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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

PRP Lead

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 et. 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.

The 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 Site. 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:

ichard ^/Cavagnero/Acting Director

Officeja Site Remediation and Restoration

Region 1
Table of Contents

I SITE NAME, LOCATION, DESCRIPTION AND RATIONALE FOR

AMENDMENT 1

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

XI STATUTORY DETERMINATIONS 39

XII DOCUMENTATION OF NO SIGNIFICANT CHANGES 43

XIII STATE ROLE 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'

14. 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 TI 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 poly chlorinated 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 etseq., 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. This 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 site 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: 10 a.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, 1 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 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 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 PAHs based on the extensive data collected during

the SCRA.

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

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 groundwater 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 ESD. 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 ground-water 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 Mg/L, benzene

at 5 //g/L and 1,4-dichlorobenzene at 27 //g/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 //g/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 /ug/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 //g/L at OW-302B in December 1998. In April 2001, the

concentration of PCBs at OW-302B was 44 //g/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 //g/L 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

13//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 //g/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 //g/L

at OW-202B and OW-301B at concentrations ranging from 3-610 //g/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 1 999, 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 1992 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 /ug/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 //g/L in MW-104B and 25-55 //g/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 along the boundary of the TI zone are in attainment

of federal MCLs and Maine MEGs (MW-501, MW-502, MW-503 and MW-510A). 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 //g/L).

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 /ug/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 groundwater 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

Contaminant

Of Concern

Benzene

1,4-

Dichlorobenzene

PCBs1

Chlorobenzene

1,2-

Dichlorobenzene

1,3-

Dichlorobenzene

1,2,3-

Trichlorobenzene

1,2,4-

Trichlorobenzene

1,3,5-

Trichlorobenzene

2UU1 Maximum

Groundwater

Concentration

(//g/L) and Location

8 - OW-302B

720 - OW-302B

44 . OW-302B

240 - OW-302B

210-OW-302B

160 - OW-302B

98 -OW-302B

770 - OW-302B

not analyzed for

MCL

(//g/L)

5

75

0.5

100

600

NS

NS

70

NS

MEG

(//g/L)

5

27

0.05

47

85

85

NS

70

40

iy«y KUL> Target

Cleanup Levels

(//g/L)

5

27

0.5

no ROD standard

no ROD standard

no ROD standard

no ROD standard

no ROD standard

no ROD standard

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 till/bedrock 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-15, 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 in 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-514, 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 well 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 RJ

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 till/bedrock 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 till/bedrock 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 till/bedrock 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 /ug/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 //g/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 wells. 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 barn 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. Implementabilitv

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.

XI. 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 will 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 CERCLA §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 groundwater 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 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

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 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 TI 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 Superfund Site

Table 2: PCS Results - TWA II

PCB Results 0/g/L) - TWA II

Sampling Date

3/98

6/98

9/98

12/98

3/99

6/99

9/99

3/00

9/00

4/01

9/01

ow202B

ND

ND

NS

ND

0.79

NS

NS

NS

NS

0.35

NS

ROD Cleanup Standard

OW- OW204B 301 B

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

0.5 //g/L

ow302B

2.5

32

1,500

8,900

930

710

NS

NS

8.6

44

NS

RW-101

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-Dichlorobenzene

1 ,3-Dichlorobenzene

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 - OW-302B

MCL

(//g/L)

5

100

600

NS

75

NS

70

NS

0.5

1992

MEG

(^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

OW301 B

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 Superfund 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

0<S/L)

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

N/A

N/A

MW-106B

(MS/L)

0.004

0.01

0.01

0.02

ND

ND

ND

ND

ND

ND

0.05

0.05

MW-503

(^g/L)

0.004

0.03

0.02

ND

ND

ND

ND

ND

ND

ND

0.06

0.09

MW-508B

(A*g/L)

0.008

0.01

ND

ND

ND

ND

ND

ND

ND

ND

0.02

0.02

MW-104B

0*8/L)

EMPC*

0.04

ND

ND

ND

ND

ND

ND

ND

ND

0.04

0.07

OW-201B

G*B/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
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WOODARD&CURRAN SITE LOCATION MAP

CENTRAL MAINE POWER

AUGUSTA, MAINE

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SUPERFUNO SITE

09 NO 205521 0.5

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WOODARD&CURRAN

Engineering • Science • Operations

PORTLAND, MAINE 1-800-426 4262

SITE SETTING

DRAWN E^Y DR

CENTRAL MAINE POWER COMPANY

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DATE SEPT 2002

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the limit of excavation and fill depths may not match

205621 03\xs-1 2

200

Figure 12

Vertical Residual Oil Distribution

along Cross Section B-B'

Central Maine Power Co.

