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SOMERVILLE PUBLIC LIBRARY 

III III I III III 

3 1155 00805 6371 


BOSTON MARBOR 



* 4 $ 

amec 

foster 

wheeler 


Phase III Remedial Action Plan 
Phase IV Remedy Implementation Plan 

Sediment Portion of the Former Everett Staging Yard Disposal Site 
1 Horizon Way, Everett, Massachusetts 

Release Tracking Number (RTN) 3-13341 


Prepared by: 

AMEC Massachusetts, Inc 
Chelmsford, MA 01824 


June 2017 


Project No. 3651160042 



© Amec Foster Wheeler 2017. 

























































PHASE III REMEDIAL ACTION PLAN 
PHASE IV REMEDY IMPLEMENTATION PLAN 


Sediment Portion of the Former Everett Staging Yard Disposal Site 

1 Horizon Way, Everett, Massachusetts 


Submitted by: 

AMEC Massachusetts, Inc 
271 Mill Road, 3 rd Floor 
Chelmsford, MA 01824 


Project No. 3651160042 


June 2017 


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EXECUTIVE SUMMARY 


The sediment portion of the Former Everett Staging Yard Disposal Site (the Disposal Site, 
Release Tracking Number 3-13341) has been impacted by: 

Metals (arsenic, lead, mercury and vanadium) from historical chemical manufacturing 
processes and operations on the upland portions of the property, 

Phthalates and polychlorinated biphenyls associated with historical operations on the 
adjacent Monsanto West property, and 

Low levels of polycyclic aromatic hydrocarbons and petroleum hydrocarbons attributed 
to other industrial and anthropogenic sources (e.g., stormwater runoff, industrial 
releases, and shipping-related impacts). 

Method 3 Risk Assessments performed for the sediment portion of the Disposal Site as part of 
previous Massachusetts Contingency Plan investigations concluded: 

No Significant Risk to human health, public welfare, and safety 

No Significant Risk for wildlife exposed to surface water, and 

No Significant Risk for birds and mammals exposed to shoreline sediment. 

However, the current Stage I Environmental Screening concluded there are potentially significant 
exposure pathways for benthic invertebrates exposed to sediment. A Stage II Ecological Risk 
Characterization based on a comparison of maximum sediment concentrations to measurement 
endpoints concluded a condition of No Significant Risk does not exist for benthic organisms which 
are exposed to sediment. Therefore, remedial actions are necessary to achieve a condition of 
No Significant Risk. 

The Phase III Remedial Action Plan (RAP) portion of this report documents the identification, 
evaluation and selection of Comprehensive Response Action Alternatives. Following an initial 
screening of technologies, five remedial action alternatives were chosen for detailed evaluation. 
The alternatives included: 

► Alternative 1 - Full Dredge and Cap 

► Alternative 2 - Partial Dredge and Cap 

► Alternative 3 - Partial Dredge, Cap, and Monitored Natural Recovery (MNR) 

► Alternative 4 - Navigation Dredge, Cap, and MNR 

► Alternative 5 - No Further Action 

The remedial action alternative selected was Alternative 2 - Partial Dredge and Cap. This 
remedial alternative represents the best combination of time to achieve a Permanent Solution, 
certainty of success (i.e., achieving a Permanent Solution), reliability, and cost. 

The Phase IV Remedy Implementation Plan (RIP) addresses the design, construction and 
implementation of the selected remedial action alternative to be implemented at the Site. 

AMEC Massachusetts, Inc. has prepared this combined Phase III RAP and Phase IV RIP for 
Wynn MA, LLC and Everett Property, LLC, the current owners of the property on which the Site 
is located. 


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TABLE OF CONTENTS 


1.0 INTRODUCTION.1 

1.1 Purpose and Scope.1 

1.2 Report Organization.1 

2.0 BACKGROUND.3 

2.1 Site Location and Locus Map.3 

2.2 Regulatory History and Status.4 

2.3 Relevant Contacts.5 

3.0 CONCEPTUAL SITE MODEL.6 

3.1 Potential Sources and Release Mechanisms.6 

3.1.1 Site-Related Sources.6 

3.1.2 Non-Site Sources.6 

3.2 Potential Migration Pathways.7 

3.3 Potential Exposure Routes and Receptors.8 

4.0 UPDATED METHOD 3 ECOLOGICAL RISK ASSESSMENT.9 

4.1 Stage I Ecological Screening.9 

4.1.1 Environmental Setting and Complete Exposure Pathways.10 

4.1.2 Evaluation of Readily Apparent Harm.10 

4.1.3 Evaluation of Significant Exposure Pathways.10 

4.1.4 Stage I ES Summary and Conclusions.11 

4.2 Stage II Environmental Risk Characterization.12 

4.2.1 Problem Formulation.12 

4.2.2 Measures of Exposure.14 

4.2.3 Analysis.14 

4.2.4 Uncertainty.14 

4.2.5 Risk Characterization.15 

4.3 Method 3 Ecological Risk Assessment Conclusions & Risk Management Recommendations 
.15 

5.0 REMEDIAL ACTION OBJECTIVES (310 CMR 40.0851).16 

5.1 General Remedial Action Objectives.16 

5.2 Site-Specific Remedial Action Objectives.16 

6.0 IDENTIFICATION AND EVALUATION OF REMEDIAL ACTION ALTERNATIVES (310 
CMR 40.0855).18 

6.1 Initial Technology Screening (310 CMR 40.0856).18 

6.1.1 Monitored Natural Recovery (MNR).18 

6.1.2 In Situ Treatment (Amendment).19 

6.1.3 Enhanced Sediment Deposition.19 

6.1.4 Mechanical Dredging.19 

6.1.5 Hydraulic Dredging.20 

6.1.6 Mechanical Capping.20 

6.1.7 Summary of Technology Screening.20 

6.2 Development of Alternatives.21 

6.2.1 Alternative 1 - Full Dredge and Cap.21 

6.2.2 Alternative 2 - Partial Dredge and Cap.23 


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6.2.3 Alternative 3 - Partial Dredge, Cap, and MNR.24 

6.2.4 Alternative 4 - Navigation Dredge, Cap, and MNR.26 

6.2.5 Alternative 5 - No Further Action (Navigation Dredge Only).26 

6.3 Detailed Evaluation of Remedial Action Alternatives (310 CMR 40.0857).27 

6.3.1 Effectiveness.28 

6.3.2 Reliability.28 

6.3.3 Implementability.28 

6.3.4 Costs 29 

6.3.5 Risks 31 

6.3.6 Benefits.31 

6.3.7 Timeliness.32 

6.3.8 Non-Pecuniary Interests.32 

6.4 Selection of the Remedial Action Alternative (310 CMR 40.08590.32 

7.0 FEASIBILITY EVALUATIONS (310 CMR 40.0860).34 

8.0 ENGINEERING DESIGN (310 CMR 40.0874(3)(b)).36 

8.1 Site-Specific Remedial Action Goals.36 

8.2 Significant Changes or New Information Related to Disposal Site Conditions.37 

8.3 Site Maps Showing Existing Features and Proposed Locations of Activities.38 

8.4 Environmental Media to be Treated/Managed.38 

8.5 Conceptual Plan of Activities, Treatment Units, Facilities, and Processes.39 

8.6 Relevant Design and Operating Parameters.39 

8.6.1 Barge Demolition and Debris Management.39 

8.6.2 Sediment Dredging.40 

8.6.3 Sediment Dewatering, Stabilization and Offload. 41 

8.6.4 Capping.42 

8.6.5 Demonstration of Achievement of Remedial Goals.43 

8.7 Design Features for Control of Spills/Discharges.43 

8.8 Management/Disposal of Treatment Residuals, Contaminated Soils and Other Waste 

Materials. .44 

8.9 Disposal Site Characteristics Affected by the Proposed Construction.45 

8.9.1 Existing Site Activities or Operations.45 

8.9.2 Natural Resource Areas, Local Planning and Development Issues.45 

8.10 Measures to Protect Environmental Receptors and Natural Resource Areas.46 

9.0 CONSTRUCTION PLANS AND TECHNICAL SPECIFICATIONS (310 CMR 40.0874(3)(c)) 

.47 

9.1 Plans, Specifications, and Procedures... 47 

9.2 Construction Schedule. 47 

10.0 OPERATION, MAINTENANCE, AND MONITORING (310 CMR 40.0874(3)(d)).49 

11.0 HEALTH AND SAFETY PLAN (310 CMR 40.0874(3)(e)).51 

12.0 PERMITS, LICENSES, AND/OR APPROVALS (310 CMR 40.0874(3)(f)).52 

13.0 PROPERTY ACCESS ISSUES (310 CMR 40.0874(3)(g)).53 

14.0 REFERENCES.54 


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TABLES 


Table 

Table 

Table 

Table 

Table 

Table 

Table 

Table 

Table 

Table 


4-1 

4-2 

4-3 

6-1 

6-2 

6-3 

6-4 

8-1 

8-2 

10-1 


Stage I Ecological Screening - Benchmark Comparison 
Comparison of Local Conditions Values to Ecological Benchmarks 
Stage II ERC Analysis 

Technology Screening 
itpion of Remedial Action Alternatives 
ed Evaluation of Remedial Action Alternatives 
ated Construction, OMM, and MNR Cost 
ated Sediment Dredge Quantities 
ated Sediment Cap Quantities 
oring Program Summary 


Initial 



FIGURES 


Figure 1-1 
Figure 1-2 
Figure 4-1 
Figure 6-1 
Figure 6-2 
Figure 6-3 
Figure 6-4 
Figure 6-5 


Site Location Map 
Site Plan 

Ecological Conceptual Site Model 
Remedial Alternative 1 Full Dredge and Cap 
Remedial Alternative 2 Partial Dredge and Cap 
Remedial Alternative 3 Partial Dredge, Cap and MNR 
Remedial Alternative 4 Navigation Dredge, Cap and MNR 
Remedial Alternative 5 No Further Action 


APPENDICES 


Appendix A 
Appendix B 
Appendix C 
Appendix D 
Appendix E 
Appendix F 


Detailed Cost Estimate 

Design Calculations and Assumptions 

Construction Drawings 

Technical Specifications 

Operation, Maintenance, and Monitoring Plan 

Health and Safety Plan 


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1.0 INTRODUCTION 

1.1 Purpose and Scope 

AMEC Massachusetts, Inc. (AMEC) has prepared this combined Phase III Remedial Action Plan 
(Phase III RAP) and Phase IV Remedy Implementation Plan (Phase IV RIP) for the sediment 
portion the Former Everett Staging Yard Disposal Site (the Disposal Site, Figure 1-1). The 
Disposal Site, which includes both uplands and a portion of an embayment of the Mystic River 
(Figure 1-2), is identified by Release Tracking Number (RTN) 3-13341. This Phase III RAP and 
Phase IV RIP Report was completed for Wynn MA, LLC and Everett Property, LLC (collectively, 
Wynn) the current owners of the property on which the Site is located. 

This Phase III RAP has been prepared in accordance with 310 CMR 40.0850. The purpose and 
scope of the Phase III RAP is to establish remedial objectives, identify and evaluate remedial 
technologies, formulate and evaluate remedial action alternatives, and select a remedial action 
alternative for the sediment portion of the Disposal Site. The objective of the Phase III RAP is to 
select a remedial action alternative that is a Permanent Solution and will reduce, to the extent 
feasible, the concentrations of oil and hazardous materials (OHM) in the environment to levels 
that achieve or approach background. 

The Phase IV RIP has been prepared in accordance with 310 CMR 40.0870. The Phase IV RIP 
addresses the design, construction and implementation of the Comprehensive Remedial Action 
(CRA) to be implemented for the sediment portion of the Disposal Site. The purpose of the CRA 
is to achieve a condition of No Significant Risk and a Permanent Solution for the Remediation 
Area (the portion of the Disposal Site to be dredged and/or capped). A Downgradient Property 
Status submittal will be prepared to address contamination on the Wynn property for which Wynn 
is not responsible. 

1.2 Report Organization 

The content and format of the report meet the specific requirements for Phase III and Phase IV 
Reports outlined in the Massachusetts Contingency Plan (MCP) at 310 CMR 40.0861 and 
40.0874, respectively. 

The remainder of this combined Phase III and Phase IV Report consists of the following sections: 

Section 2: Background - Presents the Disposal Site description, a brief summary of the 
Disposal Site history, and a discussion of regulatory history and status. 

Section 3: Conceptual Site Model - Summarizes the sources and release mechanisms, 
migrations pathways, and potential exposure routes presented in the Revised Phase II 
Report. 

Section 4: Updated Method 3 Ecological Risk Assessment - Updates the previously 
completed Risk Assessment to more closely follow the format of a Stage II Ecological 
Risk Characterization. 

Section 5: Remedial Action Objectives - Identifies the clean-up requirements to 
achieve a Permanent Solution for the sediment portion of the Disposal Site. 


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Section 6: Identification and Evaluation of Remedial Action Alternatives - Presents 
several alternatives to achieve a Permanent Solution for the sediment portion of the 
Disposal Site. 

Section 7: Feasibility Evaluations - Outlines and evaluates alternatives through a 
screening process which allows one alternative to be selected and used for the 
Engineering Design. 

Section 8: Engineering Design - Presents the approach and engineering design of the 
selected remedy for the sediment portion of the Disposal Site. 

Section 9: Construction Plans and Technical Specifications - Presents the design 
approach to implement the remedial action alternative selected. 

Section 10: Operation, Maintenance and/or Monitoring - Identifies the operation, 
maintenance and monitoring plan to maintain the remedial action alternative 
implemented. 

Section 11: Health and Safety Plan - Identifies the health and safety protocol identified 
for implementation of the remedial action alternative selected. 

Section 12: Permits, Licenses, and/or Approvals - Identifies the permits licenses and 
approvals required for implementation of the remedial action alternative selected. 

Section 13: Property Access Issues - Identifies property access issues at the Disposal 
Site. 

Supporting data are provided in figures, tables, and appendices referenced throughout the report. 

Sections 5 through 7 meet the specific requirements of a Phase III RAP. Sections 8 through 13 
meet the specific requirements of a Phase IV RIP. 


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2.0 BACKGROUND 


2.1 Site Location and Locus Map 

For the purposes of this report, the “property” refers to the combined areas of land and water 
which are currently owned by Wynn and are located at 1 Horizon Way in Everett and an 
unnumbered parcel on Alford Street in Boston (Figure 1-1). The Wynn property encompasses 
approximately 35 acres, which includes an upland portion (approximately 22 acres) and a portion 
of the adjacent Mystic River to the southwest (approximately 13 acres). The approximate latitude 
and longitude for the Site are 42.39 degrees north and 71.07 degrees west, respectively. The 
Universal Transverse Mercator (UTM) coordinates are approximately 4,695,650 meters north and 
329,600 meters east. 

The upland portion of the property is an irregularly shaped, approximately 22-acre parcel of land 
roughly bounded by Alford Street/Broadway (Route 99) to the east, Massachusetts Bay Transit 
Authority (MBTA) railroad tracks to the west, an MBTA bus repair and maintenance facility to the 
north, and the Mystic River to the south. The sediment portion of the property consists of an 
approximately 13-acre embayment of the Mystic River which is bounded to the northwest and 
north by the upland portion of the property and to the northeast and east by the Boston Water and 
Sewer Commission’s Material Handling Facility (180-220 Alford Street). 

For the purposes of this report, the Disposal Site, or more formally the Former Everett Staging 
Yard Disposal Site, includes the uplands where chemical manufacturing occurred and the portion 
of Mystic River sediment which has been impacted by chemicals from the uplands. Figure 1-2 is 
a detailed plan for the sediment portion of the property, and depicts physical features, and 
sampling locations. The disposal site boundary for the sediment portion of the property depicted 
on Figure 1-2 was drawn to separate areas where concentrations of Disposal Site-related 
chemicals are above “local conditions” 1 from areas where concentrations are generally at or local 
conditions. The disposal boundary was also drawn considering the Conceptual Site Model 
(“CSM”, see Section 3) and principles of sediment transport dynamics. Delineating the extent of 
Site-related chemicals in sediment based on local conditions indicates the maximum potential 
extent of the aquatic boundary. Given the many historical and ongoing sources of contamination 
to the Mystic River (as well as natural sources of the same chemicals) this may still be an over¬ 
estimate of the impacts directly associated with chemical manufacturing on the upland portion of 
the property. 

The Disposal Site boundary encompasses approximately 7.8 acres of sediment. The main portion 
in the embayment encompasses approximately 7.3 acres and a smaller intertidal area to the west 
is approximately 0.5 acres. The total area within the Disposal Site boundary which poses a risk 


1 The MassDEP’s Guidance for Disposal Site Risk Characterization in Support of the Massachusetts Contingency Plan (MassDEP, 
1996) defines “local conditions” as “...levels of OHM present consistently and uniformly throughout the surface water body, or 
throughout a larger section of a river that contains the area potentially affected by contamination at or from the site." The “local 
conditions” concept acknowledges that sediments in certain water bodies, particularly those located in industrial urban areas, 
contain constituents from sources such as other disposal sites, permitted discharges, and non-point sources. The data and method 
for establishing local conditions for the Site are described full in the Revised Supplemental Phase II Comprehensive Site 
Assessment Report dated December 2016. 


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to benthic communities (the Remediation Area) is approximately 7.4 acres. This includes 7.3 
acres in the main embayment and 0.1 acres in the smaller area to the west (Figure 1-2). 

2.2 Regulatory History and Status 

O’Donnell Sand & Gravel, Inc. (O’Donnell) submitted the initial notification of a release to the 
Massachusetts Department of Environmental Protection (MassDEP) in January 1996 based on 
the presence of elevated concentrations of certain metals and petroleum hydrocarbons in soil as 
well as areas of low pH. Consulting Engineers & Scientists (CES) filed a Phase I Initial Site 
Investigation and Tier Classification (classifying the Site as Tier II) on behalf of O’Donnell in 
January 1997 (CES, 1997). Following the 2001 purchase of the property by Mystic Landing, LLC 
(Mystic Landing), additional subsurface and sediment investigations were completed under Tetra 
Tech Rizzo (formerly Rizzo Associates) and a Phase II Comprehensive Site Assessment (Phase 
II CSA) Report was submitted in December 2007. FBT Everett Realty, LLC (FBT) purchased the 
property from Mystic Landing in 2009. In February 2012, GEI Consultants, Inc. (“GEI”) submitted 
a Phase II CSA along with a Notice of Delay for the Phase III and IV reports which attributed the 
delays to a property access dispute (GEI, 2012). FBT subsequently submitted additional Notices 
of Delay as the selected remedial approach could vary depending on whether the construction of 
casino on the property was approved. 

Wynn purchased the property in January 2015 and in February 2015 an Eligible Person 
Certification and Revised Tier II Classification were submitted by GZA GeoEnvironmental (GZA) 
on Wynn’s behalf (GZA, 2015a). This document included a “Supplemental Sampling and Analysis 
Plan” outlining an extensive sampling program to refine the Site boundary (GZA, 2015a). 
MassDEP issued a Notice of Responsibility (“NOR”) in March 2015 which established interim 
deadlines for supplemental Phase II and Phase III reports for the Mystic River portion of the 
property. * 2 In December 2015, GZA submitted a Supplemental Phase II Report which contained 
the results from the sediment sampling program as well as an updated Site boundary and risk 
characterization. In May 2016, MassDEP issued a letter containing questions they had with the 
Supplemental Phase II Report and requesting additional assessment and/or data review 
(MassDEP, 2016b and c). This letter also established interim deadlines for submittal of a Revised 
Phase II Report, Phase III and Phase IV reports, and a Permanent or Temporary Solution or 
Remedy Operation Status (ROS). MassDEP supplied additional comments via email (MassDEP, 
2016d) in June 2016 subsequent to GZA’s submittal of a sediment CSM (GZA, 2016a). 

In September 2016, Wynn proposed an alternative approach to characterizing the Site and 
potential risks and supplied additional information requested by MassDEP (Wynn, 2016). In 
November 2016, MassDEP and Wynn agreed upon an approach which would allow the project 
to move forward (MassDEP, 2016e). On December 30, 2016, a revised Supplemental Phase II 
CSA Report was submitted to MassDEP. This report responded to MassDEP comments and 
provided an alternate approach to Site assessment and closure (AMEC, 2016). On March 31, 
2017, MassDEP issued a letter identifying new interim deadlines for the sediment portion of the 
Site: 


2 As well as a deadline for either a Permanent Solution, Temporary Solution, or Remedy Operation Status. See MassDEP, 2015 p 

2 . 


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► Supplemental Phase III RAP and Phase IV RIP to be submitted by September 15, 
2017; and 

► A Permanent Solution, Temporary Solution, or ROS by June 30, 2019. 

Submittal of this report satisfies the first of the two interim deadlines. 

2.3 Relevant Contacts 


The following is a list of relevant contacts for the proposed remediation as required by 310 CMR 
40.0874(3)(a): 


Potentially Responsible Party/Site Owner: 

Wynn MA, LLC 

Everett Property, LLC 


101 Station Landing, Suite 2200 

Medford, MA 02155 


Contact: Robert DeSalvio 

Jacqui Krum 


Telephone: 857-770-7000 

E-mail: robert.desalvio@wynnmass.com, 
jacqui.krum@wynnmass.com 

Licensed Site Professional (LSP): 

Matthew J. Grove, PhD, LSP 

LSP No. 9932 


Amec Foster Wheeler 
(AMEC Massachusetts, Inc.) 

271 Mill Rd., 3 rd Floor 

Chelmsford, MA 01824 


Telephone: 978-392-5398 

Fax: 978-692-6633 

E-mail: matt.grove@amecfw.com 

Remedy Design and Implementation 

Danielle Ahern, P.E. 

Engineer: 

Amec Foster Wheeler 

271 Mill Rd., 3rd Floor 

Chelmsford, MA 01824 


Wynn will enter into a construction contract with a Remedial Contractor, thus Wynn will “own, 
operate, and/or maintain” the remedial action during construction. Wynn will also be responsible 
for post-construction maintenance and monitoring as further discussed in the Phase IV RIP 
portion of this report. 


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3.0 CONCEPTUAL SITE MODEL 

3.1 Potential Sources and Release Mechanisms 

3.1.1 Site-Related Sources 

The Disposal Site includes both an upland area and sediments in an embayment of the Mystic 
River. The upland portion consists of approximately 22 acres above mean high water (MHW). 
This area was the location of chemical manufacturing facilities (primarily sulfuric acid and 
alcohols) for over 100 years. Portions of the upland property were also filled at various times with 
dredged materials (and potentially manufacturing wastes) which resulted in the current 
configuration. 3 Chemical manufacturing operations began in the 1800s and continued through 
the late 1960s. The buildings on the property were demolished in the late 1960s and 1970s and 
the property was generally vacant by about 1980. Beginning in the mid-1990s, the upland areas 
were used as a material storage and staging yard. 

