EXPLANATION OF SIGNIFICANT DIFFERENCES 

(ESD) 

THE CANNONS ENGINEERING BRIDGEWATER SUPERFUND SITE (CEC) 

MANAGEMENT OF MIGRATION OPERABLE UNIT 

BRIDGEWATER, MASSACHUSETTS 

MAY 2013 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

NEW ENGLAND - REGION 1 

5 POST OFFICE SQUARE 

BOSTON, MA 02109-3912 

11I1I1IH 

SDMS DocID 536063 
I. INTRODUCTION 

A. SITE NAME & LOCATION 

Site Name: Cannons Engineering Bridgewater Superfund Site 

Site Location: Bridgewater, Massachusetts, Plymouth County 

Cannons Engineering Bridgewater Superfund Site 

B. LEAD & SUPPORT AGENCIES 

Lead Agency: United States Environmental Protection Agency (EPA) 

• Contact: Derrick Golden, EPA Remedial Project Manager, (617) 918-1448 

Support Agency: Massachusetts Department of Environmental Protection 

(MassDEP) 

• Contact: Jay Naparstek, MassDEP Deputy Division Director, (617) 292 -

5697 

C. LEGAL AUTHORITY FOR ESD 

This Explanation of Significant Differences ("ESD") is being issued for the 

Cannons Engineering Bridgewater Superfund site ("Site") to document a change 

in a component of the remedy as originally set forth in the March 31, 1988 
Record of Decision ("ROD") for the management of migration operable unit at 

the Site. 

310 CMR 40.0932, establishes groundwater classification for the purposes of 

determining remediation requirements for groundwater at waste disposal sites 

within the Commonwealth of Massachusetts. 

In October of 2012, MassDEP indicated that the groundwater classification used 

to develop the 1988 ROD was no longer appropriate and identified the current 

classification of groundwater beneath and near the site. Therefore this ESD 

revises the groundwater cleanup levels which must now be t achieved at the Site. 

This reclassification is further discussed in section I.D., below. 

The United States Environmental Protection Agency ("EPA") is required to 

publish this ESD by Section 117(c) of the Comprehensive Environmental 

Response, Compensation and Liability Act (CERCLA), 42 U.S.C. § 9617(c), and 

the rule at 40 C.F.R. § 300.435(c)(2)(i). 

Under Section 117(c) of CERCLA, 42 U.S.C. § 9617(c), the rule at 40 C.F.R. 

300.435(c)(2)(i), and EPA guidance (Office of Solid Waste and Emergency 

Response [OSWER] Directive 9200.1-23P), if the EPA determines that 

differences in the remedial action significantly change but do not fundamentally 

alter the remedy selected in the ROD, with respect to scope, performance, or cost, 

the EPA shall publish an ESD between the remedial action being undertaken and 

the remedial action set forth in the ROD, and the reasons such changes are being 

made. EPA has determined that the adjustments to the ROD provided in this ESD 

are significant, but do not fundamentally alter the overall remedy for the Cannons 

Engineering Bridgewater Superfund with respect to scope, performance, or cost. 

Therefore, this ESD is being properly issued. 

D. SUMMARY OF CIRCUMSTANCES NECESSITATING THIS ESD 

The remedy for the Site as selected in the 1988 ROD included both Source 

Control and Management of Migration ("MOM") components. The cleanup was 

divided into two operable units, as described in further detail in Section II.B., of 

this document. 

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 MOM groundwater remedy was selected in 1988, before the 1993 revisions 

to the Massachusetts Contingency Pan (MCP). In 1993 MassDEP revised its 

cleanup regulations, the MCP. Included in these revisions to the MCP was the 

establishment of a new groundwater classification written specifically for 
addressing remediation at waste sites. 

The MCP has now established the following three groundwater categories for 

aquifers located within the Commonwealth of Massachusetts. 

• GW-1 - Applies to groundwater that is either a current drinking water 

resource (e.g., within a Zone 2 of a public water supply) or a potential future 

source of drinking water. Standards for GW-1 are intended to address the 

potential use of groundwater as a drinking water source. 

• GW- 2 - Applies to groundwater that is considered both shallow and where 

there is currently a structure built on the land above the groundwater. 

Standards for GW-2 are intended to address the potential migration of volatile 

oil or hazardous material from groundwater into the indoor air. 

• GW-3 - Applies to all groundwater in the Commonwealth. Standards for GW3 are intended to address the adverse ecological effects that could result from 

discharge of oil or hazardous material to surface water. 

