J-1_Range_Decision_Document_2011.pdf

Superfund Records Center SITE: GrfbAFB MftKTAIKo

BREAK: S«V

OTHER: VftS*?2- .

United States Environmental Protection Agency

Region 1

Decision Document

J-1 Range Operable Unit

Camp Edwards

Massachusetts Military Reservation

Cape Cod, Massachusetts

May 2011

' v SDMS DocID j « 5 8 4 2 j

TABLE OF CONTENTS PAGE

PART I: DECLARATION FOR THE SDWA DECISION DOCUMENT

A. SITE NAME 4

B. STATEMENT OF BASIS AND PURPOSE 4

C. ASSESSMENT OF THE SITE 4

D. DESCRIPTION OF RESPONSE ACTIONS 5

E. DETERMINATIONS 8

F. SUPPORTING DATA 9

G. AUTHORIZING SIGNATURE 10

PART II: THE DECISION SUMMARY.. 11

A. SITE DESCRIPTION 11

B. SITE HISTORY AND ENFORCEMENT ACTIVITIES 11

1. History of Site Activities 11

2. History of Investigations and Response Actions 12

3. History of Relevant Federal and State Enforcement Activities 18

C. COMMUNITY PARTICIPATION 19

D. SCOPE AND ROLE OF OPERABLE UNITS 22

E. SITE CHARACTERISTICS 22

F. CURRENT AND POTENTIAL FUTURE SITE AND RESOURCE USES 25

G. SUMMARY OF SITE RISKS 26

H. RESPONSE ACTION OBJECTIVES FOR GROUNDWATER 27

I. DEVELOPMENT OF ALTERNATIVES FOR GROUNDWATER 28

J. DESCRIPTION OF ALTERNATIVES, SUMMARY OF COMPARATIVE ANALYSIS

AND THE SELECTED RESPONSE ACTION 31

1. Northern Plume area 31

2. Southern Plume Area

K. RESPONSE ACTION IMPLEMENTATION 45

L. DETERMINATIONS 55

M. DOCUMENTATION OF NO SIGNIFICANT CHANGES 56

N. STATE ROLE 56

57 PART III: THE RESPONSIVENESS SUMMARY

List of Figures

Figure 1: Location of J-1 Study Area

Figure 2: J-1 Range Layout

Figure 3: J-1 Range Study Areas

Figure 4: J-1 Range Interberm Area MIS Sampling Results

Figure 5: J-1 Range Firing Point Area MIS Sampling Results

Figure 6: Conceptual J-1 Range Northern Extraction Well Locations and Pipelines

Figure 7: Conceptual J-1 Range Southern Extraction Well Locations and Pipelines

Figure 8: J-1 Range 2010 Land Use Control Area

List of Tables

Table 1: Summary of Alternatives

Table 2: Summary of Regulatory Considerations

List of Appendices

A: Massachusetts Department of Environmental Protection Letter of Concurrence

B: Glossary of Terms and Acronyms

C: Index of Key Supporting Documents

D: Soil and Groundwater Screening

PART I: DECLARATION FOR THE SAFE DRINKING WATER ACT DECISION DOCUMENT

A. SITE NAMES

The subject site is the J-1 Range ("the Site"), which is located at Camp Edwards at the

Massachusetts Military Reservation (MMR).

B. STATEMENT OF BASIS AND PURPOSE

This Decision Document presents the selected response actions for the Site. The selected response actions were chosen in accordance with Section 1431(a) of the Safe

Drinking Water Act (SDWA), 42 USC § 300i(a), as amended, and the Administrative Order

(AO) concerning response actions issued thereunder, U.S. Environmental Protection

Agency Region 1 (EPA) Administrative Order No. SDWA-1-2000-0014 (A03). The authority to select the necessary response action(s) has been delegated to EPA Region

1's Regional Administrator pursuant to EPA Delegation No. 9-17 (1200-TN-350) dated May

11, 1994, and further delegated to EPA Region 1's Director, Office of Site Remediation and Restoration, pursuant to a redelegation of authorities dated April 6, 2010.

This decision is based on the Administrative Record, which has been developed in accordance with A03 and with a previous EPA Administrative Order, SDWA 1-97-1019

(A01), including consideration of the substantive cleanup standards of the

Massachusetts Contingency Plan (MCP) 310 CMR 40.0000. The Index of Key Supporting

Documents is available for review at the impact Area Groundwater Study Program

(IAGWSP) office, 1803 West Outer Road, Camp Edwards, MA. Documents included in the

Index of Key Supporting Documents are listed in Appendix C.

C. ASSESSMENT OF THE SITE

On July 13, 1982, EPA determined that the Cape Cod Aquifer is the sole or principal source of drinking water for Cape Cod, Massachusetts, and that the Cape Cod Aquifer, if contaminated, would create a significant hazard to public health (47 Fed. Reg. 30282).

Contaminants from the Training Ranges and Impact Area at MMR are present in and may enter and migrate in the aquifer. The response actions selected in this Decision

Document are necessary to protect the Cape Cod Aquifer, an underground source of drinking water on which the public relies.

