Prediction of 1,4-Dioxane Migration in Groundwater and Evaluation of Remediation Measures in an Illegal Dumping Site Using a 2D-Numerical Model

Abstract

Illegal dumping sites are usually characterized by complex contamination situations due to the presence of multiple contamination sources. To improve the efficiency of illegal waste dumping site remediation, this study developed a numerical model considering the effects of groundwater levels and hydraulic gradient changes on remediation operations. Using this model, the most likely sources of contamination for 1,4-dioxane at an illegal waste site in Iwate Prefecture, Japan, were successfully identified (including location, amount, and time of occurrence) by reproducing historical monitoring data (from 2010 to 2022) through history matching, and future contaminant migration in groundwater was predicted. In addition, based on quantitative evaluations of the remediation measures, we found that some remediation measures, such as impermeable wall construction, while having some effects on the control of contamination spreading, may accelerate the migration of contaminants off-site due to the change of hydraulic gradient. Therefore, remediation procedures should be more carefully considered for illegal dumping sites based on an understanding of the distribution of contamination sources and hydraulic gradient evolutions.