On October 23, 2012, MassDEP conducted a new groundwater use & value 

determination specifically for the Cannons Engineering Bridgewater Superfund 

site. This evaluation determined that the groundwater at the Site is actually 

located within GW-2 and GW-3 groundwater classification areas. The Site is no 

longer considered to be within a GW-1 area. As a result of this reclassification, 

drinking water standards such as MCLs are no longer applicable or appropriate 

for groundwater cleanup goals. See attachment 1 for a copy of the groundwater 

value and use determination performed by MassDEP. 

In accordance with EPA Region Fs 1996 Final Ground Water Use and Value 

Determination Guidance, MADEP recommended a "medium use and value" 

determination for the groundwater at the Site in October 2012. 

This recommendation is based on the non-drinking water status of the 

groundwater beneath and in the immediate vicinity of the site, the presence of 

current and potential drinking water source in nearby areas off-site, the presence 

of sensitive ecological resources in the immediate vicinity of the site, and the 

location of the site within a State designated Area of Critical Environmental 

Concern (ACEC). For further details, see the MassDEP groundwater value and 

use determination, attachment 1. 

As a result of MADEP's "medium use and value" determination and the fact that 

the groundwater beneath the site has a non-drinking water status, EPA considers 

that there is no reasonable likelihood that the groundwater will be used for 

drinking water purposes, and therefore there is no ingestion exposure pathway 

which would lead to unacceptable risk. 
The last three years of annual groundwater data are contained in the following 

reports: 

• Year 20 Groundwater Monitoring Report, dated 2/10/2011 

• Year 19 Groundwater Monitoring Report, dated 1/6/2010 

• Year 18 Groundwater Monitoring Report, dated 3/23/2009 

E. AVAILABILITY OF DOCUMENTS 

This ESD and all supporting documentation shall become part of the 

Administrative Record for the Site. The ESD, supporting documentation for the 

ESD, and the Administrative Record are available to the public at the following 

locations and may be reviewed at the times listed: 

U.S. Environmental Protection Agency 

Records Center 

5 Post Office Square, Suite 100 

Boston, MA 02109 

617-918-1440 

Monday-Friday: 9:00 am - 5:00 pm 

Saturday and Sunday - Closed 

Bridgewater Public Library 

15 South Street 

Bridgewater, MA 02324 

508-697-3331 

Monday-Wednesday: 9:00 am - 8:00 pm 

Thursday: 10:00 am - 5:00 pm 

Friday: 10:00 am - 2:00 pm 

Saturday: 10:00 am - 2:00 pm 

Sunday: Closed 

II. SUMMARY OF SITE HISTORY, CONTAMINATION AND SELECTED REMEDY 

A. SITE HISTORY, CONTAMINATION AND SITE RISKS 

The Cannons Engineering Bridgewater Superfund site ("CEC") facility is a 7-acre 

site located in a small industrial park 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, and 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. 

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, 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 

Junel988. 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. 

B. SUMMARY OF THE MOM REMEDY 

The ROD for the CEC Site was signed by EPA on March 31, 1988. The ROD 

separated the cleanup plan for the Site into two Operable units; Management of 

Migration (MOM) for groundwater and Source Control for soils. This ESD only 

pertains to the MOM portion of the remedy. 

1. Management of Migration 

The MOM portion of the remedy included a twenty year groundwater monitoring 

program to assure that contamination above the Maximum Contaminant Levels 

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

naturally attenuated. 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. 

The last year of groundwater sampling, the year 20 groundwater sampling event, 

was completed in September of 2012. Except for arsenic, all contaminants of 

concern currently met MCLs. However because the groundwater at the site in no 

longer considered a drinking water aquifer, the requirement to reach MCLs is no 

longer applicable nor relevant. 
The management of migration remedy also required that institutional controls be 

placed on the property to restrict the use of groundwater at the Site. The 

institutional controls were recorded with the Registry of Deeds in September of 

1991 and remain in place. 

III. BASIS FOR THE DOCUMENT 

This ESD is being issued to explain a modification to the selected cleanup levels as set 

forth in the March 31,1988, ROD for the Site. The modification described in this ESD, 

reflects the current MCP groundwater classification for waste sites in the 

Commonwealth. The current groundwater classification prompts a change in the Siterelated cleanup levels. The proposed modifications to the MOM remedy described in 

this ESD will still be protective of both human health and the environment. 

The EPA Risk Assessment Information System was used to recalculate the risks of 

arsenic and 1, 4-dioxane for a standard recreational receptor. The cancer risk for a 

receptor exposed to arsenic from childhood through adulthood for a total of 30 years 

was 5 x 10'6, which is within EPA's acceptable human health risk range of 1 x 10'6 to 

1 x 10-4. 