Historical manufacturing operations and processes resulted in the release of metals to the upland 
portion of the Disposal Site, evidenced by the presence of impacted subsurface soil (e.g., the 
CES-2 Area shown on Figure 1-2). Specific metals of concern are arsenic, lead and vanadium 
based on the following historical information: 

A material used to dry sulfur during sulfuric acid production reportedly contained 
arsenic, 

► A “lead storage house” formerly occupied a portion of the Disposal Site, and 

► Vanadium was widely used as a catalyst in the production of sulfuric acid beginning 
in the 1930s. 

In addition, the production of sulfuric acid on the upland portion of the Disposal Site resulted in 
areas of low pH in groundwater (Figure 1-2). Remediation of the upland portion of the Disposal 
Site is currently being completed under a Release Abatement Measure (RAM). 

Spillage during loading and unloading of raw materials on and near the water, principally along 
the northern and northeastern side of the embayment, likely contributed contaminants directly to 
sediment. As first noted by Tetra Tech Rizzo (2007) and subsequently confirmed by GZA (2015b), 
the highest concentrations of metals have generally been measured in the northern and 
northeastern parts of the embayment where materials were historically loaded and unloaded. 

3.1.2 Non-Site Sources 

A secondary area of high metals concentrations has been observed along a tidal channel in the 
flats on the south side of the embayment. This is likely associated with historical discharges from 
a drain pipe outlet located on Boston Water and Sewer Commission property to the south. 

Phthalates (e g., bis2-ethylhexyl)phthalate or BEHP) and polychlorinated biphenyls (PCBs) 
associated with the historical operations on the adjacent Monsanto West property have also been 
detected in sediments on the property. However, the spatial distribution of phthalates and PCBs 


3 Dredging and filling occurred over time and under a number of different licenses As noted in the Combined 401 Water Quality 
Certification (MassDEP, 2016a), the last known dredging of the embayment occurred in 1943. 


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in sediments is different than that of the metals which are attributed to Disposal Site operations. 
The distribution of phthalates and PCBs is consistent with a different (non-Site) source of these 
chemicals. 

The widespread presence of low levels of polycyclic aromatic hydrocarbons (PAHs) and 
petroleum hydrocarbons in sediments on the property can, at least partially, be attributed to other 
industrial and anthropogenic sources (e.g., stormwater runoff 4 , industrial releases, and shipping- 
related impacts). The Mystic River is a very urbanized watershed and the river and adjacent land 
areas have a very long history of commercial and industrial uses. 

3.2 Potential Migration Pathways 

Contaminated soils from the upland portion of the Disposal Site likely eroded and migrated directly 
to the Mystic River via overland flow. This migration path is likely to be eliminated in the future 
due to ongoing remediation and redevelopment of the upland portion of the Disposal Site. 

Low pH soil has caused metals (released from Disposal Site operations and naturally occurring) 
to leach from the subsurface fill into groundwater which discharges into the Mystic River. Under 
neutral pH conditions, the migration of metals in groundwater is limited by their low solubility and 
their tendency to adsorb to soil particles or precipitate out of groundwater. This migration path is 
likely to be limited in the future due to the recently completed in-situ treatment of soil and 
groundwater in the low pH area and excavation and off-site disposal of soil from the CES-2 area. 
Based on the results of surface water investigations performed by Menzie-Cura & Associates, 
Inc. (“MCA”) and GZA prior to treatment, discharge of impacted groundwater is not significantly 
or negatively impacting surface water because of dilution. 

The embayment has reportedly not been dredged since 1943 which predates the end of chemical 
manufacturing operations. 5 Sediments within the embayment do not appear to be transported 
out of the embayment by tidal currents. The low concentrations in sediment on the northern tidal 
flats (e.g. GZ-125, GZ-129, GZ-130, and GZ-131) compared to concentrations in the channel 
(e.g., GZ-112, GZ-115, and GZ-117) indicate little to no tidal transport in an upstream direction 
(towards the dam). The presence of higher concentrations at depth in the channel and close to 
the uplands indicates that the embayment is a depositional area (i.e., sediment from other areas 
is being deposited on top of the sediment impacted by historical releases related to the Site). This 
is supported by the relatively narrow range in concentrations observed along the channel bottom 
(e.g., GZ-117, GZ-119, GZ-121, GZ-123, GZ-128, GZ-134, and GZ-138). If the historic 
contamination was eroding and being transported into the Mystic River, the contaminant 
concentrations would increase towards the river (i.e., to the south) and impacted sediment would 
be expected to accumulated in the deeper hole at the edge of the property (i.e., where GZ-201 is 
located). However, the analytical data do not support this erosional scenario. Based on the 
evidence, migration of sediment out of the embayment via natural processes is not expected to 
have been a significant migration pathway in the past or be one in the future. 


4 For example, historical plans of the property indicate a drain pipe outlet located on the Boston Water and Sewer Commission 
property to the south and a 36-inch drain leading from the MBTA property to the north 
s MassDEP, 2016a; p 2. 


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3.3 Potential Exposure Routes and Receptors 

The primary potential human exposure pathway is dermal contact with sediment when wading in 
the nearshore. However, access to sediment is partially limited by a fence and bulkhead. Another 
potential exposure route for humans is the consumption of fish and shellfish which might have 
accumulated Site-related chemicals in their tissues. However, the Massachusetts Department of 
Public Health (DPH) has placed an advisory for certain marine species within Boston Harbor 
which includes the Mystic River. 6 Shellfish Growing Area Designations by the Massachusetts 
Department of Marine Fisheries (DMF), September 2009, indicate that all of the Mystic River and 
associated embayments and coves are currently classed as prohibited as a shellfish growing 
area, which means the area is closed to the harvesting of shellfish. Closure of these areas to 
shellfishing is enforced by Mass Environmental Police. 

The Mystic River below the Amelia Earhart Dam serves as habitat for fish, shellfish, benthic 
invertebrates, waterfowl, and semi-aquatic mammals (GZA, 2015b). The primary exposure 
pathways for ecological receptors are direct contact with sediments, incidental sediment 
ingestion, and consumption of contaminated prey. 


6 MassDPH, 2016. 


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4.0 UPDATED METHOD 3 ECOLOGICAL RISK ASSESSMENT 


The Ecological Risk Assessment for the sediment portion of the Site included in the Revised 
Phase II Report was presented as a Method 3 Stage I Ecological Screening (ES). The ES 
concluded that there were potentially significant exposure pathways with respect to the benthic 
community exposed to sediment. This conclusion was based on the results of a comparison of 
Disposal Site data to ecological benchmarks which is a component of a Stage II Ecological Risk 
Characterization (ERC). Following submittal of the Revised Phase II Report, MassDEP requested 
that the sediment Ecological Risk Assessment be revised to more explicitly follow a Stage II ERC 
approach. 

4.1 Stage I Ecological Screening 

This Method 3 Stage I ES, which identifies whether potentially significant exposures exist in the 
sediment within the Disposal Site boundary, was performed following: 

► Regulations for a Method 3 Environmental Risk Characterization (310 CMR 40.0995) 
(MassDEP, 2014), 

► Guidance for Disposal Site Risk Characterization (MassDEP, 1995; 1996), 

► MassDEP Interim Technical Updates (MassDEP, 2006), and 

► Other ecological risk assessment best management practices. 

The objective of the Stage I ES is to identify and document conditions which do not warrant a 
Stage II ERC, either because of the absence of a potentially significant exposure pathway or 
because environmental harm is readily apparent and therefore additional assessment would be 
redundant. 

Following a Stage I Environmental Screening, it may be concluded that: 

1. A Stage II ERC is not required because there are no complete exposure pathways that 
could result in potentially significant exposures, and a condition of No Significant Risk 
of harm to Site biota and habitats clearly exists; 

2. A Stage II ERC is not required because, for each contaminated medium, harm is readily 
apparent; therefore a condition of No Significant Risk of harm to the Site biota and 
habitats clearly does not exist, and a Stage II Environmental Risk Characterization 
would be redundant; or 

3. A Stage II ERC is required because, for one or more contaminated media, there is not 
enough information to determine whether or not a condition of No Significant Risk of 
harm exists, and therefore those media are considered to present “potentially 
significant exposures.” 

MCA previously conducted a Stage I ES and a Stage II ERC (MCA, 2006) which demonstrated: 

A condition of No Significant Risk to surface water based on modeled groundwater 
discharge from Site uplands to the embayment. 

A condition of No Significant Risk to shorebirds and other wildlife populations exposed 
to sediment based food chain models. 


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Based on the findings of the previous risk assessments, the present Stage I ES only evaluates 
risk to benthic invertebrates exposed to Site sediment. 

4.1.1 Environmental Setting and Complete Exposure Pathways 

As previously noted, the property includes approximately 13 acres of sediment within the Lower 
Mystic River. As explained in Section 2.1, the Disposal Site boundary encompasses 
approximately 7.8 acres of sediment (Figure 1-2). Located downstream of the Amelia Earhart 
Dam, this portion of the Lower Mystic River has been classified by MassDEP and other state and 
federal agencies as a marine surface water body that serves as habitat for fish, shellfish, benthic 
invertebrates, waterfowl, and semi-aquatic mammals (GZA, 2015b). A detailed description of the 
ecological resources, and sediment and aquatic communities present at and around the Disposal 
Site was previously presented in Section 2.3 of the GZA Supplemental Phase II Report (GZA, 
2015b). 

There are no Areas of Critical Environmental Concern (ACECs) within 0.5 miles of the Disposal 
Site. No state-listed species are located within 0.5 miles of the Disposal Site. The US Fish and 
Wildlife Service (USFWS) online mapper does not identify any critical habitat for threatened and 
endangered species within the Lower Mystic River (USFWS, 2016). 

Considering the presence of aquatic and benthic species observed during previous investigations, 
sediment exposure pathways are considered potentially complete. 

4.1.2 Evaluation of Readily Apparent Harm 

Disposal Site conditions do not satisfy any of the following three criteria listed in 310 CMR 
40.0095(3)(b)(1) needed to meet Readily Apparent Harm: 

Visual evidence of stressed biota attributable to the Site, including fish kills or abiotic 
conditions have not been reported. While the embayment is currently a degraded 
habitat, surveys conducted by GZA identified limited populations of shellfish, snails, 
marine worms, and crabs (GZA, 2015b). 

Estimated (MCA, 2006) and measured (GZA, 2015b) surface water concentrations 
were below water quality benchmarks including USEPA Ambient Water Quality 
Criteria and Massachusetts Surface Water Standards, and a condition of No 
Significant Risk exists for surface water. 

Oil, tar, or other non-aqueous phase hazardous material have not been observed 
within one foot of the sediment surface. Note that while sediment discolored by the 
presence of pyrite ash has been observed in the intertidal, this does not constitute 
Readily Apparent Harm as defined by the MCP. 

Therefore, Readily Apparent Harm does not exist at the Disposal Site. 

4.1.3 Evaluation of Significant Exposure Pathways 

In this section, each complete exposure pathway is evaluated to determine whether the exposures 
are significant. If significant exposures are determined to be unlikely for any pathway, that 
pathway can be eliminated from further consideration in the risk assessment. Screening criteria 
are used to rule out pathways, not individual chemicals. If a pathway is not ruled out, risks from 
all chemicals that result in exposure by that pathway should be further evaluated, even if some of 
the chemicals are present at levels below their screening criteria. 


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This exposure pathway evaluation was conducted by comparing the maximum detected bulk 
sediment concentrations to corresponding ecological screening benchmarks. Consistent with 
MassDEP guidance (MassDEP, 1996), only those compounds with concentrations that are not 
consistent with local conditions and compounds for which local conditions data are unavailable 
were compared to ecological sediment screening benchmarks. 

Marine sediment benchmarks (Table 4-1) were preferentially selected from the following source: 
NOAA Effects Range - Medium (ER-M) (Long et a/., 1995) 

ER-Ms have been previously used on this project (GZA, 2015b), and have been agreed to with 
MassDEP (MassDEP, 2016b). 

Where a compound lacked an ER-M, sediment benchmarks were selected from among the 
following sources: 

Washington State Apparent Effects Thresholds (AETs) (Washington State, 2013) 

NOAA Screening Quick References Tables (Buchman, 2008) 

The maximum detected concentrations in sediment within the Disposal Site boundary were 
compared to effects-based ecological screening benchmarks to determine whether current and 
potential future exposure could potentially be significant (Table 4-1). Note that when performing 
benchmark comparisons, concentrations were rounded to two digits in accordance with 
MassDEP’s guidance on significant figures (MassDEP, 2009). 

An analyte with a maximum detected concentration above its benchmark was identified as a 
potentially significant exposure. 

The maximum detected concentration of total PAHs, several individual PAHs, 
antimony, cadmium, and chromium were below conservative ecological screening 
benchmarks. 

The maximum detected concentration of PCBs, two phthalates, several individual 
PAHs, arsenic, lead, mercury, nickel, selenium, silver, vanadium, and zinc were above 
conservative ecological screening benchmarks. 

EPH fractions lacked screening benchmarks and thus could not be evaluated. 
Beryllium also lacked a screening benchmark but was consistent with local conditions. 

Since concentrations in sediment exceed benchmarks, direct contact to sediment represents a 
significant exposure pathway. 

4.1.4 Stage I ES Summary and Conclusions 

The previous Stage I ES (MCA, 2006) demonstrated that a condition of No Significant Risk exists 
for surface water. The 2006 Stage II ERC (MCA, 2006) demonstrated that a condition of No 
Significant Risk exists for shorebirds and other shoreline wildlife. 

The present Stage I ES concludes that there are potentially significant exposure pathways with 
respect to the benthic community exposed to sediment. Therefore, a Stage II ERC is required to 
determine whether a condition of No Significant Risk of harm exists. 


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4.2 Stage II Environmental Risk Characterization 

The purpose of the Stage II ERC is to determine whether there is significant risk of environmental 
harm or evidence of environmental harm. The goal is to determine whether the release(s) of 
OHM from the Site have adversely impacted, or may adversely impact, the ecological function of 
environmental resource areas such as wetlands, aquatic and terrestrial habitat, fisheries or rare 
and endangered species. 

4.2.1 Problem Formulation 

The problem formulation phase is designed to establish the goals, scope and focus of the Stage 
II ERC. As previously noted, the 2006 Stage II ERC (MCA, 2006) demonstrated that a condition 
of No Significant Risk exists for shorebirds and other shoreline wildlife. Therefore, the focus of 
this Stage II ERC is benthic invertebrates exposed to contaminated sediment via direct 
uptake/dermal contact and dietary ingestion. 

4.2.1.1 Environmental Setting 

A baseline site survey of the ecological resources, and sediment and aquatic communities present 
at and around the Disposal Site was previously presented in Section 2.3 of the GZA Supplemental 
Phase II Report (GZA, 2015b) and is summarized above in Section 4.1.1. 

4.2.1.2 Delineation of Nature & Extent 

The nature and extent of contamination has been delineated as described in the Revised Phase 
II Report (AMEC, 2016b), including those attributable to non-Site sources (e.g., Monsanto West) 
and local conditions. 

4.2.1.3 Complete Exposure Pathways 

Considering the presence of a benthic community, a complete exposure pathway may therefore 
exist for sediment. Chemicals move from sediment into sediment porewater, and then into benthic 
receptors through several major biological exposure mechanisms: 

Uptake from interstitial water between sediment particles (porewater) into tissue 

Incidental ingestion of chemicals bound to sediment 

Dietary ingestion of chemicals in surface water 

Direct contact with chemicals in surface water 

Dietary ingestion of chemicals in contaminated biota 

4.2.1.4 Ecological Conceptual Site Model 

The ecological site conceptual model (Figure 4-1) illustrates initial estimates of contaminant fate 
and transport mechanisms, complete exposure pathways, and primary and secondary receptors. 
As noted previously, the 2006 Stage I ES demonstrated that a condition of No Significant Risk 
exists for surface water and the 2006 Stage II ERC (MCA, 2006) demonstrated that a condition 
of No Significant Risk exists for shorebirds and other shoreline wildlife, thus Figure 4-1 illustrates 
only the sediment exposure pathways. 


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Specific assessment and measurement endpoints are not identified because generic endpoints 
were used, as discussed in Section 4.2.1.5. This model is based on the current understanding of 
Disposal Site conditions (see Section 3 of this report for the full CSM), serves as a framework for 
evaluating ecological exposure and risk, and shows: 

The source areas (i.e., historical release areas and potential non-Site related release 
areas); 

Transport mechanisms (processes that partition chemicals among various 
environmental media); 

Exposure media (those environmental media from which organisms may be exposed 
to chemicals); and 

Potential receptor organisms based on site ecological investigations. 

As previously described, chemicals associated with operation on the Disposal Site, as well as 
non-Site sources (e.g., Monsanto West) were historically released to the land surface and 
infiltrated into the embayment. These products could potentially adversely affect aquatic 
organisms, such as plants, benthic organisms, and fish which inhabit this reach of the Lower 
Mystic River, as well as aquatic and semi-aquatic birds and mammals which could nest and forage 
there. 

4.2.1.5 Assessment & Measurement Endpoints 

Endpoints in the Stage I ERC define ecological attributes that are to be protected (assessment 
endpoints) and a measurable characteristic of those attributes (measurement endpoints) that can 
be used to gauge the degree of impact that has occurred or may occur. Assessment endpoints 
for the Stage II ERC are considered generic because they are based on the broad variety of 
organisms that inhabit sediment in the embayment and are therefore considered to be 
representative of entire communities. 

The assessment and measurement endpoints are: 


Assessment Endpoint 

Measurement Endpoint 

1. Sustainability (survival, growth, 

reproduction) of the benthic community 
exposed to sediment. 

a. Comparison of bulk sediment 

concentration to ecological no-effects 
benchmarks. 

b. Comparison of bulk sediment 
concentrations to local conditions. 


Site-specific toxicity testing, field surveys, or field experiments are not being used as 
measurement endpoints due to potential confounding effects from non-Site sources of 
contamination to sediment. 


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4.2.2 Measures of Exposure 

Measures of exposure must consider the spatial and temporal distribution of OHM and represent 
the co-occurrence of contamination with the assessment endpoint organisms (i.e., the benthic 
community). For this Stage II ERC, the measure of exposure is concentration of OHM in the top 
six inches of sediment across the Site. 

4.2.3 Analysis 

To determine whether it is likely that there will be any adverse ecological effects on the benthic 
community, maximum sediment concentrations were compared to the higher of ecological 
benchmarks (Table 4-1) or local conditions (Table 4-2). By agreement with MassDEP specifically 
for this project, local conditions were established as the 75 th percentile of the local conditions 
dataset from locations upstream in the Mystic River. As shown on Table 4-2, the 75 th percentile 
local conditions value for barium, lead, mercury, vanadium, zinc, total PAHs, total PCBs, and 
BEHP are above published benchmarks, while the 75 th percentile values for the remaining 
detected chemicals other than EPH fractions are below published benchmarks. 

Table 4-3 compares the maximum concentration detected in sediment to the higher of the 75 th 
percentile local conditions value and published benchmarks. 

The maximum detected concentration of total PAHs, antimony, cadmium, and 
chromium were below measurement endpoints. 

The maximum detected concentration of PCBs, BEHP, arsenic, barium, lead, mercury, 
nickel, selenium, silver, vanadium, and zinc were above measurement endpoints. 

EPH fractions lacked screening benchmarks and thus could not be evaluated. 
Beryllium also lacked a screening benchmark but was consistent with local conditions. 

4.2.4 Uncertainty 

The following represent potential uncertainties which could affect the outcome of the risk 
characterization: 

The use of maximum concentrations is a more conservative approach than using a 
measure of the central tendency of the data (i.e., mean of 95 th percentile upper 
confidence limit of the mean or other estimate of the mean). Therefore, the risk 
assessment may be over-estimating the potential risk to benthic organisms. 

The use of screening benchmarks includes conservative assumptions, such as that 
100 percent of a given contaminant is bioavailable. Use of conservative benchmarks 
results in an overestimation of risk. 

The lack of benchmarks for EPH fractions and beryllium may result in an 
underestimation of the total Disposal Site risk. However, the maximum concentrations 
of EPH is co-located with the Site-related chemicals of concern. Therefore, remedial 
actions taken to address the risk posed by arsenic, lead, mercury and vanadium will 
also address the risk posed by EPH fractions. Beryllium is generally present at 
concentrations below local conditions except one location which is co-located with Site 
constituents of concern. Therefore, beryllium does not represent a significant risk in 
and of itself. 


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4.2.5 Risk Characterization 

This Stage II ERC considered all constituents present in the top six inches of sediment, including 
those attributable to non-Site sources (e.g., Monsanto West) and local conditions. Based on the 
comparison of maximum sediment concentrations to the measurement endpoints, and 
considering uncertainties, a condition of No Significant Risk does not exist for benthic organisms 
which are exposed to sediment. 

4.3 Method 3 Ecological Risk Assessment Conclusions & Risk Management 
Recommendations 

The 2006 Stage I ES (MCA, 2006) demonstrated that a condition of No Significant Risk exists for 
surface water. The 2006 Stage II ERC (MCA, 2006) demonstrated that a condition of No 
Significant Risk exists for shorebirds and other shoreline wildlife. 

The present Stage I ES concludes that there are potentially significant exposure pathways with 
respect to the benthic community exposed to sediment. The present Stage II ERC concludes that 
a condition of No Significant Risk does not exist for benthic organisms exposed to sediment. 

As discussed in the Revised Phase II Report (AMEC, 2016b), per agreement with MassDEP, the 
chemicals for which Wynn has liability are arsenic, lead, mercury, and vanadium. Therefore, the 
limits of risk for which Wynn is required to take remedial action are defined by the ER-M for arsenic 
and the local conditions values for lead, mercury, and vanadium (i.e., the higher of the effects 
benchmark or local conditions for each of these four metals). 

A Downgradient Property Status (DPS) Submittal will be prepared for areas on the property 
outside the Remediation Area where non-Site contaminants (e.g., BEHP and PCBs) are present. 


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5.0 REMEDIAL ACTION OBJECTIVES (310 CMR 40.0851) 


Remedial action objectives consist of specific goals for protecting health, safety, public welfare 
and the environment. These objectives will guide the development and evaluation of remedial 
action alternatives (RAAs) for the Site. The performance standards for a Phase III evaluation (310 
CMR 40.0853) require that RAAs be identified and evaluated that are “reasonably likely to achieve 
a level of No Significant Risk”, and that the recommended alternative be a Permanent Solution or 
a Temporary Solution. “No Significant Risk”, as defined in the MCP (310 CMR 40.0006), is “a 
level of control of each identified substance of concern at a Site or in the surrounding environment 
such that no such substance of concern shall present a significant risk of harm to health, safety, 
public welfare or the environment during any foreseeable period of time.” 