D. DESCRIPTION OF RESPONSE ACTIONS

This Decision Document sets forth the selected response actions taken and to be taken for addressing the source areas contributing to groundwater contamination, and the groundwater contamination at and emanating from the Site. The source areas include both soil contamination and unexploded ordnance (UXO) (or munitions and explosives of concern (MEC)) that may be in or on the soil. There may be additional areas on the site where UXO/MEC and the soil beneath may pose public safety risks, ecological risks, dermal contact risks, and/or soil ingestion risks. These potential UXO/MEC-related risks are not addressed by this Decision Document, which was issued pursuant to

Administrative Order No. SDWA-1 -2000-0014 and Section 1431(a) of the SDWA, and which focuses on potential endangerment to the health of persons deriving from contaminants present in or likely to enter the underground source of drinking water.

Based on recent sampling results presented in the remedial investigation report for the

Site, it was determined that no further action was necessary with regard to the source as a contributor to groundwater contamination associated with the Site. Soil contamination and most of the MEC at the J-1 Range source areas that was contributing to groundwater contamination was adequately removed during historical investigations as well as during response actions conducted from 1997 through 2010. Post-excavation soil samples collected at the Site revealed only low, infrequent detections of explosives compounds.

Geophysical investigations suggest it is unlikely that a significant number of MEC which could impact groundwater remain on the range. Since no further contribution of contaminants from soil or MEC to groundwater is expected, the proposed alternatives did not include any further source-area cleanup

However, based on groundwater sampling results, EPA, in consultation with MassDEP deemed it necessary to develop and evaluate a range of potential response actions to address contaminants detected in groundwater associated with the Site. The Remedial

Investigation / Feasibility Study (RI/FS) for the Site identified Hexahydro-1,3,5-trinitro

1,3,5-triazine (RDX) and perchlorate as the contaminants of concern (COCs) for groundwater.

These specific COCs were used to develop and evaluate a range of potential response actions for the Site. Groundwater modeling was used to determine the feasibility of the alternatives and the selected response action was based on the remediation of the RDX and perchlorate plumes. The cleanup objectives for the Site are to restore the useable groundwater to its beneficial use, wherever practicable, within a timeframe that is reasonable given the particular circumstances of the site; to provide a level of protection in the aquifer that takes into account that the Cape Cod Aquifer, including the Sagamore

Lens, is a sole source aquifer that is susceptible to contamination; and to prevent the ingestion and inhalation of groundwater containing the COCs (RDX and perchlorate) in excess of federal Maximum Contaminant Levels (MCLs), Health Advisories (HA), Drinking

Water Equivalent Levels (DWELs), applicable State standards or unacceptable excess lifetime cancer risk (ELCR) or non-cancer Hazard Index (HI).

There currently is no federal drinking water standard for perchlorate. However, in

December 2008, EPA issued an Interim Drinking Water Health Advisory for exposure to perchlorate in water of 15 ug/L. Also, the Massachusetts Department of Environmental

Protection (MassDEP) has promulgated a Massachusetts Maximum Contaminant Level

(MMCL) for perchlorate of 2 ug/L.

The lifetime federal Health Advisory for RDX in drinking water is 2 ug/L, the -6

Massachusetts Contingency Plan (MCP) GW-1 standard is 1 ug/L, and the 10 ELCR risk-based concentration that results in an increased lifetime cancer risk of one in a million is currently 0.6 ug/L.

The EPA, in consultation with MassDEP, has selected a response action for the Site under which the aquifer, which has been designated a Sole Source Aquifer by the EPA and a Potentially Productive Aquifer by the MassDEP, will be restored. The response action will ensure that the groundwater containing RDX at concentrations greater than -6 the 10 risk-based level and/or perchlorate greater than 2 ug/L is restored to protective levels.

For groundwater investigation and response action purposes, the J-1 Range has been divided into two sub-areas, the northern area and the southern area. The EPA selected response action for the northern area groundwater is Focused Extraction with Two Wells, Monitored Natural Attenuation, and Land-Use Controls. For the southern area groundwater, the EPA selected response action is Focused Extraction with Two Wells, Monitored Natural Attenuation and Land-Use Controls. These alternatives, as presented in the J-1 Range RI/FS, provide the best balance of the criteria used to evaluate cleanup alternatives.

The selected alternatives achieve cleanup goals in a reasonable timeframe and protect human health through the use of groundwater monitoring to ensure that groundwater modeling predictions regarding the reduction and migration of contamination at the Site are correct and that any residual contamination remains below risk-based levels. Human health will be further protected through the implementation and verification of land use controls. These controls will prevent use of contaminated portions of the aquifer at the

Site for drinking water purposes until groundwater data confirm that contamination has been reduced to below risk-based levels.

The major components of the J-1 Range northern area response action are:

• A 250 gallon per minute (gpm) pump and treat system containing two extraction wells and two mobile treatment units (MTUs);

• Development and implementation of a long-term monitoring program that would be optimized as required, as contamination levels are reduced;

• Implementation of land use controls to prevent access to and use of the contaminated portions of the aquifer for drinking water, and maintain the integrity of any current or future groundwater monitoring systems;

• Monitoring to verify actual versus predicted migration and attenuation (i.e., confirmation that cleanup levels have been achieved and to demonstrate that the source removal is adequate);

• Site cioseout documentation; and

• Well abandonment after monitoring is complete.

The major components of the J-1 Range southern area response action are:

• A 125 gpm pump and treat system containing two extraction wells and one MTU;

• Development and implementation of a long-term monitoring program that would be optimized as required, as contamination levels are reduced;

• Implementation of land use controls to prevent access to and use of the contaminated portions of the aquifer for drinking water, and maintain the integrity of any current or future groundwater monitoring wells and treatment systems;

• Monitoring to verify actual versus predicted migration and attenuation (i.e., confirmation that cleanup levels have been achieved and to demonstrate that the source removal is adequate);

• Site cioseout documentation; and

• Well abandonment after monitoring is complete.

