The object of this contract is to carry out the works for the reconstruction of the interior walls and the removal of waterproofing material applied to the interior of the roof of deposits 3 and 4 of the ETAP. In summary, the works to be carried out are: • Demolition and removal of concrete block walls. Includes loading, transport and landfill fee. • Removal of interior insulation of the tank roof. Using ultra-high pressure (UHP) robotic hydronetting method (>1,200 bar), without chemicals. Includes removal of generated residue and its management at an authorized center. • Protection of the interior part of the tank roof slabs. Once the waterproofing material is removed, an epoxy-based water-based coating will be applied to protect the concrete. • Execution of partition walls. Reconstruction with similar prefabricated dense concrete blocks, grouted and plastered with mortar. • Final cleaning of the tank according to ATL's internal instructions. And subsequent disinfection by ATL. All products or materials in contact with water will comply with RD 3/2023 and ATL's internal instruction PPR-009. Work will be carried out in each tank following the deadlines and priority criteria set by ATL's operation, taking into account that one of the two tanks must always be in service. The scope of action is within the enclosure of the water treatment plant itself, therefore there are no impacts from expropriations and there is no record of affected services.