SUPERFUND FINAL CLOSE OUT REPORT 

O.'CONNOR SUPERFUND SITE 

AUGUSTA, KENNEBEC COUNTY, MAINE 

• • ~ s 

Prepared by 

U.S. Environmental Protection Agency 

Region 1 

Boston, Massachusetts 

/Z/!7/13-. James T. ens, III, Director Date 

Office of S t Remediation and Res oration 
TABLE OF CONTENTS 

FINAL CLOSE OUT REPORT 

O=CONNOR SUPERFUND SITE 

AUGUSTA, KENNEBEC COUNTY, MAINE 

I. Introduction 

II. Summary of Site Conditions 

a. Site Background

b. Removal Actions

c. Selected Remedy and RAOs 

d. Institutional Controls

e. Final Inspection 

III. Monitoring Results 

a. Source Control Remedial Actions 

b. Riggs Brook Remedial Action 

IV. Attainment of Groundwater Restoration Cleanup Levels 

V. Summary of Operation and Maintenance 

VI. Demonstration of Cleanup QA/QC 

a. Construction QA/QC Plan 

b. O&M QA/QC Plan 

VII. Five-Year Review 

VIII. Site Completion Criteria 

IX. Bibliography 

FIGURES

1. Site Location (3-1 in legend) 

2. Site Features (3-2 in legend) 

3. Monitoring Well Locations (4-1 in legend) 

4. Technical Impracticability Zone (4-1 in legend) 

5. Soil Sampling Areas for PCBs 

6. Soil Sampling Areas for Lead and cPAHs 

APPENDICES

A. Groundwater Concentrations Graphs 1998 - 2012 

B. Groundwater Results 1986 - 2012 

C. Risk Re-Evaluation Memorandum
3

I. Introduction

This Final Close Out Report (FCOR) documents that all response actions for the O’Connor 

Superfund Site (Site) have been successfully completed in accordance with Close Out 

Procedures for National Priorities List Sites (OSWER Directive 9320.2‐22, May 2011).

This FCOR documents all decision documents have been completed and the selected remedy is 

consistent with CERCLA, the NCP, and EPA policy and guidance documents. 

II. Summary of Site Conditions 

a. Background 

The Site consists of approximately 23 acres within a 28-acre property owned by Central Maine 

Power Company (CMP) and is located on U.S. Route 17 approximately three miles east of the 

Kennebec River in Augusta, Maine. The Maine Department of Environmental Protection 

(MEDEP) also designated the same 23-acre property as a Hazardous Substance Site. The 

surrounding area is generally rural. The property is bordered on the east and southeast by Riggs 

Brook, a small northerly flowing tributary of the Kennebec River, on the north and west by 

woodlands, and on the south by Route 17. The property south of Route 17 is primarily wooded. 

A residence abuts the CMP property along its western boundary. Automotive entry to the Site is 

limited to Route 17; there are trails which enter the Site from the north and west. The location of 

the property is shown on Figure 3-1. Figure 3-2 shows features and topography of the Site. 

The land at the Site was used as farmland until the 1950s when the F. O'Connor Company 

established a salvage yard and transformer recycling operation on the property. The F. O=Connor 

Company operated until the late 1970s. This resulted in drippage and spillage of oil to the 

ground, principally in the three transformer work areas (TWAs). In February 1972, an oil spill 

was found to have migrated toward Riggs Brook. In 1976, MEDEP began investigations through 

sampling and analysis of the soils, sediments, and surface waters for polychlorinated biphenyls 

(PCBs). Soil and groundwater contamination primarily consisted of PCBs with some volatile 

and semivolatile organic compounds (VOCs and SVOCs), and inorganics. Potential sources of 

contamination that were identified included the TWAs, scrap piles, oil storage tanks, and two 

lagoons installed to help control oil migration from the property. Concern for the potential 

impact on soils, surface water, and groundwater were the primary reasons the Site was proposed 

for the National Priorities List on September 8, 1983. 

b. Removal Action 

Three removal actions were performed at the Site. In 1977, at the request of MEDEP the F. 

O’Connor Company discontinued use of the lagoons, pumped the lagoon water into storage tanks 

and excavated the lagoon sediments which were then placed in an upland area upgradient of the 

TWAs. In 1984, EPA issued a Unilateral Administrative Order to the F. O’Connor Company to 

construct a fence encompassing approximately five acres of the Site. Under a 1986 

Administrative Order by Consent between MEDEP and F. O’Connor Company and CMP, 20 

storage tanks and 21 55-gallon drums were removed off the Site. 
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c. Selected Remedy and Remedial Action Objectives 

A Record of Decision (ROD) for the Site was issued on September 27, 1989. CMP, an identified 

Potentially Responsible Party at the Site, signed a Consent Decree with the United States on 

September 3, 1991, to undertake an investigation and remediation of the Site. CMP also 

acquired ownership of the property from the F. O'Connor Company in 1992.

The 1989 ROD selected a remedy to address the risks present in the Site soils, sediment, 

groundwater, and biota from PCBs and VOCs, resulting from the operation of the salvage and 

electrical transformer recycling business. 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 onsite; and sediments and fish in Riggs 

Brook were to be sampled for ten years. 

The 1989 remedy was subsequently modified in 1994 by an Explanation of Significant 

Differences (ESD) and in 2002 by a ROD Amendment. The ESD adjusted the soil and sediment 

cleanup levels for a three- to four-acre Designated Area where soils and sediments with 

concentrations between the old and new cleanup levels would be consolidated after solvent 

extraction treatment. Following the consolidation of soils within the Designated Area, the entire 

excavation area was to be covered with one foot of clean fill brought in from offsite. In 1995 

EPA selected the contingency cleanup plan that was identified in the ESD. This contingency 

plan allowed for the disposal offsite of contaminated soil and sediment without first requiring 

treatment onsite. 

Table 1: Soil and Sediment Cleanup Standards (ppm) 

Contaminant 1989 ROD 1994 ESD

Within Designated 

Area

1994 ESD 

Outside 

Designated Area

1995 

Contingency

Cleanup Plan

Total PCBs 1 10 1 10

Total cPAHs 1 10 1 10

Lead 248 248 248 248

The 2002 ROD Amendment changed the cleanup approach for groundwater. In place of the 

pump-and-treat remedy, the 2002 ROD Amendment selected institutional controls to prevent the 

use of contaminated groundwater, a waiver of federal and state drinking water standards for a 

limited portion of the Site on the basis of technical impracticability, active recovery of separatephase oil from the overburden soil and bedrock through annual implementation of a vacuumenhanced recovery system and passive recovery between these annual implementations, and 

long-term monitoring of Site groundwater on a regular basis to evaluate changes in Site 

conditions over time. In 2003, CMP signed an Amendment to Consent Decree with the United 

States that set forth the actions to be undertaken for implementing the 2002 ROD Amendment. 