E. DETERMINATIONS

The response actions selected in this Decision Document will protect the public health from any endangerment which may be presented by the presence or potential migration of COCs from the Site into the underlying Sole Source Aquifer. The response action selected in this Decision Document, issued pursuant to A03 and Section 1431 of the

SDWA, addresses the unacceptable threats to the groundwater aquifer from the Site. In this Decision Document, EPA is making no determination regarding any remaining public safety risk, ecological risk, dermal contact risk, and/or soil ingestion risk posed by any remaining contamination at the Site.

As required by A03, the selected alternatives for the Site (Focused Extraction, Monitored

Natural Attenuation and Land Use Controls for groundwater and no further action for source areas contributing to groundwater contamination) provides a level of protection to the aquifer underlying and downgradient of the Site commensurate with the aquifer's designation as a Sole Source Aquifer and a Potentially Productive Aquifer and is protective of human health.

In addition to annual reports on groundwater monitoring and verification of land-use controls, the selected response actions include periodic reviews at frequencies not to exceed five years. The scope of each review will include, but not be limited to, sampling data, modeling data, and other relevant data. EPA, in consultation with MassDEP, will review this and any other relevant information to determine if additional measures are necessary for the protection of human health. This will include information acquired after implementation of the selected response action (such as new regulatory requirements or changes in the environmental conditions of the Site).

F. SUPPORTING DATA

Detailed information on the Site is included in the Final J-1 Range Remedial

Investigation/ Feasibility Study dated July 16, 2010. An overview of the Site, including decision factors that led to selecting the groundwater response actions, is included in the Decision Summary section of this document. The Decision Summary section also includes information on COCs and their respective concentrations, the baseline risk represented by the COCs, cleanup levels established for COCs and the basis for the levels, current and future land and groundwater use assumptions used in the baseline risk screening and Decision Document, land and groundwater use that will be available at the Site as a result of the selected response action, and decision factor(s) that led to selecting the remedy. Additional information can be found in the Index of Key

Supporting Documents, which is Appendix C to the Decision Document.

G. AUTHORIZING SIGNATURE

This Decision Document documents EPA's selected response action, under the authority of the SDWA, for remediation of the J-1 Range Operable Unit within Camp Edwards at the

MMR. The MassDEP concurs with this decision.

U.S. Environmental Protection Agency sfa/it f=tnu ' J t O Date:

James T. Owens, III

Director, Office of Site Remediation and Restoration

Region 1

PART II: THE DECISION SUMMARY

A. SITE DESCRIPTION

The J-1 Range is located on Camp Edwards on the Massachusetts Military reservation on

Cape Cod in Massachusetts (Figure 1). It is located southeast of the impact area between the J-2 and J-3 ranges. The J-1 Range is approximately 2,000 meters long and between 50- and 250-meters wide. The range is oriented southeast to northwest, with the southeastern "uprange" end near Greenway Road, and the northwestern "downrange" end extending several hundred meters into the impact area. There are large man-made berms located at various distances along the length of the range. The only structure located on the Range is a concrete bunker located near the 1,000 meter berm. Access to the J-1 Range is currently restricted by a locked gate.

B. SITE HISTORY AND ENFORCEMENT ACTIVITIES

1. History of Site Activities

The J-1 Range is a multi-purpose range where military training, munitions testing, and munitions disposal occurred. Past munitions use on the range mainly involved contractor testing. Military training, which consisted of anti-tank and small arms training, occurred from 1935 through the mid-1950s. From 1957 through the late 1980s, the J-1 Range was used for weapons testing by defense contractors. The predominant firing positions are believed to have been along the berm located near the entrance to the range, and next to the 1,000-m berm located downrange from Greenway Road (Figure 2).

The items fired consisted of various types and sizes of projectiles and ammunition.

Although the munitions included practice and high explosive (HE) rounds, available information suggests that the majority of the items fired were inert practice/test rounds.

Testing activities included direct fire to evaluate penetration and round dispersion at various downrange distances, and fuze function and warhead performance testing. The principal round was the 105mm High Explosive Anti-Tank (HEAT) munition and Sabot rounds. Similarly, mortar testing and howitzer projectiles (indirect fired munitions)

(principally 60mm and 81mm mortars, and 105mm and 8-inch rounds) were fired to test fuze performance and spotting round performance. Other testing included hazard classification tests conducted between the 1,000-m and 150-m berms, where fuels were used to ignite munitions during "cook-off' tests. Explosives, propellant and munitions were burned and buried at locations including areas along the range road near the firing points, the cook-off test location, the steel-lined pit, the popper kettle/wastewater disposal area, and numerous burn and burial pits within the interberm area of the range.

2. History of Investigations and Response Actions

Investigations were conducted at the J-1 Range between 1997 and 2010 to identify any contamination in soil and groundwater resulting from past activities. Data collected as part of these investigations were used to characterize the nature and extent of groundwater contamination emanating from the site, any continuing sources of contamination, including soil contamination and potential contamination from MEC, and to provide a basis for the evaluation of risks posed by the site. Investigations included soil sampling, geophysical surveys, groundwater sampling and a robotic technology demonstration. A brief summary of the investigations and response actions performed at the Site is provided below. A more detailed discussion can be found in Sections 3 and

4 of the July 2010 Remedial Investigation/Feasibility Study (RI/FS) Report.

