Investigation and Analysis of seasonal Groundwater Flow dynamics and Contaminant Migration at Chlorinated-Solvent-Contaminated Sites

This study establishes a systematic framework for investigating seasonal groundwater flow dynamics and contaminant migration at chlorinated-solvent-contaminated sites in Taiwan. Due to strong seasonal rainfall patterns, groundwater levels fluctuate significantly, influencing flow directions and contaminant transport behavior. Continuous groundwater-level monitoring from April to September 2025 shows noticeable seasonal variations, with well K00318 exhibiting the greatest decline, suggesting potential shifts in the local flow field. Rainfall–water level correlations further indicate high vertical hydraulic conductivity in the unsaturated zone. Seven rounds of groundwater sampling reveal exceedances of TCE, DCE, and occasionally VC in several monitoring wells, including K00407, K00381, K00296, K00237, K00284, and K00358, while all remaining wells stayed below monitoring and regulatory limits. The results highlight spatial variability in contamination severity and emphasize the need for continued monitoring to assess plume behavior and support future management decisions.