Duero Hydrographic Confederation considers sanctions over Ucero river fish deaths

The Duero Hydrographic Confederation (CHD) is considering administrative sanctions against the El Burgo de Osma City Council following a mass die-off of fish in the Ucero River this summer. Technical analyses confirmed that discharges from the municipal wastewater treatment plant (EDAR) caused a significant alteration to the riverbed. The situation was reportedly worsened because one of the plant's two biological treatment lines was out of service.

The incident was first reported by the Abión and Ucero Rivers Fishermen's Society on August 14, after hundreds of dead trout, along with other species such as gobies and crayfish, were found spanning several kilometers downstream from the treatment plant. Inspections conducted throughout August and September revealed high concentrations of ammonium and non-ionized ammonia, alongside a critical decrease in dissolved oxygen levels. While recent sampling on September 7 showed improvements in water quality, a definitive assessment of the exact causes is pending further results.