after a public enquiry held at manchester town hall on 23 august 1955, plans for the second activated sludge plant were finally approved. the nine-year project was expected to cost £5.5 million. after slow progress, the first contractor became bankrupt in february 1957, and the contract was transferred to percy trentham ltd., but progress remained slow. the railway ceased to be used in june 1958. some rails, wagons and the two diesel locomotives were sold for further use, while the rest of the system was scrapped. in 1960, the design of the activated sludge plant was changed to use the 'simplex' system rather than the bio-aeration process. it was completed in 1966, at a cost of £6.5 million, and a celebration luncheon was held at manchester town hall on 17 may.