Supplemental Sitewide Groundwater Feasibility Study Middlefield-Ellis-Whisman Superfund Study Area

Transcription

1 PRELIMINARY DRAFT FOR DISCUSSION ONLY Supplemental Sitewide Groundwater Feasibility Study Middlefield-Ellis-Whisman Superfund Study Area Mountain View and Moffett Field, California U.S. Environmental Protection Agency Region 9 June 2012 Prepared by U.S. Environmental Protection Agency Region 9

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3 PRELIMINARY DRAFT FOR DISCUSSION ONLY Contents ACRONYMS AND ABBREVIATIONS... VII 1 INTRODUCTION AND PURPOSE OVERVIEW SITE DESCRIPTION SITE HISTORY ENFORCEMENT ACTIVITIES REMEDIAL ACTIONS Initial Response Action Record of Decision and 1996 Explanation of Significant Differences ROD Amendment to Address Vapor Intrusion Groundwater Progress and Operations GEOLOGY AND HYDROGEOLOGY Regional Geology and Hydrogeology Site Geology and Hydrogeology NATURE AND EXTENT OF CONTAMINATION CONCEPTUAL SITE MODEL SUMMARY OF RISKS FROM SITE CONTAMINATION ENVIRONMENTAL FOOTPRINT ANALYSIS ARARS, RAOS, AND CLEANUP STANDARDS APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS Chemical-Specific ARARs and TBCs Location-Specific ARARs and TBCs Action-Specific ARARs and TBCs REMEDIAL ACTION OBJECTIVES GROUNDWATER CLEANUP STANDARDS AND CHEMICALS OF CONCERN IDENTIFICATION AND SCREENING OF TECHNOLOGIES POTENTIALLY APPLICABLE REMEDIAL TECHNOLOGIES In situ Redox Technologies Extraction, Removal, Treatment and Disposal Technologies Barrier Technologies Monitored Natural Attenuation REMEDIAL TECHNOLOGIES RETAINED DEVELOPMENT OF REMEDIAL ALTERNATIVES ALTERNATIVES FOR EVALUATION COMMON REMEDIAL ALTERNATIVE COMPONENTS Institutional Controls Groundwater Monitoring Slurry Walls Five Year Reviews SFO/ [SUPPLEMNTALFS.DOCX] ES BAO III

4 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Cleanup of C-Zone ALTERNATIVE 1 CURRENT GWET REMEDY ALTERNATIVE 2 OPTIMIZED GWET ALTERNATIVE 3 OPTIMIZED GWET AND MNA ALTERNATIVE 4 TARGETED IN SITU REDOX TREATMENT, OPTIMIZED GWET, AND MNA ALTERNATIVE 5 TARGETED IN SITU REDOX TREATMENT, PRBS, OPTIMIZED GWET, AND MNA CRITERIA FOR IMPLEMENTATION OF MONITORED NATURAL ATTENUATION CLEANUP TIMEFRAMES EVALUATION DETAILED ANALYSIS OF ALTERNATIVES DESCRIPTION OF EVALUATION CRITERIA INDIVIDUAL ANALYSIS OF GROUNDWATER ALTERNATIVES Alternative 1 Current GWET Remedy Alternative 2 Optimized GWET Alternative 3 Optimized GWET and MNA Alternative 4 In situ Redox, Optimized GWET, and MNA Alternative 5 In-situ Redox, PRBs, Optimized GWET, and MNA COMPARATIVE ANALYSIS OF GROUNDWATER ALTERNATIVES Overall Protection of Human Health and the Environment Compliance with ARARs Long-Term Effectiveness and Permanence Reduction of Toxicity, Mobility, or Volume through Treatment Short-Term Effectiveness Implementability Cost State Acceptance Community Acceptance INSTITUTIONAL CONTROLS GOVERNMENT CONTROLS PROPRIETARY CONTROLS ENFORCEMENT TOOLS WITH IC COMPONENTS INFORMATIONAL DEVICES OBJECTIVE, MECHANISM, TIMING, AND RESPONSIBILITY OF ICS DETAILED ANALYSES OF ICS Local Government Controls: Public Health and Safety Ordinances and Permits Proprietary Controls Enforcement Tools with IC Components Informational Devices: Notice of Well Permit Requests from Santa Clara Valley Water District to EPA REFERENCES IV SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

5 PRELIMINARY DRAFT FOR DISCUSSION ONLY CONTENTS FIGURES 1-1 Site Location Map 1-2 MEW Superfund Study Area 1-3 Placeholder 1-4 Areas of Soil Remediation South of U.S. Highway Location of Regional and Source Control Extraction Wells and Groundwater Treatment Systems South of U.S. Highway Location of Regional and Source Control Extractions Wells and Groundwater Treatment Systems North of U.S. Highway TCE Plume in the A/A1 Shallow Aquifer , 2002, and TCE Plume in the B1/A2 Aquifer- 1992, 2002, and TCE Plume in the B2 Aquifer 1992, 2002, and TCE Plume in the B3 Aquifer TCE Plume in the C Aquifer Extent of CVOCs in A/A1 Zone 1-13 Extent of CVOCs in B1/A2 Zone 1-14 Extent of CVOCs in B2 Zone 1-15 Conceptual Site Model 2-1 1,4-Dioxane Concentrations in Groundwater 4-1 Alternative 1 Conceptual Layout A/A1 Zone 4-2 Alternative 1 Conceptual Layout B1/A2 Zone 4-3 Alternative 1 Conceptual Layout B2 Zone 4-4 Alternative 2 Conceptual Layout A/A1 Zone 4-5 Alternative 2 Conceptual Layout B1/A2 Zone 4-6 Alternative 2 Conceptual Layout B2 Zone 4-7 Alternative 3 Conceptual Layout A/A1 Zone 4-8 Alternative 3 Conceptual Layout B1/A2 Zone 4-9 Alternative 3 Conceptual Layout B2 Zone 4-10 Alternative 4 Conceptual Layout A/A1 Zone 4-11 Alternative 4 Conceptual Layout B1/A2 Zone 4-12 Alternative 4 Conceptual Layout B2 Zone 4-13 Alternative 5 Conceptual Layout A/A1 Zone 4-14 Alternative 5 Conceptual Layout B1/A2 Zone 4-15 Alternative 5 Conceptual Layout B2 Zone TABLES 1-1 Summary of Groundwater Extraction and Treatment Systems 2-1 Summary of Chemical, Location and Action-Specific ARARs for the MEW Site 2-2 Chemicals of Concern (COCs) 1989 ROD and ESD 2-3 Updated Chemical of Concerns 3-1 Technology Screening for Groundwater 4-1 Summary of Estimated Groundwater Cleanup Times 4-2 Summary of Projected TCE Reduction in Concentrations 5-1 Comparative Analysis of Alternatives for the A/A1 Zone 5-2 Comparative Analysis of Alternatives for the B1/A2 and Lower Aquifer Zones 5-3 Summary of Remedial Alternative Costs for the A/A1 Zone 5-4 Summary of Remedial Alternative Costs for the B1/A2 and Lower Aquifer Zones SFO/ [SUPPLEMNTALFS.DOCX] ES BAO V

6 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY APPENDICES A Environmental Footprint Calculations for Groundwater Alternatives B Chemicals of Concern Screening Evaluation C Cost Assumptions and Estimates for Remedial Alternatives VI SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

7 Acronyms and Abbreviations PRELIMINARY DRAFT FOR DISCUSSION ONLY AOP ARAR BAAQMD bgs CDPH CERCLA CFR cis-1,2-dce COC CPEO CSM CVOC CWA DNAPL DOT EHC EPA ERH ERD ESD FFA ft/day ft/yr GAC GTE GWET advanced oxidation processes applicable or relevant and appropriate requirement Bay Area Air Quality Management District below ground surface California Department of Public Health Comprehensive Environmental Response, Compensation, and Liability Act of 1980 Code of Federal Regulations cis,1-2,-dichloroethene chemical of concern Center for Public Environmental Oversight conceptual site model chlorinated volatile organic compound Clean Water Act dense, non-aqueous phase liquid U.S. Department of Transportation combination of a carbon substrate and ZVI U.S. Environmental Protection Agency electrical resistive heating enhanced reductive dechlorination explanation of significant differences Federal Facility Agreement feet per day feet per year granular activated carbon GTE Government Systems Corporation groundwater extraction and treatment SFO/ [SUPPLEMNTALFS.DOCX] ES BAO VII

8 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY HLA IC IR ISCO μg/l MCL MEW MNA NAPL NASA NCP NPDES NPL NPV O&M OMB PCE ppb PRB RAO RCRA Harding Lawson Associates institutional control installation restoration in-situ chemical oxidation micrograms per liter maximum contaminant levels Middlefield-Ellis-Whisman monitored natural attenuation non-aqueous phase liquid National Aeronautics and Space Administration National Oil and Hazardous Substance Pollution Contingency Plan National Pollutant Discharge Elimination System National Priorities List net present value operation and maintenance Office of Management and Budget tetrachloroethene parts per billion permeable reactive barrier remedial action objective Resource Conservation and Recovery Act Regional Program Regional Groundwater Remediation Program RI ROD RSL RWQCB remedial investigation record of decision regional screening level Regional Water Quality Control Board SARA Superfund Amendments and Reauthorization Act of 1986 SCVWD Supplemental FS Santa Clara Valley Water District supplemental site-wide groundwater feasibility study VIII SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

9 PRELIMINARY DRAFT FOR DISCUSSION ONLY ACRONYMS AND ABBREVIATIONS SVE SWRCB TBC TCE UV VOC WATS ZVI soil vapor extraction State Water Resources Control Board To Be Considered trichloroethene ultraviolet volatile organic compound West-Side Aquifers Treatment System zero-valent iron SFO/ [SUPPLEMNTALFS.DOCX] ES BAO IX

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11 1 Introduction and Purpose PRELIMINARY DRAFT FOR DISCUSSION ONLY The U.S. Environmental Protection Agency (EPA) Region 9 has prepared this supplemental site-wide groundwater feasibility study (Supplemental FS) to evaluate potential optimizations to the current remedy and alternative technologies that can be used to accelerate groundwater cleanup to meet the remedial action objectives at the Middlefield- Ellis-Whisman (MEW) Superfund Study Area (MEW Site, or the Site) in Mountain View and Moffett Field, California. The current groundwater remedy selected by EPA in its 1989 Record of Decision (1989 ROD), includes groundwater extraction and treatment and slurry walls to contain and treat volatile organic compounds (VOCs), which were released to groundwater from multiple sources beginning in the 1960s. Since the initial operation of the groundwater treatment systems, over 100,000 pounds of VOCs have been removed and treated; but the systems efficiency and effectiveness are decreasing. This Supplemental FS was prepared to address recommendations in EPA s Second Five-Year Review Report (EPA, 2009), which concluded that alternative technologies and optimization of the remedy should be evaluated to address the decreasing efficiency and effectiveness of the groundwater extraction and treatment system and to address vapor intrusion remedial action objective identified in the 2010 Vapor Intrusion ROD Amendment (EPA, 2010). The vapor intrusion remedial action objective that will be addressed in this Supplemental FS is to accelerate the reduction of the source of vapor intrusion (i.e., Site contaminants in shallow groundwater and soil gas) to levels that are protective of current and future building occupants, such that the need for a vapor intrusion remedy would be minimized or no longer be necessary. 1.1 Overview EPA prepared the Supplemental FS pursuant to the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA), 42 U.S.C., Section 9601 et. Seq., and the National Oil and Hazardous Substance Pollution Contingency Plan (NCP), and 40 Code of Federal Regulations (CFR), Part 300. Development of the Supplemental FS and evaluation of remedial alternatives are based on the guidelines set forth in the Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA (EPA, 1988). Site Remedial Investigation and Feasibility Study Reports for soil and groundwater were prepared in 1987 and 1988 (HLA, 1988; Canonie, 1988) and for the Vapor Intrusion Pathway in 2009 (Haley and Aldrich, 2009a, 2009b). The human health and ecological risks were evaluated in the 1988 Endangerment Assessment (ICF-Clement, 1988). Therefore, EPA is not reevaluating human health or ecological risk as part of this Groundwater Supplemental FS. The remedial action objectives are identified in the 1989 ROD and the 2010 Vapor Intrusion ROD Amendment. The focus of the Supplemental FS is to screen, evaluate, and assemble technologies into remedial alternatives that can be used to accelerate groundwater cleanup to reach remedial action objectives. SFO/ [SUPPLEMNTALFS.DOCX] 1-1 ES BAO

12 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY EPA considered the following reports, studies, and stakeholder input in development and evaluation of the alternatives in the Supplemental FS: 1) Annual Groundwater Progress Reports, which discuss the performance and operation of the groundwater extraction and treatment system each year. 2) 2008 Optimization Evaluation Reports, which evaluated changes that could be implemented to the current groundwater remedy and potential alternative technologies to cleanup groundwater. 3) 2009 Five-Year Review Report, which evaluated the remedy progress and whether it continues to be protective of human health and the environment. 4) Results of pilot tests conducted in various areas of the plume to evaluate alternative technologies to cleanup groundwater. 5) Community Criteria and Suggestion Strategy for the MEW-Moffett Plume, prepared in April 2011 by Center for Public Environmental Oversight (CPEO) with input from the community, which recommended areas of the plume for EPA to focus cleanup as well as alternatives to evaluate. 6) Other stakeholder input received at community and stakeholder meetings. 1.2 Site Description The MEW Site is located in Mountain View and Moffett Field, California, and includes four National Priorities List (NPL) sites: Fairchild Semiconductor - Mountain View Site (EPA ID: CAD ); Intel Corporation - Mountain View Site (EPA ID: CAD ); Raytheon Company Site (EPA ID: CAD ), and portions of the NAS Moffett Field NPL Site (EPA ID: CA ). During the 1960s and 1970s, VOCs (primarily trichloroethene [TCE]) were released from several manufacturing facilities in the area south of U.S. Highway 101 (hereinafter, referred to as the MEW Area ) and subsequently impacted the soil and groundwater. The groundwater contamination migrated northward and commingled with U.S. Navy and National Aeronautics and Space Administration (NASA) sources at the former NAS Moffett Field (referred to hereinafter to as the Moffett Field Area ). The combined area of contamination is referred to as the regional groundwater contamination plume. Figure 1-1 shows the site location within the San Francisco Bay Area. Figure 1-2 shows the MEW Area, the Moffett Field Area and the regional shallow groundwater contamination plume based on TCE concentrations. The regional groundwater contamination plume is approximately 1.5 miles long with an average width of 2,000 feet. The MEW Area is currently zoned for commercial, light-industrial, and residential uses. The area bounded within Middlefield Road, Ellis Street, and Whisman Road is occupied by several office buildings and businesses and is primarily non-residential/commercial. The area west of Whisman Road is primarily residential. The Moffett Field Area overlies NASA Ames Research Center, the NASA Research Park and portions of the Wescoat Village housing area. Future land use within this area is described 1-2 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

13 PRELIMINARY DRAFT FOR DISCUSSION ONLY 1 INTRODUCTION AND PURPOSE in NASA s Development Plan (NASA Ames, 2002). Plans for NASA Research Park include: new educational, office, research and development, museum, conference center, housing, and retail spaces. The NASA Ames Research Center also has plans to redevelop unimproved land at Moffett Field into sustainable research facilities including office, recreational, and living spaces (NASA Ames, 2002, and Google Press Center, 2008). 1.3 Site History Historically, the MEW Area was used for agricultural purposes including orchards, row crops, and greenhouse gardening. In the 1960s, commercial development began in the area with light-industrial facilities. Several facilities operated in the area from the 1960s to the 1990s including semiconductor, electronics manufacturing, and metal finishing companies. These companies used solvents, primarily TCE, in operations, which were released to the subsurface from leaks in tanks and piping or during handling at the facilities. Since the 1990s, major redevelopment and reuse has occurred in the MEW Area. The current property owners and tenants in the MEW Area were not operating at the time of the contaminant releases to the environment and are not directly involved with the investigation and cleanup activities in the MEW Area. The Moffett Field Area was owned and operated by the U.S. Navy from the 1930s until July 1994 when most of the property was transferred to NASA. The Moffett Community Housing Areas, including the Wescoat Housing area, were transferred from the U.S. Navy to the U.S. Air Force in 1994 and then to the U.S. Army in During historic operations in the Moffett Field Area, chemicals including TCE and PCE used during dry cleaning, maintenance, and fuel operation activities were released, contributing to the soil and groundwater contamination. 1.4 Enforcement Activities The investigation and cleanup at the MEW Site is being conducted under several different enforcement documents as described below. EPA is the lead agency responsible for directing the cleanup process under CERCLA for the MEW Site. The San Francisco Bay Regional Water Quality Control Board (Water Board) is the support regulatory agency for the NAS Moffett Field site. The parties conducting the cleanup in the MEW Area also referred to as the MEW Companies no longer own or operate any facilities in the MEW Area. The MEW Companies are conducting investigation and cleanup activities required by the 1989 ROD under a 1990 Unilateral Administrative Order and a 1991 Consent Decree. Each MEW company is responsible for the investigation, cleanup, and source control of soil and groundwater contamination at its individual facility-specific property. The facility-specific areas of responsibility are shown on Figure 1-2. The MEW Regional Groundwater Remediation Program (Regional Program) is responsible for cleanup of the regional groundwater contamination plume that is not being captured by the individual facility-specific source control systems or that has not been attributed to a specific source area. The Regional Program, Navy, and NASA are together cleaning up the regional groundwater contamination plume north of the U.S. Highway 101 on Moffett Field, SFO/ [SUPPLEMNTALFS.DOCX] 1-3 ES BAO

14 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY except for a portion of the groundwater contamination referred to as the West-Side Aquifers Treatment System (WATS) area, which is being addressed solely by the U.S. Navy. On November 29, 1990, EPA issued a Section 106 Unilateral Administrative Order (106 Order) for Remedial Design and Remedial Action (RD/RA) to the following PRPs: Fairchild Semiconductor Corporation, Schlumberger Technology Corporation, National Semiconductor Corporation, NEC Electronics, Inc., Siltec Corporation, Sobrato Development Companies, General Instrument Corporation, Tracor X-Ray, Inc., and Union Carbide Chemicals and Plastic Company Inc. The 106 Order requires those companies to develop and implement soil and groundwater source control remedies at their individual facilities; implement potential conduit, plume definition, groundwater chemistry, and water reuse programs; and perform future operation and maintenance of the MEW Regional Groundwater Remediation Program following its construction by the Consent Decree Companies (EPA, 1990b). On April 10, 1991, EPA entered into a Consent Decree with two PRPs, Raytheon and Intel (Consent Decree Companies), that requires the Consent Decree Companies to design, construct, and operate their individual facility-specific source control soil and groundwater remediation systems and to design and construct the MEW Regional Groundwater Remediation Program system (U.S. District Court, 1991). EPA, the State of California, and the Navy entered into a Federal Facility Agreement (FFA) in September 1990 to address contamination at NAS Moffett Field. A December 1993 FFA Amendment specifies that the Navy agrees to adopt the MEW ROD and to remediate source control removal areas of FFA Attachments 4 and 5 [to the 1993 FFA Amendment] in accordance with the MEW ROD for contamination attributable to Navy Sources. The amendment further specifies that the Navy agrees to remediate, in accordance with the MEW ROD, those source areas of contamination, identified following the effective date of the FFA Amendment, that the Parties agree are the responsibility of the Navy (U.S. Navy, 1993). In addition, as part of the transfer of NAS Moffett Field to NASA, a Memorandum of Understanding between the Navy and NASA was signed, which requires the Navy to remediate contamination resulting from Navy operations (Navy and NASA, 1992). 1.5 Remedial Actions A description of remedial actions, record of decisions and groundwater operation at the MEW site is provided below Initial Response Action Fairchild, Raytheon, and Intel implemented source control measures in the 1980s before the final remedy was selected in 1989, as outlined below. 1-4 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

15 PRELIMINARY DRAFT FOR DISCUSSION ONLY 1 INTRODUCTION AND PURPOSE Facility Date Source Control Measures Fairchild 1982 Installation and operation of extraction wells Installation and operation of extraction wells and three air stripping towers 1986 Installation of three 40-feet deep underground slurry walls around each of Fairchild s former properties to physically contain on-site chemicals in the A Aquifer Raytheon 1986 Installation and operation of extraction wells 1987 Installation of an approximately 3,400-foot-long, 100-foot-deep slurry wall around Raytheon s 350 Ellis Property to contain chemicals in the A and B1 Aquifers Intel 1982 Installation and operation of one source area extraction well screened across the A and B1 Aquifer 1984 Excavation in source area of 4,000 cubic yards of soil 1985 Installation and operation of three A Aquifer Wells and one B1 Aquifer extraction well Navy (WATS Area) 1987 Closure of dry-cleaning facility, Building 88; removal of Tank 67 and sump in Record of Decision In June 1989, EPA selected the Site s soil and groundwater remedy in the 1989 ROD. The remedy selected in the 1989 ROD includes the following activities: Soil In situ soil vapor extraction (SVE) with treatment by vapor-phase granular activated carbon (GAC) and/or soil excavation with treatment by aeration. Groundwater Maintaining inward and upward hydraulic gradients by pumping inside the existing slurry walls and regular monitoring of aquifers within and adjacent to the slurry walls to monitor the integrity of each slurry wall system. Hydraulic remediation by groundwater extraction and treatment using air-stripping towers or pre-existing liquid-phase GAC at operating treatment systems. Identification and sealing of any potential conduit wells. Reuse of extracted groundwater to the maximum extent feasible, with 100 percent reuse as a goal. The soil cleanup in the MEW Area south of Highway 101 was completed in 2001 (Figure 1-4). Several abandoned agricultural wells that acted as potential conduits for migration of contamination from the shallow aquifer to the deeper aquifers were sealed in the 1980s. SFO/ [SUPPLEMNTALFS.DOCX] 1-5 ES BAO

16 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Several potential conduit studies were conducted in the 1990s, and all identified wells and potential conduits were sealed and 1996 Explanation of Significant Differences EPA issued an Explanation of Significant Differences (ESD) in September 1990, clarifying that the cleanup goals established in the 1989 ROD are the Site cleanup standards (EPA, 1990). Also, the ESD clarified that, although TCE is being used as an indicator compound, the 1989 ROD requires cleanup of the other chemicals of concern (COCs) listed in the ROD to their respective cleanup standards. The Site COCs and cleanup standards are discussed in Section 2.3. A second ESD was issued in 1996 (EPA, 1996) clarifying that liquid phase activated carbon could also be used to treat contaminants directly from the groundwater extraction and treatment systems ROD Amendment to Address Vapor Intrusion EPA amended the 1989 ROD in August 2010 to select a remedy to address the potential long-term exposure risks from TCE and other Site COCs through the vapor intrusion pathway at the MEW Site. This vapor intrusion pathway was not addressed in the 1989 ROD. The objective of the vapor intrusion remedy is to protect the health of current and future occupants, including workers and residents, of buildings overlying the Site s shallow subsurface VOC contamination. The remedy to address the vapor intrusion pathway and ensure protection of human health of building occupants in the Vapor Intrusion Study Area consists of the installation of appropriate sub-slab ventilation systems in existing and future buildings based on indoor air sampling and other lines of evidence, along with implementation of institutional controls (IC) and monitoring. The Vapor Intrusion Study Area is generally defined as the area where TCE concentrations in shallow groundwater are greater than 5 ug/l. The 2010 ROD Amendment established a remedial action objective (RAO) for the groundwater remedy: Accelerate the reduction of the source of vapor intrusion (i.e., Site contaminants in shallow groundwater and soil gas) to levels that are protective of current and future building occupants, such that the need for a vapor intrusion remedy would be minimized or no longer be necessary. This RAO ( Vapor Intrusion RAO ) is incorporated into this Supplemental FS along with the RAOs in the 1989 ROD. All of the RAOs addressed in the Supplemental FS are discussed in Section Groundwater Progress and Operations There are 12 groundwater extraction and treatment systems operating within the plume. The locations of the systems are shown on Figures 1-5 and 1-6 and are described in Table 1-1 below. 1-6 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

17 PRELIMINARY DRAFT FOR DISCUSSION ONLY 1 INTRODUCTION AND PURPOSE TABLE 1-1 Groundwater Extraction and Treatment System Summary Facility Extraction Wells Average Flow Rate (gallons per minute) Pounds of VOCs Removed in 2010 Ex-Situ Treatment Discharge Location Fairchild (System 1) GAC Stevens Creek Fairchild (System 3) GAC Stevens Creek Fairchild (System 19) GAC Stevens Creek Raytheon Oxidation/GAC Stevens Creek Intel* N/A N/A N/A Bioremediation N/A SMI GAC Stevens Creek NEC/ Renesas Vishay/SUMCO None (formerly GAC) UV/oxidation/ air stripper Sanitary Sewer Stevens Creek MEW Regional Program S GAC Stevens Creek MEW Regional Program N Air stripper/ vaporphase GAC Stevens Creek Navy WATS Oxidation/GAC Moffett storm drain system NASA Ames GAC Stevens Creek TOTAL Notes: GAC Granular activated carbon (liquid-phase GAC, unless otherwise noted) UV Ultraviolet light * Groundwater extraction at the Intel facility was suspended in August 2005 with EPA approval so that an enhanced in situ bioremediation pilot test could be performed. The groundwater extraction and treatment systems have removed over 100,000 pounds of VOCs through 2011 and treated over 5 billion gallons of contaminated groundwater. The reduction in TCE concentrations within the plume over time within the A1 Aquifer, B1/A1 Aquifer, and B2 Aquifer are shown on Figures 1-7, 1-8 and 1-9. As discussed in Section 1.5, each of the MEW Companies operate and maintain individual facility-specific source control groundwater measures (such as extraction wells and slurry walls) to contain and clean up contamination source areas in each area for which that MEW Company is responsible. The MEW Regional Program is responsible for areas of the plume not attributed to a facility and has been operating two systems since 1998 one in the MEW Area and one in the Moffett Field Area. SFO/ [SUPPLEMNTALFS.DOCX] 1-7 ES BAO

18 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY In the Moffett Field Area, the Navy and NASA have each been operating its own groundwater extraction and treatment system since 1998 and 2001, respectively. The Navy s groundwater extraction and treatment system is referred to as WATS. One additional pump and treat system was installed in 1996 and operated until 2001 in the deeper aquifers to address localized contamination near a former agricultural well (Silva Well) west of Whisman Road and south of U.S. Highway 101. The Silva Well was a suspected vertical conduit (Smith, 1996) screened across multiple aquifers. Two extraction wells (RW-13B1 and RW-1C) and three monitoring wells were installed near the Silva Well. The effluent from the extraction wells was piped to a sanitary sewer connection along Tyrella Avenue under the City of Mountain View Liquid Discharge Waste Discharge Permit No. 916 (Smith, 1996). Because the concentrations of chemicals in the groundwater were below the discharge limits for the sanitary sewer, treatment was not required prior to discharge. Additional details regarding the system are discussed in the 2009 Five-Year Review Report (EPA, 2009). Various technologies as shown in Table 1-1 are used to treat groundwater extracted by the facilities and within the regional plume. Air strippers were originally used from 1986 to Treated effluent from the systems is discharged to Stevens Creek, with the few exceptions noted in Table 1-1. Some of the treated groundwater from the RGRP system is reused for cooling water at the NASA facility. During 2010, approximately, 1.1 million gallons of treated water were reused. NASA has submitted a Notice of Intent to the Water Board for an NPDES discharge permit to facilitate plans to expand treated water reuse in the future. In addition to the groundwater extraction and treatment system used to contain the groundwater plume, four low-permeability slurry walls were installed at the site to prevent contaminant migration (Figure 1-2). The slurry walls have generally been successful at preventing contaminant migration. However, there has been difficulty consistently maintaining inward and upward gradients within the slurry walls, which was a requirement of the 1989 ROD. Inward and upward gradients help ensure contaminants do not migrate through the slurry wall. In some cases, extraction wells have been installed downgradient of slurry walls to contain potential migration of contaminants through the slurry walls and source areas. The wells are designed to provide hydraulic capture around the perimeter of the slurry wall and source areas. Based on the annual capture zone analyses, the slurry walls appear to be achieving their objective. However, the operation of these exterior extraction wells outside and below the slurry walls result in drawdown outside the slurry walls, which works against the objective of the inward and upward gradient. As discussed in Section 1.1, the groundwater remedial actions conducted at each of the individual facilities and the Regional Program are described in detail within the First Five-Year Review Report (EPA, 2004a) and the Second Five-Year Review Report (EPA, 2009). In addition, groundwater operations are documented in annual reports by individual MEW Companies, Navy, NASA, and the Regional Program. 1-8 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

