August 15, 1928. Electricians are installing conduit that will be underneath the floor of an electrical control room at the West Side plant pumping station. (MWRD photo 14241)

Looking north from the canal bank on October 23, 1928. A corner of the pumping station appears at the lower right. The illuminated sign south of the West Side plant pumping station also served as a transmission line tower for electricity from the Commonwealth Edison generating station at Crawford Avenue. (MWRD photo 14425)

Looking northwest on March 28, 1929 over the construction of West Side plant grit tanks and skimming tanks. Imhoff tank battery A is in the right background and battery B is under construction in the left background. Battery C will be constructed to the left. (MWRD photo 15555)

Looking to the northeast on June 26, 1930. Construction of the West Side plant sand sludge drying beds, covering 57 acres, are nearing completion. Each bed is 80-feet wide and a rail spur track is on one side. Construction of battery B Imhoff tanks is nearing completion in the center background. (MWRD photo 16390)

August 9, 1935. The deep foundation and wet well for the Southwest plant pumping station shows progress in installing the base for pump suction bells. Looking south, the deep excavation has reach drier stiff clay evidenced by the vertical cut. Excavation into the clay at right is for the foundations of pump discharge conduits. (MWRD photo 20214)

May 22, 1937. Huge pieces of machinery were often moved using methods considered primitive by comparison to today’s methods with heavy-duty mobile cranes. Workers are gently rolling this one-piece casting weighing several tons down a ramp from a flatbed railcar to the loading dock of the Southwest plant pump and blower building. Once in the building, the piece will be moved using the in-house overhead gantry crane. (MWRD photo 22111)

May 22, 1937. The gantry crane in the pump and blower building is lowering the casting onto the pump room floor. The casting is the lower half of the split case for a main sewage pump and is upside down. The flange on top in this view is the bottom flange of the split case and in its final position will be in the wet well beneath the floor connected to the pump suction bell. The flange to the right will connect to the discharge pipe leading out the west side of the building. (MWRD photo 23109)

Looking north over the pump floor in the Southwest plant pump and blower building on November 16, 1938. One steam-driven turbine in the foreground is driving the centrifugal pump behind it. In total, there are six pairs of turbines and pumps. Four are partially visible in this view. (MWRD photo 24524)

Looking south, March 1, 1939. Sewage pump one on the pump room floor in the plant pump and blower building. At left is the triple expansion steam driven turbine that powers the pump in the center. The upper flange of the lower half of the split case is indicated by the arrow. Above the flange is the upper volute split case with external ribs for reinforcing the volute walls. To the right and below the upper volute split case is a smaller split case part to complete the volute. (MWRD photo 24643)

March 1, 1939. Turbine rotors undergo close inspection before final assembly of a blower. Looking south on the blower floor of the pump and blower building, three other blowers are in the background. Initially, the plant had a total of four blowers, each rated at about 10,000 horsepower. (MWRD photo 24635)

July 17, 1936. The northwest corner of the pump and blower building of the Southwest plant is shown before backfilling to raise the finished grade to just below the top of the concrete wall. The two below grade rectangular holes in the concrete wall are entrances to an extensive underground tunnel network for employees and utilities. (MWRD photo 21595)

Looking north on December 7, 1936. The six raw sewage pumps at the Southwest pumping station discharge into a large plenum west of the station. The two conduits convey sewage to the preliminary settling tanks. Grit tanks were not included in the initial construction. The full capacity of the six pumps is 2,000 cubic feet per second or 1.3 billion gallons per day. (MWRD photo 22535)

Looking west from the roof of the sludge disposal building on July 5, 1938. The 12 preliminary settling tanks are positioned some distance from the west wall of the pump and blower building in the foreground. The intervening area was intentionally left for construction of aerated grit tanks, which were finally constructed in 1963. (MWRD photo 24190)

