PRELIMINARY PUBLIC HEALTH ASSESSMENT ADDENDUM
RICHARDSON FLAT TAILINGS
PARK CITY, SUMMIT COUNTY, UTAH
This document is an addendum to the preliminary public health assessment prepared for the Richardson Flat Tailings site by the Agency for Toxic Substances and Disease Registry (ATSDR) in July 1990.
The Richardson Flat Tailings Site lies in a broad valley northeast of Park City, Utah--approximately 1½ miles from Prospector Square, which is the nearest developed part of the city. The proposed NPL site includes a tailings pond area at Richardson Flat and an adjacent section of Silver Creek where tailings have accumulated. For purposes of this assessment, those areas are considered on site; and all other areas off site. The site is remote; four businesses and two presently vacant residences are within 1 mile of the site. Occasional tailings workers and cyclers are among the few who are expected to have visited the site.
Tailings are a waste product generated by mining activities. Sampling results have identified a few metals of potential concern. However, people are not being exposed at levels of public health concern in any known completed exposure pathway at the site. Furthermore, it does not appear likely that exposures associated with any past or present potential exposure pathway would exceed levels of public health concern. Finally, blowing dust, the single community health concern expressed, poses no apparent public health hazard. For these reasons, the Agency for Toxic Substances and Disease Registry (ATSDR) has concluded that this site poses no apparent public health hazard due to past or present exposures. However, should the site, or areas near the site where significant levels of contaminants may be found, be developed in the future for residential purposes, the people who live on top of soil contaminated at significant levels will have greater exposure duration to soil than those who live near the site or worked on the site. In this case, levels of contaminants on or very close to the site would be at levels of health concern. Because we are not certain of the future of this site, ATSDR considers the RFT site to pose an indeterminate public health hazard for future exposure.
ATSDR's Health Activities Recommendation Panel (HARP) has evaluated the data and information developed in the Richardson Flat Tailings Public Health Assessment. The panel determined that, because of the apparent lack of past and present public health hazards and community health concerns, no follow-up health activities are indicated at this time.
The Agency for Toxic Substances and Disease Registry (ATSDR), in Atlanta, Georgia, is a federal agency within the U.S. Department of Health and Human Services and is authorized by the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) to conduct public health assessments at hazardous waste sites. ATSDR has, under this mandate, evaluated the public health significance of this site.
This document is an addendum to a preliminary public health
assessment prepared in July 1990 for the Richardson Flat Tailings
site (RFT site) by ATSDR after the U.S. Environmental Protection
Agency (EPA) 
first proposed the site for the National Priorities
List (NPL) on June 14, 1988 (USEPA 1992b). A copy of the
previous health assessment is provided in Appendix D. In
February 1991, in response to public comments on its proposed
listing, EPA reevaluated site scoring and withdrew the site from
consideration for the NPL. EPA again proposed the site for the
NPL in February 1992 after modifying its Hazard Ranking System
and obtaining new site information. Therefore, in response to
our legislative mandate, ATSDR has prepared this preliminary
public health assessment addendum that reevaluates available
site-related information and relevant public health issues.
A. Site Description and History
The RFT site lies in a broad valley northeast of Park City--approximately 1½ miles from Prospector Square, which is the nearest developed part of the city. Figures 1 and 2 (Appendix A) show features of the vicinity and site. ATSDR's discussions with EPA indicate that the proposed NPL site includes a tailings pond area at Richardson Flat (Area A on Figure 2) and an adjacent section of Silver Creek where tailings have accumulated (Area B on Figure 2). Thus, for purposes of this assessment, Areas A and B are considered on site; and all other areas off site. Area A is enclosed within the security fence shown in Figure 2; Area B parallels the fence and is immediately outside it.
NPL Site Components
Tailings Pond
The tailings disposal pond covers approximately 160 acres; tailings are as much as 10-feet thick (USEPA 1992a). The pond has not been used since mining activity stopped in 1982. During a site visit in 1992, ATSDR observed that the disposal area is essentially flat and may nearly have reached its practical storage capacity. No water was ponded at that time. Most of the tailings are covered with soil or a dense growth of a salt grass that has a thick root mat (E&E 1992).
