A treatment technique has been demonstrated on a laboratory scale which inhibits or prevents the generation of acid mine water from waste coal refuse. Three variations of the general method were considered: Neutralization of the water-accessible refuse with a dilute solution of sodium silicate (waterglass); development of a continuous gel on the refuse surface structure which sealed off the entire pile from natural runoff waters; development within the pile structure of a continuous silica/aluminia gel to eliminate percolation through the refuse and minimize the effect of natural erosion of the gel structure. Comparison of the effluent water with an untreated pile shows that the neutralized pile was effective for a minimum of 120 in. of equivalent rainfall in inhibiting AMD generation. The surface gel was effective for a longer period of time. The most effective treatment utilized a mixed alumina/silica gel formed within the pile at depths up to 6 in. This method was effective for more than 500 in. of equivalent rainfall, the duration of the test, and appeared to be exceptionally stable at that time. The weathering resistance of the treatment methods was evaluated by heating the gel treated refuse in the laboratory and exposing it to rain, snow, and freeze-thaw cycles outdoors. (Author)

"February, 1971." U.S. Environmental Protection Agency, Water Quality Office Contract No. Contract Number: 14-12-560. Includes bibliographical references (page 69)