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FINAL CLOSE OUT REPORT 

THE CANNONS ENGINEERING CORP. (CEC) 

SUPERFUND SITE 

BRIDGEWATER, MASSACHUSETTS 

JUNE 2013 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

NEW ENGLAND - REGION 1 

5 POST OFFICE SQUARE, SUITE 100 

BOSTON, MA 02109-3912 
I. INTRODUCTION 

This Final Close Out Report (FCOR) documents that the United States Environmental 

Protection Agency (EPA) has completed all response actions for the source control 

(SC) and management of migration (MOM) operable units at the Cannon Engineering 

Corp. (CEC) Superfund (Site), located at 42 First Street, Bridgewater, Massachusetts. 

A Superfund Interim Close Out Report (ICOR) was completed and signed in September 

of 1991 for the Site. The 1991 ICOR was completed to document that the soil clean up 

levels for the SC operable unit were achieved; that the remedial actions were completed 

and that all physical construction of the remedies were also complete. The ICOR did 

not cover the MOM operable unit activities because those remedial actions consisted of 

long term groundwater, sediment, surface, and seep sampling for a period of 15-20 

years. 

Furthermore, page 10 of the 1991, ICOR states the following: A final closeout report 

will be issued for.the Bridgewater Site upon achievement of all groundwater cleanup 

target levels and completion of the long-term ground water monitoring program. The 

final closeout report (FCOR) will be a supplement to the interim closeout report and 

contain specific information concerning the groundwater monitoring program. The long 

term monitoring efforts have been completed. Therefore EPA is completing a FCOR for 

the Site. x 

This FCOR has been, completed in accordance with EPA guidance, Close Out 

Procedures for National Priorities List Sites, OSWER Directive 9320.2-22, dated May 

2011. 

II. SUMMARY OF SITE CONDITIONS 

A. BACKGROUND SUMMARY & SITE DESCRIPTION ; 

The CEC facility is a 7-acre site located in a small industrial pkrk in the western 

part of the Town of Bridgewater, Massachusetts. Prior to 1969, the industrial park 

consisted of a wooded lowland bordered to the north, south, arid east by rural 

agricultural land. Current land use around the site consists of industrial 

development in the immediate vicinity to the north and east, and a wooded 

lowland to the south and west, and agricultural and residential development in the 

outlying areas. 

The CEC Bridgewater site is located in the southeastern portion of the Town 

River watershed which has an estimated area of 56 square miles and feeds water 

supply wells for the towns of Bridgewater, West Bridgewater, and Raynham. 

Hockomock Swamp occupies a large portion of the watershed. Lake Nippenicket 

is the largest surface waterbody located within 1 mile of the Site. The nearest 

drinking water well, operated by the Town of Raynham, is located 1.3 miles west 

of the Site on the shore of Lake Nippenicket. 

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The CEC facility is one of the four separate but related sites which form the 

Cannons Site Group. The others are Cannons Plymouth Harbor located in 

Plymouth, Massachusetts; Tinkham's Garage in Londonderry, New Hampshire; 

and Gilson Road in Nashua, New Hampshire. All four sites are being handled 

under one enforcement effort. 

CEC first purchased the parcel of land at the Site in November, 1974. The 

property was developed by them to handle, store, and incinerate chemical wastes. 

These activities occurred frequently at the Site between 1974 and November, 

1980 when operations at the Site ceased after the MassDEP (then called the 

Department of Environmental Quality Engineering) revoked CEC's Waste 

License, citing document falsification and other waste reporting violations. 

Over 700 drums and approximately 155,000 gallons of liquid waste and sludge in 

bulk storage were left behind on-site by CEC. Between 1980 and 1982, the 

Massachusetts Department of Environmental Protection (MassDEP) and EPA 

conducted Site inspections, performed sampling and analyses and confirmed the 

presence of chemical contamination at the Site. Several tanks and drums were 

also observed to be leaking. In order to alleviate the problem of leaking 

contamination and wastes left on-site, the MassDEP performed a removal action. 

