Two-Dimensional Hydraulics of Recirculating Ground-Water Remediation Wells in Unconfined Aquifers

Abstract

A technique for remediating and protecting ground-water and drinking-water 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 imperfectly penetrating wells were examined experimentally in pilot-scale tanks and mathematically with numerical models in a two-dimensional domain. Ambient ground-water velocities of from 1 to 3 m/day, typical for coarse sand and gravel aquifers, were simulated in combination with in-well vertical velocities of from 2 to 16 m/day. Under some of these flow conditions, contaminants were intercepted and drawn into the wells 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 velocities and submergence by the well hydraulics of surface contaminant plumes without interception. Both types of problems were corrected by adjusting internal well velocities. Important design parameters include ambient ground-water velocity and well pumping rate.