the corporation had never liked the idea of secondary beds so far from the main works, and the plans were changed. an experimental secondary bed was built on a site close to barton locks. extra land was bought from barton and irwell rural district council, on condition that the works treated sewage from the local area. this required another of primary bacteria beds. the secondary beds was gradually brought on-line as they were completed. the area dedicated to this function increased from in march 1909, to in october 1910, and by the time the project was finished in april 1914. each secondary bed covered about , and was filled with a much finer media than the primary beds.