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1. ATSDR > Public Health Assessments & Consultations

PUBLIC HEALTH ASSESSMENT

KENNECOTT (NORTH ZONE)
MAGNA, SALT LAKE COUNTY, UTAH

APPENDICES

Appendix A -- Site Maps

LIST OF FIGURES

Figure
Number      Title

1         Vicinity Map
2         Magna Area
3         Tooele Valley Area

Figure 1. Vicinity Map


Figure 2. Magna Area


Figure 3. Tooele Valley Area

Appendix B -- Operable Units, Demographics, Land and Natural Resource Uses

Operable Units

OU-8 Wastewater Treatment Plant Sludge Ponds (22,23,24)

EPA reports this operable unit includes the wastewater treatment plant and four associated sludge ponds and any areas impacted by the sludge ponds. The facilities are on Kennecott property. Most pond segments are unlined; three of the four ponds have reached capacity and are out of service. The treatment plant is slated to terminate operation soon. The treatment plant, which is north of the Kennecott refinery, is on the northeast corner of the intersection of State Highways 201 (2100 South Street) and 202. Treated effluent is piped to the Magna Tailings Pond. ATSDR observed that plant components are fully fenced. Two sludge ponds are north and east of the highway intersection and lie between the highways and the Magna Tailings Pond. The other two ponds lie west of State Route 202 and south of Interstate 80. ATSDR's observations indicate the potential for trespass to the plant and pond areas is small because of the fence system, terrain features, and remoteness. The sludge will be permanently disposed in a lined repository, and the waste water treatment plant will become obsolete with completion of the new smelter. ATSDR observed that the nearest residence(s) are to the west about ¾ miles away in the community of Lake Point, in Tooele County, and about 2½ miles to the east, in Magna. The shore of Great Salt Lake and the Great Salt Lake visitor center are north of Interstate 80, about ½ mile north of the nearest pond.

OU-9 Magna Soils

Magna is an unincorporated community of nearly 18,000 residents located principally south of State Route 201 (2100 South Street) and immediately east of Kennecott's production area (Figure 2). Discussions with citizens indicate that the community has experienced wind-driven particulates from the Magna Tailings Pond on the north side of Route 20l. A resident reported that wind-driven tailings particles sometimes were quite noticeable while Kennecott was not operating in the mid 1980s. Data (described elsewhere) also indicate that releases (gaseous and particulate) from the facility's smelter, and probably other process facilities, have impacted the area. Transported particles deposited in the community and became a component of surface soils.

OU-13 Facility Smelter and Acid Plant (24,25,26,27)

The smelter, acid plant, and related process facilities are on the lower slope of the Oquirrh Mountain range, immediately south of State Route 201 . EPA has included several waste storage and disposal areas and rail and truck maintenance facilities in the operable unit. All of the operable unit facilities are on Kennecott property. The largest of the waste areas appears to be a slag pile (approximately 175 acres) and adjacent ponds that lie in an area bounded by State Route 201 (on the south) and Interstate 80 (on the north). The slag is being recovered for construction purposes. A dike and Interstate 80 separate the ponds from Great Salt Lake. Pond sediments will be cleaned up after storm water management modernization is completed. The process area is contained behind a fence along State Route 201; at the east end of the process area, the fence extends southward from Route 201 along the Magna boundary. ATSDR's observations indicate the potential for trespass to the process and waste areas is small because of the extensive fence system, guard gates, terrain features, and remoteness. Some contaminated soils and wastes have been removed from the smelter/acid plant area; a contaminated plume underlying a portion of the property also is being remediated. Releases occur to air primarily from the smelter stack. Potential also exists for releases from the slag pile and ponds to groundwater. The smelter stack is about 2½ miles east of the Lake Point community in Tooele County, about 5 miles west of Magna, and ½ mile south of Great Salt Lake, the County Boat Harbor, and Silver Sands Beach.

Facilities, fuels, and operations have changed substantively since smelting began in 1905. Kennecott bought the smelter in 1959 and have since modified and improved major components. A major refit in 1978 modified the gas handling equipment to capture fugitive emissions, constructed a 1,200 foot stack, installed a computerized emission control system, and provided additional acid plants to increase sulfur capture. Slag now is being processed for copper recovery in a slag concentrator. The tailings from the slag concentrator are deposited in the Magna Tailings Pond. New smelter and acid plant systems now under construction are expected to further reduce releases to the environment. Contaminated soil encountered within the smelter construction area has been removed.

