concrete (MWRA, STFP IV, 1987).
Impacts due to construction of a tunnelled inter-island conduit system are described
below. No impacts on the marine ecosystem would occur due to the inter-island
tunnel construction since all construction activity would take place completely
within the bedrock below the sea floor.
5.14.1 ENVIRONMENTAL - (INTER-ISLAND CONDUIT)
Air Emissions Control. Ventilation requirements of the inter-island conduit during
construction will be similar to those required during construction of the outfall
system.
loise Control. Noise due to construction of the vertical access shafts for the
inter-island tunnel is expected to be audible in the communities adjacent to Nut and
Deer Islands. In the Point Shirley area, where ambient daytime noise is 145 dBA and
ambient nighttime noise is 39 dBA, the highest expected noise due to construction of
the access shaft would be 55 dBA. This noise would be due to the operation of the
clamshell digger and trucks. Silenced sheet piling activities are predicted to
result in impulse sound levels of 51 dBA at Point Shirley.
According to MWRA’s analysis, the daytime ambient sound level at Nut Island is U7
dBA. A nighttime ambient sound level for Nut Island was not measured by MWRA but
was estimated to be 35 dBA based on sound data available for typical suburban
residential areas. Operation of the clamshell digger and trucks during construction
of the access shaft would cause levels of 58 dBA on nearby Great Hill. Silenced
sheetpile driving would cause a noise level of 62 dBA.
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5.11.2 ENGINEERING FEASIBILITY - (INrER-ISLANT) CONDUIT)
Reliability. The tunnelled inter—island conveyance system is expected to operate
reliably over the range of expected conditions during its design life.
Constructibility. With a tunnel boring machine (TBM) expected to progress at a rate
of 50 to 70 ft/day, construction of the inter—island tunnel is expected to take
36 months. Tunnel construction is not affected by weather and can proceed
throughout the year. The 2L ,80O_ft. conduit is well within the range of tunnel
lengths previously constructed.
5.4.3 COST - (INTER-ISLAND CONDUIT)
Present Worth Cost. The present worth cost of a tunnelled inter—island conduit
between Nut and Deer Islands is $63 million. This cost is the sum of all costs for
construction and operation of the tunnelled inter-island conduit system through the
year 2020. The value is presented in the form of a single investment in
September 1986 dollars.
Project Cost. The project cost for the tunnelled inter-island conduit system is
$83 million. This value includes all capital costs to construct the system, costs
for equipment replacement through the year 2020 and 35 percent for contingencies and
engineering- costs. Cost is presented in September 1986 dollars.
5.4.4 MATERIALS DISPOSAL - (IIITER-ISLAIJD CONDUIT)
Disposal of Tunnelled Material. All of the excavated materials resulting from the
construction of the inter-island conduit will be utilized during construction of the
secondary treatment plant (MWRA, STFP IV, 1987). Materials excavated from the
conduit total 197,000 cubic yards. Most will be used on Deer Island as fill for
vision and noise screening landforms. Three thousand cubic yards of materials
removed from the Nut Island shaft will be used as fill on Nut Island (MWRA, STFP IV,
1987).
5.4.5 INSTITuTIONAL - (INTER-ISLAND CONDUIT)
Construction Duration. MWRA estimated that construction of the inter—island conduit
system would begin in December 1991. This misses the April 1991 court—ordered
deadline by eight months (MWRA, STFP IV, 1987). Construction is expected to
proceed, uninterrupted, for 36 months. Completion of construction would coincide
with the court-imposed date of December 199 1 L
Peraitting. Only a Section 10 permit for the construction of the tunnelled inter-
island conduit system is anticipated. The tunnelled materials obtained during
construction will be used during site preparation of the construction at Deer
Island. Therefore, no disposal permitting for the tunnelled material will be
required.
Demand for Unique and Scarce Construction Resources. The demand for tunnel
construction resources, equipment and workers due to the inter—island conduit
struction will be similar to demand due to construction of the effluent outfall
system.
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511.6 HARBOR RESOURCES - (INTER-ISLANI) CONDUIT)
protection of Cultural and Historical Resources. The depth to the top of the
tunnelled inter-island conduit will range between 200 and 300 feet. This includes a
minimum of 30 feet of bedrock which will overlie the tunnel. Therefore, no cultural
or historical resources will be affected by tunnel construction.
Water Traffic. Tunnelling of the inter-island conduit system would be conducted
below the surface of the harbor floor. Tunnel spoils would be removed through the
Deer Island access shaft. All tunnel spoils from the inter-island conduit
construction would be used in the site preparation of the Deer Island Wastewater
treatment plant. Thus no barging of the material would be required. •Since all
construction of the tunnelled inter-island conduit system would be below the
ground’s surface and no barging of the tunnelled material would be required, this
alternative would have no impact on marine traffic.
5.5 SUMMARY OF ECONOMIC IMPACTS
Appendix E presents a full evaluation of economic impacts. This section summarizes
these impacts.
A complete review of the financial impacts of the new treatment facilities on the
PIWRA’s cash flow requirements was completed for MWRA’s Secondary Treatment Facility
Plan (MWRA, STFP VII, 1987). The assumptions made for the STFP concerning
inflation; MWRA capital expenditures, operating expenditures, and revenue
requirements; and estimates of local expenses for the communities analyzed were used
as the base for determining the financial impact of each of the selected outfall
alternatives.
Outfall alternatives Site 2, Site 14 and Site 5 have estimated construction costs of
$276 million, $389 million, and $‘468 million, respectively (Chapter 3). The
financial impacts on individual sewer users for each of the outfall locations is
considered.
As a part of its current revenue system, the P4WRA charges the 143 member communities
for their use of the MWRA facilities. The member communities pass the costs on to
the individual users through sewer use charges and/or property taxes, depending on
the type of recovery programs the individual towns employ. Two communities, Boston
and Needham, were selected as examples to illustrate what the impact on sewer
charges will be if each of the three alternatives were selected.
In order to evaluate the financial impact of the three alternative outfall
locations, the same bond amounts having the same duration were assumed for each
outfall site, with all construction scheduled to be complete by 1996. Therefore,
the sewer use charge would be the same for each site for each type of user for each
of the years 1997 to 2005. However, the sewer use charge would increase annually.
5.5.1 BOSTON
In the City of Boston, a financially independent agency, the Boston Water and Sewer
Co inission (BWSC), is responsible for operating the water, sewer and drainage
services, as well as recovering all costs for their expenses. All costs are
recovered through water and sewer rates. For this analysis, only the impacts on the
sewer portion of a user’s bill is considered.
5—68

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Financial impacts on three categories of sewer users are evaluated: single_family
residential (10,000 cu ft/yr), commercial (500,000 cu ft/yr) and large commercial
(5,000,000 cu ft/yr). The sewer use charges for the three types of users for each
outfall site from the year 1990 to 1997 are presented in Table 5.5.1.a. The
complete financial analysis for Boston is presented in Appendix E.
5.5.2 NEEDHAN
Needham recovers its sewer expenses through a combination of sewer use charges and
property tax assessments. A recent policy was adopted regarding wastewater expense
recovery whereby the last Metropolitan District Coninission (MDC) assessment charge
to the town, which was $297,575, plus all local wastewater-related expenses will be
recovered through a property tax assessment. All MWRA assessments in excess of the
last MDC assessment will be recovered through a local sewer use charge system.
Using this methodology, the majority of sewer charges attributable to the new MWRA
wastewater treatment facilities will be recovered through the sewer rate charge.
For the purposes of determining the impacts of the three outfall alternatives,
property tax assessment would remain equal for each alternative. Only the sewer
rate portion of the user charge would vary.
The categories of users evaluated for Needham are residential (10,000 cubic ft/yr)
and large volume (30,000 cubic ft/yr). The sewer charges, which includes a sewer
rate charge plus a property tax, for both types of users for each outfall site
location are presented in Table 5.5.2.a. The complete financial analysis for
Needham is presented in Appendix E.
5—69

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TABLE 5.5.1 .a. SUMMARY OF SEWER USE CHARGES FOR THE OUTFALL ALTERNATIVES, BOSTON
YEAR
1990 1991 1992 1993 19914(1) iggs(1) 1996(1) 1997(2)
Residential
(10,000 cu ft/yr)
Site 2 $180 $225 $260 $301 $3140 $313 $370 $14146
Site 14 182 229 265 307 3’48 370 370 14146
Site 5 183 230 267 310 352 375 1406 14146
Commercial
(500,000 cu ft/yr)
Site 2 $11,716 $114,656 $16,980 $19,637 $22, 1146 $20,1410 $214,112 $29,105
Site 14 11,8149 114,906 17,275 20,035 22,711 214,109 214,112 29,105
Site 5 11,911 15,023 17,1413 20,222 22,975 214,1489 26,515 29,105
Large Commercial
(5,000,000 cu ft/yr)
Site 2 $98,767 $123,5147 $1143,138 $165,533 $186,688 $172,053 $203,261 $2 145,3148
Site 11 99,882 125,6514 1145,623 168,896 191,14149 203,3214 203,261 2145,3148
Site 5 100,1405 126,6141 1146,786 170,1471 193,678 206,14140 223,519 2145,3148
1. Site 2 construction completed in 19914, resulting in a decrease in user charges for 1995. Site 14 construction
completed in 1995, resulting in approximately equal charges for 1995 and 1996. Site 5 construction completed in
1996.
2. From 1997 to 2005, the sewer use charge for all three sites for each category of user remains equal.

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TABLE 5.5.2 .a SU)I1ARY OF SEWER CHARGES FOR THE OUTFALL ALTERNATIVES, NEEDHAN
Site 2 construction completion in 1991 , resulting in a decrease
completed in 1995, resulting in approximately equal charges for
1996.
2. From 1997 to 2005, the sewer use charge for all three sites for
YEAR
1990
1991
1992
1993
l991I (
1995(1)
1996(1)
997(2 )
Residential,
(10,000 cu
ft/yr)
Site 2
Site )4
Site 5
$222
225
226
$279
28 4
287
$326
332
335
$379
387
391
$‘428
LtZ 1
L ’ 46
$390
‘469
1477
$k66
‘466
517
$568
568
568
Large User,
(30,000 cu
ft/yr)
Site 2
Site 14
Site 5
$1483
1492
1496
$649
665
672
$787
805
81 ’4
$9143
968
980
$1,089
1,125
1,1142
$972
1,208
1,232
$1,196
1,196
1,3149
$1,498
1,498
1,1498
1.
in user charges for 1995. Site 14 construction
1995 and 1996. Site 5 construction completed in
each type of user remains equal.

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CHAPTER 6
CUMULATIVE IMPACTS
AND
OPERATIONAL RELIABILITY
6.1 OVERVIEW
EPA’s Environmental Review Procedures for the Wastewater Treatment Construction
Grants Program (140 CFR Ch.1, Sec. 6.506) require analysis of the direct, indirect
and cumulative environmental effects of alternatives. Chapter Five of this Draft
SEIS covers the direct and indirect environmental effects of the inter-island
conveyance and effluent outfall alternatives; this chapter focuses on cumulative
effects. Section 6.2 provides background information on the proposed project’s
relationship to other major projects that could contribute to cumulative impacts and
thus affect the comparison of alternatives. Section 6.3 evaluates the prediction of
impacts and comparison of alternatives presented in Chapter Five in light of the
other projects described in Section 6.2. Section 6.14 presents a summary of the
operational characteristics of the Deer Island Wastewater Treatment Plant, as they
relate to the predicted effluent quality (full discussion in Appendix H). These
analyses insure that factors other than the location of the discharge are considered
when alternatives are compared.
Each alternative could have slightly different cumulative effects in each area of
analysis. Emphasis is placed in this discussion on those areas where the inter-
island conduit and effluent outfall are expected to contribute a significant share
of the total cumulative impact when compared to the contributions of other
projects. Those areas are:
(1) Marine Water Quality, Sediment Quality and Marine Ecosystems
(2) Disposal of Excavated Material
(3) Traffic and Transportation
(14) Socioeconomic Considerations
Regarding water/sediment quality, the alternative effluent discharges will interact
within Massachusetts Bay with the effluent discharges from other wastewater
treatment facilities and combined sewer overflows (CSO). The disposal of excavated
material from the inter-island conduit and the effluent outfall will occur
simultaneously with that from the Central Artery/Third Harbor Tunnel and other
dredging projects in Boston. Regarding traffic and socioeconomic considerations,
the construction impacts of the inter-island conduit and outfall will constitute
significant fractions of the total on-land and marine traffic and socioeconomic
impacts brought about by the entire Secondary Treatment Facilities Plan (STFP).
Figure 6.1.a shows the schedules for the STFP projects. Other projects which could
contribute to cumulative impacts (e.g. other wastewater discharges in Hull and
Gloucester) were given initial consideration but are not discussed in detail here
because their relative contributions were judged likely to be too small and/or
remote to add significantly to the impacts of the MWRA inter-island conduit and/or
effluent outfall.
6—1

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6,2 CUMULATIVE IMPACT SCENARIO
The following subsections contain summary descriptions of projects, including STFP
projects, that could interact and cause cumulative impacts.
6.2.2 WATER QUALITY, SEDIMENT QUALITY AND MARINE ECOSYSTEMS
There are several other discharges to Massachusetts Bay which could affect the water
quality, predictions done for the MWRA discharge (Figure 6.1.b). These include:
• Lynn Outfall - 22.i mgd
• Southeast Essex Sewerage District (SESD) Outfall - 26.8 mgd
• Swampscott Outfall - 2.19 mgd
• Boston Inner Harbor Combined Sewer Overflow (CSO) and Stormwater - 7.0 mgd.
In addition, other discharges in the study area, such as Hull and Gloucester, have
been judged either too small or too far from any of the alternative discharge sites
to influence water quality projections for the MWRA discharge (MWRA, STFP V,A,
1987).
6.2.3 DISPOSAL OF EXCAVATED AND DREDGED MATERIAL
The combined volume of excavated tunnel waste requiring reuse or disposal from the
MWRA inter-island conduit and outfall tunnel alternative will range from about 1 to
2 million cubic yards (MWRA, STFP IV and V, 1987). About 200,000 cubic yards would
be from the inter-island conduit and would be used on Deer Island along with
approximately 1.6 million cubic yards of drumlin material (MWRA, STFP I and IV,
1987). In an overlapping timeframe, excavations by the Massachusetts Department of
Public Works associated with depression of the Central Artery and construction of a
Third Harbor Tunnel in Boston are expected to generate some 7 million cubic yards of
material requiring disposal. The cumulative generation of material from all of
these projects could affect disposal options for excavated tunnel material.
Construction of MWRA’s on—island and on-shore pier facilities will contribute an
estimated 275,000 cubic yards of dredged material. The Third Harbor Tunnel/Central
Artery Project will generate approximately one million cubic yards of dredged
material. Estimated totals of dredged material from other projects is 3 million
cubic yards per decade. All of this material could potentially be disposed of at
the Foul Area Disposal Site. In addition, proposed Boston Harbor Navigation
Improvement projects would generate 2 to 3 million cubic yards.
6.2k TRAFFIC AND TRANSPORTATION
Mitigation requirements established in EPA’s Record of Decision (ROD) on the siting
of the Deer Island treatment plant are designed to reduce project-related impacts of
Cumulative truck traffic to and from Deer Island through Winthrop. The resulting
approach includes reliance on marine transportation by barge, ferry and roll-
6—2

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FACIUTIES PLANNING
SITE PREPARATION I
EARLY SITE PREP
COMPLETION BITE PREP I
CONCRETE BATCHING PLANT
POWER & ELECTRICAL FACILITI
IMMEDIATE POWER
PERMANENT POWER
INTER — ISLAND TUNNEL
OEOTECI4NICAL S DESIGN
CONSTRUCTION
PLANT EFFLUENT OUTFALL
GEOTECHNICAL S DESIGN
CONSTRUCTION
NUT ISLAND HEADWORKS
PRIM TREATMENT FACILITIES
ZONE A PHASE i
ZONE A PHASE 2
ZONE A PHASE 3
ZONE B
SOUTH FLOW PUMP STATION
RESIDUALS PHASE I
SITE PREPARATION II
SECONDARY TREATMENT FACIL.
ZONE A
ZONE S
SITE PREPARATION III
RESIDUALS PHASE 2
PROJECT MANAGEMENT
COURT MANDATED SCHED DATES
SOURCE: MWRA STFP VII, 1987
L(CEND:
-oEID/EIR REPORTS
• DESIGN PERIOD
CONSTRUCTION
11/111111111 iii , BID & AWARD PERIOC
• —.PROJ. MANAGEMENT
— -- - CONSTRAINT
w
— — INITIATE CONSTRUCTiON SEC TREATMENT PACIL — I2 ES
cOMPIJ TI CORPYR PRIM TREATMENT PA IL — 7 19 5
INITIATE COEMYR. NAEMCR IUNIUL — . CORIPLITE CONST* HARSOR TUNNEL 12 /94
INmATE CONUTRUCflCO C I.SU CONsTRUCTION OUTPALI. - 7 / 94
EMIM. TRIAIMIN? PACIUTY CONsISTS CONSTRUcTION SEC. TREATMENT PACI UT? 72/ES
FIGURE 6.1.a. PROJECT TIME FRAME

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o
a
SITE 4
0
OUTFALL
.
SITE 5
DEER ISLAND OUTFALL
ESSEX OUTFALL
NUT ISLAND OUTFALL
LEGEND
• SEWAGE DISCHARGE
LOCATION
NAUTICAL MILES
FIGURE 6. 1.b. SEWAGE DISCHARGE TO MASSACHUSETTS BAY
4
•
3
0
3
6-’L

