DECONTAMINATION APPROACH AND TRAINING. The basic approach to decontamination is to remove contaminated surface soil and wastes from the villages using techniques and procedures familiar to the local population. Extensive soil surveys have shown that the contaminants are largely contained in the top 5 centimeters of surface soils overlaying sub-soils densely compacted by village foot traffic. These contaminated soils can be removed using agricultural tools in an effective manner mimicking village practices. Contaminated soils are bagged in readily available sacks and transported to constructed landfills. The contaminated soils are replaced with clean soils of suitable compaction quality at all excavated surfaces. The following cleanup criteria are applied: all soils greater than 1000 mg/kg (or detectable Hg) are removed and replaced with soils containing less than 200 mg/kg Pb (generally <60 mg/kg Pb). Contaminated soils between 400-1000 mg/kg lead are covered with 8 centimeters of compacted clean soil. Soils in the 400-1000 mg/kg range can be excavated at the Village Cleanup Director’s discretion. The replacement soils offer a low-lead soil and dust exposure source to children, act as a barrier sub-surface contaminants, and dilute any contamination remaining following excavation. This procedure is applied inside the home compounds and in exterior locations inaccessible to mechanical equipment. Process wastes from former mining and mineral extraction locations are excavated by heavy equipment, if accessible, and disposed of in the landfill. These areas are also returned to grade with compacted clean soils. Wastes and contaminated soils are placed in a constructed landfill, compacted and covered with a one-meter cap of compacted local clays and suitable cover material. The buried material is largely low concentration lead contaminated soils (generally .1 to 1% lead on average), with individual loads ranging to 10% lead. Some mineral processing wastes exceed 10% lead. These wastes are inorganic weathered oxidized galena compounds, likely of low solubility in natural environments and typical pH. The landfills are constructed dense clays with low permeability, minimizing the probability of significant leachate production, transport, or release to the environment, thus avoiding the need for liners.
