By Phil Hicks, PE  |   February 12th, 2016
Industrial residuals can be complicated and expensive to clean up…especially when located in an environmentally sensitive area.
An implementation of a remedial action at a Superfund site involving potentially contaminated residuals within a wetland provided us an opportunity.  We challenged ourselves to find a better, faster and more cost effective way to achieve an appropriate cleanup.
Ahead of us were clearly defined remedial action objectives:
  • Reduce concentrations of contaminants in sediments to levels that protect the ecology.
  • Prevent continued migration of contaminants.
  • Prevent exposure of ecological systems to contaminants present in the sediments.
  • Reduce contaminant levels in fish tissues to acceptable levels. 
Conventional remediation methods would have required excavation and relocation of the lower portions of the wetland and disposal of the contaminated sediment within the upper portion of the wetland. Then a multimedia cap would be installed over the contaminated sediments in the upper portion of the wetland and a surface water diversion channel would be constructed to divert surface water around the wetland. Finally, sheet piling was to be installed to divide the wetland into cells. This originally proposed remedial action would have cost approximately $40M.
Working within guidance we proposed an alternative cleanup method that would still meet all the defined remedial action objectives, but would save time, money and reduce the impact to those areas adjacent to the residual zone. This newly proposed remedy involved in-situ capping of the contaminated sediments within upstream portion of the wetland, and the development and implementation of a monitoring and assessment program for the evaluation of the rate of recovery of downstream wetland areas as a result of the implementation of this in-situ cap. 
The engineered cap was created by using AquaBlok ® to minimize contact between the biota and the contaminated sediments. The AquaBlok® 3070FW was selected to create the cap itself.  With a nominal pre-hydrated thickness of 6.5 inches and covered with a soil layer with a nominal thickness of 2 inches it created a sequestration cap that dramatically reduced the potential for long-term diffusion of contaminants into pore water and overlying surface waters.
This innovative remedial plan using the in-situ AquaBlok® cap cost approximately $8M. Not only did this solution save over $30M; it eliminated the destruction of over 30 acres of wetland and the removal of dense hardwood tress adjacent to the wetland stretching over a half mile in length.  
 You can read the full project description HERE.
Phil Hicks, PE, Project Engineer
Phil Hicks provides engineering support for a range of projects across the company. With more than 8 years of experience, Phil assists with dredged material management planning, including evaluating the feasibility, environmental/ecological impacts, and conceptual cost estimates associated with potential sediment placement sites for the dredged material of federal channels.  He also assists with landfill regulatory compliance and preparation of associated reports and plans.  Prior to working for Hull, Phil worked in the construction and mining industry where he was responsible for quality assurance of construction activities and compliance/permitting in the mining process.
Phil holds a Bachelor of Science in Civil Engineering from the University of Toledo.
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