PRELIMINARY PUBLIC HEALTH ASSESSMENT ADDENDUM
RICHARDSON FLAT TAILINGS
PARK CITY, SUMMIT COUNTY, UTAH
The Addendum to the preliminary public health assessment for the Richardson Flat Tailings Site was available for public review and comment in a local library for a 30-day period ending September 9, 1993. The public comment period was announced in local newspapers. In addition, the public health assessment was sent to several individuals or organizations. Appendix C summarizes the public comments received on the addendum and ATSDR's response to those comments. The document has been revised, where appropriate, in response to comment issues.
| Comment 1: | A commenter says that the Tailings Impoundment (Area A) and the Floodplain Sediments (Area B) in the ATSDR report should be separate and distinct sites, rather than areas of the same site. |
| Response: | ATSDR conducts public health assessments on sites that EPA propose for its NPL. EPA identified its proposed NPL site as Richardson Flat Tailings and described it as including a tailings pond area and nearby tailings deposits in Silver Creek. Because of the proximity of Areas A and B and the potential for both areas to contribute to off-site stream, groundwater, and soil, etc., contamination, it would be impossible to develop totally independent assessments for the individual areas. Thus, it is appropriate that both areas be considered in one assessment. In the document, ATSDR made a concerted effort to attribute important background and contamination information and plausible pathway issues separately to Areas A and B. Thus, the document has not been changed in response to this comment. |
| COMMENT 2: |
Page 4--A commenter says that ATSDR should not cite rumors in a scientific evaluation of fact; a rumor should either be verified or excluded from consideration. Rumor 1--In earlier years, tailings were transported to the site via Silver Creek. Commenter says tailings were never transported in that manner. Rumor 2--Tailings were removed and used off site. Commenter says since 1982, there has been no known or approved removal of tailings from the site or approved removal of tailings from the site or use of tailings off site. |
| Response: |
ATSDR does not report rumors indiscriminately. Rumored information is included when the activity, if correct, might have substantive associated contamination and health issues; or when knowledgeable citizens might wonder whether ATSDR considered that activity in its deliberations. Rumor 1--The document has been changed to include the commenter's statement that tailings were never transported in that manner, and that the assessment does not address the issue further. Rumor 2--Reference E&E 1987a says that someone is leasing (at that time) the land the tailings are on and using the tailings material for sewer line and road base backfill. ATSDR has already identified the uncertainty of the off-site use of tailings and indicated that ATSDR cannot address the issue, but expanded discussions to provide more information. |
| COMMENT 3. | Page 4--The document says that the diversion ditch was excavated through zones of tailings. A commenter reports no knowledge of analyses of materials to prove that the ditch was excavated through zones of tailings; thus the statement is purely supposition. |
| Response: | The commenter is correct that there are no analyses of materials in the ditch as proof, but the statement is not pure supposition. ATSDR's basis for that statement was its review of a 1953 aerial photograph that appears to show that the tailings at that time extended well south of the present boundary of the tailings pond, plus Reference E&E 1989 reports taking tailings samples south of the diversion ditch, and ATSDR observed tailings-like zones in the sides of the diversion ditch while at the site. The document has been amended to provide some of this clarifying information. |
| COMMENT 4. | Pages 5 and 21--A commenter says that EPA's contractors concern for future dust associated with salt grass disappearing if the site becomes drier is unwarranted because the salt grass does not appear to be stressed and has not disappeared during the current 5-year severe drought event. |
| Response: | Although the grass's response to the current drought period appears to be satisfactory, the EPA contractor expressed concern for the consequences of the site being drier. There is no way to predict how the grass may respond to a possible future, more severe event. Therefore, because of its potential dust-related consequences, ATSDR believes the concern is relevant as reported and has not changed the document. |
| COMMENT 5. | Page 5--A commenter reports no knowledge of cattle ever having been allowed to graze on the property. |
| Response: | Reference E&E 1987a says that cattle have been observed walking across the tailings. Thus, the statement has not been changed in the document. |
| COMMENT 6. | Page 5--A commenter requests a reference for ATSDR's identification of the flood plain tailings deposits. |
| Response: | Reference USEPA 1991b (the Hazard Ranking System document) says: "Name and description of the source: Flood Plain Tailings: These tailings occupy the banks of Silver Creek..." Reference USEPA 1992 describes a 6-acre "flood plains tailing pile". Reference E&E 1989 contains a figure that shows two tailings deposits. Reference information has been added. |
| COMMENT 7. | A commenter states that there currently are three residential-type units within a mile, not four as ATSDR stated. One residential unit has been converted to a service shop for vehicle repair activities; the other two are presently vacant. Revise information on Pages 7, 10, 19, and elsewhere in document accordingly. |
| Response: | During ATSDR's site visit four residences were found within a mile of the site; one was a conventional home and the others are remembered to be trailers. Three were occupied at that time; one was vacant. The document has been changed to reflect the commenter's more recent information. |
| COMMENT 8. | Page 7--A commenter suggests that the nearest businesses should be reported to be more than 1/2 mile away rather than 1/3 mile. |
| Response: | While at the site, ATSDR made rough measurements to the nearest business. It is possible that the distance might be about 1/2 mile. The document has been changed to reflect that. |
| COMMENT 9. | Page 7--A commenter suggests that the 51 workers employed by the three businesses may not work at those specific locations. |
| Response: | ATSDR, when calling those businesses, asked for the number of employees working at those locations. Hence, the document has not been changed except to clarify that the number reported is for those locations. |
| COMMENT 10. | Page 7--A commenter says that there is an emergency clinic, not a hospital, at Prospector Square. |
| Response: | The document has been revised to reflect that information. |