A Permanent Solution is any measure or combination of measures which will, when implemented, 
ensure attainment of No Significant Risk. Permanent Solutions must also include measures that 
reduce, the levels of oil and hazardous materials in the environment to as close to background as 
feasible. A Temporary Solution is any measure, or combination of measures, which will, when 
implemented, eliminate any Substantial Hazard which is presented by a disposal site until a 
Permanent Solution is achieved. A Temporary Solution can be selected if a Permanent Solution 
is not currently feasible or response actions to achieve a Permanent Solution are feasible and 
shall be continued toward a Permanent Solution. 

5.1 General Remedial Action Objectives 

The general remedial objectives to be considered for the Phase III evaluation specified by the 
MCP are: 

Achieve a condition of No Significant Risk of harm to human health, safety, public 
welfare, and the environment, and reduce OHM to background conditions, if feasible; 

► Eliminate or control continuing sources of OHM; 

Control plumes of dissolved OHM in groundwater and vapor phase OHM in the 
vadose zone; 

► Eliminate Upper Concentration Limit (UCL) exceedances for OHM in soil and 
groundwater, if feasible; and 

► Eliminate Substantial Hazards. 

5.2 Site-Specific Remedial Action Objectives 

Site-specific remedial action objectives have been determined based on the results of the 
previous Risk Characterizations conducted for the sediment portion of the Disposal Site. 

The 2006 Stage I ES (MCA, 2006) demonstrated that a condition of No Significant Risk exists for 
surface water. The 2006 Stage II ERC (MCA, 2006) demonstrated that a condition of No 
Significant Risk exists for shorebirds and other shoreline wildlife. The present Stage I ES 
concludes that there are potentially significant exposure pathways with respect to the benthic 
community exposed to sediment. The present Stage II ERC concludes that a condition of No 


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Significant Risk does not exist for benthic organisms exposed to sediment. Therefore, remedial 
actions are necessary to address exposure to impacted sediments by benthic organisms in order 
to achieve a condition of No Significant Risk. 

A Method 3 human health risk characterization concluded that a condition of No Significant Risk 
does exist for trespassers who might wade along the shoreline. A condition of No Significant Risk 
is also considered to exist for trespassers who might catch and consume fish and shellfish 
irregularly on the property. Therefore, no remedial actions are necessary to address potential 
risks to human health. 

As discussed in Section 3.1, the primary sources of contamination to the sediment are historical 
manufacturing operations and processes on the upland portion of the property and the adjacent 
Monsanto West property. The upland portion of the property is being remediated through the 
RAM. The Monsanto West property was remediated during redevelopment of that area into the 
Gateway Center. Therefore, there are no potential uncontrolled sources for the Disposal Site. 

There are no vapor phase OHM in the vadose zone which might migrate to sediment. Migration 
of metals in groundwater from the upland portion of the property to sediment is likely to be very 
limited in the future due to the recently completed in-situ treatment of soil and groundwater in the 
low pH area and excavation and off-site disposal of soil from the CES-2 area. Migration of 
sediment out of the embayment via natural processes is not expected to have been a significant 
migration pathway in the past or be one in the future. Therefore, no actions need to be taken to 
control migration of groundwater, vapor, or impacted sediment. 

The achievement of a Temporary Solution requires elimination of any Substantial Hazards until a 
Permanent Solution is achieved. For the sediment portion of the Site there are no Substantial 
Hazards to either human or ecological receptors based on the 2016 Method 3 Risk 
Characterization. Therefore, no specific remedial actions need to be performed to address 
Substantial Hazards. 

Based on the above discussion, the Site-specific remedial action objective for sediment is to 
eliminate significant risk to benthic organisms associated with exposure to sediment at 
concentrations which exceed benchmarks or local conditions. 


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6.0 IDENTIFICATION AND EVALUATION OF REMEDIAL ACTION ALTERNATIVES (310 
CMR 40.0855) 

This section presents the results of the identification and evaluation of remedial action alternatives 
that are potentially applicable to the Site. This evaluation consisted of two steps: (i) an initial 
screening of potential applicable remediation technologies, and (ii) the formulation and evaluation 
of comprehensive remedial action alternatives. The site-specific remedial objective for the Site 
(as discussed in Section 4.2) requires that the remedial action alternatives address potential 
exposure to sediment by benthic organisms which are currently present (or likely to be present in 
the future) at the Site. 

6.1 Initial Technology Screening (310 CMR 40.0856) 

The purpose of this step is to identify remedial action technologies for further evaluation, which 
are reasonably likely to be feasible, based on the OHM present, impacted media, and disposal 
site characteristics. For the purpose of this screening step, remedial action technologies are 
considered reasonably likely to be feasible if (310 CMR 40.0856): 

The technologies to be employed by the alternative are reasonably likely to achieve a 
Permanent or Temporary Solution; and 

Individuals with the expertise needed to effectively implement available solutions would 
be available, regardless of arrangements for securing their services. 

The categories of remedial technologies/response actions that were evaluated include the 
following: 


Monitored Natural Recovery (MNR) 

In Situ Treatment (Amendment) 

► Enhanced Sediment Deposition 

► Mechanical Dredging 

► Hydraulic Dredging 

► Mechanical Capping 

Each of these technologies is described in more detail below. 

6.1.1 Monitored Natural Recovery (MNR) 

MNR is one of the three main remedial alternatives for contaminated sediment recognized by US 
EPA (dredging and capping are the others). MNR uses ongoing, naturally occurring processes to 
contain, destroy, or reduce the bioavailability or toxicity of contaminants in sediment. These 
processes include that convert contaminants to less toxic forms (biodegradation), bind 
contaminants more tightly to sediment (sorption), or bury contaminated sediment beneath clean 
sediment (sedimentation). For this Site, natural sediment burial and contaminant attenuation are 
generally the processes which constitute MNR. Long-term monitoring with sediment sampling 
occurs at a set frequency (i.e., quarterly, semi-annual, and/or annual) to document reduction in 
sediment concentrations through deposition of incoming “cleaner” sediment, and/or dilution to 
reduce concentrations of impacted sediments. 


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6.1.2 In Situ Treatment (Amendment) 

In situ treatment or amendment of the sediment, uses in situ sequestering or destruction of 
contaminants to reduce risks at a site. Materials with treatment capacity for sediment/porewater 
OHM by sorption (e.g., activated carbon, organoclays and apatite) or degradation are placed into 
or onto the sediment surface layer, into a sand cap, or within a geotextile mat. Direct amendment 
of surficial sediment with sorbents can reduce pollutant bioavailability to the food chain and flux 
of pollutants into the water column. Amendments can be spread on the surface of the 
contaminated sediment as a thin layer, intended to be mixed with the sediments through natural 
processes, or mixed into the surface using equipment similar to a rototiller. The intent in direct 
application is to change the native sediment geochemistry to reduce contaminant bioavailability 
without creating a new surface layer or cap. Amendments can also be introduced to a capping 
layer in a geotextile mat or added to capping materials before or during placement of caps. In situ 
treatment of sediment is a relatively new technology and there are uncertainties regarding 
treatment capacity, long-term permanence, and ability to retain contaminants over time. For this 
Site, migration of contamination from sediment/porewater into surface water and bioavailability 
are not the primary concerns. 

6.1.3 Enhanced Sediment Deposition 

Enhanced sediment deposition, sometimes referred to as enhanced MNR, uses structures (e.g., 
weirs, breakwaters, reefs, jetties) placed in the flow of the water body to slow the natural flow and 
allow sediment to deposit on the bottom. The intent is to disrupt the existing flow and sediment 
transport patterns and establish new equilibrium conditions where sediment deposition is 
enhanced in certain desired areas. However, enhancement of sediment deposition in one area 
may result in increased erosion in another area which may not be desirable. In addition, the 
structures must remain permanently in place or else natural equilibrium conditions will re-establish 
themselves. Selection, design, and installation of appropriate structures requires a thorough 
understanding of flow and sediment transport in the water body. For this Site, the tidal nature of 
the environment and the shifting flow directions at ebb and flood tide will make this challenging. 
The placement of structures within the embayment (and potentially the Mystic River) could also 
pose a challenge to navigation and the desired end uses of the area. 

6.1.4 Mechanical Dredging 

Mechanical dredging is a presumptive remedial technology for contaminated sediments. 
Mechanical dredging removes impacted sediments from the area of concern within a waterway 
by using direct mechanical force to dislodge and contain the material. Heavy equipment (various 
sizes of excavators and cranes) are mounted onto a barge and used to excavate the area of 
concern using precise global positioning system (GPS) guided equipment for horizontal and 
vertical accuracy. Removed sediments are placed on a materials barge where they are 
temporarily stockpiled to allow waters to drain out. Once the bulk of the water has drained back 
to the area within the environmental barriers, the sediments are transported to a land transfer 
facility. Sediments are then stabilized with a drying agent (i.e., Portland cement) to remove 
additional waters and bring the moisture content of sediments to an allowable limit for off-site 
transportation and disposal. The sediments are then conveyed from the barge into trucks for off¬ 
site for disposal, or treated on-site. 


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Due to Site constraints an off-site shipping yard will need to be used for all waterway access, 
sediment processing, transportation and disposal. Tide information, bridge clearances, 
navigation channels and underwater utility locations are important considerations in mechanical 
dredging projects and must be identified and considered during the remedial design. Proximity 
to local shipping yards and coordination with harbor masters can also affect dredging costs. 

6.1.5 Hydraulic Dredging 

Hydraulic dredging uses a pump to create a vacuum at the dredge head to remove and transport 
sediment in a slurry form. The dredged material is usually pumped through a pipeline to a settling 
lagoon or tank (typically on land). Environmental dredging using hydraulic dredges typically 
produce slurries with less than 10% solids by weight. A “cutter head” hydraulic dredge is 
commonly used to apply mechanical force to dislodge the sediments for removal by the dredge 
pump. The slurry requires extensive dewatering prior to off-site reuse, recycling or disposal of the 
dredged materials. This is often accomplished through the use of settling tanks, mechanical filter 
presses, Geotubes and stabilization agents and may require multiple steps. Water generated 
during dredging and the dewatering of the slurry is typically treated and discharged back to the 
dredge area. As with mechanical dredging, Site constraints would require the initial processing of 
the slurry to occur on a barge which will affect productivity and dredging costs. 

6.1.6 Mechanical Capping 

Capping (isolation) is also considered a presumptive remedy for contaminated sediments. 
Mechanical capping uses one or more layers of imported clean material (i.e., sand, gravel, rock 
or synthetic material) as a barrier over contaminated sediments. The cap then creates a physical 
barrier which mitigates exposure to potential receptors. In a low energy system, a single isolation 
layer may be sufficient to be an effective cap. In higher energy environments, the cap may contain 
both an isolation layer and an erosion control layer. Clean fill is loaded onto a material barge at a 
landside transfer facility and transported to the site. Material can be placed by a mechanical 
excavator, broadcast spreader, conveyor belt or other suitable method. 

6.1.7 Summary of Technology Screening 

Table 6-1 summarizes the initial screening of technologies. Each technology is briefly described 
with advantages and disadvantages of each. Relative costs are identified along with whether the 
technology is compatible with Site characteristics. Technologies were screened based on their 
likely feasibility; ability to achieve a level of No Significant Risk; and their ability to achieve a 
Permanent Solution. Based on the initial screening outlined in Table 6-1, mechanical dredging, 
mechanical capping and MNR were retained for assembly into a range of alternatives. MNR alone 
may not achieve the remedial action objective in a reasonable timeframe, particularly in intertidal 
areas where erosion and sedimentation processes may be more dynamic. However, if natural 
recovery is further verified to be occurring, it can be used (primarily in subtidal environments) with 
other technologies to achieve an overall condition of No Significant Risk. 

In situ treatment (amendment) was not retained as this technology is primarily intended to prevent 
migration of contaminants from sediment to surface water in the dissolved phase and this is not 
a concern at the Site. In addition, the amended cap material may not be a suitable habitat for 
benthic organisms. Enhanced sediment deposition was not retained as it would require the 


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installation of structures within the embayment and channel which could pose a hazard to 
navigation and limit future use of the area. In addition, the increased depositional rates might 
adversely affect benthic organisms. 

6.2 Development of Alternatives 

A combination of technologies can often be more efficient and cost-effective, rather than 
successive, Site-wide application of single technologies. The retained technologies described 
above have been assembled into a variety of remedial action alternatives that are reasonably 
likely to be feasible, achieve a level of No Significant Risk, and effectively achieve the established 
remedial action objective. The following are the remedial action alternatives for the Site, which 
will be retained for detailed evaluation: 

► Alternative 1 - Full Dredge and Cap 

^ Alternative 2 - Partial Dredge and Cap 

► Alternative 3 - Partial Dredge, Cap, and MNR 

► Alternative 4 - Navigation Dredge, Cap, and MNR 

► Alternative 5 - No Further Action (Navigation Dredge Only) 

Alternatives 1-4 combine sediment removal with capping and/or MNR to mitigate the risk to 
benthic organisms due to exposure to contaminated sediment and to achieve a condition of No 
Significant Risk. These alternatives were developed primarily by varying the extent of dredging 
and/or capping. Alternative 5 provides a basis for comparison of the other “active” alternatives 
as it assumes no further remedial actions or monitoring measures would be conducted. 
Alternative 5 does assume that the previously permitted navigational dredging 7 and removal of 
five derelict barges is completed. The navigational dredging does not constitute a remedial action 
to address risk as it does not include capping of the deeper sediment which will be exposed upon 
completion of the navigational dredging. 

Table 6-2 provides a conceptual design for each remedial action alternative including key 
elements of design and implementation, monitoring, and remediation waste. Conceptual layouts 
of each alternative are provided in Figure 6-1 through Figure 6-5. A brief description of each 
alternative is presented below: 

6.2.1 Alternative 1 - Full Dredge and Cap 

Shallow sediments within the Disposal Site boundary pose a significant risk to benthic organisms. 
Based on previous studies of the benthic communities at the Site, USEPA’s Determination of the 
Biologically Relevant Sampling Depth for Terrestrial and Aquatic Ecological Risk Assessments 
(USEPA, 2015) and other sources, the anticipated depth of bioturbation by organisms found (or 
likely to be found in the future) is 18 inches. Therefore, to achieve a condition of No Significant 
Risk, an 18-inch thick clean layer must be established. Implementation of Alternative 1 will 
remove impacted sediment to a depth of 18 inches across the area posing a Significant Risk. 


7 Dredging, structures and fill associated with navigation improvements and shoreline stabilization were previously approved by the 
U S Army Corps of Engineers (USACE), MassDEP, and Everett Conservation Commission 


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Sediment removal will be performed using mechanical dredging. Following dredging, 18 inches 
of clean sand will be placed over the newly dredged surface. 

Alternative 1 - Full Dredge and Cap includes the following primary components: 

Debris and Barge Removal: Prior to the start of dredging, a debris survey will be performed and 
the debris will be removed to and placed on a barge for stockpiling prior to transport off-site for 
disposal at an approved facility. Buried debris encountered during the dredging works will be 
segregated and handled in a similar manner. One sunken barge and four additional barges 
located in the intertidal zone will be removed. None appear to be structurally stable such that they 
can be removed with salvage equipment and floated off intact. As a result, they must be 
dismantled in place to be removed. Removal will be conducted using barge mounted equipment 
and/or land-based equipment. The demolition materials will be loaded onto a combination of 
barges and/or trucks and disposed of in accordance with all applicable laws and regulations. The 
possible presence of asbestos, lead paint and other hazardous materials may require some 
special handling. Materials will be analysed to the extent possible prior to demolition to determine 
the appropriate procedures for disposal. 

Dredging: A pre-dredge bathymetric survey will be performed to verify the existing contours 
immediately prior to the start of dredging. Sediment will be dredged using an excavator or crane 
equipped with an environmental clam shell bucket and then transferred to a hopper barge or scow. 
All work will be conducted within a turbidity curtain and turbidity monitoring will be conducted to 
assess the potential for ongoing impacts associated with sediment disturbance. Proposed 
dredging depths are anticipated to be approximately 18 inches below the existing mudline or the 
previously permitted elevation of-15 NAVD88 in the navigational dredge area. This will result in 
the removal of approximately 22,700 CY of sediment in addition to the previously approved 14,700 
CY of navigational dredging (for a total of 37,400 CY of sediment) within an area of approximately 
7.0 acres (306,000 SF). Note that the proposed area to be dredged is slightly smaller than the 
previously identified Remediation Area (7.4 acres) as some shoreline areas have already been 
addressed as part of the upland RAM. The total anticipated quantity of dredge includes an 
allowance of six inches (overdredge) to accommodate reasonable tolerances during dredge 
operations. 

Dewatering, Stabilization and Offload: The dredged material will be transferred into a hopper 
barge or scow. Free water from the sediment in the scow will be decanted and discharged within 
the turbidity curtain at the dredging area. Scows typically have a sump pit in the corner to facilitate 
decanting/dewatering of sediment. Depending on the scow size and set-up, decant water will be 
pumped from the sump through a geotextile liner placed in the scow, or using a screened suction 
hose to minimize passing of solids. To facilitate dewatering, the scow may sit in the remediation 
area to allow the sediment to air-dry or Geotubes may be used to consolidate and dry the material. 

Dewatered sediment will be transferred by barge to an off-site facility for further 
dewatering/stabilization (if necessary) and offloading. At the offloading facility it is anticipated that 
the sediment will be mixed with Portland cement (assumed 8 percent by weight) so that the 
material will have no free liquid (passing the Paint Filter Test, EPA 9095B) before it is sent to an 
off-site facility for reuse or disposal. The dredged material will be transported to a properly 


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licensed facility for reuse or disposal under a Bill-of-Lading or hazardous waste manifest (if 
required). Sediment may be pre-characterized at a frequency of one sample per 500 tons to 
identify reuse or disposal options prior to dredging. The total amount of sediment, including 
amendment, is estimated at 60,500 tons. 

Capping: Dredged materials are to be replaced to restore existing elevations or approved 
navigational dredge elevations with an 18-inch thick layer of clean backfill (plus an anticipated 6- 
inch allowance to compensate for the over-dredge allowance). Fine to medium gravel will be used 
as the surface layer of the cap in the navigational dredge area in order to minimize propeller- 
induced erosion of the cap. Sand or silty sand will likely be used in the remaining subtidal areas 
and all intertidal areas in order to minimize potential erosion of the cap by wave actions and 
currents. The total volume of cap material to be placed in the dredged areas is approximately 
25,000 CY. Once clean material has been placed following dredging, final elevations in the 
navigational dredge area will be -15 NAVD88 consistent with the permits issued for the 
navigational dredging. Elevations in intertidal areas as well as subtidal areas that are dredged will 
be consistent with existing elevations. 

Monitoring and Maintenance: As previously noted, a pre-remediation debris survey and 
bathymetric survey will be conducted and the sediment may be pre-characterized. In addition, 
background turbidity readings will be collected from the Mystic River. If not pre-characterized, 
dredged sediments will be sampled in barges or in stockpiles to determine the appropriate facility 
for disposal. Barge demolition, dredging, and capping will be conducted within a turbidity curtain 
(or curtains) and turbidity monitoring will be conducted as determined by the Water Quality 
Certificate issued for the project. Confirmation sampling may be required by selected reuse or 
disposal facilities based on the amount and type of amendments used. Following construction, 
periodic bathymetric surveys of the cap area will be performed to monitor stability and 
effectiveness (initially at an annual frequency and then less frequently after a period of five years). 
Maintenance dredging will be conducted on a periodic basis to ensure that the channel depths 
required for navigation are maintained. 

Regulatory Closure: An Activity and Use Limitation (AUL) will be filed to require continued 
maintenance and monitoring of the capped areas. A Permanent Solution with Conditions will be 
achieved in the Remediation Area upon completion of the dredging and capping and the filing of 
the AUL. A DPS submittal will be prepared to address contamination outside the Remediation 
Area for which Wynn is not responsible. 

6.2.2 Alternative 2 - Partial Dredge and Cap 

Implementation of Alternative 2 - Partial Dredge and Cap will remove impacted sediment to a 
depth of 18 inches from the intertidal and subtidal in the eastern portion of embayment 
(navigational dredge area and tidal flats) and an intertidal area to the northwest (green and tan 
areas on Figure 6-2). Sediment removal will be performed using mechanical dredging. Following 
dredging, 18 inches of clean backfill will be placed over the newly dredged surface as described 
in Alternative 1. The remaining subtidal areas within the Disposal Site boundary will be capped 
with 18 inches of clean sand. 

The primary components of Alternative 2 are as follows: 


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Debris and Barge Removal: Debris and barge removal will be conducted as described in 
Alternative 1. 

Dredging: Dredging will be conducted in the same fashion as Alternative 1. Alternative 2 will 
result in the removal of approximately 12,100 CY of sediment in addition to the previously 
approved 14,700 CY of navigational dredging (for a total of 26,800 CY of sediment) within an area 
of approximately 3.8 acres (165,000 SF). 

Dewatering, Stabilization and Offload: Dewatering, stabilization and offload will be conducted 
as described in Alternative 1. Once amended, Alternative 2 is anticipated to generate 43,400 tons 
of sediment for off-site reuse or disposal. 

Capping: Capping will be conducted in the same fashion and over the same area as Alternative 
1. The total cap volume (25,000 CY) is the same as in Alternative 1. 

Monitoring and Maintenance: Monitoring and maintenance requirements are the same as 
Alternative 1. 

Regulatory Closure: Regulatory closure requirements are the same as Alternative 1. A 
Permanent Solution with Conditions will be achieved in the Remediation Area upon completion of 
the dredging and capping and the filing of the AUL. A DPS submittal will be prepared to address 
contamination outside the Remediation Area for which Wynn is not responsible. 

6.2.3 Alternative 3 - Partial Dredge, Cap, and MNR 

Implementation of Alternative 3 - Partial Dredge, Cap, and MNR includes the dredging and 
capping of the same intertidal and subtidal areas as Alternative 2 (green and orange areas on 
Figure 6-3). In this alternative, however, the remaining subtidal areas within the Disposal Site 
boundary (approximately 3.3 acres, tan area on Figure 6-3) will be addressed through MNR. 

The primary components of Alternative 3 are as follows: 

Debris and Barge Removal: Debris and barge removal will be conducted as previously 
described in Alternative 1. 

Dredging: Dredging will be conducted using the same means and methods as Alternative 1. The 
area to be dredged and volume of sediment removal will be the same as Alternative 2 (26,800 
CY of sediment removed from an area of approximately 3.8 acres). 

Dewatering, Stabilization and Offload: Dewatering, stabilization and offload will be conducted 
as described in Alternative 1. The quantity of sediment for off-site reuse or disposal will be the 
same as Alternative 2 (43,400 tons). 