OU-14 Refinery (24,26,28)

The refinery operable unit includes the refinery, a former waste evaporation pond, and an underlying contaminated groundwater plume. The facilities are on Kennecott property south of State Route 201 and are contained behind the process area fence. The refinery is about 4½ miles east of the Lake Point Community, about 2½ miles west of the nearest Magna residences, and 1¾ miles south of Great Salt Lake. ATSDR observations indicate that trespass potential to the area is small because of the extensive fence system, guard gates, terrain features, and remoteness. The refinery was completed in 1950 and has since been modified and expanded. Process wastewater is pumped to the wastewater treatment plant (OU-8). The former evaporation pond, which operated in the 1950s and 1960s, is unlined and is the suspected source of underlying groundwater contamination. Additional discharges of spent solutions occurred as seepage through the basement floor of the refinery. Contaminated residues have been removed as part of ongoing operations or refinery modernization. Contaminated soils have been identified and either removed, contained, or controlled. ATSDR was told that Kennecott plans to remove the sediments from the pond area. Kennecott's process modifications, component replacements, and new construction are expected to deter future releases.

OU-15 Magna Tailings Pond (24,26,28)

The Magna Tailings Pond operable unit includes the pond, a landfill within the pond, the tailings slurry pipeline, the C-7 Ditch (discharges to Great Salt Lake at a remote section of Great Salt Lake Park), and the Diving Board Tailings. The facilities are wholly on Kennecott property, except for a short segment of the C-7 ditch between Interstate 80 and the lake. ATSDR observations indicate that trespass potential to Kennecott property in these areas is small because of the extensive fence system, terrain features, and remoteness.

The pond was about 2 square miles in area in 1907 and has been enlarged several times. It presently is about 170 feet high and covers about 5,700 acres; Kennecott reports they have plans for near-term expansion toward the north. The impoundment receives tailings in a slurry from several Kennecott facilities including the Copperton Concentrator, Magna Concentrator and the Slag Concentrator. It also receives fly ash from the Kennecott power plant and liquid effluent from their wastewater treatment plant. Kennecott reports the transportation routes for these materials are located totally within Kennecott property, except where the slurry pipeline crosses State Route 201. Some severe episodes of wind-blown dust from the pond has been reported by Magna residents--especially in the mid 1980s when operations were suspended. Elevated metals concentrations also have been documented in downwind air samples. An EPA document says that metals detected in shallow- and medium-depth monitoring wells located north and east of the pond suggest a release to groundwater also has occurred. Multiple measures have been implemented to counter dust and slope erosion, including sprinklers, chemical and mulch stabilization products, wind fencing, and vegetative cover. The State now requires Kennecott to keep 90 percent of the tailings pond wet at all times. This has been accomplished by constructing a tailings manifold system that allows tailings slurry to be discharged from many points on the pond perimeter. Aerial photos are taken frequently to confirm that the state's requirements are being met. The tailings slurry pipeline, which has experienced a few ruptures, is in the process of being lined with rubber. Kennecott also has initiated measures to increase dike stability near Magna; measures include slope flattening and internal slope dewatering.

Ponded water is removed from the facility via a combination of evaporation, recycling, and discharge to the C-7 Ditch which partially bounds the pond. The C-7 ditch discharges to Great Salt Lake at a remote section of Great Salt Lake Park between the visitor center and Saltaire Beach.

Various demolition debris have been placed in the impoundment landfill, which is located on the western side of the pond. The full nature of those wastes is not known. In 1992, landfill cover material found to contain high lead concentrations was removed and deposited at the USPCI.

ATSDR observed that the closest single residence is about ¼ mile east of the pond; the nearest subdivision is about ¼ mile to the southeast. The community park and golf course, on the south side of State Route 201, is a few hundred feet away.

The Diving Board Tailings consists of 8-acre and 13-acre impoundments located along the south side of State Highway 201 within the fenced process area. One impoundment is within a few hundred feet of the Magna Golf Course property. Kennecott reports they are completing relocating the tailings to the Magna Tailings Pond. The company then plans to use the area to capture localized storm water runoff. A earthen basin will be used to retain anticipated process tailings discharges and recycle them to the Magna Tailings Pond.

OU-19 Fallout in Tooele Valley

This operable unit pertains to airborne releases from the facility's smelter stack that may affect communities in Tooele Valley (Figure 3). The nearest community Lake Point, is about 2½ miles west of the facility's smelter stack, and several others (Stansbury Park, Erda, Tooele City, Grantsville) are within 15 miles in a southwesterly direction.

Demographics, Land Use, and Natural Resources Use

Magna

Magna is an unincorporated community of approximately 17,800 population, according to the 1990 census (10); the approximate boundaries ATSDR inferred from census data are shown on Figure 2 in relation to other area features and West Valley City. Ninety four percent of the population is of the white race.

