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 consultantís NA argument; the client requested my help. The regulators involved had attended the RTDF course on natural attenuation where I was an instructor. I revised the approach to be consistent with what the regulators learned in the course. We showed that concentration declines along the plume could only be accounted for if biological and/or abiotic degradation 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 (minerals known to cause abiotic reactions) and 2 other phylosilicate minerals are present at up to 15% in the rock.