Capping: Capping will be conducted in the same fashion as Alternative 1. The total cap volume 
is 13,300 CY based on an 18-inch thick layer of clean backfill (plus an anticipated 6-inch allowance 
to compensate for the over-dredge allowance) placed over an area of 3.8 acres. 


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Monitoring and Maintenance: In addition to the monitoring and maintenance requirements 
already described for Alternatives 1 and 2, Alternative 3 includes development of a detailed MNR 
work plan, a baseline assessment and periodic monitoring and reporting over a 30-year period. 
The detailed work plan will describe monitoring and sampling locations, methods and frequency 
as well as establish criteria to be used to evaluate the progress of MNR towards achieving a 
condition of No Significant Risk. The baseline assessment includes the collection of 20 sediment 
cores with 10 each from within the Disposal Site and at upgradient “local conditions” locations. 
Sediment cores will be used for the following purposes: 

High-resolution (up to 40 samples in the top four feet of sediment) analysis of metals, 
PAHs, phthalates, PCBs, total organic carbon, and grain size to establish baseline 
concentration profiles. 

Age dating via lead, cesium, and radium methods to quantitatively determine 
sedimentation rates. 

Sediment toxicity testing (28-day tests for survival, growth, and reproduction using the 
marine amphipod Leptocheirus plumulosus) consistent with previous site toxicity 
testing. 

► Measurement and modelling of sediment erosion properties in the Site cores to 
determine site-specific sediment stability. 

In addition, benthic community surveys will be conducted to document the abundance, diversity, 
and richness of benthic organisms within the Disposal Site and at the local conditions locations. 
A detailed report will be prepared to document the results of the baseline sediment 
characterization study. 

MNR monitoring events will be conducted in years 3, 5, 10, 15, 20, 25, and 30 of the program. 
Events in years three and five allows for three events (including the baseline) to be evaluated 
during the first five-year Periodic Review. Each monitoring event will include re-sampling of the 
top six inches of sediment at each of the Site and local conditions locations for high-resolution 
(assumed 1 cm increment) analysis of metals, PAHs, phthalates, PCBs, total organic carbon, and 
grain size. The depth and increment of sampling will be determined by the actual sedimentation 
rates from the baseline monitoring events. In addition, benthic surveys will be conducted to 
document any changes in abundance, diversity and richness of species at the study locations. 

Regulatory Closure: A Permanent Solution with Conditions will be achieved for the dredged 
and capped areas upon completion of the dredging and capping and the filing of the AUL. A DPS 
submittal will be prepared to address contamination outside the Remediation Area for which Wynn 
is not responsible. A ROS Submittal or Temporary Solution will be submitted for the areas where 
MNR is being employed. Status Reports will be submitted as required and a formal Periodic 
Review of the Temporary Solution (or ROS) will be performed every five years. If MNR is 
demonstrated to be effective, then a Permanent Solution will be achieved at some point in the 
future when exposure to sediments no longer poses a Significant Risk to benthic organisms. If 
MNR is demonstrated to be ineffective, then additional remedial actions will likely be performed 
in order to obtain a Permanent Solution. 


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6.2.4 Alternative 4 - Navigation Dredge, Cap, and MNR 

Implementation of Alternative 4 - Navigation Dredge, Cap, and MNR includes the dredging and 
capping of the navigational dredge area only (orange area on Figure 6-4). The remaining intertidal 
and subtidal areas within the Disposal Site boundary (approximately 5.6 acres, tan area on Figure 
6-4) will be addressed through MNR. 

The primary components of Alternative 4 are as follows: 

Debris and Barge Removal: Debris and barge removal will be conducted as previously 
described in Alternative 1. 

Dredging: Dredging will be conducted in the same fashion as Alternative 1. The area to be 
dredged is approximately 1.4 acres and volume of sediment removal will be 4,500 CY of remedial 
dredging in addition to the approved 14,700 CY of navigational dredging (for a total of 19,200 CY 
of sediment). 

Dewatering, Stabilization and Offload: Dewatering, stabilization and offload will be conducted 
as described in Alternative 1. The quantity of sediment for off-site reuse or disposal will be 31,000 
tons. 

Capping: Capping will be conducted in the same fashion as Alternative 1. The total cap volume 
is 5,000 CY based on an 18-inch thick layer of clean backfill (plus an anticipated 6-inch allowance 
to compensate for the over-dredge allowance) placed over an area of 1.4 acres. 

Monitoring and Maintenance: Monitoring and maintenance requirements are the same as 
Alternative 3 except the number of monitoring locations within the Disposal Site will be increased 
to cover the larger MNR area. 

Regulatory Closure: Regulatory closure requirements are the same as Alternative 3. A 
Permanent Solution with Conditions will be achieved for the dredged and capped areas. A DPS 
submittal will be prepared to address contamination outside the Remediation Area for which Wynn 
is not responsible. ROS or a Temporary Solution will apply for the MNR area until such time as it 
is demonstrated that MNR is (or is not) progressing towards a Permanent Solution. If MNR is 
determined to be ineffective, then additional remedial actions will likely be performed to achieve 
a Permanent Solution. 

6.2.5 Alternative 5 - No Further Action (Navigation Dredge Only) 

As previously stated, Alternative 5 - No Further Action provides a basis for comparison of the 
other “active” alternatives. This alternative assumes that only the previously permitted 
navigational dredging and removal of five derelict barges will be completed. No further remedial 
actions, including capping of exposed sediment or MNR monitoring, will be conducted. 

The primary components of Alternative 5 are as follows: 

Debris and Barge Removal: Debris and barge removal will be conducted as previously 
described in Alternative 1. 


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Dredging: Dredging will be conducted using the same means and methods as Alternative 1. 
Sediment will be dredged to achieve the previously permitted elevation of -15 NAVD88 in the 
navigational dredge area (Figure 6-5). This will result in the removal of approximately 14,700 CY 
of sediment within an area of approximately 1.4 acres. 

Dewatering, Stabilization and Offload: Dewatering, stabilization and offload will be conducted 
as described in Alternative t. The quantity of sediment for off-site reuse or disposal will be 23,800 
tons. 

Monitoring and Maintenance: Pre-dredging debris and bathymetric surveys, sediment pre- 
characterization, turbidity monitoring, and confirmation sampling will be conducted as described 
in Alternative 1. A post-dredging bathymetric survey will be performed to verify that the necessary 
channel depths have been achieved. Maintenance dredging will be conducted on a periodic basis 
to ensure that the channel depths required for navigation are maintained. 

Regulatory Closure: Alternative 5 will not achieve a Permanent Solution. A Temporary Solution 
will be filed and Definitive and Enterprising Steps to achieve a Permanent Solution will be taken. 
Periodic Reviews of the Temporary Solution will be conducted every five years in order to 
determine if a feasible alternative for achieving a Permanent Solution exists. A DPS submittal will 
be prepared to address contamination outside the Navigational Dredge Area for which Wynn is 
not responsible. 

6.3 Detailed Evaluation of Remedial Action Alternatives (310 CMR 40.0857) 

The purpose of this section is to present the detailed comparative evaluation of the remedial 
action alternatives that were identified and developed in Section 5.2 against the criteria specified 
in 310 CMR 40.0858. Alternative 5 (No Further Action) will be retained for comparison purposes 
for the detailed evaluation although it is recognized that this alternative will not address the 
remedial action objective (as described in Section 4.2). The remaining four remedial action 
alternatives are reasonably likely to be feasible because: 1) the technologies to be employed by 
the alternatives are reasonably likely to achieve a Permanent or Temporary Solution, and 2) 
individuals with the expertise needed to effectively implement the alternatives will be available. 

The Detailed Evaluation provides the basis for selection of a remedial action alternative. The MCP 
(310 CMR 40.0858) states that a remedial action alternative shall be selected based on the 
detailed evaluation criteria and should be a Permanent Solution unless its implementation is found 
to be less cost-effective and timely than a Temporary Solution. A Permanent Solution should, to 
the extent feasible, reduce the concentrations of OHM to levels that achieve or approach 
background. 

Table 6-2 shows a summary of each alternative analyzed the eight detailed evaluation criteria 
specified in the MCP: effectiveness, reliability, implementability, cost, risk, benefit, timeliness, and 
non-pecuniary interests. The table also includes a qualitative ranking (low, moderate, high) of 
each alternative and a total “score” based on the sum of those rankings. The following discussion 
is a summary of the evaluation presented in Table 6-2. As such, the focus of this discussion is 


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key elements that cause the criteria to be ranked differently, as opposed to a detailed discussion 
of each criteria and alternative. 

6.3.1 Effectiveness 

The comparative effectiveness of the remedial action alternative is evaluated in terms of: 

Achieving a Permanent or Temporary Solution 

Reusing, recycling, destroying, detoxifying or treating OHM; and 

Achieving or approaching background concentrations. 

Alternative 1 has a high effectiveness rating as a Permanent Solution will be achieved across the 
area posing a Significant Risk by physically removing contaminated sediment from the Site. This 
will also achieve background concentrations in the dredged and capped areas. Alternatives 2, 3, 
and 4 have progressively lower ratings for effectiveness primarily due to the lower amounts of 
OHM being removed from the Site. Alternative 2 is rated as high to moderate as both the 
dredged/capped area and the capped area will achieve background concentrations. Alternatives 
3 and 4 are rated as moderate and moderate to low (respectively) as background concentrations 
may be approached over time in the MNR areas. Alternative 5 (No Further Action) has a low 
effectiveness rating as it will not achieve a Permanent Solution and has the lowest removal of 
OHM. As with Alternatives 3 and 4, “local conditions” rather than background will likely be 
approached or achieved over an extended period of time. 

6.3.2 Reliability 

The comparative short and long term reliability of the alternatives is evaluated in terms of: 

The degree of certainty that the alternative will be successful; and 

The effectiveness of any measures required to manage residues or remaining wastes 
or control emissions or discharges to the environment. 

Alternatives 1 and 2 have high reliability rating as dredging and capping are both presumptive 
remedies for contaminated sediments and have a high certainty of success. Residual 
contaminated sediment in the embayment will be isolated beneath a clean cap which has a high 
degree of reliability. The use an environmental bucket, turbidity curtains, and good work practices 
will control inadvertent discharges to the environment during dredging, capping, and off-site 
processing of sediment. Alternative 3 has a moderate reliability rating primarily due to 1) the 
uncertainty associated with the use of MNR to achieve a Permanent Solution and 2) the potential 
for impacted sediment in the MNR areas to be mobilized. Similarly, Alternative 4 is rated as 
moderate to low due to the larger MNR footprint and correspondingly lower degree of certainty 
and increased potential for issues arising from residual sediment. Alternative 5 has the lowest 
rating as navigational dredging alone will not achieve a Permanent Solution and will expose more 
contaminated sediment which could then become mobile. 

6.3.3 Implementability 

The comparative difficulty in implementation of the alternatives in terms of: 

> Technical complexity; 


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Integration and disruption of facility operations and other current or potential remedial 
actions; 

Monitoring, operations and maintenance requirements or Disposal Site access 
requirements or limitations; 

► Availability of necessary services, materials, equipment or specialists; 

Availability, capacity and location of necessary off-site treatment, storage and disposal 
facilities; and 

Whether the alternative meets regulatory requirements for any likely approvals, permits, 
or licenses. 

The degree of technical complexity for the proposed alternatives is primarily related to the extent 
of the area to be dredged and/or capped. The larger the dredging footprint the more difficult 
managing materials, equipment, tidal fluctuations and existing bathymetry will be. Extensive 
planning and preparation will be necessary for successful dredging (particularly in the intertidal), 
dewatering, transporting and offloading dredged material, and placing the cap. 

Integration or disruption of facility operations is not a factor for any of the alternatives as no 
landside access or staging will be allowed. All materials and equipment will be brought into the 
work area by barge from off-site docking and transfer facilities. 

Operation, maintenance and monitoring (OMM) requirements to ensure the stability of the cap in 
Alternatives 1 and 2 are moderate and the same for each alternative as the extent of the cap is 
the same. Alternative 3 has comparable amount of OMM as there are some trade-offs between a 
smaller cap area and a more complex monitoring plan for MNR. Alternative 4 has higher OMM 
requirements than Alternatives 1 through 4 due to the large MNR area. 

The availability of services, materials, equipment, specialists and off-site facilities is generally 
good and does not vary much by alternative. However, the quantity of dredging and capping may 
affect the overall availability and capacity of these items. Therefore, Alternative 5, which has the 
lowest dredge quantity, is the least likely to be constrained by limitations on services, materials, 
equipment, specialists and off-site facilities. 

Multiple permits from the US Army Corps of Engineers (USACE), multiple MassDEP branches, 
and the Boston and Everett Conservation Commissions will be required to implement Alternatives 
1 through 4. Each of the alternatives is expected to meet the requirements established by each 
of those agencies for dredging and capping. MNR will face scrutiny from MassDEP Bureau of 
Waste Site Cleanup and may not meet with full approval even with a robust monitoring plan. The 
navigational dredging necessary for Alternative 5 has already been permitted and no additional 
approvals are required. 

Based on the combination of factors discussed above, Alternative 1 has the lowest 
implementability rating (most difficult to implement) while Alternative 5 has the highest rating 
(easiest to implement). 

6.3.4 Costs 

The comparative costs of the alternatives are evaluated in terms of: 


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► Implementing the alternative, including without limitation: design, construction, 
equipment, Disposal Site preparation, labor, permits, disposal, operation, maintenance 
and monitoring costs 

► Costs of environmental restoration, potential damages to natural resources, including 
consideration of impacts to surface waters, wetlands, wildlife, fish and shellfish habitat; 
and 

Relative consumption of energy resources in the operation of the alternatives and 
externalities associated with the use of those resources. 

Conceptual-level cost estimates developed for each of the remedial action alternatives are 
included in Appendix A. The estimates include capital costs related to materials, labor, laboratory 
analysis, oversight, and reporting, as appropriate. The cost estimates have been developed at a 
+50/-30 percent level of accuracy, consistent with USEPA guidance for conceptual 
design/feasibility study level cost estimates (USEPA, 2000). Estimated construction, cap OMM 8 
and MNR costs (rounded to the nearest $10,000) for each of the remedial alternatives are 
summarized in Table 6-4 below. 

Table 6-4: Estimated Construction, OMM, and MNR Cost 


Remedial 

Estimated 

Estimated Cap 

Estimated MNR 

Estimated Total 

Alternative 

Construction 

OMM Cost 

Cost 

Cost 


Cost 




Alternative 1 

Full Dredge and Cap 

$19,110,000 

$1,120,000 

$0 

$20,230,000 

Alternative 2 

Partial Dredge and 

Cap 

$14,670,000 

$1,120,000 

$0 

$15,790,000 

Alternative 3 

Partial Dredge, Cap, 
and MNR 

$13,560,000 

$600,000 

$2,250,000 

$16,410,000 

Alternative 4 

Navigation Dredge, 
Cap, and MNR 

$9,540,000 

$220,000 

$3,880,000 

$13,640,000 

Alternative 5 

No Further Action 

$7,260,000 

$0 

$0 

$7,260,000 


Note: Estimated costs include 20% contingency for construction, cap OMM, and MNR. 


Alternative 1 has the highest cost rating (lowest score) due to its high total cost and consumption 
of energy during dredging, capping, processing and transporting of sediment. Alternatives 2 and 
3 have both been given moderate cost ratings. Alternative 2 has a lower total cost and energy 
consumption than Alternative 1 due to the reduced dredging footprint. Both Alternatives 1 and 2 
result in the same immediate net restoration of natural resources. Alternative 3 has a higher total 


8 Costs for maintenance dredging are not included as those are operational costs which are not anticipated to vary based on the 
alternative selected. 


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cost than Alternative 2; however, the inclusion of MNR significantly reduces the overall energy 
consumption of this alternative. MNR also delays the restoration of natural resource areas relative 
to dredging and capping. The larger MNR area (and reduced dredging and capping) results in 
lower total cost and lower energy consumption. Alternative 5 has the lowest total cost and lowest 
energy consumption; however, it will not restore natural resources. 

6.3.5 Risks 

The risks of the alternatives are evaluated in terms of: 

The short and long term risks to health, safety, public welfare, and the environment 
associated with the implementation and OMM of the alternative; and 

► Potential risks to health, safety, public welfare and the environment associated with the 
residual remaining on the Site after the alternative is implemented. 

The implementation of Alternatives 1, 2, and 3 would pose moderate short-term risks to 
construction workers associated with the use of heavy equipment during dredging and capping. 
Alternatives 4 and 5 pose lower risks during implementation due to the significantly smaller 
quantities of dredging. Each of the alternatives pose a moderate risk to the public welfare and 
environment during dredging, transport, and reuse or disposal of the dredged sediments. 

Alternatives 1 and 2 are similar in that they both rely on immediate physical removal (dredging) 
and isolation (capping) to reduce sediment concentrations to below risk limits. As a result, there 
is no risk associated with the residuals left on the Site after the alternatives are implemented. 
Alternatives 3 and 4 have low to moderate risks to environmental receptors during the time 
required to achieve the remedial objective via MNR. Alternative 5 poses a high risk to the 
environment as the navigational dredging will expose more heavily contaminated sediment which 
is currently out of the zone where benthic organisms might be present. 

Based on the combination of factors outlined above, Alternatives 1 and 2 represent low to 
moderate risks, Alternative 3 poses a moderate risk, and Alternative 4 is a moderate to high risk, 
and Alternative 5 is a high risk. 

6.3.6 Benefits 

The benefits of the remedial action alternatives are evaluated in terms of: 

► Restoring natural resources; 

► Providing for the productive reuse of the Disposal Site; 

i> Avoiding costs of relocating people, businesses, or providing alternative water supplies; 
and 

► Avoiding lost value of the Disposal Site. 

Alternatives 1 and 2 provide the highest benefits with regards to mass removal, achievement of 
the remedial objective, restoration of natural resources and allowing for re-use of property in 
timely manner. Dredging and capping will remove (or isolate) significant volumes of contaminated 
sediment and immediately provide improved habitat for benthic organisms. Quick achievement of 
a Permanent Solution through dredging and capping will minimize any potential loss in value. 
Alternatives and 4 have slightly lower ratings as MNR will require more time (potentially 30 years) 


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to restore natural resources and achieve a Permanent Solution. There may also be a potential 
loss in value during the extended period of time required to achieve a Permanent Solution. 
Alternative 5 has the lowest rating as it will not directly restore natural resources (natural 
sedimentation will still occur over time) and the lack of a Permanent Solution will cause a loss in 
value in the event Wynn seeks to sell the property. 

6.3.7 Timeliness 

The comparative timeliness of the alternatives are evaluated in terms of eliminating any 
uncontrolled sources of oil and/or hazardous material and achieving of a level of No Significant 
Risk. There are no uncontrolled sources ate the Site; therefore, this evaluation focuses on 
achievement of a condition of No Significant Risk. 

Alternatives 1 and 2 will both achieve a condition of No Significant Risk upon completion of the 
dredging and capping which is anticipated to be completed in only a matter of months. Therefore, 
this alternatives have been rated high for timeliness. Alternatives 3 and 4 will require an extended 
period of time (potentially up to 30 years) to achieve a condition of No Significant Risk for the 
entire area posing a risk. This long time-frame is due to the time required for additional sediment 
to accumulate and bury the contaminated sediment in the MNR areas. Therefore, this alternatives 
have been rated as moderate. Alternative 5 will not achieve a condition of No Significant Risk 
and so has been rated low. 

6.3.8 Non-Pecuniary Interests 

The alternatives are evaluated in terms of relative effects upon non-pecuniary interests, such as 
aesthetic values, nuisance odors and disruption to public access. 

Alternative 1 will have moderate effects on non-pecuniary interests. Aesthetic values will 
immediately be improved following dredging and capping. However, there may be some nuisance 
odors during dredging and access to the embayment will be limited during remediation. 
Alternative 2 is rated slightly higher (moderate to high) due to the decreased likelihood of nuisance 
odors (less dredged material) and shorter duration of access limitations. Alternatives 3 and 4 are 
also rated as moderate as the positive effects from less dredging compared to Alternative 1 are 
offset by decreased (or at least delayed) aesthetic improvements in the MNR areas. Alternative 
5 has the lowest rating with respect to non-pecuniary interests as the lack of aesthetic 
improvements outweigh the positive effects of minimal dredging and access limitations. 

6.4 Selection of the Remedial Action Alternative (310 CMR 40.08590 

The last line of Table 6-3 shows a total ranking for each alternative based on the sum of the 
individual rankings for each of the eight criteria. Of the standard criteria for remedial option 
screening, the three primary drivers for this Site are effectiveness, cost, and timeliness. 

Alternative 1 (Full Dredge and Cap) ranks highest for effectiveness, reliability, benefits, and 
timeliness. However, it also ranks lowest for cost and implementability and for those reasons it 
has not been selected. Alternative 2 (Partial Dredge and Cap) ranks just as highly as Alternative 
1 on reliability, benefits and timeliness and better than Alternative 1 for cost and implementability 


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giving it the highest total ranking. Concerns about the acceptance of MNR as an approach and 
the extended time period likely needed to achieve a Permanent Solution resulted in Alternatives 
3 and 4 not being selected. 

Therefore, Alternative 2 has been selected as the proposed remedial action alternative for the 
sediment portion of the Former Everett Staging Yard Disposal Site. The Partial Dredge and Cap 
alternative consists of the demolition of the barges, navigational dredging, remedial dredging of 
the navigational dredge area and intertidal areas, capping the dredged areas, and capping the 
subtidal portions of the channel. This remedial alternative represents the best combination of 
time to achieve a Permanent Solution, certainty of success (i.e. achieving a Permanent Solution), 
reliability, and capital cost. 


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7.0 FEASIBILITY EVALUATIONS (310 CMR 40.0860) 


Under certain conditions, the MCP (310 CMR 40.0860) requires an evaluation of the feasibility of: 
Implementing a Permanent Solution; 

Reducing the concentrations of oil and hazardous material in the environment to levels 
that achieve or approach background; 

Reducing the concentrations of oil and hazardous material in soil at a disposal site to 
levels at or below applicable soil Upper Concentrations Limits; and 

Eliminating, preventing or mitigating Critical Exposure Pathway(s). 

Because the selected remedial action alternative, Partial Dredge and Cap (Alternative 2) is 
expected to result in a Permanent Solution, soil is not a media of concern for this portion of the 
Site, and there are no Critical Exposure Pathways, only the feasibility of reducing concentrations 
of OHM in the environment to levels that achieve or approach background is required. 