Our staff's observations indicate that essentially all of the population resides south of State Route 201, which is 2400 South (Street). The residents closest to Kennecott's production facilities live along 9200 West Street, which is adjacent to the company boundary fence. Several elementary and other schools are in the community. The nearest, a former elementary school that was recently closed due to requirements for complying with the Americans with Disabilities Act and seismic upgrades, is on the west edge of town adjoining the Kennecott property boundary. The next closest school is several blocks east of Kennecott's property. ATSDR observed that the nearest residents to Kennecott's large tailings pond north of Route 201 (Figure 2) are a single family (about 1,500 feet east of the pond rim) on 8000 West. The next nearest residents are a similar distance from the pond in a subdivision south of Route 201 and immediately west of 8000 West. A community golf course and recreational park (Figure 2) lie on the south side of Route 201, within several hundred feet of the pond. No nursing homes or hospitals are reported in the community.

A water company official reports that the Magna community obtains its public water supply from two well fields located about 1 to 3 miles east of the tailings pond. A few residences, less than 10, are not connected to the system and, instead, rely on private wells.

The Utah and Salt Lake Canal crosses the southern part of the community and carries water drawn from the Jordan River for irrigation and other nonculinary uses. Kennecott staff report that rainfall runoff in the process areas is collected and recycled to the greatest practical extent. Runoff from the tailings pond slopes collects either in the C-7 Ditch (and discharges to Great Salt Lake) or in the pond return canal (and is recycled via production facilities).

Tooele Valley

Tooele Valley extends south and west of Great Salt Lake between the Stansbury Mountains (on west) and Oquirrh Mountains (on east) (Figure 3). The mountains rise a few thousand feet above the valley floor.

Several communities in Tooele Valley comprise almost 80 percent of the entire county population. The principal population centers are Tooele (population 13,887) and Grantsville (population 4,500), which are located about 13 and 15 miles, respectively, from the facility's smelter. Communities nearest that smelter include Erda (population 1,113), Stansbury Park (population 1,049), and Lake Point (estimated population 400). Those communities are about 9, 6, and 2½ miles from the facility's smelter. The city of Tooele is about 2 miles southwest of the former International smelter. More than 93 percent of the population is of the white race (10). ATSDR learned from the county planning department that there is one nursing home in the county, in Tooele. A county school representative said there are elementary schools in Stansbury Park, Grantsville, and Tooele, a middle school in Grantsville, and a junior high and high school in Tooele. Kennecott staff report that some mining and milling have been conducted on the west slopes of the Oquirrh Mountains, principally east and southeast of Tooele. The small community of Lincoln (population about 100 (10)) is a short distance northwest of that former International smelter location (Figure 3). The Tooele Army Depot (Figure 3), immediately west of the town, advised ATSDR that they employ about 1,400 persons.

ATSDR learned from the Tooele County engineering department that everyone in the valley relies on groundwater as a drinking water source. Tooele has a public water system, but outlying areas use private wells. Grantsville also has a public water system. Two subdivisions in Erda are connected to a public system; the remainder of the residents are on private wells. Everyone residing within the Stansbury Park Water Improvement District is required to be connected to that municipal water system. In Lake Point, everyone relies on private wells for their water supply. Stansbury Park provides water to Great Lake State Park and other facilities along the lake shore.

Great Salt Lake Park Vicinity

Great Salt Lake Park, which lies to the north of the Kennecott facilities and Interstate 80, occupies about 3½ miles of shoreline, according to park officials. The park extends from about Saltaire Beach on the east to about Sunset Beach on the west (Figure 3). The county boat harbor has a capacity of about 300 craft. ATSDR was told by park officials that there were 676,000 visitors in 1994, of which only about 10 percent enter the water. Potable water at the park is supplied by the Stansbury Water Improvement District located to the southwest in Tooele County.

Appendix C -- Description of Evaluation Process

Selection of Contaminants for Public Health Significance Evaluation

ATSDR reviews contaminant data and selects those that warrant subsequent further evaluation for public health significance.

Contaminant selection considers the following factors:

1. Concentrations of contaminants in media.
   
   
2. Sample locations, field data quality, and laboratory data quality.
   
   
3. Relationship of concentrations to ATSDR's public health assessment comparison values; also, the unavailability of suitable comparison values.
   
