Five-Year Review Report for W.R. Grace and Co. Inc. (Acton Plant) Superfund Site Middlesex County Massachusetts


FIVE-YEAR REVIEW REPORT FOR
W.R. GRACE & CO., INC. (ACTON PLANT) SUPERFUND SITE
MIDDLESEX COUNTY, MASSACHUSETTS

sta?.



Prepared by

U.S. Environmental Protection Agency
Region I, New England
Boston, Massachusetts

— 	

James T. Opven, Director	Date

Office of Site Remediation and Restoration
United States Environmental Protection Agency,

Region 1 - New England

SDMS Doc ID 564060

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TABLE OF CONTENTS

LIST OF ACRONYMS	iii

EXECUTIVE SUMMARY	I IS-1

INTRODUCTION	1

PROGRESS SINCE THE LAST REVIEW	2

Remedy Implementation Activities	3

Northeast Area Groundwater Extraction and Treatment System Construction	3

Landfill Area Groundwater Extraction and Treatment System Construction	4

Sinking Pond and North Lagoon Wetland Remediation	4

Institutional Controls Implementation	5

System Operation/Operation and Maintenance Activities	6

Northeast Area Treatment System	7

Landfill Area Treatment System	7

Wetland Restoration Monitoring	7

Groundwater Monitoring	8

Industrial Landfill Closure Monitoring	8

Five-Year Review Process	9

Administrative Components	9

Community Notification and Involvement	9

Document Review	9

Data Review	9

Groundwater Monitoring	9

Site Inspection	16

Interviews	18

TECHNICAL ASSESSMENT	19

Question A: Is the remedy functioning as intended by the decision documents?	19

Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial
action objectives (RAOs) used at the time of the remedy section still valid?	20

Review of the Human Health Risk Assessments and Toxicity Factors Serving as the Basis
for the Remedy	20

Ecological Risk Review	29

ARARs Review	31

Question C: Has any other information come to light that could call into question the
protectiveness of the remedy?	32

Technical Assessment Summary	32

Issues/Recommendations and Follow-up Actions	34

Protectiveness Statement	35

Next Review	36

i

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FIGURES

APPENDIX A - EXISTING SITE INFORMATION	A-l

A.	SITE CHRONOLOGY	A-l

B.	BACKGROUND	A-5

Physical Characteristics and Land and Resource Use	A-5

History of Contamination	A-5

Initial Response	A-6

Basis for Taking Action	A-7

Remedy Selection	A-9

Remedy Implementation	A-l 1

APPENDIX B - LIST OF DOCUMENTS REVIEWED/REFERENCES	B-l

APPENDIX C - SITE INSPECTION CHECKLIST AND PHOTOGRAPHS	C-l

APPENDIX D - INTERVIEW RECORD FORMS	D-l

APPENDIX E - TOXICITY VALUE AND VI PATHWAY REVIEW	E-l

APPENDIX F - ARARS REVIEW	F-l

11

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LIST OF ACRONYMS

ACRONYM

DEFINITION

1,1-DCE

1,1-Dichloroethene (also known as vinylidene chloride)

AAL

Allowable Ambient Limits

ADAF

Age-Dependent Adjustment Factor

ARAR

Applicable or Relevant and Appropriate Requirement

ARS

Aquifer Restoration System

AWD

Acton Water District

BEHP

Bis(2-ethylhexyl)phthalate

BERA

Baseline Ecological Risk Assessment

CDM

Camp, Dresser, & McKee Inc.

CERCLA

Comprehensive Environmental Response, Compensation, and Liability Act

CFR

Code of Federal Regulations

CIC

Community Involvement Coordinator

CMR

Code of Massachusetts Regulations

COC

Contaminants of Concern

COPC

Contaminants of Potential Concern

CWA

Clean Water Act

D&A

Dewey & Almy

EPA

Environmental Protection Agency

EPH

Extractable Petroleum Hydrocarbons

FLA

Former Lagoon Area

FS

Feasibility Study

FYR

Five Year Review

gpm

gallons per minute

GPs

Government Parties

GWTS

Groundwater Treatment System

ICs

Institutional Controls

IGCLs

Interim Groundwater Cleanup Levels

111

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ACRONYM

DEFINITION

MassDEP

Massachusetts Department of Environmental Protection

MCL

Maximum Contaminant Level

MCLG

Maximum Contaminant Level Goal

MNA

Monitored Natural Attenuation

MTBE

Methyl-tert-Butyl Ether

NCP

National Contingency Plan

NE

Northeast

NPL

National Priorities List

O&M

Operation and Maintenance

ORS

Office of Research and Standards (MassDEP)

ORSG

Office of Research and Standards Guideline (MassDEP)

OSHA

Occupational Safety and Health Administration

OU

Operable Unit

PCE

Perchloroethene (also known as tetrachloroethene)

PPM

Parts Per Million

PAHs

Polycylic Aromatic Hydrocarbons

PEC

Probable Effects Concentration

PRP

Potentially Responsible Party

RA

Remedial Action

RAC

Response Action Contract

RAO

Remedial Action Objective

RCRA

Resource Conservation and Recovery Act

RD/RA

Remedial Design/Remedial Action

RfD

Reference Dose

RI

Remedial Investigation

ROD

Record of Decision

RPM

Remedial Project Manager

SDWA

Safe Drinking Water Act

SE

Southeast

SEL

Severe Effects Level

iv

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ACRONYM

DEFINITION

SOW

Scope of Work

sw

Southwest

TBC

To Be Considered

TCA

1,1,1 -Trichloroethane

TCE

Trichloroethene

TELs

Threshold Effects Exposure Limits

UCL

Upper Confidence Level

USEPA

United States Environmental Protection Agency

UU/UE

Unlimited Use and Unrestricted Exposure

VC

Vinyl Chloride

VDC

Vinylidene Chloride (also known as 1,1-dichloroethene)

VI

Vapor Intrusion

VISL

Vapor Intrusion Screening Levels

VOC

Volatile Organic Compound

VPH

Volatile Petroleum Hydrocarbons

V

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EXECUTIVE SUMMARY

This is the fourth Five-Year Review (FYR) for the W.R. Grace & Co., Inc. (Acton Plant)
Superfund (Site) located in the Towns of Acton and Concord, Middlesex County, Massachusetts
(Figure 1). The purpose of this FYR is to review information to determine if the remedy is and
will continue to be protective of human health and the environment. The triggering action for this
statutory FYR was the signing of the previous FYR on 9/23/2009.

The Site is a former chemical manufacturing facility composed of approximately 260 acres. The
Site is organized into three operable units (OUs), which are:

OU-1 Disposal areas and surficial contamination areas at the Site;

OU-2 Residual contamination in disposal areas at the Site following implementation of

OU-1; and

OU-3 Contaminated groundwater and associated sediment and surface water

contamination

The selected remedy identified in the 1989 Record of Decision (ROD) for OU-1 included
excavation of contaminated material from various source areas, off-site incineration of highly
contaminated soil and sludge, and on-site solidification of less contaminated soil, sludge, and
sediment after removal of volatile organic compounds (VOCs) by heat. Solidified waste was
then disposed on-site in the Industrial Landfill, an unlined landfill that was already in existence
at the Site and used by W.R. Grace for disposal of various wastes and sludges. The remedy
included capping of the Industrial Landfill following placement of solidified waste within it,
landfill gas collection and treatment, and grading of the excavated waste areas. In addition, prior
to the 1989 ROD, an Aquifer Restoration System (ARS) was put in place to address groundwater
contamination at the Site. The ARS was replaced in 2011 by the groundwater extraction and
treatment systems that were developed for OU-3.

The 1989 ROD stated that a remedy for OU-2 would be necessary only if, following completion
of the OU-1 remedy, residual contamination in soils under the source areas exceeded soil
cleanup goals established for OU-1. Data collected during and after the completion of the OU-1
remedy indicated that the soil cleanup goals were met for each of the source areas, and therefore
no remedy for OU-2 was necessary.

The ROD for OU-3 was issued in 2005. The selected remedy identified in the 2005 ROD for
groundwater and sediments at the Site included: active treatment of contaminated groundwater
by extraction, above-ground treatment, and discharge; monitored natural attenuation of
groundwater beyond the active treatment zones; institutional controls to restrict groundwater use
until cleanup objectives have been met; and cleanup of contaminated sediments in Sinking Pond
and the North Lagoon Wetland.

The third Five-Year Review was signed by the Director of the Office of Site Remediation &
Restoration (OSRR) on September 23, 2009, and that date is the trigger for this fourth five-year
review. Five-Year Reviews are required to be performed because hazardous substances,
pollutants, or contaminants remain at the Site above levels that allow for unlimited use and
unrestricted exposure.

ES-1

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Protectiveness Statement

This Five-Year Review concludes that the remedy for OU-1 is protective of human health and
the environment. Soil in excess of cleanup levels has been excavated, stabilized, and either
placed in the Industrial Landfill or shipped off-site for treatment and disposal. The Industrial
Landfill was then closed with an impermeable cap designed and constructed in accordance with
Massachusetts Hazardous Waste Regulations for landfills. The PRP has filed a deed notice with
the Registry of Deeds to regulate land use of the Industrial Landfill, and the PRP maintains
ownership of the landfill. Continued operation and maintenance is needed at the Industrial
Landfill in order for the remedy at OU-1 to remain protective.

There is no protectiveness statement for OU-2 because it was determined that a remedy for OU-2
was not needed.

The remedies have been constructed and implemented for OU-3. More specifically, groundwater
in the vicinity of the Industrial Landfill is currently being extracted and treated by a new system
that was constructed by W. R. Grace in 2011. In addition, a separate groundwater extraction and
treatment system was installed in the Northeast Area of the Site and operated from April 2010 to
September 2013. The system was designed and operated to reduce contaminant mass in this
area, and it had accomplished this objective as set forth in the ROD by September 2013, when
EPA and MassDEP allowed it to be shut down. Additionally, the Acton Water District provides
treatment of groundwater from the five public water supply wells in the vicinity of the Site, and
the Acton Board of Health has established an administrative hold on the installation of private
irrigation wells within 500 feet of the current groundwater contaminant plume. Areas of
contaminated sediment in the North Lagoon Wetland and in Sinking Pond were excavated for
off-site disposal during the summer and fall of 2011 and the cleanup levels established in the
ROD were achieved. The wetlands have been restored and monitoring of the effectiveness of
restoration efforts continues. As a result of all of the above, the remedy at OU-3 is protective in
the short-term, because there is no current exposure. However, in order for the remedy to remain
protective in the long-term, additional institutional control for groundwater may be needed to
supplement the administrative hold to prevent groundwater use until cleanup levels are reached.

ES-2

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Five-Year Review Summary Form

SITE IDENTIFICATION

Site Name:

W. R. Grace & Co., Inc. (Acton Plant)

EPA ID:

MADOO1002252

Region: 1

State: MA

City/County: Acton and Concord/Middlesex County

NPL Status: Final

Multiple OUs?

Yes

Has the site achieved construction completion?

Yes

Lead agency: EPA

[If "Other Federal Agency", enter Agency name]:

Author name (Federal or State Project Manager): Derrick Golden

Author affiliation: U.S. EPA

Review period: 10/1/2009 - 9/30/2014

Date of site inspection: 5/21/2014

Type of review: Statutory

Review number: 4

Triggering action date: 9/23/2009

Due date (fiveyears after triggering action date): 9/23/2014

ES-3

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Five-Year Review Summary Form (continued)

Issues/Recommendations

Ol (s) without Issues/Recommendations Identified in the hive-Year Ueview:

OU-1 - There are no issues/recommendations for OU-1.

OU-2 - There are no issues/recommendations for OU-2. It was determined that a remedy for
OU-2 was not needed.

Issues and Recommendations Identified in the Five-Year Ueview:

OU(s): 3

Issue Category: Institutional Controls



Issue: The Acton Board of Health has established an administrative hold
on the installation of private irrigation wells within 500 feet of the mapped
region of contaminated groundwater from the W.R. Grace Site. It may be
necessary to establish additional institutional controls to further prevent
groundwater use within the contaminated plume area until cleanup goals
are met. An Institutional Controls Plan was prepared in 2011 but action on
it has stalled due to concerns raised by the Town of Acton.



Recommendation: Continue efforts with the Town to ensure that the
Town administrative hold remains in place and continue discussions about
the draft IC plan.

Affect Current
Protectiveness

Affect Future
Protectiveness

Party
Responsible

Oversight
Party

Milestone Date

No

Yes

PRP

EPA/State

9/30/2019

ES-4

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Five-Year Review Summary Form (continued)

Protectiveness Statement(s)

Operable Unit:	Protectiveness Determination:

1	Protective

Protectiveness Statement:

The remedy for OU-1 is protective of human health and the environment. Soil in excess of
cleanup levels has been excavated, stabilized, and either placed in the Industrial Landfill or
shipped off-site for treatment and disposal. The Industrial Landfill was then closed with an
impermeable cap to prevent potential exposure. The PRP has filed a deed notice with the
Registry of Deeds to regulate land use of the Industrial Landfill, the PRP maintains ownership
of the landfill and maintains the cap, and there is a perimeter fence enclosing the landfill.

Protectiveness Statement(s)

Operable Unit:	Protectiveness Determination:

3	Short-term Protective

Protectiveness Statement:

The remedy at OU-3 is protective in the short-term, because there is no current exposure to
contamination in groundwater or sediment. Groundwater in the vicinity of the Industrial
Landfill is currently being extracted and treated by a new system that was constructed in 2011
(the Landfill Area). A separate groundwater extraction and treatment system was installed in
the Northeast Area of the Site and operated from April 2010 to September 2013, at which time
it was determined that it had met the ROD objective of reducing contaminant mass in this
area. The Acton Water District provides treatment of groundwater from the five public water
supply wells in the vicinity of the Site, and the Acton Board of Health has established an
administrative hold on the installation of private irrigation wells within 500 feet of the current
groundwater contaminant plume. Areas of contaminated sediment in the North Lagoon
Wetland and in Sinking Pond were excavated for off-site disposal during the summer and fall
of 2011 and the cleanup levels established in the ROD were achieved. The wetlands have
been restored and monitoring of the effectiveness of restoration efforts continues. However, in
order for the remedy to be protective in the long-term, additional institutional controls for
groundwater may be needed to supplement the town's administrative hold on installing private
wells near the plume to prevent groundwater use until cleanup levels are reached.

Sitewide Protectiveness Statement

Protectiveness Determination:

Short-term Protective

Protectiveness Statement:

The remedial actions taken are protective of human health and the environment in the short-
term because there is no current exposure to contamination. Soil and sediment have been
remediated and contaminated soil left on site in the Industrial Landfill was capped. The
Landfill Area groundwater remedy is operating and will reduce contaminant concentrations to
cleanup levels over time through a combination of active extraction and treatment combined
with monitored natural attenuation. To be protective in the long-term, additional institutional
controls may be needed for groundwater within the vicinity of the contaminant plume to
supplement the existing controls (the Town's administrative hold) already in place.

ES-5

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INTRODUCTION

The purpose of a Five-Year Review (FYR) is to evaluate the implementation and performance of
a remedy in order to determine if the remedy will continue to be protective of human health and
the environment. The methods, findings, and conclusions of reviews are documented in five-year
review reports. In addition, FYR reports identify issues found during the review, if any, and
document recommendations to address them.

The U.S. Environmental Protection Agency (EPA) prepares FYRs pursuant to the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Section
121 and the National Contingency Plan (NCP). CERCLA Section 121 states:

"If the President selects a remedial action that results in any hazardous substances,
pollutants, or contaminants remaining at the site, the President shall review such
remedial action no less often than each five years after the initiation of such remedial
action to assure that human health and the environment are being protected by the
remedial action being implemented. In addition, if upon such review it is the judgment of
the President that action is appropriate at such site in accordance with section [104] or
[106], the President shall take or require such action. The President shall report to the
Congress a list offacilities for which such review is required, the results of all such
reviews, and any actions taken as a result of such reviews. "

EPA interpreted this requirement further in the NCP, at 40 Code of Federal Regulations (CFR)
Section 300.430(f)(4)(ii), which states:

"If a remedial action is selected that results in hazardous substances, pollutants, or
contaminants remaining at the site above levels that allow for unlimited use and
unrestricted exposure, the lead agency shall review such actions no less often than every
five years after the initiation of the selected remedial action."

EPA conducted a FYR on the remedy implemented at the W. R. Grace & Co., Inc. (Acton Plant)
Superfund Site in Acton and Concord, Middlesex County, Massachusetts (Figure 1). EPA is the
lead agency for developing and implementing the remedy for the Site. The Massachusetts
Department of Environmental Protection (MassDEP), as the support agency representing the
Commonwealth of Massachusetts, has reviewed all supporting documentation and provided
input to EPA during the FYR process.

This is the fourth FYR for the W.R. Grace & Co., Inc. (Acton Plant) Superfund Site. Previous
Five Year Reviews were conducted in 1999, 2004, and 2009. All of these previous reviews
determined that the remedies were protective. The triggering action for this statutory review is
the completion date of the previous (2009) FYR. Five Year Reviews are required due to the fact
that hazardous substances, pollutants, or contaminants remain at the Site above levels that allow
for unlimited use and unrestricted exposure. The Site consists of three Operable Units, all of
which are addressed in this FYR.

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PROGRESS SINCE THE LAST REVIEW

Table 1: Protectiveness Determinations/Statements from the 2009 FYR

ou#

Protectiveness
Determination

Protectiveness Statement

1

Protective

This Five-Year Review concludes that the remedy for OU-1
currently protects human health and the environment. Soil in
excess of cleanup levels has been excavated, stabilized, and
either placed in the Industrial Landfill or shipped off-site for
treatment and disposal. The Industrial Landfill was then
sealed/closed with an impermeable cap designed and
constructed in accordance with Massachusetts Hazardous Waste
Regulations for landfills specified at 310 CMR 30.580-595 and
30.620-633. The Industrial Landfill is owned and maintained by
W.R. Grace, access is restricted by a fence, and a deed notice
has been filed with the Registry of Deeds that puts parties on
notice that the landfill cannot be disturbed except by written
permission of MassDEP.

3

Will be Protective

The remedial action is currently underway for OU-3. The
remedy at OU-3 is expected to be protective of human health
and the environment upon completion, and in the interim,
exposure pathways that could result in unacceptable risks are
being controlled.

Tab

e 2: Status of Recommendations from the 2009 FYR

ou

#

Issue

Recommendations/
Follow-up Actions

Party
Responsible

Oversight
Party

Original
Milestone
Date

Current
Status

Completion

Date (if
applicable)

1

Additional
Institutional
Controls
required for the
Industrial
Landfill to
ensure the
remedy remains
protective in
the future.

Evaluate options
for institutional

controls and
implement as part
of the Institutional

Control Plan
required under the
RD/RA SOW.

PRP

EPA/State

9/23/2014

Completed



1

Assess
additional
operation &
maintenance
options, i.e.,
more frequent
removal of
weeds and
grass clippings
from the swales

and/or
improvements
to the drainage
system.

Assess additional
operation &
maintenance
options with the
responsible parties.

PRP

EPA/State

9/23/2014

Completed



2

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Remedy Implementation Activities

Remedial implementation activities that were completed prior to the last FYR in 2009 are
summarized in Appendix A. Activities since 2009 included: 1) construction, operation and
maintenance, and shutdown of the Northeast Area groundwater extraction, treatment and
reinjection system, 2) construction and operation and maintenance of the Landfill Area
groundwater extraction and treatment system, and 3) remediation of wetland soil and sediment in
Sinking Pond and the North Lagoon Wetland and wetland restoration of remediated areas.
Former and current areas within the Site that are relevant to discussions of remedial activities are
shown on Figures 2 and 3. Work also continued to establish enforceable institutional controls
(ICs), with the submission of a draft Institutional Controls Plan that was submitted by the PRP in
May 2011 (Tetra Tech GEO, 2011). These activities are summarized below.

Northeast Area Groundwater Extraction and Treatment System Construction

The goal of the Northeast Area remedial action was to achieve mass removal from the most
highly contaminated portion of the residual VDC plume that migrates through the bedrock
aquifer to Fort Pond Brook and the School Street public water supply wells. According to the
ROD (EPA, 2005), it was estimated that the system would need to be operated for three years,
after which an evaluation was to be made to assess if continued operation (in two-year
increments) was technically and economically justified.

Prior to the 2009 FYR, pre-design investigations had been completed; a concept design had been
submitted and conditionally approved by EPA; and construction activities had begun. The
Northeast Area remedial system design was approved by EPA in June 2009, and the system was
constructed between June 2009 and March 2010. The system consisted of three primary
components: an extraction well, a groundwater treatment system, and two injection wells.

An extraction well was drilled at the location of the highest VDC concentrations in the Northeast
Area. Through an iterative program of drilling and testing, it was found that the single extraction
well could withdraw VDC-contaminated groundwater from the upper 110 feet of the bedrock
aquifer at the target rate of 20 gallons per minute (gpm).

The groundwater treatment system initially consisted of an air stripper for removal of VDC; an
arsenic reduction vessel; and vapor-phase carbon for odor control. When C5-C8 hydrocarbons
were detected in the influent and effluent from the plant, liquid-phase carbon treatment was
added to the treatment process while Grace operated the Northeast Area treatment system. Two
injection wells were drilled near the treatment system and the extraction well. The wells were
screened from approximately 20 feet above, to 20 feet below the water table in the overburden
aquifer. Each well was capable of injecting the entire effluent flow of 20 gpm. Two injection
wells were constructed so that the system would not have to be shut down if redevelopment
became necessary.

The system began operation in April 2010. As explained below, the system operated for about
3.5 years. The system is currently inactive but is capable of re-start in the rare event that
ongoing monitoring indicates that the ROD required objectives are no longer being achieved and
continued operations are warranted.

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Landfill Area Groundwater Extraction and Treatment System Construction

The goal of the Landfill Area remedial action is to capture and treat contaminated groundwater
within the ROD Capture Zone and to discharge the treated water to Sinking Pond. Based on
groundwater modeling during the Feasibility Study, it was predicted that the capture zone would
be achieved by pumping approximately 90 gpm from two existing extraction wells and two new
extraction wells. The two existing wells, MLF and WLF, were part of the Aquifer Restoration
System (ARS) that had been extracting groundwater from various areas within the Site for
decades. Groundwater beyond the ROD Capture Zone will be remediated by Monitored Natural
Attenuation (MNA). Prior to the 2009 FYR, pre-design investigations had been completed; a
concept design had been submitted and conditionally approved by EPA; and two new extraction
wells (SWLF-1 and SELF-1) had been constructed.

A third new extraction well (SELF-2) was constructed in June 2010 after an evaluation of the
four-well system indicated that it was not achieving the ROD Capture Zone. In April 2011,
extraction well SWLF-1 was replaced with SWLF-2 due to a declining yield that could not be
restored with redevelopment.

In December 2010, the Landfill Area treatment system final design was submitted. While the
ROD had envisioned that the treatment would consist of metals removal and air stripping, the
post-ROD discovery of 1,4-dioxane at the Site led to the substitution of a photocatalytic
oxidation system for the air stripper. The final design was approved by EPA in February 2011,
and construction of the treatment system was completed in April 2011.

The ARS treatment system was shut down in late April 2011, and the Landfill Area treatment
system was started up in early May 2011. The Landfill Area treatment system initially consisted
of a metals microfiltration unit to reduce concentrations of arsenic, iron, manganese, and
phosphorus, and a photocatalytic oxidation system to destroy VOCs and 1,4-dioxane. After a
shakedown period of about one year, a liquid phase carbon unit was added to the system in May
2012 to remove residual chlorine from the effluent. Prior to EPA determining that this system
was operational and functional, toxicity testing was conducted on the effluent discharge. This
was required to ensure that the effluent discharge would not negatively impact the ecology of
Sinking Pond. The results of the toxicity testing were within acceptable limits.

Sinking Pond and North Lagoon Wetland Remediation

The goal of the sediment removal action in the North Lagoon Wetland was to remediate the
wetland area such that the upper one foot of sediment had concentrations of arsenic and
manganese at or below the target cleanup levels of 28 mg/kg arsenic and 2,030 mg/kg
manganese. The goal of the sediment removal action in Sinking Pond was to remediate the inlet
area of the pond and the pond itself such that the upper one foot of sediment for both human
accessible and ecological areas had concentrations of arsenic at or below the target cleanup level
of 42 mg/kg arsenic. The ecological-based cleanup levels identified in the ROD provided for a
short-term clean up level that was based on an arsenic concentration of 730 mg/kg arsenic, and
consideration of three other metals, provided that a trend of reducing arsenic concentrations in

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surface sediment was demonstrated through monitoring. As documented in the Final Sediment
Remedial Design Report (ARCADIS, 2011), W.R. Grace developed a remedial design that was
intended to achieve the long-term goal of 42 mg/kg arsenic throughout the applicable portion of
the pond such that subsequent monitoring for a reducing trend toward 42 mg/kg would not be
necessary.

Remedial activities were implemented at Sinking Pond and North Lagoon Wetland between June
and November 2011. Excavation in North Lagoon Wetland was performed in three areas: the
sedge marsh, the channel, and the wooded swamp. Based on the confirmatory post-excavation
survey data (ARCADIS, 2012), the volume of sediment excavated from North Lagoon Wetland
was 2,040 cubic yards. These excavated areas were backfilled with a minimum of 12 inches of
topsoil to pre-construction grades, seeded, and planted. The hydraulic barrier along the border of
Fort Pond Brook was left in place to stabilize the bank.

Remedial activities in Sinking Pond included excavation of sediments in the Inlet, and between
elevations 144.5 feet and 128 feet around the border of the pond. Confirmatory sampling was
performed at least three days after dredging was completed in each area. Based on these results,
an additional one foot of sediment removal was implemented within approximately 1,720 square
yards, mainly along the eastern shore of the pond. The total volume of excavated sediment for
the entire pond and inlet area was 8,100 cubic yards. Site restoration activities at Sinking Pond
included placement of a minimum of 6 inches of clean topsoil in the excavated portions of the
pond between the water line and the historical high water elevation (144.5 feet). Disturbed
portions of the pond bank from the edge of water to 144.5 feet were seeded and planted. The
Inlet was restored to a lower final elevation than pre-design conditions, with a permanent check
dam to support a deeper emergent marsh area, planted with plugs of aquatic vegetation.

Sediment remedial activities were determined to be complete and the final site inspection
occurred on November 17, 2011.

Additional sediment sampling was conducted in Sinking Pond and the North Lagoon Wetland, in
2014, to support this 2014 Five Year Review. See the report entitled: 5 Year Sediment
Investigation Summary Report, prepared by ARCADIS, dated June 6, 2014. The results indicate
that the respective clean up goals are still being achieved and the remedy remains protective in
both areas.

Institutional Controls Implementation

Table 3 summarizes the status of the institutional controls for the Site. A draft Institutional
Controls Plan for OU-3 (groundwater) was submitted by the PRP on May 12, 2011 (Tetra Tech
GEO, 2011). The Town of Acton expressed concerns about their role in the plan in a letter dated
June 6, 2011, and EPA and MassDEP issued a letter in response to those concerns on July 11,
2011. There is currently no resolution regarding the ultimate form of the IC that will be used to
restrict installation of private wells in the vicinity of the plume, but the existing IC (an
administrative hold on the installation of private irrigation wells by the Acton Board of Health)
remains in effect.

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Table 3: Summary of Planned and/or

mplemented

ICs



Media,
engineered
controls, and
areas that do
not support
UU/UE based
on current
conditions

ICs
Needed

ICs Called
for in the
Decision
Documents

Impacted
Parcel(s)

IC
Objective

Title of IC
Instrument
Implemented
and Date (or
planned)

OU-1: Capped
Industrial
Landfill

Yes

Yes

Industrial
Landfill and
surrounding
groundwater
(landfill area
plume)

Ensure continued
maintenance and
prevent
disturbance of
the Industrial
Landfill cap.

Deed Notice is
on file with the
Registry of
Deeds.

OU-3:
Groundwater

Yes

Yes

Properties
within 500
feet of the
mapped
groundwater
contaminant
plume

Prevent
installation of
private wells
near or within
contaminant

plume
boundaries

The Acton
Board of Health

has an
administrative
hold on private
irrigation well
installations in

effect, but
additional ICs
may also be

needed.
Agreement on

the form of
additional ICs
to be used is not
yet reached
among EPA,
MassDEP, and
the Town.

System Operation/Operation and Maintenance Activities

Operation and Maintenance activities between 2009 and 2014 included: operation and
maintenance of two groundwater extraction and treatment systems, monitoring of the
effectiveness of wetland restoration activities, annual groundwater monitoring to assess the
effectiveness of the extraction and treatment systems, and maintenance of the Industrial Landfill
cap. Additional information is provided below for each O&M activity.

6

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Northeast Area Treatment System

During its 3.5 years of operation, the Northeast Area groundwater extraction and treatment
system was maintained and monitored in accordance with the O&M Plan (O&M Inc. and
GeoTrans, Inc., 2010). Following an initial period of operation during which many system
operations were monitored at least weekly, the frequency was decreased to monthly for most
monitoring activities, including influent and effluent sampling, arsenic reduction system
monitoring, odor monitoring, and extraction and injection well performance. Treatment system
inspection reports were issued monthly.

