Simulating the TCE DNAPL Source Zone Below the Water Table at the Santa Susanna Field Laboratory

Abstract

Both 2D and 3D numerical models using the CompFlow Bio were built to simulate TCE introduced from 1940 through 1990 due to industrial activities, in the fractured bedrock with a turbidities sequence of sandstones with shale interbeds underneath the Santa Susana Field Laboratory (SSFL). The domain size is 50m x 0.3m x100m and the fracture apertures are 75 and 100 microns in the 2D conceptual model; while due to computational limits, the domain size is 5m x 5m x15m and the fracture apertures are 75 ~ 150 microns in the 3D conceptual model. The bulk hydraulic conductivity estimate from 2D simulation is on the level of 10-7 m/s, which is less than that estimate from 3D one whose values is on the level of 10-6 m/s. With the rock core VOC analyses for the source zone and outflow boundary (only for 2D domain) compared with field data from SSFL, it presents that NAPL is original dominant phase of TCE in the water, and then it tends to dissolve and so as to be finally fluxed out of the domain. And by investigating the mass flux of TCE in the aqueous phase exists the fence boundary in fracture and matrix, Flow through fracture is proved to be easier than that through matrix, and larger fractures become the main conduit.