Superfuad Records Center

SHE- ^' Connor Ct>

BREAK:

IN THE UNITED STATES DISTRICT COURT

FOR THE DISTRICT OF MAINE

SDMS DocID

UNITED STATES OF AMERICA

Plaintiffs,

v.

F. O'CONNOR COMPANY

SUPERFUND SITE, et. al

Defendants.

CIVIL ACTION NO.

AMENDMENT TO CONSENT DECREE

WHEREAS, this action was filed by the United States on behalf of the United States

Environmental Protection Agency ("EPA") seeking (1) reimbursement of response costs incurred

and to be incurred for response actions at the F. O'Connor Supcrfund Site in Augusta. Maine (the

"Site"'), and (2) performance of studies and response actions at the Site pursuant to the

Comprehensive Environmental Response, Compensation, and Liability Act ("CERCLA"). 42

\ '.$. C. § %01. et seq.. as amended, and the Resource Conservation and Recovery Act

("RCRA"), 42 U.S.C. § 6901 etseq.;

WHEREAS, on July 26, 1990. the Court entered a Consent Decree ("the Consent

Decree") lodged by the United States to resolve this action;

WHEREAS, the Consent Decree in accordance with the Statement of Work (SOW)

called for source control through on-site treatment by solvent extraction of site soils and

274691
sediments, management of migration through the establishment of temporary institutional

controls until groundwater remediation levels are achieved, the construction and operation of a

groundwater extraction and treatment system to remove and treat groundwater contaminated with

PCBs, benzene, and 1,4 dichlorobenzene, on-site ground water discharge system, and

groundwater monitoring.

WHEREAS, from 1991 to 1993 an evaluation of the solvent extraction technology for

contaminated soil and sediment was performed as allowed by the Consent Decree in accordance

with the SOW. The evaluation concluded that the technology would not attain the performance

standards for soils and sediments set in the ROD. In July 1994 EPA issued an Explanation of

Significant Differences (ESD) which modified the source control portion of the remedy. Soil and

sediment containing more than ten parts per million (ppm) PCBs or cPAHs or 248 ppm lead

would be treated using solvent extraction technology, then transported and disposed of offsite to

an appropriate facility. Alternatively, the ESD provided a contingency that this material could be

sent offsite for disposal without treatment. Soil and sediment containing between one to ten ppm

PCBs or cP.AHs would he consolidated inio one area onsite and then covered wit h twelve inches

of clean fill brought in from offsite.

WHEREAS, in October 1995. EPA invoked the contingency remedy set forth in the 1994

ESD. This allowed for the offsite disposal of soil and sediment with greater than ten ppm PCBs

and cPAHs without first requiring on-site solvent extraction treatment.

Whereas the 1994 ESD conceptually delineated a five-sided area where soil and sediment

containing between one and ten ppm PCBs or cPAHs would be consolidated, following

completion of the source control this designated area had evolved into a twenty-five-sided area.
The designated area will be surveyed, the boundaries simplified to the 10-sided shape shown in

Appendix III, and permanent markers placed at the turning points.

WHEREAS, in 1992 groundwater pump tests were conducted and separate phase oil was

found in bedrock wells, a condition that was not detected at the time the Consent Decree was

entered. Further investigation found that although there was separate phase oil in the bedrock, it

appeared to be confined to a limited portion of the Site, and that dissolved concentrations of

PCBs and solvents downgradient were only slightly elevated.

WHEREAS, in 1996 and 1997, efforts were focused on oil recovery from the

groundwater to assist in the source control excavation rather than groundwater extraction and

treatment of dissolved contaminant. Following passive recovery of oil, vacuum-enhanced oil

recovery of separate phase oil continued in 2001, recovering more than 20 gallons of oil from the

bedrock. On June 4, 2002, Central Power Maine (CMP) submitted to EPA and Maine

Department of Environmental Protection (Maine DEP) a Technical Impracticability ("TI")

Evaluation Report assessing the feasibility of remediating groundwater contamination at the Site.

The TI evaluation concluded that because of the geology and hydrology of the Site, there were no

technologies that could restore the ground water beneath a limited portion of the Site to drinking

water quality within a reasonable time. EPA. after review and comment from Maine DEP,

agreed \\ii h this conclusion and approved the report in June 2002. On June 1 9. 2002. pursuant to

Section 117 of CERCLA, 42 U.S.C. §9617, EPA published a notice of the availability for public

review of the TI report and the proposed plan for amending the remedial action and provided

opportunity for public comment.

WHEREAS, EPA and the State have agreed that remediation of the groundwater is
technically impracticable, and EPA, with the concurrence of the State, issued on September 26,

2002 a Record of Decision Amendment (the "ROD Amendment"), which modifies the remedy

for remediation of the groundwater that was selected in the Record of Decision issued in 1989.

WHEREAS, this Amendment to the ROD provides for the protection of human health by

providing for long term monitoring of groundwater, active and passive oil recovery in

groundwater and a restrictive covenant between CMP and Maine DEP that prohibits the use of

groundwater without prior approval of Maine DEP. This Amended Consent Decree incorporates

the ROD Amendment and all its attendant responsibilities, requirements and obligations thereby

making it an enforceable part of the Consent Decree.

WHEREAS, the United States and the Settling Defendant have agreed to amend the

Consent Decree as set forth below to modify the obligations of the Settling Defendant to perform

certain response actions and to reimburse costs to the United States. The Parties agree that this is

a material modification to the Consent Decree.

WHEREAS, under Paragraph 108 of the Consent Decree, any material modification of

the Consent Decree must be in writing and approved by the Court:

NOW, THEREFORE, the United States and the Settling Defendant, in consideration of

the promises and covenants herein, and intending to be legally bound thereby, agree to the

followin g modifications to the Consent Decree:

1. All terms and phrases in this Amendment shall be defined as provided in the Consent

Decree except as specifically provided herein.

2. The rights and obligations of the Settling Defendant and the United States are not

modified except as specifically provided in this Amendment.
3. Section IV. shall be amended as follows:

Paragraph 3 shall include the following new and amended definitions:

"Consent Decree" shall mean the Consent Decree entered by this Court on

September 10, 1991, and this Amendment to the Consent Decree.

"Designated Area" shall mean the area conceptually identified in the 1994 BSD

and then delineated during post-source control remedial activities, where soils

containing PCBs at concentrations of less than 10 parts per million but above one

part per million, were consolidated. This area is depicted in Appendix III to this

Amendment to Consent Decree.

"Explanation of Significant Difference" or "ESD" shall mean the EPA

Explanation of Significant Differences relating to the Site signed on July 11, 1994

by the Regional Administrator. EPA Region I, and attachments thereto.

"Record of Decision" or "ROD" shall be amended to read as follows: "Record of

Decision" or "ROD" shall mean the EPA Record of Decision relating to the Site

.signed on September 27. 19RQ. by the Acting Regional Administrator. EPA

Region 1, and all attachments thereto, and the Record of Decision Amendment.

Operable Unit 2. signed on September 26. 2002 by the Director of the Office of

Site Remediation and Restoration. EPA Region 1 and all attachments thereto. The

ROD is attached as Appendix I to the Consent Decree and the ROD Amendment
is attached as Appendix I to this Consent Decree Amendment.

"Site" shall be amended to read as follows: "Site" shall mean the 23-acre parcel

defined in the ROD Amendment and Restrictive Covenant, located within a

twenty-eight acre parcel owned by Settling Defendant. With the conclusion of the

source control remedial action, principal features of the Site include the upland

marsh, a dirt road through the center of the Site, the two former lagoons, now

restored as wetlands, and various monitoring wells. This area is depicted in

Figure 5 of Appendix I to this Amendment to Consent Decree.

"Statement of Work" or "SOW" shall be amended to read as follows: "Statement

of Work" or "SOW" shall mean the statement of work for implementation of the

remedial design, remedial action, and operation and maintenance of the remedy at

the Site, as set forth in Appendix II to the Consent Decree, the 1994 revised SOW

\\hic h was attached to the 1994 ESD. and the 2003 Statement of Work as set forth

in Appendix II to this Amendment to the Consent Decree. If a conflict arises

between the Statement of Work in Appendix II to the Consent Decree and the

2003 Statement of Work, the 2003 Statement of Work shal l control.

"Technical Impracticability" or'TI" waiver shall mean the determination made by

EPA. Region I. and incorporated in the ROD Amendment, that it is technical!)

infeasible to restore the groundwater beneath a limited portion of the Site to
drinking water standards within a reasonable time frame. This area is depicted in

Figure 3 of Appendix I to this Amendment to Consent Decree.

4. Section VI. Performance of the Work by Settling Defendant shall be amended follows:

Paragraph 8.b. delete "pumping and carbon adsorption treatment of contaminated

groundwater" and insert "active oil recovery implemented annually and passive

oil recovery implemented the remainder of the year."

Paragraph 14.k., insert the following sentence at the end of the paragraph: "for

purposes of the Amended Consent Decree the Settling Defendant shall submit to

EPA two bound (2) and one (1) unbound copy of each Work Plan and any other

submission required by it or this Amendment to Consent Decree or the 2003

SOW."

Paragraph 16. shall he amended by adding the followin g language to the end of

the first sentence: "and the Cleanup and Performances Standards set forth in the

2003 SOW. Appendix II to this Amendment to Consent Decree."

5. Section IX. Quality Assurance; Sampling, shall be amended as follows:

Paragraph 24. insert the followin g sentenee at the end of the paragraph that states

"for purposes of the Amended Consent Decree the Settlin g Defendant shall

submit to EPA quarterly progress reports as described in Section XI of this

7
Consent Decree, or less frequently as agreed to by the project coordinators. The

Settling Defendant shall submit to EPA and Maine DEP the quarterly reports on

January 10, April 10, July 10 and October 10 of each calendar year, beginning

with the quarter that follows entry of this Amendment to Consent Decree, unless

the frequency has been changed by agreement of the project coordinators."

Paragraph 25, insert the following sentence at the end of the paragraph: "for

purposes of the Amended Consent Decree the Settling Defendant shall notify EPA

and the State no less than fourteen (14) days days in advance of any sample

collection activity."

7. Section XI. Reporting Requirements shall be amended as follows:

Paragraph 30, insert the following sentence at the end of the paragraph: "for

purposes of the Amended Consent Decree the Settling Defendant shall submit to

EPA two (2) copies of quarterly progress reports."

8. Section XVIII . Reimbursement of Response Costs shall be amended as follows:

Paragraph 55. insert the follouing sentence nt the end of the paragraph: "for

purposes of the Amended Consent Decree the Settling Defendant shall make

payment by means of a certified check made payable to "EPA i la/ardous

Substances Superfund." and referencing the O'Connor Co. Superfund Site Special

Account."
9. Section XXVIII. Notices and Submissions shall be amended as follows:

Paragraph 106, "As to the United States" delete "EPA RPM, O'Connor Co.

Superrund Site, Maine and Vermont Superfund Section, Waste Management

Division (HPS-CAN2), J.F.K. Federal Building, Boston. MA 02203" and replace

with

"EPA RPM - O'Connor Company Superfund Site

Maine, Vermont, and Connecticut Superfund Section (HBT)

US EPA Region I

One Congress Street

Suite 1100

Boston, MA 02114"

11. Section XXIX. Effective Date shall be amended as follows:

Paragraph 107, after the first sentence add the following sentence: "The effective

date of this Amendment to Consent Decree shall be the date this Amendment to

Consent Decree is entered by the U.S. District Court for the District of Maine."

SO ORDERED THIS DAY OF

l

:NITF.D STATI-S DISTRICT .Il'DGF.
SO AGREED: FOR THE UNITED STATES

Thomas L. Sansonetti

Assistant Attorney General

Environment and Natural Resources

Division

DATED

Ron Gluck, Assistant Section Chief

Environmental Enforcement Section

1425 New York Avenue, N.W.

Room 13063

Washineton. D.C. 20005

10
DATED

Patrick Casey

Environmental Enforcement Section

1425 New York Avenue, N.W.

Room 13063

Washington, D.C. 20005

Paula Silsby

Assistant United States Attorney

District of Maine

U.S. Department of Justice

Post Office Box 9718

Portland. Maine 04104-5018

DATED
FOR THE UNITED STATES ENVIRONMENTAL

PROTECTION AGENCY

DATED 9-23-0-3

DATED

Robert W. Varney,

Regional Administrator

U.S. Environmental Protection Agency

New England Region

1 Congress Street, Suite 1100

Boston, MA 02114-2023

Suzanne Childfess

Senior Enforcement Counsel

U.S. Environmental Protection Agency

New England Region

1 Congress Street, Suite 1100 (SES)

Boston, MA 02114-202?

12
THE UNDERSIGNED SETTLING DEFENDANT enters into this Consent Decree

relating to the O'Connor Company Superfund Site

FOR CENTRAL MAINE POWER COMPANY

Q°t/(£/C>? Signature: (T ^ .

Date Name: R. Stott Mahoney

Title: Managing Attorney

Address: 83 Edison Drive

Augusta, Maine

Agent Authorized to Accept Service on Behalf of Central Maine Power Company

Name (print): t> .

Title:

Address:

Telephone:
APPENDIX I TO AMENDMENT TO O'CONNOR CONSENT DECREE

SEPTEMBER 2002 RECORD OF DECISION AMENDMENT
cute:

m

DATE:

SUBJ:

FROM:

THRU:

TO:

United States Environmental Protection Agency

One Congress Street, Suite 1100

Boston, MA 02114-2023

MEMORANDUM

September 25, 2002

F. O'Connor Company Superfund Site

Record of Decision Amendment

f DrcrA.r^«'- .-. ''uI t ^ i

>>——-———"• -~-~-TM,.TM -J^J

Terrence Connelly

Maine, Vermont, & Connecticut Superfund Section

Mary Jane O'Donnell, Section Chief / _

Maine, Vermont, & Connecticut SuperftMfl^Section

Richard Cavagnero, Acting Director fM

OSRR //

f <•

Summary of Action

Attached for your review and signature is the Record of Decision Amendment (ROD

Amendment) for the F. O'Connor Company Superfund Site, the (Site) in Augusta, Maine.

This document amends the remedial action originally selected in the 1989 ROD for the

management of migration operable unit (OU-2). After it is fully executed and recorded,

this ROD Amendment will become part of the Administrative Record for public review

In addition, a notice which briefly summarizes this ROD Amendment will be published

in a major local newspaper of general circulation.

The ROD Amendment addresses the remedial action objective of preventing exposure

to contaminated groundwater through institutional controls. The Amendment changes the

1989 management of migration component which relied on pump-and-treat of the

groundwater to active oil recovery from the overburden soil and bedrock, long-term

monitoring, and the establishment of a technical impracticability zone for a limited area

of the Site. Chemical-Specific ARARs for PCBs and seven VOCs are being waived in an

area where residual separate phase oil remains five years after the successful completion

of the source control remedial action.

Major Issues

EPA has determined that it is technically impracticable from an engineering perspective
to attain federal and state drinking water standards for a limited portion of this Site, and is

thus waiving attainment of these ARARs. EPA has determined that active remedial

action to recover the separate phase oil in the overburden soil and in the bedrock will

reduce the volume of hazardous substances and reduce the possibility of its mobility to

other portions of the She. Therefore, this remedy satisfies the statutory preference for

remedies that utilize treatment as a principal element to reduce the toxicity, mobility, or

volume of hazardous substances.

An evaluation of the exposure pathways and risks associated with the Site was performed

in June 2002 as part of the first five-year review for the Site. This evaluation concluded

that the exposure pathways and risks applicable to groundwater had not changed since the

1989 ROD. This information was incorporated into the ROD Amendment, supporting

the TI waiver.

No further construction for remedial action is anticipated following this ROD

Amendment as the components of the selected remedy are already in place and the source

control has been successfully completed. As such, a Preliminary Close Out Report for

the Site has also been prepared for this fiscal year.

Headquarters Perspective/Involvement

Headquarters was consulted regarding the technical impracticability waiver and the

reassessment of ARARs. Headquarters reviewed the ROD Amendment and their

comments have been addressed.

Public Involvement

There has been limited public involvement associated with this site following the

successful remediation of the source control area (OU-1) in 1997. Public notice was

given in June 2002 regarding the Proposed Plan to amend the 1989 ROD. This public

notice included a press release to the major local paper as well as a mailing to all

neighbors. At a public information meeting, the public expressed support for the

proposed remedy.

Media-Congressional Involvement

There was media coverage of the public meeting held for the Proposed Plan. No

members of the public or media attended the public hearing. There has been no

congressional involvement regarding this ROD Amendment.

State Coordination

Maine DEP was actively involved in the technical impracticability evaluation for OU-2.

Maine DEP reviewed the draft Proposed Plan and entered formal comments at the public

hearing. In addition to their participation in the OU-2 ROD amendment, Maine DEP
also provided comment and proposed minor changes to the OU-1 and OU-3 remedies.

Finally, Maine DEP also actively participated in the first five-year for the entire site, a

process which occurred during the same time period. Maine DEP has concurred with this

ROD Amendment.

Recommendation

The selected remedy is protective of human health and the environment, attains or

provides the basis for a waiver of federal and state requirements that are ARARs for this

remedial action, and is cost-effective. Therefore, we recommend you sign this ROD

Amendment.

Contact Persons

Terrence Connelly, Remedial Project Manager, 918-1373

Rona Gregory, Senior Enforcement Counsel, 918-1096

Attachment: Record of Decision Amendment
Site:

O _

F. O'CONNOR COMPANY SUPERFUND SITE

RECORD OF DECISION AMENDMENT

OPERABLE UNIT 2

September 2002

U.S. Environmental Protection Agency - Region I

New England
DECLARATION FOR*THE:

 RECORD OF DECISION AMENDMENT

A. SITE NAME AND LOCATION

F. O'Connor Company Superfund Site

Augusta, Kennebec County, Maine

CERCLIS Identification Number: MED980731475

PRPLead

Operable Unit Two, Management Of Migration

B. STATEMENT OF BASIS AND PURPOSE

This decision document presents an amendment to the selected remedial action for the F. O'Connor

Company Superfund Site in Augusta, Maine which was chosen in accordance with the Comprehensive

Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), as amended, 42 U.S.C.

§§ 9601 ct. seq. and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) as

amended, 40 C.F.R. Part 300. The Director of the Office of Site Remediation and Restoration has been

delegated the authority to approve this Record of Decision Amendment (ROD Amendment)..

This decision was based on the Administrative Record, which has been developed in accordance with

Section 113 (k) of CERCLA, and which is available for review at the Lithgow Public Library in Augusta,

Maine and at the United States Environmental Protection Agency (EPA) Region 1 Office of Site

Remediation and Restoration (OSRR) Records Center in Boston, Massachusetts. The Administrative

Record Index (Appendix B of this ROD Amendment) identifies each of the items comprising the

Administrative Record upon which the selection of the remedial action is based.

"Die State of Maine has concurred with the selected remedy.

C. ASSESSMENT OF THE SITE

The response action selected in this ROD Amendment is necessary to protect the public health or welfare

or the environment from actual or threatened releases of hazardous substances into the environment.

D. DESCRIPTION OF THE SELECTED REMEDY

This ROD Amendment changes the remedy originally selected in the 1989 ROD for the management of

migration operable unit (OU-2). This ROD Amendment makes minor changes and clarifications to the

source control and Riggs Brook remedies (OU-1 and OU-3, respectively).

The major components of the selected remedy include:

• Institutional controls to prevent the use of contaminated groundwater;

• Waiver of federal and state drinking water standards for a limited portion of the Site on

the basis of technical impracticability;
Active recovery of separate-phase oil from the overburden soil and bedrock through

annual implementation of a vacuum-enhanced recovery system and passive recovery

between these annual implementations;

Long-term monitoring of site groundwater on a regular basis to evaluate changes in site

conditions over time; and

A review of the Site every five years to ensure that the remedy remains protective of

human health and the environment.

E. STATUTORY DETERMINATIONS

The selected remedy for OU-2 is protective of human health and the environment, complies with Federal

and State requirements that are applicable or relevant and appropriate to the remedial action (unless

justified by a waiver), is cost-effective, and utilizes permanent solutions and alternative treatment (or

resource recovery) technologies to the maximum extent practicable.

The remedy also satisfies the statutory preference for treatment as a principal element as the active oil

recovery system provides reduction in toxicity, mobility, and volume of contaminants through the

extraction and treatment of separate-phase PCB-laden oil.