In October 1982, MADEP's contractor, Jet Line Services, Inc., removed 

approximately 155,000 gallons of sludge and liquid wastes that were stored in 

tanks and approximately 711 drums from the Site. A subsequent removal was 

conducted by the a group of Potentially Responsible Parties (the "PRP Group") in 

June 1988. The PRP Group removed the bulk contents of an underground tank, a 

septic tank, ,3 tanker trailers and small (5 gallon or less) containers from 

laboratory and storage areas at the Site. The site was made final on the National 

Priority List (NPL) on September 8, 1983. 

B. SUMMARY OF THE SELECTED REMEDIES & REMEDIAL ACTION OBJECTIVES 

The Record of Decision (ROD) for the CEC Site was signed by EPA on March 

31, 1988 and separated the cleanup of the Site into two Operable Units; 

Management of Migration (MOM) for groundwater and Source Control (SC) for 

soils. 

1. Management of Migration Operable Unit 

The MOM portion of the remedy included a long term monitoring program to 

assure that contamination in groundwater, above Maximum Contaminant 

Levels (MCLs), did not migrate off-site and to also assure that contaminant 

levels on-site naturally attenuated over time. The 1988 ROD estimated that 

groundwater cleanup target levels, based on the ingestion of on-site 

groundwater, would be achieved within 15 to 20 years. 

Long term sampling began in 1991 and the last sampling event was 

completed in September of 2010. With the exception of arsenic, all 

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( 
contaminants of concern met MCLs. In October 2012, MassDEP completed 

a new groundwater use and value determination specific to the Cannons 

Engineering site and determined that the groundwater beneath the site is no 

longer potable drinking water because the groundwater at the site is no longer 

considered a drinking water aquifer. Therefore the requirement to reach 

MCLs is no longer applicable nor relevant. 

Furthermore, in 2013, a site specific cumulative risk assessment was 

performed using the last three year of sampling data from 2008, 2009 and. 

2010. It was determined that potential risks for both human health and the 

environment were all well within EPA's acceptable risk range of 1 x 10~4 to 

1 x 10"6. This information is documented and discussed in greater detail in 

an Explanation of Significant Differences, dated May 2013. 

Source Control Operable Unit 

In summary, the source control portion of the remedy provided for fencing the 

entire site to restrict access, onsite thermal aeration of soils contaminated with 

volatile organic compounds (VOCs) and treatment of PCB contaminated soils 

offsite by incineration. 

In addition, onsite buildings and tanks were decontaminated and removed, and 

soils under those structures were sampled, along with other soil locations. Any 

contaminated soils that posed a threat to human health and the environment, 

were remediated via one of the above mentioned thermal treatment 

technologies. 

All remedial actions, construction activities and cleanup leVels related to the 

SC Operable Unit, were completed and achieved and we're documented via 

confirmatory sampling. Therefore, on September 30, 1991, EPA prepared an 

ICOR Report for the SC Operable Unit and included it in the Administrative 

Record for the Site. 

The remedial action objectives, as set forth in the 1988 ROD, identified to 

mitigate threats to public health are, are as follows: 

• prevent direct contact with contaminated soils throughout the site 

• prevent ingestion of contaminated soils, standing water in the wet 

area 

• prevent ingestion of contaminated groundwater 

• prevent exposure to contaminants in the buildings, aboveground 

and underground tanks, and associated structures 

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The remedial action objectives identified to mitigate threats to the 

environment are as follows: 

• prevent the exposure of wildlife to contaminated soil, sediments, 

and standing water in the wet area 

• prevent future wetlands contamination from surface water runoff 

and discharge 

The remedial action work plan for the SC Operable Unit (soil treatment) was 

finalized on January 11,1990 and the remedial, actions were performed 

between February 1990 and October of 1990. 

The remedial actions (long term monitoring) for the MOM Operable Unit 

began in 1991 and were completed in September of 2010. 

The remedial actions at the Site were conducted and enforced under a 1989 

Consent Decree between EPA and the settling defendants. 