   
4. Community health concerns.

Identification and selection of these contaminants does not imply that human exposure does occur or that exposure would actually result in adverse health effects. The contaminants selected for further evaluation and the media in which sampling shows they have occurred are summarized in the data tables in Appendix E. The data tables also identify specific public health assessment comparison values ATSDR considered in the selection process. An Environmental Media Evaluation Guide (EMEG) is an estimated comparison concentration that is based on information determined by ATSDR from its toxicological profiles for a specific chemical. Reference Dose Media Evaluation Guide (RMEG) comparison concentrations are based on EPA's estimates of the daily exposure to a contaminant that is unlikely to cause adverse health effects. An Action Level (AL) is an EPA regulatory concentration that, if exceeded in a public water system, requires the system operators to initiate specified response actions. A Cancer Risk Evaluation Guide (CREG) is a comparison concentration that is based on an excess cancer rate of one in a million persons and is calculated using EPA's cancer slope factors. The Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH) standards for air in the workplace have been divided by 400 to develop a conservative comparison value for community exposure. Ambient Air Quality Standard (NAAQS) was also selected as a comparison value. An estimated (Est.) comparison value is based on ATSDR staff review of toxicologic data for a contaminant.

ATSDR also reviewed the EPA Toxic Chemical Release Inventory (TRI) for 1992 to learn whether that database would disclose any supplemental information about contaminant releases in the area. The database confirmed Kennecott's reported releases of metals and sulfuric acid to air. Examination of the database also showed that an industry about two miles south of Magna reported substantial releases of organic chemicals to air (29). Staff at the UDEQ Air Monitoring Center say they are not aware of any ambient air organic chemical sampling data for the site vicinity.

Identification of Exposure Pathways

ATSDR identifies human exposure pathways by examining environmental and human components that might lead to contact with contaminants of concern. A pathway analysis considers five elements: a source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure, and an exposed population. Completed exposure pathways are those for which the five elements are evident, indicating that exposure to a contaminant has occurred in the past, is currently occurring, or will occur in the future. ATSDR regards people who come in contact with contamination as exposed; for example, people who reside in an area with contaminants in air, or who drink water known to be contaminated, or who work or play in contaminated soil are considered exposed. Potential exposure pathways are those for which exposure seems possible, but one or more of the elements is not clearly defined. Potential pathways indicate that exposure to a contaminant could have occurred in the past, could be occurring now, or could occur in the future.

Only exposure situations associated with completed pathways are discussed in this assessment; evaluations did not disclose any potential pathways likely to be of public health significance. Key exposure pathway information is summarized in tables beginning on page 49 of Appendix E.

Determination of Public Health Implications

Determining the public health implications of a site is a two-track process: a toxicological evaluation, and, where appropriate, health outcome data evaluation.

Toxicological Evaluation

Public health implications decisions made in the public health assessment process primarily are based on toxicological evaluations that compare exposure dose (i.e., the amount of a substance individuals in an exposure pathway are exposed to daily) to an appropriate health guideline. If the contaminant being evaluated is a carcinogen, the risk from exposure to that carcinogen is determined. The methodology for calculating exposure doses and cancer risk is described in Appendix F.

Health Outcome Data Evaluation

Health outcome data can provide information on the occurrence of cancer, birth defects, or other diseases or conditions; or the results of testing for the contaminants of concern in humans. Health outcome data are evaluated if it is biologically plausible for a health outcome to occur or if the community is concerned about specific health outcomes; and if the appropriate data can be identified to evaluate a health outcome. For biological plausibility, the decision to evaluate health outcome data depends on whether a completed exposure pathway exists for a chemical suspected of causing the health outcome of concern (30). The selection of a noncarcinogenic health outcome is based on a review of the toxicologic literature for that contaminant of concern.

Appendix D -- Evaluation of Drinking Water Pathway

Analysis of Groundwater/Drinking Water Pathway

Public drinking water supplies in the Kennecott--North Zone area do not appear to be affected by past or present Kennecott operations. The water quality reports for the public water supply wells do not indicate any contaminant concentrations that would lead to adverse health effects. The water quality of public drinking water supplies is closely monitored by both the water utilities and the Utah Department of Environmental Quality. If conditions change, the department will be able to note such changes and take appropriate actions.

As in the case of public water supply wells, most private drinking water wells draw water from zones deeper than 100 feet. These wells are not likely to be affected by Kennecott operations. Water below 100 feet is at a higher pressure than water near the surface. This higher pressure prevents either natural or man-induced contaminants from leaking downward into the drinking water aquifer. High concentrations of natural salts in the shallow aquifer usually eliminates the shallow zone as source of drinking water.

Appendix E -- Contaminant and Pathways Tables

LIST OF TABLES

Table Number

Title

Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9A. Table 9B. Table 10A. Table10B. Table 11. Table 12. Table 13. Table 14A. Table 14B Table 15. Table 16. Table 17. Table 18.