With regards to 1, 4-dioxane, the cancer risk for a receptor exposure from childhood 

through adulthood for a total of 30 years was 4 x 10"8, which is well below EPA's 

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

Lastly, an evaluation of ecological risk due to exposure of aquatic organisms to arsenic 

and 1, 4-dioxane in Site groundwater that may emerge into surface water in the 

wetlands to the west of the Site, indicates that there is no actionable risk even if there 

were no dilution of the maximum concentrations of arsenic and 1, 4-dioxane on the 

Site, 

IV. DESCRIPTION OF SIGNIFICANT DIFFERENCES 

The proposed modifications to the remedy are summarized below. 

Original Remedy for the Management of Migration Operable Unit 

The original remedy for the MOM Operable Unit is described in detail in Section II.B.l 

of this document. 

Modified Remedy 

The purpose of this ESD is to modify only the MOM portion of the remedy by 

accepting the recent groundwater reclassification, and consequently modifying the 

cleanup levels for the Site. 

In order to determine the appropriate groundwater classification and groundwater 

cleanup levels, in October of 2012, MassDEP completed a new groundwater use and 

value determination specific to the Cannons Engineering site. This evaluation 

determined that groundwater beneath the Site is actually located within a GW-2 and 

GW-3 groundwater classification area. There is no ingestion of groundwater; therefore, 
MCLs, which are appropriate for a GW-1 aquifer, are no longer applicable or 

appropriate to groundwater at the Site. 

Roux Associates, Inc., consultant to the PRPs, indicated in a memorandum to EPA 

(Roux Associates, Inc., 2010) that the GW-1 area south of the Site is not receiving 

contaminated groundwater from the Site. This opinion was supported both by the 

hydrology at the Site and distance from the Site. The Site is located about 0.4 miles 

from the boundary of a Zone II. This Zone II boundary is in a hydraulically crossgradient location relative to the Site, and therefore, groundwater at the Site is flowing 

away from the Zone II and ultimately discharging into the freshwater wetlands in the 

western part of the Site and beyond to the west. Groundwater has been demonstrated to 

flow in this direction for over 20 years based on groundwater monitoring at the Site. 

The year 20, 19 & 18 annual groundwater monitoring reports from the last three years 

of annual groundwater sampling, demonstrates that all remaining contaminants of 

concern at the Site are protective of EPA's human health and ecological risk values. 

Furthermore, though the "Method I" standards outlined in the Massachusetts 

Contingency Plan (MCP) are not considered Applicable or Relevant and Appropriate 

requirements (ARARs) under CERCLA, it is important to note that groundwater also 

currently meets the GW-2 and GW-3 standards under the MCP. 

Annual groundwater monitoring reports showing data collected in the 18th, 19th, and 

20th year of monitoring provides the data which supports that the concentrations of all 

contaminants of concerns currently meet the MCP GW-2 and GW-3 standards. 

In addition, the contaminant levels in these three years of monitoring do not exceed 

EPA's range for unacceptable risks to human health and the environment. See 

attachment 2 for EPA's determination of protectiveness for both human health and the 

environment. 

Summary of Costs 

There are no additional costs associated with this 2013 ESD. 

V. SUPPORTING AGENCY COMMENTS 

The State of Massachusetts (MassDEP) has participated with the EPA in reviewing the 

modifications to the groundwater classification and cleanup levels described herein, and 

concur with this ESD. See attachment 3 for the concurrence letter from the MassDEP. 

VI. STATUTORY DETERMINATIONS 

EPA believes that the modified remedy as stated in this ESD remains protective of 

human health and the environment, complies with all Federal and State requirements 

that are applicable or relevant and appropriate to this remedial action, meets the 

remedial action objectives specified in the 1988 ROD, and is cost-effective. 
VII. PUBLIC PARTICIPATION COMPLIANCE 

In accordance with Section 117(d) of CERCLA and Section 300.825(a) of the NCP, the ESD 

and supporting documentation shall become part of the Administrative Record for the Site. 

This ESD and the Administrative Record are available for public review at the locations and 

times listed in Section 1(E) above. A public notice, which summarizes the modification to the 

remedy as set forth in the ESD shall be published in a local newspaper of general circulation 

following the signing of this ESD. 

VIII. DECLARATION 

For the foregoing reasons, by my signature below, I approve the issuance of this 2013 

Explanation of Significant Differences for the Cannons Engineering Superfund Site located in 

Bridgewater, Massachusetts and the changes and conclusions stated therein. 

