Assessing Vertical High-Permeability Barriers for Waste Contamination Control: Advective Flow Reduction and Diffusive Transport Challenges in a Sandbox Model

Landfill leachate is a source of groundwater contamination, particularly for shallow aquifers. Low-permeability vertical cutoff walls are often used to stop groundwater from flowing into contaminated areas. However, their long-term durability and performance may be adversely affected by the harsh environmental conditions they are exposed to. High-permeability barriers have emerged as a complementary technique, offering the advantage of being less sensitive to defects compared to vertical cutoff walls. Despite this advantage, limited research exists on their application in waste management. To address this gap, this study presents an experimental investigation of a high-permeability vertical barrier designed for waste isolation. To evaluate the barrier’s effectiveness in preventing flow through the isolated area, a water and salt solution was added into the sandbox model setup, and electrical conductivity sensors were placed at various locations in the experiment. An analytical solution was applied to model the flow through the barrier, demonstrating that it can reduce advective flow across the isolated area by 97.98%. Nevertheless, experimental results showed that the tracer eventually reached the points within the isolated area, albeit with lower intensity compared to the point outside the barrier. The reduction of advective flow by the barrier indicated that tracer transport to the isolated area was primarily due to diffusion, a conclusion supported by numerical simulations. In conclusion, high-permeability barriers are an effective isolation technique for reducing advective flow through a specific region. However, the barrier backfill material cannot prevent diffusive transport of contaminants. Overall, the findings of this study can guide further research to evaluate the feasibility and applicability of this isolation technique for waste management in field applications.