Because this remedy will result in hazardous substances remaining on-site above levels that allow for

unlimited use and unrestricted exposure (groundwater and/or land use restrictions are necessary), a

review will be conducted every five years after initiation of remedial action to ensure that the remedy

continues to provide adequate protection of human health and the environment.

F. SPECIAL FINDINGS

Issuance of this ROD embodies specific determinations made by the Regional Administrator or his

designee pursuant to CERCLA. EPA determined that it was technically impracticable to restore

groundwater beneath a limited area of the Site to drinking water quality within a reasonable time frame.

Therefore, EPA waived the attainment of chemical-specific ARARs for this area of the She. These

chemical-specific ARARs are either being met now or are expected to be met shortly throughout the rest

of the Site, and therefore will provide sufficient basis for EPA to make a statutory finding of compliance

for the chemical-specific ARARs presented in this ROD Amendment for the rest of the Site

G. ROD DATA CERTIFICATION CHECKLIST

The following information is included in the Decision Summary section of this Record of Decision

Additional information can be found in the Administrative Record file for this Site.

1. Chemicals of concern (COCs) and their respective concentrations.

2. Cleanup levels established for COCs and the basis for the levels.

3. Current and reasonably anticipated future land assumptions and current and potential future

beneficial uses of groundwater used in the ROD Amendment.
4. Potential land and groundwater use that will be available at the Site as a result of the selected

remedy.

5. Estimated capital, operation and maintenance (O&M), and total present worth costs; discount

rate; and the number of years over which the remedy cost estimates are projected.

6. Key factor(s) that led to selecting the remedy.

H. AUTHORIZING SIGNATURES

This ROD Amendment documents the selected remedy for the F. O'Connor Superfund Site, Operable

Unit 2. This remedy was selected by USEPA with concurrence of the Maine Department of

Environmental Protection (MEDEP).

U.S. Environmental Protection Agency

By

avagneroy Acting Director

Remediation and Restoration

Region 1
Table of Contents

I. SITE NAME, LOCATION, DESCRIPTION AND RATIONALE FOR

AMENDMENT

II. SITE HISTORY AND ENFORCEMENT ACTIVITY 3

III. COMMUNITY PARTICIPATION 5

IV. SCOPE AND ROLE OF OPERABLE UNIT 5

V. DESCRIPTION OF CHANGES TO THE 1989 REMEDY 6

DESCRIPTION OF THE 1989 REMEDY 6

CHANGES TO THE 1989 REMEDY 8

VI. SUMMARY OF SITE CHARACTERISTICS 9

VII. SUMMARY OF SITE RISKS 14

VIII TECHNICAL IMPRACTICABILITY DETERMINATION 15

IX. COMPARATIVE ANALYSIS OF THE ORIGINAL REMEDY AND

OU-2 ALTERNATIVES 29

X. THE SELECTED REMEDY , 36

XT. STATUTORY DETERMINATIONS 39

XII. DOCUMENTATION OF NO SIGNIFICANT CHANGES 43

XIII. STATEROLE 43
Figures

1. Site Location Map

2. Site Plan

3. TI Zone

4. Restrictive Covenant

5. Designated Area, 1994, 1997, and 2002

6. TWA II

7. Site Plan with Cross Sections

8. Geologic Cross Section A - A'

9. Geologic Cross Section B - B'

10. Geologic Cross Section C - C'

11. Upland Marsh Study Area

12. Vertical Residual Oil Distribution A - A'

13. Vertical Residual Oil Distribution B - B'

J 4. Vertical Residual Oil Distribution C - C'

15. Inferred Bedrock Surface Elevation

16. Inferred Groundwater Flow

17. Conceptual Hydrogeologic Model prior to SCRA

18. Conceptual Hydrogeologic Model After SCRA

Tables

1. Comparison between 1989 ROD and 2002 ROD Amendment

2 PCB Results - TWA II

3. Chemical-Specific ARARs for Tl Waiver

4. Gallons of Oil Recovered From TWA II Area Wells

5. Summary of Groundwater Monitoring Results Modified Method 680

6. Chemical-specific ARARs

7. Location-specific ARARs

8. Action-specific ARARs

Appendices

Appendix A - Responsiveness Summary

Appendix B - Administrative Record Index

Appendix C - State Concurrence Letter

Appendix D - References Cited

in
F. O'CONNOR COMPANY SUPERFUND SITE

RECORD OF DECISION AMENDMENT

OPERABLE UNIT 2

September 2002

I. SITE NAME, LOCATION, DESCRIPTION AND RATIONALE FOR

AMENDMENT

SITE NAME: The F. O'Connor Company Superfund Site.

SITE LOCATION: The F. O'Connor Superfund Site is located in Augusta, Maine (Figure 1).

The twenty-three acre O'Connor site is located on Eastern Avenue/Route 17 in a predominately

rural neighborhood. The twenty-three acre site is located within a twenty-eight acre property

owned by Central Maine Power (CMP). The site is bordered by woodlands and a small poultry

farm to the north, U.S. Route 17 to the south, private properties and residences to the west, and

the west branch of Riggs Brook and its associated wetlands to the east. Public water has been

provided to surrounding residents, and is available for future development.

SITE DESCRIPTION: The site was the former location of transformer salvaging processes,

which included stripping and recycling transformers, some of which contained PCBcontaminated oil. The F. O'Connor Company operated from the early 1950s through the late

1970s. As a result of releases of polychlorinated biphenyls (PCBs), lead, chlorinated

polyaromatic hydrocarbons (cPAHs) and volatile organic compounds (VOCs) at the site, the site

was placed on the National Priorities List (NPL) in 1983. Principal features on the property prior

to remedial actions included an Upland Marsh, two surface water impoundments (Upper and

Lower Lagoons), three former outdoor transformer work areas (TWAs), and Riggs Brook (Figure

2). Upon completion of the source control remedial action for Operable Unit 1 (OU-1) the

lagoons were restored as wetlands and the area encompassing the three TWAs was covered with

clean fill, re-graded, and successfully vegetated.

In 1996, EPA separated the site into three operable units. As noted above, OU-1 addressed the

source control remedial action, OU-2 addresses management of migration, and OU-3 addresses

Riggs Brook sediment and biota.

RATIONALE FOR AMENDMENT: On September 27, 1989, EPA, with concurrence

from the Maine Department of Environmental Protection (Maine DEP) and in accordance with

the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), 42

USC §§ 9601 et seq., issued the Record of Decision (ROD) for the O'Connor site. The ROD

selected the remedial action for the site and established the target cleanup goals for soil,
sediments, surface water, and groundwater. Specifically, the ROD required the remediation of

two site components:

• The source areas that were the TWAs and surrounding soils, sediments, and surface water

in the two lagoons (later designated as OU-1); and

• Site groundwater that was contaminated with PCBs, benzene, and 1,4-dichlorobenzene,

(later designated as OU-2) and the Riggs Brook sediment and biota (later designated as

OU-3).

These two components, described separately in the 1989 ROD, were called the source control

(SC) component and the management of migration (MOM), respectively.

Based on an implementability assessment conducted as part of the remedial design studies in the

early 1990s, EPA wrote an Explanation of Significant Difference (ESD) in June 1994 to revise

the source control component of the selected remedy.

Under the ROD, the remedial action objective for the groundwater (OU-2) was to reduce

potential future public health risks from ingestion of PCB, benzene, and 1,4-dichlorobenzenecontaminated groundwater (ROD, page 17). This objective was to be achieved using a

groundwater extraction system and an above ground treatment system. In addition, institutional

controls were to be temporarily established to reduce the potential for exposure to contaminated

groundwater and were to remain in place until the groundwater remediation was completed

(ROD, page 45). The ROD further specified that one or more pump tests would be conducted as

part of remedial design so that an appropriate groundwater extraction system could be

constructed.

In 1992, pump tests were carried out as part of the remedial design. As a result of this effort,

separate phase oil was found in bedrock wells, a condition not previously seen at the site.

Consequently, MOM efforts focused on oil recovery rather than groundwater extraction and

treatment of dissolved contaminants. Three efforts at active oil recovery using vacuum-enhanced

pumping were carried out between 1996 and 2001. In April 2002, CMP submitted an evaluation

of the technical practicability of restoring the groundwater at the O'Connor site to drinking water

quality within a reasonable period of time. This evaluation concluded that because of the

geology and hydrology at the site, there were no technologies which could accomplish this

objective. EPA and Maine DEP agreed with the conclusion of this TI evaluation.

This ROD Amendment addresses changes to the MOM component of the original 1989 ROD,

following the conclusion of the source control remedial action (SCRA) for OU-1 and the TI

evaluation. Thfs"ROD amendment includes a TI waiver for overburden and bedrock

groundwater in a small portion of the twenty-three acre site (Figure 3). This ROD Amendment

also addresses minor changes/clarifications to the original 1989 remedy for OU-1, source control,

as modified by the 1994 ESD and 1995 invocation of the contingency alternative, and for OU-3,

Riggs Brook.
Institutional controls in the form of a Declaration of Restrictive Covenant (Restrictive Covenant)

have been implemented for the twenty-three acre she to provide additional risk reduction by

controlling exposure to site groundwater (Figure 4). The use of groundwater beneath the site is

prohibited without prior written approval by Maine DEP.

This ROD Amendment and the documents which form the basis for the Amendment are

available at the following information repositories:

EPA Records Center

1 Congress Street, Suite 1100

Boston, MA 02114-2023

(617)918-1459

Hours: 10 a.m.-noon

2 p.m.-5 p.m.

Lithgow Public Library

45 Winthrop Street

Augusta, Maine 04330-5542

(207)626-2415

Hours: Tues - Wed: noon to 8 p.m.

Thurs: 8 a.m. to noon

Fri: 10a.m. to 6 p.m.

Sat: 10 a.m. to 3 p.m.

Maine DEP

Ray Building

Hospital Street Augusta, Maine 04333

(207)287-2651

Hours: (by appointment)

Mon - Thurs: 8:30 a.m to 12:30 p.m.

12:30 p.m. to 4:30 p.m.

Friday: 8:30 a.m. to 12:30 p.m.

II. SITE HISTORY AND ENFORCEMENT ACTIVITIES

Details of the earlier site history and enforcement activities are presented in the 1989 ROD. The

following is an update to the site history and enforcement activities which have occurred since

issuance of the ROD.

In September 1989, EPA issued a ROD for the O'Connor site. The barn structure was to be
decontaminated, demolished, and then disposed of offsite at appropriate facilities, standing water

and sediments in the two lagoons were to be removed, soils contaminated with PCBs, PAHs, and

lead were to be excavated and treated using solvent extraction, contaminated groundwater was to

be pumped from the soils and bedrock, treated, and then discharged, and sediments and fish in

Riggs Brook were to be sampled for ten years.

Performance standards for soil and sediment were set at 1 ppm PCBs, I ppm cPAHs, and 248

ppm lead. Performance standards for groundwater were set at 0.5 ppb PCBs, 5 ppb benzene, and

27 ppb 1,4-dichlorobenzene. Performance standards for the standing water in the lagoons were

set at 0.065 ppb PCBs, 1.94 ppb lead, and 87 ppb aluminum. Performance standards for Riggs

Brook sediment and biota were set at 1 ppm PCBs and 2 ppm PCBs, respectively.

In September 1991, a Consent Decree between EPA and CMP was approved by the U.S. District

Court of Maine. With this Consent Decree, CMP agreed to perform and fund the remedy

selected in the 1989 ROD. One of the components of the remedy was institutional controls on

site groundwater. It was EPA's intent that those institutional controls would remain in effect

until remediation of the groundwater was complete.

The Consent Decree allowed for an evaluation of the solvent extraction technology selected for

the soils. Following this evaluation, EPA and Maine DEP agreed that this technology for the site

soils would not be able to attain the clean-up goals. As a result, in June 1994 EPA issued an

Explanation of Significant Differences (ESD) which modified the soil remedy. Soils containing

more than ten parts per million (ppm) PCBs or PAHs or 248 ppm lead would be treated using

solvent extraction technology, and soils containing between one to ten ppm PCBs or PAHs

would be consolidated into one area onsite and then covered with clean fill brought in from

offsite. This designated area is shown on Figure 4. In October 1995, EPA invoked the

contingency remedy set forth in the 1994 ESD. This ESD also included a contingency that

allowed for the offsite disposal of soil and sediment with greater than ten ppm PCBs and cPAHs

without first requiring on-site solvent extraction treatment.

At the same time as the ESD, a Declaration of Restrictive Covenant was executed between CMP

and Maine DEP. This Restrictive Covenant is currently in place.

On April 25, 1996, EPA agreed to delay completion of the MOM design, and to separate the

Riggs Brook component from the MOM as a third operable unit (OU-3). This was done so that

the sampling and analysis for Riggs Brook, the remedial action required by the ROD, could

begin prior to the completion of the MOM design. The SC component of the selected remedy

was designated as OU-1 and the MOM component was designated as OU-2

Phase I of the source control remedial action was completed in 1996. This included site

preparation, and the decontamination, demolition, and off-site disposal of the barn. Phase II

activities, including the off-site disposal of contaminated soil and sediment and the covering of

the designated area, were completed in 1997.
III. COMMUNITY PARTICIPATION

This ROD amendment meets the criteria for community involvement specified in Sections

300.43 5(c)(2)(ii)(A) through(H) of the NCP.

In June 2002 EPA published a Proposed Plan to amend the 1989 ROD. The Proposed Plan for

OU-2 called for institutional controls to prevent exposure to contaminated groundwater, active

recovery of separate phase oil as long as practicable, designation of a small portion of the site as

a TI zone where state and federal groundwater standards would be waived, long-term monitoring,

and five-year reviews. The amended cleanup plan was recommended because EPA believed it

offered the best balance among the nine criteria required to be reviewed under the NCP,

including the protection of human health and the environment and the reduction of contamination

through treatment. EPA held a public information meeting on June 24, 2002 and a formal public

hearing on July 9, 2002. The public comment period ran from June 19 to July 19, 2002. All

formal comments received on the June 2002 Proposed Plan are summarized and responded to in

the Responsiveness Summary, which is included as Appendix A of this ROD Amendment. In

addition, comments received during the public information meeting are summarized in the

Responsiveness Summary.

Pursuant to Section 300.825(c) of the NCP, EPA updated the Administrative Record in June

2002 to add the documents which EPA relied on to form the basis for the decision to modify the

response action for OU-2 at the O'Connor site. See Appendix B for the Administrative Index.

IV. SCOPE AND ROLE OF OPERABLE UNIT

The O'Connor site was divided into three operable units in 1996, seven years after the ROD was

signed. The three units are as noted above, source control OU-1, groundwater OU-2, and Riggs

Brook OU-3. Remedial action for OU-1 was completed in 1997 and EPA, with concurrence

from Maine DEP, signed off on this component with the approval of the September 1998 Source

Control Remedial Action report (Woodard & Curran, 1998) The limited action required for

Riggs Brook by the 1989 ROD continues to be carried out.

This ROD amendment pertains to OU-2, although as described below, aspects of OU-1 and OU3 were discussed during the development of the TI evaluation and it was mutually agreed by all

parties (EPA, Maine DEP, and CMP) to address these aspects at the time of this ROD

amendment.

For OU-1, the 1994 BSD established that a portion of the site would be used to consolidate soil

and sediment containing levels between one and ten ppm of PCBs and/or cPAHs. This

designated area would be covered with twelve inches of clean soil, and an operation and
maintenance plan would be developed to ensure the integrity of this component. As conceptually

presented in the BSD, the designated area was three to four acres bounded on five sides with

rounded turning points. As the actual excavation for the source control remedial action evolved,

the boundary of the designated area became a 25-sided polygon. As agreed among all parties,

this created a difficult situation for "anyone inspecting the site to know where the boundary was.

EPA has determined that the following changes to the designated area shall be incorporated into

this ROD Amendment: The designated area will be surveyed, the boundaries simplified to the

12-sided shape shown in Figure 4, and permanent markers placed at the turning points.

Operation and maintenance for OU-1 shall include the following changes.

• At five year intervals coincident with each Five Year Review, composite samples from

ten locations randomly selected from the SCRA grid nodes will be collected from four to

eight inches below the surface and analyzed for PCBs.

• It is not necessary to resample for PAKs based on the extensive data collected during

the SCRA.

In all other aspects, operation and maintenance shall remain as specified in the 1994 BSD.

Regarding OU-3, the 1989 ROD set a standard of 1 ppm PCBs and cPAHs in the Riggs Brook

sediments based in part on input from US Fish & Wildlife Service (USFWS). However, it was

agreed by all parties, including USFWS, that the negative short-term impacts to the wetlands

ecology outweighed the removal of sediments to that level. A trigger level of 5 ppm PCBs for

further action was therefore established As stated in the 1989 ROD, "if an increase in the

current PCB sediment levels occurs above the 5 ppm threshold and/or the fish tissue samples are

found to be greater than 2 ppm, then a more rigorous sampling effort of such contamination will

be conducted to determine the need for and/or extent of further remedial actions to be undertaken

within Riggs Brook, if any." (ROD, page 47) This in fact occurred in 1997 when soil and

sediment above 5 ppm PCBs were removed simultaneously with the ongoing SCRA, and again

in 1999 and 2000 when additional samples were collected. The most recent data (2001) showed

that 35 of 36 sample locations were below the 5 ppm trigger level, and the majority of the

samples were non-detect. Maine DEP requested that this ROD amendment restate that the target

cleanup goal for Riggs Brook sediment remains at 1 ppm PCBs and cPAHs.

The results from two biota sampling events (1997 and 2000), demonstrate that concentrations of

PCBs detected in biota have not exceeded the ROD target level of 2 ppm, and in fact have all

been below 1 ppm.

V. DESCRIPTION OF CHANGES TO THE 1989 ROD

1. DESCRIPTION OF 1989 REMEDY
The remedy selected by the 1989 ROD was developed to satisfy the following five remedial

action objectives (RAO):

•reduce public health and environmental risks from direct contact with contaminated

soils,

•reduce public health risks from inhalations of PCB vapors,

•reduce future health risks from ingestion of contaminated ground water found on the

site,

• reduce public health risks from ingestion of PCB-contaminated fish from Riggs Brook,

and

• reduce risks to aquatic and terrestrial wildlife from exposure to contaminated sediments.

The first two RAO were achieved with the completion of the source control remedial action in

1997. The soil clean-up began in 1996 with the cleaning, demolition, and off-site disposal of the

barn situated along Route 17, and other site preparation activities. The second phase of the soil

cleanup was completed in 1997. These activities included the collection and off-site disposal of

lagoon water, and the excavation and off-site disposal of nearly 20,000 tons of soil. An

additional 3000 to 4000 tons of soils with PCBs or PAHs concentrations between 1 and 10 ppm

were placed within the designated area onsite. This area was then covered with a minimum of

one foot of clean fill brought in from offsite. The entire site was then graded. Drainage patterns

and the on-site wetlands were restored. An additional 0.4 acre of wetlands was created in the

former lagoons as replacement for wetlands lost as a result of the clean-up activities.

Laboratory tests of samples collected from the bottom and perimeter of the excavation

demonstrated that the excavation had removed the contaminated soil to the performance

standards set in the 1994 BSD. Combined with the operation and maintenance of the soil cover

and monitoring points, the risk to public health from contact with the soil and inhalation of

vapors are addressed.

A more complete description of the source control activities can be found in the September 1998

SCRA report.

The last two RAO have been achieved through the monitoring of sediments, analysis offish

tissue for PCB accumulation, and the 1997 excavation of sediment in three separate locations

where concentrations exceeded the trigger level.

A more complete description of the wetlands restoration, hot spot excavations, and Riggs Brook

monitoring can be found in the Wetlands Construction Monitoring reports for 1997-2000 (The
The groundwater remedy selected in the 1989 ROD included pumping wells, a treatment system,

and a network of monitoring wells to track contamination levels. The intent was to pump and

then treat groundwater which contained dissolved PCBs and VOCs and thereby restore the

quality of the groundwater.

In 1992, a bedrock pump test was performed. During the test a separate phase oil layer up to

three and half feet thick was pulled into three bedrock wells in Transformer Work Area II (TWA

II - see Figure 2). This was the first time that separate phase oil had been detected in the

bedrock. As a result, additional monitoring wells were installed to determine how far the oil

extended. No additional oil was discovered and it was concluded that the extent of free oil in the

bedrock was limited.

The next stage of the groundwater remedy took place in 1996-97. About 28 gallons of PCBladen oil were pumped out of the shallow bedrock during this period. The pumping system was

shut down when oil was no longer recovered.

