 In 1929, this building was flooded to a depth of 4 ft during the great floods of 1929, after which damage was repaired quickly.When the Vertical Retort was built in the 1930s, the Horizontal Retorts were removed along with chimney and replaced with a boiler and a large tar plant in the mid portion of the building with associated 3 oil tanks outside on the southern face.The brick and masonry portion of the eastern wing was re-fitted with 3 exhausters and the steel and galvanized iron portion upgraded to contain 4 more purifiers adding to a total of 8.