WOODARDikCURRAN I
Original includes color coding.

A

1

225 225

220 —^ 220

Current Surface Elevation

205

200 200

R= Refusal

Residual Oil

Present

NOTE

Previous grade line is projected on to the cross

section from the closest grid location where a

measurement was taken before and during source

control For this reason the limit of excavation and

fill depths may not match

205621 03\xs-2 2

Figure 13

Vertical Residual Oil Distribution

along Cross Section A-A'

Central Maine Power Co.

WOODARD&CURRANL
Original includes color coding.

C'

220

215

210

o>0)

u_

C

205

220

215

210

Current Surface Elevation

R = Refusal

Residual Oil

Present

NOTE:

Previous grade line is projected on to the cross section

from the cbsest grid location where a measurement was

taken before and during source control For this reason

the limit of excavation and fill depths may not match

Figure 14

Vertical Residual Oil Distribution

along Cross Section C-C'

Central Maine Power Co.

205621 03\xs-3 2

. WOODARD&CURRAN I
BU

S

ANVdWOO yONNOOO.O eoueps

NVdHDO ^ adVQOOM 'visnon

v

3NIVW 1VH1N30
ILI

S

ANVdWOO aONNOOO.O

aouapg

NVddno ^ advaooM 3Hi ONOI

V 'visnon

v

y3MOd 3NIVIM 1VH1N30
Perched ' x y

Water Table ~\ /

on Bedrock

Water

Table

Desiccated Fracture

with Residual Oil

Overland Flow of

Contaminants during

Salvage Operation

02B

Perched Water

Table on Bedrock

Bedrock Ridge

Inhibiting Flow

toward Riggs Brook

Original includes color coding.

Figure 17

Conceptual Hydrogeolog'c Model

Prior to Source Control

205621 03\model prior WOODARD<^CURRAN —I
Water

Table

Desiccated Fracture

with Residual Oil

Perched ' x y

X

Gravel Fill after

Soil Excavation

Perched Water

Table on Bedrock

Bedrock Ridge

Inhibiting Flow

toward Riggs Brook

Original includes color coding.

Figure 18

Conceptual Hydrogeologic Model

After Source Control

205621 03\model after - WOODARD&CURRAN
O'CONNOR SUPERFUND SITE

OPERABLE UNIT-2

September 2002 ROD AMENDMENT

APPENDIX A - RESPONSIVENESS SUMMARY

Comments Received on the June 2002 Proposed Plan for the O'Connor Site

1. Comments from Community Members

No comments were received from the community during the July 9, 2002 hearing for the

Proposed Plan.

Several comments were voiced during the information meeting held on June 24, 2002 and are

summarized below.

Community member: In discussing the technical impracticability of removing the oil, different

technologies were suggested which should perhaps be considered to clean up the residual oil.

EPA's Response: Although these suggestions, including the controlled blasting of the bedrock as

would be done in a quarry operation, were not looked at in the TI evaluation, EPA believes the

difficulties posed by the geology and hydrology of the site would be the same as for any of the

eighteen technologies considered in the TI. These limitations include:

residual oil tied up in fractures in the clayey soils and in the bedrock;

limited groundwater recharge to the source area so that there is limited flushing; and

the relatively impermeable clay limits the effectiveness of in-situ application of oxidizing

agents or other compounds.

The possibility of further excavation of the soil with the residual oil was evaluated as part of the

TI process. In a way, it posed a similar question that would be asked for removal of the bedrock:

how would the limits of excavation (or blasting) be determined? The source control effort

showed through extensive testing that the cleanup standards for the soils were met. In many

cases, the results were below the laboratory detection limit. So with the soils already below the

detection limit, sampling would not provide a method to determine the extent of any excavation

(or blasting). EPA believes this would lead to arbitrary excavation and hence it would be

difficult to implement, difficult to estimate costs, and difficult to provide an approach to assess

its effectiveness. Consequently, this alternative was screened out during the TI evaluation.
Community member: Several comments were made that the nine criteria used in selecting a

remedy needed to be expanded to ten, to look at the impact of a Superfund site on property

values. Additionally, there was the desire that EPA direct the City of Augusta to provide tax

relief for the surrounding properties.

EPA's Response: EPA is aware of concerns raised at this site regarding the impact of having a

Superfund site as a neighbor - this is a concern heard across the country. EPA has made changes

in its policies regarding its approach to adjacent properties where contamination has come to be

located, and EPA has studied the economic impact of Superfund sites on property values, but as

pointed out by Maine DEP at the public meeting, the Superfund law does not provide for any

method to address this issue. This issue may be more properly addressed on the state and local

levels. However, EPA hopes that by addressing the problems at the Site in a way that protects

human health and the environment in the long term there will ultimately be a positive impact in

the community.

