J-2_Range_Decision_Document_2013.pdf

Superfund Records Center

SITE: fflik //V)/3^/^ AWfk-

BREAK:

OTHER: S^X\b°\

United States Environmental Protection Agency

Region 1

Decision Document

J-2 Range Operable Unit

Camp Edwards

Joint Base Cape Cod

Cape Cod, Massachusetts

September 2013

TABLE OF CONTENTS PAGE

PART I: DECLARATION FOR THE SDWA DECISION DOCUMENT

A. SITE NAME 1

B. STATEMENT OF BASIS AND PURPOSE ; 1

C. ASSESSMENT OF THE SITE 1

D. DESCRIPTION OF RESPONSE ACTIONS 1

E. DETERMINATIONS 5

F. SUPPORTING DATA 6

G. AUTHORIZING SIGNATURE 6

PART II: THE DECISION SUMMARY 7

A. SITE DESCRIPTION 7

B. SITE HISTORY AND ENFORCEMENT ACTIVITIES 7

1. HISTORY OF SITE ACTIVITIES 7

2. HISTORY OF INVESTIGATIONS AND RESPONSE ACTIONS 7

3. HISTORY OF'RELEVANT FEDERAL AND STATE ENFORCEMENT ACTIVITIES ,13

C. COMMUNITY PARTICIPATION 14

D. SCOPE AND ROLE OF OPERABLE UNITS

E. SITE CHARACTERISTICS 16

F. CURRENT AND POTENTIAL FUTURE SITE AND RESOURCE USES 19

G. SUMMARY OF SITE RISKS. 19

H. RESPONSE ACTION OBJECTIVES FOR GROUNDWATER 20

I. DEVELOPMENT OF ALTERNATIVES FOR GROUNDWATER 21

J. DESCRIPTION OF ALTERNATIVES, SUMMARY OF COMPARATIVE ANALYSIS

AND THE SELECTED RESPONSE ACTION 23

1. Northern Plume Area 23

2. Eastern Plume Area 29

K. RESPONSE ACTION IMPLEMENTATION 34

L. DETERMINATIONS 42

M. DOCUMENTATION OF NO SIGNIFICANT CHANGES 42

N. STATE ROLE 42

PART III: THE RESPONSIVENESS SUMMARY 43

List of Figures

Figure 1: J-2 Range Location Map

Figure 2: J-2 Range Layout

Figure 3: J-2 Range Soil Study Areas

Figure 4: J-2 Range Area 2 Excavated Areas

Figure 5: J-2 Range Area 3 Excavated Areas i

Figure 6: J-2 Range Area 4 Excavated Areas

Figure 7:J-2 Range Northern Extraction Well Locations and Pipelines

Figure 8:J-2 Range Eastern Extraction Well Locations and Pipelines

Figure 9: J-2 Range 2013 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

E. Work Plan Project Notes

PART I: DECLARATION FOR THE SAF E DRINKING WATER ACT DECISION DOCUMENT

A. SITE NAME !

The subject site is the J-2 Range (also referred to as "the Site"), which is located at Camp Edwards at the Joint Base Cape Cod (JBCC) (formerly Massachusetts Military Reservation

(MMR)). ' '

• • ( c

B. STATEMENT OF BASIS AND PURPOSE

This Decision Document presents the selected response actions for the J-2 Range. 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 Administrative Record is available for review by appointment at the Impact Area Groundwater Study Program (IAGWSP) office, PB0516 West Outer Road, Camp Edwards, MA.

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 JBCC 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. The J-2 Range is also located within the Upper Cape Water Supply Reserve established pursuant to Chapter 47 of the Massachusetts Acts of 2002 and designated as conservation land under the care and control of the Massachusetts Division of Fisheries and Wildlife.

D. DESCRIPTION OF COMPREHENSIVE 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), also referred to in this Declaration and Decision Document as unexploded ordnance/discarded military munitions/munitions constituents, or UXO/DMM/MC, or UXO that may be in or on the soil. There may be additional areas on the Site where UXO and the soil beneath may pose public safety risks, ecological risks, dermal contact risks, and/or soil ingestion risks. These potential UXO-related risks are not addressed by this Decision Document, which is being 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.

