In Situ Stabilization/Solidification in the Power Industry: State of the Practice

In situ stabilization/solidification (ISS) has gained recognition as a competitive technology for remediating coal tar related impacts in soil and groundwater at former manufactured gas plant (MGP) sites. ISS technology provides a controlled engineering option compared to other conventional approaches such as excavation. Advantages of ISS, relative to excavation methods, include reduced aboveground handling of contaminated materials, emissions and odors, energy costs, and carbon footprint. The ISS process consists of mixing contaminated media with reagents (e.g., Portland cement and blast furnace slag) to produce a structurally solid monolithic mass that has low hydraulic conductivity. Leaching from the monolith is minimal; however, post-remedial monitoring is typically required and the groundwater monitoring plan must account for disruptions in groundwater flow patterns if the monolith extends below the water table.

This presentation highlights the current state of the practice, progress that has been achieved gaining community and regulatory acceptance, and future considerations for this technology. Case studies will be reviewed to highlight the above discussion points. One of these was a major ISS project recently completed in the southeastern United States that included ISS of more than 140,000 cubic yards of soil to address impacts to soil and groundwater. Design challenges included hydrogeologic modeling to address changes in groundwater flow conditions around the monolith.