Source Investigations and Results

Source characterization investigations in the J-1 Range commenced in 1997 with soil and groundwater samples collected at areas identified as having the highest probability of contaminant releases. Initial investigations focused on those features identified during a historical aerial photograph analysis of Camp Edwards. Additional range features were included in the investigation as range records became available. Significant information regarding range activities was also obtained through interviews of current and former base employees and range workers and observation noted during site reconnaissance.

Soil samples were collected at specific features noted in site records, aerial photographs and during site reconnaissance, at the locations of geophysical anomalies, proposed excavation areas, and from the base of excavations after soil removal activities.

During the period from 1997 through 2007, 1,732 soil samples were collected from 419 locations within the J-1 Range investigation area (Figure 3). The analytical data collected identified volatile organic compounds (VOC), semi-volatile organic compounds (SVOC), pesticides, herbicides, explosives, and metals at various concentrations in J-1 Range soils. Results of soil investigations at the northern or interberm area (IBA) of the range showed soil contamination in and around certain features of the range, in particular the

Popper Kettle area, the Steel-lined Pit, the Wastewater Disposal Area, cook-off test location, Polygons 9, 10 and 16 and grids J39, J36 and K36 (Figure 4) that is consistent with explosives and perchlorate found in downgradient groundwater (known as the northern plume area). Soil sampling conducted more recently (2009) identified additional soil contaminated by explosives and perchlorate proximate to the source areas described above. Analytical results indicated elevated levels of RDX and 2,4-DNT from

IBA area soils. Additional explosives compounds and perchlorate were detected, but only at levels well below relevant standards. As further discussed below, EPA believes that explosives and perchlorate soil contamination above relevant standards associated with all the various source areas contributing to groundwater contamination in this part of the range have been removed. None of the other contaminants detected from these areas were evaluated in the Feasibility Study because either the contaminant was detected infrequently, the contaminant detected is an essential human nutrient, or the contaminant concentrations were generally below relevant screening levels and/or MCP

S-1/GW-1 soil standards, or less than or similar to background (Appendix D).

Results of soil investigations at the southern area of the range showed soil contamination in the vicinity of polygons 2, 3 and 4, multiple disposal pits, and the suspected water saw operation (Figure 5) that is consistent with explosives found in the downgradient groundwater (known as the southern plume area). Soil sampling conducted more recently (2009) identified additional soil contaminated by explosives and perchlorate proximate to the contaminated soils located above polygons 2, 3, and 4.

Analytical results indicated elevated levels of RDX and HMX from southern area soils.

Additional explosives compounds and perchlorate were detected, but only at levels well below relevant standards. As further discussed below, EPA believes that explosives soil contamination above relevant standards associated with all the various source areas contributing to groundwater contamination in this part of the range have been removed.

None of the other contaminants detected from these areas were evaluated in the

Feasibility Study because either the contaminant was detected infrequently, the contaminant detected is an essential human nutrient, or the contaminant concentrations were generally below relevant screening levels and/or MCP S-1/GW-1 soil standards, or less than or similar to background levels.

In 2008, a robotics technology demonstration was conducted in the northern portion of the J-1 Range to evaluate the effectiveness of using remotely operated equipment to safely remove MEC. The technology demonstration involved the removal of soil and munitions from the up range faces of the 1,000-m, 150-m, and 2,000-m (a and b) berms.

The 1,000-m and 150-m berms lie in the IBA, and the 2,000-m berms lie within the impact area portion of the Site. A remotely operated excavator equipped with a rotating, two inch slot-screen bucket attachment was used to separate rocks and any munitions from finer soil materials. A total of 9 potentially high explosive items were recovered from the berms. A post-robotics confirmatory geophysical survey and intrusive investigation did not detect additional MEC.

Intrusive investigations identified multiple disposal pits in the southern portion of the range and in the IBA. However, the greatest number of finds consisted of munitions debris or other debris. More than 1,000 projectiles characterized as inert were identified throughout the range during the characterization of the Site. The vast majority of MEC consisted of individual items containing small quantities of energetic material (i.e., fuzes). Greater than 200 fuzes were discovered at a burial pit in the southern area of the range. Each fuze contains approximately 3 grams of RDX. Other encountered MEC items consisted of inert bodies with live fuzes or individual high explosive (HE) projectiles discovered throughout the range. Greater than 50 HE projectiles were documented individually throughout the Site. These projectiles can contain upwards of

1.4 Kg of RDX; however, these projectiles are not believed to be contributors to the known areas of groundwater contamination.

MEC clearance in support of the cumulative investigations and removal actions resulted in the removal of significant quantities of munitions, munitions debris, and range residue debris from those portions of the range responsible for development of the J-1 northern and southern plumes. Other areas of the Site are generally free from large geophysically anomalous areas. Based on the geophysical investigations, remaining geophysical anomalies are likely munitions debris or other debris. However, there is the potential for residual MEC items, likely consisting of inert projectiles with live fuzes or isolated individual HE items. None of the remaining anomalies are expected to represent disposal pits containing large quantities of MEC or explosives.

J-1 Range Source Removal Actions

The historical geophysical investigations were conducted from 1997 through 2010.

