New Jersey Department of Environmental Protection Site Remediation and Waste Management Program Commingled Plume Technical Guidance Document March 2018 Version 1.1 Table of Contents 1.0 Introduction ........................................................................................................................................................... 5 1.1 Intended Use of Guidance Document ................................................................................................................ 5 1.2 Purpose .............................................................................................................................................................. 6 1.3 Document Overview .......................................................................................................................................... 7 1.4 Definitions (as used within the context of this technical guidance) .................................................................. 8 2.0 Identifying and Characterizing Commingled Plumes ............................................................................................. 8 2.1 Commingled Plume Scenarios ............................................................................................................................ 8 2.1.1 Off-site Source Contamination Scenario - Different Constituents ............................................................ 8 2.1.2 Off-site Source Contamination Scenario - Similar Constituents ................................................................ 9 2.1.3 On-site Source Contamination Scenario - Different Constituent .............................................................. 9 2.1.4 On-site Source Contamination Scenario - Similar Constituents (Overprinting) ...................................... 10 2.2 Characterizing Commingled Plumes ................................................................................................................ 10 3.0 Techniques for Establishing MLE for Commingled Plumes .................................................................................. 11 3.1 Site Background and Existing Data Sets ........................................................................................................... 12 3.1.1 Department Databases: HazSite Data: .................................................................................................... 12 3.1.2 United States Geologic Survey (USGS) Ground Water Watch ................................................................. 12 3.1.3 NJ-Geo Web ............................................................................................................................................. 12 3.1.4 NJDEP Data Miner.................................................................................................................................... 12 3.1.5 Other Commercial Sources of Information ............................................................................................. 12 3.2 Additional Ground Water Sampling ................................................................................................................. 13 3.3 Evaluate the Potential for Preferential Pathways ............................................................................................ 13 3.4 Fate and Transport Modeling .......................................................................................................................... 13 3.5 Statistical Analysis ............................................................................................................................................ 13 3.6 Environmental Forensics .................................................................................................................................. 14 3.7 Conceptual Site Model ..................................................................................................................................... 14 3.8 High-Resolution Site Characterization ............................................................................................................. 14 3.9 Potential Lines of Evidence Checklist ............................................................................................................... 15 4.0 Selecting a Resolution Mechanism ...................................................................................................................... 15 4.1 Evaluating the Need for a PRCR to Choose a Resolution Mechanism ............................................................. 15 4.2 Potential Resolution Mechanisms ................................................................................................................... 17 4.3 Work Cooperatively with Other PRCRs ............................................................................................................ 18 2 4.3.1 Benefits of Working Cooperatively.......................................................................................................... 18 4.3.2 Challenges of Working Cooperatively ..................................................................................................... 18 4.4 Completing Work Independently ..................................................................................................................... 19 4.4.1 Benefits of remediating a commingled plume independently ................................................................ 19 4.4.2 Challenges of remediating a commingled plume independently ........................................................... 20 4.5 Uncooperative Responsible Entities ................................................................................................................ 20 4.5.1 NJDEP Technical Consultation ................................................................................................................. 20 4.5.2 Neutral Party Technical Mediation .......................................................................................................... 21 4.5.3 Other Mediation ...................................................................................................................................... 21 4.5.4 NJDEP Office of Dispute Resolution ........................................................................................................ 21 4.5.5 Seek treble damages ............................................................................................................................... 22 4.5.6 Litigation .................................................................................................................................................. 23 5.0 Administrative Requirements for Commingled Plumes ...................................................................................... 23 5.1 Separate discharge detected On-site; Source of the new discharge also located On-Site .............................. 24 5.2 Separate discharge detected On-site; Contaminants migrating onto site from Off-site location ................... 25 5.3 Contamination was detected during plume delineation that is downgradient of the site and on another property ................................................................................................................................. 27 5.3.1 Different contaminants found downgradient ......................................................................................... 27 5.3.2 Similar contaminants found downgradient ............................................................................................. 27 5.4 Requirements for Classification Exception Area (CEA) .................................................................................... 28 5.5 Discharge discovered after issuance of Remedial Action Permit (RAP-GW) ................................................... 29 5.5.1 New Discharge; Minimal Impact on Existing Remediation; No Remedial Action Permit Modification Necessary ........................................................................................................................... 30 5.5.2 New discharge; Significant Impact on Existing Remediation; RAP-GW Modifications Needed .............. 30 5.5.3 New Discharge; Significantly Impacts Existing Remediation; RAP-GW Modifications are not Possible. MLE Available to Extrapolate When Remediation Would be Complete ................................. 31 5.5.4 New Discharge; Significantly Impacts Existing Remediation. RAP-GW Modifications are not Possible; Inadequate MLE Available to Extrapolate When Remediation Would be Complete .............. 32 5.6 Issuance of the Remedial Action Outcome and Commingled Plume Notices ................................................. 32 6.0 Site Specific Case Studies of Commingled Plume Investigations ......................................................................... 34 7.0 References ........................................................................................................................................................... 35 3 Tables Table 1: Potential Lines of Evidence Checklist ......................................................................................38 Table 2: Post Remedial Action Permits Decision Tree ...........................................................................41 Appendices A. Site Specific Scenarios of Commingled Plume Investigations ..........................................................42 Case Study Scenario 1: Manufactured Gas Plant .............................................................................43 Case