Free Additional Attachments to Main Document - District Court of Arizona - Arizona

Appendix C Scope of Work U.S. v. Crane/Unidynamics Consent Decree Phoenix-Goodyear Airport North Superfund Site Groundwater, Soil Gas, Air, Soils, and Facility Structures Remedy Supplemental Remedial Investigation and Feasibility Study, and Remedial Design, and Continued Remedial Action

Case 2:03-cv-02226-ROS

Document 82-4

Filed 06/27/2006

Page 1 of 98

Table of Contents

Glossary of Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Purpose of SOW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 General Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 GROUNDWATER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Task 1.0 Operation and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Task 1.1 Operation and Maintenance Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Task 1.2 Operation and Maintenance Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Task 1.3 Operation and Maintenance of the Existing Groundwater Remedy . . . . . . . . . . . . . . . 7 Summary of Task 1.0 Deliverables and Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Task 2.0: Groundwater Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Task 2.1 Review Existing Groundwater Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Task 2.2 Groundwater Investigation Workplan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Task 2.3 FSAP, QAPP, and HASP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Task 2.4 Identify, Investigate, and Abandon Potential Conduit Wells . . . . . . . . . . . . . . . . . . . . 17 Task 2.5 Groundwater Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Task 2.6 Conduct Groundwater Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Task 2.7 Groundwater Investigation Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Summary of Task 2.0 Deliverables and Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Task 3.0 Groundwater Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Task 3.1 Update Groundwater Monitoring Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 -iCase 2:03-cv-02226-ROS Document 82-4 Filed 06/27/2006 Page 2 of 98

Task 3.2 Revise Groundwater Monitoring FSAP, QAPP, and HASP . . . . . . . . . . . . . . . . . . . . 26 Task 3.3 Conduct Groundwater Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Task 3.4 Groundwater Monitoring Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Summary of Task 3.0 Deliverables & Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Task 4.0 Protection of Drinking Water Supply Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Task 4.1 Identification of Threatened Water Supply Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Task 4.2 Wellhead Treatment/Alternative Water Supply Workplan . . . . . . . . . . . . . . . . . . . . . 30 Task 4.3 Implement Wellhead Treatment/Alternative Water Supply . . . . . . . . . . . . . . . . . . . . 31 Task 4.4 Continue Protection of Water Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Task 4.5 Wellhead Treatment/Alternative Water Supply Report . . . . . . . . . . . . . . . . . . . . . . . . 32 Summary of Task 4.0 Deliverables and Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Task 5.0 Main Drywells Source Area Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Task 5.1 Compile and Review Information Related to Main Drywells Area . . . . . . . . . . . . . . . 34 Task 5.2 Drywells Area Investigation Workplan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Task 5.3 FSAP, QAPP, and HASP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Task 5.4 Main Drywells Area Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Task 5.5 Conduct Drywells Area Treatability Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Task 5.6 Main Drywells Area Remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Task 5.7 Main Drywells Area Investigation Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Summary of Task 5.0 Deliverables and Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Task 6.0 Perchlorate Treatability Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Task 6.1 Complete GGWTP Pilot-Scale Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Task 6.2 Perchlorate Treatability Study Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 -iiCase 2:03-cv-02226-ROS Document 82-4 Filed 06/27/2006 Page 3 of 98

Summary of Task 6.0 Deliverables and Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 SOIL GAS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Task 7.0 Retrofit and Operation of SVE System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Task 7.1 SVE Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Task 7.2 SVE Operation and Maintenance Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Task 7.3 Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Task 7.4 Operation and Maintenance of the SVE System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Summary of Task 7.0 Deliverables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Task 8.0 Soil Gas Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Task 8.1 Review Soil Gas Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Task 8.2 Soil Gas Investigation Workplan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Task 8.3 Conduct Soil Gas Investigation Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Task 8.4 Soil Gas Investigation Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Summary of Task 8.0 Deliverables and Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 AIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Task 9.0 Air Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Task 9.1 Air Sampling Workplan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Task 9.2 Conduct Air Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Task 9.3 Air Investigation Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Task 9.4 Implement Mitigation Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Summary of Task 9.0 Deliverables and Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 SOILS (SURFACE AND SUBSURFACE) AND FACILITY STRUCTURES . . . . . . . . . . . . . 57 Task 10.0 Source Areas, Soils and Facility Structures Remedial Investigation . . . . . . . . . . . . . 57 -iiiCase 2:03-cv-02226-ROS Document 82-4 Filed 06/27/2006 Page 4 of 98

Task 10.1 Site Evaluation and Data Compilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Task 10.2 Source Areas, Soils and Facility Structures Workplan . . . . . . . . . . . . . . . . . . . . . . . . 60 Task 10.3 Source Areas FSAP, QAPP and Health & Safety Plan . . . . . . . . . . . . . . . . . . . . . . . 62 Task 10.4 Conduct Source Areas, Soils and Facility Structures Investigation . . . . . . . . . . . . . . 64 Task 10.5 Source Areas Treatability Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Task 10.6 Source Areas, Soils and Facility Structures Investigation Support Activities . . . . . . 65 Task 10.7 Removal Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Task 10.8 Source Areas, Soils and Facility Structures Baseline Risk Assessment . . . . . . . . . . . 66 Task 10.9 Screening Level Ecological Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Task 10.10 Source Areas, Soils and Facility Structures Investigation Summary . . . . . . . . . . . . 67 Task 10.11 Source Areas, Soils and Facility Structures Remedial Investigation Report . . . . . . 68 Summary of Task 10.0 Deliverables & Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Task 11.0 Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Task 11.1 Baseline Human Health Risk Assessment Amendment . . . . . . . . . . . . . . . . . . . . . . . 72 Task 11.2 Screening Level Ecological Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Summary of Task 11.0 Deliverables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Task 12.0 Supplemental Feasibility Study (SFS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Task 12.1 Develop, Screen, and Perform a Detailed Analysis of Remedial Alternatives . . . . . 77 Task 12.2 Identify ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Task 12.3 Supplemental Feasibility Study Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Summary of Task 12.0 Deliverables & Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Task 13.0 Supplemental Remedial Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Task 13.1 Additional Field Investigations and Pilot Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 -ivCase 2:03-cv-02226-ROS Document 82-4 Filed 06/27/2006 Page 5 of 98