The owner, United Park City Mines (UPCM), reported to ATSDR that tailings were present when they purchased the property in 1953. UPCM reports that their property boundary extends beyond the fence shown on Figure 2; however, the boundary was not defined for ATSDR. Under UPCM's ownership, most of the tailings were disposed between 1969 and 1982 from mines that were owned by UPCM and leased by Park City Ventures and Noranda Mining, Inc. (USEPA 1992a, USEPA Undated). Tailings were transported from the mine sites by slurry pipeline; UPCM reports that one to two people were present at the site to monitor the delivery. EPA reported rumors that, in earlier years, tailings were transported to the site via Silver Creek, and UPCM reported that transport mode was never used. ATSDR does not consider that possible transport mode to be a substantive issue and does not address it further in this assessment. UPCM reports that water from tailings transport, surface water runon, and snowmelt were contained within the pond and eliminated through evaporation rather than discharged to Silver Creek. UPCM reports it intends to maintain its mines, the tailings pipeline, and the tailings disposal area and will reuse those facilities when mining again becomes economically viable. UPCM reports they will not develop the property for residential use, industrial use--other than mining, or for parks or recreational uses.
A Utah Department of Environmental Quality (UDEQ) representative reported rumors that some tailings had been removed and used off site for sewer and road construction. An EPA contractor also reported use of tailings materials for sewer and road base backfill but did not provide supporting information (E&E 1987a). UPCM said there has been no activity of that nature since 1981; although, there may have been earlier. Because of uncertainty about tailings being taken off site and associated locations and any human exposure potential, ATSDR cannot address this issue.
In 1974, plans were approved for Park City Ventures to construct an embankment and perimeter dikes to contain the tailings and associated transport water (E&E 1989). A diversion ditch was excavated on site to route runoff water around the tailings impoundment. The ditch begins east of the tailings, passes the southern edge of the currently configured tailings pond, and ends in a marshy area of about 10 acres near the embankment. EPA reports that ditch was excavated through zones of tailings (USEPA 1991b). No chemical analyses are known to confirm whether tailings are present within the ditch alignment. However, in 1992, ATSDR reviewed a 1953 areal photograph that appears to show tailings extended well to the south at that time, to County Road. That photograph, together with ATSDR's on-site observation of tailings-like zones within the ditch slope, suggest that one or more segments of the ditch were excavated through tailings materials. During that visit, ATSDR noted that ditch slopes were being regraded and covered with soil to reduce erosion and off-site transport of tailings.
In June, 1985, an EPA contractor obtained photographs of clouds of fugitive dust moving off site as a result of strong winds (E&E 1987a). UPCM said they began placing soil over the tailings and planting vegetation in 1983. In 1992, UPCM estimated that they had covered about 85% of the tailings area and that the tailings should be completely covered with soil in 1993 (E&E 1992). An EPA contractor reports that UPCM intends to place soil on the small part of the tailings area that currently has no soil cover or salt grass. The contractor expressed concern about future dust because some of the cover soils are thin (less than 6 inches thick) and salt grass may disappear if the site becomes drier. UPCM reports most cover soils are being excavated from higher ground northeast of the tailings deposit. ATSDR was informed that the workforce consists of two to four persons who are provided with respirators to use during dry, dusty weather. Haul roads are watered during such weather.
The fence that encloses the tailings deposit was constructed recently. ATSDR observed that gates were locked. Before erecting the fence, motorcyclists and cattle were reported on the property (ATSDR 1990, E&E 1987a). Sheep have been observed on adjacent property.
