2025 Volume 141 Pages 66-80
The Ofunato Mine mines approximately 2,300 thousand tons of limestone annually. Of this amount, approximately 2,200 thousand tons are supplied to the Ofunato plant of Taiheiyo Cement Corporation (hereinafter “Ofunato plant”) as raw material for cement, and approximately 100 thousand tons are supplied to the local area as aggregate and other materials. For the cement raw materials, mined ore is crushed through various crushing systems, transported by long-distance conveyor belts (BC) to the Ishibashi area, stockpiled once, and then transported by rail to the Ofunato plant.
The Ofunato Mine previously mined limestone in two areas, the Sakamotozawa area in Ofunato city, and the Odaira area in Sumita town, Kesen county. (Both are in Iwate prefecture.) However, as the remaining reserves in both areas were decreasing, a development project in the Horoshi area in Sumita town was undertaken to ensure a long-term stable supply of cement raw materials for the Ofunato plant. The planning for this development began around FY2000, and various environmental assessment studies were started since FY 2007. The development work was then carried out over approximately 4.5 years from the second half of FY 2016 to the end of FY 2020. For the Ofunato plant, which resumed production promptly after the great east japan earthquake and has continued stable operations since then, this development has secured enough ore for approximately 100 years of cement raw materials at the significant milestone of 10 years after the earthquake.
After the completion of the development work, the mining in the Horoshi area began in FY2021 in parallel with the removal of topsoil, and by FY2023, approximately 3,900,000 tons had been mined (Including topsoil).
This report provides the overview of the Horoshi area development project, the initiatives aimed at harmonizing development with ecosystems, and the measures taken during construction to consider the surrounding environment.