As stated above, according to the ROD, the system was expected to operate for approximately
three years, after which it would be evaluated to determine if continued operations were
technically and economically feasible. In February 2013, Grace submitted an evaluation (Tetra
Tech, 2013a) of the system's operation that indicated that the ROD objectives had been met, and
that therefore continued operations were not warranted. After review of Grace's evaluation,
EPA conditionally approved shutdown of the system in late September 2013, but required that
the system remain in place (not be decommissioned) for at least one year. That condition was
imposed in case the 2014 annual groundwater monitoring results indicate that the ROD required
objectives are no longer being achieved, and restored operations are warranted.

Landfill Area Treatment System

The Landfill Area extraction and treatment system is maintained and monitored in accordance
with the O&M Plan (Tetra Tech GEO and O&M, Inc., 2012). Following a startup period during
which many system operations were monitored daily or weekly, the frequency was decreased to
monthly or quarterly for most monitoring activities, including individual extraction well and
treatment system effluent sampling, and monitoring of extraction and injection well flow
performance. Treatment system inspection reports are issued monthly, and performance reports
are issued annually.

Each year, as part of the Groundwater Monitoring program, groundwater elevations are
measured across the entire Site, and potentiometric maps are created for the overburden and
bedrock aquifers. As part of the evaluation of groundwater flow patterns, the capture zone of the
Landfill Area extraction system is determined to confirm that ROD-required groundwater
capture is being attained. These evaluations are included in the OU-3 annual monitoring
program reports.

Wetland Restoration Monitoring

As discussed in the Final Sediment Remedial Design Report (ARCADIS, 2011), post
construction monitoring was required to assess the establishment, quality, and survival of seeded
and planted vegetation in areas that were affected by the sediment remedial activities and
subsequently restored. The monitoring frequency for the restored wetland areas associated with
North Lagoon Wetland and Sinking Pond is twice per year for five years. Monitoring was
conducted, as required, in spring and summer of 2012 and 2013. Monitoring included

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photographs and general description of restored areas, counts of the survivorship of planted trees
and shrubs (spring), and detailed inspection of specific monitoring quadrats to evaluate the
percent cover and species composition of seeded vegetation (summer). In addition, counts of the
surviving emergent aquatic vegetation species, of the five species planted in the inlet of Sinking
Pond, were also conducted annually. The restored upland areas associated with North Lagoon
Wetland and Sinking Pond were also subject to monitoring following the first full growing
season after restoration activities were completed. The monitoring is intended to evaluate the
growth of seeded and planted vegetation and determine maintenance needs. Reports
summarizing the findings of the first two annual post construction vegetation monitoring events
have been submitted for 2012 and 2013 (ARCADIS, 2012b and 2013).

Groundwater Monitoring

Groundwater samples are collected annually from wells throughout the Site in the late summer or
early fall. Samples are analyzed for one or more of the following: VOCs, inorganics,
geochemical indicator parameters, Volatile Petroleum Hydrocarbons (VPH), Extractable
Petroleum Hydrocarbons (EPH), and 1,4-dioxane. The number of wells sampled and the number
analyzed for each substance and parameter vary from year to year in accordance with changing
conditions and data requirements for different parts of the Site. The results are reported in
annual monitoring program reports.

Industrial Landfill Closure Monitoring

The Post-Closure Operation & Maintenance Plan (CDM, 1996) forms the basis for operation,
maintenance, and monitoring of the Industrial Landfill through the year 2028. This plan applies
to the physical maintenance of fencing/security systems, roadways, drainage systems, and the
Industrial Landfill final cover and gas control systems.

Inspections are designed to evaluate the Site for signs of deterioration, malfunction, or improper
operation of various systems. Site inspections are currently performed on a quarterly basis and
documented on Inspection Log forms that are included in Progress Reports provided to EPA and
MassDEP.

Landfill Gas Control. Gas extraction wells/vents are visually examined during inspections.
Following approximately four years of active landfill gas extraction and treatment via thermal
oxidation, it was determined that system shutdown (change to passive venting only) would not
cause an unacceptable health risk. However, as noted in the concurrence by EPA and MassDEP
(EPA, 2002), the thermal oxidation unit and all associated piping and equipment were to remain
in place and be maintained. The purpose of maintaining this equipment was so that it could be
activated again if long-term air quality monitoring detected an unacceptable health risk. The
final round of air quality monitoring was completed in 2007 and results confirmed that passive
venting was not causing an unacceptable health risk (Sullivan DCM, 2007). As a result, EPA, in
consultation with MassDEP, gave approval that the thermal oxidizer could be decommissioned
and the landfill gas passively vented to the atmosphere.

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FIVE-YEAR REVIEW PROCESS

Administrative Components

The PRP was notified of the initiation of the five-year review on February 13, 2014. The W. R.
Grace & Co., Inc. (Acton Plant) Superfund Site Five-Year Review was led by Derrick Golden of
the U.S. EPA, Remedial Project Manager for the Site and Sarah White, the Community
Involvement Coordinator (CIC). Jennifer McWeeney of the MassDEP assisted in the review as
the representative for the support agency.

The review, which began on February 13, 2014, consisted of the following components:

• Community Involvement;

• Document Review;

• Data Review;

• Site Inspection; and

• Five-Year Review Report Development and Review.

Community Notification and Involvement

A press release was issued by EPA Region 1 on February 13, 2014 announcing the start of the
FYR for this site as well as multiple other sites in the region. A Site-specific fact sheet
announcing the start of the FYR was issued on March 19, 2014 and distributed to local officials.
It stated the purpose of the review and where the results of the review would be made available;
i.e., the EPA web site and the Site information repository located at the Acton Town Library.

Document Review

This five-year review consisted of a review of relevant documents, including O&M records and
monitoring data. Applicable soil, sediment, and groundwater cleanup standards, as listed in the
Records of Decision for OU-1 (September 1989) and OU-3 (September 2005), were also
reviewed. Appendix B lists the documents reviewed for this current FYR as well as other
references cited throughout this report.

Data Review

Groundwater Monitoring

Five rounds (2009 through 2013) of annual groundwater monitoring have been performed since
the last FYR. In each round, samples were collected from a varying number of wells and
analyzed for one or more of the following: VOCs, inorganics, geochemical parameters, EPH and
VPH, and 1,4-dioxane. VDC, VC, and benzene continue to be the most frequently detected

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compounds at concentrations greater than their Interim Groundwater Cleanup Levels (IGCLs),
and 1,4-dioxane is a compound of interest. Figures 4 through 7 illustrate the extent of each of
these compounds in the groundwater at the Site in 2013. For comparison purposes, a depiction
of the extent of VDC in the groundwater in 2001 (Figure 8) is also included. Since VDC is
widespread at the Site, a comparison of Figure 5 to Figure 8 gives a good visual summary of the
extent of the improvement in groundwater quality since the FS and the ROD were completed.

The presence of 1,4-dioxane at the Site was first noted in 2006, when EPA requested that Grace
sample for it. Since then, the concentrations of 1,4-dioxane have been monitored in various
wells throughout the entire Site. EPA has determined that even using the maximum detected
concentration of 1,4-dioxane found in Site groundwater (36 |ig/L), 1,4-dioxane-contaminated
groundwater does not pose an unacceptable cancer risk necessitating an EPA cleanup
action. This issue was discussed in detail in a fact sheet issued by EPA in March 2012 (USEPA,
2012). There is no enforceable federal or Massachusetts maximum contaminant level (MCL) for
1,4-dioxane.

In 2011, MassDEP reduced the drinking water guideline for 1,4-dioxane from 3 |ig/L to 0.3
|ig/L. The MassDEP drinking water guideline is not considered an enforceable standard.
Similarly, in 2014, MassDEP reduced the Method 1 GW-1 standard for 1,4-dioxane (used to
regulate cleanup of MassDEP sites) from 3.0 |ig/L to 0.3 |ig/L.

The appropriate level of monitoring for 1,4-dioxane has undergone several cycles of review and
revision by the AWD and MassDEP Drinking Water Program staff, as well as by EPA and
MassDEP Superfund program staff. As a result, Grace is performing additional monitoring
activities, including additional sampling of the public water supply wells. Selected monitoring
for 1,4-dioxane will continue into the future, with results for this compound reported as part of
the monitoring program reports that are produced on an annual basis. The annual sampling
program will be re-evaluated each year by EPA and MassDEP as part of their review of Site-
wide groundwater quality.

For evaluation of groundwater conditions, the Site has historically been divided into six areas:
the Former Lagoon Area, the Northeast Area, the Southwest Area, the Assabet River Area, the
Southwest Landfill Area, and the Southeast Landfill Area. These areas are shown on Figure 4.
The results of groundwater monitoring in each of these areas is discussed below, with emphasis
on the 2013 data (Tetra Tech, 2013b).

Former Lagoon Area. The four extraction wells (SLBR, SLGP-R, NLBR-R, and NLGP) in the
Former Lagoon Area (FLA) that were part of the former (ARS) groundwater extraction system
were shut down in late 2008 and early 2009. The groundwater remedy for this area is
Monitored Natural Attenuation (MNA), and those four ARS extraction wells were not included
in the remedial action for this area.

Until 2010, the results from the monitoring well sampling in the FLA had shown that the
groundwater had fairly low levels of residual contamination. In 2010, the concentrations of
VDC and benzene in well OSA-13B increased to about 100 |ig/L. These results were presumed
to reflect changes in groundwater flow resulting from the shutdown of the extraction wells in this
area in 2008 and 2009. In response to the increase in contaminant levels found in OSA-13B,

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sampling was expanded in 2011 to include other nearby existing wells. The expanded
monitoring showed that the extent of the more highly-contaminated groundwater around OSA-
13B is limited both vertically and horizontally.

In other parts of the FLA, data from 2013 showed that the three primary groundwater
contaminants at the Site, VDC, VC, and benzene, exceeded their IGCLs of 7 |ig/L, 2 |ig/L, and 5
|ig/L, at four, three, and one monitoring well(s), respectively. With the exception of benzene at
OSA-13B (77 |ig/L), the concentrations that exceed IGCLs are within an order of magnitude of
the levels noted above.

Six monitoring wells (one bedrock and five overburden) in the FLA were analyzed for
geochemical parameters in 2013, including arsenic, manganese, and iron. Arsenic and/or
manganese concentrations remained notably elevated (As >50 |ig/L, Mn > 700 |ig/L) in four of
the six monitoring wells that are sampled for these parameters in the FLA. Site data suggest that
geochemical conditions associated with Site activities near former source areas have resulted in
increased solubility of naturally-occurring arsenic, as well as manganese and iron. As the
organic contaminant concentrations decline, it is expected that geochemical conditions will
return to a state in which the solubility of the naturally-occurring metals is no longer enhanced in
groundwater.

Sampling for 1,4-dioxane in the FLA was limited to one sample from each of three wells in
2011. The detected concentrations were 0.11J |ig/L, < 0.2 |ig/L, and 2.07 |ig/L. The highest
concentration was detected in well OSA-13B.

Northeast Area. When the lagoons at the Site were in operation, contaminated groundwater
flowed south and northeast from the FLA. The operation of the ARS extraction wells in the FLA
captured the contaminated groundwater in the source area near the former lagoons; however, the
portions of the plumes that were already beyond the area of capture were left to migrate toward
discharge points along portions of Fort Pond Brook or towards the School Street water supply
wells (where the contaminants are removed by treatment systems). The groundwater
contamination in the Northeast Area is the cut-off portion of the plume that flowed northeast
from the FLA. Cut off from its original source area, the plume is being flushed from the aquifer
as the groundwater flows to Fort Pond Brook or the School Street public water supply wells.
The plume is in the bedrock aquifer across much of the Northeast Area but rises into the
overburden north of Lawsbrook Road to discharge to the brook or the supply wells. The primary
plume contaminants are VDC and VC.

The untreated water from the School Street public water supply wells is currently, and has been
for decades, treated by air stripping to remove VOCs. The concentrations of COCs (VDC and
VC) in the untreated water have been close to or below MCLs in recent years. However, at the
time the OU-3 ROD was written, a portion of the plume in the bedrock aquifer beneath the Linde
(then BOC Gases) property had VDC concentrations in excess of 200 |ig/L (see Figure 8), and
the ROD was written to require mass removal in that area to hasten the decline of VOC
concentrations in the well field.

As described above, an extraction, treatment and reinjection system was constructed in the NE
Area and operated from April 2010 to September 2013. During that time, the VDC

The success of the extraction system in removing VDC was also reflected in the monitoring
wells in the NE Area. In 2009, before the system was activated, VDC concentrations in the NE
plume were >100 |ig/L in the area between the Linde facility and Lawsbrook Road, and were
>60 |ig/L from there to well cluster AR-31 in the School Street Well Field. By 2013, just prior
to the shutdown of the system, VDC concentrations in the northeast plume were >60 |ig/L only
in the immediate vicinity of well cluster AR-31 (66 |ig/L), and were 30 |ig/L or less at all other
sampled locations (see Figure 5). VC concentrations were equal to the MCL of 2 |ig/L near the
former extraction well and were slightly higher (3.3 |ig/L) at well cluster AR-31.

In 2013, one bedrock and six overburden monitoring wells in the NE Area were sampled for
inorganics. Extraction well NE-1 was sampled for arsenic, manganese, and iron. None of the
wells had a concentration of arsenic greater than the IGCL of 10 |ig/L. One of the overburden
wells had a highly elevated manganese concentration (2,600 |ig/L), and one of the bedrock wells
had a moderately elevated manganese concentration (620 |ig/L).

Sampling of monitoring wells in the NE Area between 2006 and 2009 indicated that 1,4-dioxane
was present in the groundwater in the vicinity of the School Street Well Field at concentrations
up to about 2 |ig/L. Samples from the water supply wells in the well field only had
concentrations of 1,4-dioxane less than 0.25 |ig/L, since supply wells tend to "average" the water
quality in their zones of contribution. In well MW-06B, located in the area targeted for mass
removal, the 1,4-dioxane concentration was about 1 |ig/L during this same time period.
Upgradient of that area, the concentration was 3.7 |ig/L in well MW-07B.

Although there is no MCL for 1,4-dioxane, the concentrations in the wells in the School Street
Well Field were well below a concentration level that would pose an unacceptable cancer risk
and necessitate an EPA cleanup action. The concentrations were also below the MassDEP ORS
non-enforceable drinking water guideline concentration of 3 |ig/L for 1,4-dioxane that existed in
2009. However, continued monitoring of 1,4-dioxane was (and still is) required by the agencies
as a precaution.

When the NE Area remediation system was started up in April 2010, extraction well NE-1 had
1,4-dioxane concentrations of about 0.7 |ig/L. After about four months of operation, the
concentrations rose to about 2 |ig/L and, for the remainder of the period of operation, the
concentrations averaged about 2 |ig/L. The NE Area treatment system was not designed to treat
for 1,4 dioxane, and the effluent that was injected into the upper overburden aquifer also had an
average concentration of about 2 |ig/L.

From the fall of 2013 to the fall of 2014, an expanded program for 1,4-dioxane sampling was
implemented by Grace in response to agency requests. In the NE Area, the concentrations of
1,4-dioxane in the Lawsbrook and Scribner supply wells were greater than 0.3 |ig/L in multiple
samples, though no concentration exceeded 0.35 |ig/L. The concentrations of 1,4-dioxane in the
Christofferson supply well were 0.2 |ig/L or less in multiple samples. The results from the
monitoring wells in the NE Area generally were similar to previous rounds, with a maximum

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concentration of 1.6 |ig/L in well PS-22B. All of these levels are well below EPA Superfund
requirements.

Southwest Area. The groundwater contamination has been almost completely flushed from the
bedrock and overburden aquifers in this area. VDC, VC, and benzene concentrations were well
below IGCLs in the few monitoring wells that were still being sampled in this area between 2009
and 2013.

Arsenic and manganese were analyzed at one bedrock and one overburden monitoring well in the
Southwest Area in 2013. The arsenic concentrations were below 10 |ig/L in both wells. The
overburden well had a highly elevated manganese concentration (4,300 |ig/L), and the bedrock
well had a moderately elevated manganese concentration (600 |ig/L). Any residual
contamination in this area will be remediated by MNA.

The expanded program for 1,4-dioxane sampling implemented by Grace in 2013 and 2014
included some wells in the Southwest (SW) Area. In the SW Area, the concentrations of 1,4-
dioxane in the Assabet 1A supply well were greater than 0.3 |ig/L in three of four quarterly
samples, with a maximum concentration of 0.38 |ig/L. In the nearby Assabet 2A water supply
well, concentrations of 1,4-dioxane were greater than 0.3 |ig/L in one of four samples (0.39
Hg/L).

The results for 1,4-dioxane from the monitoring wells in the SW Area in 2013 and 2014 were
generally similar to previous rounds and show that 1,4-dioxane is widespread in the bedrock
aquifer in this area at concentrations in the range of 1 |ig/L to 2 |ig/L. The 1,4-dioxane
concentration in well PT-03B1 was marginally higher at 2.9 |ig/L in 2013; the 1,4-dioxane in this
well is believed to originate from a source area on the opposite side of the Assabet River from
the Grace Site.

Assabet River Area. Similar to the Northeast Area, the groundwater contamination in the
Assabet River Area is the cut-off portion of a plume that flowed south in this area when the Site
was an active facility. Cut off from its original source area by the decades of operation of the
ARS, the plume is being flushed from the aquifer as the groundwater flows to the Assabet River.
The plume is present only in the downgradient part of this area, close to the river. Investigations
completed during the OU-3 RI showed that the bedrock aquifer exhibited low levels of
contamination across this area. The plume is primarily in the overburden aquifer and rises in
response to upward vertical gradients to discharge to the river.

Two overburden monitoring wells in the downgradient part of this area, close to the Assabet
River, were sampled between 2009 and 2013. Only VOCs were analyzed. By 2013, the benzene
concentrations in both wells had declined to levels below the IGCL of 5 |ig/L. The VDC
concentration (44 |ig/L) in one well exceeded the IGCL of 7 |ig/L, and the VC concentrations
(6.9 |ig/L and 20 |ig/L) in both wells exceeded the IGCL of 2 |ig/L. The remediation of this area
will be by MNA, as the end of the cut-off plume discharges to the Assabet River.

Southwest and Southeast Landfill Areas. The groundwater in these two areas downgradient of
the Industrial Landfill exhibits high levels of VDC, VC, benzene, and arsenic. The OU-3 ROD
requires that groundwater with the highest levels of these contaminants be captured and treated

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for discharge to Sinking Pond. Lower levels of contamination beyond the required capture zone
will be remediated by MNA.

In the Southwest Landfill Area, groundwater is extracted from wells MLF and WLF in the
overburden and from SWLF-2 in the bedrock. The highly-contaminated part of the plume is
within the capture zone of the extraction wells in both the bedrock and overburden aquifers.

This part of the plume was characterized in 2013 by VDC concentrations up to 310 |ig/L in the
bedrock and up to 200 |ig/L in the overburden. VC concentrations were up to 130 |ig/L in the
bedrock and up to 55 |ig/L in the overburden. Benzene concentrations in the SW Landfill Area
were lower, with a maximum of 15 |ig/L in the bedrock and 24 |ig/L in the overburden.

In the Southeast Landfill Area, groundwater is extracted from wells SELF-1 and SELF-2 in the
overburden. The highly-contaminated part of the plume is present in the overburden aquifer and
was characterized in 2013 by benzene concentrations up to 270 |ig/L. VDC and VC
concentrations in the Southeast Landfill Area in 2013 were lower, with maximum levels of 34
and 75 |ig/L, respectively.

In 2013, one bedrock and five overburden monitoring wells in the two Landfill Areas were
sampled for geochemical parameters including arsenic, manganese, and iron. The five extraction
wells (one bedrock and four overburden) were sampled for arsenic, manganese, and iron. The
arsenic concentrations in the two bedrock wells (SWLF-2 and AR-21), which are in or close to
the SW Landfill Area, were less than the IGCL of 10 |ig/L. The three overburden wells in the
SW Landfill Area had arsenic concentrations in the range of 16 |ig/L to 60 |ig/L. In the SE
Landfill Area, two overburden wells that are screened near the water table had arsenic
concentrations less than 10 |ig/L. However, the other four overburden wells in that area had
significantly higher arsenic concentrations, in the range of 50 |ig/L to 310 |ig/L.

Like the arsenic concentrations, the manganese concentrations in the two bedrock wells were
relatively low, less than 300 |ig/L. However, except for one overburden well in the SW Landfill
Area which also had a manganese concentration less than 300 |ig/L, the other overburden
extraction and monitoring wells had manganese levels in the range of 1,700 |ig/L to 4,500 |ig/L.

Most of the data concerning the concentrations of 1,4-dioxane in the Landfill Areas are from the
extraction wells, which have been sampled three or four times per year since 2009. In the SW
Landfill Area, the concentrations in the extraction wells range generally from 1 |ig/L to 6 |ig/L.
No monitoring wells in this area have been sampled for 1,4-dioxane since 2006. In the SE
Landfill Area, concentrations are as high as about 35 |ig/L in the extraction wells and about 25
|ig/L in the two monitoring wells that are sampled for it. The levels of 1,4-dioxane in the SE
Landfill Area are the highest at the Site but are still considered within acceptable limits by EPA.

Summary of Groundwater Monitoring Results. In the NE Area, the area of elevated VDC
concentrations that was the target of the remediation system (see Figure 8) was nearly gone by
2013 (see Figure 5). The end of the plume is currently in the vicinity of well AR-3 ID, which has
the highest remaining concentrations of VDC (66 |ig/L) and VC (3.3 |ig/L) in the NE Area. It is
anticipated that these levels will continue to decline.

VOCs are mostly below IGCLs in the FLA, the SW Area, and the Assabet River Area.

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Concentrations of VOCs and inorganics that are above IGCLs, located mostly in the
downgradient portion of the Assabet River Area and at several isolated areas in the FLA, are
expected to decline as the MNA remedy proceeds.

In the SW and SE Landfill Areas, concentrations of VOCs and inorganics are elevated but
mostly declining. The highest levels of contamination are within the capture zone of the
extraction system, which is being sustained as required by the ROD. Beyond the capture zone,
the concentrations of VOCs and inorganics are expected to decline as the MNA remedy for that
portion of the Landfill Area proceeds.

The highest concentrations of 1,4-dioxane are detected in the Landfill Areas, where
concentrations in the range of 4 |ig/L to about 35 |ig/L occur currently. EPA has determined that
even using the maximum detected concentration of 1,4-dioxane found in Site groundwater (36
|ig/L), 1,4-dioxane-contaminated groundwater does not pose an unacceptable cancer risk that
would necessitate an EPA cleanup action (USEPA, 2012). There is no MCL for 1,4-dioxane,
and a cleanup level was not established by EPA in the ROD; however, concentrations of 1,4-
dioxane continue to be monitored, in response to stakeholder concerns.

North Lagoon Wetland Monitoring

Monitoring of the restored wetland areas of North Lagoon Wetland and Sinking Pond, affected
by the remedial activities, was conducted in 2012 and 2013, the first two years after sediment
removal activities. The results of the 2012 monitoring activities identified several conditions that
could affect the ability of the Site to meet all vegetation performance standards within the
prescribed monitoring period. Adaptive management steps, including additional seeding,
supplemental planting, and invasive species removal were undertaken in 2012 to facilitate
achievement of the restoration goals.

The 2013 spring monitoring results showed that the total percent of the planted trees and shrubs
was 80%, below the 85% survivorship standard. Maintenance activities have been proposed to
address replacement plantings, in 2014. In 2013, counts of aquatic plants in the inlet of Sinking
Pond showed that the number of observed aquatic plants significantly exceeded the number of
plants originally planted in this area. A total of six different species were observed. These results
indicate that planted plugs have helped to colonize the Inlet.

Results of the 2013 monitoring activities indicate that maintenance work performed in 2012 and
early 2013 was successful in improving conditions in the restored habitats of the Site. The
ground cover performance standard was met in all restored habitats in 2013, sedges now
dominate the sedge marsh, and aquatic plants at the Inlet to Sinking Pond are almost triple the
number originally introduced.

Overall the monitoring of restored wetland habitats indicates that restoration has been largely
successful. In order to meet performance standards, in 2014, there will be additional monitoring
and management of invasive species, and possibly planting of more trees and shrubs.

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Sinking Pond Sediment Monitoring

Post-construction monitoring and maintenance procedures established in the Final Sediment
Demonstration of Compliance and Maintenance Plan (ARCADIS, 2012c) included sampling of
both sediment remediation areas (North Lagoon Wetland and Sinking Pond) in advance of this
Five Year Review. Sediment sampling was performed in the Sinking Pond and North Lagoon
Wetland areas in April 2014, in compliance with remedy monitoring requirements. This
sampling included collection of sediment from 20 locations in Sinking Pond and 15 locations in
the North Lagoon Wetland at a depth of 0-12 inches below the surface of the sediment.

Data for the Sinking Pond and North Lagoon Wetland sediments were evaluated using EPA's
ProUCL software to determine 95% upper confidence level (UCL) values for the following
datasets:

• Arsenic results for all Sinking Pond samples (i.e., representing the portion of the pond
above the thermocline where the cleanup levels apply).

• Arsenic results for the 10 Sinking Pond samples located within the defined "human
accessible" portion of the pond (as described in the Sediment Remedial Design Report,
ARCADIS 2011).

• Arsenic and manganese data for all samples from the North Lagoon Wetland area.

Based on the ProUCL results, each of the data sets had 95% UCL values below the
corresponding clean-up target values. The calculated 95% UCL concentrations of arsenic were
9.7 mg/kg for all of the areas of Sinking Pond, and 15 mg/kg for the subset of samples in human-
accessible areas. Both of these values are below the target clean-up level for sediments of 42
mg/kg. Similarly, the 95% UCLs for sediment in the North Lagoon Wetland were 14 mg/kg
arsenic and 240 mg/kg manganese, which are both also below the target clean-up levels of 28
mg/kg arsenic and 2,030 mg/kg manganese, for this area.

Site Inspection

The inspection of the Site was conducted on May 21, 2014. In attendance were Derrick Golden,
U.S. EPA; Jennifer McWeeney, MassDEP; Thor Helgason (de maximis - site manager for the
PRP); Anthony Esposito (ARCADIS - wetland restoration contractor for the PRP); and Sean
Czarniecki and Deborah Roberts (AECOM - oversight contractor for EPA). The purpose of the
inspection was to assess the protectiveness of the remedy. The Site Inspection Checklist and
selected photographs taken during the inspection are included in Appendix C. The inspection
included the following items: 1) Industrial Landfill inspection, 2) inspection of Landfill Area
groundwater treatment system; and 3) inspection of restored areas (North Lagoon Wetland and
Sinking Pond).

Landfill Area Inspections. The purpose of the Industrial Landfill and Landfill Area treatment
system inspections was to help assess the protectiveness of the OU-1 and OU-3 remedies by

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observing the condition of the site fence, the landfill cover and drainage system, the landfill gas
passive vent system, and the landfill area groundwater collection/treatment system.

Similar to the previous (2009) inspection, minor issues were noted during the site inspection of
the landfill:

• There is standing water in several locations in the rip-rapped perimeter drainage swale
around the landfill. Standing water in the perimeter swale on the south, southeast, and
northwest areas appears to either be the result of sedimentation adjacent to and directly
below the rip-rap down chutes just downstream of the standing water, or the result of
localized settling. The vegetation is trimmed regularly and there does not appear to be
any impact to the underlying liner.

• An apparent groundhog burrow was observed on the side of the landfill, near one of the
landfill gas monitoring points.

• One passive landfill gas vent on the southern side of the landfill was noticeably leaning,
as if struck by a mowing tractor. Onsite personnel stated that it is still venting. There
was no visual evidence of gas buildup or emissions elsewhere (via stressed vegetation).

Monitoring of vegetative growth in the perimeter swale should continue. Sediment and mowing
clippings should be removed from the perimeter swale to promote positive drainage and
eliminate standing water on the south, southeast and northwest sides of the landfill.

Construction of the landfill area groundwater treatment system was completed in 2011, so the
equipment/operation is fairly new and appears to be operating efficiently. There are no floor
drains leaving the building. Containment areas and closed sumps will capture any spills that may
occur. Chemicals appear to be stored properly. A bypass piping system was developed for the
extraction system to allow for cleaning (pigging) of the piping due to iron fouling. It may be
appropriate to revise the O&M plan to include the procedure for establishing a bypass during the
cleaning process.

Wetland Restoration Inspection. The site visit included an inspection of the wetlands
restoration at Sinking Pond and the North Lagoon Wetland. Areas of the Site impacted by
excavation of sediments and subsequently restored had been seeded and planted in 2011
following the removal actions. Site observations during the inspection were consistent with the
wetland monitoring results reported by ARCADIS in the 2013 Vegetation Monitoring Report,
discussed above.

