Chemical company saves millions of euros through monitored natural attenuation, Germany
A chemical company wanted to develop a former plant factory site in western Germany for commercial and residential use. The plant ceased production in the 1990s after a long operational history. Contaminated soil from the large-scale site had been excavated and stored in former tank-farm areas with sheet-pile walls and rain covers, and the land had been developed. However, at one of the two deposits, significant residual soil contamination outside the sheet-pile walls releases cancerous-causing chemicals, such as polycyclic aromatic hydrocarbons and benzene, and total petroleum hydrocarbons into the groundwater. The company had set aside tens of millions of euros for active groundwater remediation, but, before work began, it learned of a more cost-effective potential alternative at an RSK Alenco seminar: monitored natural attenuation (MNA).
RSK Alenco applied its alternative remediation programme to the site, thus demonstrating to the regulator that the groundwater contamination was being naturally attenuated and active measures such as cost-intensive pump-and-treat systems were not necessary. To do this, the RSK Alenco team developed a detailed, risk-based-MNA concept. The contaminants and hydrogeological conditions were investigated, and a network of 19 boreholes monitored the groundwater contamination levels, but low-flow rates prevented the use of standard groundwater sampling methods. To overcome this, the team persuaded the regulator to allow low-flow sampling using specialist micropurge equipment with bladder pumps.
The results demonstrated that the contaminant plume was not spreading, and natural attenuation was controlling it. The regulator agreed to the MNA concept, thereby avoiding the costly active remediation. More than 15 years of monitoring has confirmed the initial assessment that the contaminated soil is better contained and poses no risk to residents’ health.
RSK’s tailor-made solution was the correct approach for the client, and it saved the client substantial costs. By persuading the regulator to allow MNA to continue, the chemical company avoided remediation measures that otherwise would have cost tens of millions of euros.