Measurement of LNAPL Flux Using Single-Well Intermittent Mixing Tracer Dilution Tests
Article first published online: 10 APR 2012
© 2012, The Author(s). Ground Water © 2012, National Ground Water Association
Volume 50, Issue 6, pages 840–850, November/December 2012
How to Cite
Smith, T., Sale, T. and Lyverse, M. (2012), Measurement of LNAPL Flux Using Single-Well Intermittent Mixing Tracer Dilution Tests. Ground Water, 50: 840–850. doi: 10.1111/j.1745-6584.2012.00931.x
- Issue published online: 6 NOV 2012
- Article first published online: 10 APR 2012
- Received January 2011, accepted February 2012.
The stability of subsurface Light Nonaqueous Phase Liquids (LNAPLs) is a key factor driving expectations for remedial measures at LNAPL sites. The conventional approach to resolving LNAPL stability has been to apply Darcy's Equation. This paper explores an alternative approach wherein single-well tracer dilution tests with intermittent mixing are used to resolve LNAPL stability. As a first step, an implicit solution for single-well intermittent mixing tracer dilution tests is derived. This includes key assumptions and limits on the allowable time between intermittent mixing events. Second, single-well tracer dilution tests with intermittent mixing are conducted under conditions of known LNAPL flux. This includes a laboratory sand tank study and two field tests at active LNAPL recovery wells. Results from the sand tank studies indicate that LNAPL fluxes in wells can be transformed into formation fluxes using corrections for (1) LNAPL thicknesses in the well and formation and (2) convergence of flow to the well. Using the apparent convergence factor from the sand tank experiment, the average error between the known and measured LNAPL fluxes is 4%. Results from the field studies show nearly identical known and measured LNAPL fluxes at one well. At the second well the measured fluxes appear to exceed the known value by a factor of two. Agreement between the known and measured LNAPL fluxes, within a factor of two, indicates that single-well tracer dilution tests with intermittent mixing can be a viable means of resolving LNAPL stability.