Office of S^itejRemediation and Restoration 

USEPA New England - Region 1 

5 Post Office Square, Suite 100 

Boston, MA 02109-3912 

Attachment 1 

Attachment 2 

Attachment 3 

-MassDEP Groundwater Use and Value Determination 

- Copy of March 2013 EPA memorandum 

- MassDEP Concurrence Letter 
Attachment 1 - MassDEP Groundwater Use and Value Determination 
ff 

Commonwealth of Massachusett s 

Executive Office of Energy & Environmental Affairs 

Department of Environmental Protection 

One Winte r Street Boston, M A 02108 •617-292-5500 

DEVAL L PATRICK 

Governor 

RICHARD K. SULLIVAN JR. 

Secretary 

TIMOTHY P. MURRAY 

Lieutenant Governor 

KENNETH L KIMMELL 

Commissioner 

October 23, 2012 

Derrick Golden, Remedial Project Manager 

US EPA Region 1 

Mail Code OSRR07-4 

5 Post Office Square, Suite 100 

Boston, MA 02109-3912 

Subject: Cannons Engineering Corporation Superfund Site, Bridgewater, Massachusetts 

Groundwater Use and Value Determination 

Dear Derrick: 

Attached please find the Groundwater Use and Value Determination prepared by the Department 

(MassDEP) for the Cannons Engineering Corporation Superfund Site located in Bridgewater, MA. This Use 

and Value Determination was developed by Mass, pursuant to MOA between EPA and MassDEP and 

consistent with EPA's Groundwater Use and Value Determination Guidance. 

In determining the use and value of the groundwater in the vicinity of the Cannons Bridgewater Site, 

we referred to the aquifer classification contained in the Massachusetts Contingency Plan (MCP). The 

classification in the MCP gives consideration to all of the factors in the Use and Value Guidance. 

Enclosed with the Use and Value Determination is the GIS 21E Resource map (0.5 and 1 mile radii) 

used to develop the Use and Value Determination. This maps provides a variety of information, including the 

USGS yield classification, the locations of public water supplies and zones of protection, and areas of sensitive 

ecological resources. 

If you have any questions regarding this letter, please feel free to contact me at 292-5697. 

Very truly yours, 

Jay Naparstek 

Deputy Division Director 

This Information is available in alternate format. Call Michelle Waters-Ekanem, Diversity Director, at 617-292-5751. TDD# 1-866-539-7622 or 1-617-574-6868 

MassDEP Website: www.mass.gov/dep 

Printed on Recycled Paper 

SDMS Doc ID 524010 
GROUNDWATER USE AND VALUE DETERMINATION 

Cannons Engineering Superfund Site, Bridgewater, MA 

October, 2012 

Pursuant to the Memorandum of Agreement (MOA) between the EPA and MassDEP concerning 

Ground Water Use and Value Determinations, and consistent with EPA's 1996 Final Ground 

Water Use and Value Determination Guidance, the Department has developed a Use and Value 

Determination of the groundwater beneath and in the vicinity of the Cannons Engineering 

Superfund site located in Bridgewater, MA (the "Site"). The purpose of the Use and Value 

Determination is to identify whether the local area groundwater is of high, medium, or low use 

and value. These are designations contained in EPA's guidance. In the development of this 

Determination, as agreed to in the MO A, the Department has applied the criteria for groundwater 

classification promulgated in the Massachusetts Contingency Plan (MCP). The classification 

contained in the MCP considers criteria similar to those recommended in EPA's Use and Value 

Guidance. 

The Departments recommendation for the groundwater at the Cannons Engineering Bridgewater 

site is medium use and value. This recommendation is based on the non-drinking water status of 

the groundwater beneath and in the immediate vicinity of the site, the presence of current and 

potential drinking water source areas off-site but within the study area, the presence of sensitive 

ecological resources in the immediate vicinity of the site, and the location of the site within a 

State designated Area of Critical Environmental Concern (ACEC). This recommendation is 

explained in more detail below. 

For the purposes of this Determination, the groundwater under evaluation is defined as that 

underlying the Site and the surrounding area extending in a two mile radius from the central 

portion of the Site. 

The Cannons Engineering site in Bridgewater occupies approximately 6 acres of land between 

Route 24 and First Street. Operations at the site that included the transportation, storage, and 

incineration of hazardous wastes resulted in contamination of on-site soils, sediments, buildings, 

groundwater, and surface waters. Contaminants of concern included volatile organic compounds 

(VOC), polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), pesticides, 

and metals. Groundwater beneath the site contained VOCs including toluene, as well as heavy 

metals. 

The completed source control portion of the cleanup had several components, including on-site 

thermal desorption of upland area and wet area soils that were contaminated with VOCs, and offsite incineration of PCBs contaminated soils in excess of 9 parts per million (ppm). 