| COMMENT 11. | A commenter says that the availability of water from Silver Creek for irrigation has severely diminished because of water uses by Park City. For example, little, if any, water from the creek has been available for at least 4 years to produce forage for livestock on three nearby properties in the watershed; this condition is expected to continue for the foreseeable future. Affected parties are compensated via crop-loss payments and purchase feed from out of the watershed area. Revise information on Pages 8, 9, 21, and 22 and elsewhere in the document. |
| Response: | Pages 8 and 9 of the document have been changed. No changes are warranted for Pages 21 and 22 because the pathways are viable as stated, even though the availability of irrigation water has been reduced. |
| COMMENT 12. | Page 8--A commenter says that a statement about the diversion ditch should say that it diverts water around the southern edge of the tailings impoundment. |
| Response: | The document has been changed. |
| COMMENT 13. | Page 8--A commenter reports the document should say that the Pace-Homer irrigation withdrawal is upstream of the tailings pond area. |
| Response: | The document has been changed to reflect this information. |
| COMMENT 14. | Page 9--A commenter says there is no scientific data to evidence the presence of cutthroat trout in Silver Creek and no evidence of a fishery. Some exhibits submitted document discussions with a Utah Division of Wildlife representative who said that state investigations in 1970 and also one he conducted in 1986 produced no fish. The commenter desires that ATSDR either provide hard data that evidence a cutthroat trout population or delete the passage referring to the presence of those trout. |
| Response: | ATSDR has reviewed the exhibits submitted. ATSDR also re-reviewed two memoranda that summarize EPA contractor discussions in 1991 with other personnel in the Utah Division of Wildlife. In summary, those memoranda say that 1) a survey conducted in 1954 found a small number of trout, 2) electroshocking data in 1970 did not show a presence of game fish, and 3) more recent conversations with a biologist indicate the presence of a good, but unquantified, cutthroat trout population in the creek. EPA reported seeing pan-sized trout at the site in the spring of 1992. Using the information, it is reasonable to consider that a trout fishery is not likely to be substantive, if one exists at all. ATSDR has revised trout discussions to include the varying information and has reconsidered how fishery is addressed in remaining sections of the document. |
| COMMENT 15. | Page 10, A commenter requests a reference for the seepage studies mentioned. Commenter also requests that ATSDR's belief with respect to creek water losses to the underlying valley fill aquifers should be substantiated with scientific evidence. |
| Response: | A reference has been added. ATSDR has some limited evidence of stream losses to the valley fill aquifers. The reference says (without describing weather, location, flow rate, loss amount, etc.,) that seepage studies on the creek did not show any areas of significant losses. To ATSDR, that means that some--apparently "small"--losses were recorded somewhere on the creek. That information suggests that stream seepage losses could be a mechanism for transporting dissolved contaminants to underlying groundwater. The document has been revised to clarify ATSDR's position. |
| COMMENT 16: | Pages 10, 18, 19--A commenter says ATSDR implies there may be a connection between three public water supply wells and the Silver Creek alluvial aquifer, or the site. Commenter says there is no evidence of a connection. Commenter reports the public wells are not located in the alluvial valley associated with Silver Creek, the wells draw from artesian aquifers in bedrock below the alluvial zones, and the wells are hydrogeologically upgradient of the creek. |
| Response: | ATSDR has revised discussion to minimize the likelihood of a hydraulic connection between site contaminants and the public water systems. |
| COMMENT 17A: | A commenter says that the document should rely on EPA's 1989 water and sediment sampling and EPA's 1992 air sampling rather than flawed 1985 water sampling and 1986 air sampling. In addition the document makes unwarranted claims about the site as a source of contaminants found in various media. More specific issues raised by the commenter are presented below. |
| Response: | See more detailed comments below. |
| COMMENT 17B: | Commenter says that EPA's Supplemental Site Inspection Report concludes that analytical results of surface water and sediment samples from Silver Creek and the diversion ditch do not support an observed release of contaminants to surface water. In summary, no observed release of contaminants attributable to the site has been clearly documented. |
| Response: | On Page 11, ATSDR initiated its discussions of contaminants by saying that the sampling data and supporting site-related information suggest that contaminants have been released. Neither that statement, nor any subsequent discussions, are intended to say, or imply, that there is clear documentation that contaminants were released from the site. For example--EPA's Supplemental Site Inspection Report concludes that the contribution of contaminants from the flood plain tailings and historic depositing of metals into the streambed cannot be clearly segregated from contamination contributed by the Richardson Flat tailings. ATSDR agrees that those data do not prove a site release to a full certainty. It is not the intent of a public health assessment to prove releases or sources; EPA has that responsibility for sites it proposes for its National Priorities List. ATSDR addresses sources and releases because that information can provide insight to exposure pathways. ATSDR uses available environmental sampling data, observations, along with its knowledge of contaminant migration mechanisms to identify exposure pathways. Where the sampling evidence considered for identifying pathway components, including the contaminant source, is weak or equivocal, ATSDR attempts to appropriately tailor its discussion of those issues--while at the same time asserting an appropriate level of concern for plausible exposures to the contaminants found and any associated public health issues. ATSDR has slightly modified portions of the document to reflect appropriately on source/release issues. |
| COMMENT 17C: |