The MCP at 310 CMR 40.0006 defines background concentrations as “levels of oil and hazardous 
material that would exist in the absence of the disposal site of concern, including both Natural 
Background and Anthropogenic Background.” Natural Background reflects concentrations “that 
would exist in the absence of the disposal site of concern, are ubiquitous and consistently present 
in the environment at and in the vicinity of the disposal site of concern, and are attributable to 
geologic or ecological conditions.” Anthropogenic Background includes atmospheric deposition 
of industrial process or vehicle emissions, Historic Fill, and petroleum residues incidental to the 
normal operation of motor vehicles. 

MassDEP has not published background concentrations for sediment which can be used for direct 
comparison. However, they have established naturally occurring levels of metals and PAHs in 
soil, and background concentrations of metals and PAHs in sediment would not be expected to 
be any lower than background concentrations in natural soil. 

The selected alternative, Partial Dredge and Cap, will reduce the concentrations of OHM in 
sediment to background in the areas that are dredged and capped as the clean backfill material 
used in the cap is presumed to be equivalent to background. Concentrations in the small area of 
sediment outside the Remediation Area but within the Disposal Site boundary will exceed 
background. A condition of No Significant Risk with respect to Disposal Site contaminants exists 
in this area as concentrations are below ecological benchmarks. Therefore, no remedial actions 
are required to achieve No Significant Risk for Disposal Site contaminants. Remedial actions to 
achieve or approach background are therefore infeasible as the cost of any such actions 
(dredging and/or capping) are more than 20 percent of the cost of achieving a condition of No 
Significant Risk (Section 9.3.3.4 of MassDEP Policy #04-160). Therefore, the cost far outweighs 
the incremental benefit in risk reduction. In addition, remedial actions to achieve or approach 
background would disturb approximately 20,000 SF of intertidal habitat which exceeds the 5,000 
SF threshold in Section 3.0 of MassDEP Policy #04-160. 

4 

It is important to note that the local conditions concept for sediments is not the same as the MCP 
definition of background. Local conditions acknowledges that sediments in certain water bodies, 
particularly those located in industrial urban areas, contain constituents from sources such as 
other disposal sites, permitted discharges, and non-point sources. In the case of the Mystic River 


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and this Site, the established local conditions concentrations chemicals are significantly elevated, 
which means that sediments entering the Site from the surrounding area will likely exceed 
background. 


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8.0 ENGINEERING DESIGN (310 CMR 40.0874(3)(b)) 


This section documents the engineering concepts and design criteria used for the design of the 
final Comprehensive Remedial Action. The remedy described in this section is based on, but is 
not identical to, Alternative 2 - Partial Dredge and Cap described in Section 6 of this report. The 
final remedy described in this section reflects the ongoing construction at the property, the results 
of additional information collected following completion of the feasibility study and other 
refinements to increase constructability, reduce cost, and ensure the long-term stability of the 
proposed cap. Therefore, the areas and quantities referenced within this section are slightly 
different than those presented for conceptual remedy in Section 6. 

The relevant items listed under 310 CMR 40.0874(3)(b) are addressed in this section, including: 

► goals of the remedial action; 

► any significant changes in or new information that affects the design; 
any significant changes in design or new information; 

► Site maps showing existing features and proposed locations of activities; 

► characteristics, quantity and location of environmental media or materials to be treated 
or otherwise managed; 

conceptual plan of the activities, treatment units, facilities and processes to be used; 

► relevant design and operating parameters; 

► design features for control of spills and accidental discharge or system malfunction; 

methods for management or disposal of any treatment residual, contaminated soils, 
and other waste materials; 

► Site-specific characteristics, which may be affected by the remedial action; 

► measures to avoid any deleterious impact on environmental receptors and natural 
resource areas; and 

► Inspections and monitoring, which will be performed to ensure adequate construction 
and performance. 

Performance standards are based on applicable requirements contained in the MCP, related 
guidance and policy issued by the MassDEP, and other relevant regulations, guidance and policy 
referenced in the MCP. The overriding objective of the performance standards is conformance 
with the Response Action Performance Standard (RAPS, 310 CMR 40.0191) in the MCP. 

Design standards are based on applicable standards of engineering design generally accepted 
by the profession, materials and product standards and minimum design standards in related 
regulations, policy and guidance. 

8.1 Site-Specific Remedial Action Goals 

The overall goal of the selected remedial action alternative is to achieve a Permanent Solution for 
the sediment portion of the Site. This will be accomplished by eliminating significant risk to benthic 


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organisms associated with exposure to contaminated sediment at concentrations which exceed 
benchmarks or local conditions. 

Sediment remediation will be accomplished through the dredging and capping or capping of 
contaminated sediments. Dredged materials will be transported off-site for reuse or disposal. 
These remedial actions will address sediment contamination associated with Site-related metal 
contamination (arsenic, lead, mercury and vanadium) as well as non-Site contamination (other 
metals, petroleum hydrocarbons, PAHs, and PCBs). 

Successful implementation and completion of the remedial action will be achieved when a clean 
surficial sediment layer (within the top 18 inches) is present across the area which poses a 
significant risk. Post-remediation monitoring (primarily topographic and bathymetric surveys) will 
be used to assess the stability of the cap following completion of cap placement. A Permanent 
Solution with Conditions will be achieved following the implementation of an AUL to memorialize 
the limits of the capped area and post-construction operation, maintenance and monitoring 
requirements. 

8.2 Significant Changes or New Information Related to Disposal Site Conditions 

A geotechnical investigation and evaluation was required for final design of the sediment 
remediation to confirm the applicability of the capping system, the structural integrity of the deeper 
sediments, and structural stability of the bulkhead during and after dredging and cap installation. 
In order to evaluate the strength of the sediments, a total of 14 sediment cores were collected for 
geotechnical testing (field and lab). 

The following core depths were collected: 

3 cores to 3 feet below the sediment surface (GZ-114, GZ-119, and GZ-134) 

5 cores to 20 feet below the sediment surface (GZ-2, GZ-6, GZ-12, GZ-17, and GZ-108) 

6 cores to 5 feet below the sediment surface (GZ-122, GZ-129, GZ-205, GZ-211, GZ- 
215 and GZ-226) 

These locations are shown in the geotechnical design memo included in Appendix B. 

Sediment cores were collected by TG&B Marine Services, Inc. (TG&B) of Bourne, MA. Sediment 
samples were collected using a vibracore sampler mounted on a boat outfitted with a GPS unit. 
The boat navigated to the predetermined locations shown in Figure 2 for sample collection. A 
three-inch outer diameter steel sampler was loaded with a dedicated hard plastic or polycarbonate 
liner and fitted with a driving shoe. The sampler was then advanced from the sediment surface 
to the desired depth using either the weight of the corer or the vibration from the vibracore head 
causing the sediment sample to fill the liner. Undisturbed sample cores were delivered to AMEC 
for visual characterization and sample collection. Samples were characterized using the Modified 
Burmeister Classification System with Unified Soil Classification System (USCS) codes assigned 
to each distinct stratigraphic unit. Field shear strength testing by ASTM D4648 using a calibrated 
mini-vane device was then performed on undisturbed cores. 

Select portions of four of the cores were sent for laboratory testing including index testing and 
consolidation: 

Incremental Consolidation (method B) - ASTM D2435 


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Density (Unit Weight) - ASTM D2937 

Moisture Content - ASTM D2216 

Specific Gravity - ASTM D854 

Atterberg Limits - ASTM D4318 

Grain Size Analysis with Hydrometer - ASTM D422 

Geotechnical analyses described in Appendix B include bearing capacity, consolidation and 
sediment cap mixing. Based on these analyses and the design cap materials, the bearing 
capacity and anticipated settlement from consolidation of the soft cap subgrade sediments 
should not damage the cap or cause significant sloughing during construction or after the cap 
has been constructed. Based on the sediment-cap mixing calculations, it is estimated that 
approximately 2 inches of material (or more) may mix into the soft sediments in the main 
channel, 4 to 6 inches in the Navigational Dredge Area and minimal (<1 inch) mixing will occur 
in the tidal flats. 

The design incorporates limitations on the thickness of cap layers which can be placed at any 
one time to reduce mixing. Placing large quantities of material at one time will not be allowed. 
The performance objective for the capping is the achievement of an 18-inch thick clean zone, 
excluding any mixing which may occur. As described in more detail in subsequent sections and 
the specifications, cap thickness will be determined by pre- and post-capping surveys with 
verification by cores, pans, or other methods if necessary. 

8.3 Site Maps Showing Existing Features and Proposed Locations of Activities 

Existing Site features including the limit of work, demolition, dredge/cap and cap areas, and 
previously completed shoreline features are shown on the Construction Drawings included in 
Appendix C. Existing site features are shown on Drawing C-101. The demolition work is shown 
on Drawing C-102. The location of the proposed remedial action including dredging and capping 
and environmental controls are shown on Drawings C-103 and C-104. Cross sections showing 
the proposed depths of dredging and final surface elevations are shown on Drawings C-105 and 
C-106. Construction related details are included on Drawings C-501 and C-502. 

8.4 Environmental Media to be Treated/Managed 

Environmental media to be treated and/or managed as part of the remedy include contaminated 
sediment within the intertidal and subtidal portions of an embayment of the Mystic River and water 
which drains from the sediment following dredging (effluent). 

The dredged sediment will be transferred into a hopper barge or scow. The rubber seals and 
overlapping sides of the environmental dredge bucket will minimize the quantity of sediment that 
will flow into the water column when the dredged sediment is conveyed into the accompanying 
collection barge or scow. Once the material is loaded into the receiving vessel, the contractor will 
have the option to decant water at the Site or to decant the effluent once the material has reached 
the contractor's offloading facility. 

It is anticipated that the contractor will decant the free water from the sediment in the scow within 
a turbidity curtain within the limit of work. Scows typically have a sump pit in the corner to facilitate 


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decanting/dewatering of sediment. Depending on the scow size and set-up, decant water will be 
pumped from the sump through a geotextile liner placed in the scow, or using a screened suction 
hose to minimize passing of solids. 

Effluent will be tested for turbidity using a portable multiparameter water quality meter (such as 
an YSI 6920). Should turbidity field results exceed the background (upstream) sample by a 
predetermined action level, then the effluent decanted into the settling tank/holding barge will be 
subjected to longer settling times or run through a filter fabric screen into a secondary settling 
tank as needed, and tested again, prior to discharge. 

8.5 Conceptual Plan of Activities, Treatment Units, Facilities, and Processes 

The conceptual plan for the selected remedial action alternative, Alternative 2 - Partial Dredge 
and Cap, includes: 

► Barge demolition and debris removal, 

► Dredging, 

► Dewatering, stabilization and off-load of dredged material, 

► Capping, 

► Monitoring and maintenance, and 

► Regulatory closure. 

The following sections describe the refined design of Alternative 2 as outlined in Section 5.2.2 as 
selected to address the areas, media, and constituents of concern identified in Section 3. 

8.6 Relevant Design and Operating Parameters 

The MCP requires that the following information be included in the RIP: 

► Design criteria, assumptions and calculations; 

Expected treatment, destruction, immobilization or containment efficiencies and 
documentation of how that degree of effectiveness was determined; and 

Demonstration that the selected remedial action alternative will achieve the identified 
remedial goals. 

The following sections discuss the relevant design and operating parameters for the major 
components of the proposed remedy. 

8.6.1 Barge Demolition and Debris Management 

Barge demolition and debris removal are required for construction but are not in and of themselves 
remedial actions. 

Debris from the barge demolition is likely to include asphalt, brick, and concrete (ABC), granite 
blocks, sheet metal and wood. Barge demolition may also include asbestos containing material 
(ACM). All demolition debris will be segregated and directly loaded into barges or trucks and 
transported to an off-site facility for proper recycling or disposal. 


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Any solid material identified within the dredge area that does not pass through a grid opening of 
24 inches by 24 inches square will also be considered debris. Anticipated debris encountered 
during dredging may include, but not be limited to: timber piles, granite blocks, concrete, brick, 
plastics, tires, wire/cable/chain, sheet metal, anchors, wood debris, and other miscellaneous 
materials. 

Debris that is removed from the dredge area will be decontaminated on a barge located within 
the limits of work and will then be transported to an off-Site location for off-loading and 
transportation to a disposal facility. Decontamination water will be collected and treated as 
described in Section 7.6.3. 

Debris from the barge demolition and encountered during dredging will be segregated into 
categories such as non-impacted ABC; non-hazardous waste landfill material (e.g., impacted 
ABC, impacted PPE, used adsorptive pads, booms, and other containment materials and 
equipment, used polyethylene sheeting, and spent particulate media filters); solid waste landfill 
material (e.g., general refuse, trash, unstained/untreated wood waste); metals; treated wood 
waste; and ACM. The anticipated quantities of debris to be removed from the Site have not been 
calculated as the barges are unsafe for inspection. Prior to mobilization for demolition, the 
contractor shall perform a pre-demolition survey of the barges as well as conduct a debris survey 
of the dredge area to quantify the potential amount of debris to be removed from the Site. 

8.6.2 Sediment Dredging 

Mechanical dredging is proposed for the portion of the Remediation Area to be dredged. 
Proposed dredge depths are anticipated to be approximately 18 inches below the existing mudline 
or the previously permitted navigation dredge elevation of -15 NAVD88 with an anticipated 
overdredge allowance of up to six inches. 

Sediment will be dredged using an excavator or crane equipped with an environmental clam shell 
bucket. The bucket will be lowered through the water column to the bottom. The bucket will close 
around the bottom sediment and the operator will be notified by a signal that the bucket is sealed. 
If the bucket does not seal, then the operator will investigate for obstructions and take appropriate 
action to allow the bucket to seal before raising it through the water column. This type of operation 
will result in a reduction in the amount of turbidity during construction as compared to a standard 
bucket. The dredged material will be transferred into a hopper barge or scow. 

The area proposed for dredging is separated into two distinct dredge areas: 

► Dredge (elevation based) - proposed dredge to elevation -16.5 NAVD88 

► Dredge (depth based) - proposed dredge to 1.5 feet below existing mudline 

These two dredge areas equal approximately 4.3 acres (2.2 acres in the main part of the 
embayment and 2.1 acres in the intertidal area). Note that the total area to be dredged has differs 
from that in Alternative 2 - Partial Dredge and Cap (described in Section 6 of this report) by 1) 
squaring off the dredging area to be more constructable and 2) excluding additional portions of 
the Remediation Area which are being addressed from land. 

In the elevation based dredge area, sediment will be removed to elevation -16.5 NAVD88 to allow 
for sufficient depth for navigational purposes after capping (approximately 16,530 CY). This 


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includes targeted dredging of up to 12 inches in certain areas of the deeper channel to achieve a 
final capped elevation of -15 NAVD88. In the depth based dredge area, remedial dredging will 
generally be performed to a depth of 18 inches below existing mudline (approximately 7,580 CY). 
Including a six-inch overdredge allowance the total estimated dredge volume to be removed is 
27,540 CY. Material quantities for the total projected dredge volume are summarized in Table 8- 
1 

Table 8-1: Estimated Sediment Dredging Volume 


Dredge Area 

Neatline Dredge (CY) 

6-Inch Overdredge (CY) 

Elevation Based Dredge 
(Elevation -16.5 NAV88) 

16,530 

1,335 

Depth Based Dredge 
(1.5 feet below mudline) 

7,580 

2,090 

Total Dredge 

24,110 

3,425 

Total with Overdredge 


27,540 


The dredging rate has been estimated at 300 CY/day using a 2 CY environmental bucket. 
Removal of 27,540 CY at 300 CY/day assuming a 12 hour shift will require approximately 92 
working days for sediment removal. Additional project time will be required for mobilization, 
demolition, capping and demobilization. 

8.6.3 Sediment Dewatering, Stabilization and Offload 

As described above, the dredged sediment will be transferred into a hopper barge or scow. Once 
the material is loaded into the receiving vessel, the contractor will have the option to decant water 
within the limit of work or to decant the effluent once the material has reached the contractor's 
offloading facility. It is anticipated that the contractor will decant the free water from the sediment 
in the scow within a turbidity curtain within the limit of work. Depending on the scow size and set¬ 
up, decant water will be pumped from the internal scow sump through a geotextile liner placed in 
the scow, or using a screened suction hose to minimize passing of solids. 

It is anticipated that the dewatered sediment will be transported to a local processing and receiving 
facility. An 8% Portland cement addition is proposed for additional dewatering at the processing 
facility to allow the sediment to meet the processing facilities requirements to be off-loaded and 
acceptable for transportation and disposal. 

The amended sediment will be off-loaded from the scow at a rate sufficient to maintain the 
production requirements and the approved project schedule. A drip apron will be utilized during 
the off-loading process to prevent sediment from entering the surrounding water. The Contractor 
will manage construction water from the dredged material dewatering process; runoff collected 
from the drip apron and sediment transport scows; and water from other water-generating 
activities conducted. This water will be collected, treated, and discharged in accordance with all 
permits and specifications. 


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8.6.4 Capping 


Once dredging has been completed, clean cap materials will be placed to restore the dredged 
areas to pre-construction elevations or the previously permitted elevation -15 NAVD88. In the 
portion to be capped only, 18 inches of clean cap material will be placed directly on the underlying 
sediment. The primary function of the cap material is to provide a clean substrate suitable as 
habitat for benthic organisms. 

Sand is anticipated to be the primary component of the cap throughout. However, the specific 
nature of the material to be placed is influenced by the physical location of the cap and regulatory 
requirements covering those areas. The Remediation Area has been broken into three distinct 
capping areas/types: 

Navigation Subtidal Cap - a 2-layer cap composed of a layer of coarse sand capped 
with a medium gravel material to resist propeller induced erosion (see propeller wash 
technical memo in Appendix B). 

Subtidal Cap - capped with a coarse sand material for stability and to resist propeller 
induced erosion in the channel. 

Intertidal Cap - capped with a silty sand to match existing material. 

The total capping area is approximately 7.26 acres (5.17 acres in the main part of the embayment 
and 2.09 acres in the intertidal area). As with the dredging area, the total capping area differs 
from that that in Alternative 2 - Partial Dredge and Cap (described in Section 6 of this report) by 
1) squaring off the area to be more constructable and 2) excluding a portion of the Remediation 
Area which is being addressed from land. The cap in the Navigation Dredge Area will be 
composed of medium gravel and sand (approximately 2,770 CY total). In the other subtidal areas, 
the cap material will be coarse sand (approximately 9,665 CY). For cap placement within the 
intertidal areas, 1.5 feet of silty sand material (6,735 CY) will be placed to restore the existing tidal 
mud flats to original condition. The cap quantities above do not include an overplacement 
allowance of two inches. Including the overplacement allowance, the total cap volume is 
approximately 21,120 CY. The quantities for the total projected cap volume are summarized in 
Table 8-2 


Table 8-2: Estimated Sediment Capping Volume 


Cap Areas 

1.5 Foot Cap (CY) 

-+2-lnch Overplacement (CY) 

Navigation Subtidal Cap 

2,770 

310 

Subtidal Cap 

9,665 

1,080 

Intertidal Cap 

6,735 

560 

Total 

19,170 

1,950 

Total with Over-placement 


21,120 


Adjacent to the existing BWSC outfall in the southern corner of the tidal flats, a stone outlet 
protection structure will be installed to protect the installed cap from erosion. Based on the 


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dimension of the pipe, assumed slope, and calculated discharge velocity, the stone outlet 
protection is proposed to be 34 feet long and 15 feet wide at its widest point. A geotextile filter 
fabric will be placed in this portion of the dredge area to prevent migration of the fine soil 
particles through voids in the armor stone and distribute the weight of the stone to prevent 
settlement of the stone into the underlying sediments. The median stone size will be 8-inch 
diameter (50% of the stone will be greater than 8-inches) to be placed at an average thickness 
of two feet. The total volume of stone is estimated to be approximately 20 CY. 

There are several viable methods for placing the cap in the subtidal and intertidal areas. The 
means and methods to be used will be identified by the contractor once the job is bid and 
contracted. However, potential methods for placement of the cap are discussed below. 

One method for placing the cap in the subtidal areas consists of essentially reversing the dredge 
operation, using the same equipment as was used during the dredging operations. The equipment 
would be decontaminated after the completion of dredging operations. The silty sand, coarse 
sand, gravel, or other material would be imported, likely on a material barge from the transfer 
facility. The material barge would then be maneuvered to the capping location. When the material 
barge is tied off to the work barge, the excavator or crane would lower the environmental bucket 
to the required depth and slowly spreads the sand over the previously dredged area. Use of tremie 
pipe to direct material from a floating barge through the water column or thin-layer placement 
through the water column (by way of measured placement at the water surface which is allowed 
to settle through the water column) may also be employed. 

In the intertidal, the cap material will be slowly placed into the surveyed excavation in lifts and 
graded to the design thickness. In the event that backfilling activities cannot be completed during 
one low tide period, the leading dredge face (excavation face) may be covered with a temporary 
plastic membrane and secured with sandbags/backfill material until the next tidal cycle that 
permits work to resume. 

8.6.5 Demonstration of Achievement of Remedial Goals 

The initial limits of proposed sediment dredging and capping are defined within the Revised Phase 
II Report (AMEC 2014b). The limits of dredging and capping as defined in this Phase III 
RAP/Phase IV RIP follow those initial limits of impacts and have been redefined for 
constructability purposes. 

As previously noted, the performance objective for is the achievement of an 18-inch thick clean 
zone, excluding any mixing which may occur. Bathymetric surveys and sediment coring will be 
used to verify the in-place cap thickness to determine the final vertical elevation of capping 
material placed. The horizontal and vertical limits will be surveyed by the Contractor prior to the 
start of work for comparison and demonstration that the remedial goals are achieved. Monitoring 
of the stability of the cap is discussed in detail in the OMM Plan in Appendix E. 

8.7 Design Features for Control of Spills/Discharges 

Monitoring will be conducted throughout the work to document compliance with criteria 
established by the bid specifications, including acceptable VOC and dust levels described in 
Specification Section 01 35 43 - Environmental Procedures. In addition, in-water turbidity 
monitoring will be conducted for compliance with the requirements of the Water Quality Certificate 


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and Specification Section 01 57 30 - Marine Resuspension Control. A Waste Management Plan 
(WMP), and Environmental Control Plan (ECP) will be prepared by the contractor prior to 
construction and will be implemented during remediation activities. 

Actions to control, minimize, and/or eliminate the risk of an accidental spill or discharge of oil, 
hazardous or sediment materials have been incorporated into the Specifications, and include the 
following: 

The stand-alone permeable turbidity curtain with flotation collar or equivalent with 
reefing lines and billow controls as shown on the 60% Issued for Permitting package 
of Drawings (Drawings) in Appendix C and described in the 60% Issued for Permitting 
package of the Specifications (Specifications) in Appendix D. 

A secondary oil containment boom as described in the Specifications. 

Sorbent booms and pads as described in the Specifications. 

