Off-site

It's important to have an off-site backup of all the data on your computer.

Source: tatoeba (4638807)

For 75 years, it has fulfilled a wide range of roles: producing weapons-grade plutonium for early atomic weapons in the aftermath of the Second World War; the world's first commercial nuclear power station supplying electricity to the National Grid; reprocessing and storage of nuclear fuel; and the processing of lower grades of radioactive waste for off-site storage.

Source: wiktionary

Unlike South Heath, where the tunnel segments are made on site, the ones used here are made off-site and brought in by road.

Source: wiktionary