A commenter says that EPA's 1986 air testing was flawed in a number of ways and site conditions have been significantly altered since the 1986 samples were obtained. The commenter says that ATSDR should rely on EPA's 1992 air data which accurately reflects current site conditions. The commenter, in supplemental information, raises concerns that the only data used by EPA (for scoring the site) from a 5-day sampling activity was a 12-hour period when local windstorms were strong enough to entrain some of the then uncovered tailings. An additional concern is that the air sampler that detected the "release" was placed 20 feet from the tailings on the tailings embankment for the purpose of qualifying it as an "off-site" air sample, which it certainly is not. Other issues are EPA's method of comparing those data to National Air Quality Standards for lead, and that, after capping, receptors at more distant locations (e.g., Park City) can hardly be considered to have even the slightest increase in risk. |
| Response: | ATSDR considers the flaws alleged by the commenter that might affect this public health assessment either were corrected by EPA, or were appropriately considered by ATSDR's document, or have no effect on its contents. ATSDR reviewed the 1986 air sampling report and a 1991 memorandum that included corrected concentrations for all 5 days data. ATSDR considered all the corrected 5 days of data when preparing the assessment document. ATSDR correctly identified and reported the on-site and off-site information provided on Pages 14 and 16, respectively. Both pages also acknowledge that because of the short sampling interval, the monitoring data may not be representative of conditions over time. On Page 16, ATSDR also noted for the 1992 air data that most of the tailings were covered at that time and only zinc was detected at a low concentration. Discussion of off-site air pathways (Page 21) includes descriptions of past observed wind-borne dust and indicates that the 1992 sampling suggests that levels of site-related wind-borne contamination may be inconsequential when cover soils are (fully) in place providing cover and salt gras are maintained. Thus, ATSDR considers its uses of the 1986 and 1992 data accounted for alleged flaws that might be pertinent to the document and were appropriate. The document has not been changed with respect to these issues. |
| COMMENT 18: | Page 12--A commenter says that it is inappropriate to make comparison between unfiltered monitoring well samples and drinking water standards. |
| Response: | ATSDR uses the comparison value concept to "screen" an array of contaminants--it is not a determination of actual or implied toxicity, exposure, or health outcome for any of the chemicals being screened. However, each comparison value has a health-related basis--hence, for some contaminants in water, certain comparison values are based on current drinking water standards. As stated on Page 11, ATSDR uses its comparison values to identify contaminants of potential concern that can be evaluated in subsequent sections of the assessment to determine whether exposure to them has public health significance. As stated there, identifying contaminants in that section does not imply that exposure will result in adverse health effects (nor does identification in that section establish whether any exposure occurs). ATSDR considers the comparison values to have been used appropriately, and the document has not been changed. |
| COMMENT 19: | A commenter, citing information on Page 13, says that no valid conclusions can be drawn by a comparison of unfiltered samples from the upgradient monitoring well and the downgradient monitoring wells or their comparison to drinking water wells and standards. |
| Response: | ATSDR has eliminated the comparisons made between data from upgradient and downgradient monitoring wells. However, ATSDR has applied its comparison value process appropriately to monitoring well data, thus no changes are made with respect to that issue. |
| COMMENT 20: | A commenter, citing information on Page 13 takes issue with ATSDR's application of its comparison value procedure to surface water because no drinking water intakes are located downstream. |
| Response: | The screening process, as described in an earlier comment response, uses comparison values that have a health-related basis to identify contaminants that may warrant further evaluation in the assessment. For water, ATSDR's health-based comparison can include some drinking water standards, irrespective of whether the water in question is used as a public water supply. The document has not been changed. |
| COMMENT 21: | Page 14--A commenter says the discussion of sediment should not include a conclusion regarding the Richardson Flat site's contribution. |
| Response: | That discussion mentions where samples were taken but does not mention contribution. The document has not been changed. |
| COMMENT 22: | Pages 14 and 15--A commenter says it is inappropriate to compare unfiltered and filtered groundwater samples to each other or to drinking water standards or to comparison values. |
| Response: | The unfiltered samples have not been compared to the filtered samples; only the concentration information is provided. The relevance of ATSDR's comparison value procedure has been addressed in earlier comment responses. The document has not been changed. |
| COMMENT 23: | Page 17--A commenter says that ATSDR incorrectly assumes that the data it relied on is within the limits for adequate QA/QC. Some of the data are without QA/QC and some data were estimated values. The validity of ATSDR's conclusions is profoundly affected by the poor quality of the data used in its assessment. |
| Response: | ATSDR stated on Page 17 that only some of the documents contained quality assurance information. ATSDR also stated that it presumed that protocols and results are valid and acknowledged that information reliability could affect the validity of conclusions drawn. ATSDR does not concede that data should be presumed to be of poor quality when QA/QC information is not reported. Also, ATSDR has found that estimated concentrations identified through the QA/QC process frequently can be applied to at least portions of the health assessment process. ATSDR, during this comment response activity, has modified or withdrawn some statements or conclusions that its review has shown are not sufficiently supported by the data, observations, and other information. However, ATSDR has reviewed the Conclusions Section on Page 28 and find none that are affected by the issues raised in this comment. |
| COMMENT 24: | A commenter says that potential pathways should be supported by facts. Particularly, on Page 20, the supposition that deposition of wind-blown tailings has contaminated off-site soils is made with no corroborating evidence and must be considered merely a hypothetical exposure scenario. |
| Response: |
