Title: Investigation Area H1 Draft Feasibility Study
1Investigation Area H1Draft Feasibility Study
2H1 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
3Area 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
4Containment Area
5Containment 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
7RCRA Liner Cross-Section
8Non-RCRA Liner Cross-Section
9Wetland 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
10Existing Seasonal Wetlands Within Containment
11History of Wetland X
Wetland X
1970
1966
1954
12Wetland X Vicinity Subsurface Conditions
3 inch projectile shipping containers
13IA H1 Existing Wetlands, Anticipated Wetland Loss
(Fill) Areas, and Proposed Wetland Creation Areas
14Containment 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
15Comparison 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.
16Upland Area
17Upland 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
18Upland Hot Spots and Soil Cover (Alternative 2)
19Upland 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
20Upland 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.
21Upland Hot Spots and Soil Cover (Alternative 3)
22Upland 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.
23Comparison 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.
24Non-tidal Wetland Areas
25Non-tidal Wetland Alternatives
- Alternative 1-No Action
- Alternative 2-Institutional Controls, Hot Spot
Removal, and Sediment Monitoring - Alternative 3-Institutional Controls and Wetland
Excavation
26Non-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
27Non-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
28Comparison 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
29Next 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