Task 13.2 Remedial Design Workplan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Task 13.3 Technical Memorandum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Task 13.4 Final Design Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Summary of Task 13.0 Deliverables and Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Task 14.0 Remedial Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Task 14.1 Remedial Action Workplan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Task 14.2 Pre-construction Meeting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Task 14.3 Construction Quality Assurance Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Task 14.4 Construction Health and Safety Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Task 14.5 Remedial Action Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Task 14.6 Operation and Maintenance Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Task 14.7 Pre-final Construction Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Task 14.8 Final Construction Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 Task 14.9 Final Remedial Action Construction Complete Report . . . . . . . . . . . . . . . . . . . . . . . 89 Task 14.10 Work Completion Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Summary of Task 14.0 Deliverables and Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Task 15.0 Data Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Task 15.1 Document Field Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Task 15.2 Sample Management and Tracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 Task 15.3 Database Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 Summary of Task 15.0 Deliverables and Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

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Glossary of Acronyms
1989 ROD - 1989 Record of Decision 1998 O&M Plan - 1998 Operation and Maintenance Plan ADEQ - Arizona Department of Environmental Quality ADWR - Arizona Department of Resources ARARs - Applicable or Relevant and Appropriate Requirements CHASP - Construction Health and Safety Plan CLP - Contract Lab Program COCs - contaminants of concern CQAP - Construction Quality Assurance Plan CQAPP - Construction Quality Assurance Project Plan DNAPL - Dense Non-Aqueous Phase Liquids ESDs - Explanation of Significant Differences FSAP - Field Sampling & Analysis Plan GAC - Granulated Activated Carbon GWWTP - Goodyear's Wastewater Treatment Plant HASP - Health and Safety Plan HEAs - Health Effects Assessment documents HEAST - Health Effects Assessment Summary Tables IRIS - Integrated Risk Information System MAU - Middle Alluvial Unit NCP - National Contingency Plan NELAP - National Environmental Laboratory Accreditation Program O&F - Operational and Functional O&M - Operation & Maintenance O&M Plan - Operation and Maintenance Plan PGA - Phoenix-Goodyear Airport PRGs - Preliminary Remediation Goals QA - Quality Assurance QAPP - Quality Assurance Project Plan QA/QC - Quality Assurance/Quality Control QA/R-2 - Quality Management Plans OSHA - Occupational Safety and Health Administration RA - Remedial Action RAA - Risk Assessment Amendment RAO - Remedial Action Objective RfDs - Reference Doses

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RI/FS - Remedial Investigation/Feasibility Study SCM - Site Conceptual Model SFS - Supplemental Feasibility Study SOW - Scope of Work SRD - Supplemental remedial design SVE - Soil Vapor Extraction SVM - Soil Vapor Monitor SWMUs - Solid Waste Management Units UAU - Upper Alluvial Unit VI Guidance - Vapor Intrusion to Indoor Air Pathway from Groundwater & Soils VOC - Volatile Organic Compound

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------APPENDIX C------GROUNDWATER, SOIL GAS, AIR, SOILS, AND FACILITY STRUCTURES REMEDY SUPPLEMENTAL REMEDIAL INVESTIGATION/FEASIBILITY STUDY, REMEDIAL DESIGN, AND CONTINUED REMEDIAL ACTION SCOPE OF WORK Phoenix-Goodyear Airport North Superfund Site Goodyear, Arizona PURPOSE OF SOW This Scope of Work ("SOW") is Appendix C to, and incorporated as part of, the Consent Decree ("CD") between the United States and Unidynamics/Phoenix, Inc., and Crane Co. ("Settling Defendants") in the matter captioned United States v. Unidynamics/Phoenix, Inc. et al., No. CV-04-1400-PHX-JAT, regarding the release of hazardous substances at the PhoenixGoodyear Airport (North) Superfund Site ("PGA-North" or "Site"). The purpose of this SOW is to complete the investigation, including treatability studies, and the remedial design, and construction, maintenance, operation and evaluation of removal and remedial action response activities for the following Site components: C C C C C Groundwater Soil Gas Air Soils (surface and subsurface) Facility Structures

In designing, implementing, and submitting deliverables for the ongoing response action at the Site, Settling Defendants shall follow this SOW, the appropriate U.S. Environmental Protection Agency ("EPA") Superfund Guidance for Remedial Investigations and Feasibility Studies, Remedial Design, and Remedial Action, the September 1989 Record of Decision and subsequent Explanations of Significant Differences (collectively referred to herein as the "ROD"), all

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approved Investigation Workplans, all approved Remedial Design and Remedial Action Workplans, all approved Operation and Maintenance Plans, all additional approved plans, any additional guidance provided by EPA, and the provisions of the CD.

GENERAL PROVISIONS

Definitions The definitions set forth in the CD are incorporated herein by reference and shall apply to this SOW unless expressly provided otherwise herein.

EPA Approval of Workplans and Other Deliverables Where Settling Defendants are required to submit a workplan or other deliverable to EPA for review and approval, EPA will either approve, disapprove, or require modification(s) to the submission in accordance with the procedures set forth in Section XI (EPA Approval of Plans and Other Submissions) of the CD. The Arizona Department of Environmental Quality ("ADEQ") shall also have a reasonable opportunity to review and comment on workplans or other deliverables submitted pursuant to this SOW. Settling Defendants acknowledge and agree that nothing in this SOW or any approved plans or deliverables constitutes a warranty or representation of any kind by the United States that compliance with the work requirements set forth in this SOW or any approved plans or deliverables will achieve the Site Performance Standards. Nothing in this SOW or any approved plans or deliverables shall be construed to limit any authority of the United States to take all appropriate action to protect human health and the environment or to prevent, abate, respond to, or minimize an actual or threatened release of Waste Material on, at, or from the Site, or to require performance of further response actions as otherwise provided in the CD.