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on/roll-off (RO/RO) vessels between Deer Island and proposed pier and construction
staging areas in Quincy and Charlestown and personnel ferry piers in Hinghain, Boston
and Quincy. There will be cumulative marine traffic/transportation impacts in
Boston Harbor and these are discussed in Appendix D. Cumulative on—land
traffic/transportation effects will occur near the staging areas and are covered in
EPA ’s environmental review of the WTFP. However, the magnitude of the individual or
cumulative traffic movements has yet to be reconciled among various estimates
presented in different elements of the STFP documentation. In particular, truck
traffic estimates for the tunnel and outfall construction have yet to be reconciled
by MWRA between those presented in Volumes III and V of the STFP and Volumes 8 and 9
of the WTFP. There will also be traffic impact due to interim residuals processing
activities at the Quincy staging site between 1991-95 and potential impacts from
long term sludge management facilities. This will be addressed in the environmental
reviews now being prepared for residuals management.
6.2.5 SOCIOECONOMIC CONSIDERATIONS
The combined inter-island conduit and outfall construction could make measurable and
potentially significant contributions to total cumulative impacts on two categories
of socioeconomic considerations: these are the total capital costs of the Secondary
Treatment Facility Plan and the construction labor force requirements for major
excavation projects in the Boston area in the 1990-95 time frame. Capital costs are
part of EPA’s considerations in Its environmental review of construction grants
projects, while construction labor requirements are of concern because they could
impact the timely implementation of the harbor cleanup.
Depending on the selected outfall location, construction costs of’ the inter-island
conduit and outfall are estimated by MWRA to range between $350 million and
$550 million, of which the inter—island conduit represents about 15 to 25 percent
(14WRA, STFP IV and V, 1987). Detailed discussion of these costs is presented in
Appendix E. The cumulative total capital costs of the STFP have been estimated to
be about $2.8 billion, with the inter-island conduit and outfall representing about
20 percent of the total (MWRA, STFP III, 1987). These figures do not reflect costs
of the residuals management facilities, which have been projected at about
$650 million.
Daily construction labor requirements for the inter-island conduit and outfall are
projected by MWRA in the range from 100 to 600 workers each between 1990_91$,
depending on the activities underway (MWRA, STFP IV and V, 1987). The demand for
these workers would occur at the same time as a demand for similar workers for
construction of the Third Harbor Tunnel.
6.3 PREDICTION OF CIMJLATIVE IMPACTS
6.3.1 WATER QUALITY, SEDIMENT QUALITY AND MARINE ECOSYSTENS
Other discharges in the study area affect various wastewater constituents and
alternative discharge locations differently. Appendix A provides a description of
the loadings of’ compounds of concern in the other major discharges in the study
area. The water quality analyses performed in Appendix A takes these other loadings
6—5

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into account in predicting the potential for exceeding Water Quality Criteria. The
other discharges make a larger contribution at the alternative discharge site closer
to shore (Site 2). For the metals arsenic, cadmium, chromium, copper and mercury
and for bis(2-ethylhexyl) phthalate, most of the differences among sites are due to
the different contributions from other discharges. Consequently these cumulative
impacts were taken into account when a comparison of sites based on the
concentrations of these metals was made (Chapter 7).
Predictions of sediment quality did not specifically include other discharge sources
within the study area. However, existing background levels of both sediments and
water column particulates were used in the analyses, and since the other discharges
In the study area are the predominant modeled sources of these materials, the effect
was to take these sources were effectively taken into account.
The prediction of impacts on marine ecosystems was based on alterations in water
quality and sediment quality. Since the water and sediment analyses in Chapter 5
took other sources into account as described above, the evaluation of marine
ecosystems did also. Therefore, these cumulative impacts are discussed in the
chapter 5 treatment of alternatives.
6.3.2 DISPOSAL OF EXCAVATED AND DREDGED MATERIAL
Excavated materials from the inter-island conduit and effluent outfall tunnels will
consist of crushed rock and may be utilized in the construction of the Third Harbor
Tunnel/Central Artery Depression highway project for low—strength concrete
aggregate. Any tunnel materials which cannot be utilized will exacerbate demand for
landfill space by adding to the 7 million cubic yards of materials from the Third
Harbor Tunnel/Central Artery Depression requiring landfilling. The amount of tunnel
terial requiring disposal is greatest for Site 5, less for Site 14, and least for
Site 2.
Dredged materials resulting from diffuser construction would likely be disposed of
at the Foul Area Disposal Site. The amount of material resulting from construction
of a drilled riser diffuser (12,000 cubic yards) would not add significantly to the
amount of material normally disposed of at the site. The amount of material
resulting from the construction of a dredged trench pipe diffuser (1 to 1.1! million
cubic yards), however, when added to the materials from other projects, would
represent an increase in the amount of materials normally disposed of at the site.
6.3.3 TRAFFIC AND TRANSPORTATION
The evaluations in Appendix D and Chapters 14 and 5 present a cumulative description
and discussion of marine traffic from all sources. A complete evaluation of land
traffic at the shore facilities cannot be performed until MWRA reconciles the STFP
and WTFP evaluations as discussed in Section 6.2.14, but will be addressed in EPA’s
review of the water transportation program.
63.11 SOCIOECONOMIC CONSIDERATIONS
Total capital costs (which will be reflected in sewer rate increases) and
construction labor requirements are the factors that contribute to cumulative
lapacts. As explained in Appendix E, the financial impacts of the MWRA rate
6—6

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increases required to fund treatment facility and related construction are
significant. The construction of the inter-island conduit and effluent outfall are
major contributors to the increase and thus to the cumulative impacts. Appendix E
addresses all projected MWRA sewer costs and thus addresses cumulative economic
impacts. However, as discussed in the appendix, the cost difference among outfall
location alternatives averages less than $15 per user per year. This is less than
5 percent of the total projected sewer user fee and thus does not indicate that
cumulative economic impact analyses would make a substantial difference in the
overall economic analyses done on outfall alternatives in Appendix E.
Demand for labor for treatment plant, inter—island conduit, and outfall construction
will occur at the same time as the peak labor demand for the Third Harbor
Tunnel/Central Artery Depression highway project. A shortfall in availability of
construction workers could occur. Investigation and prospective mitigation of this
situation has begun with the establishment of a Task Force by the Governor’s Office
of Economic Development which is specifically concerned with the concurrent MWRA and
Third Harbor Tunnel projects. The Task Force is developing a model of regional
construction labor demand and is promoting increasing the number of construction
apprenticeships to provide for future needs.
The demand for construction resources is greater for the longer outfall
alternatives. This difference among sites is accentuated by the cumulative
construction demand in the area. The Governor’s Task Force provides a vehicle for
mitigation if a longer alternative is selected.
6.11 OPERATIONAL RELIABILITY
The effluent characteristics described for this Draft SEIS are based on the
operational reliability of the reconunended secondary treatment plant. For the STFP,
the concept of reliability was viewed as enhancing the overall integrity of the
wastewater treatment system. For the secondary treatment plant, stress was placed
on the need for a design which could, even with anticipated power outages, variable
loading and mechanical failure, produce an effluent that consistently satisfied the
NPDES permit. A detailed review of the operational reliability of the recommended
treatment plant is given in Appendix H of this Draft SEIS. The conclusion of this
review is that adequate standby equipment, extra volume in the clarifiers, and off-
site and on—site power supply is available to ensure that the plant will be able to
function properly and produce an effluent that consistently satisfies the NPDES
permit. Operating scenarios that are likely to occur during the life of the
treatment plant are considered based on the operational reliability.
6.11.1 TREATI IT PLANT OVERVIEW
The reconinended plan for the MWRA secondary treatment plant is a pure
oxygen-activated sludge process with stacked primary and secondary clarifiers. A
site layout of the recommended treatment facilities on Deer Island is presented i
Figure 6.lt.1.a. The stacked clarifier concept has been used widely in Japan for the
past 13 years, but has not yet been constructed in the United States.
6-7

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OWl
PRW Y OPERAflCP4S B(JtDING
SOUTH SYSTEM PUMPING STATiON
PWMARY SPLITTER 50*
ELEC1RICA&S$ ECHN4ICAL oosm
ORAcLrrv(rYPcw 2 )
PRIMAIIY ODOR CONTROL (TYP CF 2)
PRIMARY CLARIFIER BATTERY A
PRIMARY CLIJBFIER BATTERY S
PRALARY CLARIFIER BATTERY C
PRIMARY CLARIFIER BATTERY 0
CRYOGENC FACU Y (TYP CF 2)
COMPRESSOR BULDP4G
liOulO OXYGEN STORAGE
PR VARY SCREENING
SECONDARY SPUTTER BOX
SECONDARY 00CR CONTROL (TYP OP 2)
ANAEROBIC SELECTOR BASIN A
ANAEROBIC SELECTOR BASIN S
ANAEROBIC SELECTOR BASIN C
ANAEROBIC SELECTOR BASIN 0
AERATiON BASIN BATTERY A
AERATION BASIN BATTERY S
AERATION BASIN BATTERY C
AERATION BASIN BATTERY 0
SECONDARY OPERATIONS BUISDING
SECONDARY SLUDGE PUMP STATiONS
SOOIUM HYPOCI tORITE STORAGE
SODIUM METABISIA .FIOE STORAGE
DISINFECTION BASINS
OUTFALL SHAFT
POTA&E WATER TANK
CEMETERY MARKER
SECONDARY CLARIFIER BATTERY A
SECONDARY CLARIFIER BATTERY B
SECONDARY CLARIFIER BATTERY C
SECONDARY CLARIFIER BATTERY 0
GATE HOUSE
ELECTRICAL SUBSTATIONS
POWER FACE TIES
DIESEL STORAGE) TYP OF 2)
NORTH MAIN PtJUPINO STATiON
WINTHROP TERMINAL
DRY STORAGE
VEHICLE MAINTENANCE
MAINTENANCE IWAREHOUSE
LABORATORY
ADMIN6TRAT1ON JtOBdG
PIERS
BUISAHEAD DOCKS
RESIDUAL PROCESSING
/ II
I ,
. so’
I4O
FIGURE 6.4 .1*. K 0 i iJt i) MWRA TREATMENT FACILITIES
600
0
SCALE IN FEET
IT
‘5
LEGEND
S
‘0
2
‘3
4
IS
I ,
‘7
‘S
I,
20.
21
22.
23
24
25
21
27
25
25
30
31
32
33
34.
35.
3..
37
3.
3,
40
4’
42
43
11
45
45
47
4 1
4,
So
SI
SOURCE: MWRA, STFP III , 1987
600

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The anticipated operation of the treatment plant assumes that the primary treatment
facilities will be on—line in 1995, with primary treatment only until mid-bOO when
the secbndary treatment facilities come on-line. The primary treatment facilities
are designed for a maximum flow of 1270 mgd. Secondary treatment facilities are
designed for a maximum flow of 1080 mgd. During peak flow periods, up to 190 mgd of
primary treated effluent and 1080 mgd of secondary treated effluent are mixed prior
to disinfection.
6.14.2 REDUNDANCY
In terms of reliability, the recommended treatment plant was reviewed to determine
the adequacy of the mechanical backup system and volume of tankage provided. More
than adequate redundancy has been provided for the mechanical systems to eliminate
the possibility of one piece of equipment or process failing and causing a
disruption in the wastewater treatment process. A suiiin ry of the standby units
provided is presented in Table H.2.a in Appendix H.
Approximately 12 and 1 4 percent standby tank capacity is available for the primary
and secondary clarifiers, respectively, during periods when maintenance of tanks is
required. The reliability of the various treatment processes depends upon
expeditious repair or maintenance of the equipment or tanks. Reliability could be
reduced if long periods elapsed before the equipment or tanks were repaired and
standby equipment were to break down, consequently reducing the total number of
standby units available.
6.14.3 PONER
Adequate power supply is essential to the operational reliability of the treatment
plant. To ensure a reliable power supply, power must be provided by two separate
and independent sources (USEPA, 197 4). The recommended plan includes the
installation of two Boston Edision Company 115Kv, 70 MW permanent feeder cables.
One cable will originate from the K Street substation in South Boston and the second
from the Chelsea substation. A 25,700 Kw combined cycle power plant will be
constructed on Deer Island to provide power during peak periods of power usage and
provide protection for periods of catastrophic off-site power failure.
6.14.14 OPERATING SCE3IARIOS CONSIDERED
Based on review of the various components of the recommended treatment plant,
probable operating scenarios were developed. During the primary only treatment
phase, two scenarios were considered: 1) primary treatment of wastewater and
2) primary treatment with less than adequate disinfection. For the period after the
secondary treatment facilities come online in 1999, three operating scenarios were
considered: 1) secondary treatment of up to 1080 mgd, 2) 1080 mgd of secondary
treated effluent mixed with 190 mgd of primary treated effluent, and 3) during major
power outages, up to 1270 mgd of primary treated effluent flowing through secondary
treatment facilities. Effluent concentrations of conventional and non-conventional
pollutants listed on the Chemicals of Concern List (MWRA, STFP V,A, 1987) are
calculated for each of these operating scenarios (Tables 6.’4.ZLa through 6.LL 4.f).
6—9

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TABLE 6. k I4 a EFFLUENT CONCENTRATIONS AF7ER P1 IJ ARY TREATMENT
YEAR 1999, AVERAGE FLOW CONDITIONS LhJ
Average
Influent
Loadj n s,
Pollutant lbfd” 2 ’
Removal
Rate,
Percent
Effluent
Loadings,
ib/d
Effluent
Cone.,
mg/i
537,000 36 380,000 121
TSS 481,000 60 211,000 67
METALS
Arsenic 7.6 25 5 ,7 0.00181
Cadmium 8.14 15 7.1 0.00227
Chromium 88.5 140 53.1 0.01689
Copper 399.8 35 259.9 0.08265
Lead 69.5 46 37.5 0.011914
Mercury 5.0 22 3.9 0.00124
Nickel 79.1 15 67.2 0.02138
Selenium 53.3 10 148.0 0.01526
Silver 18.0 30 12.6 0.001401
Zinc 866.2 40 519.7 0.16530
ACID BASE NEUTRALS
Butylbenzyl Phthalate 63.7 0 63.7 0.02026
Bis (2-Ethyihexyl)
Phthalate 78.3 0 78.3 0.021490
Di-N-Octyl Phthalate 65.8 0 65.8 0.02093
Florene 16.5 0 16.5 0.00525
VOLATILE ORGANICS (3)
Bromomethane 62.3 MA 62.3 0.01981
Nethylene Chloride 120.3 0 120.3 0.03826
Chloroform 22.3 NA 22.3 0.00709
Trichioroethylene 143.6 20 314.9 0.01109
Benzene 16.5 0 16.5 0.00525
Tetrachlorethylene 61.7 0 61.7 0.01962
Ethylbenzene 33.14 0 33.14 0.01062
Styrene 37.5 0 37.5 0.01193
PESTICIDES AND PCB
PCB 3.2 0 3.2 0.00102
Aidrin 0.7 0 0.7 0.00022
DDT 0.2 0 0.2 0.00006
1-leptachior 0.8 10 0.7 0.00023
Dieldrin 0.1 0 0.1 0.00003
1. Wastewater flow of 377 mgd was used to calculate effluent concentrations .
2. Average influent loadings were estimated during the Facilities Plan (MWRA,
STFP III, 1987).
3. “NA” represents no information available. No removal of pollutant was assumed.
6-10

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TABLE 6. k .11. b NON-CONVENTIONAL POLLUTANT EFFLUENT CONCENTRATIONS
AFTER PRIMARY TREATMENT YEAR 1999,
MAXIMUM LOADING CONDITIONS ON STORM DAY 1
Max irnum
Influent
Removal
Effluent
Effluent
Load n s,
Pollutant lb/d’ 2
Rate,
Percent
Loadings,
ib/d
Cone.
mg/i
,
BOD 1,305,000 21 1,026,000 971
TSS 1, 1180,000 882,000 83
METALS
Arsenic 12.3 25 9.23 0.00087
Cadmium 111.8 15 12.58 0.00119
Chromium 157.11 140 94.414 0 00892
Copper 639.3 35 1115.514 0.03923
Lead 130.2 146 70.31 0.00664
Mercury 17.5 22 13.65 0.00129
Nickel 1119.8 15 127.33 0.01202
Selenium 153.9 10 138.51 0.01308
Silver 26.8 30 18.76 0.00177
Zinc 2840.1 140 17011.06 0.16088
ACID BASE NEUTRALS
Butylbenzyi Phthalate 120.5 0 120.50 0.01 138
Bis (2-Ethylhexyl) Phthalate 1211.14 0 121 1.40 0.01 1711
Di-N-Octyl Phthalate 115.2 0 115.20 0.01088
Florene 16.5 0 16.50 0.00156
VOLATILE ORGANICS (3)
Bromomethane 106.8 NA 106.80 0.01008
Methylene Chloride 293.3 0 293.30 0.02769
Chloroform 42.8 NA 42.80 0.004011
Trichioroethylene 90.0 20 72.00 0.00680
Benzene 22.6 0 22.60 0.00213
Tetrachiorethylene 1314.0 0 134.00 0.01265
Ethylbenzene 63.7 0 63.70 0.00601
Styrene 55.7 0 55.70 0.00526
PESTICIDES AND PCB
PCB 11.0 0 4.00 0.00038
Aldrin 0.8 0 0.80 0.00008
DDT 0.2 0 0.20 0.00002
Heptachior 0.8 10 0.72 0.00007
Dieldrin 0.1 0 0.10 0.00001
1. Wastewater flow of 1270 mgd was used to calculate effluent concentrations.
2. Maximum influent loadings were estimated during the Facilities Plan (MWRA,
STFP VA, 1987).
3. “NA” represents no information available. No removal of pollutant was assumed.
6—11

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TABLE 6. 1 L 1 1.c EFFLUENT
CONCENTRATIO$J AFTER SECOWDARY TREATMENT,
YEAR 2O2O ’ 1
Average
Influent
Removal
Effluent
Effluent
pollutant
Load n s,
lb/d’ 2 ’
Rate,
Percent
Loadings,
ib/d
Cone.,
mg/i
BOD
570,000
28
1 408,000
125
TSS
515,000
56
227,000
70
METALS
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Silver
Zinc
7.6
8.14
88.5
399.8
69.5
5.0
79.1
53.3
18.0
866.2
50
50
76
82
57
75
32
50
90
76
3.8
4.2
21.2
72.0
29.9
1.3
53.8
26.7
1.8
207.9
0.00117
0.00129
0.00653
0.02213
0.00919
0.00038
0.0165 1 1
0.00819
0.00055
0.06391
ACID BASE NEUTRALS
0.00098
Butylbenzyl Phthalate
Bis (2-Ethyihexyl) Phthalate
Di-N-Octyl Phthalate
Florene
63.7
78.3
65.8
16.5
95
90
90
90
3.2
7.8
6.6
1.7
0.002141
0.00202
0.00051
VOLATILE ORGANICS
3.1
0.00096
Brornomethane
Methylene Chloride
Chloroform
Trichioroethylefle
62.3
120.3
22.3
143.6
16.5
95
95
90
95
95
6 .0
2.2
2.2
0.8
0.00185
0.00069
0.00067
0.00025
Benzene
Tetrachiorethylefle
61.7
33.1 )
90
95
6.2
1.7
0.00190
0.00051
Ethylbenzene
90
3.8
0.00115
Styrene
PESTICIDES AND PCB
92
0.3
o.oooo8
PCB
3.2
90
0.1
0.00002
Aidriri
0.2
90
0.0
0.00001
DDT
0.8
90
0.1
0.00002
Heptachlor
Dieldrin
0.1
90
0.0
0.00000
1. Wastewater flow of 390 mgd
2. Average influent loadings
STFP III, 1987).
was used to calculate effluent concentrations.
were estimated during the Facilities Plan (MWRA,
6-12