In general, both restoration locations are well-vegetated. The upland banks around Sinking Pond
are covered with herbaceous vegetation, mostly grasses, with no major areas of wash-outs. The
water levels at Sinking Pond appeared lower than previous years and were to be confirmed by
ARCADIS in a later data collection event in June 2014. The areas of bordering vegetated
wetlands at the edge of the water line around the pond were developing wetland vegetation
slowly. The vegetation planted in the inlet of Sinking Pond appeared to be maturing, thereby
meeting performance standards. There has been some mortality of shrubs and trees around the
bank of Sinking Pond since data was collected for the 2013 monitoring report. Data on the

-------
number of surviving trees and shrubs will be included by ARCADIS in a 2014 monitoring report.

The area of the sedge marsh within the North Lagoon Wetland has developed a good density of
wetland vegetation, dominated by sedges along the edges of the marsh, with cattails and sedges
prominent in the center of the marsh. The remainder of the North Lagoon Wetland, located in the
wooded marsh and along Fort Pond Brook, has become covered with suitable wetland
vegetation. There seems to be an increase in the mortality of planted trees and shrubs since data
collection in 2013. Data on the number of surviving trees and shrubs in the North Lagoon
Wetland area will be included by ARCADIS in a 2014 monitoring report. Depending on the
percentage rate of survival, additional trees and/or shrubs may need to be planted.

Interviews

During the FYR process, interviews were conducted with Town of Acton and Acton Water
District officials, citizens who have been involved in Site activities, the PRP representative, and
the MassDEP project manager. The purpose of the interviews was to document any perceived
problems or successes with the remedy implementation to date. Most respondents elected to
provide written responses to questions submitted to them in advance. Others responded to
questions provided in advance during a telephone conversation that was subsequently
documented on an interview record form. Completed interview record forms for all parties are
included in Appendix D.

18

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TECHNICAL ASSESSMENT

Question A: Is the remedy functioning as intended by the decision documents?

The review of documents indicates that the OU-1 remedy was implemented in accordance with
the ROD for OU-1 and is functioning as intended. The Industrial Landfill is owned and
maintained by W.R. Grace, wastes were solidified and capped, access is restricted by a fence,
and a deed notice has been filed with the Registry of Deeds that puts parties on notice that the
landfill cannot be disturbed except by written permission of MassDEP; hence, there is no current
potential for exposure to waste left in place. The fence surrounding the landfill is intact and kept
in good repair. The passive venting of landfill gas does not pose an unacceptable health risk or
hazard (see Question B below for details of this evaluation). W.R. Grace has stated that it
intends to maintain ownership of the land surrounding the Industrial Landfill, and control access
to it.

The OU-3 groundwater remedial action is performing as expected, and it is anticipated that
cleanup levels will be achieved in a reasonable time frame. The Landfill Area groundwater
extraction system is containing the plume within the ROD-required capture zone. Operation
procedures are adequate to maintain extraction well yields. Beyond the capture zone,
contaminant concentrations are decreasing through MNA. The Landfill Area groundwater
treatment system is removing VOCs and inorganics from the influent and meeting the standards
for discharge of the effluent to Sinking Pond. Operation and maintenance procedures are
adequate to maintain the functionality of the treatment system at the required level of
performance.

Also part of OU-3, the Northeast Area groundwater extraction and treatment system operated for
3.5 years. The system reduced the VOC concentrations in the most contaminated portion of the
plume, as intended, and the concentrations of the remaining contaminant mass are still
decreasing through continued MNA. In 2013, no VOCs were detected at concentrations above
MCLs in the supply wells in the School Street Well Field. The Town of Acton has expressed
concern regarding EPA's decision to shut down the Northeast Area treatment system in 2013.
However, EPA continues to believe that the system has served its purpose as intended under the
ROD, and the decision to shut down the system was the correct one.

Treated water is supplied to Town residents and there is an administrative hold on private
irrigation well installation within 500 feet of the plume areas. Ongoing monitoring and
evaluation of groundwater contaminant concentrations Site-wide will continue, as planned, until
cleanup goals are attained.

Under OU-3 actions, contaminated sediments were removed from Sinking Pond and the North
Lagoon Wetland between June and November 2011 and disposed off-site. Confirmatory
samples were collected and additional excavation was performed, as needed, to attain cleanup
levels, and both areas were restored in late 2011. Monitoring of restored wetland habitats is
ongoing and indicates the restoration has been largely successful.

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Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial
action objectives (RAOs) used at the time of the remedy selection still valid?

Question B is addressed by reviewing the human health and ecological risk assessments that
formed the basis for the selected remedies, describing any significant differences as compared to
current risk assessment practice, and qualitatively evaluating the impact of any such differences
on remedy protectiveness.

Review of the Human Health Risk Assessments and Toxicity Factors Serving as the
Basis for the Remedy

The risk assessment conducted for OU-1 (Alliance, 1989) evaluated the risks and hazards
associated with the ingestion of groundwater, direct human contact with soil, and ingestion of
surface soil, for: (1) the entire Site considered as a single source; and (2) each individual source
area. The primary risks and hazards observed in this analysis were those associated with
ingestion of contaminated groundwater by a small child and adult/youth. The primary risk
contributors for the groundwater ingestion pathway were VDC, VC, arsenic, lead, and zinc. The
risks and hazards associated with incidental ingestion of and dermal contact with surface soil
were less significant than those estimated for groundwater ingestion. However, elevated risks
and hazards for soil exposures were attributable to VDC, VC, and arsenic.

The risk assessment conducted for OU-3 (Menzie-Cura, 2005) included a re-evaluation of the
risks and hazards of contaminated groundwater used as household water or as irrigation water, as
well as direct contact with shallow groundwater contaminants by excavation workers. The
potential for vapor intrusion (VI) from groundwater contaminants into structures overlying the
groundwater was also considered. In addition, the analysis also quantified the risks and hazards
associated with recreational exposure to contaminants in surface water and sediment by
incidental ingestion and dermal contact. Potential risks associated with the VI pathway, worker
contact with shallow groundwater, and recreational exposures to surface water were deemed to
be insignificant. However, risks and hazards above EPA's risk management guidelines were
calculated for groundwater used in households or as irrigation water for all six geographic areas
of the Site, and for sediment in Sinking Pond and at North Lagoon Wetland. The primary risk-
contributing chemicals for groundwater included benzene, methyl tert-butyl ether (MTBE),
VDC, VC, trichloroethene (TCE), bis(2-ethylhexyl) phthalate (BEHP), arsenic, chromium,
manganese and nickel. Beryllium and lead, though not contributing significantly to risk and
hazard, exceeded MCLs or MCLGs. For sediment, arsenic was the primary risk contributor.

For soil, EPA established cleanup goals for future residential land use for five indicator
chemicals (VDC, VC, ethylbenzene, benzene, and BEHP) listed in Table 3 of the OU-1 ROD.
The attainment of cleanup goals for the five chemicals was expected to reduce residual
contamination of other compounds found at the Site to such low levels as to present no
significant risk from direct contact or from migration of contaminants to groundwater. The
indicator chemicals selected also included compounds identified in underlying soils that could
contribute to risk following leaching to groundwater. The soil cleanup goals were generated
based on a model that calculated the level of the indicator chemical which, if left in soil as a
residual, would not lead to further contamination of groundwater at levels that exceed drinking
water standards (i.e., MCLs). A number of additional chemicals were identified as soil and
groundwater "indicator chemicals", as listed in Table 1 of the OU-1 ROD.

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The OU-3 ROD established IGCLs as MCLs or MCLGs, if available. For chemicals lacking
regulatory limits, risk-based values or practical quantitation limits were used as IGCLs.

Sediment cleanup goals for arsenic in Sinking Pond and at North Lagoon Wetland were set at
site-specific background concentrations.

In this Five-Year Review report, the toxicity values that served as the basis for the soil,
groundwater, and sediment cleanup levels, as contained in the OU-1 and OU-3 RODs, as well as
the toxicity values used for the soil "indicator chemicals" have been re-evaluated to determine
whether any changes in toxicity impact the protectiveness of the remedy. Any changes in current
or potential future exposure pathways or exposure assumptions that may impact remedy
protectiveness are also noted, as described below. In addition, environmental data, available
since the last Five-Year Review, have been qualitatively evaluated to determine whether
exposure levels existing at the Site present a risk to current human receptors.

Changes in Toxicity Values

Appendix E, Table 1, presents the changes in toxicity values (oral reference doses and oral
cancer slope factors) of compounds for which soil cleanup levels were developed, as well as
compounds selected as soil "indicator chemicals" in 1989 and for compounds of potential
concern selected in the 2005 risk assessment. Updated toxicity information was obtained from
the Integrated Risk Information System (IRIS; USEPA, 2014) and other current EPA sources
(e.g., the Superfund Technical Support Center).

For most contaminants, changes to toxicity information have been minimal and primarily reflect
decreases in toxicity (e.g., VDC and barium), though some compounds are now believed to have
greater toxicity than thought in 1989 (e.g., arsenic, TCE, and benzene). Changes in toxicity
values for most groundwater compounds (e.g., arsenic, VDC, and TCE) would not affect remedy
protectiveness since IGCLs are based on MCLs or MCLGs. Toxicity values have not changed
since 2005 for those groundwater compounds with risk-based cleanup levels (nickel, manganese,
and MTBE). Once IGCLs are achieved, an evaluation should be performed to demonstrate that
the risk associated with potable groundwater use is within or below EPA's risk management
guidelines. Until IGCLs are achieved and groundwater use is demonstrated to not pose a risk to
human health, the installation of private wells and associated groundwater exposure pathways
should be prevented. The Town provides treated water for use in the community, and the Acton
Board of Health has established an administrative hold on the installation of private irrigation
wells within 500 feet of the mapped region of contaminated groundwater that lies within the
Town, preventing current exposure to remaining groundwater contamination.

One compound not identified as a groundwater compound of potential concern in the risk
assessment is 1,4-dioxane. Though commonly associated with chlorinated solvent
contamination, sampling for this compound was not conducted until after the OU-3 ROD was
signed. Because it has now been detected in groundwater, the risk evaluation to be performed
after achieving IGCLs should include 1,4-dioxane as a potential risk contributor.

To assure that the soil cleanup goals for the selected indicator compounds in soil do not present a
direct contact risk using current toxicity information, a comparison of the soil cleanup goals to

21

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EPA 2014 risk-based residential soil screening levels is provided in Table 4. The residential soil
screening levels are developed based on current toxicity information and correspond to a
carcinogenic risk of 1 x 10"6 and a noncarcinogenic hazard of 1. Soil cleanup levels are below
the risk-based screening level except for the highest cleanup level developed for VC at the
Secondary Lagoon. However, the highest cleanup level for VC (75 |ig/kg) only slightly exceeds
the screening level set at a cancer risk of 1 x 10"6 (59 |ig/kg). Therefore, this comparison
indicates that the soil cleanup levels would not be associated with a cumulative cancer risk and
noncancer hazard greater than EPA's risk management criteria, and the soil cleanup levels
remain adequately protective for future residential land use.

Table 4. Comparison of ROD Soil Cleanup Levels to 2014 Risk-Based Screening Levels

Pollutant

Low Range of
Soil Cleanup
Level (|ig/kg)

High Range of
Cleanup Level
(l-ig/kg)

2014 Residential Risk-
Based Screening Level
(l-ig/kg)

Ethylbenzene

619

4914

5,800

Vinyl chloride

Benzene

1,200

Bis(2-

ethylhexyl)phthalate

491

38,000

1,1 -Dichloroethene

230,000

Even though soil cleanup goals remain protective, soil containing contaminant levels in excess of
cleanup goals exists in the capped Industrial Landfill. In order to prevent direct contact
exposures and the leaching of contaminants from these soils, continued maintenance of the
landfill cap is required.

Sediment cleanup levels for Sinking Pond and the North Lagoon Wetland were established based
on site-specific background concentrations, protective of future recreational exposures. Because
residual sediment arsenic concentrations in human accessible portions of Sinking Pond and the
North Lagoon Wetland are consistent with background concentrations, based on a 95% Upper
Confidence Level comparison, the remedy remains protective for recreational sediment
exposures, should they occur in the future.

Emissions from the Industrial Landfill were not evaluated in the 1989 risk assessment, but have
been evaluated since then to support the change from an active landfill gas collection and
treatment system to passive venting. Air dispersion modeling was performed most recently on
November 2007 landfill gas emission data for six target compounds to estimate exposure
concentrations during passive venting. The November 2007 sampling was the final round of
sampling of emissions, per the O&M plan for the landfill (CDM, 1996). These data were
evaluated in the 2009 Five-Year Review, and it was concluded that the landfill emissions do not
cause an unacceptable human health risk or hazard. Due to changes in toxicity values between

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2009 and 2014, the 2007 modeled air concentrations are compared in Table 5 to risk-based
screening levels (EPA, 2014), to be protective of continuous exposures to the most sensitive
receptor populations and based on the most up-to-date toxicity information available. The target
risk levels for the screening levels are a noncarcinogenic hazard quotient of 1 and an incremental
lifetime cancer risk of 1 x 10"6. Because the modeled air concentrations are significantly below
the risk-based screening levels, the landfill emissions do not cause an unacceptable human health
risk or hazard.

Table 5. Comparison of Modeled Air Concentrations to 2014 Risk-Based Screening Levels

Pollutant

24-hour Impact
(Hg/m3)

Annual Impact
(Hg/m3)

2014 Risk-Based Screening
Level for Residential Air
(Hg/m3)

Ethylbenzene

0.0618

0.01

1.1

Vinyl chloride

0.0396

0.005

0.17

Xylenes

0.1226

0.015

100

Benzene

0.0480

0.006

0.36

Toluene

0.0560

0.007

5200

1,1 -Dichloroethene

0.0595

0.007

210

Changes in Exposure Pathways/Assumptions

There have been no changes in land use since the last Five-Year Review. The W.R. Grace
property continues to be vacant and partially fenced, preventing exposures to remaining
contamination except for the possible occasional trespasser. The OU-3 remedy is complete at
Sinking Pond and at North Lagoon Wetland, and residual concentrations of arsenic are consistent
with site-specific background concentrations. With respect to groundwater use, the Town
provides treated water for use in the community, and the Acton Board of Health has an
administrative hold on issuing permits for the installation of private irrigation wells in and near
the plume area. The current institutional controls, consisting of the deed notice on the Industrial
Landfill and the administrative hold on private well installation, may need to be supplemented
with additional controls.

A new method to evaluate compounds with mutagenic modes of action is now recommended by
EPA. The currently recommended method was not implemented in the 1989 and 2005 risk
assessments because the EPA carcinogen risk assessment guidance was published after
completion of the risk assessments. The current methodology calls for the use of age-specific
adjustment factors to account for an increased sensitivity during early life for compounds
including methylene chloride, VC, TCE, and carcinogenic PAHs detected at the Site. In the 2005
Supplemental Guidance for Assessing Susceptibility from Early-Life Exposures to Carcinogens,
EPA recommends evaluating chemicals with mutagenic modes of action using either chemical-
specific data on susceptibility from early-life exposures or age-dependent adjustment factors

23

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(ADAF) applied to the cancer slope factor. Because chemical-specific data on susceptibility
from early-life exposure were available for the derivation of VC's updated cancer slope factor,
the updated slope factor is used for risk characterization and an ADAF is not applied. ADAFs
are applied when assessing risk for methylene chloride, TCE, and the carcinogenic PAHs.

The 2005 risk assessment included the early-life calculation for VC since guidance was available
for this compound at that time. However, the supplemental early life calculation was not
performed for the other chemicals in 2005. Carcinogenic PAHs and methylene chloride were
largely non-detect in groundwater, while the MCL is used as the IGCL for TCE. For sediment,
TCE and methylene chloride were largely non-detect. Carcinogenic PAHs in sediment were
minor risk contributors and, in retrospect, their significance would not increase to a level of
concern if the early-life risk was added to the 2005 sediment risk. Therefore, the lack of the
early-life calculation for methylene chloride, TCE, and carcinogenic PAHs does not affect
remedy protectiveness for sediment or groundwater. Based on the report entitled: 5 Year
Sediment Investigation Summary Report, prepared by ARCADIS, dated June 6, 2014, and the
extent of soil clean-up performed, it is likely that these compounds are present in soils at
negligible levels or at levels consistent with background concentrations.

In February 2014, EPA published updated default exposure assumptions for Superfund Sites,
based on exposure studies considered and evaluated in the 2011 Exposure Factors Handbook.
Some of the recommended exposure assumptions are more conservative than those used
previously, while some are less conservative. Overall, however, use of the 2014 recommended
exposure assumptions results in a slight decrease in risk levels, which supports the continued
protectiveness of the remedies. It should also be noted that because the Industrial Landfill is
capped, there is no potential exposure. Also, the 2014 sediment monitoring results indicate that
background concentrations have been achieved. Lastly, once groundwater cleanup levels are
achieved, groundwater risk will then be re-evaluated.

Though the VI pathway from groundwater to indoor air was evaluated in the 2005 risk
assessment and was determined, at that time, to be associated with negligible risk, this pathway
has been re-evaluated due to the February 2014 update in the standard default exposure factor
assumptions and recent updates to toxicity values. The VI screening evaluation is presented in
the following section (Evaluation of Recent Sampling Data). The re-evaluation determined that
the remedies still remain protective and the VI pathway is not a concern.

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Evaluation of Recent Sampling Data

Groundwater

The VI pathway updated risk-based screening has been conducted in a manner generally
consistent with that used in the 2005 risk assessment. Nine exposure areas were evaluated, as
presented on Table 6 below. The two most recent rounds of groundwater data (see Table 2 in
Appendix E for specific dates) were assessed using the new screening levels as part of an updated
assessment of the VI pathway for each exposure area. For the Assabet River Area, none of the
applicable wells had been sampled more recently than for the 2005 risk assessment (i.e., 2000 or
2001). As a result, for this area, the 2000/2001 data were re-screened using updated groundwater
VI screening levels (VISLs). For all other exposure areas, monitoring well VOC data collected
between 2005 and 2013 were used, as available (see Table 2 in Appendix E for specific details).
In addition, for the Northeast Area, baseline well data from four wells installed in 2011 were also
used to assess the VI pathway.

At each exposure area, groundwater concentrations were compared to VISLs to see if there could
be a potential impact to indoor air. The VISLs were calculated from formulas obtained from
EPA's 2014 VISL calculator (version 3.2.1) and EPA's May 2014 residential indoor air RSLs, as
presented in Appendix E, Table 3. The VISLs correspond to a cancer risk of 1 x 10"6 for
carcinogens or a hazard quotient of 1 for noncarcinogens.

VOC concentrations are below the VISLs presented in Table 6, except for benzene, 1,2-
dichloroethane, ethylbenzene, TCE, and VC, at select locations. For benzene, 1,2-
dichloroethane, ethylbenzene and TCE, the maximum detected concentrations exceed the VISLs
based on a cancer risk of 1 x 10"6 by less than 2-fold, indicating the cancer risk is less than
2 x 10"6 for each of these compounds. For VC, the maximum detected concentrations exceed the
cancer-based VISL by less than 10-fold, except for the maximum concentration in the Former
Lagoon Area, which exceeds the VISL by 12-fold. This indicates that VC may be associated
with a cancer risk of up to approximately 1 x 10"5, which is within the EPA acceptable risk range
of 10"4to 10"6.

Therefore, the VI pathway would not be associated with a cumulative cancer risk and
noncarcinogenic hazard greater than EPA's risk management criteria, confirming the conclusions
of the 2005 risk assessment and indicating that the remedy is protective of VI. This pathway may
require further consideration as methods used to evaluate this complex pathway evolve.

However, it is expected that the potential for VI should decrease as groundwater cleanup
progresses and concentrations of volatile groundwater contaminants continue to decrease over
time.

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Table 6: Comparison of Maximum Groundwater Concentrations to Vapor Intrusion

Screening Criteria

voc

Maximum Groundwater
Concentration (|ig/L)

Vapor Intrusion Screening
Level (|ig/L)(a)

Assabet Wellfield Public Water Supply

Chloromethane

0.32

260

Methyl tert-butyl ether

0.83

460

Trichloroethene

0.23

1.2

Assabet River Area

Acetone

1.4

22,000,000

Benzene

0.23

1.6

2-Butanone

1.3

2,200,000

1,1 -Dichloroethene

1.7

200

Trichloroethene

0.39

1.2

Vinyl chloride

0.2

0.15

Former Lagoon Area

Acetone

59

22,000,000

2-Butanone

3.1

2,200,000

Carbon disulfide

1.7

1,200

1,1 -Dichloroethene

14

200

Ethylbenzene

5.8

3.4

Styrene

0.72

8,900

Toluene

7.5

19,000

Vinyl chloride

1.8

0.15

Northeast Area

Acetone

64

22,000,000

Benzene

0.45

1.6

2-Butanone

1.3

2,200,000

Carbon disulfide

0.68

1,200

Chloroform

0.35

0.8

26

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Chloromethane

0.26

260

Dibromochloromethane

0.77

3.1

Cis-1,2-Dichloroethene

0.66

NA

1.1 -Dichloroethene

28

200

Methyl tert-butyl ether

1.1

460

Methylene chloride

1.9

750

T etrachl oroethene

0.33

15

Trichloroethene

2.4

1.2

Vinyl chloride

0.97

0.15

Powder Mill Plaza Irrigation Well

Methyl tert-butyl ether

0.31

460

Trichloroethene

1.2

1.2

Southeast Landfill Area

Acetone

24

22,000,000

Benzene

3

1.6

2-Butanone

3.1

2,200,000

1,1 -Dichloroethane

2.6

7.8

1,2-Dichloroethane

3.9

2.3

1,1 -Dichloroethene

8

200

Cis-1,2-Dichloroethene

0.3

NA

1,2-Dichloropropane

1.5

2.4

Vinyl chloride

0.74

0.15

School Street Wellfield Public Water Supply

1,1 -Dichloroethene

4.1

200

Methyl tert-butyl ether

0.27

460

Southwest Area

1,1 -Dichloroethene

0.95

200

Southwest Landfill Area

Acetone

97

22,000,000

27

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2-Butanone

2.8

2,200,000

Chloromethane

0.34

260

1,1 -Dichloroethane

0.34

7.8

1,2-Dichloroethane

2.3

1,1 -Dichloroethene

4.1

200

1,2-Dichloropropane

0.51

2.4

Methyl tert-butyl ether

0.54

460

(a) Values taken from Appendix E, Table 3. The screening concentrations corresponding to a cancer risk of 10"6 and
noncancer hazard of 1.

NA - Not available.

Starting in 2006, groundwater samples were collected for analysis of 1,4-dioxane. Monitoring for
1,4-dioxane will continue as part of the annual program. 1,4-Dioxane has not been included in
this VI screening. However, because 1,4-dioxane does not readily volatilize from groundwater
and does not meet EPA's definition of a volatile compound, the lack of inclusion of this
compound in the VI screening does not affect EPA's conclusion that the remedies still remain
protective and the VI pathway is not a concern.

Discharge Effluent to Sinking Pond

The Landfill Area Groundwater Treatment System (GWTS) began operation in 2011. Extracted
groundwater is being treated for removal of arsenic, manganese, iron and VOCs, including 1,4-
dioxane and chlorine, before surface discharge to Sinking Pond. According to the 2013 and
2014 GWTS reports, effluent concentrations ranged from non-detect to 1.5 |ig/L for VDC, non-
detect to 1.3 |ig/L for benzene and were non-detect for VC. Concentrations of arsenic, iron and
manganese ranged from 0.62 to 2.9 |ig/L, non-detect to 83 |ig/L and 0.79 to 200 |ig/L,
respectively, in the discharge effluent. The low levels of VOCs being discharged to the pond
quickly volatilize and dilute into the surface water, posing a negligible risk to potential
trespassers at the pond. The concentrations of arsenic, iron and manganese, as well as other
metals measured in the effluent discharge in 2013 and 2014, are lower than or consistent with
those evaluated in the 2005 risk assessment, indicating that surface water exposure pathways
continue to be associated with negligible risk to potential current as well as future users of the
pond.

With the remedial action completed, arsenic levels in Sinking Pond sediment are consistent with
site-specific background concentrations. The arsenic concentrations in the GWTS effluent have
been in the range of approximately 0.6 |ig/L to 3 |ig/L, and the discharge limit is 4 |ig/L. At a
flow rate of about 50 gpm, the rate at which arsenic is being added to the pond by the GWTS is
too low to significantly re-contaminate the sediment. Note that the elevated concentrations of
arsenic that existed in the sediment prior to remediation were believed to have been the result of
decades of ARS discharge of effluent with arsenic concentrations in the range of 20 |ig/L to 30
|ig/L, at a flow rate nearly an order of magnitude higher than the GWTS.

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Ecological Risk Review

A Baseline Ecological Risk Assessment (BERA) was completed for OU-3 in 2005 (Menzie-
Cura, 2005b). The two habitats of concern that were the focus of the BERA were North Lagoon
Wetland and Sinking Pond. North Lagoon Wetland is a wetland area between the former North
Lagoon and the perennial stream Fort Pond Brook. Sinking Pond is a kettle pond located in the
southwestern portion of the Site that does not have an outlet, and receives discharges from the
Landfill Area groundwater treatment system and storm water runoff from surrounding areas. In
the BERA, risks were identified to semi-aquatic wildlife and benthic invertebrates in sediment
from the North Lagoon Wetland and Sinking Pond and additionally to fish in Sinking Pond.
The 2005 BERA concluded that there were no unacceptable ecological risks from exposure to
surface water.

The BERA was conducted using methodology which would generally comply with current EPA
risk assessment guidance. The minor discrepancies between current guidance and previous
guidance exist in the areas of benchmarks and toxicity values utilized. For most contaminants,
changes to toxicity information have been minimal. The selection of contaminants of concern
(COCs) in sediment was based on screening that is generally consistent with methodology and
benchmarks currently used in ecological risk assessments and consistent with guidance.

The ROD for OU-3 developed RAOs for sediments for the protection of the environment,
including the control of discharge of treated effluent groundwater to prevent unacceptable
impacts to sediment and surface water in Sinking Pond, and prevention of exposure to
contaminants in sediment that pose unacceptable risk to the environment. As stated in the 2005
ROD, the selected remedy included excavation of contaminated sediments exceeding cleanup
levels within Sinking Pond and the North Lagoon Wetland.

Cleanup levels were set in the ROD for ecological receptors in the North Lagoon Wetland and in
Sinking Pond to address exposure to sediments. In the North Lagoon Wetland, the basis of the
ecological clean-up goal for arsenic was 28 mg/kg (maximum background concentration) for the
protection of both invertebrates and semi-aquatic wildlife receptors. The protective level for
manganese in sediments was set at 2,030 mg/kg and was a site-specific risk-based level based on
dietary models for mammalian receptors in the North Lagoon Wetland.

The ROD identified the short-term goal for the most biologically active areas of Sinking Pond
(the inlet and areas where the ground slope is shallow) as remediation of the areas with arsenic
greater than 730 mg/kg or where any of the four COCs (arsenic, copper, iron and manganese)
exceeds an effects-based benchmark [Probable Effects Concentration (PEC) or Severe Effects
Level (SEL)]. The short term goal for sediments in other areas of the pond that were covered by
less than 12 feet of water included areas with arsenic concentrations greater than 730 mg/kg and
copper, iron, or manganese above an effects-based benchmark, and then evaluate the need to
remediate such areas based on risks, feasibility, and implementability. The basis of the short-
term clean-up level of 730 mg/kg sediment arsenic was evaluation of toxicity testing data in
Sinking Pond sediments that indicated this was the lowest arsenic concentration at which toxicity
was observed in sediment toxicity testing. The long-term goal under the 2005 ROD is to achieve
sediment concentrations at or below the maximum background concentration of 42 mg/kg
sediment arsenic within the top two inches of sediment.

-------
Using these clean-up levels, additional data collected in pre-design investigations served as the
basis for the extent of excavation of sediments. As documented in the Final Sediment Remedial
Design Report (ARCADIS, 2011), W.R. Grace developed a remedial design that was intended to
achieve the long-term goal of 42 mg/kg arsenic throughout the applicable portion of the pond
such that subsequent monitoring for a reducing trend toward 42 mg/kg would not be necessary.

The remedy included excavation of 2,040 cubic yards of sediment from North Lagoon Wetland
and restoration of the excavated areas by backfilling with a minimum of 12 inches of topsoil to
pre-construction grades, seeding and planting to restore wetland habitats. Approximately 8,000
cubic yards of sediment were excavated from Sinking Pond. Site restoration activities at Sinking
Pond included placement of a minimum of 6 inches of clean topsoil in the excavated portions of
the pond between the water line and the historical high water elevation (144.5 feet). Disturbed
portions of the pond bank from the edge of water to 144.5 feet were seeded and planted.