ATSDR agrees that the potential pathway scenarios are hypothetical, but they are based on the available information plus the agency's experience in other assessments with similar pathways for which documentation is more complete. Here, and elsewhere in the document, where ATSDR's judgement has been applied, there is a possibility of judgement error. When such an error is possible, the agency chooses to err in the direction of public health. The specific scenario identified by the commenter is described in the document under the heading of Potential Exposure Pathways. The potential pathway concept is described on Page 17. On Page 20, ATSDR said that wind has likely deposited tailings contaminants on surface soils in the vicinity of the site. This statement is founded on reported observed wind-blown dust at the site and contamination data from air sampling, plus the virtual certainty that at least some of the contaminants suspended by the wind would be deposited beyond the site boundary. However, principally because of uncertainties about deposition at identifiable receptor locations, the pathway is considered potential, rather than completed. ATSDR considers the potential pathway concept to be adequately described; therefore, additional characterization has not been provided. |
| COMMENT 25: | Page 20--A commenter says that ATSDR's statement that runoff from on-site tailings is contaminating creek water is merely supposition. The tailings impoundment has no run-off potential because it has run-on and run-off controls. |
| Response: | ATSDR has revised the statement. |
| COMMENT 26: | Page 25--A commenter says that ATSDR's statement that potential future exposure to beryllium would be of health concern has no basis since beryllium was detected in the tailings at concentrations within normal ranges for western soils. |
| Response: | ATSDR has revised the statement. |
| COMMENT 27: | A commentor notes that ATSDR cites findings of an ATSDR study conducted at Prospector Square in discussing exposure to contaminants at Richardson Flat. On page 26, the Prospector Square study is described as indicated that exposure to tailings did not result in any increase in blood lead, arsenic or cadmium levels, as compared to local controls; ATSDR then states that, because the frequency and duration of exposure to tailings in the residential Prospector Square area are expected to be significantly higher than the frequency and duration of exposure to tailings at Richardson Flats, it is likely that exposure to lead at Richardson Flats will not result in an increase in blood lead levels. However, ATSDR concludes that, should Richardson Flat be developed for residential purposes, contaminant levels would be of public health concern. The commenter finds this conclusion to be inconsistent with the statement comparing Richardson Flat with Prospector Square, and asks for a justification regarding the conclusion about residential development at Richardson Flat, in light of the findings of no public health concern at the current residential area at Prospector Square. |
| Response: | ATSDR has reevaluated the Prospector Square study, and has revised the Public Health Assesment to eliminate ambiguity. |
APPENDIX D: ATSDR PRELIMINARY PUBLIC HEALTH ASSESSMENT OF 1990
HEALTH ASSESSMENT
RICHARDSON FLAT TAILINGS SITE
PARK CITY, SUMMIT COUNTY, UTAH
EPA FACILITY ID: UTD980952840 
July 24, 1990
SUMMARY
The Richardson Flat Tailings, an Update 7 site proposed for the National Priorities List, is located 3.5 miles northeast of Park City, Summit County, Utah. From 1975 to 1981, the 160-acre site was used for disposing mine tailing wastes from the Keetly Ontario Mine and other mines owned by United Park City Mines. Currently no tailings are dumped at the site; however, soil from the site is being excavated and used to cover the tailings piles. Several metal contaminants, including arsenic, cadmium, chromium, lead, and zinc, have been detected in on-site and off-site areas. Contaminants may migrate from the site to off-site areas through surface water, groundwater, and airborne-associated pathways. Human exposure to site contaminants may occur through the ingestion of contaminated groundwater, food-chain entities, and soil; through dermal contact with contaminants; and through the inhalation of airborne dusts. The site is considered to be of potential public health concern because of the high levels of on-site contaminants.
BACKGROUND
A. Site Description and History
The Richardson Flat Tailings site (RFT), consisting of 160 acres located in a topographic depression approximately 3.5 miles northeast of Park City, in Summit County, Utah, is an Update 7 site proposed for the National Priorities List (NPL) (see Figures 1 and 2). From 1975 until 1981, mine tailings from the Keetly Ontario Mine and other mining operations in the area were disposed of at the site and currently range up to 10 feet in depth. Until 1987, mine tailings were removed from the site and used as backfill for sewer construction projects.
Currently, mine tailings at the site are being covered by soil excavated from on-site areas. The thickness of the soil cover varies over the surface of the site, and, as noted during the April 1989 site visit, the soil layer covering the mine tailings was less than 1-inch thick in certain areas. Site features include a pond that covers the northeastern corner of the site and is contained by a dam at the northwestern corner, and a ditch in the central portion of the site.
B. Site Visit
Staff from the Agency for Toxic Substances and Disease Registry (ATSDR) and the Utah Department of Health conducted a visit to the RFT site on April 19, 1989. During the site visit, conditions on-site and off-site were observed, including land uses in areas adjacent to the site, the proximity of residential areas to the site, the ease of site access, the presence of on-site physical hazards, and the general physical characteristics of the site. Specific observations made during the site visit will be discussed in appropriate sections of this Preliminary Health Assessment.
C. Community Health Concerns
Staff from the Utah Department of Health indicated that they were not aware of any community health concerns related to the RFT site.
DEMOGRAPHICS, LAND USE, AND NATURAL RESOURCE USE
The site lies in a rural area with very widely scattered residences. It is within 1.5 miles of Prospector Square, which is an extension of Park City, a popular recreational and ski area of Utah. The area within a 1-mile radius of the site consists of open, undeveloped rangeland and agricultural fields. Only three residences are within a 1-mile radius of the site; however, because the site is close to a popular resort, which has expanded in recent years, future development of the area may increase residential, commercial, and recreational land uses (1).
Recreational land uses in the site vicinity include fishing in Silver Creek, a popular stream for trout fishing, and downhill skiing at nearby ski slopes. Piles of mine tailings on-site are commonly used for unauthorized recreational motorcycling.
Other land uses in the site vicinity include pastureland for cattle and sheep and land parcels used for cultivating hay and grain. No industrial or commercial land uses are within 1-mile of the site.
