ABSTRACT
Liquid (LNAPL) .............................................................................. 388 6.2.5 Tides and Groundwater Modeling ................................................... 388 6.2.6 Data Presentation ............................................................................. 389 6.2.7 Suspended Particulates..................................................................... 389 6.2.8 Shallow Aquifer ............................................................................... 389 6.2.9 Seawater Intrusion............................................................................ 390 6.2.10 Reductive Dissolution ...................................................................... 390 6.2.11 Conclusions ...................................................................................... 390 6.2.12 Recommendations ............................................................................ 391
6.3 Lessons Learned from Selected Investigations ............................................ 391 6.4 Coastal Contamination Monitoring Technologies ....................................... 394
6.4.1 Trident® Probe................................................................................. 395 6.4.2 UltraSeep® Meter ............................................................................ 396 6.4.3 Recommendations ............................................................................ 397
6.5 Coastal Zone Modeling ................................................................................ 398 6.6 Detailed Case Study ..................................................................................... 398
6.6.1 Feasibility Analysis/Interim Remedial Action Plan for a Large Confidential Port Bulk Fuel Terminal in California ........................ 398 6.6.1.1 Site Location and Description ........................................... 398
6.6.1.1.1 Surfacewater Flow .......................................... 399 6.6.1.1.2 Stormwater Flow............................................. 399
6.6.1.2 Geology and Soil .............................................................. 400 6.6.1.2.1 Soil Analytical Results ................................... 400
6.6.1.3 Groundwater Occurrence and Flow.................................. 400 6.6.1.3.1 Hydrostratigraphic Units................................. 400 6.6.1.3.2 Tidal Influence................................................ 400 6.6.1.3.3 Groundwater Flow .......................................... 401
6.6.1.4 Groundwater Quality......................................................... 401 6.6.1.4.1 Initial Vapor Extraction Pilot Testing ............ 402 6.6.1.4.2 Initial Air Sparging Pilot Testing ................... 402
6.6.1.5 Hydrogeology.................................................................... 402 6.6.1.6 Chemical Analyses-Liquid Phase Hydrocarbons .......... 403
6.6.1.6.1 Petroleum Constituents ................................... 403 6.6.1.6.2 Bioremediation Indicator Parameters ............. 404
6.6.1.7 Results of Initial Vapor Extraction Pilot Test .................. 406 6.6.1.7.1 Vapor Flow vs. Applied Vacuum
Relationship .................................................... 406 6.6.1.7.2 Radius of Influence ........................................ 407 6.6.1.7.3 Extracted Soil Vapor Analytical Results........ 407 6.6.1.7.4 Hydrocarbon Mass Removal Rate.................. 407 6.6.1.7.5 Mass Removal Calculations ........................... 408 6.6.1.7.6 Vacuum Influence, Permeability, and
Recommended Design Radius of Influence .. 408 6.6.1.7.7 Air Flow vs. Sparging Well Pressure............. 408 6.6.1.7.8 Pressure Response .......................................... 408 6.6.1.7.9 Dissolved Oxygen Concentration................... 408 6.6.1.7.10 Ferrous Iron Concentrations ........................... 409
6.6.1.8 Estimated Radius of Influence.......................................... 409 6.6.1.9 Method Observed Radius of Influence............................. 409
6.6.1.9.1 Measurement of Relative Permeability .......... 410 6.6.1.10 Risk Assessment under Current Conditions..................... 410
6.6.1.10.1 Site Conceptual Model.................................. 410 6.6.1.11 Summary of Exposure Assessment .................................. 410 6.6.1.12 Human Health Risk Characterization ............................... 411 6.6.1.13 Ecological Screening Evaluation ...................................... 411 6.6.1.14 Parallel Preferential Pathway/Tidal Study Investigation
and Risk Assessment ........................................................ 412 6.6.2 Remedial Action Objectives — Mitigation of Human
Health Risks ..................................................................................... 412 6.6.2.1 Control of Long-Term Methane Rebound........................ 412 6.6.2.2 Preliminary Action Levels ................................................ 413 6.6.2.3 Soil Vapor.......................................................................... 413 6.6.2.4 Soil .................................................................................... 414 6.6.2.5 Groundwater...................................................................... 414 6.6.2.6 Risk Assessment for Cessation of Active Remediation... 414 6.6.2.7 General Response Actions ................................................ 414
6.6.3 Technology Identification-Soil and Soil Vapor ............................ 414 6.6.3.1 Natural Attenuation ........................................................... 414 6.6.3.2 Passive Venting ................................................................. 415 6.6.3.3 Vapor Extraction ............................................................... 416 6.6.3.4 Bioventing ......................................................................... 416 6.6.3.5 Soil Excavation and Offsite Disposal............................... 416
6.6.4 Groundwater..................................................................................... 417 6.6.4.1 Natural Attenuation ........................................................... 417 6.6.4.2 Enhanced Bioremediation ................................................. 417 6.6.4.3 Air Sparging with Concurrent Vapor Extraction.............. 417 6.6.4.4 Air-Ozone Sparging ......................................................... 418 6.6.4.5 Groundwater Pump and Treat........................................... 418
6.6.5 Analysis of Remedial Alternatives .................................................. 418 6.6.5.1 Technologies for Remediation of Soil and Soil Vapor .... 419 6.6.5.2 Natural Attenuation........................................................... 419 6.6.5.3 Passive Venting ................................................................. 419 6.6.5.4 Vapor Extraction ............................................................... 420 6.6.5.5 Bioventing ......................................................................... 420 6.6.5.6 Soil Excavation and Offsite Disposal............................... 420
6.6.6 Technologies for Remediation of Groundwater .............................. 421 6.6.6.1 Natural Attenuation........................................................... 421 6.6.6.2 Enhanced Bioremediation ................................................. 421 6.6.6.3 Air Sparging with Concurrent Vapor Extraction.............. 421 6.6.6.4 Air-Ozone Sparging ......................................................... 422 6.6.6.5 Groundwater Pump and Treat........................................... 422
6.6.7 Recommended Alternatives ............................................................. 422 6.6.7.1 Soil and Soil Vapor Remediation ..................................... 422 6.6.7.2 Groundwater Remediation ................................................ 423
6.6.8 Remedial Action Plan ...................................................................... 423 6.6.8.1 Summary Overview ........................................................... 423
6.6.9 Long-Term Monitoring and Assessment of Remedial Actions — Remedial Progress Monitoring ........................................................ 424
6.6.10 Methane Rebound Testing and Evaluation...................................... 425 6.6.11 Risk Assessment for Cessation of Active Remediation.................. 425
The conceptual model for migration of contaminants from groundwater to coastal surfacewater is shown in Figure 6.1.1. The impact, both chemical and physical, may be heightened in smaller bodies of water such as embayments and lagoons due to their limited volume and restricted fluid exchange with the open ocean.
