Risk analysis and Backfill Materials: SNPA guidelines applied to an heavy metal contaminated site

In Italy, the regulatory framework for backfill materials has long been a critical issue, as these materials were, in some ways, excluded from both waste regulations and environmental remediation regulations. The lack of a clear legal reference created uncertainties in their management, which were only recently addressed with the enactment of Law No. 108 of July 29, 2021, introducing specific provisions for their treatment within remediation procedures. Following this legislation, the National System for Environmental Protection (SNPA) published Guidelines No. 46/2023, aiming to establish clear criteria for the management of backfill materials in contaminated sites. These guidelines provide instructions on the characterization, classification, and treatment of this environmental matrix, distinguishing it from soil and other environmental compartments. Since, under certain conditions, Guidelines No. 46/2023 allow for the risk assessment application to evaluate contamination, SNPA subsequently issued Guidelines No. 46 bis/2023, specifying the necessary modifications to the equations in the APAT Manual, used as a reference for risk assessment, that were originally developed for soils, in order to adapt them to backfill materials. Based on these regulatory and methodological advancements, this study analyzes the risk assessment application through the Risk-net 3.2 Pro software, which, in its most recent version, has integrated a dedicated section for backfill materials, distinct from other environmental matrices. Finally, a case study is presented, concerning a contaminated site with backfill materials containing heavy metals, where the characterization procedure and the risk assessment are conducted following the SNPA Guidelines, using the aforementioned software, which returned acceptable risk values for the site.