Permeable Reactive Barriers
http://en.wikipedia.org/wiki/Groundwater_remediation
Permeable reactive barriers
use silica embedded in iron to create a soft barrier. Water filters through
barrier and silica absorbs toxins.
The iron dechlorinates the solvents in the
groundwater, often reducing toxicity levels below detectable limits with no
toxic daughter products, no solid waste removal, and no air pollution.