Community member: Several long-time community members asked about the impact on Riggs

Brook, tying in their recollections of oil being visible in the brook and far downstream of the site.

In addition, questions were asked regarding the appropriateness of sampling fish when perhaps

other organisms might provide a better indication of PCB-contamination

EPA's Response: EPA acknowledges that conditions at the O'Connor property impacted other

areas, such as Riggs Brook. However, the current data has indicated that the PCB concentrations

are quite low where groundwater discharge to Riggs Brook is occurring and that there does not

appear to be any more overland transport from the source area to Riggs Brook.

Monitoring well MW-106B is a bedrock well located in the Riggs Brook wetlands and is a

flowing artesian well - that is, water flows out of the well head at the ground surface. Sampling

for the past several years have shown low levels of contamination which are below the ROD

performance standards. Yearly sediment sampling has indicated that PCB concentrations are

typically below the trigger level of 5 ppm and often below the clean up goal of 1 ppm. Analysis

of the data suggests that the concentrations in both groundwater and sediment are decreasing and

EPA anticipates that the concentrations will continue to decrease following the source control

remedial action.

The use offish rather than other organisms as an indicator of PCB s was determined at the time of

the 1989 ROD. Personnel from U.S. Fish and Wildlife Service (USFWS) and National Oceanic

Atmospheric Administration (NOAA), as natural resource trustees, were involved with this

aspect of the remedy selection. As they are the individuals with the expertise in this field,

selection offish was based on their knowledge of PCB bioaccumulation. Personnel from

USFWS continue to be involved with the Riggs Brook monitoring as well as EPA and Maine

DEP ecological risk assessors. It is noted that several species offish have been collected as part

of the monitoring program.

Community member: Concern was raised about the prospect that contaminated groundwater may

2
pass beyond the CMP property to potentially impact other properties.

EPA's Response: The highest priority in selecting a remedy is to ensure that it is protective of

human health as well as the environment. With the acknowledgment that it is technically

impracticable to clean up the groundwater beneath a portion of the site, EPA must select a

remedy that prevents further migration of the contamination, and Maine DEP strongly agrees

with this. EPA believes the selected remedy does this. Concentrations at monitoring wells

MW-106A and MW-106B, located in the Riggs Brook wetlands, plus the wells downgradient of

the TWA-II area have been meeting the performance standards set in the ROD for the past

several years. EPA believes that the groundwater system has reached equilibrium and that

contamination will not move beyond the CMP property. However, should the concentrations

change in these wells, and residential wells be installed in adjacent properties, then EPA would

have these wells tested.

2. Comments from Maine Department of Environmental Protection

At the hearing for the Proposed Plan, Maine DEP entered a statement into the site record. The

State noted the following concerns and stated that their concurrence on the ROD amendment was

contingent on these concerns being addressed.

Maine DEP: USEPA must better identify and define the criteria for discontinuing use of the VER

system.

EPA's Response: In the Proposed Plan, EPA stated the active recovery of oil using the VER

would continue on an annual basis as long as it was practical. This ROD amendment provides

more detail regarding the VER application. It sets forth a framework under which the VER will

operate, states that it will be operated for the next five years, and that the reevaluation of its

operation will be tied in with the next five-year review scheduled for summer 2007.

Maine DEP: All site work will be performed in compliance with the revised cleanup plan and all

applicable standard operating procedures, laws, and regulations.

EPA's Response: All work performed onsite will follow approved work plans and all applicable

requirements.

Maine DEP: MEDEP will be given at least 2 weeks notice prior to each sampling event.

EPA's Response: This will be addressed in any enforcement agreement that is entered into to

conduct the remedy selected in this ROD Amendment.

Maine DEP: It must be periodically demonstrated that there is a continuous twelve inches of

clean soil over the Designated Area. The details of such demonstration will be established prior
to the finalization of the ROD Amendment.

EPA's Response: As part of the change in the soil remedy, as documented in the 1994 ESD,

twelve inches of clean soil were to be placed over the designated area. This soil, defined as

containing less than one ppm of PCBs, was to be brought in from offsite. Concurrent with the

ESD, Maine DEP and CMP signed a Restrictive Covenant which states that CMP or subsequent

owner "shall maintain all drainage ways... permeable or impervious caps or covers (including

areas covered by topsoil or other clean fill)"

EPA agreed to address this issue concurrently with the TI evaluation. As noted in Section IV.