In 1996, EPA separated the Site into three operable units (OUs). Operable Unit OU-1 addressed 

the soils, OU-2 addressed groundwater, and OU-3 addressed Riggs Brook sediment and biota. 
7

Five Remedial Action Objectives (RAOs) were set in the 1989 ROD: 

1 Reduce potential present and future public health and environmental risks from direct 

contact, ingestion, and/or dermal absorption with the PCB-, cPAH-, and leadcontaminated soils and sediments located on- and offs ite; 

2. Reduce potential, present and future public health risks from the inhalation of PCB 

vapors from the Site; 

3. Reduce potential, present and future public health risks from the ingestion of PCBcontaminated fish from Riggs Brook; 

4. Reduce potential future public health risks from the ingestion of PCB-, benzene-, and 1,4-

dichlorobenzene contaminated groundwater found on the Site; and 

5. Reduce potential present and future environmental risks to aquatic and terrestrial wildlife 

from exposures to the PCB-, lead-, and aluminum-contaminated onsite surface water. 

The ESD, while modifying the source control remedy for soils and sediment, did not change the 

RAOs. The 2002 ROD Amendment noted that RAOs 1, 2, 3, and 5 had been achieved. The 

ROD Amendment changed the approach to achieving the fourth RAO through institutional 

controls, a Technical Impracticability waiver, active and passive oil recovery, and long-term 

monitoring. The 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. See Figure 4-1. 

The September 1998 OU-1 RA Report provides a comprehensive review of source control 

activities and the September 2007 OU-3 RA Report provides a review of monitoring activities 

performed for Riggs Brook sediment and biota. All Remedial Action activities for OU-1 and 

OU-3 were implemented under a 1992 Consent Decree signed by CMP and EPA (MEDEP did 

not sign the Consent Decree). 

See below, Section III, Monitoring Results, for further details concerning the initiation and 

completion of the RA activities described above. 

d. Institutional Controls

The 1989 ROD required temporary institutional controls for the entire Site until the cleanup 

goals were met. In 1994, CMP and MEDEP signed an agreement in the form of a Declaration of 

Restrictive Covenant, which was not recorded but held by MEDEP “in escrow” until 2002. With 

the recognition that the 1994 ESD and 2002 ROD Amendment changed the cleanup goals, which 

in turn would result in some waste being left in place at the Site, thus preventing unlimited 

exposure and unrestricted use, EPA requested the restrictive covenant be recorded to make the 

(previously temporary) institutional controls permanent. Accordingly, on September 13, 2002, 

the Declaration of Restrictive Covenant was recorded in the Kennebec County Registry of 

Deeds. 
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This covenant includes the following: 

 Any use of the groundwater beneath the Site is prohibited without the written approval of 

MEDEP;

 Any activity which might disrupt remedial or monitoring measures is prohibited without 

the written approval of MEDEP; 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. 

By its terms, the covenant runs to MEDEP and is enforceable only by MEDEP. 

Accordingly MEDEP will monitor and enforce the institutional controls. 

e. Final Inspection Activities

On November 12, 1997, an inspection for OU-1 was conducted with representatives from EPA, 

MEDEP, and CMP. A few punch list items were identified and were to be completed during the 

next field season. 

An inspection for OU-3 was conducted on April 25, 2007, with representatives from EPA, 

MEDEP, CMP, and CMP’s contractor. A follow-up inspection was performed on July 26, 2007,

to assess the vegetative cover during the height of the growing season. No significant issues 

were identified in either inspection. 

An inspection for OU-2 was conducted on April 26, 2012, with representatives from EPA, 

MEDEP, CMP, and CMP’s contractor. A follow-up inspection was performed on June 29, 2012.

These inspections included checking the Designated Area boundary and observations of the 

vegetated cover, monitoring wells and restored wetland areas. No significant issues were 

identified in either inspection. 

III. Monitoring Results 

a. Source Control Remedial Action (OU-1) 

The Source Control Remedial Action (SCRA) was conducted in two phases. Phase I was 

completed in 1996. A subset of the soils were remediated, the barn was decontaminated, 

demolished and disposed of offsite, non-native debris was collected and disposed offsite, and the 

Support Area for Phase II was constructed. Phase II activities were conducted in 1997. During 

Phase II, surface water from the Upper Lagoon, Lower Lagoon, and Upland Marsh was collected 

and disposed of offsite, the remaining soils and sediments were remediated (described below), 

the lagoons and marsh were reconstructed, and the Site re-graded and vegetated. 

All soils and sediments within OU-1 containing greater than 10 ppm PCBs, 10 ppm cPAHs, and 

248 ppm total lead were excavated and disposed of at approved disposal facilities offsite. A total 

of 19,357 tons of soil and sediment were excavated and disposed of: 8,010 tons characterized as 

Special Waste (a State of Maine designation) were transported to two facilities in Maine; 11,222 

tons characterized as TSCA and/or RCRA wastes to a facility in New York; and 125 tons 

characterized as RCRA waste to a facility in Quebec. 
10

Soils and sediments within the Designated Area containing less than or equal to 10 ppm PCBs or 

cPAHs and less than 248 ppm total lead were not excavated. Approximately 3,000 to 4,000 tons 

of soil and sediments located outside the Designated Area and containing between 1 and 10 ppm 

PCBs or cPAHs and less than 248 ppm total lead were excavated and placed within the 

Designated Area. 

The limits of excavation within and outside the Designated Area were based on analytical 

results, isopachs, and visual examination of the contamination. Following excavation, 

confirmation samples were collected at the base of the excavation to determine if the 

concentrations of PCBs, cPAHs, and total lead were below the respective cleanup goals. If a 

sample exceeded the target cleanup goal, excavation continued. If the target cleanup goals were 

met, the sample was used as a confirmation sample, and the area represented by the sample node 

was confirmed as closed. Pre-excavation and most confirmation samples were collected at 

specified locations on a sampling grid that was developed to provide a statistically valid 

approach for confirming that the soils and sediments had meet the target cleanup goals. 

Additional random samples were collected as determined necessary in the field to confirm 

attainment of target cleanup goals. 

The Site was divided into five sample areas in the 100% Remedial Design, based on 

contaminants, target cleanup goals, Site history, geology, and a review of the Remedial 

Investigation data. Based on all this information, a work plan was developed, approved, and 

implemented. Areas 1, 2, and 3 were sampled for PCBs, Area 4 for lead, and Area 5 for cPAHs. 

See Figures 5 and 6 for the location of the sampling areas. 

Sample Area 1 was the Designated Area. A total of 209 confirmation samples were collected 

and analyzed for PCBs. The 95% upper confidence limit of the mean of the data was determined 

to be 0.63 ppm, well below the target cleanup goal of 10 ppm. In addition, the maximum value 

reported by the PCB analysis was 9.63 ppm. Consequently, with 100% of the analytical results 

below the 10 ppm target cleanup goal, it was determined that Area 1 met the PCBs performance 

standard. 

Sample Area 2 consisted of three separate subareas adjacent to the Designated Area: 2A, west 

and south of the Designated Area; 2B, east and downgradient of TWA II in the Designated Area; 

and 2C, also east and downgradient of the Designated Area. A total of 114 confirmation samples 

were collected and analyzed for PCBs. The 95% upper confidence limit of the mean of the data 

was determined to be 0.23 ppm, below the target cleanup goal of 1 ppm. In addition, the 

maximum value reported by the PCB analysis was 0.81 ppm. Consequently, with 100% of the 

analytical results below the 1 ppm target cleanup goal, it was determined that Area 2 met the 

PCBs performance standard. 