During the investigations of the Site, several response actions were taken to remove the sources of groundwater contamination. Disposal pits containing UXO and contaminated soil are believed to be the cause of much of the groundwater contamination. Soil contamination and UXO were alsojdiscovered in other areas of the range including areas believed to be targets, firing points and areas used for burning propellants. It is believed that most of these source areas were identified and removed during the previous investigations. However, there are a few areas on the rarjige located up-gradient of the plume that require additional investigation to confirm that potential sources have been completely addressed. Confirmatory soil sampling and UXO clearance in select areas of the range will be conducted as part of the remedy to verify source removal jis complete. Work plans describing this work have been approved by EPA and MassDEP (Appendix E). Soil contamination and munitions posing a threat to groundwater will be removed.

Based on groundwater sampling results, EPA, in consultation with the Massachusetts Department of Environmental Protection (MassDEP), deemed it necessary to develop and evaluate a range of potential response actions to address contaminants detected in groundwater associated with the J-2 Range. 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 COCs were used to develop and evaluate a range of potential response actions for the Site. The Site contains two distinct and separate groundwater plumes identified as the J-2 Northern groundwater plume and the J-2 Eastern groundwater plume. .Groundwater modeling was used to determine the feasibility of the alternatives for each of these plumes. The cleanup objectives for the J-2 Range groundwater plumes 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 and 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; to prevent ingestion and inhalation of groundwater containing the contaminants of concern (COCs) (RDX and perchlorate), in excess of federal maximum contaminant levels (MCLs), Health Advisories (HA), drinking water equivalent levels (DWELs), , applicable State standards or an unacceptable excess lifetime cancer risk (ELCR) or non cancer Hazard Index (HI); and, for the J-2 Northern groundwater plume, to protect the current water supply by preventing groundwater in excess of Health Advisories, drinking water equivalent levels (DWELs), applicable State standards or an unacceptable excess lifetime cancer risk or non-cancer Hazard Index from migrating past Gibbs Road located on Camp Edwards.

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, MassDEP promulgated a Massachusetts Maximum Contaminant Level (MMCL) for perchlorate of 2 ug/L in July2006.

The lifetime federal Health Advisory for RDX in drinking water is 2 ug/L, the Massachusetts Contingency Plan (MCP) GW-1 standard is 1 ug/L, and the 10-6 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 in the J-2 Range groundwater plumes 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 groundwater response actions will ensure that the groundwater containing RDX at

-6 concentrations greater than the 10 risk-based level and/or perchlorate greater than 2 ug/L is restored to protective levels.

The selected response action consisting of Focused Extraction with Monitored Natural Attenuation with Land-Use Controls (LUCs), and confirmatory soil sampling and UXO clearance to verify all sources have been addressed provides the best balance of the criteria used to evaluate cleanup alternatives.

The selected response action achieves cleanup goals in a reasonable timeframe and protects human health through the use of groundwater extraction and treatment and groundwater monitoring to ensure that groundwater modeling predictions regarding the reduction and migration of contamination are valid and that contamination levels continue to decline. The groundwater extraction and treatment system will be designed and operated to protect the public water supply located down gradient. Human health will be further protected through the implementation and verification of LUCs. These LUCs will prevent use of contaminated portions of the.aquifer at the Site for drinking water purposes until groundwater data confirms that contamination has been reduced to below risk-based levels. The LUCs will also prevent activities that may interfere with the treatment and monitoring systems..

