Hydraulic Conductivity of Environmentally Controlled Landfill Liner Test Pad

Laboratory and field hydraulic conductivity tests have been conducted on soil samples to develop and verify the zone of acceptance for liner placement. Compaction testing and flexible wall hydraulic conductivity tests were performed on fifteen (15) samples to determine the dry unit weight, molding water content, and laboratory permeability. Five of the fifteen samples were compacted at Standard proctor energy, five were compacted at 75 percent of Standard proctor energy, and five were compacted at 50 percent of Standard proctor energy. The results obtained from the laboratory portion of the testing program (the zone of acceptance) are presented. A ten foot-long by ten foot-foot wide by four foot tall box was created in an environmentally controlled environment (indoor lab). Six inches of sand were placed in the bottom of the box and overlain with a geotextile filter fabric. An eight-inch thick loose lift of clay was then placed, and compacted into a six-inch thick lift using two passes of a vibratory plate compactor. Five nuclear density tests were conducted on the first lift to ensure the soil was compacted within the zone of acceptance. This procedure was then continued for the remaining three lifts. A two-stage borehole (TSB) hydraulic conductivity test was conducted at the center of the test pad. The first stage (vertical) was conducted at 10 inches below the top of the liner, and the second stage (horizontal) was conducted from 10 inches to 16 inches below the top of the liner. The results obtained from the environmentally controlled TSB test were compared against tests conducted on landfill liner tests pads constructed at three different landfills within the state of Missouri. Two of the landfill liner tests pads were covered with tents while one was not covered. The results obtained from the environmentally controlled TSB did not display the same changes in hydraulic conductivity associated with diurnal cycles of direct sunlight that were observed in the landfill test pads. These diurnal cycles may result in a placement technique being rejected