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TABLE 6.11.14. d EFFLUENT CONCENTRATIOM AFIER SECONDARY TREAThENT,
YEAR 2O2O ‘ ‘
Average
Influent Removal Effluent Effluent
Loadj gs, Rate, Loadings, Conc.,
Pollutant lb/d’ ‘ Percent ibid mg/i
BOD 1,227,000 71 360,300 140
TSS 1,391,000 711 360,300 140
METALS
Arsenic 7.6 50 3.8 0.000142
Cadmium 8.11 50 11.2 0.000117
Chromium 88.5 76 21.2 0.00236
Copper 399.8 82 72.0 0.00799
Lead 69.5 57 29.9 0.00332
Mercury 5.0 75 1.3 0.000114
Nickel 79.1 32 53.8 0.00597
Selenium 53.3 50 26.7 0.00296
Silver 18.0 90 1.8 0.00020
Zinc 866.2 76 207.0 0.02308
ACID BASE NEUTRALS
Butylbenzyl Phthalate 63.7 95 3.2 0.00035
Bis (2-Ethyihexyl) Phthalate 78.3 90 7.8 0.00087
Di-N—Octyl Phthalate 65.8 90 6.6 0.00073
Florene 16.5 90 1.7 0.00018
VOLATILE ORGANICS
Bromomethane 62.3 95 3.1 0.00035
Methylene Chloride 120.3 95 6.0 0.00067
Chloroform 223 90 2.2 0.00025
Trichioroethylene 113.6 95 2.2 0.0002 14
Benzene 16.5 95 0.8 0.00009
Tetrachiorethylene 61 .7 90 6.2 0.00069
Ethylbenzene 33.1$ 95 1.7 0.00019
Styrene 37.5 90 3.8 0.000142
PESTICIDES AND PCB
PCB 3.2 92 0.3 0.00003
Aidrin 0.7 90 0.1 0.00001
DDT 0.2 90 0.0 0.00000
Heptachior 0.8 90 0.1 0.00001
Dieldrin 0.1 90 0.0 0.00000
1. Wastewater flow of 1080 mgd was used to calculate effluent concentrations. —
2. Average Influent loadings were estimated during the Facilities Plan (MWRA,
STFP III, 1987).
6—13

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TABLE 6.14.14. e EFFL1JEN r CONCEIITRAT IONS AFTER SECOt3I) RY TREATMENT
YEAR 2020, MAXU4UP( LOADING CONDITIONS”’)
Maximum
Influent
Removal
Pollutant
Loadj. s,
lb/d ‘
Rate,
Percent
Effluent
Loadings,
ib/d
Effluent
Cone.,
1,227,000 71 360,300
1,391,000 714 360,300 40
METALS
Arsenic 12.3 50 6.2 0.00068
Cadmium 14.8 50 7,4 0.00082
Chromium 157.4 76 37.8 0.001419
Copper 639.3 82 115.1 0.01278
Lead 130.2 57 56.0 0.00622
Mercury 17.5 75 4.4 0.00049
Nickel 149.8 32 101.9 0.01131
Selenium 153.9 50 77.0 0.00854
Silver 26.8 90 2.7 0.00030
Zinc 2840.1 76 681.6 0.07568
ACID BASE NEUTRALS
Butylbenzyl Phthalate 120.5 95 6.0 0.00067
Bis (2—Ethyihexyl) Phthalate 1214.14 90 12.14 0.00138
Di-N-Octyi Phthalate 115.2 90 11.5 0.00128
Florene 16.5 90 1.7 0.00018
VOLATILE ORGANICS
Broniomethane 106.8 95 5.3 0.00059
Methylene Chloride 293.3 95 114.7 0.00163
Chloroform 142.8 90 4.3 0.00048
Trichioroethylene 90.0 95 14.5 0.00050
Benzene 22.6 95 1.1 0.00013
Tetrachiorethylene 1314.0 90 13.14 0.00149
Ethylbenzene 63.7 95 3.2 0.00035
Styrene 55.7 90 5.6 0.00062
PESTICIDES AND PCB
PCB 3.2 92 0.3 0.00003
Aldrin 0.7 90 0.1 0.00001
DDT 0.2 90 0.0 0.00000
Heptachlor 0.8 90 0.1 0.00001
Dieldrin 0.1 90 0.0 0.00000
1. Wastewater flow of 1080 mgd was used to calculate effluent concentrations.
. Maximum influent loadings were estimated during the Facilities Plan (MWRA,
STFP VA, 1987).
6—1)4

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TABLE 6.J1.is.f MIXED PRIMARY-SECONDARY FL(ZW , YEAR 2020(1)
Average
Influent
Priniary 2
Secondary 3
Plant
Effluent
Effluent
RemovalEffluent
Effluent
Removal
Effluent
Effluent
Loadings,
Pollutant ib/d
Rate,Loadings ,
Percentib/d
Cone.,
mg/l
Rate,
Percent
Loadings,
ib/d
Cone.,
mg/i
Loading,
ib/d
Cone.,
mg/i
BOD 1,305,000 25 146,500 911 68360,300 40 506,800 48
TSS 1,480,000 50 111,100 70 71360,300 40 1171,400 kIt
METALS
Arsenic 7.6 25 0.9 0.00054 140 3.9 0.000113 11.7 0.000 1 15
Cadmium 8.4 15 1.1 0.00067 40 4.3 0.00048 5.14 0.00051
Chromium 88.5 110 7.9 0.00501 60 30.1 0.003311 38.0 0.00359
Copper 399.8 35 38.9 0.021154 70 102.0 0.01132 1110.9 0.01330
Lead 69.5 116 5.6 0.00354 70 17.7 0.00197 23.3 0.00220
Mercury 5.0 22 0.6 0.00037 70 1.3 0.00014 1.9 0.00018
Nickel 79.1 15 10.1 0.00635 30 47.1 0.00523 57.1 0.005110
— Selenium 53.3 10 7.2 0.00453 110 27.2 0.00302 34.4 0.00325
Silver 18.0 30 1.9 0.00119 80 3.1 0.00034 11.9 0.000117
Zinc 866.2 40 77.8 0.04907 70 221.0 0.02453 298.7 0.02820
ACID BASE NEUTRALS
Butyibenzyl Phthalate 63.7 0 9.5 0.00601 70 16.3 0.00180 25.8 0.0021 13
Bis (2.-Ethyihexyl) Phthalate 78.3 0 11.7 0.00739 50 33.3 0.00370 45.0 0.00425
Di-N-Octyl Phthalate 65.8 0 9.8 0.00621 70 16.8 0.00186 26.6 0.00251
Florene 16.5 0 2.5 0.00156 70 4.2 0.000117 6.7 0.00063
VOLATILE ORGANICS ( 14)
Bromomethane 62.3 NA 62.3 0.03932 75 13.2 0.00147 75.5 0.00713
Methylene Chloride 120.3 0 18.0 0.01136 40 61.4 0.00681 79.11 0.007149
Chloroform 22.3 NA 22.3 0.01407 50 9.5 0.00105 31.8 0.00300
Trichioroethylene 43.6 20 5.2 0.00329 70 11.1 0.00123 16.3 0.00154
Benzene 16.5 0 2.5 0.00156 70 4.2 0.000117 6.7 0.00063

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TABLE 6.1$ . 1$. f (Continued) MIXED PRIMARY-SECONDARY EFFLUENT, YEAR 2O2O 1)
Average
Influent
Primary 2
Secondary 3
Plant
RemovalEffluent Effluent
Removal
Effluent
Effluent
Effluent
Effluent
Loadings,
Rate,Loadings, Cone.,
Rate,
Loadings,
Cone.,
Loading,
Cone.,
Pollutant
lb/d
Percentlb/d mg/l
Percent
lb/d
mg/l
lb/d
mg/l
VOLATILE ORGANICS (Cont.)
Tetrachlorethylene
Ethylbenzene
61.7
33.14
0 9.2 0.00583 70
0 5.0 0.00315 70
15.7
8.5
0.00175
0.00095
25.0
13.5
0.00236
0.00128
Styrene
37.5
0 5.6 0.00354 70
9.6
0.00106
15.2
PESTICIDES AND PCB
PCB
3.2
0 0.5 0.00030 70
0.8
0.00009
1.3
0.00012
Aldrin
0.7
0 0.1 0.00007 70
0.2
0.00002
0.3
DDT
0.2
0 0.0 0.00002 70
0.1
0.00001
0.1
0.00001
Heptachlor
0.8
10 0.1 0.00007 70
0.2
0.00002
0.3
0.00003
0.00000
Dieldrin
0.1
0 0.0 0.00001 70
0.0
0.00000
0.0
1. Flow conditions are up to 190 mgd primary treated effluent mixed with 1080 mgd secondary treated effluent for a total of 1270 mgd .
2. Estimates based on 190 mgd.
3. Estimates based on 1080 mgd.
14. “NA” represents no information available. No removal of pollutant was assumed.

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CHAPTER 7
SELECTION AND EVALUATION OF THE RECOMMENDED PLAN
7.1 ALTERNATIVE COMPARISON AND RECOMMENDATION
7.1.1 COMPARISON AND RECOMMENDATION FOR DISCHARGE LOCATION
The objective of the alternative outfall site comparison is to select a location for
the long-term discharge of effluent from a secondary wastewater treatment plant. To
accomplish this objective, the sites are evaluated using the criteria listed in
chapter 3 and then compared. The comparison is based on the impacts expected from
the discharge of secondary effluent. However, under the court-ordered schedule for
construction, the secondary facilities is to be phased. Primary facilities are to
be built first, followed by secondary facilities, and there will be an interim
discharge of primary effluent at the outfall site for approximately 5 years. This
primary discharge is also evaluated for each site to determine if it would cause
unacceptable or irreversible impacts. If so, the recommendation for secondary
discharge will be revisited.
The consequences of effluent discharge at each of the alternative sites are
described in Chapter 5 using the site comparison criteria presented in Chapter 3.
en the consequences are applied to the criteria (Tables 7.1.1.a and 7.1.1.b), it
becomes obvious that there are a limited number of criteria that show potentially
significant differences among sites. After evaluation, certain criteria showed no
jor differences among sites. These include:
• Air Emission
• Noise
• Safeguarding Protected Species
• Sensitive and/or Important Habitat
• Cultural and Historic Resources
• Commercial Fishing Activities
• Water Traffic
• Reliability
• Constructability
• Permitting
• Demand on Unique or Scarce Resources
7—1

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TABLE 7.1.1.a SITE COMPARISON FOR NON-DETERMINATIVE CRITERIA
SITES
2 1! 5
Air nissions Minor Minor Minor
Noise Minor Minor Minor
Safeguarding Protected Species
from Habitat Modifications Minor Minor Minor
Sensitive and/or Important Habitat Minor Minor Minor
Cultural and Historical Resources Moderate Low Low
Potential Potential Potential
(Mitigable) (Mitigable) (Mitigable)
Commercial Fishing Activities Moderate Moderate Moderate
Water Traffic Minor Minor Minor
Reliability Reliable Reliable Reliable
Constructabili ty Moderate Moderate Moderate
Permitting Moderate Moderate Moderate
Demand of Unique or Scarce Extensive Extensive Extensive
Construction Resources

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TABLE 7.1.1 .b SITE CCNPARIS0 FOR I)ETEW4INATIVE CRITERIA
Criteria —-
Mass Surface Water Quality
Standards
U.S. EPA Aquatic Life
Water Quality Criteria
U.S. EPA Public Health
Water Quality Criteria
Pollutants at Shorel mel
Off ore Recreation
and Aesthetics
Sedi.ent Enrichaent
Draft
SEIS
Secondary
Measure 2
Sites
Primary
Sites
Reference
5
2
14
5
Mm DO (mg/i)
Number of Exceedances
Number of Exceedances
Hours to Shore
% Effluent at Shore
km 2 Degraded
km 2 Changed
km 2 Degraded
km 2 changed
km 2 of Effect
PCB km 2 >0.1 ppm
Relative
6.6
1.3
I
5
1
158
0
6
9.14
0.6
0
3
0
5
0
5
15.5
0.6
0
3
0
14
0
14
5.9 6.3 6.14 2.2 5.0 5.7
2 1 0 5 5 14
4 2 2 6 5 14
9.4 15.5
0.6 0.6
1 1
19 ¶2
0 0
5 14
2 2
13 10
Moderate Minor Minor Minor Minor Minor
389 1168
51 56
1.3 •1.9
6.6
1.3
2
33
158
3
18
Water Colu EnricI ent
Sediment Toxicity
Coercial and Recreational
Species
Coat
Construction Duration
Disposal of Excavated Material
Ch. 5.1.1.8.1; App. A.3.8.1
Ch. 5.1.1.8.3; 5.1.3.1.4; App. A.3.8
Ch. 5.1.14
MWRA, STFP V,A, 1987
Ch. 5.1.1.7; App. A.3.7.1
Ch. 5.1.3.1.1
Ch. 5.1.3.1.3
Ch. 5.1.3.1.2
Ch. 5.1.5
Ch. 5.2.3
Ch. 5.2.5
Ch. 5.2.14
$ Millions
276
389
1468
276
Months
1 17
51
56
47
Million yds 3
0.8
1.3
1.9
0.8

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Effluent discharge at Sites 2, 14 and 5 and are predicted to have similar and
acceptable impacts for each of these categories.
Criteria which do demonstrate differences among sites are:
• Water Quality Standards
• Aquatic Life Water Quality Criteria
• Public Health Water Quality Criteria
• Shoreline and Recreation Impacts
• Sediment Enrichment
• Water Column Enrichment
• Sediment Toxicity
• Commercial and Recreational Species
• Cost
• Duration of Construction
• Materials Disposal
The site evaluations and comparisons for each criteria are detailed in
Appendices A through E and the corresponding sections of chapter 5. This Chapter
presents a sun n ry of the results for each criteria for each site with a specific
reference to the detailed treatment of the critical areas of comparison (Table
7.1.1.b) Also presented is a brief comparison of the results for each criterion
and an integration of all criteria to form a recommendation.
1.1.2.1 Comparison of Long-Term Impacts From Secondary Effluent Discharge
) ssachusetts Water Quality Standards
For a secondary discharge, conformance with the current dissolved oxygen (DO)
standard of 6 mg/l (considering natural background conditions and hydrologic
conditions (3114 CMR 14.02)) is the site determinative measure for this decision
criterion. During most of the year, Massachusetts Bay is unstratified and the
effluent from any site mixes throughout the water column (Appendix A and Section
5.1.1). Under these conditions DO depletion would be minimal and DO would be well
over 7.0 mg/l at all sites. During summer stratified conditions, DO concentrations
would be above 6.0 mg/l at all sites and above 7.0 mg/l at Sites 14 and 5.
The worst case DO concentrations were predicted after a quiescent period where
sediments build up and then are resuspended during a storm or breakup of
stratification. This type of significant resuspension event occurs at most once or
twice a year and may occur to some degree every year. For such a major resuspension
event, predicted minimum DO levels are 6.3 and 6.14 mg/l for discharges at Sites 14

-------
and 5, respectively, and 5.9 mg/i for a Site 2 discharge. Although the prediction
for Site 2 is slightly below the Mass. standard, it is not expected to have adverse
effects on the marine ecosystem because of its rare occurrence and short duration.
U.S. EPA Aquatic Life Water Quality Criteria
Measurement of this decision criterion involves comparing aquatic life Water Quality
Criteria with the predicted concentration at the edge of the mixing zone. For
secondary effluent discharge, there are no exceedances predicted for Site 5. Only
heptachlor at Site 2 and mercury at both Sites 2 and 14 exceed the criteria (Appendix
A and Section 5.1.1). As discussed in Section 5.1.3, no significant marine
ecosystem effects are expected from these exceedances due to: the relatively small
areal extent of exceedance; the continuous exposure assumption for the criterion
(Section 5.1.1); and the level of exceedance (1% for heptachior and 90% and 26% for
mercury at Sites 2 and 14, respectively). Therefore, no significant effects are
expected at any site and there are only minimal differences in impacts exist among
sites.
U.S. EPA Public Health Water Quality Criteria
EPA ’s Public Health Water Quality Criteria are based on risks assessed from lifetime
consumption of fish from the affected area, i.e., the mixing zone. Differences
among the sites evaluated here are seen in the application of the Public Health
Water Quality Criteria. Four com pounds (PCB, arsenic, aldrln and DDT), exceed the
criteria for one in 100,000 (l0 ) risk level at Site 2 while only two compounds
(PCB and arsenic) exceed the criteria at the other sites. However, ambient levels
of two of the compounds currently exceed criteria by significant amounts at all
sites.
Without such high ambient levels, the MWRA discharge alone would exceed the criteria
for arsenic (Appendix A). MWRA discharge alone would exceed the criteria for PCB by
an additional 50%, 20% and 10% at Sites 2, 14 and 5, respectively (Section 5.1.1),
but since the ambient exceedances are already so large, the increase in risk as well
as the differences among sites for PCB is small. The additional exceedances at Site
2, although small, (1)4 and 1.2 times criteria for aidrin and DDT respectively),
could produce some additional risk and thus make Site 2 less acceptable for this
criterion.
Criteria representing a one in 1,000,000 (10-6) risk can also be used to evaluate
sites (Section 5.1.5). Although this lower risk factor has been set as a goal it
does not represpnt a regulatory requirement. Comparison using criteria for a one in
1,000,000 (10°) risk predict more exceedances at all sites, but the relative
comparison of sites is the same.
Shoreline and Recreation Impacts
As discussed in Appendices A and D, discharge at any of the sites is not predicted
to produce significant shoreline impacts even under extreme events. However,
increased protection of the shoreline is a benefit because the area supports a
sensitive marine ecosystem, is highly used for recreation and is highly visible.
Also, assurance of decreased impact at the shoreline can provide extra protection in
the event of less than full treatment.
7—5

