37 Construction work relating to the installation and maintenance of electrical systems; construction and maintenance of underground structures, and consultancy relating thereto; underground structure construction supervision; construction and maintenance services relating to civil engineering; installation, maintenance and repair of mechanical apparatus; extraction of oil; mining extraction; excavating; on-site construction supervision; industrial plant maintenance; maintenance services for industrial plants; industrial plant repair; construction of industrial plants; on site building project management; building project management; quarrying services; rock blasting; drilling; oil drilling; rock drilling.