From 1997 to 2001, CMP continued to recover oil from wells by using absorbent materials to

remove any oil which accumulated in the wells. A little under seven gallons of PCB-laden oil

was recovered during this period from wells in TWA II.

A third effort at oil recovery took place from August to October 2001. Five wells in TWA II

were alternately pumped. Just under 20 gallons of PCB-laden oil were recovered. This pumping

effort was also shut down when oil was no longer pulled into the system.

2. CHANGES TO THE 1989 REMEDY

In April 2002, CMP submitted an evaluation of the technical practicability of restoring the

groundwater at the O'Connor site to drinking water quality within a reasonable period of time

This evaluation concluded that because of the geology and hydrology at the site, there were no

technologies which could accomplish this objective (the third RAO in the 1989 ROD). The

evaluation was resubmitted in June 2002 following EPA and Maine DEP comments. EPA, with

concurrence from Maine DEP, approved the June 2002 report.

This ROD amendment for OU-2 selects a remedy consisting of institutional controls, active oil

recovery, long-term monitoring of groundwater, and five-year reviews. This ROD amendment

recognizes the technical impracticability of achieving the third RAO (reduction of future health

risks from ingestion of contaminated groundwater found on the site) within a reasonable time

frame. It establishes a technical impracticability zone for a portion of the site where state and

federal drinking water standards are waived.

A comparison of the original 1989 remedy for groundwater and the modified remedy for OU-2 is

provided in Table 1.
VI. SUMMARY OF SITE CHARACTERISTICS

This section of the report provides a summary of the groundwater data at the site, starting from

the upgradient position at MW-101A/B, through the upland marsh area, the TI zone (TWA II and

VER), the area downgradient of the TI zone (MOM wells), and to the groundwater discharge

area represented by MW-106A/B. See figure 3 for monitoring well locations.

Groundwater cleanup standards established in the ROD include total PCBs at 0.5 //g/L, benzene

at 5 Aig/L and 1,4-dichlorobenzene at 27 /ug/L. In addition, based on the ARARs review

discussed in Section VIII. 1 of this ROD amendment, five other VOCs were identified which

since the 1989 ROD have had ARARs established and for which a.TI Waiver will apply. These

ARARs include Maximum Contaminants Levels (MCLs) and Maine Maximum Exposure

Guidelines (MEGs) for eight VOCs and PCBs. For each of these five compounds, the MEG is

either the same or lower than the respective MCL.

1. Upgradient Location

Monitoring wells MW-101A and MW-101B are upgradient of the TWAs, located near the

western boundary of the site in an upland area. These wells were installed during the RI to

provide an indication of regional water quality as groundwater flows easterly beneath the site

toward Riggs Brook. MW-101 A monitors groundwater in the overburden soil and MW-101B

monitors the bedrock groundwater. Annual sampling of these wells since 1996 has not detected

any PCBs or VOCs.

2. Upland Marsh Area

An investigation to determine the presence and extent of oil in the desiccated clay in the Upland

Marsh area was completed in 1998 and 1999. The intent of the investigation was to determine the

likely source of oil that accumulated in a wetland piezometer (UM-1) in the Upland Marsh and to

determine the distribution of any additional residual oil in that area. The investigation involved

completing 19 GeoProbe borings with continuous sampling (figure 11). The samples were

retrieved and logged with respect to the soil type and tested for oil. Based on the GeoProbe

borings, the soil stratigraphy and extent of residual oil was determined in the Upland Marsh.

The brown desiccated clay has a blocky fracture structure where oil resides in both vertical and

horizontal fractures. A slight to moderate oil sheen was found coming from discrete fractures in

the clay. All oil found resided as a residual coating on the clay fractures walls. The results of the

analysis indicated that PCBs in soils around and including the fractures were found to range from

non-detect (ND) to 1000 //g/kg (i.e. from ND to 1 ppm). The ROD target level for PCBs in the

overall mass of soil outside the Source Control Designated Area, specified during the source

control remedial action, is 1 ppm. Therefore, concentrations of PCBs found in these samples did

not exceed the target level.
The data collected suggest that the oil, which originated from TWA II during transformer

salvaging operations, ran off the land surface toward the Upland Marsh and infiltrated into the

upper brown desiccated clay during the time that the site was active. Unable to move downward,

both from the underlying soft clay and the lack of the entrance pressures necessary for an

immiscible liquid to overcome surface tension forces, the oil has remained relatively immobile in

the upper clay fractures. In the northern portion of the study area, where the desiccated clay is in

direct contact with the till, there is no evidence that suggests the oil has migrated along the

till/bedrock interface. It appears that the oil has migrated vertically downward into the clay

reaching an equilibrium between surface tension forces imposed by the clay fracture capillaries,

the density considerations of an immiscible liquid in a saturated medium and a unit infiltration

gradient. Very little horizontal movement has occurred at depth because the horizontal gradient

across the site is not great enough to overcome the resisting forces described above. It is

believed that the oil found in the area surrounding UM-1 is residual in nature and without a

significant gradient does not migrate.

3. TI Zone Wells

A. PCBs Data Evaluation

The groundwater from the five wells in the TWA II Area was not sampled in 1996 or 1997

because oil was found in these wells and it was agreed that the wells would not give

representative results of the dissolved concentrations. After 1997, the four groundwater

observation wells (OW-202B, OW-204B, OW-301B, and OW-302B) and the VER extraction

well (RW-101) were sampled quarterly for PCBs and the seven target VOC compounds if oil

was not detected in the wells. However, the results of TWA II well sampling indicated a wide

variation in contaminant concentrations. It was determined that this was due to the presence of

emulsified oil in the well water and associated VOCs in an oil emulsion which was not present

sufficiently to be measured by the interface probe, but was visually detected in the samples and

purge water. The samples taken were not representative of actual dissolved contaminants in the

groundwater.

Table 2 gives the results of PCB data collected from TWA II from 1998 to 2001. The results in

bold print are above the ROD cleanup goal for PCBs of 0.5 /zg/L and represent the impact of oil

emulsions in the samples, not dissolved PCBs in groundwater.

Table 2 indicates that two wells, OW-301B and OW-302B continually had PCBs detected at

greater concentrations than the ROD cleanup standard of 0.5 /zg/L. These are the same two wells

that had groundwater that regularly exceeded the VOC cleanup standards. Separate phase oil has

been observed in three other TWA II wells, OW-202B, OW-204B, and the VER extraction well,

RW-101, on an ongoing basis since September 1998.

PCBs were detected at 8,900 /zg/L at OW-302B in December 1998. In April 2001, the

concentration of PCBs at OW-302B was 44 pg/L. The PCB results at OW-302B have ranged

10
from 2.5 to 8,900//g/L. Separate phase oil has also been observed in this well over time. In

November 2001, 1.25 feet of oil was measured. The increased thickness of oil in OW-302B in

November 2001 is most likely the result of the operation of the VER system (Phase III) in

September 2001 and extremely low water table elevation. The observed oil is likely responsible

for the PCB concentrations detected at OW-302B.

The historic PCB results report can be found in the June 2002 Technical Impracticability

Evaluation Report, Appendix C.

B. VOC Data Evaluation

The ROD cleanup goals are 5 //g/L for benzene and 27 ^g/L for 1,4-dichlorobenzene.

Additional ARARs for which a TI waiver will apply are listed in Table 3.

Benzene concentrations from the groundwater in TWA II wells ranged from 0 to 8.0 //g/L

between 1998 and 2001. Benzene concentrations from OW-302B were regularly (6/98, 9/98,

12/98, and 6/99) detected at 6.0 //g/L, which is 1 ^g/L over the MCL/MEG. The last sampling

event at this well detected benzene at 8.0 ftgfL in April 2001. No other TWA II wells exhibited

an exceedance of the benzene MCL/MEG.

The Maine MEG for 1, 4-dichlorobenzene (27 //g/L) was regularly exceeded at both OW-301B

and OW-302B between 1998 and 2001. The 1,4-dichlorobenzene results at these two wells

ranged from 89-720 //g/L. Several other target VOCs were also detected in OW-301B and OW302B. The two TWA II wells with the exceedance for VOCs are located close together in the

center of TWA II. These two wells are located immediately adjacent to well OW-202B, which

was used for the 1992 pumping test and is responsible for drawing oil into the bedrock aquifer.

1,4-dichlorobenzene was also detected in low concentrations (below the MEG) in observation

wells OW-204B (up to 0.7 //g/L), OW-202B (up to 20 //g/L) and the VER well RW-101 (up to

B/.g/L).

The TI evaluation of ARARs identified MCLs/MEGs for five other VOCs which have been

detected in the groundwater. In addition, another VOC, 1,2,3-trichlorobenzene, has been

detected but does not have either an MCL or MEG. Three of these VOCs, chlorobenzene, 1,2-

dichlorobenzene, and 1,2,4-trichlorobenzene, were detected in the RI sampling. Five of these

other VOCs were detected in the TWA II wells between 1998 and 2001. Concentrations of

chlorobenzene ranged from 4 to 240 //g/L at OW-301B and OW-302B, exceeding the Maine

MEG of 47 /zg/L. 1,2-Dichlorobenzene and 1,3-Dichlorobenzene (ME MEG of 85 //g/L) were

detected at OW-301B and OW-302B at concentrations ranging from 3-210 //g/L and 2-160 //g/L,

respectively. These compounds were detected at relatively low concentrations at the other TWA

II wells.

Concentrations of 1,2,4-trichlorobenzene have been detected above the Maine MEG of 70 A*g/L

at OW-202B and OW-301B at concentrations ranging from 3-610 Mg/L, and ranging as high as

11
3200 ^g/L at OW-302B.

The historic VOC results are included in the June 2002 Technical Impracticability Evaluation

Report, Appendix D.

C. VER Operation

The vacuum-enhanced recovery system (VER) has been operated for three periods of time

following post-ROD pilot tests. The total amount of oil recovered from the five TWA II wells

since their installation is approximately 85.2 gallons. A summary of oil recovered from the

TWA II wells is presented in Table 4.

Five wells (OW-202B, OW-204B, OW-301B, OW-302B and RW-101) in the former TWA II

Area and piezometer UM-1 have been monitored for groundwater elevation and oil thickness on

a monthly basis since 1998. Whenever oil was detected in a well, an absorbent sock was lowered

into the well to adsorb and remove the oil. Since the last oil recovery effort in the fall 2001, 1 .25

feet of oil accumulated in OW-302B and was removed using absorbent socks.

4. Management of Migration

A. PCB Data Evaluation

Included in this section is a discussion of those wells which are located in the area downgradient

of the TI zone. Aside from a few initial sampling events (prior to 1994) where elevated

concentrations of PCBs may have resulted from PCB adsorption onto soil particles in the

groundwater samples, concentrations of PCBs in groundwater samples collected from wells

outside of the TWA II Area have not exceeded the 1989 ROD target cleanup level for PCBs (0.5

In March 1999, the groundwater samples from six MOM monitoring wells were analyzed using

USEPA Modified Method 680 for total homologue PCBs. The results of the 680 analyses are

summarized in Table 5. Concentrations of PCBs were below the ROD target cleanup level. As

stated in Section VIII. 1 ., current ARARs have been reviewed and concentrations of PCBs at

several wells are at or slightly above the 1 992 Maine MEG of 0.05 /^g/L. Future analysis of

groundwater from MOM wells will be done using a lower detection limit, to determine if

groundwater outside the TI Zone (see Figure 3) meets the 1992 Maine MEG of 0.05 Mg/L.

B. VOC Data Evaluation

This section will discuss the VOC results compared to federal MCLs and Maine MEGs (see

Figure 2 for well locations).

The VOC results from MW-104B and OW-201B indicate the presence of low to moderate levels

12
of VOCs in the bedrock at these locations. The MEG for 1,4-dichlorobenzene (27 //g/L) has

been exceeded at both wells. Prior to June 1998, the concentration of 1,4-dichlorobenzene

ranged from 26-91 /zg/L in MW-104B and 25-55 /zg/L in MW-201B. Since then, the

concentration of 1,4-dichlorobenzene has been consistently between 20-40 //g/L in MW-104B

and 20-36 //g/L in MW-201B. These are reductions and if these decreasing trends continue, the

concentrations of 1,4-dichlorobenzene at OW-201B and MW-104B are expected to be

consistently below the MEG in the near future.

For the VOCs with post-ROD MCLs/MEGs, 1,2-dichlorobenzene exceeded the MEG of 85 //g/1

at these wells prior to 1997, but has been below the MEG since, and 1,3-dichlorobenzene has not

exceeded its MEG of 85//g/L. Concentrations of benzene, chlorobenzene, 1,2,3 -

trichlorobenzene and 1,2,4-trichlorobenzene have been very low to moderate and have not

exceeded MEGs at MW-104B and OW-201B, except for 1,2,4-trichlorobenzene prior to 1995.

Results of analysis of groundwater from monitoring wells MW-507A and MW-508B, placed in

the bedrock trough, indicate the presence of five VOCs in MW-507A and four VOCs in MW508B. The relative VOC concentrations are generally higher in the shallow groundwater

monitored by MW-507A. Monitoring well MW-507A is located in a bedrock trough and

screened in the till/bedrock surface specifically to monitor VOC concentrations in the primary

migration pathway where contaminated groundwater from the former TWA source areas flows

slowly in a southeasterly direction. Monitoring well MW-508B was installed into the bedrock to

monitor VOC concentrations in the secondary bedrock migration pathway. The concentrations

of 1,4-dichlorobenzene in MW-507A ranged from ND-81 //g/L in the past five years.

The concentrations of 1,4-dichlorobenzene at MW-503, downgradient of MW-507A, are much

lower (ND-8 /^g/L) than at MW-507A. The same decrease in concentrations was observed for

1,2-dichlorobenzene and 1,3-dichlorobenzene. This reduction in VOC concentrations between

MW-507A and MW-502/MW-503 indicates that very little contaminant mass is flowing past the

bedrock trough area. Concentrations of benzene, chlorobenzene, 1,2,3-trichlorobenzene and

1,2,4-trichlorobenzene were detected at low concentrations in all four wells MW-507A, MW508B, MW-502 and MW-503.

In addition, concentrations of VOCs at MW-501 (downgradient of TWA III) and MW-511A

(downgradient of TWA I) have been non detect to trace levels.

Based on this evaluation of VOC data, wells alopg the boundary of the TI zone are in attainment

of federal MCLs and Maine MEGs (MW.501, MW-502, MW-503 and MW-51 OA). These

decreasing trends in VOC concentrations are likely due to the successful completion of the

SCRA and removal of residual oil with the VER system, and are expected to continue.

C. Discharge Zone, MW-106A/B

Concentrations of PCBs in groundwater samples collected from MW-106A/B have not exceeded

13
the ROD target cleanup level for PCBs (0.5

The VOC concentrations from the groundwater in MW-106A and MW-106B have been

relatively consistent over the past six years. MW-106A monitors the overburden aquifer at this

location and flows under low artesian conditions during periods of high groundwater. Nondetect to trace concentrations of the seven VOCs have been detected. The deeper well (MW106B), flows under artesian conditions most of the year, and is believed to be intercepting a

portion of the bedrock groundwater migrating from the site and represents the bedrock water

quality. Low levels of six VOC compounds are regularly detected at MW-106B. The

concentrations of 1,2,3-Trichlorobenzene and 1,2,4-Trichlorobenzene have generally been

decreasing at MW-106B since March 1997 and March 1995, respectively, with more significant

decreases in 2000 and 2001.

The 1,2,4-trichlorobenzene concentrations are well below the MCL and 1992 MEG of 70 yUg/L.

(There is no MCL or MEG for 1,2,3-trichlorobenzene. However, it can be generally assumed

that its risk factors would be similar to 1,2,4-trichlorobenzene, and the detected concentrations of

1,2,3-trichlorobenzene are also well below 70 //g/L.)

Historic PCBs and VOCs results of the MOM monitoring conducted between October 1995 and

September 2001 and prior analytical results are included in the June 2002 Technical

Impracticability Evaluation report, Appendices G and H.

VII. SUMMARY OF SITE RISKS

Human health and environmental risk assessments were conducted as part of the Feasibility

Study leading up to the 1989 Record of Decision. These assessments identified seven exposure

scenarios as posing current and potential future risks to human health or the environment. (ROD.

page 13) Of these seven, five were associated with the soils and lagoon sediments, one with

ingestion offish from Riggs Brook, and one with ingestion of groundwater from the bedrock:

• direct contact with soils by children;

• inhalation of vapors from surface soils,

• ingestion offish caught in Riggs Brook,

• future direct contact with soils by on-site inhabitants

• future direct contact with sediments in the lower lagoon by children, and

• future inhalation of vapors by on-site inhabitants; and,

• future ingestion of groundwater from within the bedrock.

14
Following the completion of the SCRA, only two potential exposure scenarios remain. They are

future ingestion of groundwater from within the bedrock, and ingestion offish caught in Riggs

Brook.

A site-wide five-year review was performed in 2002 for all three operable units. The exposure

assumptions, toxicity data, and cleanup levels for groundwater were evaluated as part of the

overall protectiveness determination. The review did not identify any changes in the exposure

assumptions, found the toxicity data have had only minimal changes (some slightly increasing,

others decreasing) and concluded that there had been no significant change in site risks. (EPA,

2002) Since the 1989 ROD, the State of Maine has promulgated by reference the 1992 MEGs.

The 1992 MEG for PCBs is 0.05 ppb, an order of magnitude lower than the MCL of 0.5 ppb,

which is the ROD standard. Except for the immediate area surrounding and including TWA II,

PCB concentrations in the groundwater were close to this standard (0.02 to 0.09 ppb in the one

sampling event where a lower detection limit was reached). The Restrictive Covenant currently

ensures that there will be no exposure to the groundwater beneath the site.

VIII. TECHNICAL IMPRACTICABILITY DETERMINATION

The continued presence of separate phase PCB-laden oil four years after the successful

completion of the source control remedial action suggested restoration of the groundwater using

the VER or a groundwater extraction and treatment system is not possible. Consequently, EPA,

with concurrence from Maine DEP, agreed to a proposal by CMP to evaluate whether it would

be technically practicable to restore contaminated groundwater to drinking water standards,

including MCLs and MEGs.

Restoration of contaminated grouudwater is one of the primary objectives of the Superfund

program. The NCP states that "EPA expects to return usable ground waters to their beneficial

uses wherever practicable, within a time frame that is reasonable given the particular

circumstances of the site." Section 300.430(a)(l)(iii)(F) of the NCP. Generally, restoration

cleanup levels in the Superfund program are established by applicable or relevant and appropriate

requirements (ARARs), such as the use of federal or state standards for drinking water quality.

Further, under CERCLA, an alternative selected to address contamination at a site must achieve

the ARARs identified for the action, or provide the basis for waiving the ARARs. ARARs may

be waived for any of six reasons, including where compliance with the requirement is technically

impracticable from an engineering perspective. See Section 121(d)(4) of CERCLA and Section

300.430(f)(l)(ii)(C) of the NCP. The primary considerations for determining the technical

impracticability (TI) of achieving ARARs are engineering feasibility and reliability. See NCP

Preamble, 55 Fed. Reg. 8748 (March 8, 1990).

EPA's Guidance for Evaluating the Technical Impracticability of Ground-Water Restoration.

(OSWER Dir. 9234.2-25, September 1993, Interim Final) specifies the following components as

necessary for a TI evaluation:

15
1. Specific ARARs or media standard for which TI determinations are sought,

2. Spatial area over which the TI decision will apply;

3. Conceptual model that describes site geology, hydrogeology, groundwater contamination

sources, fate and transport;

4. An evaluation of the restoration potential, including predictive analyses of the timeframes

to attain required cleanup levels and a demonstration that no other remedial technologies

could be capable of achieving groundwater restoration; and

5. Cost estimates of the proposed remedy options.

Following a TI evaluation, EPA's goal of restoring contaminated groundwater within a

reasonable time frame will be modified where restoration is found to be technically

impracticable. In such cases, EPA will select an alternative remedial strategy that is technically

practicable, protective of human health and the environment, and satisfies the requirements of

CERCLA and the NCP. Where groundwater ARARs are waived at a Superfund site due to

technical impracticability, EPA's general expectations are to prevent further migration of the

contaminated groundwater plume, prevent exposure to the contaminated groundwater, and

evaluate further risk reduction measures as appropriate. See Section 300.430(a)(l)(iii)(F) of the

NCP. These expectations should be evaluated along with the nine remedy selection criteria

provided in the NCP.