Scope and Role of Operable Unit, of this ROD Amendment, operation and maintenance will

include provisions for periodic monitoring of the soil cover as well as random sampling of the

surface soils to be performed at the time of the five-year reviews. Maine DEP indicated this was

an acceptable resolution for this issue.

Maine DEP: Clarify, by incorporation into the ROD Amendment, that the clean up goal for PCBs

in sediment is actually 1 ppm, not 5 ppm. However, MEDEP agrees that the 5 ppm trigger level

for remedial action is acceptable.

EPA's Response: EPA has clarified in Section IV. Scope and Role of Operable Unit of this ROD

amendment that the clean up goal for PCBs in Riggs Brook and associated wetland sediments is

1 ppm.

A review of the 1991 Consent Decree and the 1994 Revised Statement of Work found that

neither document provides any criteria to define a hot spot excavation. Similarly, the approved

October 1997 Final Riggs Brook Sediment and Biota Sampling and Analysis Plan is also silent

on this issue. To clarify this, the clean up goal for Riggs Brook and associated wetland sediment

is 1 ppm, but should a hot spot excavation occur, the extent of that excavation would be to less

than 5 ppm.

This is consistent with the intent of the 1989 ROD to protect ecological receptors. As noted in the

1989 ROD, in addition to the clean up goal for sediments, the trigger for additional sampling is also tied

to the goal of less than 2 ppm for PCBs in fish tissue samples. Should this sampling indicate 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 action to be undertaken within Riggs Brook, if any". (1989

ROD, page 47)

Maine DEP: All significant erosion occurring in the Designated Area on site will be addressed in

a timely manner to prevent exposure to levels of PCB above 1 ppm and lead above 248 ppm.

EPA's Response: See the response above regarding maintenance of the soil cover.

• Comments from the Settling Party

Central Maine Power Co. (CMP) provided comments during the public comment period for the
site record in response to two of Maine DEP's comments. CMP noted it supports the amended

ROD for the O'Connor site.

CMP: Cover Soil Effectiveness. The Source Control Remedial Action (SCRA) required that a

12-inch cover of soil containing less than 1 ppm of PCBs be placed over the Designated Area ,

the portion of the site where residual PCB concentrations in the soil could be up to 10 ppm. That

cover soil was placed during SCRA, and a cover crop of vegetation was established to stabilize

the soil and control erosion. The operating plan requires periodic inspections of the site by CMP

to identify any areas of erosion, and remedial action to be taken to repair those areas. To address

the concern that long-term gradual erosion could reduce the thickness of soil cover in some areas

without being visually obvious, discussions were held with Maine DEP and EPA to develop a

sampling program for the soil cover.

EPA's Response: As stated above, operation and maintenance will include confirmatory

sampling of the soil cover coincident with the five-year reviews for the site. Ten locations will

be randomly generated for sampling, using the grid nodes from the SCRA. Composite samples

from 4 - 8" below grade will be collected and analyzed for PCBs. Should the results be above 1

ppm, EPA, Maine DEP, and CMP will determine appropriate steps to take.

CMP: Riggs Brook PCB Concentrations. The US Fish and Wildlife Service (USFWS)

evaluation of Riggs Brook discussed in the 1989 ROD suggested a target cleanup level for PCBs

of 1 ppm. However, the ROD selected a remedy for the site that allowed the existing maximum

of 5 ppm PCBs in the sediment to remain because the short-term impacts of excavation would be

more damaging to the wetland area. The selected remedy required that a 10-year monitoring

program be instituted, and that a more rigorous sampling effort be undertaken if sampling found

sediment values above 5 ppm or fish tissue samples above 2 ppm. The results of this more

rigorous sampling would be used to determine if additional remediation of Riggs Brook were to

be required. Because excavation in Riggs Brook could cause short-term damage to the

ecosystem, as recognized by the ROD, CMP believes the limits of any remediation should be

established with respect to meeting the 5 ppm target level for PCBs, and not necessarily the

1 ppm target suggested by USFWS if doing so creates an unacceptable short-term impact to

Riggs Brook.

EPA's Response: EPA agrees that the limit of any excavation based on an exceedance of 5 ppm

would be to get below 5 ppm. However, the possibility exists that the levels identified in fish

tissue sampling could be greater than 2 ppm yet the sediment data be below 5 ppm. Should such

a situation arise, then the triggering of further sampling with possible remedial actions is

appropriate.
O'CONNOR SUPERFUND SITE

OPERABLE UNIT 2

September 2002 ROD AMENDMENT

APPENDIX B- ADMINISTRATIVE RECORD INDEX

4 FEASIBILITY STUDY (FS)

1 FACT SHEET EPA PROPOSES TO AMEND THE CLEAN-UP PLAN FOR THE F O'CONNOR

SUPERFUND SITE

AUTHOR US EPA REGION 1

DOC ID 32499 06/01/2002 15 PAGES

2 REPORT TECHNICAL IMPRACTICABILITY EVALUATION FOR OU-2 MANAGEMENT OF

MIGRATION (WITH TRANSMITTAL) [1 OF 2]

