Prior to the widespread construction of natural gas lines in the U.S. in the 1950s, the gas needed for streetlights, manufacturing and residences was produced from coal at more than 50,000 manufactured gas plants (MGPs) across the country. Though the plants are now abandoned or demolished, some former MGP sites continue to pose environmental and public health concerns. Volatile organic compounds (VOCs), polynuclear aromatic hydrocarbons, creosote and coal tar are among the hazardous substances that can be found in surrounding soil, surface water and groundwater.
To identify and pinpoint the location of this contamination, environmental investigators traditionally employed test pits and conventional soil and groundwater sampling techniques. Efforts focused first on the areas most likely impacted and then radiated outward until the site-specific remedial objectives were met.
When hazardous chemicals were found in soil, remediation commonly involved excavating the contaminated soil and then transporting it off-site for disposal. This highly disruptive process often resulted in significant truck traffic and odor-control concerns in the smaller towns where MGPs are frequently located. In an effort to meet regulatory requirements, significant quantities of unimpacted material are often removed unnecessarily to access the impacted materials. Because multiple contaminants are usually involved, groundwater and surface water remediation often require both liquid phase- and vapor phase-activated carbon adsorption and purification solutions.
Advances in investigative techniques have resulted in the development of high-resolution site characterization (HRSC) strategies that facilitate more targeted remedies to deliver higher degrees of certainty. In addition to being more sustainable, less disruptive and more cost-effective over the life of the project than conventional methods, HRSC strategies have proven to accurately characterize the extent and volume of impact. How? By allowing the practitioner to increase the amount and type of data that can be collected and considered and ultimately identify the primary transport and fate mechanisms.
Site-specific objectives should be defined prior to implementing a comprehensive site characterization plan. Once those objectives are in place, a few specific HRSC investigative techniques and tools can be applied to achieve precise, predictable results.