Geophysical investigations proceeded in a sequential manner; each of which used information collected during previous investigations to guide the next step of the process. Generally, the largest and/or most densely distributed anomalies were investigated during each investigative phase, which resulted in smaller anomalies being investigated as the phases of the investigation progressed and, ultimately, a thorough evaluation of potential source areas. These activities resulted in the investigation of over

150 geophysically anomalous areas. These investigations also resulted in the excavation and off-site disposal of approximately 1,000 cubic yards of contaminated soil from 19 of the geophysical investigation locations. In addition to the soil removals, these investigations also removed MEC from 39 locations. The locations where contaminated soil and MEC was removed included the Popper Kettle area, the Steel-lined Pit, the

Wastewater Disposal Area, cook-off test location, Polygons 9, 10 and 16 and grids J39, J36 and K36. MEC removed from burn pits in these locations primarily consisted of small quantity energetic items including fuzes, cartridge cases with live primers, suspect electronic explosive devices, stab detonators, and propellant. The soils and MEC were removed as a result of the various geophysical survey and investigations conducted at the Site. These materials were disposed of at off-site locations. In addition, approximately 150 cubic yards of screened, contaminated soil generated from the robotics technology demonstration at the 150-m berm was disposed of at a permitted off-site facility.

The recent sampling results identified soils with elevated concentrations of explosives compounds in three areas of the range (J-1 south grids 11-3 and J2-3, J-1 IBA grids L38, J37/38 and K38/39, and J-1 north target 34) (Figures 4 and 5). Soil from these areas with explosives detections were excavated to depths ranging from of 0.5- to 1.5-feet below ground surface and mechanically screened to remove any remaining munitions.

Excavation activities were conducted between September 2009 and April 2010.

Approximately 2,400 cubic yards of contaminated soil was excavated. Post-excavation, 100-pt multi-increment soil samples were collected in each of the excavation area units from 0 to 3 inches below the excavation floor. Results from post-excavation sampling indicated no detections of explosives.

The excavated soils were treated beginning in May 2010. The soils were treated using alkaline hydrolysis, which involved raising the pH of the soil by blending it with water and hydrolyzed lime to mineralize the explosives compounds to more elemental compounds of inorganic nitrogen and carbon dioxide. After blending, the soils were staged in a lined treatment cell at the L Range. After treatment, the soils were sampled to determine the effectiveness of treatment. Explosives compounds were detected in some samples from the treated soils but were below relevant standards. The soils will be removed from the treatment cell and utilized on the L Range as backfill. This treatment activity will be documented in a J-1 Range Source Remediation Report.

Groundwater Investigations and Results

More than 150 groundwater monitoring wells were sampled at and downgradient of the J

1 range. Results of this sampling indicated the presence of groundwater plumes of both perchlorate and RDX (Figures 5 and 6). For the purposes of groundwater evaluation the

J-1 northern and southern groundwater plume areas are discussed separately. This is due to the diverging flow directions of the two plumes emanating from the J-1 Range.

The northern plume is flowing in a north-northwesterly direction and the J-1 southern plume is flowing in a southeasterly direction.

In the northern area, a groundwater contaminant plume consists of perchlorate and RDX.

The perchlorate contamination is detached from the source area, has migrated further than the RDX plume and has the highest concentrations in the downgradient portion of the plume. The RDX portion of the plume has the higher concentrations closer to the source. The maximum concentrations in the northern plume as of 2009 are 13 ug/L for

RDX and 55 ug/L for perchlorate. The maximum historical detections were 32 ug/L for

RDX in 2004 and 78 ug/L for perchlorate in 2008. Based on the nature and extent of contamination, RDX and perchlorate are considered as the groundwater contaminants of concern for the northern plume.

The primary contaminant of concern in the J-1 Range groundwater southern area is RDX.

The southern RDX plume is defined by an on-base portion, which extends from the source area and terminates at the base boundary at an extraction well; and a downgradient portion that extends approximately 1,000 feet beyond the base boundary, beneath a residential area. There is believed to be no exposure to the plume as all residences in the off-base area of the plume are believed to be connected to the municipal water supply. The maximum RDX concentration in the on-base portion of the plume as of 2009 was 14 ug/L. The maximum RDX concentration in the off-base portion of the plume as of 2009 was 20 ug/L. Recent preliminary data obtained during a drive point investigation conducted during the spring of 2010 found RDX at 71 ug/L at one location. The maximum historical concentration in the plume was 130 ug/L in 2006.

Other contaminants detected in the groundwater were not retained as COCs because the contaminant was detected infrequently, the contaminants detected were essential human nutrients, or the contaminant concentrations were generally below relevant screening levels, or less than or similar to background levels. Based on the nature and extent of contamination and the risk-screening process, RDX and perchlorate in the northern area, and RDX in the southern area were retained as COCs since they are detected in a number of wells at concentrations above risk-based standards indicating the presence of a plume of groundwater contamination (Appendix D).

J-1 Range Groundwater Response Action

A 75 gpm (reduced to 45 gpm in September 2009) extraction, treatment and infiltration system consisting of an extraction well, modular treatment unit and infiltration trench was installed at the base boundary in 2007 and has been actively treating the southern

RDX plume. Over 81 million gallons of water have been treated through 2009. The objective of the J-1 southern system was to mitigate further migration of the plume by capturing and treating contaminated water at the base boundary until the entire plume extent was determined.

