Montmorillonite clay has been modified by the addition of humic acid (HA) and aluminum hydroxide (A1OH) coatings to enhance the sorption of organics, attenuate their transport, and minimize changes in hydraulic conductivity. Batch sorption experiments and hydraulic conductivity tests have been performed to compare this HA-AlOH-Clay with commercially available Claymax^®. Claymax^® has an approximately 6.8–19 times greater Langmuir adsorption maximum for Pb²⁺ than that of HA-A1OH-Clay, but the partition coefficients of chlorobenzenes to the HA-A1OH-Clay are 14–25 times greater than that to Claymax^®. Hydraulic conductivity tests for Claymax^® with and without HA-AIOH-Clay have been performed using tap water, a synthetic leachate, and pure methanol. Synthetic leachate increased the hydraulic conductivity of the HA-A1OH-Clay together with Claymax^® to 1.2*10^-9 cm/s or about 3 times over that for tap water. The hydraulic conductivity of HA-AIOH-Clay alone is greater than the minimum required value (k = 1*10^-7 cm/s) but can be used together with Claymax^® to control chemical fluxes.