CPV code 90491000 designates Sewer survey services in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
90491000 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 90490000 (Sewer survey and sewage treatment consultancy services).