8.8 Management/Disposal of Treatment Residuals, Contaminated Soils and Other Waste 
Materials 

A pre-characterization sampling program may be implemented by Wynn or the selected contractor 
within the proposed dredge areas to characterize and profile the dredged material prior to 
processing, transportation and off-site recycling or disposal. If not pre-characterized, dredged 
and dewatered/stabilized sediments will be sampled in barges or in stockpiles to determine the 
appropriate facility for disposal. Waste characterization samples will be collected in-situ based on 
the total volume of impacted sediments and requirements established by the waste disposal 
facilities. The following parameters will be tested for at an anticipated frequency of one sample 
per 500 tons of sediment: 

MCP 14 metals by USEPA Method 6020A/7471B 

Total VOCs by USEPA Method 8260C; 

Total SVOCs (including pyridine) by USEPA Method 8270; 

Total PCBs by USEPA Method 8082A; 

Total pesticides/herbicides (including toxaphene) by USEPA Methods 8081 A/8151 A; 

► Total Petroleum Hydrocarbons by USEPA Method 815C; 

► Toxicity Characteristic Leaching Procedure (TCLP) for metals, VOCs, SVOCs and 
pesticides/herbicides; 

► Specific Conductance by USEPA Method 9050; 

► Reactive Cyanide/Sulfide by USEPA Method 7.3; 

► Corrosivity (pH) by USEPA Method 9045; and 

► Ignitability by USEPA Method 1030. 

The characterization waste results will be reported in ether a Phase IV Status Report or the Phase 
IV Final Inspection Report, along with the total volume of sediment transported for off-site 
recycling and disposal. 


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Sediment that meets criteria defining a listed hazardous waste or is a characteristic hazardous 
waste will be transported off-site for disposal using a Uniform Hazardous Waste Manifest. 
Sediment that is not classified as a hazardous or characteristic waste will be managed using the 
MassDEP Bill of Lading (BOL) process for contaminated media. The BOL includes the Licensed 
Site Professional (LSP) Opinion rendered in accordance with 310 CMR 40.0030. 

The contractor will also be required to manage construction water from the dredged material 
dewatering process; runoff collected from the drip apron and sediment transport scows; and water 
from other water-generating activities conducted. This water will be collected, treated, and 
discharged in accordance with all permits and specifications and as discussed in Section 7.6.3 
above. 

8.9 Disposal Site Characteristics Affected by the Proposed Construction 

8.9.1 Existing Site Activities or Operations 

Currently there are no active operations in the sediment remediation area of the waterway. The 
upland portions of the Site are very active, however access is restricted for this sediment 
remediation work and shall not interfere. 

8.9.2 Natural Resource Areas, Local Planning and Development Issues 

The remediation efforts will result in removal of impacted sediment from the proposed dredge 
areas and replacement with a clean cap material within both the dredging and capping portions 
of the Site. The capping material will generally create a restored habitat for benthic organisms. 

8.9.2.1 Short Term Impacts to Local Infrastructure 

The primary short-term impact to local infrastructure is associated with the transport of equipment 
and materials to and from the Site. As described earlier, the upland portions of the Site are 
generally not accessible for the remediation. Therefore the shipment of the majority of equipment 
and waste via barge instead of by land will greatly reduce anticipated impacts to local roadways 
during the project. There may be some limited impacts during the barge removals which may be 
conducted from land. With the majority of the construction access by water, the project will have 
short-term impacts on waterways associated with dredging and capping activities and the 
concurrent barge or scow transportation of dredged sediments and cap materials. 

8.9.2.2 Long Term Impacts to Local Infrastructure 

The long-term impacts to natural resource areas and local infrastructure are anticipated to be 
positive. Currently, the Site has five abandoned barges and impacts to the sediment restricting 
benthic habitat. Following remediation, the area will be restored to provide waterfront views and 
for visitors. The project is also being coordinated with efforts to install a new floating dock system 
to provide upgraded landing facilities. Within the embayment, commercial and private boaters 
will benefit from increased water depth within the navigation channel following the completion of 
the project. Natural resource areas will be restored with material that will provide significantly 
improved habitat for benthic organisms. 


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8.10 Measures to Protect Environmental Receptors and Natural Resource Areas 

The environmental controls proposed for the Site to protect the environmental receptors and 
natural resources areas are those already described in Section 7 above and also in the 
Specifications included in Appendix D. 


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9.0 CONSTRUCTION PLANS AND TECHNICAL SPECIFICATIONS (310 CMR 40.0874(3)(c)) 


9.1 Plans, Specifications, and Procedures 

Appendix C provides the 60% Issued for Permitting package of Drawings that were generated to 
support this combined Phase III RAP/Phase IV RIP. Similarly, Appendix D provides the 60% 
Issued for Permitting package of the Specifications that were developed. The Specifications 
selected for inclusion in this Phase III RAP/Phase IV RIP are those that most directly pertain to 
the implementation of the remedy, including the performance of key tasks such as demolition, 
dredging and backfill, and management and disposal of dredged materials; related inspections 
and monitoring requirements; and essential procedures including health and safety protocols, 
environmental protocols, security procedures, and installation and maintenance of erosion and 
sedimentation controls and marine resuspension controls. 

Revisions to the Drawings and Specifications may be implemented during the final design process 
and/or proposed by the selected contractor during procurement. If these design or 
implementation changes are deemed appropriate by the project engineers, these modifications 
will be documented in the Phase IV Final Inspection Report. If significant modifications are 
necessary, then an As-Built Construction Report will be submitted to MassDEP documenting 
those changes. 

9.2 Construction Schedule 

The current design and procurement schedule is as follows: 

90% Design and Issue for Bid - June 6, 2017 

Contractor Bids due - June 30, 2017 

Contractor Award and Notice to Proceed - July 28, 2017 

Contractor Mobilization / Begin In-Water Work - September 30, 2017 

Construction is planned to occur over one construction season starting in September 2017. The 
following restrictions are anticipated to apply to this project schedule: 

Silt-producing in-water work will be subject to time of year (TOY) restrictions 
established by DMF, which restricts activities between February 15 and June 30 to 
avoid effects on winter flounder (Pseudopleuronectus americanus ) spawning 
activities. 

Silt-producing in-water work will be subject to TOY restrictions established by USACE, 
which restricts activities between February 15 and September 30 to avoid effects on 
shellfish and diadromous fish spawning activities. 

The primary silt-producing activities during this project will include the barge demolition and debris 
removal, dredging of sediments, and cap installation. To comply with TOY restrictions, the project 
schedule calls for the project to begin on September 30, 2017 and be substantially completed by 
February 15, 2018. Every effort will be made to coordinate and expedite activities such that in¬ 
water work is completed prior to February 15; however, a variance from TOY restrictions may be 
requested to allow for the completion of remaining work in some localized sections of the work. 


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BMPs and environmental controls will be used throughout the remediation work to limit adverse 
impacts to environmental receptors. 


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10.0 OPERATION, MAINTENANCE, AND MONITORING (310 CMR 40.0874(3)(d)) 


The MCP requires that an OMM Plan be developed and included in the RIP when such activities 
are required to ensure the effective performance and integrity of the remedial action and/or the 
achievement of remedial goals. 

A draft OMM Plan has been developed to address the inspection, maintenance and monitoring of 
the capping system installed as part of the remedial action implementation. The draft OMM Plan 
is included in Appendix E and includes routine OMM activities such as visual inspections, 
bathymetric and topographic surveys. 

The primary objective of the OMM Plan is to assess the integrity of the cap after installation. The 
Specifications provide details on materials to be used, testing required to verify proper materials 
are used, tolerances for placement, and methods to be used to verify proper material thicknesses 
and characteristics are actually placed. After installation, the OMM Plan will: 

Verify the presence and physical integrity of the cap material. 

Provide for repairs and maintenance to the cap(s) if monitoring efforts indicate that such 
activities are necessary. 

Physical monitoring of the cap will be performed to verify the presence and stability of the cap 
material. Bathymetric and topographic surveys will be conducted upon the completion of the 
remediation to establish “as-built” conditions, as required by the Specifications. The results of this 
survey will establish baseline post-construction conditions for comparison to information collected 
during long-term monitoring of the OMM Plan. 

Bathymetric and topographic surveys will be performed periodically to monitor the elevation of the 
sediment cap surface within the remediation area. A summary of the proposed monitoring 
program frequency is provided in Table 10-1 below. 


Table 10-1: Proposed Monitoring Program Frequency 


Data Collection 

Schedule 

Schedule 

Schedule 

Program 

(Years 1-5) 

(Years 6-11) 

(Years 12+) 

Bathymetric and 
Topographic 
Survey 

Annual 
(5 surveys) 

Biennial 
(3 surveys) 

Every 5 Years 


Surveys will be conducted in a manner that will provide resolution and accuracy consistent with 
the procedures followed to perform the “as-built” survey. Specifications for topographic and 
bathymetric surveying, including the development of a Survey Work Plan (to be prepared by the 
remediation contractor and submitted for approval), are presented in the Specifications and 
Contract Drawings. The methodology specified in the Survey Work Plan to perform the as-built 
survey (or equivalent) will be used to perform the OMM surveys. 

Sediment cores will be collected in place of bathymetric and topographic surveys if future in-water 
use at the Site interferes with the ability to obtain bathymetric and topographic surveys. Sediment 
cores may also be collected to assess whether changes in cap elevation are due to erosion, 
subsidence, or compaction. Cores will be progressed via push or vibratory methods to a depth 


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sufficient to obtain both cap material and native sediment based on final as-built cap thickness or 
the most recent survey data, as applicable. A minimum of 80% recovery is required to consider 
the core acceptable for comparison. The core will be split and layers measured to verify cap 
thickness. 

In the event that the bathymetric or topographic surveys identify areas where the sediment 
elevation is significantly different from the post-construction elevation (or the most recent survey), 
then additional data will be collected (e.g., re-survey, sediment cores, underwater video 
surveying, or diver survey) and response actions will be taken, as appropriate, to repair or 
enhance the cap. 

If the periodic surveys indicate the cap thickness criteria are not met, but inspection results 
indicate that substrate settlement has occurred rather than loss of cap thickness, such settlement 
would not trigger maintenance activities. The settled surface elevations would serve as the new 
baseline for future monitoring comparisons. If results indicate loss of cap thickness, one of the 
following response actions would be conducted: 

Repair the area where unacceptable loss of material was observed through addition of 
material to the cap area. 

Increase armoring in the area where unacceptable loss was observed with larger 
material type or a thicker layer of material, and consider similar changes in areas that 
may be susceptible to similar damage in the future. 


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11.0 HEALTH AND SAFETY PLAN (310 CMR 40.0874(3)(e)) 


The Health and Safety Plan (HASP) for the remediation program is provided in Appendix F. The 
HASP addresses activities that AMEC personnel may conduct during the implementation and 
construction of the selected remedial alternative as described in this Phase III RAP/Phase IV RIP. 
Compliance with the HASP is required of all personnel involved with this remediation program. 
However, the HASP is not intended to and may not address the activity-specific health and safety 
needs or requirements of any contractors and their employees and therefore cannot be used as 
the sole HASP document by contractors or their personnel. As required by the Occupational 
Safety and Health Administration (OSHA), contractors must provide applicable job hazard 
analyses for each task/activity they will perform during remediation. 

The remediation HASP may be revised to incorporate additional or updated information made 
available to health, safety, and environmental (HSE) personnel. This information may include 
monitoring results, changes in remediation activities or equipment, etc. Any changes proposed 
must be reviewed by HSE staff and are subject to approval by the HSE Manager and the Project 
Manager. Approved HASP changes will be communicated to all affected on-site personnel. 


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12.0 PERMITS, LICENSES, AND/OR APPROVALS (310 CMR 40.0874(3)(f)) 


Construction and implementation of the selected Remedial Action Alternative primarily consists 
of demolition, dredging and capping. These activities require federal, state, and local permits 
and/or approvals as outlined below. Inspection, sampling and analysis requirements for permits 
are included in the actual permits. 

Permits that have already been obtained by Wynn include: 

Massachusetts Environmental Protection Act (MEPA) - Notice of Project Change 
(Remediation) 

MEPA - Multiple Filings (Resort and Navigational Dredging, including removal of sunken 
barge) 

Massachusetts Wetlands Protection Act (WPA) Notice of Intent (NOIs) for resort project 
(Everett) - Order of Conditions (Navigational Dredging, including sunken barge removal) 

Massachusetts Department of Environmental Protection (MassDEP) Combined 401 
Water Quality Certification (Navigational Dredging, including sunken barge removal) 

MassDEP Waterways - Chapter 91 License (Resort and Navigational Dredging, 
including sunken barge removal) 

USACE Clean Water Act (CWA) Section 404 Individual Permit (Resort and Navigational 
Dredging, including sunken barge removal) 

Permit applications that are in process or have been submitted by Wynn include: 

Massachusetts WPA Notices of Intent (NOIs) for remediation (Boston and Everett) 
(Remediation) 

MassDEP Combined 401 Water Quality Certification (Remediation) 

MassDEP Waterways - Chapter 91 License (Remediation) 

USACE CWA Section 404 Individual Permit Modification (Remediation) 


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13.0 PROPERTY ACCESS ISSUES (310 CMR 40.0874(3)(g)) 


The property is currently an active construction site for the Wynn Boston Harbor project. A small 
portion of the eastern upland area adjacent to the abandoned barges may be available for use 
during the demolition portion of the work. It is not anticipated that there will be landside access 
at the Disposal Site during sediment dredging and capping. Therefore, all work performed during 
the remediation will be completed by using water access. 

The current upland construction project requires all workers to attend a safety training course for 
access to the construction site. If upland access is allowed for the barge demolition, this training 
will be required for workers who may perform work from the uplands. 


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r 

















14.0 REFERENCES 


AMEC Massachusetts, Inc. (AMEC), 2016a. Letter to MassDEP dated September 29, 2016. 
“Subject: Supplemental Phase II Comprehensive Site Assessment, Former Everett 
Staging Yard, Water-side, 1 Horizon Way; Everett, MA, RTN 3-0013341.” Included in 
Wynn, 2016. 

AMEC, 2016b. Revised Supplemental Phase II Comprehensive Site Assessment, Sediments 
Adjacent to the Former Everett Staging Yard, 1 Horizon Way, Everett, Massachusetts, 
Release Tracking Number 3-13341. December 29, 2016. 

Consulting Engineers & Scientists, Inc. (CES), 1997. Phase I Initial Site Investigation Report, 
Alford Street, Everett, Massachusetts. January 15, 1997. 

GEI Consultants, Inc. (GEI), 2010. Eligible Person Certification and Revised Tier Classification 
Submittal, Alford Street, Everett, MA, DEP RTN 3-13341. February 9, 2010. 

GEI, 2012. MassDEP RTN 3-13341, Phase II Comprehensive Site Assessment, Everett Staging 
Yard, 1 Horizon Way, Everett, Massachusetts. February 10, 2012. 

GZA GeoEnvironmental (GZA), 2015a. Eligible Person Submittal and Tier II Classification 
Submittal, (Former) Everett Staging Yard, 1 Horizon Way, Everett, Massachusetts, 
Release Tracking Number 3-13341. February 5, 2015. 

GZA, 2015b. Supplemental Phase II Comprehensive Site Assessment, Former Everett Staging 
Yard, Water-Side, Everett, Massachusetts, Release Tracking Number 3-13341. 
December 2015. 

GZA, 2016a. Email communication from Lawrence Feldman (GZA) to Eric Worrall (MassDEP) 
dated June 16, 2016. ’’Subject: Wynn sediment CSM.” 

MassDEP, 2014a. 310 CMR 40.0000, Massachusetts Contingency Plan (MCP). Bureau of Waste 
Site Cleanup. Boston, Massachusetts. April 25, 2014. 

MassDEP, 2014b. Letter to Paul Feldman, Esq. (Davis, Malm & D’Agostine, P.C.) dated June 10, 
2014. “RE: FBT Everett Realty, LLC, 1 Horizon Way, Everett, MassDEP File No. ACO- 
NE-14-3R004, MassDEP Release Tracking No. 3-13341. Includes copy of signed 
Administrative Consent Order between FBT Everett Realty, LLC and MassDEP. 

MassDEP, 2015a. Letter addressed to Wynn, MA LLC c/o Mintz, Levin, Cohn, Ferris, Glovsky & 
Popeo, PC dated February 24, 2015. “RE: Everett, Everett Staging Yard, 1 Horizon Way, 
RTN 3-133341, Notice of Responsibility/Establishment of Interim Deadlines.” 

MassDEP, 2016a. Letter from MassDEP to Wynn MA, LLC dated January 22, 2016. “Re: 
Combined 401 Water Quality Certification, BRP WW07, Major Project Dredging, BRP WW 
10, Major Excavation/Fill, At: Mystic River, Everett, 401 WQC Transmittal No. X266062, 
Wetlands File No. 22-0098, ACoE Application No. NAE-2013-1023.” 

MassDEP, 2016b. April 22, 2016 Memorandum from Greg Braun (MassDEP) to Andrew Clark 
(MassDEP) entitled “December 2015 Supplemental Phase II Comprehensive Site 
Assessment.” Included with MassDEP letter to Wynn, MA LLC dated May 12, 2016. 


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MassDEP, 2016c. Letter addressed to Wynn, MA LLC dated May 12, 2016. “RE: EVERETT, 1 
Horizon Way, RTN 3-13341, Review of Supplemental Phase II Comprehensive Site 
Assessment; Establishment of Interim Deadline; Extension of Interim Deadline”. Includes 
April 22, 2016 Memorandum from Greg Braun (MassDEP, 2016b). 

MassDEP, 2016d. Email communication from Stephen Johnson (MassDEP) to Lawrence 
Feldman (GZA GeoEnvironmental) dated July 28, 2016. “Subject: Wynn Everett 
Sediments”. 

MassDEP, 2016e. Email communication from John Fitzgerald (MassDEP) to Matthew Grove 
(AMEC) dated November 18, 2016. “Subject: Wynn sediment meeting - key points”. 

Massachusetts Department of Public Health (DPH), Freshwater Consumption Advisory for 
Marine and Freshwater Bodies. Available online at: 

http://www.mass.gov/eohhs/docs/dph/environmental/exposure/statewide-fish-advisory- 

poster.pdf 

Menzie-Cura Associates, Inc. (MCA). 2006. Stage I & II Environmental Risk Characterization, 
Everett Staging Area, Alford Street, Everett, MA, RTN 3-13341. December 19, 2006. 

Tetra Tech Rizzo, 2007. Phase II - Comprehensive Site Assessment, Everett Staging Yard, 
Chemical Lane, Everett, Massachusetts, DEP RTN 3-13341. December 26, 2007. 

United States Environmental Protection Agency (USEPA), 2015. Determination of the Biologically 
Relevant Sampling Depth for Terrestrial and Aquatic Ecological Risk Assessments (Final 
Report). U.S. Environmental Protection Agency, Ecological Risk Assessment Support 
Center, Cincinnati, OH, EPA/600/R-15/176, 2015. 

Wynn MA, LLC (Wynn), 2016. Letter addressed to MassDEP dated September 30, 2016. “Re: 
Wynn Boston Harbor (Former Everett Staging Yard), Review of Supplemental Phase II 
Comprehensive Site Assessment.” Includes AMEC memo dated September 29, 2016 and 
GZA memo dated September 30, 2016. 


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I 
















TABLES 












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Table 4-1 

Stage I Ecological Screening - Benchmark Comparison 
Sediments Adjacent to the Former Everett Staging Yard 

RTN 3-13341 


h 


Parameter (mg/kg) [a] 

Maximum Detected 
Concentration [b] 

Ecological Sediment 
Screening Benchmark 

Source [c] 

Is Max > 
Benchmark? [d] 

PCBs 





Total PCBs 

3.4 

0.18 

ER-M 

Yes 

SVOCs 





Bis(2-ethylhexyl)phthalate 

131 

3.1 

WA AET 

Yes 

Di-n-octylphthalate 

7.9 

6.2 

WA AET 

Yes 

Hexachlorobutadiene 

0.28 

0.12 

WA AET 

Yes 

PAHs 





2-Methylnaphthalene 

0.17 

0.67 

ER-M 

No 

Acenaphthene 

0.24 

0.5 

ER-M 

No 

Acenaphthylene 

0.65 

0.64 

ER-M 

Yes 

Anthracene 

0.97 

1.1 

ER-M 

No 

Benzo(a)anthracene 

1.9 

1.6 

ER-M 

Yes 

Benzo(a)pyrene 

2.0 

1.6 

ER-M 

Yes 

Benzo(b)fluoranthene 

3.2 

1.8 

WA AET 

Yes 

Benzo(k)fluoranthene 

1.2 

1.8 

WA AET 

No 

Benzo(g,h,i)perylene 

1.7 

0.67 

WA AET 

Yes 

Chrysene 

2.1 

2.8 

ER-M 

No 

Dibenzo(a,h)anthracene 

0.46 

0.26 

ER-M 

Yes 

Fluoranthene 

3.6 

5.1 

ER-M 

No 

Fluorene 

0.32 

0.54 

ER-M 

No 

lndeno(1,2,3-cd)pyrene 

1.9 

0.69 

WA AET 

Yes 

Naphthalene 

0.83 

2.1 

ER-M 

No 

Phenanthrene 

2.1 

1.5 

ER-M 

Yes 

Pyrene 

3.3 

2.6 

ER-M 

Yes 

Total PAHs 

22 

45 

ER-M 

No 

EPH 





C11-C12 Aromatics 

472 

— 

— 

— 

C9-C18 Aliphatics 

114 

— 

— 

— 

C19-C36 Aliphatics 

783 

— 

— 

— 

Total EPH 

1274 

— 

— 

— 

Metals 





Antimony 

2.5 

9.3 

NOAA Squirt 

No 

Arsenic 

182 

70 

ER-M 

Yes 

Barium 

190 

48 

NOAA Squirt 

Yes 

Beryllium 

1.5 

— 

— 

— 

Cadmium 

9.0 

9.6 

ER-M 

No 

Chromium 

169 

370 

ER-M 

No 

Lead 

1070 

218 

ER-M 

Yes 

Mercury 

2.5 

0.71 

ER-M 

Yes 

Nickel 

84 

51.6 

ER-M 

Yes 

Selenium 

53 

1 

NOAA Squirt 

Yes 

Silver 

5.1 

3.7 

ER-M 

Yes 

Vanadium 

354 

57 

NOAA Squirt 

Yes 

Zinc 

1230 

410 

ER-M 

Yes 


Created by: AMR 12/4/2016 
Checked by: SM 12/52016 


Page 1 of 2 




































































Stage I Ecological Screening - Benchmark Comparison 
Sediments Adjacent to the Former Everett Staging Yard 

RTN 3-13341 


Table 4-1 



foster 

wheeler 


Notes: 

[a] Only detected parameters are shown. 