The management of migration portion of the clean up included restricting the use of groundwater 

at the site by the use of a deed restriction/institutional controls, installing additional monitoring 

wells, and implementing a long term groundwater quality monitoring program to observe the 

presence, distribution and migration of contaminants. The Record of Decision anticipated that 

removal and treatment of contaminated soils would eliminate sources of further groundwater 

SDMS Doc ID 524009 
contamination and that the residual low levels of contamination found in the groundwater would 

meet drinking water standards through monitored natural attenuation over 20 years. 

Long-term groundwater monitoring began in 1991. Annual sampling was required to be 

conducted for at least twenty years to demonstrate and ensure that monitored natural attenuation 

was occurring. The 20th annual sampling event was completed in September 2010. Analytical 

results indicate that all VOCs have met their respective MCLs. However, the 2009 analytical 

data for inorganics showed that 7 out of 24 groundwater samples exceeded the MCL for arsenic. 

The arsenic exceedences are isolated and appear to be confined to within the site boundaries. It 

is suggested by the parties conducting the cleanup that the arsenic exceedences are indicative of 

a reducing environment associated with the chlorinated organics contamination. They anticipate 

that the arsenic will become adsorbed to aquifer matrix materials and/or precipitate out of 

solution as the aquifer gradually returns to a more oxidized state now that VOC concentrations 

have been significantly reduced. EPA's 2010 Five Year Review recommended an additional 

round of groundwater sampling for arsenic be conducted prior to the next Five Year Review 

(2015). 

The land use surrounding the Site is mostly light industrial with some residential areas. The 

nearest residence is located 1/8 of a mile from the site. The closest municipal drinking water 

well is located in Raynham, approximately 1 mile southwest of the site. The Bridgewater 

municipal Town wells are located 2.6 miles east of the site. Sensitive ecological areas are 

located near the site and include wetland areas to the east and west of the site, and Lake 

Nippenicket to the west. The site is within a Massachusetts designated Area of Critical 

Environmental Concern, the Hockomock Swamp ACEC. 

The aquifer immediately beneath the Site is classified as a low yield aquifer by the United States 

Geological Survey. This groundwater is not considered to be a Current or Potential Drinking 

Water Source Area (MCP Category GW-1) and is category GW-3 under the MCP. Drinking 

water standards do not apply at GW-3 areas. However, there are both Current and Potential 

Drinking Water Source Areas within the study area. Approximately

 lA mile to the east of the site 

is a medium yield aquifer as defined by the USGS. This is a category GW-1, Potential Drinking 

Water Source Area. Approximately 1/3 mile to the southwest is another medium yield aquifer, 

and the edge of a delineated Zone II for a series of Raynham municipal wells. 1.3 miles to the 

east is the edge of a delineated Zone II for a series of Bridgewater municipal wells that are 

located approximately 2.6 miles east of the Site. These areas are category GW-1 groundwaters 

and considered to be Current or Potential Drinking Water Source Areas. State and federal 

drinking water standards apply to these areas. Any groundwater migrating from the site should 

meet or exceed State and federal drinking water standards (MCLs/GW-1) if and when it reaches 

any of these areas. 

In summary, groundwater directly beneath and in the immediate vicinity of the site is category 

GW-3 and GW-2 and not considered a source of drinking water. Drinking water standards are 

not directly applicable in these areas. However, some groundwater areas outside the site 

boundary and the immediate vicinity of the site, but within the study area, are category GW-1 

and should be evaluated as drinking water source areas. Drinking water standards do apply in 

these locations. Finally, there are sensitive environmental receptors within the study area. 
Decisions on final remedy and protectiveness should include evaluation of the impacts to these 

areas. Definitions of the various groundwater categories in the MCP are summarized as follows: 

GW-1 The groundwater is located within an area that is currently used for drinking water or is 

considered to be a location that has the potential to be developed for public water supply. State and 

federal drinking water standards are directly applicable to these areas. 

GW-2 This designation addresses areas where there is a potential for migration of vapors from 

groundwater to occupied structures. The classification applies to locations where groundwater 

has an average annual depth of 15 feet or less and where there is an occupied building or 

structure within a 30 foot surface radius of that groundwater. In these cases, evaluation of risk 

should include indoor air exposures through contaminant vapor intrusion. 

GW-3 This designation considers the impacts and risks associated with the discharge of 

groundwater to surface water and therefore applies to all groundwater in the Commonwealth, 

regardless of any other category it may also fall within. Evaluation of risk should include human 

health and environmental exposure resulting from discharge of contaminated groundwater to 

surface water bodies. 

