Combining In Situ Chemical Oxidation and In Situ Solidification for Coal Tar – Synergy or Conflict?

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Poster:

Combining In Situ Chemical Oxidation and In Situ Solidification for Coal Tar – Synergy or Conflict?

Presenter: Mark Klemmer (Arcadis US, Inc.)
Authors: Mark Klemmer,  Adam Chwalibog and Andy Baumeister (Arcadis US, Inc.), Heather Prentice (Consumers Energy)

Abstract:

Where In Situ Solidification was once considered only for inorganic contaminants, it has now gaining popularity for soils impacted with organic-based NAPL such as MGP coal tar. The lagging popularity for use with organics was based on documented interference with pozzolanic reactions when too much organic mass is present. Performance metrics have been another sticking point due to binding in place of contaminant rather than destruction, as well as the ability to collect representative samples from the resulting monolith. Primary performance metrics include achieving desired soil strength and a reduction in permeability, and to a lesser extent the leachability from the monolith, which is also a challenge to demonstrate at field-scale. This paper will discuss benefits and disadvantages of using binder and oxidant simultaneously, presenting data from multiple laboratory studies that elucidate some outstanding questions regarding the validity of such an approach. Laboratory studies were conducted in stages, where samples were split to determine appropriate dosing of oxidant required to destroy organic COCs, and separately to determine optimal dosing of binder for the desired soil strength and permeability reduction. Once complete, the reagents were added to soil simultaneously. The primary ISS performance indicators (soil compressive strength and permeability) varied with dosing of sodium persulfate as the binder was held constant. One of the main findings of these studies indicate that soil strength increases and resulting permeability decreases, with increasing sodium persulfate dosing. This result is likely from removal of organics from the soil samples, which are known to interfere with pozzolanic reactions of the binder. Therefore, advantages exist to both ISS and ISCO remedies, by implementing/combining technologies simultaneously. Addition of sodium persulfate to the binding mixture also reduces the concentration of soluble compounds within the monolith, thereby reducing the overall risk of leaching to groundwater post-remedy.

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http://mgpsymposium.com/poster-presentations/

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