| In-situ thermal soil and aquifer remediation technologies (e.g., electrical resistance heating (ERH), conductive heating (CH), steam injection (SI), etc.) have undergone rapid development and application in recent years. These technologies offer the promise of more rapid and thorough treatment of non-aqueous phase liquid (NAPL) source zones; however, their field-scale application has not been well-documented in the technical literature.;Available documents from 182 applications were reviewed, which included 87 electrical resistance heating, 46 steam-based heating, 26 conductive heating, and 23 other heating technology applications conducted between 1988 and 2007. Approximately 90% of the 182 applications were implemented after 1995 and about half since 2000. More specifically, this review identified the geologic settings in which these technologies were applied, chemicals treated, design parameters, operating conditions, and performance metrics. The results of this study are summarized in a table linking this information to five generalized geologic scenarios; this table was designed to be useful for practitioners considering thermal technologies. The user selects one of five geologic settings that most closely resembles their site, and then can quickly review which technologies have been applied in that setting, the designs employed, operating conditions, and the performance achieved.;Groundwater impacts, as quantified by dissolved concentrations and mass flux (discharge) into the aquifer, were determined by high spatial density sampling and analysis at five thermal treatment sites. The range of concentration and mass flux reductions ranged from about <10X to 1000X, and was strongly linked to how well the source zone was delineated prior to treatment.;Physical model experiments were also conducted to gain insight into heat propagation and the resulting vapor flow distributions in aquifers using electrical resistance heating (ERH) and conductive heating. This information provides the basis for a better visual understanding of how ERH and conductive applications work. |