Sample Area 3 consisted of two separate subareas, which were located downgradient of Areas 

2B and 2C and were within the delineated limits of the Riggs Brook wetlands. A total of 49 

confirmation samples were collected in Area 3 and analyzed for PCBs. The maximum value 

reported by the PCB analysis was 4.3 ppm. Consequently, with 100% of the analytical results 

below the ROD established 5 ppm trigger level for sediments in Riggs Brook and its associated 

nearby wetlands, it was determined that Area 3 met its PCBs performance standard. (The 95% 

upper confidence limit of the mean was not calculated since all of the results were below the 

trigger level, and therefore the mean was also below the trigger level) 
11

Sample Area 4 consisted of five subareas almost entirely within the Designated Area and was 

used to assess the extent of total lead contamination. A total of 209 confirmation samples were 

collected and analyzed for total lead. The 95% upper confidence limit of the mean of the data 

was determined to be 52.1 ppm, well below the target cleanup goal of 248 ppm. In addition, the 

maximum value reported by the lead analysis was 222 ppm. Consequently, with 100% of the 

analytical results below the 248 ppm target cleanup goal, it was determined that Area 4 met the 

lead performance standard. 

Similarly, samples for total lead were collected outside the Designated Area and analyzed for 

Toxicity Characteristic Leaching Procedure (TCLP) lead, for disposal characterization purposes. 

The maximum concentration TCLP lead was 55.6 ppm. Based on these results, these soils were 

disposed of offsite as RCRA-hazardous waste. 

Sample Area 5 consisted of two subareas outside the Designated Area where samples were 

collected and analyzed for cPAHs. The maximum concentration in the nine samples collected in 

5A was 0.237 ppm, below the target cleanup goal of 1 ppm. Area 5B underwent two rounds of 

excavation and three rounds of sampling. Analyses of the third round of samples collected at 1.4 

to 3.3 feet below ground surface found cPAHs concentrations ranging between 1.2 to 6.6 ppm. 

In a letter dated October 27, 1997, MEDEP approved that no further removal actions were 

warranted in subarea 5B after calculating toxicity equivalence factors for the individual cPAH 

concentrations remaining in subarea 5B. The total toxicological equivalency value was found to 

be 1 ppm, which was less than the applicable worker standard of 7 ppm and less than the more 

conservative residential scenario of 2 ppm. EPA provided prior approval for no further action at 

subarea 5B. 
WOODARD

CURRAN COMMITMENT & INTEGRITY DRIVE RESULTS

| www.woodardcurran.com

41 HUTCHINS DRIVEPORTLAND, MAINE 04102800.426.4262
WOODARD

CURRAN COMMITMENT & INTEGRITY DRIVE RESULTS

| www.woodardcurran.com

41 HUTCHINS DRIVEPORTLAND, MAINE 04102800.426.4262
14

b. Riggs Brook Remedial Action (OU-3) 

The 1989 ROD selected yearly sediment sampling for ten years for Riggs Brook and its 

associated wetlands. In addition, biota sampling was to be performed at least once, after five 

years of sediment sampling. 

CMP conducted annual sediment monitoring of Riggs Brook for ten years (1996-2005) as 

required by the ROD. At EPA’s request, the 2000 annual sediment sampling program was 

supplemented with a sampling grid with 51 locations adjacent to Riggs Brook in adjacent source 

control areas. 

Biota sampling was first conducted in 1997 with the collection of twenty samples. Following a 

recalculation of the data from mg/kg dry weight to mg/kg wet weight, it was determined that all 

samples were below the target level of 2 mg/kg (or ppm). A second biota sampling occurred in 

September 2000, when a total of twenty biota samples were collected from Riggs Brook and 

analyzed for PCBs. As was the case in 1997, all samples were below the target level of 2 mg/kg. 

A comparison to the 1997 data indicated that the biota PCB concentrations had decreased. 

Considering the results from the 2000 sediment and biota sampling, EPA and MEDEP agreed 

that with the decrease of PCBs in the biota samples as well as the scattered locations of the 

sediment exceedances, remedial efforts to address the scattered sediment exceedances were not 

required at that time. Instead, the 2001 sampling (year six of the ROD-required ten) was to be 

expanded to monitor the locations identified in the supplemental sampling grid. The 2001 

sediment sampling had one exceedance above the 5 ppm trigger level of the thirty-six samples. 

This one location (location 3018, at 6.1 ppm) is located near the wetland/upland boundary and 

within the area excavated during the SCRA.

The results of the ten-year sampling program showed the sediments in Riggs Brook to be stable, 

with no indication that PCBs were migrating or increasing in concentration. Over 95% of the 

samples were below the PCB action trigger level of 5 ppm with the annual mean varying 

between 0.38 to 1.93 ppm. With one location, sediment 3018, having the maximum PCB 

concentration from 2001 through 2005, CMP proposed to excavate a ten-foot square centered on 

that sediment location. EPA, after opportunity for review and comment by MEDEP, approved 

this approach. Approximately three tons of material were excavated and disposed offsite at a 

Special Waste landfill in Maine.

IV. Attainment of Groundwater Restoration Cleanup Levels 

Under the ROD, the RAO for the groundwater (OU-2) was to reduce potential future public 

health risks from ingestion of PCBs, benzene, and 1,4-dichlorobenzene-contaminated 

groundwater. The ROD established cleanup standards of total PCBs at 0.5 μg/L, benzene at 5 

μg/L and 1,4-dichlorobenzene at 27 μg/L. In 2002, based on the ARARs review conducted for 

the ROD Amendment, five other VOCs were identified which since the 1989 ROD have had 

ARARs established. These ARARs include federal Maximum Contaminants Levels (MCLs) and 

Maine Maximum Exposure Guidelines (MEGs) for five VOCs and PCBs. For each of these five 

compounds, the MEG is either the same or less than the respective MCL. The cleanup standards 

are presented in table 2 below. 
15

Table 2: Groundwater Cleanup Standards 

Contaminant

Of Concern

1989 ROD 

Target

Cleanup Levels

(μg/L)

1992

MEG

(μg/L)

MCL

(μg/L)

2002 ROD A

Target

Cleanup 

Levels

(μg/L)

Benzene 5 5 5

5

Chlorobenzene no ROD 

standard

47 100 47

1,2-

Dichlorobenzene

no ROD 

standard

85 600 85

1,3-

Dichlorobenzene

no ROD 

standard

85 NS 85

1,4-

Dichlorobenzene

27 27 75 27

1,2,3-

Trichlorobenzene

no ROD 

standard

NS NS NS

1,2,4-

Trichlorobenzene

no ROD 

standard

70 70 70

1,3,5-

Trichlorobenzene

no ROD 

standard

40 NS 40

PCBs 0.5 0.05 0.5 0.05

NS - no standard 

Groundwater cleanup standards defined in the 2002 ROD Amendment and in the 2003 SOW for 

VOCs have been met at all wells at the TI boundary and beyond the TI Zone since Spring 2002, 

and the cleanup standard for PCBs has been met at all wells at the TI boundary and beyond the 

TI Zone since Spring 2006. Graphs showing groundwater concentrations over time from 1998 

(post-Source Control) to 2012 for five Contaminants of Concern listed in Table 2 are presented 

in Appendix A. The remaining three compounds (benzene, 1,3,5-trichlorobenzene, and PCBs) 

were not found in sufficient concentration to be meaningfully graphed. Graphs are also shown 

for four of the nine remaining monitoring wells at the Site (MW-104B, OW-201B, MW-507A in 

the TI Zone, and MW-106B in the Riggs Brook wetlands), as the majority of the contamination 

was seen in the three TI Zone wells. Concentrations of the eight compounds have been very low 

or non-detect at the remaining five monitoring wells at the Site. Groundwater results from 1986 

to 2012 are included in Appendix B and monitoring well locations are shown in Figure 4-1. 