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
A. On-Site and Off-Site Contamination
Monitoring results were analyzed for groundwater, surface water, soil, and air samples collected during initial site investigations conducted in 1985. These results are only of preliminary and are not sufficient to characterize the full nature and extent of site contamination.
1. Groundwater
Groundwater samples were collected from monitoring wells located upgradient and downgradient from the site. Groundwater samples were analyzed for total metals, cyanide, sulfate, and dissolved metals. The highest concentrations of contaminants were detected in unfiltered groundwater samples collected from monitoring wells located downgradient from the site (see Table 1).
| Maximum Concentration [ppb] | Drinking Water Criteria+ | ||
| Contaminant | Off-Site Upgradient | On-Site | |
| Arsenic | <5 | 349 | 50 |
| Cadmium | <5 | 48 | 10 |
| Chromium | <5 | 104 | 50 |
| Lead | <30 | 1,080 | 20# |
| Manganese | 20 | 10,400 | 50 |
*Unfiltered samples.
+National Interim Primary Drinking Water Regulations. U.S. Environmental
Protection Agency, Office of Drinking Water, 1976.
#Proposed Maximum Contaminant Level at the tap.
2. Surface Water
Surface water samples were collected from the east bank of Silver Creek and from an intermittent stream that flows through the tailings. Surface water samples were analyzed for total metals and sulfate. The highest contaminant levels in Silver Creek were found immediately downstream from the site and at the discharge point for the intermittent, on-site stream (see Table 2). Approximately 2 miles upstream from the RFT site, the Prospector Square tailings may also serve as an important source of surface water contaminants.
|
Maximum Concentration [ppb]
|
||
| Contaminant | Upstream Silver Creek | Downstream Silver Creek |
| Arsenic | 14 | 65 |
| Copper | 12 | 60 |
| Lead | 147 | 1,985 |
3. Soil
Samples of surface and subsurface soil were collected from on-site and off-site areas (see Table 3 and 4). Soil samples were analyzed for total metals. Samples of subsurface, on-site soil samples (tailings) were analyzed for total metals and cyanide. Results of analyses of on-site surface soil (tailings) and off-site surface soil indicate levels of arsenic, cadmium, lead, and zinc substantially higher than the mean concentrations for the western United States.
Results of sample analyses of subsurface mine tailings indicated elevated levels of heavy metals and arsenic (see Table 4). Off-site, subsurface samples did not have contaminant levels above mean concentrations for the western United States, indicating the likelihood that off-site soil contamination is generally limited to the upper portions of the soil profile (2).
Table 3. Surface Soil and Tailings, 1986
|
Maximum Concentration [ppb]
|
|||
| Background* | On-Site | Mean for Western U.S. | |
| Arsenic | 58,000 | 3,600,000 | 5,500 |
| Cadmium | 17,000 | 80,000 | 200 |
| Lead | 1,110,000 | 8,530,000 | 17,000 |
| Selenium | 6,700 | <400,000 | 230 |
| Zinc | 1,570,000 | 6.360,000 | 55,000 |
*Levels reported as background may not be true background because they were collected adjacent to the site and in an area with a history of mining activity.
Table 4. Subsurface Soil and Tailings, 1986
|
Maximum Concentration [ppb]
|
|||
| Background* | On-Site | Mean for Western U.S. | |
| Arsenic | 6,500 | 328,000 | 5,500 |
| Cadmium | 7,400 | 169,000 | 200 |
| Lead | 37,000 | 4,920,000 | 17,000 |
| Selenium | <100 | 9,400 | 230 |
| Zinc | 70,000 | 23,200,000 | 55,000 |
*Levels reported as background may not be true background because they were collected adjacent to the site and in an area with a history of mining activity.
4. Air
Preliminary air monitoring was conducted using five high-volume air samplers at four sampling locations over a 5-day period. Air samples were analyzed for arsenic, cadmium, lead, and zinc. During air monitoring, weather conditions were dry with winds varying up to 20 miles per hour, although winds gusted up to 40 miles per hour during the first day of sample collection. The highest levels of airborne contaminants were detected during the first day of sampling at the air monitoring station downwind from the site (see Table 5). Air monitoring results verify that releases of airborne contaminants have occurred at the RFT site.
|
Maximum Concentration [micrograms per cubic meter]
|
||
| Contaminant | Upwind | Downwind |
| Arsenic | 0.002 | 0.093 |
| Cadmium | < 0.010* | 0.082* |
| Lead | 0.103 | 1.648 |
| Zinc | 0.091+ | 1.155+ |
*Matrix spike recovery was 65% for cadmium; actual value may be higher.
+Matrix spike recovery was 60% for zinc; values given are estimates.
B. Quality Assurance and Quality Control
Quality assurance and quality control procedures were used to ensure the accuracy of the monitoring programs conducted during site investigations at the RFT site. Sample collection and analyses were determined to have been performed according to approved procedures; therefore, monitoring results were determined to be acceptable. The conclusions contained in this report are based on the data package supplied to ATSDR. The accuracy of these conclusions depends on the reliability and comprehensiveness of the data contained in the materials reviewed.
C. Physical and Other Hazards
No on-site physical hazards were noted during the site visit.
PATHWAYS ANALYSES
A. Environmental Pathways (Fate and Transport)
1. Groundwater
Groundwater was encountered within 12 feet of the site's surface during the collection of on-site soil samples. In the site vicinity, the uppermost aquifer, with an average depth of 60 feet, lies within alluvial deposits overlying consolidated rocks of tertiary origin. It is not clear whether this alluvial aquifer is hydrologically connected to the deeper aquifer found in the consolidated rock formation. Groundwater flow beneath the site and in the site vicinity is to the north-northwest.