Identification of Exposure Situations (in text) Air Exposure Situations (in text) Contaminants of Concern for Magna Air Exposure Situation (in text) Contaminants of Concern for Great Salt Lake Air exposure Situation (in text) Exposure to Soil Contaminants (in text) Contaminants of Concern for Magna Soil Exposure Situation (in text) Exposure to Contaminants in Surface Water (in text) Contaminants of Concern for Great Salt Lake Park Surface Water Exposure Situation (in text) Magna Operable Unit---On-Site Data 10, Sulfur Dioxide Magna Operable Unit---On-Site Data Air Quality---Metals Vicinity of Great Salt Lake Park---Off-Site Data Air Quality---PM10 Vicinity of Great Salt Lake Park---Off-Site Data Air Quality---Metals Tooele Valley Operable Unit, Erda and Mill Junction Vicinity---On-Site Data Air Quality---PM10, Sulfur Dioxide Tooele Valley Operable Unit, Grantsville Vicinity---On-Site Data Air Quality---PM10 Tooele Valley Operable Unit, Grantsville Vicinity---On-Site Data Air Quality---Metals Magna Operable Unit---On-Site Data Surface Soils---Metals Magna Operable Unit---On-Site Data Surface Soils---Metals Great Salt Lake---Off-Site Data Surface Water---Metals, TDS Magna Operable Unit Vicinity Summary--Exposure Pathways Tooele Valley Operable Unit Vicinity Summary--Exposure Pathways Great Salt Lake Park Vicinity Summary--Exposure Pathways

LIST OF TERMS AND ACRONYMS

Note: See Appendix C for discussion of Comparison Values

AL B CREG EMEG Est. J mg/Kg mg/L NA NAAQS ND NIOSH NR OSHA PM10 ppm RMEG TDS XRF µg/m3 µg/L <

USEPA Action Level material also detected in laboratory blank Cancer Risk Evaluation Guide Environmental Media Evaluation Guide estimated (by ATSDR) value estimated (by laboratory) milligrams per kilogram milligrams per liter (water) not analyzed National Ambient Air Quality Standards not detected National Institute for Occupational Safety and Health not reported Occupational Safety and Health Administration airborne particles 10 microns and smaller in diameter (relevant to inhalation exposure) parts per million Reference Dose Media Evaluation Guide total dissolved solids x-ray fluorescence analyses micrograms per cubic meter (ambient air) micrograms per liter (water) less than the stated value

Table 9A. Magna Operable Unit--On-Site Data: Air Quality--PM₁₀, Sulfur Dioxide

Table 9B. Magna Operable Unit---On-Site Data: Air Quality---Metals

Table 10A. Vicinity of Great Salt Lake Park---Off-Site Data: Air Quality---PM₁₀

Table 11. Tooele Valley Operable Unit, Erda and Mill Junction Vicinity---On-Site Data: Air Quality--- PM₁₀, Sulfur Dioxide

Table 12. Tooele Valley Operable Unit, Grantsville Vicinity---On-Site Data: Air Quality---PM₁₀

Table 13. Tooele Valley Operable Unit, Grantsville Vicinity---On-Site Data: Air Quality---Metals

Table 14A. Magna Operable Unit---On-Site Data: Surface Soils---Metals (Also see Table 14B)

Table 14B. Magna Operable Unit---On-Site Data: Surface Soils---Metals

Table 15. Great Salt Lake---Off-Site Data: Surface Water---Metals, TDS

Table 16 Magna Operable Unit Vicinity: Summary--Exposure Pathways

Table 17. Tooele Valley Operable Unit Vicinity: Summary--Exposure Pathways

Table 18. Great Salt Lake Park Vicinity: Summary--Exposure Pathways

Appendix F -- Exposure Dose and Cancer Risk Calculations
and Results

Comparison of Exposure Dose to Health Guidelines

Inhalation

The air concentrations for a contaminant are compared directly to inhalation minimal risk levels without any additional calculation. The results of those comparisons are recorded in Table A which is on the following page.

Soil Ingestion

The exposure doses for soil ingestion were calculated in the following manner. The maximum concentration for a contaminant was multiplied by the soil ingestion rate for adults, 0.0001 Kg/day; children, 0.0002 Kg/day, or pica children, 0.005 Kg/day. (The habit of ingesting large amounts of soil is called pica.) This product was divided by the average weight for an adult, 70 Kg (154 pounds) or for a child, 10 Kg (22 pounds). Those calculations assume that there is frequent daily exposure to soil contaminated at the maximum level. The results of the actual calculations are recorded in Table B which follows.

