Electrical Resistance Heating (ERH), Thermal Conductive Heating (TCH), and Steam Enhanced Extraction (SEE) are the in situ thermal technologies available in the marketplace which are capable of effectively remediating a variety of contaminant species from different geological settings, ranging from tight clays to more permeable gravel aquifers. Petroleum hydrocarbon compounds, which are often resistant to conventional remedial methods, are remediated by all three of these ISTR technologies, often down to MCLs. These technologies have now been successfully applied to hydrocarbon impacted sites, ranging from historic gas station spills impacted with LNAPL to former MGP Sites with appreciable quantities of coal tar and creosote LNAPL and DNAPL.
During 100⁰C ISTR remediation strategies, multiple physical removal mechanisms work in concert to remove hydrocarbon mass through the vapor phase. As ISTR sites reach the water/contaminant mixture boiling point, the lighter end hydrocarbons (C2 through C14) transition to vapor, while the heavier hydrocarbons (BTEX, mid-range hydrocarbons, and naphthalene) are entrained through in situ steam generation and stripping and removed from the subsurface. Both contaminant vapors and contaminant- laden steam are removed from the subsurface by vapor extraction.
In addition to vapor phase removal, one of the most effective ways to remove contaminant mass from a subsurface that features free-product is to extract it as a pumpable liquid. Each ISTR technology is often combined with LNAPL extraction systems and MPE wells in order to effectively remove appreciable quantities of LNAPL and DNAPL, respectively. The ISTR process leaves behind immobile contaminant fractions with limited impact on groundwater quality. In some instances, ISTR is used to heat the subsurface to more than 300oC for complete removal of the hydrocarbons.
This presentation will discuss how ISTR technologies are capable of removing petroleum hydrocarbons, design considerations necessary for varying conditions typically encountered at these sites, and several case studies. These case studies will include gas station sites impacted with TPH-g and BTEX; leaking UST sites featuring TPH-g, TPH-d, and oil range organics; LNAPL and DNAPL impacted Sites; as well as MGP sites with high SVOC contaminant mass. Future solutions for large refinery sites will also be discussed – including sustainable options where the energy for the remedy is provided by the extracted hydrocarbons. Through this presentation, Cascade Thermal will present ISTR solutions for the majority of petroleum impacted Sites - offering efficient, reliable solutions capable of reaching Site closure in a matter of months rather than years or decades, increasing the overall return on remediation investment (RORI) for the project lifecycle.
