ABSTRACT
Leachate resulting from percolation of precipitation or groundwater movement through the wastes severely contaminated local groundwater resources. Interception of shallow groundwater moving through a trench/pond would destroy the leachate plume and dilute concentrated contaminants with natural groundwater moving into the trench. Depending upon the porosity of the sands and gravels, the excavated volume below the water table will contain about three to four times the volume of water that would be stored in a similar volume of saturated sands. From 1975 to 1979, city personnel monitored groundwater quality in the area each fall and spring to evaluate effectiveness of the trench in providing groundwater treatment and to determine the quality of groundwater leaving the landfill site. The trench at the Brookings landfill has protected shallow groundwater in the area by several mechanisms including dilution mixing, gas interchange, metal oxidation, and biological treatment.
