Borealis Naphtha Cavern, Kilpilahti, Finland

We built a new naphtha cavern in the Kilpilahti industrial area. The project won first prize in the Uusimaa Occupational Safety Competition (Turvallisesti 2000-luvulla) in the Infrastructure business and Site categories.

In addition to excavation and reinforcement work, the contract included demanding reinforced concrete structures (pressure and gas-tight wall) and demanding pipeline and steel installations in the shaft.

The rock cavern has a volume of about 80,000 cubic metres and is located about 80 metres below ground level. A total of approximately 100,000 cubic metres of rock material was excavated from the cavern. The cavern is, on average, 22 metres high and wide, and about 200 metres long.

A pumping station well 10.5 metres deep with a diameter of 5.6 metres was placed at one end of the cavern. Above it rises a shaft 57 metres high with a diameter of approximately 5 metres. The shaft was cast continuously for five and a half days with self-compacting concrete and it was reinforced with special fibre. Pipes were installed in the shaft, for example, as naphtha filling and discharge pipes and for sensors.

“The rock cavern for the storage of naphtha, or special boiling point gasoline, is a strategically important project for us and will improve the storage capacity of the Borealis petrochemical plants. From a safety and environmental point of view, the rock cavern is the best option for storing large amounts of feed material,” says Jari Koivumäki, Operations Manager for petrochemical plants.

In its life cycle, a cavern is a safer and cheaper option than above-ground storage. Excluding technology, it is also maintenance-free.

Top-notch safety requirements

The project achieved a high level of safety in a demanding industrial environment and won first prizes in the Uusimaa Occupational Safety Competition (Turvallisesti 2000-luvulla) in the Infrastructure business and Site categories in 2019.

Safety was invested in through additional planning meetings with the customer, careful mapping of risks, advance supervision and preparation, for example, for plant shutdowns and disruptions by reviewing escape routes and assembly points.

YIT Rock and mine construction

YIT voitti Uudenmaan työturvallisuuskilpailussa Infra-alan yritys- sekä työmaasarjan (in Finnish)


Project name
Borealis Naphtha Cavern
Project status
Business segment