Formatted Title
Treating below Critical Infrastructure Using ISTR
Background/Objectives
Contaminant source zones are frequently found below buildings, roadways, water bodies, utilities, subsurface structures, and other critical infrastructure. In situ thermal remediation (ISTR) has emerged as a promising technique for treating below these obstacles, allowing for treatment of heavily contaminated source zones otherwise considered inaccessible to other remediation techniques. This presentation will examine the various types of thermal remediation technologies commonly employed, such as electrical resistance heating (ERH), steam enhanced extraction (SEE), and thermal conduction heating (TCH) and their applicability, effectiveness, and limitations in the context of remediating subsurface contamination beneath critical infrastructure based on more than twenty ISTR projects implemented under critical structures and infrastructure. The challenge is two-fold – how can access be gained for installation of ISTR components and what measures should be taken to monitor and protect buildings and control exposure for workers within the building and treatment zone during the installation, operation, and cool-down phases of the thermal remedy.
Approach/Activities
This presentation will discuss limitations and flexibility in ISTR wellfield patterns affecting well installations for ERH, SEE and TCH and the technical benefits for one ISTR technology over another in different settings. Examples will be provided of ISTR infrastructure installed at a site from the outside using directional technologies and reaching more than 80 ft in below a building where building operations had to continue during operations. Another case study presents a site where more than 20,000 cy (15,300 m3) of soils treated to a depth of more than 70 ft (21.3 m) bgs were addressed by installing heater clusters with up to 8 heaters per cluster installed at angles as shallow as 22 degrees from horizontal using sonic drilling technologies.
Results/Lessons Learned
The presentation will highlight the design and installation challenges for each of the technologies and drilling methods utilized, - not only from a heating standpoint but also related to optimizing pneumatic and hydraulic capture under the challenging conditions. The 3-dimensional site models utilized to design the ISTR wellfields will be presented along with the measurement approaches to confirm and adjust during installation, the azimuth, installation angle and curvature for each individual boring during drilling to ensure that the heating system had sufficient coverage. By incorporating these elements, thermal remediation can provide a reliable and efficient solution for remediating contamination in challenging subsurface environments, ultimately facilitating the restoration and cleanup of heavily contaminated source zones located in areas that just a few years ago were considered inaccessible for cleanup.