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The measures of relative shoreline impacts are the time for effluent to reach shore
under an extreme onshore wind event and the concentration of effluent at the shore
during such an extreme event. The difference in travel time to share among sites is
relatively small (6.6 to 15.5 hours). However, the travel time from Site 2 to the
shoreline (6.6 hours) is close to the duration of a flood tide. Consequently, the
effluent could, during extreme events, travel directly to the shore with minimal
additional dilution beyond the mixing zone. This is reflected in the highest
percent effluent (1.3%) at the shore from Site 2 discharge. Travel time from the
other sites is in excess of a flood tide duration and thus would not travel directly
to shore but rather would oscillate back and forth before reaching the shore.
During this oscillation additional dilution would be achieved and thus there would
be a lower concentration of effluent (0.6%) from discharge at Sites 14 and 5.
Discharge at any of the proposed sites is predicted to have minimal shoreline
impacts and all sites will represent a significant improvement over existing
conditions. Sites 14 and 5 provide a significant extra level of protection of the
important shoreline resources.
Benthic Enrichment
Discharge from any of the sites is not expected to produce a “degraded” benthos (see
Section 5.1.3 for definition), event within the mixing zone (Table 7.1.1.b). There
is an area of changed benthos about the size of the mixing zone predicted for each
of the sites. This changes area would have a higher density of organisms and could
have a higher relative abundance of certain species. However, there would be no
effect on the larger marine community outside the immediate area. The differences
in sites is small compared to the precision of the prediction method and thus this
criterion does not show much difference between sites. All sites have an acceptable
level of impact.
Water Column Enrichment
The comparison of sites based on water column enrichment shows that discharge at any
site will not produce a potentially “degraded” (see Section 5.1.3 for discussion)
area outside the mixing zone. There will however be a change in the level of
phytoplankton production due to the discharge. The area of increased production is
generally similar for Sites 14 and 5 but much larger for Site 2. The predicted
impact at Site 2 is of particular concern because it will occur over a larger area
which includes Boston Harbor. Boston Harbor is already stressed and receives
pollutant discharges from numerous other sources. The cumulative effect on the
Harbor could have significant implications for the biological community in the
Harbor and could also affect the aesthetics which could impact other Harbor uses.
Therefore, Site 2 is substantially less acceptable than Sites 4 and 5 for this
criterion, and there is no difference between Sites 14 and 5.
Sediment Toxicity
In EPA’s evaluation of sediment toxicity, two approaches were used to assess impacts
and compare alternative discharge locations. The first was to determine the area of
seafloor where sediment concentrations of various compounds are above the “no effect
level” reported for marine ecosystems (see Section 5.1.3 for a description of these
levels). The discharge of secondary effluent at any of the sites is not predicted
7—6

-------
to result in any area with sediment concentration above the presumed “no effect
level” (Table 7.1.1.b and Section 5.1.3). Therefore, no adverse effects are
expected from deposition of these compounds and there is no significant difference
among sites.
The second approach for assessment and comparison of sediment toxicity was an
evaluation of PCB concentrations. No direct toxic effects on marine organisms are
expected to result from sediment PCB concentrations from a discharge at any of the
sites (Section 5.1.3). However, PCB’s can bloaccumulate and thus potentially create
food web effects. There are no established sediment threshold concentrations for
predicting where food web or other potential impacts can be expected.
In the absence of criteria or other applicable PCB sediment concentrations reported
in the literature, a level of 0.1 ug/g PCBs was used in this analysis as a threshold
concentration for site comparison purposes only. This level was chosen as
representing a midway point between levels of PCBs in areas known to have negligible
PCB effects, and levels of PCBs in areas known to have potentially adverse
bioaccuinulat ion.
The existing background concentration at the alternative outfall sites is
approximately 0.01 ug/g. This level is representative of areas where little to no
PCB effects are reported. Areas where potentially adverse bioaccumulat ion is
occurring include Quincy Bay and New Bedford Harbor. Maximum sediment levels in
Quincy Bay are about 1.0 ug/g and levels generally range from 0.5 to 0.9 ug/g
(USEPA, 1987). High levels of PCBs in the tissues of bottom dwelling organisms have
been found in the same areas in the Bay. Similarly, sediment PCB levels in New
Bedford Harbor ranging from 0.3 to 78 ug/g are reported for areas closed to fishing
due to high PCB levels in fish and shellfish tissue (Boehni, 1981 ).
The level of 0.1 ug/g chosen for this analysis represents a conservative estimate of
sediment PCBs which could result in bioaccumulation. This level has no established
regulatory or accepted scientific basis, but is used to differentiate sediment PCB
impacts between sites for this analysis.
As discussed in Section 5.1.2, PCB concentrations are predicted to build up during
discharge of primary effluent. With the cessation of primary discharge and the
initiation of secondary treatment, the amount of both PCBs and solids discharged
will be greatly reduced. Also, the constant addition of relatively uncontaminated
background sediment will also dilute the PCB concentration built up during the
primary discharge, sediment resuspension and resettlement are predicted to
redistribute to the sediment PCB’s. The result of these processes is that after 5
years of secondary discharge, the area of sediment with a PCB concentration greater
than the comparison level of 0.1 ug/g will be largely confined to the mixing zone
and similar for all sites. Consequently, long-term build up of PCB in the sediment
Is similar and of minimal impact for all sites.
Cc ercia1 and Recreational Species
As discussed in Appendix D and Section 5.1.k predicted impacts on commercial species
are moderate at Site 2 and minor at the other sites. Site 2 is inside the winter
flounder spawning closure line. Discharge of the solids associated with primary
effluent could have an effect on the incubating flounder eggs in the sediments in
the vicinity of Site 2. Consequently, Site 2 is less acceptable for this criterion.
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Cost
The cost of constructing a tunnelled outfall system increases with distance from
Deer Island (Table 7.1.2.a). Site 2 is the least expensive discharge location
alternative while Site 5 is the most expensive. In addition, the cost per foot of
tunnel construction increases with distance from Deer Island. The range of $172
million from Site 2 to Site 5 represents a substantial difference among sites.
TABLE 7.1.2. a COSTS OF THE TUNNELLED OUTFALL SYSTEM
TO THE ALTERNATIVE DISCHARGE SITES
Site
Tunnel
Length
(feet)
Cost
($
of Tunnel
million)
Cost per
of Tunnel
foot
(5)
Average
Annual
User Cost ($)
1990—1996
2
28,000
1141
5,036
2814
14
143,000
238
5,535
296
5
514,000
313
5,796
303
Duration of Construction
MWRA (STFP V, 1987) has estimated that the time required for completion of outfall
construction of Sites 2, 14 and 5 would be 47, 51 and 56 months, respectively. Such
estimates have not yet been accepted by the EPA and should not be construed as EPA
approval or agreement to modification of the court-ordered schedule for outfall
completion. Construction of Site 2 would be completed one month after the court-
ordered deadline of July 19914 while construction to Sites 14 and 5 would require five
and ten months, respectively, beyond the court-ordered deadline. However,
construction completion to all sites is estimated to coincide or precede completion
of the new primary facility. Therefore, based on MWRA’s estimates, Site 2 would be
the preferred site for maintaining the court-ordered schedule but all are equal for
connecting to the new facility.
I terial Disposal
Disposal of tunnelled material from construction of the outfall conduit will become
increasingly more difficult with an increase in volume of material (Chapter 5).
MWRA estimated that construction of an outfall to Site 2, 14 and 5 would create 0.77,
1.28 and 1.86 million cubic yards of excavated material respectively. The impacts
of disposal are greatest for Site 5 but acceptable for all sites.
Based on the above criteria, it is apparent that discharge of secondary effluent at
Site 2 is not preferred. There are major differences in the level of impacts
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expected from discharge at this site as opposed to Sites 14 or 5. In particular, the
following criteria are of concern at Site 2:
• Pollutants in the effluent could travel to shoreline receptors in less than
one tidal cycle (under extreme shoreward wind events), resulting in levels
of effluent at the shore over twice that expected from either Site 14 or
Site 5 under the same conditions;
• Nutrients from the discharge would travel into Boston Harbor and impact
primary production over a much larger area than that predicted for Sites 14
or 5. Additionally, this impact will occur in the Harbor area which is
already stressed and receives pollutant discharges from numerous other
sources;
• Nominal excursions of the Dissolved Oxygen standard could occur under late
sunmier resuspension scenarios. While these excursions are not of
biological concern, they pose regulatory problems.
In contrast, the differences in impacts between Sites 14 and 5 are relatively small,
and are generally within the precision of the prediction methods. The major
differences between these two sites is the additional cost ($79 million) required to
construct the tunnel to Site 5.
Considering the impacts of secondary discharge then, Site 2 is not preferred. Sites
14 and 5 are acceptable and produce similar levels of impacts. These conclusions
will be cross—checked with the conclusions reached after evaluating the impacts of
any interim primary discharge at any of the sites. Should any unacceptable or
irreversible impacts be seen, these conclusions may be revised.
7.1.1.2 Evaluation of Interim Impacts From Primary Effluent Discharge
Impacts on predicted cost, materials disposal, construction duration, recreation and
aesthetics, and water column enrichment are identical for both long term discharge
of secondary effluent and interim discharge of primary effluent. An evaluation of’
each of the other potentially site determinative criteria follows.
I ssachusetts Water Quality Standards
The predicted DO concentrations for a primary discharge are substantially different
from those for a secondary discharge and show major differences among sites
(Appendix A and Section 5.1.1). Under summer stratified conditions, DO
concentrations at Site 2 are expected to be below 4 mg/i, levels for potentially
extended periods of time. During worst case resuspension events, Site 2 DO levels
could drop close to 2 mg/l. Not only are these violations of standards, they could
produce significant adverse impacts on the marine community over the area
experiencing frequent DO concentrations below 5 mg/l (Section 5.1.3). In contrast,
DO levels at Sites 1$ and 5 will not be below 6 mg/i for normal stratified conditions
and not below 5 mg/l for resuspension events. Even with standard violations
occurring during resuspension events, no significant marine ecosystem impacts are
projected for these events of short duration and infrequent occurrence. Examination
of this criterion for the interim primary discharge indicates that there are
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differences among sites and that the impacts at Sites 2, although predicted to be
infrequent, would be significant.
U.S. EPA Aquatic Life Water Quality Criteria
There are four (Site 5) or five (Sites 2 and 14) exceedances of Aquatic Life Criteria
for a primary discharge as compared to two, one and none (at Sites 2, 14 and 5,
respectively) for a secondary discharge. The magnitude and implications of the
exceedances are discussed in Section 5.1.3. These exceedances represent a greater
impact than for secondary; however, the relative comparison of sites is generally
the same for the interim primary discharge and the impacts are neither unacceptable
nor irreversible.
U.S. EPA Public Health Water Quality Criteria
The number of exceedances of Public Health Water Quality Criteria (for a one in
100,000 (iO’ ) risk factor) is greater for the interim primary discharge than for
secondary effluent (14 to 6 versus 2 to 4). Again, although this represents a
greater impact, the relative comparison of the sites remains the same and the
impacts are not considered to be unacceptable or irreversible, particularly because
public health criteria are based on life time exposure and the primary discharge is
only for 5 years. The impact for primary do not affect the relative comparison of
sites.
Benthic Enrichment
In contrast to the conditions predicted for long—term impacts of secondary effluent
discharge, during the interim discharge of primary effluent, there would be areas of
predicted “degraded” benthos (Table 7.1.1.b). However the area is similar for all
sites and is generally within the mixing zone. There is also an area of “changed”
benthos for all sites. The area is substantially larger than the mixing zone and
varies among sites (Figure 7.1.1.b). The predicted “changed” area for Sites 14 and 5
are similar, but the area for Site 2 is about twice as large. For this criterion,
Site 2 appears to be less acceptable but the resulting impact due to primary
effluent would not be irreversible.
Sediment Toxicity
As for secondary effluent, two approaches were used to assess impacts of sediment
toxicity from primary effluent discharge: comparison to “no effect levels” for
various toxic compounds, and comparison to the 0.1 ug/g level for PCBs. For primary
effluent, there are either one or two compounds predicted to exceed the presumed “no
effect level” at all sites (Table 7.1.1.b, Chapter 5). These exceedances are
confined to the mixing zone and thus are acceptable and not site determinative.
The area of sediments with PCB concentrations greater than the 0.1 ug/g level (Table
7.1.1.b) is of concern fo all sites during the interim primary treatment period.
Areas of 18, 13 and 10 km respectively at Sites 2, 4 and 5 constitute potentially
unacceptable impacts.
One alternative for decreasing this potential impact is to reconsider discharge of
primary effluent at President Roads. Although the PCB discharge rates for a primary
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outfall at Presidents Roads would be identical to those for a primary outfall at
Site 2, k or 5, the potential impacts may be decreased due to the already degraded
condition of Boston Harbor. The primary discharge would simply exacerbate
conditions in the Harbor, where sediment PCB levels are already at or above 0.1
ug/g. However, as discussed in Chapter 3 and Appendix F, discharge of primary
effluent at Presidents Roads would result in increased Water Quality Criteria
exceedances at the edge of the mixing zone, increased percentages of effluent at the
shorelines of Winthrop, Hull and Nahant, decreased compliance with the Massachusetts
dissolved oxygen standard and more chance of further stressing the Boston Harbor
ecosystem.
As discussed earlier, the 0.1 ug/g level used in this analysis represents a
conservative estimate of sediment PCBs potentially associated with
bioaccumulation. In addition, in order to arrive at the areas shown in Table 7.1.b,
three other very conservative assumptions were made:
• Because PCBs were not detected in the influent sampling program, the level
of PCBs entering the plant was assumed to be equal to the detection limit
(0.5 ug/l) for that analysis. Actual PCB levels lower than this assumed
level could result in decreases in the extent of impacted areas at all
discharge sites.
• No removal of PCBs was assumed during the interim primary period, even
though 60 percent solids removal normally is achieved, and it is likely
that PCBs will preferentially remain with the solids. Should PCB removal
actually take place during treatment, significant decreases in the
predicted impacted areas would occur.
• It was conservatively assumed that mixing of the sediments by benthic
organisms (bioturbation) involved only the top 3 cm of sediments. Some
MWRA survey data shows that bioturbation is taking place over a much deeper
level, mixing as much as 8 cm of sediments. Mixing to a deeper level would
result in dilution of the PCB solids from the discharge with cleaner
sediments, and decreases in the impacted areas.
As seen in the discussion of sediment toxicity for secondary treatment, the impacts
of PCB accumulation are temporary and reversible, The areas containing sedimen 9
with PCBs greater than 0.1 u /g reduce from 18 km at Site 2, from 13 to 5 km
at Site 1$ and from 10 km ‘ to L km 2 at Site 5 after five years of secondary
treatment.
As discussed in Appendix B, this is due to sediment concentrations building up
during primary discharge and then decreasing during secondary discharge. This
reduction is predicted based on dilution with cleaner background sedimentation and
natural redistribution of inpiace sediments. Assessment of present sediment
concentrations (MWRA, STFP V,S, 1987) indicate that there is an area of relatively
high sediment concentrations in the area between Sites 2 and t. Neither the source
of this material nor the mechanisms which produce the concentrations are known.
However, the data indicate that reduction in concentrations built up during
discharge of primary in this area may be reduced. This would make any discharge in
the area between Sites 2 and L less desirable.
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These impacts would be judged as unacceptable if long-term in nature or
irreversible. However, because of the conservative assumptions made in this
analysis, the temporary and reversible nature of the impact, the negative impacts of
discharging primary effluent into Presidents Roads, and the sediment tovicity
impacts at Sites 2, 24 or 5, EPA determines that these impacts are acceptable.
Therefore, they will not alter the siting decision made for secondary discharge.
Siminiry
Based on application of the above criteria for a 5-year interim primary discharge,
only a discharge at Site 2 would result in unacceptable impacts. Specific concerns
at Site 2 are:
• Dissolved Oxygen standards would be violated under several scenarios, with
DO levels dropping down as low as 2.2 mg/l for summer resuspension
events. These levels could result in adverse impacts to the marine
community in the area of the discharge, including some mortality. The
impacts on the marine community are unacceptable, although reversible.
• Accumulation of PCBs in the sediments surrounding the discharge could reach
levels that have been associated with bioaccujnuj.atjons of the PCBs in the
tissue of benthic organisms, including lobster and flounder. Sublethal
effects of PCB bioaccuinulation on the health of individual marine organisms
has not been established. The accumulation of PCBs in the individual
organisms is irreversible, but the overall community impacts would be
reversible when PCB levels in the sediments decreases after startup of
secondary treatment.
• A relatively large area of sediment would be impacted by deposition of
carbon, which could cause changes to the benthic community species
composition and density. These changes would be reversible after the onset
of secondary treatment.
• Impacts on shoreline receptors and phytoplankton production similar to
those discussed for discharge of secondary effluent are predicted.
Sites 4 and 5 also would not meet DO standards (Table 7.L1.b) under certain
conditions, but the predicted DO levels are not expected to impact the health of the
urine community. Also, concerns related to sediment PCB accumulation and organic
enrichment remain at Sites 14 and 5. As discussed above, however, these concerns are
reversible.
The analysis of discharge of interim primary effluent results in Site 2 being
determined unacceptable. Impacts at Sites 14 and 5, although of concern, are
reversible. Therefore, the analysis undertaken for secondary effluent for Sites 14
and 5 is not changed after consideration of interim primary effluent impacts.
1.1.1.3 Reco inended Discharge Location
Site 2 is not preferred for discharge of secondary effluent due to potential long-
term impacts. Consideration of interim impacts further reveals that discharge at
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Site 2 would incur unacceptable impacts. Sites L and 5 show little difference in
impact for a secondary discharge and both appear to be acceptable. In addition,
during the interim discharge of primary effluent, the impacts predicted for Sites L
and 5 are similar and not predicted to be severe or irreversible. Given the minor
differences in impacts between Sites 4 and 5 and the substantial cost differences,
the area between these sites would be acceptable as a discharge location.
Therefore the recommended plan for discharge location is to build a diffuser which
lies entirely with in the area shown in Figure 7.1.3.a. This area is bounded to the
west by Site l and extending to the east of Site 5 and north and south by one
diffuser length as necessary to accommodate geotechnical conditions in the area.
7.1.2 RECOMMENDED PLAN FOR OUTFALL CONDUIT CONSTRUCTION
The tunnelled outfall alternative was evaluated in detail in Chapter 5. Impacts due
to tunnel construction are not expected to be major, therefore, the recommended plan
for construction for the effluent outfall conduit is the deep rock tunnel
alternative.
7.1.3 RECOMMENDED PLAN FOR DIFFUSER CONSTRUCTION
Either the drilled riser on the pipeline diffuser alternative can be selected as the
recommended diffuser alternative. The major difference between the two diffuser
alternatives, aside from construction techniques, is that the pipeline diffuser
alternative would generate 1. million cu. yds. of material while the drilled riser
alternative would generate only 12,000 cu. yds. of material. Material from either
construction alternative would be disposed at the Foul Area Disposal Site. Trench
excavation for the pipeline diffuser would cause the loss of significantly more
benthic habitat than would the drilling of 80 risers. Construction of the pipeline
diffuser would also have a larger temporary adverse impact on water quality
conditions at the construction and disposal sites than would the drilled riser
diffuser. Despite these differences, it would be difficult to select one diffuser
type as preferred. A recommended diffuser type could be selected when both the
collection of geologic data by MWRA in spring 1988 and cost estimates of the two
diffuser types are complete.
7.1 .11 RECOMMENDED PLAN FOR INTER-ISLAND CONDUIT CONSTRUCTION
The tunnelled inter-island conduit alternative was evaluated in detail in Chapter
5. Impacts associated with tunnel construction are not expected to be major,
therefore the recommended plan for construction of the inter-island conduit is the
deep rock tunnel.
7.2 MITIGATION
Based on the recommendation made above and the adverse impacts associated with these
recommendations (Chapter 5), several mitigation measures should be implemented.
A more thorough understanding of the physical, chemical and biological processes of
Massachusetts Bay is needed. MWRA should implement a monitoring program to better
understand these processes. The program could include a regular sampling and
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2:0 9
2.0
STATUTE MILES
1:5 9 1 .5
NAUTICAL MILES
FiGURE 7.1.3.a RECOMMENDED LOCATION
OF THE DEER ISLAND WWTP DISCHARGE
/
,
/
/
U?
/
2
0
5’
0
Ds
,Th.c’$ ls
C-.
Og
il ’
POSNT ALLIRTON

