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LIST OF TABLES

Table 1
Maximum Concentration of Various Site-Related Contaminants in Ore, Slag, and Gypsum at the Eastern Michaud Flats Contamination National Priorities List Site, Pocatello, Bannock County, Idaho

Table 2
Maximum Surface Soil Contamination Found at the FMC or J.R Simplot Facilities, Eastern Michaud Flats Contamination National Priorities List Site, Pocatello, Bannock County, Idaho

Table 3
Maximum Surface Soil Contamination Found Beyond the FMC or J.R. Simplot Facility Fence Lines, Eastern Michaud Flats Contamination National Priorities List Site, Pocatello, Bannock County, Idaho

LIST OF FIGURES

Appendix A, Figure 1
Location Map for the Eastern Michaud Flats Contamination National Priorities List Site, Pocatello, Bannock County, Idaho

Appendix A, Figure 2
Map Delineating Land Ownership near the FMC and J.R. Simplot Company Facilities, Eastern Michaud Flats Contamination National Priorities List Site, Pocatello, Bannock County, Idaho

Appendix A, Figure 3
Location Map of the Surface Soil Sampling Sites not at the FMC or J.R. Simplot Facilities, Eastern Michaud Flats Contamination National Priorities List Site, Pocatello, Bannock County, Idaho

PURPOSE

As recommended in the March 11, 1997, Site Review and Up-Date for the Eastern Michaud Flats Contamination National Priorities List (NPL) site (1), the Agency for Toxic Substances and Disease Registry (ATSDR) committed to reviewing recently released environmental data generated by the Remedial Investigation conducted at this site. The Remedial Investigation (2) provides most of the data and information needed by ATSDR to re-evaluate human exposure pathways associated with the Eastern Michaud Flats Contamination NPL site. ATSDR had previously evaluated the potential for human exposures to site-related contaminants in the 1990 Preliminary Public Health Assessment (3). Specifically, ATSDR will develop health consultations that address the potential for human exposures (past, present, and future) to site-related contaminants in the groundwater, surface water and sediment, surface soil, biota, and ambient air. This health consultation will evaluate the potential for human exposures to site-related contaminants in surface soils.

This health consultation will focus on characterizing the surface soil contamination at and off the two facilities that are a part of the Eastern Michaud Flats NPL site. It does not attempt to characterize any contamination that may exist inside the facility buildings or the exposures the workers may experience within those buildings. Exposures that may occur to workers inside the buildings are regulated by the Occupational Safety and Health Administration (OSHA) and can be evaluated, if so requested, by the National Institute of Occupational Safety and Health (NIOSH), Centers for Disease Control and Prevention (CDC).

In the past, the slag generated by the FMC process was used as road bedding and fill material (1). This slag has some associated radioactivity. To address concerns about the human health effects from exposure to radioactive slag, a technical workgroup (Phosphorus Slag Technical Working group -- members include EPA, ATSDR, other federal officials, state officials, local officials, the affected Tribes, citizens, and industry representatives) was formed. As an outcome of the group's recommendations, a study is presently underway to address this issue. Therefore, this health consultation will not discuss the possible health effects of contaminated slag.

BACKGROUND AND STATEMENT OF ISSUES

The Eastern Michaud Flats Contamination NPL site is located west of Pocatello, Idaho (1-3). Two manufacturing facilities, FMC Elemental Phosphorus Plant and Simplot Don Plant, are located on the NPL site (see Appendix A, Figure 1 for location map).

The FMC facility, FMC Elemental Phosphorus Plant, covers an estimated 1,189 acres and adjoins the western boundary of the Simplot Don Plant (2). Approximately 560 people are employed at the FMC Elemental Phosphorus Plant. Elemental phosphorus production at the facility has changed little since the plant operations began in 1949. Phosphate-bearing shale is shipped to FMC via the Union Pacific Railroad during the summer months. Ore cannot be shipped during the winter months because the ore tends to freeze in the rail cars. Therefore, the ore is stockpiled at the facility. Ore from the stockpiles is processed in four electric arc furnaces. The furnace reaction yields gaseous elemental phosphorus in addition to by-products, some of which contain radiological components. The elemental phosphorus is subsequently condensed to a liquid state and eventually shipped off-site. Approximately 1.5 million tons of ore are processed at the plant annually. The disposal of by-product waste material at and around the facility has resulted in slag piles covering large areas of land. In addition, air emissions (fugitive and direct discharges) from the facility have contributed to the environmental contamination associated with the Eastern Michaud Flats Contamination NPL site (1).

The Simplot Don Plant covers approximately 745 acres and adjoins the eastern property boundary of the FMC facility (2). Around 460 people work at the Simplot Don Plant. The plant began production of single superphosphate fertilizer in 1944. In 1954, the facility began producing phosphoric acid. The phosphoric acid is presently produced by using a wet (aqueous) process. Formerly phosphate ore was transported from the mines to the facility via rail. As of September 1991, the Simplot plant receives phosphate ore through a slurry pipeline. The phosphate ore slurry is processed at the Simplot Don Plant in phosphoric acid reactors and then further processed into a variety of solid and liquid fertilizers. The plant produces 12 principal products, including five grades of solid fertilizers and four grades of liquid fertilizers. The disposal of by-product waste material (e.g., gypsum) at and around the facility and air emissions (fugitive and direct discharges) from the facility have contributed to the environmental contamination associated with the Eastern Michaud Flats Contamination NPL site (1).

Neither facility is located near any large populations centers. The nearest residence is approximately one mile north of the facilities (1-3). The plant boundaries are fenced. Representatives of FMC and Simplot have told ATSDR that trespassers are rarely found on their facilities. In addition, the land directly across US 30 from the plants is predominantly owned by either FMC or Simplot (see Appendix A, Figure 2). Deed restrictions to prevent future residential development have or will be placed on the properties across from the plants. Currently some of the land across US 30 is used for a drag racing strip (the old airport runaway) and for a softball/baseball field (on Simplot property).

During the Remedial Investigation (RI) for this NPL site, an extensive surface soil sampling and analysis program was undertaken (2). Composite samples of the raw materials and major waste products were taken. Surface soil samples were taken at various locations throughout the facilities. In addition, surface soil samples were taken off the facility properties (16 equally spaced transects with samples collected at regular intervals within a three mile radius). Supplemental samples of surface soil north of the facilities were also collected.

Tables 1, 2, and 3 present the maximum results of the RI. As indicated in Appendix B, comparing the maximum results of the surface soil sampling and analysis program to comparison values is conducted to select contaminants for further evaluation.

The highest surface soil contamination was found at the two plants. The highest surface soil contamination found beyond the FMC or Simplot facility fence lines was on the land directly across US 30 from the plants (the land is presently owned by either FMC or Simplot) (2). The pattern of surface soil contamination found beyond the FMC or Simplot facility fence lines is coincident with the prevailing wind patterns (i.e., the highest contamination was found northeast and northwest of the facilities). In addition, the surface soil contamination decreases with distance from the facilities (2). Analytical results of samples taken from residential areas are either at or below background levels or comparison values (i.e., there is no site-related contamination at levels of health concern within residential areas).

Since the RI, FMC and Simplot have taken actions to limit human exposures to site-related surface soil contaminants. Roads at the FMC facility have been paved and specific areas have been capped to prevent both direct contact and fugitive emissions releases. In addition, deed restrictions to prevent future residential development have or will be placed on the properties across from the plants.



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