Subsurface Injection Technologies and Monitoring Systems for in-Situ Chemical and Bio-Chemical Remediation Systems – It's a Contact Sport

The use of in-situ chemical and bio-chemical treatment methods for soil and ground water contamination has overtaken mechanical methods of physical removal and/or treatment over the past two decades.  Technological improvements, economy of scale, site disturbance, “greener” treatment methods, efficiency, carbon footprint, and other advantageous and economic factors have driven this shift.   
     In the rush to move into the clean up phase for a contaminated site, injection designs are often based on initial site characterization without collecting additional data to properly design a remediation program.  Contaminant mass, soil oxidant demand, and precision pinpointing of contaminant intervals and thickness are ften not considered.  This can result in significant under or over dosing a site, increasing the eventual cost of the remediation.  Numerous “Triad” type methods for characterizing sites aid in the remediation design and can include direct-push sampling, mobile laboratories, borehole logging, membrane interface probes and other technologies. 
     Early in-situ treatment methods included application of treatments through monitoring wells already in place and resulted in limited contact with the contaminants and biased monitoring samples.  Direct push technology (DPT) was soon discovered as a more efficient delivery of treatments and improved physical contact and contact time of the treatment chemicals with the contaminants.  Early methods used simple “bottom-up” injection methods, which are still commonly used today, and are applicable under certain conditions, but can result in failure in others.  Numerous types of injections methods, hydro-fracturing techniques, and tooling have since been developed that further improve the ability to make contact between the treatment chemicals or biologic system and the contaminant.  In addition, advances in real-time down-bore monitoring have furthered the ability to monitor the performance, distribution, and rate of treatment both spatially and temporally in both unconsolidated and fractured-bedrock media.  Methods will be compared and discussed along with the advantages and disadvantages of each technology.