MODELING OF PLUME CAPTURE BY CONTINUOUS, LOW-PERMEABILITY BARRIERS

Modeling was performed to simulate ground water ow through reactive ba rriers of lower hydraulic conductivity than the surrounding aquifer to determine the plume capture widths. As a plume approaches such a barr ier, it spreads laterally. Therefore, to intercept an entire plume, th e barrier must be wider than the upgradient width of the undisturbed p lume. The results indicate that, for practical values of barrier thick ness and plume width, hydraulic conductivities ten-fold less than that of the aquifer can be accommodated by making the width of the barrier approximately 20% greater than the upgradient width of the plume. Bar rier hydraulic conductivities one-hundred-fold less than that of the a quifer may require barrier widths up to twice the width of the upgradi ent plume for plumes 100 feet wide (33 m) and as little as 1.1 times f or plumes 1000 feet wide (325 m). The results presented here lend supp ort to the view that novel emplacement methods that create zones of sl ightly lower hydraulic conductivity than the native aquifer may be via ble alternatives to the excavation-and-backfill approaches which have thus far been used for installing permeable reactive barriers.