KGS 2020 LTMMP AOC A7 Sudbury.pdf

FINAL

LONG-TERM MONITORING

AND MAINTENANCE PLAN

FOR AREA OF CONTAMINATION A7

FORMER SUDBURY TRAINING ANNEX

SUDBURY, MASSACHUSETTS

JULY 2020

Prepared for:

U.S. Army Corps of Engineers New England District

696 Virginia Road Concord, Massachusetts 01742

Prepared by:

KOMAN Government Solutions, LLC 293 Boston Post Road West, Suite 100

Marlborough, MA 01752

Contract No.: W912WJ-18-C-0011

NOTICE

The United States Department of Defense, Department of Army, funded wholly or in part the preparation of this document and work described herein under Contract No. W912WJ-18-C- 0011. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

LONG-TERM MONITORING

AND MAINTENANCE PLAN

FOR AREA OF CONTAMINATION A7

FORMER SUDBURY TRAINING ANNEX

DRAFT FINAL

JUNE 2020

CERTIFICATION:

I hereby certify that the enclosed Report, shown and marked in this submittal, is that proposed to be incorporated with Contract Number W912WJ-18-C-0011. This document was prepared in accordance with the U.S. Army Corps of Engineers (USACE) Scope of Work and is hereby submitted for Government Approval.

Reviewed By:

06/02/2020

KGS Project Manager Date

Received By:

USACE Project Manager Date i

1.0 INTRODUCTION..................................................................................................................... 1-1

1.1 PURPOSE ........................................................................................................................ 1-1

1.2 BACKGROUND ............................................................................................................. 1-1

2.0 LONG-TERM MONITORING AND MAINTENANCE PROGRAM ............................ 2-1

2.1 PREVIOUS AND UPDATED LONG-TERM MONITORING AND

MAINTENACE PROGRAM .......................................................................................... 2-1

2.1.1 Current Evaluation of LTM Data to COC Trends in Groundwater .......... 2-2

3.0 SAMPLING AND ANALYSIS PLAN FOR GROUNDWATER ...................................... 3-1

3.1 OBJECTIVES .................................................................................................................. 3-1

3.2 MONITORING WELL SAMPLING .............................................................................. 3-1

3.3 LANDFILL GAS VENT MONITORING ....................................................................... 3-1

3.4 SAMPLING FREQUENCY SUMMARY ...................................................................... 3-2

3.5 ANALYTICAL METHODS AND ANALYTES ............................................................ 3-2

3.5.1 Groundwater Analytical Methods and Analytes .................................................. 3-2

3.6 PRE-SAMPLING ACTIVITIES ..................................................................................... 3-2

3.6.1 Equipment and Supplies ...................................................................................... 3-2

3.6.2 Site Location, Security and Access ...................................................................... 3-3

3.6.3 Initial Well Opening and Inspection .................................................................... 3-3

3.6.4 Water Level Measurements ................................................................................. 3-4

3.7 SAMPLING PROCEDURES .......................................................................................... 3-4

3.7.1 Equipment Calibration ......................................................................................... 3-4

3.7.2 Low-Flow Well Purging ...................................................................................... 3-4

3.7.3 Sample Containers and Preservatives .................................................................. 3-6

3.8 SAMPLE COLLECTION ................................................................................................ 3-6

3.8.1 Sample Identification ........................................................................................... 3-6

3.8.2 Quality Assurance/Quality Control Samples ....................................................... 3-7

3.9 POST-SAMPLING ACTIVITIES ................................................................................... 3-8

3.9.1 Total Well Depth Measurement ............................................................. 3-8

3.9.2 Chain of Custody ................................................................................................. 3-8

3.9.3 Sample Delivery/Shipment to Laboratory ........................................................... 3-8

3.9.4 Equipment Decontamination ................................................................................ 3-9

3.9.5 Investigation-Derived Waste ................................................................................ 3-9

3.9.6 Data Validation .................................................................................................. 3-10

3.10 FIELD DOCUMENTATION ........................................................................................ 3-11

3.10.1 Field Logbooks .................................................................................................. 3-11

3.10.2 Field Forms ........................................................................................................ 3-12

3.10.3 Daily Quality Control Reports ........................................................................... 3-12

3.10.4 Photographic Documentation ............................................................................. 3-13

3.10.5 Project File ......................................................................................................... 3-13

4.0 LAND-USE CONTROL IMPLEMENTATION AND MONITORING PLAN ............ 4-1

4.1 GENERAL ....................................................................................................................... 4-1

4.2 LAND-USE CONTROL INSPECTION ......................................................................... 4-1

4.2.1 Physical On-Site Inspection ..................................................................... 4-1

4.3 INTERVIEW ................................................................................................................... 4-1 ii

5.0 REPORTING REQUIREMENTS ........................................................................................... 5-1

5.1 ANNUAL REPORTS ..................................................................................................... 5-1

5.2 ANALYTICAL RECORDS ............................................................................................ 5-1

5.2.1 Analytical Electronic Data Format ............................................................ 5-1

5.2.2 Analytical Data Review ............................................................................ 5-1

6.0 HEALTH AND SAFETY .......................................................................................................... 6-1

7.0 REFERENCES ............................................................................................................................ 7-1

LIST OF FIGURES

Figure 1-1 Site Location, Former Sudbury Training Annex Figure 1-2 Site Layout, AOC A7