C. INSTITUITONAL CONTROLS 

The management of migration remedy also required that institutional controls' 

(IC's) be placed on the property to restrict the use of groundwater at the Site. The 

IC's were recorded with the Registry of Deeds in September of 1991 and remain 

in place. The IC's prohibit any groundwater use, prohibit excavation below the 

depth of the groundwater table without the prior approval of EPA and MassDEP, 

and limit future use of the property to specific commercial, industrial and 

municipal uses. 

MONITORING RESULTS 

A. Management of Migration Operable Unit 

The MOM portion of the remedy included an extensive groundwater monitoring 

program to assure that groundwater contamination above the Maximum 

Contaminant Levels (MCLs) did not migrate off-site, and to assure that on-site 

contaminant levels naturally attenuated to levels below drinking water standards. 

The long term groundwater, sediment, surface and seep monitoring requirements 

are detailed.in the report entitled: Long Term Groundwater Monitoring Plan, 

Cannons Bridgewater Superfund site, Bridgewater, Massachusetts, dated June 

1992, prepared by GEI consultants. This long term sampling was conducted at 

the site from 1991 until 2010. 

As of 2010, all contaminants of concern met MCL's, with the exception of 

arsenic, in several onsite monitoring well locations. However, on October 23, 

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2012, MassDEP conducted a new groundwater use & value determination 

specifically for the Cannons Engineering Bridgewater site. As*a result of this 

reevaluation, it was determined that drinking water standards such as MCLs are 

no longer applicable or appropriate for groundwater cleanup goals because the 

ingestion of site groundwater is not an exposure pathway. See-EPA's Explanation 

of Significant Differences (ESD) dated May 2013, for additional details and to 

view a copy of the groundwater use and value determination. ' 

Prior to conducting the 2012 groundwater use and value determination, the 2010 

Five Year Review (page ES-3) anticipated that over time, arsenic concentrations 

would decrease naturally to background levels as the aquifer gradually returned to 

a more oxidized state, now that MCL's for both VOCs and SVOC's have been 

achieved on-site. 

In March of 2013, EPA's risk assessor conducted a cumulative evaluation of risks 

for a standard recreational receptor. This evaluation considered all residual 

groundwater contaminants and used the last three years of groundwater sampling 

data from 2008, 2009 and 2010 in the risk calculations. The results of this 

cumulative risk assessment determined that the human health risks are within 

EPA's acceptable risk range of 1 x 10"4to 1 x 10"6. 

An evaluation of ecological risk due to exposure of aquatic organisms to on-site 

levels of arsenic and 1, 4-dioxane in groundwater was conducted. This evaluation 

assumed that even if the residual concentrations of arsenic and 1, 4-dioxane 

emerged into surface water in the wetlands to the west of the Site, there would be 

no actionable risk even if there were no dilution of the maximum concentrations 

of arsenic and 1, 4-dioxane. For specific details about these risk assessments, see 

the risk assessment memo which is included as Attachment 2, to the May 2013, 

ESD 

The 2008, 2009, and 2010 annual monitoring reports are included in the 

administrative record and in the deletion docket for the site. 

B. Source Control Operable Unit 

Post confirmatory sampling of the excavated areas was conducted for 

Polychlorinated Biphenyl's (PCB's), Volatile Organic Compounds (VOCs) and 

semi volatile organic compounds (SVOCs) in order to verify that soils were 

removed in accordance with the remedial design excavation levels. The 

excavations were deemed complete once the clean up levels were verified via 

confirmatory sampling. The attainment of the soils clean up levels are further 

discussed and documented in EPA's 1991, ICOR for the site. 

ATTAINMENT OF GROUNDWATER RESORATION CLEANUP LEVELS 

See above section III. A, Monitoring Results for the Management of Migration 

Operable Unit. 

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V. SUMMARY OF OPERATION & MAINTENANCE REQUIRED 

The responsible parties (RP's) will provide support to EPA (as directed) and EPA will 

conduct future Five Year Reviews at the site to ensure the remedies remain protective of 

both human health and the environment. The RP's shall adhere to and maintain 

compliance with the institutional controls/deed restrictions for the Site. At some point in 

the future, the RP's may need to properly abandon the groundwater monitoring wells as 

directed by EPA, with MassDEP concurrence. 