As discussed above, an assumption of the ecological exposures for the remedy included removal
of sediment from the most biologically active area of the pond encompassing the sediments
above an elevation of 128 feet. This was the elevation selected to represent the location of the
thermocline based on pre-design data. In 2009, field data indicated that the thermocline was at
approximately 12 feet below the surface of the pond in the fall when the surface elevation was at
140 feet. Therefore, at that time the thermocline corresponded to an elevation of 128 feet. In
2014, field data indicated the early summer thermocline (June 24, 2014) was at approximately 8
-10 feet below the surface of the water. The surface elevation at the time of sampling in 2014
was approximately 135 feet. This places the early summer thermocline at 127 to 125 feet in
2014. This thermocline will likely stabilize several feet lower at the end of the summer. Since
the implementation of the remedy in 2011, the pond surface water elevation has been observed to
be several feet lower than pre-design conditions (formerly about elevation 140 feet to 145 feet).
This may be due to the fact that less water is being discharged to Sinking Pond compared to
when the ARS system was operational.

The current pond conditions will result in the upper, warm water area of the pond (epilimnion)
being at an elevation lower than the estimated 128 feet based on pre-design estimates. This
affects exposure assumptions that were the basis of the remedy, since the depression of the
surface water elevation, and correspondingly the thermocline elevation, may result in the change
in elevation of the epilimnion, including in areas below the level of the sediment removal area.
The intent of the remedy was to remove contaminated sediments at elevations above 128 feet in
order to limit exposures of aquatic organisms to sediment contaminants in the most ecologically
sensitive areas of the pond. The depression of the thermocline of Sinking Pond is not likely to
have a significant effect on the effectiveness of the remedy as a whole, as this area represents a
small potential exposure area within the larger area of Sinking Pond. Over the long term, we
expect the redisposition of new clean sediment to continue to cover and layer the existing
sediment. Several samples in the area 4 or 5 feet below the 128 feet remedy depth showed
elevated arsenic concentrations at the time of the Sediment Pre-Design Results Report
(ARCADIS, 2008). While it is not likely to affect the protectiveness of the remedy, it is
recommended that additional temperature profile data and surface water elevations be collected
in fall of 2015 and 2016, to confirm the location of the existing thermocline. Based on those
data, in can be determined if reevaluation of exposure assumptions or additional sampling will be
needed prior to the next five year review.

-------
In conclusion, since the BERA was prepared in 2005, there are no newly promulgated standards
relevant to the Site that impact on protectiveness of the remedy. The reference values and
exposure assumptions in the BERA were conservative and therefore protective. Other than the
elevation of the thermocline post-remediation, there are no major changes in site conditions or
exposure assumptions that would result in increased exposure or risk.

The results of the April 2014 sediment sampling demonstrate that the sediment remedial
activities undertaken in 2011 continue to be effective in the area of sediment removal. For both
the Sinking Pond and North Lagoon Wetland areas, the 95% UCL values remain below the long-
term cleanup goals that were targeted and achieved via the remedial activities.

ARARs Review

EPA has reviewed the Applicable or Relevant and Appropriate Requirements (ARARs) to check
for possible impacts on the remedy due to changes in standards that were identified as ARARs in
the RODs for OU-1 and OU-3, newly promulgated standards for chemicals of potential concern,
and TBCs (to be considered).

The tables in Appendix F provide an evaluation of ARARs using the regulations and requirement
synopses listed in the OU-1 ROD (Table 1) and the OU-3 ROD (Table 2). The evaluation
includes a determination of whether the regulation is currently an ARAR or TBC and whether
the requirements have been met. Most of the regulations and requirements remain ARARs for
the site and all are being complied with. Some regulations/requirements that were originally
identified as ARARs are now either applicable requirements that apply to off-site activities or
other laws that must be met at the site (e.g., OSHA).

The Massachusetts Sanitary Landfill Regulations are no longer considered ARAR. They would
have been applicable to capping in place of the Battery Separator Area chip piles, which was part
of the ROD-specified remedy for OU-1. However, the chip piles were excavated and placed in
the Industrial Landfill instead of being capped in place.

In 2011, the MassDEP Office of Research and Standards (ORS) lowered their drinking water
guideline (ORSG) for 1,4-dioxane from 3 |ig/L to 0.3 |ig/L. MassDEP's MCP (Massachusetts
Contingency Plan) contains promulgated (Method 1) generic soil and groundwater standards that
may be used at sites that meet the Method 1 criteria. The Method 1 GW-1 standard for 1,4-
dioxane was recently reduced from 3.0 |ig/L to 0.3 |ig/L to match the Massachusetts drinking
water guideline.

The lowered ORSG for 1,4-dioxane has been considered, in so far as it has led to increased
monitoring of groundwater and public water supply wells for this compound, in response to
concerns raised by the Acton Water District and the MassDEP Drinking Water Program.
However, the changed guideline does not affect remedy protectiveness, as measured
concentrations of 1,4-dioxane in samples from public water supply wells are well below the level
that would pose an unacceptable cancer risk and necessitate an EPA cleanup action.

-------
Question C: Has any other information come to light that could call into question the
protectiveness of the remedy?

Although there have been changes in toxicity values, exposure assumptions and risk assessment
methods since the risk assessments for the Site were completed, the changes do not affect
remedy protectiveness as long as the Industrial Landfill cap remains intact, treated water is
supplied to Town residents, the administrative hold on private irrigation well installation within
500 feet of the plume area continues, and ongoing monitoring and evaluation of groundwater
contaminant concentrations continue. The depression of the thermocline of Sinking Pond 4 or 5
feet below the target elevation of 128 feet is not likely to have a significant effect on the
protectiveness of the remedy as this area (between 128 feet and 123 feet) would represent a small
exposure area.

Technical Assessment Summary

According to the data reviewed and the site inspection, the OU-1 remedy is functioning as
intended by the ROD. Remedial actions for OU-1 have been completed. No remedy for OU-2
was necessary, as residual contamination in soils under the source areas did not exceed soil
cleanup goals established for OU-1. The OU-1 soil cleanup goals remain adequately protective
for a residential exposure scenario, based on a comparison of the goals to 2014 residential soil
risk-based screening levels.

According to the data reviewed and the site inspection, the OU-3 remedy is also functioning as
intended by the ROD. Sediments have been remediated and wetlands restored, groundwater is
being extracted and treated in the Landfill Area of the site, and in other areas of the site
groundwater contaminant concentrations continue to decline due to natural attenuation. A
groundwater extraction, treatment and reinjection system operated in the Northeast Area for 3.5
years and has met the 2005 ROD objectives. Annual groundwater monitoring continues to
evaluate remedy effectiveness.

The toxicity values that served as the basis for the soil, groundwater, and sediment cleanup
levels, as contained in the OU-1 and OU-3 RODs, as well as the toxicity values used for the soil
"indicator chemicals" were re-evaluated to determine whether any changes in toxicity impact the
protectiveness of the remedy, and no changes affecting protectiveness were noted. Other than
the location of the thermocline in Sinking Pond post-remediation, there are no major changes in
site conditions, risk assessment methods, or exposure assumptions upon which the risk
assessment was based that would result in increased exposure or risk. The depression of the
thermocline of Sinking Pond is not likely to have a significant effect on the protectiveness of the
remedy, as this area represents a small exposure area.

The remedy for OU-1 is protective of human health and the environment as long as the Industrial
Landfill cap remains intact, treated water is supplied to Town residents, the administrative hold
on private irrigation well installation within the plume area is continued, and ongoing monitoring
and evaluation of groundwater contaminant concentrations continue.

The remedy at OU-3 is protective in the short-term, because there is no current exposure to
contamination in groundwater or sediment. However, in order for the remedy to be protective in

32

-------
the long-term, additional institutional controls may be needed to supplement the administrative
hold on installing wells near the plume, to prevent groundwater use until cleanup levels are
reached.

Site-wide, the remedial actions taken are protective of human health and the environment in the
short-term because there is no current exposure to contamination. Soil and sediment have been
remediated and contaminated soil left on site in the Industrial Landfill was capped. The Landfill
Area groundwater remedy is operating and will reduce contaminant concentrations to cleanup
levels over time through a combination of active extraction and treatment combined with
monitored natural attenuation. However, to be protective in the long-term, additonal institutional
controls may need to be implemented for groundwater within the vicinity of the contaminant
plume to supplement the existing controls (the Town's administrative hold) already in place.

33

-------
ISSUES/RECOMMENDATIONS AND FOLLOW-UP ACTIONS

Table 7: Issues and Recommendations/Follow-up Actions

ou

#

Issue

Recommendations/
Follow-up Actions

Party
Responsible

Oversight
Agency

Milestone
Date

Affects
Protectiveness?
(Y/N)

Current

Future

3

The Acton Board
of Health has
established an
administrative hold
on the installation
of private irrigation
wells within 500
feet of the mapped
region of
contaminated
groundwater that
lies within the
town. It may be
necessary to
establish additional
institutional
controls to prevent
groundwater use
within the
contaminated
plume area until
cleanup goals are
met. An
Institutional
Controls Plan was
prepared in 2011
but action on it has
stalled due to
concerns raised by
the Town of Acton.

Continue efforts with
the Town to establish
additional

institutional controls
if needed.

PRP

EPA/State

9/30/2019

No

Yes

In addition, the following are recommendations from this FYR that do not affect protectiveness,
but could improve the effectiveness of the remedies and/or support future FYRs in drawing
conclusions regarding protectiveness:

•	OV-1: Industrial Landfill Maintenance: Monitoring of vegetative growth in the
perimeter swale should continue. Sediment and mowing clippings should be removed
from the perimeter swale to promote positive drainage and eliminate standing water
on the south, southeast and northwest sides of the landfill. Checking swale grades
should also be considered, and if necessary the swale bottom should be re-graded to
provide positive drainage to the outlet.

•	OU-3: Sinking Pond Monitoring: In order to confirm the effectiveness of the
remedy, it is recommended that additional temperature profile data and surface water

34

-------
elevations be collected in fall of 2015 and 2016, to confirm the location of the
existing thermocline. Based on those data, in can be determined if reevaluation of
exposure assumptions or additional sampling will be needed prior to the next five
year review.

PROTECTIVENESS STATEMENT

Protectiveness Statement(s)

Operable Unit: Protectiveness Determination:

1 Protective

Protectiveness Statement:

The remedy for OU-1 is protective of human health and the environment. Soil in excess of
cleanup levels has been excavated, stabilized, and either placed in the Industrial Landfill or
shipped off-site for treatment and disposal. The Industrial Landfill was then closed with an
impermeable cap to prevent potential exposure. The PRP has filed a deed notice with the
Registry of Deeds to regulate land use of the Industrial Landfill, and the PRP maintains
ownership of the landfill and maintains the cap, and there is a perimeter fence enclosing the
landfill.

Protectiveness Statement(s)

Operable Unit: Protectiveness Determination:

3 Short-term Protective

Protectiveness Statement:

The remedy at OU-3 is protective in the short-term, because there is no current exposure to
contamination in groundwater or sediment. Groundwater in the vicinity of the Industrial
Landfill is currently being extracted and treated by a new system that was constructed in 2011
(the Landfill Area). A separate groundwater extraction and treatment system was installed in
the Northeast Area of the Site and operated from April 2010 to September 2013, at which time
it was determined that it had met the ROD objective of reducing contaminant mass in this
area. The Acton Water District provides treatment of groundwater from the five public water
supply wells in the vicinity of the Site, and the Acton Board of Health has established an
administrative hold on the installation of private wells within 500 feet of the current
groundwater contaminant plume. Areas of contaminated sediment in the North Lagoon
Wetland and in Sinking Pond were excavated for off-site disposal during the summer and fall
of 2011 and the cleanup levels established in the ROD were achieved. The wetlands have
been restored and monitoring of the effectiveness of restoration efforts continues. However, in
order for the remedy to be protective in the long-term, additional institutional controls for
groundwater may be needed to supplement the town's administrative hold on installing wells
near the plume to prevent groundwater use until cleanup levels are reached.

-------
Sitewide Protectiveness Statement

Protectiveness Determination:

Short-term Protective

Protectiveness Statement:

The remedial actions taken are protective of human health and the environment in the short-
term because there is no current exposure to contamination. Soil and sediment have been
remediated and contaminated soil left on site in the Industrial Landfill was capped. The
Landfill Area groundwater remedy is operating and will reduce contaminant concentrations to
cleanup levels over time through a combination of active extraction and treatment combined
with monitored natural attenuation. To be protective in the long-term, additional institutional
controls may be needed for groundwater within the vicinity of the contaminant plume to
supplement the existing controls (the Town's administrative hold) already in place..

NEXT REVIEW

The next (2019) five-year review report for the W. R. Grace & Co., Inc. (Acton Plant) Superfund
Site is required five years from the completion date of this review.

36

-------
FIGURES

-------
m



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Christofferson Well 1l", VNf\	4

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FIGURE 1.

W.R, GRACE & CO (ACTON PLANT) f
SUPERFUND SITE

ACTON, MASSACHUSETTS

-i- . .-A

Metcalf &Eddy

Source:

MassGIS, Commonwealth of Massachusetts
Executive Office of Environmental Affairs

SCALE IN FEET

-------
X /

Potential Source Areas

W.R. Grace, Acton, MA.

A TETRA TECH COMPANY A A %f|A	f J

CHECKED

AEB

DRAFTED

RMK

FILE

So4-Ramd.ct»g

DATE

July 2005

FIGURE:

2

-------
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OUSTER)

W.R. GRACE EXTRACTION HELL
W.R. GRACE NJEETKW TELL
FORMER EXTRACTION WEUL
NON-GRACE EXTRACTION WELL
PUBLIC WATER SUPPLY HELL
PROPOSED PUBLIC WATER SUPPLY KH
RIVER TRANSECT

SURFACE WATER MEASURMEHT LOCATION

TTTLE:

LOCATION:

WH-LS «uPim mB 1.4-DIOXANE

LF-06

C 0.16 (13)

I I	 ELBMTON OF SCREEN BOTTOM

I	 1^-OKWIC CONCENTRATION

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ND [2] NOT DETECTED AT SPECFED REPORTNG HIT

UWMJU 1.4 DUXIHE CONCENIRADONS DETECTED M
SAMPLES KUECTTO 6EI1EEN NW. 1 2012 AW OCT.
31, 2013

conoenimtions M n/L

MAXIMUM 1,4-DIOXANE CONCENTRATIONS
IN GROUNDWATER, 2013

W.R Grace, Acton, Massachusetts

Scale in feet

TETRA TECH

APPROVED

ABS

DRAFTED

RMK

PROJECT#

117-3008080

DATE

DEC 2013

FIGURE

-------
W'irftg.THkWJ

:aiJv67-1i-6ATA-RH\FALH3-VBt-B.BWfl

NDTEi BASE MAP BY COL-EAST 1998. WELL LOCATIONS, W.R. GRACE PROPERTY
LINE & MISC. SITE FEATURES COMPILED FROM INFORMATION PROVIDED BY CAMP
DRESSER & McKEE. SURROUNDING PROPERTY LINE LOCATIONS ARE FROM THE
TOWN OF ACTON AND CONCORD ASSESSORS MAPS.

— W.R. GRACE PROPERTY BOUNDARY
(APPROXIMATE)

e MONITORING WELL
(SINGLE OR CLUSTER)

•	WR GRACE EXTRACTION WELL
o	WR GRACE INJECTION WELL
®	FORMER EXTRACTION WELL
®	NON-GRACE RECOVERY WELL
©	PUBLIC WATER SUPPLY WELL

•	PROPOSED PUBLIC WATER SUPPLY WELL
RIVER TRANSECT

VDC CONCENTRATION 20I3

>200 - 310 ugA VDC
>100-200 ug/L VDC
>60-100 ugA VDC
>30-60 ugA VDC
>7-30 ugA VDC

SAMPLES COLLECTED BETWEEN AUG. 21 AND SEPT. 19, 2013

VDC CONCENTRATIONS SHOWN ARE MAXIMUM REGARDLESS OF
DEPTH. CONCENTRATION BOUNDARIES ARE APPROXIMATE.

VDC = VINYUDENE CHLORIDE = 1.1-DICHL0R0ETHENE

DISTRIBUTION OF VDC IN GROUNDWATER, 2013

W.R. Grace, Acton, MA.

TETRA TECH

APPROVED

ABS

DRAFTED

RMK

PROJECT#

117-3008080

DATE

DEC. 2013

FIGURE

-------


NDTEi BASE MAP BY COL-EAST 1998. WELL LOCATIONS, W.R. GRACE PROPERTY
LINE & MISC. SITE FEATURES COMPILED FROM INFORMATION PROVIDED BY CAMP
DRESSER & McKEE. SURROUNDING PROPERTY LINE LOCATIONS ARE FROM THE
TOWN OF ACTON AND CONCORD ASSESSORS MAPS.

— W.R. GRACE PROPERTY BOUNDARY
(APPROXIMATE)

e MONITORING WELL
(SINGLE OR CLUSTER)

•	WR GRACE EXTRACTION WELL
o	WR GRACE INJECTION WELL
®	FORMER EXTRACTION WELL
®	NON-GRACE RECOVERY WELL
©	PUBLIC WATER SUPPLY WELL

•	PROPOSED PUBLIC WATER SUPPLY WELL
RIVER TRANSECT

VINYL CHLORIDE CONCENTRATION 20I3

| | >100-130 ug/L VINYL CHLORIDE
>30-100 ug/L VINYL CHLORIDE
>2-30 ug/L VINYL CHLORIDE

SAMPLES COLLECTED BETWEEN AUG. 21
AND SEPT. 19, 2013

VINYL CHLORIDE CONCENTRATIONS
SHOWN ARE MAXIMUM REGARDLESS OF
DEPTH. CONCENTRATION BOUNDARIES
ARE APPROXIMATE.

DISTRIBUTION OF VINYL CHLORIDE IN GROUNDWATER, 2013

LOCATION:











W.R. Grace, Acton, MA.











APPROVED

ABS

FIGURE





TETRA TECH

DRAFTED

RMK





It

PROJECT#

117-3008080









DATE

DEC 2013

-------


NDTEi BASE MAP BY COL-EAST 1998. WELL LOCATIONS, W.R. GRACE PROPERTY
LINE & MISC. SITE FEATURES COMPILED FROM INFORMATION PROVIDED BY CAMP
DRESSER & McKEE. SURROUNDING PROPERTY LINE LOCATIONS ARE FROM THE
TOWN OF ACTON AND CONCORD ASSESSORS MAPS.

W.R. GRACE PROPERTY BOUNDARY
(APPROXIMATE)

•	WR GRACE EXTRACTION WELL
o	WR GRACE INJECTION WELL

a	FORMER EXTRACTION WELL

®	NON-GRACE RECOVERY WELL

©	PUBLIC WATER SUPPLY WELL

•	PROPOSED PUBLIC WATER SUPPLY WELL
RIVER TRANSECT

BENZENE CONCENTRATION 20I3

>100-270 ugA BENZENE
>30-100 ug/L BENZENE
>5-30 ug/L BENZENE

SAMPLES COLLECTED BETWEEN AUG 21
AND SEPT 19, 2013

BENZENE CONCENTRATIONS SHOWN ARE
MAXIMUM REGARDLESS OF DEPTH.
CONCENTRATION BOUNDARIES ARE
APPROXIMATE

DISTRIBUTION OF BENZENE IN GROUNDWATER, 2013

W.R. Grace, Acton, MA.

TETRA TECH

APPROVED

DRAFTED

PROJECT#

117-3008080

DEC 2013

FIGURE

-------

-------
APPENDIX A - EXISTING SITE INFORMATION
A. SITE CHRONOLOGY

The chronology of the Site, including significant site events and dates, is included in Table A-l.

Table A-l: Chronology of Site Events

Event

Date

Dewey & Almy Chemical Company manufactures various
products at the Acton site at various times, such as: latex,
resins, plasticizers, and paper battery separators

1945 - 1954

W.R. Grace acquires Dewey & Almy and continues
various chemical manufacturing processes at the Acton
site

1954 - 1991

Organic contaminants (vinylidene chloride,vinyl chloride,
ethylbenzene, and benzene) detected in municipal wells,
Assabet #1 and #2

1978

The United States sues W.R. Grace to require cleanup of
the Site

April 17, 1980

MassDEP issues an Administrative Order to W.R. Grace,
specifying procedures and requirements for evaluating and
correcting Site contamination

July 14, 1980

W.R. Grace and EPA enter into a Consent Decree to clean
up waste disposal areas and restore groundwater in
drinking water aquifers. The provisions of the Consent
Decree are similar to the requirements of the July 14, 1980
MassDEP Administrative Order.

October 21, 1980

MassDEP issues an Amended Order to W.R. Grace,
amending MassDEP's July 14, 1980 order to conform
with the Consent Decree language

April 15, 1981

Site added to the National Priorities List

September 8, 1983

Aquifer Restoration System construction completed and
operation begins

March 1985

Phase IV Report and Addendum, detailing the OU-1
remedy, was completed by Camp, Dresser & McKee
(CDM) for W.R. Grace

June 6, 1989

Risk Analysis Report completed by Alliance Technologies
Corporation for EPA

June 30, 1989

Record of Decision for OU-1 signed by Paul G. Keough,
Acting Regional Administrator

September 29, 1989

A-l

-------
Table A-l: Chronology of Site Events

Event

Date

CDM issued Remedial Design/Remedial Action (RD/RA)
Work Plan for OU-1

January 1991

CDM issued report on Field Pilot Programs for upgrading
air stripping tower portion of ARS

May 1991

Quarterly well monitoring begins

March 1992

Odor controls for air-stripping tower installed and
operational; Site security measures implemented

September 1992

CDM submitted revised 100% design package for OU-1
remedial action

August 1993

GZA issued Final Site Work Plan and Construction
Quality Control Plan for OU-1 remedial action

July 1994

OU-1 Remedial Action initiated; Air monitoring system
installed

October 17, 1994

Landfill gas treatment system delivered and installed;
Permanent fencing around landfill installed

March 1997

Final site inspection performed

June 1997

Remedial Action Report for OU-1 issued by EPA

September 30, 1997

Revised Construction Quality Assurance Closeout Report
for OU-1 issued by CDM for W.R. Grace

February 1998

Statement of Work for OU-3 Remedial
Investigation/Feasibility Study is signed

March 25, 1998

First 5-year review report issued by EPA for the Site

September 1999

Draft Remedial Investigation Report and Phase 2 Work
Plan for OU-3 issued by GeoTrans for W.R. Grace

August 30, 2002

Phase 2 Remedial Investigation Report issued by
GeoTrans for W.R. Grace

May 14, 2003

Draft Baseline Ecological Risk Assessment issued by
Menzie-Cura for W.R. Grace

July 30, 2004

Draft Public Health Risk Assessment Deliverable 3 issued
by Menzie-Cura for W.R. Grace

August 5, 2004

Second 5-year review report issued by EPA for the Site

September 29, 2004

Public Review Remedial Investigation and Feasibility
Study Reports for OU-3 issued by GeoTrans for W.R.
Grace

July 1, 2005

A-2

-------
Table A-l: Chronology of Site Events

Event

Proposed Plan for OU-3 released to public

Date

July 8, 2005

Public Meeting on Proposed Plan for OU-3

July 19, 2005

Public Hearing on Proposed Plan for OU-3

August 4, 2005

OU-3 ROD signed

September 30, 2005

W.R. Grace and EPA come to agreement on a Remedial
Design/Remedial Action Statement of Work for OU-3

August 30, 2006

Approval for performing a topographical survey and
wetland assessment/delineation is granted by EPA and
MassDEP

April 3, 2007

Sediment Pre-Design Work Plan is Conditionally
Approved by EPA

July 24, 2007

Landfill Area and Northeast Area Groundwater Pre-
Design Work Plans are Conditionally Approved by EPA

August 30, 2007

Request to Discontinue Pumping from Existing Recovery
Well RLF is Conditionally Approved by EPA, with
Existing Recovery Well ELF to remain operational until
new recovery wells (SELF-1 and SWLF-1) are brought on
line

January 15, 2008

Northeast Area Groundwater Pre-Design Results Report
Conditionally Approved by EPA

November 26, 2008

Petition to discontinue pumping from extraction wells
NLBR-R, NLGP, SLBR, and SLGP-R in the Former
Lagoon Area is Conditionally Approved by EPA

January 9, 2009

Sediment Pre-Design Results Report Conditionally
Approved by EPA

February 26, 2009

Northeast Area Groundwater Concept Design
Conditionally Approved by EPA

April 24, 2009

Landfill Area Groundwater Pre-Design Results Report
Conditionally Approved by EPA

June 9, 2009

Northeast Area Design Approved by EPA

June 11, 2009

Landfill Area Concept Design Submitted

September 8, 2009

Third 5-year review report issued by EPA for the Site

September 23, 2009

Landfill Area Concept Design Approved by EPA

January 22, 2010

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Table A-l: Chronology of Site Events

Event

Date

Startup of Northeast Area Groundwater Extraction and
Treatment System

April 5, 2010

Northeast Area Groundwater Extraction and Treatment
System determined to be "Operational and Functional" by
EPA

May 14, 2010

Sediment Concept Design Report Submitted

June 2010

Sediment 100% Design Submitted

September 2010

Sediment 100% Design Conditionally Approved by EPA

September 30, 2010

Landfill Area Extraction System Capture Zone
Conditionally Approved by EPA

October 29, 2010

Landfill Area Final Design Submitted

December 10, 2010

Landfill Area Final Design Approved by EPA

February 14, 2011

Revised Sediment 100% Design Submitted

March 2011

Startup of Landfill Area Treatment System

May 2, 2011

Shake-down of Landfill Area Treatment System

May 2011 - May 2012

Sediment Construction Final Inspection

November 17, 2011

Sediment Construction determined to be "Operational and
Functional" by EPA

January 10, 2012

Preliminary Closeout Report for the Site issued by EPA

February 8, 2012

Landfill Area Groundwater Extraction and Treatment
System determined to be "Operational and Functional" by
EPA

May 25, 2012

Grace submits evaluation of first 2.5 years of NE Area
remediation system operations, with petition to shut down
in April 2013

February 25, 2013

EPA conditionally approves shutdown of NE Area
remediation system

September 20, 2013

NE Area remediation system shut down

September 24, 2013

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B. BACKGROUND

Physical Characteristics and Land and Resource Use

The Site is a former chemical manufacturing facility which occupies approximately 260 acres in Acton
and Concord, Massachusetts. The Site is located off Independence Road and is bounded to the
northwest by Fort Pond Brook and to the southeast by the Assabet River. The Site is bounded by
industrial parks to the south and northeast, and by residential housing to the northwest, east, and west. A
sand and gravel pit is located south of the Site. All buildings associated with the former chemical
manufacturing operations have been demolished. Only those buildings associated with the remedial
action currently exist on the Site.

Waste disposal areas identified on-site include the former Battery Separator Area, the former Blowdown
Pit, the former Primary Lagoon, the former North Lagoon, the former Tank Car Area, the former
Secondary Lagoon, the former Emergency Lagoon, the former Boiler Lagoon (located between the
Battery Separator Area and the Tank Car Area), the former Acid Neutralization Pit, and the Industrial
Landfill (see Figure 2).

Groundwater beneath the Site is classified as GW-1 by MassDEP, defined as a current or potential
future drinking water source area. The Site straddles a groundwater divide, so groundwater from the
Site flows either to the northwest toward Fort Pond Brook or to the southeast and south toward the
Assabet River. The Assabet Wellfield, which supplies water for the Town of Acton, is located
southwest of the Site. The wellfield consists of two municipal drinking water wells, Assabet #1 and
Assabet #2A. Assabet #2A replaced Assabet #2 as a public water supply well in May 2001. Presently,
both wells are operating, and the extracted water is treated with an air stripping unit prior to public
distribution. The Acton Water District is currently in the process of developing Assabet 3 as a future
public supply well within this area. Assabet 3 was a former production well used by W.R. Grace when
the Acton manufacturing facility was operational. The Lawsbrook, Scribner, and Christofferson wells,
comprising the School Street Wellfield, are located approximately 3,700 feet north of the Site. All three
wells are within the Fort Pond Brook watershed. The Scribner and Lawsbrook wells are 150 and 1,000
feet south of Fort Pond Brook, respectively. The Christofferson well is immediately north of Fort Pond
Brook. Water from the School Street wells is also treated using an air stripper prior to public
distribution.

In addition to the five public wells, six private water supply wells (1 Lisa Lane, 5 Bellantoni Drive,
Powder Mill Plaza, Valley Sports Arena, and two wells at the Starmet-Nuclear Metals Superfund Site
property) were identified during the private well survey conducted for the Site. The Lisa Lane and
Bellantoni Drive wells were located in a residential area north of the W.R. Grace property and south of
the School Street Wellfield. Both wells withdrew water from the bedrock aquifer for residential
irrigation. When it was discovered that these two wells were within the plume from the Site, the well at
1 Lisa Lane was converted into a monitoring well, and the well at 5 Bellantoni Drive was properly
decommissioned. The other four wells identified during the private well survey were found to be
unaffected by Site-related contaminants.