Looking northeast from the concrete mixing tower, May 26, 1936. An overview of construction of battery A at the Southwest plant. Several final settling tanks are on the left; farther to the left are a few aeration tanks. Both north and south (on the right) cableway towers can travel the full quarter-mile width of batteries A and B. The West Side plant and water tank are in the background. Today, the north-south Central Avenue overpass traverses the area between the two plants. (MWRD photo 21337)

Looking northeast across the excavation for the bottom of final settling tanks at the Southwest plant on October 2, 1935. A piledriver is sinking piles into the soft clay subsoil. Thousands of piles were driven to support the reinforced concrete floors of the 32 aeration tanks and 24 final tanks in each battery. Each battery covered about 20 acres and 4 batteries were eventually built. (MWRD photo 20372)

April 21, 1936. Still under construction, this tank is the first bay in the aeration tanks for battery A. Air in the steel pipe in the tank bottom will be purged through diffusers to mix with sewage from the preliminary settling tanks. The rising air bubbles induce a helical motion as the flow proceeds from one end of the tank to the other. Microorganisms in the flow will thrive on the dissolved oxygen and digest the organic matter, producing a mixed liquor of water and floc. (MWRD photo 21087)

March 5, 1936. This final settling tank in battery A at the Southwest plant is still under construction. Aerated liquor from the aeration tanks will enter the tank flowing vertically in the center column. Floc formed in the aeration tank settles to the bottom of the final tank and is moved to the center by the scrapers on the bottom of the four rotating arms. (MWRD photo 20850)

Looking northeast, October 20, 1938. An overview of battery A at the Southwest plant. Final settling tanks are in the foreground and aeration tanks are in the middle ground. The long low building between the aeration and final tanks is the operating gallery. Industries on Chicago’s West Side are in the background. (MWRD photo 24472)

Looking northwest on November 16, 1938, over the sludge concentration tanks. Settled, more dense sludge on the tank bottom is moved to the near end by scrapers mounted on the chains and piped to the sludge disposal building for further processing. where the sludge was dewatered in rotary vacuum filters prior to heat drying. (MWRD photo 24547)

Looking from the southeast, November 16, 1938. The sludge disposal building. Deep beneath the southeast corner of the building, influent sewers converge and sewage flows into the coarse screen chamber and then on to the pumping station at the west end of the building. The building housed the boilers, steam-driven electric generators, rotary vacuum sludge filters, and sludge heat drying apparatus. The heat dried sludge conveyor bridge is seen at left. (MWRD photo 24543)

March 1, 1939. The brand-new condition of these screens would not last long as sludge is corrosive and the moving parts require continual maintenance. Three types of sludge passed through fine screens to remove debris before further processing, raw primary sludge from the preliminary settling tanks, waste activated sludge from the final clarifiers, and the combination of raw and waste activated sludges pumped from the North Side plant. (MWRD photo 24625)

October 20, 1938. Installation of 96 rotary vacuum filters is nearing completion. Most of the water in sludge is extracted by rotary vacuum filters. A vacuum is maintained inside the drum, sludge is drawn onto the filter cloth from a trough on one side of the drum while the drum rotates slowly. By the time the drum rotates one-half turn, the sludge becomes a moist cake and is scraped off the filter cloth on the opposite side of the drum. (MWRD photo 24497)

November 16, 1938. The south elevation of the original pump and blower, and sludge disposal buildings. The south end of the pump and blower building is at left behind the coal and heat dried sludge elevator tower. A few years later, expansion of both buildings filled the space up to the elevator tower. (MWRD photo 24541)

This sign, erected at Cicero Avenue and Pershing Road, was a requirement of the Works Progress Administration to inform the public of the federal loan program to provide employment during and economic recovery after the Great Depression. Shown on July 2, 1936, it listed the major contractors and suppliers for construction of the Southwest plant. (MWRD photo 21520)

The main buildings of the West-Southwest plant as they appeared in 1970 looking southeast from the final settling tanks of battery C. The sludge disposal building with four smokestacks is behind the pump and blower building, and the coal and heat dried sludge conveyor slopes down to the right. Two smokestacks at left are part of the original building and the two at right came with the expansion of both buildings. (MWRD unnumbered photo)