Residual sandy‐clay to sandy‐loam soils range from a few feet to greater than 70 feet in thickness on a sandy dolomite bedrock.
Soil moisture samples were extracted at different depths from beneath two of the refuse cells using suction lysimeters.
Water samples were also bailed from these cells and pumped from a water table well beneath the landfill.
Monthly or less frequent analyses performed on water samples included Eh, pH, temperature, specific conductance, BOD, Cl, SO4, total alkalinity, NH3, NO2, NO3, PO4, Ca, Mg, Na, K, and total Fe.
The study showed that the quality and quantity of leachate beneath a landfill varies considerably with the topographic setting of landfill trenches or cells.
Upon reaching a depth of 14.5 feet after about 21/2 years or more, maximum values of these species in the leachate had been reduced by 83%, 80%, >99%, >99%, and 98% respectively.
In contrast, more water, including precontaminated surface and subsurface runoff from adjacent upslope cells; infiltrated a downslope cell, saturating the refuse.
Even after moving downward in the soil to a depth of 36 feet in 7 years, the leachate beneath this cell had a conductance of 6600 μmhos, 600 mg/1 Cl, over 9000 mg/1 BOD, 40 mg/l NH3‐N, and 100 mg/1 total Fe.
However, concentrations of BOD and redox sensitive species such as Fe and NH3 in the leachate have fluctuated in response to changes in the moisture content and temperature of the refuse.
Although renovation takes place, it is incapable of preventing highly contaminated leachate from moving to depths of 50 feet or more in soils beneath downslope cells.