-------
analysis of PCBs and other constituents of concern, in water, sediment and animal
tissue in the vicinity of the proposed and existing discharges. This would allow
post operation assessment and provide a better understanding of sediment
bioaccumulation relationships.
This program should include a two to three years of preoperational ecological
sampling to establish an adequate statistical baseline. In addition, the monitoring
program should include regular bioassay and bloaccumulat ion testing around the
outfall site to continue to assess long—term impacts of the discharge. This is a
requirement of the existing NPDES permit for the discharge aznd may also be required
by the new NPDES discharge permit. This monitoring program should be developed in
close coordination with State and Federal agencies.
A pollutant source identification and control program should be implemented by MWRA
to help identify and reduce concentrations of pollutants of concern which would
enter the 14WRA system and to estimate pollutant concentrations at the edge of the
mixing zone.
A pilot treatment program should be run by MWRA to determine actual removal
efficiencies of pollutants which would be expected to occur at the Deer Island WWTP
during operation of both primary and secondary treatment to ensure that the analysis
presented in this Draft SEIS and MWRA’s STFP are accurate.
To ensure proper site selection for the diffuser and to gain more information
concerning the economic and environmental benefits associated with each of the
diffuser alternatives, a thorough geotechnical investigation of the proposed
discharge location should be conducted prior to design and construction of either
the pipeline or the drilled riser diffuser alternative. In addition, a complete
geotechnical investigation of the subsurface bedrock will be necessary to determine
if tunnel construction will be able to proceed at the expected rate of 50 to 70 feet
per day. This information is necessary to determine when construction of either the
outfall or the inter-island conduit would be completed.
A physical model of the selected diffuser alternative should be constructed and
tested to assure that initial dilutions predicted by the computer modeling done in
this Draft SEIS will actually be achieved during diffuser operation. The physical
model of the diffuser should also be used to determine if the diffuser will function
properly with respect to hydraulic requirements, such as purging of seawater.
The diffuser system should be designed to incorporate features which would minimize
conflicts with fishermen dragging activities.
Disposal of material from tunnel construction of the outfall should be closely
coordinated with ongoing local construction projects to maximize beneficial use of
this material and to minimize the volume of material which would have to be
landfilled. Construction projects which could potentially use the tunnelled
excavate include the Third Harbor Tunnel, depression of the Central Artery and other
MWRA construction projects.
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Demand for scarce or unique construction resources by the several major construction
projects planned for the Boston region could potentially slow the pace of
construction of the outfall and inter-island conduits. I4WRA should continue to
develop an integrated construction management approach and should participate in the
Governor’s Office of Economic Development Task Force (see Chapter 6).
7—16

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U.S. ENVIRONMENTAL PR(Y ECT ION AGENCY
REGION I
CHAPTER 8
LIST OF PREPARERS
Ronald G. Manfredonia, MS, Reviewer
Gwen S. Ruta, BS, Reviewer
David A. Torney, MS, Preparer
Edward H. Dettmann, PhD, Reviewer
Stephen F. Ells, AB, JD, Reviewer
Jonathan C. Kaledin, BA, JD, Reviewer
John Paul, PhD, Reviewer
METCALF & EDDY, CONSULTANTS
Richard L. Ball, Jr., 143, Reviewer
David Bingham, MS, Reviewer
David Bova, BS, Reviewer
Robert J. Reimold, PhD, Reviewer
Richard Sherman, BS, Reviewer
James T. Maughan, PhD, Preparer
Richard Baker, MS, Preparer
Kathleen Baskin, BS, Preparer
Donna Benjamin, BS, Preparer
Dominique Brocard, PhD, Preparer
John Cardoni, 143, Preparer
Sue Cobler, 143, Preparer
Charles B. Cooper, BS, Preparer
Larry Dechaine, BS, Preparer
Edward lonata, MS, Preparer
Larry Krasner, MS, Preparer
Lynn Miller, MS, Preparer
Frank Prendergast, Preparer
Amy Prouty Gill, BS, Preparer
Linda Travaglia, Preparer
Marc Wallace, BS, Preparer
John Wigger, BS, Preparer
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BARRY LAWSON ASSOCIATES, INC.
Barry R. Lawson, PhD, Reviewer
Anne P. Jackson, MA, Preparer
Lynne Newman Lawson, BA, Editor
CEO/PLAN ASSOCIATES
Peter Rosen, PhD, Preparer
Michu Tcheng, 115, Preparer
JSTON UNIVERSITY, OFFICE OF PUBLIC ARCHAEOLOGY
Ricardo Elia, PhD, Preparer
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CHAPTER 9
PUBLIC PARTICIPATION
9.1 INTRODUCTION
The Environmental Impact Statement (EIS) process ensures that the public is offered
an opportunity for involvement in assessing the environmental impacts of projects.
In addition, U.S. EPA’s National Environmental Policy Act regulations for
implementation of projects funded by the Clean Water Act (under Ito CFR Parts 6 and
25) and the Council of Environmental Quality’s regulations ( ito CFR 1500 et seq.)
require a public participation program. The public participation program conducted
for this Draft SEIS, consisting of EPA’s program supplemented by and coordinated
with MWRA’s full—scale public participation program for its Deer Island Secondary
Treatment Facilities Plan (STFP), satisfies these requirements.
The purposes of the public participation program for this Draft SEIS have been:
• to provide the public with information on the Draft SEIS and SEIS processes
and the related technical studies being performed; and
• to ensure that the public has ample opportunity to provide input to the SEIS
study team and responsible agencies.
Throughout development of this Draft SEIS the public was supplied with background
information needed to understand the Draft SEIS work program, to make informed
comments, and to ask pertinent questions. The major areas of activity include:
• Public scoping meetings
• Public participation coordination
• Public participation workplan
• Citizen’s Advisory Committee (CAC) formation, participation and presentations
• Technical Advisory Group (TAG) participation
• Public meetings and hearing
• Informational activities
• Summary of public comments for public hearing
These activities were timed to solicit public input at important decision points in
the SEIS process. The activities are described in more detail below.
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9.2 PUBLIC PARTICIPATION ACTIVITIES
9.2.1 SCOPING
The Notice of Intent (NOl) for the preparation of this Draft SEIS, distributed to
the public in November 1986 prior to the scoping meetings, outlined the purpose of
the SETS and the key issues to be addressed (Attachment 1).
In preparing this Draft SEIS, EPA held two public scoping sessions in December 1986
to solicit citizen and public agency views on alternative locations, routes, and
construction techniques for the inter-island conduit and effluent outfall. Public
comments on the environmental, economic, legal, institutional, and other issues that
the SETS would evaluate were received. Principal comments received at the scoping
sessions included the need for evaluation of the interim primary discharge, the need
for locating the diffuser in water deep enough to guarantee significant initial
dilution, the concern for water quality in areas from Nahant northward and the
desire of some people to have the secondary treatment plant in operation sooner than
scheduled to avoid interim primary discharge. The comments received at the scoping
meetings, as well as those received by EPA during the siting EIS project and by MWRA
during the STFP preparation, served as a basis for developing the Draft SEIS scope
and were considered in the evaluation of the principal siting and technology
alternatives in this Draft SEIS. The public issues responded to by this Draft SEIS
are discussed in Section 9.24.
9.2.2 WORKPLAN AND COORDINATION
A public participation workplan was developed by EPA. The workplan included all the
activities summarized here and was modified as appropriate to meet the changing
needs of EPA and the public.
Many public agencies and consultants were involved in MWRA’s STFP and EPA ’s SEIS
processes. The U.S. Army Corps of Enginers (U.S. ACOE) cooperated on this Draft
SEIS because of a requirement for a Department of Army Permit. EPA also coordinated
or consulted with U.S. and State senators and representatives, local officals,
federal and state agencies, regional and local entities, and concerned citizens
(Table 9.2.a). EPA conducted Section 7 consultation under the Endangered Species
Act with the National Marine Fisheries Service and the U.S. Fish and Wildlife
Service (Appendix G). In compliance with the National Historic Preservation Act,
EPA also consulted with the Massachusetts Historical Commission and other parties in
conducting a Section 106 review (Appendix G). EPA will submit a Memorandum of
Agreement to the Advisory Council on Historic Preservation.
EPA coordinated its public participation program with MWRA’s full-scale public
participation program for the STFP. EPA participated in MWRA’s program which
included:
• Citizen’s Advisory Committee formation, participation, and support
• Technical Advisory Group participation
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• Public meetings, including forums, information and community meetings, and
public hearings
• Preparation of responsiveness sirninaries of all public meetings and hearings
• Production of informational materials
Throughout the preparation of this Draft SEIS and the STFP the SEIS project team
attended meetings at least weekly (since June 1987) to coordinate with other
agencies and consultants, obtain information and data from MWRA, and hear the
concerns of the CAC and other interested public groups. From these meetings an
understanding of concerns was developed by EPA so that these concerns could be
addressed in this Draft SEIS. A weekly meeting schedule was maintained by the
public participation coordinator to ensure that EPA and the SEIS study team were
informed of all upcoming events.
9.2.3 FOf 1ATI(Il OF THE CITIZEN’S ADVISORY C(II1Irn,z
A Facilities Planning Citizen’s Advisory Coemittee (CAC) was formed in October 1986
to serve both MWRA and EPA by reviewing MWRA’s STFP and this SEIS. The CAC was
appointed by Secretary James S. Hoyte of the Massachusetts Executive Office of
Environmental Affairs (EOEA). The 27 members and 13 alternates to the CAC represent
various interests: environmental, business, comunity, government, scientific, and
others (Table 9.2.a). The CAC has been supported by staff from MWRA’s STFP project.
9.2. CITIZEN’S ADVISORY COII1Irr rINGS: PARTICIPATION AND PRESENTATIONS
EPA actively participated in CAC monthly meetings and in the CAC’s Outfall and Deer
Island Secondary Treatment Plant subconunittee meetings throughout the STFP and SEIS
projects. EPA informed the CAC and subconinittees of its study results and
recomendations as they became available and responded to CAC questions and
suggestions. All efforts were made to incorporate the CAC’s concerns into this
Draft SEIS.
In addition to regularly attending the CAC meetings, EPA made three formal
presentations to the CAC. In June 1987, the scope of work for this Draft SEIS was
mailed to the CAC and a detailed presentation made at its monthly meeting. A second
presentation, at the December 1987 CAC meeting, covered the relationship of EPA’s
SEIS to MWRA’s STFP, the detailed outline of this Draft SEIS, and the scope of the
public participation program. EPA presented the results of the Draft SEIS
investigations and the report’s reconinendations at the March 1988 meeting.
Appropriate handouts were prepared and distributed in advance of the meetings or at
the presentations.
EPA participated in two coninunity-sponsored outfall meetings during the preparation
of this Draft SEIS. EPA was represented at the South Shore Coalition outfall
meeting in August 1987 and at the North Shore town meeting in September 1987. P t
both meetings EPA presented its role in the outfall siting process and the
relationship of MWRA’s STFP to EPA’s SEIS.
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TABLE 9.2.a COORDINATIOIJ LIST
U.S. SENATORS AND REPRESENTATIVES
Senators
Edward M. Kennedy
John F. Kerry
Representatives
Brian J. Donnelly
Joseph P. Kennedy, 2nd
Nicholas Mavroules
John J. Moakley
Gerry Studds
MASSACHUSETTS STATE SENATORS AND REPRESENTATIVES
Senators
Lawrence R. Alexander
Carol C. Ainick
Walter J. Boverini
William M. Bulger
Francis D. Doris
William B. Golden
Paul D. Harold
Arthur Joseph Lewis Jr.
Michael LoPresti
Joseph B. Walsh
Representatives
Francis F. Alexander
Robert B. Ambler
Steven Angelo
Thomas F. Brownell
Robert A. Cerosoli
Joseph M. Connolly
Salvatore F. Dimasi
Charles Robert Doyle
Patricia G. Fiero
Thomas M. Finneran
Kevin W. Fitzgerald
Mary Jeanette Murray
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TABLE 9.2.a COORDINATION LIST (Continued)
MASSACHUSETTS STATE S ATORS AND REPRESE3ITATIVES (Continued)
Michael F. Flaherty
William F. Galvin
George ICever ian
Vincent Lozzi
John E. MeDonough
Thomas W. McGee
Michael W. t4orrissey
Shirley Owen-Hicks
Reoresentatives
( Continued )
William G. Reinstein
Mark Roosevelt
Richard J. Rouse
Michael J. Rusane
Byron Rushing
Angelo M. Scaccia
Rnvn rnual Gus Serra
Paul W. White
MA33AcIWSE’rrs LOCAL OFFICALS
Honorable Raymond L. Flynn
Mayor, City of Boston
Boston, MA 02201
Honorable George Colella
Mayor, City of Revere
Revere, NA 02151
Honorable James Conway
Mayor, City of Malden
Malden, MA 0211 8
Honorable Albert Divirgillo
Mayor, City of Lynn
Lynn, MA 01901
Honorable Francis X. McCauley
Mayor, City of Quincy
Quincy, MA 02171
9-5

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Karen Adams
US Army Corps of Engineers
Waltham, MA 02151t
Facilities Plan TAG
Dr. Michael Bothner
US Geological Survey
Woods Hole, MA 0251 3
EOEA—TAG
CAC Alternate
Dr. Bradford Butman
US Geological Survey
Woods Hole, MA 0251 3
EOE A-TAG
CAC Representative
Ken Carr
US Fish & Wildlife Service
Concord, NH 03301
Facilities Plan TAG
Center for Disease Control
Center for Environmental Health
and Injury Control
Special Programs Group
Atlanta, GA 30333
Don L. Klima
Advisory Council on
Historic Preservation
Washington, D.C. 20001$
Christopher Mantzaris
Nat’l Marine Fisheries Serv.
Gloucester, MA 09130
EOEA-TAG
William Patterson
US DOl. Off . of Env.
Boston, MA 02109
Facilities Plan TAG
Dr. John Pearce
Northeast Fisheries Center
Woods Hole, MA 0251 13
EOEA—TAG
TABLE 9.2.a
COORDINATION LIST (Continued)
FEDERAL AGENCIES
Proj. Review
Lt. Commander Michael Wade
U.S. Coast Guard Marine Safety Div.
Boston, MA 02109
Facilities Plan TAG
9-6

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TABLE 9.2.a COORDINATION LIST (Continued)
STATE AGENCIES
Leigh Bridges
Mass. Division of Marine Fisheries
Boston, MA 02202
EOEA-TAG
Eric Buehrens
Department of Environmental Mgmt.
Boston, MA 02114
Facilities Plan TAG
Steve Davis
EOEA/MEPA
Boston, MA 02202
Fred Hoskins
Executive Office of Economic Affairs
Boston, MA 02108
Facilities Plan TAG
Marilyn Hotch
MWRA
Boston, MA
02129
Dr. Russell Isaac
Div. of Water Pollution Control
Westboro, MA 01581
EOEA-TAG
Roberta Ellis
MASSPORT Planning
Boston, MA 02116
EOEA-TAG
Department
Elaine Krueger
Mass. Dept. of Public Health
Boston, MA 02111
EOEA-TAG
Jack Elwood
MWRA
Boston, MA 02129
Richard Fox
MWRA
Boston, MA 02129
Ms. Phyllis Giller
Exec. Office of Env. Affairs
Boston, MA 02202
EOEA-TAG
Steve Halterman
DEQE-DWPC-TSB
Westboro, MA 01581
EOEA-TAG
Glenn Haas
DEQE/DWPC
One Winter Street
Boston, MA 02108
Kathy Hearn
MWRA
Boston, MA 02129
Ron Lyberger
DEQE/DWPC
Boston, MA 02108
Facilities Plan TAG
Steve Lipman
DEQE/DWPC
Boston, MA 02108
Facilities Plan TAG
EOEA-TAG
Jerry McCall
DEQE
Westboro, MA 01551
Mary Lou Mottola
MWRA
Boston, MA 02129
Mary Ann Nelson
Exec. Office of Communities &
Development
Boston, MA 02202
Facilities Plan TAG
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TABLE 9.2.,a COORDINATION LIST (Continued)
STATE AGENCIES
Daniel K. O’Brien Jan Smith
MWRA Office of’ Coastal Zone Mgmt.
100 First Avenue Boston, MA 02202
Boston, MA 02129 Facilities Plan TAG
Julia O’Brien Bruce W. Tripp
MDC Planning Office Executive Office of Environmental
Boston, MA 01108 Affairs
Facilities Plan TAG Boston, MA 02202
EOEA-TAG
Dr. Judy Pederson
Office of Coastal Zone Mgmt. George Zoto
Boston, MA 02202 DEQE
EOEA-TAG Boston, MA 02108
EOEA-TAG
John Piotti
MWRA Advisory Board Kim Zullo
Boston, MA 02108 MASSPORT Development Dept.
CAC Representative Boston, MA 02116
Facilities Plan TAG
Brona Simon
Massachusetts Historical Commission
Boston, MA 02216
Facilities Plan TAG
9-8

