November 12, 1919. Excavation for and construction of the foundation of the main building at the Des Plaines plant. Sewage pumps were included in the main building and deep excavation in the left foreground was necessary for the pump intake, a.k.a. the wet well. Formwork for wall building is in the right background. (MWRD photo 7357)

The main building for the Des Plaines plant, July 8, 1924, contained a laboratory, maintenance shop and electrical substation, as well as sewage pumps and aeration tank blowers. New landscaping around the building improved the appearance for public visitors. The smaller building at right contained coarse and fine screens. Open grit tanks occupied the space between the buildings. (MWRD photo 10863)

Looking east from the main building, September 3, 1924. The four types of aeration tanks at the Des Plaines plant are in the foreground. The operating gallery is the long building beyond the aeration tanks. Behind it are final settling tanks and sludge concentration tanks. In the background are the store house (left) and the drying house (right). The store house included worker accommodations and space for storing dry sludge. Sludge dewatering equipment is in the drying house. (MWRD photo 11147)

May 21, 1924. The Des Plaines plant has been in operation less than two years when new filter plates were installed in the Manchester-type aeration tanks. Four different types of tanks were built and tested to study performance characteristics. District engineers conducted studies to determine the most efficient tank design for later plants. (MWRD photo 10627)

Construction of the West Side plant began late in 1926, and by April 20, 1927, the foundations of the Imhoff tanks for battery A are being prepared. Looking northeast, the tanks run in an east-west direction. The sloping tank bottoms of the lower compartment rest on native soil. Under drainage and drain piping has already been installed. (MWRD photo 13275)

Looking west on May 7, 1927. Steel reinforcing rods are placed for battery A Imhoff tank bottoms at the West Side plant. The heavily reinforced tank bottoms acted like an undulating plane floating on the native soil. When finished, the top of the tank was several feet above the ground surface. (MWRD photo 13308)

August 5, 1927. Concrete is being placed for the bottoms of battery A Imhoff tanks. Reinforcing rods protruding above the tank bottoms are for the vertical tank walls. The north cableway tower is in the right background. All equipment and materials for construction are delivered via the overhead cableway. (MWRD photo 13404)

Looking northeast on June 24, 1927. Walls are being constructed for battery A Imhoff tanks at the West Side plant. The upper and lower compartments of Imhoff tanks require tall side walls. Backfill will be placed against the wall raising the ground surface. (MWRD photo 13339)

Looking northwest on June 24, 1927. Concrete is being placed for Imhoff tank interior compartment vertical walls for battery A at the West Side plant. The vertical walls, including end walls, are notched and curbed to receive precast panels that separate the upper and lower compartments. (MWRD photo 13340)

July 29, 1927. A close-up of an end wall and first interior vertical wall shows the intricate construction of the Imhoff tanks for all three batteries at the West Side plant. The rectangular notched boxes cast into the end wall are inlets and outlets for flow through the upper compartment of the Imhoff tank. (MWRD photo 13388)

Looking southwest on August 5, 1927. Laborers are busy preparing forms and placing steel reinforcing rods before concrete is poured for the panels separating the upper and lower compartments of the Imhoff tanks at the West Side plant. The south cableways tower is in the background. (MWRD photo 13407)

August 24, 1927. An overview looking west of construction of battery A at the West Side plant from the concrete mixing tower shows the south end of the Imhoff tanks and the precast wall panels at right. Mixed concrete is transported by rail to the south cableway tower in the center. Both rail-mounted cableway towers move synchronously in the east-west direction. (MWRD photo 13429)

October 4, 1927. Back fill has been placed against the exterior walls of battery A and the other batteries at the West Side plant to create a new elevated ground level for operating employees to service the tanks. After pumping sewage from underground to the top of the new ground level, gravity is used for sewage to flow through the treatment process. (MWRD photo 13474)

Simultaneous to work on battery A, construction was underway on the West Side pumping station. Looking northeast on May 31, 1927: The excavation for the foundation has been partially completed and concrete is being poured for the floor of the wet well. A chemical plant in the background occupied the site east of Laramie Avenue. (MWRD photo 13328)

Looking south on June 24, 1927. Less than a month later, construction of the West Side plant pumping station wet well has expanded rapidly. Spoil piles from excavation of the Sanitary & Ship Canal 30 years earlier are visible in the background. The spoil was used for plant construction backfill. (MWRD photo 13345)

Looking northeast, November 25, 1927. Once the West Side plant pumping station substructure was completed, erection of the superstructure commenced and was proceeding well. (MWRD photo 13612)

Looking northeast, November 25, 1927. Once the West Side plant pumping station substructure was completed, erection of the superstructure commenced and was proceeding well. (MWRD photo 13612)

Looking northwest from the roof of the West Side pumping station on January 11, 1928. Additional construction is underway. In the foreground, five of six large pipes lead from the pumping station that will distribute flow to the treatment processes. At left, skimming tanks are under construction. Battery A and the cableway is in the right background. (MWRD photo 13704B)

November 25, 1927. Construction of the conduit from the pumping station at the West Side plant to convey sewage to the skimming tank and grit chamber. In the foreground, the conduit begins to turn west. (MWRD photo 13614)

July 30, 1928. Construction of the floor slab for an electrical substation is underway directly south of the West Side plant pumping station. Electrical energy from the Lockport hydroelectric plant and the Commonwealth Edison grid was used. Looking east, the Sanitary & Ship Canal and spoil piles are in the background. (MWRD photo 14193)