A fractured granite bedrock site is impacted with TCE, Freon 113 and daughter products to 300 feet. The Nevada Department of Environmental Protection (NDEP) rejected the consultant’s NA argument and the client requested my help.
The regulators involved had attended the RTDF course on natural attenuation in which I was an instructor. I revised the approach to NA to be consistent with what the regulators had learned in the course. We showed that concentration declines along the plume could only be accounted for if a degradation mechanism, biological and/or abiotic, played a role and suggested possible reactions (Basel and Lehmicke 2002). MNA was accepted as the major component of the remedy, at a cost savings to the client of more than $6 million.
I provided support for 5-year reviews in 2005/2010/2015. CSIA data was collected to support the 2015 review. Analysis of rock by XRD showed magnetite, biotite and 2 other phylosilicate minerals (all known to cause abiotic reactions) are present at up to 17% in the rock. The 2020 review was just completed; everything is still good.