VI. DEMONSTRATION OF CLEANUP ACTIVITY QA/QC 

A. Management of Migration Operable Unit 

A quality assurance/quality control plan (QA/QC) established procedures to be 

followed throughout the duration of the long term monitoring plan. The QA/QC 

requirements are included in section 3.0 of the approved Long-term Ground Water 

Monitoring Plan, Cannons Bridgewater Superfund site, Bridgewater, MA, dated 

1991. This plan was later updated, at the request of EPA, to include changing from 

sampling with bailers to using low-flow sampling protocol techniques. 

In the 2005 Five Year Review, EPA noted and recommended that RP's use a 

laboratory method which would achieve a lower reporting limit for four SVOCs, 

hexachlorobenzene, atrazine, pentachlorophenol, and benzo(a)pyrene. The RP's 

implemented this recommendation for subsequent sampling events. 

Furthermore, EPA conducted split sampling of the groundwater for the last three 

years of annual sampling performed by the RP's. These split groundwater samples 

were sent for analysis to EPA's laboratory located in Chelmsford, Massachusetts. 

Comparison of the two data sets indicated that the results were comparable, thereby 

assuring that appropriate QA/QC requirements were being achieved. 

B. Source Control Operable Unit 

In order to ensure the quality of the remedial action activities being performed, 

Quality Control (QC) procedures were implemented throughout the remedial 

actions. QC procedures were also used to assess the applicability of the activities 

being performed and, based on site conditions, correct or revise those activities to 

ensure that they were consistent with the objectives of the remedial action. 

These procedures included supervision, equipment calibration, document review, 

inspection, audits, and data validation. Additionally, QC suggestions were 

provided by EPA and our oversight representative on an informal (daily) basis 

and on a formal basis at weekly meetings and were implemented throughout the 

remedial action. A description of the major remedial activities and the QC 

procedures and QC corrective actions implemented for the SC remedial actions 

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are described in further detail in section 11.0 of the Remedial Action Report, 

prepared by Canonie Environmental, dated October 1991. 

Furthermore the 1991, ICOR documents that all appropriate soil cleanup levels 

were achieved and were verified with confirmatory sampling in the excavated 

areas. 

FIVE YEAR REVIEWS 

r Statutory Five Year Reviews are required at the site because the ROD was signed 

after the Superfund Amendments and Reauthorization Act of 1986 (SARA) and 

contaminants remain on . the Site above levels that allow for unlimited use and 

unrestricted exposure, i.e., the Site was remediated to commercial/industrial use. 

The following Five Year reviews have been completed for the CEC Site: 

• 1995 Five Year Review Report 

• 2000 Five Year Review Report 

• 2005 Five Year Review Report 

• 2010 Five Year Review Report 

All of the above listed Five Year Review determined that: 

• The source control remedy, as documented by EPA, was complete 

in 1991, and judged by EPA to still be protective 

• The groundwater remedy for the Cannon Engineering Corp. Site is 

expected to be protective of human health and the environment upon 

completion, and in the interim, exposure pathways that could result 

in unacceptable risks are being controlled through institutional 

controls. 

The following are the site related issues that were identified in the 2010 Five Year 

Review: 

1. No sampling has been conducted for 1,4-dioxane, as it was not a 

well-known chemical at the time the monitoring plan was 

established. 

2. Groundwater concentrations in 7 of the Site monitoring wells 

exceeded the MCL for arsenic in the Year 19 data. 

3. During the interview process, several Town officials indicated that 

they were unfamiliar with the history of the Site and were not 

aware of the deed restriction requirements. 

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The following actions were taken to address the issues that were identified in the 

2010 Five Year Review: 

1. The RP' s sampled for 1,4-dioxane during the 2010 annual 

sampling event. The 2013 cumulative risk assessment evaluated 

risks from 1,4-dioxane and determined that the remaining levels in 

groundwater are within EPA's acceptable risk range of 1 x 10"4 to 

1 x 10"6. Therefore the remaining level of 1,4-dioxane in 

groundwater is protective of both human and ecological health. 

