Composed of a pH sensitive polymer and potassium phosphate buffer, macrocapsules offer a new remediation alternative for acidic ground water.  A field trial was carried out at a monitoring well within a coal pile runoff (CPR) contaminant plume at the Savannah River Site (SRS) to compare macrocapsule and traditional limestone remedial treatments.  Macrocapsules or limestone, a data logging pH probe, and a pump for water recirculation were deployed for several two-week treatments.  pH was measured hourly and weekly ground water samples were analyzed for total and dissolved concentrations of phosphate, aluminum, iron, and sulfate.  Both macrocapsule treatments were effective in raising the ~2.5 pH ground water to above 6, though pH returned to baseline values within 10 days.  Limestone treatments had no effect on pH.  Total and dissolved compound concentrations varied between treatments but aluminum, iron, and sulfate concentrations remained within historical ranges.  Phosphate concentrations were higher during macrocapsule treatments due to the phosphate buffer release.  In this system, macrocapsules were more effective than limestone as a passive treatment.  Though not currently commercially available, this field trial confirms the ability of macrocapsules to effectively increase pH in highly acidic ground water.