No private or monitoring wells are on-site. Two private domestic wells are located about 4,000 feet southwest of the site. Both of these wells are completed to a depth of about 210 feet below the ground's surface. A single municipal well used as a backup source for the Park City municipal water system is located 2.5 miles southwest of the RFT site (1). Groundwater samples were not collected from the above-mentioned private and municipal wells; however, because these wells are located upgradient from the site, they are not expected to be impacted by site contaminants.
2. Surface Water
Surface water and leachate from the site may transport site contaminants into nearby streams and creeks. The largest surface water feature in the site vicinity is Silver Creek, located about 200 feet west of the site. Approximately 1,000 feet downstream from the site, surface water from Silver Creek is diverted for the irrigation of pastureland and hay fields. Silver Creek does not serve as a source of drinking water source for humans.
Several leachate (mine tailing drainage) seeps were noted on the northwest side of the on-site earth dam; however, surface water samples were not collected in this area. These seeps flow from the site to the northwest into a swampy area that drains into Silver Creek. Leachate from the mine tailings pile may serve as an important source of surface water contamination.
3. Soil
Mine tailings consist of finely crushed rock that are easily eroded by surface water runoff and wind. Erosion of the mine tailings is likely because portions of the mine tailing piles are uncovered and lack a vegetative cover. Although a soil cover is being placed over the surface of the mine tailings, the thickness of the cover varies considerably and may be less than 1 inch. Soil used to cover the tailings may also be contaminated because it is being excavated from on-site areas in which mine tailings were dumped. The soil covering the tailings is expected to have a minimal impact on the migration of tailing contaminants into groundwater.
As precipitation percolates through the mine tailings, sulfates in the tailings dissolve, increasing the acidity of water as it seeps downward. As infiltrating water becomes more acidic, it dissolves the arsenic and heavy metal compounds in the tailings and carries these contaminants downward. Monitoring results indicate that contaminants have already migrated to lower levels of the tailing piles and impacted local groundwater and nearby surface waters. Contaminants will continue to impact groundwater and surface water if no remediation is performed.
4. Air
The small particle size of the tailings increases the likelihood that wind may be an important mechanism for dust transport to off-site areas. Site documents indicate that releases of windblown contaminants to off-site areas have been observed, especially in the summer months when winds from the southwest blow dust from the site across Interstate 40.
5. Contaminated Food-Chain Entities
Site contaminants may bioaccumulate in food-chain entities. In the site vicinity, approximately 315 acres of agricultural land are irrigated with surface water diverted from Silver Creek. Irrigated lands are used for pastureland and the production of grains and hay. Crops irrigated with contaminated surface water may bioaccumulate contaminants.
Animals may also become contaminated if they graze in areas impacted by the site, feed on crops irrigated with contaminated water, or ingest contaminated surface water, soil, or sediments. Cattle and sheep are known to graze in shrub land adjacent to the site.
Fish from Silver Creek may also bioaccumulate contaminants from surface water and sediment. Silver Creek is known to support recreational trout fishing.
B. Human Exposure Pathways
Several potential routes exist by which humans may be exposed to contaminants from the RFT site. Ingestion of contaminated groundwater, soil, and food-chain entities and inhalation of dust are all potential routes of human contaminant exposure.
1. Soil - and Tailings-Associated Pathways
Ingestion, inhalation, and dermal exposures to soil and tailings may adversely impact human health. The highest contaminant levels were found in on-site subsurface soil and tailings; however, on-site and off-site surface soil and tailings were also contaminated. The site is located in a rural area and because access to it is not restricted, trespassers may come in contact with these contaminated media during cycling or other activities on or near the site.
2. Groundwater-Associated Pathways
Human exposure to groundwater contaminants may result from the use of contaminated groundwater for domestic, industrial, and agricultural purposes. Local residents are known to rely on groundwater as a potable water supply; however, monitoring data for off-site groundwater are limited to results from a single upgradient well and two downgradient wells. The likelihood of human exposure to groundwater contaminants is minimized by the rural nature of the site and the lack of supply wells for potable water downgradient from the site; however, without monitoring results from nearby private wells, this pathway of human exposure can not be ignored. The potential exists for completing this pathway of human exposure in the future if groundwater wells are installed on-site or downgradient from the site.
3. Food-Chain-Associated Pathways
Another potential pathway for human exposure to contaminants is through the consumption of food-chain entities that may bioaccumulate contaminants. Cultivated grains and vegetables and other edible plants may bioaccumulate soil contaminants and result in food-chain contamination. Cattle, sheep, and wildlife that consume contaminated plant material or surface water may also bioaccumulate contaminants.
Aquatic animals, such as trout in Silver Creek, that inhabit contaminated surface water or aquatic systems with contaminated sediments may also bioaccumulate contaminants. Analytical results of surface water samples collected from Silver Creek indicate contaminants at levels significantly in excess of Federal Ambient Water Quality Criteria. These contaminants are known to bioaccumulate in fish and may reach levels that make Silver Creek trout unsuitable for human consumption.
4. Airborne-Associated Pathways
Inhalation of contaminated dusts may be a human exposure pathway. On-site activities, including cycling, soil remediation, or excavation of tailings for use as fill may result in the generation of dust and the exposure of motorcyclists, on-site workers, and area residents to site contaminants. The relative remoteness of the site may help reduce the impact of this pathway of human exposure.
5. Surface-Water-Associated Pathways
Surface water obtained from local sources is not a source of drinking water within the site vicinity; however, surface water is used to irrigate pastureland and hay and grain fields. As a result, human exposure to site-related contaminants may result from the ingestion of contaminated grains, animal products, or fish.