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Notification and Reporting of Field Support Activities: Settling Defendants shall notify EPA at least fifteen (15) days in advance of any field support activities in order to allow EPA to provide oversight of those activities. Field support activities include, but are not be limited to, obtaining access to private and public properties where investigative activities are to be conducted, scheduling activities, and procurement of field equipment, laboratory services, and contractors.

Each workplan submitted pursuant to this SOW shall list all permits, property, leases, and easements required for implementation of the investigation or response activity and a schedule for submittal of permit applications and acquisition of property leases or easements. Where normally required, permits must be obtained for all off-site activities. Settling Defendants are not required to obtain permits for on-site remedial activities, but must comply with all substantive requirements, including local building codes. Where permits will not be obtained for an on-site activity where a permit is normally required, Settling Defendants shall describe all consultative or coordination activities planned to identify and satisfy the substantive requirements. The status of permitting issues will be updated monthly in the monthly progress reports.

Where applicable, workplans shall describe the roles and responsibilities of all other parties expected to play a significant role in the design, construction, or operation of the remedial action. The workplan shall summarize and provide copies of memoranda of understanding and draft or final agreements with water purveyors and other third parties expected to participate in implementation of the remedial action. If legally-binding agreements are not in place, the workplan shall describe commitments made to date and planned efforts to secure necessary commitments, including an estimated schedule. If the participation of a third party is uncertain, the workplan shall describe alternatives to be implemented in the event that the party does not fulfill its planned role. Possible third party roles include agreeing to the use of existing

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equipment (e.g., groundwater extraction wells, groundwater monitor wells, water treatment facilities, pipelines, groundwater recharge facilities, power supplies), treatment plant operation, and acceptance of treated groundwater.

GROUNDWATER The purpose of the groundwater component of this SOW is to conduct activities related to the investigation, removal, and remediation of contaminated groundwater in Subunits A, B and C (collectively known as the Upper Alluvial Unit ("UAU")), and related to the investigation of and, if appropriate, removal and remediation of contaminated groundwater in the Middle Alluvial Unit ("MAU") at the Site.

The activities outlined under Tasks 2.0 - 6.0 and 10.0 shall be conducted concurrent with the ongoing operation and maintenance ("O&M") of the existing groundwater remedy as set forth in Task 1.0 pursuant to the ROD. As described under Task 1.0, Settling Defendants shall update the existing Operation and Maintenance Plan ("O&M Plan") (Task 1.1), as needed, to ensure that the plan is current and meets the operation and maintenance requirements of this SOW (Task 14.6).

The activities under Tasks 2.0 - 6.0 and 10.0 include investigation to identify other Site potential contaminants of concern ("COCs"), to identify potential sources of groundwater contamination and contaminant migration pathways, to determine the vertical and lateral extent of groundwater contamination, and to develop and/or update a groundwater flow model and a contaminant fate and transport model, the conduct of treatability studies to evaluate alternatives to remove COCs not currently addressed in the ROD, such as perchlorate, enhancement of the existing groundwater remedy, and development of a Supplemental Feasibility Study ("SFS") for any potential fundamental changes to the present groundwater remedy. Should EPA determine that a fundamental change to the existing groundwater remedy is necessary, Settling Defendants

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shall perform the modified remedy consistent with the CD and in accordance with the requirements of Task 13.0 (Supplemental Remedial Design) and Task 14.0 (Remedial Actions) of this SOW.

Task 1.0 Operation and Maintenance of Existing Groundwater Remedy The objectives of Task 1.0 are to: C C C C update the O&M Plan for the existing groundwater remedy; continue treatment of Site COCs with the current extraction and treatment systems; operate and maintain current extraction and treatment systems and monitoring well network; and make adjustments to the remedy as necessary to address findings made during the Groundwater Investigation (Task 2.0), the Main Drywells Area Investigation (Task 5.0), and the Source Areas, Soils and Facility Structures Investigation (Task 10.0).

Task 1.1 Operation and Maintenance Plan Settling Defendants shall update the Groundwater and Soil Remediation Operation and Maintenance Plan for Unidynamics/Phoenix, Inc. Phoenix-Goodyear Airport (PGA) Superfund Site (North) (Malcolm Pirnie, Inc., March 1998) ("1998 O&M Plan") to meet the requirements of this SOW and to reflect any modifications to the ongoing O&M of the existing groundwater remedy that are not described in the 1998 O&M Plan. The updated O&M Plan for the existing groundwater treatment plants, the groundwater extraction well network, and the groundwater monitoring well network shall be developed in accordance with Task 14.6 of this SOW.

Settling Defendants shall submit to EPA for review and approval an updated O&M Plan by December 1, 2004. Unless otherwise directed by EPA, O&M of the groundwater remedy shall continue in accordance with the applicable sections of the 1998 O&M Plan until development and EPA approval of the updated O&M Plan. EPA may also request periodic

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updates of the O&M Plan as more information is gathered, as conditions change during investigation and remedial action, and/or as the groundwater treatment system is modified. Should EPA make a written determination that an update of the O&M Plan is warranted, Settling Defendants shall submit an updated O&M Plan within forty-five (45) days of EPA's determination.

Task 1.2 Operation and Maintenance Reporting Settling Defendants shall submit an Annual O&M Report describing all engineering O&M activities for that calendar year, including, but not limited to, a summary of equipmentrelated maintenance, carbon replacement, a summary of air quality monitoring in the treatment plant areas and of the granular activated carbon ("GAC") contactor vessels, and a summary of any structural changes to the extraction or monitor well network.

Should any significant repairs or deviations from the applicable O&M Plan be required, such as repair activities that cause extraction wells or any treatment facility to be offline for more than twenty-four (24) hours, Settling Defendants shall notify EPA within forty-eight (48) hours either through correspondence or through a telephone call followed by written confirmation no later than five (5) days after the repair or deviation.