The major components of the source and groundwater response actions for the J-2 Range

Northern groundwater plume are:

i I

• Extraction and treatment of groundwater by shifting pumping stress between the three existing ^extraction wells within the current system design and expanding the system if necessary to ensure complete containment of the plume at each extraction.well;

treatment with granular activated carbon and ion exchange resin at the existing or expanded treatment units; and infiltration' of the treated water at a minimum of four infiltration trenches. A work plan (J-2 Range Priority 2 Data Gap Drilling Project Note, dated 08/28/2013) which has been approved by EPA and MassDEP, will be implemented as part of the remedy and includes the installation of additional monitoring wells to determine if each extraction well is achieving containment (Appendix E). If containment is not achieved, a work plan will be developed to explain how the extraction and treatment system will be altered and augmented to insure that containment at each extraction well is achieved. This work plan will be implemented as part of the selected rremedy after approval by EPA and MassDEP.

• A contingency for additional active treatment in the area of Gibbs Road on Camp Edwards, and modifying the system to optimize the system performance to ensure protection of the Upper Cape Water Supply. A work plan (J-2 Range Northern Plume Priority 1 Data Gap Drilling Project Note, dated 07/11/2013) describing the monitoring program necessary to verify that contamination has not migrated past Gibbs Road has been approved by EPA and MassDEP and will be implemented as part of the remedy (Appendix E). A second work plan will be developed that will include the groundwater monitoring and modeling work necessary to make this demonstration periodically. If groundwater monitoring data or modeling suggests that contamination above federal or state regulatory or risk-based levels for COCs will likely migrate past Gibbs Road, additional extraction wells will be installed and begin operation within 12 months of that determinjation. ^

• An investigation including soil sampling and removal of additional geophysical anomalies in select Jareas of the range to verify source removal is complete. A work plan (Confirmatory Soil Sampling for Areas 1, 2 and 3 at the J-2 Range Project Note, dated 08/29/20|13, and Confirmatory Intrusive Geophysical Investigations at the J-2 Range Project Note, dated 08/28/2013) describing the soil sampling and geophysical investigations has been approved by EPA and MassDEP and will be implemented as part of thje remedy (Appendix E). Soil contamination and munitions posing a threat to groundwater shall be removed.

• Long-term groundwater monitoring at existing and new monitoring wells to verify the effectiveness of the source response action; to ensure that groundwater modeling predictions regarding the reduction and migration of contamination are valid; and to ensure that any remaining contamination remains below risk-based levels.

• Implementation and verification of Land Use Controls to prevent use of contaminated portions of the aquifer for drinking water until contamination is reduced to below risk-based levels and to prevent actions that would interfere with the remedy.

• Five year reviews to determine if the groundwater treatment system is still protective and achieving the goals established and to determine if source response actions continue to protect groundwater.

The major components of the source and groundwater response actions for the J-2 Range Eastern groundwater plume are:

• Optimization and continued long-term operation of the current J-2 Range Eastern groundwater extraction treatment and injection system. The J-2 Range eastern groundwater plume system consists of three extraction wells and three infiltration trenches located to the northeast, southeast, and southwest of the plume.

• An investigation including'soil sampling and removal of additional geophysical anomalies in select areas of the range to verify source response is complete. A work plan (Confirmatory Soil Sampling for Areas 1, 2 and 3 at the J-2 Range Project Note, dated 08/29/2013, and Confirmatory Intrusive Geophysical Investigations for the J-2 Range Project Note, dated 08/28/2013) describing the soil sampling and geophysical investigations has been approved by EPA and MassDEP and will be implemented as part of the remedy (Appendix E). Soil contamination and munitions posing a threat to groundwater shall be removed.

• Long-term groundwater monitoring at existing and new monitoring wells to verify the effectiveness of the source response action; to ensure that groundwater modeling ' predictions regarding the reduction and migration of contamination are valid; and to ensure that any remaining contamination remains below risk-based levels.

• Implementation and verification of Land Use Controls to prevent use of contaminated portions of the aquifer for drinking water until contamination is reduced to below risk-based levels and to prevent actions that would interfere with the remedy.

• Five year reviews to determine if the groundwater treatment system is still protective and achieving the goals established and to determine if source response actions continue to protect groundwater.

