Obayashi constructed Japan’s first hydraulically sealed, underground liquefied petroleum gas (LPG) storage tank capable of holding 450,000 tons as part of the national LPG stockpiling system. We excavated a super large 650 square meters (6,997 square feet) section cave in the bedrock more than 150 meters (492 feet) below ground. We overcame a variety of technological issues and completed this major project that took approximately 10 years.