PUBLIC HEALTH IMPLICATIONS
Results of preliminary groundwater and soil sampling indicate that the RFT site is of potential public health concern because of contaminants in on-site air, soil, mine tailings, and groundwater and on-site and off-site surface water and sediments.
A brief discussion of the identified site contaminants of public health concern follows.
Arsenic
Human exposure to arsenic is possible through three major pathways: ingestion, inhalation, and dermal contact. Common effects from ingestion of arsenic include irritation of the digestive tract leading to pain, nausea, vomiting, and diarrhea. Ingestion of inorganic arsenic, the form most likely found at the RFT site, also causes a pattern of skin abnormalities, such as dark and light spots on the skin and small "corns" on the palms, soles, and trunk. Some of the corns may progress to skin cancer. Other health effects of arsenic ingestion include an increased risk of liver, bladder, kidney, and lung cancer. Long-term exposure (greater than 14 days) to inorganic arsenic at levels as low as 20 micrograms per kilogram of body weight per day may result in mild health effects. The severity of symptoms tends to increase as exposure duration increases. The Environmental Protection Agency (EPA) estimates that a dose of 1 microgram per kilogram of body weight per day corresponds to a cancer risk of 1.5 in 1,000 (3). Arsenic levels are sufficiently high in surface soil to be of public health concern for ingestion, inhalation, or dermal exposures.
Inhalation of inorganic arsenic dusts may also result in mild irritation of the digestive tract. The inhalation route of human exposure is more likely to increase the risk of lung cancer than is the ingestion route. Air concentrations of about 200 micrograms per cubic meter are associated with irritation of the nose, throat, and exposed skin. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) for occupational exposure to arsenic in air at 2 micrograms per cubic meter not to be exceeded for more than 15-minutes. EPA has estimated that a lifetime inhalation exposure to 1 microgram per cubic meter causes a lifetime cancer risk of 4 in 1,000 (3). The maximum level of airborne arsenic detected at the RFT site (0.093 micrograms per cubic meter) is at a level of public health concern. Soil-disturbing activities, such as excavation of soils or motorcycling, are likely to cause an increase in airborne arsenic levels.
Dermal exposure to arsenic-containing compounds may result in mild-to-severe irritation of the skin, eyes, or throat. No reliable dose estimates are available on the exposure levels at which these effects begin to appear.
Cadmium
Human exposure to cadmium at the RFT site can occur either through the ingestion of contaminated soil, mine tailings, and food-chain entities or through the inhalation of contaminated dusts. Very small amounts of ingested cadmium are absorbed into the blood (1%-5%) while 30%-50% of that which is inhaled is taken into the blood (4). Once cadmium enters the body, it is retained very strongly. A proposed reference dose (a daily dose that is estimated to be without appreciable human health risk) of 0.5 micrograms per kilogram of body weight per day for oral exposure is currently under review (4).
Ingestion of cadmium may result in damage to the kidneys and may cause hypertension, although the importance of cadmium in hypertension is unclear. Dermal exposure to cadmium compounds has not been observed to cause significant health effects. Long-term inhalation exposures to cadmium at levels of 100 micrograms per cubic meter may increase the risk of lung disease, such as emphysema, and may also cause kidney injury. Lifelong inhalation of air containing 0.03 micrograms per cubic meter is estimated to cause a lifetime cancer risk of 1 in 10,000 (4). Air monitoring results at the RFT site detected airborne cadmium levels (0.082 microgram per cubic meter) at levels of public health concern (1). Site remediation activities or on-site cycling activities are likely to increase airborne cadmium levels.
Under current land use, cadmium levels in surface soil are not high enough to be of public health concern. If the site is developed for residential or recreational uses, the levels may become a public health concern.
Lead
Human exposure to lead at the RFT site may occur through two major pathways: the ingestion of contaminated soil, mine tailings, and food-chain entities or the inhalation of airborne contaminated dusts. Levels of lead in surface soil and tailings, subsurface soil and tailings, and air are sufficiently high to be of public health concern.
Children are especially susceptible to the health effects of lead exposure. Low levels of lead exposure may cause decreased growth and may result in lower intelligence quotient (IQ) scores. Low levels of lead exposure may also cause hypertension in middle-aged men. Pregnant women exposed to lead transfer lead to the fetus, and this may cause preterm birth, reduced birth weight, and decreased neurological development in the infant. Results of studies have shown that lead causes cancer in laboratory animals; however, it is not known whether lead causes cancer in humans.
Human inhalation of lead-contaminated dust or lead fumes may result in the same health effects that ingestion exposure causes. Air monitoring results at the RFT site indicated lead (1.65 micrograms per cubic meter) at levels above EPA's National Primary and Secondary Ambient Air Quality Standards for lead (1.5 micrograms per cubic meter) (5). Airborne lead levels are expected to be even higher if soil is disturbed by on-site activities such as soil excavating or cycling.
The Centers for Disease Control (CDC) has cautioned that concentrations of lead greater than 500-1,000 parts per million (ppm) in residential soil could lead to elevated blood lead levels in children who inhale or ingest soil. Lead levels in excess of these values were found in on-site surface soil and mine tailings and in subsurface soil and tailings. Site trespassers, site workers, and recreational cyclists may experience short-term exposures to lead-contaminated media.
Selenium
Human exposure to selenium at the RFT site may occur through the ingestion of contaminated groundwater or soil and through the inhalation of airborne dust. Once ingested, selenium in both the organic and inorganic forms is readily absorbed. Although selenium is an essential nutrient, it may have toxic effects at levels moderately above the daily nutritional requirement. The Food and Nutrition Board of the National Academy of Sciences (NAS) suggests that 0.05 to 0.20 mg of selenium per person per day is an adequate and safe level of dietary intake in adults (6).