Groundwater has been monitored at the Site since 1986. Beginning in Spring 2008, the sampling 

frequency was changed from semi-annual to annual. The monitoring program currently consists 

of nine wells, four outside the TI Zone and five within the TI Zone and downgradient of the 

TWA II area. Based on steady improvements in groundwater, and the fact that groundwater had 

met target cleanup goals for the Site in all wells outside the TI Zone since 2006, 28 monitoring 

wells and piezometers at the Site were decommissioned in September 2008. Groundwater 
16

monitoring reports have been prepared by CMP’s consultant Woodard & Curran and present the 

data demonstrating the attainment of the cleanup levels for the Site. 

In addition to the monitoring of water quality at the TI boundary and downgradient of it, the 

2002 ROD Amendment included active and passive oil recovery. Investigations completed 

following the 1989 ROD determined that the migration of contaminants in the shallow 

groundwater in the downgradient direction was limited; the bedrock aquifer had low 

groundwater storage and therefore a relatively small volume of water. It was also concluded that 

the 1992 pump test had mobilized the PCB transformer oil and other contaminants vertically 

downward into the bedrock flow regime. Based on these findings, CMP’s consultant 

recommended continued groundwater monitoring and the use of vacuum extraction recovery 

(VER) rather than conventional groundwater pumping to eliminate the potential for drawing 

free-floating product farther into the bedrock aquifer. 

Seepage of the transformer oil into the TWA II wells had been observed since it was first 

induced into the wells during the 1992 pump test. The total amount of oil recovered from the 

five TWA II wells since their installation using a combination of VER and passive oil recovery is 

about 125 gallons. Approximately 79 gallons of oil (about 63%) were recovered prior to the 

completion of the source control work, and approximately 35 gallons (about 28%) after the 

completion of source control through the summer of 2002. Since the resumption of the VER in 

2002, 11.3 gallons of transformer oil have been recovered (or about 9% of the total). 

Approximately 7.4 gallons of oil were recovered by the VER system in 2002, 2.5 gallons in 

2003, and about 0.3 gallons in both 2004 and 2006. The system was not operated in 2005 

because of equipment failure. Significantly there was not any increase in the amount recovered 

passively nor was any increase observed when the active recovery resumed in August 2006. The 

amount of oil removed from the wells using the VER system decreased steadily over time to 

minimal amounts. In December 2006, the VER system was decommissioned because the rate of 

oil recovery using passive recovery was equal to or greater than with the VER system. Prior to 

2005, the passive oil recovery program was conducted monthly. Since 2005, passive oil 

recovery has continued on a quarterly basis. 

V. Summary of Operation & Maintenance 

The O&M activities associated with the SCRA and long-term monitoring at the Site were 

initiated in 1998 upon completion of the SCRA. Inspections of the Site have been conducted 

semi-annually. The O&M Plan for the Site was last updated in October 2009 and describes the 

long-term activities for OU-1 and OU-2 at the Site, including inspections, soil cover sampling, 

routine maintenance, and repairs as necessary. Sediment and biota sampling have been 

completed for OU-3, and therefore, there are no O&M activities associated with OU-3. 

Inspections have been conducted at the Site and have documented that the vegetation is well 

developed and minor ruts in the access road have been repaired. There has been no significant 

erosion of the soil cover over the Designated Area or on the slope leading down to the Riggs 

Brook since the completion of the SCRA. Because contamination remains that prevents 

unlimited exposure and unrestricted use of the Site, it is anticipated that maintenance and 

inspections will continue for an extended period of time. 

The 2002 Declaration of Restrictive Covenant places several restrictions on the entire Site 

property (including the TI zone). CMP (and any future owner) is prohibited from any use of 
17

groundwater or any activity which might disrupt remedial or monitoring measures without prior 

written approval from MEDEP. 

Additionally, the restrictive covenant provides that CMP and all subsequent owners shall 

maintain the Site property in a condition adequate to ensure the continued compliance with all 

applicable cleanup standards and to ensure the ongoing adequacy of the remedial action 

implemented under the Consent Decree. Specific examples of required ongoing activities 

include, but are not limited to maintenance of “all drainage ways, berms, monitoring wells, 

permeable or impervious caps or covers (including paved portions of the property and areas 

covered by topsoil or other clean fill), piping, pumps and electrical equipment constructed or 

installed under the Consent Decree.” 

By its terms, the restrictive covenant is enforceable only by MEDEP. Compliance with this 

covenant is confirmed at the same time as the spring Site inspection. 

VI. Demonstration of Cleanup QA/QC 

a. Construction Quality Assurance/Quality Control Plan 

Source control activities at the Site were consistent with the ROD, the ESD, and all work plans. 

Specifically, the construction activities associated with the SCRA were generally conducted in 

compliance with the approved 100% Remedial Design which was consistent with EPA Quality 

Assurance and Quality Control (QA/QC) procedures. Detailed work plans for all activities 

including sampling and analyses were reviewed and approved by EPA prior to initiation of field 

work. Only EPA approved sampling and analytical methods were utilized for these studies. All 

analytical data were reviewed and validated according to EPA approved data validation 

procedures. 

All procedures and protocol utilized during the development and implementation of response 

actions are described in the work plans and summary reports submitted for each activity. These 

documents are available for review at the EPA Region I Record Center and the MEDEP office in 

Augusta, Maine. 

The QA/QC program utilized throughout the Remedial Action was sufficiently rigorous and was 

complied with to enable EPA and MEDEP to determine that analytical results reported were 

accurate to the degree needed to assure satisfactory execution of the RA, consistent with the 

1989 ROD, 1994 ESD, 2002 ROD Amendment, and Remedial Design plans and specifications. 

b. Operation and Maintenance Quality Assurance/Quality Control Plan 

Operation and maintenance activities at the Site are consistent with the October 2009 O&M Plan. 

Specifically, the O&M activities have been conducted in compliance with the approved O&M 

Plan which is consistent with EPA QA/QC procedures. Work plans for all activities including 

sampling and analyses are reviewed and approved by EPA prior to initiation of field work. Only 

EPA approved sampling and analytical methods have been utilized for these studies. All 

analytical data were reviewed and validated according to EPA approved data validation 

procedures. 
18

VII. Five-Year Review

Statutory five-year reviews are required at the O’Connor Superfund Site since hazardous 

substances remain at the Site above levels that allow for unlimited use and unrestricted exposure. 