Should any action or occurrence during performance of activities pursuant to this SOW cause an actual release or threaten a release of hazardous waste that constitutes an emergency situation or may present an immediate threat to public health or welfare or the environment, Settling Defendants shall immediately notify the EPA Region 9 Duty Officer, Regional Response Center, at (800) 300-2193 (24-hour line) and the Site Remedial Project Manager ("RPM"). In addition, in the event of any actual release of a hazardous substance from the Site, Settling Defendants shall immediately notify the National Response Center at (800) 424-8802. In the event of a spill of untreated Site groundwater, in an amount over five (5) gallons, Settling

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Defendants shall notify the Site RPM within forty-eight (48) hours. In each of these circumstances, Settling Defendants shall submit a written report to EPA within seven (7) days of any release setting forth the events that occurred and the measures taken or to be taken to mitigate any release or endangerment caused or threatened by the release and to prevent the reoccurrence of such a release.

Task 1.3 Operation and Maintenance of the Existing Groundwater Remedy Settling Defendants shall operate and maintain the existing groundwater extraction and treatment remedy and monitoring system as set forth in the current remedial design documents and the applicable sections of the 1998 O&M Plan, or any updated O&M Plan developed pursuant to Task 1.1, until otherwise directed by EPA.

Summary of Task 1.0 Deliverables and Schedule C C C C Draft Groundwater O&M Plan Final Groundwater O&M Plan Revised Groundwater O&M Plan Annual O&M Report 12/1/04 30 days after receipt of EPA comments 45 days after EPA determination 90 days after end of calendar year

Task 2.0: Groundwater Investigation The objectives of Task 2.0 are to: C C C identify the Site COCs in groundwater; define the vertical and lateral extent of Site contamination, including but not limited to TCE and perchlorate, in the UAU and in the MAU; characterize the aquifer properties of the UAU and the MAU by a program of drilling and soil analyses, well installation, geophysical testing and aquifer testing to measure the hydraulic connection between Subunits A, B, and C of the UAU and the MAU throughout the known extent of contamination;

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C C C C

characterize the contaminant pathways from the Source Areas to deeper aquifers; develop and regularly update Site three-dimensional groundwater flow model and contaminant fate and transport model; determine the ability of the current remedial system to contain the vertical and lateral extent of contamination in the UAU, and, where applicable, in the MAU; and identify and properly abandon potential conduit wells.

Task 2.1 Review Existing Groundwater Information Settling Defendants shall review all existing information, including EPA's Phase II Source Area Groundwater Investigation ("Phase II") Report, regarding the distribution of contamination in the UAU (Subunits A, B, and C), and in the MAU, update the Site Conceptual Model ("SCM") accordingly, and identify data needed to define the extent of contamination in groundwater and to develop a comprehensive model of the flow and transport of contaminants in and between the UAU and the MAU. The review and data gap identification shall include, but not be limited to, the data and information on hydrogeology of the Site, the well inventory for the Site, potential conduit wells, potential COCs, potential sources of contamination, potential Dense Non-Aqueous Phase Liquids ("DNAPL"), and other factors that may impact groundwater characterization and groundwater quality that need to be identified for investigation in the Groundwater Investigation Workplan (Task 2.2).

Task 2.2 Groundwater Investigation Workplan Settling Defendants shall develop a Groundwater Investigation Workplan that includes, but is not limited to, identification of the project team, the updated SCM (Task 2.1), description of the groundwater models that will be used to model groundwater flow and to model contaminant fate and transport, description of data gaps to identify COCs and to characterize the vertical and lateral extent of groundwater contamination, description of other data requirements to support the groundwater models, description of the groundwater investigation data quality objectives ("DQOs"), overview of groundwater investigation strategy, description of the tasks associated

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with performing the groundwater investigation including a detailed well installation plan, and a schedule for performing the investigation.

The Groundwater Investigation Workplan shall include tasks and activities to meet the following objectives: C Identify the full range of COCs in groundwater by sampling and analyzing groundwater in existing wells for compounds that may be present, such as 1,4-dioxane and radionuclides, and for explosives, including nitro aromatics, trinitrotoluene (TNT), RDX (2,3,5-trinitro1,3,5-triazine) and HMX (oxyhydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). Contaminants that are detected above defined background concentrations or EPA Region IX Preliminary Remediation Goals ("PRGs") shall be considered as Site COCs and further characterized accordingly. C Determine the vertical and lateral extent of contamination in the vicinity of COG-02, and identify the preferential pathway for contamination in COG-02, by installing temporary boreholes to conduct geophysical, geotechnical, and depth-specific sampling. C Determine the vertical and lateral extent of contamination to the east and southeast of the Unidynamics facility and to the east of Litchfield Road through geophysical, geotechnical, and depth-specific sampling. Gather sufficient data to install additional monitor wells to characterize the extent of groundwater contamination and extraction wells, if determined necessary, for plume capture and/or groundwater cleanup. C Determine the vertical and lateral extent of contamination at the southern end of the Unidynamics facility and to the south and southwest through geophysical, geotechnical and depth-specific sampling. Gather sufficient data to install additional monitor wells to characterize the extent of groundwater contamination and to confirm whether a groundwater divide exists in Subunit A near Yuma Road, and extraction wells, if determined necessary, for plume capture and/or groundwater cleanup. C Determine the vertical and lateral extent of contamination at the west and northwest of the Unidynamics property in the direction of the Southern Pacific railroad tracks through