Considering these classifications, evaluation of the groundwater risks remedy performance at the 

Cannons Bridgewater site should include, but is not limited to, the following: 

Human Health: 

a) vapor seepage into buildings, 

b) migration of contaminants to GW-1 areas off-site, 

c) use of the water in industrial processes, 

d) excavation into groundwater (i.e., worker exposure), 

e) potential exposures resulting from discharge to surface water (e.g. wading, recreation, 

fishing). 

Ecological: 

a) ecological risks posed by discharge of groundwater to nearby wetlands and Lake 

Nippenicket. 

In light of the use and value factors contained in EPA's guidance and similar criteria established 

in the MCP that were examined in this determination, the Department recommends a medium 

use and value for the Site groundwater. 
USE AND VALUE FACTORS CANNONS ENGINEERING CORP. SITE j 

SITE-SPECIFIC DETERMINATION 

1.) Quantity Low Yield on and in immediate vicinity of site; 

Areas of medium and high yield off-site but 

within 1/3 mile 

2.) Quality Groundwater not impacted by the site is of good 

quality to the best of our knowledge. Municipal 

wells are located approximately 1 mile southwest 

of the site; Delineated Zone 1 l's are located 

southeast and west of the site. 

3.) Current Public Water Supply Wells Municipal wells and Wellhead Protection Areas 

are located within Study Area 

4.) Current Private Drinking Water Supply Wells No known private wells within Study Area 

5.) Likelihood and Identification of Future 

Drinking Water Use 

Groundwater directly beneath and in the 

immediate vicinity of the site is notbelieved to be 

suitable for public water supply development 

Aquifer to the SE is already in use for public 

water supply; aquifer to the west has potenrial for 

water supply development; No known current 

plans for this. 

Study area consists of agricultural, residential, 

and industrial development 

Approximately 800 people live within a 1 mile 

radius of site 

6.) Other Current or Reasonable Expected 

Ground Water Use in Review Area 

• Unkown 

7.) Ecological Value Shallow groundwater discharge to drainage 

canals and nearby wetlands to the south and west 

Deeper groundwater discharge to southern 

portion of Hockomock Swamp 

Potential receptors of contaminated groundwater 

are aquatic and terrestrial biota inhabiting the 

wetlands (discharge area for shallow water) 

Endangered species habitat exists on-site 

SDMS Doc ID 524011 
8.) Public Opinion 
Map Output Page 1 of 1 

MassDEP - Bureau of Waste Site Cleanup 

MCP Numerical Ranking System Map: 500 feet & 0.5 Wile Radii 

ft£AQft3 MA Coorthft*!** 

n MassDEP 

SDMS Doc ID 524008 
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US EPA New England 

Superfund Document Management System / 

RCRA Document Management System 

Native Files Target Sheet 

SDMS Document ID #: 524008 

Site Name: Cannon Engineering Corp. . 

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Attachment 2 - Copy of March 2013 EPA risk memorandum 
MEMORANDUM 

To: 

From: 

Date: 

Subject: 

Derrick Golden 

Richard Sugatt 

March 21,2013 

Residual risk evaluation for Cannons Engineering Superfund Site, 

Bridgewater, MA 

The purpose of this memorandum is to evaluate the potential for human health and 

ecological risk due to residual contaminants in groundwater at the Cannons Engineering 

Superfund Site in Bridgewater, MA. As documented below, it is concluded that there is 

no actionable human health or environmental risk due to residual contaminants in 

groundwater at the Site. 

On October 23, 2012 Mass DEP conducted a new groundwater use and value 

determination specifically for the Cannons Engineering Bridgewater Superfund Site, and 

this evaluation determined that groundwater at the Site is actually located within GW-2 

and GW-3 groundwater classification areas. The Site is no longer considered to be 

within a GW-1 area. As a result of this reclassification, drinking water standards such as 

MCLs are no longer applicable or appropriate for groundwater cleanup goals. 

As shown on Table 1, the latest available groundwater data (2009, 2010) indicate that 

arsenic and 1, 4-dioxane are the only two groundwater contaminants that exceeded 

human health standards or guidance. Arsenic at a maximum concentration of 40 ug/L 

exceeded the MCL and Massachusetts MCL, both 10 ug/L. 1, 4-dioxane at a maximum 

concentration of 4.9 ug/L exceeded the Massachusetts Drinking Water Guideline of 3 

ug/L. Since the GW-1, MCL, MMCL, and Massachusetts Drinking Water Guideline are 

not applicable or appropriate, and use of groundwater at the Site for drinking water is not 

reasonably foreseeable, there is no current or future completed human health exposure 

pathway to groundwater, and therefore, no human health risk. 

