CPV code 45221250 designates Underground work other than tunnels, shafts and subways in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
45221250 is a leaf code — the most specific level of its branch — so it can be used directly as the main CPV code of a contract notice. If it does not quite fit, check the neighbouring codes under 45221200 (Construction work for tunnels, shafts and subways).