This video explains the remediation of a low-concentration, wide-spread chlorinated solvent plume under the train station and surrounding urban area in Bologna, Italy. Technologies used: PlumeStop and HRC. Video length: 4m30s
This is Bologna Centrale, one of Italy’s busiest railway stations. Each year, 58 million passengers pass through here, and weather out 800 train movements per day. It is an important public transport hub connecting the south of the country to the north, and beyond. In the early 2000s, a site investigation was carried out in preparation for the construction of a new underground, high-speed railway station to be linked with the existing terminal.
The site investigation discovered that historic groundwater contamination had created a widespread plume under the entire site, and also, the surrounding urban area. The plume consists of low concentrations of chlorinated ethenes dissolved into the groundwater of two aquifers. The upper and lower aquifer are impacted with concentrations in the microgram-per-liter range.
The University of Rome La Sapienza has been responsible for formulating the remediation strategy for this public site. They determined that for such low concentrations, physical and chemical remediation processes would not be appropriate. Even an enhanced biological degradation approach would be inefficient due to a lack of contact between the suspended contamination and the biodegrading bacteria on the sediment surface.
The university identified PlumeStop as a new technology that would be able to treat such low but persistent concentrations. PlumeStop is a liquid-activated carbon, which remediates groundwater contamination through wide dispersion, rapid absorption and enhance biological degradation. PlumeStop achieves very low groundwater contaminant targets in a short period of time. The treatment is maintained for years after a single injection.
Initially, a pilot test was completed to validate the injection method, verify the distribution of PlumeStop, and observe initial concentration reductions in the groundwater. Results from the pilot study were also to be used to adjust the injection spacing and dosage of the full-scale treatment in order to provide the most accurate application.
The pilot test was successful in demonstrating the applicability of the technology. It also provided useful information to refine the design for full-scale implementation. Due to the scale of the plume and the lack of access due to buildings, roads and rail, the intention of the full-scale works is to target hotspot areas of higher concentrations within the plume.
To date, three of these areas have been applied with PlumeStop, including one area located directly under a railway platform at the main station. Injections have been carried out partly through pre-drilled injection locations, and also, via direct push injections using a rig that is able to get underneath the platform canopy.
In these full-scale works, PlumeStop has been co-applied with two electron donors of the REGENESIS product family, HRC and HRC Primer, in order to promote and sustain the microbial dechlorination of the contaminants dissolved onto the PlumeStop. Validation monitoring is ongoing and initial results showed good, decreasing trend in the contaminants.
REGENESIS and the University of Rome La Sapienza have worked closely together to design the tailored approach for this large and public site. The new high-speed rail tracks and station were completed in 2013 with surrounding work and tiling still in progress today. Due to the innovative institute remediation approach that PlumeStop offers, neither the busy railway station nor the construction works have been affected by our remediation activities.