History of Contamination

The Site is a former chemical manufacturing facility, used for industrial purposes for over one hundred

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years. American Cyanamid Company and the Dewey & Almy Chemical Company (D&A) were former
occupants of the Site. American Cyanamid manufactured explosives, and D&A produced synthetic
rubber container sealant products, latex products, plasticizers, and resins. W. R. Grace acquired the
property in 1954, and chemical operations were continued at the Site. Operations at the W. R. Grace
facility included the production of materials used to make concrete and organic chemicals, container
sealing compounds, latex products, and paper and plastic battery separators. Wastewater and solid
industrial wastes from these operations were disposed of in several unlined lagoons (the Primary
Lagoon, Secondary Lagoon, North Lagoon, and Emergency Lagoon), and were buried in or placed onto
an on-site Industrial Landfill and several other waste sites (see Figure 2). These other waste sites
include the Battery Separator Area (lagoon and chip pile), the Tank Car Area, and the Boiler Lagoon
which was located between the Battery Separator and Tank Car Areas. Periodically, sludge from the
Primary Lagoon was dredged, dried along the banks, and trucked to the landfill for disposal. In
addition, the by-products of some chemical processes were disposed of in the Blowdown Pit. Discharge
to all lagoons and the Battery Separator Area ceased in 1980. The production of organic chemicals was
discontinued in 1982. A small distribution center for concrete additives was moved to another location
in September 1996. A second plant for the manufacture of battery separators, known as the Daramic
facility, was constructed in 1979, but operations there ceased in 1991. All buildings, with the exception
of those associated with the remedial actions, have been demolished.

Investigations in 1978 indicated that two Acton municipal wells, Assabet #1 and Assabet #2, were
contaminated with vinylidene chloride (VDC, also known as 1,1-dichloroethene or 1,1-DCE).
Significant levels of vinyl chloride (VC), ethylbenzene, and benzene were also detected in these wells.
Shortly thereafter, the Town took the precautionary action of closing the two wells. As a result of the
discovery of the municipal well contamination, W. R. Grace and EPA entered into a Consent Decree
requiring cleanup of the Site in October 1980 (1980 Consent Decree) under the Resource Conservation
and Recovery Act. A similar settlement was reached between W.R. Grace and the state of
Massachusetts. In September 1983, the Site was added to the National Priorities List (NPL).

Initial Response

The 1980 Consent Decree outlined the procedural framework for cleanup of the Site. One requirement
of the Consent Decree was cleanup and restoration of the drinking water in the aquifer, the source of
water for Assabet Wells #1 and #2. W. R. Grace initiated development of an engineering plan for
aquifer cleanup which included a recovery well network to capture contaminated groundwater and
prevent further off-site migration. Contaminated groundwater extracted from the network of wells
would be pumped to a central treatment facility or treated at the well-head. Following EPA and State
approval of this cleanup plan, construction of the Aquifer Restoration System (ARS) was begun in
December 1983. Construction of the ARS was completed in March 1985. As explained below, parts of
the ARS extraction well network were deactivated in 2002 and in 2008, while other parts remain in
operation as part of the groundwater remedy. As required by the 2005 ROD, the ARS treatment system
will be replaced by a new treatment system currently being designed by W. R. Grace.

The 1980 Consent Decree also required W.R. Grace to assess and control sources of waste on-site using
a phased investigation under EPA oversight. In Phases I and II, W.R. Grace prepared plans for studying
and determining the nature and extent of contamination at the source areas, and after EPA approval,
performed the study. In Phase III of the source area investigation, W.R. Grace identified, analyzed, and
evaluated cleanup and remedial measures for the source areas. Following conditional approval of the
Phase III scope of work, W.R. Grace performed the evaluations and submitted the results to EPA in a
Phase IV Report. The final draft of the Phase IV Report was submitted to EPA on August 31, 1988.

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Following a series of meetings to discuss revisions to the report, W.R. Grace submitted an Addendum to
the draft Phase IV Report on June 6, 1989. The remedial measures evaluated in the Phase IV Report and
Addendum provided the basis for the remedy that was selected in the ROD for OU-1, signed on
September 29, 1989.

As described in the Record of Decision (ROD) for OU-1, the Site remedy was organized into three
operable units (OUs):

• OU-1 Disposal areas and surficial contamination areas at the Site;

• OU-2 Residual contamination in disposal areas at the Site following implementation of OU-1;
and

• OU-3 Contaminated groundwater in the area of the Grace facility that is not contained or
adequately addressed by the Aquifer Restoration System. OU-3 also includes contaminated
sediments and surface water.

Basis for Taking Action

Two major series of investigations have been conducted at the Site. The first occurred in the 1980s and
led to construction of the ARS, development of the 1989 ROD for OU-1, and cleanup of the source areas
at the Site. The second set of investigations, conducted mainly between 2000 and 2002, resulted in
development of the 2005 ROD for OU-3 and led to the remedial designs that are currently underway.

OU-1. The investigations of the nature and extent of contamination at the Site that were conducted in the
1980s were focused on source areas and groundwater. The contaminants that were detected in various
media at the Site during those investigations are summarized below.

Soil & Sludge. Soil and sludge were identified as "surface materials" in the 1989 ROD. The
Blowdown Pit contained the most highly contaminated material on the Site (primarily VDC),
while material in and under the Boiler Lagoon demonstrated lower contaminant levels than the
other lagoons.

VDC, VC, benzene, and ethylbenzene were the primary contaminants identified in the Primary
Lagoon, Secondary Lagoon, and Emergency Lagoon sludge and underlying soils. Benzene,
toluene, and ethylbenzene were the prominent compounds in soils underlying the Industrial
Landfill. In North Lagoon sludges and underlying soils, VOC contamination was detected along
with phthalates, metals, and cyanide. The principal contaminants found in Boiler Lagoon
sludges and underlying soils were phthalates and metals, while VDC, benzene, ethylbenzene,
formaldehyde, phenol, and metals predominated in Battery Separator Area soils/sludges. Soils in
the Tank Car Area were contaminated with VDC, phthalates, and metals. Eight chemicals were
selected for evaluation in the risk assessment. The eight chemicals included: VDC, VC,
benzene, toluene, ethylbenzene, formaldehyde, arsenic, and cadmium.

Groundwater. Fifteen groundwater contaminants were identified as indicator chemicals in the
1989 ROD for OU-1. The fifteen indicator chemicals were VDC, VC, benzene, toluene,
ethylbenzene, trichloroethene (TCE), formaldehyde, arsenic, beryllium, cadmium, chromium,
copper, lead, nickel, and zinc.

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Surface Water. VDC and 1,1,1-trichloroethane (TCA) were detected in surface water samples
from the Assabet River. VDC, benzene, toluene, xylene, tetrachloroethene (PCE) and
chloroform were detected in Fort Pond Brook surface water samples.

A risk assessment was performed by Alliance Technologies Corporation (Alliance, 1989) that evaluated
future human health risks associated with site-wide exposure to surface materials and groundwater, and
specific source area exposures assuming residential use of the property. The risk assessment concluded
that the W. R. Grace property was likely to pose significant carcinogenic and non-carcinogenic risk to
human health in the event the property was developed and used for residential purposes, in the absence
of remediation. Significant groundwater risk contributors included VDC, VC, arsenic, lead, and zinc.
Risks associated with exposure to surface material were primarily attributed to VDC, VC, and arsenic.
These conclusions formed the basis of the selected remedy for OU-1 and OU-2. The OU-1 remedial
actions were completed in 1997, and no follow-up OU-2 actions were needed.

OU-3. The objectives for the investigations associated with OU-3, which were described in the OU-3
Remedial Investigation/Feasibility Study (RI/FS) Statement of Work (approved by EPA and MassDEP
April 1998), were to define the extent of groundwater contamination and its impacts, if any, on surface
water, sediments, and air at the Site. The RI for OU-3 began with the preparation of an Initial Site
Characterization Report (ISCR) by HSI GeoTrans in August 1998. The data gaps that were identified in
the ISCR were addressed by investigations conducted between April 2000 and November 2002. Human
health and ecological risk assessments were completed in 2005. The contaminants that were detected at
the Site as a result of the remedial investigations and sampling for the risk assessments are summarized,
by medium, below.

Groundwater. The primary chemicals that were identified as groundwater contaminants at the Site
include VDC, VC, benzene, 1,2-dichloropropane, 1,2-dichloroethane, methylene chloride, bis (2-
ethylhexyl) phthalate, arsenic, and manganese. Contaminants that were detected less frequently include
TCE, methyl-tert-butyl-ether, 1,4-dioxane, chromium, and nickel.

Sediment. The Human Health Risk Assessment identified future risks to receptors from exposure to
sediments in North Lagoon Wetland and in Sinking Pond. Unacceptable risks to potential future
recreational receptors (waders) were identified in Sinking Pond and in North Lagoon wetland due to
elevated arsenic in sediments.

Unacceptable risks to the environment were also identified and attributed to arsenic in portions of
Sinking Pond (above the thermocline) in water less than 12 feet deep, and to exposure to elevated
concentrations of other metals in sediments of Sinking Pond including manganese, iron, and copper. The
band of shallow water around the pond posing a risk to ecological receptors overlaps with areas of
potential human exposure and risk to human receptors from swimming/wading. Risks to ecological
receptors in sediments of the North Lagoon Wetland were attributed to arsenic and manganese.

Surface Water. VDC and TCA were detected in surface water samples from the Assabet River. VDC,
benzene, toluene, xylene, PCE, and chloroform were detected in Fort Pond Brook surface water
samples.

These conclusions formed the basis of the selected remedy for OU-3 of the Site. Design and
construction of the OU-3 remedies were completed between 2009 and 2012, and operation and
maintenance activities are ongoing.

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C. REMEDIAL ACTIONS

Remedy Selection

This section describes the selected remedies for the three operable units (OU-1, OU-2, and OU-3) that
comprise the Site.

OU-1. The ROD for OU-1 was signed on September 29, 1989. This ROD addressed the first of three
operable units planned for the Site. The remedial action objectives as presented in the ROD for the Site
were to:

• Protect exposure points, where humans or wildlife may be exposed to contaminants in soil,
groundwater, surface water, and sediments, during and after site remediation.

• Prevent the migration of contaminants in groundwater from sources on-site to public drinking
water supplies.

• Protect on- and off-site groundwater from contamination by site contaminants in excess of
drinking water quality.

• Eliminate the potential for contact in the future with waste materials by the public and the
environment.

• Protect on- and off-site surface water from contamination by site contaminants.

• Prevent the migration of contaminated run-offfrom the waste sites.

• Protect against direct contact with site contaminants and minimize environmental exposure
during remedial activities.

• Reduce to the maximum extent practicable the number of source areas to eliminate long-term
management and permit unrestricted use.

The goals of the selected remedy were to protect the drinking water aquifer by minimizing further
contamination of the groundwater and surface water, and to eliminate the threats posed by direct contact
with or ingestion of contaminants in soil and waste sludges at the Site.

The selected remedy for OU-1 (source control), as identified in the ROD, consisted of the following
components:

• Excavation and transportation off-site for incineration of highly contaminated material from the
Blow down Pit;

• Excavation and stabilization of the remaining contents of the Blow down Pit, as well as the
contaminated sludges and soils of the Primary Lagoon, Secondary Lagoon, North Lagoon, and
Emergency Lagoon;

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•	Excavation of contaminated soils from the Battery Separator Lagoons, Boiler Lagoon, and Tank
Car Area;

•	Placing both the stabilized and the non-stabilized materials excavated from the Site on the
existing Industrial Landfill, and covering these materials with an impermeable cap;

•	Post-excavation sampling and analysis;

•	Capping the Battery Separator Chip Pile;

•	Covering any disposal area which attains the soil cleanup goals;

•	Modifying the ARS to address air stripper emission controls; and

• Establishing long-term environmental monitoring at each disposal area designed to monitor the
effectiveness of the proposed remedy.

OU-2. The ROD for OU-1 stated that a remedy for OU-2 would be necessary only if, following
completion of the OU-1 remedy, residual contamination in soils under the source areas exceeded soil
cleanup goals established for OU-1. Data collected during and after the completion of the OU-1 remedy
indicated that the soil cleanup goals were met for each of the source areas; therefore, no remedy for OU-
2 was necessary (USEPA, 1999).

OU-3. The ROD for OU-3 was signed on September 30, 2005. This ROD addresses the third and final
operable unit for the Site.

The goals of the selected remedy are to restore the drinking water aquifer and to eliminate the threats
posed by direct contact with or ingestion of contaminants in sediment in the North Lagoon Wetland and
Sinking Pond.

The selected remedy for OU-3, as identified in the ROD, consists of the following components:

•	Cleanup of contaminated sediments and soils posing an unacceptable risk to human health
and/or the environment in Sinking Pond and the North Lagoon Wetlands;

•	Extraction and treatment of groundwater contamination in the Southeast and Southwest
Industrial Landfill Areas on the Grace property and at targeted areas in the Northeast Area;

•	A redesigned and/or modified Aquifer Restoration System that will treat extracted groundwater
for both metals and organic contaminants. Treatment processes for extracted groundwater
would include air-stripping, activated carbon (air treatment), and metals precipitation prior to
surface water discharge to Sinking Pond;

•	Monitored Natural Attenuation of areas of groundwater contamination not captured by the
extraction system;

•	Institutional Controls such as deed restrictions and/or local ordinances to prevent unacceptable
exposures to contaminated groundwater until cleanup levels are met and to protect against

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unacceptable future exposures to any wastes left in place on-Site;

• Long-term groundwater, surface water, and sediment monitoring, and periodic Five-Year
Reviews of the remedy.

Remedy Implementation

OU-1. The remedial design/remedial action activities for OU-1 were performed by W. R. Grace under
the 1980 Consent Decree. For more detailed information on OU-1 remedial activities, see the Remedial
Action Report for Operable Unit One, which was prepared by Foster Wheeler Environmental
Corporation (September 1997).

Consistent with the 1989 ROD the following work has been conducted at the Site:

• The contents of the Battery Separator Lagoons, Boiler Lagoon, and the Tank Car Area were
excavated to a depth of at least five feet. Additional excavation greater than five feet in depth
was performed until the soil cleanup goals (see page 30 of the 1989 ROD) were met. These
materials were then placed on the Industrial Landfill. The contaminant level of all excavated
materials from these areas was analyzed prior to placement on the landfill. If unexpected levels
of contaminants were detected that could present implementation problems or impact the
effectiveness of the landfill remedy, then those materials were stabilized prior to placement on
the landfill or were disposed of off-site. Post-excavation sampling and analysis was conducted
to ensure that soil cleanup goals were attained.

• Sludges and at least two feet of soil in each of the Primary, Secondary, and Emergency Lagoons
were excavated, stabilized using the VFL process (developed by VFL Technology Corporation
and consisting of mixing contaminated soils/sludges with quicklime, flyash, and portland
cement), and placed on the Industrial Landfill. Additional excavation greater than two feet in
depth was performed until the soil cleanup goals were met. Sediments from the North Lagoon
were removed to a depth equivalent to the low groundwater level. These sediments were trucked
to the treatment area, stabilized using the VFL process and placed on the Industrial Landfill.
Materials in the Blowdown Pit containing greater than 100 parts per million (ppm) of VDC were
excavated and shipped to an off-site disposal facility. Remaining sludge and other contaminated
materials and at least two feet of underlying soil were excavated, stabilized using the VFL
process and placed on the Industrial Landfill. Post-excavation sampling was then conducted to
ensure that soil cleanup goals were attained.

• The Industrial Landfill was covered with excavated soils and then with stabilized materials from
the lagoons and Blowdown Pit and then graded using excavated materials from the other waste
disposal areas. The landfill was then sealed/closed with an impermeable cap designed and
constructed in accordance with Massachusetts Hazardous Waste Regulations for landfills
specified at 310 CMR 30.580-595 and 30.620-633. The impermeable cap included a synthetic
cover to prevent infiltration of surface water into the waste materials beneath the cap.

The cap was also constructed with vents to allow gases generated from the existing and new
material to vent to the surface outside the landfill. Emissions from the Industrial Landfill were
initially controlled utilizing a thermal oxidation unit, but, after proper evaluation, have since
been allowed to vent passively to the atmosphere (USEPA, 2002).

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Additionally, a groundwater monitoring and recovery system was designed and installed at the
Industrial Landfill to supplement the existing ARS recovery wells.

• Originally, the Battery Separator Chip Pile was to be capped in place, but the need to remove the
underlying soils made in-place capping not feasible. Therefore, the battery separator chips were
excavated and placed in the Industrial Landfill and were covered with non-solidified material
excavated from the source areas.

• Prior to implementation of the remediation work provided for in the ROD for OU-1, W.R. Grace
constructed an ARS. This system began treating contaminated groundwater that was extracted
from bedrock and overburden wells through an air stripping tower. The ARS began operation in
March 1985 and has continued, with modifications, to treat groundwater through the present.
The air stripping tower component of the ARS required upgrading by installing carbon filters to
control vapors and odors; these upgrades were completed in September 1992 (Foster Wheeler,
1997).

All of the above remedial action activities were completed and the contractor, Camp, Dresser & McKee,
Inc. (CDM) certified that the remedy was constructed according to all approved plans and specifications,
as documented in the Revised Construction Quality Assurance Closeout Report, prepared by CDM,
dated February 1998.

OU-3. The remedial designs were completed and the remedial actions were constructed by W.R. Grace
since the last FYR in 2009, as discussed in the section of this report entitled "Progress Since the Last
Review."

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APPENDIX B - LIST OF DOCUMENTS REVIEWED/REFERENCES

Alliance Technologies Corporation, 1989. Risk Analysis of the W.R. Grace Site, Acton, Massachusetts.
Prepared for U.S. Environmental Protection Agency, Office of Waste Programs Enforcement,
Washington, DC, Contract No. 68-W9-0003. June 30, 1989.

ARCADIS. 2008. W.R. Grace Superfund Site Sediment Pre-Design Results Report. April 2008.

ARCADIS. 2011. W.R. Grace Superfund Site Final Sediment Remedial Design Report. March 2011.

ARCADIS, 2012a. Draft 2012 Vegetation Monitoring Report. W.R. Grace Superfund Site, Operable
Unit 3, Acton-Concord, Massachusetts. October 2013.

ARCADIS. 2012b. W.R. Grace Superfund Site Final Sediment Construction
Summary and Final Sediment Remedial Action Report. June 2012.

ARCADIS, 2012c. W.R. Grace Superfund Site Final Sediment Demonstration of Compliance and
Maintenance Plan. April 2012.

ARCADIS, 2013. Draft 2013 Vegetation Monitoring Report. W.R. Grace Superfund Site, Operable
Unit 3, Acton-Concord, Massachusetts. October 2013.

ARCADIS, 2014. 5-Year Sediment Investigation Summary Report, W.R. Grace Superfund Site, Acton,
Massachusetts. June 2014.

Camp Dresser & McKee. 1988. Appendix D Risk Assessment for W.R. Grace Site, Acton,
Massachusetts. August 31, 1988.

Camp Dresser & McKee. 1996. Post-Closure Operations and Maintenance (O&M) Plan. W.R. Grace
Superfund Site, Acton, Massachusetts. August 15, 1996.

GeoTrans and O&M, Inc. 2011. Northeast Area Groundwater Remedial Action Report, January 20,
2011.

HSI GeoTrans, 1998. Initial Site Characterization Report - Operable Unit Three. W.R. Grace
Superfund Site, Acton, Massachusetts, prepared for W.R. Grace & Co. August 12, 1998.

Menzie-Cura & Associates. 2005a. Public Health Risk Assessment. July.

Menzie-Cura & Associates. 2005b. Baseline Ecological Risk Assessment. July.

O&M Inc. and GeoTrans, Inc. 2010. Northeast Area Groundwater Operation and Maintenance Plan.
June 2010.

Sullivan Design and Construction Management (DCM), P.C. 2007. November 2007 Landfill Gas
Emission Monitoring. W.R. Grace Landfill, Acton, Massachusetts. January 3, 2008.

TetraTech, 2013a. Evaluation of Northeast Area Remedial Action, February 25, 2013.

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TetraTech, 2013b. OU3 Monitoring Program Report, 2013, W.R. Grace Superfund Site, Acton, MA,
December 20, 2013.

Tetra Tech GEO and O&M, Inc. 2012a. Landfill Area Groundwater Operation and Maintenance Plan,
July 10, 2012.

Tetra Tech GEO and O&M, Inc. 2012b. Final Landfill Area Groundwater Remedial Action Report,
September 25, 2012.

TetraTech GEO, 2011. Institutional Controls Plan, May 12, 2011.

United States Environmental Protection Agency (USEPA). 1988. Record of Decision, September 1988.

United States Environmental Protection Agency (USEPA). 1989. Record of Decision, W.R. Grace
(Acton Plant) Superfund Site, Acton, Massachusetts. September 29, 1989

United States Environmental Protection Agency (USEPA). 1999. Five Year Review, W.R. Grace
(Acton Plant) Superfund Site, Acton, Massachusetts. September 1999.

United States Environmental Protection Agency (USEPA). 2001. Comprehensive Five-Year Review
Guidance. June 2001.

United States Environmental Protection Agency (USEPA). 2000. Institutional Controls: A Site
Manager's Guide to Identifying, Evaluating and Selecting Institutional Controls at Superfund and
RCRA Corrective Action Cleanups. EPA 540-F-005. September 2000.

U. S. Environmental Protection Agency (USEPA), 2005. Record of Decision, W.R. Grace & Co. (Acton
Plant) Superfund Site, Operable Unit Three, September 2005.

U. S. Environmental Protection Agency (USEPA), 2009a. Regional Screening Levels Table. Oak Ridge
National Laboratories. U.S. EPA. http://epa-prgs.ornl.gov/chemicals/index.shtml April 2009.

U. S. Environmental Protection Agency (USEPA), 2014. Integrated Risk Information System (IRIS).
On-line Database. July 2014.

U.S. Environmental Protection Agency (USEPA). 2002. Letter from Derrick S. Golden, EPA Remedial
Project Manager, to Maryellen Johns, Remedium Group, Inc., Re: The Thermal Oxidation Unit on the
Industrial Landfill at the W.R. Grace Superfund Site - Acton, Massachusetts. October 31, 2002.

U. S. Environmental Protection Agency (USEPA), 2012. Fact Sheet: 1,4-Dioxane, W.R Grace (Acton
Plant, Acton, MA. U.S. EPA - Hazardous Waste Program at EPA New England. March 2012.

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APPENDIX C - SITE INSPECTION CHECKLIST AND PHOTOGRAPHS

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Five-Year Review Site Inspection Checklist

("N/A" refers to "not applicable.")

I. SITE INFORMATION

Site name: W.R. Grace (Acton Plant) Superfund Site

Date of inspection: May 21, 2014

Location and Region: Acton, MA; Region I

EPA ID: MAD001002252

Agency, office, or company leading the five-year
review: USEPA/AECOM

Weather/temperature: Clear/75°F

Remedy Includes: (Check all that apply)
X Landfill cover/containment
X Access controls
X Institutional controls
X Groundwater pump and treatment

~	Surface water collection and treatment

~	Other

Attachments: ~ Inspection team roster attached	~ Site map attached

II. INTERVIEWS

Interviews were performed by USEPA/AECOM and are included separately.

X Monitored natural attenuation

~	Groundwater containment

~	Vertical barrier walls

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III. ON-SITE DOCUMENTS & RECORDS VERIFIED (Check all that apply)

1.

O&M Documents

X O&M manual
~ As-built drawings
X Maintenance logs

X Readily available
~ Readily available
X Readily available

~	Up to date

~	Up to date
X Up to date

~	N/A

~	N/A

~	N/A



Remarks: While the O&M manual was not reviewed (besides noting that it was there),
fouling of extraction system may justify review/revision in the near future.

recent iron

2.

Site-Specific Health and Safety Plan X Readily available
~ Contingency plan/emergency response plan ~ Readily available

~	Up to date

~	Up to date

~	N/A

~	N/A



Remarks: Not reviewed beyond noting that it was available at the treatment plant.



3.

O&M and OSHA Training Records

~ Readily available

~ Up to date

~ N/A



Remarks: Not reviewed (records available at home offices)





4.

Permits and Service Agreements

~	Air discharge permit

~	Effluent discharge

~	Waste disposal, POTW

~	Other permits

~	Readily available

~	Readily available

~	Readily available

~	Readily available

~	Up to date

~	Up to date

~	Up to date

~	Up to date

XN/A
XN/A
XN/A
XN/A



Remarks: Annual fee paid to Acton for storage of hazardous materials (verbal discussion).

5.

Gas Generation Records

Remarks: No ongoing monitoring

~ Readily available

~ Up to date

XN/A

6.

Settlement Monument Records

Remarks: No settling monuments

~ Readily available

~ Up to date

XN/A

7.

Groundwater Monitoring Records

Remarks: Not reviewed - available offsite

X Readily available

X Up to date

~ N/A

8.

Leachate Extraction Records

~ Readily available

~ Up to date

XN/A



Remarks: No leachate collection







9.

Discharge Compliance Records

~	Air

~	Water (effluent)

~	Readily available

~	Readily available

~	Up to date

~	Up to date

XN/A
XN/A

10.

Daily Access/Security Logs

Remarks:

~ Readily available

~ Up to date

XN/A

C-3

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IV. O&M COSTS

1.

O&M Organization

~	State in-house ~ Contractor for State

~	PRP in-house X Contractor for PRP

~	Federal Facility in-house ~ Contractor for Federal Facility

~	Other

2.

O&M Cost Records

Not Reviewed

3.

Unanticipated or Unusually High O&M Costs During Review Period

Describe costs and reasons: Electricity costs for oxidation system very high. Looking at other options
for cost reduction.

V. ACCESS AND INSTITUTIONAL CONTROLS X Applicable ~ N/A

A.

Fencing

1.

Fencing damaged ~ Location shown on site map X Gates secured ~ N/A
Remarks: Fencing appeared to be in good shape.

B.

Other Access Restrictions

1.

Signs and other security measures ~ Location shown on site map X N/A
Remarks

C-4

-------
C. Institutional Controls (ICs)

1. Implementation and enforcement

Site conditions imply ICs not properly implemented	L Yes L No XN/A

Site conditions imply ICs not being fully enforced	L Yes L No XN/A

Type of monitoring (e.g., self-reporting, drive by)
Frequency 	

Responsible party/agency
Contact

Name	Title	Date Phone no.

Reporting is up-to-date	L Yes L No XN/A

Reports are verified by the lead agency	L Yes L No XN/A

Specific requirements in deed or decision documents have been met	~ Yes ~ No X N/A

Violations have been reported	~ Yes ~ No X N/A
Other problems or suggestions: ~ Report attached

ICs not yet in place. 	

2. Adequacy	~ ICs are adequate	~ ICs are inadequate	X N/A

Remarks

D. General

1.	Vandalism/trespassing ~ Location shown on site map X No vandalism evident

Remarks	Sapling protection tubes were removed, apparently by someone who thought that the tubes

	weren't good for the trees.	

2.	Land use changes on site X N/A

Remarks	

3.	Land use changes off site XN/A

Remarks	

VI. GENERAL SITE CONDITIONS

A. Roads	X Applicable L N/A

1. Roads damaged	~ Location shown on site map X Roads adequate	L N/A

Remarks

C-5

-------
B.

Other Site Conditions

Remarks Conditions around Sinking Pond and North Lagoon Wetland were reviewed by wetlands
specialist, Deb Roberts.

VII. LANDFILL COVERS X Applicable ~ N/A

A.

Landfill Surface

1.

Settlement (Low spots) ~ Location shown on site map X Settlement not evident

Areal extent Depth

Remarks

2.

Cracks ~ Location shown on site map X Cracking not evident

Lengths Widths Depths

Remarks

3.

Erosion ~ Location shown on site map X Erosion not evident

Areal extent Depth

Remarks

4.

Holes ~ Location shown on site map ~ Holes not evident
Areal extent Depth

Remarks One hole near LFG monitoring point 4 - appears to be groundhog burrow

5.

Vegetative Cover X Grass X Cover properly established X No signs of stress

~ Trees/Shrubs (indicate size and locations on a diagram)

Remarks

6.

Alternative Cover (armored rock, concrete, etc.) X N/A

Remarks

7.

Bulges ~ Location shown on site map X Bulges not evident

Areal extent Height

Remarks

8. Wet Areas/Water Damage X Wet areas/water damage not evident

~	Wet areas ~ Location shown on site map Areal extent

~	Ponding ~ Location shown on site map Areal extent

~	Seeps ~ Location shown on site map Areal extent

~	Soft subgrade ~ Location shown on site map Areal extent
Remarks

9.

Slope Instability ~ Slides ~ Location shown on site map X No evidence of slope instability

Areal extent

Remarks

C-6

-------
B.

Benches X Applicable ~ N/A

(Horizontally constructed mounds of earth placed across a steep landfill side slope to interrupt the slope
in order to slow down the velocity of surface runoff and intercept and convey the runoff to a lined
channel.)

1.

Flows Bypass Bench

Remarks

~ Location shown on site map X N/A or okay









2.

Bench Breached

Remarks

~ Location shown on site map X N/A or okay









3.