LIST OF TABLES

Table 3-1 Groundwater Monitoring Locations Selected for Long-Term Monitoring at

AOC A7

Table 3-2 Fall LTM Sample Analysis and Methods for AOC A7 Table 3-3 Sample Preparation, Analysis Methods, Containers, Preservatives and Holding

Times for AOC A7 Table 3-4 Action Levels for AOC A7 Table 3-5 Sample and Analytical Summary for IDW Characterization and Disposal Table 4-1 ROD Objectives for AOC A7 Table 5-1 Summary of Sampling and Reporting Requirements

LIST OF APPENDICES

Appendix A LandTec GEM-500 Calibration Procedure Appendix B Field Forms Appendix C Groundwater Sampling Checklist Appendix D USEPA Region 1 Low Stress (Low-Flow) Purging and Sampling Procedures Appendix E Annual Land Use Control Checklists Appendix F Responses to Comments iii

LIST OF ACROYMNS OR ABBREVIATIONS

ADR Automated Data Review AOC area of contamination Army U.S. Army ASTM American Society for Testing and Materials bgs below ground surface BRAC Base Realignment and Closure oC degree Celsius CERCLA Comprehensive Environmental Response, Compensation and Liability Act CFR Code of Federal Regulations CMR Code of Massachusetts Regulations COC contaminant of concern COD chemical oxygen demand

DCL Devens Consolidation Landfill Devens former Fort Devens Army Installation DO dissolved oxygen DoD Department of Defense DQCR Daily Quality Control Report DQO Data Quality Objective

EDD electronic data deliverable eQAPP electronic Quality Assurance Project Plan ESD Explanation of Significant Differences

FEMA Federal Emergency Management Agency FS Feasibility Study FTP file transfer protocol FYR five year review

GPS Global Positioning System

HGL HydroGeoLogic, Inc.

HLA Harding Lawson Associates

ID identification IDW investigation-derived waste ITRC Interstate Technology and Regulator Council

KGS KOMAN Government Solutions, LLC

L/min liters per minute LEL lower explosive limit iv

LCS laboratory control sample LTM long-term monitoring LTMM long-term monitoring and maintenance LTMMP Long-Term Monitoring and Maintenance Plan LUC Land-Use Control LUCIP Land-Use Control Implementation Plan µg/L micrograms per liter MAROS Monitoring and Remediation Optimization System MassDEP Massachusetts Department of Environmental Protection MCP Massachusetts Contingency Plan mg/kg milligrams per kilogram MOA Memorandum of Agreement MS matrix spike MSD matrix spike duplicate MWPAR Massachusetts Wetlands Protection Act Regulations

NAD North American Datum NVGD National Vertical Geodetic Datum NFA No Further Action NFG National Functional Guidelines NPL National Priorities List NTU nephelometric turbidity units

O&M operations and maintenance ORP oxidation-reduction potential OU Operable Unit

% Percent PARCCS precision, accuracy, representativeness, completeness, comparability, and sensitivity PID photoionization detector PM Project Manager POL petroleum, oils, and lubricant PPE personal protective equipment

QA Quality Assurance QAPP Quality Assurance Project Plan QC Quality Control QSM Quality Systems Manual RAO Remedial Action Objective RCRA Resource Conservation and Recovery Act RI Remedial Investigation ROD record of decision

SEDD Staged Electronic Data Deliverable v

SOW Statement of Work

USACE U.S. Army Corps of Engineers USEPA U.S. Environmental Protection Agency USFWS U.S. Fish and Wildlife Service USGS U.S. Geological Survey

VOA volatile organic analyte VOC volatile organic compound

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1.0 INTRODUCTION

1.1 PURPOSE

The U.S. Army Corps of Engineers (USACE)-New England District contracted KOMAN Government Solutions, LLC (KGS) to conduct environmental remediation services required to meet the objectives of the Statement of Work (SOW) for Contract Number W912WJ-18-C-0011.

KGS has prepared this Long-Term Monitoring and Maintenance Plan (LTMMP) for Area of Contamination (AOC) A7 to update the current long-term monitoring (LTM) approach for the former Sudbury Training Annex (“the Annex”). Updates to the LTM approach are warranted to account for changes in contaminant distribution and progress towards achieving the goals stated in the Record of Decision (ROD) (OHM, 1995) and the ROD for Management of Migration (ABB, 1997). This LTMMP updates and supersedes the Sudbury Annex portion of the 2015 Devens and Sudbury Annex Long-Term Monitoring Plan (Sovereign/HGL, 2015) with additional revisions and optimization recommendations included based on current conditions at the Annex.

The LTM optimization recommendations provided in this revised LTMMP are derived in part from the Optimization Evaluation (Sovereign, 2015) for the Annex and are provided here to document changes to the sampling program. This LTMMP revision includes the optimization recommendations determined during performance of the optimization evaluation (see Appendix A of the 2015 LTMMP, Sovereign, 2015) and does not reproduce the in-depth discussions contained within the optimization report.

AOC A7 is the only AOC at the Annex with an existing Remedial Action including operation and maintenance, institutional controls, and land use restrictions. No monitoring or land use controls were specified for AOC A9 in the RODs. AOC P31 was the subject of a No Further Action decision in April 1999 following conclusion of the Final Supplemental Site Investigation Report (HLA, 1999). Groundwater at AOC P58 was monitored by the Army through May 2001 per a 1999 addendum to the existing LTMMP for AOC A7 (USACE, 1998); however, groundwater monitoring at AOC P58 ceased in 2002 and all four monitoring wells were decommissioned and no further action is required.