TO CENTRAL MAINE POWER COMPANY

AUTHOR WOODARD & CURRAN INC

DOC ID 31877 06/01/2002 135 PAGES

3 REPORT TECHNICAL IMPRACTICABILITY EVALUATION FOR OU-2 MANAGEMENT OF

MIGRATION, APPENDICES [2 OF 2]

TO CENTRAL MAINE POWER COMPANY

AUTHOR WOODARD & CURRAN INC

DOC ID 31881 06/01/2002 303 PAGES

6 REMEDIAL DESIGN (RD)

1 REPORT MANAGEMENT OF MIGRATION FLOATING FREE PRODUCT OIL STUDY

AUTHOR ALTON P DAVIS, GEI CONSULTANTS INC

JOANNE O MORIN, GEI CONSULTANTS INC

MURIEL S ROBINETTE, GEI CONSULTANTS INC
DOC ID 31925 02/14/1993 79 PAGES

2 REPORT REMEDIAL DESIGN/REMEDIAL ACTION REVISED STATEMENT OF WORK

AUTHOR US EPA

DOC ID 32078 10/20/1994 50 PAGES

3 REPORT MANAGEMENT OF MIGRATION GROUNDWATER MONITORING PROGRAM SAMPLING

AND ANALYSIS PLAN, VOLUME I OF E

AUTHOR WOODARD & CURRAN INC

DOC ID 31933 12/01/1996 156 PAGES

4 LETTER AMENDMENTS TO THE MANAGEMENT OF MIGRATION SAMPLING AND ANALYSIS

PLAN

TO ERIN HESKETT, US EPA REGION 1

AUTHOR JAMES M MOODY, WOODARD & CURRAN INC

DOC ID 31953 03/14/2000 10 PAGES

7 REMEDIAL ACTION (RA)

1 REPORT VACUUM ENHANCED RECOVERY PILOT TEST, PHASE 1 INSTALLATION AND

OPERATION REPORT (WITH TRANSMITTAL)

