Formatted Title
Optimizing Remedial Strategies in Brazil: An Evaluation of Dual Thermal Treatment Technologies Using Dynamic Cost Modeling
Background/Objectives
A site in Brazil impacted with chloroanilines, chlorobenzenes and chloronitrobenzenes has been the subject of investigation and research over the past decades. Remedial action objectives (RAOs) consist of short-, medium-, and long-term objectives focusing on the removal of primary and secondary sources in the vadose zone and in groundwater. Two decommissioned operating units at the site have been fully investigated and pilot testing completed in the vadose zone, now full-scale remediations are in the design phase. To inform remedial decision making and to create an optimal cost-performance outcome, an evaluation of remedial options was completed, along with a cost sensitivity analysis.
Approach/Activities
After considering several remedial options, a combined approach using in-situ thermal desorption (ISTD) for deep impacts, with excavation and treatment via ex situ smoldering for shallow impacts was selected as the preferred remedy. A dynamic cost model was created to assess the technical practicability and assess potential costs. One of the major variables considered in the model was vadose zone NAPL saturation. However, this factor required further field investigation to assess contaminant leachability. Other variables considered in the sensitivity analysis included excavation method (i.e., sloping, or stabilized vertical excavation), and excavation depth (i.e., 0 to 2 mbgs, 0 to 3 mbgs, etc.).
Results/Lessons Learned
The results of the remedial options evaluation indicated a combined remedial approach using ISTD and ex situ smoldering would be optimal considering practicability, cost, and sustainability factors. A sensitivity analysis was performed on the preferred remedy using a dynamic cost model, with multiple cost factors and design elements simultaneously modeled. Although the analysis was complex and indicated additional data were necessary, the analysis provided useful insight and informed confident remedial decision making.