Silver Creek Flood Plain Tailings
Large floodplain tailings deposits are reported to exist upstream of the site as well as downstream to as far as the confluence of the Weber River (USEPA 1993). An EPA representative reports that the agency has not yet determined the linear extent of the Silver Creek flood plain that will be part of the proposed NPL site. For this assessment, ATSDR defined Area B in Figure 2, which includes two tailings deposits EPA has already investigated (E&E 1989). The specific source(s) of those tailings is not known, but ATSDR's review of area topography suggests that their origin is upstream in the watershed, not UPCM's tailings pond.
NonNPL Elements
Park City Sanitary Landfill
UPCM property also contains a closed Park City sanitary landfill; EPA reports that the landfill is not part of the proposed NPL site.
A Park City representative reports the landfill was opened in 1973 and closed in 1985. Wastes were deposited below ground in trenches and also were mounded above ground. An EPA contractor told ATSDR that the landfill materials are mostly sanitary wastes, but are believed to include some tailings from Prospector Square, and sketchy information suggests some chemical wastes like PCBs and paints might be present. City officials have said that the materials placed in the landfill materials are sanitary wastes, and the absence of substantive industry makes it unlikely that chemicals are present other than those that are used in households. During part of the operation, Park City had a policy prohibiting disposal of electrical transformers, hazardous waste, or toxic substances. In 1990, a relocation of U.S. Route 40 resulted in that highway being constructed through the middle of the landfill. ATSDR was told that wastes encountered in the path of the highway were excavated, placed on the adjoining landfill remnants, and covered with soil. Figure 2 shows the approximate limits of the landfill remnants.
Laboratory data were reviewed for samples taken from borings drilled at the landfill during highway development planning (UDT 1989). These data showed that a few inorganic elements detected were not at high concentrations, and no polychlorinated biphenyls, pesticides, or semivolatile organic compounds were detected. One volatile organic compound was detected in two samples at extremely low concentrations (maximum of 0.03 parts per million [ppm]). In addition, although landfill workmen are likely to have been exposed to waste-related contaminants in the past, no exposure is plausible now, and none is expected in the future unless the landfill is disturbed. The city does not intend to reopen the landfill; Summit County provides a landfill for the Park City area at another location. Also, UPCM reports that their property, including the part where the landfill is located, will not be developed.
Based on the information about the landfill and its operation, ATSDR is excluding the landfill and its workers from further evaluation in this public health assessment.
Prospector Square, Silver Maple Claims
Prospector Square, a large residential and commercial development in the northeast part of Park City, was partially constructed on a large deposit of mine tailings. Prospector Square is along Silver Creek about 1½ miles upstream from the RFT site (Figure 1). In 1988, ATSDR conducted a human exposure study to determine the effect of mine tailings contaminated with lead, arsenic, and cadmium on biological levels of those metals among persons living in the immediate vicinity (ATSDR 1988).
Silver Maple Claims, another location along Silver Creek at which tailings are reported, lies upstream from the RFT site, between the site and Prospector Square. The specific location and boundary of Silver Maple Claims has not been defined.
Although some contaminants released at Prospector Square and Silver Maple Claims might migrate to the RFT site, ATSDR review of available information indicates that the RFT site is not likely to have a definable impact on either of those locations. Therefore, ATSDR will not further evaluate contamination or health issues potentially associated with those locations.
ATSDR representatives--Ms. Stephanie Prausnitz and Messrs. Don Gibeaut and Glenn Tucker--visited the site area on August 18 and 19, 1992. A public availability session was held on the morning of the 19th. With the exception of representatives of UPCM and the press, no community members attended the meeting. Pertinent information obtained during that visit is described in appropriate sections of this document.
C. Demographics, Land Use, and Natural Resource Use
Demographics
The site is in a rural area. In 1992, ATSDR found one home and three house trailers within a mile of the site. The residences are ½ to ¾ mile southwest (upstream) of the RFT site and are within 100 to 400 feet of Silver Creek. Three of the residences were occupied at that time. Information received in late 1993 indicates there are now two trailers plus one former home that has been converted to vehicle repair activities--neither of the two trailers are now occupied. Three larger businesses--two concrete and aggregate suppliers and an electric power company service center--are near Silver Creek about ½ mile northwest (downstream) of the site. ATSDR learned those businesses employ a total of 51 persons at those locations. The nearest residence to Silver Creek downstream from the RFT site was observed to be about 4 miles away.