3. History of Relevant Federal and State Enforcement Activities

Federal Enforcement Activities

In February 1997, EPA Region 1 issued SDWA Administrative Order 1-97-1019 (A01) requiring the investigation of the impact of contamination at or emanating from the training ranges and impact area upon the Sole Source Aquifer.

In May 1997, EPA issued Administrative Order 1-97-1030 (A02), which prohibited all live firing of mortars and artillery, firing of lead from small arms, planned detonation of ordnance or explosives at or near the Training Ranges and Impact Area except for UXO activities, and certain other training-related activities.

In January 2000, EPA issued SDWA Administrative Order 1-2000-0014 (A03), which required implementation of Rapid Response Actions (RRAs) and Remedial Actions (RAs) to address contamination from past and present activities and sources at and emanating from the training ranges and impact area. The RRAs specifically required by A03 addressed elevated concentrations of contaminants in soil and have been completed.

The comprehensive response action component of A03 requires that a feasibility study, remedial design and response action be completed for several areas of concern.

State Enforcement Activities

On May 14, 1998, MassDEP issued Notice of Noncompliance (NON) number NON-SE-98

3F-023 to the Commonwealth of Massachusetts Military Division, Office of the State

Quartermaster for failure to manage a cache of over 1000 Unexploded Ordnance (UXO) unearthed at the J-1 Range in compliance with the requirements for the management of remediation waste pursuant to 310 CMR 40.0000, the MCP and to the management requirements at 310 CMR 30.0000, the Massachusetts Hazardous Waste Regulations.

The NON required the Office of the State Quartermaster to provide MassDEP by June i

1998 a comprehensive plan and an aggressive schedule for implementation of the requirements cited.

On November 8, 1999, MassDEP issued a Notice of Responsibility (NOR) with Release

Tracking Number 4-15035 to Textron Systems Corporation for a release of copper, barium, lead and cadmium at the 'Steel Lined Pit' at the J-1 Range at concentrations greater than the Reportable Concentrations for Soil Category 1 (RCS-1) pursuant to 310

CMR 40.1600, the MCP. The NOR required Textron to perform the necessary response actions required by the MCP.

C. COMMUNITY PARTICIPATION

Throughout the Site's history, the IAGWSP, EPA and MassDEP have kept the community and other interested parties informed and involved with response activities at the J-1

Range through informational meetings, fact sheets, press releases, public comment periods and public meetings. Below is a brief chronology of public involvement efforts.

The Impact Area Review Team (IART) was a citizen advisory committee established in

1997 under A01 . The IART served as a technical advisory resource, allowing the EPA, the National Guard Bureau, the Army, and MassDEP to hear first hand the concerns of the public related to the ongoing investigation and cleanup effort at Camp Edwards, in

2007, this team was merged with the Plume Cleanup Team, the citizens' advisory team for the Air Force Center for Engineering & Environment's MMR Installation Restoration

Program, and renamed the MMR Cleanup Team (MMRCT). The combined team meets regularly throughout the year to hear updates and provide public input on the MMR investigations and cleanup efforts.

The IAGWSP also briefs the Senior Management Board (SMB), which advises MMR organizations on environmental programs and policies. Members of the SMB include selectmen or their designated representative from the towns of Bourne, Falmouth, Mashpee, and Sandwich and representatives from the EPA, MassDEP, Massachusetts

Department of Public Health, Massachusetts National Guard, U.S. Coast Guard, and a representative from the Mashpee Wampanoag Tribe.

Ail IART, MMRCT, and SMB meetings related to the Site's investigation and response activities were advertised in the Cape Cod Times and the local edition of The Enterprise newspapers.

In October 2001, the IAGWSP, EPA and MassDEP released a Public Involvement Plan outlining activities to address community concerns and to keep citizens informed about and involved in response activities.

From the time the initial investigations at the Site began, through the present, the

IAGWSP regularly presented updates on the investigation and response activities at the

Site. With respect to this Decision Document, the most important updates were:

• On February 10, 2010, an informational meeting was held at Camp Edwards, MA, to present the findings of the RI/FS report for the J-1 Range to the MMR Cleanup Team and the public. A display ad regarding the meeting was placed in the February 5, 2010 editions of the Cape Cod Times and The Enterprise newspapers and a news release regarding the meeting was sent to the local media on February 8, 2010.

• On March 24, 2010, an informational meeting was held at Camp Edwards, MA, to describe the Remedy Selection Plan for the J-1 Range to the MMR Cleanup Team, Senior

Management Board and the public. At the meeting, the IAGWSP gave a presentation on the Site, the Remedy Selection Plan and the proposed response and answered questions from the MMR Cleanup Team and Senior Management Board. The IAGWSP notified the public of the meeting in a display ad placed in the March 18, 2010 editions of the Cape

Cod Times and The Enterprise newspapers.

• From July 19, 2010 through August 17, 2010, a Public Comment Period was held on the Remedy Selection Plan for the J-1 Range. The IAGWSP placed copies of the

Remedy Selection Plan in the lAGWSP's information repositories at the Bourne, Falmouth, and Sandwich, MA, public libraries. The repositories contain documents on the J-1 Range investigations and findings supporting selection of the response action including the RI/FS report for the J-1 Range, along with other relevant documents. The

Remedy Selection Plan also was made available on the IAGWSP Web site, which also contains the supporting documents and which offered a means of submitting public comments on the Remedy Selection Plan. In addition, the IAGWSP provided copies of the Remedy Selection Plan to MMR Cleanup Team members and distributed it to individuals in attendance at the public meeting and public hearing.

