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Ibaraki Prefecture, Mito City - Hexavalent Chromium Contamination Remediation Measures - December 2021 In December 2021, a survey conducted in Mito City, Ibaraki Prefecture, revealed that hexavalent chromium concentrations in groundwater had reached 10 times the standard limit (0.5 mg/L). In response to this issue, the city and prefecture secured a total budget of 1.5 billion yen and initiated a remediation project. Approximately 5,200 tons of contaminated soil were excavated from an area of about 10,000 square meters and rendered harmless at a treatment facility. Additionally, 20 tons of ferrous sulfate were injected to reduce hexavalent chromium to trivalent chromium. Fifteen observation wells were installed to monitor the contamination status in real time. By 2023, the hexavalent chromium concentration in the groundwater had decreased below the standard limit (less than 0.05 mg/L), and further purification plans are underway. This project is attracting attention as a model
case for groundwater contamination countermeasures in other municipalities.