E. DETERMINATIONS

The following determinations apply to both the J-2 Range Northern area and the J-2 Range Eastern area. 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

• ~ . 5

Natural Attenuation, and Land Use Controls for groundwater and confirmatory soil sampling and UXO clearance) 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 the 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-2 Range Remedial Investigation/ Feasibility Study dated July 2013. An overview of the Site, including decision factor(s) 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 RDX and perchlorate, their respective concentrations, the baseline risk, the cleanup levels established 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 the selected response actions for remediation of the J-2 Range within Camp Edwards at the JBCC, The response actions were selected by EPA under the authority of the SDWA. The MassDEP concurs with this decision.

U.S. Environmental Protection Agency

Director, Office of Site Remediation and Restoration Region 1

PART II: THE DECISION SUMMARY

A. SITE DESCRIPTION

The J-2 Range is located on Camp Edwards on the JBCC on Cape Cod in Massachusetts " (Figure 1). It is located southeast of the impact area, and north of the J-1 range. The J-2 Range is approximately 1,200 meters long and between 100- and 180-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 beyond Chadwick Road into the impact area. There were five man-made berms located at various areas within the range. The only remaining structures located on the range are a concrete/earthen wall, a former ammunition bunker surrounded by fencing, a wooden subsurface vault that housed valves/well, and the foundations of a small concrete melt/pour facility, and concrete pad.

Access to the J-2 Range is currently restricted by a locked gate at Greenway Road.

B. SITE HISTORY AND ENFORCEMENT ACTIVITIES

1. History of Site Activities

The J-2 Range was a multi-purpose range where military training, munitions testing, and munitions disposal occurred. Military training, which consisted of small arms training, occurred from 1935 to the 1980s/From 1953 through the late 1980s, the J-2 Range was used for weapons testing by defense contractors. The predominant firing positions are believed to have been in the southern area of the range. The items fired consisted of various types and sizes of projectiles and ammunition.

Testing activities included fuzes for the 30mm High Explosive Incendiary (HEI) round, propellants and fuzes in 81mm mortars, fuzes in 105mm and 155mm projectiles and 8-inch rounds. Other testing included fin assemblies for wax-filled 60mm mortars, 105mm High Explosive Anti-Tank munitions and discarding sabot rounds, over-pressure testing on the 105mm tank barrels, and other miscellaneous tests. An on-site, melt/pour facility was used at the range to melt, mix, and mold explosives for use in various munition's. Testing for development of the LAW rocket was conducted at the range between 197,1 and 1974. Disposal activities conducted at the range consisted of propellant and waste burning in pits and along the range road near the firing points. Munitions and other items; including fireworks, were disposed of at various locations throughout the range, including a significant disposal area identified as Disposal Area 2 near the Impact Area boundary.

2. History of Investigations and Response Actions

Investigations were conducted at the J-2 Range between 1997 and 2012 to identify the nature-and extent of contamination in soil and groundwater resulting from past military 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 future contamination from UXO, and to provide a basis for the evaluation of risk(s) posed by the Site.

During response actions conducted from 2004 to 2006, approximately 6,474 cubic yards of soil contaminated with explosives and perchlorate were excavated from the central and southern portions of the J-2 Range and treated on-site by thermal desorption. In 2009 and 2010, approximately 1,100 cubic yards of contaminated soil was removed from the J-2 extension area and treated by alkaline hydrolysis. Finally, approximately 1,110 additional cubic yards of contaminated soil generated as a result of various intrusive investigations of geophysical anomalies were disposed of off-site at permitted facilities.

Geophysical investigations were conducted from 1997 through 2009 in several different phases utilizing several approaches to identify and remove munitions. Many of the investigations focused on identifying and removing disposal pits. Over the course of these ongoing removal actions, approximately 21,600 munitions containing high explosives (HE) were removed. In addition, approximately 11,100 munitions containing small quantities of explosives were removed along with 114,000 pounds of range debris.

