Abstract (Go to Manuscript)
Technology Sequencing to Reduce Groundwater Remediation Cost
By Richard Sloan, Chickadee Remediation Company
Leaks and spills of fuels, solvents, cleaning fluids, and other organic chemicals have contaminated groundwater at many locations. Typically, the chemicals have resulted in a plume of contaminated groundwater which migrates in response to the local hydrogeological conditions. In many cases the plume of contaminated groundwater represents a threat to the public health or the environment, and remedial action is required to reduce the threat to acceptable levels.
There are a number of groundwater remediation technologies available to address a particular site. Generally, the most cost-effective approach is to use a site-specific sequence of technologies starting with receptor protection and source control, continuing to free-phase recovery/treatment and to dissolved phase treatment, and ending with monitored natural attenuation. The actual site-specific sequence depends on:
1. Chemicals of concern
2. Status of the nearest receptors and the groundwater pathway
3. Physical and chemical properties of the chemicals of concern
4. Status of the chemical source(s)
5. Available facilities, utilities, and "room to work"
The various groundwater remediation technologies typically have an optimum efficiency and cost range depending on the site-specific conditions. For example, in-situ thermal desorption, combined with soil vapor extraction and thermal oxidation, can be cost effective for high concentrations (7,200 ppm) of volatile chlorinated organics in the vadose zone; when the concentration reaches 20 to 30 ppm, conversion to in-situ bioremediation is usually cost effective. Several technology sequencing case studies will be discussed in detail.
The design, construction, operation, and maintenance of the overall remediation program must accommodate the sequencing from one technology to the next; the program must be such as to allow modifications and refinements as the remediation proceeds. It is necessary to implement an effective progress, cost, and data management program so that the cost/benefit can be continually evaluated and thus expedite quick, cost-effective sequencing. The progress and cost management for several sites will be presented with emphasis on the level of detail needed to make effective technology sequencing decisions.
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