Nearby Park City is a center for skiing and recreation; its full-time population is about 4,500 (USBC 1991). The census also identifies 3,800 vacant housing units in the city; thus, when the units are filled with visitors, the total population increases substantially. EPA reports that about 4,300 residents are within a radius of 3 miles of the site (USEPA 1991b). The nearest residents within the city are at Prospector Square. The nearest schools in the city are on Route 248, next to Prospector Square. A health clinic that provides some emergency care is also in Prospector Square, but no nursing homes are in the site vicinity.
Land Use
Essentially all of the area within a 1-mile radius of the site is open, undeveloped rangeland that supports generally low-density populations of sheep, cattle, and horses. Beyond 1 mile of the site, land use is principally open, undeveloped rangeland except for development associated with Park City, skiing, and residential and commercial development along a narrow zone by I-80, which is about 4 miles north of the RFT site (Figure 1). Park City officials report they expect future development will extend northwest of town along State Route 224 (Figure 1), rather than along Route 248 toward the RFT site.
The county extension agent reported that there has been limited agriculture, consisting of about 200 acres of pasture, in Silver Creek watershed between the site and I-80. A commenter reports that the amount of irrigated pasture has been substantially reduced for several years and for the foreseeable future because the Park City Municipal Corporation uses some of the creek water for municipal purposes. This apparently affects principally the users who withdraw from the Pace Homer Ditch for which the diversion point is well upstream of RTF. Affected parties are compensated via crop-loss payments and purchase livestock feed from out of the watershed area. Pasture is primarily grasses and some alfalfa. Stock in this watershed segment includes a dairy herd, beef cattle, and sheep. The dairy cattle are near I-80. Some grain is being raised farther north in the watershed near the community of Wanship, which is about 6 miles beyond I-80.
Natural Resource Use
Mining
The Park City area was once a major lead- and silver-mining district, but mines have not been active recently (UDNR 1986).
Surface Water
Average annual rainfall in the Park City area ranges from 16 inches at low altitudes to more than 40 inches in the Wasatch Mountains, a few miles west of the site. The Silver Creek watershed drains an area of about 26 square miles. The creek originates south of Park City and flows generally northward through the city, passes the RFT site, and discharges into the Weber River about 10 miles downstream from the site. Silver Creek is a perennial stream with an average annual discharge of 3.3 cubic feet per second (cfs) (USEPA 1991b). Flow, however, is quite variable; substantially greater flow occurs during snow melt, and ATSDR observed essentially no flow velocity at the RFT site in August. Weber River, which has an average annual discharge of 214 cfs, is a major stream in the region and discharges into Great Salt Lake about 50 miles downstream of the site (USEPA 1991b).
The on-site diversion ditch receives surface runoff from land areas that are upgradient of the tailings deposit and transports that water around the southern edge of the current tailings impoundment to a wetland area of about 10 acres by the embankment (USEPA 1991b). From there, the runoff enters Silver Creek at a point ATSDR observed a few hundred feet northwest of the embankment.
Silver Creek is not used for human water supply (E&E 1985). Stock obtain water directly from the creek and from diversion ditches. Creek water is also withdrawn for stock watering and irrigation. Utah Division of Water Rights reports there are three diversions of Silver Creek water downstream from the RFT site (UDNR 1992). The nearest diversion is at the G.M. Pace Ditch that begins about 600 feet north of U.S. Route 189 (US-189) (UDNR 1992). Based on discussion with a Park City official and other information, it appears that G.M. Pace ditch also receives water directly from the Pace Homer ditch, which originates at a spring in Park City (E&E 1987b). Water from G.M. Pace ditch has been reported to be used for irrigating 316 acres of pasture (USEPA 1991b). The next closest diversion is north of I-80, about 7 miles downstream from the site; water is reported to be used for livestock (UDNR 1992). The third diversion, reported to be for irrigation, is farther north of I-80, about 9 miles downstream from the site and about 2 miles upstream from Wanship where Silver Creek discharges into the Weber River, a major water course in the region (UDNR 1992). As previously noted, availability of creek water for withdrawal has been substantially reduced for several years and for the foreseeable future because the Park City Municipal Corporation uses some of the creek water for municipal purposes. The curtailment apparently has been most severe for those who are served by the Pace Homer Ditch for which the diversion point is well upstream of RTF.