2. The 2013 ESD removed the requirement to reach MCL's.for all 

contaminants of concern in groundwater. The use of site 

groundwater for drinking water is not reasonably foreseen, and 

there is no current or future completed pathway for human health 

exposure to groundwater. Recreational and aquatic organism 

pathways to surface water exposures were evaluated. The 2013 

cumulative risk assessment (attachment 2 of the 2013 ESD) 

evaluated potential risks from all residual groundwater 

contamination (including arsenic and 1,4-dioxane) and determined 

that the remaining levels in groundwater are within EPA's 

acceptable risk range of 1 x 10"4 to 1 x 10"6. Therefore the 

remaining levels of contamination in the groundwater are 

protective of both human and ecological health. Also, the 2010 

Five Year Review stated that "It is likely that the arsenic 

; exceedances, as well as the elevated iron and manganese 

concentrations, are indicative of a reducing environment associated 

with chlorinated organic contamination, and that the arsenic will 

become adsorbed and/or precipitate as the aquifer gradually returns 

to a more oxidized state. 

3. A cover letter and a copy of the 2010 Five Year Review was 

provided to the clerk and health agent for the Town of 

Bridgewater. The cover letter also reiterated the institutional 

control requirements. 

SITE COMPLETION CRITERIA 

The remedial actions which have been implemented for the SC and MOM operable 

units achieves the clean up requirements identified in the 1988 ROD and the 2013 

ESD for the Site. Furthermore the remaining site related contaminants in are 

protective of both human health and the environment and are within EPA's 

acceptable risk range of 1 x 10"4 to 1 x 10"6 for all appropriate exposure pathways. 

All of the selected remedial and removal actions and the remedial action objectives 

and associated cleanup goals are consistent with the Comprehensive Environmental 

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Response, Compensation, and Liability Act (CERCLA), the National Contingency 

Plan (NCP) and EPA policy and guidance. 

All Institutional Controls are in place and currently EPA expects that no further 

Superfund response is needed to protect human health and the environment, 

except future Five Year Reviews. 

IX. BIBLIOGRAPHY 

• Long Term Groundwater Monitoring Report Plan, Cannons Bridgewater 

Superfund Site Bridgewater, MA, dated June 1992, prepared by GEI 

consultant. 

• Final Report, Remedial Investigation, Cannons Engineering Corporation 

Site, Bridgewater, MA, prepared by Ebasco Services Inc., dated May 1987. 

• Record of Decision (ROD), Cannons Engineering Corporation (CEC) 

Site, Bridgewater, MA, prepared by EPA, dated March 1988. 

• Superfund Site Interim Close Out Report (ICOR), prepared by EPA, dated 

September 1991. 

• Remedial Action Report Cannons Bridgewater Superfund Site, dated 

October 1991, prepared by Canonie . 

• Groundwater Monitoring and Reporting - September 2008 - Year 18 

Cannons Engineering Superfund Site, Bridgewater, Massachusetts, 

prepared by Roux Associates Inc., dated March 2009. 

• Groundwater Monitoring and Reporting - September 2009 - Year 19 

Cannons Engineering Superfund Site, Bridgewater, Massachusetts, 

prepared by Roux Associates Inc., dated January 2010. 

• Groundwater Monitoring and Reporting - September 2010 - Year 20 

Cannons Engineering Superfund Site, Bridgewater, Massachusetts, 

prepared by Roux Associates Inc., dated February 2011. 

• ' Explanation of Significant Differences (ESD), The Cannons Engineering 

Bridgewater Superfund Site (CEC), Management of Migration Operable 

Unit, prepared by EPA, dated May 2013. 

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3- '3 

les T. Owens III, Director 

ffice of Site Remediation and Restoration 

JSEPA New England - Region 1 

5 Post Office Square, Suite 100 

Boston, MA 02109-3912 

Date 

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