Five-year reviews were completed for the Site in 2002, 2007, and 2012. The 2012 Five-Year 

Review stated that remedial actions at all OUs are protective, and therefore the Site is protective 

of human health and the environment. The 2012 Five-Year Review made the following 

protectiveness statements for each operable unit and sitewide: 

OU-1: The remedial action for OU-1 has been completed and is protective of human health and 

the environment. Exposure pathways that could result in unacceptable risk are being controlled 

through a clean soil cap that covers remaining contamination and institutional controls that have 

been placed on the Site. The O&M plan was updated and approved in 2009 and its 

implementation will ensure that the OU-1 remedy remains protective. 

OU-2: The remedy for OU-2 is protective of human health and the environment. Exposure 

pathways that could result in unacceptable risk are being controlled with institutional controls 

covering the entire Site. Outside the TI Zone, groundwater has met the performance standards 

for VOCs since Spring 2002 and for PCBs since Spring 2006. Long-term monitoring will 

continue to ensure that the performance standards continue to be met. 

OU-3: The remedy at OU-3 is protective of human health and the environment. Annual 

sampling of sediments for ten years resulted in over 95% of the samples being below the 5 ppm 

trigger level with the annual mean PCB concentration varying between 0.38 and 1.72 ppm. 

Results from the two biota sampling events were below the threshold level of 2 ppm for all 

samples, with the overall average being below 1 ppm. Site inspections have documented 

functioning habitat in both the uplands and wetlands. 

Sitewide: Because the remedial actions at all OUs are protective, the Site is protective of human 

health and the environment. 

The 2012 Five-Year Review did not identify any issues in any of the operable units. As noted 

above, the Final Remedial Action Report for OU-1 was signed in 1998 and the Final Remedial 

Action Report for OU-3 was signed in 2007. EPA signed the Superfund Property Reuse 

Evaluation Checklist for Reporting the Sitewide Ready for Anticipated Use Government 

Performance and Results Act Measure in 2009. 

With the groundwater cleanup standards having been met for an extended period (ten years for 

VOCs, six years for PCBs) and no changes in land use, the 2012 Five-Year Review identified reevaluation of the groundwater monitoring program as a possible opportunity for optimization. 

Therefore the review recommended that the groundwater monitoring program be re-evaluated. 

VIII. Site Completion Criteria 

The implemented remedy has achieved the degree of cleanup or protection specified in the 1989 

ROD, 1994 ESD, and 2002 ROD Amendment for all pathways of exposure. The activities for 

OU-1 remedy were successfully completed in 1997 and the activities for OU-3 remedy were 

successfully completed in 2006. With the 2002 Technical Impracticability waiver, groundwater 

(OU-2) beyond the TI Zone has met all cleanup standards since 2006. 
19

The five response action RAOs presented in the ROD (see Section II.c. above) and associated 

cleanup goals and the remedial action selected and implemented to achieve these RAOs are 

consistent with agency policy and guidance. The Endangerment Assessment (the 1998 human 

health and ecological risk assessment) identified seven exposure scenarios including three 

potential current exposures and four potential future exposures. According to the 2002 ROD 

Amendment, following the completion of the source control component of the remedy, only two 

potential exposure pathways remained: future ingestion of groundwater from within the bedrock 

and ingestion of fish caught in Riggs Brook. Since the 2002 ROD Amendment, EPA released 

draft guidance on the vapor intrusion pathway. The 2007 FYR noted that the potential existed 

for this pathway if buildings were constructed onsite. However, there are currently no plans for 

any construction onsite and the VOC concentrations in the shallow groundwater do not suggest a 

significant source of vapors. 

Section X of the 1989 ROD, Selected Remedy, stated that the Site would be re-evaluated to 

determine the risk posed by the Site at the completion of the remedial action (i.e., before the Site 

is proposed for deletion from the NPL). EPA completed a risk evaluation in 2013 and concluded 

the remaining contamination beyond the TI Zone did not pose an unacceptable risk to human 

health or the environment. See the September 30, 2013 memorandum in Appendix C for the risk 

evaluation. 

Future ingestion of groundwater is prohibited without the prior written approval of MEDEP and 

potential future exposure to vapor intrusion is prevented by the same institutional controls. The 

two biota sampling events demonstrated that ingestion of fish caught in Riggs Brook will not 

create an unacceptable risk. Consequently no further Superfund response is needed to protect 

human health and the environment. 

IX. Bibliography

A bibliography of all reports relevant to the completion of this Site under the Superfund program 

follows. 

Central Maine Power (CMP), 1997. O’Connor Company Superfund Site Monthly Progress 

Report October 1997 – No. 83; November 5 

CMP, 2004. Letter from Roy Koster, CMP to Terrence Connelly, USEPA Region 1 RE: 

O’Connor Company Superfund Site VER Operation 2004; October 7. 

CMP, 2006. Letter from Roy Koster, CMP to Terrence Connelly, USEPA Region 1 RE: 

O’Connor Company Superfund Site 2005 Riggs Brook Sediment Monitoring Report; January 23. 

CMP, 2006. Letter from Roy Koster, CMP to Terrence Connelly, USEPA Region 1 RE: 

O’Connor Company Superfund Site VER Operation 2006; September 8. 

CMP, 2008. O’Connor Company Superfund Site Remediation of Riggs Brook Sampling 

Location 3018 Closure Report; May 20. 

City of Augusta, Maine, Land Use Ordinance. 
20

Flood Insurance Rate Map, City of Augusta, Maine, Kennebec County, Community-Panel 

Number 230067 0011; June 15, 1994. 

ICF – Clement, Inc., 1988. Endangerment Assessment for the O’Connor Site in Augusta, Maine, 

(Table 8-1). 

Tetra Tech NUS, Inc., 2002. Five-Year Review Report, O’Connor Company Site, Augusta, 

Maine; September. 

The Smart Associates, 2003. 2002 Wetland Construction Monitoring Report, O’Connor 

Company Site, Augusta, Maine; Prepared for U.S. Environmental Protection Agency; January. 

USEPA, 1989. Record of Decision Summary; U.S. Environmental Protection Agency, Region 1, 

Boston, Massachusetts; September. 

USEPA, 1994. Declaration for the Explanation of Significant Differences, O’Connor Company 

Superfund Site, Augusta, Maine; July 11. 

USEPA, 2001. Comprehensive Five-Year Review Guidance, USEPA 540-R-01-007; June. 

USEPA, 2002. Record of Decision Amendment Operable Unit 2, F. O’Connor Company 

Superfund Site; September. 

USEPA, 2002. OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air 

Pathway fromGroundwater and Soils (Subsurface Vapor Intrusion Guidance); November 29. 

USEPA, 2007. Second Five-Year Review Report for F. O’Connor Site Augusta, Kennebec 

County, Maine; September. 

USEPA, 2011. Close Out Procedures for National Priorities Sites, OSWER Directive 9320.2-22; 

May. 

USEPA, 2012. Third Five-Year Review Report for F. O’Connor Site Augusta, Kennebec 

County, Maine; September. 

United States of America v. F. O’Connor Company Superfund Site, et. al, U.S. District Court for 

the District of Maine, 1991. Consent Decree – United States of America, Plaintiff v. Central 

Maine Power Company, Defendant; September 3. 