AUTHOR WOODARD & CURRAN INC

DOC ID 31937 12/01/1996 126 PAGES

2 REPORT DATA COLLECTION AND INTERPRETATION OF THE PHASE 2 OPERATION OF

THE VACUUM ENHANCED RECOVERY (VER) SYSTEM AT THE O'CONNOR SITE IN

AUGUSTA, MAINE

TO ROSS GILLELAND, US EPA REGION 1

AUTHOR ERIC T CARLSON, WOODARD & CURRAN INC

DOC ID 31948 06/27/1997 33 PAGES

3 REPORT MANAGEMENT OF MIGRATION COMPREHENSIVE EVALUATION

AUTHOR WOODARD & CURRAN INC

DOC ID 31957 08/01/1997 185 PAGES

4 MEMO FINAL INSPECTION OF THE SOURCE CONTROL REMEDIAL ACTION

TO MARY JANE ODONNELL, US EPA REGION 1
AUTHOR ROSS GILLELAND, US EPA REGION 1

DOC ID 31996 12/01/1997 2 PAGES

5 REPORT WETLAND CONSTRUCTION MONITORING REPORT

TO CENTRAL MAINE POWER COMPANY

AUTHOR SMART ASSOCIATES

DOC ID 31992 03/12/1998 49 PAGES

6 REPORT FINAL SOURCE CONTROL REMEDIAL ACTION REPORT [1 of 2]

AUTHOR WOODARD & CURRAN INC

DOC ID 31985 09/01/1998 421 PAGES

7 REPORT FINAL SOURCE CONTROL REMEDIAL ACTION REPORT [2 of 2]

AUTHOR WOODARD & CURRAN INC

DOC ID 31991 09/01/1998 358 PAGES

8 LETTER OIL STUDY IN THE UPLAND MARSH AREA AT THE CMP O'CONNOR SITE

TO ROY KOSTER, CENTRAL MAINE POWER COMPANY

AUTHOR ERIC T CARLSON. WOODARD & CURRAN INC

DOC ID 31997 01/26/1999 19 PAGES

9 REPORT 1998 WETLAND CONSTRUCTION MONITORING REPORT

TO CENTRAL MAINE POWER COMPANY

AUTHOR SMART ASSOCIATES

DOC ID 32028 04/08/1999 31 PAGES

10 REPORT 1999 RIGGS BROOK SEDIMENT MONITORING REPORT

TO ROY KOSTER, CENTRAL MAINE POWER COMPANY

AUTHOR HENRI J VINCENT, WOODARD & CURRAN INC

DOC ID 32059 02/01/2000 103 PAGES

11 REPORT 1999 WETLAND CONSTRUCTION MONITORING REPORT

TO CENTRAL MAINE POWER COMPANY

AUTHOR SMART ASSOCIATES

DOC ID 32024 08/15/2000 39 PAGES

12 LETTER COMMENTS ON 1999 WETLAND CONSTRUCTION MONITORING REPORT (DATED

AUGUST 15,2000)
TO CORNELL ROSIU, US EPA REGION 1

ERIN HESKETT, US EPA REGION 1

AUTHOR STEVEN E MffiRZYKOWSKI, US DOI/US FISH & WILDLIFE SERVICE

DOC ID 32022 10/19/2000 5 PAGES

13 REPORT 2000 WETLAND CONSTRUCTION MONITORING REPORT

TO CENTRAL MAINE POWER COMPANY

AUTHOR SMART ASSOCIATES

DOC ID 32020 03/13/2001 43 PAGES

14 LETTER COMMENTS ON 2000 WETLAND CONSTRUCTION MONITORING REPORT (DATED

MARCH 13,2001)

TO CORNELL ROSIU, US EPA REGION 1

TERRENCE R CONNELLY, US EPA REGION 1

AUTHOR STEVEN E MffiRZYKOWSKI, US DOI/US FISH & WILDLIFE SERVICE

DOC ID 32012 06/29/2001 4 PAGES

15 REPORT DRAFT 2000 RIGGS BROOK SEDIMENT AND BIOTA MONITORING REPORT

TO ROY ROSTER, CENTRAL MAINE POWER COMPANY

AUTHOR HENRI J VINCENT, WOODARD & CURRAN INC

DOC ID 32058 07/01/2001 159 PAGES

16 REPORT REVISED LONG-TERM GROUNDWATER QUALITY MONITORING PROGRAM AND

PHASE m VACUUM ENHANCED RECOVERY OF OIL WORK PLAN

AUTHOR WOODARD & CURRAN INC

DOC ID 32061 07/01/2001 28 PAGES

17 REPORT MANAGEMENT OF MIGRATION, SAMPLING AND ANALYSIS SEMI-ANNUAL REPORT

AUTHOR WOODARD & CURRAN INC

DOC ID 32066 10/01/2001 112 PAGES

18 REPORT DRAFT 2001 RIGGS BROOK SEDIMENT MONITORING REPORT

AUTHOR WOODARD & CURRAN INC

DOC ID 32062 12/01/2001 118 PAGES

19 REPORT DRAFT VER PHASE m REPORT

AUTHOR WOODARD & CURRAN INC

DOC ID 32069 12/01/2001 28 PAGES
20 LETTER COMMENTS ON DRAFT VER PHASE m REPORT

TO TERRENCE R CONNELLY, US EPA REGION 1

AUTHOR WILKES B HARPER, ME DEPT OF ENVIRONMENTAL PROTECTION

DOC ID 32072 02/16/2002 2 PAGES

10 ENFORCEMENT/NEGOTIATION

1 LITIGATION CONSENT DECREE, UNITED STATES OF AMERICA, PLAINTIFF, V

CENTRAL MAINE POWER COMPANY, DEPENDENT

TO JOEC COLLIER, CENTRAL MAINE POWER COMPANY

AUTHOR CYNTHIA S HUBER, US DEPT OF JUSTICE

ELISSA TONKIN, US EPA REGION 1

JULIE BELAGA, US EPA REGION 1

RICHARD B STEWART, US DEPT OF JUSTICE

DOC ID 32075 07/26/1990 80 PAGES

13 COMMUNITY RELATIONS

1 FACT SHEET O'CONNOR COMPANY MAINE, EPA ID# MED980731475

AUTHOR US EPA REGION 1

DOC ID 32080 01/01/1996 3 PAGES

2 LETTER LETTER TO NEIGHBORS/ABUTTERS OUTLINING THE CONTINGENCY REMEDY

WITH A QUESTIONNAIRE AND TACTS AT A GLANCE SHEET' [INCLUDING FAX

TRANSMITTAL SHEET]