19 PRELIMINARY DRAFT FOR DISCUSSION ONLY 1 INTRODUCTION AND PURPOSE 1.6 Geology and Hydrogeology Regional Geology and Hydrogeology The MEW Site is located in the Santa Clara Valley, a large structural depression in the Central Coastal Ranges of California, bounded by the Diablo Range on the east and the Santa Cruz Mountains on the west. Valley fill is up to 1,500 feet thick, comprised of alluvial sediments derived from flanking highlands that were deposited by valley streams during the past several hundred thousand years. The alluvial deposits are gravel, sand, silt, and clay, mixed or interbedded laterally and vertically. The alluvium is generally coarser in the upland areas, grading downstream to finer materials. The Santa Clara Valley Groundwater Subbasin is the northern-most of the three interconnected groundwater basins within Santa Clara County (Santa Clara Valley Water District [SCVWD], 2001). The Santa Clara Valley Groundwater Subbasin is comprised of three general hydrostratigraphic units: (1) the elevated (forebay) margins, where recharge occurs, and (2) the upper and (3) lower aquifer zones in the flatter subbasin interior, where the aquifers are stratified and separated by significant aquitards (SCVWD, 1989). The general groundwater flow gradient is from the edges of the subbasin toward San Francisco Bay, generally in the direction of the ground slope to the north. Groundwater in the southern area and margins of the subbasin is unconfined (SCVWD, 2005). The division between the upper and lower aquifer zones is an extensive regional aquitard that is present in the northern areas of the subbasin at depths ranging from about 100 feet below ground surface (bgs) near the margins to about 150 to 250 feet bgs in the northern interior portion of the subbasin and beneath San Francisco Bay. Thickness of the aquitard varies from 20 feet to more than 100 feet. Groundwater in the upper aquifer zone is either unconfined or confined by leaky or competent aquitards. Groundwater in the lower aquifer zone occurs below the regional aquitard under confined conditions Site Geology and Hydrogeology Groundwater aquifers within the MEW Site consist of shallow and deeper aquifer systems, which are separated by a laterally extensive aquitard approximately 40 feet thick. South of U.S. Highway 101 the shallow aquifer system is generally less than 160 feet bgs, and north of U.S. Highway 101 the shallow aquifer system is generally less than 100 feet bgs. Subdivisions within the shallow aquifer have been designated A/A1, B1/A2, B2 and B3 as specified on the table below. The aquitard separating the A and B1 Aquifers is the A/B Aquitard. The A/B Aquitard appears to be laterally continuous across the study area south of U.S. Highway 101, but may be discontinuous north of the highway (TetraTech FW, 2005). The regional aquitard is designated the B/C Aquitard, and separates the B and C Aquifers. The zones below the B/C Aquitard are termed the C Aquifer and the Deeper Aquifers. Geologic cross sections showing the complex stratigraphy of the MEW Site and the designation of aquifer zones are provided in the RI (HLA, 1988). The aquifer zones are generally comprised of lenses and channels of sandy material interconnected to some degree and separated laterally and vertically by fine-grained units. Depth to groundwater is generally 10 to 20 feet bgs in the MEW Area and 1 to 10 feet bgs in the Moffett Field Area. SFO/ [SUPPLEMNTALFS.DOCX] 1-9 ES BAO

20 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Groundwater flow in the shallow aquifer zone is generally to the north, while groundwater flow in the C and Deeper Aquifers is generally to the northeast. Aquifer Depths by Zone Zone A or A1 or Upper A (a) B1 or A2 or Lower A (b) B2 B3 C Deeper Aquifers Approximate Depth Interval Below Ground Surface 0 to 45 feet 50 to 75 feet 75 to 110 feet 120 to 160 feet 200 to 240 feet > 240 feet (a) MEW Companies refer to this aquifer as A both south and north of Highway 101. North of Highway 101, NASA refers to it as A1 and Navy refers to it as Upper A. (b) MEW Companies refer to this aquifer as B1 both south and north of Highway 101. North of Highway 101, NASA refers to it as A2 and Navy refers to it as Lower A. Although the direction of groundwater flow at the MEW Site is generally to the north, the construction of underground slurry walls and operation of groundwater extraction wells have altered the direction of groundwater flow in certain locations (for example, the groundwater may flow to the west or east around slurry walls). Vertical gradients between the A and B1 Zones are generally upward, although downward gradients have been observed in localized areas including the northwestern portion of the regional plume, the area east of the northern Fairchild slurry wall, and within portions of the Raytheon slurry wall. Results for pumping tests conducted for the 1987 RI indicated that the A/B1 Aquitard restricts vertical flow between the A and B1 Zones, but does not completely prevent hydraulic communication between the two zones in all locations. In the WATS area of Moffett Field, the A/B1 Aquitard is not present and the A and B1 Zones form a single hydrostratigraphic unit. Additional pumping test results have shown that the B1/B2 Aquitard is leaky and that there is localized hydraulic communication between the B1 and B2 Zones (Geomatrix, 2004; HLA, 1988). Data collected during the 1987 RI (HLA, 1988) indicate that a downward hydraulic gradient existed at times across the regional B/C Aquitard. However, groundwater elevation data collected by the MEW Regional Program indicate that an upward gradient has been observed since the early 1980s (Geosyntec, 2008). B3 and C Zone VOC impacts have not been positively correlated, except where the two zones were connected by a vertical conduit (for example, the former Rezendes agricultural wells near the location of DW3 wells) (HLA, 1988). Several pumping tests have been performed to estimate aquifer parameters such as transmissivity and hydraulic conductivity (Northgate, 2008). The estimated ranges of hydraulic conductivity, horizontal gradient, saturated thickness, and transmissivity for the A Zone and B Zones is summarized below. Groundwater transmissivity is greatest in the A and B1 zones of the shallow aquifer. Based on the ranges below and an assumed effective porosity of 0.25, groundwater velocity within the A Zone is estimated to be between 35 and 2,800 feet per year (ft/yr), and groundwater velocity within the B 1 Zone is estimated to be 1-10 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

21 PRELIMINARY DRAFT FOR DISCUSSION ONLY 1 INTRODUCTION AND PURPOSE between 90 and 1,100 ft/yr. Other site-specific evaluations have identified slower groundwater velocities, such as approximately 60 feet per year for the A and B Zones at the Intel site (Weiss, 1995). Water Bearing Zone Estimated Hydraulic Conductivity Approximate Horizontal Gradient Saturated Thickness (ft) Transmissivity (ft 2 /day) Low High Low High A-zone ,400 B1-zone ,600 B2-zone to B3-zone to Nature and Extent of Contamination Groundwater contamination at the MEW Site has generally been defined by the extent of TCE contamination. The Vapor Intrusion Study Area is generally defined as the area where TCE concentrations in shallow groundwater (A/A1 Zone) are greater than 5 g/l, or parts per billion (ppb). The estimated extent of TCE in shallow groundwater and the Vapor Intrusion Study Area are shown in Figure 1-2. The maximum concentrations of TCE have been found in the A, B1, and B2 Zones, with limited presence in the B3 and C Zones and the Deep Aquifer. Changes in TCE concentrations since 1992, when the original plume definition program was completed, are shown on Figures 1-7 through 1-9. TCE concentrations in the B3 zone are now near or below cleanup levels (Figure 1-10) and TCE concentrations in the C Zone and deeper range from below cleanup levels to approximately 28 μg/l and have decreased over time (Figure 1-11). In addition to TCE, other chlorinated VOCs (CVOCs) are present in Site groundwater. The distribution of four CVOCs (TCE, tetrachloroethene [PCE], cis,1-2,-dichloroethene [cis-1,2-dce], and vinyl chloride) in the A/A1, B1/A2, and B2 Zones are provided in Figures 1-12 through These CVOCs were evaluated since they are either primary chlorinated solvents identified at the site (TCE and PCE) or are primary degradations products of these chemicals (1,2-DCE and vinyl chloride). The extent of CVOCs is primarily determined by the distribution of TCE and cis-1,2-dce, with PCE and vinyl chloride present in limited locations. Details about the presence of individual CVOCs can be found in the facility-specific annual reports. Dense, non-aqueous phase liquid (DNAPL) is suspected to be present at the Site but has not been directly observed in any samples collected at the Site. Groundwater samples in the vicinity of originally suspected source areas had TCE concentrations greater than one percent of TCE s theoretical solubility limit, which is an indication of the likely presence of DNAPL (Cherry and Fienstra, 1991). For TCE, this translates to approximately 10,000 μg/l. Although areas of TCE greater than 10,000 μg/l have been significantly reduced over time, concentrations still remain greater than 10,000 μg/l within the A/A1 Zone in the vicinity of the former Vishay/SUMCO facility and within portions of the Raytheon slurry wall (see SFO/ [SUPPLEMNTALFS.DOCX] 1-11 ES BAO

22 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Figures 1-7, 1-8, 1-9 and 1-10). PCE also has been detected recently at concentrations greater than one percent of its solubility limit (2,000 μg/l) in the Navy WATS Area (Site 28) (Navy, 2011; Figure 2-14). However, the Navy s subsequent investigation in 2011 to further characterize the area including testing for DNAPL did not indicate the presence of DNAPL (Navy 2012). 1,4-dioxane, an emerging chemical, was detected in influent and effluent samples collected from groundwater extraction and treatment systems at the Site in early ,4-dioxane sampling results are discussed in Section Conceptual Site Model The conceptual site model for the regional groundwater contamination plume is shown on Figure From the 1960s to the 1980s, facilities used chlorinated solvents, primarily TCE, which were released from tanks and piping that leaked or were spilled. Once released, these solvents migrated downward through the soil to the groundwater table. Chlorinated solvents are a DNAPL and, being denser than water, they continued to migrate downward below the water table. As the solvents migrated below the water table, they dissolved into groundwater and migrated with groundwater flow by advection within the higher permeability zones (transmissive zones). The solvents continued downward, filling pore spaces and sorbing to silt and clay lenses, until one or more lower permeability layers impeded further migration. At this point, the solvents either slowly dissolved into groundwater, diffused into the low permeability layers, or (in the case of large solvent volume) may have flowed laterally along the low permeability layer until able to continue migrating downward. Diffusion into low permeability silt and clay occurred because of the concentration gradient between high concentrations surrounding the silt and clay and low (originally zero) concentrations within the silt or clay. The MEW Companies completed the soil cleanup of identified source areas in the vadose zone (above the groundwater table) in 2001 (Figure 1-4). Operation of the groundwater extraction and treatment systems for over 20 years has extracted dissolved solvents from the transmissive zones. As groundwater extraction and treatment lowered dissolved concentrations in the transmissive zones, the concentration gradient surrounding some low permeability zones has been reversed, leading to diffusion back out from the silts and clays into the transmissive zones. The process of back-diffusion from silts and clays into the transmissive zones is termed the matrix diffusion effect. The matrix diffusion effect is a slow process and, depending on the quantity of solvents originally sorbed into the low permeability zones, can be a long-term source of low concentrations of dissolved solvents within the transmissive zones. Chlorinated solvents released to groundwater have been removed by natural processes in addition to physical removal by groundwater extraction and treatment. These natural processes include reductive dechlorination and aerobic degradation, which can generally be attributed to activity by subsurface microorganisms or natural chemical interactions. The groundwater plume observed today is the result of the general fate and transport processes described above SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

23 PRELIMINARY DRAFT FOR DISCUSSION ONLY 1 INTRODUCTION AND PURPOSE Exposure pathways at the Site are discussed below in Section Summary of Risks from Site Contamination While groundwater at the Site is not currently used for drinking water or other domestic purposes, cleanup actions are being taken at the Site to restore groundwater to its potential beneficial use as a potable drinking water source. A baseline human health risk assessment for the MEW Site is summarized in the 1988 Endangerment Assessment for the Middlefield-Ellis- Whisman Site in Mountain View, California (ICF-Clement, 1988). The exposure pathways that were evaluated in the Endangerment Assessment used exposure assumptions that were considered appropriate in evaluating risk at that time. The Endangerment Assessment evaluated the potential for future exposure to contamination if the groundwater and its contaminant sources were left untreated and if that water was used for domestic purposes (for example, drinking, showering, and washing). The Endangerment Assessment concluded that potential exposure to Site contaminants through the inhalation pathway presented negligible risks. Therefore, no RAOs to address the subsurface vapor intrusion pathway were identified at that time. However, EPA determined that the vapor intrusion response actions selected in the 2010 ROD Amendment were necessary to protect the public health of building occupants in the Vapor Intrusion Study Area from actual or threatened releases of hazardous substances into the environment via the subsurface vapor intrusion pathway. EPA established indoor air cleanup standards for TCE and the Site COCs based on Site-specific factors and chronic exposure. Currently, potential exposure pathways at the MEW Site include direct exposure to impacted saturated soil during earth-moving (dermal contact, ingestion, or inhalation of impacted particulates), direct exposure to impacted groundwater during earth-moving (dermal contact, ingestion, or inhalation of volatilized VOCs) or through its use as domestic, agricultural, and/or industrial supply (ingestion, dermal contact, or inhalation of volatilized VOCs), discharge of impacted groundwater to surface water, and VOC vapor intrusion into structures overlying impacted soil or groundwater (Figure 1-15). Of these, the only potentially complete exposure pathway is vapor intrusion pathway, which is being addressed by the vapor intrusion remedy described in the 2010 ROD Amendment (EPA, 2010). Other pathways are currently incomplete, but could potentially become complete in the future if conditions change. Since the remedy was implemented, the Chemical of Concern (COC) list has been reevaluated and updated. Several COCs are no longer a concern because of infrequent low detections. One new COC (1,4-dioxane) was identified. COCs are discussed in more detail in Section 2.3 In September 2011, EPA issued a Final TCE Toxicological Assessment, which includes cancer risk and non-cancer toxicity values for TCE ( While the TCE toxicity values have been updated, the TCE groundwater cleanup level of 5 ug/l, the maximum contaminant level (MCL) for drinking water, is still considered health protective and meets current ARARs. SFO/ [SUPPLEMNTALFS.DOCX] 1-13 ES BAO

24 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY 1.10 Environmental Footprint Analysis An environmental footprint analysis was conducted in accordance with the Greener Cleanups Policy, EPA Region 9 (EPA, 2009) for each of the alternatives. This footprint analysis is based on EPA s draft methodology for Understanding and Reducing a Project s Environmental Footprint (EPA 2011) and represents the sum of environmental impacts of each of the alternatives using the following metrics: the quantity of water, materials, and energy used; air emissions; and waste generated. The purpose of the footprint analysis is to consider the environmental impact of an alternative and potentially reduce its footprint. It is important to note that any remedy selected must still meet all the requirements of the NCP, which includes selecting remedies that are protective of human health and the environment. The results of the footprint analysis are presented in detail in Appendix A, and are discussed in Section SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

25 PRELIMINARY DRAFT FOR DISCUSSION ONLY 2 ARARs, RAOs, and Cleanup Standards This section describes the applicable or relevant and appropriate requirements (ARARs), RAOs, and cleanup standards that apply to the groundwater cleanup remedy at the MEW Site. A summary of these ARARs is presented in Table Applicable or Relevant and Appropriate Requirements Section 121(d) of CERCLA requires that remedial actions at Superfund sites achieve (or justify the waiver of) any state and federal environmental standards, requirements, criteria, or limitations that are determined to be legally applicable or relevant and appropriate. This section identifies ARARs affecting the groundwater remedy at the Site. ARARs for the current groundwater remedy were identified in the 1989 ROD. ARARs are the substantive standards, controls, and provisions that apply to the hazardous substances, remedial action being taken, location, or other site circumstance (applicable requirements) as well as those standards, controls, or provisions that are not necessarily applicable to specific site activities but address similar circumstances that will be encountered at the site (relevant and appropriate requirements). Federal ARARs can be requirements under any federal environmental law. State ARARs are those environmental requirements that are more stringent or broader in scope than federal requirements. In those cases where California state law delegates enforcement authority to local agencies that develop and implement state requirements, local regulations may also be ARARs. Requirements that are not federal or state requirements, are not environmental in nature, and are not substantive are not ARARs. However, these requirements may still be applied to activities at the Site by the relevant regulating authority. An ARAR may be either applicable or relevant and appropriate but not both. If there is not a specific federal or state ARAR related to a remedial action, compliance with the ARAR is found to be technically impracticable, or if the existing ARARs are not considered sufficiently protective, then other criteria or guidelines may be identified to ensure the protection of public health and the environment. To Be Considered (TBC) information is nonpromulgated criteria, advisories, guidance, and proposed standards that have been issued by the federal or state government. TBCs are not legally binding and do not have the status of potential ARARs, but they may be useful for determining the necessary level of cleanup for protection of human health and/or the environment. ARARs fall into three categories: chemical-specific, location-specific, and action-specific ARARs. Chemical-specific ARARs are restrictions on the mass or concentration of chemicals remaining in, or discharged to, a given media. Location-specific ARARs are restrictions on certain types of activities based on characteristics of the site locale. Action-specific ARARs govern particular activities or technologies involved in a remedy. SFO/ [SUPPLEMNTALFS.DOCX] 2-1 ES BAO

26 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Chemical-Specific ARARs and TBCs Chemical-specific ARARs include federal and state drinking water standards or maximum contaminant levels (MCLs). The MCLs include concentration-based limits for certain contaminants that ensure the quality of public drinking water supplies. A list of federal and state MCLs for the MEW COCs is presented in Section 2.3. State Water Resources Control Board (SWRCB) Resolution (Anti-degradation Policy): This resolution requires the continued maintenance of high-quality for waters of the State. Water may not be degraded below conditions necessary to protect the beneficial uses of the water source. The Site s groundwater beneficial uses of groundwater are identified in the San Francisco Bay Regional Water Quality Control Board s (Water Board s) Basin Plan. SWRCB Resolution is potentially applicable. SWRCB Resolution 92-49, III-G: In order to maintain high-quality waters of the state, this resolution requires clean-up that abates the effects of discharges so that receiving waters attain either background water quality or the best water quality, whichever is reasonable. SWRCB Resolution No , III-G is potentially relevant and appropriate. San Francisco Bay RWQCB Basin Plan (Basin Plan): The State of California established water quality objectives for the protection of groundwater and surface water under the Porter-Cologne Water Quality Control Act, and specific water quality objectives are established at the regional board level. In the Site area, the Water Board establishes these water quality objectives in its Basin Plan. The Basin Plan, latest amended on December 31, 2010, established the beneficial use for groundwater in this area as drinking water. Accordingly, the Basin Plan requires that [a[ll groundwater shall be maintained free of organic and inorganic chemical constituents in concentrations that adversely affect beneficial uses. At a minimum, groundwater designated for use as a domestic or municipal supply shall not contain concentrations in excess of the maximum (MCLs) or secondary maximum contaminant levels. The substantive provisions of the Basin Plan, Chapters II and III are potentially applicable. California Department of Public Health (CDPH) Notification Levels: The California Department of Public Health (CDPH) has established chemical notification levels. Notification levels are health-based advisory levels for chemicals found in drinking water that do not have MCLs promulgated under the California Health and Safety Code (a). CDPH requires water purveyors to notify consumers and report to CDPH and local governmental agencies if treated water exceeding the notification level is delivered to the consumer. Because the concentrations are notification advisory levels, they are procedural and thus are not ARARs. However, notification levels can be used to help develop risk-based requirements for the Site, so may be TBCs. CDPH currently has notification levels for 30 chemicals; the notification level for 1,4-dioxane is 1 g/l Location-Specific ARARs and TBCs No location-specific ARARs and TBCs were identified. 2-2 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

27 2.1.3 Action-Specific ARARs and TBCs PRELIMINARY DRAFT FOR DISCUSSION ONLY 2 ARARS, RAOS, AND CLEANUP STANDARDS Action-specific ARARs are requirements for the activities undertaken as part of the remedial action. The potential action-specific ARARs associated with the MEW groundwater remedy are described below and summarized in Table Excavation, Treatment and Disposal of Soil The Resource Conservation and Recovery Act (RCRA) requirements, as established at 22 CCR, are applicable if the waste is a hazardous waste and if the activity being considered as part of the remedial alternative constitutes generation, treatment, storage, or disposal as defined by RCRA. These requirements are ARARs where the excavation of soil is involved. These ARARs govern whether the soils to be managed are considered hazardous waste and whether they must be treated as contaminated. The State of California implements the RCRA regulations as well as its own Hazardous Waste Control Act. The RCRA and California regulations may be relevant and appropriate to Site activities if the contaminated soils are not considered a hazardous waste, but are sufficiently similar in characteristic or composition to a RCRA hazardous waste. The RCRA requirements are considered an ARAR and any potential excavation and disposal activities will require compliance with RCRA waste management standards including accumulation, storage, transportation, and land disposal restrictions. The remedy selected in the 1989 ROD included soil excavation, and thus several RCRA requirements were selected as action-specific ARARs at that time. Although not anticipated, if additional soil excavation and remediation is required for the groundwater remedy, then these requirements remain applicable Discharge to Surface Waters The Clean Water Act (CWA) provides authority for each state to adopt water quality standards to protect beneficial uses of each water body and requires states to designate uses for each water body. For remedial actions at the Site involving soil excavation or construction, engineering controls must be implemented to prevent discharges that may affect the water quality of surface waters. California implements the CWA and regulates point source discharges to surface water through the NPDES program, which addresses stormwater discharges and wastewater discharges to surface water. Point source discharges are discrete conveyances such as pipes or man-made ditches. California has three programs that address storm water discharges: discharges from industrial facilities, discharges from construction activities, and discharges to municipal storm sewers. For this project, the construction stormwater requirements would likely be ARARs. Construction sites that discharge to surface water must implement the substantive provisions of the California construction stormwater general permit; obtaining the permit itself is a procedural requirement and not an ARAR. California construction stormwater requirements call for measures to prevent erosion and reduce sediment and other pollutants in the discharges. If remedial-construction activities will disturb 1 acre or more of land, then the construction storm water requirements are applicable; if the area disturbs is less than one acre, then the construction storm water requirements would be relevant and appropriate. SFO/ [SUPPLEMNTALFS.DOCX] 2-3 ES BAO

28 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Point source discharges to surface water are also regulated under the NDPES program. Discharge treatment requirements and limits are specified in individual permits or in general permits. Where the discharge occurs offsite, then both substantive and procedural requirements must be met and a permit must be obtained. If the discharge is fully on the CERCLA site, compliance with the substantive permit requirements that protect surface water quality would be potentially applicable or relevant and appropriate. The San Francisco Bay RWQCB regulates NPDES discharges in the Site area. The state uses Ambient Water Quality Criteria to set Water Quality Standards, and these standards are set forth in the Basin Plan. Standards in the Basin Plan are used by the Water Board to set NPDES effluent discharge limitations. The current groundwater extraction and treatment systems maintain NPDES permits. The NPDES permit requirements include effluent limitations and monitoring requirements. The NPDES permit for the Site area is San Francisco Bay Water Board Order R Order R provides general waste discharge requirements for discharge or reuse of extracted and treated groundwater resulting from the cleanup of groundwater polluted by VOCs. The Order addresses groundwater treatment facilities located at active or closed sites with solvent leaks that discharge treated water from these treatment facilities directly to surface waters or through constructed storm drains. This order is applicable to new discharges as well as existing discharges. Because the Site groundwater is contaminated with VOCs and is discharged through a treatment facility, the substantive requirements of Order R are applicable; these include specific contaminant discharge concentrations that the effluent must meet and trigger concentrations that drive further evaluation of the treatment system Underground Injection The federal Underground Injection Control Regulations (40 CFR Parts ) and the California Toxic Injection Well Control Act (California H&S Code ) require permits to reinject treated groundwater into underlying aquifer zones. The substantive provisions of these regulations would be relevant and appropriate for any reinjection conducted as a part of the remedy. Under the California Water Code, Section 13260, injection of materials such as potassium permanganate, hydrogen peroxide, persulfate, or Fenton s reagent into the groundwater is considered a discharge of waste. The waste disposal restriction is intended to provide monitoring and discharge guidelines and requirements to provide full and complete containment of any by-product of the chemical oxidation process; to prevent any discharge of any by-products into any surface, surface water drainage course, or surface waters; and to minimize any adverse impacts caused by the injection Chemical Storage and Transportation In June 2004, the Department of Homeland Security issued risk-based performance standards for chemical facilities. A chemical facility or facility is defined as any establishment that possesses or plans to possess a quantity of a chemical determined to be potentially dangerous or that meets other risk-related criteria. Appendix A of 6 CFR Part 27 identifies chemicals of interest, which include commercial grade potassium permanganate 2-4 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

29 PRELIMINARY DRAFT FOR DISCUSSION ONLY 2 ARARS, RAOS, AND CLEANUP STANDARDS at quantities of 400 pounds or more and a minimum concentration of 35 percent hydrogen peroxide at quantities of 400 pounds or more. These regulations may be applicable for onsite storage of these chemicals as part of an in-situ remedy Bay Area Air Quality Management District Requirements Air emissions from onsite treatment processes such as air strippers or other chlorinated solvent-removal processes must comply with the Bay Area Air Quality Management District (BAAQMD) regulations (Regulation 8, Rule 47). The substantive requirements of this regulation would be an applicable ARAR to the remedial alternatives that use these processes. Any new source that emits more than 1 pound per day of benzene, vinyl chloride, perchloroethylene, methylene chloride and/or trichloroethylene, to the atmosphere (Section ) must have authorization to construct and operate. Although on-site treatment facilities are exempted by CERCLA from the administrative requirements of the permit (e.g., obtaining a permit to construct and operate.), the substantive emission limits of Section , Standards, may be relevant and appropriate. Specifically, these requirements include: (1) Section which apply to any air stripping and soil vapor extraction operations that emit benzene, vinyl chloride, perchoroethylene, methylene chloride and/or trichloroethylene; such emissions must be vented to a control device which reduces emissions to the atmosphere by at least 90 percent by weight; and (2) Section requires any air stripping and soil vapor extraction operations with a total organic compound emission greater than 15 pounds per day to vent to a control device that reduces the total organic compound emissions to the atmosphere by at least 90 percent by weight. 2.2 Remedial Action Objectives The RAOs from the 1989 ROD and the 2010 ROD Amendment as related to groundwater are presented below: Restore the shallow and deep aquifers to meet MCLs except for TCE in the C and deeper aquifers, where 0.8 ug/l was selected as the cleanup standard; Prevent vertical migration of contamination in the aquifers; Prevent lateral migration of contaminants and maintain plume stability; Maintaining inward and upward hydraulic gradients by pumping inside the existing slurry walls and regular monitoring of aquifers within and adjacent to the slurry walls to monitor the integrity of each slurry wall system. Reuse of extracted groundwater to the maximum extent feasible, with 100 percent reuse as a goal. Accelerate the reduction of the source of vapor intrusion (i.e., Site contaminants in shallow groundwater and soil gas) to levels that are protective of current and future building occupants, such that the need for a vapor intrusion remedy would be minimized or no longer be necessary. SFO/ [SUPPLEMNTALFS.DOCX] 2-5 ES BAO

30 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY The RAO to address the reduction of the source of vapor intrusion, which is shallow groundwater, is applicable to the shallow A/A1 Zone. The RAOs related to containment and restoration of the groundwater aquifer for drinking water apply to both the shallow and deeper aquifer zones. 2.3 Groundwater Cleanup Standards and Chemicals of Concern The supplemental FS evaluates alternatives that can achieve cleanup standards for the COCs at the MEW Site. The cleanup standards for COCs that were identified in the 1989 ROD and subsequent ESD are listed below. COC MCL (μg/l) Findings and Comments Chloroform 100 1,2-Dichlorobenzene -- 1,1-Dichloroethane (1,1-DCA) - 1,1-Dichloroethene (1,1-DCE) 6 1,2-Dichloroethene -- Freon-113 (1,1,2-Trichloro-1,2,2- Trifluoroethane) -- Phenol -- Tetrachloroethene -- 1,1,1-Trichloroethane (1,1,1- TCA) 200 Trichloroethene (TCE) 5/0.8 5 μg/l in shallow aquifer; 0.8 μg/l deeper aquifers Vinyl Chloride 0.5 Antimony -- Cadmium 10 Arsenic 50 Lead 50 Since the remedy was selected in 1989, COCs were reevaluated at the Site to assess whether any of the COCs were no longer a concern, whether new information changed the toxicity information for any chemicals, if the cleanup levels met ARARs, and if any new chemicals were identified. The COC evaluation is included in Appendix B. COCs were evaluated using the following criteria: Maximum detected concentration exceeds the tap water RSL or MCL; Frequency of detection is greater than 5% and the frequency of samples that exceed a screening level (RSL or MCL), is greater than 1% for organics and greater than 10% for naturally occurring metals. 2-6 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