United States of America v. F. O’Connor Company Superfund Site, et. al, U.S. District Court for 

the District of Maine, 2003. Amendment to Consent Decree – United States of America, 

Plaintiff v. Central Maine Power Company, Defendant; Appendix II to Amendment to O’Connor 

Consent Decree Remedial Design/Remedial Action 2003 Statement of Work. 

Woodard & Curran, 1996. Source Control Remedial Action Community Relations Plan, 

O’Connor Company Superfund Site, Augusta, Maine; July. 

Woodard & Curran, 1996. Source Control Remedial Action Project Operation Plan, 100% 

Remedial Design, O=Connor Superfund Site, Augusta, Maine; July. 
21

Woodard & Curran, 1997. Final Riggs Brook Sediment and Biota Sampling and Analysis Plan, 

O’Connor Superfund Site, Augusta, Maine; October. 

Woodard & Curran, 1997. cPAHs at Sample Area 5B @ O’Connor Superfund Site; October. 

Woodard & Curran, 1998. 1997 Riggs Brook Sediment and Biota Monitoring Report, O’Connor 

Company Superfund Site, Augusta, Maine; February. 

Woodard & Curran, 1998. Final Source Control Remedial Action Report, O’Connor Company 

Superfund Site, Augusta, Maine; September. 

Woodard & Curran, 1999. 1998 Riggs Brook Sediment Sampling Report, O’Connor Company 

Superfund Site, Augusta, Maine; January. 

Woodard & Curran, 2000. 1999 Riggs Brook Sediment Monitoring Report, O’Connor Company 

Superfund Site, Augusta, Maine; February. 

Woodard & Curran, 2001. 2000 Riggs Brook Sediment and Biota Monitoring Report, O’Connor 

Company Superfund Site, Augusta, Maine; July. 

Woodard & Curran, 2001. 2001 Riggs Brook Sediment Monitoring Report, O’Connor Company 

Superfund Site, Augusta, Maine; December. 

Woodard & Curran, 2002. MOM Sampling and Analysis Semi-annual Report, April 2002, 

O’Connor Company Superfund Site, Augusta, Maine; June 10. 

Woodard & Curran, 2002. Technical Impracticability Evaluation for OU-2 Management of 

Migration, O’Connor Company Superfund Site, Augusta, Maine. Prepared for Central Maine 

Power Company, Augusta, ME; June. 

Woodard & Curran, 2002. MOM Sampling and Analysis Annual Report, September 2002, 

O’Connor Company Superfund Site, Augusta, Maine; October 30. 

Woodard & Curran, 2002. 2002 Riggs Brook Sediment Monitoring Report, O’Connor Company 

Superfund Site, Augusta, Maine; October. 

Woodard & Curran, 2003. MOM Sampling and Analysis Semi-annual Report, April 2003, 

O’Connor Company Superfund Site, Augusta, Maine; June 26. 

Woodard & Curran, 2003. MOM Sampling and Analysis Annual Report, September 2003, 

O’Connor Company Superfund Site, Augusta, Maine; December 2. 

Woodard & Curran, 2003. 2003 Riggs Brook Sediment Monitoring Report, O’Connor Company 

Superfund Site, Augusta, Maine; December. 

Woodard & Curran, 2004. MOM Sampling and Analysis Semi-annual Report, April 2004, 

O’Connor Company Superfund Site, Augusta, Maine; June 26. 

Woodard & Curran, 2004. MOM Sampling and Analysis Fall 2004 Report, September 2004, 

O’Connor Company Superfund Site, Augusta, Maine; November 17. 
22

Woodard & Curran, 2004. 2004 Riggs Brook Sediment Monitoring Report, O’Connor Company 

Superfund Site, Augusta, Maine; December. 

Woodard & Curran, 2005. MOM Sampling and Analysis Semi-annual Report, April 2005, 

O’Connor Company Superfund Site, Augusta, Maine; July 22. 

Woodard & Curran, 2005. MOM Sampling and Analysis Fall 2005 Report, September 2005, 

O’Connor Company Superfund Site, Augusta, Maine; September. 

Woodard & Curran, 2005. 2005 Riggs Brook Sediment Monitoring Report, O’Connor Company 

Superfund Site, Augusta, Maine; January. 

Woodard & Curran, 2006. MOM Sampling and Analysis Semi-annual Report, April 2006, 

O’Connor Company Superfund Site, Augusta, Maine; June 28. 

Woodard & Curran, 2006. MOM Sampling and Analysis Semi-annual Report, September 2006, 

O’Connor Company Superfund Site, Augusta, Maine; December. 

Woodard & Curran, 2007. MOM Sampling and Analysis Semi-annual Report, April 2007, 

O’Connor Company Superfund Site, Augusta, Maine; June 19. 

Woodard & Curran, 2008a. Recommendation for Monitoring Well Decommissioning Activities, 

O’Connor Company Superfund Site, Augusta, Maine; July 18. 

Woodard & Curran, 2008b. Monitoring Well Decommissioning Summary O’Connor Company 

Superfund Site, Augusta, Maine; October 8. 

Woodard & Curran, 2009. Operations and Maintenance Plan, O’Connor Company Superfund 

Site, Augusta, Maine; October 27. 

Woodard & Curran, 2012. O’Connor Company Superfund Site Quality Assurance Project Plan 

(QAPP) Amendment, O’Connor Company Superfund Site, Augusta, Maine; June 
23

APPENDIX A 

GROUNDWATER CONCENTRATIONS GRAPHS 1998-2012

O’CONNOR SUPERFUND SITE

1,2 Dichlorobenzene 

180 

160 • 

140 

120 • 

1048 • ... t 100 .. ~ ... . • A A.Jo • 2018 

sa - • 1068 

60 . -= " .... • e 507A 

. ~ • - Roo 

40 

• ., -: .. ... . 

20 ... 

• • l ,.,. A .A. "AA 1111 . _, 0 . rTT'" ~ ...... "'"'"rTT'"~...t-TrO-n-...1 

Ill Ill 8 - s 8 <?; 8 8 s I!! g 0 N 0 

~ ~ fl fl fl fl fl fl fl fl fl fl ~ ~ ~ Dote 

1,4 Dichlorobenzene 

70 

60 • 

• 

50 

• ... 1048 ... 40 • 2018 

~ ~ . ... . ... ,. • 1068 0. 30 . ... . 

• 507A 

20 . ~ • .... • - Roo 

• "'= ~ .: . ... 10 • 

• • ,.,. .. !!' • ......... · A l'\ a ..J 0 1-rrH-rT\ · 

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 0 N i'i i'i i'i 

Dote 

C«<traal.lale Power Ccmpa'\y (225545.00) A-1 

O'C<:rlnor CO,_ S~O Site- 2012 Fll\al Clo6e-OUI Report 

JIAy27. 2012 
24

1.2.4 Trichlorobenzene 

.. 