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TABLE 9.2.a COORDINATION LIST (Continued)
LOCAL AND REGIONAL AGENCIES & ORGANIZATIONS
Libby Blank
Boston Water and Sewer Conmiiss ion
Boston, MA 02210
Facilities Plan TAG
Susan Bregman
Boston Traffic and Parking
Boston, MA 02201
Facilities Plan TAG
Chief Engineer
Boston Water & Sewer Coniniss ion
Boston, MA 02210
Robert DeLeo
Chairman Wintrop Selectmen
Winthrop, MA 02152
Joan Engler
Boston Conservation Coninission
West Roxbury, MA 02132
Alice Hennessey
Boston City Council
Boston, MA 02201
Emil Holland
Executive Director
Upper Blacketone Water
Pollution Abatement District
Milbury, MA 01527
Mary Kelley
Winthrop Conservation
Coemission
CAC Representative
Kevin Kilduff
BRA Harbor Planning
Charlestown, MA 02129
Facilities Plan TAG
Robert Luongo
Office of Community Development
Chelsea, AA 02150
CAC Alternate
Jack Murray
Environmental Department
Boston, MA 02201
Robert Lyons
Winthrop Board of Selectmen
Winthrop, MA 02152
Robert Noonan
Winthrop Board of Selectmen
Winthrop, MA 02152
Martin Pillsbury
Metro Area Planning Council
Boston, MA 02108
CAC Representative
Judith Schiosser
Office of Community Development
Chelsea, MA 02150
CAC Representative
Myra Schwartz
BRA Housing Planning and Development
Charlestown, MA 02129
Facilities Plan TAG
John Silva
Hull, Ma
CAC Representative
Virginia Wilder
Office of Community Development
Town Hall
Winthrop, MA 02152
CAC Alternate
9—9

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TABLE 92..a COORDINATION LIST (Continued)
CONCERNED CITIZENS
Dr. Eric Adams
Dept. of Civil Engineering
MIT
Cambridge, MA 02139
EOEA—TAG
Orris Albertson
Enviro Enterprises, Inc.
Salt Lake City, Utah 814115
Nader Andalan
Jung/Brannon Associates
Boston, MA 02109
Rebecca Backman
Wright & Moehrke
Boston, MA 02116
Lois Baxter
Winthrop, MA 02152
CAC Alternate
William Benson
Greenfield, MA 01301
CAC Representative
Peter Blanchard
Mass. Bankers Association
Boston, MA 02199
CAC Representative
Dr. Paul Boehm
Battelle Laboratories
397 Washington Street
Duxbury, MA 02332
EOEA-TAG
Dr. Robert Bowen
Environmental Sciences Program
Boston Harbor Campus
University of Massachusetts
Boston, MA 02125
EOEA-TAG
Doug Boyle
chelsea Record/Winthrop Sun
chelsea, MA 02150
Dr. Paul Boyle
Senior Scientist
New England Aquarium
Boston, MA 02109
EOEA—TAG
Polly Bradley
SWIM
Nahant, MA 01908
CAC Representative
Shirley Brown
Natick MA 01760
CAC Representative
Eugene Canty
Brookline, MA
CAC Alternate
Michael Cheney
Quincy, MA 02169
CAC Alternate
Joseph F. Conoby
Honeywell Bull Inc.
Billerica, MA 01821
Randy Braley
Camp, Dresser & McKee
Boston, MA 02108
021146
Dr. Judith McDowell Capuzzo
Woods Hole Oceanographic
Institution
Woods Hole, MA 025113
EOEA-TAG
Priscilla Chapman
Sierra Club New England
CAC Alternate
Mr. Joseph Cooney
Environmental Science Program
University of Massachusetts
Boston, MA 02125
EOEA-TAG
9-. 10

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TABLE 9.2.a COORDINATION LIST (Continued)
CONCERNED CITIZENS
Dr. Eugene Gallagher
Environmental Sciences Program
Boston Harbor Campus
University of Massachusetts
Boston, MA 02125
EOEA-TAG
Astrid Glynn
Glynn & Dempsey P.C.
Boston, MA 02110
CAC Representative
Jamen Goldstein
Energy Systems Research Group
Boston, MA 02109
Lydia Goodhue
The Boston Harbor Associates
Wellesley, MA 02181
CAC Representative
Phillip Goodwin
Mass. Bay Yacht Clubs Association
Quincy, MA 02169
CAC Representative
David Graber
Stoughton, MA 02072
Facilities Plan TAG
Allan Hodges
Bechtel/Parsons Brinckeroff
Boston, MA 02110
Dr. Thomas Hruby
Massachusetts Audubon Society
Boston, MA 02108
EOEA-TAG
Ann Jacobson
Barry Lawson Associates, Inc.
Concord, MA 01742
Dr. David Jenkins
Professor of Sanitary Engineering
Kensington, CA 94708
Dr. Clyde Dawe
Woods Hole, MA 0251 3
EOEA-TAG
Sharon Dean
N.E. Aquarium
CAC Representative
Clifford deBuan
Sierra Club New England
Milton, Ma 02186
CAC Alternate
Leonard DeModena
East Boston, Ma 02128
CAC Representative
Emilie DiMento
Winthrop Concerned Citizens
CAC Representative
Harlon Doliner
Winthrop Counsel
Joe Duggan
Greater Boston Chamber of Conmierce
Boston, MA 02110
CAC Representative
Wes Eckenfelder
AWARE Incorporated
Nashville, TN 37228
Stan Elkerton
Universal Engineering
William Elliott
Amherst, MA 01002
CAC Representative
Joseph Ferrino
Winthrop Concernecd Citizens
Winthrop, MA 02152
John Gall
Camp, Dresser & McKee
Boston, MA 02107
9—11

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TABLE 9.2.a COORDINATION LIST (Continued)
CONCERNED CITIZENS
Betsy Johnson
Mass. Audubon Boston
Boston, MA 02108
CAC Representative
Martin Nee
do Rep. M. Flaherty
Boston, MA 02133
CAC Representative
David Kelluni
Save Our Beaches
Hull, MA 020 45
Jan O’Brien
North River
Marshfield,
Coal it ion
MA 02050
Joseph Lagnese
Allison Park, PA 05101
Sheldon Lipke
Passaic Valley Sewerage Commission
Newark, NJ 07105
Joseph MacRitchie
Squantum, MA 02171
CAC Representative
Jean L. McCluskey
Stone & Webster
Boston, MA 02107
Tom McNiff
Winthrop, MA 02152
CAC Alternate
Herbert Meyer
Mystic River Watershed Association
Arlington, MA 02171 1
CAC Representative
Phil Mitchell
Construction Industries of Mass.
Norwood, MA 02062
CAC Alternate
Franklin D. Munsey
Superintendent
Milwaukee Metropolitan Sewerage
District
Jones Island Treatment Facility
Milwaukee, WI 53207
Joanne Muti
Walpole, MA 02032
Marjorie O’Neil
Brookline, MA 021116
CAC Alternate
Jeff Paul
Boston Survey Consultants
Boston, MA 02210
John Salcione
East Boston, MA 02128
CAC Representative
Stewart Sanders
Mystic River Watershed Association
Belmont, MA 02178
CAC Alternate
Lawrence Schafer
Newton, MA 02158
CAC Representative
Dr. Kenneth Sebens, Director
Marine Science Institute
Northeastern University
Nahant, MA 01908
EOEA-TAG
Gary Shimp
Black & Veatch
Cambridge, MA 021110
David Standley
Center for Environmental Management
Curtis Hall, Tufts University
Medford, MA 02155
Facilties Plan TAG
9—12

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TABLE 9.2.a COORDINATION LIST (Continued)
CONCERNED CITIZENS
Dr. Keith Stoizenbach Jack Walsh
Department of Civil Engineering Quincy, MA 02169
MIT CAC Representative
Cambridge, MA 02139
EOEA-TAG Diane Wood
Save the Harbor/Save the Bay
Dr. David Terkia Boston, MA 02108
Boston University CAC Representative
Boston, Ma 02215
EOEA-TAG Walter Woods
Wellesley, MA 02181
Eric Thomson
Utility Contractors’ Association Nicholas Yannoni
Braintree, MA 02184 Newton, MA 02162
CAC Representative CAC Alternate
Regina Villa
Regina Villa Associates
Boston, MA 02108
Dr. Gordon Wallace
Environmental Sciences Program
Boston Harbor Campus
University of Massachusetts
Boáton, MA 02125
EOEA-TAG
9—13

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EPA also participated in the CPIC sponsored Outfall Forum on August 11, 1987. The
purpose of the forum was to bring together and elicit information from the involved
agencies and interested scientific and community groups. The CAC used the
information received as a basis for its recommendations concerning the scope of the
treatment plant outfall siting studies.
EPA attended three public informational meetings sponsored by MWRA: Winthrop in
October 1987; Weymouth in November 1987; and Revere in November 1987. The concerns
voiced by the citizens attending these meetings were considered by EPA in preparing
this Draft SEIS.
EPA maintains a reference system by which comments received by EPA and MWRA on the
STFP and Draft SEIS and related projects are tracked. EPA has considered the
comments in the this Draft SEIS.
9.2.5 TECHNICAL ADVISORY GROUPS: FACILITIES PLAN TAG AND EOEA TAG
The Facilities Plan Technical Advisory Group (TAG), formed by the Massachusetts
Environmental Policy Act Unit (MEPA), has provided the CAC with technical assistance
and scientific input. The TAG has 19 members from state and federal agencies, the
scientific community, former members of the original EPA treatment plant siting EIS
TAG, and the public (Table 9.2.a). The TAG members have met periodically and often
attend the CAC and its subcommittee meetings.
The Secretary of Environmental Affairs, James Hoyte, created the Executive Office of
Environmental Affairs’ TAG (EOEA TAG) in 1985. Scientists from Massachusetts
institutions and public agencies were requested to serve in an advisory capacity on
matters of environmental concern related to projects in Boston Harbor
(Table 9.2.a). The EOEA TAG’s focus has been expanded since its formation to
include projects in all coastal areas of Massachusetts. The EOEA TAG is currently
being re-formed to coincide with the EOEA Massachusetts Bay/Cape Cod Bay Program.
The EOEA TAG meets monthly at the Massachusetts Coastal Zone Management Offices.
EPA has attended and participated in the Facilities Plan and EOEA TAG meetings. The
interaction between EPA and the TAGs has been beneficial to EPA. EPA’s knowledge of
the TAGs’ concerns and questions allowed EPA to consider them in this Draft SEIS.
9.2.6 PUBLIC MEETINGS
9.2.6.1 Information Meetings
Two public information meetings will be held in April 1988 on the North and South
Shores after the release of this Draft SEIS. The purposes of these meetings are to
brief the public on the results of the Draft SEIS investigations and the recommended
alternatives for the inter—island conduit and effluent outfall. These meetings will
occur at a key point in the SEIS analysis process to encourage public input. The
meetings’ format will consist of presentations by EPA and its technical consultants,
followed by a public question and answer session.
9 114

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9.2.6.2 Public Hearing
A public hearing is scheduled to be held in May 1988 after the release of this Draft
SEIS. Public testimony will be recorded. The Final SEIS will then be prepared and
will contain a snnin ry of the public comments and EPA’s responses to the issues
raised by this Draft SEIS.
9.2.7 INFORMATIONAL ACTIVITIES
9.2.7.1 Fact Sheets
Two fact sheets were prepared and mailed to the project mailing list (described in
Section 9.3.1). A fact sheet published in early March 1988 included a summary of
the project background and status and EPA’s selection of outfall location
alternatives for detailed evaluation. A second fact sheet, to be distributed in
early April 1988, will s’rnrt rize the results of this Draft SEIS and the recommended
alternatives for both the inter-island conduit and effluent outfall.
9.3 OTHER SERVICES
9.3.1 MAILING LIST
The mailing list for this project includes both EPA’s Boston Harbor mailing list and
MWRA’s STFP and On The Waterfront mailing lists, together containing over 3200 names
of concerned Federal arid State officials, citizens, agencies, organizations, and
media representatives. The list is continually updated and used for distribution of
fact sheets and announcements of public participation events.
9.3.2 INFORMATION REPOSITORIES
This Draft SEIS has been distributed to information repositories in the project area
(Table 9.3.a) where the public can review it, or interested persons can obtain a
copy by contacting Dave Tomey at U.S. EPA Region I, Boston, MA (see cover page).
The appendices of this Draft SEIS and fact sheets published by EPA for the project
were also placed in the repositories.
9.3.3 ANNOUNCEMENTS
Public notices will be prepared announcing the public meetings, public hearing, and
coninent period for this Draft SEIS, and placed in the local media. Press releases
and public service announcements were also produced as appropriate during the study.
9-15

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TABLE 9.3.a
LIST OF REPOSITORIES
University Library
Attn: William Thompson
U/Mass Amherst
Amherst, MA 01003
14 13 5 1 45 ..0 150
Mon.—Thurs. 8-12; Fri. 8—10;
Sat. 10-6; Sun. 10-12
Boston Public Library
Attn: Lloyd Jaineson
P.O. Box 286
Boston, MA 02117
536 5 1100
Mon.-Thurs. 9-9; Fri.-Sat. 9-5;
Sun. 2-6
State House Library
Attn: Jennifer Mason
State House Room 3141
Boston, MA 02133
727-2590
Mon.—Fri. 9-5
MWRA Library
Attn: Mary Lydon
100 First Ave.
Charlestown, MA 02129
2l42 6000
Mon.—Fri. 8:30—14:30
Maiden Public Library
Attn: Dma Maigeri
36 Salem Street
Maiden, MA 021148
3214-0218
Mon.-Thurs. 9-9; Fri.-Sat. 9-6
Nahant Public Library
Attn: Doug Cisney
15 Pleasant Street
Nahant, MA 01908
581-0306
Morrill Memorial Library
Attn: Mrs. Maddox
Walpole Street
Morwood, MA 02062
769-0200
Mon.-Fri. 9-9; Sat. 9-5;
Sun. 1-5
Thomas Crane Public Library
Attn: Linda Beeler - Reserve Dept.
140 Washington Street
Quincy, MA 02169
9814—1950
Mon.-Thurs. 9-9; Frl.-Sat. 9-5
Hough’s Neck Community Center
Attn: Patricia Redlen
1193 Sea Street
Quincy, MA 02169
1471-8251
Mon. 9—8:30; Tues.-Fri. 9_14
U.S. EPA Technical Library
15th Floor
JFK Federal Building
Boston, MA 02203
565-3715
Mon.—Fri. 8:30—4:30
Wellesley Public Library
Attn: June Robertson
530 Washington Street
Wellesley, MA 02181
235-1610
Mon.—Thurs. 10-9; Fri 10-7;
Sat. 9-5; Sun. 2-5
Winthrop Public Library
Attn: George Pillion
2 Metcalf Square
Winthrop, MA 02152
8)46-1703
Mon., Tues., Thurs. 1-9; Wed. 10-9;
Fri. 10—6; Sat. 10—5
9—16

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9); PUBLIC ISSUES
During the preparation of this Draft SEIS and EPA’s participation in the public
participation process as described above, several issues of concern about the
project were raised by the public and various agencies. The major areas of concern
are presented below, along with a description of how chey are addressed in this
Draft SEIS. Many issues raised are not contained in this discussion because they
are not within, the scope of an EIS or are too general.
9.11.1 DISCHARGE OF INTERIM PRIMARY
Concern was raised over the location of’ the primary effluent discharge. This Draft
SEIS has addressed this issue by first screening the potential discharge locations
for acceptability of primary effluent (Chapter 3), and then evaluating in full the
impacts from primary effluent at each of the alternative sites considered in detail
(Chapter 5). The evaluation includes assessment of shoreline impacts at Winthrop,
Nahant, and Hull. Methods used to assess impacts were consistent with the methods
used for primary treatment waiver studies.
9.11.2 ALTERNATIVES EVALUATED
The selection by !4WRA of alternative sites for discharge of effluent was an issue
raised during the public participation process. The potential for a site seaward of
Site 5 was a particular question. This issue was addressed in this Draft SEIS by a
thorough site screening process (Chapter 3 and Appendix F). This process eliminated
clearly unsuitable areas and identified sites for detailed evaluation which
represented the range of environmental conditions in the area.
9.11.3 EFFLU IT QUALITY
Several people were concerned that the wastewater treatment plant would not perform
at specified levels or that unexpected conditions, such as equipment malfunction,
would result in an effluent of significantly lower quality. This issue was
addressed by a complete review of the proposed treatment removal efficiencies and an
evaluation of the possibility of various less-than-full-treatment operational
scenarios (Chapter 5 and Appendix H). Discharge modelling incorporates the mixture
of’ primary and secondary effluent for maximum flows.
9.11.11 FATE AND EFFECT OF SOLIDS DEPC ITION
To address this concern this Draft SEIS predicts solids deposition and sediment
resuspension for each of the alternative locations, estimates buildup of potentially
toxic compounds (Appendix B), and compares these to literature values reported for
marine impacts (Appendix C). A discussion of these analyses is contained in
Chapter 5.
9—17

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9 i4 5 DISSOLVED OXYGEN (DO) CONCENTRATIONS DURING STRATIFIED CONDITIONS
The public was concerned about DO concentrations during stratified conditioL s. This
concern was addressed in two ways. First the mathematical models used by MWRA were
modified to determine DO concentrations throughout the area modelled. Next the
models were modified to represent stratified conditions (Chapter 5 and Appendix A).
9.14.6 NUTRIENT ENRICHMENT
Concern was expressed about the effects of nutrient loading in the marine
environment. The potential for enrichment was analyzed by first using the model to
predict nutrient concentrations and then comparing the concentrations to literature
values for comparable systems that resulted in excessive production (Section 5.1.3).
9)4.7 ASSESSMENT USING LIMITED DATA
Concern was raised over making a decision on outfall location with less than a full
year of data. This was an issue both for biological and physical systems. The
impacts on biota were assessed based on predicted levels of stress (such as
concentrations of’ toxic compounds or nutrient enrichment) that were reported to
affect marine biota at their most sensitive life stage, whenever the season.
Therefore the impacts during all seasons were addressed.
Impacts on physical systems were based on measurements which covered the full range
of environmental conditions such as: extreme freshwater runoff; maximum
stratification; high temperatures; high shoreward currents (as determined from long
term wind records); north and south boundary tilt; no net drift. Also the data
covered the summer period which is most susceptible to discharge-related impacts,
such as low DO, high sediment deposition, and maximum production.
9.14.8 CUMULATIVE IMPACTS
A major area of public concern was interaction of the MWRA discharge with discharges
from other sources. This Draft SEIS presents an entire chapter on cumulative
impacts (Chapter 6). Other discharges were input to the water quality assessment
(Appendix A).
914.9 TOXIC COMPOUNDS
EPA recognizes the concern over toxic compounds. A modelling of all potential toxic
compounds was included for both water column and sediments. The results of the
evaluation were included in the site comparison. Where compounds exceed criteria at
all sites, EPA recommends the control of these compounds at the source.
9-18