31 PRELIMINARY DRAFT FOR DISCUSSION ONLY 2 ARARS, RAOS, AND CLEANUP STANDARDS Based on these criteria, the following compounds that were originally identified in the 1989 RODs as COCs and no longer meet the criteria established for COCs include: chloroform, 1,2-DCB, Freon 113, 1,1,1-TCA, phenol, and the metals (antimony, arsenic, cadmium and lead). Exceptions to the above criteria were benzene, toluene, ethylbenzene, and toluene. These compounds, which were associated with petroleum releases at specific sites, were not selected as COCs in the 1988 FS or 1989 ROD and are currently being addressed as part of the state s cleanup response. One new potential COC, 1,4-dioxane, was identified during the COC evaluation. 1,4- dioxane, which was commonly used as a stabilizer for another industrial solvent, 1,1,1-TCA, has been detected in the influent and effluent of some GWET systems at concentrations above the NPDES permit requirements (3 μg/l). The NPDES permit establishes discharge limits for discharges to navigable waters. The distribution of 1,4-dioxane in groundwater at the MEW Site is shown on Figure ,4- dioxane, which is more mobile than TCE, is present in groundwater throughout the plume at relatively low concentrations. A comparison of earlier data to more recent data indicates concentrations have significantly decreased over time (Figure 2-1). The maximum concentration of 1,4-dioxane detected in on-site monitoring wells between 2002 and 2009 is 24 μg/l in Well RE5A. 1,4-dioxane does not present a potential vapor intrusion risk due to its low potential to volatilize from groundwater and comparison to groundwater-to-indoor air screening levels. The primary pathway of concern for 1,4-dioxane is ingestion. There is no MCL for 1,4-dioxane. The tap water regional screening level is 0.67 μg/l. The California Department of Public Health has established a notification level (formerly action level) for 1,4-dioxane of 1 μg/l. Since no MCL is available for 1,4-dioxane a cleanup level using the notification level of 1 ug/l established by the California Department of Public Health (CDPH) is considered appropriate as a restoration goal at the Site. As discussed above in Section 2.1.1, notification levels are health-based advisory levels for chemicals in drinking water. The level of 1 ug/l is based on a 10-6 risk lifetime cancer risk. Notification to the CDPH is required in the event treated water exceeding the notification level is delivered to a municipal water purveyor. The NPDES permit requirement of 3 ug/l is based on the previous public health goal for 1,4-dioxane ( and is still considered appropriate for treatment of groundwater at the site. Limited ecological benchmarks for 1,4-dioxane have been developed. The most common method to destroy 1,4-dioxane is advanced oxidation using ultraviolet light, hydrogen peroxide, or ozone, and is typically applied during ex situ treatment following extraction. Because concentrations of 1,4-dioxane detected within the plume are relatively low and have been decreasing within the regional plume over time (Geosyntec, 2009), advanced oxidation treatment systems have not been required at the MEW Site. At this time, three of the facilities have advanced oxidation systems (see Table 1-1). The updated COC list is presented below. SFO/ [SUPPLEMNTALFS.DOCX] 2-7 ES BAO

32 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY TABLE 2-3 Proposed Revised Chemicals of Concern for Groundwater Groundwater Cleanup Standard COC (micrograms/l) Basis for Proposed Standard 1,1-Dichloroethane (1,1-DCA) 5 California MCL 1,1-Dichloroethene (1,1-DCE) 6 California MCL Cis-1,2-Dichloroethene 6 California MCL Trans-1,2-Dichloroethene 10 California MCL 1,4-Dioxane 1 No promulgated MCL; California Department of Public Health Notification Level of 1 ug/l Tetrachloroethene 5 California and Federal MCL Trichloroethene (TCE) 5 California and Federal MCL Vinyl Chloride 0.5 California MCL 2-8 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

33 PRELIMINARY DRAFT FOR DISCUSSION ONLY 3 Identification and Screening of Technologies EPA screened potential technologies to expedite groundwater cleanup. Technologies were screened based on their potential effectiveness and implementability and data collected during pilot tests within the regional groundwater contamination plume. Technologies, which are or have been used as part of the existing remedy, are also included in the screening evaluation. The technologies screened and retained are discussed below and summarized in Table 3-1. Cleanup technologies will vary in effectiveness depending on the concentration of contaminant present and the extent of contamination (localized source or disperse plume). For these reasons, EPA has defined different concentration areas within the plume as follows: High concentration areas = Total CVOC concentrations greater than 1,000 ppb Medium concentration areas = Total CVOC concentrations between 100 and 1,000 ppb Low concentration areas = Total CVOC concentrations between 5 ppb and 100 ppb CVOCs include PCE, TCE, 1,2-DCE, and vinyl chloride. The approach for cleanup of the plume in the FS is based on these different concentration areas and is discussed in Section 4.1. The locations and extents of these plume areas for the A/A1, B1/A2, and B2 Zones, respectively, are illustrated on Figures 1-12 through 1-14, respectively. Most of the technologies screened and retained can be used to address the shallow and deeper aquifers except where noted. As discussed in Section 2.2, the RAOs apply to the shallow and deep aquifers, with the exception of the RAO related to vapor intrusion, which only applies to the shallow aquifer (A/A1 Zone). 3.1 Potentially Applicable Remedial Technologies Four broad categories of technologies were considered in the FS: In situ oxidation or reduction (redox) treatment Extraction, removal, treatment and disposal Subsurface barriers Monitored natural attenuation In situ Redox Technologies In situ redox technologies involve the introduction of treatment amendments to the subsurface to modify the chemical or biological conditions of the affected aquifer. The amendments directly degrade, or create conditions supporting the degradation of, contaminants in place including increasing desorption and dissolution of chemicals into the dissolved phase. The in situ technologies evaluated here are in situ chemical oxidation (ISCO), enhanced reductive dechlorination (ERD), and abiotic dechlorination using zerovalent iron (ZVI). Each of the technologies have been pilot tested at various facility-specific source areas at the Site as described below. SFO/ [SUPPLEMNTALFS.DOCX] 3-1 ES BAO

34 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY In situ Chemical Oxidation ISCO involves the injection of oxidants such as permanganate, hydrogen peroxide, persulfate, Fenton s reagent, or ozone into the aquifer. Oxidants react with chlorinated ethenes to form carbon dioxide, chloride ions, and solid or soluble salts, depending upon the oxidant used and the ph in the treatment zone. The oxidant injection can be performed using temporary (direct-push) borings, vertical wells, and horizontal wells. The distribution of oxidant within the subsurface can be enhanced by hydrofracturing or pumping and recirculation. ISCO is generally applied in high concentration areas where conditions are aerobic or only mildly reducing and there is little chemical oxidant demand from reduced species. ISCO does not generally form any undesirable intermediate degradation products such as vinyl chloride but can mobilize naturally occurring metals present in subsurface soil. ISCO requires direct contact between the oxidant and the contaminant, which can limit implementation in areas with significant surface access restrictions and effective oxidant delivery is more difficult within heterogeneous materials. Oxidant persistence in the subsurface is generally on the order of hours to months (depending upon the oxidant selected), and multiple injections can be necessary depending upon initial contaminant concentrations and remedial concentration targets. Of the peroxides, permanganates generally persist the longest. Two oxidation pilot tests have been conducted at the MEW Site and another pilot test was performed at the nearby former GTE Government Systems Corporation (GTE) site in Mountain View, California, all using permanganate. The two MEW oxidation pilot tests were conducted at the former Raytheon facility area (350 Ellis Street) and the former SMI facility area (455/487 East Middlefield Road) facilities, and both included a single oxidant injection event. The Raytheon oxidation test was conducted in 1999 (IT Corporation [IT], 2000) and concluded the following: Average concentrations in saturated soils sampled after the injection showed a 19 percent decline in TCE concentrations relative to the baseline data for soil. Groundwater data collected in monitoring wells near the injection points did not show decreases in TCE concentrations. Some wells showed an increase in concentrations. This was attributed to preferential pathways for permanganate migration, and to the position of the monitoring wells with respect to the groundwater gradient. An approximate reduction rate of 70 percent in TCE concentrations was observed in grab groundwater samples collected along the assumed direction of the water flow from the injection point. Hexavalent chromium was detected in groundwater subsequent to the injection, but the concentration declined rapidly. The physical extent of the VOC oxidation was limited by the heterogeneous nature of the subsurface. 3-2 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

35 PRELIMINARY DRAFT FOR DISCUSSION ONLY 3 IDENTIFICATION AND SCREENING OF TECHNOLOGIES The above conclusions for the Raytheon test indicated that TCE can decrease after injection of permanganate, but the test showed some contradicting results that Raytheon attributed to the direction of groundwater flow. Data indicated that TCE concentrations in the pilot test area returned to pre-test conditions within weeks (in one injection well, concentrations decreased from 5,700 μg/l to non-detect in the first week, then increased to up to 3,100 μg/l five weeks after injection). The SMI oxidation test (PES Environmental [PES], 2001) showed TCE concentration decreases of up to 90 percent and a radius of influence of about 20 feet. TCE concentrations rebounded to pre-test conditions after 4.5 months. Although SMI Holdings originally recommended an expanded injection of permanganate, it later proposed treatment using anaerobic biodegradation. The GTE oxidation pilot test was performed during December 2008 with the following observations and findings: Oxidant injection flow rates ranging between 8 and 15 gallons per minute were achieved. Permanganate was effectively distributed within an approximate 25 to 30 foot radius from each row of injection wells, and injection spacing of 20 feet was determined to be appropriate. Permanganate persisted in the subsurface for approximately 20 weeks (more in limited instances). TCE typically returned to pre-injection concentrations following depletion of oxidant. Transient increases in groundwater concentrations of arsenic, selenium, and total dissolved solids were observed shortly after oxidant injections, but concentrations returned to baseline within 6 to 8 weeks; hexavalent chromium concentrations increased within and immediately downgradient of permanganate injections, but returned to baseline in most wells within 6 months following injection. Preferential groundwater flow paths appeared to limit oxidant contact time (and effectiveness) in some areas. Release of TCE bound within low permeability soils (matrix diffusion effect) may require multiple oxidant injections for effective treatment. Each of the oxidation pilot tests utilized a single oxidant injection event, with a general return to pre-injection concentrations several weeks following injection. This return to original concentrations (rebound) was likely due to a combination of matrix diffusion effects and/or migration of untreated upgradient groundwater into the treatment area. While limited success was observed with in situ chemical oxidation at these pilot test locations with single injection events, this technology can be effective following multiple injection events and was retained as discussed in Table Enhanced Reductive Dechlorination Some native subsurface microorganisms can metabolize chlorinated ethenes biologically in the presence of a suitable carbon substrate, as described in Section Enhanced reductive SFO/ [SUPPLEMNTALFS.DOCX] 3-3 ES BAO

36 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY dechlorination is a form of in situ bioremediation in which a carbon source such as lactate, cheese whey, molasses, or vegetable oil is injected into the subsurface to support and increase the microbial populations that metabolize chlorinated ethenes. The microorganisms utilize the carbon substrate as an electron donor (food source) while the chlorinated ethenes act as electron acceptors (cometabolized), and are sequentially reduced to less chlorinated compounds. The process of reductive dechlorination generally proceeds from PCE (if present) to TCE to cis-1,2-dce, to vinyl chloride, to ethene. In some cases, the native microorganisms are unable to metabolize cis-1,2-dce and/or vinyl chloride, leading to potential accumulation of these compounds. In such cases, the carbon substrate can be bioaugmented with microorganisms capable of completing the reductive dechlorination sequence through ethene. Different carbon substrates support this process over varying timeframes. Donors with fewer carbon atoms such as lactate, molasses and cheese whey are utilized more quickly but are generally more soluble. Such carbon substrates are frequently selected when multiple dosing is necessary or within recirculation systems. The carbon substrate injection can be performed using temporary (direct-push) borings, vertical wells, horizontal wells or infiltration galleries. The distribution of carbon substrate within the subsurface can be enhanced by hydrofracturing or pumping and recirculation. ERD does not require direct contact between the carbon substrate and the contaminant, which provides greater implementation flexibility in areas with significant surface access restrictions. Effective carbon substrate delivery is more difficult within heterogeneous materials. ERD is generally applied in moderate to high concentration areas where conditions are anaerobic or only slightly oxidizing and where some evidence of appropriate contaminantreducing microbes is present. Appropriate microbes can be injected with the carbon substrate (bioaugmentation) when their presence is uncertain. ERD is generally implemented using a gridded injection array or using a series of injection transects spaced along the length of a contaminant plume. Application using transects is common when used to treat large contaminant plumes. Pilot-scale ERD testing has been conducted at the former Intel facility (365 East Middlefield Road) in three phases since The first phase was conducted in August and September 2005 and included injection of emulsified vegetable oil within temporary injection points along a single transect of nine wells. The second phase was conducted in July 2006 and included injection of emulsified vegetable oil within temporary injection points at four separate transects approximately 40 feet apart, each consisting of 10 injection points. The second phase of injection included bioaugmentation within the two downgradient transects. The third phase was conducted in July 2009, and again in May 2010, and included the injection of sodium lactate and a nutrient/vitamin supplement within the first and second phase areas. The general findings of the Intel enhanced reductive dechlorination pilot test were: The first and second phases of injection were successful in inducing highly reducing conditions within the treatment area, and sequential dechlorination of TCE to cis-1,2-dce to vinyl chloride to ethene was clearly observed in several wells. 3-4 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

37 PRELIMINARY DRAFT FOR DISCUSSION ONLY 3 IDENTIFICATION AND SCREENING OF TECHNOLOGIES For the first phase of injection, a 96 percent decrease in TCE concentration was observed within a short time following injection in one treatment area well (TW-2A), and a second treatment area well (TW-3A) had a 91 percent decrease in TCE shortly following injection and increasing to a 99 percent reduction two years following injection. For the first and second phases of injection, cis-1,2-dce in some treatment area wells reached molar concentrations greater than the initial concentration of TCE in the wells, indicating the dissolution of TCE from the sorbed phase. For the first phase of injection, increased and generally persistent concentrations of cis-1,2-dce and vinyl chloride in some wells indicated stalling at cis-1,2-dce; the appropriate dechlorinating microorganisms Dehalococcoides ethenogenes were either not present or the activity of existing microorganisms was low. At one well, this may have been attributable to poor distribution of amendments at that location. Following the injection of sodium lactate during the third phase, TCE concentrations decreased markedly, including at former stalled well TW-4A where concentrations were reduced to below the MCL. Six months following the third phase injection, 12 wells had TCE concentrations below the MCL. Between 12 and 18 months following the third phase sodium lactate injection TCE concentrations at well TW-4A increased to above pre-injection values, which was interpreted as possible dissolution of TCE from the sorbed phased. The seasonal groundwater table rose significantly during this time (to values not present since spring 2007), which may have further mobilized TCE that was bound within the capillary fringe and unsaturated zone. Pilot testing of ERD at the former Intel facility indicates that ERD does accelerate the degradation of TCE via reductive dechlorination, and that complete degradation to ethene occurs. However, multiple injections are necessary to complete degradation through ethene, and to provide continued treatment as mass from fine-grained materials is released. Navy conducted a treatability study (TS) using ERD with emulsified vegetable oil and lactate in two separate test areas in the WATS area (Site 28). Lactate was used in one test area located near former former dry cleaning facility (Building 88), and emulsified vegetable oil (LactOil ) was used at a nearby traffic island, where solvents from former Building 88 migrated along a buried utility line. The test injections were performed in July and August 2010, with monitoring conducted through June 2011 (Shaw Environmental Inc. 2012). At the former Building 88 Area, sodium lactate with bioaugmentation (SDC-9 culture) was injected using 10 injection wells in an offset grid pattern on 13.5-foot centers. Three observation well clusters were installed within, upgradient of, and downgradient of the active treatment zone. Each observation well cluster included one well screened within a low permeability layer and one well screened within the higher permeability zone to evaluate the treatment effectiveness within separate lithologies. Initial test results were generally favorable, with strongly reducing conditions initiated quickly following injection. Within the treatment zone, initial favorable results occurred in both low and high permeability soil, with particularly favorable results within the low permeability treatment area well. Within four months treatment appeared to stall at cis-1,2-dce within the high SFO/ [SUPPLEMNTALFS.DOCX] 3-5 ES BAO

38 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY permeability zone of the treatment area, but progressed to ethene within the low permeability zone of the treatment area. However, after four months concentrations in the high permeability zone of the treatment area began returning to pre-injection values, and no further degradation was apparent in the low permeability zone of the treatment area. At the downgradient observation well, limited reductive dechlorination was apparent within the low permeability well screen, indicating poor delivery of carbon substrate in this zone. Active reductive dechlorination was apparent within the downgradient high permeability well screen, although again treatment appeared to stall at cis-1,2-dce and vinyl chloride within four months. Concentrations of PCE, and TCE had decreased within the treatment zone to levels below the upgradient concentrations. Recent sampling events have shown increases in the treatment zone and downgradient concentrations, which is attributed to a lack of sufficient substrate to complete the degradation process. At the Traffic Island Area, bioaugmented (SDC-9 ) LactOil was injected using 15 injection wells in an offset grid pattern on approximately 13-foot centers and within separate treatment intervals of 10 to 50 feet bgs (upper interval) and 50 to 65 feet bgs (lower interval). Observation wells were installed within, upgradient of, and downgradient of the treatment zones, but were not separated by lithology for this test. Initial test results were favorable, with generally more complete reductive dechlorination of PCE and TCE to ethene than observed at the former Building 88 Area. The concentrations of PCE and TCE were reduced to below their cleanup levels in all treatment area wells within four months, although the concentrations in one well increased back above the cleanup levels by the last monitoring event (12 months after injection). Elevated concentrations of ethene in the treatment area confirmed that complete dechlorination of PCE and TCE was occurring. Results were more varied at downgradient observation wells, with only slight changes observed at the shallowest depth, degradation through vinyl chloride (stalling) occurring at mid-depths, and substantial initial degradation followed by concentration increases to preinjection values at the deepest depths. These differences were attributed to variable distribution of substrate within the heterogeneous aquifer. Substantial substrate remained at one treatment area observation well one year after injection, and degradation in this area appeared ongoing as of the conclusion of the Navy TS. The Navy TS indicates that ERD does accelerate the degradation of PCE and TCE via reductive dechlorination and that complete degradation to ethene occurs. However, variability in substrate delivery indicates that a single injection may not be sufficient to initiate treatment throughout all aquifer zones. Based on the initial favorable results obtained from pilot testing at the former Intel facility and Navy WATS Area, the ERD technology was retained Abiotic Dechlorination with ZVI In situ abiotic (chemically rather than biologically mediated) dechlorination using ZVI entails the reduction of chlorinated ethenes during the reciprocal reactions that occur as ZVI placed into the subsurface is oxidized. When in contact with ZVI, chlorinated ethenes are sequentially reduced to less chlorinated compounds (PCE to TCE to DCE to vinyl chloride to ethene), at a rate faster than with ERD. Intermediate degradation products such as DCE (dichloroethene) and vinyl chloride do not generally persist with ZVI treatment, providing a 3-6 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

39 PRELIMINARY DRAFT FOR DISCUSSION ONLY 3 IDENTIFICATION AND SCREENING OF TECHNOLOGIES benefit over ERD. However, ZVI must be in direct contact with the target contaminants as is the case with ISCO. Since ZVI is a solid, it is immobile once injected, which limits implementation flexibility in the presence of significant surface access restrictions. ZVI treatment can also be combined with injection of carbon substrates to provide both abiotic and biotic dechlorination of chlorinated ethenes.. ZVI can be delivered to the subsurface through temporary borings, and delivery can be enhanced by hydrofracturing; however, the injection infrastructure is typically more specialized than that for either ISCO or ERD. Saturated soils can also be amended in place using deep soil mixing. Commonly, ZVI treatment is applied as a permeable reactive barrier, as discussed in Section 3.2.3, or is applied using a gridded injection array within moderate to high concentration areas. Treatability studies utilizing the Adventus Group product EHC, a combination of a carbon substrate and ZVI, have been conducted in the WATS Area at the Navy s Installation Restoration (IR) Sites 26 and 28. The IR Site 26 pilot test injection was performed in May and June 2009, with monitoring conducted for one year following injection (Shaw Environmental Inc., 2010). Approximately 23,000 pounds of EHC was injected as a slurry through 22 injection points screened across a 32-foot-thick target treatment horizon, with a documented injection radius of greater than seven feet. The results of the pilot-scale test were positive, and complete dechlorination of PCE and TCE to ethene and ethane was documented. Rebound of contaminant concentrations within, and downgradient of, the treatment area was not observed during the one-year monitoring period. However, geochemical data indicated that EHC -induced reducing conditions did not persist as long as anticipated (approximately 9 months rather than 1 to 2 years). At the end of the monitoring period, vinyl chloride concentration remained above the cleanup criteria, but exhibited a decreasing trend over several monitoring events. Biological, geochemical, and CVOC data indicated that dechlorination was due primarily to biologically-mediated reductive dechlorination (ERD) rather than abiotic processes, since the abiotic dechlorination product acetylene was not identified. However, acetylene is very short-lived and can be difficult to quantify accurately. The IR Site 26 pilot test report concluded that without direct evidence for abiotic degradation there did not appear to be an advantage to including ZVI with the carbon substrate that would compensate for the added cost and operational requirements to inject EHC. The IR Site 28 test injection was performed in July and August 2010, with monitoring conducted through June 2011 as part of the same Navy TS evaluating ERD described previously (Shaw Environmental Inc. 2012). The Navy experienced difficulty in injecting the EHC material into the subsurface, and the radius of influence observed in the treatment zone was generally limited to approximately 6 feet. The high injection pressures required to distribute the material led to some mounding (and cracking) of the overlying asphalt surface, and pressure limitations to minimize this effect caused a smaller radius of distribution at shallow depths than at deeper depths. The results of the IR Site 28 pilot study were mixed, with near complete dechlorination observed at treatment area wells where amendment placement was successful, and no appreciable degradation in areas where amendment distribution was poor. At locations where injection was successful appropriate reducing conditions for degradation were established and maintained for substantially SFO/ [SUPPLEMNTALFS.DOCX] 3-7 ES BAO

40 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY longer than with the substrates used in the ERD TS at Site 28. As with the IR Site 26 pilot test, the abiotic degradation byproduct acetylene was not detected during the IR Site 28 TS. The IR Site 28 TS concludes that the absence of acetylene, which is prone to rapid break down, does not confirm or refute the occurrence of the abiotic degradation process. Based on the results of these pilot tests, ZVI was retained as an in situ treatment technology (Table 3-1). The pilot test results indicate that injection of ZVI can be significantly more difficult to control than injection of carbon substrates (ERD), but that where ZVI injection is successful appropriate reducing conditions may be maintained for a longer period Extraction, Removal, Treatment and Disposal Technologies These technologies involve the removal of free-phase contaminants or contaminants dissolved in groundwater by physical means such as excavation or groundwater extraction. Contaminants can also be volatilized and removed as a vapor phase with technologies including thermal treatment, air sparging, or in-well groundwater circulation In situ Flushing In situ flushing is the addition of surfactants, cosolvents, acids, bases, oxidants, or other fluids into the vadose zone, capillary fringe, or saturated aquifer to enhance migration of contaminants to the dissolved phase for removal by groundwater extraction and treatment at the ground surface. Surfactants or cosolvents are generally used for treatment of CVOCs and other hydrophobic compounds, and increase the mobility or solubility of contaminants and accelerate geochemical reactions and transport processes such as desorption, advection, dispersion, diffusion, and solubilization. Flushing fluids can be delivered by a variety of means including gravity feed or pressure injection, both above and below the water table. Groundwater and flushing fluids are recovered via extraction wells and directed to a treatment plant. Success of in situ flushing depends on the delivery and migration of flushing fluids through the zone of contamination and their complete recovery. Because of the intentional enhancement of contaminant mobility, a robust understanding of aquifer heterogeneity is generally required to support the design of recovery/extraction systems. This technology was not retained. There has been limited application of this technology at similar sites to demonstrate that it would be more effective at this site than other available technologies Air Sparging Air sparging is the injection of air through injection wells installed within the saturated portion of an aquifer. The air is displaced into the aquifer and bubbles (rises) through the groundwater to the water table, where it can either escape to the atmosphere or be captured using soil vapor extraction (SVE) within the vadose zone. Volatilization of contaminants occurs by the partitioning of contaminants from the groundwater and aquifer matrix into the air phase, effectively acting as an in situ air stripping system. Air sparging can be operated in continuous or cycled modes. The application of air sparging is typically limited to homogeneous, high-permeability aquifers. The technology is significantly less effective within heterogeneous, low- 3-8 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

41 PRELIMINARY DRAFT FOR DISCUSSION ONLY 3 IDENTIFICATION AND SCREENING OF TECHNOLOGIES permeability environments, similar to the MEW, because of inability to control air travel pathways. An air sparging pilot test was performed at the SMI facility during late 1995 and early 1996, followed by installation of a full-scale air sparging system that operated during the later half of The air sparging system was shut down following a rise in the local water table which flooded the air sparging wells. NASA has been operating an air sparging system between Orion Park and NASA Ames to treat contaminated groundwater flowing on the property. Sparge wells were installed within a preferential-flow channel deposit, in sandy lenses between 6 and 16 feet bgs. The system has been able to treat the shallow groundwater effectively. Because of the limited success with the air sparging system within the MEW plume and the technical limitations in heterogeneous systems, this technology was not retained Groundwater Circulation Wells/In-Well Stripping Groundwater circulation wells, also known as in-well vapor stripping, typically integrate the principles of groundwater recirculation with air stripping of VOCs. Using vertical circulation wells, groundwater is extracted from the aquifer within a lower screened interval, circulated upward, and discharged through an upper screened interval. Circulation is generally performed using a submersible pump or air lifting. Treatment of groundwater is carried out within the well bore. For air lifting, treatment is conducted by volatilization of contaminants from the water phase into the air phase during the air lifting process. When using a submersible pump, treatment can be carried out using various processes including air stripping, biodegradation, or oxidation. The technology can be implemented with standard well constructions and typically does not require specialized tools for installation or operation. However, the technology requires additional process piping and treatment infrastructure (versus groundwater extraction and treatment) for treatment of stripped vapors. This technology was not retained as it is not considered as viable as other technologies because of infrastructure restrictions Groundwater Extraction and Treatment GWET is the existing groundwater remedy for the MEW Site and has been operating effectively at the Site. Groundwater is extracted from one or more wells and piped to treatment systems. These treatment systems include liquid phase active carbon, air strippers with granular activated carbon, various advanced oxidation systems, or combinations of these. Overall, the groundwater extraction and treatment systems have been effective at removing VOCs, but over time have primarily served to limit lateral and vertical migration from source areas and provide hydraulic containment of the regional groundwater plume. The current GWET system operations and layout can be modified to address different objectives. Groundwater extraction rates or the locations of individual extraction wells can be modified to enhance contaminant mass removal. Alternate well placement strategies for preventing contaminant migration, such as linear transects of wells used as hydraulic barriers, can be used. Pulsed groundwater extraction can be applied to remove more mass SFO/ [SUPPLEMNTALFS.DOCX] 3-9 ES BAO