The results of the TI Evaluation for O'Connor are provided below.

1. ARARs

Under the EPA Groundwater Protection Strategy, EPA has classified the aquifer beneath the site

as a Class II aquifer, i.e., groundwater which potentially could be a source for drinking water in

the future. Thus, Maximum Contaminant Levels (MCLs), and non-zero Maximum Contaminant

Level Goals (MCLGs), established under the Safe Drinking water Act, are ARARs.

The state Maximum Exposure Guidelines (MEGs) are chemical-specific ARARs that are healthbased guidelines intended to determine drinking water quality for private residential wells.

MEGs are relevant and appropriate requirements in establishing groundwater remediation goals

The MCLs and MEGs for which a technical impracticability waiver will apply are as follows:

16
Table 3: Chemical-Specific ARARs for TI Waiver

I! contaminant

II Of Concern

II Benzene

1,4-

2001 Maxunum

Groundwater

Concentration

(//g/L) and Location

8 - OW-302B

720 - OW-302B

MUL

5

75

MEG

5

27

iy»y KULJ target ||

Cleanup Levels

(Mg/L)

2

5

7

Dichlorobenzene

PCBs1

44 - OW-302B 0.5 0.05 0.5

Chlorobenzene

1,2-

Dichlorobenzene

1,3-

Dichlorobenzene

1,2,3-

Trichlorobenzene

1,2,4-

Trichlorobenzene

1,3,5-

Trichlorobenzene

240 - OW-302B

210-OW-302B

160 - OW-302B

98 -OW-302B

770 - OW-302B

not analyzed for

100

600

NS

NS

70

NS

47

85

85

NS

70

40

no ROD standard 1

no ROD standard

no ROD standard

no ROD standard

no ROD standard

no ROD standard

II

1

 detection limit varies with location and are generally greater than the 1992 MEG.

NS - no standard

2. Spatial Extent of the Technical Impracticability Zone

This section describes the horizontal and vertical extent over which the Technical

Impracticability decision would apply (TI Zone). This includes the portion of groundwater

known to contain VOCs above federal MCLs and State MEGs that would require substantial

timeframes to remediate using currently available technologies.

The proposed TI Zone horizontally encompasses the TWA II Area and the area associated with

shallow groundwater flow to the south of the TWA II Area. Vertically, the proposed TI Zone

extends into bedrock. The TI Zone, as shown in Figure 3, includes areas where VOCs and PCBs

are present in groundwater at concentrations above ROD target cleanup goals and current MCLs

and MEGs. This is principally the TWA-II area. Overall, analytical results from monitoring

wells MW-501, MW-502, MW-503, MW-505, MW-509A, MW-510A, and MW-511A located

along the boundary of the TI Zone, show that concentrations of the seven VOCs and PCBs

detected during semi-annual groundwater monitoring events are below ROD target cleanup goals

and current MCLs and MEGs.

17
In review of the TI evaluation report, Maine DEP noted that the TI zone included most of the

former upper lagoon. EPA recognizes, just as the boundary of the Designated Area is being

simplified in this ROD Amendment so that it may be easily identified, the TI zone has also been

established in part to allow for its easy identification while onsite. Consequently, while the

upper lagoon was successfully remediated during the SCRA, a portion of it falls within the TI

zone as a result of simplifying the TI boundary.

3. Conceptual Model

The conceptual model serves as a foundation for evaluating the restoration potential of the site

and, thereby assessing the technical impracticability as well. It includes the site geology and

hydrogeology, nature and extent of Contaminants of Concern in groundwater, fate and transport

processes, and current or potential receptors. This conceptual model has been developed through

review of reports of previous investigations and the visual inspection of subsurface materials

during source control work. The SCRA involved the excavation of a significant portion of the

site's overburden, and, in some places, exposure of the bedrock surface.

This summary of the conceptual model was presented in the June 2002 Technical

Impracticability Evaluation report.

A. Site Geology and Hydrogeology

A summary of the geology and hydrogeology for the overburden and bedrock at the site is

provided below.

1. Overburden Geology

Soil materials on the site include glacial marine silts and clays and glacial till overlying bedrock.

The upper clay unit has two stratigraphic members: an upper, stiff, desiccated brown member

and a lower, soft, gray member. The upper brown member which typically makes up the upper

10 to 20 feet of the clay unit, is blocky and highly fractured. The lower gray member is absent or

discontinuous in the upland areas, where total overburden thickness thins to less than 20 feet.

The clay tends to be absent only in areas of shallow bedrock.

The till is discontinuous, varying in thickness from 0 to approximately 42 feet (B-503). The till

ranges from a coarse granular material overlying the shallow bedrock in the northern and western

portions of the site, to thick, dense, fine-grained soils overlying the deeper bedrock in the central

and eastern portions of the site. In the TWA II Area, the till is approximately 0 to 9 feet thick.

The till is essentially absent along the axis of the bedrock ridge from the central to the northern

portion of the site. The changes in the observed textures of till are inferred to result from

weathering.

Figure 7 shows the location of three geologic cross sections across the site. Figure 8, Figure 9,

and Figure 10 are the geologic cross sections showing the inferred soil stratigraphy and bedrock

18
morphology. The stratigraphic elevations have been inferred from the borings represented on the

profiles. The inferred geologic stratigraphy is the result of the MOM Additional Investigations

Report (W&C 1996a) and existing borings on the site prior to 1996.

The till/bedrock interface is the primary migration pathway of contaminants. The results from

several wells, including B-506, B-510, B-514, and MW-504, indicate a relatively highly

conductive water-bearing zone along the till/bedrock interface. In each of these borings, very

little water was observed during the drilling process until the drill bit penetrated the lower 2 to 3

feet of the till immediately above the bedrock surface. The potentiometric surface in each of

these borings was several feet higher than the permeable zone, indicating a confined condition.

The permeable zone associated with the til^edrock interface could be the result of an erosional

water-worked environment in the initial stages of till deposition.

The soil stratigraphy in the Upland Marsh area and TWA II Area was further refined during an

Upland Marsh investigation conducted to identify the presence and distribution of oil detected in

an Upland Marsh piezometer UM-1. This study helped refine the hydrogeology in the TWA II

Area and the hydrogeologic interaction of the desiccated clay with the till/bedrock migration

pathway.

The stratigraphy of the soil material in the Upland Marsh area consists of approximately 4 to 10

feet of desiccated brown clay overlying approximately 1.5 to 7 feet of soft, unfractured gray clay

that overlies 2 to 4 feet of till directly in contact with bedrock. These different layers pinch out

in areas of shallow bedrock (GeoProbe boring G-14). Groundwater is confined in the till and

predominately moves along the till/bedrock interface. Surface water infiltrates into the fractures

in the brown clay and is quasi-perched on top of the soft clay, making itself available for

evapotranspiration. Based on historic Water elevation data, the quasi-perched water table in the

brown clay fluctuates as much as 6 to 8 feet during the year. Figure 11 shows a plan view of the

site with the GeoProbe locations and the location of three cross section lines. Figure 12, Figure

13, and Figure 14 are the geologic cross sections through the Upland Marsh area depicting the

stratigraphy, original ground surface prior to source control, and the existing ground surface after

source control.

In general, the thickest portions of the desiccated clay were in the Upland Marsh area where the

site topography flattens (G-8, G-9). The stratigraphy remains relatively consistent except in the

northern portion of the study area (probes G-12, G-13, G-14, G-l 5, and G-16) where the bedrock

surface rises and the soft clay pinches out. See Figure 13 and Figure 14. In this area the

desiccated clay is in contact with the till.

2. Bedrock Geology

The shallow and deep bedrock flow system at the site was studied in several pre- and post-ROD

investigations. The 1996 field study investigated the bedrock surface in an effort to understand

the potential migration pathway along the top of the bedrock. The inferred bedrock surface

elevation is depicted in Figure 15. The bedrock surface morphology can also be viewed on the

19
geologic profiles on Figures 8-10 and Figures 12-14. The bedrock surface was verified during

source control work, in locations where soil was excavated down to the bedrock surface.

The bedrock surface consists of a hard, minimally weathered quartz monzonite. Drilling logs

from former investigations indicate metasedimentary bedrock interspersed with the quartz

monzonite on the eastern portion of the site (MW-406B) suggesting a contact between the

intruded monsonite and the surrounding metasedimentary rock.

The bedrock structural features were evaluated both locally and regionally in the

Photogrammetric Analysis and Outcrop Study (E. C. Jordan, 1986). This evaluation utilized

photogrammetric analysis including the examination of aerial photographs and radar imagery.

Additionally, five bedrock outcrops were examined in the vicinity of the site. This study

included information regarding the existence and orientation of bedrock fractures present in the

crystalline rocks in the area. Results of this study determined that the regional structural

orientation is in a northeast-southwest orientation. Three prominent NE/SW lineaments were

identified in the vicinity of the site hi the E. C. Jordan study. The study also determined that the

most common strike orientation was NE/SW.

The Inferred Bedrock Surface map provided in Figure 15 shows that the bedrock ridge is oriented

generally on a northeast-southwest axis coincident with the previously identified regional

structural orientation. The bedrock ridge is a natural feature that has been scarred and rounded

by the last glacial advance and retreat. It is a quartz monzonite and as such has no bedding or

structural folding orientation. The major structural trends outlined in the E.G. Jordan study refer

to a NE/SW structural orientation associated with regional tectonic compression history of the

•coast of Maine (refer to the bedrock geologic map of Maine). The monzonite intrusive is part of

the Devonian intrusives which intruded the country rock of the region and is generally elongated

parallel to bedding strike of the country rock. This may have had influence on the cooling

history and post placement fracturing of the monzonite, but is believed to have no direct

influence on fracturing of the intrusive body and thus no influence on groundwater movement.

Conclusions of the 1986 E.G. Jordan Study are as follows:

• regional and local strike orientation is northeast/southwest;

• exfoliation type of near-horizontal fracture surfaces are uniform and widespread

throughout the area,

• "fractures will have the most significant impact on groundwater flow patterns within the

rock mass";

• groundwater flow from the site is expected to be generally coincident with topography,

and

• the potential exists for a northeast-southwest flow barrier or groundwater sink in the

vicinity of Riggs Brook.

20
The bedrock drilling in all investigations indicated mostly competent rock with very few

recognizable fractures. The rate of bedrock drilling was unusually slow. Occasionally, at

random depths below the bedrock surface, the downhole drilling equipment would advance

rapidly for 0.2 to 0.4 feet, indicating the existence of a weak weathered layer or fracture in the

bedrock. After encountering a weak layer in the bedrock or a bedrock fracture, an increase in the

available formation water would be observed, indicating the presence of groundwater in the

fractures in the upper bedrock. During source control work where the bedrock surface was

exposed during soil removal, the bedrock appeared very competent. Very few fractures appeared

to be exposed along the bedrock surface and none appeared to be able to supply any significant

amount of recharge to the bedrock flow system. Bedrock outcrops are found in the area of TWA

II and to the south in the vicinity of TWA I (refer to Figure 2).

Generally, the bedrock forms a saddle, with the center of the saddle immediately northeast of the

upper lagoon (Figure 2). The center of the saddle forms a trough filled with till and the overlying

marine clay. Figure 7 contains geologic cross sections depicting the bedrock trough in the center

of the saddle. Figure 9 is a cross section along the center of the saddle and Figure 10 shows the

bedrock ridge to the northeast of the center of the saddle. The till is absent along the top ridge

and marine clay is in direct contact with bedrock.

The limited fracture network of the bedrock flow system and limited available recharge from the

overburden limits flow in the bedrock aquifer. Recharge to the bedrock from the overburden is

limited by the low permeability overburden soils and lack of shallow groundwater in the

overburden. Because the bedrock is tight, limited flow moves through the bedrock system.

3. Groundwater Flow in the Overburden and Bedrock Flow System

The principal groundwater migration pathway on the site is a discrete zone within the till along

the top of the bedrock surface. The groundwater flow direction is a subdued reflection of the

bedrock surface. Figure 16 shows the inferred groundwater flow direction superimposed on the

bedrock surface map. Groundwater flow from the large recharge basin (Upland Marsh) to the

northwest of the source control area is confined and channeled through the bedrock trough in the

center of the bedrock saddle. The reworked till along the bedrock surface is the primary

migration pathway leaving the source area. The bedrock ridge where the till is absent (refer to

Figure 10) inhibits movement of the shallow groundwater flow from the source control area to

the southeast toward Riggs Brook. The upper till and clay tend to confine the groundwater, not

allowing flow over the bedrock ridge as depicted in Figure 16, and forcing flow through the

bedrock trough. On the northwest side of the ridge and within the bedrock trough, groundwater

under pressure was observed during the drilling of borings B-5I4, MW-504, B-510, and B-506.

On the southeast side of the ridge, i.e., B-515, B-509, MW-501, B-508, and B-504 (Figure 16),

very little groundwater was observed and the groundwater was very slow to recharge the wells.

Under steady-state conditions, groundwater in this area was less than 1 -2 feet above the bedrock

surface.

Conceptually, precipitation recharges the fractured clay, till, and bedrock (where exposed at the

21
surface), and flows within the shallow groundwater flow regime. Under static, non-stressed

conditions, there is very little vertical mixing between the overburden and bedrock groundwater

in the immediate area surrounding the transformer work areas. Although a downward vertical

gradient exists, the relatively low vertical permeability of the bedrock inhibits vertical migration.

Groundwater recharge to the fill soils used to re-grade the site following the SCRA does not

change the overall groundwater flow patterns.

The bedrock ridge inhibits the southeasterly flow of shallow groundwater. The only water

available to flow on the southeast side of the ridge comes from recharge through the clay surface

soils and groundwater discharging from the bedrock. Both sources of recharge to the til^edrock

migration pathway southeast of the bedrock ridge are very limited, leaving somewhat dry

conditions within this migration pathway. The contaminant distribution along the till/bedrock

interface and the recharge of the monitoring wells in this area, as described above, supports this

understanding. Long-term monitoring of shallow overburden monitoring wells, MW-501 and

MW-502, indicates very little overburden groundwater in this area of the site.

The bedrock flow regime has very little water in storage. The exfoliated fracture network is farreaching and derives its recharge from the upland areas surrounding the TWAs. The vertical

permeability of the bedrock is believed to be very low, creating the "quasi" perched condition of

the shallow overburden groundwater flow system. Over most of the site, the bedrock

groundwater is under a confined condition. In the southeastern end of the site the potentiometric

surface of the bedrock groundwater is above the ground surface. MW-106B is in the

southeastern portion of the site and is a free-flowing artesian well. As an artesian well, it creates

a pressure release, and provides a condition for contaminants that have entered the bedrock flow

regime to discharge to the ground surface.

The overburden groundwater is "quasi" perched; releasing groundwater from storage to supply

recharge to the bedrock fractures where possible. The horizontal permeability in the upper

bedrock zone is higher than the vertical permeability. This is evident when comparing the

potentiometric surface of the bedrock and overburden. Groundwater elevation data including

potentiometric surface maps and time series plots at four well pairs are provided in the June 2002

Technical Impracticability Evaluation report. Although most of the bedrock wells are open holes

(i.e., no screened zones set) the well couples (i.e., MW-103 A, B) are separated by a casing

advanced into rock. Typically, the overburden wells are set on top of the bedrock surface while

the bedrock wells are open holes with grouted casing approximately five feet or less into the

bedrock surface. Historically, the difference in groundwater potentials across this relatively short

distance has been on the order of 1 to 2 feet. This downward gradient in the source control area

is likely due to the low vertical permeability of the bedrock and supports the "quasi" perched

understanding of the vertical groundwater flow from the overburden into the bedrock.

The vertical gradient is downward over most of the site. The vertical gradient is downward at

well pair MW-507A/MW-508B. Prior to the abandonment of well pairs MW-102A/B, MW105A/B and MW-401A/B for Source Control, these wells exhibited downward vertical gradients.

22
The vertical gradient is upward at the location of wdl pair MW-106A/B. This well pair is

located adjacent to Riggs Brook and monitors the confined bedrock flow system downgradient

from the site. Bedrock at this location drops considerably in elevation and is confined by

approximately 50 feet of clay soils confining the upland flow from the site to Riggs Brook.

The horizontal gradients have been calculated for both the overburden aquifer and the bedrock

aquifer. The gradients are similar in both aquifers. In the upland portions of the site, the

horizontal gradients are approximately 0.01 and 0.024 on the overburden and bedrock aquifers,

respectively. In the steeper area between the Upper Lagoon and the Lower Lagoon, the

horizontal gradients are approximately 0.09 and 0.06 in the overburden and bedrock aquifers,

respectively.

During the 1992 pumping test, the bedrock observation wells (MW-103B, MW-104B, MW105B, OW-201B, OW-204B, OW-301B, and OW-302B) responded relatively quickly and, with

time, significant drawdown was observed in bedrock wells as far away as MW-105B. This

indicates that groundwater in storage moved quickly to the pumping well and that recharge

(vertical) from the overburden into the bedrock was slow. Because groundwater was taken from

storage within the bedrock and was vertically inhibited from recharging the bedrock from the

overburden, recharge to the pumping well came predominately from the more regional network

of bedrock fractures. Significant drawdown was observed long distances from the pumping well.

The rapid response observed in the bedrock observation wells during pumping and the extent of

drawdown within the bedrock supports the conceptual understanding that the bedrock has a farreaching, interconnected fracture network with a very low density of fractures and thus, a

relatively slow vertical permeability and very little storage.

The large variability in hydraulic properties of the bedrock lends to the conceptual understanding

that the fracture network, although loosely connected, in the bedrock is comprised of very fine

micro fractures that do not yield much water and larger fractures that may yield as much as 1 -2

gpm. The bedrock is relatively tight on a site-wide basis, as observed by the perched water table,

visual observations during source control, and bedrock RQD analysis done during the RI.

The bedrock in the lower elevations (near well MW-106B) is confined, and all flow leaving the

site through the bedrock flow system is confined to flow from the site toward Riggs Brook

flowage, then parallel to the Riggs Brook flowage, and eventually discharging to the Kennebec

River Basin. Because of the confined nature of the bedrock system, associated low gradients

across the site, and the low hydraulic conductivities of the bedrock, very little water flows

naturally through the system.

Well MW-106B intersected a deeper fracture that is relatively well connected to the bedrock

fracture network flowing from the site. When well MW-106B was drilled, initial concentrations

of site contaminants at this location were non-detect. Because of the confined conditions and the

fact that well MW-106B was allowed to flow continuously, bedrock flow was short circuited

increasing the gradient from the site and flushing the bedrock flow system toward MW-106B and

eventually up and out of the flow system through this well. As is shown by the chemical data

23
from MW-106B, site contaminants increased after the 1992 pump test, when oil was drawn down

into the bedrock. Contaminant concentrations measured at MW-106B, however, never exceeded

ROD cleanup goals. Since then, with groundwater flow under steady state conditions, the

chemical data has shown a steady and consistent decreasing trend. MW-106B has provided a

release of a portion of the bedrock flow system to the ground surface rather than flowing off the

site.

Conceptual depictions of the site hydrogeology before and after source control are presented in

figures 17 and 18.

B. Source of Contamination

An assessment of the groundwater collected from the monitoring wells installed during the RI

indicated the presence of low levels of chlorinated benzenes in monitoring wells downgradient of

TWA II and the Upper Lagoon area (MW-104 and MW-103). PCBs were only detected in

samples collected from MW-104B. From subsequent investigations, it was found that the PCBs

in this well were not in the groundwater but were adsorbed to the soil particles purged from the

well during sampling. The PCBs associated with these particles were the result of drilling

through PCB-contaminated surficial soils. Well MW-104B has only one foot of casing set into

rock. Surficial sediments can easily migrate into the boring during well purging. Metals

detected in on-site wells were generally comparable in concentration to upgradient monitoring

and domestic wells.

The results of the RI sampling work indicated that PCBs from the transformer salvage operations

occurred in three former work areas located in the western portion of the site. These activities

led to uncontrolled releases of oil containing PCBs. In addition, surface erosion had caused

PCBs to migrate a short distance from the work areas. Smaller amounts of PCBs had permeated

into the subsurface soils. Low levels of PCBs were found in surface waters, sediments, and biota

samples. Low levels of other organic and inorganic chemicals were also found in some media.

