HRC barriers treat contamination in sandstone under a school
Due to an industrial spill, high concentrations of chlorinated solvents were measured in a sandstone bedrock in southwest Germany. The plume was found to extend beneath a primary school and remediation was required in order to reduce the risk posed to human health.
Four rows of application wells were drilled into the bedrock across the site, perpendicular to the groundwater flow. Reagents HRC® and HRC X® were gravity-fed into the wells in order to disperse and diffuse into the surrounding bedrock. This created and maintained four optimum zones of enhanced reductive dechlorination, through which groundwater would pass, but the chlorinated solvent contamination would be degraded.
Total CHC, before treatment
Total CHC after treatment, three and a half years later
- The groundwater in the sandstone bedrock was cost effectively treated using enhanced reductive dechlorination.
- The contamination was fully dechlorinated, with no build-up of break-down products occurring.
- The HRC and HRC X application did not affect the permeability of the fracture-flow dominated bedrock; instead the products created anaerobic treatment zones through which groundwater could flow and be remediated.
- The treatment minimised site disturbance, with only a short period of drilling and application by pouring into the wells. After which the slow-release of electron donor from the HRC provided years of treatment in situ.
After 5 years of remediation, of the 6 validation wells used for compliance:
- 4 monitoring wells below detection limit
- 2 monitoring wells below 3 μg/l
- Stimulation of anaerobic degradation worked in fractured bedrock to remediate high CHC concentrations
- Good distribution of electron donor with simple injection method
- No disturbance on site with very sensitive site use
- Remediation was finished within expected time frame and within budget despite the complex conditions
Validation Well – Chlorinated Solvent Concentration Over Time