Soil Flushing

The problem:  Site soil is impacted with perchlorate due to historical activities at the site.  The impacted soil is a continuing source of perchlorate contamination in groundwater.  Because groundwater treatment systems are already in place, the client sought to assess the feasibility of rapidly flushing perchlorate from the soil using water from a nearby lake.

How PRIMA helped:  PRIMA conducted large-scale column tests to evaluate the ability of added water to flush perchlorate and other constituents from vadose soils containing low (6.18 mg/kg), medium (145 mg/kg), and high (3,130 mg/kg) concentrations of perchlorate.  Columns were 6 inches in diameter and 6 feet tall.  Approximately 2 pore volumes of water were added to the top of each column and allowed to gravity drain for up to 9 days.  Effluent was collected for 24 hour periods and analyzed for various parameters; soil was analyzed for perchlorate post-treatment.  Over 99.7% of the perchlorate was removed from soil with 33-110% accounted for in the leachate.  Arsenic and hexavalent chromium were also leached.   These results confirm that perchlorate and other constituents can be removed by flushing with 2 pore volumes or less of clean water.

For more information about this project, see our presentation “Column Tests to Assess Flushing of Perchlorate” on our Resources– Webinars and Presentations page.