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LIST OF TABLES

Table 1
Maximum Site-Related Shallow Groundwater Contamination
Found at the FMC or Simplot Facilities and in the Old Pilot House Cafe
Well and the Frontier Well, Eastern Michaud Flats Contamination National
Priorities List Site, Pocatello, Bannock County, Idaho

Table 2
Maximum Site-Related Contaminant Concentrations Found in the
Batiste and Swanson Road Springs, 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 the Locations of the Monitoring
Wells, the Drinking Water Wells, the Production Wells, and Springs at and
near the 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 groundwater.

BACKGROUND AND STATEMENT OF ISSUES

The Eastern Michaud Flats Contamination NPL site is located west of Pocatello, Idaho (1-3). Two manufacturing facilities, FMC Corporation and J.R. Simplot Company, 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). 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.

The Simplot Don Plant covers approximately 745 acres and adjoins the eastern property boundary of the FMC facility (2). 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 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.

Since 1972, the State of Idaho, the U.S. Geological Survey, the U.S. Environmental Protection Agency (EPA), and the owners of the two facilities have conducted various investigations at and around the two facilities that make up the Eastern Michaud Flats Contamination NPL site (2,4). The results of these investigations indicated that the activities at the two facilities have resulted in the contamination of the surrounding environment. Because of the environmental contamination and the potential for human exposure to the contaminants, the EPA placed the site on the NPL.

Based upon the various investigations, it has been determined that there are two separate aquifers (shallow and deeper) underlying the Eastern Michaud Flats Contamination NPL site (2). The shallow aquifer is a 10 to 20-feet thick gravel and sand aquifer that is locally overlain by a silt aquitard. The deeper aquifer is the gravel unit of the Sunbeam Formation and the underlying basalt and rhyolite. These two aquifers are separated by an aquitard, American Falls Lake Beds.

Analysis of groundwater samples taken from the deeper aquifer indicate that no site-related contamination has entered the deeper aquifer at levels of health concern (2). However, analysis of groundwater samples taken from the shallow aquifer indicate that the activities at the two facilities have resulted in significant contamination of the shallow aquifer (2). Table 1 presents the maximum results of the shallow groundwater contamination investigation. Only those contaminants found above comparison values are presented in Table 1 (see Appendix B for an explanation of the comparison values and their purpose). As indicated in Appendix B, comparing the maximum results of the groundwater sampling and analysis program to comparison values is conducted to select contaminants for further evaluation.

Under the two facilities, the groundwater within the shallow aquifer tends to flow towards the Batiste Spring, the Swanson Road Spring, and the Portneuf River (2). The Batiste and Swanson Road Springs are major discharge points of the shallow groundwater that flows under the two facilities. It is there that the shallow groundwater discharges to the Portneuf River (via the Batiste ans Swanson springs and direct groundwater migration through the river bed). The location of the springs is delineated on Appendix A, Figure 2.

Table 2 presents the maximum analytical results for samples taken from the Batiste and Swanson Road springs. As indicated in Appendix B, comparing the maximum results of the groundwater sampling and analysis program to comparison values is conducted to select contaminants for further evaluation. These springs could have been impacted by the groundwater contamination that originates from the Eastern Michaud Flats Contamination NPL site (2).

In the past, water withdrawn from the Batiste Spring was used by the Union Pacific Railroad as process water and drinking water for the railroad workers and 30 residences of Pocatello (3). Presently, the spring is not being used by the Union Pacific Railroad. In the future, the Simplot Don plant is planning to withdraw water from the Batiste Spring and use the water in its manufacturing processes (non-drinking water). Analytical results of samples taken from the Batiste Spring indicate that only arsenic and nitrate/nitrites have been detected above comparison values. (Note: The maximum concentrations of radium-226 and radium-228 detected in the Batiste Spring were found in different samples. The summation of radium-226 and Radium-228 for any one sample never exceeded the comparison value.)

The Swanson Road Spring has never been used as a drinking water source for human consumption. Analytical results of samples taken from the Swanson Road Spring indicate only arsenic has been detected above comparison values.

The Meadow Gold Dairy, located just north of Batiste Spring (near the Rowlands well shown on (Appendix A, Figure 2), bottles water which is sold in local grocery stores (Tenton Spring Water). The Dairy obtains the water from a spring located within the Dairy building. This spring is not the Batiste Spring. However, a majority of water for this spring probably comes from the shallow aquifer. Analytical results of groundwater samples taken from the monitoring wells (524 and 525) between Batiste Spring and the Dairy indicate that no site-related contaminants have moved towards the Dairy Spring (2). In addition, recent analytical results of a sample taken from the spring located within the Dairy building did not find any site-related contaminants (5). However, it may be possible for site-related contaminants to move towards this spring in the future if no remedial actions are taken (e.g., pumping and treatment of the groundwater contamination before it reaches this spring).

There are several drinking water wells located on the properties currently owned by FMC or Simplot or near the Eastern Michaud Flats NPL site (2,3,4). Of these wells, only the Old Pilot House Cafe well and the Frontier well have been contaminated with site-related contaminants. All of the other drinking water wells (i.e., Williamsen well, Lindley well, Tank Farm well, Rowlands well, Indian Springs Trout Farm well, or Idaho Power well) at or near the Eastern Michaud Flats Contamination NPL site are not contaminated with any site-related metals, nutrients, or radiological parameters above comparison levels.

Analytical results of samples taken from the Old Pilot House Cafe well indicate that this well is contaminated with site-related metals (i.e., arsenic and boron), nutrients (i.e., nitrates), and radiological parameters (i.e., gross alpha and gross beta) at levels above comparison levels (2,4). Analysis of samples taken by the State of Idaho indicate that arsenic contamination in the Old Pilot House Cafe well was present above comparison values as early as 1972. This well obtained water from the shallow aquifer. From the early 1950's to 1976, the Old Pilot House Cafe well was the only source of drinking water for the Pilot House Cafe. In 1976, this well was replaced with a well that withdraws water from the deeper aquifer. Analytical results of samples taken from the New Pilot House Cafe well demonstrate that this well is not contaminated. In the spring of 1994, the Pilot Cafe moved to a different location in Pocatello.

Prior to the late 1980's, drinking water for the Frontier Building (Research and Development Department for the Simplot Company) and the Simplot softball/baseball field was obtained from the Frontier Well (6). It is believed that the well was constructed in 1943. Analysis of samples taken by the State of Idaho indicate that arsenic contamination was present above comparison values as early as 1972. Since the late 1980's, the well was removed from service and clean drinking water has been provided to the Frontier Building (e.g., bottled water).

FMC and Simplot currently own all of the land that overlays the area of groundwater contamination. Deed restrictions have either been placed or will be placed upon this land so that the contaminated shallow aquifer will not be used as a drinking water source.

 

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