• On August 2, 2010, a Public Information Session and Public Hearing was held on the Remedy Selection Plan for the J-1 Range in Sandwich, MA. The public information session, along with a presentation on the Remedy Selection Plan and EPA's proposed response, was held prior to the opening of the public hearing. Local residents and officials, news media representatives, and members of the public interested in site activities and cleanup decisions were invited to attend both meetings. Representatives from EPA, MassDEP and IAGWSP were available to answer questions. The IAGWSP notified the public of the August 2, 2010 information session and public hearing, and reminded them about the public comment period in a display ad placed in the July 23 and

July 30, 2010 editions of the Cape Cod Times and The Enterprise newspapers. A news release regarding the meeting and the public comment period was sent to the local media on July 16, 2010. In addition, the Remedy Selection Plan and an invitation to the information session was mailed to Forestdale residents on July 22, 2010.

Al l draft and final reports related to the Sites' investigation and response activit ies were made available through the Information Repository at the public libraries in Bourne, Falmouth, and Sandwich, MA. These documents also were made available to the public through the IAGWSP Web site:

groundwaterprogram.army.mil (formerly www.groundwaterproqram.org) and the

Administrat ive Record located at 1803 West Outer Road, Camp Edwards, MA.

Media releases on presentations and the Public Comment Period for the Site were distributed to the Cape Coo* Times and other area media including newspapers, radio and television media.

Fact sheets were published and distributed regarding the Site's investigation and response activities. General fact sheets pertaining to the IAGWSP investigations and findings and on related issues, such as the contaminants of concern, were also published and distributed.

The IAGWSP, EPA, and MassDEP also participated in general information sessions, such as open houses, information sessions, community meetings and annual updates to the local Town Managers, Boards of Selectmen, and Boards of Health on MMR investigation http://groundwaterprogram.army.mil http://www.groundwaterproqram.org and response activities.

D. SCOPE AND ROLE OF OPERABLE UNIT

The Site consists of source areas contributing to groundwater contamination (i.e., soil and MEC) and groundwater operable units. The source areas contributing to groundwater contamination for the J-1 Range were addressed through the removal of geophysical anomalies (including MEC) and the excavation and removal of contaminated soils. Based on the removal of these contaminated soils and MEC, the EPA, in consultation with MassDEP, determined that no further action with respect to the source area was necessary at this time. Therefore, the analysis of alternatives in the RI/FS was limited to groundwater.

E. SITE CHARACTERISTICS

Site Geology

The surficial geology of western Cape Cod comprises glacial sediments deposited during the retreat of the Wisconsin stage of Holocene glaciation. Three extensive sedimentary units dominate the regional geology: the Buzzards Bay and Sandwich Moraines, and the

Mashpee Pitted Plain. The Buzzards Bay Moraine and the Sandwich Moraine are located and visible as hummocky ridges along the western and northern boundaries of Camp

Edwards, respectively. The Buzzards Bay Moraine and Sandwich Moraine are composed of ablation till, which is unsorted material ranging from clay to boulder size that was deposited at the leading edge of two lobes of the Wisconsinian glacier at its furthest advance. The Mashpee Pitted Plain is a broad outwash plain that lies between the two moraines and consists of fine to coarse-grained sands and is underlain by fine-grained giaciolacustrine sediments and a basal till layer over bedrock. The Mashpee Pitted Plain underlies most of MMR, including the J-1 Range.

Site Hydrogeology

A single groundwater-flow system underlies western Cape Cod including MMR. Camp

Edwards lies over the Sagamore Lens, which is part of the larger, Cape Cod Aquifer. The primary source of natural fresh water recharge to this groundwater system is rainfall and snow melt-water that averages approximately 48 inches per year. Additional water is returned to the aquifer as wastewater from domestic septic systems. Municipal sewer systems at the MMR and in parts of Falmouth return treated wastewater to the groundwater flow system through infiltration beds at the sewage treatment facilities.

Wastewater return flow accounts for approximately 5 percent of the total groundwater recharge in the MMR region.

The high point of the water table within the western Cape Cod groundwater system occurs as a groundwater mound located beneath the east central portion of MMR.

Groundwater flows radially outward: north to either the Cape Cod Canal or the Cape Cod

Bay, east to the Bass River, south and southeast to Nantucket Sound, and west and southwest to Buzzards Bay.

The height of the water table in and around the MMR can fluctuate up to seven feet annually due to seasonal variations in groundwater recharge and pumping demand.

Groundwater levels are highest in the spring when recharge rates are high and pumping demand is low; levels are lowest in the late summer/early autumn when rainfall is minimal and pumping demand is at its maximum. The total thickness of the aquifer varies from approximately 80 feet in the south to approximately 350 feet in the north. The variation in thickness is due to the episodes of glacial advance and retreat, the underlying bedrock geology, and the presence of fine-grained materials in the deeper sediments beneath the southern portion of the aquifer. Within the J-1 Range, the groundwater elevation is typically between 66 and 76 feet national geodetic vertical datum (ngvd) or approximately 100 feet below ground surface.