Bench Overtopped

Remarks

~ Location shown on site map X N/A or okay









C.

Letdown Channels X Applicable ~ N/A

(Channel lined with erosion control mats, riprap, grout bags, or gabions that descend down the steep side
slope of the cover and will allow the runoff water collected by the benches to move off of the landfill
cover without creating erosion gullies.)

1.

Settlement

Areal extent
Remarks

~ Location shown on site map
Depth

X No evidence of settlement









2.

Material Degradation

Material type

~ Location shown on site map
Areal extent

X No evidence of degradation



Remarks













3.

Erosion

Areal extent
Remarks

~ Location shown on site map
Depth

X No evidence of erosion









C-7

-------
4.

Undercutting ~ Location shown on site map X No evidence of undercutting

Areal extent Depth

Remarks







5.

Obstructions Type X No obstructions

~ Location shown on site map Areal extent

Size

Remarks









6.

Excessive Vegetative Growth Type
X No evidence of excessive growth

~	Vegetation in channels does not obstruct flow

~	Location shown on site map Areal extent

Remarks:









D.

Cover Penetrations X Applicable ~ N/A



1.

Gas Vents ~ Active X Passive

~	Properly secured/locked X Functioning ~ Routinely sampled

~	Evidence of leakage at penetration ~ Needs Maintenance

~	N/A

X Good condition



Remarks: One vent is noticeably leaning on southern side of landfill. Onsite personnel state that it is
still venting. No visual evidence of gas buildup or emissions elsewhere.

2.

Gas Monitoring Probes

X Properly secured/locked ~ Functioning ~ Routinely sampled
~ Evidence of leakage at penetration ~ Needs Maintenance

~	Good condition

~	N/A



Remarks: Manholes locked. Many of the plastic Keep Out signs are no longer on the manhole covers,
but there is no evidence of trespassers on the landfill.

3.

Monitoring Wells (within surface area of landfill)

~	Properly secured/locked ~ Functioning ~ Routinely sampled

~	Evidence of leakage at penetration ~ Needs Maintenance
Remarks

~ Good condition

XN/A







4.

Leachate Extraction Wells

~	Properly secured/locked ~ Functioning ~ Routinely sampled

~	Evidence of leakage at penetration ~ Needs Maintenance
Remarks

~ Good condition

XN/A







5.

Settlement Monuments ~ Located ~ Routinely surveyed
Remarks

XN/A







C-8

-------
E.

Gas Collection and Treatment ~ Applicable X N/A

1.

Gas Treatment Facilities

~	Flaring X Thermal destruction ~ Collection for reuse

~	Good condition ~ Needs Maintenance

Remarks: No longer active. Not inspected.

2.

Gas Collection Wells, Manifolds and Piping

~ Good condition ~ Needs Maintenance

Remarks: No longer active. Not inspected.

3.

Gas Monitoring Facilities (e.g., gas monitoring of adjacent homes or buildings)

~ Good condition ~ Needs Maintenance X N/A

Remarks

F.

Cover Drainage Layer X Applicable ~ N/A

1.

Outlet Pipes Inspected ~ Functioning ~ N/A
Remarks: Not inspected

2.

Outlet Rock Inspected ~ Functioning ~ N/A
Remarks: Not inspected

G.

Detention/Sedimentation Ponds ~ Applicable X N/A

1.

Siltation Areal extent Depth ~ N/A
~ Siltation not evident

Remarks: Siltation was observed. Detention basin still appears to be functioning properly.

2.

Erosion Areal extent Depth
~ Erosion not evident
Remarks

3.

Outlet Works ~ Functioning ~ N/A
Remarks

4.

Dam ~ Functioning ~ N/A
Remarks

C-9

-------
H. Retaining Walls ~ Applicable XN/A

1.

Deformations ~ Location shown on site map ~ Deformation not evident
Horizontal displacement Vertical displacement
Rotational displacement
Remarks

2.

Degradation ~ Location shown on site map ~ Degradation not evident
Remarks

I. Perimeter Ditches/Off-Site Discharge X Applicable ~ N/A

1.

Siltation ~ Location shown on site map X Siltation not evident

Areal extent Depth

Remarks

2.

Vegetative Growth ~ Location shown on site map ~ N/A
X Vegetation does not impede flow
Areal extent Type

Remarks: There was some minor vegetative growth in the perimeter channel due to standing water.
Regrading may need to be looked into in the future, but it currently doesn't appear to be a problem.

3.

Erosion ~ Location shown on site map X Erosion not evident

Areal extent Depth

Remarks

4.

Discharge Structure X Functioning ~ N/A

Remarks: Actual structure not inspected. Flow does not appear to be restricted leaving the perimeter
ditch.

VIII. VERTICAL BARRIER WALLS ~ Applicable XN/A

1.

Settlement ~ Location shown on site map ~ Settlement not evident

Areal extent Depth

Remarks

2.

Performance Monitoring Type of monitoring
~ Performance not monitored

Frequency ~ Evidence of breaching

Head differential

Remarks

C-10

-------
IX. GROUNDWATER/SURFACE WATER REMEDIES X Applicable UN/A

A.

Groundwater Extraction Wells, Pumps, and Pipelines X Applicable ~ N/A

1.

Pumps, Wellhead Plumbing, and Electrical

~ Good condition ~ All required wells properly operating ~ Needs Maintenance ~ N/A
Remarks: Not inspected. Records show operating as designed.

2.

Extraction System Pipelines, Valves, Valve Boxes, and Other Appurtenances

~ Good condition ~ Needs Maintenance

Remarks: Not inspected. Exterior piping system developed for bypass when primary piping requires
cleaning.

3.

Spare Parts and Equipment

~ Readily available ~ Good condition ~ Requires upgrade ~ Needs to be provided
Remarks: Not inspected.

B. Surface Water Collection Structures, Pumps, and Pipelines ~ Applicable X N/A

1.

Collection Structures, Pumps, and Electrical

~ Good condition ~ Needs Maintenance
Remarks

2.

Surface Water Collection System Pipelines, Valves, Valve Boxes, and Other Appurtenances

~ Good condition ~ Needs Maintenance
Remarks

3.

Spare Parts and Equipment

~ Readily available ~ Good condition ~ Requires upgrade ~ Needs to be provided
Remarks

C-ll

-------
c.

Treatment System X Applicable UN/A

1.

Treatment Train (Check components that apply)

X Metals removal ~ Oil/water separation ~ Bioremediation

~	Air stripping X Carbon adsorbers
X Filters: microfiltration and filter presses

X Additive (e.g., chelation agent, flocculent)

~	Others

X Good condition ~ Needs Maintenance

~	Sampling ports properly marked and functional

X Sampling/maintenance log displayed and up to date
X Equipment properly identified

~	Quantity of groundwater treated annually

~	Quantity of surface water treated annually
Remarks

2.

Electrical Enclosures and Panels (properly rated and functional)
~ N/A X Good condition ~ Needs Maintenance
Remarks

3.

Tanks, Vaults, Storage Vessels

~ N/A X Good condition ~ Proper secondary containment ~ Needs Maintenance
Remarks

4.

Discharge Structure and Appurtenances

~ N/A X Good condition ~ Needs Maintenance
Remarks

5.

Treatment Building(s)

~ N/A X Good condition (esp. roof and doorways) ~ Needs repair

X Chemicals and equipment properly stored

Remarks

6.

Monitoring Wells (pump and treatment remedy)

X Properly secured/locked ~ Functioning X Routinely sampled ~ Good condition
~ All required wells located ~ Needs Maintenance ~ N/A

Remarks: One location near railroad tracks damaged and will require repair.

D. Monitoring Data: Not reviewed

1. Monitoring Data

~ Is routinely submitted on time ~ Is of acceptable quality

2. Monitoring data suggests:

~ Groundwater plume is effectively contained ~ Contaminant concentrations are declining

C-12

-------
D.

Monitored Natural Attenuation

Monitoring Wells (natural attenuation remedy)

X Properly secured/locked ~ Functioning X Routinely sampled ~ Good condition
~ All required wells located ~ Needs Maintenance ~ N/A

Remarks: One location near railroad tracks damaged and will require repair.

OTHER REMEDIES

If there are remedies applied at the site which are not covered above, attach an inspection sheet describing
the physical nature and condition of any facility associated with the remedy. An example would be soil
vapor extraction.

XL OVERALL OBSERVATIONS

Implementation of the Remedy

Describe issues and observations relating to whether the remedy is effective and functioning as designed.
Begin with a brief statement of what the remedy is to accomplish (i.e., to contain contaminant plume,
minimize infiltration and gas emission, etc.).

This source control/containment remedy appears to be operating as designed.

Adequacy of O&M

Describe issues and observations related to the implementation and scope of O&M procedures. In
particular, discuss their relationship to the current and long-term protectiveness of the remedy.

The landfill cover and landfill gas systems appear to be well-maintained.

C. Early Indicators of Potential Remedy Problems

Describe issues and observations such as unexpected changes in the cost or scope of O&M or a high
frequency of unscheduled repairs that suggest that the protectiveness of the remedy may be compromised
in the future.

None

D. Opportunities for Optimization

Describe possible opportunities for optimization in monitoring tasks or the operation of the remedy.

The operators are currently attempting to optimize removal of 1,4-dioxane. This effort should continue,
as there are significant costs associated with that removal.

C-13

-------
Northwest entrance of landfill, facing southeast

Northwest entrance of landfill, facing east
C-14

-------
View of northwest bottom-of-slope drainage channel with minor vegetative growth

05/2171

View of inactive thermal oxidizer unit stack
C-15

-------
View of southern bottom-of-slope drainage channel, facing west

C-16

-------
Tilted passive landfill gas vent in southwest area of landfill

C-17

-------
Groundwater equalization tank in southwest area of landfill

C-18

-------
View inside groundwater treatment plant
C-19

-------
View inside groundwater treatment plant - Purifies unit

View inside groundwater treatment plant
C-20

-------
View inside groundwater treatment plant
C-21

-------
C-22

-------
feM RQBERTS

y Environmental Consulting, Inc.

OVERSIGHT REPORT
W.R. Grace Superfund Site
Acton, Massachusetts

DATE PREPARED:

May 25, 2014

REPORT NO:

WRGRACE240514

DATE ON SITE :

May 21, 2014

HOURS AT SITE:

10:15-13:00

PREPARED BY:

D. Roberts

WEATHER
CONDITIONS:

Sunny, 73°

I. SUMMARY OF WORK PERFORMED:

I. The purpose of the visit was to conduct an inspection of the wetlands restoration at
Sinking Pond and the North lagoon wetlands and in addition, for EPA and MassDEP to complete
a five-year review Inspection of the Landfill Area Treatment System (LATS) and the Industrial
Landfill at the site. The group (see list, Section III, below) met at the parking area near the
former trailer location. We walked first to Sinking Pond, then to North Lagoon wetland to
observe site conditions. Everyone then toured the treatment facility with the exception of
Anthony.

II. GENERAL COMMENTS AND OBSERVATIONS:

1. Sinking Pond. The upland area and banks of Sinking Pond have filled in with dense rye
grass cover. No large areas of wash-out or sparse vegetation were observed from the
northern end of the pond. Only a very limited number of the aquatic vegetation
plantings appeared to have germinated from the plug planting of the inlet area. A few
leaves of pond lilies and arrowhead were visible. Anthony indicated that the need for
supplemental planting will be evaluated upon performance of the summer vegetation
monitoring in August.

The tree and shrub survivorship appeared to be high. Most of the woody plantings
observed were in good health around the inlet and northern end of the pond.

There was dense growth of rye grass mixed with a few other species along the edge of the
pond. However, no evidence of germination of plants that were seeded as part of the
wetland seed mix was observed.

A large number of bullfrog tadpoles were observed along the edge of Sinking Pond,
along with some small fish (possibly minnows) and a turtle.

2. Similar to the area around Sinking Pond, there was dense growth of rye grass mixed with
a few other species in the upland bordering North Lagoon Wetland. The tree and shrub
survivorship here also appeared to be high. Even those tree tubes that appeared empty
had small high bush blueberry shrubs in them which appeared in good condition.

The deeper area of the sedge marsh had been planted with a sedge seed mix. There was
no evidence of sedges germinating. However, the area is still inundated with several
inches of standing water. Tadpoles were observed in the sedge marsh.

WR GRACE Remedial Oversight

Page C-23

-------
ROBERTS

Environmental Consulting, Inc.

The water levels in the North Lagoon Wetland near Fort Pond Brook showed areas of
inundation and other areas of saturation, which appeared to be appropriate conditions for
the time of the season. The woody plantings in the tubes appeared to be in good
condition. Some sparse herbaceous vegetation is starting to grow, dominated by beggar's
tick (Bidens sp.) which was in the seed mix, but is also a common first year wetland plant
that appears in mitigation areas in New England. The detailed vegetation monitoring will
be done by Arcadis later in the summer when more of the wetland plants are established.

The haybales that formed part of the bank stabilization along Fort Pond Brook were still
in place, and will be left as part of the bank.

3. Thor Helgason gave us a tour of the treatment plant. The landfill area treatment system is
in operation, and yesterday EPA received preliminary results of the toxicity tests on the
effluent collected from a pipe just before the treated effluent is discharged from the plant.
The preliminary results were discussed with Bart Hoskins of EPA. AECOM will prepare
a memo to EPA regarding the test results after the final report on the results is received.
Another round of toxicity tests on the effluent water is scheduled for August.

WR GRACE Remedial Oversight

Page C-24

-------
III. SUMMARY OF CONTRACTORS AND PERSONNEL:

Personnel

Derrick Golden
Jennifer McWeeney
Sean Czarniecki
Deborah Roberts

Thor Helgason

Anthony Esposito

Contractor	Site Activity/Role

EPA	Oversight/TOPO

DEP	Oversight/Project manager

AECOM	Oversight/Project engineer

AECOM	Oversight/Ecological Risk-Wetlands

de maximis	Construction Management

ARCADIS	Remedial Contractor/Wetland Specialist

C-25

-------
RQBERTS

Environmental Consulting, Inc.

DAILY PHOTO LOG
WR Grace Superfund Site
Acton, Massachusetts

DATE PREPARED: May 22, 2014
DATE ON SITE : May 21,2014

PHOTO LOG NO: WRGR21May2014
PREPARED BY: D. Roberts

Photo File
Name

Description

P1100295

Sinking Pond discharge from culvert to inlet

P1100296

Sinking Pond Inlet

P1100297

Sinking Pond Inlet

P1100298

Sinking Pond Inlet looking south toward weir

P1100299

Sinking Pond west shore

P1100300

Sinking Pond looking south from inlet area

P1100301

Sinking Pond northeast shore

P1100302

Sinking Pond upland at northern end of pond with tree tubes

P1100303

Sinking Pond at North Lagoon Wetland

P1100304

North Lagoon Wetland looking north up the channel from sedge marsh

P1100305

North Lagoon Wetland looking up the channel to the south toward
sedge marsh

P1100306

North Lagoon Wetland - wooded swamp area

P1100307

North Lagoon Wetland - wooded swamp area

P1100308

North Lagoon Wetland - wooded swamp area, looking north toward
marsh and the brook

P1100309

Fort Pond Brook - restored stream bank

P1100310

North Lagoon Wetland emergent marsh area

P1100311

North Lagoon Wetland looking back toward area of wooded swamp

P1100312

North Lagoon Wetland - sediment sample North Lagoon Wetland-01
near Fort Pond Brook

WR Grace, Acton Oversight

-------
RQBERTS

Environmental Consulting, Inc.

P1100313

Sinking Pond at the discharge of the inlet, Shoreline in the vicinity of
vegetation plot P-ll, on the west side of the outlet channel near tall
metal stake.

P1100314

Sinking Pond - Shoreline in the vicinity of vegetation plot P-ll near tall
metal stake.

P1100315

Sinking Pond- along the Bordering Vegetated Wetland (BVW) at water's
edge, north shore

P1100316

Sinking Pond - BVW and bank, north shore

P1100317

Sediment location Sinking Pond-75 in sandy delta area of BVW, north
shore

WR Grace, Acton Oversight

-------
Site Photographs
WR Grace Superfund Site
May 21, 2014

-------
* rWi ' "

P1100296

-------
ffilTOtW' ills 1

P1100298

-------
P1100300

-------
P1100300

P1100301

-------
P1100303

-------
P1100304

P1100305

-------
P1100307

-------
P1100309

-------
P1100311

-------
P1100313

-------
P1100315

-------
1 *1

P1100316

P1100317

-------
APPENDIX D - INTERVIEW RECORD FORMS

D-l

-------
INTERVIEW RECORD

Site Name: W. R. Grace Superfund Site (Acton, MA)

EPA ID No.: MAD001002252

Subject: Five Year Review

Time: 9:30 AM Date: 7/28/2014

Type: ¦ Telephone ~ Visit ~ Other
Location of Visit:

~ Incoming ¦ Outgoing

Contact Made By:

Name: Barbara Weir Title: Task Order Manager

Organization: AECOM

Individual Contacted:

Name:

Jane Ceraso

Title:

Organization:

ACES and Green Acton

Telephone No:

Fax No:

E-Mail Address: jane.ceraso@paragon-c.com

Street Address:

1.	What is your overall impression of the project? (general sentiment)

The project seems to have changed over time - in earlier years, there was a great deal of public involvement
but in the past 5 or 6 years, the public involvement has become less extensive. ACES members noted that
after about 2006 is when the change occurred. This corresponds to when the ROD was signed (September
2005). After 2006, ACES member Mary Michelman (since deceased) noted to Jane that she felt that ACES
had a lesser seat at the table.

2.	Are you aware of any community concerns or complaints related to the site (e.g., odor, noise,
health, etc.)?

People are concerned about the 1,4-dioxane issue and impacts to their drinking water, and do not want it to
become a secondary issue to the rest of the contamination issues. There is concern because the Acton Water
District cannot remove 1,4-dioxane from the water. People's biggest concern is that the drinking water be
protected.

3.	Do you feel well informed about site activities and progress of the cleanup?

Jane said yes, she feels well informed and that there has been a fair bit of back and forth - EPA has done a
good job and people can become informed pretty easily.

4.	Do you have any comments, suggestions, or recommendations regarding the site's management or
operation?

Jane recommends that ongoing monitoring for 1,4-dioxane continue. She thinks it is important that EPA
continue to keep track of the issue and that everyone has a handle on what is present in the aquifer.	

Page 1 of 2

-------
5. Do you have any other comments, suggestions, or recommendations regarding the project?

See above regarding monitoring for 1,4-dioxane. In general - keep up the monitoring and do not shut down
systems too soon. She noted that it is really difficult to say when a cleanup is "done" and that it takes a long
time, especially for groundwater, and that this is even more difficult because of the impacts to drinking water.
People are concerned about "cutting corners" and it is important to keep people informed about the progress
of the cleanup to help address these concerns.

6. EPA understands that the old Acton Citizens for Environmental Safety is being merged into the
Green Acton organization - could you provide some information on Green Acton and its
mission?

Jane explained that ACES decided to merge into Green Acton because of attrition in its members (deaths,
relocation) and it was a struggle to keep ACES going. Green Acton is a new organization with lots of energy
and the mission of ACES fits within it - its mission is more general than ACES (which focused on health and
safety and the Grace site) and is about sustainability, education, recycling, and waste reduction efforts. Green
Acton is not incorporated as ACES is. By the end of the year they will become one organization and be an
incorporated non-profit. Funds from ACES will be used to help with programs Green Acton has started. Jane
will continue to be active in Green Acton as well as a couple of other ACES members (Pam Resor for one),
and the Green Acton members are ready to take up health and safety issues that were ACES mission,
including keeping tabs on the Grace site. Jane offered to communicate to EPA once the merger is final.

Page 2 of 2

-------
INTERVIEW RECORD

Site Nsimr; \\ R. Grace v,t;u*rftiit>S Nitf t A.cioti. M> t

IT% 10 No.: MA!K»Oi<,i"2251

Subjivt: t ivr Year Rev lev.-

Time: j Hate:

Tjpe: II idcplione C V'sit ~other
Location of Vimi:

~ Incoming • * nttgoing

Contact Made B>;

Name;

Tftlrr

Organization:

Individual Contacted;

Narur:

Douh ISiill'e*

1 it if:

Health Dirsctpr

Organisation:

Acion Board . •!'! lejith

Teieptiow No: 978-264-%

Fav No:

E-Mail Vidros: uhalie> Slav* t> ..ktoruna,us

Street Address:

A,ctun Board of Mould)

-•~?2 Main Sirert. Alton. MA CHT2r>

1 What is your overall impression of the project? (general sentiment)

In genera! i am satisfied with the continued effort by WR Grace, the oversight provided by
EPA and MADE? and the information provided to the Town and the Water Dsfnct However, (
renvoin concerned with Qma's shutdown of the treatment system tor she Northeast Ruma, ihc»
continued reliance on the Water District's treatment system to capture ana treat Grace's
contaminant plumes, .wd the reliance on natural attenuation to tesolve unaddresseeS plumes of
contamination. Noting thai this project started m 137S it b discouraging lhaf 36 years Sate''
Gfare has not yet achieved ar,c ca-nw yes tnenfify an errd date fof ccntaw.aiKW. ave's to
?each puD'ic health stanoa'cs.

2. Have there been any health or safety issues associated with the site?
if, •;t necessary tor the Board of Health to have an administrative 'to«d on tre
installation of private welis. As of this date EPA has not provided a strategy -as D how and
whun the right to use the ground water resources wilt be restored

Page I nf 3

-------
3, Are you aft-are of fr&soessan- entering the oroperty, ana if yes. Hew often and in
whut typa of activities do they engage?

Abutters and the gerwrai puDitc continue to use ?tie urace property p.*> an seotssibie place
to walk/hike Willi the exception s>i Ihe fencea off area at the landfifi it is not unusual to
see someone walking the ptcpety aft a daw bas-t

4 Are you aware af any changes In lama use in the vicinity of tf»« srte7 If so, please
describe,

~ne Water 0»stna is in lha process t>f Dutldiny a Water Tmacrsnf F ability just sooth of ttie
Grace property. Some minor commercial devetapment is on-going along Knox Trail, There
!ias seen some ami ii is anticipated fh&m wll be more resioemia! aevelopmern r, area
due io public sewers along Patter Sweet and independence Road.

5. Has the site been »he subject of any community concerns or complaints (e.g ,
cdor, noae, health, etc,)?

Theie remains a strong community concern regarding trie recent shutdown ot the Northeast
Piur'ie treatment system. T'he- vvatfif District 'ate payers continue io fund public reagent
systems to protect againsi and remove Grace's contaminants, yet Grace as the responsible'
osny is riot held to the sarr>e stanciiitcJ or required to apply we same measures. The Wster
District cannot rely upon Natural Attenuation as a means tc» bring safe drinking water to its
customers, yet Grace has tae-ers relieved c" the cfaiigai'C" to rea? tHe ground Mate' »
remove «u. contaminants.

? ts Ihe Town planning Io maintain trie administraf've hold on private irrigation well
p^f.tts in the plume arra ontii the cleanup ts complete"5

The Board of Health needs an updated map of tfie area of concern that is Ned io the
current 'e^eis of contamtnft< ^comneindao stiategy from
fc" cn hoy/ aid when ihe administrative bold shoulc be re-evaluated and «nst findings
fiiuat oe evident to determine its necessity. As Health Director, I remain concerned thai
EPA ss reiy>ng on the administrative hold to prevent (tie public from utilizing ground water

PliSi- 2 cf 3

-------
resources winin allowing pentose' ic 3/iuk down ? treatment system winch would have

aeceterateti «« clean-up c" the aqytef

j	8, Do you have ftrsy comments. suggestions. or rocofpwendafions regarding the si'e'?

management or operation?
rhe Board of Health femains concerned thai the shutdown or trie No*ir*
-------
INTERVIEW RECORD

Site Name: W. R. Grace Superfund Site (Acton, MA)

EPA ID No.: MAD001002252

Subject: Five Year Review

Time: 10:29
AM

Date: 7/17/2014

Type: ~ Telephone ~ Visit ¦ Other
Location of Visit: NA. Jennifer provided written responses using this
form and submitted them to EPA and B. Weir via email.

~ Incoming ~ Outgoing

Contact Made By:

Name: Barbara Weir

Title: Task Order Manager

Organization: AECOM

Individual Contacted:

Name:

Jennifer McWeeney

Title:

Project Manager

Organization:

MassDEP

Telephone No: 617-654-6560
Fax No:

E-Mail Address: jennifermcweeney@state.ma.us

Street Address:

MassDEP

One Winter Street, Boston, MA 02108

1.	What is your overall impression of the project? (general sentiment)

My overall impression is that the project is well managed and is making progress
towards its cleanup goals.

As you know, contaminated sediment in both Sinking Pond and North Lagoon
wetland has been successfully remediated and vegetation in these areas is being
restored.

Groundwater contaminant levels in both the Landfill Area and the Northeast Area
of the site continue to decline. The Landfill Area groundwater treatment system
continues to operate. VDC levels in the Northeast Area declined enough to
warrant shutdown of that temporary system after 3 years of operation. Natural
attenuation is expected to further reduce VDC levels in the Northeast Area, and
groundwater monitoring will continue to be conducted confirm this.

2.	Has the site been the subject of any community complaints directed to your
agency (e.g., odor, noise, health, etc.)?

Yes. The Town of Acton complained about the shutdown of the Northeast Area

Page 1 of 2

-------
groundwater treatment system after 3 years of operation. As you know,
MassDEP considered all information, including the information provided in their
complaint, when we made our recommendation for shutdown of this temporary
system.

Secondly, the Acton Water District complained that groundwater extracted at
the School Street and Assabet public water supply wells sometimes exceeds
MassDEP's Drinking Water Guideline for 1,4-dioxane.

3.	Are there any areas of known or suspected contamination at the site that you feel
are not being adequately addressed by the remedial actions?

Yes, MassDEP continues to be concerned about the concentrations of 1,4
dioxane being detected at the School Street and Assabet public water supply
wells, at concentrations near and exceeding MassDEP drinking water guideline
of 0.3 ug/L.

4.	Do you have any comments, suggestions, or recommendations regarding the
project?

Yes, we recommend that USEPA continue to work with MassDEP (including
MassDEP's Drinking Water Program) to maintain an adequate groundwater
monitoring program for 1,4-dioxane at and near the Acton Water District water
supply wells. We also recommend that USEPA continue to work with
MassDEP to evaluate and possibly implement appropriate response measures
to address future dioxane levels.

6. Is there any other information that you wish to share that might be of use?
No.

Page 2 of 2

-------
INTERVIEW RECORD

Site Name: W. R. Grace Superfund Site (Acton, MA)

EPA ID No.: MAD001002252

Subject: Five Year Review

Time: 3:13 pm Date: 7/30/14

Type: ~ Telephone ~ Visit ~ Other
Location of Visit: NA. Matt provided written responses using this
form and submitted them to EPA and B. Weir via email.

~ Incoming ~ Outgoing

Contact Made By:

Name: Barbara Weir Title: Task Order Manager

Organization: AECOM

Individual Contacted:

Name:

Matthew Mostoller

Title:

Environmental

Compliance

Manager

Organization:

Acton Water District

Telephone No: 978-263-9107

Fax No: 978-264-0148

E-Mail Address: Matt@actonwater.com

Street Address:

Acton Water District

693 Massachusetts Avenue, Acton, MA 01720

1.	What is your overall impression of the project? (general sentiment)

Due to the major cleanup activities being complete, I feel that the site does not have the
same level of attention from EPA. The long range clean up goals seem to be pushed along
from year to year with out a full vetting of how effective cleanup actions are or if gains are
sustainable.

2.	Do you feel well informed about site activities and progress of the cleanup?

Yes, however, not as well informed or included in the review process as in prior years. This
includes a lack of stakeholder conference calls and unclear timeframes for providing feedback,
if it is actively solicited at all.

Page 1 of 2

-------
3.

Have you received any inquiries from the District's customers expressing concern



about the site?



Yes. Customers, especially new residents, regularly inquire about the site. Many are



surprised to learn that a Superfund site is in Acton and that we pump water in the area of the



site. In particular, home owners in areas impacted by the site are concerned with possible



soil and vapor intrusion issues.

4.

What is the current status of the new treatment system for the Assabet well field?



It is under construction and is required to be operational no later than January 15,



2015.

5.

Do you have any comments, suggestions, or recommendations regarding the site's management or



operation?



Site management (EPA, MassDEP, and WR Grace) should continue outreach efforts to



the community. With a large turnover in residents, ongoing education about the site



and long term clean strategies is necessary. The outstanding issue of 1,4-dioxane



should be addressed in conjunction with the on-going site cleanup at the NMI/Starmet



Superfund site.

6.

Do you have any other comments, questions or concerns regarding the site?



The District is interested in the long term re-use of the site and what opportunities and



risks this might present to the public water supply.

Page 2 of 2

-------
INTERVIEW RECORD

Site Name: W. R. Grace Superfund Site (Acton, MA)

EPA ID No.: MAD001002252

Subject: Five Year Review

Time: Date: 8/25/2014

Type: ~Telephone ~ Visit ¦ Other

Location of Visit: NA. Mr. Helgason provided written responses using

this form and submitted them to EPA and B. Weir via email on

8/25/2014.