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geophysical, geotechnical, and depth-specific sampling. Gather sufficient data to identify contaminant sources, characterize potential preferential pathways initially identified in the Phase II Report, and to install additional monitor wells to characterize the extent of groundwater contamination and extraction wells, if determined necessary, for plume capture and/or groundwater cleanup. C Determine the vertical and lateral extent of contamination at the north, northwest and northeast of Litchfield Road and Van Buren Street through geophysical, geotechnical, and depth-specific sampling. Gather sufficient data to identify contaminant sources, to identify and characterize potential pathways (such as transmissive intervals in Subunits B and C identified in the Phase II Report), and to install additional monitor wells to characterize the extent of groundwater contamination and extraction wells, if determined necessary, for plume capture and/or groundwater cleanup. C Determine the vertical and lateral extent of potential contamination to the north-northwest of Well 33A and to the east and northeast of MW-16 through geophysical, geotechnical, and depth-specific sampling. Gather sufficient data to identify contaminant sources, define potential preferential pathways, and to install additional monitor wells to characterize the vertical and lateral extent of groundwater contamination and extraction wells, if determined necessary, for plume capture and/or groundwater cleanup. C Measure the hydraulic properties of the UAU and the MAU at the Source Area beneath the Unidynamics facility by conducting aquifer testing. Characterize the hydraulic properties and hydraulic connection between Subunits A, B, and C of the UAU and the MAU throughout the known extent of contamination, focusing on areas where stratigraphic data suggests relatively high vertical permeability. C Define the three-dimensional flow of contaminants of groundwater in the area through Site-specific groundwater modeling. Evaluate the effectiveness of the remedial system through use of a Site-specific, three-dimensional groundwater model to simulate groundwater flow, quantification of plume capture, and simulation of fate and transport of contaminants in the UAU (Subunits A, B and C combined) and the MAU. Update all

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groundwater models with new data as acquired.

The Groundwater Investigation Workplan shall be an iterative document, utilizing investigation phases, and shall be updated at least annually until the objectives of the Groundwater Investigation are met. The first Groundwater Investigation Workplan shall be entitled the Initial Groundwater Investigation Workplan and all subsequent workplans shall be considered amendments to the Groundwater Investigation Workplan.

The Draft 2005 Groundwater Investigation Workplan submitted by Settling Defendants on November 1, 2004, shall constitute a draft of the Initial Groundwater Investigation Workplan. The Initial Groundwater Investigation Workplan shall provide a description and schedule for installation of wells according to the established priorities and conditions described in the Initial Borehole and Well Installation Schedule (Attachment C-1) and as shown on the Well Location Map (Attachment C-2), and include the development of a Site-specific groundwater flow model as described in Task 2.5. The Initial Groundwater Investigation Workplan may also include development of decision-making mechanisms, such as a decision tree, to assist in identification, investigation and evaluation of future locations to investigate to complete the Site groundwater characterization. Development and use of any such decision-making mechanisms shall be contingent upon the availability of sufficient groundwater analytical data and completion of an updated groundwater flow model developed in accordance with Task 2.5. The determination as to whether and to what extent such decision-making mechanisms will be utilized will be made by EPA, in its sole discretion. The progress of the Groundwater Investigation shall not be impeded due to the lack of sufficient data to fully utilize any decision-making mechanism. Until such mechanisms are fully developed, Settling Defendants shall continue to conduct the Groundwater Investigation by gathering sufficient data to meet the objectives of the Groundwater Investigation.

The Initial Groundwater Investigation Workplan must include a full description of well

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locations, sampling locations and depths, pump test plans, aquifer test plans, and groundwater modeling plans (Task 2.5). The Groundwater Investigation Workplan must set forth procedures to conduct the following activities: C installation of exploratory boreholes with Simulprobe or equivalent devices (similar to those used in the EPA Phase II Groundwater Investigation) to define the vertical and lateral extent of contamination, to characterize aquifer properties, and to characterize the contaminant pathways; C C C installation of permanent monitoring wells to define the contaminant plumes and to monitor the effectiveness of remedial systems; geophysical measurements, pump testing, and aquifer testing to characterize the hydraulic properties of the UAU and MAU in the contaminated area; and groundwater modeling to simulate groundwater flow, hydraulic capture, and contaminant fate and transport.

The Initial Groundwater Investigation Workplan shall also include the methodology to be used to evaluate whether wells identified for previously deferred locations are required to fill data gaps for groundwater characterization and completion of the groundwater flow model and the fate and transport model (Task 2.5). The evaluation methodology may include use of decision-making mechanisms as discussed above.

The Groundwater Investigation Workplan shall be amended annually, at a minimum, as groundwater analytical data and modeling data results become available until EPA determines that the objectives of the Groundwater Investigation have been met. Any proposed decisionmaking mechanisms may be developed and refined concurrently, and the status of those mechanisms and the data gaps to complete them shall be included in each Amended Groundwater Investigation Workplan.

Task 2.2.1 Schedule for Performance of Groundwater Investigation

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Settling Defendants submitted a Draft 2005 Groundwater Investigation Workplan as the Initial Groundwater Investigation Workplan on November 1, 2004. The Final Initial Groundwater Investigation Workplan shall be submitted by Settling Defendants within thirty (30) days of receipt of EPA's comments on the Draft Workplan.

Each of the first two Groundwater Investigation Workplans shall provide a schedule for installation of individual wells according to established priorities and conditions as set forth in the Initial Well Installation Schedule (Attachment C-1) and as shown on the Well Location Map (Attachment C-2). Settling Defendants shall initiate installation of Priority 1 wells within thirty (30) days of EPA approval of the Initial Groundwater Investigation Workplan. Within the first twelve (12) months after EPA approval of the Initial Groundwater Investigation Workplan, Settling Defendants shall install all Priority 1 wells and all Priority 3 wells related to the Priority 1 wells that are required based upon the contingencies set forth in Attachment C-1. Within the subsequent twelve (12) months and pursuant to the first Amended Groundwater Investigation Workplan, Settling Defendants shall install all Priority 2 wells and all Priority 3 wells related to the Priority 2 wells that are required based upon the contingencies set forth in Attachment 1-A.

Within fifteen (15) days of completion of development of each well, Settling Defendants shall conduct water quality sampling and provide sampling results to EPA. Where sampling results indicate Site-specific contamination above Site-specific cleanup levels in wells identified as sentinel wells, Settling Defendants shall continue to sample that well monthly until sampling shows levels below Site-specific cleanup levels for six (6) months. Where sampling results do not indicate Site-specific contamination above Site-specific cleanup levels and in wells not serving the function of sentinel well, each well shall be sampled quarterly. Sampling frequency of wells may be decreased or increased as deemed appropriate by EPA. Settling Defendants may submit recommendations for changes to the sampling frequency of specific monitor wells in the Annual Groundwater Monitoring Report (Task 1.2).

