Summary of Alternatives Evaluated   Assessment Criteria   Evaluation and Comparison of Alternatives   Questions & Answers

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Four action alternatives:

  FPS-2 Physical containment/hydraulic control + removal of NAPL

  FPS-3 Physical containment/hydraulic control + treatment/removal of NAPL/DBCP Areas and Potential Source Areas

  FPS-5 Physical containment/hydraulic control + treatment/removal of NAPL/DBCP Areas and Potential Source Areas + in situ treatment of shallow soil and groundwater

  FPS-7 Hydraulic control + treatment of NAPL/DBCP Areas + Excavation of all soil from unsaturated zone

The remediation alternatives have common elements.

DBCP = 1,2-dibromo-3-chloropropane in situ = “in place”, in the subsurface NAPL = Non-aqueous phase liquid 3

  Excavation of soil in residential neighborhood   Replacement of the City water supply   Groundwater extraction and treatment   NAPL recovery   Site restoration   Groundwater monitoring   Institutional controls

The remediation alternatives build up from the common elements.

NAPL = Non-aqueous phase liquid 4

Alternative Component FPS-1 FPS-2 FPS-3 FPS-5 FPS-7

Neighborhood Soil Excavation and Offsite Disposal X X X X Engineered cap (physical containment) X X X X Vertical barrier (physical containment) X X X Perimeter drain system X X X Existing NAPL/GWCS and new NAPL collection trenches

X X X X

In situ treatment/removal of NAPL X X X In situ treatment of DBCP areas X X X Treatment/removal of potential source areas X X X In situ soil treatment X In situ groundwater treatment X Excavation X Offsite disposal X Groundwater extraction wells X Lower Outwash Unit Groundwater City water supply replacement X X X X Groundwater extraction wells X X X X Removal of NAPL (collection sump) X X X X

Alternative FPS-2

DBCP = 1,2-dibromo-3-chloropropane in situ = “in place”, in the subsurface GWCS = Groundwater collection system NAPL = Non-aqueous phase liquid 5

Alternative Component FPS-1 FPS-2 FPS-3 FPS-5 FPS-7

Neighborhood Soil Excavation and Offsite Disposal X X X X Engineered cap (physical containment) X X X X Vertical barrier (physical containment) X X X Perimeter drain system X X X Existing NAPL/GWCS and new NAPL collection trenches

X X X X

In situ treatment/removal of NAPL X X X In situ treatment of DBCP areas X X X Treatment/removal of potential source areas X X X In situ soil treatment X In situ groundwater treatment X Excavation X Offsite disposal X Groundwater extraction wells X Lower Outwash Unit Groundwater City water supply replacement X X X X Groundwater extraction wells X X X X Removal of NAPL (collection sump) X X X X

Alternative FPS-3

DBCP = 1,2-dibromo-3-chloropropane in situ = “in place”, in the subsurface GWCS = Groundwater collection system NAPL = Non-aqueous phase liquid 6

Alternative Component FPS-1 FPS-2 FPS-3 FPS-5 FPS-7

Neighborhood Soil Excavation and Offsite Disposal X X X X Engineered cap (physical containment) X X X X Vertical barrier (physical containment) X X X Perimeter drain system X X X Existing NAPL/GWCS and new NAPL collection trenches

X X X X

In situ treatment/removal of NAPL X X X In situ treatment of DBCP areas X X X Treatment/removal of potential source areas X X X In situ soil treatment X In situ groundwater treatment X Excavation X Offsite disposal X Groundwater extraction wells X Lower Outwash Unit Groundwater City water supply replacement X X X X Groundwater extraction wells X X X X Removal of NAPL (collection sump) X X X X

Alternative FPS-5

DBCP = 1,2-dibromo-3-chloropropane in situ = “in place”, in the subsurface GWCS = Groundwater collection system NAPL = Non-aqueous phase liquid 7

Alternative Component FPS-1 FPS-2 FPS-3 FPS-5 FPS-7

Neighborhood Soil Excavation and Offsite Disposal X X X X Engineered cap (physical containment) X X X X Vertical barrier (physical containment) X X X Perimeter drain system X X X Existing NAPL/GWCS and new NAPL collection trenches

X X X X

In situ treatment/removal of NAPL X X X In situ treatment of DBCP areas X X X Treatment/removal of potential source areas X X X In situ soil treatment X In situ groundwater treatment X Excavation X Offsite disposal X Groundwater extraction wells X Lower Outwash Unit Groundwater City water supply replacement X X X X Groundwater extraction wells X X X X Removal of NAPL (collection sump) X X X X

Alternative FPS-7

DBCP = 1,2-dibromo-3-chloropropane in situ = “in place”, in the subsurface GWCS = Groundwater collection system NAPL = Non-aqueous phase liquid 8

  Long-Term Effectiveness and Permanence

  Short-Term Effectiveness

  Reduction of Toxicity, Mobility, and Volume Through Treatment

  Implementability

  Cost

  Compliance with ARARs

  Overall Protection of Human Health and the Environment

  State Acceptance

  Community Acceptance

ARARs= Applicable or Relevant and Appropriate Requirements 9