[b] 0-6 inch sediment interval 

[c] Sources: 

ER-M: NOAA Effects Range - Median concentrations (Long et al ., 1995) 

WA AET -Washington State marine sediment apparent effects thresholds (AETs) (WAC 173-204, 2013) 

NOAA Squirt - NOAA Screening Quick References Tables (Buchman, 2008) 

[d] A maximum (max) detected concentration that is higher than the screening benchmark indicates a potentially significant expsoure 

-- Benchmark not available 
EPH - Extractable petroleum hydrocarbons 
PAHs - Polycyclic aromatic hydrocarbons 
PCBs - Polychlorinated biphenyls 

NOAA - National Oceanographic & Atmospheric Administration 
mg/kg - milligrams per kilogram 


Page 2 of 2 



Table 4-2 

Comparison of Local Conditions Values to Ecological Benchmarks 
Sediments Adjacent to the Former Everett Staging Yard 

RTN 3-13341 


3 


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Parameter 

75th Percentile 
[a] 

ER-M [b] 

Antimony 

<5 

9.3 

Arsenic 

19 

70 

Barium 

140 

co 

Beryllium 

0.9 

— 

Cadmium 

4 

9.6 

Chromium 

96 

370 

Lead 

430 

218 

Mercury 

0.979 

0.71 

Nickel 

37.5 

51.6 

Selenium 

<6.29 

1 

Silver 

2.1 

3.7 

Vanadium 

65 

57 

Zinc 

827 

410 

Total PAHs 

224 

45 

Total PCBs 

0.87 

0.18 

Bis(2-Ethylhexyl)phthalate 

32.6 

3.1 

C11-C22 

478 

— 

C19-C36 

1000 

— 

C9-C18 

<157 

— 


[a] For parameters with small data sets (Bis(2-Ethylhexyl)phthalate, C11-C22, C19-C36, and C-9-C18), 
the maximum value is presented. 

If ER-M is not avaialble, equivalent value is shown (see Table 4-1 for source). 

- ER-M or other benchmark not available 

< - Parameter indicated was not detected at the concentration shown. 




























































































































































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Table 4-3 

Stage II ERC Analysis 

Sediments Adjacent to the Former Everett Staging Yard 


RTN 3-13341 


[u. 


Parameter (mg/kg) [a] 

Maximum Detected 
Concentration [b] 

Measurement Endpoint 
Value 

Source [c] 

Is Max > 

Measurement 
Endpoint? [d] 

Metals 





Antimony 

2.5 

9.3 

NOAA Squirt 

No 

Arsenic 

182 

70 

ER-M 

Yes 

Barium 

190 

140 

LC 

Yes 

Beryllium 

1.5 

— 

— 

— 

Cadmium 

9.0 

9.6 

ER-M 

No 

Chromium 

169 

370 

ER-M 

No 

Lead 

1070 

430 

LC 

Yes 

Mercury 

2.5 

0.979 

LC 

Yes 

Nickel 

84 

51.6 

ER-M 

Yes 

Selenium 

53 

1 

NOAA Squirt 

Yes 

Silver 

5.1 

3.7 

ER-M 

Yes 

Vanadium 

354 

65 

LC 

Yes 

Zinc 

1230 

827 

LC 

Yes 

PAHs 





Total PAHs 

22 

224 

LC 

No 

SVOCs 





Bis(2-ethylhexyl)phthalate 

131 

32.6 

LC 

Yes 

PCBs 





Total PCBs 

3.4 

0.87 

LC 

Yes 

EPH 





Cl 1-Cl2 Aromatics 

472 

— 

— 

— 

C9-C18 Aliphatics 

114 

— 

— 

— 

C19-C36 Aliphatics 

783 

— 

- 

- 


Notes: 

[a] Only detected parameters are shown 

[b] 0-6 inch sediment interval 

[c] Sources: 

ER-M NOAA Effects Range - Median concentrations (Long et al ., 1995) 

WA AET - Washington State marine sediment apparent effects thresholds (AETs) (WAC 173-204, 2013) 

NOAA Squirt - NOAA Screening Quick References Tables (Buchman, 2008) 

LC = 75th percentile value from local conditions datasel 

[d] A maximum (max) detected concentration that is higher than the screening benchmark indicates a potentially significant expsoure 

— Benchmark not available 
EPH - Extractable petroleum hydrocarbons 
PAHs - Polycyclic aromatic hydrocarbons 
PCBs - Polychlorinated biphenyls 

NOAA - National Oceanographic & Atmospheric Administration 
mg/kg - milligrams per kilogram 


Page 1 of 1 























































































































































Table 6-1 

Initial Technology Screening 

Sediment Portion of Former Everett Staging Yard Disposal Site 

RTN 3-13341 




amec 
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Technology 

Description 

Advantages 

Disadvantages 

Relative 

Cost 

Can Achieve a Condition of 
No Significant Risk for 
Sediments? 

Retained for 
Further 
Evaluation? 

Rationale 

Monitored Natural 

Recovery (MNR) 

Monitoring of natural recovery 

processes which will bury 
contaminated sediment 
beneath clean sediment 
(sedimentation). 

• Not a disruptive process (no 

in water construction or 
landside processing). 

• Can naturally reduce current 
risks. 

• No disposal or waste 
stream. 

• Low capital cost. 

• Slow process. 

• Sedimentation rates may not be even 
across all areas. 

• Less predictable sedimentation processes 
in dynamic environments (tidal). 

• Long-term sampling and monitoring 
required to demonstrate effectiveness. 

• Contaminants remain in place. 

• Risk of re-exposure. 

Low 

Yes 

Yes for a 

portion of the 
Site 

• Minimal disruption to embayment and 
benthic community. 

• Could achieve Permanent Solution in 
areas where active sedimentation 

occurs. 

In Situ Treatment 
(Amendment) 

Placement of a substrate, such 
as activated carbon, to treat 
dissolved phase constituents 
that migrate from the sediment 
to surface water. 

• Treats dissolved phase 
constituents. 

• Flux of dissolved phase constituents to the 
embayment is not a concern at this Site. 

• Does not address risk to benthic 
organisms from direct contact with 
contaminated sediments. 

• Amended sediment may not be good 
substrate for benthic organisms. 

Moderate 

No 

No 

• Flux of dissolved phase constituents to 
the embayment is not a concern at this 

Site. 

• Does not address risk to benthic 

organisms. 

Enhanced Sediment 
Deposition 

Installation of structure(s) to 
alter flow dynamics and 
increase deposition of 
sediment on the bottom. 

• Deposited sediment would 
cover subtidal areas to 
mitigate and eventually 
eliminate risk to benthic 
organisms. 

• Would require placement of structures in 
embayment and possibly in channel which 
could pose a risk to navigation. 

• May not be approved by Army Corps of 
Engineers 

• Increasing sedimentation limits depth of 
embayment for navigation. 

• Could adversely affect benthic community. 

• Unlikely to be effective in intertidal areas. 

Moderate 

Yes 

No 

• Adversely affects uses of the 
embayment, and potentially the river, 

for navigation. 

• Could adversely affect benthic 
community. 

Mechanical 

Dredging 

Physical removal of 
contaminated sediment 
through the use of an 
excavator and bucket mounted 
on a barge. 

• Navigational dredging 
already permitted through 
mechanical dredging. 

• Eliminates Significant Risk 
in dredged areas. 

• Quickly meets requirements 
for a Permanent Solution. 

• Less dewatering required 
than hydraulic dredging. 

• Significant disruption to embayment and 
benthic community during dredging. 

• Could expose more contaminated 
sediments present at depth. 

• No access from upland areas due to resort 
construction. 

• Turbidity controls required during 
implementation. 

High 

Yes 

Yes 

• Navigational dredging already 

approved. 

• Effective presumptive remedy for 
sediments. 

• Quickly meets requirements for 
Permanent Solution in dredged areas. 

Hydraulic 

Dredging 

Physical removal of 
contaminated sediment 
through loosening the 
sediment with a cutter head 
and then sucking the sediment 
into a holding tank. 

• Eliminates Significant Risk 
in dredged areas. 

• Quickly meets requirements 
for a Permanent Solution. 

• Significant disruption to embayment and 
benthic community during dredging. 

• Could expose more contaminated 
sediments present at depth. 

• No access from upland areas due to resort 
construction. 

• Significant quantity of water to be 
treated/managed. 

• Turbidity controls required during 
implementation. 

High 

Yes 

No 

• No landside access available for 
sediment processing and dewatering 
(holding tanks, piping, processing, etc.) 


Page 1 of 2 

































Table 6-1 

Initial Technology Screening 

Sediment Portion of Former Everett Staging Yard Disposal Site 

RTN 3-13341 


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foster 
wheeter 




Technology 

Description 

Advantages 

Disadvantages 

Relative 

Cost 

Can Achieve a Condition of 
No Significant Risk for 
Sediments? 

Retained for 
Further 
Evaluation? 

Rationale 

Mechanical Capping 

Placement of clean cover 
material (sand, gravel, rip rap, 
synthetic) over contaminated 
sediment. 

• Eliminates Significant Risk 
in capped areas. 

• Quickly meets requirements 
for a Permanent Solution. 

• Leaves sediment posing a risk in place 
which could become exposed. 

• Significant disruption to embayment and 
benthic community during capping. 

• No access from upland areas due to resort 
construction. 

• Turbidity controls required during 
implementation. 

• Monitoring of cap to ensure stability will 
likely be required. 

Moderate 

t 

Yes 

Yes 

• Effective presumptive remedy for 
sediments. 

• Quickly meets requirements for 
Permanent Solution in capped areas. 


Page 2 of 2 











Remedial Action Alternative 2 - Figure 6-2 Remedial Action Alternative 1 - Figure 6-1 


Table 6-2 

Description of Remedial Action Alternatives 
Sediment Portion of Former Everett Staging Yard Disposal Site 

RTN 3-13341 


amec 

foster 

wheeler 


Alternative 1 


Full Dredge 
and Cap 
(Navigation 
Dredge, Full 
Remedial 
Dredge, and 
Cap) 


Design and Implementation 


• Install environmental controls. 

• Demolish five existing barges and remove miscellaneous debris. 

• Removal of sediments via mechanical dredging system. 

• Dewatering on hopper barge within turbidity barriers. 

• Sediment processing at facility off-site (8% amendment rate). 

• Off-site transportation and disposal of dredged sediments. 

• Off-site facility loading for imported fill. 

• Mechanical placement of cap material via hopper barge and broadcast 
spreader equipment. 


Monitoring _ 

Pre-Constructinn 

• Collect background turbidity readings from the Mystic River. 

• Conduct pre-demolition survey of barges and existing debris for removal prior to 
dredging. 

• Conduct pre-construction survey of proposed dredge area using bathymetric and 
topographic survey methods. 

• Collect pre-characterization samples to identify waste disposal options. 
Alternatively, sediment can be characterized in barges or stockpiles following 
dredging. 


R emediation Waste __ 

• redged sediments will be removed from the Site 
and transported to an off-site sediment 
processing and transfer facility. 

• Sediments will be reused or disposed of at a 
licensed off-site facility. 

• Sediments could be amended with a stabilization 
agent to reduce moisture content prior to off-site 
reuse or disposal. 

• Miscellaneous municipal solid waste, and spent 
sedimentation controls. 


Navigational Dredging 

• Approximately 1.39 acre area with removal of material to elevation -15 
feet (14,700 CY). 

Remedial Dredging 

• Approximately 7.03 acre area with removal of 18-inches of material 
(plus a 6-inch overdredge) (22,700 CY). Area overlaps Navigational 
Dredging area. 

Post Dredge Cap Installation 

• Approximately 7.03 acre cap with 18-inches of material (plus 6-inches 
to account for the overdredge) (25,000 CY includes 10% material 
bulking). 


Construction 

• Conduct environmental sampling and monitoring as determined by permit 
conditions. 

• Confirmation sampling as required by selected disposal facility if amendment is 
needed for moisture content control. 

Post Remediation 

• Perform periodic bathymetric and topographic survey of cap area to monitor 
stability and effectiveness (annual initially and then decreasing frequency). 

• Perform periodic maintenance dredging to maintain navigational channel. 

• Perform periodic cap maintenance as required to maintain cap thickness. 


Approximate Sediment Weight Anticipated: 

• 60,500 tons impacted sediment (includes 8% 
amendment bulking rate). 


Alternative 2 

Partial Dredge 

and Cap 

(Navigation 

Dredge, 

Limited 

Remedial 

Dredge, and 

Cap) 


Design and Implementation 

• Install environmental controls. 

• Demolish five existing barges and remove miscellaneous debris. 

• Removal of sediments via mechanical dredging system. 

• Dewatering on hopper barge within turbidity barriers. 

• Sediment processing at facility off-site (8% amendment rate). 

• Off-site transportation and disposal of dredged sediments. 

• Off-site facility loading for imported fill. 

• Mechanical placement of cap material via hopper barge and broadcast 
spreader equipment. 


Monitoring ___ 

Pre-Construction 

• Collect background turbidity readings from the Mystic River. 

• Conduct pre-demolition survey of barges and existing debris for removal prior to 
dredging. 

• Conduct pre-construction survey of proposed dredge area using bathymetric and 
topographic survey methods. 

• Collect pre-characterization samples to identify waste disposal options. 
Alternatively, sediment can be characterized in barges or stockpiles following 
dredging. 


Remediation Waste __ 

• Dredged sediments will be removed from the Site 
and transported to an off-site sediment 
processing and transfer facility. 

• Sediments will be reused or disposed of at a 
licensed off-site facility. 

• Sediments could be amended with a stabilization 
agent to reduce moisture content prior to off-site 
reuse or disposal. 

• Miscellaneous municipal solid waste, and spent 
sedimentation controls. 


Navigational Dredging 

• Approximately 1.39 acre area with removal of material to elevation -15 
feet (14,700 CY). 

Remedial Dredging 

• Approximately 3.76 acre area with removal of 18-inches of material 
(plus a 6-inch overdredge) (12,100 CY). Area overlaps Navigational 
Dredging area. 


Construction 

• Conduct environmental sampling and monitoring as determined by permit 
conditions. 

• Confirmation sampling as required by selected disposal facility if amendment is 
needed for moisture content control. 

Post Remediation 

• Perform periodic bathymetric and topographic survey of cap area to monitor 
stability and effectiveness (annual initially and then decreasing frequency). 

• Perform periodic maintenance dredging to maintain navigational channel. 

• Perform periodic cap maintenance as required to maintain cap thickness. 


Approximate Sediment Weight Anticipated: 

• 43,400 tons impacted sediment (includes 8% 
amendment bulking rate). 


Page 1 of 3 

















































Remedial Action Alternative 4 - Figure 6-4 Remedial Action Alternative 3 - Figure 6-3 


Table 6-2 

Description of Remedial Action Alternatives 
Sediment Portion of Former Everett Staging Yard Disposal Site 

RTN 3-13341 


+ 3 $ 

amec 

foster 

wheeler 


Post Dredge Cap Installation 

• Approximately 7.03 acre cap with 18-inches of material (plus 6-inches 
to account for the overdredge) (25,000 CY includes 10% material 
bulking). 


Alternative 3 

Partial Dredge, 
Cap and MNR 
(Navigation 
Dredge, 

Limited 
Remedial 
Dredge and 
Cap, MNR) 


Design and Implementation 

Install environmental controls. 

Demolish five existing barges and remove miscellaneous debris. 
Removal of sediments via mechanical dredging system. 

Dewatering on hopper barge within turbidity barriers. 

Sediment processing at facility off-site (8% amendment rate). 

Off-site transportation and disposal of dredged sediments. 

Off-site facility loading for imported fill. 

Mechanical placement of cap material via hopper barge and broadcast 


spreader equipment. 
Navigational Dredging 


• Approximately 1.39 acre area with removal of material to elevation -15 
feet (14,700 CY). 


Remedial Dredging 

• Approximately 3.76 acre area with removal of 18-inches of material 
(plus a 6-inch overdredge) (12,100 CY). Area overlaps Navigational 
Dredging area. 

Post Dredge Cap Installation 

• Approximately 3.76 acre cap with 18-inches of material (plus 6-inches 
to account for the overdredge) (13,300 CY includes 10% material 
bulking). 


Alternative 4 


Design and 


Implementation 


Navigation 
Dredge, Cap 
and MNR 
(Navigation 
Dredge with 
Cap and MNR) 


• Install environmental controls. 

• Demolish five existing barges and remove miscellaneous debris. 

• Removal of sediments via mechanical dredging system. 

• Dewatering on hopper barge within turbidity barriers. 

• Sediment processing at facility off-site (8% amendment rate). 

• Off-site transportation and disposal of dredged sediments. 

• Off-site facility loading for imported fill. 

• Mechanical placement of cap material via hopper barge and broadcast 
spreader equipment. 


Navigational Dredging 

• Approximately 1 39 acre area with removal of material to elevation -15 
feet (14,700 CY). 


Monitoring 


Remediation Waste 


Pre-Construction 

• Collect background turbidity readings from the Mystic River. 

• Conduct pre-demolition survey of barges and existing debris for removal prior to 
dredging. 

• Conduct pre-construction survey of proposed dredge area using bathymetric and 
topographic survey methods. 

• Collect pre-characterization samples to identify waste disposal options. 
Alternatively, sediment can be characterized in barges or stockpiles following 
dredging. 

• Baseline assessment of sediment concentrations, sedimentation rates, sediment 
stability, and benthic community. 

Construction 

• Conduct environmental sampling and monitoring as determined by permit 
conditions. 

• Confirmation sampling as required by selected disposal facility if amendment is 
needed for moisture content control. 

Post Remediation 

• Perform periodic bathymetric and topographic survey of cap area to monitor 
stability and effectiveness (annual initially and then decreasing frequency). 

• Conduct periodic sampling of sediment to evaluate MNR effectiveness. 

• Perform periodic maintenance dredging to maintain navigational channel. 

• Perform periodic cap maintenance as required to maintain cap thickness. 


• Dredged sediments will be removed from the Site 
and transported to an off-site sediment 
processing and transfer facility 

• Sediments will be reused or disposed of at a 
licensed off-site facility. 

• Sediments could be amended with a stabilization 
agent to reduce moisture content prior to off-site 
reuse or disposal. 

• Miscellaneous municipal solid waste, and spent 
sedimentation controls 

Approximate Sediment Weight Anticipated: 

• 43,400 tons impacted soil (includes 8% 
amendment bulking rate) 


Monitoring 


Remediation Waste 


Pre-Construction 

• Collect background turbidity readings from the Mystic River. 

• Conduct pre-demolition survey of barges and existing debris for removal prior to 
dredging. 

• Conduct pre-construction survey of proposed dredge area using bathymetric and 
topographic survey methods. 

• Collect pre-characterization samples to identify waste disposal options. 
Alternatively, sediment can be characterized in barges or stockpiles following 
dredging. 

Construction 

• Conduct environmental sampling and monitoring as determined by permit 
conditions. 

• Confirmation sampling as required by selected disposal facility if amendment is 


• Dredged sediments will be removed from the Site 
and transported to an off-site sediment 
processing and transfer facility 

• Sediments will be reused or disposed of at a 
licensed off-site facility. 

• Sediments could be amended with a stabilization 
agent to reduce moisture content prior to off-site 
reuse or disposal. 

• Miscellaneous municipal solid waste, and spent 
sedimentation controls. 

Approximate Sediment Weight- 

• 31,000 tons impacted sediment (includes 8% 
amendment bulking rate) 


Page 2 of 3 























































i auie t>-z 


uo 


<D 


No Further 
Action 
(Navigation 
Dredge only) 


5 .. Description of Remedial Action Alternatives 
Sediment Portion of Former Everett Staging Yard Disposal Site 

RTN 3-13341 


Ip 


Remedial Dredging 

• Approximately 1,39 acre area with removal of 18-inches of material 

(plus a 6-inch overdredge) (4,500 CY). Area is the Navigational 
Dredging area. 

Post Dredge Cap Installation 

• Approximately 1.39 acre cap with 18-inches of material (plus 6-inches 

to account for the overdredge) (5,000 CY includes 10% material 
bulking). 


Alternative 5 | Design and Implementation 


► Install environmental controls. 

Demolish five existing barges and remove miscellaneous debris 

► Removal of sediments via mechanical dredging system. 

' Dewatering on hopper barge within turbidity barriers. 

• Sediment processing facility off-site (8% amendment rate). 

Off-site transportation and disposal of removed sediments. 

Navigational Dredging 

Approximately 1.39 acre area with removal of material to elevation -15 
feet (14,700 CY). 


needed for moisture content control. 

Post Remediation 

* ^': e rr S r nt0fSedlmentCOnCentratl0nS ' sedime "<a‘i°" rates, sediment 
stability, and benthic community in MNR area. 

* Pe ?°« C bathymetric and topographic suivey of cap area to monitor 
stability and effectiveness (annual initially and then decreasing frequency). 

• Conduct periodic sampling of sediment to evaluate MNR effectiveness. 

• Perform periodic maintenance dredging to maintain navigational channel. 
^Perfo rm periodic cap maintenance as required to maintain c ap thickness. 

Monitoring 


Pre-Construction 

• Collect background turbidity readings from the Mystic River. 

. Conduct pre-demolition survey of barges and existing debris for removal prior to 
dredging. K 

• Conduct pre-construction survey of proposed dredge area using bathymetric and 
topographic survey methods. 

• Collect pre-characterization samples to identify waste disposal options. 

Alternatively, sediment can be characterized in barges or stockpiles followinq 
dredging. a 

Construction 

• Conduct environmental sampling and monitoring as determined by permit 
conditions. 

• Confirmation sampling as required by selected disposal facility if amendment is 
needed for moisture content control. 

Post Remediation 

• Conduct post dredging bathymetric and topographic survey to confirm necessary 
channel depths have been achieved. 

• Perform periodic maintenance dredging to maintain navigable channel. 




amec 
foster 
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Remediation Waste 


' Dredged sediments will be removed from the Site 
and transported to an off-site sediment 
processing and transfer facility 

• Sediments will be reused or disposed of at a 
licensed off-site facility. 

• Sediments could be amended with a stabilization 
agent to reduce moisture content prior to off-site 
reuse or disposal. 

• Miscellaneous municipal solid waste, and spent 
sedimentation controls. 

Approximate Sediment Weight Anticipated 

• 23,800 tons impacted sediment (includes 8% 

amendment bulking rate) 


Notes: 

Quantities are engineer’s estimates and are anticipated to be within minus 30% and plus 50% of actual quantities. 