Weber River has only one diversion for public water supplies, at a point about 45 miles downstream from the site: UDEQ reports there are many diversions for irrigation and livestock watering (UDEQ 1992a).
Fishery
Available information provides an uncertain picture of Silver Creek as a fishery. A survey in 1954 found a small number of trout. Electroshocking data obtained from Silver Creek in 1970 did not show the presence of game fish. Biologists, more recently, report cutthroat trout in the creek; although, there is no information to quantify the population or the location where the trout are present (E&E 1991a). The last known investigation, in 1986, produced no fish. EPA reported seeing pan-sized trout at the site in the spring of 1992 (USEPA 1993). From this information, ATSDR concludes that the creek, at best, is not an important fishery. The Weber River is an important trout fishery.
Groundwater
Groundwater exists in both consolidated rocks and unconsolidated valley fill (soils) (UDNR 1986). Consolidated rocks crop out over most of the Park City area, except along stream channels where unconsolidated valley fill is exposed at the surface. Valley fill is primarily alluvial or glacial in origin and consists of clay, silt, sand, gravel, cobbles, and boulders. The alluvium is primarily in low areas, along stream channels. The average thickness of valley fill in the Silver Creek drainage system is about 100 feet.
Silver Creek is flanked by lines of hills that rise a few hundred to 1000 feet above the valley floor. The valley floor slopes downward in a generally northerly direction, the direction of flow in Silver Creek. The RFT site lies along Silver Creek in an area that is blanketed by unconsolidated fill. The thickness of that soil zone at the RFT site is not known. EPA reports that groundwater has been encountered at relatively shallow depths at the RFT site, but a specific depth has not yet been defined. ATSDR believes that water levels beneath the site might be relatively high during wet periods of the year and may drop during drier months.
Water in consolidated rocks moves along faults and fractures from high altitudes toward discharge areas at lower elevation. Studies show that groundwater in valley fill flows in the same general direction as the streams (UDNR 1986). According to studies, the creek gains water inflow over time from the valley fill aquifer system. A study, which does not describe weather, stream segments, flows, or loss quantities, did not show any areas of significant losses (UDNR 1986). ATSDR interprets that finding to mean that some limited stream losses to valley fill aquifers did occur in that study.
UPCM reports there has never been a groundwater supply well on the property. The formerly occupied residences and the vehicle repair business that are within a mile southwest of the site obtain potable water supplies from private wells that appear to be hydraulically upgradient from the RFT site. It is unknown whether the wells draw water from a valley fill aquifer or from bedrock. The three businesses to the northwest use bottled water for drinking and obtain industrial water from wells that are hydraulically downgradient from the RFT site (E&E 1991d). These wells are reported to be more than 300 feet deep and are probably drawing from a bedrock aquifer rather than from a valley fill aquifer.
ATSDR learned that Atkinson Special Improvement District, High Valley Water Company, and Summit County Service Area #3--serving 240, 250, and 75 persons, respectively--obtain their water from wells in the Silver Creek watershed. The wells are about 2, 3½, and 4 miles, in a generally northwesterly direction from the RFT site and are set back about ¾ to 1 mile from the creek. Park City's public water system gets its supply for its 4,500 residents and many visitors from wells and tunnels that are 1½ miles, or more, upgradient from the RFT site (UDEQ 1992a).