These targeted removals of soil and munitions have likely removed most of the items posing as active sources of groundwater contamination: A brief summary of the investigations and response actions performed at the Site is provided below. To simplify the'discussion, the range has been divided into four subareas (Areas 1 through 4) (Figure 2). The areas were chosen based on historical range use, range features and the conceptual site model of the range. A more detailed discussion can be found in Sections 3 and 4 of the July 2013 Remedial Investigation/Feasibility Study (RI/FS) Report.

Source Investigations and Results

Source characterization investigations on or at the J-2 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 observations 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, before and after blow-in-place (BIP) events, proposed excavation areas, and from the base of excavations after soil removal activities.

During the period from 1997 through 2009, 3,178 soil samples were collected from 753 locations within the J-2 Range investigation area (Figure 3).

Area 1 j

Area 1 is located in the southernmost portion of the J-2 Range. This area of the range had multiple features, including firing points from which munitions were fired dqwnrange, a building used to melt, mix, and mold explosives for use in various munitions, an area where propellant was loaded into cartridges, and a staging and administrative area for the munitions testing that occurred on the range. Results of soil investigations and geophysical investigations in Area 1 indicated no widespread surface soil contamination. Area 1 had the lowest number of UXO items of the J-2 Range. Approximately 340 HE items were removed from Area 1. The majority of UXO items removed were from the burial pits that were discovered in five grid locations in the northern portion of Area 1. The majority of UXO found in these pits contained small quantities of explosives (e.g. 20mm and 40mm, 60mm). None of the disposal locations were identified as.

burn pits and there are no known impact or target locations within Area 1. While there is a potential for residual single UXO items, the investigation findings suggest that there is a low likelihood of the presence of uninvestigated UXO burials or the potential for widespread distribution of UXO items. Items that could remain in Area 1 containing HE or a small quantity of energetic include 20mm projectiles, 66mm LAW rockets, 60mm mortars, 81mm mortars, 3.5 inch rockets, 37mm projectiles, 30mm projectiles, and fuses. Large residual anomalies are associated with cultural features and metallic structures from contractor testing. Isolated medium to small sized geophysical anomalies still remain on the range and it is likely that they are due to fragmentation, metallic debris, or individual intact munitions that could be either inert or HE.

Area 2

Area 2 is the largest of the four J-2 Range areas and is situated in the central portion of the J-2 Range. This area of the range had multiple features including firing points, target areas, and areas along the range road where propellant was allegedly burned. Thirteen burial locations containing UXO were identified. Approximately 2,400 munitions containing HE were removed from Area 2. Individual projectiles have been identified throughout Area 2. Significant quantities of 30mm high explosive incendiary (HEI) projectiles were identified in the southwestern portion of Area 2 centered on grids M19/M20. Many of the projectiles within grids

• M19 and M20 were determined to be cracked and/or leaking (see Table 5 of Appendix G of the RI/FS). In addition to these individual projectiles, found at depths ranging from 0 to greater than 12 inches below ground surface, two munitions burial pits containing mostly 30mm HEI projectiles were identified within grids M19 and M20. These features are considered the primary contributors to the J-2 Eastern groundwater plume.

All large geophysical anomalies in Area 2 have been investigated. Large anomalies that still remain are associated with concrete structures. Some small to medium-size anomalies still remain, and it is likely that additional single 30mm HEI projectiles, 57mm projectiles and 66mm HE rockets could be found within this area. Some single 60mm or 81mm mortars also likely remain on the range that could have inert bodies with live fuses. Surface soil contamination was identified in the area around the firing locations and at.certain impact locations. Soil contamination was also associated with certain burial locations that contained UXO. Soil removal activities were conducted in this area, as discussed below in J-2 Range Response Actions (Figure 4). The UXO and soil contamination associated with Areas 1 and 2 likely contributed to the generation of the J-2 Eastern groundwater plume.

Area 3

Area 3 is located in the north-central portion of the J-2 Range. The primary activity conducted in the area was burning and burial of munitions and fireworks. Investigations in Area 3 included a quality control survey with an intrusive investigation of residual anomalies over most of the area.

