Cogoleto-Stoppani chromium works

The company opened in the Lerone valley on 15 March 1900 and processed chromite to make sodium dichromate. For decades the chromite ore processing residue (COPR) was piled on the site and, until the early 1980s, dumped on the beaches of Arenzano and Cogoleto. The last kiln was shut down in 2003, when the works closed.

The residue readily releases hexavalent chromium into the water passing through it: a 2021 mineralogical study measured up to 375 mg/L of leached Cr(VI) and identified highly soluble sodium chromate and crocoite. In soil the SENTIERI documentation lists total and hexavalent chromium, nickel and vanadium; in groundwater, chromium.

At the end of 2006 the Government declared an emergency and set up a commissioner's office. It built a treatment plant for water pumped from the aquifer and a reinforced-concrete barrier 250 m long and 8 m deep below the stream bed between the Pian Masino landfill and the Lerone, removed all asbestos and demolished the plant (the last kiln in 2015). Almost 8,000 t of yellow sulphate abandoned in the warehouses was disposed of. The beaches on both sides of the Lerone were dug out to five metres, removing 66,000 t of chromium 'crusts', and rebuilt over almost a kilometre.

Since 2008 the sea off the site has been monitored with bioindicators for chromium: values fell over the years, except in 2009 after heavy storms. In 2019 the Region estimated that about 10% of the works remained and that stopping treatment would send chromium into surface water and the sea. SENTIERI (2023) still reports high hexavalent chromium concentrations in wells inside the former industrial area.