42 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY from the system by suspending extraction systems for a short period of time to allow contaminants in lower permeability zones to desorb. This technology was retained because of its proven effectiveness in removing and treating contaminants at the MEW Site and the potential to adjust the system to enhance mass recovery Multi-Phase Extraction Multi-phase extraction is the simultaneous extraction of contaminants in multiple phases, such as dissolved phase and vapor phase, or dissolved phase and non-aqueous phase liquids (NAPL). Multi-phase extraction most commonly refers to the simultaneous removal of both groundwater and soil vapor from individual wells screened above and below the groundwater table. Groundwater extraction is used to lower the groundwater table and soil vapor extraction draws volatile contaminants from the dewatered formation. The technology is particularly effective when residual contaminant mass is present within unsaturated soils and when contaminants are concentrated within the capillary fringe above the water table. Extraction wells are spaced to provide the requisite dewatering. In low permeability formations, the groundwater cones of depression are steep and closer well spacing is required to provide uniform dewatering; the technology is most cost-effective in higher-permeability settings where the well spacing can be greater. For sites with good surface sealing (such as asphalt or concrete paving), the radius of vapor influence often exceeds the radius of groundwater influence, while at sites with poor surface sealing (bare earth or turf grass) the radius of vapor influence can be significantly less than the radius of groundwater influence. The groundwater extraction rate required to maintain sufficient dewatering is generally significantly greater than the extraction rate required for simple hydraulic containment of a contaminant plume. Multi-phase extraction can be implemented using the same general methods as groundwater extraction, but requires additional process piping and treatment infrastructure to treat the additional extracted soil vapor. Because of the increased groundwater extraction rates, the size of conveyance piping and treatment systems is generally greater than for traditional pump and treat systems. Multi-phase extraction was considered for areas within the slurry walls, where dewatering could be used to expose soil saturated with solvents beneath the water table for treatment by vapor extraction. However, dewatering was considered challenging to implement given the relatively large size of the slurry walls at the MEW Site, and multi-phase extraction was not retained for these areas. In addition, it is assumed that the predominant source of vapors at the site is shallow groundwater since identified soil sources at the site were removed via soil excavation or soil vapor extraction during the soil cleanup completed in As discussed previously, multiphase extraction is most effective when both soil and groundwater sources need to be remediated, which is not the case for the MEW Site. Although it is an effective technology, multi-phase extraction was not retained because without a soil source it does not provide significant benefit over other technologies. If additional soil sources are identified for cleanup, soil vapor extraction could be implemented SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

43 PRELIMINARY DRAFT FOR DISCUSSION ONLY 3 IDENTIFICATION AND SCREENING OF TECHNOLOGIES Thermal Treatment In situ thermal treatment (either conductive or electrical resistive heating) is an applicable technology for treatment of high concentrations of dissolved- and sorbed-phase VOCs, and can also address DNAPL. In situ thermal treatments involve the active heating of the subsurface to force volatile contaminants into the vapor phase where they can vent to the ground surface or be removed by an active soil vapor extraction system for ex-situ treatment. Thermal treatments also typically vaporize some or all of the pore water within an aquifer to steam, which either carries or flushes contaminants to a vapor extraction point. The two primary heating methods are direct conductive heating and electrical resistance heating. Electrical resistive heating (ERH) involves the placement of a network of electrodes in the subsurface and the application of current through the subsurface. Resistance to current flow within the subsurface produces heat. ERH is typically used to raise subsurface temperatures to the boiling point of the contaminant, causing partial vaporization of the contaminant within the treatment zone. Steam generated by this process acts as a contaminant carrier and migrates upward to the vadose zone, where co-located vapor extraction wells remove the steam for further treatment at an aboveground treatment system. Conductive heating involves the application of a network of direct-heating probes installed within subsurface wells. Heat from the probes, typically installed within a well also used for vapor extraction, is transmitted through the subsurface by conductance. Conductive heating is typically used to raise subsurface temperatures significantly above the water boiling point, forcing the complete vaporization of all pore water near the heating probes. Vaporized steam can then be extracted at depth without requiring steam to migrate to the vadose zone first. One benefit of thermal technologies is that heterogeneities in subsurface lithology have less effect on thermal treatment technology than other in situ methods. The technology may perform better in clays and low-permeability zones, which are particularly difficult to treat using injection-based in situ techniques. However, the technology requires the installation of significant infrastructure including process piping for conveyance of extracted vapors, electrical power lines to operate the electrode or heater, control wiring for operational control and a central treatment facility. The need to install significant infrastructure (network of well heater probes or electrodes, recovery piping, and electrical wiring) can be particularly limiting in developed areas. While this technology is effective, there were no areas within the plume with limited development and infrastructure that were identified for use of the technology. Therefore, this technology was not retained Excavation Soil excavation was implemented as part of the existing remedy and was an effective component in cleaning up vadose zone (unsaturated soil) source areas. Vadose zone or saturated soil can be removed directly using various excavation equipment. Excavation and off-site disposal (or on-site treatment) can be particularly effective in shallow highconcentration or DNAPL-containing areas. Deep excavations require significant shoring and frequently dewatering, and large excavations are difficult to perform in highly developed areas. SFO/ [SUPPLEMNTALFS.DOCX] 3-11 ES BAO

44 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Excavation was not retained as a technology for treatment of groundwater contamination Barrier Technologies Barrier remediation technologies involve the placement of subsurface permeable or nonpermeable barriers across the flow path of a groundwater plume to control or limit groundwater migration or treat groundwater during passage through the barrier. Slurry walls already exist at some properties as part of the existing groundwater remedy and are discussed in Section Other types of barriers include permeable reactive barriers, which contain a reactive media that cleans up groundwater as it flows through, and phytoremediation, which uses vegetation to clean up groundwater Permeable Reactive Barriers Permeable reactive barrier (PRB) walls can be installed across the flow path of a contaminated groundwater plume to provide passive groundwater treatment as groundwater passes through the wall. PRB walls can incorporate a number of reactive media, including activated carbon, ZVI, or organic matter (carbon source), depending on the reactive process desired within the wall. PRB walls are designed to provide sufficient residence time for complete reaction of COCs to benign degradation products. Factors affecting the residence time within the barrier include the hydraulic conductivity of the aquifer, the hydraulic gradient, and the thickness of the barrier wall or reactive zone. The reactive lifespan of a PRB depends upon the type and quantity of reactive material used. PRBs that use ZVI frequently have a design life of 10 to 20 years. Heterogeneous conditions in the aquifer and potential uneven distribution of reactive materials within the PRB may lead to uneven aging of the PRB. Geochemical reactions within the PRB can potentially lead to chemical precipitation, which reduces the permeability and effectiveness of the PRB. Rejuvenation activities such as ultrasound, pressure-wave hydraulic pulses, or agitation with augers may break up such precipitates and extend the life of the PRB. PRBs can be installed at shallow depths using traditional trenching equipment such as a track hoe or backhoe. Deeper PRBs can be installed using modified, long-reach track hoes and slurry trenching techniques, using a slurry to stabilize the excavation. Since trenchbased PRBs are contiguous features, emplacement of a large, continuous PRB in a developed area can be logistically difficult because of structures, property access, and underground utilities. PRB-like treatment zones also can be installed to depths as great as 100 ft or more using azimuth-controlled vertical fracturing techniques whereby a series of boreholes are drilled to the target depth along a linear alignment, vertically-oriented fractures are induced in the subsurface between each borehole, and reactive material is injected into the fractures to generate a thin (two to nine inches) vertical wall along the alignment. Another installation technique involves the use of large diameter augers with overlapping spacing to mix in reactive material to the target depth. One 30-foot long and 6-foot wide reactive cell (PRB) was installed by the Navy in the WATS area on Moffett Field to evaluate the lifespan and hydraulic performance of a PRB SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

45 PRELIMINARY DRAFT FOR DISCUSSION ONLY 3 IDENTIFICATION AND SCREENING OF TECHNOLOGIES Investigations at Moffett Field have revealed no evidence of precipitates that impede groundwater flow through the PRB, although there was some concern regarding groundwater flow around the wall (NAVFAC, 2005) PRBs were retained as a viable technology for groundwater Slurry Walls Physical barriers to subsurface groundwater flow can be installed to isolate source areas or other portions of groundwater plumes and limit plume migration. Such low-permeability barriers can be installed using the same trenching techniques as PRBs, with trench backfill consisting of a bentonite clay slurry. In addition, large diameter augers can be used to mix in low permeability materials, or sheet pile walls can be installed. Low-permeability slurry walls were installed at several source areas at the MEW Site as part of the current groundwater remedy. The existing slurry walls will remain in place; however, the installation of additional slurry walls is not being contemplated by EPA as the main source areas have already been controlled at the site. Modification of the existing slurry walls to create permeable reactive sections (gates), allowing passive treatment of groundwater, potentially in-lieu of current groundwater extraction within the slurry walls, was considered. Although technically plausible, to EPA s knowledge, the modification of an existing slurry wall to include a reactive gate has not been constructed at other sites, and thus, is unproven. The existing slurry walls are limiting downgradient migration of high-concentration groundwater in certain source areas, and breaching the integrity of the slurry walls may result in the potential release and migration of these high concentration areas of the plume. Should the approach be found ineffective, there would be substantial costs to restore the slurry wall. For these reasons, installation of new and modification of existing slurry walls was not retained Phytoremediation Various plant and trees intercept groundwater with their root mass and can control the migration of shallow groundwater, and remove or demobilize a variety of contaminants, including chlorinated ethenes. A variety of phytoremediation mechanisms may act to control the migration of contaminants including phyto-accumulation and phytovolatilization. Phytoremediation can provide passive groundwater pumping for plume containment and can effectively treat many VOCs within root zones or within the plants themselves. Phytoremediation is most easily implemented in non-developed areas. Phytoremediation was considered for pilot testing at Site 26 near Hangar 1, but because of concerns that trees/flowers would attract more wildlife and may affect air traffic in the area, it was eliminated from consideration. Because of the concerns with the runway and the likelihood that the areas beneath the plume both north and south of Highway 101 will remain developed or will have future redevelopment, this technology was not retained. SFO/ [SUPPLEMNTALFS.DOCX] 3-13 ES BAO

46 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Monitored Natural Attenuation Natural attenuation is the name given to the combination of natural processes that result in a decrease in concentration of a contaminant with time or distance from a source, and natural attenuation mechanisms can be classified as either destructive or nondestructive. Destructive mechanisms remove the parent compound from the environment by breaking it down into one or more simpler compounds. Nondestructive mechanisms generally transfer the parent compound from one environmental medium into another or spread the parent compound over a greater volume of the same environmental medium. The most common destructive natural attenuation mechanism is biodegradation. Nondestructive mechanisms include dilution, dispersion, advection, sorption, and volatilization. As a remedial treatment technology, monitored natural attenuation (MNA) consists of routine monitoring of site conditions to document that natural attenuation mechanisms continue to provide sufficient contaminant reductions and progress toward remedial goals and that the plume is stable. MNA does not require the installation of infrastructure other than a network of monitoring points. Natural attenuation mechanisms generally take a longer time to achieve remediation goals since MNA is limited by naturally existing physical, biological, and geochemical processes. In some cases, native geochemical and biological conditions may not be sufficient to completely reduce existing contamination. In such conditions, MNA relies solely on the slower physical processes of diffusion and dispersion. The Regional Program has performed an MNA assessment at the Site, and concluded that several lines of evidence suggest that natural attenuation processes are occurring in certain portions of plume (Geosyntec, 2011a). Because MNA is a proven process, and natural attenuation processes have been demonstrated to be occurring at portions of the Site, it was retained as a viable technology to be used in conjunctions with other technologies for this FS. 3.2 Remedial Technologies Retained The following remedial technologies are retained for further evaluation either as independent treatment alternatives, or as a component of combined-technology remediation alternatives (Section 4): In situ redox (ISCO, ZVI and ERD) Groundwater extraction and treatment (existing remedy) PRBs MNA The technology screening is summarized in Table 3-1. Note that a number of in situ redox technologies have been retained for evaluation as a single alternative because these technologies have been used within different portions of the plume with relative success. If in-situ redox is selected, the various technologies under this category in situ chemical oxidation (ISCO), Enhanced Reductive Dechlorination (ERD) and Abiotic Dechlorination with ZVI (ZVI) would be acceptable. This approach is similar to the 1989 ROD remedy for 3-14 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

47 PRELIMINARY DRAFT FOR DISCUSSION ONLY 3 IDENTIFICATION AND SCREENING OF TECHNOLOGIES soils, which allowed for use of either soil excavation or SVE to address soil contamination at individual source facilities based on facility-specific conditions such as geology, physical access restrictions, and initial concentrations. SFO/ [SUPPLEMNTALFS.DOCX] 3-15 ES BAO

48

49 PRELIMINARY DRAFT FOR DISCUSSION ONLY 4 Development of Remedial Alternatives This section presents the development of remedial alternatives from the technologies retained in Section 3, and describes the projected performance of each alternative with respect to the RAOs. A combination of the technologies were assembled into the alternatives. 4.1 Alternatives for Evaluation Five alternatives have been developed for this Supplemental FS: Alternative 1 Current GWET remedy Alternative 2 Optimized GWET Alternative 3 Optimized GWET and MNA Alternative 4 - Targeted in situ redox treatment, optimized GWET, and MNA Alternative 5 Targeted in situ redox treatment, PRBs, optimized GWET, and MNA As a baseline against which to compare other alternatives, Alternative 1 assumes no change to the existing groundwater remedy (i.e. continued operation of the existing GWET systems). Alternative 2 is an optimized version of the existing groundwater remedy, where optimization measures are utilized to accelerate groundwater cleanup. Alternative 3 includes a transition from optimized GWET to MNA, where MNA is demonstrated. Alternatives 4 and 5 build upon Alternative 3 with additional technologies (in situ redox treatment in high concentration and source areas for Alternative 4, and in situ redox treatment and PRBs for Alternative 5). The list of alternatives is applicable for all groundwater aquifer zones. Because the vapor intrusion RAO is only applicable to the shallow A/A1 Zone, the alternatives are evaluated separately for the shallow A/A1 Zone and for the lower aquifers. Ultimately, the alternative selected for the A/A1 Zone may differ from the alternative selected for the lower aquifer zones in order to meet the vapor intrusion RAO. There are many challenges to groundwater cleanup at the MEW Site including multiple source areas; the disperse nature of plume; the potential for matrix diffusion effects; the heterogeneity of the subsurface; existing infrastructure and buildings, which limit implementation of technologies; and the potential to recontaminate treatment areas from onflow of higher concentration upgradient areas, depending on treatment timing across the plume. Given these challenges, and the need to address the vapor intrusion RAO by accelerating groundwater cleanup, EPA developed an overall strategy for cleanup of the plume. This strategy involves aggressively targeting certain areas of the plume based on the concentration of the chlorinated volatile organic compounds (CVOCs) (PCE, TCE, 1,2-DCE and VC) within the shallow A/A1 Zone. For purposes of the FS, EPA defines these targeted areas to include former source areas and high concentration areas (i.e., CVOC concentrations greater than 1,000 ug/l). As additional information is collected during SFO/ [SUPPLEMNTALFS.DOCX] 4-1 ES BAO

50 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY implementation of the vapor intrusion remedy and additional data is obtained during further site characterization, pilot tests, and targeted cleanup, EPA may revise the definition of the areas requiring targeted cleanup. In areas not proposed for targeted cleanup, the existing or optimized GWET systems would continue to operate to contain and treat the plume until cleanup levels are reached or to levels appropriate for MNA if MNA is selected and can be demonstrated. One concern is the potential for treated areas to be recontaminated by upgradient flow once groundwater in an area is cleaned up. The slurry walls act as barriers to onflow from upgradient areas and high VOCs concentrations within the slurry walls could be reduced without concerns of recontamination. Application of optimized GWET or in situ redox within the slurry walls could ultimately result in residual contamination levels acceptable for MNA, if demonstrated. Some source and high concentrations areas are within the larger plume where there are no barriers upgradient to prevent contaminant migration into areas that have been cleaned up. In these cases, more aggressive initial reduction to upgradient or surrounding concentrations is appropriate given the potential for recontamination. Following clean up of such unprotected source and high concentration areas to surrounding regional concentrations, treatment would progress to an approach suitable for the larger regional contaminant plume. The 1989 ROD provided the remedy for soil cleanup by soil excavation and aeration or offsite disposal and soil vapor extraction with treatment by vapor-phase carbon. This FS is only addressing the contaminated groundwater and not the soil or soil gas. If soil contamination is identified as a source of vapor intrusion, soil excavation and SVE could still be applied as part of the original remedy. Conceptual designs have been developed for each alternative for alternative comparison and costs estimating purposes only. The actual design of the selected groundwater remedy will occur during the remedial design. The conceptual designs incorporate the elements of the existing conceptual site model, a general understanding of technology implementation limitations because of existing infrastructure and access restrictions, and the results of pilotscale applications of individual treatment technologies within the MEW Site. The configuration of the alternative components such as the location and number of extraction wells, the area for in situ redox treatment, and location of PRBs will likely be modified during the remedial design of the selected remedy but are considered sufficient to develop and estimate costs within the range of uncertainty specified by EPA guidelines (+50 to -30 percent) and to evaluate the effectiveness of each alternative. For purposes of developing and comparing costs, an operation and maintenance period of 50 years is assumed, although the need for remedial action for all of the alternatives is likely to extend beyond 50 years. After 50 years, costs are considered difficult to predict and the value of money becomes so heavily discounted that there is little difference between a 50 year cost and a 1,000 year cost. While using the present worth analysis method is valuable for evaluating source treatment technologies that typically are completed in relatively short timeframes and is also required by EPA guidance, such an analysis limits the ability to compare and account for life cycle project cost differences for longer remediation timeframes (e.g., extending beyond 50 years). These longer remediation timeframes and life 4-2 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

51 PRELIMINARY DRAFT FOR DISCUSSION ONLY 4 DEVELOPMENT OF REMEDIAL ALTERNATIVES cycle project costs often occur for groundwater cleanups, such as the MEW Site, where groundwater cleanup levels are low. Total life cycle cost savings that may be realized by reductions in these longer remediation timeframes are not accounted for by this analysis. 4.2 Common Remedial Alternative Components The following subsections discuss components of the remedial alternatives that are common for each alternative Institutional Controls The applicable ICs are identified, described, and evaluated separately in Section 6 of this FS Groundwater Monitoring Groundwater monitoring will be required as part of the Remedial Action regardless of the alternative selected the MEW Site. Currently, groundwater elevations are monitored semiannually within the plume and annual sampling of select wells in the facility-specific areas and regional plume for the COCs are conducted. For the FS, the following assumptions were made: Groundwater elevation measurements would continue to be measured semi-annually Groundwater sampling would continue annually for select wells within the facilityspecific areas and regional plume Additional wells would be installed and sampled to monitor the performance of the technologies specified for each alternative to ensure the RAOs are being met. The assumptions associated with installation and sampling of additional wells are described within each alternative. It is assumed that some of the wells from the existing network could be used for the performance monitoring. Facilities would continue to treat groundwater with systems currently in place (Table 1-1) Slurry Walls As discussed previously, four low-permeability slurry walls were installed at the site to prevent contaminant migration. The 1989 ROD required an extraction system for each slurry wall to maintain an inward and upward gradient within the slurry walls. Although, the slurry walls have generally been successful at preventing contaminant migration, there has been difficulty consistently maintaining inward and upward gradients within the slurry walls. Inward and upward gradients help ensure contaminants do not migrate through the slurry wall or escape through slurry wall defects. However, the overarching objective is to prevent migration of contamination from the high source areas. All alternatives will require the slurry walls to be maintained, and the groundwater extraction and treatment within the slurry walls operated. The requirement for inward and upward gradients may be waived if the following can be demonstrated: SFO/ [SUPPLEMNTALFS.DOCX] 4-3 ES BAO

52 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Operation of the remedy (exterior recovery wells) outside the slurry wall is required to prevent lateral migration of contaminants. An extraction plan will be developed to contain as much of the source contamination within the slurry walls as possible; or Operation of additional extraction wells outside the slurry wall, as required by optimization, results in the inability to maintain the inward and upward gradient in the slurry wall. An extraction plan will be developed to contain as much of the source contamination within the slurry walls as possible; or Remedy reduces concentrations within slurry walls to levels comparable to the upgradient plume concentrations. The extraction system within the slurry wall may be discontinued in this circumstance Five Year Reviews Five-Year Reviews will be required at the MEW Site regardless of the alternatives selected to implement the Remedial Action, since varying amounts of contamination will remain on site. Therefore Five-Year Reviews are built in as a common component of all alternatives for costing purposes Cleanup of C-Zone The extent of the TCE plume in the C-zone (Silva Well) is limited to a localized area south of the Hetch-Hetchy aqueduct (Figure 1-11). The concentrations in the C-zone are low and detections are sporadic, (maximum concentration is 28 ppb of TCE). Groundwater extraction and treatment is an effective option given the depth of contamination and low, localized area of contamination. MNA could also be evaluated and possibly implemented given the current concentrations. 4.3 Alternative 1 Current GWET Remedy The NCP requires analysis of a no action alternative to provide a baseline for comparison to other alternatives. A No Further Action alternative was evaluated in the 1989 Proposed Plan for the MEW Site, and it was eliminated from consideration because it allows continued migration of groundwater, does not reduce toxicity, mobility, or volume through treatment, does not meet ARARs, and is not protective of human health and the environment (EPA, 1989). Hydraulic gradients and contaminant plume locations in the aquifer system at the MEW Site at present remain similar to the conditions in 1989, and shutting down the existing treatment systems would result in a similar outcome as the 1989 no action alternative, that is, further migration of contamination. Additionally, the 1989 remedy is in place and currently operating while this FS is being conducted. Therefore, for this FS, rather than reconsidering the no action alternative, EPA will use the 1989 groundwater remedy, as currently implemented without optimization, as Alternative 1. The current remedy includes multiple GWET systems for cleanup and containment of specified facility source areas and the regional groundwater plume. In addition, low permeability slurry walls surround four separate source areas to prevent contaminant migration (Figure 1-2). Three of the slurry walls were installed in 1986 to surround former Fairchild facility properties (Buildings 1-4, 9, and 19) and extend vertically approximately 4-4 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

53 PRELIMINARY DRAFT FOR DISCUSSION ONLY 4 DEVELOPMENT OF REMEDIAL ALTERNATIVES 40 feet bgs to the A/B1 Aquitard. One slurry wall was installed in 1987 to surround the former Raytheon facility property and extends vertically approximately 100 feet bgs, partially penetrating the B2 Zone. The current groundwater remedy requires the maintenance of inward and upward gradients within the confines of the slurry walls. Individual MEW parties operate source control recovery wells and the Regional Program operates regional recovery wells, with extracted groundwater directed to a total of 11 GWET systems at the MEW Site. Eight GWET systems operate south of Highway 101, consisting of seven facility-specific systems and the southern regional system. Three GWET systems operate north of Highway 101, consisting of the northern regional system, the Navy s WATS, and the NASA system. The GWET systems direct treated effluent to Stevens Creek or to storm and sanitary sewer systems under NPDES permits (see Table 1-1). Figures 4-1 through 4-3 provide the locations of the slurry walls, extraction wells, and GWET systems operating at the MEW Site for the A/A1 Zone, B1/A2 Zone, and B3 Zone, respectively. The 2009 Second Five-Year Review Report (EPA, 2009) identified issues with the performance of the current pumping scheme, as summarized below: The slurry walls are not fully functioning as intended, as outward gradients are consistently observed along the northern (downgradient) segments of these walls, indicating that some chemical migration is occurring across the walls. This is further demonstrated by the fact that despite over two decades of pumping, the plume has not separated itself from the source areas contained within the slurry walls. However, any contaminated groundwater migrating across the slurry walls appears to be fully captured by downgradient source control and regional extraction wells. Downgradient vertical gradients observed in portions of the plume correlate with increasing VOC concentrations in those areas, indicating that some downward vertical migration may be occurring. The Regional Plume is not fully captured by the current extraction scheme in certain areas, particularly the downgradient portion of the plume on Moffett Field (north of U.S. Highway 101). While concentrations within the core of the TCE plume have decreased, the outer extent of the plume, as defined by the 5 g/l TCE isoconcentration contour line, appears to be increasing slightly, particularly in the B1/A2 and B2 Aquifers. The pumping scheme was slightly adjusted in 2010 [Geosyntec, 2010]; however, the concerns raised in the Five-Year Review have not been sufficiently addressed. The estimated costs for Alternative 1 (the current remedy) are presented in Section 5. The cost estimates and assumptions used to prepare the cost estimates are presented in Appendix C. Costs are presented separately for the shallow and lower aquifers, and include only the O&M and performance monitoring costs for the current system for continued operation over a 50-year time period. Additional costs for wells are included to improve hydraulic containment of the plume, including capture at the toe of the plume, a concern identified in the 5-Year Review. SFO/ [SUPPLEMNTALFS.DOCX] 4-5 ES BAO

54 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY The original capital costs and former O&M costs are not included. This allows the 50-year costs for various alternatives that might be implemented in the future to be compared against the 50-year cost of continued operation of the current remedy. As noted above and discussed in Section 4.1, a 50-year operation period is not expected to be sufficient for the current remedy (Alternative 1) to meet the RAOs for the MEW Site. 4.4 Alternative 2 Optimized GWET Alternative 2 is the current GWET remedy optimized to enhance mass recovery and to improve hydraulic containment of the regional groundwater plume and targeted cleanup to address the VI RAO. Specifically, the alternative would consist of the following: The GWET systems would be optimized to improve mass recovery by installing additional wells and modifying pumping rates. Wells would also be installed in areas specified for targeted cleanup (see Section 4.1) and medium concentrations areas of the plume, where additional extraction would likely improve mass recovery. The optimization goal for improved mass recovery is an approximate doubling of the extracted contaminant mass per unit volume of extracted groundwater at targeted areas, as compared with the 2009/2010 mass recovery rates. It is estimated that this alternative will reduce the high concentrations in the targeted areas approximately 30% more in the first decade as compared to the current remedy (Alternative 1). Conceptual designs for application of Alternative 2 within the shallow A/A1 Zone, B1/A2 Zone, and the B2 Zone are provided in Figures 4-4, 4-5, and 4-6, respectively. These figures include the location of existing and new extraction wells associated with the optimized GWET system along with their extraction rates. Where possible, existing extraction wells are utilized to limit the amount of new infrastructure required. Where new extraction wells are required, locations have been selected that limit the amount of new conveyance piping required to tie-in to existing piping. The increase in mass removal rates is not expected to require significant changes to the existing groundwater treatment systems. Optimization components noted above are evaluated in the environmental footprint analysis for Alternative 2, which is presented in Appendix A. Although the conceptual designs for GWET optimization under this alternative are based on increased mass recovery from existing and new extraction wells, optimization of the existing remedy may also consist of measures such as pulsed extraction or incorporation of hydraulic barriers. As discussed in Section , pulsed extraction can provide an increase in mass recovery for the same volume of extracted groundwater by allowing dissolved groundwater concentrations to increase because of desorption when extraction wells are off, then restarting the wells before contaminants migrate beyond the hydraulic capture zone. Pulsed extraction is a common optimization strategy when dissolved groundwater concentrations asymptotically approach a value greater than the cleanup standard because of matrix diffusion, or similar, effects. Modifications to extraction well placement, including the use of linear transects of wells (hydraulic barriers) rather than a dispersed network of wells, may also be considered as part of optimization. 4-6 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

55 PRELIMINARY DRAFT FOR DISCUSSION ONLY 4 DEVELOPMENT OF REMEDIAL ALTERNATIVES Other optimizations or environmental footprint reduction practices that may be considered in the future include: reevaluation of the existing ex-situ treatment technologies to determine if systems can be scaled back, modified, or operated to use less energy; reinjection of some treated water into the aquifer to enhance cleanup rather than discharge to Stevens Creek; and installing on-site renewable energy sources. These possible optimization practices are included as part of the footprint analysis in Appendix A. The estimated costs for Alternative 2 are presented in Section 5. The cost estimates and assumptions used to prepare the cost estimates are presented in Appendix C. The cost estimates for this alternative include the installation of all necessary infrastructure as well as operation and maintenance (O&M) costs, and have been separated into the cost for application within the shallow A/A1 Zone and the cost for application within the lower aquifer zones. 4.5 Alternative 3 Optimized GWET and MNA Alternative 3 consists of a similar optimized version of the existing GWET groundwater remedy and targeted cleanup to address VI RAO as Alternative 2, but also includes transition to MNA if it is demonstrated that MNA is capable of achieving the RAOs in specific areas of the plume. Specifically, the alternative would consist of the following: GWET systems would be optimized to improve mass recovery in high and medium concentration areas and to achieve complete hydraulic containment of the regional plume, except where MNA is demonstrated. The optimization target for improved mass recovery is an approximate doubling of the extracted contaminant mass per unit volume of extracted groundwater for the overall MEW Site (combined GWET systems), as compared with the 2009/2010 mass recovery rates. It is estimated that this alternative will reduce the high concentrations in the targeted area c approximately 30% more in the first decade as compared to the current remedy (Alternative 1). GWET would also be used to address targeted areas for groundwater cleanup in the shallow A/A1 Zone (see Section 4.1). For Alternative 3, some portions of the plume are assumed to already have sufficient lines of evidence to warrant entering a MNA demonstration phase (see Section 4.8), reducing the number of extraction wells operating under Alternative 3 compared to Alternative 2. Optimized GWET systems would operate until groundwater COCs are reduced to a concentration where sufficient evidence demonstrates that subsequent passive treatment using MNA would be capable of meeting the RAOs within a reasonable timeframe and it is determined that there is no risk from vapor intrusion into overlying buildings (see section 4.8). Continued groundwater monitoring would be used to document that MNA is meeting the RAOs within these areas. The conceptual designs for Alternative 3 applied within the shallow A/A1 Zone and the lower aquifer zones are similar to those for Alternative 2, and are shown in Figures 4-7 through 4-9. The figures include the location of existing and new extraction wells associated with the optimized GWET system along with their extraction rates. SFO/ [SUPPLEMNTALFS.DOCX] 4-7 ES BAO