AUTHOR ROY LANE, CENTRAL MAINE POWER COMPANY

DOC ID 32083 03/26/1996 6 PAGES

3 MEMO RESPONSES TO MARCH 22,1996 NEIGHBOR/ABUTTER QUESTIONNAIRE

TO ROSS GILLELAND, US EPA REGION 1

AUTHOR TERENCE R PEACOCK, CENTRAL MAINE POWER COMPANY

DOC ID 32085 06/10/1996 26 PAGES

4 LETTER UPDATE ON COMMUNITY RELATIONS

TO KATHLEEN B FULLER, AUGUSTA (ME), CITY OF

AUTHOR ROY LANE, CENTRAL MAINE POWER COMPANY

10
DOC ID 31998 07/10/1996 2 PAGES

5 PUBLIC MEETING RECORD SUMMARY OF CLEANUP ACTIVITY, PREPARED FOR SITE

NEIGHBORS AND ABUTTING LANDOWNERS

AUTHOR ROY LANE, CENTRAL MAINE POWER COMPANY

DOC ID 32000 07/24/1996 10 PAGES

6 PUBLIC MEETING RECORD PUBLIC MEETING, AMERICAN LEGION POST 205, AGENDA

AUTHOR ROY LANE, CENTRAL MAINE POWER COMPANY

DOC ID 32002 12/12/1996 12 PAGES

7 NEWS CLIPPING EPA TESTS CONY ROAD HOMES

AUTHOR DAVE CHEEVER, KENNEBEC JOURNAL

DOC ID 32004 06/26/1997 2 PAGES

8 NEWS CLIPPING CITY JUNKYARD OFFICIALLY CLEAN

AUTHOR GARY J REMAL, KENNEBEC JOURNAL

DOC ID 32005 11/13/1997 2 PAGES

9 NEWS CLIPPING WEEKLY UPDATE, O'CONNOR SUPERFUND CLEAN-UP CELEBRATED

AUTHOR CENTRAL MAINE POWER COMPANY

DOC ID 32006 11 '20/1997 2 PAGES

10 FACT SHEET EPA TO REVIEW PROGRESS OF CLEANUP AT O'CONNOR SUPERFUND SITE

AUTHOR ALICE KAUFMAN, US EPA REGION 1

DOC ID 32008 05/08/2002 2 PAGES

20 RECORDS MANAGEMENT

1 LIST LIST OF GUIDANCE DOCUMENTS

AUTHOR US EPA REGION 1

DOC ID 32519 06/20/2002 1 PAGE

11
O'CONNOR SUPERFUND SITE

OPERABLE UNIT 2

September 2002 ROD AMENDMENT

APPENDIX C - STATE CONCURRENCE LETTER

12
STATE OF MAINE

DEPARTMENT OF ENVIRONMENTAL PROTECTION

ANGUS S KING. JR. MARTHA KIRKPATRICK

GOVERNOR COMMISSIONER

September 19,2002

Mr. Richard Cavagnero

Acting Director - Office of Site Remediation and Restoration

US EPA

One Congress Street - Suite 1100 (HBT)

Boston, MA. 02114-2023

Regarding: O'Connor Junkyard Superfund Site

(F. O'Connor Company Superfund Site)

Augusta, Maine

Dear Mr. Cavagnero,

The Maine Department of Environmental Protection (MEDEP) has completed its review of the Record of

Decision Amendment - Operable Unit 2 - for the F. O'Connor Company Superfund Site (Site) in Augusta,

Maine dated September 2002.

Based on this review the MEDEP is pleased to provide its concurrence on, with caveats, the revised remedy

selected for OU-2. This remedy relies on active and passive oil recovery, long term monitoring of the

groundwater, and land use restrictions specified in a Declaration of Restrictive Covenants recorded at the

Kennebec County Registry of Deeds on September 13, 2002 - Book 7058, page 42.

This concurrence is contingent upon the following caveats:

1. Finalize an Operations and Maintenance Plan (O&M).

The O&M must be finalized to the satisfaction of the MEDEP within a reasonable time frame

following our concurrence with the ROD Amendment.

A draft O&M was submitted to MEDEP on June 6, 2002 by Woodard and Curran (W&C) on

behalf of Central Maine Power Company (CMP). This plan failed to address the monitoring and

maintenance requirements regarding the clean soil cover overlying the Designated Area (DA); therefore,

it was rejected by MEDEP. The Designated Area is a subsection of the property where soils

contaminated with up to 10 parts per million (ppm) of polychloronated biphenyls (PCBs) and 248 ppm

lead were left on site.

During a meeting August 14,2002 held onsite between representatives of CMP, W&C, and

MEDEP, it was unanimously agreed that the draft O&M will be revised to include provisions for periodic

monitoring and maintenance of the DA cover. Specifically, sampling of the DA cover will be performed

to coincide with each 5 Year Review process beginning in 2007. A total of 10 sampling points will be

chosen randomly for each sampling event. Discrete soil samples will be collected from 4" to 8" below

the surface of the DA and analyzed for PCBs. MEDEP will be given at least 2 weeks notice prior to

each sampling event.

