Environmental feasibility of using coal ash as a fill material to raise the ground level

Batch leach tests (BLTs) and column leach tests (CLTs) were conducted on bottom ash (BA), lagoon ash (LA), soil (S), and bottom ash-soil (BA-S) and lagoon ash-soil (LA-S) mixtures to evaluate the environmental feasibility of using these as fill materials to raise the ground level at construction sites. For the BLTs, the leachability of the elements (i.e., Cr, Mn, Ni, and Zn) generally increased with decreasing pH from 6.3 to 3.0. In addition, the concentration of all the elements analyzed in the leachates increased with decreasing the liquid-to-solid (L/S) ratio. Freezing-thawing cycles had no significant effect on the leachability of the elements found in the BLTs. The initial concentrations of the leachates from the CLTs were higher than those of the leachates from the BLTs regardless of the materials tested due to the lower L/S ratio. The initial concentrations of As, Ni, Mn, Se, Cl^-, and SO₄^2- in the leachates from the CLTs for the LA, BA, and LA-S and BA-S mixtures exceeded the drinking water standards (DWSs), which suggests that these materials may pose a risk to groundwater when these materials are used in areas where there is little dilution.