Although GW-2 and GW-3 standards are not considered applicable or relevant and 

appropriate requirements (ARARs) under the Superfund Program, I have reviewed siterelated data against these state standards as another basis of comparison. Table 1 

demonstrates that the maximum concentrations of all detected chemicals do not exceed 

these standards. GW-2 standards are designed to be protective against vapor intrusion of 

volatile organic chemicals (VOCs) from groundwater into buildings. The absence of GW2 exceedances supports the conclusion that vapor intrusion is not of concern. This 

conclusion is also supported by the conclusion in the most recent Five Year Review 

Report (EPA, 2010) that there was no complete vapor intrusion pathway based on Site 

conditions, as well as conservative Johnson & Ettinger modeling 

Similarly, the absence of GW-3 exceedances supports the conclusion that ecological 

impacts to surface water are unlikely when Site groundwater reaches surface water. All 

groundwater in Massachusetts is classified as GW-3, and the GW-3 standards are 

designed to be protective of aquatic organisms after 10-fold dilution of groundwater as it 

emerges into surface water. 
Roux Associates, Inc., consultant to the PRPs, indicated in a memorandum to EPA (Roux 

Associates, Inc., 2010) that the GW-1 area south of the Site is not receiving contaminated 

groundwater from the Site. This opinion was supported both by the hydrology at the Site 

and distance from the Site. The Site is located about 0.4 miles from the boundary of a 

Zone II. This Zone II boundary is in a hydraulically cross-gradient location relative to 

the Site, and therefore, groundwater at the Site is flowing away from the Zone II and 

ultimately discharging into the freshwater wetlands in the western part of the Site and 

beyond to the west. Groundwater has been demonstrated to flow in this direction for over 

20 years based on groundwater monitoring at the Site. 

To address the potential concern that groundwater at the Site migrating to the off-Site 

wetlands may pose a human health risk, this memorandum evaluates the human health 

risk to off-Site recreators as described below: 

Although unlikely, it might possible that people who explore the off-Site wetlands to the 

west of the Site may contact surface water comprised in part of groundwater from the 

Site. The risk calculator at the Risk Assessment Information System 

(http://rais.ornl.gov/cgi-bin/Drg/RISK search?select=chem) was used to calculate the 

risks of arsenic and 1, 4-dioxane for a standard recreational receptor, using the undiluted 

maximum concentration of 40 ug/L arsenic and 4.9 ug/L of 1, 4-dioxane in Site 

groundwater. 

Standard exposure assumptions for dermal contact and incidental ingestion of surface 

water for recreational adults and children included ingestion of 0.05 L/day, exposure time 

of 1 hour/day, exposure frequency of 45 days/year, exposure duration of 30 years, over a 

lifetime of 70 years. As shown in the attached printout for 40 ug/L arsenic, the noncancer Hazard Quotient for both adults and children was less than 1, indicating that noncarcinogenic effects are unlikely. As shown in the attached printout for arsenic, the 

cancer risk for a receptor exposed from childhood through adulthood for a total of 30 

years was 5 x 10'6, which is within EPA's acceptable risk range of 1 x 10"6 to 1 x 10 . 

As shown in the attached printout for 4.9 ug/L of 1, 4-dioxane, the non-cancer Hazard 

Quotient for both adults and children was less than 1, indicating that non-carcinogenic 

effects are unlikely. As shown in the attached printout for 1, 4-dioxane, the cancer risk 

for a receptor exposure from childhood through adulthood for a total of 30 years was 4 x 

10"8, which is well below EPA's acceptable risk range of 1 x 10"6 to 1 x 10'4. 

To address the potential concern that arsenic in groundwater at the Site migrating to the 

off-Site wetlands may pose an ecological risk, it is sufficient conclude there is no 

potential ecological risk because the National Recommended Water Quality Criteria for 

protection of aquatic life for chronic exposure is 150 ug/L as the Criteria Continuous 

Concentration (CCC). This indicates no risk to aquatic life because the maximum 

concentration of 40 ug/L in groundwater at the Site is lower than the CCC. 
Similarly for 1, 4-dioxane, the available aquatic information indicates that aquatic 

toxicity is low and does not occur at concentrations below 145 mg/L. The 1995 OPPT 

Chemical Fact Sheet for 1, 4-dioxane (EPA, 1995) (http://www.epa.gov/chemfact/dioxasd.txt) cites reports describing acute and chronic toxicity of 1,4-dioxane to Pimephales 

promelas (fathead minnows). Acute effects occurred at 10,000 mg/L but not at 6000 

mg/L, which was the highest no observed adverse effect level (NOAEL). A 32-day 

embryo-larval test identified a Maximum Allowable Toxicant Concentration (MATC) 

>145 mg/L, which means that no chronic effects occurred at 145 mg/L. Additional acute 

toxicity studies indicated that the 96-hour LC50 value for Lepomis macrochirus (bluegill) 

was 10,000 ppm (10,000 mg/L) in fresh water, and the 96-hour LC50 value for the fish 

Menidia beryllina in synthetic seawater was 6,777 ppm (6777 mg/L). These toxicity data 

are sufficient to conclude that the maximum concentration of 1, 4-dioxane in Site 

groundwater (4.9 ug/L) is much lower than the levels that are toxic to aquatic organisms. 

