Confined Disposal Facilities and In Situ Capping

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Confined Disposal Facilities and In Situ Capping

• Site characterization / selection
• Engineering design
• Operational considerations
• Contaminant pathways and controls
• Long-term management
• Monitoring
• http//www.youtube.com/watch?vLbh9c0noR4s

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Potential Contaminant Release Pathways for
Dredging and Upland Disposal
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Confined Disposal Alternatives
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Engineering Issues

• Reduce Contaminant Pathways
• Disposal pathways
• Physical disturbance
• Seepage
• Optimize Capacity
• Safely dispose of the greatest amount of material
  in the smallest area

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Physical Disturbance

• Excavation and removal of contaminated sediments
• Erosion and Scour at the disposal site
• Slope Stability
• Nature of underlying materials
• Stability of existing and future slopes
• Intended end use of site
• Consolidation and settling
• Cap Properties

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Seepage

• Excess pore water in upland sites
• Consolidation and compaction induced seepage
• Groundwater-driven seepage

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Other Considerations

• Dredged disposal volume
• Area of land desired
• Habitat mitigation requirements
• Cost comparisons

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Local Example Ross Island
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Ross Island Locator Map
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Aerial Photo
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History of the Ross Island Sand Gravel Site

• July 1926 RISG acquires the islands and ownership
  is established over the area defined by the low
  water line surrounding the islands
• October 1967 RISG issued removal permit following
  effective date of Oregons removal law
• 1972 RISG proposed to mine entire islands away -
  denied by Oregon AG
• 1972 RISG proposed to connect the northern ends
  of the islands forming a private pond - denied by
  COE

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RISG History Contd

• 1979 RISGs removal permit amended to include
  fill
• 1980 City of Portland issued Conditional Use
  Permit specifying details of eventual reclamation
• 1983 RISG began accepting fill materials from
  outside sources
• 1992 first confined disposal event of Port of
  Portland dredged sediments

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Typical Cross Section
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Disposal Methods
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Potential Contaminant Migration Pathways -
Disposal Processes
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Potential Contaminant Migration Pathways -
Groundwater Transport (Present and Future)
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Potential Contaminant Migration Pathways -
Physical Disturbance
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Groundwater Movement through Cells
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Potential Groundwater Transport from Containment
Cells

• Upward groundwater flow
• Cap design minimizes discharge via this sort of
  flow
• Predicted discharge concentrations below
  risk-based criteria.

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Potential Physical Disturbance of Containment
Cells

• Natural erosion (floods).
• Human influence (mining).
• Geotechnical stability.

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Slope Instability
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Potential Physical Disturbance of Cells

• Minimal erosion potential due to a control dike.
• Mining controls would avoid future impacts.
• Slopes are presently receiving fills.

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RISG CDF Conclusion

• Final decision not yet made about CDF and the
  future of the island as a city park or preserve
• Engineering studies strongly suggest the CDF is
  presently secure and presents an acceptable risk

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GREENFill Areas ConsideredYELLOWFill Areas
ProposedREDAreas to be Dredged
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Wyckoff/Eagle Harbor
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Wyckoff/Eagle Harbor

• Bainbridge Island, in Central Puget Sound
• 3,780-acre site
• Land use in the area is predominantly
  residential, with some commercial and industrial
  uses
• The harbor supports several fish resources, a
  wide variety of resident and migratory birds, and
  other wildlife

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Eagle Harbor
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Wyckoff/Eagle Harbor

• Sources of Contamination
• Inactive 40-acre wood treating facility owned by
  Wyckoff
• Adjacent 500-acre Eagle Harbor
• Other upland sources of contamination (Shipyard)

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Site History

• Shipyard operated from 1903 to 1959 on the
  northwest shore of Eagle Harbor, resulting in
  releases of metals and organic contaminants.
• 1905 to 1988, wood treating operations were
  conducted on the southeast shore involving
  pressure treatment with creosote and
  pentachlorophenol

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Discovery

• During the 1970s, efforts were made to address
  oil seepage on beaches adjacent to the Wyckoff
• 1984 NOAA investigations of the Harbor revealed
  that sediment, fish, and shellfish from Eagle
  Harbor contained elevated levels of PAHs

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The Response to Discovery

• EPA required Wyckoff to conduct environmental
  investigation activities under RCRA
• Washington State required immediate action to
  control stormwater runoff and seepage of
  contaminants

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Response, Contd

• September 1985 Proposed to the Superfund NPL
• 1985Washington State Hazardous Waste Cleanup
  Program, (Ecology) Preliminary Investigation of
  sediment contamination in Eagle Harbor

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Response, Contd

• 1985 NOAA completed a study relating the
  presence of PAHs in sediment to the high rate of
  liver lesions in English Sole from Eagle Harbor
• March 1987, Wyckoff Company entered into an
  Administrative Order on Consent with EPA for
  further investigation of the facility (RI/FS)

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Historical Sources

• Preservative chemicals were stored in tanks on
  the property.
• Contamination of soil and ground water at wood
  treatment facility led to seepage into adjacent
  sediments.
• Wastewater discharged into Eagle Harbor for many
  years storing treated pilings and timber in the
  water continued until the late 1940's.

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Contaminants of Concern

• Shipyard Levels toxic to marine life
• Polyaromatic hydrocarbons (PAHs) and other
  organics
• Heavy metals such as mercury, copper, lead, and
  zinc

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Contaminants of Concern

• Wyckoff facility, soil and groundwater are
  contaminated with
• Creosote
• Accompanying PAHs
• Pentachlorophenol (PCP penta)

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CERCLA Operating Units

• 1991, EPA defined three operable units at the
  Wyckoff/Eagle Harbor site
• Wyckoff (OU1)
• East Harbor (OU2)
• West Harbor (OU3)
• Wyckoff Facility groundwater (OU4, 1994)

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Selected Remedial Actions

• Dredging, excavating dewatering intertidal
  sediment that exceeds levels of 5 mg/kg mercury
  and/or lower, moderate PAH concentrations
• Approximately 1,000 to 7,000 cubic yards
• Solidification/stabilization, as necessary, to
  comply with disposal rules
• Transporting sediment, which cannot be treated to
  meet rules offsite for disposal at a
  RCRA-permitted (Subtitle C or D) landfill

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Remedial Actions (contd)

• Treating dewatering wastewater onsite using
  carbon adsorption before discharge into the
  harbor
• Capping the sediment in areas of high concern
  with a 1- meter thick layer of clean sediment
• Placing a thin layer of clean sediment in
  subtidal areas of low to moderate concern to
  enhance natural sediment recovery

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Remedial Actions (contd)

• Long-term environmental monitoring
• Institutional controls to prevent exposure to
  contaminated fish and shellfish.
• The estimated cost is up to 16,000,000
• Most work done but site still on NPL

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Eagle Harbor Cap Areas
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East Harbor Capping (OU2)

• Sept 1993-March 1994, EPA and the Corps of
  Engineers covered contaminated sediments in the
  East Harbor
• Cap of clean sediment at water depths of 17 m and
  13 m, respectively.
• Sediment was dredged from the Snohomish River as
  part of an annual project for ship navigation

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Capping Methods
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Capping Methods

• Split Hull Fast but uneven.

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Capping Methods

• Hydraulic washoff

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West Harbor CDF (OU3)
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Final sediment cleanup actions

• Monitoring the success of natural recovery in
  intertidal areas
• Monitoring contaminated areas where active
  remediation cannot be implemented.