Leo Lehmicke - Co2 and Water
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Abiotic Natural Attenuation (Southern California)

Large volumes of TCE were released at a site located over fractured sandstone. John Cherry and Beth Parker are on an expert team evaluating the site and showed most of the TCE is trapped in the formation's matrix porosity (13%) resulting in substantially slowed plume migration. As a team member, I observed that parent:daughter product ratios in distant wells indicated degradation was limiting TCE and DCE distribution, consistent with TCE/DCE never being observed in down gradient springs. Modelling indicates a small degradation rate would prevent offsite migration.

A lab study designed as a "3rd line of evidence" for an NA remedy, used 14C-labeled TCE and DCE to show both biological and abiotic degradation reactions are removing TCE and DCE at a significant rate, including transformation to CO2 (Darlington et. al. 2008, Darlington et. al. 2013). MNA is being considered as a portion of the site remedy and John Wilson (retired EPA) has been added as a team member.