For a time line, go to Contamination and Chronology.

St. Louis Downtown Site (SLDS) 

In 1942 during World War II, the Manhattan Engineer District (MED) achieved the first self-sustained nuclear chain reaction at Stagg Field at the University of Chicago, using uranium oxide produced by the Destrehan Street Refinery and Metal Plant (later Mallinckrodt Chemical Works) in downtown St. Louis.

Following the success of the Stagg Field experiment, MED contracted with Mallinckrodt to process uranium. Under this contract, uranium and radium were extracted from ore and used to make the first atomic bombs. Years later, this facility became known as the St. Louis Downtown Site (SLDS).

From 1942 to 1957, under contracts with the Manhattan Engineer District (MED) and the Atomic Energy Commission (AEC), the site was used for processing various forms of uranium compounds, for machining and for recovery of uranium metal.

In 1946, the manufacture of uranium dioxide from pitchblende (the essential ore of uranium) began at a newly constructed plant.

At the time of the MED/AEC operations, the plants were owned by Mallinckrodt and/or leased by AEC. Certain buildings in those plants were also constructed for and owned by AEC. From 1942 through 1945, uranium processing was conducted at Plants 1, 2 and 4. In 1945, operations at Plant 2 were terminated. Some uranium metallurgical research continued at Plant 4 through 1956. From 1945 to 1957, uranium concentrate or ore was processed in buildings at Destrehan Street (Plants 6, 6E and 7). All uranium-extraction operations at the Destrehan Street location ceased in 1957. 

St. Louis Airport Site (SLAPS) 

In 1946, the Manhattan Engineer District (MED) acquired the 21.7-acre tract of land now known as the St. Louis Airport Site (SLAPS) to store residues from uranium processing at the Mallinckrodt facility in St. Louis. 

The uranium processing, conducted under a contract with MED/AEC (Atomic Energy Commission), continued through 1957; the resulting radioactive residues accumulated at SLAPS. These materials included pitchblende raffinate residues, radium-bearing residues, barium-sulfate cake, Colorado raffinate residues, and contaminated scrap. Some of the residues were stored in bulk on open ground. Others were stored in drums that were stacked across the site. Some contaminated materials and scrap iron were buried at the western end and in other parts of the property. To limit direct radiation exposure of the public, the property was fenced to prevent casual entry.

In 1966 and 1967, most of the stored residues were sold to a private entity for recycling and were removed from SLAPS. On-site structures were razed, buried on the property and covered with 1 to 3 feet of clean fill material. Although these activities reduced the surface dose rate to levels acceptable at the time, buried deposits of uranium-238, radium-226 and thorium-230 remained on the property. 

Madison Site 

During the late 1950s and early 1960s, Dow Chemical Company, a division of Dow Metal Products, in Madison, Illinois, operated as a uranium-extrusion and rod-straightening facility, working with Mallinckrodt Chemical to support Atomic Energy Commission (AEC) needs.

Latty Avenue Properties 

In early 1966, ore residues and uranium- and radium-bearing process wastes that had been stored at SLAPS were purchased by the Continental Mining and Milling Company and moved to a storage site on Latty Avenue. 

These wastes were generated at the Mallinckrodt plant in St. Louis from 1942 through the late 1950s under contracts with the Manhattan Engineer District and the Atomic Energy Commission (MED/AEC). Residues on the property at that time included 74,000 tons of Belgian Congo pitchblende raffinate containing approximately 13 tons of uranium; 32,500 tons of Colorado raffinate containing roughly 48 tons of uranium; and 8,700 tons of leached barium sulfate containing about 7 tons of uranium. 

The Commercial Discount Corporation of Chicago, Illinois, purchased the residues in January 1967. Much of the material was then dried and shipped to Cañon (pronounced "Canyon") City, Colorado. The material remaining at the Latty Avenue storage site was sold to Cotter Corporation in December 1969. From August through November 1970, Cotter Corporation dried some of the remaining residues and shipped them to its mill in Cañon City. In December 1970, an estimated 10,000 tons of Colorado raffinate and 8,700 tons of leached barium sulfate remained at the Latty Avenue properties. 

St. Louis Airport Site Vicinity Properties (SLAPS VPs) 

Low-level radioactive contamination at St. Louis Airport Site vicinity properties (SLAPS VPs) is linked to both SLAPS and the Latty Avenue Properties. 

In 1966, Continental Mining and Milling Company of Chicago purchased uranium-bearing residues from the Manhattan Engineer District (MED) and removed them from SLAPS. 

The company placed the residues in storage at Latty Avenue under an Atomic Energy Commission (AEC) license. Over time, residues migrated from other sites or were deposited as the residues were hauled along transportation routes, contaminating the soils and sediments of the vicinity properties.