56 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY The increase in mass removal rates is not expected to require significant changes to the existing groundwater treatment systems. Optimization components noted above are evaluated in the environmental footprint analysis for Alternative 3, which is presented in Appendix A. The estimated costs for Alternative 3 are presented in Section 5. The cost estimates and assumptions used to prepare the cost estimates are presented in Appendix C. The cost estimates for this alternative include the installation of all necessary infrastructure as well as operation and maintenance (O&M) costs, and have been separated into the cost for application within the shallow A/A1 Zone and the cost for application within the lower aquifer zones. 4.6 Alternative 4 Targeted In Situ Redox Treatment, Optimized GWET, and MNA Alternative 4 includes targeted treatment of the areas specified in Section 4.1 using in situ redox technologies (ISCO, ERD, and ZVI). Outside of these areas, hydraulic containment and treatment of the regional groundwater plume would continue, with transition to MNA where demonstrated. Specifically, the alternative includes the application of technologies within different areas of the plume as follows: All high-concentration areas in the A/A1 Zone (defined as CVOC concentrations exceeding 1,000 µg/l) and facility-specific source areas (low to medium concentration areas) would be treated with any of the three in situ redox technologies (ISCO, ERD, ZVI), except where it is demonstrated that those technologies are infeasible whereupon optimized GWET will be utilized. It is estimated that this alternative will reduce the high concentrations in the targeted area approximately 50% more in the first decade as compared to the current remedy (Alternative 1). In the lower aquifer zones, where high-concentration areas are more extensive and the concern about vapor intrusion does not apply, in situ redox technologies would be targeted only at facility-specific source areas with high residual concentrations. The extent of these treatment areas would be determined during the remedial design. For purposes of this FS, it is assumed that approximately 15 percent of the facility-specific source areas shown on the conceptual design figures would ultimately require treatment by in situ redox technologies. Where it is demonstrated that those technologies are infeasible, optimzed GWET may be utilized. Groundwater within the remaining regional plume (all aquifer zones) would be hydraulically contained and treated using optimized GWET. Active treatment and hydraulic containment may be transitioned to MNA when and if sufficient evidence demonstrates, and ongoing monitoring confirms, that natural attenuation processes are capable of meeting the RAOs within a reasonable timeframe (see Section 4.8). The conceptual designs for Alternative 4 within the A/A1 Zone and the lower aquifer zones are shown on Figures 4-10 through The figures illustrate the application areas for 4-8 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

57 PRELIMINARY DRAFT FOR DISCUSSION ONLY 4 DEVELOPMENT OF REMEDIAL ALTERNATIVES in situ redox technologies and the conceptual location of extraction wells associated with the optimized GWET system. Where possible, existing extraction wells are utilized to limit the amount of new infrastructure required. Where new extraction wells are required, locations have been selected that limit the amount of new conveyance piping required to tie-in to existing piping. The estimated costs for Alternative 4 are presented in Section 5. The cost estimates and assumptions used to prepare the cost estimates are presented in Appendix C and are based on estimates using RACER and actual costs from the pilot tests cost data as well as previous engineering experience at similar sites. The cost estimates for this alternative include the installation of all necessary infrastructure as well as operation and maintenance (O&M) costs, and have been separated into the cost for application within the shallow A/A1 Zone and the cost for application within the lower aquifer zones. 4.7 Alternative 5 Targeted In Situ Redox Treatment, PRBs, Optimized GWET, and MNA Alternative 5 combines in situ redox treatment in the areas described for Alternative 4 with installation of permeable reactive barriers (for example, ZVI barriers) downgradient of these areas to treat residual contamination. GWET would still be used to control and treat portions of the plume not address by the PRBs, with an eventual transition to MNA where demonstrated. Specifically, the alternative includes the application of technologies within different areas of the plume as follows: All high-concentration areas in the A/A1 Zone (defined as CVOC concentrations exceeding 1,000 µg/l) and facility-specific source areas (low to medium concentration areas) would be treated with any of the three in situ redox technologies (ISCO, ERD, ZVI), except where it is demonstrated that those technologies are infeasible, whereupon optimized GWET will be utilized; In the lower aquifer zones, where high-concentration areas are more extensive and the concern about vapor intrusion does not apply, in situ redox technologies would be targeted only at facility-specific source areas with high residual concentrations. For purposes of this FS, it is assumed that approximately 15 percent of the facility-specific source areas shown on the conceptual design figures would ultimately require treatment by in situ redox technologies. Where it is demonstrated that those technologies are infeasible, GWET will be utilized. In the A/A1 Zone, regional and facility-specific PRBs would be installed downgradient of high concentration areas. In the B1/A2 Zone, regional PRBs would be installed downgradient of highconcentration areas. Groundwater not in targeted areas of the plume in the A/A1 and B1/A2 Zones (for example, downgradient edge of plume, and between facility boundaries where PRBs do not exist), and the entire plume area in B2 Zone, would be treated and hydraulically contained using optimized GWET. SFO/ [SUPPLEMNTALFS.DOCX] 4-9 ES BAO

58 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Active treatment and hydraulic containment may be transitioned to MNA when and if sufficient evidence demonstrates, and ongoing monitoring confirms, that natural attenuation processes, in combination with the PRBs, are capable of meeting the RAOs within a reasonable timeframe (see Section 4.8). The conceptual designs for Alternative 5 within the A/A1 Zone and the lower aquifers are shown on Figures 4-13 through 4-15, respectively. The figures illustrate the application areas for in situ redox technologies, the locations of regional and facility-specific PRBs, and the locations of extraction wells associated with the optimized GWET system. For Alternative 5, one facility-specific PRB and three regional PRBs would be installed. The facility-specific PRB would be installed in the A/A1 Zone only at the former Vishay facility, to treat residual contamination following in situ treatment. The regional PRBs would be installed in both the A/A1 Zone and the B1/A2 Zone in the following areas: (1) on the north side of Highway 101 (mid-plume PRB); (2) on Moffett Field along Wescoat Road (Wescoat PRB); and (3) on Moffett Field along King Road (downgradient PRB). The estimated costs for Alternative 5 are presented in Section 5. The cost estimates and assumptions used to prepare the cost estimates are presented in Appendix C and are based on estimates from permeable reactive barrier wall vendor and previous engineering experience at similar sites. The cost estimates for this alternative include the installation of necessary infrastructure to construct the remedy, as well as O&M costs, and have been separated into the cost for application within the shallow A/A1 Zone and the cost for application within the lower aquifer zones. 4.8 Criteria for Implementation of Monitored Natural Attenuation Alternatives 3, 4, and 5 include the potential implementation of MNA as a component of the overall remedial alternative, if it can be demonstrated that MNA is capable of meeting the RAOs. As discussed in Section 3.1.4, the Regional Program has performed an MNA assessment at the Site, and concluded that several lines of evidence suggest that natural attenuation processes are occurring in parts of the plume (Geosyntec, 2011a). In other parts of the plume, evidence is less clear that natural attenuation is viable. Different parts of the plume and depths within the aquifer zones exhibit varying redox states and variable evidence of natural attenuation by reductive dechlorination. Therefore, an area-specific approach will need to be implemented to demonstrate MNA. EPA technical resource documents that support an analysis of MNA as a viable remedial alternative include EPA s 1998, Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground Water (EPA, 1998). This guidance identifies parameters that are useful in the evaluation of natural attenuation of chlorinated solvents, and provides recommendations to analyze and interpret data collected when incorporating natural attenuation into an integrated remediation approach. In 2004, EPA identified data needs and evaluation methods useful for designing monitoring networks and determining remedy effectiveness for remedial actions which include MNA, in Performance Monitoring of MNA Remedies for VOCs in Ground Water (EPA, 2004b). These technical resource documents 4-10 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

59 PRELIMINARY DRAFT FOR DISCUSSION ONLY 4 DEVELOPMENT OF REMEDIAL ALTERNATIVES identify general lines of evidence, which can be used to document the performance of natural attenuation processes at a site and support a transition from an active remedy component, such as in situ redox technologies or GWET, to an MNA component. When evaluating a transition from an active remedy to MNA, the following general process would be followed: Identify potentially applicable area for MNA transition Complete MNA analysis based on lines of evidence criteria Prepare a plan for MNA implementation and demonstration Obtain EPA concurrence on the approach Implement MNA Perform MNA demonstration monitoring The MNA analysis will need to include the following elements before EPA would approve use of MNA. MNA would not be implemented in residential or commercial areas if there is an existing risk or potential increase in risk for vapor intrusion: Document VOC loss Document indirect (geochemistry) or direct (biological) evidence supporting natural biodegradation processes Estimate time to achieve RAOs under MNA Document that vertical and downgradient containment is in place during MNA demonstration Once implemented, the MNA demonstration program should meet or demonstrate the following general criteria: Demonstrate that natural attenuation is occurring to expectations Detect changes in conditions that may reduce the efficacy of natural attenuation Identify potentially toxic or mobile transformation products Verify the groundwater plume is stable Verify there are no unacceptable impacts to receptors Document the efficacy of institutional controls Verify attainment of (or suitable progress toward) RAOs 4.9 Cleanup Timeframes Evaluation To evaluate the time required to reach cleanup goals for each alternative, a spreadsheet box model was developed to simulate the primary fate and transport processes affecting TCE, the primary contaminant at the Site. The box model is an adaptation of a mathematical matrix diffusion model developed by Parker et al. (1994) and adapted by Tom Sale (AFCEE, 2007), and includes changes to TCE mass in the transmissive zone of the aquifer because of advection and degradation, in addition to matrix diffusion. The box model is a screeninglevel model, most useful for comparison between alternatives for the long term and does not model accurately localized responses to a particular remedy. The box model is described in detail in the Draft Plume Cleanup Time Evaluation report (Geosyntec, 2012). SFO/ [SUPPLEMNTALFS.DOCX] 4-11 ES BAO

60 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY The box model was used to determine the time required to meet the following reductions in TCE concentrations: Reducing TCE concentrations to the 5 g/l MCL Reducing TCE concentrations to 10% of 2009 concentrations (90% reduction) Reducing TCE concentrations to a placeholder value where MNA may be appropriate (for purpose of the modeling, 200 g/l was used) for areas of the plume where 2009 concentrations exceed that value Table 4-1 summarizes the results of the cleanup time analysis for the A/A1, B1/A2, and B2 Zones for the overall plume. The table shows the percentages of the modeled plume areas that exceed each of the three identified cleanup targets for each of the alternatives, at selected points in the future. The Draft Plume Cleanup Time Evaluation Report (Geosyntec, 2012) also presents the results of the box model analysis in various graphic forms including changes to the plume for each alternative over 10, 50 and 100 years periods. The results of the box model do not indicate a clear advantage of one alternative over others with respect to the time required for the plume to meet MCLs. This is primarily because of the way the model simulates the lasting effects of matrix diffusion, which becomes the dominant driver of lengthy cleanup times even when aggressive treatments quickly treat high concentration areas. Due to the extent of the contamination and the large amount of mass in the fine-grained material, the time to achieve MCLs is projected to be many centuries under all alternatives, as modeled. While there is no clear advantage for using one alternative over another with respect to the time required for overall plume cleanup, the analysis does indicate that high concentrations areas in the A/A1 Zone can be reduced more quickly by using in situ redox treatment (Alternative 4). Table 4-2 presents the predicted TCE concentrations over time using different initial starting concentrations of TCE. Under Alternative 4, TCE concentrations are predicted to be reduced from 2,000 ug/l to 555 ug/l in 10 years (53% reduction). For Alternatives 2 and 3, over the 10-year period, TCE concentrations are only reduced to 799 ug/l (32% reduction). For Alternative 5, TCE concentrations are actually predicted to increase during the 10-year period as contaminants released through in situ redox would be desorbed and would migrate with groundwater flow until treatment by the permeable reactive barriers. Alternative 4 also results in more TCE concentration reductions compared to Alternatives 2, 3 and 5 for the 50-year and 100-year timeframes (Table 4-2). The analysis also indicates that the time required to reach a placeholder value where MNA may be appropriate (200 g/l was modeled) is less than 100 years for the A/A1 Zone and B1 Zone for all alternatives except Alternative 5, where a longer timeframe is needed to complete the cleanup (Table 4-1). The mathematical matrix diffusion model within the box model appears to be limited in how it represents the effects of some technologies, particularly in situ redox treatment. Aggressive treatments such as in situ redox technologies have been shown to have a surfactant effect, which greatly enhances desorption and dissolution from soil into the dissolved phase. In instances of partial penetration of contaminants into low permeability 4-12 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

61 PRELIMINARY DRAFT FOR DISCUSSION ONLY 4 DEVELOPMENT OF REMEDIAL ALTERNATIVES zones, such treatments may be more effective than indicated by the box model, which assumes even distribution of contaminants throughout the low permeability zones. The results of in situ redox pilot studies at the former Intel facility have suggested such a surfactant effect, in that the amount of cis-1,2-dce generated was greater than what would be expected from the initial dissolved TCE concentrations indicating that TCE was desorbed because of the treatment (see Section ). Depending on the actual distribution of contaminants within various permeability zones at the site, the cleanup time predicted by the box model may be overly conservative for Alternatives 4 and 5, which include targeted in situ redox treatment. Rebound studies could be used to identify any desorption/dissolution benefits within the plume that may be realized by amendment injections that may reduce the influence of matrix diffusion effects. Any measurable reductions in the matrix diffusion could then be taken into account. SFO/ [SUPPLEMNTALFS.DOCX] 4-13 ES BAO

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63 5 Detailed Analysis of Alternatives PRELIMINARY DRAFT FOR DISCUSSION ONLY Section 5 presents a detailed analysis of the remedial alternatives using the nine evaluation criteria specified in the NCP and concludes with a comparative analysis of the remedial alternatives to facilitate EPA s selection of a preferred alternative. 5.1 Description of Evaluation Criteria The nine CERCLA evaluation criteria specified in the NCP (40 CFR Section (e)(9)(iii)) are discussed below. The NCP categorizes the nine CERCLA evaluation criteria into three groups: (1) threshold criteria, (2) primary balancing criteria, and (3) modifying criteria. Each category of criteria has its own weight when applied to the evaluation of alternatives. 1. Threshold criteria are requirements that each alternative must meet to be eligible for selection as the preferred alternative. Threshold criteria include the overall protection of human health and the environment, and compliance with ARARs (unless a waiver is obtained). 2. Primary balancing criteria weigh the effectiveness and cost trade-offs among alternatives. Primary balancing criteria include long-term effectiveness and permanence; reduction of toxicity, mobility, or volume through treatment; short-term effectiveness; implementability; and cost. The primary balancing criteria are the main technical criteria upon which the alternatives evaluation is based. 3. Modifying criteria include state and community acceptance, which may be used to modify aspects of the selected alternative when preparing the ROD. These criteria are generally evaluated after public comment on the FS and the proposed plan. The two threshold and the five primary balancing criteria are used to evaluate alternatives in the detailed analysis phase. State and community acceptance criteria will be considered in preparation of the Final FS and ROD. This draft FS incorporates comments received from stakeholders during the preparation of this Supplemental FS. The nine CERCLA criteria include: 1. Overall protection of human health and the environment - This criterion assesses whether an alternative achieves overall protection of human health and the environment. Alternatives are assessed to determine whether they are adequately protective, in both the short and long term, from unacceptable risks posed by site contamination. The assessment of overall protection draws on the assessments conducted under other evaluation criteria, especially long-term effectiveness and permanence, short-term effectiveness, and compliance with ARARs. 2. Compliance with ARARs - This criterion assesses whether an alternative can attain the federal and state ARARs or whether there is a basis for invoking a waiver of those ARARs. The potential ARARs for the remedial alternatives are described in Section 2. SFO/ [SUPPLEMNTALFS.DOCX] 5-1 ES BAO

64 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY 3. Long-term effectiveness and permanence - This criterion assesses the extent to which each remedial alternative reduces risk after the remedial action objectives are met. Residual risk can result from exposure to untreated waste or treatment residuals. The magnitude of the risk depends on the quantity and concentration of the wastes and the adequacy and reliability of controls, if any, that are used to manage untreated waste and treatment residuals. For the alternatives evaluated in this Supplemental FS, treatment residuals may include spent carbon, iron from PRBs, concentrated brines, or sludges. 4. Reduction of toxicity, mobility, or volume through treatment - This criterion addresses the preference, as stated in the NCP, for selecting remedial actions employing treatment technologies that permanently and significantly reduce toxicity, mobility, or volume of the hazardous substances as a principal element of the action. This preference is satisfied when treatment is used to reduce the principal threats at a site through destruction of toxic contaminants, reduction of total mass of toxic contaminants, irreversible reduction in contaminant mobility, or reduction of total volume of contaminated media. 5. Short-term effectiveness - This criterion evaluates the effects of each remedial alternative on human health and the environment during construction and operation, as well as the time required to meet the RAOs. 6. Implementability - This criterion evaluates the technical and administrative feasibility of implementing an alternative and the availability of various services and materials required during its implementation. 7. Cost - This criterion estimates the total cost of each alternative. Costs include capital expenditures (design, initial permitting, construction, startup, and contingencies), annual O&M (labor, materials, energy, laboratory analysis, and other services), periodic costs (major infrastructure overhaul or replacement, five year reviews), and net present value (total cost in today s dollars for capital, O&M, and periodic costs, assuming a discount rate of 2.0 percent and a period of operation of 50 years). The cost estimates are considered order-of-magnitude level estimates, with an expected accuracy of +50 to -30 percent. 8. State acceptance - This criterion evaluates the technical and administrative issues and concerns the state may have regarding each alternative. This criterion is addressed more fully after issuance of the Proposed Plan in the ROD Responsiveness Summary. 9. Community acceptance - This criterion evaluates the issues and concerns the public may have regarding each alternative. This criterion will be addressed in the ROD and responsiveness summary, after public comments on this Supplemental FS and the Proposed Plan have been received. 5.2 Individual Analysis of Groundwater Alternatives This section provides an assessment of the groundwater alternatives based on the threshold and balancing NCP evaluation criteria described in Section 5.1. Descriptions of each alternative are provided in Section SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

65 5.2.1 Alternative 1 Current GWET Remedy PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES Alternative 1 includes multiple GWET systems for cleanup and containment of specified facility-specific source areas and the regional groundwater plume. In addition, low permeability slurry walls surround four separate source areas to prevent contaminant migration Overall Protection of Human Health and the Environment Groundwater extraction and treatment would continue to limit the migration of the regional groundwater plume, and existing slurry walls would continue to limit migration of contaminants from facility-specific source areas where they are installed, thereby offering protection of human health and the environment from direct exposure to groundwater. However, under the current pumping scenario, groundwater concentrations in many of the extraction wells have become asymptotic in the A/A1 Zone and the existing GWET systems are generally becoming less effective in achieving the groundwater RAOs and meeting the vapor intrusion RAO. In addition, the Second Five-Year Review for the MEW Site (EPA, 2009) identified issues with the performance of the existing pumping scenario, and concluded that the remedy is not fully functioning as intended (see Section 4.3) Compliance with ARARs The existing GWET remedy continues to make progress toward chemical-specific federal and state ARARs in the lower aquifer zones, but treatment is becoming significantly less effective over time and RAOs are not expected to be achieved for many decades to centuries. The existing GWET systems are being operated in compliance with ARARs Long-Term Effectiveness and Permanence The existing GWET systems have been in operation for more than 20 years and generally have been effective at controlling the migration of the regional groundwater plume and successfully removing VOCs. Ongoing operation of the existing GWET systems is expected to provide continued long-term hydraulic control of the lower aquifer zones and continued groundwater treatment. However, the decline in the effectiveness of the GWET systems means that a very long time period will be required to achieve the groundwater RAOs. During such an extended operational timeframe, individual components of the GWET system may exceed their service life and require replacement. The footprint analysis indicates that continued operation of the GWET over time is estimated to result in more energy and water use and greater greenhouse gas emissions, as compared with some of the alternatives (Appendix A). Approximately 1.9 million MMBTU will be used over a 50-year period along with generation of approximately 98 million pounds of CO2 equivalents. For the other metrics, GWET is estimated to result in approximately equal or lower levels of emissions of criteria pollutants, usage of materials, and waste generation as compared with some of the other alternatives Reduction of Toxicity, Mobility and Volume through Treatment While the existing GWET remedy has reduced concentrations within the groundwater plume appreciably over its more than 20 years of operation, concentrations in many of the extraction wells in the A/A1 Zone are reaching asymptotic levels and the GWET systems SFO/ [SUPPLEMNTALFS.DOCX] 5-3 ES BAO

66 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY are generally becoming less effective in reducing groundwater concentrations. In addition, the extent of the plume defined by groundwater exceeding MCLs has not been significantly reduced over time, and this is not expected to change with continued operation of the remedy over the foreseeable future. The existing GWET systems do limit overall plume mobility by providing hydraulic containment. Once groundwater is extracted, the existing GWET systems provide irreversible removal of CVOCs from groundwater via transfer to the treatment media (such as GAC) Short-Term Effectiveness The existing GWET system has already been installed, and continued operation would present no new risks to remediation workers Implementability The existing GWET system has already been constructed and is currently operating. No system modifications are anticipated as part of this alternative Cost The capital cost, annual O&M costs, periodic costs, and present value for Alternative 1 are listed below. Appendix C provides details of the estimated costs for Alternative 1. Shallow Aquifer (A/A1) Alternative 1 - Current GWET Remedy Capital Costs Annual Costs Net Present Value Capital Costs $408, Capital Contingency $60, Capital Supervision and Design $80, Total Capital Costs $600,000 Annual O&M Year $2,256,000 $20,300,000 Annual O&M Year $2,256,000 $16,600,000 Annual O&M Year $2,065,000 $12,500,000 Annual O&M Year $2,027,000 $10,100,000 Annual O&M Year $2,004,000 $8,200,000 O&M Contingency $3,400,000 Total O&M Costs $71,000,000 Periodic Costs $5,200,000 Total Periodic Costs $5,200,000 Total Alternative 1 Costs (Shallow Aquifer): $77,000, SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

67 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES Lower Aquifers Alternative 1 - Current GWET Remedy Capital Costs Annual Costs Net Present Value Capital Costs $645, Capital Contingency $100, Capital Supervision and Design $170, Total Capital Costs $900,000 Annual O&M Year $1,568,000 $14,100,000 Annual O&M Year $1,530,000 $11,300,000 Annual O&M Year $1,453,000 $8,800,000 Annual O&M Year $1,377,000 $6,800,000 Annual O&M Year $1,362,000 $5,500,000 O&M Contingency $2,300,000 Total O&M Costs $49,000,000 Periodic Costs $3,800,000 Total Periodic Costs $3,800,000 Total Alternative 1 Costs (Lower Aquifers): $54,000,000 Total Alternative 1 Costs: $131,000,000 GWET- Groundwater extraction and treatment O&M Operations and maintenance Net Present Value Future Costs presented in current dollars using discount rate of 2.0% over a 50 Year period. Capital costs include costs for installation of new wells or GWET infrastructure. O&M costs include annual expense for operation and sampling of monitoring wells. Periodic costs include GWET system overhaul after 20 years and 5-Year Reviews. See Appendix C for detailed cost assumptions and backup sheets Alternative 2 Optimized GWET Alternative 2 consists of an optimization of the current GWET remedy to enhance mass recovery and to improve hydraulic containment of the regional groundwater plume and targeted cleanup of groundwater to address the VI RAO Overall Protection of Human Health and the Environment The existing pumping scenario would be optimized to improve overall mass recovery and to achieve complete hydraulic capture of the regional plume. Groundwater extraction and treatment would control the migration of the regional groundwater plume, and existing slurry walls would control migration of contaminants from facility-specific source areas where they are installed, thereby offering protection of human health and the environment from direct exposure to groundwater. Institutional controls also would be implemented to limit potential groundwater exposure risks (see Section 6). SFO/ [SUPPLEMNTALFS.DOCX] 5-5 ES BAO

68 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY The increase in mass recovery rates and targeted cleanup for groundwater is expected to accelerate removal of a primary source of vapor intrusion, and meet the vapor intrusion RAO for the shallow A/A1 Zone Compliance with ARARs The alternative includes application of an optimized GWET pumping scenario and targeted cleanup, which is expected to accelerate progress toward chemical-specific federal and state ARARs compared with the current pumping scenario. The increase in mass recovery rates for the optimized GWET and targeted cleanup would meet the vapor intrusion RAO for the shallow A/A1 Zone Long-Term Effectiveness and Permanence The existing GWET systems have been in operation for more than 20 years and generally have been effective at providing hydraulic control of the regional groundwater plume. The optimized GWET remedy under this alternative is expected to provide continued long-term effective hydraulic control and somewhat accelerated groundwater treatment, although a very long time period will still be required to achieve all RAOs. During such an extended operational timeframe, individual components of the GWET system may exceed their service life and require replacement. In addition, targeted cleanup is expected to reduce the need for VI mitigation over the long-term. Alternative 2 is expected to result in a similar environmental footprint (i.e., energy, water, and materials usage, waste generation, and air emissions) as Alternative 1 since its main component is GWET (see Appendix A) Reduction of Toxicity, Mobility and Volume through Treatment While optimizing the existing remedy is not expected to reduce the extent of groundwater contamination significantly in the foreseeable future, it would result in greater removal of contaminant mass from groundwater, and would result in the reduction of toxicity. The optimized GWET systems would improve hydraulic capture by addressing areas identified in the Year Review. Once groundwater is extracted, optimized GWET would provide irreversible removal of CVOCs from groundwater via transfer to the treatment media (such as GAC). In the shallow A/A1 Zone, accelerating the removal of groundwater contamination through optimization and targeted cleanup would reduce the mobility of contamination from groundwater to vapor, and therefore reduce the potential for vapor intrusion into overlying buildings Short-Term Effectiveness The GWET system has already been installed, but the installation of extraction wells or conveyance piping as part of optimization or targeted cleanup will require the construction of new infrastructure, with new impacts to the community, site workers, and the environment. Drilling of new extraction wells and installation of conveyance piping would require coordination with the community, property owners, and regulators, procurement of access agreements, implementation of traffic and access control plans, and various monitoring activities during construction. Short-term community and property owner impacts would occur during construction of these new GWET components, and would 5-6 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

69 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES include disruptions to local traffic, parking, noise, and potentially nuisance lighting if construction occurs after typical working hours. Risks to site workers can be managed through appropriate health and safety practices Implementability The alternative is technically implementable using conventional construction methods and equipment that were already successfully used to install the existing GWET system. Any required revisions to the GWET system (for example, new wells or conveyance piping) are anticipated to be readily implemented, because of flexibility in specific locations of such infrastructure. Services and materials necessary for implementation of the alternative are readily available and competitive bids can be obtained from multiple equipment and remedial construction vendors. No significant difficulties are anticipated in obtaining permits for the installation of any new groundwater extraction wells. Access agreements will need to be obtained from current property owners. Effectiveness monitoring can be readily performed using a network of existing and/or newly-installed groundwater monitoring wells Cost The capital cost, annual O&M costs, periodic costs, and present value for Alternative 2 are listed below. Appendix C provides details of the estimated costs for Alternative 2. Shallow Aquifer (A/A1) Alternative 2 - Optimized GWET Capital Costs Annual Costs Net Present Value Capital Costs $1,160, Capital Contingency $170, Capital Supervision and Design $230, Total Capital Costs $1,600,000 Annual O&M Year $2,333,000 $21,000,000 Annual O&M Year $2,333,000 $17,200,000 Annual O&M Year $2,165,000 $13,100,000 Annual O&M Year $2,103,000 $10,400,000 Annual O&M Year $2,081,000 $8,500,000 O&M Contingency $10,500,000 Total O&M Costs $80,700,000 Periodic Costs $5,310,000 Total Periodic Costs $5,300,000 Total Alternative 2 Costs (Shallow Aquifer): $88,000,000 SFO/ [SUPPLEMNTALFS.DOCX] 5-7 ES BAO