1.2 BACKGROUND

The Annex was listed as a National Priorities List (NPL) site from February 1990 through January 2002, under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA). The former training annex occupies approximately 4.3 square miles in the towns of Hudson, Marlborough, Maynard, Stow, and Sudbury, Massachusetts. Hudson Road divides the installation into a larger northern section, and a smaller southern section (Figure 1-1). The Annex became part of the Fort Devens Army Installation in 1982. The Annex was removed from the NPL in January 2002. At that time, 2,205 acres of the property were transferred to the U.S. Fish and Wildlife Service (USFWS), 4.1 acres were transferred to the U.S. Air Force (USAF), and 71.4 acres were transferred to the Federal Emergency Management Agency (FEMA). In June 2002, all known monitoring wells at the former annex were decommissioned

1-2 except for those at Area of Contamination (AOC) A7, which required continued investigation under a long-term monitoring and maintenance (LTMM) program.

AOC A7 is a 10-acre site located by the Assabet River in the northern portion of the Annex (Figure 1-1). The site layout of AOC A7 is shown on Figure 1-2. AOC A7 is the only site remaining at the Annex that requires continued environmental sampling. AOC A7 is a former waste disposal site that was used as a landfill for general refuse, demolition debris, and chemical lab waste disposal. The lab waste area was limited to a pit of about 5,000 square feet within the landfill. General refuse was reportedly buried at shallow depths from 1941 until the 1980s, with occasional burning to reduce volume. The laboratory waste was excavated in 1996 and transported offsite for treatment and disposal at an approved facility. The laboratory waste was removed because it is considered to be the primary source of groundwater contamination at the site. The Army constructed a Resource Conservation and Recovery Act (RCRA) Subtitle C (impermeable) landfill cap in 1996 following the removal of the waste. The Army has completed Remedial Investigations (RIs), Feasibility Study (FS), a Source Control ROD, and a Management of Migration ROD for AOC A7. The Army has been conducting long-term monitoring and maintenance at AOC A7 since that time.

1.3 ROD OBJECTIVES AND SELECTED REMEDY

The LTMMP strategies implemented at the Annex are driven by the requirements in the ROD.

In general, the objectives of the monitoring and maintenance program at the Annex are to monitor groundwater conditions on-site, monitor for potential off-site contaminant migration, and to document that concentrations of the contaminants of concern (COC) decrease over time to a level that achieves the objectives stated in the ROD. A description of current site LTMM activities is provided in Section 2.0.

The remedial action objectives (RAOs) established in the ROD are site-specific, quantitative goals defining the extent of cleanup required to achieve response objectives. The RAOs are formulated to achieve the overall U.S. Environmental Protection Agency (USEPA) goal of protecting human health and the environment.

The ROD for the Source Control of the Operable Units (OU) 1 and 2 at AOCs A7 and A9 was signed in September 1995 (ABB, 1997). The ROD for Management of Migration for OUs 1, 2, and 3 (AOCs A4, A7, and A9) was signed in September 1997 (OHM, 1997). The following RAOs were developed to mitigate existing and future potential threats to public health and the environment:

Eliminate potential risk to human health and the environment associated with exposure to contaminated wastes;

Minimize off-site migration of contaminants; and, Limit infiltration of precipitation to the underlying waste within the landfill area, thereby minimizing leachate generation and groundwater degradation (OHM, 1995).

The remedy selection for the source control OU for AOC A7 was the installation of an impermeable landfill cover system that met RCRA Subtitle C requirements. The landfill remedy also included the following:

1-3 removal and off-site disposal of chemical waste debris in the laboratory dump area;

operations and maintenance (O&M);

Land Use Controls (LUCs) and land use restrictions;

long-term groundwater monitoring; and five-year reviews to assess whether the remedy remains protective of human health and the environment.

The selected remedial action also specified the creation of a wetland at AOC A7 in fall 1996 to replace “Wetland B”, which was a seasonal wetland that is now incorporated as part of the landfill. Wetland B was classified as a natural resource area under the Massachusetts Wetlands Protection Act Regulations (MWPAR), as an “Isolated Land Subject to Flooding”. Based on size (40 feet by 60 feet [ft], or 2,400 ft2), Wetland B was not subject to regulation under the MWPAR. Nonetheless, the decision to replace Wetland B was made in accordance with the USACE policy of “No Net Loss of Wetlands” and the requirements of Army Regulation 200-3 (Natural Resources - Land, Forest and Wildlife Management). Post-construction inspections in 1997 found that the wetland had been successfully established and no further action was recommended. Subsequent inspections in 2000 and 2004 similarly concluded that the area had been successfully restored to a functioning wetland.

1.4 MASSACHUSETTS SOLID WASTE LANDFILL REGULATIONS

The landfill at AOC A7 was constructed in 1996 and has been in operation since 1996 (23 years).

