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Investigation Area H1 Draft Feasibility Study

Investigation Area H1 Draft Feasibility Study. H1 Feasibility Study Objectives. Develop remediation alternatives Evaluate each alternative against nine specified criteria: Overall protection of human health and the environment

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Investigation Area H1 Draft Feasibility Study

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  1. Investigation Area H1Draft Feasibility Study

  2. H1 Feasibility Study Objectives • Develop remediation alternatives • Evaluate each alternative against nine specified criteria: • Overall protection of human health and the environment • Compliance with applicable and relevant and appropriate requirements (ARARs) • Long-term effectiveness and permanence • Reduction of toxicity, mobility, or volume • Short-term effectiveness • Implementability • Cost • State acceptance • Community acceptance

  3. Area H1 Feasibility Study • Discussed in three sections following the Remedial Investigation format • Containment Area • Upland Areas Outside the Containment Area • Non-tidal Wetland Areas Outside the Containment Area

  4. Containment Area

  5. Containment Area Alternatives • Alternative 1─No Action • Alternative 2─Multilayer Cap, Institutional Controls, Groundwater Containment, and Landfill Gas Monitoring • Alternative 3─Removal and Disposal

  6. IA H1 Landfill Remedy - Containment • Interim Remedy – Groundwater Containment Barrier • Completed October 2004 • 7,300 linear feet of slurry wall • Groundwater extraction/collection system • Extracted groundwater discharged to local POTW • Remedy – Multilayer Cap • Containment for approximately 70 acres • Includes roughly 7 acres of disposal areas that are seasonal wetlands; Wetland X and two smaller areas • Wetlands are isolated low value wetlands but contain some pickleweed which may provide habitat for the salt marsh harvest mouse

  7. RCRA Liner Cross-Section

  8. Non-RCRA Liner Cross-Section

  9. Wetland Mitigation • A Multilayer Cap will cover non-tidal Wetland inside containment area • Wetland mitigation includes creation of new higher value pickleweed wetlands in the upland areas • A Wetland mitigation plan is being reviewed by the interested agencies and experts to develop final workable plan

  10. Existing Seasonal Wetlands Within Containment

  11. History of Wetland X Wetland X 1970 1966 1954

  12. Wetland X Vicinity Subsurface Conditions 3 inch projectile shipping containers

  13. IA H1 Existing Wetlands, Anticipated Wetland Loss (Fill) Areas, and Proposed Wetland Creation Areas

  14. Containment Area Removal and Disposal • Includes removal of all waste and transport to other facilities • Not usually considered due to past EPA experience and development of presumptive remedy for landfills • Requires approximately 48,000 truckloads of waste to be removed from the site • Time to complete is years (2-3) • Moves waste from one area to another • Exposes workers to more potential hazards • Exposes public to waste transportation hazards

  15. Comparison of Alternatives Containment Area • Containment and Removal meet required criteria • Containment is much more implementable • Removal creates higher short term hazards in handling large amounts of waste material on-site and trucking to final disposal facilities • Containment can be implemented in months not years • Containment cost is $36,775,000 versus removal cost of $233,000,000.

  16. Upland Area

  17. Upland Areas Alternatives • Alternative 1-No Action • Alternative 2-Institutional Controls, Hot Spot Removal, Groundwater Monitoring and 2-Foot Soil Cover • Alternative 3-Institutional Controls, Limited Hot Spot Removal, Groundwater Monitoring, and 2-Foot Soil Cover • Alternative 4-Institutional Controls, Upland Excavation and Disposal

  18. Upland Hot Spots and Soil Cover (Alternative 2)

  19. Upland Areas Alternative 2 - Hot Spot Removal • Risk based determination of hot spots • Hot spots include all areas with • Unacceptable ecological risk • Human cancer Risk estimate of 1x10-4 • Areas posing a threat to groundwater • Exhibiting visible oil/free product

  20. Upland Areas Alternative 2 - continued • Remaining risk for Human cancer risk would be 1x 10-5 or better. • After hot spot excavation an additional 2-foot soil cover would be placed over the entire area to provide a good base for vegetation. • Groundwater monitoring in shallow water bearing zone would be conducted at the margins of the upland area to evaluate and ensure groundwater is not impacting the non-tidal wetlands.

  21. Upland Hot Spots and Soil Cover (Alternative 3)

  22. Upland Areas Alternative 3 -& 4 Limited Hot Spot Removal and Removal • Similar to alternative 2 however would remove only hot spots that pose a threat to groundwater or have visible oil/free product • All other actions are the same as Alternative 2 including the 2-foot soil cover and groundwater monitoring. • Alternative 4 would remove all the Upland areas to a depth ranging from 2-14 feet bgs.

  23. Comparison of Alternatives Upland Areas • Alternative 2,3, and 4 satisfy the required criteria • Alternatives 2 and 3 provide thegreatest protection to the environment, and are preferred based on short- and long-term effectiveness, implementability, and cost • Alternative 4 is much more difficult to implement and has more severe short-term impacts due to the large amount of material required to be excavated • Alternatives 2 and 3 are the preferred remedy with a total cost of $6,363,000 and $5,844,000, respectively.

  24. Non-tidal Wetland Areas

  25. Non-tidal Wetland Alternatives • Alternative 1-No Action • Alternative 2-Institutional Controls, Hot Spot Removal, and Sediment Monitoring • Alternative 3-Institutional Controls and Wetland Excavation

  26. Non-tidal Wetland Areas Alternative 2 - Hot Spot Removal • Risk based determination for hot spots. Same definitions as in the Upland Areas • Three hot spots would be removed • One current hot spot for manganese would be monitored because removal would likely result in more harm to the wetland than the available threat from manganese • Sediment monitoring will be conducted to confirm that concentrations in sediment are not increasing to hazardous levels over time

  27. Non-tidal Wetland Areas Alternative 3 - Wetland Excavation • This alternative includes removal of the upper 2-feet of sediment and surface soil. • Destruction of habitat would occur but contaminants would be removed • Would have a substantial short term impact on wetlands

  28. Comparison of Alternatives Non-Tidal Wetland Areas • Alternative 2 and 3 satisfy the required criteria • Alternative 2 provides the greatest protection to the environment, and is preferred based on short-term and long-term effectiveness, implementability, and cost • Alternative 3 provides the most long-term effectiveness and permanence however, it presents the most risk of impacts to the wetlands because the wetlands would essentially be removed and then replaced • Alternative 2 is the preferred remedy for the Non-Tidal Wetlands outside the Containment Barrier with a total cost of $400,000. This alternative removes key hot spots while maintaining the functional wetlands

  29. Next Steps • Comments due on Draft FS mid-January 2005 • Selection of the Remedy • Proposed Plan – Public Input – Design in progress • Remedial Action Plan/Record of Decision (RAP/ROD) • Public Comment • Target RAP/ROD Approval Date – June 30, 2005 • Remedial Action – Summer/Fall 2005

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