Proven Methods for Successfully Engineered Introduction of Remediation Amendmentsinto Impacted Groundwater Environments

Reagents can be emplaced in aquifer systems by means of Permeable Reactive Barriers (PRBs) to treat a contaminated plume or injected directly close to the source of the contamination to reduce the remediation time. Over the past 15 years, the use of iron-based PRBs has evolved from innovative to accepted standard practice for the treatment of a variety of groundwater contaminants (ITRC, 2005). Although, a variety of excavation methods have been developed, backhoe (hydraulic excavators) are commonly used for the construction of PRBs in North America. In Europe, the most common method of slurry excavation is with a hydraulic grab and crane. A comparison of the two techniques will be presented from a general point of view. And then the case study of Avigliana (TO, Italy) PRB will be described. At this site a 0.6 m thick, 120 m long and 13 m deep continuous PRB was excavated using a crane mounted grab to remediate a chlorinated hydrocarbons plume. Instead, the injection of reagents can be performed using different technologies: gravity injection, fracturing, jetting, pressure pulse technology (PPT), injection in valved tubings, soil mixing but one of the most effective is to exploit the versatility of direct push systems. Relative merits of the different technologies will be analyzed.