Massachusetts landfill post-closure requirements are specified under 310 Code of Massachusetts Regulations (CMR) 19.142 and include a minimum 30-year post-closure period. During the post-closure period, the landfill owner/operator must perform site maintenance, conduct environmental monitoring, maintain the landfill gas control system, and conduct periodic site inspections. The Army has been performing these activities, as described in the site LTMMPs, since 1996 (23 years) and will continue these activities through the 30-year period (2026) unless a waiver is sought in accordance with 310 CMR 19.142(3). After the 30-year period, the Army can apply for termination of the post-closure period in accordance with 310 CMR 19.142(8) and/or will reduce the LTMM program depending on site conditions at that time.

Post-closure changes to the LTMM are not proposed at this time, however, potential future modifications to the LTMM program after the 30-year period may include the following:

Ceasing landfill gas monitoring if methane levels remain low. Currently, the landfill gas vents are sampled once every five years in support of the Five-Year Review (next sampling is planned for fall 2020). As a mature landfill, methane generation appears to have greatly slowed or stopped. Methane concentrations in the gas vents were very low to non-detect during the most recent gas vent samplings conducted in 2016 (maximum 0.2% methane) and 2017 (non-detect).

Ceasing groundwater monitoring if COC concentrations are below cleanup levels.

During the most recent (November 2019) sampling event, there were no exceedences of

1-4 cleanup goals in the downgradient sentinel well SUDWP-A07-011, as VOCs and pesticides were non-detect and there were only very low levels of cyanide and chemical oxygen demand (COD). If insufficient data are available for complete cessation of the monitoring program at the end of the post-closure period, then the sampling frequency may be reduced to coincide with the Five-Year Reviews.

Reducing or ceasing landfill maintenance. Annual inspections have found no significant structural/erosional problems with the landfill. After the 30-year post-closure period, annual inspections and mowing may no longer be required except perhaps the periodic removal of deep-rooted vegetation on the cap (i.e., large trees) and/or inspections coinciding with the Five-Year Reviews.

1 Replaced by well SUD-A7-19-01 in 2019.

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2.0 LONG-TERM MONITORING AND MAINTENANCE PROGRAM

This section provides a summary of the current LTMM program implemented at the Annex, and summarizes the recommended optimization strategy for the site where optimization is appropriate based on changes in site conditions or progress made towards achieving the goals stated in the ROD. The Optimization Evaluation (Sovereign, 2015) provided a detailed discussion of the rationale for the selected optimization approach and is not reproduced within this section; however, the Army’s rationale for implementing LTM optimization can be summarized by the following:

The LTM sites do not pose a risk to human health and the environment based on the lack of an exposure pathway. LUCs are in place and historical groundwater monitoring data indicate that the concentrations of COC are either stable, or in most cases, steadily declining since inception of the monitoring program.

The LTM site conditions (as established by prior removal actions), remaining source/groundwater COCs concentrations, and current and historical monitoring data do not indicate (and are not conducive to) any significant contaminant migration beyond the boundary of the monitoring networks.

The recommended changes to the monitoring well network and/or sampling frequency of wells within the site’s monitoring program, where indicated, are based on the need to properly define plume extent and/or monitor changes in the plume composition over time. Wells were selected for elimination if the sampling point/data collected from the sampling point was determined to not add value to the monitoring program. The frequency of monitoring was reduced at other wells where frequent monitoring did not enhance the site’s data set and the groundwater from a particular well had established a defined concentration trend and did not show evidence of rapid contaminant or geochemical variations between sampling events. Other wells were selected for reduced sampling frequency where data have shown little change over time but data from the particular well would help to confirm plume delineation. A statistical analysis of data trends was performed through the Monitoring and Remediation Optimization System (MAROS) program (Sovereign, 2015) and the analysis supported the proposed changes where reduction in frequency was recommended. Since 2015, a review of chemistry trends was performed to align site conditions to monitoring needs.

2.1 PREVIOUS AND UPDATED LONG-TERM MONITORING AND MAINTENACE

PROGRAM

The current program, which was last revised in 2018 (KGS, 2018a), includes annual sampling of one downgradient well (SUD-A7-19-01) and biennial (every other year) sampling of four wells:

OHM-A7-08 (landfill well), SUD-A07-065 (downgradient well), SUD-A07-014 (upgradient well) and SUD-A7-19-01 (downgradient well). Samples are analyzed for VOCs, organochlorine pesticides, total cyanide, and chemical oxygen demand (COD). The samples are collected during the Army’s fall LTM event (October/ November).

The four, 6-inch landfill gas vents are to be monitored once every five years (next event in 2020) using a handheld meter (MultiRAE or GEM 2000) for total VOC levels, hydrogen sulfide, lower explosive limit (LEL), carbon dioxide, carbon monoxide, oxygen, and methane.

2-2

The depth to water is measured at 13 monitoring wells and at one of two staff gauge surface water locations during each annual and biennial LTM event.

Landfill maintenance is also performed annually and includes lawn mowing, clearing of debris from fence line, and ensuring the toe drain, as well as the riprap areas, are clear of moss and excess sediment. If necessary, herbicide is applied to areas encroached with invasive vegetation.

Because there is no active or passive remediation in progress at the landfill, the performance metric will consist of evaluating the annual LTM data against established COC trends. The collection frequency of landfill gas monitoring results is every five years, prior to the Five-Year Reviews. The next Five-Year Review is scheduled for 2021.

Over time, the landfill also will be evaluated for transition from Post-Closure Care to Custodial Care per the ITRC guidance.