Approximately 18,760 UXO items were removed during Area 3 investigations including a rapid response action. Soils contaminated with significant levels of explosives and/or perchlorate were found at Disposal Area 2, which contained thirty-two burn/burial pits. Note that Area 3 is the only area on J-2 Range in which burn pits were found. These areas were addressed during soil removal actions, and with a few exceptions, no significant soil contamination remains. The highest percentage of UXO items were recovered during the burial investigations. No known burials remain. Single UXO items were also discovered in Area 3 and it is possible that some may remain at isolated medium-sized to small geophysical anomaly locations. It is likely that these anomalies are fragmentation, metallic debris or individual intact munitions, both inert and HE. As a result of former disposal operations in Disposal Area 2, kick-outs are possible. Area 3 also lies within the down-range portion of the J-2 Range and could contain residual munitions from testing and training. These residual munitions may include single UXO items such as 20mm projectiles, 30mm projectiles, 37mm projectiles, 40mm projectiles, and/or 57mm projectiles. It is unlikely that any subsurface burials still remain in the Area 3. This area was subsequently targeted for excavation of the highest levels of TNT, nitroglycerin, RDX and HMX during the removal activities discussed below in J-2 Range Response Actions (Figure 5). This area has been identified as the primary source of the J-2 Range Northern groundwater plume.

Area 4

Area 4 is located at the northern end of the range, north of Barlow Road (the Impact Area boundary). Area 4 was presumed to be a demolition area as this area lacked surface features indicative of historical contractor use and testing. Soil sampling activities around the demolition area indicated elevated levels of RDX and HMX in the north central portion of Area 4. No significant groundwater contamination has been detected down gradient of Area 4. This area was subsequently targeted for excavation (Figure 6). Large anomalous areas identified throughout the geophysical survey were excavated. Approximately 175 HE items were removed from Area 4. Isolated medium to small sized geophysicaLanomalies still remain on the.range and it is possible that they represent.fragmentation, metallic debris, or individual munitions that could be either inert or HE.

Groundwater Investigations and Results

Two large-scale plumes of comingled RDX and perchlorate contaminated groundwater have been found to be migrating from sources at the J-2 Range. The J-2 Range Northern groundwater plume is thought to be derived from Disposal Area 2 located near Barlow Road and is migrating in a northerly direction. The J-2 Eastern groundwater plume is more fan-shaped and consists of a main lobe, which migrates in a northeasterly direction and several smaller lobes that migrate in both an easterly and northerly direction.

In the Northern area, the groundwater 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 detected concentrations in the up gradient portion of the plume. The RDX portion of the plume is enveloped within the perchlorate groundwater plume. The extent of the perchlorate plume, as defined by detections above 2 ug/L, is approximately 8,100 feet long and 850 feet wide. Prior to the start up of the rapid response action, the RDX plume was approximately 2,400 feet long and 900 feet wide but has since diminished to the point where concentrations of RDX above 0.6 ug/L have only been detected in two well samples collected in 2012. The maximum historical detections were 16.1 ug/L for RDX and 198 ug/L for perchlorate and the current maximum detected are 2.9 ug/L for RDX and 115 ug/L for perchlorate.

Monitoring data collected in 2012 indicates that significant perchlorate"concentrations exist at MW-588 and MW-589 which are located outside of the simulated capture zones of extraction well J2EW001. This extraction well had been pumping at 75 gpm since the startup of the RRA system in September 2006. In March 2013, the pumping rate at J2EW0001 was increased to' 150 gpm in order to expand the capture zone enough to encompass these two monitoring wells.

In addition, the pumping rate at J2EW0002 was also reduced from 175 to 100 gpm to accommodate the flow rate capacity in the treatment system. Further investigations are needed to verify the extent of contamination beyond the two monitoring wells and to determine whether these changes are sufficient to capture contamination in this area. The treatment system design capacity for extraction wells J2EW001 and J2EW0002 is currently 250 gpm. In August 2013, the pumping rate at J2EW0003 was increased to 190 gpm (to be increased to 225 gpm) in order to expand the capture zone enough to encompass contamination recently seen at

MW-296.