Summary and Conclusions 

Although the maximum concentration of arsenic and 1, 4-dioxane in Site groundwater 

exceeded human health standards or guidelines, it is concluded there are no human health 

risks due to ingestion of on-Site groundwater because there is no reasonably foreseeable 

use of this groundwater for drinking water purposes, as shown by the MassDEP 

reclassification of groundwater at the Site from GW-1 to GW-2 and GW-3. There are no 

on-Site human health risks due to vapor intrusion because it was concluded in the most 

recent Five Year Review report that there is no completed vapor intrusion exposure 

pathway. According to available data, Site groundwater moves to the west rather than to 

the south towards the nearest GW-1 area, therefore, there is no risk due to use of off-site 

drinking water. An evaluation of human health risk due to contact with arsenic and 1, 4-

dioxane in Site groundwater that may emerge into surface water in the wetlands to the 

west of the Site indicates that there is no actionable risk even if there were no dilution of 

the maximum concentrations of arsenic and 1, 4-dioxane on the Site. An evaluation of 

ecological risk due to exposure of aquatic organisms to arsenic and 1, 4-dioxane in Site 

groundwater that may emerge into surface water in the wetlands to the west of the Site 

indicates that there is no actionable risk even if there were no dilution of the maximum 

concentrations of arsenic and 1, 4-dioxane on the Site. It is concluded that there is no 

actionable human health or environmental risk due to residual contaminants in Site 

groundwater. 

References 

Roux Associates, Inc. May 21, 2010. Memorandum to Derrick Golden from Ian Phillips, 

LSP, Roux Associates, Inc. 

U.S. EPA. 2010. Five-Year Review Report Fourth Five-Year Review Report for Cannons 

Engineering Bridgewater Superfund Site, Town of Bridgewater Plymouth County, 

Massachusetts. September 2010. 

U.S. EPA. 1995. OPPT Chemical Fact Sheet 1, 4-Dioxane Fact Sheet: Support Document 

(CAS No. 123-9-1). February, 1995. EPA 749-F-95-010a. 
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Attachment 3 - MassDEP Concurrence Letter 
3 Commonwealth of Massachusetts 

• Executive Office of Energy & Environmental Affairs 

One Winter Street Boston, MA 02108 • 617-292-5500 

Department of Environmental Protection 

DEVAL L PATRICK 

Governor 

RICHARD K SULLIVAN JR. 

Secretary 

TIMOTHY P. MURRAY 

Lieutenant Governor 

KENNETH L. KIMMELL 

Commissioner 

May 2, 2013 

Derrick S. Golden 

Remedial Project Manager 

US Environmental Protection Agency Region 1 

5 Post Office Square 

Boston, MA 02109-3912 

Dear Derrick, 

EPA has proposed an Explanation of Significant Differences (ESD) for the Cannons Engineering 

Bridgewater Superfund site to document a change in a component of the remedy contained in the 1988 

Record of Decision (ROD) for the management of migration operable unit. MassDEP has reviewed the 

final draft of the ESD and concurs with the proposed revisions. 

The purpose of the ESD is to revise the groundwater cleanup criteria contained in the ROD to reflect the 

current criteria contained in the Massachusetts Contingency Plan (MCP). The 1988 ROD reflected the 

groundwater cleanup criteria that existed prior to the 1993 revisions to the MCP which established a 

new groundwater classification intended to address remediation at waste disposal sites. MassDEP 

outlined the criteria that currently apply at the Cannons Bridgewater site in a recently completed 

Groundwater Use and Value Determination. 

Thank you for the opportunity to review the ESD. We look forward to continuing our work with you on 

the Cannons Bridgewater site. Please feel free to contact me if you have any questions regarding this 

matter. 

Very truly yours / 

day Naparstek 

Deputy Division Director 

Bureau of Waste Site Cleanup 

This information is available in alternate format. Call Michelle Waters-Ekanem, Diversity Director, at 617-292-5751. TDD# 1-866-539-7622 or 1-617-574-6868 

MassDEP Website: www.mass.gov/dep 

Printed on Recycled Paper