2.1.1 Current Evaluation of LTM Data to COC Trends in Groundwater

Evaluation of contaminants of concern trends in groundwater since the landfill cap was construction in 1996 through fall 2019 are summarized below. It should be noted that groundwater is not used as a source of drinking water at AOC A7 and groundwater discharges to the Assabet River. The AOC A7 ROD did not include groundwater RAOs, ARARs, or specific cleanup levels. To assess the data and trends, groundwater concentrations are compared to the state and federal standards in Table 3-4 and discussed below:

1,1,2,2-Tetrachloroethane – 1,1,2,2-Tetrachloroethane results have been reported for 20 years beginning in July 1996 and ending in October 2016. In 18 years of sampling at well OHM-A7-51, the concentrations have decreased significantly. The downward trend began in April 1997 with concentrations reported below the Massachusetts Contingency Plan (MCP) GW-1 standard of 2.0 µg/L from November 2009 to November 2013. This contaminant is unregulated under the federal National Primary Drinking Water regulations and no MCL has been established. In 20 years of sampling at Well JO-A07- M63/SUD-A07-065, 1,1,2,2-tetrachloroethane concentrations increased until 1998 following a steady decrease until levels were below the GW-1 standard in 2015.

Tetrachloroethene – Tetrachloroethene results have been reported for 21 years beginning in July 1996 and ending in November 2019. No results were reported in 2016 and 2017.

OHM-A7-08 showed elevated levels of tetrachloroethene from July 1996 until October 1998 when concentrations began to decline. The highest tetrachloroethene concentration at this well was reported in October 1998 at 130 µg/L. October 2015 marked the first sampling result below the federal MCL and MCP GW-1 standard of 5.0 µg/L. Well OHM-A7-51 concentrations dropped dramatically in 1996. By 2004, levels were first reported below the GW-1 standard. The tetrachloroethene results from 2004 until 2013 were reported below the federal and state standard and the location has not been sampled since. Well JO-A07-M63/SUD-A07-065 has experienced both upward and downward trends in the 21 years of collected samples and will require further sampling until results are below the GW-1 standard.

Trichloroethene – Trichloroethene results have been reported for 20 years beginning in July 1996 and ending in October 2016. Throughout 20 years of sampling, JO-A07-

2-3

M63/SUD-A07-065 has not developed a clear trend. Results have increased and decreased without an established trend. From 2006 to 2016; however, levels began to plateau and results were reported below the federal MCL and MCP GW-1 standard of

5.0 µg/L. Because of the variance in trends with trichloroethene, evidence points to further sampling until results are below the standard.

Gamma-BHC (Lindane) – Lindane results have been reported at three different wells over the course of 23 years. Well OHM-A7-08 has been experience a downward trend throughout 21 years of results. From 1996 until 2001, Lindane was experiencing an upward trend. After 2001, Lindane concentrations continued to drop until results were below the federal MCL and MCP GW-1 standard of 0.2 µg/L in 2015. Well SUD-A07- 065 has had low concentrations with little variance and the results over the past three rounds have not exceeded the standard.

If concentrations continue to remain below the federal and state regulatory standards and/or show downward concentration trends, then as part of the 2021 Five Year Review, the Army may propose further reductions in the sampling frequency (e.g., sampling of the four wells every 2 to 5 years).

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3.0 SAMPLING AND ANALYSIS PLAN FOR GROUNDWATER

This section constitutes a project-specific sampling and analysis plan and was prepared in accordance with the guidelines set forth in the USACE Engineer Manual (EM) EM200-1-2, Technical Project Planning Guidance for HTRW Data Quality Design (USACE, 1995); EM 200- 1-3, Requirements for the Preparation of Sampling and Analysis Plans (USACE, 2001); and USEPA, Region 1, Low Stress (low flow) Purging and Sampling Procedure for the Collection of Ground Water Samples from Monitoring Wells (USEPA, Region 1, 2017).

3.1 OBJECTIVES

The following subsections were developed to ensure that data quality objectives specific to this project are met; field sampling protocols are implemented, documented and reviewed in a consistent manner; and data collected are scientifically valid and defensible.

3.2 MONITORING WELL SAMPLING

Based on recommendations from the Optimization Evaluation (Sovereign/HGL, 2015) and current site conditions, groundwater samples from the following AOC A7 monitoring wells will be collected at the given frequency during the fall (October-November):

Annual sampling of downgradient well SUD-A7-19-01

Biennial (every other year) sampling of wells OHM-A7-08, SUD-A07-014 and SUD-A07-065, beginning in 2021 (then 2023, etc.)

Groundwater monitoring wells selected for LTM and the rationale for their selection are summarized in Table 3-1. Groundwater monitoring wells were selected to confirm the absence or presence of COCs at downgradient locations or to document the anticipated decrease in COCs over time within source areas at AOC A7. Historical groundwater sampling results also were used to select groundwater monitoring wells for LTM.

The location of groundwater monitoring wells that are included in fall LTMM sample event for sample collection within AOC A7 are identified in Figure 1-2. The locations that will be sampled and the sample methods to be used during LTMM sample events are listed in Table 3-2.

3.3 LANDFILL GAS VENT MONITORING

A passive gas venting system was installed at Sudbury landfill to facilitate the ventilation of any methane generated from the degradation of waste material beneath the landfill cover system.