In the Eastern area, the groundwater plume consists of perchlorate and RDX. Since there were multiple sources of contamination for the J-2 Range eastern plume, this plume is more heterogeneous in nature. The perchlorate plume is detached from the source area and has the highest detected concentrations in the middle portion of the plume. The extent of the J-2 Range eastern perchlorate plume (above 2 ug/L) is approximately 4,200 feet long and 1,700 feet wide.

The RDX plume extends slightly further down gradient than the perchlorate plume. The main body of the J-2 Range eastern RDX plume (above 0.6 ug/L), is approximately 5,800 feet long and up to approximately 1,150 feet wide. There are also three smaller lateral plumes. The maximum historical detections were 17 ug/L for RDX and 88 ug/L for perchlorate and are currently 14 ug/L for RDX and 44 ug/L for perchlorate.

Perchlorate was detected in the groundwater from MW-519M1 located downgradient of the J-2 Extension area at 0.21 ug/L. RDX was not detected from this location.

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 were retained as COCs for both the northern and eastern groundwater plumes. (Appendix D).

J-2 Range Response Actions

Several soil response actions have been undertaken in the J-2 Range to reduce, levels of contamination from certain areas. These include soil and UXO removals at the following areas:

Area 1 Approximately 215 cubic yards of soil was removed from Area 1, primarily associated with two munitions burial pits.

Area 2 and Area 3 During response actions conducted from 2004 to 2006, approximately 6,474 cubic yards of soil contaminated with explosives and perchlorate were excavated from 15 locations in Areas 2 and 3 of the J-2 Range and treated onsite by thermal desorption. In addition, approximately 300 cubic yards of.contaminated soil was excavated from Area 2 in 2006 and disposed of off-site.

Area 4 Approximately 1,100 cubic yards of contaminated soil was removed in 2009 and 2010 and treated by alkaline hydrolysis at the on-site treatment cell located at the L Range.

Locations throughout Areas 1, 2 and 3

Geophysical investigation of 271 anomalies from 1997 through 2010 resulted in the removal of UXO from 62 locations. These investigations also resulted in the excavation and off-site disposal or on-site thermal treatment of approximately 1,110 cubic yards of contaminated soil from 34 investigation locations.

In summary, soil removal actions have been conducted at numerous locations and approximately 9,000 cubic yards of contaminated soil has been excavated and treated on-site, or disposed of off-site. Cumulatively, approximately 21,600 munitions containing high explosives were removed as a result of the soil and UXO removal actions. In addition, approximately 11,100 munitions containing small quantities of explosives were removed along with 114,000 pounds of range debris.

A Rapid Response Action (RRA) was initiated at the J-2 Northern groundwater plume in 2006.

The objective of the RRA system was to provide accelerated protection of the water supply wells and aquifer restoration by capturing and treating contaminated groundwater until the long-term remedy could be selected for the plume. The Extraction, Treatment, and Infiltration (ETI) system consisted of three axial extraction wells pumping at a combined rate of 375 gpm and four infiltration trenches located to the northeast, southeast, southwest, and northwest of the .

northern J-2 plume. Since the start of the system, approximately 1.2 billion gallons of groundwater have been treated. The plume appears to be becoming segmented into four lobes due to the operation of the ETI system and natural attenuation. However, additional characterization of groundwater is necessary to determine whether any contamination lies beyond and down gradient of the existing capture zones and to provide continued protection. ofj the water supply wells. •

A RRA was initiated at the J-2 Eastern plume in 2008. The objective of this RRA system was to prevent further off base migration of the plume and to protect the down gradient water supply wells. The ETI system consisted of three axial extraction wells pumping at a combined rate of 425 gpm and three infiltration trenches located to the northeast, southeast, and southwest of the Eastern J-2 plume. Since the start of the system, approximately 1 billion gallons of groundwater have been treated. The J-2 Eastern plume also appears to be becoming segmented due to the operation of the ETI system and natural attenuation.