Utah maintains birth and death certificate databases and a tumor (cancer) registry. No health outcome data were requested, as discussed in the Health Outcome Data Evaluation section below. In 1988, ATSDR conducted a human exposure study to evaluate whether mine tailings contaminated with lead, arsenic, and cadmium had an effect on biological levels of those elements among persons living in the immediate vicinity (ATSDR 1988). The study results are described in the Health Outcome Data Evaluation Site section below. No additional relevant databases or health studies were identified.
ATSDR staff noted community members' concern about dust blowing off site. Staff are unaware of any other site-related community health concerns. No health concerns were expressed to ATSDR representatives at the Public Availability session. Furthermore, ATSDR staff contacted residents of nearby houses and representatives of the EPA, UT Department of Environmental Quality, UT Department of Health, Summit County Health Department, and the town of Park City. Concern had been expressed about blowing dust. No one was aware of any other site-related community health concerns.
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. Comments were received.
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
ATSDR's preliminary public health assessment of 1990 used sampling data obtained in 1985 and 1986 and addressed several inorganic contaminants: arsenic, cadmium, chromium, copper, lead, manganese, selenium, and zinc. This addendum considers that sampling data in addition to more recent data and site-related information.
Sampling data and supporting site-related information suggest that contaminants have been released into the air, groundwater, surface water, and sediment on and off site. This section identifies contaminants of potential concern that have been selected for further evaluation in subsequent sections of this public health assessment to determine whether exposure to them has public health significance. Identifying contaminants in this section does not imply that exposure will result in adverse health effects.
Contaminant selection considers the following factors:
ATSDR also conducted a search of the EPA Toxic Chemical Release Inventory (TRI) to determine whether that database identifies any chemical releases for the RFT site or other facilities in the vicinity. TRI contained no data for any facilities in Summit County.
The contaminants of potential concern selected to be addressed further in the public health assessment are listed in each of the data tables (Appendix B), and many are discussed within this section. The data tables contain several abbreviations that identify sources of public health assessment comparison values:
* EMEG Environmental Medial Evaluation Guide * RMEG Reference Dose Media Evaluation Guide * CREG Cancer Risk Evaluation Guide * LTHA Lifetime Health Advisory Guide * AL Action Level
EMEGs are estimated comparison concentrations that are based on information determined by ATSDR from its Toxicological Profiles for specific chemicals. RMEG comparison values are based on EPA's estimates of the daily exposure to a contaminant that is unlikely to cause adverse health effects. CREGs are estimated comparison concentrations for specific chemicals based on an excess cancer rate of one in a million persons and are calculated using EPA's cancer slope factors. EPA's LTHA identifies the contaminant level in drinking water at which adverse health effects would not be anticipated over a lifetime. All of the foregoing comparison values are guides and do not have a regulatory basis. An AL comparison value is an EPA regulatory concentration that, if exceeded, requires public water systems to initiate specific actions.
Groundwater, tailings, soil, surface water, sediment, and ambient air have been sampled. No data are available for food chain elements.
Groundwater: Area A
Several samples of groundwater obtained from monitoring wells installed next to the tailings pond and next to the landfill have been analyzed. Data for unfiltered samples show that several of the contaminants of potential concern were found at levels that exceed ATSDR's comparison values for drinking water use--antimony, arsenic, barium, beryllium, cadmium, copper, lead, manganese, silver, vanadium, and zinc. Maximum concentrations are shown in Table 1 (Appendix B). Several of those maximum concentrations were detected at a monitoring well near the landfill.
Tailings Deposits: Areas A and B
Several tailing samples were analyzed from Area A and two from Area B. Maximum concentrations of substances are presented in Table 2 (Appendix B). Arsenic, beryllium, and cadmium were present at levels that exceed ATSDR's comparison values for incidental ingestion. In addition, lead, zinc, and calcium were at especially elevated levels.