CY - cubic yard 
ft- feet 

MNR - Monitored Natural Recovery 


Page 3 of 3 

















































Table 6-3 

Detailed Evaluation of Remedial Action Alternatives 
Sediment Portion of the Former Everett Staging Yard Disposal Site 

RTN 3-13341 


■ 

amec 
foster 
wheeler 



Criteria 
Effectiveness 


Alternative 1 
Full Dredge and Cap 

Navigation Dredge, Full Remedial Dredge, 
and Cap 
(Figure 6-1) 

High (3) 

• Will achieve a Permanent Solution with 
impacts removed by dredging and 
isolated by capping 

• Impacted sediment which poses a risk to 
be reused or disposed of off-site 

• Background concentrations will be 
achieved in areas that are dredged and 
capped 


Alternative 2 

Partial Dredge and Cap 

Navigation Dredge, Limited Remedial 
Dredge, and Cap 
(Figure 6-2) 

High to Moderate (2.5) 

• Will achieve a Permanent Solution with 
impacts removed by dredging and 
isolated by capping 

• Significant quantity of impacted sediment 
which poses a risk to be reused or 
disposed of off-site 

• Background concentrations will be 
achieved in areas that are dredged and 
capped or just capped 


Reliability 


High (3) 

• High certainty of success for potential to 
achieve a Permanent Solution with 
impacts removed by dredging and 
isolated by capping 

• High reliability of measures to manage 
residues or control discharges from site 
with turbidity controls and off-site 
sediment processing and disposal 


High (3) 

• High certainty of success for potential to 
achieve a Permanent Solution with 
impacts removed by dredging and 
isolated by capping 

• High reliability of measures to manage 
residues or control discharges from site 
with turbidity controls and off-site 
sediment processing and disposal 


Implementability | Low to Moderate (1.5) 

1 High technical complexity due to large 
footprint for sediment dredging and 
capping, tide fluctuations, and existing 
bathymetry 

, Limited to no integration with or 
disruption to facility operations as no 
landside access will be allowed 
, Moderate operation, maintenance, and 
monitoring (OM&M) to ensure stability of 

cap 

* Moderate availability of necessary 
services, materials, equipment and 
specialists locally 
» Moderate availability of off-site 
processing, treatment and disposal 
facilities 


Moderate (2) 

• Moderate technical complexity due to 
smaller footprint for sediment dredging 

• Limited to no integration with or 
disruption to facility operations as no 
landside access will be allowed 

• Moderate OM&M to ensure stability of 
cap 

• Moderate availability of necessary 
services, materials, equipment and 
specialists locally 

• Moderate to high availability of off-site 
processing, treatment and disposal 
facilities due to smaller quantities of 
dredge material 

• Will meet requirements of multiple 
permits needed for implementation 


Alternative 3 

Partial Dredge, Cap, and MNR 

Navigation Dredge, Limited Remedial 
Dredge and Cap, and MNR 
(Figure 6-3) 

Moderate (2) 

• Will achieve a Permanent Solution with 
impacts removed by in dredged and 
capped areas 

• May achieve Permanent Solution with 
time in MNR area 

• Significant quantity of impacted sediment 
which poses a risk to be reused or 
disposed of off-site 

• Background concentrations will be 
achieved in areas that are dredged and 
capped or just capped 

• Background conditions may be 
approached in MNR area over time 


Moderate (2) 

• High certainty of success for potential to 
achieve a Permanent Solution in dredged 
and capped areas 

• Moderate to low certainty of success to 
achieve a Permanent Solution in MNR 
areas 

• High reliability of measures to manage 
residues or control discharges from site 
with turbidity controls and off-site 
sediment processing and disposal 

• Moderate reliability of MNR to manage 
residual impacted sediment 

Moderate (2) 

• Moderate technical complexity due to 
smaller footprint for sediment dredging 

• Limited to no integration with or 
disruption to facility operations as no 
landside access will be allowed 

• Moderate OM&M to ensure stability of 
cap and effectiveness of MNR 

• Moderate availability of necessary 
services, materials, equipment and 
specialists locally 

• Moderate to high availability of off-site 
processing, treatment and disposal 
facilities due to smaller quantities of 
dredge material 

Will meet requirements of multiple 
permits needed for implementation 


Alternative 4 
Navigation Dredge, Cap, and MNR 

Navigation Dredge with Cap and MNR 
(Figure 6-4) 


Moderate to Low (1.5) 

• Will achieve a Permanent Solution with 
impacts removed by in dredged and 
capped areas 

• May achieve Permanent Solution with 
time in MNR area 

• Lower quantity of impacted sediment 
which poses a risk to be reused or 
disposed of off-site 

• Background concentrations will be 
achieved in areas that are dredged and 
capped or just capped 
Background conditions may be 
approached in MNR area over time 

Moderate to Low (1.5) 

• High certainty of success for potential to 
achieve a Permanent Solution in limited 
dredged and capped areas 

• Moderate to low certainty of success to 
achieve a Permanent Solution in MNR 
areas 

• High reliability of measures to manage 
residues or control discharges from site 
with turbidity controls and off-site 
sediment processing and disposal 

• Moderate reliability of MNR to manage 
residual i mpacted sediment 

Moderate to High (2.5) 

• Moderate to low technical complexity due 
to smaller footprint for sediment dredging 

• Limited to no integration with or 
disruption to facility operations as no 
landside access will be allowed 

• Moderate to high OM&M to ensure 
stability of cap and effectiveness of MNR 

• Moderate availability of necessary 
services, materials, equipment and 
specialists locally 

High availability of off-site processing, 
treatment and disposal facilities due to 
smaller quantities of dredge material 
Will meet requirements of multiple 
permits needed for implementation 
MNR may not meet with full approval by 
MassDEP 


Alternative 5 
No Further Action 

Navigation Dredge Only 
(Figure 7-5) 


Low (1) 

• Will not achieve a Permanent Solution in 
Navigation Dredge Area as dredging 
alone will expose more contaminated 
sediment 

• Will achieve a Temporary Solution 

• Limited quantity of impacted sediment 
which poses a risk to be reused or 
disposed of off-site 

• Background concentrations may be 
approached over time 


Low (1) 

• Low certainty of success for potential to 
achieve a Permanent Solution with 
navigational dredging only 

• High reliability of measures to manage 
residues or control discharges from site 
with turbidity controls and off-site 
sediment processing and disposal 

• Low reliability of measures to manage 
residual impacted sediment 


High (3) 

• Low technical complexity due to smaller 
footprint for sediment dredging 

• Limited to no integration with or 
disruption to facility operations as no 
landside access will be allowed 

• Low OM&M to ensure navigable channel 
maintained 

• Moderate to high availability of necessary 
services, materials, equipment and 
specialists locally (less specialized 
equipment) 

• High availability of off-site processing, 
treatment and disposal facilities due to 
smaller quantities of dredge material 

• Navigational dredging already permitted 


Page 1 of 3 




















Criteria 


Costs 1 3 


Risks 3 


Benefits 


Timeliness 


Table 6-3 

Detailed Evaluation of Remedial Action Alternatives 
Sediment Portion of the Former Everett Staging Yard Disposal Site 

RTN 3-13341 


Alternative 1 
Full Dredge and Cap 

Navigation Dredge, Full Remedial Dredge, 
and Cap 
(Figure 6-1) 

Will meet requirements of multiple 
permits needed for implementation 


Alternative 2 

Partial Dredge and Cap 

Navigation Dredge, Limited Remedial 
Dredge, and Cap 
(Figure 6-2) 


High (1) 

• $19.1M for barge removal, sediment 
dredging, and capping 

• $1,1M for long term O&MM of cap 

• Restores natural resources in dredged 
and capped areas 

• High relative consumption of energy 
during dredging and capping 

Low to Moderate (2.5) 

• Moderate short-term risk to construction 
workers during implementation 
associated with use of heavy equipment 
and dredging of impacted sediment 

• Moderate short-term risk to 
public/environment during dredging, 
transport and reuse or disposal 

• Minimal risk during short time required to 
achieve remedial objective 

• Minimal risk to health, safety, public 
welfare or the environment following 
completion of remedial action 


High (3) 

• Highly likely to remove mass, achieve 
remedial objectives, restore natural 
resources and allow for re-use of 
property in timely manner 


Moderate (2) 

• $14.7M for barge removal, sediment 
dredging, and capping 

• $1.1 M for long term O&MM of cap 

• Restores natural resources in dredged 
and capped areas 

• High relative consumption of energy 
during dredging and capping 

Low to Moderate (2.5) 

• Moderate short-term risk to construction 
workers during implementation 
associated with use of heavy equipment 
and dredging of impacted sediment 

• Moderate short-term risk to 
public/environment during dredging, 
transport and reuse or disposal 

• Minimal risk during short time required to 
achieve remedial objective 

• Minimal risk to health, safety, public 
welfare or the environment following 
completion of remedial action 


High (3) 

• Highly likely to remove mass, achieve 
remedial objectives, restore natural 
resources and allow for re-use of 
property in timely manner 


Alternative 3 

Partial Dredge, Cap, and MNR 

Navigation Dredge, Limited Remedial 
Dredge and Cap, and MNR 
(Figure 6-3) 

MNR may not meet with full approval by 
MassDEP 


Moderate (2) 

• $13.6M for barge removal, sediment 
dredging, and capping 

• $1,8M for MNR baseline and monitoring 

• $0.6M for long term O&MM of cap 

• Lower immediate restoration of natural 
resources 

• Lower relative consumption of energy 
due to redu ced dredging and capping 

Moderate (2) 

• Moderate short-term risk to construction 
workers during implementation 
associated with use of heavy equipment 
and dredging of impacted sediment 

• Moderate short-term risk to 
public/environment during dredging, 
transport and reuse or disposal 

• Low risk to health, safety, public welfare 
or the environment following completion 
of dredging and capping 

• Low to moderate risk during time 
required to achieve remedial objective 
via MNR 


Moderate (2) 

• Moderate likelihood to remove mass, 
achieve remedial objectives, restore 
natural resources and allow for re-use of 
property in timely manner 


amec 

foster 

wheeler 


Alternative 4 
Navigation Dredge, Cap, and MNR 

Navigation Dredge with Cap and MNR 
(Figure 6-4) 


Moderate to Low (2.5) 

• $9.5M for barge removal, sediment 
dredging, and capping 

• $3.2M for MNR baseline and monitoring 

• $0.2M for long term O&MM of cap 

• Lower immediate restoration of natural 
resources 

• Lower relative consumption of energy 
due to reduced dredging and capping 


Moderate to High (1.5) 

• Low to moderate short-term risk to 
construction workers during 
implementation associated with use of 
heavy equipment and dredging of 
impacted sediment 

• Moderate short-term risk to 
public/environment during dredging, 
transport and reuse or disposal 

• Low to moderate risk to health, safety, 
public welfare or the environment 
following completion of dredging and 
capping 

• Moderate risk during time required to 
achieve remedial objective via MNR 


Moderate to Low (1.5) 

• Moderate to low likelihood to remove 
mass, achieve remedial objectives, 
restore natural resources and allow for 
re-use of property in timely manner 


Moderate (2) 

• 5 months to achieve level of No 

Significant Risk in dredged and capped 
areas 


High (3) 

• 3.5 months to achieve level of No 
Significant Risk in dredged and capped 
areas 


Moderate (2) 

• 3 months to achieve level of No 

Significant Risk in dredged and capped 
areas 


Moderate to Low (1.5) 

• 2 months to achieve level of No 

Significant Risk in dredged and capped 
areas 


Alternative 5 
No Further Action 

Navigation Dredge Only 
(Figure 7-5) 


Low (3) 

$7.3M for barge removal and 
navigational dredging 
Does not restore natural resource areas 
Lowest relative consumption of energy 
due to limited dredging and no capping 


High (1) 

• Low to moderate short-term risk to 
construction workers associated with use 
of heavy equipment and dredging of 
impacted sediment 

• Moderate short-term risk to 
public/environment during dredging, 
transport and disposal 

• High risk to environment due to exposed, 
more contaminated sediments 


Low (1) 

• Will remove limited mass in navigation 
dredge area only. 

• Unlikely to achieve remedial objectives 
and restore natural resources 

• Will allow for re-use of property in timely 
manner 


Low (1) 

• WII not achieve level of No Significant 
Risk 


Page 2 of 3 












































Table 6-3 

Detailed Evaluation of Remedial Action Alternatives 
Sediment Portion of the Former Everett Staging Yard Disposal Site 

RTN 3-13341 


a mec 
foster 




Criteria 

Alternative 1 

Full Dredge and Cap 

Navigation Dredge, Full Remedial Dredge, 
and Cap 
(Figure 6-1) 

Alternative 2 

Partial Dredge and Cap 

Navigation Dredge, Limited Remedial 
Dredge, and Cap 
(Figure 6-2) 

Alternative 3 

Partial Dredge, Cap, and MNR 

Navigation Dredge, Limited Remedial 
Dredge and Cap, and MNR 
(Figure 6-3) 

Alternative 4 

Navigation Dredge, Cap, and MNR 

Navigation Dredge with Cap and MNR 
(Figure 6-4) 

Alternative 5 

No Further Action 

Navigation Dredge Only 
(Figure 7-5) 




• Potentially extended period of time 
(years to decades) to achieve level of No 
Significant Risk in MNR area 

• Potentially extended period of time 
(years to decades) to achieve level of No 
Significant Risk in large MNR area 


Non-pecuniary 

interests 3 

Moderate (2) 

• Dredging and capping will immediately 
improve aesthetics of site 

• Some nuisance odors may occur during 
dredging 

• Access to embayment limited for during 
of dredging and capping 

Moderate (2) 

• Dredging and capping will immediately 
improve aesthetics of site 

• Limited nuisance odors may occur during 
limited dredging period 

• Access to embayment limited for shorter 
duration of dredging and capping 

Moderate (2) 

• Dredging and capping will immediately 
improve aesthetics of limited area of site 

• Limited nuisance odors may occur during 
limited dredging period 

• Access to embayment limited for shorter 
duration of dredging and capping 

Moderate (2) 

• Dredging and capping will immediately 
improve aesthetics of limited area of site 

• Limited nuisance odors may occur during 
limited dredging period 

• Access to embayment limited for shorter 
duration of dredging and capping 

Moderate to High (2.5) 

• Navigation dredging will provide limited 
aesthetic improvement compared to 
other alternatives 

• Low likelihood of nuisance odors 

• Very short duration of limited access 

Total Ranking 2 

18 

20 

16 

15 

13.5 


Notes: 

Notes: 

1 Costs are engineer’s estimates and are anticipated to be within minus 30% and plus 50% of actual quantities consistent with USEPA feasibility study guidance. 

2 Ranking evaluations based on High (3), Moderate (2) and Low (1). 

3 Ranking for Cost, Risk and Non-pecuniary interests are reversed to reflect accurate ranking (i.e., high cost was given a low ranking). 


MassDEP - Massachusetts Department of Environmental Protection 
MNR - Monitored Natural Recovery 
O&MM - Operation and Maintenance 


Page 3 of 3 
























— 










FIGURES 















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^RTN 3-13341 


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SITE: 


TITLE: 


Former Everett Staging Yard 
1 Horizon Way, Everett, MA 
RTN 3-13341 


Site Location Map 


□ Approximate Parcel Boundary 


—scalt:— 

1 inch = 2,000 feet 

DATE: 

12/23/2016 

PROJECT: 

3651160042 003 

DRAWN BY: M Martin 

CHECKED BY: c Piatt 


LOCATION: P \Comm-lnd\Projects\Clients T to Z\Wynn\3651160042\GIS 



























































































































Disposal Site Boundary 


Limit of Sediment 
Posing Significant Risk 


Limit of Sediment 
Posing Significant Risk 


CES Area 
(High Arsenic Area) 


GZ-120R 


GZ-108GT 


GZ-2R&GT 


GZ-112R 

-^GZ-112 


GZ-115R 


GZ-117R 


GZ-119R&GT^GZ-119 


GZ-108R 


GZ-134 

r&gt) 


GZ-114R&GT 


GZ-206R 


GZ-17R&GT 


GZ-11AR 


GZ-204R 


GZ-203R 

GZ-203 


GZ-205R&GT 


GZ-104R 


GZ-110R&GT* %. 5 ■ ■ • 


Limit of Sediment 
Posing Significant Risk 

and 

Disposal Site Boundary 


X5Z-216R 


GZ-218R 


■GZ-215R&GT 


. from nian* or electronic files provided by "Feldman Land Surveyors” entitled ” Existing 

1> Th H e , baSe nl P d W Q2 20 2015 O, a,nal scale1 “/awing NO ,45,/. CAD II.. ",45,7-EX-DRAFT-03-20.,5 DWG 
2)The !oca„ons and elevatons of the corings sampling locations selected s„e ,eatures and explorations were approximatly 
determined by GPS This data should be considered accurate only to the degree implied by the method used 

— provided by GZA GeoEnivronmental. Inc. 


3) The base data and map package were 


Site Plan 

Former Everett Staging Yard 
1 Horizon Way, Everett, MA 
_RTN 3-13341_ 


j CES Area (High Arsenic Area) 
Low pH Area 
Salt Marsh 


Mean High Water 
Mean Low Water 

Bathymetric Contour (<0) NAVD88 
Topographic Contour (>0) NAVD88 


| Approximate Parcel Boundary 
” “ ] Limit of Sediment Posing Significant Risk 
Disposal Site Boundary 
0 AMEC Sediment Sample Locations 
0 GZA Sediment Sample Locations 


FIGURE NO 


Checked By: D. Ahern 


Drawn By: E. Flanary 


amec 

foster 

wheeler 


Date -.6/21/2017 


PROJECT NO 


3651160042.003 


Document Path: P:\BOS\Wynn Design & Development\3651160042 - Wynn Everett Sediments\7.0 Drawings\7.3 GIS\Figure_site_plan_3-24-2017.mxd 

























































































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SALT MARSH 

EXISTING DETERIORATED BARGE 







PROJECT: 

FORMER EVERETT 
STAGING YARD 
1 HORIZON WAY 
EVERETT, MA 
RTN 3-13341 











1 REV 

DATE 

DESCRIPTION 


ISSUE / REVISION: 


DRAWN BV: 
MRF 


DATE: 

FEBRUARY 2017 


ISSUE /REVISION: 
0 


PROJECT NUMBER: 
3651160042 




REMEDIAL 
ALTERNATIVE 1 
FULL DREDGE AND 
CAP 



55=L I FIGURE NUMBER: 


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wheeler 


AMEC FOSTER WHEELER 
ENVIRONMENT & INFRASTRUCTURE, INC 
271 MILL ROAD 

CHELMSFORD MASSACHUSETTS 01824 
TELEPHONE: (978) 692-9090 
FAX: (978) 692-6633 
WEB: WWW.AMECFW.COM 



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BOSTON HARBOR 

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(RIZON WAY 

ERETT, MA 
"N 3-13341 







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MRF 

DRAWN BY: 

MRF 

CHECKED BY: 

DAA 

DATE: 

FEBRUARY 2017 

SCALE: 

AS SHOWN 

ISSUE/REVISION: 

0 

PROJECT NUMBER: 

3651160042 

TITLE: 

REMEDIAL 
ALTERNATIVE 2 
PARTIAL DREDGE AND 
CAP 

: FIGURE NUMBER: 

6-2 

i 














































































































































































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foster 
wheeler 

AMEC FOSTER WHEELER 
| ENVIRONMENT & INFRASTRUCTURE, INC. 

271 MILL ROAD I g 

CHELMSFORD MASSACHUSETTS 01824 |-§ 
TELEPHONE: (978) 692-9090 |£ 

FAX: (978) 692-6633 I 

WEB. WWW.AMECFW.COM || 

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MEAN HIGH WATER (4.35' NAVD88) 

MEAN LOW WATER (-5.21’ NAVD88) 

PROPERTY LINE 

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NAVIGATION DREDGE WITH REMEDIATION DREDGE AND CAP BELOW 
MONITORED NATURAL RECOVERY 

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PROJECT: 

FORMER EVERETT 
STAGING YARD 
1 HORIZON WAY 
EVERETT, MA 
RTN 3-13341 


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DATE 

DESCRIPTION 


\ __ 


A. 


1 


ISSUE/REVISION: 


DESIGNED BY: 
MRF 


CHECKED BY: 
DAA 


SCALE: 

AS SHOWN 


DRAWN BY: 
MRF 


DATE: 

FEBRUARY 2017 


ISSUE/REVISION: 
0 


PROJECT NUMBER: 
3651160042 


TITLE: 


REMEDIAL 
ALTERNATIVE 3 
^PARTIAL DREDGE, CAP|| 
AND MNR 

"t2 


FIGURE NUMBER: 


6-3 


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amec 

foster 

wheeler 


AMEC FOSTER WHEELER 
ENVIRONMENT & INFRASTRUCTURE, INC. 
271 MILL ROAD 

CHELMSFORD MASSACHUSETTS 01824 
TELEPHONE: (978) 692-9090 
FAX. (978) 692-6633 
WEB: WWW.AMECFW.COM 

CLIENT: 


BOSTON HARBOR 


PROJECT: 

FORMER EVERETT 
STAGING YARD 
1 HORIZON WAY 
EVERETT, MA 
RTN 3-13341 


REV DATE 


ISSUE/REVISION: 

DESIGNED BY: 

MRF_ 

CHECKED BY: 

DAA 

SCALE: 

AS SHOWN 

PROJECT NUMBER: 
36511600 42 

TITLE: 


DESCRIPTION 


DRAWN BY: 

MRF 

DATE: 

FEBRUARY 2017 

ISSUE/REVISION: 
0 


REMEDIAL 
ALTERNATIVE 4 
NAVIGATION DREDGE, 
CAP AND MNR 


FIGURE NUMBER: 


6-4 


FILE: \\WFD-FS1\Projects\old_WFD-FS3_Dato\Departments\- CAD Projects\Wynn Everett Sediments - 3651160042\7.0 CAD\7.1 Design - Permitting\Sheets\Feasibility Study Attemativesl (2).dwg BY: dano.dempsey DATE: 20 Jun 2017 - 2:04pm 











































































































































































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amec 
foster 
wheeler 

. AMEC FOSTER WHEELER 

ENVIRONMENT & INFRASTRUCTURE, INC. 

1 271 MILL ROAD 

CHELMSFORD MASSACHUSETTS 01824 

TELEPHONE: (978) 692-9090 I £ 

FAX: (978) 692-6633 | p. 

WEB: WWW.AMECFW.COM 


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PROJECT NUMBER: 
i 3651160042 


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MRF 


DATE: 

FEBRUARY 2017 


\ 


I TITLE: 




A 


Is 


PROJECT: 

FORMER EVERETT 
STAGING YARD 
1 HORIZON WAY 
EVERETT, MA 
RTN 3-13341 


ISSUE/REVISION: 

0 li 


■ r- j 

t2 


REMEDIAL 
ALTERNATIVE 5 

NO FURTHER ACTION 11 

l> 

- J5 

FIGURE NUMBER: 

6-5 





























































































































































































APPENDICES 













I