2-DIMENSIONAL HYDRAULICS OF RECIRCULATING GROUNDWATER REMEDIATION WELLS IN UNCONFINED AQUIFERS

A technique for remediating and protecting ground-water and drinking-w ater wells from contamination is presented. A ground-water remediation well design is proposed in which ground water is drawn into the well bottom, treated in the well casing, and returned clean to the aquifer at the well top. The hydraulics of ground-water circulation around imp erfectly penetrating wells were examined experimentally in pilot-scale tanks and mathematically with numerical models in a two-dimensional d omain. Ambient ground-water velocities of from 1 to 3 m/day, typical f or coarse sand and gravel aquifers, were simulated in combination with in-well vertical velocities of from 2 to 16 m/day. Under some of thes e flow conditions, contaminants were intercepted and drawn into the we lls for treatment. Hydraulic problems identified with the experimental apparatus and simulated by the computer models included blow through of contaminant at the well intake by high ambient ground-water velocit ies and submergence by the well hydraulics of surface contaminant plum es without interception. Both types of problems were corrected by adju sting internal well velocities. Important design parameters include am bient ground-water velocity and well pumping rate.