Based on the data collected during post-ROD investigations, the primary source of both oil and

chlorobenzenes was the fractures in the clay. Contaminants were held in tension in the fractures

of the clay and, under gravity, slowly migrated to the primary migration pathway along the

till/bedrock surface. Due to the immiscible nature of the oil and its measured specific gravity of

0.91, the oil has remained in the TWA II Area with only small amounts entering into the primary

migration pathway. The chlorobenzenes were able to dissolve into the groundwater and migrate

to a greater degree within the primary migration pathway.

Contaminant migration has not been significant beyond the TWA II area. The following factors

served to control and/or diminish the movement of chemicals in soils and water:

• low solubility of PCBs in water;

• the strong affinity for PCBs to adhere to soil particles; and

24
• the presence of thick clay and till deposits in the near surface and deep groundwater regimes.

Precipitation falling on the TWA II Area either runs off as surface water or infiltrates downward

into the overburden. A large portion of the infiltrating water is held in tension in the upper

desiccated clay layer and is quasi-perched on top of the soft clay layer, making itself available for

evapotranspiration. Very little recharge enters the deeper soft clay layers, and even less

infiltrates into the till/bedrock flow system under normal conditions. The desiccated clay

fractures allow a limited migration pathway for water to move downward toward the till/bedrock

migration pathway.

C. Fate and Transport Processes

Contaminants on site migrate with the direction of the groundwater flow. The groundwater flow

direction is a subdued reflection of the bedrock surface (Figure 16). The low vertical

permeability of the bedrock acts to form a "quasi perched" condition along the top of the

bedrock. Although it is believed that the bedrock receives recharge from the upland areas

northeast of the bedrock trough, the vertical permeability of the bedrock is extremely low,

making the bedrock a minor secondary migration pathway. Very little contaminant mass enters

the bedrock flow system through natural groundwater flow and groundwater recharge.

Contaminant mass that is able to enter the bedrock flow regime under static non-stressed

conditions flows within the fracture network of the rock. The storage of groundwater within the

bedrock is extremely low. Recharge to a purged well most likely comes from a significant

distance away from the monitoring well due to the low storage capacity of the bedrock. The

overlying till and marine clay confines the bedrock aquifer at lower elevations. MW-106B has

been left flowing, providing a release for contaminants migrating within the deep bedrock flow

regime and likely represents the groundwater within the bedrock system that would have

otherwise migrated from the site. If MW-106B did not exist, it is believed that bedrock

groundwater discharging from that well would leave the site flowing to the east, where it would

then flow north roughly parallel to the Riggs Brook drainage and towards the regional

groundwater sink of the Kennebec River Basin.

Groundwater within the primary til^edrock migration pathway moves along the bedrock surface

in the till layer. This migration pathway, like the bedrock flow system, has very low storage and

slow groundwater velocities. Therefore, even in the tillfoedrock migration pathway, very little

water is moving. Contaminants entered this flow system by slow recharge from the overlying

clay fracture network. Contaminants in groundwater, once in the till/bedrock migration pathway,

are restricted from flowing southeasterly by the bedrock ridge and flow toward the natural

bedrock trough immediately northeast of the upper lagoon (refer to figure 16). The bedrock

trough acts as a spillway, channeling flow from the upland areas surrounding the TWAs and

releasing it to flow southeasterly toward Riggs Brook. Sentinel monitoring wells (MW-502 and

MW-503), placed along the front edge of contaminants moving through the bedrock trough,

monitor the long-term contaminant migration within the tilMedrock migration pathway.

25
Dissolved VOCs are migrating with the groundwater, however, due to dilution, the

concentrations of VOCs at wells along the boundary of the TI Zone are below the ROD target

cleanup goals and current MCLs and MEGs.

Residual oil containing PCBs and VOCs is held in tension in the desiccation cracks in the clay

and to a limited extent in fractures in the bedrock. Under natural conditions, there is very little

movement of this oil. Concentrations of PCBs in monitoring wells along the boundary of the

proposed TI Zone have been below the ROD target cleanup level of 0.5 ^g/L. However, during

a sampling event conducted in March 1999 using lower detection limits, concentrations of PCBs

were at or slightly above the 1992 Maine MEG of 0.05 /zg/L at MW-503 and MW-106. These

wells are on the boundary or outside of the proposed TI Zone. Continued monitoring will be

conducted to determine if concentrations of PCBs outside the proposed TI Zone meet the 1992

Maine MEG.

4.0 Evaluation of the Restoration Potential

This section evaluates the restoration potential by assessing the performance of remedial actions

previously conducted and those that are ongoing at the site, and evaluates additional technologies

to determine if any could realistically attain drinking water standards for the site within a

reasonable time frame.

Remedial actions have been conducted in three operable units at the site; OU-1 Source Control

Operable Unit, OU-2 Management of Migration Operable Unit, and OU-3 Riggs Brook.

Remedial actions at operable units OU-1 and OU-2 are discussed below, as they are relevant to

the concentration of contaminants in groundwater at the site.

A. Source Control Measures

The SCRA for OU-1 was successfully completed on November 11, 1997. The source

remediation was conducted by sampling and excavating soils and sediments contaminated with

PCBs, lead, and cPAHs above the ROD and ESD target cleanup goals. Approximately 20,000

tons of soil and sediment were removed from the site. Another 3,000 tons were excavated and

consolidated into the designated area (refer to Figure 5) to meet the ESD target cleanup goals.

Soil and sediment in OU-1 were sampled, excavated and re-sampled until there was no indication

of soil containing PCBs, cPAHs or lead above the target cleanup goals. By meeting the required

target cleanup goals for soils and sediment, and removing site surface waters, the SCRA

achieved the remedial action objectives established for the Source Control component in the

1989 ROD.

Even after the successful completion of the SCRA, some residual oil containing PCBs and VOCs

remains trapped in desiccation cracks in the clay and to a limited extent in fractures in bedrock at

the site. Although residual oil remains in tension in cracks in the clay, when it has been analyzed

in a homogenized clay sample, the concentrations have been below the target cleanup goals.

Therefore, although this remedy was not able to remove all the residual oil, the approved SCRA

26
remediated the source area and met the remedial action objectives stated in the ROD. The

subsequent Upland Marsh study confirmed that the remedial objectives of the SCRA were met,

even though some residual oil remains. The Upland Marsh Study also confirmed that

concentrations of PCBs detected in the dessication cracks in the clay containing oil ranged from

ND to 1 ppm. Therefore, concentrations of PCBs in the fractures did not exceed the ROD target

cleanup level of 1 ppm established for the site.

B. Analysis of Remedial Action Performance and Restoration Timeframe

The groundwater remedial alternative stipulated in the 1989 ROD was the installation and

operation of a pump and treat system. During the development of the conceptual understanding

of the site, the effectiveness of the pump and treat system was evaluated. This evaluation

indicated that a traditional pump and treat system could mobilize contaminants vertically

downward and further contaminate groundwater. Consequently, a VER system was chosen

rather than a traditional pump and treat system. The construction and operation of the VER

system differed from the pump and treat system, as originally conceived, in that it extracts oil

and water from the site without significantly lowering the groundwater table. This would limit

the drawdown of the water table into the bedrock and therefore not allow mobilized residual oil

to enter the bedrock, which could further contaminate the bedrock groundwater.

As described in detail in the Draft Proposed Final Management of Migration Remedy (W&C,

1997d), the VER pilot study was conducted with the objective of recovering oil both in the

saturated and unsaturated zones without further contaminating the bedrock groundwater. The

operation of the VER pump and treat system (Phases I and II conducted in 1996 and 1997),

coupled with the long-term operation and pulsing of the system, resulted in the removal of 26.6

gallons of oil from within the primary migration pathway and from source areas within clay

fractures in the TWA II Area (see Table 4).

During Phase II of the VER system operation, the limitations of the aquifer were realized with

respect to oil recovery. Some of the residual oil in the immediate vicinity of the VER well was

removed, but as vacuum pressure decreased away from the well, surface tension forces and

limitations inherent with multi-phase flow inhibited the movement of residual oil to the well.

The VER system was then pulsed, to create a stress in the system, in an effort to induce product

recharge to the extraction well. Following two weeks of operations (Phase II), the system was

pulsed for another three months in an effort to try and remove as much oil as possible. During

this time, approximately 10 gallons of oil was removed only when the system was pulsed.

Following the completion of the SCRA, passive oil recovery has been conducted in bedrock

wells in the TWA II Area. The amount of oil recovered passively between December 1997 and

August 2001 was 7.1 gallons. In the past, the VER system had successfully removed oil from

the till/bedrock interface; therefore, in August 2001 VER Phase III system operation was

initiated to address the removal of oil in both the bedrock and overburden soils. A total of 19.8

gallons were recovered during this VER operation compared to 26.6 gallons collected during

Phase I and Phase II VER operation. Following the VER Phase III, between November 2001 and

27
March 2002, 1.9 gallons of oil were recovered passively from the wefls. Most of this oil (1.7

gallons) was recovered in OW-302B, and appears to be directly related to oil induced to the well

by the VER. The total oil since the SCRA completion is 28.8 gallons (Phase III and the passive

recovery).

Based on the results of groundwater monitoring data and the studies completed onsite, the

groundwater and mass flux through both the bedrock and overburden flow systems appears to be

very low. Due to removal of contaminated source soils during the SCRA, and removal of

additional residual oil from the overburden and bedrock, the concentrations of VOCs in

groundwater have been reduced and are expected to continue to decrease. Concentrations of

VOCs are below MCLs and MEGs outside of the TI Zone. At MW-104B and OW-201B, just

inside the proposed TI Zone, but outside of the TWA II Area, VOCs slightly exceed MEGs.

Based on the observed trends of decreasing VOC concentrations in these wells, it is estimated

that VOC concentrations will be below MCLs and MEGs at wells outside the TWA II Area

within the next 5 to 10 years.

As noted in the discussion of oil movement within the subsurface, recovery and or treatment of

residual oil will be difficult. It is believed that it could take hundreds of years to remove the

residual oil and meet drinking water standards for PCBs and VOCs within the TWA II Area. As

previously stated, residual oil, the primary source of PCBs and VOCs, is trapped in fractures in

clay and bedrock within the TWA II Area. The quantity of residual oil remaining is unknown

and due to surface tension and other forces holding this residual oil in equilibrium, there is little

migration under normal conditions.

Even though the VER system has removed a moderate amount of residual oil, and may continue

to remove oil, the difficulty of inducing oil movement within the clay desiccation cracks and the

bedrock fractures makes it unlikely that the residual oil can be completely removed. Therefore,

there will always be residual oil available to water infiltrating into the TWA II Area. Because

the TWA II Area is at the top of the ridge, there is little groundwater flow through this area

Most of the groundwater flow through the TWA II Area is from the infiltration of rainwater and

snowmelt. The infiltrating water will dissolve PCBs and VOCs to their respective solubilities,

continuing to add dissolved source to the groundwater within the TWA II Area.

In order to estimate the dissolution time of PCBs within the oil, a simple solubility calculation

was done. This calculation did not incorporate the dissolution of the oil itself. It is believed that

the oil will remain essentially unchanged and the PCBs will dissolve out of the oil Assuming

that there is approximately 100 gallons of oil left as residual, with an average concentration of

3000 ppb and a solubility of 2.7 ppb (USEPA, 1990) and assuming approximately 2.5 gpm

groundwater flow through the system at a dissolution concentration of 20% of solubility, the time

to dissolve the PCB's would be 372 years. Given dissolution of 10% of solubility, time to

dissolve would be 744 years. As noted above, since the quantity of residual oil remaining in the

subsurface is unknown, one hundred gallons was chosen as a reference point.

The technical impracticability evaluation identified and screened eighteen technologies to assess

28
their ability to restore the groundwater to drinking water quality within a reasonable timeframe.

These technologies included insitu application of oxidizers, alternate groundwater containment

approaches, as well as excavation of all overburden soil. The evaluation concluded that none of

these technologies would achieve the cleanup goals within a reasonable timeframe.

In summary:

• The majority of PCBs were removed during the SCRA in 1996 and 1997; residual oil

containing PCBs and VOCs remains trapped in bedrock fractures and desiccation fractures in

the clay;

• Site investigations show that there is little movement of residual oil containing PCBs and

VOCs from the TWA II Area;

• The VER system has had moderate success removing oil from the bedrock and overburden;

• A Restrictive Covenant has been signed by CMP and Maine DEP that prohibits use of the

groundwater beneath the site. Public water is available on Route 17 to the south and Cony

Road to the west. The nearest known residential well is approximately a half mile to the east,

situated on a hill about two hundred feet above the Riggs Brook discharge area. This well

intercepts flow moving west toward Riggs Brook. Therefore, there is no current drinking

water exposure;

• Based on the observed trends of decreasing VOC concentrations in groundwater since the

completion of the SCRA, it is estimated that VOC concentrations at wells outside of the

TWA II Area will be below MCLs.and MEGs within the next 5 to 10 years; and

• Due to the difficulty of removing residual oil, it is believed that it could require hundreds of

years to remove residual oil and meet drinking water standards for PCBs and VOCs within

the TWA II Area.

5. Cost Estimates

The cost estimate of the amended remedy is described in Section X below.

More detailed information regarding the technical impracticability of restoration of the

overburden and bedrock groundwater can be found in the Final Technical Impracticability

Evaluation Report. (W&C, June 2002)

IX. COMPARATIVE ANALYSIS OF THE ORIGINAL REMEDY AND

OU-2 ALTERNATIVES

Section 121(b)(l) of CERCLA presents several factors that EPA is required to consider in its

29
assessment of alternatives. Building upon these specific statutory mandates, the NCP articulates

nine evaluation criteria to be used in assessing remedial alternatives. These criteria are as

follows:

Threshold Criteria

In accordance with the NCP, two threshold criteria must be met in order for the alternative to be

eligible for selection:

1. Overall protection of human health and the environment addresses whether or not a

remedy provides adequate protection, and describes how risks posed through each

exposure pathway are eliminated, reduced or controlled through treatment, engineering

controls or institutional controls.

2. Compliance with applicable or relevant and appropriate requirements (ARARs)

addresses whether or not a remedy will meet all of the ARARs of promulgated state and

federal environmental and facility-siting requirements, and if not, provides the grounds

for invoking a CERCLA waiver(s) for those requirements.

Primary Balancing Criteria

The following five criteria are used to compare and evaluate those alternatives which fulfill the

two threshold criteria.

3. Long-term effectiveness and permanence assesses alternatives for the long-term

effectiveness and permanence they afford, along with the degree of certainty that they

will be successful.

4 Reduction of toxicity, mobility or volume through treatment addresses the degree to

which alternatives employ treatment to reduce toxicity, mobility or volume, and how

treatment is used to address the principle threats posed by the site.

5. Short term effectiveness addresses the period of time needed to achieve protection and

any adverse impacts on human health and the environment that may be posed during the

construction and implementation of the alternative until cleanup goals are achieved.

6. Implementability addresses the technical and administrative feasibility of an alternative,

including the availability of materials and services needed to implement a particular

option.

7. Cost includes estimated capital as well as operation and maintenance costs, on a net

present-worth basis.

Modifying Criteria

30
The two modifying criteria discussed below are used in the final evaluation of remedial

alternatives generally after EPA has received public comment on the RI/FS and Proposed Plan.

8. State acceptance addresses the State's position and key concerns related to the preferred

alternative and other alternatives, and the State's comments on ARARs or the proposed

use of waivers.

9. Community acceptance addresses the public's general response to the alternatives

described in the feasibility study and Proposed Plan.

The following is a comparison of the 1989 ROD remedy and the alternatives evaluated for this

ROD amendment, contrasting each remedy's components with respect to the nine evaluation

criteria.

1989 Remedy

The 1989 ROD selected a comprehensive approach to the contamination. The source control

actions included the cleaning, demolition, and off-site disposal of the bam situated along Route

17, removal and off-site disposal of the standing water in the two lagoons, and the excavation

and treatment by solvent extraction of the soils and sediments contaminated with PCBs, cPAHs,

and lead. Management of migration actions included the pumping, treatment, and disposal of the

contaminated groundwater from the soil and bedrock, and sampling of sediment and fish in

Riggs Brook for ten years.

Alternative 1: Institutional Controls, Long-Term Monitoring, and Passive Oil Recovery

In this alternative, EPA recognizes that the groundwater beneath a portion of the site (TI zone,

see Figure 3) will not be of drinking water quality for an extended period of time, potentially

more than a hundred years for reasons stated above in Section VIII. While the area of Augusta

where the site is located has not seen rapid growth during the time the F. O'Connor Company

operated or since its closing, the area can reasonably be expected to experience some growth

during the time period needed to reach the drinking water quality. Therefore, established and

formal controls are needed to prevent use of the groundwater on the site and to prevent the

contamination from spreading by stressing the aquifer beneath the site. CMP and Maine DEP

have entered into a Restrictive Covenant that prohibits use of the groundwater without prior

approval from Maine DEP. This Restrictive Covenant will remain in place until terminated by

Maine DEP. Should, however, EPA find that this covenant is no longer protective, effective, or

it interferes with the performance of the remedy, additional institutional controls will be placed

on the property.

Operation and maintenance activities will ensure that the institutional controls remain in place

and are effective for their stated purpose and that the Site is managed properly to maintain the

31
protective layer of clean soil above those soils with low levels of PCBs.

Long-term monitoring of the groundwater will allow EPA and Maine DEP to track the residual

oil and dissolved PCBs and VOCs within the TI zone and outside of it. This data will allow the

agencies to evaluate whether the concentrations are continuing to decrease, whether the

contamination is moving beyond its current limit, and whether there is a change in concentrations

discharging into Riggs Brook wetlands. In the event that the monitoring data indicate an

increase in PCB or VOC levels, response actions will be evaluated, and as appropriate,

implemented as part of this amended ROD.

In addition to these components, Alternative 1 would include passive oil recovery where

absorbent materials would periodically be used to recover free oil which has drained under

normal conditions into the TWA II wells. This would continue until free oil was no longer

observed in the wells. The absorbent materials would be disposed of at a licensed TSD facility.

The estimated period of operation for this alternative is in excess of one hundred years. The

estimated net present worth for this alternative is $622,000. (Costs were developed for thirty

years per EPA guidance; however, EPA expects it will take considerably longer to reach drinking

water quality.)

Alternative 2: Institutional Controls, Long-Term Monitoring, Active and Passive Oil

Recovery

This alternative is EPA's selected alternative. It adds active recovery of residual oil to the

components included in Alternative 1. On an annual basis, a vacuum would be applied to wells

within TWA II to draw the residual oil and VOCs from the soil and bedrock. EPA is proposing

the annual application to coincide with normal low groundwater levels as that has been the time

when the amount of oil in the wells has been the greatest. Each application would continue as

long as it was practical to remove the oil (the criteria for this is further discussed in Section X.2.).

Past application suggests that each application would last about four to six weeks. The annual

application, from year to year, would continue as long as it was practical. Passive oil recovery

would be implemented between the active pumping efforts. The recovered oil and the absorbent

materials would be disposed of at a licensed TSD facility.

The estimated period of operation for this alternative is in excess of one hundred years. The

estimated period of operation for the active oil recovery is five to ten years. The estimated net

present worth for this alternative is $1,055,000. (As with Alternative 1, costs were developed for

thirty years per EPA guidance)

EPA developed these alternatives based on information contained in the 2002 Technical

Impracticability Evaluation submitted by CMP, which in turn followed discussions with EPA

and Maine DEP regarding site conditions.

32
Comparison of the Original Remedy for Groundwater and the OU-2 Alternatives to the

Nine Criteria

1. Overall Protection of Human Health and the Environment

This criterion considers whether the remedy, as a whole, will protect human health and the

environment. This includes an assessment of how public health and environmental risks are

properly eliminated, reduced, or controlled through treatment, engineering controls, or

institutional controls.

The original remedy included pump and treat technology as the method to achieve groundwater

restoration throughout the Site. While this technology was to be implemented, short-term

institutional controls were to be set in place to prevent exposure to the contaminated

groundwater. This selection was consistent with the belief at the time that this technology could

effectively restore contaminated groundwater. In 2002, EPA concluded that restoration was not

feasible. Therefore, without achieving restoration within a reasonable time frame or having a

long-term means to prevent exposure to the contaminated groundwater, the original remedy is no

longer protective of human health and the environment in the long-term.

