When soil or groundwater remediation becomes necessary, Conrad Geoscience evaluates alternatives and selects an appropriate methodology, usually in consultation with regulatory agencies. Depending on the situation, the remedial program may include one or more of the following approaches:

• Source removal
• Extraction
• In situ treatment
• Monitored natural attenuation.

Source removal is almost always part of the remedial program, because eliminating an ongoing source of contamination will invariably decrease the duration and cost of other remedial efforts. Source removal may consist of underground storage tank removal, soil excavation, recovery of buried drums, or free-product skimming, among others.

In situ treatment methods are used to treat contaminated groundwater in place, or in situ. Treatment alternatives include sparge technologies and a variety of chemical oxidation and enhanced bioremediation technologies, among them: coaxial groundwater circulation wells, injection of oxidants such as ozone, peroxide and Fenton’s reagent (sometimes in combination); oxygen release compounds; and hydrogen release compounds.

Monitored natural attenuation (MNA) is sometimes employed in combination with extraction or in situ methods in order to bring a project to closure. Natural processes, such as biodegradation and dispersion, act on spilled chemicals or petroleum to reduce their concentration or degrade them in to less harmful substances. MNA is the process of gathering data to determine whether and how such processes are occurring, and to monitor geochemical indicators and attenuation trends.

Extraction methods are sometimes used to physically remove contaminated groundwater, or control contaminant migration, usually by some form of “pump and treat” technology, in which contaminated water is pumped to the surface via recovery wells, then treated to remove contaminants. Above-grade treatment alternatives include air stripping, granular activated carbon filtration, oil/water separation, and biologic treatment. Treated effluent is usually discharged to the surface. Extraction can be used primarily for plume control, to keep contaminated groundwater from moving further from its source or off-site. Volatile contaminants can sometimes be extracted from the vadose (unsaturated) zone via vapor extraction.