To control the environmentally detrimental impact of acid rock drainage, two different counter-measures, layers of acid-buffering materials and sodium dodecyl sulfate addn., were tested for their efficiency in lab. percolation expts. In the expt. with a layer of calcium bentonite, only the iron output was reduced. The expts. with layers of concrete grains demonstrated a decrease of the microbial activity as well as a pptn. of heavy-metal ions, whereas the cell nos. did not decrease. Furthermore, finely grained concrete (1-5 mm) formed a water-tight hard-pan (self-sealing layer). In the expt. with 1mM sodium dodecyl sulfate, all the microorganisms were killed and hence metal sulfide dissoln. was stopped. With 0.1mM sodium dodecyl sulfate only a short, transient inhibition of leaching was achieved. The bacteria remained alive.