Why In Situ Thermal Desorption Can Be the Most Cost-Effective Remediation Method for Many Sites

Three case studies are presented, showing that thermal remediation utilizing In Situ Thermal Desorption (ISTD) is often less expensive than alternatives. The life-cycle costs of implementing ISTD compare favorably with those for alternative remediation technologies such as excavation, pump-and-treat, soil vapor extraction, multiphase extraction, bioremediation and in situ chemical oxidation. With respect to excavation, ISTD is not only less expensive and less obtrusive, but also much more community friendly. The most significant cost of an ISTD project is the capital cost associated with the installation, while the operation and maintenance (OM development of simpler approaches for recovering off-gas; reliance on off-the-shelf off-gas treatment equipment; efficiencies in use of manpower; and economies of scale. Meanwhile the effectiveness of the ISTD technology in reliably achieving cleanup goals in soil and groundwater has been proven at full scale for a wide variety of contaminant types (e.g., chlorinated volatile organic compounds (CVOCs), semivolatile organic compounds (SVOCs), coal tar, polychlorinated biphenyls (PCBs)) and hydrogeologic settings (above and below the water table, in sandy, silty and clayey soil, and in fractured rock). ISTD projects are frequently completed and sites closed, after less than one year of heating. By contrast, projections of the required duration of treatment for other in situ technologies have frequently proven to be overly optimistic. Mass removal is often seen initially, but due to subsurface heterogeneity and associated mass transport limitations, the required treatment and monitoring period often persists for many years. ISTD is fundamentally different because thermal conductivity is nearly invariant even within heterogeneous sites. Thus source zones targeted for treatment are fully heated and treated. Further rounds of treatment are not required.