The passive system for Sudbury consists of four 6-inch diameter gas vents. Gas vent locations are depicted on Figure 1-2. Screens were installed at the end of each vent pipe to prevent access by birds or other animals. Field monitoring is performed at the landfill gas vents for carbon dioxide, oxygen, and methane. Barometric pressure is also measured. A LandTec GEM-500 or equivalent gas monitor is typically used to monitor the gas vents. Landfill gas parameters are collected by inserting the monitoring equipment intake tube into the landfill gas vent and recording the parameter values after 1 to 2 minutes. The monitoring equipment intake tube is inserted past the landfill gas vent elbow to ensure that the parameters are reflective of landfill gas and not ambient air. Landtec calibration procedures are included in Appendix A. The gas monitoring field form is included in Appendix B.

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3.4 SAMPLING FREQUENCY SUMMARY

Based on the Optimization Evaluation recommendations (Sovereign/HGL, 2015) and recent data trends through fall 2019, the LTM sample event includes annual sampling from one well and biennial sampling from four wells. Field monitoring of the AOC A7 landfill gas vents will be performed every five years for AOC A7. Specific analytical methods and analytes are discussed in Section 3.5.

3.5 ANALYTICAL METHODS AND ANALYTES

Analytical methods and analytes utilized for the LTM sample event will be in accordance with this document and the Generic Quality Assurance Project Plan (QAPP) (KGS, 2016). Analytical detection limits are lower than the project action levels (see QAPP Worksheet #15 for Reference Limits and Evaluation table for specific analytes). Table 3-3 lists the analytical parameters, sample container quantities, preservation, holding times and quality control (QC) samples required for groundwater monitoring. The sample methods for groundwater monitoring are presented in Table 3-2. Action levels to be used in the assessment of potential COC off-site migration are presented in Table 3-4. Specific analytical parameters and methods to be used during LTM sample event are summarized below.

3.5.1 Groundwater Analytical Methods and Analytes

The following groundwater laboratory and field parameters will be performed or collected during the LTM sample event at the AOC A7 landfill:

VOC (SW-846 method 8260B [SW8260B])

Pesticides (SW-846 method 8081A [SW8081A])

COD (410.4)

Cyanide (SM4500CN-CE)

Field measurements will be collected during groundwater monitoring low-flow well purging activities to compliment laboratory analytical methods. Specific parameters will include pH, temperature, specific conductance, DO, ORP, and turbidity. The collection of field measurements is discussed in Section 3.7.2.

3.6 PRE-SAMPLING ACTIVITIES

The Groundwater Sampling Checklist presented in Appendix C summarizes action items that need to be performed before and during the LTM sample event to ensure that LTM tasks are completed. The following sections provide a more detailed discussion of the pre-sampling activities that will be conducted prior to the collection of groundwater samples at the Annex.

3.6.1 Equipment and Supplies

The following equipment and supplies will be utilized in the collection of low-flow groundwater samples:

Geotech Peristaltic pump and Teflon®-lined tubing, Water level indicator, 3-3

DO, pH, specific conductance, ORP and temperature probes (within a single unit) and appropriate calibration solutions, turbidity meter (separate meter from the above unit), flow-through cell, Certified clean sample containers with preservative, provided by the subcontract analytical laboratory.

Decontamination supplies including isopropyl alcohol and Alconox detergent, Laboratory grade deionized water, 500-milliliter graduated cylinder, Graduated 5-gallon buckets for purge water and decontamination, Plastic Ziploc® sealable bags,

0.45 micron in-line filters, Well and gate keys, Field logbook and field sampling forms, Chain of custody forms, Cooler with packing material and ice to cool all samples to 4 degrees Celsius (ºC), +/- 2 ºC, Temperature blank for each cooler to be submitted to the laboratory, Trip blanks (VOCs only), Polyethylene sheeting, and

Paper towels.

3.6.2 Site Location, Security and Access

The Annex is located within the Assabet River National Wildlife Refuge where access is restricted to the general public at AOC A7 and groundwater monitoring wells are located in a secured fenced area. Security measures will be enacted if evidence of tampering or suspicious damage is noted. Damage observed at sampling locations will be reported to the Army for appropriate action. Information to be reported will include a written description and photograph of each damaged sample location. Arrangements will be made to coordinate LTM activities at any groundwater monitoring wells that are located in areas whose ownership has been transferred from the Army to another entity in an effort to ensure that LTM activities are conducted in a timeframe that is acceptable to all stakeholders and the property owner. Sampling activities of the wells within security fencing at the Annex, will be coordinated through the property owner, USFWS.

3.6.3 Initial Well Opening and Inspection

Olfactory and visual observations will be made upon opening the well casing protective cap. All observations, including any observed odors, will be documented in the logbook and on the Static

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Groundwater Elevation Form presented in Appendix B. The general condition of the protective cover, its associated concrete apron, well casing protective cap, and the well casing will be inspected and noted in the logbook. Any damage, evidence of tampering, or immediately necessary repairs will be communicated to the USACE-NAE Project Manager (PM) within 24 hours.