70 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Lower Aquifers Alternative 2 - Optimized GWET Capital Costs Annual Costs Net Present Value Capital Costs $2,510, Capital Contingency $380, Capital Supervision and Design $480, Total Capital Costs $3,400,000 Annual O&M Year $1,950,000 $17,500,000 Annual O&M Year $1,912,000 $14,100,000 Annual O&M Year $1,775,000 $10,700,000 Annual O&M Year $1,721,000 $8,500,000 Annual O&M Year $1,706,000 $6,900,000 O&M Contingency $8,700,000 Total O&M Costs $66,400,000 Periodic Costs $4,540,000 Total Periodic Costs $4,500,000 Total Alternative 2 Costs (Lower Aquifers): $74,000,000 Total Alternative 2 Costs: $162,000,000 Notes: GWET = Groundwater extraction and treatment O&M = Operation and maintenance Net Present Value Future Costs presented in current dollars using discount rate of 2.0% over a 50 Year period. Capital costs include costs for installation of new wells or GWET infrastructure. O&M costs include annual expense for operation and sampling of monitoring wells. Periodic costs include GWET system overhaul after 20 years and 5-Year Reviews. See Appendix C for detailed cost assumptions and backup sheets Alternative 3 Optimized GWET and MNA Alternative 3 includes an optimized version of the existing GWET groundwater remedy and targeted cleanup of groundwater to address VI RAO similar to Alternative 2, but also includes transition to MNA if demonstrated capable of achieving the RAOs in specific areas of the plume Overall Protection of Human Health and the Environment The existing pumping scenario would be optimized to improve overall mass recovery and to achieve complete hydraulic capture of the regional plume. Groundwater extraction and treatment would control the migration of the regional groundwater plume, and existing slurry walls would control migration of contaminants from facility-specific source areas where they are installed, thereby offering protection of human health and the environment from direct exposure to groundwater. Institutional controls also would be implemented to limit potential groundwater exposure risks (see Section 6). 5-8 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

71 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES The increase in mass recovery rates for groundwater and targeted cleanup of groundwater is expected to accelerate removal of a primary source of vapor intrusion, and meet the vapor intrusion RAO for the shallow A/A1 Zone. MNA would only be implemented where demonstrated to be capable of achieving RAOs within a reasonable timeframe, and where there are no unacceptable impacts to receptors Compliance with ARARs The alternative is expected to accelerate progress toward chemical-specific federal and state ARARs compared with the current pumping scenario. The increase in mass recovery rates for the optimized GWET and targeted cleanup would meet the vapor intrusion RAO for the shallow A/A1 Zone. MNA is expected to be slower than GWET to achieve RAOs Long-Term Effectiveness and Permanence The existing GWET systems have been in operation for more than 20 years and generally have been effective at providing hydraulic control of the regional groundwater plume. The optimized GWET remedy under this alternative is expected to provide continued long-term effective hydraulic control and somewhat accelerated groundwater treatment, although a very long time period will still be required to achieve all RAOs. During such an extended operational timeframe, individual components of the GWET system may exceed their service life and require replacement. The natural attenuation processes providing treatment and control at the Site could be expected to operate in perpetuity, and could potentially provide permanent treatment if MNA can be demonstrated capable of achieving the RAOs. Because MNA is passive, it is expected, if it can be demonstrated at the site, to result in less energy and water usage and generation of greenhouse gas emissions over the long-term compared with Alternative 1 and 2 (Appendix A). This alternative does result in similar levels of criteria pollutant emissions, materials usage, and waste generation, as compared with Alternative 1 (see Appendix A) because it is assumed that pumping would still be required over some portions of the plume Reduction of Toxicity, Mobility and Volume through Treatment While optimizing the existing remedy is not expected to reduce the extent of groundwater contamination significantly in the foreseeable future, it would result in greater removal of contaminant mass from groundwater, and would result in the reduction of toxicity. The optimized GWET systems would improve hydraulic capture and therefore reduce mobility. Once groundwater is extracted, optimized GWET would provide irreversible removal of CVOCs from groundwater via transfer to the treatment media (such as GAC). In the shallow A/A1 Zone, accelerating the removal of groundwater contamination through optimization and targeted cleanup of groundwater would reduce the mobility of contamination from groundwater to vapor, and therefore reduce the potential for vapor intrusion into overlying buildings and the need for mitigation over the long-term. MNA, where applied, would also serve to reduce the toxicity and mobility of contamination. Some natural attenuation processes provide irreversible treatment of CVOCs, such as sequential dechlorination during biodegradation, while other processes, such as volatilization, transfer SFO/ [SUPPLEMNTALFS.DOCX] 5-9 ES BAO

72 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY mass from one media to another. If incomplete reductive dechlorination occurs, some more toxic intermediate byproducts such as vinyl chloride could be formed and would need to be monitored and mitigated. MNA would not be applied where there is risk of increasing the potential for vapor intrusion Short-Term Effectiveness The GWET system has already been installed, but the installation of extraction wells or conveyance piping as part of optimization or targeted groundwater cleanup will require the construction of new infrastructure, with new impacts to the community, site workers, and the environment. Drilling of new extraction wells and installation of conveyance piping would require coordination with the community, property owners, and regulators, procurement of access agreements, implementation of traffic and access control plans, and various monitoring activities during construction. Short-term community and property owner impacts would occur during construction of these new GWET components, and would include disruptions to local traffic, noise, and potentially nuisance lighting if construction occurs after typical working hours. Risks to site workers can be managed through appropriate health and safety practices. The application of MNA where demonstrated in specific areas of the plume would involve groundwater monitoring activities and would present no new risks to remediation workers Implementability The alternative is technically implementable using conventional construction methods and equipment that were already successfully used to install the existing GWET system. Any required revisions to the GWET system (for example, new wells or conveyance piping) are anticipated to be readily implemented, because of flexibility in specific locations of such infrastructure. Services and materials necessary for implementation of the alternative are readily available and competitive bids can be obtained from multiple equipment and remedial construction vendors. No significant difficulties are anticipated in obtaining permits for the installation of any new groundwater extraction wells. Access agreements will need to be obtained from current property owners. Effectiveness monitoring can be readily performed using a network of existing and/or newly-installed groundwater monitoring wells. Groundwater monitoring associated with MNA would require conventional sampling and monitoring equipment and is readily implementable Cost The capital cost, annual O&M costs, periodic costs, and present value for Alternative 3 are listed below. Appendix C provides details of the estimated costs for Alternative SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

73 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES Shallow Aquifer (A/A1) Alternative 3 - Optimized Capital Net Present GWET and MNA Costs Annual Costs Value Capital Costs $1,160, Capital Contingency $170, Capital Supervision and Design $230, Total Capital Costs $1,600,000 Annual O&M Year $2,072,000 $18,600,000 Annual O&M Year $921,000 $6,800,000 Annual O&M Year $668,000 $4,000,000 Annual O&M Year $649,000 $3,200,000 Annual O&M Year $649,000 $2,600,000 O&M Contingency $5,300,000 Total O&M Costs $40,500,000 Periodic Costs $5,230,000 Total Periodic Costs $5,200,000 Total Alternative 3 Costs (Shallow Aquifer): $47,000,000 Lower Aquifers Alternative 3 - Optimized Capital Net Present GWET and MNA Costs Annual Costs Value Capital Costs $2,510, Capital Contingency $380, Capital Supervision and Design $480, Total Capital Costs $3,400,000 Annual O&M Year $1,766,000 $15,900,000 Annual O&M Year $775,000 $5,700,000 Annual O&M Year $569,000 $3,400,000 Annual O&M Year $550,000 $2,700,000 Annual O&M Year $550,000 $2,200,000 O&M Contingency $4,500,000 Total O&M Costs $34,400,000 Periodic Costs $4,620,000 Total Periodic Costs $4,600,000 Total Alternative 3 Costs (Lower Aquifers): $42,000,000 Total Alternative 3 Costs: $89,000,000 GWET- Groundwater extraction and treatment O&M Operations and maintenance MNA = Monitored natural attenuation Net Present Value Future Costs presented in current dollars using discount rate of 2.0% over a 50 Year period. Capital costs include costs for installation of new wells or GWET infrastructure. O&M costs include annual expense for operation and sampling of monitoring wells. Periodic costs include GWET system overhaul after 20 years and 5-Year Reviews. See Appendix C for detailed cost assumptions and backup sheets. SFO/ [SUPPLEMNTALFS.DOCX] 5-11 ES BAO

74 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Alternative 4 In situ Redox, Optimized GWET, and MNA Alternative 4 includes targeted treatment in the area specified in Section 4.1 using in situ redox technologies (ISCO, ERD, ZVI). Outside of these areas, hydraulic containment and treatment of the regional groundwater plume would continue, with transition to MNA where demonstrated Overall Protection of Human Health and the Environment Application of in situ redox technologies within high concentration areas and facilityspecific source areas is expected to accelerate removal of the source of vapor intrusion to occupied buildings overlying those portions of the MEW Site, and meet the vapor intrusion RAO for the shallow A/A1 Zone. In the lower aquifer zones, where vapor intrusion is not of concern, application of in situ redox technologies within targeted high-concentration areas will also accelerate mass removal and offer protection of human health and the environment. Optimized GWET in the remaining areas of the plume would control the migration of the regional groundwater plume, and existing slurry walls would control migration of contaminants from facility-specific source areas where they are installed, thereby offering protection of human health and the environment from direct exposure to groundwater. Institutional controls also would be implemented to limit potential groundwater exposure risks (see Section 6). MNA would only be implemented where demonstrated to be capable of achieving RAOs within a reasonable timeframe, and where there are no unacceptable impacts to receptors Compliance with ARARs Cleanup using in situ redox technologies is expected to accelerate progress toward chemical-specific federal and state ARARs, with GWET and MNA expected to meet these ARARs over time. The application of in situ redox technologies (in all high concentration areas in the A/A1 Zone and targeted high concentration areas in the lower aquifer zones) is expected to accelerate the potential transition point from GWET to MNA for regional plume management. The alternative can be operated in compliance with the ARARs. The acceleration of groundwater cleanup using in situ redox technologies, in combination with GWET and MNA, meets the vapor intrusion RAO for the shallow A/A1 Zone Long-Term Effectiveness and Permanence The alternative, with its mix of treatment technologies, can be appropriately designed to meet long-term RAOs and reduce residual risks. In situ redox technologies have been proven reliable methods of treating CVOCs and providing permanent mass removal, but are generally sensitive to effective distribution of the injectants. Matrix diffusion effects would generally require multiple treatments over time for dissolved groundwater concentrations to meet RAOs or (potential) MNA transition criteria. In-situ redox technologies are generally less energy intensive than GWET systems, produce less waste, and conserve the groundwater resource (no extraction). Alternative 4 is estimated to use approximately 5,000,000 MMBtu compared to Alternative 1 through 3, which use from 13,000,000 to 19,000,000 MMBtu over the 50-year timeframe. 1,4-dioxane can be treated 5-12 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

75 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES using certain ISCO injectants or groundwater extraction and Advanced Oxidation Process Systems. In situ biotic reduction technologies such as ERD have generally not been found to provide successful treatment of 1,4-dioxane. The existing GWET systems have been in operation for more than 20 years and generally have been effective at providing hydraulic control of the regional groundwater plume. The optimized GWET component of this alternative is expected to provide continued long-term effective hydraulic control and somewhat accelerated groundwater treatment, although a very long time period will still be required to achieve all RAOs. During such an extended operational timeframe, individual components of the GWET system may exceed their service life and require replacement. The natural attenuation processes providing treatment and control at the Site could be expected to operate in perpetuity, and could potentially provide permanent treatment if MNA can be demonstrated capable of achieving the RAOs Reduction of Toxicity, Mobility and Volume through Treatment While this alternative is not expected to reduce the extent of groundwater contamination significantly in the foreseeable future, it would result in a significantly greater removal of contaminant mass from groundwater by targeting high concentration and potential source areas, and would result in the reduction of toxicity. In situ redox technologies provide irreversible treatment of CVOCs via direct oxidation to carbon dioxide, water, and chloride (ISCO) or via sequential dechlorination through a series of intermediary products (ERD and ZVI). These intermediary products (for example vinyl chloride) can be equally or more toxic and would need to be monitored or mitigated until complete reduction to ethenes are achieved. More toxic metals generated by changes to subsurface conditions that result from injection on in situ redox amendments are generally only temporarily present during treatment. 1,4-dioxane can be treated using certain ISCO injectants or groundwater extraction and Advanced Oxidation Process Systems. In situ biotic reduction technologies such as ERD have not been found to provide successful treatment of 1,4-dioxane. In the shallow A/A1 Zone, accelerating the cleanup of high concentration areas (and other targeted areas where vapor intrusion may be a concern) would reduce the mobility of contamination from groundwater to vapor, and therefore reduce the potential for vapor intrusion into overlying buildings. The temporary presence of intermediary products would need to be managed through mitigation measures. The optimized GWET systems in the remaining areas of the plume would improve hydraulic capture and therefore reduce mobility. Once groundwater is extracted, optimized GWET would provide irreversible removal of CVOCs from groundwater via transfer to the treatment media (such as GAC). MNA, where applied, would also serve to reduce the toxicity and mobility of contamination. Some natural attenuation processes provide irreversible treatment of CVOCs, such as sequential dechlorination during biodegradation, while other processes, such as volatilization, transfer mass from one media to another. MNA would not be applied where there is an existing risk or risk of increasing the potential for vapor intrusion. SFO/ [SUPPLEMNTALFS.DOCX] 5-13 ES BAO

76 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Short-Term Effectiveness The application of in situ redox technologies will require the construction of new infrastructure, with new impacts to the community, site workers, and the environment. Each in situ redox technology requires drilling and installation of suitable injection wells or points, and application of multiple injection events, that will require coordination with the community, property owners, and regulators, procurement of access agreements, implementation of traffic and access control plans, and various monitoring activities during construction. Short-term community and property owner/tenant impacts would occur during construction of the large number of required injection wells or points and during individual injection events, and may include disruptions to local traffic, reductions in available parking spaces, temporary utility disruptions, noise, and potentially nuisance lighting if construction occurs after typical working hours. Impacts to the public and property owners/tenants can be reduced by scheduling work during non-business hours or weekends. Risks to site workers can be managed through appropriate health and safety practices. In situ redox technologies may generate equally or more toxic intermediary products during treatment, although such effects are generally temporary and limited to active treatment areas. These intermediary products would need to be managed using mitigation measures during treatment. The GWET system has already been installed, but the installation of extraction wells or conveyance piping as part of optimization would require construction of new infrastructure, with new impacts to the community, site workers, and the environment. The application of MNA where demonstrated in specific areas of the plume would involve groundwater monitoring activities and would present no new risks to remediation workers Implementability The alternative is technically implementable using conventional construction methods and equipment. Current engineering practice and existing pilot-scale tests of in situ redox technologies demonstrate that they provide reliable treatment of CVOCs when treatment amendments can be adequately distributed in the subsurface, which is a recognized challenge for heterogeneous sites such as the MEW Site. Additional pilot-scale tests of in situ redox technologies at the MEW Site would be necessary to support the remedial design, refine the source area, and select specific technologies for application at individual areas. The administrative components of implementing this alternative may be challenging. Implementability of the in situ redox treatments will be dependent upon physical access restrictions (for example, buildings) and the ability to obtain access agreements with current property owners. Some in situ redox technologies provide greater flexibility than others within areas having challenging physical restrictions or access issues; the mix of technologies and specific injection locations will be tailored to individual facility and highconcentration areas during the remedial design. Any required revisions to the GWET system (for example, new wells or conveyance piping) are anticipated to be more easily implemented, because of the greater flexibility in specific locations of such infrastructure SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

77 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES Services and materials necessary for implementation of the alternative are readily available and competitive bids can be obtained from multiple equipment and remedial construction vendors. No significant difficulties are anticipated in obtaining permits for the injection of treatment amendments into groundwater. Effectiveness monitoring can be readily performed using a network of existing and/or newly-installed groundwater monitoring wells Cost The capital cost, annual O&M costs, periodic costs, and present value for Alternative 4 are listed below. Appendix B provides details of the estimated costs for Alternative 4. Shallow Aquifer (A/A1) Alternative 4 - Targeted In Situ Redox Treatment, Optimized GWET, and MNA Capital Costs Annual Costs Net Present Value $29,810, Capital Costs Capital Contingency $4,480, Capital Supervision and Design $5,110, Total Capital Costs $39,400,000 Annual O&M Year $1,537,000 $13,806,000 Annual O&M Year $592,000 $4,360,000 Annual O&M Year $439,000 $2,650,000 Annual O&M Year $424,000 $2,100,000 Annual O&M Year $424,000 $1,720,000 O&M Contingency $3,690,000 Total O&M Costs $28,300,000 Periodic Costs $4,280,000 Total Periodic Costs $4,300,000 Total Alternative 4 Costs (Shallow Aquifer): $72,000,000 SFO/ [SUPPLEMNTALFS.DOCX] 5-15 ES BAO

78 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Lower Aquifers Alternative 4 - Targeted In Situ Redox Treatment, Optimized GWET, and MNA Capital Costs Annual Costs Net Present Value $18,220, Capital Costs Capital Contingency $2,730, Capital Supervision and Design $3,330, Total Capital Costs $24,200,000 Annual O&M Year $1,919,000 $17,238,000 Annual O&M Year $722,000 $5,320,000 Annual O&M Year $531,000 $3,210,000 Annual O&M Year $508,000 $2,520,000 Annual O&M Year $508,000 $2,070,000 O&M Contingency $9,120,000 Total O&M Costs $39,500,000 Periodic Costs $5,080,000 Total Periodic Costs $5,100,000 Total Alternative 4 Costs (Lower Aquifers): $69,000,000 Total Alternative 4 Costs: $141,000,000 Notes: GWET- Groundwater extraction and treatment O&M Operations and maintenance Net Present Value Future Costs presented in current dollars using discount rate of 2.0% over a 50 Year period. Capital costs include costs for installation of new wells or GWET infrastructure. O&M costs include annual expense for operation and sampling of monitoring wells. Periodic costs include GWET system overhaul after 20 years and 5-Year Reviews. See Appendix C for detailed cost assumptions and backup sheets Alternative 5 In-situ Redox, PRBs, Optimized GWET, and MNA Alternative 5 combines in situ redox treatment in the areas described for Alternative 4 with installation of permeable reactive barriers (for example, ZVI barriers) downgradient of these areas to treat residual contamination. GWET would still be used to control and treat portion of the plume not address by the PRBs, with an eventual transition to MNA where demonstrated Overall Protection of Human Health and the Environment Application of in situ redox technologies within high concentration areas and facilityspecific source areas of the shallow A/A1 Zone is expected to accelerate removal of a primary source of vapor intrusion to occupied buildings overlying those portions of the MEW Site, and meet the vapor intrusion RAO for the shallow A/A1 Zone. In the lower 5-16 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

79 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES aquifer zones, where vapor intrusion is not of concern, application of in situ redox technologies within targeted high-concentration areas will also accelerate mass removal and offer protection of human health and the environment. Passive treatment using PRBs would be implemented downgradient of high-concentration areas and facility-specific treatment areas to treat residual contamination from in situ redox applications. Passive treatment of groundwater by PRBs can be expected to be significantly slower than active treatment (such as extraction), but provides protection of human health and the environment in the long term by treating residual CVOCs to achieve RAOs on the downgradient side of each PRB. However, this alternative would not immediately address the potential for vapor intrusion in lower concentration areas between PRBs that are not targeted for cleanup by an in situ redox technology. PRBs also do not provide inherent hydraulic control of groundwater but can modify local groundwater flow regimes, which must be accounted for as part of a remedial design in order to provide adequate protection of the environment (limit lateral plume migration). Optimized GWET in targeted areas of the plume in the A/A1 and B1/A2 Zones (for example, downgradient edge of plume and between facility boundaries where PRBs do not exist), and in the entire plume area in B2 Zone, would control the downgradient migration of the regional groundwater plume. Existing slurry walls would control migration of contaminants from facility-specific source areas where they are installed, thereby offering protection of human health and the environment from direct exposure to groundwater. Institutional controls also would be implemented to limit potential groundwater exposure risks (see Section 6). MNA would only be implemented where demonstrated to be capable of achieving RAOs within a reasonable timeframe, and where there are no unacceptable impacts to receptors Compliance with ARARs It is anticipated that groundwater exiting the downgradient side of each PRB will meet ARARs, but that groundwater treatment between PRBs will be slow because of the passive nature of treatment. The time required to achieve groundwater MCLs will depend upon overall effectiveness of the in situ redox treatments in the high concentration areas and the facility-specific source areas and the natural groundwater flow velocities through the PRBs. Natural attenuation processes will continue to operate between PRBs and may be demonstrated capable of achieving RAOs, allowing a transition to an entirely passive longterm regional remedy for the MEW Site (PRBs and MNA). The application of in situ redox technologies in high concentration areas and facility-specific source areas of the shallow A/A1 Zone is expected to accelerate removal of a primary source of vapor intrusion to occupied buildings overlying those portions of the MEW Site, and meet the vapor intrusion RAO for the shallow A/A1 Zone Long-Term Effectiveness and Permanence The alternative, with its mix of treatment technologies, can be appropriately designed to meet long-term RAOs and reduce residual risks. In situ redox technologies have been proven reliable methods of treating CVOCs and providing permanent mass removal, but are generally sensitive to effective distribution of the injectants. Matrix diffusion effects would generally require multiple treatments over time for dissolved groundwater SFO/ [SUPPLEMNTALFS.DOCX] 5-17 ES BAO

80 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY concentrations meet RAOs or (potential) MNA transition criteria. 1,4-dioxane can be treated using certain ISCO injectants or groundwater extraction and Advanced Oxidation Process Systems. In situ biotic reduction technologies such as ERD have generally not been found to provide successful treatment of 1,4-dioxane. PRBs using ZVI generally have an effective lifetime of approximately 30 years, at which point they would need to be replaced. If appropriately designed, PRBs are expected to passively reduce groundwater concentrations to cleanup goals over a long period of time and require less energy use than GWET systems. However, material usage and emissions generated during installation of PRBs are relatively high. The footprint analysis for Alternative 5 is presented in Appendix A. The existing GWET systems have been in operation for more than 20 years and generally have been effective at providing hydraulic control of the regional groundwater plume. The optimized GWET component of this alternative is expected to provide continued long-term effective hydraulic control, although a very long time period will still be required to achieve all RAOs. During such an extended operational timeframe, individual components of the GWET system may exceed their service life and require replacement. The natural attenuation processes providing treatment and control at the Site could be expected to operate in perpetuity, and could potentially provide permanent treatment if MNA (in combination with the PRBs) can be demonstrated capable of achieving the RAOs Reduction of Toxicity, Mobility and Volume through Treatment While this alternative is not expected to reduce the extent of groundwater contamination significantly in the near future, it would result in a significantly greater removal of contaminant mass from groundwater by targeting high concentration and facility-specific source areas, and would result in the reduction of toxicity. In situ redox technologies provide irreversible treatment of CVOCs via direct oxidation to carbon dioxide, water, and chloride (ISCO) or via sequential dechlorination through a series of intermediary products (ERD and ZVI). These intermediary products (for example vinyl chloride) can be equally or more toxic, and would need to be monitored and mitigated. More toxic metals generated because of subsurface changes created by in situ amendment injections are generally only temporarily present during treatment. 1,4-dioxane can be treated using certain ISCO injectants or groundwater extraction and Advanced Oxidation Process Systems. In situ biotic reduction technologies such as ERD have generally not been found to provide successful treatment of 1,4-dioxane. Passive treatment of groundwater using PRBs would limit or eliminate the migration of groundwater exceeding ARARs beyond them. However, PRBs do not provide active hydraulic control of groundwater and can modify local groundwater flow fields, leading to unintended migration of contaminants if such potential impacts are inadequately assessed during the remedial design. PRBs provide irreversible reductive dechlorination of contaminants during passage through the reactive material; intermediary products may remain if the PRB thickness provides inadequate residence time for complete treatment. In the shallow A/A1 Zone, accelerating the cleanup of high concentration areas and facilityspecific source areas would reduce the mobility of contamination from groundwater to 5-18 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

81 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES vapor, and therefore reduce the potential for vapor intrusion into overlying buildings. The temporary presence of intermediary products would need to be managed through mitigation measures. Optimized GWET would be applied in targeted areas of the plume in the A/A1 and B1/A2 Zones (for example, downgradient edge of plume, and between facility boundaries where PRBs do not exist), and the entire plume area in B2 Zone, improving hydraulic capture and therefore reducing mobility of the overall plume. Once groundwater is extracted, optimized GWET would provide irreversible removal of CVOCs from groundwater via transfer to the treatment media (such as GAC). MNA, where applied, would also serve to reduce the toxicity and mobility of contamination. Some natural attenuation processes provide irreversible treatment of CVOCs, such as sequential dechlorination during biodegradation, while other processes, such as volatilization, transfer mass from one media to another. MNA would not be applied where there is risk of increasing the potential for vapor intrusion Short-Term Effectiveness Construction of PRBs can have significant community impacts within highly developed areas such as the MEW Site; these impacts are sufficiently severe to prevent installation of PRBs using traditional trenching techniques and requiring installation using oriented vertical fracturing techniques. Even with these techniques, borings are advanced approximately every 15 feet along the PRB alignment, and vertical fractures are mechanically propagated between borings, which can significantly disrupt traffic when installed along active roadways (which would be typical). Such PRBs installed within parking lots would restrict available parking spaces. The application of in situ redox technologies will require the construction of new infrastructure, with new impacts to the community, site workers, and the environment. Each in situ redox technology requires drilling and installation of suitable injection wells or points, and application of multiple injection events, that will require coordination with the community, property owners, and regulators, procurement of access agreements, implementation of traffic and access control plans, and various monitoring activities during construction. Short-term community and property owner/tenant impacts would occur during construction of the large number of required injection wells or points and during individual injection events, and may include disruptions to local traffic, reductions in available parking spaces, temporary utility disruptions, noise, and potentially nuisance lighting if construction occurs after typical working hours. Impacts to the public and property owners/tenants can be reduced by scheduling work during non-business hours or weekends. Risks to site workers can be managed through appropriate health and safety practices. In situ redox technologies may generate equally or more toxic intermediary products during treatment, although such effects are generally temporary and limited to active treatment areas. These intermediary products would need to be managed using mitigation measures during treatment. The GWET system has already been installed, but the installation of extraction wells or conveyance piping as part of optimization would require construction of new infrastructure that may present new risks to remediation workers. SFO/ [SUPPLEMNTALFS.DOCX] 5-19 ES BAO

82 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY The application of MNA where demonstrated in specific areas of the plume would involve groundwater monitoring activities and would present no new risks to remediation workers Implementability The alternative is technically implementable using a combination of conventional and specialty construction methods and equipment. Services and materials necessary for implementation of the in situ redox portion of the alternative are readily available and competitive bids can be obtained from multiple equipment and remedial construction vendors. No significant difficulties are anticipated in obtaining permits for the injection of treatment amendments into groundwater. PRB installation via oriented vertical fracturing is a patented process requiring specialty fracture-generation equipment, and has limited to no opportunities for competitive bidding among multiple vendors. Effectiveness monitoring can be readily performed using a network of existing and/or newly-installed groundwater monitoring wells. Current engineering practice and existing pilot-scale tests of in situ redox technologies demonstrate that they provide reliable treatment of CVOCs when treatment amendments can be adequately distributed in the subsurface, which is a recognized challenge for heterogeneous sites such as the MEW Site. Additional pilot-scale tests of in situ redox technologies at the MEW Site would be necessary to support the remedial design and the selection of specific technologies for application at individual areas. The administrative components of implementing this alternative may be especially challenging. Specific alignments of PRBs will be subject to a detailed review of physical access restrictions, property ownership and right-of-way issues, and utilities during the remedial design. Implementability of the in situ redox treatments will be dependent upon physical access restrictions (for example, buildings) and the ability to obtain access agreements with current property owners. Some in situ redox technologies provide greater flexibility than others within areas having challenging physical restrictions or access issues; the mix of technologies and specific injection locations will be tailored to individual facility and high-concentration areas during the remedial design. GWET would be utilized at depths or locations where PRBs or in situ redox cannot be implemented. Any required revisions to the GWET system (for example, new wells or conveyance piping) are anticipated to be more easily implemented, because of the greater flexibility in specific locations of such infrastructure Cost The capital cost, annual O&M costs, periodic costs, and present value for Alternative 5 are listed below. Appendix C provides details of the estimated costs for Alternative SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