~ Incoming ~ Outgoing

Contact Made By:

Name:

Barbara Weir

Title:

Task Order Manager

Organization:

AECOM

Individual Contacted:

Name:

Thor Helgason

Title:

Project Manager

Organization:

de maximis, inc.

Telephone No: 781-642-8775

Fax No: 781-642-1078

E-Mail Address: thelgas@demaximis.com

Street Address:

135 Beaver Street, 4th Floor
Waltham, MA 02452

l.A. What is your overall impression of the project? (general sentiment)

Overall, the project is going well, although W.R. Grace remains concerned
about the technical feasibility of treating 1,4-dioxane to discharge levels of
less than 3.0 ug/l.

l.A. Is the remedy functioning as expected? How well is the remedy
performing?

The Sediment Remedy is performing as expected. The Landfill Area
Groundwater Treatment system continues to meet all discharge criteria.

4.A. Is there a continuous on-site O&M presence? If so, please describe
staff and activities. If there is not a continuous on-site presence, describe
staff and frequency of site inspections and activities.

The Landfill Area Treatment system is staffed four to five days per week. The
hours on-site vary day to day.	

Page 1 of 4

-------
5.A.	Have there been any significant changes in the O&M requirements,
maintenance schedules, or sampling routines since start-up or in the last
five years? If so, do they affect the protectiveness or effectiveness of the
remedy? Please describe changes and impacts.

No significant changes have taken place.

6.A.	Have there been unexpected O&M difficulties or costs at the site since
start-up or in the last five years? If so, please give details.

The Purifies photocatalytic oxidation unit within the Landfill Area Treatment system
has not performed as W.R. Grace expected, based on bench-scale testing conducted
during the design phase. Adjustments were made to the Purifies unit following start-
up to enhance the treatment efficiency for 1,4-dioxane. After several months of
working closely with the designers of the Purifies unit, performance was optimized by
introducing a 25 mg/l solution of sodium persulfate immediately prior to the Purifies
unit. This approach resulted in reducing 1,4-dioxane from a range of 3 ug/l - 5 ug/l
in the influent to about 2.6 ug/l in the effluent. The discharge criterion for the
Landfill Area Treatment system is 3.0 ug/l. W.R. Grace remains concerned about the
technical feasibility of consistent treatment of groundwater containing 1,4-dioxane to
discharge criteria below 3.0 ug/l.

7.A.	Have there been opportunities to optimize O&M, or sampling efforts?

Please describe changes and resultant or desired cost savings or improved
efficiency.

The Landfill Area Treatment system is fully optimized. See response to 6. A
for information concerning the optimization of the groundwater treatment
system

8.A.	Do you have any comments, suggestions, or recommendations
regarding the project?

The technical feasibility of treating 1,4-dioxane to criteria below 3.0 ug/l is of
considerable concern to W.R. Grace, given the extensive work performed to
optimize the Landfill Area Treatment system following system start-up in May
2011. W.R Grace does not believe adequate treatment technology currently
exists commercially to consistently treat 1,4-dioxane to levels below 3.0 ug/l,
given the current influent quality and flow rate.	

Page 2 of 4

-------
SUPPLEMENTAL QUESTIONS

1.B.	How have the treatment processes changed or been adjusted over the
last five years?

See the response to Question 6A.

2.B.	Have there been any health and safety issues on-site?

No.

3.B.	Has site ownership changed?

No.

4.B.	What is the zoning of the property? Are there any institutional
controls/deed restrictions in place? Are additional IC's anticipated? When?
Where (location)?

The property is zoned as "Technology District". A groundwater use
restriction, dated November 19, 2007, is in place.

5.B.	How frequently are authorized individuals present at the property
(days/week)?

Authorized individuals are at the property 4 to 5 days per week.

6.B.	What are the planned future uses of the property (if different from
current uses)?

W.R. Grace is attempting to sell the property.

Page 3 of 4

-------
7.B. What measures have been taken to secure the site and the
contaminated areas (e.g., fencing, locks, signage etc.)? How successful have
these measures been?

The main gate to the site at Independence Drive is locked, and "No
Trespassing" signs are posted along Independence Drive, and elsewhere along
the perimeter of the property. While much of the property is fenced, there
have been instances where the fencing and gates have been vandalized and
breached.

8.B.	Is there evidence or sightings of trespassers on the property? If yes,
how often and what type of activities do they engage in? What actions are
taken if trespassing occurs? What actions are taken to prevent trespassing?

Trespassers enter the site to engage in motorized dirt bike operation, as well as
drinking, as evidenced by remnants of campfires and discarded beverage
containers. The Acton Police have been notified, and have increased patrols
of the area.

9.B.	Have there been any events of vandalism at the property?

See response to 7.B, above. None of the treatment equipment has been
vandalized.

10.B. Have there been any unusual or unexpected activities or events at the
site (e.g., flooding)?

No.

ll.B. Has the site been the subject of any community complaints (e.g.,
odor, noise, health, etc.)?

No.

Page 4 of 4

-------
APPENDIX E - TOXICITY VALUE AND VI PATHWAY REVIEW

E-l

-------
TABLE 1. COMPARISON OF 1989/2005/2009 AND 2014 ORAL REFERENCE DOSES AND ORAL
CANCER SLOPE FACTORS FOR COMPOUNDS OF POTENTIAL CONCERN
W.R. GRACE SUPERFUND SITE, ACTON, MASSACHUSETTS

Contaminant of
Potential Concern

1989

Oral Reference Dose (RfD)
(mg/kg-day)
2005 2009

2014



1989

Oral Slope Factor (SF)
(mg/kg-day)"1
2005 2009

2014

1,1-Dichloroethene

0.009

0.05

0.05

0.05



0.6

N/A

N/A

N/A

1,2-Dichloroethane

NE

0.02

0.02

0.006



NE

0.091

0.091

0.091

1,2-Dichloropropane

NE

0.02

0.09

0.09



NE

0.068

0.036

0.036

1,1,2-Trichloroethane

NE

0.004

0.004

0.004



NE

0.057

0.057

0.057

2-Butanone

NE

0.6

0.6

0.6



NE

N/A

N/A

N/A

2-Hexanone

NE

0.04

0.08

0.005



NE

N/A

N/A

N/A

4-Methylphenol

NE

0.005

0.005

0.1



NE

N/A

N/A

N/A

Acetone

NE

0.9

0.9

0.9



NE

N/A

N/A

N/A

Benzene

N/A

0.004

0.004

0.004



0.029

0.055

0.055

0.055

Bromodichloromethane

NE

0.02

0.02

0.02



NE

0.062

0.062

0.062

Chloroethane

NE

0.4

N/A

N/A



NE

N/A

N/A

N/A

Chloroform

NE

0.01

0.01

0.01



NE

N/A

0.031

0.031

Chloromethane

NE

N/A

N/A

N/A



NE

N/A

N/A

N/A

Dibromochloromethane

NE

0.02

0.02

0.02



NE

0.084

0.084

0.084

Ethylbenzene

0.1

0.1

0.1

0.1



N/A

N/A

0.011

0.011

Methyl tert-butyl ether

NE

0.3

N/A

N/A



NE

0.0018

0.0018

0.0018

Methylene chloride

NE

0.06

0.06

0.006



NE

0.0075

0.0075

0.002

Tetrachloroethene

NE

0.01

0.01

0.006



NE

0.54

0.54

0.0021

Toluene

0.3

NE

0.08

0.08



N/A

NE

N/A

N/A

Trichloroethene

0.007

0.0003

N/A

0.0005



0.011

0.4

0.013

0.046

Vinyl chloride

N/A

0.003

0.003

0.003



2.3

0.75

0.72

0.72

Xylenes

NE

0.2

0.2

0.2



NE

N/A

N/A

N/A

Benzo(a)anthracene

NE

0.03

N/A

N/A



NE

0.73

0.73

0.73

Benzo(a)pyrene

NE

0.03

N/A

N/A



NE

7.3

7.3

7.3

Benzo(b)fluoranthene

NE

0.03

N/A

N/A



NE

0.73

0.73

0.73

bis(2-chloroethyl)ether

NE

N/A

N/A

N/A



NE

1.1

1.1

1.1

bis(2-ethylhexyl)phthalate

NE

0.02

0.02

0.02



NE

0.014

0.014

0.014

Dibenz(a,h)anthracene

NE

0.03

N/A

N/A



NE

7.3

7.3

7.3

Dibenzofuran

NE

0.002

N/A

0.001



NE

N/A

N/A

N/A

lndeno(1,2,3-cd)pyrene

NE

0.03

N/A

N/A



NE

0.73

0.73

0.73

Naphthalene

NE

0.02

0.02

0.02



NE

N/A

N/A

N/A

4,4'-DDD

NE

0.002

N/A

N/A



NE

0.24

0.24

0.24

4,4'-DDE

NE

0.0003

N/A

N/A



NE

0.34

0.34

0.34

4,4'-DDT

NE

0.0005

0.0005

0.0005



NE

0.34

0.34

0.34

Aldrin

NE

0.00003

0.00003

0.00003



NE

17

17

17

alpha-BHC

NE

0.0005

0.008

0.008



NE

6.3

6.3

6.3

Chlordane

NE

0.0005

0.0005

0.0005



NE

0.35

0.35

0.35

Dieldrin

NE

0.00005

0.00005

0.00005



NE

16

16

16

Heptachlor epoxide

NE

0.000013

0.000013

0.000013



NE

9.1

9.1

9.1

PCB Aroclors

NE

0.00002

0.00002

0.00002



NE

2

2

2

Antimony

NE

0.0004

0.0004

0.0004



NE

N/A

N/A

N/A

Arsenic

0.001

0.0003

0.0003

0.0003



15

1.5

1.5

1.5

Barium

NE

0.07

0.2

0.2



NE

N/A

N/A

N/A

Beryllium

0.0005

0.002

0.002

0.002



N/A

N/A

N/A

N/A

Cadmium (food)

0.0005

0.001

0.001

0.001



N/A

N/A

N/A

N/A

Cadmium (water)

0.0005

0.0005

0.0005

0.0005



N/A

N/A

N/A

N/A

Chromium (as VI)

0.005

0.003

0.003

0.003



N/A

N/A

N/A

0.5

Copper

0.037

NE

0.04

0.04



N/A

NE

N/A

N/A

Lead (a)

0.0014

N/A

N/A

N/A



N/A

N/A

N/A

N/A

Manganese (non-water)

NE

0.07

0.07

0.07



NE

N/A

N/A

N/A

Manganese (water)

NE

0.024

0.024

0.024



NE

N/A

N/A

N/A

Methyl mercury

NE

0.0001

0.0001

0.0001



NE

N/A

N/A

N/A

Nickel

0.02

0.02

0.02

0.02



N/A

N/A

N/A

N/A

Thallium

NE

0.000066

0.000065

0.00001



NE

N/A

N/A

N/A

Vanadium

NE

0.007

0.007

0.005



NE

N/A

N/A

N/A

Zinc

0.2

NE

0.3

0.3



N/A

NE

N/A

N/A

N/A = Not Applicable or Not Available

NE = Not evaluated as a COPC

COPC = Contaminant of Potential Concern

(a) Lead is currently evaluated through the use of exposure modeling for adults and children.

E-2

-------
Table 2

Wells Used for Groundwater Vapor Intrusion Screening

Area

Well Identifier

Dates of Most Recent Sampling

Assabet Wellfield

ASSABET1A

2012/2013

Public Water Supply

ASSABET 2A

2012/2013

Assabet River Area

AR-04P

2000



AR-14B1

2001



AR-15P

2001



CLF-2B

2001

Former Lagoon Area

NLBR-R

2012/2013



NLGP

2009/2010



NMGP

2011/2012



OSA-01A

2012/2013



OSA-02A

2012/2013



OSA-06B

2005/2006



OSA-09B

2005/2006



OSA-11A

2005/2006



OSA-13A

2012/2013



SLGP-R

2012/2013

Northeast Area

AR-31S

2009/2010



PS-22B

2012/2013



RE-IOBS

2011



RE-20BS

2011



RE-1

2011



RE-2

2011

Powder Mill Plaza Irrigation Well

POWDERMILL

2002

Southeast Landfill Area

AR-22

2005/2006



B-08D

2005/2006



ELF

2008/2009



LF-06S

2005/2006



LF-15

2005/2006



RLF

2008/2009

School Street Wellfield

CHRISTOFFERSON

2012/2013

Public Water Supply

LAWSBROOK

2012/2013



SCRIBNER

2012/2013

Southwest Area

B-05B2

2005/2006



RP-1

2005



WRG-1

2011

Southwest Landfill Area

AR-20A

2009/2010



LF-12A

2005/2006



LF-21D

2005/2006

E-3

-------
Table 3

Vapor Intrusion Screening Levels for Groundwater



Residential Target
Indoor Air
Concentration
(ILCR=1E-06)

Residential Target
Indoor Air
Concentration
(HQ=1)



Target Groundwater
Concentration
(ILCR=1E-06)

Target Groundwater
Concentration
(Hl=1)



Basis of Target

















Concentration









Dimensionless







C=Cancer Risk;

InhalationUnit Risk

Reference





Henry's Law





Chemical

N/C=Non cancer Risk

(Mg/m3)"1

Concentration (ng/m3)

Mg/m3

Mg/m3

Constant (unitless)

Mg/L

Mg/L

Acetone

NC

NA

3.1E+04 A

NA

3.2E+04

1.43E-03

NA

2.2E+07

Benzene

C

7.8E-06 1

3.0E+01 I

3.6E-01

3.1E+01

2.27E-01

1.6E+00

1.4E+02

2-Butanone

NC

NA

5.0E+03 I

NA

5.2E+03

2.33E-03

NA

2.2E+06

Carbon disulfide

NC

NA

7.0E+02 I

NA

7.3E+02

5.89E-01

NA

1.2E+03

Chloroform

C

2.3E-05 1

9.8E+01 A

1.2E-01

1.0E+02

1.50E-01

8.0E-01

6.7E+02

Chloromethane

NC

NA

9.0E+01 I

NA

9.4E+01

3.61 E-01

NA

2.6E+02

Dibromochloromethane

C

2.7E-05 C

NA

1.0E-01

NA

3.20E-02

3.1E+00

NA

1,1-Dichloroethane

C

1.6E-06 C

NA

1.8E+00

NA

2.30E-01

7.8E+00

NA

1,2-Dichloroethane

C

2.6E-05 I

7.0E+00 P

1.1E-01

7.3E+00

4.82E-02

2.3E+00

1.5E+02

1,1-Dichloroethene

NC

NA

2.0E+02 I

NA

2.1E+02

1.07E+00

NA

2.0E+02

1,2-Dichloropropane

C

1.0E-05 C

4.0E+00 I

2.8E-01

4.2E+00

1.15E-01

2.4E+00

3.6E+01

Ethylbenzene

C

2.5E-06 C

1.0E+03 I

1.1E+00

1.0E+03

3.22E-01

3.4E+00

3.1E+03

Methylene chloride

C

1.0E-08 I

6.0E+02 I

1.0E+02

6.3E+02

1.33E-01

7.5E+02

4.7E+03

Methyl tert-butyl ether

C

2.6E-07 C

3.0E+03 I

1.1E+01

3.1E+03

2.40E-02

4.6E+02

1.3E+05

Styrene

NC

NA

1.0E+03 I

NA

1.0E+03

1.12E-01

NA

8.9E+03

Tetrachloroethene

C

2.6E-07 I

4.0E+01 I

1.1E+01

4.2E+01

7.24E-01

1.5E+01

5.8E+01

Toluene

NC

NA

5.0E+03 I

NA

5.2E+03

2.71 E-01

NA

1.9E+04

Trichloroethene

C

4.1E-06 I

2.0E+00 I

4.8E-01

2.1E+00

4.03E-01

1.2E+00

5.2E+00

Vinyl chloride

C

4.4E-06 I

1.0E+02 I

1.7E-01

1.0E+02

1.14E+00

1.5E-01

8.8E+01

cis-1,2-Dichloroethene

NA

NA

NA

NA

NA

1.67E-01

NA

NA

1 Table Footnotes:

Toxicity Values used as basis of Target Indoor Air and Groundwater Concentrations are available on the Regional Screening Levels Table at http://www.epa.gov/reg3hwmd/risk/human/index.htm (May 2014)
NA - Not Available.

Toxicity Value References: C = CalEPA; I = IRIS; A = Agency for Toxic Substances and Disease Registry; P = Provisional Peer-Reviewed Toxicity Value for Superfund
Henry's Law Constants from Regional Screening Levels Table (May 2014)

Screening value is based on 1x10"6 cancer risk or HI = 1.

Residential Target Indoor Air values are found in Regional Screening Levels table (http://www.epa.gov/reg3hwmd/risk/human/index.htm).

The equation for the target groundwater concentration (Cgw) is:

Cia, target

Cgw =	

AFgw x (1000 L/m3) x HLC

where Cia is the target indoor air concentration, AFgw is the generic attenuation factor for groundwater (default value = 0.001) and HLC is Henry's Law Constant.

The lower of the target groundwater concentration based on an ILCR of 1E-06 or a HQ=1 is selected as the groundwater Vapor Intrusion Screening Level (VISL).

E-4

-------
APPENDIX F - ARARS REVIEW

F-l

-------
TABLE 1. CHEMICAL-SPECIFIC ARARS AND CRITERIA, ADVISORIES, AND GUIDANCE
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 1 - ACTON AND CONCORD, MASSACHUSETTS

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

Federal Regulatory
Requirements

SDWA - Maximum Contaminant Levels
(MCLs) (40 CFR 141.11 - 141.16)

MCLs have been promulgated for a
number of organic and inorganic
contaminants. These levels regulate the
concentration of contaminants in public
drinking water supplies, but may also be
considered relevant and appropriate for
groundwater aquifers used for drinking
water.

MCLs for indicator compounds were
used as target cleanup levels for
groundwater under each waste area.
Attaining soil cleanup goals was
expected to ensure that any future
migration of residual contaminants in the
soil will not cause exceedances of MCLs
in groundwater under each waste area.

Soil cleanup goals were met
during the OU-1 source control
remedy. Soil cleanup goals
were selected so that these
standards can be met in the
future.

State Regulatory
Requirements

Massachusetts Drinking Water
Regulations (310 CMR 22.00)

Establishes MCLs for drinking water
supplies, as the federal MCLs. State
drinking water standards are the same as
the federal MCLs that were used.

See above.

F-2

-------
TABLE 1. CHEMICAL-SPECIFIC ARARS AND CRITERIA, ADVISORIES, AND GUIDANCE
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 1 - ACTON AND CONCORD, MASSACHUSETTS

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Massachusetts Groundwater Quality
Standards (314CMR6.00)

Establishes minimum groundwater
quality criteria.

Similar to MCLs, groundwater quality
criteria were expected to be attained by
reducing residual soil contaminants to
the Soil Cleanup Goals.

This regulation was rescinded in March
2009 because revisions to 314 CMR 5.00
(Groundwater Discharge Permits)
promulgated in March 2009 eliminated
the needfor this regulation.

Soil cleanup goals were met
during the OU-1 source control
remedy. Soil cleanup goals
were selected so that these
standards could be met in the
future. Groundwater quality
criteria attainment is being
evaluated as part of OU-3.

F-3

-------
TABLE 2. ACTION-SPECIFIC ARARS

W.R. G]

RACE SUPERFUND SITE - OPERABLE UNIT 1 - ACTON AND CONCORD, MASSACHUSETTS

ARARs

REQUIREMENTS

ORIGINAL
STATUS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

Federal Regulatory
Requirements

Clean Air Act - National Air Quality
Standards for Total Suspended
Particulates
(40 CFR 50.6)

Applicable

This regulation specifies maximum
primary and secondary 24-hour
concentrations for particulate
matter.

These requirements are not
ARARs per se, but are
implemented through the
State implementation
requirements.



OSHA - Worker Safety Regulations
(29 CFR 1926)

Applicable

This regulation specifies the type of
safety equipment, training and
procedures to be followed during
construction of the remedy.

These regulations were applicable
during construction of the selected
remedy.

The OSHA rules are not
ARARs per se, but they are
worker safety rules that
must always be complied
with during operations,
maintenance, and
monitoring activities at the
site.



Protection of Archaeological
Resources (32 CFR 229.4)

Applicable

This provides procedures for the
protection of archaeological
resources.

If any of these resources are found
during soil excavation, work would
stop until the area has been
reviewed by federal and state
archaeologists. Research
performed prior to remedy
construction suggested that none
would be found at this site.

No archaeological
resources were found
during remedy
implementation.

F-4

-------
TABLE 2. ACTION-SPECIFIC ARARS

W.R. G]

RACE SUPERFUND SITE - OPERABLE UNIT 1 - ACTON AND CONCORD, MASSACHUSETTS

ARARs

REQUIREMENTS

ORIGINAL
STATUS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



DOT Rules for the Transportation of

Hazardous Materials

(49 CFR 107, 171.1 - 171.500)

Applicable

This regulation outlines procedures
for the packaging, labeling,
manifesting, and transport of
hazardous materials.
Any shipments to and from the site
during the remedy are to comply
with these rules.

DOT rules are not ARARs
because they regulate off-
site activities. DOT rules
were complied with for off-
site shipments.

State Regulatory
Requirements

Massachusetts Standards for All
(Permitted Hazardous Waste)
Facilities (310 CMR 30.510-516)

Relevant and
Appropriate

This regulation provides general
facility requirements for waste
analysis, security measures,
inspections, and training
requirements.

The Industrial Landfill was
constructed and is operated
in accordance with these
requirements. These
requirements remain
relevant and appropriate
and are being complied
with.



Contingency Plan, Emergency
Procedures, Preparedness and
Prevention (310 CMR 30.520-524)

Relevant and
Appropriate

This regulation outlines the
requirements for emergency
procedures to be used following
explosions and fires, as well as
safety equipment and spill-control
requirements. This regulation also
requires that threats to public health
and the environment be minimized.

These requirements remain
relevant and appropriate
and are being complied
with.



Massachusetts Manifest System,
Recordkeeping, and Reporting (310
CMR 30.530-544)

Relevant and
Appropriate

Requires manifesting hazardous
waste shipped off-site for disposal.
Any off-site shipments of waste
materials were to be manifested.

These requirements are not
ARARs, as they are
considered off-site
requirements.

F-5

-------
TABLE 2. ACTION-SPECIFIC ARARS

W.R. G]

RACE SUPERFUND SITE - OPERABLE UNIT 1 - ACTON AND CONCORD, MASSACHUSETTS

ARARs

REQUIREMENTS

ORIGINAL
STATUS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

State Regulatory

Requirements

(continued)

Massachusetts Closure and Post-
closure (310 CMR 30.580-596)

Relevant and
Appropriate

This requirement details the
specific requirements for closure
and post-closure of hazardous waste
facilities.

The landfill cap was
constructed in accordance
with these requirements.
These requirements remain
relevant and appropriate.
Post-closure operations,
maintenance and
monitoring are currently
being performed in
accordance with the Post
Closure Operations and
Maintenance Plan.
The landfill closure was
designed to meet RCRA
requirements for landfill
closure.

F-6

-------
TABLE 2. ACTION-SPECIFIC ARARS

W.R. G]

RACE SUPERFUND SITE - OPERABLE UNIT 1 - ACTON AND CONCORD, MASSACHUSETTS

ARARs

REQUIREMENTS

ORIGINAL
STATUS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Massachusetts - Landfills (310 CMR
30.620-633)

Relevant and
Appropriate

Establishes requirements for
construction, operation, monitoring,
and maintenance of hazardous
waste landfills.

The landfill cap was
constructed in accordance
with these requirements.
Operations and
maintenance have also
been performed in
accordance with these
requirements. These
requirements remain
relevant and appropriate.
The landfill closure was
designed to meet the
requirements for landfill
closure. Post-closure
operations, maintenance
and monitoring are
currently being performed
in accordance with the Post
Closure Operations and
Maintenance Plan.

F-7

-------
TABLE 2. ACTION-SPECIFIC ARARS

W.R. G]

RACE SUPERFUND SITE - OPERABLE UNIT 1 - ACTON AND CONCORD, MASSACHUSETTS

ARARs

REQUIREMENTS

ORIGINAL
STATUS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

State Regulatory

Requirements

(continued)

Massachusetts Groundwater
Protection (310 CMR 30.660-675)

Relevant and
Appropriate

Provides performance requirements
for a groundwater monitoring
network, and standards for a
monitoring program and sample
analysis.

Groundwater at each
disposal area is monitored
to determine the
effectiveness of the
remedial measures. An
annual groundwater
monitoring program has
been ongoing for the
Landfill Area as well as
other portions of the plume,
and is reviewed each year
and adjusted as necessary.
These regulations are still
relevant and appropriate.

F-8

-------
TABLE 2. ACTION-SPECIFIC ARARS

W.R. G]

RACE SUPERFUND SITE - OPERABLE UNIT 1 - ACTON AND CONCORD, MASSACHUSETTS

ARARs

REQUIREMENTS

ORIGINAL
STATUS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Massachusetts Ambient Air Quality
Standards (310 CMR 6.00) and Air
Pollution Control Regulations (310
CMR 7.00)

Applicable

Establishes primary and secondary
standards for emissions of dust and
odor from construction and
remedial activities.

These requirements remain
applicable. The Northeast
Area treatment system air
stripper (now shut down,
but the equipment remains
in place in case it is needed
again) includes vapor-
phase carbon for odor
control. The Landfill Area
treatment system currently
does not require emissions
control because it does not
employ an air stripper.
Particulate emissions
during excavation and
solidification activities
were controlled to meet the
requirements. Odor
emissions from the
previous groundwater
treatment air stripper (the
ARS) were controlled with
Best Available Control
Technology (BACT). A
gas control system utilizing
BACT was installed during
landfill cap construction to
control emissions.

F-9

-------
TABLE 2. ACTION-SPECIFIC ARARS

W.R. G]

RACE SUPERFUND SITE - OPERABLE UNIT 1 - ACTON AND CONCORD, MASSACHUSETTS

ARARs

REQUIREMENTS

ORIGINAL
STATUS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

State Regulatory

Requirements

(continued)

Massachusetts Solid Waste
Management Facility Regulations
(310 CMR 19.000)

Applicable

This regulation outlines the
requirements for closure of solid
waste landfills.

The Battery Separator Area chip
piles were to be closed as a solid
waste landfill with, among other
things, an intermediate cover
consisting of impervious material or
flexible membrane which prevents
the percolation of surface or rain
water.

These requirements are no
longer applicable. These
requirements would have
applied to capping of the
Battery Separator Area
chip piles, which was part
of the OU-1 ROD-specified
remedy. However, the
chips were actually
excavated and placed in the
Industrial Landfill.

F-10

-------
TABLE 3. CHEMICAL-SPECIFIC ARARS AND CRITERIA, ADVISORIES, AND GUIDANCE
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

GROUNDWAT]

ER REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

Federal Criteria,
Advisories, and Guidance

Safe Drinking Water Act ("SDWA")
National Primary Drinking Water
Regulations Maximum Contaminant
Levels ("MCLs"), 40 C.F.R. § 141.11-
141.16, 141.60-141.62

ROD Status: Relevant and
Appropriate

5-Year Review Status: Relevant and
Appropriate

Maximum Contaminant Levels (MCLs)
have been promulgated for several
common organic and inorganic
contaminants. These levels regulate the
concentration of contaminants in public
drinking water supplies. MCLs are
applicable only at the tap, but are
relevant and appropriate because the
groundwater underneath parts of the Site
may be or is being used as a drinking
water source.

MCLs are exceeded in
groundwater at some site
locations. However, the
groundwater remedy is
expected to attain MCLs in the
future. Groundwater is being
extracted and treated or is
attenuating naturally as part of
the remedy and is monitored
annually to evaluate
progression towards cleanup
goals. Institutional controls
prevent use of affected
groundwater in the meantime.



Non-zero SDWA Maximum Contaminant

Level Goals ("MCLGs"), 40 C.F.R. §

141.50-141.51.

ROD Status: Relevant and

Appropriate

5-Year Review Status: Relevant and
Appropriate

MCLGs, defined by SDWA regulations
as the maximum level of a contaminant
in drinking water at which no known or
anticipated adverse effect on the health
of persons would occur, and which
allows an adequate margin of safety, are
non-enforceable health goals under the
SDWA. Because MCLGs are not
enforceable regulatory standards, they
are not applicable. However, they are
relevant and appropriate because
groundwater aquifers beneath parts of
the Site may be or is being used as a
source for drinking water.

MCLGs are exceeded in
groundwater at some site
locations. However, the
remedy is expected to attain
non-zero MCLGs in the future.
Groundwater is being extracted
and treated or is attenuating
naturally as part of the remedy
and is monitored annually to
evaluate progression towards
cleanup goals. Institutional
controls prevent use of affected
groundwater in the meantime.