Surface Water Ingestion

The exposure doses for surface water ingestion were calculated in the following manner. The maximum concentration for a contaminant was multiplied by a water ingestion rate for adults and children, 0.02 liter/day. This product was divided by the average weight for an adult, 70 Kg (154 pounds) or for a child, 10 Kg (22 pounds). These results were then multiplied by a factor of 0.03, which represents the maximum number of visits a year, 10, that we assume might occur, divided by days in a year, 365. Those calculations assume that anyone entering the water, actually ingests 20 milliliters (which is about cup) of water. The results of the actual calculations are recorded in Table C which follows.

Calculation of Risk of Carcinogenic Effects

Inhalation

Carcinogenic risks from the inhalation of contaminated air were calculated through the following process. The mean air concentration for arsenic or cadmium was divided by the inhalation cancer risk evaluation guideline (CREG) to identify the risk per 1 million persons. The CREG is the air level at which the additional cancer risk is 1 in 1,000,000 for lifetime exposure. Depending on its size, the result was then adjusted to put it in the form of 1 per 10,000, 100,000, or other appropriate number. For example, the mean arsenic level for the Magna Vicinity (0.021 µg/m³) divided by the CREG for arsenic (0.0002 µg/m³) equals a 105 in 1,000,000 or 1 in 10,000. The results for the Magna Vicinity situation represent the maximum risk for cancer after 70 years of daily exposure.

In the Great Salt Lake Park air situation, the most exposed individuals appear to be the park staff. We assumed that some staff may have exposure for 8 hours a day, 5 days a week, 50 weeks a year, for 30 years. Those assumptions were used to adjust the calculations described above by a factor of about 0.3.

Soil Ingestion

Carcinogenic risks from the ingestion of soil were calculated through the following procedure. The adult exposure doses for ingestion of soil (calculated as described previously) were multiplied by the EPA's Cancer Slope Factor for the contaminants of concern. The results represent the maximum risk for cancer after 70 years of exposure to the maximum concentration of the contaminant. A cancer slope factor was available only for arsenic. The results of the calculation of carcinogenic risk from exposure to arsenic can be found on Table B which follows. The results are discussed in the Public Health Implications (on Page 12) part of the Public Health Evaluation of Contaminants in Soil section.

Surface Water

Carcinogenic risks from the ingestion of surface water were calculated through the following procedure. The adult exposure doses for ingestion of surface water (calculated as described previously) were multiplied by the EPA's Cancer Slope Factor for the contaminants of concern. The results represents the maximum risk for cancer after 70 years of exposure to the maximum concentration of the contaminant. A cancer slope factor was available only for arsenic. The results of the calculation of carcinogenic risk from exposure to arsenic can be found on Table C which follows. The results are discussed in the Public Health Implications (on Page 17) portion of the Public Health Evaluation of Contaminants in Surface Water section.

Uncertainties in Calculating Cancer Risk

The actual risk of cancer is probably lower than the calculated number. The method used to calculate EPA's Cancer Slope Factor assumes that high dose animal data can be used to estimate the risk for low dose exposures in humans (31). The method also assumes that there is no safe level for exposure (32). There is little experimental evidence to confirm or refute those two assumptions. Lastly, the method computes the 95 percent upper bound for the risk, rather the average risk, which results in there being a very good chance that the risk is actually lower, perhaps by several orders of magnitude (33).

Appendix G -- Public Comments

The public health assessment was available for public review and comment in the local library for a period ending June 28. The public comment period was announced in local newspapers. In addition, the public health assessment was sent to several individuals and the Kennecott Corporation. Specific comments and responses are summarized below. Page numbers mentioned in this appendix refer to pagination in the public comment version of the document.

1. COMMENT: Page 1 and Page 10
   The recommendation for additional sulfur dioxide air quality monitoring to evaluate the effects of the Kennecott smelter in the Tooele Valley is unwarranted.

Response:

ATSDR has reviewed recently acquired ambient sulfur dioxide air quality data gathered at the Kennecott Ranch, located in Tooele Valley between Lakepoint and Tooele. The very low concentrations of sulfur dioxide recorded at that location together with corresponding data gathered at Magna and Great Salt Lake State Park lead ATSDR to conclude that additional sulfur dioxide monitoring is not required in Tooele Valley. The document has been changed to reflect this opinion.

2. COMMENT: Page 11, in "Public Health Evaluation of Contaminants in Soil", and in Subsection B. "Background--Overview"
   It is not appropriate to refer to the contaminants in tailings deposited by air as being "additions" to those occurring naturally in soils. Also, contaminants deposited by air are near background levels and pose no apparent public health hazard.

Response:

ATSDR has changed the text in Subsection B to indicate that wind-blown tailings deposition has caused some metals concentrations in affected surface soils to be somewhat greater than their corresponding concentrations in unaffected soils. Health effects issues are not intended to be presented in Subsection B. ATSDR summarizes soil-related health effects in Table 5 ("No Apparent Health Hazard") and describes in Subsection E ("Public Health Implications") that exposures to metals in Magna soil are unlikely to result in health effects in area residents.

