PowerPoint Presentation Proposed Active Caps

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Implementation of Anacostia RiverComparative
Validation of Innovative Capping Technologies
Status Report to AWTA

• Danny D. Reible
• W. David Constant
• Hazardous Substance Research Center/South
• Southwest, Louisiana State University
• Yuewei Zhu
• Horne Engineering Services, Inc.
• September 30, 2003

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Location Map
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Summary of Field Investigations

• Geophysical investigation -bathymetry, sonar,
  magnetometry
• Sediment profile imaging (SPI) survey
• Sampling of the sediment - contaminant concent.
  and profiles
• River current velocity via Acoustic Doppler
  Current Profiler
• Multicoring for sediment radionuclide
  characterization.
• Geotechnical to evaluate sediment stability and
  consolidation behavior loads imposed by the
  active cap materials
• Benthic investigation
• Draft Report 9/26/03 w/o seepage or dating work
• Seepage Tests (September 2003)
• Objective Establish baselines for placement and
  assessment

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Bathymetry Map
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Geophysical Survey Findings

• Gently undulating surface with few surface
  irregularities. River depths from 5 near shore
  to 20 at southern bound.
• Fine grained sediments likely ranging from soft
  aqueous silts muds to aqueous fine grained sand
  silt. Sonar mosaics were superimposed on the
  depth contours.
• Sonar mosaics are representative of features
  extending above the river bed (dark), while light
  areas represent shadows behind features or
  surface depressions.
• Subbottom penetration of the profiler system was
  restricted due to the presence of gaseous-type
  sediments in the near-subsurface.
• Organically derived gases in sediments is not
  uncommon and often characterizes sediments in
  upland rivers, bays and estuaries.

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SPI Image

• The sediment was primarily fine silt and
  clay sediment
• Biogenic activity of epifauna and infauna was
  not a predominant factor in structuring surface
  sediment
• There was no evidence at Areas 1 that SAV were
  present

Bubble
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Sediment Contamination Delineation

• 13 EPA priority metals
• PAHs
• PCBs (both aroclors and congeners)
• Pesticides
• Total phosphorus
• TKN
• TOC
• Acid volatile sulfide/simultaneously extracted
  metals

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PAHs Contour Map
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Geotechnical Investigation

• Five deep borings ranging from 21 feet to 27 feet
• Samples collected for engineering properties
  testing
• Vane shear tests performed at adjacent offset
  location
• Inferred subsurface profile defining 5 sediment
  strata

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Inferred Subsurface Profile
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Field River Flow Velocity Measurement

• Workhorse Sentinel ADCP used
• 4 tide stages (maximum flood, maximum ebb, high
  slack, and low slack).
• Variability of magnitude between the four tide
  stages was not significant.
• Median magnitudes for the averaged ensemble data
  from 0.13 ft/s for high slack to 0.21 ft/s for
  maximum flood.
• Maximum magnitudes ranged from 0.64 ft/s at high
  slack to 1.29 ft/s at maximum ebb

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Averaged Velocities During Maximum Flood
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Radionuclide Testing Preliminary Results
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Benthic Survey Preliminary Results -1
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Benthic Survey Preliminary Results -2
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Seepage Test Field Photos
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Active Caps for Demo

• AquaBlokTM with EPA SITE
• Coke breeze CMU/CETCO
• Apatite - UNH
• Sand (for evaluation purpose)
• Sevenson Environmental

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Pilot Study Cell Considerations

• Within 200x300, each cap is 100x100
• Three active caps plus a traditional sand cap
• A control (blank) cap.

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Pilot Study Cell Area Selection Considerations

• Known elevated contamination
• Identified for potential remedial action by the
  AWTA
• Outside of the navigation channel
• A relative slow flow segment of the Anacostia
  -confirmed with the field measurements
• Pilot study cells footprint has minimal slope (lt
  4)

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Pilot Study Cell Layout
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Measured Heavy Metals in Coke Leachate and
corresponding Criterion Maximum Concentrations
(CMC)1
Other Elements Detected in Coke Leachate (DI, PW)
and Anacostia Porewater
a. Porewater generated by equilibrating DI water
with Anacostia Sediment
a. Metals with detection limits exceeding CMC
values. b. Criterion Maximum Concentrations (CMC)
were obtained at on the EPA website (1) and
defined as an estimate of the highest
concentration of a pollutant in freshwater, to
which an aquatic community can be exposed briefly
(acute limit) without resulting in an
unacceptable effect.
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Cap Thickness Considerations

• A thin composite cap consists of a component of
  materials in which the reactive cap materials
  will be placed first. Once placed, these
  reactive cap materials will be overlain by a
  clean sand layer.
• A nominal 6-inch thick sand layer atop the active
  cap materials.
• An estimated 6-inch thick reactive cap layer
  (varying thickness based on the feasibility
  studies).
• A total of 12- to 14-inch thick cap thickness
  expected.

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Permit Activity

• U.S. Corps of Engineers
• National Park Service EA in Public period
  October 24..\NPS EA\Capping Project EA.pdf
• DC EHA
• GSA Sevenson Environmental

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Construction Planning

• Negotiated with the vendors to purchase cap
  materials
• Working with Sevenson Environmental Services on
  placement/handling/staging with GSA
• Cap placement now planned to start in
  October/November 2003

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Cap Placement Considerations

• The cap material will be placed with a clamshell
  bucket in a manner that provides the necessary
  layer thickness while minimizing resuspension of
  the contaminated sediment
• The actual method of placement could be modified
  if necessary during the cap placement depending
  on actual conditions encountered in the field.
  Mat for Coke Breeze
• Silt Curtain will be used during the cap
  placement.
• Cap thickness will be monitored using instrument
  and manual methods.
• Required water quality monitoring will be
  performed accordingly.

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Plans and Scheduling -1

• September - baseline sampling of seepage rates in
  vicinity of test area completed.
• Oct/Nov. placement of 4 technologies with a 6
  layer of sand on each
• Aquablok with SITE
• Apatite for metals sequestration
• Coke Breeze organic sequestration
• Placement with laminated mat sized/washed

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Plans and Scheduling - 2

• Issues at hand
• Program in review by Corps, DC and NPS EA
• Some delay with materials/permitting so now
  planning on mid-October mobilization
• Addressing GSA Concerns
• Placement Windows
• Done before Thanksgiving
• Do right after Thanksgiving finish by mid-Dec.
• Or we are in January?
• Questions?