AUGUSTA

17 STATE HOUSE STATION BANGOR PORTLAND PRESQUE ISLE

AUGUSTA, MAIN E 043S3-0017 106 HOGAN ROAD 112 (.'ANCO ROAD 1235 CENTRAL DRIVE, SKYWAY PARK

(207 ) 287-7688 BANGOR, MAIN E 04401 PORTLAND, MAIN E 0410? PRESQUli ISLE, MAINE 04769-2094

RAY HI D(;., HOSPITAL ST. (207) 941-4570 FAX: (207) 941-4584 (207) 822-6100 EAX: (207) 822-650! (207) 764-0477 FAX: (2O7) 764-1507

ep primed on recycled paper
2 Establish Criteria for Termination of the Vacuum Enhanced Recovery System (VER)

Based on the site conceptual model residual oil remains onsite trapped in the clay layers between

the overburden and bedrock Addition oil may be present trapped in the bedrock fractures The amount

of this residual oil is unknown, however, it is understood that any reduction in the overall quantity of oil

remaining on site will have a beneficial effect on groundwater quality

The VER system was first used in 1996 Since then approximately 85 gallons of PCBcontammated oil has been recovered through the use of this system However, criteria for continued use

or termination of this system has never been adequately defined

MEDEP, following discussions with EPA, requires that as long as a significant amount of oil can

be recovered using the VER system, then operation of the VER will continue A significant amount of

oil is defined as an increase m the amount of oil recovered relative to the amount recovered through

passive methods using absorbent materials This means that if the VER system is effectively increasing

the amount of oil being passively recovered from a particular well, it will continue to be applied to that

well

Use of the VER will continue to be used annually until at least the next Five Year Review process

(i e 2007) An evaluation will be made at that time to determine if further use of the VER is still

warranted

3. Continued Adherence to the Existing Long Term Monitoring Program

The O&M also includes a long term monitoring plan requiring bi-annual groundwater sampling on

selected wells Samples from these wells will be analyzed for PCBs and volatile organic compounds

This information will be used to evaluate whether the remedy is successful

Such long term monitoring will continue as long as the groundwater fails to attain all applicable

standards

4. Consideration of Contingencies in Case the Selected Remedy is Not Successful

In the event the provisions of the selected remedy are not successful, remedial contingency plans

must be considered and implemented as appropriate

The MEDEP has enjoyed the cooperation of the USEPA in addressing the issues of concern posed by this

Site, and looks forward to ultimately resolving them through this Record of Decision Amendment If you

need additional information, please do not hesitate to contact Mark Hyland or members of his staff

Sincerely,

David Lennett

Director, Bureau of Remediation and Waste Management

cc Martha G Kirkpatrick, Commissioner - MEDEP

Mark Hyland, Director - Division of Remediation

Denise Messier, Supervisor - Superfund and Federal Facilities Unit
F. O'CONNOR SUPERFUND SITE

OPERABLE UNIT 2

September 2002 ROD AMENDMENT

APPENDIX D - REFERENCES CITED

US Environmental Protection Agency, "Record of Decision Summary O'Connor Company

Superfund Site", September 27, 1989.

, "Consent Decree, United States of America, Plaintiff v. Central Maine Power,

Defendant", Septembers, 1991

, "Explanation of Significant Differences for the F. O'Connor Company Superfund Site",

July 11, 1994.

, "Remedial Design/Remedial Action Revised Statement of Work, O'Connor Company

Superfund Site, Augusta, Maine", October 1994 (SOW is appendix A to CD)

, "Invocation of Contingency Remedy for the F. O'Connor Company Superfund Site",

October 10, 1995.

Woodard & Curran, Inc., "Management of Migration Comprehensive Evaluation, O'Connor

Superfund Site", August 1997

, "Final Source Control Remedial Action Report" September 1, 1998.

, Oil Study in the Upland Marsh Area at the CMP O'Connor Site in Augusta, Maine,

Woodard & Curran, January 1999

, "1999 Riggs Brook Sediment and Biota Monitoring Report, O'Connor Company

Superfund Site", February 2000

, "2000 Riggs Brook Sediment and Biota Monitoring Report, O'Connor Company

Superfund Site", July, 2001

, "Management of Migration Sampling and Analysis Quarterly Report, O'Connor

Company Superfund Site", October 26, 2001

, "2001 Riggs Brook Sediment and Biota Monitoring Report, O'Connor Company

Superfund Site", December 13, 2001

, "Technical Impracticability Evaluation for OU-2 Management of Migration, O'Connor

Company Superfund Site", June 7, 2002