70 

60 

so .. 1048 

• 10fil 

8:40 • ''"" • S07A 

30 - ROO 

"' • 

........ :-. ... .. 10 • 

0 t-... ;-,...,., 

... , , ., -rtrt. . . "' ...... ~ , ,, -,.. .f'T'".. , , rr, ~ , 1 ~ 1 . rr!'A .-~ \\.rri · ' -t-n-l~ ·rrrt" 1TT' l"l 

~ I ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 0 .. ii ii ii 

Dote 

t .3 Oichlaoben.zene 

100 

go 

80 

70 ... 1048 

60 • 1068 .A& • • t 50 ~ " • 2018 

40 

•• • • ... - "' • 507A 

30 . ~ ••• • - Roo 

20 • • 

10 & • --

11/>. • - • 

0 • It · · I • ~ ';''"'~ ~~..f!l-r. ' t-rrM-n-:"h-r( I 

~ .. "' ~ ., ., ~ .. .. 0 .. !! !! ~ ~ ~ ~ ~ ~ ~ ~ ~ ii ii ii 

Dale 

C«<traal.lale Power Ccmpa'\y (225545.00) A-2 

O'C<:rlnor CO,_ S~O Site- 2012 Fll\al Clo6e-OUI Report 

JIAy27, 2012 
25

Chlorobenzene 

50 

45 • 

40 

35 • • ... 1048 

30 1068 " .. • i 25 • 2018 • 

20 ..... -. • • 507A 

... ;'. c:, .. .. - - Roo 15 

10 . - . - • • • .. •• 5 

0 ~·· llt + ;.. ., "' ~ ~ ~ i=l " ii • •••• ~~ . i"'fll , l ; l l iiiil l iiiil l 

I I § 8 § § 8 ~ § 8 § § 0 N 0 0 0 - - N N N N N N N N N N N N N 

Dale 

C«<traal.lale Power Ccmpa'\y (225545.00) A-3 

O'C<:rlnor CO,_ S~O Site- 2012 Fll\al Clo6e-OUI Report 

JIAy27. 2012 
26

O'Connor VOCs - 1048 

120 

100 -. • • 

80 •• ·- ~ "' • • • • , 60 

. t . • 

40 ..... -..--- . ;. .......... . . 

20 

~ . ···-s· * • 

o .. L- •=···"'""'·"· ~ • ~ "' 0 

~ N "' ... "' <0 ... .. "' 0 

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Date 

O'Connor VOCs - 1068 

25 

• 

20 

· . 

15 • 

! • 

10 • 

• 

• 

5 

~--. • • • • 

:i L ;. .. .! It • • 0 • • • 

; . ! ; ! . ! ! ; ; ! ! ~ 

-

Central M~ne PoWer CCI1lpany(22SS4S.OD) A-4 

O"Cmnor co. Supertl.l'losne- 2012 Final aose-ou! Report 

~ N 

~ ~ 

• • 

! 

~ .. ~ 

··-

WOOO~RO 

&OJRRA!i 

·

+ -\2 Dici*IIO-

• \3 Dici*IIOt4 Dii:I*IIO~ 

• \2.4 Tlif:llleee-.. 

··-

COo-

• "Old" • =· • ttOidK • == 6 \4o CildK • =· + tt.4 Tlidt)IO""-

Jlily27. 2012 
27

a<:onnor VOCs - 2018 

120 

• 

100 

80 •• 

•• •.t> • ~. 

.. • • • • ~ • • .. ... •• • 1/11 • .... ,. ....... ~ fll ~ • ..., .... 

o-ctd-' 

~~ ~~ ~~ l. t ~ 

40 

l 60 

20 

0 ~ 0 0 ~ N M • ~ ~ ~ ~ 0 0 N 

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ... 

O'Connor VOCs - 5J)7A 

e 

e • 

~ 

® 

- ~ 

"9 ~ -. • 

~ 

• • • • ~ ... ,. t ... • • • .. . ... ~,.~ ~o ,t 

·m ~ ~ ~ ~ ~ ~ 2 ~ ~ ~ ~ ~ 1'i ~ 

""" 

C«<traal.lale Power Ccmpa'\y (225545.00) A-5 

O'C<:rlnor CO,_ O Site- 2012 Fll\al Clo6e-OUI Report 

l(--- • ew.. ... "-... 

2Ciiclfoooo~ 

•"l:lir:lfoooob-- .. l:lir:lfoooo -­

• t2,t Tn._ob_ 

...... 

. ~ ... --- • \2 Clk:Ho ... ~ 

• , , Clk:Ho ... ~ 

A \ 4 1lic:Hoi'Ob--

* U..4T..._.IO_ 

JIAy27. 2012 
28

APPENDIX B 

GROUNDWATER RESULTS 1998 – 2012

O’CONNOR SUPERFUND SITE
29
30
31
32
33
34
35
36
37
38
39
40
41

APPENDIX C 

O’CONNOR SUPERFUND SITE

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

Region 1

5 Post Office Square, Suite 100 

BOSTON, MA 02109-3912 

From: Claire Willscher, Human Health Risk Assessor, OSRR 

To: Terrence Connelly, RPM, OSRR 

Re: Risk evaluation for O’Connor Superfund Site 

Date: September 30, 2013 

Per your request, please find in this memorandum a screening of site groundwater data available 

from Woodard & Curran’s April 2012 Management of Migration Sampling and Analysis Annual 

Report for the O’Connor Superfund Site (“Site”). This memorandum also includes a 

conservative risk evaluation of the site-related contaminants of concern using the risk ratio 

approach, and a discussion regarding the soil cleanup levels outside of the Designated Area at the 

Site. 

In this memorandum the Site groundwater data are screened against EPA’s generic residential 

risk-based screening levels for direct contact with groundwater, Site cleanup levels, and 

screening levels developed for the residential vapor intrusion pathway. EPA’s risk-based 

screening levels are developed for chemicals with both cancer and non-cancer affects, following 

EPA Superfund guidance and using available toxicity values, standard risk methodology and 

standard default exposure values. The residential risk-based screening levels specific to direct 

contact with groundwater account for the exposure pathways of: incidental ingestion of tap 

water; dermal contact with tap water; inhalation of volatiles in tap water while 

bathing/showering; and, using tap water to do household chores. In this memorandum the Site 

groundwater data are also screened against both the Site cleanup levels and against residential 

screening levels developed for the vapor intrusion pathway. 

For purposes of this risk evaluation at the O’Connor Site, both the direct contact with 

groundwater risk-based screening levels and the risk-based screening levels for the vapor 

intrusion pathway are based on a target cancer risk level of 1E-6 or non-cancer hazard quotient 

(HQ) of 1.0 as the point of departure, with the lower value being used when there are both cancer 

and non-cancer screening levels. Please note that Region 1’s common practice is to use noncancer screening levels at HQ of 0.1 when there is a long list of non-carcinogenic contaminants 
42

to account for cumulative effects of more than 10 contaminants on the same target organs. 

However, since there are fewer than 10 non-carcinogens identified at this Site and they have 

effects on different target organs, there is no adding the health effects; therefore non-cancer 

screening levels used for this evaluation are based on HQ of 1. 

EPA’s generic risk-based screening levels used in this memorandum can be found on this EPA 

website: http://www.epa.gov/reg3hwmd/risk/human/rbconcentration_table/Generic_Tables/index.htm

The risk-based screening levels specific to the vapor intrusion pathway can be found on this EPA 

website: http://www.epa.gov/oswer/vaporintrusion/guidance.html

The groundwater wells that are relevant to this screening and risk evaluation at the O’Connor 

Site are those that are outside of the TI zone: MW-106A, MW-106B, MW-501, and MW-503. 