3. COMMENT: Pages 6, 7, and 16.
   The ATSDR Cancer Risk Evaluation Guide (CREG) and Environmental Media Evaluation Guide (EMEG) comparison values should be explained more thoroughly in the text or in Appendix C. It is not intuitively obvious why contaminant levels above the comparison values do not constitute a health threat (page 10, F, 1). A lay reader would be alarmed by the contaminant levels as compared to the CREG and EMEG comparison values. Although CREG and EMEG are referenced in Appendix C, they are not explained sufficiently. Additional information is required for the reader to make an informed comparison of the values.

Response:

Thanks for bringing this to our attention. We alerted the reader to this problem in the first paragraph of the Environmental Contamination section.

4. COMMENT: Page 16 (Table 8)
   Comparison values shown in Table 8 for drinking water are not relevant to the potential exposure pathway (dermal) of visitors to the Great Salt Lake. Visitors do not drink water from the lake.

Response:

ATSDR has reported that park visitors obtain water for potable purposes from a public water system. In the section "Public Health Evaluation of Contaminants in Surface Water". ATSDR described visitor contact with lake water via wading and swimming but focused on incidental ingestion exposure during those activities (Table 7 and Subsection D. "Exposure Pathway Analyses"). Thus, ingestion-based drinking water comparison values are considered to be the best available criteria for selecting contaminants for incidental ingestion exposure evaluations. As noted in Table 7 and the supporting discussion, ingestion exposure is not expected to occur more than a few times a year to any one person, and there is no apparent health hazard associated with that exposure. The text has been modified to clarify the ingestion focus.

5. COMMENT:
   The following language is suggested for addition to Appendix C: "The EMEG is based on a conservative Minimum Risk Level (MRL) that is lower than the EPA reference dose (RfD). In addition, the MRL is based on a dose per body weight in an adult that would result in cumulative effects on the kidney after lifetime exposure. The MRL is not applicable to the calculation of a safe exposure level for short-term exposure in a 10 kg child."

Response:

This suggestion is not accurate. MRLs can be the same, above, or below a RfD. Also the discussion of EMEGs in Appendix C is a general one, not specific to any MRL. Lastly, there are MRLs for short-term or acute exposures to some chemicals.

6. COMMENT: Page 14. Portions of the information pertaining to the Magna, Utah Childhood Lead Exposure Study were incorrect.

Response:

We appreciate being provided the updated information. The document has been revised accordingly.

7. COMMENT: Page 18, Concern 2. The following is suggested: 'A study in Taiwan has documented that ingesting arsenic in drinking water can cause skin cancer.

Response:

We have revised this sentence.

8. COMMENT: General
   Many of the tables show the range of contamination to be from "nondetect to the highest concentration". Please indicate what the nondetect value is as it reflects the quality of the laboratory data used in the health assessment.

Response:

ATSDR uses maximum contaminant concentrations (and sometimes average concentrations) in its evaluations of public health issues. Detailed information about nondetect values would not enhance our presentation of public health issues; thus it is not provided.

9. COMMENT: Surface water
   Selenium is not evaluated in the surface water exposure scenario, yet it is present in surface water in the area. Please indicate why it is not assessed.

Response:

Great Salt Lake water quality is evaluated only for the metals that ATSDR believes might have been released by Kennecott facilities at concentration levels that might have contributed perceptibly to lake water concentrations.

10. COMMENT: General
    It would be helpful to the reader to know if there will be any follow up regarding the lack of data for air exposure pathways in Tooele Valley.

Response:

ATSDR has recommended that air samples being taken by the state in Grantsville be analyzed more frequently for metals at least for the next year or two. Those data, then, should be evaluated to decide whether there may be an associated health threat. ATSDR does not yet know whether the state will undertake this activity. Sulfur dioxide sampling data show that concentrations have been well below levels of concern.

11. COMMENT: Page 12, Section C
    Zinc is considered one of the principal metals analyzed in the surface soils and was identified to be "somewhat elevated"; yet Table 6 does not mention zinc nor does the text indicate that zinc is no longer to be considered. Please modify the document accordingly.

Response:

The second to the last paragraph on the Page 11 says, " Arsenic, cadmium, copper and lead were found to be key contaminants for soils. Zinc was also detected in soil; but concentrations are not great enough for this metal to warrant further evaluation". In a footnote to Table 5, key contaminants are described as being contaminants which initial evaluations showed had some potential to be a public health hazard. The document has not been changed.

