One of DoD’s most challenging environmental restoration issues is determining how to deal with contaminants that have seeped into the fractures in bedrock and are a continuing source of groundwater contamination. A recent SERDP-funded research project found that studying the fundamental features of the bedrock itself may hold a key to addressing this challenge.
Dr. Charles Schaefer of CB&I and his team measured and evaluated the ways in which the mineralogy of the bedrock can affect how chemicals are stored and how long it takes for those contaminants to break down through natural attenuation. For this project, the researchers focused on trichloroethene (TCE), a toxic cleaning solvent used for much of the twentieth century by the military and private industry. TCE is one of the most widely dispersed contaminants in the United States, and it is found on nearly all military installations in the country. On those installations that are known to have fractured bedrock, TCE migrates through conductive fractures, and also into the rock itself. For these sites, it is extremely difficult and, in many cases cost-prohibitive, to locate the contaminant source and remove it.
The study found that the mineralogy of the bedrock can have a significant effect on the rate of natural attenuation of TCE. For example, the presence of ferrous iron minerals within the rock, which is common in many types of bedrock, can hasten the rate of TCE dechlorination. While it was long believed that natural attenuation of TCE in bedrock would take hundreds of years, the results of this study suggest that in fact it could occur within our lifetime.
The data from this study can be used to better predict rates of TCE dechlorination at bedrock sites on military installations, providing DoD with an essential tool to guide decisions on how best to treat contaminated sites. At sites where acceptable rates of monitored natural attenuation (MNA) can be demonstrated, more aggressive and expensive treatment can be avoided.
For this significant work, Dr. Schaefer received the 2013 SERDP Project-of-the-Year Award for Environmental Restoration. Project Summary