Advanced Environmental Interface

There are four basic remediation technologies:

Dig it up. The simplest remediation is usually to dig out contaminated soil and haul it off for disposal. For small areas of well-defined contamination, this is generally the best (fastest, cheapest, most certain) method. But sometimes, the contamination is very extensive because it has spread with time, or because it has moved downward to the water table and migrated in the direction of the natural groundwater movement.

Pump and treat the water. If groundwater has been contaminated in a drinking water aquifer, removal of contaminants from the soil and/or groundwater may be required. This is typically done for contaminated groundwater by intercepting the plume and pumping it to a treatment system. If the contaminants are volatile (for example, gasoline or solvents) they may be stripped out of the pumped water, or filtered out through charcoal or other sorbent.

Vacuum out vapors. It is also possible to remove volatile contaminants from soils above the water table by applying a vacuum to shallow soil layers. Solvent or gasoline vapors are readily drawn through the pores in the soil and out through the vacuum exhaust. Such devices are called soil vapor extraction (SVX) systems. They work best with contaminants that are more volatile, and with soils that have a good percentage of open pore space (such as sands and gravels). In addition, compressed air can be pumped into the groundwater to encourage release of contaminants from groundwater and from saturated soils below the water table. Multiphase extraction (MPX) systems are similar, but apply a higher vacuum to remove free product, contaminated groundwater, and vapor phase contaminants all in one step.

Help Mother Nature. Bioreclamation of contaminated soils (with or without excavation) is an evolving remediation technology. Naturally-occurring or cultured bacteria will act to break down many organic contaminants, provided they are provided with an adequate supply of oxygen and nutrients. The remediation system is therefore structured to feed nutrients and air to contaminated soils at a rate which encourages the bacterial population to grow and adapt, and consume the contaminant as its food source.

Hot Topic Archive

Who needs to conduct a cleanup, and to what standards?

Conduct a cleanup if an "establishment" (as named in the Connecticut property transfer statute).
Conduct cleanup if a voluntary remediation requiring certification by DEP or an LEP.
Prevailing standards are the Connecticut remediation standard regulations (called the RSRs -- these are numerical criteria for how-clean-is-clean).
There is no need to remediate a site if contaminant levels are low (i.e., already below the RSRs).

Examples of the remediation technologies described above:

A slide show illustrating soil excavation of an historical coal tar facility.
A slide show illustrating a groundwater recovery (pump-and-treat) system.

What about "brownfields" cleanups?

Brief synopsis of brownfields from a development point of view.
EPA information and programs on brownfields.
HUD information and programs on brownfields.