12. COMMENT: Page 20, Community Health Concerns.
    The authors identify "permissible levels" for exposure to sulfur dioxide by an inhalation route but do not indicate the source of where the information was obtained.

Response:

The "permissible levels" are EPA's National Ambient Air Quality Standards (NAAQS) and has been so noted.

13. COMMENT:
    Page 4 says that Operable Units 8, 13, 14, and 15 were not addressed because the community does not have or has very limited incidental access to them. However, more detailed information should be provided on each of those units and a thorough discussion presented regarding potential offsite exposure from those units. Some specific concerns include:
    o Details should be provided regarding groundwater monitoring data, groundwater cleanup activities, and the status of remediation.
    o C-7 ditch water treatment and contaminant information should be included.
    o Data should be presented about the depth of monitoring wells north and east of the tailings pond, the corresponding depth of the potable groundwater supply and the possibility of movement of the contaminated plume off site should be discussed.

Response:

ATSDR believes the document adequately addresses the off-site health related effects of on-site impoundments and contaminated areas and does not believe that additional facility, release, migration, etc. details would enhance the health purpose of the document. o Page 15 says--"Kennecott's operations contribute to lake contaminant levels to a limited extent via runoff and C-7 ditch outflow, and through releases to shallow groundwater that drains into the lake." Page 15 also says--"The evaluation results lead ATSDR to conclude that the Great Salt Lake Park surface water exposure situation poses not (sic) apparent public health hazard." o Page 4 says--"ATSDR also evaluated data for...surface water in the C-7 ditch; these will not be described further because we concluded that human exposures are not significant." o Page 4 says--"Our evaluation of Magna area drinking water supplies also indicated that there are no significant human exposures." On Page 19, in response to concerns about private well water raised by a resident living next to the tailings pond, the document says that the concentrations reported for well water appear to be within a natural range of concentrations for the aquifer and unaffected by the tailings pond. On Page 40, Appendix D says that public drinking water supplies in the area do not appear to be affected by Kennecott operations; and most private drinking water wells draw water from zones deeper than those that might be affected by Kennecott operations.

14. COMMENT: Page 44, Table 10B
    The comparison value used for lead detected in Great Salt Lake Park off-site air was the OSHA standard ÷ 400 (0.125 g/m³) instead of the EPA ambient air standard of 1.5 g/m³. Since the maximum ambient concentration reported in Table 10B is 0.786 g/m³, ATSDR's use of the OSHA standard ÷ 400 (0.125 g/m³) indicates a health hazard. ATSDR should explain why this comparison value was used.

Response:

In Appendix C (Page 37) ATSDR explains that comparison values are used to select contaminants that warrant further evaluation for public health significance. Comparison values are not threshold levels above which public health will necessarily be affected. Comparison values are levels below which public health is not likely to be affected. Page 37 says that identification and selection of contaminants based on comparison value considerations does not imply that human exposure occurs or that exposures would actually result in adverse health effects. For Table 10B, our author selected the OSHA standard ÷ 400 (=0.125 g/m3) which is less than--and more conservative than--the EPA ambient air standard of 1.5 g/m3. Thus, ATSDR's intent for comparison values is adequately served by this conservative selection.

15. COMMENT: Comparison Values and Public Health Hazard Conclusions
    Exposure concentrations often are shown in tables and elsewhere to be greater than the associated comparison values, but the exposure situations are reported to be of no apparent health hazard. Please clarify this apparent conflict.

Response:

As discussed in the preceding comment, comparison values are levels below which public health is not likely to be affected and are used to select contaminants that warrant further evaluation for public health significance. Health Guidelines are discussed in Appendix F and are also used to identify contaminants that need further evaluation. The determination that a public health hazard exists is done by comparing the specific exposure situations to data in the toxicological literature.

16. COMMENT: Page 12, Affected Populations.
    A detailed description should be provided in the report on those areas in Magna in which metals in soils are elevated with corresponding contaminant levels. A map of Magna should be included in the report showing areas of Magna affected by high levels of those metals.

Response:

ATSDR does not believe that a map is needed in this situation. We identified little or no clustering of the above-background metal levels. The possible health implications (there were none) of the above-background levels are discussed in the Public Health Implications section.

17. COMMENT: Page 13, Arsenic Availability.
    The report states that arsenic appears to be less available in soil compared to water. A reference should be provided to support that statement.

Response:

The statement has been deleted.

1. ATSDR Staff (John Crellin, Don Gibeaut, John Mann, and Glenn Tucker) visited the site vicinity during the weeks of September 4 and October 23, 1994. Pertinent information obtained during those visits is described in appropriate sections of this document.

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