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To estimate aquifer transmissivity in the vicinity of the new wells, within thirty (30) days of well installation and development, Settling Defendants shall perform aquifer tests (of a minimum of 8-hour duration) in at least one MAU well, in all Priority 1 and Priority 2 Subunit C wells, and in all Subunit A wells. Settling Defendants shall conduct additional longer-term aquifer testing of specified wells where required by EPA.

Settling Defendants shall submit a First Well Installation Report within ninety (90) days of the installation of the last Priority 1 well and a Second Well Installation Summary Report within ninety (90) days of the installation of the last Priority 2 well. The Well Installation Summary Reports shall summarize all data findings, including all geophysical, geotechnical, and water quality data, and include copies of maps showing locations of all test boreholes and new wells and copies of well-logs, analytical reports, and other supporting documentation related to well installation activities, and the findings therein shall be summarized in the Initial Groundwater Investigation Report (Task 2.7).

Following the well installation and testing activities as required in the Initial and First Amended Groundwater Investigation Workplans, Settling Defendants shall provide a summary of the results of these activities and how they met the objectives of this Groundwater Investigation. The summary shall identify any data gaps to be addressed in order to meet the Groundwater Investigation objectives. Should EPA determine that additional investigation is necessary in order to meet the objectives, Settling Defendants shall submit an Amended Groundwater Investigation Workplan to EPA within sixty (60) days of EPA's determination. Each Draft Amended Groundwater Investigation Workplan shall describe the objectives of additional investigations, the DQOs, overview of the investigation strategy, description of the tasks associated with performing the groundwater investigation, and a schedule for performing the additional investigation. Settling Defendants shall submit an Amended Groundwater Investigation Workplan within thirty (30) days of receipt of EPA comments on the Draft. Settling Defendants shall conduct the additional groundwater investigations pursuant to that Amended

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Workplan.

At the conclusion of field work conducted pursuant to each Amended Groundwater Investigation Workplan, Settling Defendants shall provide a summary of the results of the activities and how they met the objectives of this Groundwater Investigation. If, based on a review of the summary and an evaluation of other Site-related information, and following consultation with Settling Defendants, EPA makes a written determination that additional data must be collected to meet the objectives of the Groundwater Investigation, Settling Defendants shall submit to EPA for review and approval a Draft Amended Groundwater Investigation Workplan within thirty (30) days of EPA's written determination. Settling Defendants shall submit the Amended Groundwater Investigation Workplan within thirty (30) days of receipt of EPA comments on the Draft. The scope of each Amended Groundwater Investigation Workplan shall be to obtain the necessary data to meet the objectives of the Groundwater Investigation through a quantified groundwater model and other relevant hydrogeological or water quality data for the Site. Settling Defendants shall conduct the additional groundwater investigations pursuant to the Amended Groundwater Investigation Workplan. Each Amended Groundwater Investigation Workplan shall include an update of the FSAP, QAPP, and Health and Safety Plan ("HASP") (Task 2.3).

Task 2.3 FSAP, QAPP, and HASP An FSAP, QAPP, and HASP shall be developed, and/or existing plans shall be amended, to cover the groundwater investigation activities described in the Groundwater Investigation Workplan (Task 2.2). The FSAP and QAPP shall be developed in accordance with this Task and submitted as part of the Groundwater Investigation Workplan (Task 2.2).

Settling Defendants shall use quality assurance, quality control, and chain of custody procedures for all treatability, design, compliance and monitoring samples in accordance with EPA Requirements for Quality Assurance Project Plans (QA/R5) (EPA/240/B-01/003, March

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2001), A Guidance for Quality Assurance Project Plans (QA/G-5) (EPA/600/R-98/018, February 1998), and subsequent amendments to such guidelines upon notification by EPA to Settling Defendants of such amendments. Amended guidelines shall apply only to procedures conducted after such notification. Prior to the commencement of any monitoring under this SOW, Settling Defendants shall submit to EPA for review and approval a QAPP that is consistent with this SOW, the National Contingency Plan ("NCP"), and the applicable guidance documents described under this Task.

Settling Defendants shall ensure that laboratories utilized for the analysis of samples taken pursuant to this SOW analyze all samples pursuant to the QAPP for quality assurance monitoring. Settling Defendants shall ensure that those laboratories perform all analyses according to accepted EPA methods. Accepted EPA methods consist of those methods which are documented in A Contract Lab Program Statement of Work for Inorganic Analysis, ILM05.3 (updated from ILMO5.2 on February 2004) and A Contract Lab Program Statement of Work for Organic Analysis, OLMO4.3 (updated from OLMO4.2 on August 2003), and any amendments made thereto during the course of the implementation of this SOW; however, upon approval by EPA, Settling Defendants may use other analytical methods which are as stringent as or more stringent than the Contract Lab Program ("CLP") -approved methods. Settling Defendants shall ensure that all laboratories they use for analysis of samples taken pursuant to this CD participate in an EPA or EPA-equivalent Quality Assurance/Quality Control ("QA/QC") program. Settling Defendants shall only use laboratories that have a documented Quality System that complies with ANSI/ASQC E4-1994, A Specifications and Guidelines for Quality Systems for Environmental Data Collection and Environmental Technology Programs (American National Standard, January 5, 1995), and EPA Requirements for Quality Management Plans (QA/R-2) (EPA/240/B-01/002, March 2001) or equivalent documentation as determined by EPA. EPA may consider laboratories accredited under the National Environmental Laboratory Accreditation Program ("NELAP") as meeting the Quality System requirements. Settling Defendants shall ensure that all field methodologies utilized in collecting samples for subsequent

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analysis pursuant to this SOW are conducted in accordance with the procedures set forth in the QAPP approved by EPA.

Settling Defendants shall submit to EPA a HASP for field investigation activities that conforms to the applicable Occupational Safety and Health Administration ("OSHA") and EPA requirements including, but not limited to, 29 C.F.R. § 1910.120.