83 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES Shallow Aquifer (A/A1) Alternative 5 - Targeted In Situ Redox Treatment, PRBs, Capital Net Present Optimized GWET, and MNA Costs Annual Costs Value Capital Costs $42,150, Capital Contingency $6,950, Capital Supervision and Design $7,190, Total Capital Costs $56,300,000 Annual O&M Year $614,000 $5,515,000 Annual O&M Year $645,000 $4,750,000 Annual O&M Year $582,000 $3,520,000 Annual O&M Year $582,000 $2,890,000 Annual O&M Year $582,000 $2,370,000 O&M Contingency $2,850,000 Total O&M Costs $21,900,000 Periodic Costs $11,760,000 Total Periodic Costs $11,800,000 Total Alternative 5 Costs (Shallow Aquifer): $90,000,000 Lower Aquifers Alternative 5 - Targeted In Situ Redox Treatment, PRBs, Capital Net Present Optimized GWET, and MNA Costs Annual Costs Value Capital Costs $31,740, Capital Contingency $4,760, Capital Supervision and Design $5,520, Total Capital Costs $42,000,000 Annual O&M Year $740,000 $6,647,000 Annual O&M Year $677,000 $4,990,000 Annual O&M Year $614,000 $3,710,000 Annual O&M Year $614,000 $3,040,000 Annual O&M Year $614,000 $2,500,000 O&M Contingency $3,140,000 Total O&M Costs $24,000,000 Periodic Costs $15,020,000 Total Periodic Costs $15,000,000 SFO/ [SUPPLEMNTALFS.DOCX] 5-21 ES BAO

84 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Total Alternative 5 Costs (Lower $81,000,000 Aquifers): Total Alternative5 Costs: $171,000,000 Notes: GWET = Groundwater extraction and treatment MNA= Monitored natural attenuation O&M = Operations and maintenance PRB = Permeable reactive barrier Net Present Value Future Costs presented in current dollars using discount rate of 2.0% over a 50 Year period. Capital costs include installation of new wells, GWET infrastructure, PRBs, and targeted in situ redox treatment. O&M costs include annual expense for operation and sampling of monitoring wells. Periodic costs include GWET system overhaul after 20 years, MNA work plans/implementation, and 5- Year Reviews. Periodic costs also include replacement of PRBs after 30 years. 5.3 Comparative Analysis of Groundwater Alternatives This section presents an overall comparison of the remedial alternatives that were described in Section 4 and individually evaluated in Section 5.2. The alternatives are compared to each other on the basis of the NCP threshold and balancing criteria. A summary of the comparative analysis for the groundwater alternatives for the A/A1 Zone and lower aquifer zone are provided in Tables 5-1 and 5-2, respectively Overall Protection of Human Health and the Environment This threshold criterion assesses the adequacy of protection of human health and the environment for each alternative, and describes how site risks for exposure pathways are eliminated, reduced, or controlled through treatment, engineering, and/or institutional controls. In the shallow A/A1 Zone, Alternative 1 does not meet the vapor intrusion RAO, which requires accelerated treatment of groundwater acting as a source of vapor intrusion to occupied buildings overlying the shallow groundwater plume. The 2010 ROD Amendment stipulates the operation of vapor intrusion mitigation systems for potentially impacted buildings, but these systems only divert contaminants from entering indoor air and do not remove their source. Alternatives 2, 3, 4, and 5 each provide a varying degree of accelerated groundwater treatment to meet the shallow groundwater vapor intrusion RAO in the shallow A/A1 Zone. Alternatives 2 and 3 provide improved protection of human health and the environment versus the existing remedy (Alternative 1), since optimization of the GWET system will improve contaminant mass recovery and treatment. The overall protectiveness of Alternatives 2 and 3 is moderate, as optimized GWET is less aggressive than in situ redox technologies at treating high-concentration areas, and therefore slower to reduce a primary source of vapor intrusion into overlying occupied buildings. Alternatives 4 and 5 both 5-22 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

85 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES provide good protection of human health and the environment for the shallow A/A1 Zone by accelerating treatment in high concentration and facility-specific source areas using in situ redox technologies along with hydraulic control and treatment of the remaining areas of the plume using GWET. Active hydraulic containment by GWET for Alternative 4 provides more robust protection than the passive PRBs used in Alternative 5, in the event natural groundwater flow regimes change over time. For the lower aquifer zones where the vapor intrusion RAO does not apply, Alternative 1 continues to provide fair protection of human health and the environment using the existing GWET systems. Alternatives 2 and 3 provide greater protectiveness than the existing remedy (Alternative 1), by optimizing GWET to improve mass recovery rates and hydraulic capture. For the lower aquifer zones, Alternative 4 provides the greatest protection of human health and the environment by active in situ redox treatment of targeted high concentrations areas. The passive PRBs used in Alternative 5 provide moderate overall protection, but are somewhat less protective of lower aquifer zones than active groundwater extraction approaches used within Alternatives 2, 3, and 4. Passive PRBs do not offer the active hydraulic control of a groundwater plume that groundwater extraction approaches provide, and cannot address natural flow regime changes that may occur over long time periods. Institutional controls would be applied as part of Alternatives 2, 3, 4, and 5 to provide further protection of human health and the environment from direct exposure to groundwater Compliance with ARARs This threshold criterion assesses whether an alternative would attain legal Federal and State requirements, standards, and criteria (ARARs). Chemical-specific ARARs for groundwater are the MCLs. Without intervention, the CVOCs would be expected to remain in site groundwater above the MCLs for the indefinite future. Each of the alternatives presented herein is expected to be capable of ultimately achieving the ARARs for the shallow A/A1 Zone and the lower aquifer zones but within varying timeframes from decades to centuries (see Section 4-9). Alternative 1, the existing remedy, has made progress toward ARARs over more than 20 years of operation but concentrations of CVOCs in many of the extraction wells have become asymptotic and the existing GWET systems are generally becoming less effective in achieving the groundwater RAOs across all aquifer zones. A timeframe in the order of centuries is expected to be necessary to achieve MCLs across the plume under Alternative 1. Optimization of the current remedy under Alternative 2 would provide greater mass recovery, particularly within high-concentration areas, and would be expected to nominally decrease the time required to achieve MCLs. Alternative 3 would provide the same improvement in mass recovery within high-concentration areas, but allows for passive achievement of MCLs over expected longer time periods using MNA (if demonstrated capable of achieving RAOs). Alternatives 4 and 5 will accelerate contaminant mass removal within specific area of the plumes (facility-specific source areas and high concentration areas) via application of in situ redox technologies. Because of the lasting effects of matrix diffusion, it is presently unclear the degree to which such accelerated mass removal will shorten the timeframe to achieve MCLs across the plume. However, as discussed in Section 4.9, the model may be overly SFO/ [SUPPLEMNTALFS.DOCX] 5-23 ES BAO

86 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY conservative in its prediction of cleanup timeframes by not accounting for the surfactant effects of in situ redox technologies. Pilot test results conducted by Intel and Navy using in situ redox treatment technologies appear promising in reducing COC concentrations from high concentrations to low concentrations. Compared to Alternative 4, Alternative 5 would be slower to achieve groundwater cleanup in the lower concentration areas of the plume because of the passive nature of PRBs compared to GWET. Estimated cleanup timeframes for the various alternatives are presented in Table 4-1. For Alternatives 3, 4, and 5, active groundwater treatment, particularly in high concentration areas, may provide sufficient mass removal for MNA to be demonstrated capable of achieving RAOs (including MCLs) over longer time periods, allowing for a potential transition to a passive, rather than active, long-term groundwater remedy Long-Term Effectiveness and Permanence This balancing criterion assesses the ability of each alternative to maintain reliable protection of human health and the environment over time, as well as evaluating the adequacy and reliability of controls and the residual risks at a site after completing a remedial action. The current remedy, Alternative 1, has generally been effective at controlling the migration of the regional groundwater plume over more than 20 years of operation. Operation of the current GWET system is expected to provide continued long-term hydraulic control of the lower aquifer zones and continued groundwater treatment. However, the decline in the effectiveness of current GWET systems means that a very long time period will be required to achieve the groundwater RAOs. During such an extended operational timeframe, individual components of the GWET systems may exceed their service life and require replacement. Residual risks associated with groundwater in facility-specific and regional high concentration areas remain higher over longer time periods for Alternative 1, the existing remedy, and Alternative 5. Alternatives 2, 3 and 4 are expected to provide continued long-term effective hydraulic control and somewhat accelerated groundwater treatment, but a very long time period will still be required to achieve all RAOs (greater than 1,000 years). Alternatives 4 and 5 provide a high degree of long-term effectiveness and permanence by aggressively removing contaminant mass within high-concentration areas (and targeted lower concentration areas in the A/A1 Zone) while continuing to treat and/or hydraulically contain the regional groundwater plume. Aggressive treatment of these areas accelerates the reduction of residual risk of vapor intrusion into overlying occupied building, although it does not necessarily lead to significant reduction in the time required to achieve overall groundwater RAOs. In situ redox technologies have been proven reliable methods of treating CVOCs and providing permanent mass removal, but are generally sensitive to effective distribution of the injectants. Matrix diffusion effects would generally require multiple treatments over time for dissolved groundwater concentrations meet RAOs or (potential) MNA transition criteria. Not all in situ redox technologies provide effective cleanup of 1,4-dioxane. 1,4-dioxane can be treated using certain ISCO injectants or groundwater extraction and Advanced Oxidation Process Systems. Under Alternative 5, the expected effective lifetime of PRBs using ZVI is approximately 30 years, at which point they 5-24 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

87 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES would need to be replaced. If appropriately designed, PRBs are expected to passively reduce groundwater concentrations to cleanup goals over a long period of time. Alternatives 3, 4, and 5 allow for a potential transition to MNA if demonstrated capable of achieving the RAOs. Natural attenuation processes can be expected to operate in perpetuity, and MNA could therefore provide reliable long-term effectiveness and permanence. In general, Alternatives 1 through 3, which require more pumping, result in higher energy use, water use and greenhouse gas emissions. Installation of PRBs in Alternative 5 result in elevated criteria pollutant emissions, materials usage, and waste generation, compared to Alternatives 1 through 3, but its energy use and greenhouse gas emissions over time are lower as the system is passive. Overall, Alternative 4 results in the smallest environmental footprint over the long-term Reduction of Toxicity, Mobility, or Volume through Treatment This criterion addresses the statutory preference for selecting remedial actions that utilize treatment technologies that provide significant and permanent reduction in the toxicity, mobility, or volume of hazardous substances. The assessment against this criterion evaluates the anticipated performance of the specific treatment technologies an alternative may employ. All of the alternatives would limit overall contaminant mobility with active hydraulic containment of the regional plume using (current or optimized) GWET. The extent of the GWET system for overall hydraulic containment of the regional plume varies for these alternatives, based on other treatment components utilized within the plume interior. Alternatives 1, 2, and 3 would reduce toxicity of contaminated groundwater using GWET systems through treatment of extracted groundwater. Alternative 2 and 3 would result in greater reduction of toxicity and mobility compared to Alternative 1 by increasing mass removal and improving hydraulic capture. Alternatives 4 and 5 would provide significant additional permanent reduction in toxicity of high-concentration areas via aggressive application of in situ redox technologies. In situ redox technologies provide irreversible treatment of CVOCs via direct oxidation to carbon dioxide, water, and chloride (ISCO) or via sequential dechlorination through a series of intermediary products (ERD and ZVI). These intermediary products (for example vinyl chloride) can be equally or more toxic and would need to be mitigated and monitored until complete reduction to ethenes is achieved. 1,4-dioxane can be treated using certain ISCO injectants or groundwater extraction and Advanced Oxidation Process Systems. In situ biotic reduction technologies such as ERD have not been found to provide successful treatment of 1,4-dioxane. For the shallow A/A1 Zone, Alternatives 2, 3, 4, and 5 would all accelerate mass removal in shallow groundwater and meet the vapor intrusion RAO. However, in situ redox technologies utilized in Alternatives 4 and 5 would provide significantly greater initial reductions in toxicity within the shallow A/A1 Zone than would optimized GWET utilized in Alternatives 2 and 3. In addition, accelerating the cleanup of high concentration areas and facility-specific source areas using in situ redox treatment would reduce the mobility of contamination from groundwater to vapor, and therefore reduce the potential for vapor intrusion into overlying buildings and the need for mitigation. The temporary presence of intermediary products would need to be managed through mitigation measures. SFO/ [SUPPLEMNTALFS.DOCX] 5-25 ES BAO

88 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Natural attenuation processes may at some point be demonstrated capable of achieving RAOs at the MEW Site, and MNA associated with Alternatives 3, 4, and 5 could provide permanent passive reductions in toxicity, mobility, and volume Short-Term Effectiveness This criterion assesses the effectiveness of alternatives in protecting human health and the environment during the construction and implementation of a remedy, until the response objectives have been met. Alternative 1 would have minimal impact to remediation workers or the community since the GWET system is already constructed. Alternatives 2, 3, 4, and 5 may require the installation of new groundwater extraction wells and/or conveyance piping in association with optimization of the GWET system component, which would pose direct exposure risks to remediation workers. Limited exposure risks to remediation workers during GWET system O&M activities would also remain in association with these alternatives. Alternatives 4 and 5 would have the greatest potential impact to remediation workers and the community because of activities associated with construction and operation of in situ redox treatment systems. Application of in situ treatment technologies requires the installation of a large number of injection wells, and regular injection events over time, which would be disruptive to property owners, tenants, and the general public. Impacts to the public or property owners/tenants could include disruptions to local traffic, reductions in available parking spaces, temporary utility disruptions, noise, and potentially nuisance lighting if construction occurs after typical working hours. Impacts to the public and property owners/tenants can be reduced by scheduling work during non-business hours or weekends. Certain in situ redox technologies may generate equally or more harmful intermediary products during treatment or mobilize toxic metals, although such effects and would need to be monitored and mitigated. Such effects can be limited by performance of site-specific pilot-scale treatment tests and detailed evaluation of aquifer geochemistry during the remedial design. Alternative 5 may have additional constraints, as construction of PRBs can have significant community impacts within highly developed areas such as the MEW Site; these impacts are sufficiently severe to prevent installation of PRBs using traditional trenching techniques and requiring installation using oriented vertical fracturing techniques. Even with these techniques, borings are advanced approximately every 15 feet along the PRB alignment, and vertical fractures mechanically propagated between borings, which can significantly disrupt traffic when installed along active roadways (which would be typical). Such PRBs installed within parking lots would restrict available parking spaces. For all alternatives, risks to site remediation workers can be managed through appropriate health and safety practices Implementability This criterion addresses the technical and administrative feasibility of implementing each alternative, from the remedial design through construction and operation. The criterion 5-26 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

89 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES considers factors such as the availability of equipment, materials, and services and coordination with property owners or other governmental entities. Alternative 1, the existing remedy, has been operating for more than 20 years and presents no new implementation challenges. Alternatives 2 and 3 include optimization of the existing GWET system, and may require installation of additional extraction wells or conveyance piping; however, such infrastructure can be readily constructed using standard construction techniques. Alternatives 4 and 5 would be the most difficult to implement, because of the significant construction requirements associated with the treatment of high-concentration areas using in situ redox technologies. Although the physical drilling and construction requirements utilize standard construction techniques with numerous available vendors, there are significant administrative issues associated with physical access restrictions, property ownership and access, and administrative requirements. Of these two alternatives, Alternative 4 is easier to implement. Alternative 4 applies in situ redox technologies within high-concentration areas, while allowing either in situ redox technology or GWET treatment at other facility-specific treatment areas depending upon property-specific access restrictions. Where significant access restrictions exist, GWET has significantly greater implementation flexibility than in situ redox technologies. Alternative 5 has the same implementation challenges as Alternative 4 for application of in situ redox technologies with the added challenge of installing PRBs downgradient of various facility-specific and highconcentration areas. Access restrictions are likely to limit PRBs installed using oriented vertical fracturing techniques, which are more flexible than direct trenching but still require regularly-spaced borings for generation of a fracture plane Cost A summary of the capital, annual O&M, and net present value (NPV) cost for each alternative is presented in Table 5-3 for the A/A1 Zone, and Table 5-4 for the lower aquifer zones. The present worth has been calculated using the real interest rate on 30-year federal treasury notes and bonds as reported in the December 2010 revision of the federal Office of Management and Budget (OMB) Circular A-94, Appendix C (OMB, 2011), which is 2.0 percent. The present worth costs have been calculated for a 50-year evaluation period. SFO/ [SUPPLEMNTALFS.DOCX] 5-27 ES BAO

90 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY TABLE 5-3 Summary of Remedial Alternative Costs for the A/A1 Zone Total Cost in $MM Alternative (Shallow A/A1 Zone) (50 Yr NPV)* Cost Breakdown in $MM (50 Yr NPV)* Cos t Capital Cost O&M Cost Periodic Cost 1: Existing Remedy (GWET/slurry walls) $77 $0.6 $71 $5.2 2: Optimized GWET $88 $1.6 $80.7 $5.3 3: Optimized GWET and MNA** $47 $1.6 $40.5 $5.2 4: Targeted In-Situ Redox Treatment, Optimized GWET, and MNA** $72 $39.4 $28.3 $4.3 5: Targeted In-Situ Redox Treatment, PRBs, P&T, and MNA** $90 $56.3 $21.9 $11.8 Notes: *Costs are presented as NPV using a discount rate of 2.0%, based on the year real interest rate on Treasury notes and bonds, published by the U.S. Office of Management and Budget in memorandum M dated December **MNA where demonstrated $MM = Million dollars 50 Yr NPV = Costs for a 50-year period in net present value PRBs = Permeable reactive barriers O&M = Operations and maintenance GWET = Groundwater extraction and treatment MNA = Monitored natural attenuation TABLE 5-4 Summary of Remedial Alternative Costs for the B1/A2 Zone and Lower Aquifers Total Cost $MM Alternative (50 Yr NPV)* (Lower Zones) Cost Capital Cost Cost Breakdown $MM (50 Yr NPV)* O&M Cost Periodic Cost 1: Existing Remedy (GWET/slurry walls) $54 $0.9 $49 $3.8 2: Optimized GWET $74 $3.4 $66.4 $4.5 3: Optimized GWET and MNA** $42 $3.4 $34.4 $4.6 4: Targeted In-Situ Redox Treatment, Optimized GWET, and MNA** $69 $24.2 $39.5 $5.1 5: Targeted In-Situ Redox Treatment, PRBs, P&T, and MNA** $81 $42 $24 $15 Notes: * Costs are presented as NPV using a discount rate of 2.0%, based on the year real interest rate on Treasury notes and bonds, published by the U.S. Office of Management and Budget in memorandum M dated December $MM = Million dollars. 50 Yr NPV = Costs for a 50 year period in net present value. PRBs = Permeable reactive barriers. O&M = Operations and maintenance. P&T = Pump and treat. MNA = Monitored natural attenuation SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

91 PRELIMINARY DRAFT FOR DISCUSSION ONLY 5 DETAILED ANALYSIS OF ALTERNATIVES Details of the cost estimates for each alternative are provided in Appendix C. As described in Appendix C, several assumptions have been made in estimating these costs. For both the A/A1 Zone and the lower aquifer zones, Alternative 1 reflects actual annual O&M costs for the current groundwater remedy from the 2009/2010 operating period. In comparison, Alternative 2 has higher capital and O&M costs that reflect the costs associated with additional well installations and an overall increase in extraction and mass removal rates as part of optimized GWET. Alternatives 2 and 3 share the same network of extraction wells at remedy startup and have the same initial capital costs. The long-term O&M costs for Alternative 3 are lower than for Alternative 2, however, because Alternative 3 allows wells to be turned off in areas where MNA can be demonstrated over time. Alternative 4 has high capital costs compared against Alternatives 2 and 3 because of active treatment using in situ redox technologies. Alternative 4 has lower O&M costs than Alternatives 2 and 3, particularly in the A/A1 zone, because application of in situ redox treatment reduces the number of extraction wells. The total cost of Alternative 4 is approximately twice that of Alternative 3 and approximately 50 percent greater than Alternative 2. Alternative 5 has the highest capital costs because it includes in situ redox treatments and the installation of PRBs. Although capital costs for Alternative 5 are high, it has the lowest O&M costs of any alternative because passive treatment with PRBs requires limited extraction wells. The periodic costs for Alternative 5 are greater than for other alternatives because it is assumed the PRBs will require replacement in 30 years. Alternative 5 is the most expensive alternative, and has a cost approximately 20 percent greater than Alternative State Acceptance The state s acceptance of the alternative will be evaluated after the proposed plan and public comment period Community Acceptance The community s acceptance of the alternatives will be evaluated after the proposed plan and public comment period. However, prior to preparation of the draft EPA, EPA met with the commercial property owners, the Community Advisory Board and Restoration advisory board. Comments EPA received regarding the FS have been considered in preparation of the FS. The commercial property owners have expressed concern with disruption of the properties and economic loss during implementation of the various cleanup alternatives. Concern was also expressed with the potential for generation of harmful byproducts (specifically vinyl chloride) generated during in situ redox treatment using in situ bioremediation. The community, represented by the community advisory board and CPEO, prepared a paper Community Criteria and Suggestion Strategy for the MEW-Moffett Plume. This paper recommended that the FS focus on the following: in areas with high mass in areas that continue to act as a source in areas that reduce the need for long term vapor intrusion mitigation to enable reasonable future reuse of the property in areas where the detectable plume encroaches on residential areas, schools and other sensitive uses SFO/ [SUPPLEMNTALFS.DOCX] 5-29 ES BAO

92 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY The paper also recommended to EPA that the results of the remedial process optimization evaluations prepared by each PRP in 2008 be incorporated into the FS along with technologies previously considered to accelerate groundwater cleanup. The community also believes that the Feasibility Study should require an adaptable optimization strategy that continually looks at new ways to attain cleanup standards SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

93 PRELIMINARY DRAFT FOR DISCUSSION ONLY 6 Institutional Controls ICs are a component of all the remedial alternatives described in this FS. ICs are nonengineered legal and administrative instruments that help to minimize the potential for human exposure to contamination and protect the integrity of a remedy. There are four categories of ICs: government controls, proprietary controls, enforcement tools with institutional control components, and informational devices. Each of these types of ICs can be used, alone or in combination, to ensure the protectiveness of an engineered remedy. 6.1 Government Controls Government controls use the regulatory authority of a governmental entity to impose restrictions on citizens or property under its jurisdiction and typically include general and specific land use plans, zoning restrictions, ordinances, statutes, building permits, or other restrictions on land or resource use at a site. Generally, EPA relies on state or local governments (such as a city or county) to establish these kinds of government controls. Once adopted, the local and state entities often use traditional police powers to enforce the controls. Because this type of IC is usually implemented and enforced by a local jurisdiction, it may be changed or terminated with little notice to EPA. 6.2 Proprietary Controls Proprietary controls are based on state property law and can be used to restrict or affect the use of a property. The most common proprietary controls are easements and covenants. These controls may involve recording legal instruments in the chain of title of the property. These types of ICs are intended to be long-term or permanent as they can be binding on subsequent property owners and are transferable. 6.3 Enforcement Tools with IC Components Enforcement tools include federal and state orders or decrees (for example, 106 Orders and Consent Decrees) that are issued or negotiated to prohibit a party from using its land in certain ways or from conducting certain activities at a property. These tools can also be enforceable by the state if the state is a signatory or if state enforcement tools are used. 6.4 Informational Devices Informational devices are tools used to provide information or notification about whether a remedy is operating as designed and/or notification to the public about contamination at a site. Examples include public notices, deed notices, fact sheets, and advisories. Because these informational devices do not compel or forbid an action, they are not typically a sufficient IC in and of themselves and are often used in conjunction with other types of ICs. SFO/ [SUPPLEMNTALFS.DOCX] 6-1 ES BAO

94 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY 6.5 Objective, Mechanism, Timing, and Responsibility of ICs ICs are response actions under CERCLA and are subject to the nine evaluation criteria discussed in Chapter 5 of this Supplemental FS. In accordance with EPA guidance, the objective, mechanism, timing, and responsibility of ICs are determined before applying the evaluation criteria. The objective of any IC is to help to minimize the potential for human exposure to contamination and protect the integrity of a remedy. The Vapor Intrusion ROD Amendment adopted ICs to protect against exposure to Site contamination through the inhalation pathway. For this FS, the primary IC objective will be to prevent exposure to groundwater at the Site and to minimize any impact to the cleanup operations. Certain IC mechanisms, such as government controls, for the alternatives discussed in this FS, are already in place under state and local law. These pre-existing mechanisms will need to continue to be monitored and updated as necessary to ensure that they meet the remedy objectives. Other IC mechanisms, such as proprietary controls, are in place at certain properties (i.e. source properties) but would have to be negotiated at other properties and thus could be more complex to implement. All ICs have to be monitored in order to ensure that they are maintained in an ongoing manner. Generally, the PRPs have the responsibility to ensure that the ICs for this remedy continue to meet the objectives of the remedy. However, some ICs, by their very nature, rely on enforcement by other entities. For example, enforcement of government controls in the area south of U.S. Highway 101, such as local permits, is the responsibility of the government entities. On Moffett Field, NASA owns the land and enforces its own land use restrictions through its Master Plan (NASA Ames, 1994) and conditions in its Environmental Issues Management Plan (NASA, 2005). In those instances, the PRPs would have the responsibility to track the enforcement of the ICs and ensure that other mechanisms are used should the governmental controls on private property or proprietary controls on Moffett Field fail. 6.6 Detailed Analyses of ICs This section provides an analysis of ICs using seven of the nine evaluation criteria from the National Contingency Plan. The other two evaluation criteria, state acceptance and community acceptance, will be evaluated following public comment after issuance of the Proposed Plan. The evaluation criteria are: Protectiveness of Human Health and the Environment. This threshold criterion is used to assess whether the IC is protective of human health and the environment. Compliance with Applicable or Relevant and Appropriate Requirements (ARARs). This second threshold criterion assesses whether an IC meets federal and state ARARs. Long-term Effectiveness and Permanence. This criterion assesses the reliability and effectiveness of ICs to minimize the potential for human exposure to contaminated groundwater. Reduction of Toxicity, Mobility, or Volume through Treatment. ICs are not treatment measures; therefore, this criterion does not apply and is not considered in this analysis. 6-2 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

95 PRELIMINARY DRAFT FOR DISCUSSION ONLY 6 INSTITUTIONAL CONTROLS Short-term Effectiveness. This criterion evaluates impacts on human health and the environment during implementation of the remedy in the near term. Implementability. This criterion evaluates the feasibility of implementing the IC itself. Administrative feasibility of an IC looks at coordination among offices and agencies and whether the entity responsible to implement the IC possesses the jurisdiction, authority, and willingness to establish, monitor, and enforce the IC. This factor also assesses how complex it may be to coordinate all parties necessary to enact the IC and whether all necessary parties are likely to participate. Cost. This criterion is used to evaluate the estimated cost for implementing, monitoring, and enforcing these ICs. Costs may include legal fees and agency costs to monitor and enforce the ICs Local Government Controls: Public Health and Safety Ordinances and Permits A local government can place a requirement on property owners by implementing and amending local health and safety ordinances designed to protect public health and safety. For instance, the Santa Clara Valley Water District ( District ) has implemented Ordinance 90-1, which places restrictions on the construction and handling of wells that could impact groundwater in the area of the Site. Ordinance 90-1 provides government oversight of activities that may impact groundwater by requiring a permit for the construction of or for certain subsequent changes to wells constructed in Santa Clara County. Ordinance 90-1 provides that [n]o person within the County of Santa Clara shall construct, modify, or destroy a well unless a written permit has first been obtained from the District. ( 5.1) Further, Ordinance 90-1 states that [n]o person shall dig, bore, drill, deepen, modify, repair, or destroy a water well, cathodic protection well, observation well, monitoring well, or any other excavation that may intersect ground water without first applying for and receiving a permit as provided in this ordinance unless exempted by law. ( 6.1) Permits are subject to the conditions set forth in the ordinance. ( 6.4) The District may impose on any permit additional conditions that it deems necessary, and the District must deny any application for a permit if the District believes the issuance is not in the public interest. ( ) In addition, Ordinance 90-1 incorporates well sealing requirements. Ordinance 90-1 requires standards for the construction and destruction of wells and other deep excavations to be in accordance with the District Well Standards and Department of Water Resources Bulletin (and any subsequent revisions). ( 7.1) The District s most recent well standards specify for the Confined Area of the Santa Clara Valley Basin (where the Site is located) that: For wells constructed to a depth less than 150 feet wells must have a sanitary seal that is a minimum of 50 feet in depth ending at least five feet into a significant aquitard; and For wells constructed to a depth greater than 150 feet wells must have a sanitary seal that is a minimum of 150 feet in depth, and the seal well must extend through the full length of the major aquitard. SFO/ [SUPPLEMNTALFS.DOCX] 6-3 ES BAO

