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April 2014
Authors: John A. Collins4, Gary Loveland3, Howard Evans3, John Rice2, Katherine Vater2and Shayne A. Wiesemann 1 1 DTE Energy 2 TRC Environmental 3 Terra Contracting Services, LLC 4 AquaBlok, Ltd.
Installation of an Impervious Cap for Control of Residual NAPL Migration:
Construction Issues and Solutions
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Presentation Outline
I. Overview of Material Technology Utilized
II. The Problem – Ebullition – Shoreline Seeps
III. Case Study – DTE Energy Ann Arbor Site
IV. Summary/Q & A
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powder coating
AquaBlok “composite particle”
+
aggregate core
=
Key Technical Advantages:
¤ Efficient delivery of high-value materials at low concentrations ¤ No field mixing or blending ¤ Low cost handling & installation ¤ Unique geotechnical attributes: self-compacting; shear strength ¤ Highly versatile: custom- formulate for project-specific need
Allows a particle to be uniformly coated with fine-grained (i.e. powdered) materials For efficient/effective placement in both freshwater and saltwater environments
Variables:
¤ Coating composition: - AquaGate™ for treatment; - AquaBlok® for isolation/sealing ¤ Coating to aggregate ration ¤ Permeability: 1 x 10-2 to 5 x 10-9 cm/s (dependent on composition) ¤ Particle size: -1/4” to -3/4”
Coating
Core
Overview of Technology
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Low-Permeability for Sub-Aqueous Capping & Lining
Applied through standing water or in the dry
MGP Sites
PAH / PCBs
Landfill Cap
Refinery/PAH Sites
Metals/DDT
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Demonstrating Compliance in a Dynamic Environment
Split-core from Section A (2.5 yrs after placement)
New sediment Deposits
AquaBlok Clean Cap Layer
Discrete boundary
Contaminated Sediment
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Permeable Materials for In-Situ Treatment & Remediation Applications
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
2,000
0 20 40 60 80 100
Residence Time ( hrs )
Con
cent
ratio
n ( µ
g/L
)
AsCr
+Sorbster® +ORGANOCLAY AquaGate+PAC
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not to scale
Organoclay Treatment Layer
Water Column
Clean Backfill
Residual Contamination
Armoring Layer
Example: Use of Permeable AquaGate+ORGANOCLAY Layer to Protect from Sheen Must Vary Thickness to Provide for Adequate Residence Time for Adsorption AND Capacity Must Have Adsorption Capacity to Protect from Higher Concentration Areas of an Isolated Seep Zone Granular Organoclay will Swell and Reduce Permeability as Oleophilic Clay Adsorbs NAPL – Can Cause “Blinding-Off” of Unused Adsorptive Capacity
Treatment of Groundwater Through A Permeable Treatment Layer
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Conceptual Model - Gas Carries Coal Tar from Sediment to Water Surface (modified from McLinn & Stolzenburg, 2009)
The Problem: Ebullition – Shoreline Seeps
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Conceptual Design - NAPL Trapping Cap A sediment capping system made of geological materials (clay, sand, gravel, boulders ) that can be used to capture NAPL permanently and predictably as it migrates from sediments
* NAPL Trapping Cap was designed by TRC
Patent Nos: US 8,419,314 and US 8,651,768
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Site Location: U.S. EPA Region 5 MGP Impacted River – Ann Arbor, MI
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Overview of Site
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Overall Project Details
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Cap Cross-Section / Layers
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Initial Survey and Removal Area
Significant Effort was placed on protection of the river – a soil berm and boom system was employed
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Removal of Impacted Sediments
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AquaBlok - Bulk Transport and Loading
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Placement of Gas Transmission Layer – Formation of the Base of the Cap
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AquaBlok Low Permeability Layer
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Cover Layers & Armor
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View of Cap Layers – As Placed
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Cap Completion and Restoration
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View of Site
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• All Natural Clay Material Provides Low Hydraulic Conductivity for Effective Contaminant Isolation (Addresses Food Chain Uptake Issues)
• Serves as a Delivery System for a Wide Range of Treatment Materials
• Easy to Handle and Install
• Provides Ability to Perform Low Cost Post-Cap Monitoring
• Implementable in Connection with Either MNA or Dredge/Cap Strategy
• Highly Cost-Effective Alternative and Less Invasive than Dredging
Engineered Thin Capping Materials Provide Remediation Alternative for Sub Aqueous Treatment
and Sequestration of Contaminants at MGP Sites
Summary – Q&A