Alternatives 1 and 2 recognize that for a portion of the site, it is technically impracticable to

restore the groundwater to drinking water quality, and therefore, to prevent exposure to the

contaminated groundwater for an extended period of time, a long-term institutional control is a

component of both alternatives. In addition, both alternatives include long-term monitoring of

groundwater to demonstrate that the contamination is not expanding and that natural processes

will continue to decrease the contaminant concentrations. Alternative 2 provides greater overall

protection by actively removing separate phase oil from the overburden soil and bedrock and

thus more quickly reduces the toxicity. Thereby, with the institutional control provided by the

Restrictive Covenant, this component ensures the protectiveness of the remedy.

The protection of human health and the environment is the most important criterion The

Restrictive Covenant protects human health as it prevents human exposure to contaminated

groundwater. The environment is protected through the soil removal and recovery of the free oil

(by removing the source of contamination, the amount of residual contamination available to

aquatic and terrestrial receptors is expected to continue to decrease). Long-term monitoring will

allow EPA and Maine DEP to know whether the remedy is appropriate. Both alternatives EPA

evaluated rely on the Restrictive Covenant and long-term monitoring.

2. Compliance with Applicable and Relevant and Appropriate Requirements

This criterion addresses whether or not a remedy complies with all promulgated state and federal

environmental and facility siting requirements that apply or are relevant and appropriate to the

conditions and remedy at a specific site. If an ARAR cannot be met, the analysis of a remedy

must provide the grounds for invoking a statutory waiver.

33
When the original remedy was selected in the 1989 ROD, it was believed that the remedy would

attain all identified federal and state ARARs.

Both alternatives include a TI waiver of drinking water standards for the area identified as the TI

zone (See Figure 3) and would comply with all other identified federal and state regulations as

well as drinking water standards outside of the TI zone. PCB and VOC levels outside the TI zone

are currently below EPA's standards but at times are slightly above Maine's standards. As the

concentrations have decreased following the 1997 soil removal action, and active and passive oil

recovery will continue, it is anticipated that the Maine standard will be consistently met outside

the TI zone in five to ten years. EPA anticipates that active recovery of the oil under Alternative

2 will more quickly lower the PCB and VOC concentrations in the TI zone than just the passive

recovery provided in Alternative 1. However, it is likely that at the conclusion of active recovery

the dissolved concentrations within the TI zone will still be above the drinking water standards.

Because the ROD Amendment waives federal and state drinking water standards for a portion of

the site, EPA sought comment from the public regarding this during the public comment period.

3. Long-term Effectiveness and Permanence

This criterion refers to the ability of a remedy to maintain reliable protection of human health and

the environment over time once the remedial action is complete.

The original remedy would have provided long-term effectiveness and permanence once site

groundwater had been restored to drinking water quality. However, since it was demonstrated

that the pump and treat technology could not restore the groundwater within a reasonable

timeframe, there were concerns that the Restrictive Covenant alone would not have the ability to ,

provide and maintain reliable long-term effectiveness. For this reason, additional institutional

controls could be used in the future to ensure long-term effectiveness and permanence under both

alternatives evaluated by EPA.

The long-term protection criterion would be met by both alternatives EPA evaluated. If the

Restrictive Covenant is not effective or protective in the future, additional institutional controls

will be required by EPA. The groundwater monitoring will continue under both alternatives as

long as the PCB and VOC concentrations remain above drinking water quality. Additionally,

operation and maintenance activities will continue to ensure the effectiveness and protectiveness

of the institutional controls

4. Reduction of Toxicity, Mobility, and Volume through Treatment

This criterion contains three measures of the overall performance of a remedy The 1986

amendments to the Superfund statute emphasize that, whenever possible, EPA should select a

remedy that uses a treatment process to permanently reduce the level of toxicity of contaminants

at the site, inhibit or eliminate the spread of contaminants away from the source of

contamination, and reduce the volume, or amount of contamination at the site.

34
The original remedy for the groundwater operable unit used a proven technology, pump and

treat, to reduce toxicity, mobility, and volume in the overburden and bedrock groundwater.

However, as noted elsewhere, the presence of separate phase oil with PCBs and VOCs in both

the fractures in the overburden clay soil and in the bedrock, and the limited recharge of

groundwater in the contaminated source area greatly limited the effectiveness of pump and treat

technology in reducing toxicity, mobility, and volume.

Both alternatives would include the removal of residual oil. Alternative 1 would remove the oil

as it moves under natural conditions into monitoring wells, whereas Alternative 2 would also

employ a pumping system to increase the rate of the recovery. The recovered oil is transported

offsite to a licensed TSD facility. Using active recovery under Alternative 2, the volume of the

residual oil will be reduced much more quickly then relying on natural conditions as proposed in

Alternative 1. In turn, this will further decrease its mobility through the subsurface. Therefore

Alternative 2 provides the greatest reduction of toxicity, mobility, and the volume of

contaminants through treatment.

5. Short-term Effectiveness

This criterion refers to the likelihood of adverse impacts on human health or the environment that

may be posed during the construction and implementation of a remedy.

EPA does not believe that the original remedy for groundwater posed significant short-term

effectiveness concerns. The potential exposure of site workers and area residents to

contaminated air emissions during construction of the extraction and re-injection wells was

minimized by using standard safety plans that included air emissions controls and a network of

ambient air monitors to assess potential releases to the air during drilling operations. The

implementation of the pump and treat technology likewise did not pose significant short-term

effectiveness concerns.

Both alternatives meet the short-term effectiveness criterion in similar ways. The

implementation of institutional controls reduces site risks from groundwater quickly. The only

remedial actions are the long-term monitoring and the oil recovery, both of which have been

ongoing for years, and the sampling crews follow established health and safety procedures. As

stated above, the recovered oil and absorbent materials are currently transported to a licensed

TSD facility and will continue to be shipped offsite safely and in accordance with all legal

requirements.

6. Implementability

This criterion refers to the technical and administrative feasibility of a remedy, including the

availability of materials and services needed to implement the remedy.

The original groundwater remedy was implementable as demonstrated by the installation of

recovery and re-injection wells that were operated successfully during the pilot pumping studies.

35
Both alternatives evaluated in this ROD Amendment for OU-2 can be easily implemented. The

materials and equipment needed for maintenance of the site, long-term monitoring, and oil

recovery are all readily available. The VER system is already installed and has been operated in

three separate trials spanning several months. The Restrictive Covenant is currently in place. If

additional institutional controls are needed, they also can be readily implemented.

7. Cost

This criterion includes the net present worth estimates for capital (up-front) and operation and

maintenance costs of implementing each alternative evaluated for OU-2. The costs described

below do not include previous site-wide costs which were substantial. The cost estimates only

reflect those costs that would be incurred henceforth to implement the alternatives evaluated.

The estimated total present worth costs associated with the management of migration component

in the 1989 ROD was $679,000 with operation and maintenance costs for thirty years comprising

$631,000 of the total.

In evaluating the alternatives for costs, EPA notes that the net present worth has been calculated

for thirty years, following EPA guidance, whereas it is the expectation of all parties that the

cleanup activities will last considerably longer. The net present worth of Alternatives 1 and 2

are $622,000 and $1,055,000, respectively.

8. State Acceptance

This criterion addresses whether, based on its review of the data derived from the site and the

Proposed Plan, the State concurs with, opposes, or has no comment on the amendment that EPA

has selected for the site.

Maine DEP has reviewed the June 2002 Proposed Plan to amend the 1989 Cleanup Plan and a

draft of this amendment. The Maine DEP concurs with the remedy change with certain

conditions. These conditions have been addressed. The Maine DEP has provided a letter of

concurrence which is provided in Appendix C.

9. Community Acceptance

This criterion addresses whether the public concurs with EPA's proposed Amendment.

Compliance with this criterion is based on the comments received at the public meeting and

public hearing.

Based on the public information and public hearing meetings and comments received during the

public comment period, it appears that the proposed amendment has community support.

X. THE SELECTED REMEDY FOR OU-2

36
EPA has selected the remedy described below as the best balance between the nine criteria. The

selected remedy relies on institutional controls, active oil recovery, and long-term monitoring of

overburden and bedrock groundwater. This remedy was selected within the context of the

determination by EPA that it is technically impracticable to restore the groundwater for a limited

portion of the Site within a reasonable timeframe.

For the amended cleanup plan for OU-2, EPA has selected a remedy which ensures

protectiveness of human health and the environment, attains all federal and state regulations with

the exception of waiving drinking water standards for a portion of the site, provides long-term

and short-term effectiveness, is implementable, and reduces toxicity, volume, and mobility

through treatment. The amended cleanup plan for OU-2 includes:

1. Institutional controls to prevent exposure to the contaminated groundwater

• In 1994, CMP and Maine DEP signed a Restrictive Covenant on a portion of the property

which prevents certain activities without written approval from Maine DEP (see Figure 4).

The Covenant requires CMP to maintain the property to ensure that the remedy remains

protective. The Covenant runs with the land and is binding on all future owners. The

Restrictive Covenant was recorded at the Kennebec County Registry of Deeds on September

13, 2002. If the Covenant is released prior to the completion of the remedy, or if EPA finds

that it is not effective and protective, EPA will require other institutional controls be put in

place on the site.

•An operation and maintenance plan will be implemented to ensure that the institutional

controls are being followed, that they are effective and protective, and that the Site is

managed properly. The O&M plan will include a schedule for monitoring the soil cover,

resurveying of the designated area, and periodic sampling and analysis to ensure the integrity

of the soil cover over the designated area. This sampling will coincide with the five-year

reviews and will consist of a limited number of soil samples collected from about 6-8 inches

below the ground surface and analyzed for PCBs.

2. A combination of active and passive removal of the oil and associated PCBs

• A vacuum-enhanced pumping system will be used annually to remove oil from the

groundwater. This system will be operated on an annual basis in late summer- early fall until

it is determined to be no longer effective. Criteria to be used to make this determination

include the following:

apply the VER to four wells (101, 202B, 310B, and 302B) in the TWA II area at

least once every year for the next five years (2007). The necessity and conditions

for continuation of the VER would be addressed during the next five 5-year

review, scheduled for September 2007, and each subsequent 5-year review period.

After application of the VER to a well, recovery of oil will be observed over a

37
period of up to one week.

If a "significant" amount of oil is recovered from the well, the VER will be

reapplied to the well. A "significant" amount of oil will be defined as an increase

in the amount of oil recovered relative to the amount of oil recovered through

passive means. Basically this means that if the VER is effectively increasing the

amount of oil being recovered from a well, it will continue on that well.

•The operation of the VER will continue for a period of up to two months if significant

amounts of oil are recovered. After this time weather constraints and rising groundwater

elevations are expected to limit the effectiveness of the VER.

It is expected that the VER will be operated for the next five years and this determination

regarding the continued operation of the VER as part of this ROD Amendment will be made in

conjunction with the next five-year review scheduled for summer 2007.

This component of the remedy requires placement of absorbent materials in monitoring wells

after the conclusion of the pumping to absorb any remaining residual oil. The use of absorbent

materials will continue until as long as it is practical, i.e, as long as oil is visibly detectable.

Between active operation of the VER, the wells are currently monitored on a monthly basis. It is

anticipated that this frequency will be reduced to quarterly in the future. All recovered oil and

used absorbent material will be disposed of at a licensed TSD facility.

3. Monitoring the groundwater to demonstrate that the contamination is not expanding and that

natural processes will continue to decrease the contaminant concentrations.

• This component of the remedy requires implementation of a long-term groundwater

monitoring program to track dissolved PCB and VOCs. This program will be a modification

of the current monitoring program

• It will also require tracking the progress of attenuation by monitoring dissolved

contaminant levels beyond the area where the oil is present in the groundwater. This

monitoring data will be used to verify that the dissolved contaminant concentrations are

decreasing.

•Finally this component of the remedy will include contingencies should the groundwater

monitoring indicate the contamination is moving beyond its current limits. Contingencies

may include increased sampling frequency, implementation of additional sampling locations,

including any residential wells installed on adjacent properties, reevaluation of the conceptual

model, and increased operation of the VER.

4. Evaluating the cleanup approach to confirm that it is protective of human health and the

environment

38
•As long as contamination remains which prevents unrestricted use of the site, the Superfund

law requires reviews every five years to evaluate the effectiveness of the implemented

cleanup plan. As part of each five year review, EPA will review the site conditions to

determine if the cleanup action remains protective, consider new technologies, and refine the

time estimates necessary to reach the groundwater standards.

In addition to these components for OU-2, monitoring Riggs Brook for OU-3 will continue as

specified in the 1989 ROD, to track changes in PCB concentrations and to demonstrate no

unacceptable impact on sediment quality or aquatic or terrestrial organisms.

XL STATUTORY DETERMINATIONS

The remedial action selected herein for implementation for O'Connor OU-2 is consistent with

CERCLA and, to the extent practicable, the NCP.

A. The Selected Remedy is Protective of Human Health and the Environment

The selected remedy will be protective of human health and the environment. Exposure to

contaminated groundwater will be prevented through the Restrictive Covenant or other

institutional controls. This Covenant includes the following:

• any use of the groundwater beneath the site is prohibited without the written approval of

Maine DEP;

• any activity which might disrupt remedial or monitoring measures is prohibited without the

written approval of Maine DEP; and

•CMP or any subsequent owner shall maintain the site in a condition adequate to ensure the

continued compliance with all applicable standards and to ensure the ongoing adequacy of

the remediation.

If other institutional controls are required, they will ensure the protectiveness of the remedy.

Active recovery of PCB-oil will decrease the mass and volume of the contaminants of concern as

well as reduce its mobility. Long-term monitoring of the groundwater will allow EPA to track

the decreasing concentrations present in the overburden soils and bedrock aquifer. There are no

significant short-term risks to human health or the environment during implementation of the

selected remedy. The potential exposure of site workers and area residents during the annual oil

recovery will be monitored to assess potential releases to the air during cleanup operations. As

active oil recovery has been implemented at the site since 1996, its continuation as part of the

ROD Amendment remedy is not anticipated to pose any significant risks to site workers or area

residents.

39
B. The Selected Remedy Attains or Appropriately Waives ARARs

ARARs for the site were identified during the development of the 1989 ROD. As a part of the TI

Evaluation process, a review of current ARARs was conducted and is summarized below.

Section 300.430 (e) of the National Contingency Plan (NCP) requires that on-site remedial

actions at CERCLA sites must meet ARARs under federal or state environmental or facility

siting laws unless there are grounds for invoking a waiver. A waiver is required if ARARs

cannot be achieved. Other federal and state advisories, criteria, or guidance, as appropriate (to be

considered - TBCs), should be considered in formulating the remedial action.

ARARs are promulgated, enforceable federal and state environmental or public health

requirements. There are two categories of requirements, "applicable" and "relevant and

appropriate". CERCLA does not allow a regulation to be considered as both "applicable" and

"relevant and appropriate". These categories are defined below:

Applicable Requirements - Section 300.5 of the NCP defines applicable requirements as "those

cleanup standards, standards of control, and other substantive environmental protection

requirements, criteria, or limitations promulgated under Federal or State law that specifically

address a hazardous substance, pollutant, contaminant, remedial action, location, or other

circumstance at a CERCLA site".

Relevant and Appropriate Requirements - Section 300.5 of the NCP defines relevant and

appropriate requirements as "those cleanup standards, standards of control, and other substantive

environmental protection requirements, criteria, or limitations promulgated under Federal or

State law that, while not 'applicable' to a hazardous substance, pollutant, contaminant, remedial

action, location, or other circumstance at a CERCLA site, address problems or situations

sufficiently similar to those encountered at a CERCLA site that their use is well suited to the

particular site."

To be considered (TBCs) guidelines are non-promulgated criteria, advisories, and guidance

issued by the federal or state governments. Along with ARARs, TBCs may be used to develop

interim action limits necessary to protect human health and the environment.

ARARs and TBCs are divided into three categories: chemical-specific, location-specific, and

action-specific. This section briefly summarizes the most significant chemical, location and

action specific ARARs for the remedy and identifies those for which a technical impracticability

waiver is sought

Chemical-Specific ARARs

Chemical-Specific ARARs are usually health- or risk-based numerical values or methodologies

which, when applied to site-specific conditions, result in the determination of numerical values

that establish the acceptable amount or concentration of a chemical that may be found in, or

40
discharged to, the ambient environment. These requirements do not consider the mixture of

chemicals. A summary of chemical specific ARARs is presented in Table 6.

The federal Maximum Contaminant Levels (MCLs) are chemical-specific ARARs that govern

the quality of drinking water provided by public water supply. MCLs are relevant and

appropriate requirements in establishing remediation goals for groundwater at the site and are

ARARs outside the TI zone.

The 1992 State of Maine Maximum Exposure Guidelines (MEGs) are chemical-specific ARARs

that are health-based guidelines intended to determine drinking water quality for private

residential wells. MEGs are relevant and appropriate requirements in establishing remediation

goals for groundwater at the site. Maine MEGs were revised in 2000, but have not been

promulgated and therefore, the 2000 Maine MEGs are TBCs.

The MCLs and MEGs for which a technical impracticability waiver wil] apply are noted in the

Table 3 in Section VIII above.

Location-Specific ARARs

Location-specific ARARs are restrictions placed on the concentrations of hazardous substances,

or the conduct of activities solely because they are in specific areas. The general types of

location-specific ARARs that apply to the site are briefly described below and are presented in

Table 7.

Several federal and state ARARs regulate activities that may be conducted in wetlands and

floodplains. Regulations governing endangered species at the federal and state levels would need

to be considered for any proposed on-site actions. The Maine Natural Resources Protection Act

governs activities that may occur in or adjacent to wetlands or surface water bodies. The Maine

Site Location Development Law regulates activities that may adversely affect existing land uses,

and scenic character or natural resources, and needs to be considered in the implementation of an

alternative.

No waiver of location-specific ARARs is being sought for the technical impracticability

evaluation for the Site.

Action-Specific ARARs

Action-specific ARARs are usually technology- or activity-based requirements or limitations on

actions taken with respect to hazardous wastes. These requirements are generally focused on

actions taken to remediate, handle, treat, transport, or dispose of hazardous wastes. These actionspecific requirements do not in themselves determine the remedial alternative; rather they

indicate how a selected alternative must be implemented. The general types of action-specific

ARARs that apply to the site are briefly described below and are presented in Table 8.

The Toxic Substances Control Act (TSCA) regulates the marking, storage, disposal and cleanup

41
of spills of PCBs greater than 50 ppm PCBs. In addition, the Maine Hazardous Waste

Management Rules also regulate treatment, storage and disposal of hazardous wastes, including

PCBs. These regulations would need to be in the implementation of any alternative that includes

the removal and/or treatment of contaminated groundwater and residual oil.

No waiver for action-specific ARARs is being sought for the technical impracticability

evaluation for the Site.

C. The Selected Remedial Action is Cost-Effective

The selected remedy is cost-effective since it provides overall effectiveness proportional to its

cost.

The projected net worth costs over thirty years for the two amendment alternatives evaluated

were $0.622 million for Alternative 1 and $1.055 million for Alternative 2. The selected remedy

Alternative 2 actively removes contamination through treatment from the groundwater whereas

Alternative 1 does not include active removal. Additionally, EPA believes the actual cost

difference for the two alternatives is not as great at it appears. These costs have been calculated

based on thirty years, yet it is anticipated that the long-term monitoring for OU-2 will continue

considerably longer. However, by actively removing the oil on an annual basis as long as it is

practical, EPA expects this will shorten the time period for groundwater restoration and thereby

require less long-term monitoring compared to Alternative 1.

D. The Selected Remedy Does Utilize Permanent Solutions and Alternative Treatment or

Resource Recovery Technologies to the Maximum Extent Practicable

The selected remedy provides a permanent solution and alternative treatment or resource

recovery technologies to the maximum extent practicable for the separate phase oil through

active oil recovery. Through institutional controls, the groundwater is isolated from human use

and thus prevents exposure Extrapolations of groundwater monitoring data downgradient of the

TI zone indicate that the groundwater beyond the TI zone will attain the cleanup standards within

the next ten years.

Through the active recovery of oil on an annual basis, the selected remedy reduces the mass of

contamination more quickly than natural attenuation processes. Following the completed SCRA,

the active oil recovery seeks to permanently further reduce the source of contamination for the

downgradient groundwater and Riggs Brook.

E. The Selected Remedy Does Satisfy the Preference for Treatment as a Principle Element

The selected remedy does use treatment of the PCB oil-contaminated groundwater as a principle

element of the remedy. The recovered oil is transported offsite to a licensed TSD facility.