F-ll

-------
TABLE 3. CHEMICAL-SPECIFIC ARARS AND CRITERIA, ADVISORIES, AND GUIDANCE
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

GROUNDWAT]

ER REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Office of Research and Standards
Guidelines ("ORSGs"), as found in
Massachusetts Drinking Water Standards
and Guidelines for Chemicals in
Massachusetts Drinking Waters (last
updated in the spring of 2014)

ROD Status: TBC

5-Year Review Status: TBC

The ORS has identified risk-based
guidelines applicable to drinking water.
Because the ORSGs are not regulations,
they are TBCs, rather than ARARs.

ORSGs are exceeded in
groundwater at some site
locations. However, the
remedy is expected to attain
ORSGs in the future.



Human health Reference Doses (RfDs)
and Cancer Slope Factors (CSFs) found
in USEPA's IRIS database.
ROD Status: TBC
5-Year Review Status: TBC

USEPA requires the use of these values
in the assessment of human health risk.

These values were used in the
risk assessment and calculation
of numerical remediation
goals. Any future evaluation
of residual risk is expected to
also use these values. The FYR
text presents a qualitative
evaluation of changes in these
values relative to what they
were in 2005 when the ROD
was written, and concludes that
the changes do not affect
protectiveness.

F-12

-------
TABLE 3. CHEMICAL-SPECIFIC ARARS AND CRITERIA, ADVISORIES, AND GUIDANCE
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

GROUNDWAT]

ER REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

State Criteria, Advisories,
and Guidance

Massachusetts Drinking Water
Regulations, 310 CMR 22.06, 22.06B,
22.07A, 22.07B
ROD Status: Relevant and
Appropriate

5-Year Review Status: Relevant and
Appropriate

These regulations set forth
Massachusetts MCLs ("MMCLs"),
based on health and technical
practicality, for public water systems.
The aquifer on site is not a public water
system, but the requirements are relevant
and appropriate for those areas of the
Site that are "GW-1" areas under the
MCP, because the groundwater in those
areas of the Site may be potentially used
as a source for drinking water. When
MMCLs are more stringent than federal
levels, the state levels must be met. The
MMCLs for 1,4-Dichlorobenzene (also
known as para-Dichlorobenzene in 310
CMR 22.07B) and ethylene dibromide
are more stringent than the MCLs, but
these are not contaminants of concern at
the site.

MMCLs are exceeded in
groundwater at some site
locations. However, the
alternative is expected to attain
MMCLs in the future.

F-13

-------
TABLE 3. CHEMICAL-SPECIFIC ARARS AND CRITERIA, ADVISORIES, AND GUIDANCE
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

GROUNDWAT]

ER REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Massachusetts Ground Water Quality
Standards ("GWQS"), 314 CMR 6.01-
6.10

ROD Status: Relevant and
Appropriate

5-Year Review Status: Not ARAR -
regulation was rescinded in March
2009

The GWQSs were numeric limits for
certain contaminants (e.g., arsenic,
cadmium, copper, lead, manganese,
mercury and non-numeric health-based
standards for others (e.g., pathogenic
organisms), as well as a pH range. This
regulation was rescinded in March 2009
because revisions to 314 CMR 5.00
(Groundwater Discharge Permits) that
were promulgated in March 2009
eliminated the need for this regulation.

Not ARAR - regulation was
rescinded in March 2009

F-14

-------
TABLE 4. LOCATION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

GROUNDWAT]

ER REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

State Regulatory
Requirements

Massachusetts Wetlands Protection Act
and Regulations, M.G.L. c. 131, § 40;
310 CMR 10.00

ROD Status: Applicable

5-Year Review Status: Applicable

The Wetlands Protection Act (WPA)
imposes requirements and limitations for
alteration of wetlands and establishes
performance standards for projects that
affect wetlands. Because there are lands
under water bodies on the Site that are
being remediated, these regulations are
applicable.

The discharge of treated
groundwater to Sinking Pond
was designed to comply with
applicable provisions of the
WPA and regulations.



Massachusetts Groundwater Supply
Protection Regulations, 310 CMR 22.21

ROD Status: Applicable

5-Year Review Status: Applicable

310 CMR 22 requires that protective
zones around a wellhead be established
that limit activities and land uses (such
as storage of chemicals and removal of
soil) in the zones. Because the Assabet
and School Street wellfields are within
the Site, and because the Assabet 1 and
2, Christofferson, Scribner, and
Lawsbrook wells have DEP-approved
Zone II wellhead protection areas which
overlap with the site, these requirements
are applicable.

The groundwater treatment
remedy was designed to
comply with 310 CMR 22.21.

F-15

-------
TABLE 5. ACTION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

GROUNDWAT]

ER REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

Federal Regulatory
Requirements

Clean Water Act (CWA) § 402 (33
U.S.C. §1342)

ROD Status: Relevant and
Appropriate

5-Year Review Status: Relevant and
Appropriate

Section 402 of the CWA requires
issuance of an NPDES permit prior to
discharge of any pollutant to a water of
the United States. Permits can only be
issued in compliance with applicable
technology standards.

The discharge for the
groundwater remedy was
designed to meet applicable
substantive standards under
NPDES regulations.



Clean Water Act (CWA) § 304(a) (33
U.S.C. §1314(a))

ROD Status: Relevant and
Appropriate

5-Year Review Status: Relevant and
Appropriate

Federal National Recommended Water
Quality Criteria (NRWQC) include (1)
human health-based criteria and (2)
other water quality parameters protective
of fish and aquatic life. NRWQC for the
protection of human health provide
levels for exposure from drinking water
and consuming aquatic organisms, and
from consuming fish alone. Discharges
subject to NPDES permitting
requirements must not result in
exceedances of NRWQCs.

The discharge to Sinking Pond
will not cause or contribute to
an exceedance of NRWQC.



Resource Conservation and Recovery Act
(RCRA, 42 USC 6901-6992) -
Groundwater Protection; 40 CFR Part
264, Subpart F.

ROD Status: Relevant and
Appropriate

5-Year Review Status: Relevant and
Appropriate

These regulations establish acceptable
concentrations of hazardous constituents
in the groundwater at licensed RCRA
hazardous waste facilities. The point of
compliance is set at the edge of the
waste management unit(s). The
regulations also establish groundwater
monitoring requirements.

The groundwater monitoring
provisions of Subpart F are
considered when developing
the long-term monitoring plan
for the Site. The monitoring
plan for groundwater is re-
evaluated annually by Grace,
EPA, and MassDEP.

F-16

-------
TABLE 5. ACTION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

GROUNDWAT]

ER REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



RCRA - Identification and Listing of
Hazardous Wastes; 40 CFR Part 261
ROD Status: Relevant and
Appropriate

5-Year Review Status: Not ARAR

Part 261 establishes requirements for
determining whether wastes are
hazardous.

These regulations were used to
determine whether any
wastewater treatment residuals
are hazardous waste, and no
residuals were found to be
such.



RCRA Generator Requirements; 40 CFR
Part 262

ROD Status: Relevant and
Appropriate

5-Year Review Status: Not ARAR

RCRA establishes requirements
applicable to generators of hazardous
waste. Those requirements include
provisions addressing hazardous waste
determinations, manifesting, pre-
transport requirements, and
recordkeeping.

No wastewater treatment
residuals have been determined
to be hazardous waste.



Safe Drinking Water Act, Underground
Injection Control Requirements, 40 CFR
Part 144

ROD Status: Applicable

5-Year Review Status: Applicable

The Underground Injection Control
program regulations promulgated under
Part C of the Safe Drinking Water Act
(SDWA) establish requirements for
underground injection of treated
groundwater.

These requirements were met
when treated water is re-
injected as part of the
groundwater remedy. Re-
injection of treated
groundwater was practiced for
the Northeast Area treatment
system when it was in
operation.

F-17

-------
TABLE 5. ACTION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

GROUNDWAT]

ER REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Policy on Control of Air Emissions

Superfund Sites

OSWER Directive 9355.0-28

ROD Status: TBC

5-Year Review Status: TBC

Provides EPA Policy regarding control
of emissions from air strippers used
during cleanup at Superfund Sites

This policy was considered in
the design of the air stripper
used in the Northeast Area
treatment system. Emissions
were found to not pose a risk
but emissions were treated with
carbon as a means of
controlling the potential for
odors.



USEPA Region 1 Memo Lois Gitto to
Merrill Hohman, July 12, 1989

ROD Status: TBC

5-Year Review Status: TBC

Lays out Regional policy on emissions
from air strippers at Superfund Sites

See above.

State Regulatory
Requirements

Massachusetts Air Pollution Control
Regulations, 310 CMR 7.00

ROD Status: Applicable

5-Year Review Status: Applicable

These regulations set requirements on
the control of fugitive emissions and
dust.

These requirements were met
during construction activities.



Massachusetts Clean Water Act; G.L. ch.
21, § 26-53; 314 CMR 3.00 Surface
Water Discharge Permit Program
ROD Status: Applicable
5-Year Review Status: Applicable

The Massachusetts Clean Water Act and
regulations impose requirements for
permits prior to discharges to waters of
the Commonwealth.

The groundwater remedy was
designed and is being operated
in compliance with the
substantive requirements of
MCWA and 314 CMR 3.00.

F-18

-------
TABLE 5. ACTION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

GROUNDWAT]

ER REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Massachusetts Clean Water Act, G.L. ch.
21, § 26-51; 314 CMR4.00 Surface
Water Quality Standards.

ROD Status: Applicable
5-Year Review Status: Applicable

The Massachusetts regulations provide
that discharges to waters of the
Commonwealth shall not result in
exceedances of Massachusetts Surface
Water Quality Standards. These
standards are the same as the NRWQCs
for the compounds analyzed for at the
Site.

The discharge to Sinking Pond
was designed and is operated
so that it will not cause or
contribute to an exceedance of
the MSWQS.



Massachusetts Hazardous Waste Rules
for Identification and Listing of
Hazardous Waste; 310 CMR 30.100.
ROD Status: Applicable
5-Year Review Status: Not ARAR

310 CMR 30.100 establishes
requirements for determining whether
wastes are hazardous.

These regulations were used to
determine whether any
wastewater treatment residuals
are hazardous waste, and no
residuals were found to be such



Massachusetts Hazardous Waste Rules
for Generators of Hazardous Waste; 310
CMR 30.300.

ROD Status: Applicable

5-Year Review Status: Not ARAR

310 CMR 30.300 establishes
requirements applicable to generators of
hazardous waste. Those requirements
include provisions addressing hazardous
waste determinations, manifesting, pre-
transport requirements, and
recordkeeping.

No wastewater treatment
residuals have been determined
to be hazardous waste.



Massachusetts Rules for Remedial Air
Emissions, 310 CMR 40.0049
ROD Status: Relevant and
Appropriate

5-Year Review Status: Relevant and
Appropriate

The Massachusetts rules set forth
standards for emissions from remedial
activities, including a general
requirement for 95% control over
emissions from the remedial system,
unless it is not feasible or necessary
based upon an evaluation of
conventional treatment technologies and
risks to surrounding human or ecological
populations..

The Northeast Area
groundwater remedy was
designed and operated in
compliance with these
requirements. Emissions
control was employed as a
means of odor control only, as
the emissions were found to
pose no significant human
health risk.

F-19

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TABLE 5. ACTION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

GROUNDWAT]

ER REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Massachusetts Threshold Exposure
Limits (TELs) and Allowable Ambient
Limits (AALs) for Ambient Air
ROD Status: TBC
5-Year Review Status: TBC

DEP has issued guidance setting out
permissible concentrations of air toxics
in ambient air. The TELs and AALs are
used to guide permitting decisions for
sources of air toxics.

The groundwater remedy was
designed and operated so that
remedial air emissions did not
cause any exceedances of
TELs or AALs.



Massachusetts Wetlands Protection Act
and Regulations, M.G.L. c. 131, § 40;
310 CMR 10.00

ROD Status: Applicable

5-Year Review Status: Applicable

The Wetlands Protection Act imposes
requirements and limitations for
alteration of wetlands. It establishes
performance standards for projects that
affect wetlands. Because there are
wetlands on the Site, these regulations
are applicable.

The discharge of treated
groundwater to Sinking Pond
was designed to comply with
applicable provisions of the
WPA and regulations.



Massachusetts Well Decommissioning
Requirements, 313 CMR 3.03

ROD Status: Applicable

5-Year Review Status: Applicable

Massachusetts regulations provide for
certain notification requirements upon
well abandonment.

The Massachusetts regulations
will be followed to the extent
that the remedy involves
decommissioning any wells.

F-20

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TABLE 6. CHEMICAL-SPECIFIC ARARS AND CRITERIA, ADVISORIES, AND GUIDANCE
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

SINKING POND SEE

UMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

State Criteria, Advisories,
and Guidance

Consensus-Based Sediment Quality
Guidelines; MassDEP, 2002. Technical
Update, Freshwater Sediment Screening
Benchmarks for Use Under the
Massachusetts Contingency Plan.
ROD Status: TBC
5-Year Review Status: TBC

MassDEP recommends using the
MacDonald et al. (2000) screening
values for evaluating freshwater
sediment and risks to benthic organisms.

MacDonald, D.D., C.G. Ingersoll, and
T.A. Berger, 2000. Development and
evaluation of consensus-based sediment
quality guidelines for freshwater
ecosystems. Archives of Environmental
Contamination and Toxicology, 39, 20-
31.

These guidelines were
considered in the risk
assessments and in developing
risk-based remedial goals for
sediment. Any future
evaluation of residual risk is
expected to also use these
values.

F-21

-------
TABLE 6. CHEMICAL-SPECIFIC ARARS AND CRITERIA, ADVISORIES, AND GUIDANCE
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

SINKING POND SEE

UMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

Other Criteria,

Advisories, and Guidance

Ontario Provincial Sediment Quality
Guideline

ROD Status: TBC

5-Year Review Status: TBC

The Ontario Provincial Lowest Effect
Levels (LEL) are used to identify
sediment at which most benthic
organisms are unaffected. (Ontario
Ministry of the Environment, 1993 a and
b, 1994).

Ontario Ministry of the Environment and
Energy, 1993 a. Development of the
Ontario Provincial Sediment Quality
Guidelines for PCBs and the
Organochlorine Pesticides, Water
Resources Branch.

Ontario Ministry of the Environment and
Energy, 1993b. Development of the
Ontario Provincial Sediment Quality
Guidelines for Arsenic, Cadmium,
Chromium, Copper, Iron, Lead,
Manganese, Mercury, Nickel, and Zinc,
Water Resources Branch.

Ontario Ministry of the Environment and
Energy, 1994. Development of the
Ontario Provincial Sediment Quality
Guidelines for Polycyclic Aromatic
Hydrocarbons (PAH), Water Resources
Branch.

These guidelines were
considered in the risk
assessments and in developing
risk-based remedial goals for
sediment. Any future
evaluation of residual risk is
expected to also use these
values.

F-22

-------
TABLE 7. LOCATION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

SINKING POND SEE

UMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

State Regulatory
Requirements

Massachusetts Wetlands Protection Act
and Regulations, M.G.L. c. 131, § 40;
310 CMR 10.00

ROD Status: Applicable

5-Year Review Status: Applicable

The Wetlands Protection Act (WPA)
imposes requirements and limitations for
alteration of areas subject to protection
under the WPA, including land under
water bodies and establishes
performance standards for projects that
affect land under water bodies. Because
Sinking Pond contains areas subject to
jurisdiction under the WPA, these
regulations are applicable.

The remedial action was
designed to be consistent with
the performance standards in
the Wetlands Protection Act
Regulations.



Bordering Vegetated Wetland
Delineation Criteria and Methodology,
Issued: March 1, 1995

ROD Status: TBC

5-Year Review Status: TBC

This policy defines which plant species
or other plants are wetland indicator
plants as specified in the wetland
regulations (310 CMR 10.55(2)(c)). This
policy also identifies a standard
methodology for determining the
boundary of Bordering Vegetated
Wetlands (BVWs) in accordance with
310 CMR 10.55(2)(c)(l-3).

The remedy was implemented
in compliance with this Policy.

F-23

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TABLE 8. ACTION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

SINKING POND SEE

UMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

Federal Regulatory
Requirements

RCRA - Identification and Listing of
Hazardous Wastes; 40 CFRPart 261
ROD Status: Relevant and
Appropriate

5-Year Review Status: Relevant and
Appropriate

Part 261 establishes requirements for
determining whether wastes are
hazardous.

The remedy was implemented
to comply with the Part 261
regulations in determining
whether any excavated
sediments are hazardous waste.
No sediments were determined
to be hazardous waste.



RCRA Generator Requirements; 40 CFR
Part 262

ROD Status: Relevant and
Appropriate

5-Year Review Status: Not ARAR

RCRA establishes requirements
applicable to generators of hazardous
waste. Those requirements include
provisions addressing hazardous waste
determinations, manifesting, pre-
transport requirements, and
recordkeeping.

No excavated sediments were
determined to be hazardous
waste.

State Regulatory
Requirements

Massachusetts Hazardous Waste Rules
for Identification and Listing of
Hazardous Waste; 310 CMR 30.100.
ROD Status: Applicable
5-Year Review Status: Applicable

310 CMR 30.100 establishes
requirements for determining whether
wastes are hazardous.

The remedy was implemented
to comply with 310 CMR
30.100 in determining whether
any excavated sediments are
hazardous waste. No
sediments were determined to
be hazardous waste.



Massachusetts Hazardous Waste Rules
for Generators of Hazardous Waste; 310
CMR 30.300.

ROD Status: Applicable

5-Year Review Status: Not ARAR

310 CMR 30.300 establishes
requirements applicable to generators of
hazardous waste. Those requirements
include provisions addressing hazardous
waste determinations, manifesting, pre-
transport requirements, and
recordkeeping.

No excavated sediments were
determined to be hazardous
waste.

F-24

-------
TABLE 8. ACTION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

SINKING POND SEE

UMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Massachusetts Wetlands Protection Act
and Regulations, M.G.L. c. 131, § 40;
310 CMR 10.00

ROD Status: Applicable

5-Year Review Status: Applicable

The Wetlands Protection Act (WPA)
imposes requirements and limitations for
alteration of areas subject to protection
under the WPA, including land under
water bodies and establishes
performance standards for projects that
affect land under water bodies. Because
Sinking Pond contains areas subject to
jurisdiction under the WPA, these
regulations are applicable.

The remedial action was
designed to be consistent with
the performance standards in
the Wetlands Protection Act
Regulations.



Massachusetts Solid Waste Management
Regulations (310 CMR 19.000)
ROD Status: Applicable
5-Year Review Status: Not ARAR

These regulations address non-hazardous
waste and closure, post closure and
maintenance of solid waste landfills. If
non-hazardous wastes are left on site as
part of this remedy, the disposal
Closure/Post Closure Standards would
be met.

No non-hazardous wastes were
left on site as part of this
remedy.

F-25

-------
TABLE 9. CHEMICAL-SPECIFIC ARARS AND CRITERIA, ADVISORIES, AND GUIDANCE
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

NORTH LAGOON WETLAND SEDIMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

State Criteria, Advisories,
and Guidance

Consensus-Based Sediment Quality
Guidelines; MassDEP, 2002. Technical
Update, Freshwater Sediment Screening
Benchmarks for Use Under the
Massachusetts Contingency Plan.
ROD Status: TBC
5-Year Review Status: TBC

MassDEP recommends using the
MacDonald et al. (2000) screening
values for evaluating freshwater
sediment and risks to benthic organisms.

MacDonald, D.D., C.G. Ingersoll, and
T.A. Berger, 2000. Development and
evaluation of consensus-based sediment
quality guidelines for freshwater
ecosystems. Archives of Environmental
Contamination and Toxicology, 39, 20-
31.

These guidelines were
considered in the risk
assessments and in developing
risk-based remedial goals for
sediment. Any future
evaluation of residual risk is
expected to also use these
values.

F-26

-------
TABLE 9. CHEMICAL-SPECIFIC ARARS AND CRITERIA, ADVISORIES, AND GUIDANCE
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

NORTH LAGOON WETLAND SEDIMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

Other Criteria,

Advisories, and Guidance

Ontario Provincial Sediment Quality
Guideline

ROD Status: TBC

5-Year Review Status: TBC

The Ontario Provincial Lowest Effect
Levels (LEL) are used to identify
sediment at which most benthic
organisms are unaffected. (Ontario
Ministry of the Environment, 1993 a and
b, 1994).

Ontario Ministry of the Environment and
Energy, 1993 a. Development of the
Ontario Provincial Sediment Quality
Guidelines for PCBs and the
Organochlorine Pesticides, Water
Resources Branch.

Ontario Ministry of the Environment and
Energy, 1993b. Development of the
Ontario Provincial Sediment Quality
Guidelines for Arsenic, Cadmium,
Chromium, Copper, Iron, Lead,
Manganese, Mercury, Nickel, and Zinc,
Water Resources Branch.

Ontario Ministry of the Environment and
Energy, 1994. Development of the
Ontario Provincial Sediment Quality
Guidelines for Polycyclic Aromatic
Hydrocarbons (PAH), Water Resources
Branch.

These guidelines were
considered in the risk
assessments and in developing
risk-based remedial goals for
sediment. Any future
evaluation of residual risk is
expected to also use these
values.

F-27

-------
TABLE 10. LOCATION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

NORTH LAGOON WETLAND SEDIMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

Federal Regulatory
Requirements

Protection of Wetlands Executive Order
No. 11990 (May 24, 1977), 42 Fed. Reg.
26961, 18 C.F.R. § 725.

ROD Status: Applicable
5-Year Review Status: Applicable

The Executive Order (EO) imposes
requirements on federal agencies that
oversee projects undertaken in wetlands
areas, including natural ponds. It
requires federal agencies to avoid
construction in wetlands unless there is
no practicable alternative to such
construction. If there is no practical
alternative to conducting work in the
wetlands, all practicable measures to
minimize harm to wetlands from such
construction must be taken. The North
Lagoon Wetland is a jurisdictional
wetland area. Because there are
wetlands on the Site and a federal
agency is overseeing the remediation,
this requirement is applicable.

Because the contamination that
was remediated was located in
wetlands, there was no
practical alternative to address
this contamination. Measures
were taken to minimize
impacts and the wetland has
been restored. Ongoing
monitoring is evaluating the
success of the restoration
effort.

F-28

-------
TABLE 10. LOCATION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

NORTH LAGOON WETLAND SEDIMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Floodplain Management Executive Order
No. 11988 (May 24, 1977), 42 Fed. Reg.
26951, 18 C.F.R. § 725.

ROD Status: Applicable
5-Year Review Status: Applicable

The Executive Order (EO) imposes
requirements on federal agencies that
oversee projects undertaken in
floodplains. It requires federal agencies
to avoid activities in floodplains unless
there is no practicable alternative to such
activities. If there is no practical
alternative to conducting work in the
floodplain, all practicable measures to
minimize impacts must be taken.
Because there is a floodplain on the Site
and a federal agency is involved with the
remediation, this requirement is
applicable

Because some of the
contamination in the North
Lagoon Wetland that presented
an unacceptable risk was
located in a floodplain, there
was no practical alternative to
address this contamination.
Measures were taken to
minimize impacts.

State Regulatory
Requirements

Massachusetts Wetlands Protection Act
and Regulations, M.G.L. c. 131, § 40;
310 CMR 10.00

ROD Status: Applicable

5-Year Review Status: Applicable

The Wetlands Protection Act (WPA)
imposes requirements and limitations for
alteration of wetlands and establishes
performance standards for projects that
affect wetlands. Because the North
Lagoon Wetland contains areas subject
to jurisdiction under the WPA, these
regulations are applicable.

The remedial action was
conducted in accordance with
these regulations.

F-29

-------
TABLE 10. LOCATION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

NORTH LAGOON WETLAND SEDIMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Bordering Vegetated Wetland
Delineation Criteria and Methodology,
Issued: March 1, 1995

ROD Status: TBC

5-Year Review Status: TBC

This policy defines which plant species
or other plants are wetland indicator
plants as specified in the wetland
regulations (310 CMR 10.55(2)(c)).
This policy also identifies a standard
methodology for determining the
boundary of Bordering Vegetated
Wetlands (BVWs) in accordance with
310 CMR 10.55(2)(c)(l-3).

This guidance was used to
define the boundary of the
wetlands for state wetland
purposes.

F-30

-------
TABLE 11. ACTION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

NORTH LAGOON WETLAND SEDIMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW

Federal Regulatory
Requirements

RCRA - Identification and Listing of
Hazardous Wastes; 40 CFRPart 261
ROD Status: Relevant and
Appropriate

5-Year Review Status: Relevant and
Appropriate

Part 261 establishes requirements for
determining whether wastes are
hazardous.

The remedy was implemented
to comply with the Part 261
regulations in determining
whether any excavated
sediments are hazardous waste.
No sediments were determined
to be hazardous waste.



RCRA Generator Requirements; 40 CFR
Part 262

ROD Status: Relevant and
Appropriate

5-Year Review Status: Not ARAR

RCRA establishes requirements
applicable to generators of hazardous
waste. Those requirements include
provisions addressing hazardous waste
determinations, manifesting, pre-
transport requirements, and
recordkeeping.

No excavated sediments were
determined to be hazardous
waste.



Clean Water Act (CWA) § 402 (33

U.S.C. §1342)

ROD Status: Applicable

5-Year Review Status: Applicable

Section 402 of the CWA requires
issuance of an NPDES permit prior to
discharge of any pollutant to a water of
the United States. Permits can only be
issued in compliance with applicable
technology standards.

Impacted water generated
during remedial activities
resulted primarily from
equipment cleaning activities
and precipitation that contacted
impacted materials in the
sediment dewatering and
decontamination pads. This
water was collected, filtered,
and treated in the new Landfill
Area groundwater treatment
system which discharges into
Sinking Pond. Effluent
limitations were met.

F-31

-------
TABLE 11. ACTION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

NORTH LAGOON WETLAND SEDIMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Clean Water Act (CWA) § 304(a) (33

U.S.C. §1314(a))

ROD Status: Applicable

5-Year Review Status: Applicable

Federal National Recommended Water
Quality Criteria (NRWQC) include (1)
human health-based criteria and (2)
other water quality parameters protective
of fish and aquatic life. NRWQC for the
protection of human health provide
levels for exposure from drinking water
and consuming aquatic organisms, and
from consuming fish alone. Discharges
subject to NPDES permitting
requirements must not result in
exceedances of NRWQCs.

The discharge from the
dewatering operations was
treated and discharged to
Sinking Pond. Collection and
treatment was designed and
operated so that it would not
cause or contribute to an
exceedance of the NRWQC.

State Regulatory
Requirements

Massachusetts Clean Water Act, G.L. ch.
21, §26-51; 314 CMR 3.00.
ROD Status: Applicable
5-Year Review Status: Applicable

The Massachusetts regulations provide
that discharges to waters of the
Commonwealth shall not result in
exceedances of Massachusetts Surface
Water Quality Standards. These
standards are the same as the NRWQCs
for the compounds analyzed for at the
Site.

The discharge from the
dewatering operations was
treated and discharged to
Sinking Pond. Collection and
treatment was designed and
operated so that it would not
cause or contribute to an
exceedance of the MSWQS.



Massachusetts Hazardous Waste Rules
for Identification and Listing of
Hazardous Waste; 310 CMR 30.100.
ROD Status: Applicable
5-Year Review Status: Applicable

310 CMR 30.100 establishes
requirements for determining whether
wastes are hazardous.

The remedy was implemented
to comply with 310 CMR
30.100 in determining whether
any excavated sediments are
hazardous waste. No
sediments were determined to
be hazardous waste.

F-32

-------
TABLE 11. ACTION-SPECIFIC ARARS
W.R. GRACE SUPERFUND SITE - OPERABLE UNIT 3 - ACTON AND CONCORD, MASSACHUSETTS

NORTH LAGOON WETLAND SEDIMENT REMEDIATION

ARARs

REQUIREMENTS

REQUIREMENT SYNOPSIS

FIVE YEAR REVIEW



Massachusetts Hazardous Waste Rules
for Generators of Hazardous Waste; 310
CMR 30.300.

ROD Status: Applicable

5-Year Review Status: Not ARAR

310 CMR 30.300 establishes
requirements applicable to generators of
hazardous waste. Those requirements
include provisions addressing hazardous
waste determinations, manifesting, pre-
transport requirements, and
recordkeeping.

No excavated sediments were
determined to be hazardous
waste.



Massachusetts Air Pollution Control
Regulations, 310 CMR 7.00

ROD Status: Applicable

5-Year Review Status: Applicable

These regulations set requirements on
the control of fugitive emissions and
dust.

These requirements were met
during construction activities.



Massachusetts Solid Waste Management
Regulations (310 CMR 19.00)

ROD Status: Applicable

5-Year Review Status: Not ARAR

These regulations address non-hazardous
waste and closure, post closure and
maintenance of solid waste landfills. If
non-hazardous wastes are left on site as
part of this remedy, the disposal
Closure/Post Closure Standards would
be met.

No non-hazardous wastes were
left on site as part of this
remedy.

F-33

-------