development not above ground level required in connection with the provision, improvement, maintenance or repair of a sewer, outfall pipe, sludge main or associated apparatus;

the provision of a building, plant, machinery or apparatus in, on, over or under land for the purpose of survey or investigation;

the maintenance, improvement or repair of works for measuring the flow in any watercourse or channel;

the installation in a sewerage system of a pumping station, valve house, control panel house or switch-gear house;

any works authorised by or required in connection with an order made under section 73 of the Water Resources Act 1991 (power to make ordinary and emergency drought orders) M1;

any other development in, on, over or under their operational land, other than the provision of a building but including the extension or alteration of a building.