3.6.4 Water Level Measurements

Water level measurements will be collected at each groundwater monitoring well before purging and sampling activities are performed. Field personnel will wait approximately 1 hour after the opening of each monitoring well before water level measurements are collected to ensure that the well’s water level has adequate time to equilibrate with atmospheric conditions. Water level measurements will be collected on the marked side of the riser pipe and will be accurate to the nearest 0.01 ft. Water level measurements will be collected on the north side of any riser pipe that has not been previously marked. Water level data will be recorded on a Static Groundwater Elevation Form (Appendix B). The water level probe end and tape will be decontaminated before use in the first well, between each well, between sample locations, and at the conclusion of sample activities in accordance with the procedures specified in Section 3.9.4. Total well depth measurements will be collected as part of the post-sampling activities described in Section 3.9.1. In some instances, however, total well depth measurements will be collected prior to the collection of water samples if information is not available for a particular well and is necessary to facilitate the correct placement of a groundwater sample pump.

3.7 SAMPLING PROCEDURES

3.7.1 Equipment Calibration

Some equipment that will be used during the LTM event will require periodic calibration to ensure optimum performance, including a LandTec GEM-500, a water quality meter, and a turbidity meter. This equipment will be calibrated in accordance with manufacturer’s instructions before its initial use at the site and at the beginning of each workday thereafter. The equipment calibration also will be checked at the conclusion of each workday. Calibrations and the end of the day drifts will be documented on field forms included in Appendix B. The calibration procedure for the LandTec GEM-500 is included in Appendix A.

3.7.2 Low-Flow Well Purging

Each groundwater monitoring well will be purged in accordance with the USEPA Region 1 Guidance Document titled Low Stress (low-flow) Purging and Sampling Procedure for the Collection of Ground Water Samples from Monitoring Wells (USEPA, 2017), included as Appendix D, prior to sampling. The goal of low-flow purging and sampling is to remove stagnant water from the well and collect representative samples from the aquifer at near ambient conditions. A peristaltic pump will be used to purge the wells. Dedicated or disposable teflon-lined tubing will be used during purging and sampling activities.

The depth to water will be measured with a water level indicator in accordance with Section 3.6.4. Caution will be exercised to minimize disturbance of the well water. The

3-5 dedicated or disposable tubing of the peristaltic pump will be placed into the well gently such that the intake will be located in the middle or slightly below the middle of the screened interval to ensure that most of the water will be pumped directly from the formation.

A properly calibrated water quality parameter probe will be fitted into the flow-through cell provided with the instrument with the included mounting hardware. The line from the pump will be attached to the barbed hose fitting on the bottom of the flow-through cell. A T-valve and spigot will be attached to the line from the in-well submersible pump prior to the flow-through cell for the purpose of collecting turbidity samples. A drain line will be attached to the top fitting of the flow-through cell to direct the effluent to a bucket.

The depth to water will be continuously recorded during purging and measurements will be recorded on the field sampling form and in the field logbook. Flow rates of 0.1 to 0.5 liters per minute (L/min) will be used for purging. The pump will be operated at a flow rate where minimal drawdown occurs during purging. The goal of low-flow purging is for the drawdown to be less than or equal to 0.3 ft.

Water quality measurements will be used as the basis for establishing the stabilization of the well water. Well stabilization parameters will include pH, specific conductance, temperature, ORP, DO and turbidity. Turbidity samples must be collected from a spigot placed on the sample tubing prior to the flow-through cell and measured with a stand-alone meter. The parameters will be measured every 5 minutes until stabilization of all parameters is achieved. Stabilization has been reached when pH measurements remain constant within 0.1 standard unit, specific conductance is constant within 3 percent (%), the temperature is constant within 3%, ORP is constant within 10 millivolts, dissolved oxygen is either constant within 10% for values above 5 milligrams per liter (mg/L) or below 5 mg/L for three consecutive readings and the turbidity is either constant within 10% for values above 5 Nephelometric Turbidity Units (NTU) or below 5 NTUs for three consecutive readings. Field measurements will be tabulated for comparison on the Groundwater Field Forms (Appendix B). Observations such as odors, color of water or the appearance of soil particles or iron floc will also be recorded on the Groundwater Field Sampling Data Sheet. Final measurements will be recorded in the sampling logbook.

If the water level drops more than the goal of 0.3 ft during purging, additional measures such as reducing the purge flow rate, will be enacted to reduce drawdown. These activities will be documented. Purging will continue until well stabilization parameters stabilize, the water level drops to the screened interval for wells with shorter screened intervals, or until the water level drops to the top of the pump for wells with longer screened intervals that encompass the pre-purging groundwater level. If the water level drops to the top of the pump or the screened interval, purging will be stopped and up to 24 hours will be allowed to pass for the well to recharge. The well will be sampled using low-flow sample collection procedures although it will not be purged and it will not be necessary for field parameters to stabilize.

It should be noted that one of the current LTM program wells at the Annex, OHM-A7-08 has a 15-foot screen interval, which is greater than the 10-foot guideline referenced in the USEPA Region 1 guidance document. This well will be purged until a minimum of three screen volumes are pumped from the well, or until purging has been conducted for a minimum of 2 hours. A notation will be made on the Groundwater Field Sampling data sheet if samples are collected when water quality parameter stabilization or purge volume criteria have not been met.

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3.7.3 Sample Containers and Preservatives

Laboratory provided sample containers will be used during LTM event. The laboratory will provide pre-preserved sample containers as appropriate for the analysis to be performed. Field personnel will conduct a visual check to ensure that pre-preserved sample containers contain preservative. A summary of the sample containers, preservation, and holding times for water samples are presented in Table 3-2.

