Investigation Area H1 Draft Feasibility Study

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Investigation Area H1Draft Feasibility Study
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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

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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

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Containment Area
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Containment Area Alternatives

• Alternative 1-No Action
• Alternative 2-Multilayer Cap, Institutional
  Controls, Groundwater Containment, and Landfill
  Gas Monitoring
• Alternative 3-Removal and Disposal

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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

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RCRA Liner Cross-Section
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Non-RCRA Liner Cross-Section
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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

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Existing Seasonal Wetlands Within Containment
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History of Wetland X
Wetland X
1970
1966
1954
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Wetland X Vicinity Subsurface Conditions
3 inch projectile shipping containers
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IA H1 Existing Wetlands, Anticipated Wetland Loss
(Fill) Areas, and Proposed Wetland Creation Areas
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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

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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.

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Upland Area
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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

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Upland Hot Spots and Soil Cover (Alternative 2)
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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

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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.

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Upland Hot Spots and Soil Cover (Alternative 3)
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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.

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Comparison of Alternatives Upland Areas

• Alternative 2,3, and 4 satisfy the required
  criteria
• Alternatives 2 and 3 provide the greatest
  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.

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Non-tidal Wetland Areas
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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

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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

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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

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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

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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