The Stava mudflow of 19 July 1985 (Northern Italy): a disaster that effective regulation might have prevented

Abstract

Abstract. The disaster occurring in the Eastern Italian Alps in the summer of 1985 was caused by the failure of two tailings dams located just upstream from the village of Stava in the municipality of Tesero (Trento province, Italy). The structure comprised two small storage basins for the deposition of tailings from the separation process of the Prestavel fluorite mine. On their downstream sides, the basins were contained by steep earth embankments, whereas upstream they rested directly on the natural slope. The total height from the base of the lower dam to the crest of the upper dam was over 50 m.On 19 July 1985, the front of the upper dam suddenly burst, triggering a vast mudflow (180 000 m 3 ) that flowed down-channel through Stava, a small village of 20 buildings. The mudflow rapidly traveled over 4.2 km along the Stava Valley and passed through Tesero, before flowing into the Avisio River. The mudflow destroyed many buildings and resulted in 268 fatalities and 20 injuries. From an analysis of the data collected and field observation, several factors may be cited as having contributed to increasing instability, as the upper dam continued to be raised until the disastrous collapse of 19 July. Foremost among these factors is the mistaken assumption that the tailings deposited in the impoundments would consolidate fairly quickly. Indeed, no monitoring system was ever installed to verify the assumed consolidation. Other operational shortcomings and construction errors were contributing factors. Regulations requiring construction standards, operational monitoring, and independent periodic inspection could have prevented this disaster. Comprehensive legislation is required to effectively limit the adverse consequences of tailings dam failures by providing a regulatory environment where the safety and welfare of the local area can be balanced with the economic benefits of mining operations.

The Application of the Seismic Cone Penetration Test (SCPTU) in Tailings Water Conditions Monitoring

“…Monitoring of water conditions in hydrotechnical facilities, which includes the outflowed postflotation tailings storage facility, is one of the basic operations to ensure the safe exploitation of such facilities. The literature on this issue indicates inadequate water conditions as the main cause of failures of TSF [3][4][5]7,30,31]. Hence, the problem of proper recognition and reliable monitoring of water conditions is of particular importance.…”

Tailings-flow runout analysis: examining the applicability of a semi-physical area–volume relationship using a novel database

“…When a tailings dam breach occurs, a destructive flow of mine tailings can develop (e.g. Macías et al, 2015). These flows may travel over substantial distances and impact large areas (Rico et al, 2008a).…”

“…Tailings flows can take various forms, ranging from a massive debris flood consisting of water and sediment to a flowslide (Hungr et al, 2014). These flows can travel long distances at extremely rapid velocities (> 5 m s −1 ) (Blight, 1997;Blight et al, 1981;Harder and Stewart, 1996;Jeyapalan et al, 1983a, b;Kossoff et al, 2014;Macías et al, 2015;Rico et al, 2008a). Runout modelling and inundation mapping of tailings dam breaches are essential steps for estimating the potential consequences of a tailings dam failure, determining appropriately stringent design criteria and developing emergency response and preparedness plans (Canadian Dam Association (CDA), Knight Piésold Ltd., 2014;Martin et al, 2015Martin et al, , 2019Mc-Dougall, 2017).…”

“…2). Most of the commonly used numerical models were developed primarily for either clear water flood analysis (Brunner, 2016;Danish Hydraulic Institute (DHI), 2007;Martin et al, 2019) or the analysis of flow-like landslides (McDougall, 2017;McDougall and Hungr, 2004;Pastor et al, 2002;Pirulli et al, 2017) and do not necessarily account for the compositional variety of tailings and its potential influence on the downstream flow behaviour (Dibike et al, 2018;Macías et al, 2015;Pirulli et al, 2017). Due to these limitations, hazard maps delimiting potential inundation areas based on current techniques may not reliably characterize the extent and intensity (e.g.…”

Fluorine

“…In 1985, approximately 180,000 cubic meters (m 3 ) of tailings slurry was inadvertently released and flowed into a valley, destroying a small town and causing destruction in another small town; this event caused 268 deaths and 100 injuries. The failure was owing to construction errors and a lack of operational monitoring during tailings deposition (Luino and De Graff, 2012). In more recent times, technical and scientific investigations on tailings impoundments and new legislation and regulations for stricter control and monitoring are helping to minimize tailings dam failures.…”