3.8 SAMPLE COLLECTION

Dedicated and disposable Teflon-lined tubing connected to a peristaltic pump will be used to collect samples from groundwater monitoring wells. The objectives and methods for this procedure are described in USEPA’s Region 1 Guidance Document entitled Low Stress (low-flow) Purging and Sampling Procedure for the Collection of Ground Water Samples from Monitoring Wells (USEPA, Region 1, 2017) presented in Appendix D. The goal of sampling monitoring wells is to provide groundwater quality data that is representative of actual aquifer conditions with minimal alteration caused by inappropriate or variable sampling techniques.

Typically, flow rates of 0.1 to 0.5 L/min are used; however, this is dependent on site-specific hydrogeology (USEPA, 2017).

Once groundwater quality parameters have stabilized, groundwater samples will be collected directly from the tubing connected to the pump. The sampling flow rate will be the same flow rate that was used during the purging process to maintain equilibrium between the well and the formation. The flow-through cell will be bypassed or disconnected during the collection of samples. Sample containers will be filled by allowing water from the pump to gently enter the containers with minimal disturbance. Sampling will begin with the collection of the VOC samples and continue collection for the remaining parameters. Collected sample containers will be stored in a cooler and placed on ice immediately. All samples will be labeled as described in Section 3.8.1 and immediately placed in a cooler with ice to maintain a sample temperature of approximately 2 to 6 C.

3.8.1 Sample Identification

All samples will be assigned a unique field sample identifier. Field personnel will generate a label for each sample container that will contain the sample identifier, date and time of sample collection, the sampler’s initials, analytical parameters, and type of preservation used. The sampler will initial any change in the label information prior to the sample collection.

A sample numbering system will be used to identify each sample collected and submitted for analysis. The purpose of the numbering system is to assist in the tracking of samples and to facilitate retrieval of analytical results. The sampling number will be used on sample labels, sample tracking forms, chain of custody forms (Appendix B), field logbooks, and for other applicable documentation. The field sample numbering system will follow the format used for previous LTM events and will include the suffix for month and year (e.g., OHM-A7- 08_MONTHYEAR). The sample identification (ID) for groundwater monitoring wells will be the name of the particular groundwater monitoring well. Duplicate sample IDs will specify the AOC from which the sample was collected without revealing the parent sample ID to the laboratory. Matrix spike (MS)/matrix spike duplicate (MSD) sample IDs will be indicative of the parent sample ID. Examples are listed below:

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Sample Location: Sample ID:

AOC A7 Monitoring Well OHM-A7-08 OHM-A7-08_MONYR

Blind Duplicate from Monitoring Well SUD-A07-014 A7-Dup1

Matrix Spike from Monitoring Well OHM-A7-08 OHM-A7-08_MONYR-MS

Matrix Spike Duplicate from Monitoring Well OHM-A7-08 OHM-A7-08_MONYR-MSD

3.8.2 Quality Assurance/Quality Control Samples

Quality assurance/quality control (QA/QC) samples will be collected during each LTM event.

The following sub sections specify the type and quantity of samples to be collected for QA/QC purposes.

Duplicate Sample

Field duplicate samples will be collected and submitted for analysis in conjunction with all analyses associated with primary field samples. Field duplicates are additional samples subjected to the same collection methods, preparation and analysis as the original sample but are identified with a unique identification number so that they are blind to the laboratory. These samples will be used to evaluate the precision of sample collection, field sample preparation and laboratory analysis. Blind field duplicates will be collected and analyzed at a frequency one per sampling event for all analyses or 10% if more than 10 samples are planned to be collected. The planned locations and numbers of duplicate samples are listed in Table 3-2.

Rinsate Blank

Sampling methods called for in this plan include the use of both dedicated and non-dedicated sampling equipment. Therefore, some gauging or sampling equipment will be used in more than one well and will require decontamination between uses. Rinsate blanks will be prepared and submitted for analysis to determine the potential for cross-contamination from the sampling equipment. Rinsate blanks will be prepared at a frequency of one per LTM event if non-dedicated equipment is used. Rinsate blanks are prepared by decontaminating the field equipment according to the procedure specified in Section 3.9.4.

Trip Blank

Trip blanks will be submitted to the laboratory in conjunction with VOC samples. Trip blanks are used to identify the potential for VOC contamination associated with sample shipment, containers, and storage. Trip blanks are prepared in the laboratory by filling preserved volatile organic analyte (VOA) vials with American Society for Testing and Materials (ASTM) Type II water and shipped to the field with the sample bottles. A set of trip blanks is included in each cooler containing samples for VOC analysis and returned to the laboratory with the environmental samples. The expected number of project trip blanks for the Annex monitoring program is listed in Table 3.2.

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Matrix Spike/Matrix Spike Duplicates

MS/MSD samples will be submitted for the analyses in conjunction with primary field samples.

Results from MS/MSD samples will be used to evaluate the potential for sample matrix interferences versus laboratory analytical errors as well as to assess the accuracy of the analysis.

MS/MSD samples will be collected at a frequency of one per AOC for each analysis. Extra volume will be collected from sample locations for MS/MSD analyses. MS/MSD sample locations are listed in Table 3.2.

3.9 POST-SAMPLING ACTIVITIES

3.9.1 Total Well Depth Measurement

The total depth in each well will be measured and recorded following the collection of groundwater samples. Every effort will be made to minimize the physical disturbance of water in the monitoring wells.