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9.14.10 CONSTRUCTION SCHEDULE
Several people were concerned that the time allowed in the court schedule to
construct the outfall would dictate the outfall length. The court schedule was not
a criteria used to evaluate the alternative sites in this Draft SEIS (Chapter 7),
although the length of time required to construct the outfall was considered. All
outfall alternatives can be constructed prior to startup of the new primary
treatment plant.
9.14.11 QUANTITATIVE EVALUATION OF BOATING ACTIVITIES
The issue of impacts on boating activities is addressed in Appendix D, existing
conditions and impacts on harbor resources sections.
9.14.12 EVALUATION OF COMPOUNDS WITHOUT CRITERIA
The issue of evaluating all compounds was addressed for sediments by comparing
predicted levels of sediment contamination to literature values of levels producing
no effects (Appendix B). EPA criteria were considered sufficient to assess water
column impacts.
9.14.13 SIZE OF THE MIXING ZONE
Although the mixing zone is a dynamic concept changing with ambient currents,
Chapter 5 on stratification and wastewater flow provides a discussion of the
potential size and location of the mixing zone.
9.14.114 FRESHWATER DISCHARGED TO MASSACHUSETTS BAY
The potential impact of freshwater discharged to Massachusetts Bay was not addressed
in this Draft SEIS. The discharge at any site will be diluted a minimum of
50 times. This would lower the salinity a maximum of 2 percent, or change the
ambient salinity (approximately 31 parts per thousand (ppt)) less than 1 ppt. This
change is well within the normal seasonal and vertical salinity range.
9—19

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ATTACHMENT 1
BOSTON HARBOR
MARINE WASTE WATER CONVEYANCE SYSTEMS
SUPPLEMENTAL ENVIRONMENTAL IMPACT STATEMENT
NOTICE OF INTENT
9-20

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.,cD Ii
____ UNITED $TATE$ ENVIRONMENTAL PROTECTION AGENCY
>4( REGION I
J. F. KENNEDY FEDERAL BUILDtNG, BOSTON. MASSACHUSETtS OV
TO: All persons interested in the Marine Wastewater Conveyance
Systems Supplemental Environmental Impact Statement (SEIS)
for Boston Harbor
Enclosed for your review is the Notice of Intent for the preparation
of a Supplemental Environmental Impact Statement (SEIS) on marine
wastewater conveyance systems and outfall(s) for the Massachusetts
Water Resources uthority’s (MWRA) wastewater treatment facilities
at Deer Island, Boston, Massachusetts.
This SEIS will be prepared by the U.S. Environmental Protection Agency.
The MWRA is preparing an Environmental Impact Report (EIR) under the
Massachusetts Environmental Policy Act on the facilities plan for all
components of the Deer Island facilities. This SEtS will satisfy the
need for further federal environmental review of the wastew ter convey-
ance facilities and outfalls.
Vull public participation by interested Federal, state and local agencies,
concerned organizations, and private citizens is invited. A scoping
meeting for the general public will be held on Thursday, December 11,
1986, 4:00—6:00 P.M., in the auditorium of the Department of Transpor-
tation at 55 Broadway, Kendall Square, Cambridge. A second scoping
meeting for Federal and State agencies and public groups will be held on
Monday, December 15, 9:30 A.M. in the Executive Dining Room, (Rm: E—226)
JFK Federal Building, Boston, MA. Should you have any questions,
please feel free to contact Mr. Ronald Manfredonia of EPA at
(617) 565—3555.
9—21

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Notice of Intent
To Prepare a Supplemental Environmental Impact
Statement
Agency: U.S. Environmental Protection Agency (EPA), Region I
Action: Preparation of a Supplemental Environmental Impact
Statement (SEIS) on the Marine Wastewater Conveyance
Facilities and Outfall(s) for the Massachusetts Water
Resources Authority (MWRA) wastewater treatment
facilities at Deer Island, Boston, Massachusetts.
Purpose: The MWRA is undertaking facilities planning for the
construction of major wastewater treatment facilities
serving metropolitan Boston pursuant to a schedule
mandated by the U.S. District Court, District of
Massachusetts, in US. v. MD.C. et al. , Civil Action
No. 85—0489—MA and a related case. In accordance
with the EPA procedures for the implementation of
the National Environmental Policy Act (NEPA), 40
CFR Part 6, EPA intends to prepare a SEIS on the
marine wastewater conveyance facilities and outfall(s)
associated with these facilities. This notice of
intent is issued pursuant to 40 CFR cS 6.510(a)(l) and
6.105(e). The decision to prepare a SEIS is consistent
with Section l502. (c) of the Council on Environmental
Quality (CEO) Regulations, 40 CFR Sl502.9(c).
This SETS will be prepared concurrently with MWRA
facilities planning for the wastewater treatment
facilities. Other related actions being undertaken
by the MWRA include facilities planning for residuals
management (the subject of a separate SETS) water
transportation facilities, combined sewer overflows
and scum removal facilities.
Preparation of the SETS is consistent with EPA’S
Record of Decision (ROD) issued February 28, 1986 on
the Final Environmental Impact Statement (FEIS) for
the MWRAs Proposed Siting of Wastewater Treatment
Facilities for the cleanup of Boston Harbor. The
ROD specified that additional environmental reviews
were required for the construction of an unde —harbor
tunnel or pipeline and for the water quality impacts
and construction impacts of an outfall pipe or
pipes. This SEIS will supplement the FEIS on the siting
of the wastewater treatment facilities.
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SUMMARY:
A Background :
Planning for treatment of metropolitan Boston’s wastewater
has been proceeding for several years. A major aspect of
this planning, the siting of the wastewater treatment
facilities, culminated in February, 1986 with the MWRA’s
decision to site the treatment plant at Deer Island. The
MWRA’s siting decision was supported by EPA’s ROD. The
FEIS and ROD concluded that the environmental impacts of
certain components of the facilities planning, which
included the wastewater conveyance facilities and outfall(s),
were not site determinative. This SEIS will satisfy the
need, identified in the ROD, for further federal environ-
mental review of the wastewater conveyance facilities and
the outfall(s).
The MWRA is now preparing an Environmental Impact Report (EIR)
under the Massachusetts Environmental Policy Act (MEPA)
on the facilities plan for all components of the Deer Island
facilities. The EIR will include evaluation of the wastewater
conveyance facilities and outfall(s). The SEIS will be de-
veloped as a separate document from the EIR. However, to the
maximum extent feasible, EPA, MWRA and other affected state
agencies intend to coordinate this SEIS with the EIR, in
accordance with 40 CFR §1506.2. The U.S. Army Corps of
Engineers will act as a cooperating agency for this envi-
ronmental review pursuant to 40 CFR S 1501.6.
B. Description of EPA Action :
EPA action in connection with construction of the wastewater
conveyance systems and construction and operation of the out-
fall(s) may include Federal construction grants, requiring
NEPA compliance. Other related federal actions requiring en-
vironmental review in connection with the wastewater convey-
ance systems and outfall(s) may include:
o dredge and fill permits and
o designation of an ocean disposal site for excavated
materials resulting from construction and tunneling
9—23

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C. Principal Issues and Alternatives :
3. Selection of the type of conveyance systems (pipelines,
tunnels, combination and outfall/diffuser design) and the
appropriate construction methods to be used. Key environmental
issues associated with each technique are shown in Table 1.
2. Selection of the appropriate route for the conveyance
systems.
3. Selection of the appropriate site for the outfall. Key
environmental issues associated with the outfall location
are shown in Table 2.
D. Public and Private Involvement and Participation :
Full public participation by interested Federal, state, and
local agencies as well as other concerned organizations and
private citizens is invited. Citizen advisory groups and
committees will be utilized to facilitate effective public
participation. All interested persons are encouraged to
submit their names and addresses to the person listed above
for inclusion on the mailing list for newsletters, the draft
SEIS and related public information. A full public
participation program will he managed by the MWRA and will
be supplemented, as necessary, by EPA.
The Massachusetts Executive Office of Environmental Affairs
(EOEA) and EPA have agreed to utilize a single Citizens
Advisory Comr ittee (CAC) for state and Federal environmental
reviews of both the Residuals Management Facilities Plan and
the Deer Island Wastewater Treatment Facilities Plan, of
which planning for the wastewater conveyance system and the
outfall(s) is a part. EPA, Region I, EOEA, and MWRA will
conduct two scoping meetings to ascertain public and agency
views on the options, sites, construction techniques, eco-
nomic and environmental considerations, legal, institu-
tional and other issues that should he evaluated in this
SEIS. The first meeting will be for the general public
and will assist EPA in developing the scope of work for
the SEIS. This meeting will be held on December 11,
4:00—6:00 P.M. in the auditorium of the Department of
Transportation at 55 Broadway, Kendall Square, Cambridge,
MA. The second meeting will be held for Federal and
State agencies and public groups on December 15, 9:30 A.M.
in the Executive Dining Room (Rm E226), JFK Federal
Building. Rocton, MA. EPA invites written comments On
the proposed scope of work for the SEIS until December
19, 1986. All comments on this Notice of Intent should
be addressed to Director, Water Management Division, EPA,
Region I, JFK Federal Building, Boston, MA.
9—24

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It S. anticipated that the draft SEIS will be available by
September 1987 and the Final SEIS will be issued in February,
1988. Copies will be available at EPA, Region I and local
depositories.
For Further Information Contact:
Ronald G. Manfredonia
EPA — Water Management Division
John F. Kennedy Federal Building
Boston, MA 02203
Telephone — (617) 565—3555
FTS 835—3555
9—25

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Table 1
Summary of Key EIS Issues
Wastewater and Effluent Conveyance Systems
Conveyance Systems Construction and Operational Issues
Pipelines ° indigenous ecosystem impacts
plankton, benthos, fish
during construction
o dissolved oxygen depletion
due to sediment resuspension
during construction
• toxicity due to sediment
resuspension during construction
• disturbance to recreational
boating and fishery
• disturbance to commercial
shipping and fishery
• wetland impacts
• dredge material testing and
disposal
• traffic and storage of pipeline
construction materials
• ACOE and Coast Guard requirements
with respect to anchorage areas,
channel maintenance, LNG and
explosives transport, etc.
o construction feasibility
• operational reliability
Tunnels • blasting effects
• excavated material transport and
disposal
• traffic and storage of tunnel
construction material
• land and/or water impacts due tO
shaft operation
9-26 • wetland impacts

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Table 1 Continued
Conveyance Systems
Con
struction and Operational Issues
Tunnels
°
ACOE and Coast Guard requirements
with respect to anchorage areas,
channel maintenance, LNG and
explosives transport, etc.
during construction
°
construction feasibility
°
operational reliability
Diffusers ° issues the same as under Pipelines
o impacts due to a single or a split
discharge of primary and/or
secondary wastewater treatment
facility’s effluents — see Table 2
9—27

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Table 2
Summary of Key EIS Issues
Discharge of Primary and Secondary Effluents
Issues To Be Evaluated Primary Reasons for Evaluation
• initial dilution modeling ° to determine water quality standards
violations (WOC, toxicity, E. coli)
• long term dilution modeling ° determine water quality standards
violations (dissolved oxygen)
• sedimentation and resus— determine water quality standards
pension of effluent solids violations (dissolved oxygen, impacts
modeling on benthos)
• upwelling and surface • effects of average and peak flows
transport modeling on use of beaches and coastal resources
• modeling of other point • possibility of combined impacts
sources from several sources at a specific
location
• toxicity of effluents • possibility of adverse environmental
impacts
• marine c ununity structure • possibility of adverse environmental
and pathology impacts
• study of use of shoreline possibility of impacts on recreational
and marine resources and commercial activities
• study of existing ambient • possibility of adverse environmental
water and sediment quality impacts
in relation to existing
pollution sources and ob-
served environmental
impacts
Above issues will be evaluated with regards to specific diffuser
locations, degree of treatment of average and peak flows, under
a split flow (two diffusers) and total flow (single diffuser)
options.
9—28

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MyRA, 1987. Outfall Siting Assessment Memorandum, FG3I4D, Secondary Treatment
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MWRA, STFP III,B, 1987. Secondary Treatment Facilities Plan, Volume III,
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MWRA, STFP III,C, 1987. Secondary Treatment Facilities Plan, Volume III, Appendix
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MWRA, STFP III,J, 1987. Secondary Treatment Facilities Plan, Volume III,
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MWRA, STFP III,H, 1987. Secondary Treatment Facilities Plan, Volume III, Appendix
H, Power.
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Outfall, Appendix D, Conceptual Diffuser Design.
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MWRA, STFP V,E, 1987. Secondary Treatment Facilities Plan, Volume V, Appendix E,
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ROV Reconnaissance I.
MWRA, STFP 7,0, 1987. Secondary Treatment Facilities Plan, Volume 7, Appendix 0,
ROV Reconnaissance II.
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REMOTS Reconnaissance I.
MWRA, STFP V,Q 1987. Secondary Treatment Facilities Plan, Volume V, Appendix Q,
REMOTS Reconnaissance II.
MWRA, STFP V,R, 1987. Secondary Treatment Facilities Plan, Volume 7, Appendix R,
Sediment Grain Size Sampling.
MWRA, STFP V,S, 1987. Secondary Treatment Facilities Plan, Volume V, Appendix 5,
Benthic Chemistry Sampling.
MWRA, STFP V,T, 1987. Secondary Treatment Facilities Plan, Volume 7, Appendix T,
Benthic Biology Sampling.
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Fish & Epibenthic Shellfish.
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Fish Histopathology.
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Nutrient Analysis.
P4WRA, STFP V,Z, 1987. Secondary Treatment Facilities Plan, Volume V, Appendix Z,
Primary Productivity Program.
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Marine Archaeology.
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MWRA, STFP VII, 1987. Secondary Treatment Facilities Plan, Volume VII,
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GLOSSARY
1st order kinetics - when modeling the decay of an effluent constituent as a
first order process, the decay rate at any time is proportional to the
remaining constituent concentration. This results in an exponential
decrease in constituent concentrations over time
acute effects - lethal response resulting from short term exposure to
toxicant(s). Ninety-six hours has been established as the generally
accepted exposure time for bioassays determining acute toxicity
ambient - conditions, e.g., concentration, current speeds, etc., measured at a
specific location or throughout the receiving waters, resulting from
factors exclusive of future wastewater discharges
amphipod - a small crustacean
argillite - a metamorphic rock, intermediate between shale and slate, that
does not possess true slaty cleavage
arochior - mixture of PCB’s
ascidians — a class of sessile tunicates or sea squirts
background buildup concentration - constituent concentrations in the receiving
waters immediately outside the mixing zone, which provide dilution water
for the initial dilution process. Background concentrations develop
because of the return of previously discharged constituents to the
diffuser area due to the tidally reversing currents
benthic - of or pertaining to the ocean floor
benthos - organisms that are attached to, live on or live in the ocean bottom
bimodality - two distinct peaks
bioaccumulation - accumulation of toxicants in tissues of organisms resulting
from direct exposure or by ingestion
bioconcentration - concentration of contaminants by an aquatic organism
through its digestive tract or gill tissues
biomagnification - transfer of bioaccumulated toxicants through the food web
biogenically bound mud - marine sediments
biomass - the amount of living material per unit area
bioturbulation - mixing of bottoms sediments by benthic organisms

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bivalve - a molluse with two shells hinged together as a clam
Broad Sound - coastal embayment of Massachusetts Bay, generally bound y
Nahant and Deer Island
bryozoans - sessile, colonial marine organisms living attached to hard
substrate
calibration - variation of model input parameters, e.g., mixing and decay
rates, within reasonable bounds until model predictions match field
measurements for the system under study
capitelled - a family of polychaete worms known for their pollution tolerance
carcinogencity - the ability of an effluent constituent or its reaction
byproducts to cause tumors in organisms inhabiting the receiving waters
chemical tracer - a conservative or slowly decaying constituent within a
discharge, which can be tracked following release into the receiving
waters to provide information on rates of turbulent mixing and other data
used for numerical model calibration
chlorophyll — green pigment in plant cells that is the receptor of light
energy in photosynthesis
cirratulid - a family of polychaete worms
chronic effects - lethal response or debilitating damage to an organism(s)
resulting from prolonged exposure to the toxicant(s). Exposure time may
be several days, weeks, months or even years
coliforms — a group of bacteria characteristic of the intestinal tract of warm
blooded vertebrates, which are used as indicators of the presence of
domestic wastes
conduit - a tube-like structure that conducts fluid
copepods - very small crustraceans, usually planktonic living in the water
column
coriolis force - a force perpendicular to the direction of motion due to the
rotation of the earth
CTDO - indicates simultaneous field measurements of conductivity, temperature
and dissolved oxygen at a given location
decay rate (conservative, 20, 60-day 1/2 life) - the rate of disappearance of
an effluent constituent following discharge into a receiving water due to
its transformation Into other compounds. Expressed as a decay per unit
time (k) or as a half-life, which is the amount of time required for loss
of 1/2 the original constituent mass.