Task 2.4 Identify, Investigate, and Abandon Potential Conduit Wells On September 30, 2004, Settling Defendants submitted a Draft Revised Conduit Well Investigation and Abandonment Workplan. Settling Defendants shall submit a Final Conduit Well Investigation and Abandonment Workplan by January 14, 2005, that addresses EPA's comments provided by letter dated December 3, 2004, and provides protocols for identification, investigation, and proper abandonment of wells that may be acting or could act as conduit wells for Site contamination. The Conduit Well Investigation and Abandonment Workplan shall also identify specific wells to be investigated, a priority ranking of those wells, where possible a priority ranking of wells to be potentially abandoned, and a schedule for conduit well investigation and abandonment.

Protocols to be followed in the Conduit Well Investigation and Abandonment Workplan shall include, but not be limited, to the following, as deemed appropriate by EPA: C C C C C C C C obtaining necessary access to investigate potential conduit wells; cleaning out potential conduit wells and exposing the well screens; completing video logs of the wells; conducting spinner log testing; conducting depth-specific water quality sampling; if aquifer data are needed, conducting pump tests, with transducers in nearby wells; installing temporary boreholes and/or permanent monitor wells adjacent to conduit wells; documenting the wells' as-built construction and completion designs; and

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C

setting forth well abandonment procedures in accordance with Arizona Department of Resources ("ADWR") regulations.

Within thirty (30) days of completion of investigation of any potential conduit well, Settling Defendants shall submit a Draft Conduit Well Investigation Report to EPA, ADEQ, and ADWR. The Conduit Well Investigation Report shall include a description of the well investigation activities, a description of the well condition, a schematic of the well, and the basis for concluding whether that well is a potential conduit well. If the Conduit Well Investigation Report indicates that the well is a potential conduit, the Report shall include a detailed description of the proposed method to abandon that well in accordance with ADWR abandonment regulations, and a proposed schedule for conducting well abandonment activities. Should Settling Defendants propose use of an alternative well investigation or abandonment procedure where it is not feasible to conduct any of the activities described in the previous paragraph for a particular well due to that well's particular conditions (e.g., in cases where the well or casing has potential for collapse, or where obstructions are present in the well that cannot be removed), the Conduit Well Investigation Report shall provide full documentation of the well conditions, including photographs and video-logs, along with any alternative well abandonment proposal. Within thirty (30) days after receipt of EPA's comments on the Draft Report, Settling Defendants shall submit a Final Conduit Well Investigation Report that addresses those comments.

Should the Final Conduit Well Investigation Report set forth conduit well abandonment procedures, within thirty (30) days of EPA approval of the Report or in accordance with the schedule set forth in the Report, Setting Defendants shall implement the activities in the Final Conduit Well Investigation Report.

Should EPA or Settling Defendants identify a well as one that should be abandoned in an expedited manner, Settling Defendants shall indicate this fact in its Draft Conduit Well

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Investigation Report and submit the Conduit Well Investigation Report to EPA, ADEQ, and ADWR within fifteen (15) days of the conclusion of the investigation.

Within thirty (30) days of completing a well abandonment, Settling Defendants shall submit a Conduit Well Abandonment Report to EPA, ADEQ and ADWR documenting the well abandonment and detailing any deviations from well abandonment procedures described in the Final Conduit Well Investigation Report.

Task 2.5 Groundwater Models Based on the data gathered in the Groundwater Investigation and existing information gathered pursuant to Task 2.1, Settling Defendants shall develop two groundwater models for the Site: a Site-specific groundwater flow model and a Site-specific fate and transport model. The models shall be prepared in sequence as discussed below. Should EPA make a written determination that the models must be updated, Settling Defendants shall update the models within ninety (90) days of EPA's determination.

Task 2.5.1. Groundwater Flow Model: By January 15, 2005, Settling Defendants shall submit to EPA for review and approval a Draft Site-specific, three-dimensional, quantitative Groundwater Flow Model and accompanying Groundwater Flow Model Report. The Groundwater Flow Model shall incorporate all existing Site information, including the distribution of contamination in the UAU (Subunits A, B, and C) and in the MAU. In addition, the Groundwater Flow Model shall utilize information gathered from ongoing activities, including data from pertinent groundwater withdrawal locations and recharge locations that may influence Site-related contamination. The Groundwater Flow Model shall be developed to be compatible with and support contaminant fate and transport modeling.

The Groundwater Flow Model shall meet the following objectives: C assist in optimization of design of remedial systems to control the movement of

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contaminants from the former Unidynamics facility; C C C C evaluate the potential threat to water supply wells from Site COCs; evaluate the effects of changes in local pumping patterns and recharge distribution on Site contamination; appropriately locate and screen monitor wells based on current and future anticipated groundwater flow directions; and estimate and compare relative rates of remediation alternatives.

The Groundwater Flow Model Report shall describe how output from the Groundwater Flow Model will be validated and updated with Site-specific monitor well data. The Groundwater Flow Model Report shall present the updated well and recharge location inventory, the model domain, construction and calibration details, modeling results, and a full electronic copy of the model code. The Groundwater Flow Model Report shall also include a delineation of 5-year capture zones for each water supply well, consistent with the most recent version of EPA's Wellhead Protection Area ("WHPA") program model and maps, based on various pumping scenarios, that identify threatened or "at-risk" supply wells, in accordance with Task 4.1. A water supply well shall be considered "at-risk" if it or a well within the well's 5-year time of travel contains detectable levels of any Site-related contamination. Following EPA approval of the initial Groundwater Flow Model, Settling Defendants shall submit Updated Model Reports every six (6) months (January 15 and July 15 of each year), unless reporting frequency is changed by EPA.

Task 2.5.2 Contaminant Fate and Transport Model: Within ninety (90) days of completion of installation of the Priority 1 and 2 wells, Settling Defendants shall submit to EPA for review and approval a Draft Site-specific Contaminant Fate and Transport Model that incorporates all existing Site information, including the distribution of contamination in the UAU (Subunits A, B, and C) and in the MAU. The Contaminant Fate and Transport Model shall utilize information gathered from ongoing activities as well as data from pertinent groundwater

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withdrawal and recharge locations that may influence Site-related contamination. To the extent possible with available data, the Contaminant Fate and Transport Model shall consider the effects of low permeability materials or "dead" zones within the groundwater flow field that will act to inhibit the progress of remediation. The Contaminant Fate and Transport Model shall be used in conjunction with the Groundwater Flow Model to estimate the time required to remediate Site-related COCs.

