Hydraulic/partitioning tracer tomography for characterization of dense nonaqueous phase liquid source zones

[1] A new technology, hydraulic/partitioning tracer tomography (HPTT), is proposed to survey spatial distributions of hydraulic properties and dense nonaqueous phase liquids (DNAPLs) in the subsurface. HPTT is nothing more than a set of multiple hydraulic/ partitioning tracer tests and synthesis of all the tests to map the spatial distributions. It involves injection of water at one borehole in a source zone to create a steady state forced gradient flow field, then release of conservative/partitioning tracers at the same borehole, and monitoring heads and tracer breakthroughs at the others. The same operation is repeated using different boreholes for the water and the tracer injections. To analyze the head and tracer data obtained from the proposed tomographic survey, a joint stochastic estimator was developed. Numerical experiments were then conducted to evaluate the effectiveness of HPTT as well as the stochastic estimator. Results show that prior knowledge of hydraulic heterogeneity is critical for mapping the distribution of DNAPLs. In addition, the results suggest that the proposed HPTT in conjunction with the stochastic estimator is potentially a viable tool for high-resolution characterization of subsurface heterogeneity and contamination.