Twenty-two laboratory columns packed with flue gas desulfurization (FGD) wastes from tests of the Coolside Technology were constructed and are being monitored for leaching characteristics at the UK-CAER for approximately 8 months. FGD materials from the four pilot plant runs conducted by Consol in Library PA as well as two composite samples from demonstration-plant runs 1 and 3 conducted by Ohio Edison in the Edgewater Power Plant near Loraine Ohio were included in the investigation. Details of the packing procedure and test matrix have been described in a previous report. Variables investigated in the test matrix include solids packing density (49 and 65 lb/ft{sup 3}), contact with a variable CO{sub 2} atmosphere (0, 2.5, and 5 vol%), the rate and method of water addition (fixed-47 and 94 mL/wk; rain simulation), and prehydration (0, 15, 30, and 45 wt% prehydration water-dry basis).