Inhalation of selenium may cause damage to the respiratory tract, gastrointestinal and cardiovascular effects, and irritation of the skin and eyes (7). Air samples collected from the RFT site were not analyzed for selenium; however, the levels found in surface soil and tailings and the air monitoring results for other site contaminants indicate that airborne selenium levels may be of public health concern under normal site conditions. Soil disruption by such activities as soil excavation or cycling could increase airborne selenium levels.
Selenium may also bioaccumulate in plants and animals. The health effects from long-term exposure to selenium via ingestion of contaminated food or water include loss of hair, loss and deformities of nails, problems with walking, diminished reflexes, and some paralysis. These health effects were reported from a study of populations in China that lived in areas with extremely high selenium levels in the soil and in the rice and vegetables they consumed. Selenium levels in the food were 1.6 parts per million or higher, and the period of exposure was months or even years (8).
Zinc
Human exposure to zinc at the RFT site may occur through two major pathways: the ingestion of contaminated soil, tailings, and groundwater or the inhalation of airborne contaminated dust. Which health effects result from exposure to excess levels of zinc depends on the pathway of exposure.
Ingestion of excess zinc may cause stomach or digestive problems. NAS has estimated the recommended dietary allowance (RDA) for zinc to be 15 milligrams per day (6). Long-term exposure to excessive levels of zinc (2.1 milligrams per kilogram of body weight per day) may result in copper deficiency (8); however, exposures of this magnitude are not expected to occur at the RFT site.
Inhalation of zinc dust may lead to breathing difficulties and nonspecific neurological effects such as headaches and malaise (9). Air monitoring results at the RFT site did not show zinc to be at levels of public health concern; however, during soil-disturbing activities, such as soil excavation or cycling, airborne zinc levels may become a public health concern.
CONCLUSIONS
Using the available information, ATSDR has concluded that this site is of potential public health concern because humans may be exposed to hazardous substances by ingestion of contaminated soil, groundwater, and food-chain entities; dermal contact with contaminated soil; and inhalation of contaminated dust. This Preliminary Health Assessment is based on incomplete monitoring data for groundwater and surface water. A full assessment of the public health implications of this site is not possible with the information presently available.
In accordance with the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended, the Richardson Flat Tailings site has been evaluated for possible follow-up with health effects studies. However, because no documentation or indication exists that human exposure to site-related contaminants is occurring or has occurred in the past, this site is not being considered for follow-up health studies at this time.
As ATSDR receives additional information, such information may indicate that further assessment is warranted by site-specific public health issues.
RECOMMENDATIONS
ATSDR recommends the following:
1. Restrict public access to the site to reduce unauthorized site entry and use of the site for recreational purposes.
2. Monitor private wells within 1 mile of the site to determine whether these wells are being impacted by site contaminants and whether water from these wells can continue to be used for potable purposes.
3. Conduct additional surface water monitoring, both upgradient and downgradient from the site, to determine the site's impact on Silver Creek and other nearby bodies of surface water.
4. Sample leachate seeps from along the north side of the on-site earthen dam, and analyze these samples for site-associated contaminants.
5. Collect additional off-site soil samples from areas adjacent to the site, especially downwind of the site, to characterize off-site contamination.
6. Collect and analyze edible portions of trout from Silver Creek to determine whether they are suitable for continued human consumption.
7. Include the following in the remediation workplan if additional site remediation occurs:
Provide adequate personal protective equipment that meets the standards of the Occupational Safety and Health Administration (OSHA) for workers conducting remedial activities in and around the site.
Follow appropriate precautionary guidelines, regulations, and advisories from the National Institute for Occupational Safety and Health (NIOSH) and OSHA.
Employ optimal dust control measures if remedial activities will involve ground-disturbing activities. In addition to on-site air monitoring, appropriate real-time air monitoring at the worksite periphery should be conducted during working hours in addition to on-site air monitoring. Levels of contaminants in the ambient air at the periphery of the site should not exceed National Ambient Air Quality Standards (NAAQS) or NIOSH recommendations.
8. When indicated by public health needs, and as resources permit, the evaluation of additional relevant health outcome data and community health concerns, if available, is recommended.
PREPARERS OF REPORT
Environmental and Health Effects Assessor:
Richard Earl Gillig, M.C.P.
Environmental Health Scientist
Remedial Programs Branch
ATSDR Regional Representative
Tamara Kicera
Regional Services
Office of the Assistant
Administrator, ATSDR
REFERENCES
1. Hazardous Ranking Score Package, Richardson Flat Tailings Site, Park City, Utah.
2. Shacklette, J.T., and Boerngen, J.G., 1984, Elemental Concentrations in Soil and Other Surficial Materials of the Conterminous United States. U.S. Geological Survey Professional Paper 1270.
3. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Arsenic. Atlanta: ATSDR, March 1989.
4. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Cadmium. Atlanta: ATSDR, March 1989.
5. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Lead. Atlanta: ATSDR, 1987.
6. Recommended dietary allowances. 1980. 9th Rev. National Resource Council. Washington, DC: Food and Nutrition Board, National Academy of Sciences., 162-164.
7. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Selenium. Atlanta: ATSDR, December 1989.
8. Yang, G., Wang, S., Zhou, R., et al. 1983: Endemic selenium intoxication of humans in China. Am J Clin Nutr 37:872-881.
9. Porter K.G., McMaster D., Elmes M.E., et al. 1977. Anemia and low serum-copper during zinc therapy. Lancet:744.
10. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Zinc. Atlanta: ATSDR, December 1989.