Task 2.6 Performance of Groundwater Investigation Settling Defendants shall notify EPA with a Notification of Initiation of Field Work at least fifteen (15) days prior to initiating any physical work in the field. Upon submission of the Notification of Initiation of Field Work, Settling Defendants shall provide weekly field progress reports via electronic mail. The Notification of Initiation of Field Work must include the expected dates for field activities so that EPA may adequately schedule oversight tasks. Settling Defendants shall provide a written Notification of Completion of Field Work within five (5) days of completion of field work activities. Unless EPA disapproves the Notification of Completion of Field Work, weekly field progress reports may be discontinued upon Notification of Completion of Field Work.

Task 2.7 Groundwater Investigation Report Within ninety (90) days of submittal of the Notification of Completion of Field Work, Settling Defendants shall submit a Groundwater Investigation Report that incorporates the results of the entire Groundwater Investigation. The Groundwater Investigation Report shall include, but not be limited to, a description of the groundwater investigation objectives, a description of the field investigations to meet the identified objectives, a description of the groundwater modeling conducted to meet the identified objectives, a revised SCM, a summary of all the data results including copies of original analytical reports, a description of the nature and extent of groundwater contamination based on the field investigations and modeling results, a

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description of the fate and transport of groundwater contamination based on the field investigations and modeling results, and recommendations for additional phases of investigative activities where data gaps were not adequately filled.

Within thirty (30) days of receipt of EPA's comments on the Draft Groundwater Investigation Report or within sixty (60) days of completion of field work required by the Final Amended Groundwater Investigation Workplan, whichever comes later, Settling Defendants shall submit to EPA for review and approval a Final Groundwater Investigation Report that incorporates EPA comments.

Consistent with Paragraph 13 of the Consent Decree, as an addendum to the Groundwater Investigation Report, Settling Defendants may submit a petition requesting that EPA consider specific modifications to implementation of the existing remedy or fundamental changes to the remedy selected in the ROD. Such petition must include a description of the proposed modifications or remedy changes, a discussion of how the proposed modifications or changes may enhance or expedite Site cleanup, reduce cleanup costs, or provide other substantial benefit sufficient to justify the modifications or remedy changes, and all information and analyses supporting the proposed modifications or remedy changes.

Should EPA make a written determination pursuant to Paragraph 14 of the CD, based on Settling Defendants' petition or on an independent evaluation of Site-Related information, that a modification to the implementation of the remedy selected in the ROD is appropriate, Settling Defendants shall, within thirty (30) days of EPA's determination, submit a Modification Workplan to EPA for review and approval. The Modification Workplan shall include a description of the technical basis for the proposed modification, a specific proposal for implementing the proposed modification, and a proposed schedule for implementing the modification. Upon approval of the Modification Workplan, Settling Defendants shall implement the proposed modification in accordance with the approved Modification Workplan

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and schedule.

Should EPA make a written determination pursuant to Paragraph 18 of the CD, based on Settling Defendants' petition or on an independent evaluation of Site-related information, that a fundamental change to the remedy selected in the ROD may be required, Settling Defendants shall initiate the SFS process as directed by EPA and consistent with Task 12.0 of this SOW.

Summary of Task 2.0 Deliverables and Schedule: C Draft Initial Groundwater Investigation Workplan and draft FSAP, QAPP, and amended HASP C C Final Initial Groundwater Investigation Workplan and Final FSAP and QAPP Initiate Installation of Initial Wells 30 days after EPA approval of Initial Groundwater Investigation Workplan and Schedule C Initial Well Installation Summary Reports C 90 days of installation of last Priority 1 well and Second Report within 90 days of installation of last Priority 2 well Draft Amended Groundwater Investigation 12 months after EPA approval of Initial Workplan, revised draft FSAP and QAPP Groundwater Investigation Workplan or 30 days after EPA written determination that an amendment is necessary C C Final Amended Groundwater Investigation 30 days after receipt of EPA comments Workplan, and Final FSAP and QAPP Initiate Additional Field Investigation 30 days after EPA approval of Final Amended Groundwater Investigation Workplan and Schedule 30 days after receipt of EPA comments November 1, 2004

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C

Draft Groundwater Modification Workplan 45 days after notification from EPA that modification of groundwater extraction system is necessary

C C C C

Final Groundwater Modification Workplan 30 days after receipt of EPA comments Initiate Groundwater Remedy Modification 30 days after EPA approval of Workplan Draft Groundwater Investigation Report 90 days of submittal of Notification of completion of field work Final Groundwater Investigation Report Report 30 days after receipt of EPA comments or within 60 days of completion of field work required by an investigation amendment, whichever comes later

C C C C C C

Draft Groundwater Flow Model Report Draft Groundwater Fate and Transport Model Updated Groundwater Flow Model Reports Updated Groundwater Fate and Transport Model Final Conduit Well Investigation and Abandonment Workplan and Schedule Conduit Well Investigation Reports

January 15, 2005 90 days after installing last Priority 2 well

January 15 and July15, unless EPA changes Reporting frequency 90 days after EPA review of Draft Model and every 6 months thereafter January 14, 2005

30 days after completion of investigation or 15 days after completion of investigation if expedited abandonment is necessary

C C

Initiate Abandonment of Conduit Wells

30 days after EPA approval of Conduit Well Investigation Report

Conduit Well Abandonment Reports

30 days after completion of well abandonment

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Task 3.0 Groundwater Monitoring The objectives of Task 3.0 are to: C C continue the current Site groundwater monitoring program while establishing an updated Site Groundwater Monitoring Plan; continue periodic (annual, semi-annual, quarterly, monthly and/or weekly, as specified in the annual Groundwater Monitoring Plan) monitoring of all wells, with greater monitoring freque