The concentrations used for this screening and risk evaluation are from the three most recent 

sampling rounds (2010, 2011, 2012), and correspond to the maximum detected concentrations at 

these wells, or the highest detection limit for a specific compound if all sampling rounds reported 

non-detect or if detected concentrations are lower than the greatest detection limit. 

Concentrations that exceed any screening levels are bolded in the tables. 

1) Groundwater screening

Groundwater COC

Conc for 

Screening

(ppb)

Residential 

Risk-Based 

Screening 

LevelGroundwater 

Exposure 

Pathway (ppb)

Basis for 

Screening 

Level

GW 

Cleanup 

Level 

(ppb)

Residential 

Risk-Based 

Screening 

Level-Vapor 

Intrusion 

Pathway 

(ppb)

Basis for 

Screening 

Level

1,2-Dichlorobenzene 1 280 HQ=1 85 2700 HQ=1

1,3-Dichlorobenzene 1 NA NA 85 NA NA

1,4-Dichlorobenzene 1 0.42 1E-6 risk 27 2.2 1E-6 risk

1,2,3-Trichlorobenzene 1 5.2 HQ=1 ns NA NA

1,2,4-Trichlorobenzene 1 0.99 1E-6 risk 70 36 HQ=1

1,3,5-Trichlorobenzene 1 NA NA 40 NA NA

Benzene 1 0.39 1E-6 risk 5 1.4 1E-6 risk

Chlorobenzene 1 72 HQ=1 100 410 HQ=1

PCBs 0.05 0.004 1E-6 risk 0.05 NA NA

As shown in the table above, the concentration used for screening for 1,4-dichlorobenzene, 1,2,4-

trichlorobenzene, benzene and PCBs exceeds their respective residential risk-based screening 

levels for the direct contact with groundwater exposure pathway. However, the concentration 

used for screening, for all groundwater COCs, does not exceed their respective Site groundwater 

cleanup level or their respective residential risk-based screening level for the vapor intrusion 

pathway. 
43

2) Groundwater risk evaluation 

Based on the screening above, the concentration used for screening for 1,4-dichlorobenzene, 

1,2,4-trichlorobenzene, benzene and PCBs exceeds their respective residential risk-based 

screening levels for the direct contact with groundwater exposure pathway. If these 

concentrations are used as exposure point concentrations to calculate risks, with the risk ratio 

approach, the risks for residential scenario from being exposed to groundwater at the Site would 

be: 

Groundwater COC

Residential 

Cancer Risk -

Groundwater 

Exposure 

Pathway

Residential 

Non-cancer 

Hazard -

Groundwater 

Exposure 

Pathway

Residential 

Cancer Risk -

Vapor Intrusion 

Pathway

Residential 

Non-cancer 

Hazard -

Vapor Intrusion 

Pathway

1,4-Dichlorobenzene 2.38E-06 0.002 4.55E-07 0.0001

1,2,4-Trichlorobenzene 1.01E-06 0.254 NA 0.0278

Benzene 2.56E-06 0.034 7.14E-07 0.0071

PCBs 1.25E-05 0.161 3.57E-07 NA

Total Risk 1.85E-05 1.53E-06

Cancer risk and non-cancer hazards, for each the direct contact with groundwater exposure 

pathway and vapor intrusion pathway, do not exceed EPA’s acceptable risk level. 

3) Soil Cleanup Levels for Areas inside and outside of the Designated Area 

The cleanup standards for soil and sediment inside of the Designated Area, as established in the 

1994 ESD, are 10 ppm for Total PCBs, 10 ppm for Total cPAHs and 248 ppm for lead. The 

1994 ESD identifies that these cleanup goals are “within EPA’s acceptable range of 10-4 to 10-6

for a residential setting”. These standards were attained in 1997, and the 2012 Five Year Review 

site inspection and soil sampling show that the integrity of the soil cover placed over the 

Designated Area has been maintained. Even though the 28-acre property, which includes the 23-

acre Site is zoned as RRES – rural residential district, where residential development that 

conserves the rural character of the area is permitted, institutional controls are in place which 

prevent current and future exposures to soils inside of the Designated Area. Specifically, the 

Declaration of Restrictive Covenant prohibits any activity which might disrupt remedial or 

monitoring measures installed pursuant to the Consent Decree without the prior written approval 

of the DEP, and requires that the owner shall maintain permeable or impervious caps or covers 

(including areas covered by topsoil or other clean fill). 

The cleanup standards for soil and sediment outside of the Designated Area are 1 ppm for Total 

PCBs, 1 ppm for Total cPAHs and 248 ppm for lead. These standards were attained in 1997. 

These cleanup levels remain appropriate at the O’Connor Site: 

 EPA’s current Guidance on Remedial Actions for Superfund Superfund Sites with PCB 

Contamination (August 1990) identifies that for soils, the preliminary remediation goals 

for PCBs should generally be 1 ppm for sites in or expected to be in residential areas. 
44

 The cleanup standard was set for Total PAHs at 1 ppm. Current risk assessment 

methodology allows for the calculation of cancer risk and non-cancer hazards, and 

corresponding risk-based cleanup standards, for individual PAHs. The residential riskbased screening level for benzo(a)pyrene (the most toxic of the cPAHs) is 0.015 ppm. As 

a conservative approach, assuming that the cPAHs at the Site are comprised entirely of 

benzo(a)pyrene, and using an exposure point concentration of 1 ppm (equivalent to the 

cleanup standard), the risks for the residential scenario, using the risk ratio approach, 

would be 6.67E-05. This risk is with EPA’s acceptable risk range, and therefore the 

cleanup standard remains protective of human health. 

 The EPA Office of Solid Waste and Emergency Response Directive: Revised Interim 

Soil Lead Guidance for CERCLA Sites and RCRA Corrective Action Facilities (August 

2004) recommends a screening level of 400 ppm for lead in soil for residential land use. 

The directive states that residential areas with soil lead below 400 ppm generally require 

no further action. 

Notes: 

a. This risk evaluation is a quick evaluation using the conservative maximum detected 

concentrations or detection limits to show a quick estimate of the risks at the Site. In 

traditional risk assessment, the full dataset would be evaluated and exposure 

concentrations would be closer to the mean, likely to be the 95% upper confidence limits 

instead of the maximum. In that case, the estimated risks would be lower than the risks 

estimated using the maximum in this memorandum. 

b. Toxicity information specific to Arochlor 1221 and Arochlor 1254 was used in the 

screening and the evaluation of the cancer risk and hazard associated with exposure to 

PCBs in order to provide for the most conservative assessment of PCBs. The direct 

contact with groundwater and vapor intrusion carcinogenic screening levels for PCBs 

correspond to those of Arochlor 1221, the most toxic of the PCBs. Because Arochlor 

1221 does not have toxicity values associated with non-cancer hazards, the direct contact 

with groundwater non-carcinogenic screening level for PCBs corresponds to that of 

Arochlor 1254. There is no residential risk-based screening level for non-cancer hazards 

for the vapor intrusion pathway because Arochlor 1254 is not volatile.