42
F. Five Year Reviews

Because this amendment would result in contaminants remaining onsite, EPA will review the site

at least once every five years after the initiation of the remedial action at the site to assure that the

remedial action continues to be protective of human health and the environment. This review

will be consistent with the CERGLA §121(c) applicable for five-year site reviews in effect at the

time of the review. The first five-year review for the site was triggered by the start of the source

control remedial action and was completed in September 2002.

XII. DOCUMENTATION OF NO SIGNIFICANT CHANGES

The Proposed Plan to amend the 1989 ROD, as it pertained to the MOM, was released for public

comment in June 2002. The proposed change calls for attaining protectiveness of human health

through institutional controls and long-term monitoring rather than attaining protectiveness of

human health through restoration of the site ground water through active remedial action. The

amended cleanup plan does include active recovery of the PCB laden-oil, thereby providing

treatment as a component of the remedy.

EPA determined that, based on comments received during the public comment period which

concluded on July 19, 2002, no significant change is needed to the proposed amended cleanup

plan. EPA has prepared a responsiveness summary to address the comments received during the

public comment period. The responsiveness summary is attached as Appendix A.

XIII. STATE ROLE

The Maine Department of Environmental Protection has reviewed the remedy change and

concurs with the selected remedy described in Section X of this Amendment. A copy of the

State concurrence letter is attached as Appendix C.

43
September 2002 ROD Amendment

F. O'Connor Superfund Site

Table 1: Comparison between 1989 ROD and 2002 ROD Amendment

1989 ROD - Groundwater components

# 1: temporary institutional controls. This

would prevent exposure to site groundwater

while remediation was underway.

#2: pump-and-treat system. The appropriate

sizing of the system, including the number of

extraction wells, pumping rate, treatment

components such as granular activated carbon,

sand filters, air stripper, and number of recharge

wells was to be determined during the remedial

design phase.

#3: a network of monitoring wells. The wells

used in the Rl would be assessed and augmented

with additional wells in both overburden soil

and bedrock.

#4: Riggs Brook sediment and biota monitoring.

Brook sediments were to be monitored yearly

for ten years to assess PCB concentrations.

Biota sampling was to occur five years after

initiation of the monitoring.

#5: five-year reviews. Tlie progress toward

restoration of the site groundwater and the target

clean up goal for the sediment were to be

assessed during each five-year review.

2002 ROD Amendment for OU-2

#1 permanent institutional controls. With the

1994 BSD, CMP and Maine DEP signed a

restrictive covenant which prevented certain

activities at the she without written approval of

Maine DEP.

#2: annual application of the VER system. The

VER has been operated three times post-ROD,

recovering PCB-laden oil from the overburden

and bedrock. The VER will be applied annually

in TWA II area wells to recover as much oil as

is practical.

#3 monthly monitoring of oil levels in TWA II

wells and removal using absorbent materials.

Between the annual operations of the VER, the

TWA II will be monitored for separate phase

oil. Detected oil will be removed using

absorbent material. It is expected that

monitoring frequency will decrease as the

amount of oil draining into the wells decreases.

#4:long-term monitoring. It will be performed

to track contaminant levels in the Tl zone and

outside it.

#5: Riggs Brook sediment and biota monitoring.

It will continue as OU-3, established in 1996

#6: five-year reviews Reviews will be

conducted to ensure that the site remedy for all

three OU's remains protective.
September 2002 ROD Amendment

F. O'Connor Superftind Site

Table 2: PCB Results - TWA II

Sampling Date OW202B

3/98

6/98

9/98

12/98

3/99

6/99

9/99

3/00

9/00

4/01

9/01

ND

ND

NS

ND

0.79

NS

NS

NS

NS

0.35

NS

FCB Results (/fg/L) - TWA 11

ROD Cleanup Standard 0.5 /zg/L

OW- OW- OW- RW-101

204B 301 B 302B

ND

ND

0.64

Jl.O

ND

1.17

NS

NS

0.62

ND

NS

5.6

1.2

1.7

7.1

3.1

2.9

NS

NS

8.6

3.5

NS

2.5

32

1,500

8,900

930

710

NS

NS

8.6

44

NS

2.3

1.5

NS

NS

2.32

NS

NS

NS

NS

0.12

NS

Number of

Exceedances

3

3

5 -

4

4

5

5

5

5

2

5

ND - non detected above PQLs

NS - not sampled due to presence of oil in well (considered an exceedance)

J - estimate due to the percent difference of continuing calibration greater than 15%.

Bold - ROD exceedance
September 2002 ROD Amendment

F. O'Connor Superfund Site

Table 3: Chemical-Specific ARARs for TI Waiver

Contaminant

Of Concern

Benzene

Chlorobenzene

1 ,2-D ichlorobenzene

1 ,3-Dicblorobenzene

1,4- Dichlorobenzene

1,2,3-

Trichlorobenzene

1,2,4-

Trichlorobenzene

1,3,5-

Trichlorobenzene

PCBs1

2001 Maximum

Groundwater

Concentration

(//g/L) and Location

8 - OW-302B

240 - OW-302B

210 - OW-302B

160 - OW-302B

720 - OW-302B

98 - OW-302B

770 - OW-302B

not analyzed for

44 . QW-302B

MCL

(/^g/L)

5

100

600

ns

75

NS

70

NS

0.5

1992

MEG

0/g/L)

5

47

85

85

27

NS

70

40

0.05

1989 ROD Target

Cleanup Levels

(/^g/L)

5

no ROD standard

no ROD standard

no ROD standard

27

no ROD standard

no ROD standard

no ROD standard

0.5

1

 detection limit varies with location and are generally greater than the 1992 MEG.

NS - no standard
September 2002 ROD Amendment

F. O'Connor Superfund Site

Table 4: Gallons of Oil Recovered From TWA II Area Wells

Period

Pump Test -

VER

VER Phases I &

II

Source Control

Passive

Collection

VER Phase III

Post VER Phase

III

Total

1992-1994

1996-1997

1997

1997-2001

2001

2001-2002

OW202B

15.8

0.0

0.0

2.1

1.9

0.1

19.9

ow204B

0.0

0.0

0.0

0.1

0.0

0.0

0.1

OW301B

8.3

0.0

0.0

0.2

4.6

0.0

13.1

OW-302B

5.7

0.0

0.0

2.3

10.1

1.7

19.8

RW101

—

26.6

NA

2.4

3.2

0.1

32.3

Total

29.8

26.6

0.0

7.1

19.8

1.9

85.2
September 2002 ROD Amendment

F. O'Connor Superfimd Site

Table 5: Summary of Groundwater Monitoring Results Modified Method 680

Analytes

Total Mono CB

Total DiCB

Total TriCB

Total TetraCB

Total PentaCB

Total HextaCB

Total HeptaCB

Total OctaCB

Total NonaCB

DecaCB (#209)

Total PCB

Total PCB &

EMPC

MW106 A

fog/L)

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

N/A

N/A

MW-106B

fcg/L)

0.004

0.01

0.01

0.02

ND

ND

ND

ND

ND

ND

0.05

0.05

MW-503

fczg/L)

0.004

0.03

0.02

ND

ND

ND

ND

ND

ND

ND

0.06

0.09

MW-508B

fcg/L)

0.008

0.01

ND

ND

ND

ND

ND

ND

ND

ND

0.02

0.02

MW-104B

(Mg/L)

EMPC*

0.04

ND

ND

ND

ND

ND

ND

ND

ND

0.04

0.07

OW-201B

fcg/L)

0

0.05

ND

ND

ND

ND

ND

ND

ND

ND

0.06

0.07

Notes: EMPC - Estimated Maximum Possible Concentration

* - EMPC-0.03
Table 6: Identification of Chemical-Specific ARARs

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GROUNDWATER

Federal Regulatory Requirements

SDWA - Section 1412 -MCLs (40 CFR

141.11-141.6)

SDWA- Section 1412 -MCLGs (40 CFR

141.50-141.51)

CWA - Section 304(a)

AWQC

USEPA Risk Reference Doses (RfDs)

USEPA Carcinogen Assessment Group

Carcinogenic Potency Factors (CPFs)

USEPA Health Advisories (HAs)

U.S. Environmental Protection Agency

(USEPA) Risk Reference Doses (RfDs)

: * ^

"V^ sf ,'!*;.

••> " : " •• •.' SV^

Relevant and

Appropriate

Relevant and

Appropriate

Relevant and

Appropriate

To be considered

To be considered

To be considered

To be considered

\ MQXBIUi^INTS^HOPSlS ;

'"<•• ">/!'** ' ' <-"- " ' -

:, ; ^

MCLs have been promulgated for several common 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.

MCLGs are health-based criteria established for a number of organic and

inorganic contaminants as water quality goals for drinking water supplies.

These goals may also be considered relevant and appropriate for groundwater

aquifers used for drinking water.

Federal AWQC include (1) health-based criteria developed for 95 carcinogenic

and noncarcinogenic compounds and (2) other water quality parameters |

protective of fish and aquatic life. AWQC for the protection of human health |j

provide levels for exposure from drinking water and consuming aquatic

organisms, and from consuming fish alone. Remedial actions involving

contaminated surface water or groundwater must consider the uses of the water

and the circumstances of the release or threatened release; this determines

whether AWQC are relevant and appropriate.

RfDs are considered the levels unlikely to cause significant adverse health

effects associated with a Lhreshold mechanism of action in human exposure for

a lifetime.

Carcinogenic effects present the most up-to-date information on cancer risk

potency derived from USEPA's Carcinogen Assessment Group.

HAs are issued as non-regulatory guidance. HA values represent the

concentration of contaminants in drinking water at which adverse health effects

would not be expected to occur. HAs are established for one-day and ten-day

exposure durations.

RfDs are an estimate of a daily exposure concentration that is likely to be

without appreciable risk of deleterious effects during a lifetime exposure.
State of Maine Regulatory Requirements

Maine Standards for Classification of

Groundwater (38 M.R.S.A., Chapter 3,

Section 470)

Applicable Groundwater is classified under the Maine Standards. The groundwater at the

O'Connor Site is classified as GW-A (i.e., water shall be of such quality that it

can be used for domestic purposes.

Maine Drinking Water Rules (10-144A

CMR Chapters 231-233)

Relevant and

Appropriate

Maine's Primary Drinking Water Standards are equivalent to federal MCLs.

1992

Maine Maximum Exposure Guidelines

(MEGs)

Relevant and

Appropriate

MEGs are the Bureau of Health's recommendations for concentrations of

chemical contaminants in drinking water. MEGs are health-based guidelines

and are not legally enforceable.

2000

Maine Maximum Exposure Guidelines

(MEGs)

To be considered MEGs are the Bureau of Health's most recent recommendations for

concentrations of chemical contaminants in drinking water. MEGs are healthbased guidelines and are not legally enforceable.
TABLE 7: IDENTIFICATION OF LOCATION-SPECIFIC ARARs

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Federal Regulatory Requirements

National Environmental Policy Act

(NEPA, 42 USC § 4341) and Wetland

Executive Order (EO11990), 40 CFR

Part 6, Appendix A

National Historic Preservation

Act(NHPA, 16 USC 470 etseq.. 40 CFR

800)

Clean Water Act Section 404

Requirements for Dredged or Fill

Material (33 USC 1344; 40 CFR 230)

State of Maine Regulatory Requirements

Maine Natural Resources Protection Act

(NRPA, 38 MRSA § 480) and Permit By

Rule Standards (MEDEP Regulations

Ch. 305

& ••• ^i^

VK * "~ws*"-»

Applicable

Applicable

(if encountered)

Applicable

Applicable

The Wetlands Executive Order requires federal agencies to mimmize the

destruction, loss, or degradation of wetlands, and preserve and enhance natural

and beneficial values of wetlands.

CERCLA response actions are required to consider possible effects of the

response activities on any historic property included in or eligible to be included

in the National Register of Historic Places.

Under this requirement, no activity that adversely affects a wetland shall be 1

permitted if a practicable alternative is available. |

This act outlines requirements and performance standards for certain activities

in, on, over, or adjacent to freshwater wetlands, streams, ponds, or brooks. The

activities must not unreasonably interfere with certain natural features, such as

natural flow or quality of any waters, nor harm significant aquatic habitat,

freshwater fisheries, or other aquatic life.
vlaine Endangered Species Act and

Regulations (12 MRSA Section 7751-

7756; 09-137 CMR 008)

Wi^^^i^iiAl^M^IS^^ •••:;-•

Federal Regulatory Requirements

Endangered Species Act (ESA, 16 USC

§§ 1531-1534)

State of Maine Regulatory Requirements

Maine Standards for Classification of

Groundwater (38 MRSA, §§ 465 -C and

470)

Maine Endangered Species Act (MESA,

38 MRSA §§ 7001, 7751-7759) and

Maine Inland Fisheries and Wildlife

Laws and Regulations (12 MRSA § 703 1

et seq.)

Applicable (if

endangered species

are identified or

encountered)

'••:• ':': ;t:te:d-;:

Applicable (if

encountered)

Applicable

Applicable (if

encountered)

The state of Maine has the authority to research, list, and protect any species that

are determined to be threatened or endangered, according to state regulations.

The ME Department of Inland Fisheries and Wildlife has developed the

following categories for the consideration of important species that not

threatened or endangered: Maine Watch List, Special Concern List, and

Indeterminate Category. The department determines habitat uses on a case-bycase basis. The Maine lists of species may differ from the federal.

!

tx-;/: •:;Mli;&^

This act requires action to avoid jeopardizing the continued existence of listed

endangered or threatened species or notification of their habitat.

This law establishes the classification of the -state's groundwater to protect,

conserve, and maintain groundwater resources in the interest of the health,

safety, and general welfare of the people of the state. Groundwater is classified

as GW-A, the highest groundwater classification, and is designated as a

potential water supply. This classification applicable to remedial objectives.

The State of Maine has authority to research, list, and protect any species

deemed endangered or threatened. These species are listed as either endangered

or threatened in the state regulations. The Maine Department of Inland Fisheries

and Wildlife has also developed the following administrative categories for

species not considered endangered or threatened but considered important for

research and further evaluation: Maine Watch List, Special Concern List, and

Indeterminate Category. The Department determines appropriate use(s) of

various habitats on a case-by-case- basis. The Maine lists may differ from the

federal lists of endangered species. {
Maine Site Location and Development

Law and Regulations (38 MRS A

Sections 481 through 490; MEDEP

Regs. Ch. 371-377)

Applicable This act and regulations govern new development, including new developments

that handle hazardous wastes and oil. Activities cannot adversely affect existing

uses, scenic character, or natural resources in the municipality or neighboring

municipality.

vlaine Critical Areas Program and Maine

Natural Heritage Program

To Be considered These state programs issue policies and regulations governing special habitats or

communities.

Maine Critical Areas Act (5 MRS A §§

3310-3316)

To Be considered This non-regulatory legislation allows Maine agencies such as the Critical Areas

Program and the Natural Heritage Areas Program to identify, research, and

protect critical areas and endangered or threatened plants.

Municipal Regulatory Requirements

Mandatory Shoreland Zoning (38 MRS A

§§ 435-449)

Town Shoreland Zoning Ordinances and

State Minimum Guidelines (38 MRS A

§§ 1801-1803,1841-1843-A, 1901-1905,

2013) and City of Augusta

Comprehensive Plan/Shoreland Zoning

Plan

To Be considered These minimum guidelines and town ordinances apply to activities proposed

within 250 feet of a high-water mark of a stream or other body of water.
TABLE 8: IDENTIFICATION OF ACTION-SPECIFIC ARARs

Federal Regulatory Requirements

TSCA (15 USC §§ 2601-2692) and

Polychlorinated Biphenyls (PCBs) Regulations

(40 CFR 761: Subpart G, PCB Cleanup Policy;

and Subpart C and D, Markings, Storage and

Disposal)

These requirements apply to the marking, storage, disposal, and cleanup of PCBs greater than 50

ppm that occur after their respective effective dates. The PCB Spill Cleanup Policy, Subpart,

applies to spills of PCB greater than 50 ppm that occurred after its effective date (i.e., May 4,

1987).

U.S. Department of Transportation Rules for

Transportation of Hazardous Materials (49

C.F.R. Parts 107, 171.1-172.558)

This regulation outlines procedures for the packaging, labeling, manifesting, and transportation

of hazardous materials. If residuals from groundwater treatment and/or recovered free product

are classified as hazardous, the materials will be packaged, manifested, and transported to a

licensed off-site disposal facility in compliance with these regulations.

USEPA RCRA - Standards Applicable to

Generators of Hazardous Waste (40 CFR Part

262)

This requirement sets standards for generators of hazardous waste that address (1) accumulating

waste, (2) preparing hazardous waste for shipment, and (3) preparing the uniform hazardous waste

manifest. These requirements are integrated with DOT regulations. Any RCRA hazardous wastes

being shipped off-site must be shipped in proper containers that are accurately marked and

labeled, and the transporter must display proper placards. All waste shipments must be

accompanied by an appropriate manifest.

USEPA RCRA - Standard Applicable to

Transporters of Hazardous Waste (40 CFR Part

263)

These regulations outline the standards for transportation of hazardous waste off-she.

Transporters of hazardous waste must comply with manifest, record keeping, and reporting

requirements set forth in these rules. These requirements will be attained through compliance

with U.S. DOT Rules for Transportation of Hazardous Waste.
USEPA Guidance for Evaluating Technical

Impracticability of Groundwater Restoration

(9234.2-25).

Consistent Implementation of the FY 1993

Guidance on Technical Impracticability of

Groundwater Restoration at Superfund Sites

(9200.4-14)

Use of Monitored Natural Attenuation at

Superfund, RCRA Corrective Action, and UST

Sites (9200. 4- 17P)

Overview of ARARs, focus on ARAR Waivers

(OSWER9234.2-03/FS)

This guidance clarifies how USEPA will determine whether groundwater restoration is technically

impracticable and what alternative measures or actions must be undertaken to ensure that the final

remedy is protective of human health and the environment.

This memorandum outlines the basic process for evaluating at Tl decision document and is

intended to promote technically sound, nationally consistent implementation of the Tl guidance.

This directive clarifies ERA's policy regarding the use of monitored natural attenuation for the

cleanup of contaminated soil and groundwater in the Superfund program (among others).

This memorandum provides an overview of ARARs, with a focus on ARAR waivers.

State of Maine Regulatory Requirements

Waste Discharge Licenses (38 M.R.S.A. §

413)

Maine Hazardous Waste, Septage, and Solid

Waste Management Act Title 38, Chapter 13

and MEDEP Regulations, Chapters 800-802,

850. 851.853-8571)

Direct or indirect discharges to the waters of the state require a license.

The rules provide a comprehensive program for handling, storage, and record keeping at

hazardous waste facilities. They supplement the RCRA regulations.
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AUGUSTA. MAINE

O'CONNOR COMPANY

SUPERFUND SITE

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FIGURE 1
APPENDIX II TO AMENDMENT TO O'CONNOR CONSENT DECREE

REMEDIAL DESIGN/REMEDIAL ACTION

2003 STATEMENT OF WORK

A. Introduction and Purpose of Plan

It is the purpose of this Remedial Design/Remedial Action 2003 Statement of Work (2003

SOW) to define the remedial actions to be undertaken and funded by the Settling Defendant

under the Amendment to Consent Decree at the O'Connor Site in Augusta, Maine. The SOW

describes the extent of remedial activities required at the Site based on the September 2002

Record of Decision Amendment (ROD Amendment) and sampling results available to EPA as of

September 2002. This Appendix II supersedes Appendix II of the September 3, 1991 Consent

Decree, as amended in the 1994 revised SOW (1994 RSOW) following the July 11, 1994

Explanation of Significant Differences. The 2003 SOW follows the same format as the 1991

SOW and 1994 RSOW.

The remedial actions described in this Appendix II include elements which have been completed

pursuant to the 1991 Consent Decree (source control components, management of migration

components, Riggs Brook components, and institutional controls); elements which are carried

forward from the 1994 RSOW (source control and Riggs Brook components); and those

remedial actions that the Settling Defendant has consented to undertake pursuant to this amended

settlement agreement (management of migration components).

Part B of this SOW provides definitions of terms used in this Appendix. Part C provides an

update of activities since the 1994 RSOW and an overview of the Remedial Action selected for

the Site. Parts D. E. F. and G of this SOW describe and update each of the remedial components

for remediation that \\ere required b\ the 1 ^91 SOW and 1994 RSOW: contaminated on-sile

surface waters, contaminated on-site soils and sediments, contaminated groundwater, and Riggs

Brook. Parts H, I, J, and K of this SOW describe further requirements and procedures for site

access and institutional controls, remedial design, remedial action, and operation and

maintenance.