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deep rock tunnel - a conduit which is constructed by boring a tunnel through
bedrock
de.ersal - residing on the ocean bottom. Pelagic of or pertaining to the
ocean bottom waters
density - the density of seawater is its mass per unit volume. It is
frequently expressed in sigma-t units, which is the density in grams per
cubic centimeter minus 1, times 1000, e.g., a density of 1.020 gm/cm 3 is
equal to a sigma-t of 20.
depositional areas - areas of low wave energy where part iculates in the water
column settle to the ocean bottom
detection limit - the smallest quantity that can be measured with certainty by
a given analytical method
diato - dominant planktonic algal form with a cell wall composed of silica;
occurring as single cells or chains of cells
diffuser - a manifold at the end of an outfall which discharges wastewater,
allowing the wastewater to be diluted with seawater
digested sludge - the thickened mixture of sewage solids with water that has
been decomposed by anaerobic or aerobic bacteria
dinoflagellates - dominant planktonio algal form occurring as single cells
dragging - counercial fishing method using trawl
drifters - impermeable cards released in the water and to be mailed back upon
discovery by third parties; used to characterize long-term water transport
drogue — floating object released and tracked with time to characterize water
movements over a period of one to several days
dry ton - 2000 pounds of material (sludge) with approximately 20% moisture
content
effluent - the outflow from a wastewater treatment plant
— a two-dimensional element water quality transport model used for
si lating the impacts of effluent discharges into tidal waters
e ntraIi o’it - incorporation of ambient water into an effluent plume due to
turbulence within the plume
epifaima - animals living on the surface of the ocean floor
euphotia zone - zone in the water column in which light penetration is
sufficient for photosynthesis

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euryhaline estuarine - wide range of salinities
facilities plan - the conceptual design of a wastewater treatment system
fall velocity - the downward vertical velocity at which suspended particles
settle in the water column
farfield - zone removed from the discharge point where the effluent is
affected by ambient transport, diffusion and decay independently from the
design of the discharge structure
flaggellates - see dinoulagellates
flocculation - to become a loosely aggregrated mass of material suspended in
liquid
forcing frequency - frequency of a force driving the water motion
Fourier amplitude & lag - amplitude and lag of the sinusoidal component of a
signal (such as water surface elevation or current speed) at a given
frequency
gillnetting - fish harvesting method utilizing stationary nets
harmonic analysis - analysis in which the Fournier amplitude and lag (q.v.)
are determined as a function of frequency
headworks - where wastewater is collected and pumped to a wastewater treatment
plant
hydroids - sessile, colonial invertebrates related to jellyfish with branched
structure living attached to hard substratum
infauna - animals living within the sediments of the ocean bottom
influent - inflow to a wastewater treatment plant
initial dilution - dilution which occurs in the effluent plume close to the
diffuser by entrainment of ambient water
interceptor system - a large sewer used to intercept a number of main or trunk
sewers and convey the wastewater to treatment facilities
isolume - zone in water column in which light penetrates to the same degree
nannoplanktOfl - the smallest plankton; generally less than )O i in size
marine pipeline — a conduit constructed by lying a pipeline on or below (in a
trench) the ocean floor

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ss flux - rate at which a constituent is discharge expressed in mass per
unit time, e.g. mg/sec
im.iltiport - having numerous openings for discharge
neap tide — tide of small amplitude which occurs when sun and moon influences
are in opposition
nearfield - area close to the discharge where the effluent is rapidly diluted
by turbulent entrainment of ambient fluid
neritic — of or pertaining to those regions of the ocean over the continental
shelves
net drift — net movement of water over one or several complete tide cycles
non—tidal current - currents of driven by forces other than the tides
North System - the region of MWRA’s system which receives wastewater treatment
from the Deer Island Wastewater Treatment Plant
nutrients - anything other than the elements carbon, hydrogen and oxygen that
is needed in the synthesis of organic matter. Common nutrients are
nitrates and phosphates.
oceanic - of or pertaining to the deeper regions of the oceans beyond the
continental shelves
oligochaetes - marine worm species related to the common earthworm living
within the sediments
outfall - the conduit which conveys effluent from the wastewater treatment
plant to its discharge location
oxygen de nd — consumption of oxygen by bacteria to oxidize organic matter
palpi — mouth parts used in obtaining food
Pb -210 - lead radioactive isotope used to determine the date of deposited
sediments
pH - a numerical measure of the acidity or alkalinity of a chemical solution
pi ytoplankton - a microscopic marine algae in the water column
pycnocline — zone of the water column where density changes rapidly with
depth. The pycnocline separates upper and lower layers when the water
column is stratified.
po1yct ete - annulated marine worm living in sediments

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port - an opening on a diffuser through which effluent discharges
primary productivity - the rate at which organic matter is produced in
photosynthesis
primary treatment - preliminary treatment of wastewater including: pumping,
screening, grit removal and settling of heavy solids and floatable
materials
progressive vector plots - plots of the horizontal movement of a small parcel
of water or a neutrally buoyant particle over time, based on either
continuous current measurements at one location or model predicted
circulation fields
removal efficiency - the efficiency which a process has in reducing a
constituent in an effluent
resuspension — lifting of inpiace bottom sediments into the water column by
waves or other bottom currents
riser - vertical tube from seafloor to deep rock tunnel for diffusing effluent
salinity - the total amount of solid material in grains contained in one
kilogram of seawater when all the carbonate has been converted to oxide,
the bromine and iodine replaced by chlorine, and all organic matter
completely oxidized
saturation - seawater in contact with the atmosphere will tend to reach
equilibrium with respect to dissolved gases, such that the partial
pressures of gases in both will be equal. The seawater is said to be
saturated with a given gas, such as oxygen, when this equilibrium is
reached, for a specific pressure, temperature and salinity.
secchi disk measurements - measurement of light depth penetration in the water
column
secondary treatment - biological treatment of wastewater following primary
treatment involving removal of dissolved organics
sediment - soil and organic particles which accumulate on the sea floor
sedimentation - the deposition of sediment particles
semi—diurnal- tides - the dominant tidal component along the east coast of
North America, which has a period of 12.142 hours. There is little
difference between the corresponding tides of successive half-day cycles,
i.e., there is very little diurnal inequality
sewerage/sewage — liquid or solid waste which is transported through drains
and/or by sewers to a wastewater treatment plant for processing

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South Syst - the region of MWRA’s system which receives wastewater treatment
from the Nut Island Wastewater Treatment Plant
spionids - a family of polychaete worms
spring tide— the tides occurring about the times of’ new and full moon (twice
per month) which rise higher and tall lower than during other times
ator iater — precipitation which either runs off or enters a sewer system
stratified conditions - during the spring and sumer months, gradual warming
of surface waters results in formation of a very stable vertical density
profile, with less dense warm water near the surface and more dense cold
water at greater depths. This vertically stable water column constitutes
stratified conditions
sunken tube - a conduit constructed by sinking a tube such that it lies on or
below (in a trench) the ocean floor
supersaturation - the partial pressure of a gas in seawater can exceed the
saturation level. For example, algal production of oxygen can result in
supersaturation of’ the seawater with respect to dissolved oxygen
taxalta .zon — a grouping of organisms with coenon characteristics
TEA—Ifi. - model used to calculate circulation in Massachusetts Bay for the
water quality analysis
thermocline - zone in the water column where temperature varies rapidly with
depth. Usually coincident with the pycnocline (q.v.)
tidal ourrent - currents due to the tide
tidal elevation - variations of the water level due to tides
tidal eUlpee - locus of the end of the velocity vector at a point during a
tide cycle
tidal pri — volume of water entering and leaving a tidal embayment during
the flood and ebb parts of a tide cycle
tilt - difference in average sea level between Gloucester and ProvincetOWn,
which drives net drift in Massachusetts Bay
total ke1 h nitrogen - total of organic and ai onia nitrogen
toxicity - degree to which an element or compound is capable of causing
toxicosis when introduced into body tissues
trawling - coamercial fishing method which utilizes a net towed behind a boat
tubionlous species - tube dwelling

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turbidity - presence of suspended solids in the water, affecting its
transparency
UDJUIDEN - nearfield model used to calculate the dilution and final height of
rise of the effluent plume in the zone of initial dilution
ULINE — nearfield model used to calculate the dilution and final height of
rise of the effluent plume in the zone of initial dilution
UMERGE - nearfield model used to calculate the dilution and final height of
rise of the effluent plume in the zone of initial dilution
wastewater - liquid waste collected in a sewer system and transported to a
wastewater treatment plant for processing
zooplankton - microscopic animals living suspended in the water column and
incapable of moving against currents

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ACRONYMS
AMSA Association of Metropolitan Sewerage Agencies
BWSC Boston Water and Sewer Commission
CAC Citizen Advisory Committee
CBOD Carbonaceous biochemical oxygen demand
CCC Criterion Continuous Concentration
CFR Code of Federal Regulations
CMC Criterion Maximuni Concentration
CSO Combined Sewer Overflows
CTDO Conductivity, Temperature and Dissolved Oxygen
DDT Dichlorod ipheny ltr ichioroethane
DEIS Draft Environmental Impact Statement
DIF Deer Island Facilities Plan
CMF Division of Marine Fisheries
DO Dissolved Oxygen
DOD Dissolved Oxygen Deficits
EC o Effluent Concentration at which 50% of the Test
Organisms Exhibit Sublethal Effects
EIR Environmental Impact Report
EIS Environmental Impact Statement
ELA Eulerian_Lagragian Analysis
C’EA The Massachusetts Executive Office of Environmental
Affairs
FEIR Final Environmental Impact Report
i’EIS Final Environmental Impact StatementS
L 90 Noise level which is exceeded 90 percent of the time

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LC 50 The effluent concentrations at which 50% of ‘the test
organisms are killed
MARMPP Marine Monitoring Assessment Program
MBO t4anomet Bird Observatory
MDC Metropolitan District Co mnission
MDMF Massachusetts Division of’ Marine Fisheries
MEPA Massachusetts Environmental Policy Act
MLW Mean Low Water
MWRA Massachusetts Water Resources Authority
NBOD Nitrogenous Biochemical Oxygen Demand
ND Not Detected
NEA New England Aquarium
NEPA National Environmental Policy Act
NGVD National Geodetic Vertical Datum
NMFS National Marine Fisheries Services
NOEL No Observed Effect Level
NOl Notice of Intent
NPDES National Pollution Discharge Elimination System
OTW On the Waterfront
PAH Poly Aromatic Hydrocarbons
PCB Polychi.orinated Biphenol
RO/RO Roll—on/Roll-Off
ROD Record of Decision
SDEIS Supplemental Draft Environmental Impact Statement
SEIS Supplemental Environmental Impact Statement
SOD Sediment Oxygen Demand

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SS -Suspended solids
STFP Secondary Treatment Facilities Plan
SWIM Nahant Citizens Comittee for Safer Waters in
Massachusetts
Site PR President Road Site
TAG Technical Advisory Group
Tunnel Boring Machine
TEA-NI. Tidal Fabayment Analysis - Nonlinear
TKN -Total Ljeldhahl Nitrogen
TPI4 MIT Transient Plume Model
TRIGON The Research Institute of the Cult of Maine
TSS Total Suspended Solids
USACE United States Army Corps of Engineers
USEPA/EPA United States Envirorental Protection Agency
YOC Volatile Organic Compound
VOHC Volatile Halogenated Organic Compounds
WTFP Water Transportation Facilities Plan
WTP Waste Water Treatment Plant
ZID Zone of Initial Dilution

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LIST OF UNITS
ft foot
km kilometer
hrs hour
sec second
m meter
cm centimeter
cm/sec centimeter per second
g gram
g/com grams per cubic centimeter
ing milligram
1 liter
mg/i milligrams per liter
iig/l micrograms per liter
ng nanogram
r ig/i nanograrns per liter
ppi parts per million
micron
d 1 per day
mgd millions of gallons per day
m 3 /s cubic meters per second
g/m 2 /day grams per square meter per day
m 2 /sec square meters per second
g/m 2 grams per square meter
cm 3 cubic centimeters

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millimeter
yr year
square centimeters
1Lg/g micrograms per gram
square kilometers
lbs pounds
dBA decibals
yd yard
cu yd (yd 3 ) cubic yards
cu ft (ft 3 ) cubic feet

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INDEX
TERM PAGE(S)
archaeology 14.J 4 6, 52 , 55 , 5—57,65
background build-up 3—5, 4-3, 5-7,8,23,24
beaches 1—1, i4 49,52, 5-53,58, 9-12
benthos p4—24,30,32,36,38,44, 5—1,18,34,35,41,42,45,51,52,
5—58,63,65 7—6,10,11,12,13
biomagnification 5-45,50,54,58
BOD 14_5, 5—1,2,3,4,11,21,45,53, 6—10,11,12,13,14
carcinogenicity 14_15,17,18,19, 5_214,25,26,53,54,55
CCC 14..17,18,19,21,23, 5 214,25,26,49,50
CMC 14_15,17,18,19,21,23, 5—24,26,49,50
coliform 14_15,17,49
con nercial fisheries 5—56,63
contamination 1—1, 3—5, 11—17,19,28,29,44,49,52,58, 5—32,45,53,
5—54,55,58,60,65, 7—7, 9—19
cost 3—5,7,9,22,26, 4—57, 5—7,59,60,67,68, 6-5,6,7,
7—4,8,9,13
CSO 1—1,2,4, 4—21, 5_2 1 1,149, 6—1,2
currents 4—1,3,5,6,10,13,14,58, 5—4,6,7,8,11,18,35, 9—18,
9-19
DDT 14 29,30, 5—2,26,27,45,49,50,54, 6—10,11,12,13,14,
7—5
degraded 1—1, 3—1, 5_3L 1,35,41,142,47,49,52, 7—6,10,11
deposition rate 14_27,28, 5-1,18,21,34,35,42
diffuser 1—2,6, 3—1,3,16,22, 4_1,3,6,10,24,41,52,55,58
5—3,4,6,7,8,11,18,23,24,25,27,52,56,57,61,62,63,
5_614,65,66, 6—6, 7—13,15, 9—2
dilution 3—3,5,7, 14_3,10,111,28,30, 5—4,6,7,8,23,24,27,
5—32,34,52,53,57, 7—6,7,11,15, 9—2,19
1

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dissolved oxygen 3-9, 14-7,17,20, 5-1,3,14,7,11,17,18,21,22,314,51,
5—52,65, 7 A4,9,11,12, 9—18
dredge 1- 4, 3—9,22, 14—28,30,116,58 5—56,57,62,614,65,66,
6—1,2,6
ELA 14_3, 5_8,11,211,25
enrichment 5—18,314,35,141,142,145,147,51,52,57,58, 7_L1,6,9,
7—10,12, 9—18
excavated material 1—2, 11-57, 5—60,66,67, 6-1, 7-8
fall velocity 5-5,18
farfield 3—5, 14-3,7, 5 3,14,7,8,9,10,12,13,15,16,18,21,22,
5 .2 14
fish 1—1, 14_1,15,17,32,140,113,141,1414,146,149,52,58,59,
5—214,32,141,145,149,52, 5—53,514,56,58,63,614,65,66,
7—5,7, 15
flounder 1—1, 11 _141,143,1414,149,58,59, 5 141,55,56, 7—7,12
foul area 14 58, 5_59,62,63,614,65, 6—2,6, 7—13
health 1—1,2, 3—3,5, 14_15,17,18,19,29,52, 5 2 14,25,53,
5_514,55,58, 7—14,5,10,12, 9—6,7
Hull 3-7, 14 146,149, 5—18,21, 6—1,2, 7—11, 9—9,12,17
lobster 1-1, 1 4_32,114,146, 1 19, 5-141,55, 7-12
14-32,145, 5—45,149,52
marine traffic 14-146, 5—68, 6—1,5,6
mercury Ll 19,29,31, 5_2,25,26,149,50, 6—6,10,11,12,13,
6—114, 7—5
2

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mixing zone 3—7, LI_b, 5—ll,17,23,214,25,32,3J4,145, 149,50,52,53,
5 5 4,57, 7—5,6,7,10,11,15, 9-19
Model LI_3,7,114, 5—3,6,7,8,9,10,1118,21,214,25,314,514,55,
6—6,7, 7—15, 9—17,18
Nahant 3—7, 4—52, 5—18,21,61,62,614, 7—11, 9—2,10,12,16,
9—17
navigate 14_146, 5-56,57, 6-2
nearfield 3—5, 14_3,A1,7,10, 5-3,14,6,7,8,23,2 4
net drift 14_3,6,10,114, 5—8,11,18,23,214,147,149, 9—18
nonstratified 5-27,35
nutrients 14_16,39,140, 5 _1,5,314,145,147,149,51,52,57,58, 7_9,
9-18
organic carbon 5_314,35
PCB 14_19,214,25,29,30, 1414, 5_2,3,25,26,27,32,314,15,149,
5_50,514,55, 6—10,11,12,13,114, 7—5,7,10,11,12,15
permits 5—18,57,60,61
pH 14—15,17,21, 5-1,5,23
plankton 1t_32,38,39, 140, 5_145,149,51,52, 7-6,12
pycnocline l4_6,7,114,20,21, 5_1 4,8,21
reaeration 5 .14,11
recreation 1—1, 3-9,22, 14_1,15,145,146,149,52, 5—53,56,58, 7.14,
7—5,7,9
reliabilIty 1—6, 5—59,62,614,67, 6—1,7,9, 7—1
removal 3—22, 14—27, 5—1,2,3,5,8,57,63, 6—10,11, 7—11,15,
9—17
resuspension 14 ..5,21,27,30, 5—1,14,21,22,23,27,32,51,52, 7_Lt,7,
9,12, 9—17
3

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risk 3-5, 4—17,19,20, 5 25,26,53,5 14,55,58,59,614, 7...5,
7-10
sediment oxygen demand 5 .1,14,11,142
sediment 1—1,6, 3—1,22, 14 5,16,24,27,28,29,30,31,32,36,38,
14.J414,58, 5—1,14,6,8,11,18,21,25,27,32,314,35,14 ,1.I2
5...1t5, 52,514,55,57,58,61,63,614,65, 6-1,2,5,6,
7—14,6,7,10,11,12,15, 9—17,18,19
shipping 1—1, 3—26, 14.1,146, 5—63,66
shoreline 1—1, 3—7, 11.1,3,7,27,149,52, 5—14,18,57,58, 7-5,6,
7—9,11,12, 9—17
stratification 1l 1,3,6,7,l14, 5—14,6,18,211,141, 7 1 1, 9—18,19
stratified 3—5, 14 .3, 111,39, 5.11,8,11, 114, 17,18,22,23,214,27,35
5.111,112,51, 7 41,9, 9-18
suspended solids 14.21,30, 5-1,5,25,142
TEA 14-3,7,111, 5—8,11,214,25
tidal 14—3,5,6,10,114,20, 5—8,11,21, 7—9
toxic 3—1, 14—15,16,17,18,19,21,28, 5—1 ,2,3,5,6,214,25,3L
5.112,145,119,50,52,57,58, 7 14,6,7,10,11,12, 9—17,18
turtle 14.32,145,58, 5—51,52
Winthrop 3—7, 5—59,61,62, 6—2, 7—11, 9—9,10,11,12,114,16,17
14

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