96 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY (Standards for the Construction and Destruction of Wells and Other Deep Excavations in Santa Clara County, Santa Clara Valley Water District (1989) ( Standards ), p. 6). If the enforcing agency requires that compliance is impractical for a particular location, alternate requirements meeting performance standards may be specified. (Id.) Finally, the District has the authority to enforce the provisions of Ordinance 90-1 and the incorporated Standards. Ordinance 90-1 details the methods by which the District may enforce the ordinance and well standards. ( 10) Ordinance 90-1 could serve as an IC for the MEW groundwater remedy if the District is appropriately informed of the regional plume and the potential impacts of well installations in the MEW area. Informational mechanisms must be in place to alert the District to the groundwater plume footprint and to assist the District in determining whether wells installed near the groundwater plume would possibly impact plume stability Overall Protection of Human Health and the Environment A health and safety ordinance is an effective part of a plan to protect human health at the Site. Because the Ordinance 90-1 applies to the entire Site, as an IC it ensures that health and safety standards are incorporated into the government permitting processes and all persons attempting to access groundwater in the area will be bound by those standards Long-Term Effectiveness and Permanence A local ordinance is not considered a permanent IC because the city or other entity can revoke an ordinance without notice to EPA. While in effect, however, use of local public health and safety ordinances such as Ordinance 90-1 can be effective methods to ensure remedy implementation. In order to be effective, the implementing agency must be informed of the concerns regarding the remedy that might be impacted by installation of wells. Any such ordinance would require ongoing provision of information, monitoring, and enforcement to ensure implementation Short-Term Effectiveness A local public health and safety ordinance such as Ordinance 90-1 can be an effective method of prohibiting access to groundwater in the short term Implementability The Santa Clara Valley Water District Act ( Act ) authorizes the District to provide comprehensive water management in Santa Clara County, including enacting ordinances and resolutions to further the objectives of the Act (Cal. Uncod. Water Deer., Act , 9). Thus, the District has the authority to issue and enforce ordinances regarding groundwater in Santa Clara County. As Ordinance 90-1 and the District Standards are already in place, there are no issues regarding initial implementability Cost As Ordinance 90-1 and the District Standards are already in place, there is no implementation cost. However, as discussed above in section , monitoring of this IC would be necessary. The estimated annual cost to monitor and enforce the performance of 6-4 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

97 PRELIMINARY DRAFT FOR DISCUSSION ONLY 6 INSTITUTIONAL CONTROLS the ordinance is included in the costs associated with preparation of the 5-Year Review Reports Proprietary Controls Proprietary controls in the form of covenants and easements provide a method to ensure that property owners are informed of any contamination on their property, ways to ensure that the contamination is not exacerbated, and how to avoid impacting any remedial measures being taken on the property. Currently there are recorded land use controls at the source properties which among other things, inform the property owner of the environmental conditions of the property, efforts that must be made to avoid impacting any remedial measures taken on the property, and provisions for access for the PRPs to operate the remedy Overall Protection of Human Health and the Environment Recorded land use covenants provide an ongoing informational mechanism to property owners of Site contamination and remedial action being taken. Where a property owner takes an action that would impact the remedy, a covenant would either prohibit the action or require that the PRPs and EPA receive timely notice so that any impacts to the remedy can be mitigated Long-Term Effectiveness and Permanence Recorded covenants that run with the land and are binding on future owners are considered permanent. Where EPA is a third-party beneficiary for enforcement of the covenant, EPA would be informed if the covenant was proposed to be removed. Any land use covenant does require monitoring to ensure no property interests supersede it Short-Term Effectiveness Recorded covenants provide protectiveness in the short-term. Following recording, any activities that could impact the remedy would be prohibited or the property owner would be required to consult with the MEW PRPs and EPA regarding how to avoid impacting the remedy Implementability As discussed above, land use covenants have been implemented at the former source properties. In the cases where those covenants are determined to cover the concerns raised by any of the alternatives under consideration, the PRPs already have a mechanism to enforce protection of the remedy. EPA is not a third party beneficiary to those covenants, so the PRPs would have to be the entities to enforce the conditions of the covenants. The remaining properties in the MEW Study Area South of Highway 101 that are not former source properties do not already have covenants. Implementing covenants at these properties may prove more complex because of the lack of prior relationship with the MEW PRPs. Additionally, there is less of a need for covenants at these properties because generally the active portions of the remedy are not sited on these properties. Should any of the alternatives under consideration change this, covenants may be appropriate. SFO/ [SUPPLEMNTALFS.DOCX] 6-5 ES BAO

98 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Cost Where land use covenants are already in place and provisions are applicable to any change in the remedy, there would be no implementation cost. However, for these properties, monitoring will be necessary to ensure that the covenants contain the appropriate provisions and remain in place. The estimated annual cost to monitor land use covenants is included in the costs associated with preparation of the 5-Year Review Reports Enforcement Tools with IC Components The MEW Companies are implementing the MEW remedy under a 106 Order and a Consent Decree. The remedy is being implemented pursuant to these enforcement tools. Because the MEW Companies no longer own or occupy any of the MEW Site properties, ICs components to restrict land use would not be appropriate in this case Informational Devices: Notice of Well Permit Requests from Santa Clara Valley Water District to EPA Informational devices could be utilized to inform EPA or the MEW Companies of any request for a permit to install a well in the area of the Site. A procedure would need to be developed to notify EPA or the MEW companies when a permit to install a well within or near the MEW plume occurs. In that way, appropriate conditions can be conveyed to the District to assure public health and safety. Additionally, information will have to be conveyed to the District, such as updated plume maps, to ensure that the District knows when to contact EPA. Finally, informational devices could be used to inform EPA and the MEW Companies should Ordinance 90-1 change in any way that could adversely affect this remedy Overall Protection of Human Health and the Environment Timely notice of any request to access groundwater at the Site could help assure that responses to the requests can include requirements that would prevent exposure to Site groundwater contaminants and that would notify EPA and the MEW parties if a well may impact remedial effectiveness Long-Term Effectiveness and Permanence For the same reasons a local ordinance is not considered permanent, an informational device informing EPA of permit requests under the ordinance would not be considered permanent. As a result, any such informational device would require monitoring to ensure implementation Short-Term Effectiveness An informational device informing EPA of any permit application to use groundwater at the Site would be protective of human health and the environment by allowing EPA to advise the Santa Clara Valley Water District of conditions under Ordinance 90-1 that are necessary to allow access to groundwater as well as informing EPA and the MEW Companies if the remedy may be impacted. 6-6 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

99 PRELIMINARY DRAFT FOR DISCUSSION ONLY 6 INSTITUTIONAL CONTROLS Implementability The Santa Clara Valley Water District Act ( Act ) authorizes the District to provide comprehensive water management in Santa Clara County, including enacting ordinances and resolutions to further the objectives of the Act (Cal. Uncod. Water Deer., Act , 9). Thus, the District has the authority to issue and enforce ordinances regarding groundwater in Santa Clara County and to impose conditions on access and/or use to the groundwater. As Ordinance 90-1 and the District Standards are already in place, there are no issues regarding initial implementability of the relevant ordinance as long as the remedy is included in the District s analysis. Informational devices to advise EPA of any permit application to access groundwater at the Site or to ensure that the District is apprised of current relevant Site information can be accomplished through the use of an informational service Cost As Ordinance 90-1 and the District Standards are already in place, there is no implementation cost. However, monitoring will be necessary to ensure that they remain in place. The estimated annual cost to monitor and enforce the performance of the ordinance and the ancillary informational device is included in the costs associated with preparation of the 5-Year Review Reports. SFO/ [SUPPLEMNTALFS.DOCX] 6-7 ES BAO

100

101 PRELIMINARY DRAFT FOR DISCUSSION ONLY 7 References AFCEE, Source Zone Initiative: Final Report Submitted to Air Force Center for Environmental Excellence, May Canonie Environmental Services, Corp (Canonie), Feasibility Study, Middlefield-Ellis- Whisman Area, Mountain View, California, November. Center for Public Environmental Oversight. Community Criteria and Suggestion Strategy for the MEW-Moffett Plume. April 15, Cherry, J. & Feenstra, S., 1991, Identification of DNAPL Sites: An Eleven Point Approach, Waterloo Centre for Groundwater Research, August United States Environmental Protection Agency (EPA), Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA, Interim Final, EPA 540/G 89/004, OSWER , October EPA, Record of Decision, Fairchild, Intel, and Raytheon Sites, Middlefield-Ellis-Whisman Study Area, Mountain View, California, Superfund Records Center Document No , June 9, EPA, EPA Superfund Explanation of Significant Differences: Middlefield-Ellis-Whisman Study Area, Mountain View, CA, September 1, EPA, EPA Superfund Explanation of Significant Differences: Middlefield-Ellis-Whisman Study Area, Mountain View, CA, April 16, EPA, 1998, Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground Water, EPA/600/R-98/128. EPA Ecological Screening Levels. Region 5. ( Revised August. EPA, 2004a. Final First Five-Year Review Report for Middlefield-Ellis-Whisman (MEW) Superfund Study Area, Mountain View, California, September EPA, Performance Monitoring of MNA Remedies for VOCs in Ground Water, April EPA, Green Remediation: Incorporating Sustainable Environmental Practices into Remediation of Contaminated Sites, April EPA, Final Second Five-Year Review Report for Middlefield-Ellis-Whisman (MEW) Superfund Study Area, Mountain View and Moffett Field, California, September EPA Region 5 ESLs. EPA, Record of Decision Amendment for the Vapor Intrusion Pathway, Middlefield-Ellis- Whisman (MEW) Superfund Study Area, Mountain View, California, August 16. SFO/ [SUPPLEMNTALFS.DOCX] 7-1 ES BAO

102 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY EPA, "Groundwater Road Map: Recommended Process for Restoring Contaminated Groundwater at Superfund Sites."July. OSWER EPA Draft Methodology for Understanding a Project s Environmental Footprint. September 16. Geomatrix, Aquifer Test and Off-Site B2 Source Control Evaluation, 401/405 National Avenue, Mountain View, California, consultant s report prepared for Vishay General Semiconductor, Fairchild Semiconductor Corporation, SUMCO Oregon Corporation, and Schlumberger Technology Corporation, August Geosyntec Consultants (Geosyntec), Optimization Evaluation, Regional Groundwater Remediation Program, Middlefield-Ellis-Whisman (MEW) Area, Mountain View, California, September Geosyntec, Letter from Geosyntec Consultants to Mr. Bruce Wolfe, Re: 1,4-Dioxane Treatment, Fairchild Semiconductor Corporation, System No. 3. December 16, Geosyntec, Addendum to 3 September 2008 Optimization Evaluation, Fairchild Sites, MEW Area, Mountain View, California. April 28. Geosyntec, 2011a. Draft MNA Assessment and Implementation Approach. Middlefield-Ellis and Whisman Regional Groundwater Remediation Program. May 27. Geosyntec, Draft Plume Cleanup Time Evaluation, Middlefield-Ellis-Whisman Regional Groundwater Remediation Program, Mountain View, California, April. Google Press Center, NASA and Google Announce Lease at Ames Research Center. NASA and Google, Inc., Mountain View, CA, June 4. Haley & Aldrich, 2009a. Final Supplemental Remedial Investigation for the Vapor Intrusion Pathway, Middlefield- Ellis-Whisman road Study Area, Mountain View and Moffett Field, CA. June. Haley & Aldrich, 2009b. Final Supplemental Feasibility Study for the Vapor Intrusion Pathway, Middlefield- Ellis-Whisman road Study Area, Mountain View and Moffett Field, CA. June. Harding Lawson Associates (HLA), Remedial Investigation Report, Remedial Investigation/Feasibility Study, Middlefield-Ellis-Whisman Area, Mountain View, California, Vol. 1-8, July 1987 (revised in 1988). ICF-Clement, Endangerment Assessment for the Middlefield-Ellis-Whisman Site in Mountain View, California, September 2. IT Corporation, Potassium Permanganate Pilot Study, Volumes 1 and 2, Former Raytheon Facility, Mountain View, California. September. 7-2 SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

103 PRELIMINARY DRAFT FOR DISCUSSION ONLY 7 REFERENCES National Aeronautics and Space Administration Ames Research Center (NASA Ames), Moffett Field Comprehensive Use Plan. NASA Ames Research Center. Moffett Field, California, September. NASA Ames, NASA Ames Development Plan, Mountain View, CA, December. NASA, NASA Environmental Management Plan. Naval Facilities Engineering Command (NAVFAC), Contract Report: Cost and Performance Report Nanoscale Zero-Valent Iron Technologies for Source Remediation, Prepared by Battelle, Gavaskar, A., Tatar, L., Condit, W., Columbus, Ohio. September. United States Department of the Navy (Navy), Annual Groundwater Report for Installation Restoration Sites 26 and 28, Former NAS Moffett Field, Moffett Field, California, June Northgate Environmental Management, Inc., (Northgate) 2008a. Draft Site-wide Focused Feasibility Study and Technical Impracticability Evaluation, Volume I, prepared for Schlumberger Oilfield Services, April 14. Office of Management and Budget (OMB), Discount Rates for OMB Circular No. A- 94, December 2010 Revision. Parker BL, Gillham RW, and Cherry JA, Diffusive Disappearance of Immiscible Phase Organic Liquids in Fractured Geologic Media. Groundwater, 32(5): PES Environmental, Inc. (PES), Chemical Oxidation Pilot Test Report, Siemens-Sobrato Properties at 455, 485/487, and 501/505 East Middlefield Road, Mountain View, California. September 14, Santa Clara Valley Water District (SCVWD), Geology and Ground Water Quality of the Santa Clara Valley. SCVWD, Santa Clara Valley Water District Groundwater Management Plan, Prepared by Vanessa Reymers and Tracy Hemmeter under the direction of Behzad Ahmadi, Unit Manager, Groundwater Management Unit, July SCVWD, Groundwater Conditions 2002/2003, Prepared under the direction of Behzad Ahmadi, Unit Manager, Groundwater Management Unit, January. Shaw Environmental, Inc., Draft Technical Memorandum, Abiotic/Biotic Treatability Study, IR Site 26, Former Naval Air Station Moffett Field, Moffett Field, California, October Shaw Environmental, Inc Final Technical Memorandum, Abiotic/Biotic Treatability Study, IR Site 26, Former Naval Air Station Moffett Field, Moffett Field, California, March Tetra Tech FW, Inc., West-Side Aquifers Treatment System Optimization Completion Report, prepared for Department of the Navy, Southwest Division, DCN No. FWSDRAC , Revision 0, May 17, SFO/ [SUPPLEMNTALFS.DOCX] 7-3 ES BAO

104 SUPPLEMENTAL SITEWIDE GROUNDWATER FEASIBILITY STUDY MIDDLEFIELD-ELLIS-WHISMAN SUPERFUND STUDY AREA MOUNTAIN VIEW AND MOFFETT FIELD, CALIFORNIA PRELIMINARY DRAFT FOR DISCUSSION ONLY Weiss Associates (Weiss), 1995, VOC Transport Report for Intel Mountain View, 365 Middlefield Road, Mountain View, California. July 6. Weiss, Implementation and Performance Monitoring Report for Enhanced In-Situ Bioremediation Pilot Test for Former Intel Mountain View Facility, 365 East Middlefield Road, Mountain View, CA 94043, April In: 2009 Annual Progress Report for Former Intel Mountain View Facility, 365 East Middlefield Road, Mountain View, CA 94043, April SFO/ [SUPPLEMNTALFS.DOCX] ES BAO

105 Figures

106 San Francisco UV13 Oakland UV24 Concord Antioch UV Livermore UV 4 UV4 UV UV 4 4 Discovery Bay!( Tracy UV UV84 Half Moon Bay UV 92 MEW Regional Study Area 1 UV 82 UV UV 130 UV San Jose UV UV UV85 UV9 UV 236 UV9 101 Gilroy--Morgan Hill Legend P:\GIS\MEW\Project\Regional\LocationMap.mxd ³ Miles Watsonville Draft for Discussion Figure 1-1 Site Location Map Supplemental Groundwater Feasibility Study Middlefield-Ellis-Whisman (MEW) Study Area Mountain View and Moffett Field, California ES BAO_Fig_1-1_SiteLocation.ai_082411_lho

107 San Francisco Bay Perimeter Rd. NASA RESEARCH PARK NASA AMES RESEARCH CENTER. Ave t r igh De France Ave. NASA Ames Treatment System Lindbergh Ave. Zook Rd. Sa yre FORMER NAS MOFFETT FIELD ORION PARK STEVENS CREEK WESCOAT HOUSING Mo tt B lvd. Clark Rd. Durand Rd. King Rd. N. Akron S. Akron W e s Bayshore Freeway - Hwy. 101 c oat C t. Bushnell Rd. McCord Ave. B ailey R d. Severyns Ave. Dugan Ave. Wescoat Rd. Gorsky Rd. Cummins Ave. Girard Rd. Navy West-Side Aquifers Treatment System (WATS) Sa yre Regional Program Treatment Facility Cody Macon Rd. Stevens Creek Mo tt B lvd. Leong Dr. E mily Dr. Walker Dr. Sherland Ave. Flynn Ave. Evandale Av. Devonshire Murlagan Walker Dr. Fairchild 3 Hetch Hetchy Aq ueduct National Av e. Slurry Walls MEW Hwy. 85 E asy St. Tyrella Ave. Gladys Ave. Central Expy. Estrada Whisman Rd. Chetwood Magnolia Pacific 2 Kent Whisman Pk. Dr GTE Ellis St. Logue Ave. Maude Ave. Cly de Ave. Alviso Rd. - Hwy. 237 Nicholas LEGEND SLURRY WALLS APPROXIMATE TCE EXTENT IN SHALLOW A/A1 AQUIFER (5 μg/l) NASA AREA OF RESPONSIBILITY NAVY AREA OF RESPONSIBILITY MEW AREA OF RESPONSIBILITY ES BAO_Fig_1-2_MEW-Superfund-Studyarea.ai_061212_lho MIDDLEFIELD ELLIS WHISMAN (MEW) FORMER MEW FACILITY LOCATIONS RAYTHEON COMPANY INTEL CORPORATION FAIRCHILD SEMICONDUCTOR CORP. / SCHLUMBERGER TECHNOLOGY CORP. NEC ELECTRONICS AMERICA, INC. SUMITOMO MITSUBISHI SILICON CORPORATION / VISHAY GENERAL SEMICONDUCTOR SMI HOLDING LLC N Approximate Scale in Feet Draft for Discussion Figure 1-2 MEW Superfund Study Area Supplemental Groundwater Feasibility Study Middlefield-Ellis-Whisman (MEW) Study Area Mountain View and Moffett Field, California

108 Placeholder Only Draft for Discussion Figure 1-3 Supplemental Groundwater Feasibility Study Middlefield-Ellis-Whisman (MEW) Study Area Mountain View and Moffett Field, California ES BAO_MEW_PotentialInferredSourceArea_Placeholder.ai_061212_lho

109 N Draft for Discussion Figure 1-4 Area of Soil Remediation Implementation South of U.S. Highway 101 Supplemental Groundwater Feasibility Study Middlefield-Ellis-Whisman (MEW) Study Area Mountain View and Moffett Field, California Source : Locus, Five-Year Performance Review, Regional Groundwater Remediation Program, December 17, ES BAO_Fig_1-4_AreaSoilRemediation.ai_082411_lho

110 Fairchild Drive HIGHWAY 101 REG-5B(1) REG-2A REG-12B(1) REG-3B(1) Evandale Drive Murlagen Devonshire 38B2 FAIRCHILD TREATMENT SYSTEM NO. 3 (Carbon Adsorption) RW-4(B2) RW-5(B1) RW-4A RW-4(B1) RW-5(B2) RW-5A RW-12(B1) RW-17A Sealed RW-7(B1) RW-7A RW-7(B2) RW-19A Sealed RW-28A RW-9(B1)R RW-9A RW-9(B2) RW-9(B1) RW-27A REG-11A REG-11B(1) RW-18A RW-25A REG-1B(2) REG-1B(1) REG-12A REG-10A REG-2B(1) REG-3B(2) REG-1A MEW REGIONAL GROUNDWATER REMEDIATION PROGRAM SOUTH OF 101 TREATMENT SYSTEM (Liquid Phase Carbon Adsorption) Walker Drive FAIRCHILD TREATMENT SYSTEM NO. 1 (Carbon Adsorption) RW-3A RW-3(B2) RW-3(B1) RW-16A RW-10A Sealed AE/RW-9-1 GSF1A GSF1B1 GSF1B2 VISHAY / SUMCO TREATMENT SYSTEM (UV Peroxide Followed by Air Stripping) EX4 EX3 National Avenue RW-21A AE/RW-9-2 EX2 EX1 Sherland Drive RW-2A RW-2(B1) RW-2(B2) RW-11(B1) RW-24A RW-20A DW3-244 DW3-505R DW3-364 DW3-334 DW B3 SIL15A Hetch Hetchy Aqueduct NEC27AE NEC28AE NEC1AE NEC TREATMENT SYSTEM (Carbon Adsorption) Flynn Avenue Whisman Road RW-11A RW-22A Sealed RW-1A RW-1(B1) RW-1(B2) RW-10(B1) FAIRCHILD TREATMENT SYSTEM 19 (Carbon Adsorption) RW-23A RW-15A Sealed RW-12A RW-29A R65B1(B2) RE25A RAY-1B1 RE23A RE24A RE5A RAY-1A Ellis Street REG-4B(1) RW-26A 71A RW-13A Sealed RW-14A Sealed I-1B2 RAYTHEON TREATMENT SYSTEM (Oxidation Followed by Carbon Adsorption) PW-4 PW-3 Middlefield Road Louge Avenue IE1A PW-2 EW-3 EW-1 INTEL TREATMENT SYSTEM (Carbon Adsorption) PW-1 EW-2 EW-4 SMI TREATMENT SYSTEM (Carbon Adsorption) Legend Regional Recovery Well Inactive Regional Recovery Well Destroyed Regional Recovery Well Source Control Recovery Well Inactive Source Control Recovery Well Destroyed Source Control Recovery Well Treatment Pipeline Discharge Pipeline Treatment Plant Slurry Wall Building Road VTA Light Rail Feet Draft for Discussion Figure 1-5 Locations of Regional and Source Control Extraction Wells and Groundwater Treatment Systems South of U.S. Highway 101 Supplemental Groundwater Feasibility Study Middlefield-Ellis-Whisman (MEW) Study Area Mountain View and Moffett Field, California Source: Geosyntec, Response to EPA Information Request for Five-Year Review, prepared for Regional Program, May-June ES BAO_Fig_1-5_treatmentsSof101.ai_082311_lho

111 De France Road Oarf Road Zook Road Undbergh Avenue # NASA-4A Wright Avenue NASA-3A # MOFFETT FIELD Allen Road N. Warehouse Road NASA TREATMENT SYSTEM (Carbon Adsorption) Pioneer Road Hunsaker Road Parsons Avenue Walcott Road NASA-1A # # NASA-2A S. Warehouse Road Warner Road De France Road Durand Road King Road Ú ð REG-6A # EA1-6 King Road # Ú ð # EA1-4 REG-9B(1) EA2-2 # # EA2-3 EA1-5 Moffett Boulevard Bush Circle Ú Bushnell Road ð REG-10B(1) Ú ð REG-7A McCord Avenue # EA1-3 # EA2-1 Cummins Avenue WATS TREATMENT SYSTEM (Oxidation and Carbon Adsorption) Hanger No. 1 Arnold Avenue Clark Road Berry Road N. Akron Road S. Akron Road Westcoat Court Ú ð REG-9A REG-8B(1) Ú ð Ú ð Westcoat Road REG-8A Daily Road Ú ð Dugan Avenue Gorsky Road Severyns Avenue REG-6B(1) REG-4A EA1-1 # # MEW REGIONAL GROUNDWATER REMEDIATION PROGRAM NORTH OF 101 TREATMENT SYSTEM (Air Stripping Followed by Vapor Carbon Adsorption) REG-3A Ú ð Ú ð Edquiba Road EA1-2 Cody Road REG-7B(1) Macon Road HIGHWAY 101 Ú ð REG-5A Girard Road Fairchild Drive Ú ð REG-3B(1) REG-5B(1) Ú ð Ú ð REG-2A Ú ð REG-12B(1) Legend Ú Regional Recovery Well # Source Control Recovery Well ð Treatment Pipeline Discharge Pipeline Treatment Plant Building Road ³ Feet Draft for Discussion Figure 1-6 Locations of Regional and Source Control Extraction Wells and Groundwater Treatment Systems North of U.S. Highway 101 Source: Geosyntec, Response to EPA Information Request for Five-Year Review, prepared for Regional Program, May-June ES BAO_Fig_1-6_treatmentsNof101.ai_082411_lho Supplemental Groundwater Feasibility Study Middlefield-Ellis-Whisman (MEW) Study Area Mountain View and Moffett Field, California

112 ???? Note: Contours taken from Middlefield-Ellis-Whisman Site Report (Locus 1992). Supporting data for contours are posted on original figures. Areas inside slurry walls estimated from Remedial Investigation Report (HLA, 1988). Note: Contours taken from Middlefield-Ellis-Whisman Site Report (Locus 2003). Supporting data for contours are posted on original figures. Note: Contours taken from Appendix C of 2010 Annual Progress Report (Geosyntec 2011). Supporting data for contours are posted on original figures. Legend 1992 TCE Concentration 1-10 ug/l ug/l 100-1,000 ug/l 1,000-10,000 ug/l Greater than 10,000 ug/l 2002 and 2010 TCE Concentration ug/l 100-1,000 ug/l 1,000-10,000 ug/l Greater than 10,000 ug/l Slurry Wall Building Road Feet ,500 3,000 TCE PLUME IN THE A/A1 SHALLOW AQUIFER Change in TCE Distribution 1992, - A 2002, Zone AND 2010 Supplemental Groundwater Feasibility Study MEW - Regional Middlefield-Ellis-Whisman Groundwater Remediation (MEW) Program Study Area Mountain View, California and Moffett Field, California Figure 1-7 Project WR1128 P:\GIS\MEW\Project\Regional\Comp_TCE_92-07_A.mxd

113 ???? Note: Contours taken from Middlefield-Ellis-Whisman Site Report (Locus 1992). Supporting data for contours are posted on original figures. Areas inside slurry walls estimated from Remedial Investigation Report (HLA, 1988). Note: Contours taken from Middlefield-Ellis-Whisman Site Report (Locus 2003). Supporting data for contours are posted on original figures. Note: Contours taken from Appendix C of 2010 Annual Progress Report (Geosyntec 2011). Supporting data for contours are posted on original figures. Legend 1992 TCE Concentration 1-10 ug/l ug/l 100-1,000 ug/l 1,000-10,000 ug/l 10, ,000 ug/l Greater than 100,000 ug/l TCE Concentration TCE PLUME IN THE B1/A2 AQUIFER 1992, 2002, AND ug/l Supplemental Groundwater Feasibility Study Slurry Wall 100-1,000 ug/l Middlefield-Ellis-Whisman (MEW) Study Area Building Mountain View and Moffett Field, California 1,000-10,000 ug/l Greater than 10,000 ug/l Road Feet Figure ,500 3,000 P:\GIS\MEW\Project\Regional\Comp_TCE_92-07_B1.mxd

114 ?? Note: Contours taken from Middlefield-Ellis-Whisman Site Report (Locus 1992). Supporting data for contours are posted on original figures. Note: Contours taken from Middlefield-Ellis-Whisman Site Report (Locus 2003). Supporting data for contours are posted on original figures. Note: Contours taken from Appendix C of 2010 Annual Progress Report (Geosyntec 2011). Supporting data for contours are posted on original figures. Legend 1992 TCE Concentration 1-10 ug/l ug/l 100-1,000 ug/l 1,000-10,000 ug/l Greater than 10,000 ug/l 2002 and 2010 TCE Concentration ug/l 100-1,000 ug/l 1,000-10,000 ug/l Greater than 10,000 ug/l Slurry Wall Building Road Feet ,500 3,000 TCE PLUME IN THE B2 AQUIFER 1992, 2002, AND 2010 Change in TCE Distribution - B2 Zone Supplemental Groundwater Feasibility Study MEW - Regional Middlefield-Ellis-Whisman Groundwater Remediation (MEW) Study Program Area Mountain View, and California Moffett Field, California Figure 1-9 Project WR1128 P:\GIS\MEW\Project\Regional\Comp_TCE_92-07_B2.mxd