Kenneth Albin
Bechtel National, Inc.

Several sites in the St. Louis area are being remediated under the Formerly Utilized Sites Remedial Action Program (FUSRAP). Residual radioactive contamination at these properties originated from uranium processing at the Mallinckrodt facility in downtown St. Louis in the 1940s and 1950s and subsequent transportation and storage of process residues at two sites near the airport (the St. Louis Airport Site and the Hazelwood Interim Storage Site on Latty Avenue) in northern St. Louis County. Cleanup progress at FUSRAP sites in the St. Louis District between 1996 and 1997 included demolition of 13 buildings at the St. Louis Downtown Site (Mallinckrodt) and cleanup of several vicinity properties in the airport area. These activities were conducted before October 1997, under the purview of the U.S. Department of Energy. Plans for 1998 include continuing building remediation at the downtown site, cleanup of additional vicinity properties in the airport area, and removal of contaminated soil from the western side of the St. Louis Airport Site near Coldwater Creek. Topics highlighted by this progress report include (1) demolition of Buildings 116, 117, and 704-707 at the downtown site, including asbestos removal and special handling of undefined chemical and radioactive vials stored in the buildings; (2) demolition of the 50-series buildings at the St. Louis Downtown Site and actions taken to mitigate the threat of an uncontrolled collapse of the building; (3) continued progress in the cleanup of thorium-230 contamination at airport area vicinity properties; (4) initial phases of final cleanup at the St. Louis Airport Site near Coldwater Creek; (5) extensive community relations efforts to encourage community involvement in remedy selection and determination of cleanup sequencing priorities; and (6) site safety performance.

Several sites in the St. Louis District are being remediated under the Formerly Utilized Sites Remedial Action Program (FUSRAP). Residual radioactive contamination at these properties originated from uranium processing at the Mallinckrodt Chemical Works facility in downtown St. Louis in the 1940s and 1950s in support of World War II and later cold war activities. The contamination left from these activities was widespread but at relatively low concentrations. Waste products were subsequently transported and stored at two sites (the St. Louis Airport Site and the Hazelwood Interim Storage Site on Latty Avenue) near the present Lambert-St. Louis International Airport in northern St. Louis County. These sites are being managed under FUSRAP, formerly a U.S. Department of Energy program that is now administered by the U.S. Army Corps of Engineers. Significant cleanup activities have occurred during the past 2 calendar years; this paper recounts the successes achieved at the St. Louis Downtown Site (SLDS), St. Louis Airport Vicinity Properties, and the St. Louis Airport Site (SLAPS).

The first phase in the cleanup of SLDS involved the demolition of masonry and steel-framed structures within the Mallinckrodt Chemical Plant, noted as Building 50 Series and Plant 6/7 in Figure 1. Before demolition began, all asbestos-containing materials were removed from the buildings and shipped for offsite disposal. In addition, 1,250 small-volume vials were safely sorted in a room of one of the buildings scheduled for demolition; the contents of the vials were stabilized and disposed of offsite.

The Building 50 Series demolition required careful planning because these structures were completely surrounded by operating chemical and pharmaceutical plants. Traditional implosive or Awrecking ball@ techniques were not acceptable because significant dust suppression measures needed to be employed. Therefore, the structures were surrounded by a plastic curtain wall with a plastic tent-like structure above, and significant water misting was used during the demolition to mitigate any fugitive dust. However, during the early stages of the demolition, a latent defect in an interior load-bearing wall was detected. This forced the demolition team into an around-the-clock scenario to prevent instantaneous collapse and significant impact on the surrounding operating plants. In just 2 days, the buildings were safely razed without any worker exposure or airborne release. During summer 1997, 10 more structures were demolished in the Plant 6/7 area using conventional demolition techniques, as shown in Figure 2.

During fiscal year 1995, an entire city block (Plant 10) was remediated by demolishing several warehouse structures and excavating more than 10,640 cubic meters of subsurface soils affected by uranium (see Figure 2). After the cleanup, the area was restored and used as a plant personnel parking lot. Additionally, a portion of the Mississippi Riverfront was remediated to allow completion of a bicycle trail that parallels the Mississippi River and stretches from North St. Louis County to the Gateway Arch in downtown St. Louis (see Figure 1). This cleanup was also significant because it implemented a dose-based risk assessment to allow low levels of subsurface contamination to remain in place based on the intended future use of the property for recreational activities.

The St. Louis Airport Vicinity Properties (see Figure 3) presented special challenges for the cleanup. The thorium-230 contamination along secondary roadways in North County was contained in the first few meters of soil and at the same depth and location as gas, water, and telephone utilities supporting the light industrial development in the area. Magnetic and inductive current cable detectors were used to identify the locations of these utilities more precisely than the "Missouri One Call" service could do. Once the surface expressions of the utilities were identified, hand digging was used to verify the routing and depths of these lines. Through these efforts, more than 11,400 cubic meters of radioactively contaminated soils was successfully excavated from 26 vicinity properties along 4.8 kilometers of roadway (see Figure 4) and shipped to a licensed, out-of-state disposal facility.

SLAPS (see Figure 3) contains the highest concentrations of radionuclide-contaminated soils in St. Louis and is located near an ecologically sensitive area, Coldwater Creek. The initial cleanup began along the western end, abutting the Creek, and involved construction of extensive run-on and runoff controls to prevent contaminated soils from being eroded and washed into the creek and to prevent the surface drainage at the site from recontaminating the area after excavation (see Figure 4). In addition, low-permeability clayey soils were used as backfill to provide a barrier to horizontal and vertical subsurface migration of contamination after the western end excavation was completed.

Stakeholder involvement has been an important element in the success of cleanup activities at the St. Louis site. In August 1994, representatives of affected property owners, local, county, and city officials, and utility companies joined with federal and state regulatory agency staff (ex officio members) to form the St. Louis Site Remediation Task Force. The Task Force completed its mission in September 1996 by publishing a report of its conclusions and recommendation for future cleanup activities. Since then, the St. Louis FUSRAP Oversight Committee was formed and continues to provide valuable feedback and support for current and future cleanup plans.

Finally, through fiscal year 1997, work at the St. Louis Site has progressed more than 1,000 days without a lost time accident, OSHA recordable accident, or injury requiring a doctor's visit. During this period, 26 North County vicinity properties have been cleaned up, 14 masonry and steel-framed multistory buildings have been demolished, a St. Louis downtown city block has been restored, the North Riverfront bicycle trail has been remediated, 1,250 small-volume vials and bottles have been safely sorted (and the contents stabilized and transported offsite), and more than 26,600 cubic meters of radioactively contaminated soils has been safely packaged, transported, and disposed of at a licensed, out-of-state disposal facility.

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