B. Definitions

The following definitions shall apply to this SOW.

Grounduaier performance standards shall mean those uroundwater performance standards

specified in the ROD Amendment:

Benzene: 5 ug/L (same as the 1989 ROD)

1.4- Dichlorobenzene: 27 ug/L (same as the 1989 ROD)

1
PCBs': 0.05 ug/L (the 1989 ROD performance standard was 0.5 ng/L)

Chlorobenzene: 47 u,g/L (there was no performance standard for this in the 1989 ROD)

1,2-Dichlorobenzene: 85 ng/L (there was no performance standard for this in the 1989 ROD)

1,3-Dichlorobenzene: 85 ^g/L (there was no performance standard for this in the 1989 ROD)

1,2,4-Trichlorobenzene: 70 u.g/L (there was no performance standard for this in the 1989 ROD)

1,3,5-Trichlorobenzene: 40 (jg/L (there was no performance standard for this in the 1989 ROD)

1

 detection limit varies with location and is generally greater than the 0.05 u.g/L.

"Active Oil Recovery" shall mean the use of vacuum-enhanced pumping from wells located

within the Technical Impracticability Zone. The intent of the active oil recovery effort is to

remove separate-phase oil that is located or has come to be located above the seasonable water

table in the overburden and bedrock without removing groundwater.

"Passive Oil Recovery" shall mean the use of absorbent materials placed within extraction and

monitoring wells within the TI zone. The intent of the passive oil recovery is to remove separatephase oil that is located or has come to be located above the seasonable water table in the

overburden and bedrock between periods of active oil recovery.

C. Remedial Action Overview

The remedy selected by the 1989 ROD was developed to satisfy the following five remedial

action objectives (RAOs):

•reduce public health and environmental risks from direct contact with contaminated

soils,

•reduce public health'risks from inhalations of PCB vapors.

•reduce future health risks from ingestion of contaminated groundwater found on ili e MIC.

•reduce public health risks from ingestion of PCB-contaminated fish from Riggs Brook,

and

•reduce risks to aquatic and terrestrial wildlif e from exposure to contaminated sediments.

The 1994 ESD modified the selected source control remedy in three aspects: redefinition of the

Site to include 23 acres of the parcel: change of the cleanup standards for PCBs from one ppm to

ten ppm for a designated area onsite with concurrent requirement of regrading the designated

area with twelve inches of clean fill above the consolidated soils; and a contingency cleanup

plan. This contingency plan allowed for the off-site disposal of contaminated soil without prior

treatment, and was invoked by EPA on October 10. 1995.
In April 2002, the Settling Defendant submitted an evaluation of the technical practicability of

restoring the groundwater at the O'Connor Site to drinking water quality within a reasonable

period of time. This evaluation concluded that because of the geological and hydrological

conditions at the Site, there were no technologies which could accomplish this objective (the

third RAO in the 1989 ROD). The evaluation was resubmitted in June 2002 following EPA and

Maine DEP comments. EPA, with concurrence from Maine DEP, approved the June 2002

evaluation.

With recognition that it was technically impracticable to restore the groundwater within a limited

area of the Site to drinking water standards, EPA issued a Proposed Plan in late June 2002. In

this Plan, EPA proposed to changed the remedy for the Site. Following a period of public

comment, and after receiving categorical concurrence from Maine DEP, EPA issued a ROD

Amendment.

The September 2002 ROD Amendment selected a remedy consisting of institutional controls,

active and passive oil recovery, long-term monitoring of groundwater, and five-year reviews.

This ROD Amendment recognized the technical impracticability of achieving the third RAO

through active pump-and-treat for a limited area of the Site within a reasonable time frame. It

established a technical impracticability zone for this portion of the Site where state and federal

drinking water standards are waived.

A comparison of the original 1989 remedy for groundwater and the modified remedy is provided

in Table 1.

D. Remedial Design/Remedial Action for Contaminated On-Site Surface Waters

The 1991 Statement of Work required as part of the source control component the following

actions for on-site surface water: draining and off-site transport of surface waters, off-site

treatment of surface waters: and surface water drainage modifications.

Surface water from the Upper Lagoon and storm water were disposed offsite at special waste and

TSCA facilities. Samples collected from the Lower Lagoon were below detection limits, and

following review and comment by Maine DEP. EPA approved the on-site discharge of the

surface water from the Lower Lagoon. At the end of source control activities, the site drainage

patterns were restored to pro-source control conditions.

No further activities are required for on-site surface water. A more complete description of the

source control activitie s can be found in the September 1998 Source Control Remedial Action

(SCRA) report.

L

:

. Remedial Design/Remedial Action for Contaminated On-Site Soil and Sediments

To meet the first two RAOs. reduction of public health and environmental risks from direct
contact with contaminated soils, and reduction of public health risks from inhalations of PCB

vapors, the 1994 RSOW (revised to coincide with the changes described in the ESD) required as

part of the source control component the following actions for on-site soils and sediments:

decontamination/demolition of the on-site barn; site preparation activities; excavation and

consolidation of soil and sediment with PCB concentrations between 1 and 10 ppm into the

designated area; off-site disposal of soil and sediment with greater than 10 ppm PCBs to

permitted RCRA/TSCA facilities; replacement of the top twelve inches of the designated area

with clean fill from off-site sources; replacement of the excavated areas outside the designated

area with clean fill from off-site sources; site restoration; and establishment of compensatory

wetlands.

The first two RAOs were achieved with the completion of the source control remedial action in

1997. The soil clean-up began in 1996 with the cleaning, demolition, and off-site disposal of the

barn situated along Route 17, and other site preparation activities. The soil cleanup was

completed in 1997. These activities included the excavation and off-site disposal of nearly

20,000 tons of soil. An additional 3000 to 4000 tons of soils with PCBs or PAHs concentrations

between 1 and 10 ppm were placed within the designated area onsite. This area was then covered

with a minimum of one foot of clean fill brought in from offsite. The entire Site was then graded.

The on-site wetlands were restored. An additional 0.4 acre of wetlands was created in the former

lagoons as replacement for wetlands lost as a result of the clean-up activities.

Laboratory tests of samples collected from the bottom and perimeter of the excavation

demonstrated that the excavation had removed the contaminated soil to the performance

standards set in the 1994 ESD.

With the completion of the source control activities and the approval of the SCRA report, the

Settling Defendant initiated operation and maintenance activities per Section K. of the 1994

RSOW. Operation and Maintenance activities specific to source control include monitoring of

wetland restoration and maintenance of the soil cover in the designated area. The restored

wetlands have been monitored annually from 1998 through 2002. The next and final scheduled

wetland monitoring activity shall be performed in 2007.

In addition to periodic monitoring of the soil cover for crosional features, the Settling Defendant

shall also demonstrate the integrity ol the soil cover through sampling. At five year intervals

coincident with each five-year review, the Settling Defendant shall collect composite samples

from ten locations randomly selected from the SCRA grid nodes. These samples shall be

collected from four to eight inches below the surface and analyzed for PCBs.

The 1994 ESD established that a portion of the Site would be used to consolidate soil and

sediment containing levels between one and ten ppm of PCBs and or cPAl Is. As conceptuall\

presented in the ESD, the designated area was three to four acres bounded on five sides with

rounded turning points. As the actual excavation for the source control remedial action evolved.

the boundary of the designated area became a 25-sided polygon. This created a difficult situation
for anyone inspecting the Site to know where the boundary was. The Settling Defendant shall

survey the designated area, the boundaries shall be simplified to the 10-sided shape shown in

Figure 5 of the 2002 ROD Amendment, and permanent markers shall be placed at the turning

points.

A more complete description of the source control activities can be found in the September 1998

SCRA report.

F. Remedial Design/Remedial Action for Contaminated Groundwater

To meet the third RAO, reduction of future health risks from ingestion of contaminated

groundwater found on the Site, the 1991 SOW required the establishment of temporary

institutional controls, installation of groundwater extraction wells and additional monitoring

wells, and installation and operation of a groundwater treatment and discharge system.

The groundwater remedy selected in the 1989 ROD included pumping wells, a treatment system,

and a network of monitoring wells to track contamination levels. The intent was to pump and

then treat groundwater which contained dissolved PCBs and VOCs and thereby restore the

quality of the groundwater.

As part of design activities, a pumping test was conducted in TWA II in 1992 to determine the

number of wells and components of the pump and treat system. Subsequent to this test, separate

phase oil was detected in the bedrock. Consequently, the focus turned to removal of oil from the

subsurface rather than pumping and treating groundwater. A vacuum-enhanced system to

recover separate phase oil was operated in 1996 - 1997, prior to the source control excavation

and removal activities. Following the source control activities, oil was recovered by placing

absorbent materials in the extraction and monitoring wells. From August to October 2001, the

vacuum-enhanced system was again operated as part of the TI evaluation. Approximately twenty

gallons ofoi l were recovered.

The 1989 ROD was amended in September 2002 following an evaluation of the technical

practicability of restoring the groundwater within a reasonable time period. The ROD

Amendment changed the remedy for groundwater in order to meet the Remedial Action

Objective. Rather than achieving this objective through pump-and-treat. the 2002 ROD

Amendment included designation of a '11 zone, active and passi\c oil recover). insiiUiliviia l

controls, long-term monitoring, and five year reviews.

Tl Zone

Following the evaluation of the technical practicability of restoring groundwater to drinkin g

water standards, a TI zone was established for a limited portion of the Site (see figure 3 of the

ROD Amendment for the TI zone). Groundwater beyond the TI zone shall meet the performance

standards listed above.
Active and Passive Oil Recovery

The Settling Defendant shall operate, on an annual basis, a vacuum-enhanced recovery system

(VER) to remove oil and associated PCBs which has accumulated above the water table. This

system shall be operated on an annual basis in late summer- early fall until it is determined to be

no longer effective. Criteria to be used to make this determination include the following:

apply the VER to four wells (101, 202B, 301B, and 302B) in the TWA II area at least

once every year for the next five years (through 2007);

after application of the VER to a well, recovery of oil will be observed over a period of

up to one week. If a "significant " amount of oil is recovered from the well, the VER will

be reapplied to the well. A "significant" amount of oil is defined as an increase in the

amount of oil recovered relative to the amount of oil recovered through passive means.

Therefore, if the VER is effectively increasing the amount of oil being recovered from a

well, it will continue on that well;

the operation of the VER shall continue for a period of up to two months if significant

amounts of oil are recovered. After this time weather constraints and rising groundwater

elevations are expected to limit the effectiveness of the VER; and

the necessity and conditions for continuation of the VER shall be addressed during the

next five 5-year review, scheduled for September 2007, and each subsequent 5-year

review period.

Following operation of the VER, absorbent materials shall be placed in monitoring wells to

absorb any remaining residual oil. The use of absorbent materials shall continue until as long as

it is practical, i.e. as long as oil is visibly detectable. Between active operation of the VER. the

\\clls shall be monitored for oil accumulatio n on a monthl y basis. It is anticipate d that this

frequency will be reduced to quarterly in the future. All recovered oil and used absorbent

material shall be disposed of at a licensed TSD facility.

Institutiona l Controls

The Settling Defendant shall implement the components of the restrictiv e covenan t recorded in

the Kennebec County Registry of Deeds on September 13. 2002. as discussed further in Section

H of this SOW.

1.one-Term Monitoring

The Settling Defendant shall continue the groundwater monitoring program to track dissolved

PCB and VOCs. This long-term monitoring program shall be conducted twice yearly, in spring

and fall. The monitoring program will also require tracking the attenuation of dissolved
contaminant levels beyond the area where the oil is present in the groundwater. This monitoring

data shall be used to verify that the dissolved contaminant concentrations are decreasing. Finally,

this component of the remedy shall include contingencies should the groundwater monitoring

indicate the contamination is moving beyond its current limits. Contingencies may include

increased sampling frequency, implementation of additional sampling locations, including any

residential wells installed on adjacent properties, reevaluation of the conceptual model, and

increased operation of the VER.

This program shall be maintained until it has been determined by EPA, after opportunity for

review and comment by Maine DEP, that the groundwater in the overburden soils and in the

bedrock have achieved the performance standards defined above.

The scope of the long-term monitoring program will be reviewed periodically by the Settling

Defendant and EPA, with opportunity for review and comment by Maine DEP. Reviews will

occur at least yearly, following receipt of the sampling report following the fall sampling event.

In addition, the scope of the long-term monitoring program shall also be reviewed in connection

with the five-year reviews. Upon these reviews or at any other time EPA, after opportunity for

review and comment by Maine DEP, may require modification to the monitoring program being

conducted by the Settling Defendant. Such modifications would be effective thirty (30) days after

written notice by EPA, unless EPA specifies a longer period of time. The Settling Defendant

may request modifications of the monitoring program, including reduction in sampling

frequency. If warranted, EPA, after opportunity for review and comment by Maine DEP, shall

grant such modifications based on the available data and evaluation of the data.

The results of the groundwater sampling performed in accordance with the monitoring program

shall be submitted to EPA and Maine DEP within forty-five days of receipt of the data from the

laboratory.

Five-Year Reviews

As long as contamination remains which prevents unrestricted use of the Site, five-year reviews

shall be performed to evaluate the effectiveness of the implemented cleanup plan. As part of

each five-year review. EPA shall review the site conditions to ensure that the remedy continue s

to provide protection ol human health and the environment.

As noted above, sampling of the soil cover for the Designated Area will be done coincident with

the five-year reviews to demonstrate the integrit y of the soil cover. In addition, coincident with

the five-year reviews, the PCB analysis performed for the groundwater outside the TI zone shall

use methods capable of lower detection limits in order to compare the concentration levels wit h

the Maine MEG of 0.05 uG/L..
G. Remedial Design/Remedial Action for Riggs Brook

To meet the fourth and fifth RAOs of the 1989 ROD, reduction of public health risks from

ingestion of PCB-contaminated fish from Riggs Brook, and reduction of risks to aquatic and

terrestrial wildlife from exposure to contaminated sediments, the 1991 Statement of Work

identified four activities for Riggs Brook as part of the management of migration control

component. They were the establishment and implementation of a ten year sediment sampling

and analysis program; at least one fish tissue sampling event after five years of sediment

sampling, public relations procedures to inform the community about the potential risks

associated with Riggs Brook; and five-year reviews.

Performance standards for Riggs Brook sediment and biota were set in the 1989 ROD at 1 ppm

PCBs and 2 ppm PCBs, respectively. However, it was agreed at that time that the negative shortterm impacts to the wetlands ecology outweighed the removal of sediments to that level. A

trigger level of 5 ppm PCBs for further action was therefore established As stated in the 1991

SOW, "if the PCB levels within Riggs Brook are found to exceed 5 ppm in the sediments and/or

2 ppm in the fish tissue samples, the Settling Defendant shall design and implement a more

rigorous sampling effort within Riggs Brook to determine the need and/or extent of further

Remedial Action within Riggs Brook, if any." This occurred in 1997 when soil and sediment

above 5 ppm PCBs were removed simultaneously with the ongoing source control remedial

action, and again in 1999 and 2000 when additional samples were collected.

The Settling Defendant began sediment sampling in 1996, and lias conducted tuo fish tissue

sampling events (1997 and 2000). The last two sediment sampling events have had only one

exceedance of the 5 ppm trigger out of thirty-six locations; the majority of results have been

below detection limits. The fish tissue analysis demonstrated that concentrations of PCBs

detected did not exceed the ROD target level of 2 ppm, and in fact have all been below 1 ppm.

The Settlin g Defendant shall continue the annua l sediment sampling throug h 2005. Furthe r fish

sampling may be necessary as part of the further Remedial Action specified alxnc should the

PCB concentrations exceed 5 ppm.

11. Site Access and Institutional Controls

A Restrictive Covenant has been signed by the Settling Defendant and Maine DEP that prohibits

use of the groundwater beneath the Site. Public water is available on Route 17 to the south and

to residential properties on Cony Road to the west. The nearest known residential \\ell is

approximate!) a half mile to the east, situated on a hil l about tuo hundred feet above the Riggs

Brook discharge area. This well intercepts flo\\ mo\ ing \\est toward Riggs Brook. 1 heretore.

there is no current drinking water exposure to the groundwater which flows beneath the Site.

This Restrictive Covenant shall remain in place until terminated by Maine DHP. Should 1 PA.
however, find that this covenant is no longer protective, effective, or it interferes with the

performance of the remedy, additional institutional controls shall be placed on the property.

I. Remedial Design

The 1991 SOW required the Settling Defendant to perform pre-design activities for both source

control and management of migration. These included a pilot-scale treatability study of the

solvent extraction process for the source control component and a pilot-scale aquifer test and

treatability study for the management of migration component. These .were completed and the

results submitted to EPA in November 1993.

The 1994 RSOW required the Settling Defendant to submit a series of work plans and design

documents (30%, 60%, 95%, and 100% designs). The work plans and design documents, with

the exception of the O&M plan, have been approved by EPA, after opportunity for review and

comment by Maine DEP.

There are no further remedial design requirements.

J. Remedial Action

The 1994 RSOW established a schedule for implementing remedial action for source control and

management of migration components as well as documentation requirements. The source

control components were completed in 1997 and final documentation for source control was

submitted in September 1998. With the determination of technical impracticability for a limited

portion of the Site, the management of migration component has been modified as noted above.

K. Operation and Maintenance

The Settlin g Defendant submitted an Operation and Maintenanc e Plan as part of the SC'RA and

then revised it for review and approval in 2002. Upon approval b\ F.PA. after opportunity for

review and comment by Maine DEP. the Settling Defendant shall implement the O&M plan.
Table 1: Comparison between 1989 ROD and 2002 ROD Amendment

1989 ROD - Groundwater components

#1: temporary institutional controls. This

would prevent exposure to site groundwater

while remediation was underway.

#2: pump-and-treat system. The appropriate

sizing of the system, including the number of

extraction wells, pumping rate, treatment

components such as granular activated carbon,

sand filters, air stripper, and number of recharge

wells was to be determined during the remedial

design phase.

#3: a network of monitoring wells. The wells

used in the RI would be assessed and augmented

with additional wells in both overburden soil

and bedrock.

#4: Riggs Brook sediment and biota monitoring.

Brook sediments were to be monitored yearly

for ten years to assess PCB concentrations.

Biota sampling was to occur five years after

initiation of the monitoring.

#5: five-year reviews. The progress toward

restoration of the site groundwater and the target

clea n up goal for the sedimen t uere to he

assessed durum each five-year revieu.

2002 ROD Amendment

#1 permanent institutional controls. With the

1994 BSD, CMP and Maine DEP signed a

restrictive covenant which prevented certain

activities at the Site without written approval of

Maine DEP.

#2: annual application of the VER system. The

VER has been operated three times post-ROD,

recovering PCB-laden oil from the overburden

and bedrock. The VER will be applied annually

in TWA II area wells to recover as much oil as

is practical.

#3 monthly monitoring of oil levels in TWA II

wells and removal using absorbent materials.

Between the annual operations of the VER. the

TWA II will be monitored for separate phase

oil. Detected oil will be removed using

absorbent material. It is expected that

monitoring frequency will decrease as the

amount of oil draining into the wells decreases.

#4:long-term monitoring. It will be performed

to track contaminant levels in the Tl zone and

outside it.'

??5: Rigu.s Brook scdmien! ami bioia

It will continue as established in 1996

#6: five-year reviews. Reviews wil l be

conducted to ensure tha t the site remedy remain s

protective.

10
APPENDIX II TO AMENDMENT TO O'CONNOR CONSENT DECREE

REMEDIAL DESIGN/REMEDIAL ACTION

STATEMENT OF WORK

ATTACHMENT A

PROJECT OPERATION PLAN

The Settling Defendant submitted a Project Operations Plan in accordance with the 1994 revised

SOW. The Project Operation Plan included four site-specific plans:

Site Management Plan

Sampling and Analysis Plan

Health and Safety Plan

Community Relations Support Plan.

EPA, after review and comment by Maine DEP, approved the POP.

The Sampling and Analysis Plan consisted of two parts: a Quality Assurance Project Plan, and a

Field Sampling Plan. As a requirement of this Statement of Work, the Settling Defendant shall

submit an update of the QAPP. The revised QAPP shall be in accordance with EPA guidance

document QAMS-OO5/80 and appropriate EPA handbooks, manuals, and guidelines, including

Region I's October 1999 Compendium of Quality Assurance Project Plan Requirements and

Guidance.

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