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 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.

C. COMMUNITY PARTICIPATION

Throughout the Site's history, the Impact Area Groundwater Study Program (IAGWSP), EPA and MassDEP have kept the community and other interested parties informed and involved with response activities at the J-2 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 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 JBCC investigations and cleanup efforts.

The IAGWSP has briefed the Senior Management Board (SMB), which had advised JBCC organizations on environmental programs and policies. Members of the SMB included 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.'

All 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 rresponse 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 March 14, 2012, an informational meeting was held at Camp Edwards, MA, to present the findings of the RI/FS report for the J-2 Range to the MMRCT and the public. A display ad regarding the meeting was placed in the editions of the Cape Cod Times and The Enterprise newspapers and a news release regarding the meeting was sent to the local media on March 7, 2012 '

• On July 24, 2013, a Public Information Session was held on the Remedy Selection Plan for the J-2 Range at Camp Edwards. At the meeting, the IAGWSP gave a presentation on the findings of the investigations and the alternatives evaluated and EPA presented the proposed response for the Site. The MMRCT, local residents and officials, news media representatives, and members of the public interested in site activities and cleanup decisions were invited to attend the meeting. Representatives from EPA, MassDEP and IAGWSP were available to answer questions. The IAGWSP notified the public of the information session, and reminded them about the public comment period in a display ad placed in the 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 17, 2013. In addition, the Remedy Selection Plan and an invitation to the information session were mailed to Forestdale residents on July 17, 2013. N ' _

• From July 17 through August 16, 2013, a Public Comment Period was held on the Remedy Selection Plan for the J-2 Range. The IAGWSP placed copies of the Remedy Selection Plan in theJAGWSP's information repositories at the Bourne, Falmouth, and Sandwich, MA, public libraries. The repositories contain documents on the J-2 Range investigations and findings supporting selection of the response action including the RI/FS report for the J-2 Range, along with other relevant documents. The Remedy Selection Plan also was made available on the both the EPA and IAGWSP Web sites, which also contains the supporting documents and offered a means of submitting public comments on the Remedy Selection Plan. In addition, the IAGWSP provided copies of the Remedy Selection Plan to the MMRCT members and distributed it to individuals in attendance at the public meeting.

All draft and final reports related to the Sites' investigation and response activities 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 (formerlywww.groundwaterprogram.org), the EPA Web site',(www.epa.gov/region1/mmr) arid the Administrative Record located at PB0516 West Outer Road, Camp Edwards, MA.

http:formerlywww.groundwaterprogram.org http:groundwaterprogram.army.mil

Media releases on presentations and the Public Comment Period for the Site were distributed to the Cape Cod 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 JBCC investigation and response activities. , D. SCOPE AND ROLE OF OPERABLE UNIT

The Site consists of source areas contributing to groundwater contamination (i.e., contaminated soil and the areas known or suspected to contain UXO, DMM or MC) and two distinct groundwater plumes. Several source areas contributing to groundwater contamination for the J 2 Range were addressed through the removal of geophysical anomalies and the excavation and removal of contaminated soils. The effectiveness of the source removal will be evaluated as part of the selected remedy. The selected remedy also includes a groundwater response action for each groundwater plume. Since complete range clearance has not been conducted, UXO items may remain. In addition, these remaining munitions, and the soil beneath, may also pose public safety risks, ecological risks, dermal contact risks, and/or soil ingestion risks. However, 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.

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 hummbcky 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 glaciolacustrine sediments and a basal till layer over bedrock. The Mashpee Pitted Plain underlies most of the JBCC , including the J-2 Range.

Site Hydrogeology

A single groundwater-flow system underlies Western Cape Cod including JBCC. Camp Edwards lays 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 JBCC 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 JBCC 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 JBCC. 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 JBCC 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.