Surface water is not significantly retained due to the excessively drained sandy soils of

Camp Edwards. No large lakes, rivers, or streams exist on the property, only small, marshy wetlands and ponds. Most of the wetlands and surface waters in the Sandwich and Buzzards Bay Moraines on Camp Edwards are considered to be perched. Surface water is present at MMR in a few ponds in kettle holes. The kettle-hole ponds are land-surface depressions that generally extend below the water table. Where these kettle holes do not extend down to the water table, they are merely surface depressions.

Larger and deeper ponds have greater effect on slope and direction of the regional water table near the pond. While horizontal groundwater flow is dominant in the aquifer system, vertical flow is important in areas near ponds and near the top of the groundwater mound for the Sagamore Lens aquifer.

Movement of Contaminants in Groundwater

Contaminated groundwater from the northern J-1 plume flows in a north-northwest direction. Contaminated groundwater from the southern J-1 plume flows in a south-southwesterly direction and crosses the base boundary downgradient of Greenway Road into a residential neighborhood. The groundwater flow rate is approximately one foot/day in an unconfined sandy aquifer comprised of glacial outwash deposits.

Groundwater flow is influenced locally by discontinuous fine-grained units, hydraulic gradients, and proximity to the top of the groundwater mound.

Two COCs are present in groundwater at the Site: RDX and perchlorate. RDX and perchlorate readily leach from soil to the groundwater, with perchlorate more readily dissolving than RDX. Movement of RDX is slightly retarded in the soil and the aquifer due to limited sorption to soil particles. Therefore, RDX will generally move at a velocity slightly less than that of normal advective flow, while perchlorate generally will move at the same rate as the advective front. Longitudinal dispersion is a significant transport process for both perchlorate and RDX and a factor in natural attenuation.

Estimate of the Contaminant Volume and Mass

The total volume of the northern plume was estimated to be 318 million gallons as of

2010. The total mass of perchlorate with concentrations greater than 2.0 ug/L was approximately 9.8 kilograms (Kg) and the total mass of RDX with concentrations great than 0.6 ug/L was approximately 3.8 Kg.

The total volume of the southern plume was estimated to be 46 million gallons as of

2010. The total mass of RDX with concentrations greater than 0.6 ug/Lwas approximately

0.8 Kg.

Current Exposure Pathways

There are no known private or public water supplies located within the J-1 Range groundwater study area and no one is currently believed to be drinking water related to the J-1 Range that contains COCs at concentrations that exceed applicable drinking water standards, Health Advisories, and/or risk-based concentrations.

Potential Exposure Pathways

The development of new water supply wells and consumption of groundwater resources in areas contaminated or predicted to be contaminated by the J-1 Range plumes are potential future exposure pathways. As noted above, the Cape Cod Aquifer is the sole or principal source of drinking water for Cape Cod. Portions of Camp Edwards, including the on-base portions of the Site, have been set aside as a drinking water supply reserve by the Massachusetts legislature.

F. CURRENT AND POTENTIAL FUTURE SITE AND RESOURCE USES

The J-1 Range site northern plume area is located on the MMR and is designated as an active military training area. The J-1 Range site southern plume area originates on base but extends into an adjacent off-base residential neighborhood. It is anticipated that the northern area and the on-base portion of the southern area of the J-1 Range Site will remain under the control and direction of government agencies and will continue to be used for military training and support purposes until at least 2052. The area also is designated as a water and wildlife preserve by Chapter 47 of the Massachusetts Acts of

2002. The source area overlays portions of a sole source aquifer that is a valued water supply for the upper portion of Cape Cod. The land-use controls (described in section K) will prevent the installation of new water supply wells, or use of existing water supply wells (if any), that could provide a pathway for ingestion of drinking water that contains

COCs in concentrations that exceed applicable drinking water standards, Health

Advisories, and/or risk-based levels, and maintain the integrity of any current or future groundwater monitoring wells and treatment systems.

G. SUMMARY OF SITE RISKS

A Risk Screening was conducted for the J-1 Range. The objective of the risk screening was to identify any contaminants of concern detected at the J-1 Range that required further evaluation in the Feasibility Study.

Constituents detected in soil samples were evaluated by comparing the maximum concentration of each detected constituent to a series of federal and state risk-based criteria. Soil samples collected from the J-1 Range were screened for explosives, perchlorate, metals, SVOCs, pesticides/herbicides/PCBs, VOCs, EDB/MTBE, TOC, phosphate, nitrate/nitrite as nitrogen, ammonia as nitrogen, and cyanide. A number of metals, SVOCs and VOCs exceeded one or more of their respective screening levels.

However, on further analysis, it was determined that the detections of metals and SVOCs were below or consistent with background levels or were common laboratory artifacts.

VOC detections were sporadic and at low levels, so none of these constituents were carried forward in the feasibility study. Perchlorate was detected, but only at very low levels, throughout the range and well below screening values. Elevated detections of explosives, including RDX, HMX, and 2,4-DNT, were found in the J-1 Range source areas.

These explosives-contaminated soils were excavated and treated on site. Post-excavation soil sampling results were all non-detect for explosives. As a result of this screening process and the subsequent analysis of the anticipated leaching behavior of the constituents that were highlighted by the screening, none of the analytes detected in soil were found to pose a risk.

Constituents detected in groundwater samples were evaluated by comparing the maximum concentration of each detected constituent to a series of risk-based criteria including Federal Maximum Contaminant Levels (MCLs), Health Advisory Levels (HAs), EPA Regional…