Soil Cover Layer On Tailings: Area A
Five samples of the soil cover layer in Area A were analyzed. No sampling has been conducted on site for natural soils at or beyond the perimeter of the tailings deposit. Maximum concentrations of substances are presented in Table 3 (Appendix B). Arsenic and beryllium slightly exceed ATSDR's comparison values for incidental ingestion, but the concentrations detected are typical of soils in the western part of the country.
Surface Water: Area A and Area B
Seventeen surface water samples from the diversion ditch and marsh at Area A and 10 samples from Silver Creek at Area B were analyzed. Because water quality varies with changing flow rates, the sample data may not be indicative of conditions over time. Maximum concentrations of substances are presented in Table 3 (Appendix B).
Many of the substances were detected at levels that exceed ATSDR's comparison values for drinking water. For Area A, the substances include antimony, arsenic, barium, beryllium, cadmium, copper, lead, manganese, mercury, silver, thallium, vanadium, and zinc. At Area B, antimony, arsenic, beryllium, cadmium, mercury, silver, thallium, and vanadium exceeded comparison values; the concentration of lead was identical to its comparison value.
Sediment: Area A and B
Maximum concentrations of substances found in sediment samples from Areas A and B are presented in Table 5 (Appendix B).
Twelve samples taken in Area A from the diversion ditch, marsh, and areas where water ponds on the tailings were analyzed. Arsenic, beryllium, cadmium, and manganese were present at levels that exceed ATSDR's comparison values for incidental ingestion. Lead was found at an elevated level; antimony, iron, and zinc are also elevated when compared to their concentrations in the soil cover data presented in Table 3.
At Area B, two samples of sediment from Silver Creek were analyzed. Arsenic and beryllium were found at levels that exceed ATSDR's comparison values for incidental ingestion. Lead was present at an elevated concentration; antimony, iron, and zinc are also elevated.
Ambient Air: Area A
Ambient air sampling was conducted in 1986 at four locations within Area A. Because of the short sampling duration, the data may not be representative of air quality over time. The samples were analyzed for arsenic, cadmium, lead, and zinc; maximum concentrations reported are presented in Table 6 (Appendix B). The concentrations for arsenic and cadmium exceed ATSDR's comparison values for ambient air. Lead and zinc also occurred at levels greater than would be expected in a rural setting.
Ambient air sampling was also conducted in 1992 at locations along the security fence. These results are described in the next section.
Groundwater
Background Monitoring Well and Nearby Industrial Wells
Analytical results for unfiltered groundwater samples obtained from the monitoring well south of County Road, topographically upgradient of the property, and from three nearby downgradient industrial wells are presented in Table 7 (Appendix B).
Data for two samples from the monitoring well show that arsenic, beryllium, and lead exceed ATSDR's comparison values for drinking water. Other substances are not at extraordinary concentrations.
Samples from the nearby industrial wells, which are not used for potable water supplies, were analyzed only for arsenic, cadmium, chromium, and lead. Results for seven unfiltered samples suggest that arsenic and lead are present at levels that exceed ATSDR's comparison values for drinking water (E&E 1992).
Public Water Supply Wells
Analytical data were reviewed for a few unfiltered groundwater samples from three public water supply wells (Atkinson Special Improvement District, High Valley Water Company, Summit County Service Area #3) located to the northwest of RTF on the flanks of the Silver Creek watershed. Maximum concentrations are shown in Table 8 (Appendix B). Several contaminants of potential concern were not reported in analyses of the samples, including; aluminum, antimony, beryllium, cobalt, thallium, and vanadium. ATSDR's comparison values for drinking water were exceeded only for arsenic, which was present at low levels in the samples from the High Valley and Summit County Service systems. Other substances were not at extraordinary levels.
Soils
Five samples of surface soils and two of subsurface soils were obtained near the site. Four of the surface samples were from 2 to 50 feet from roads; the fifth sample location was about 400 feet south of the county road. Maximum concentrations are shown in Table 9 (Appendix B). For surface soils, arsenic and beryllium were present at levels greater than ATSDR's comparison values for incidental ingestion. Lead and zinc were elevated in the sample obtained south of County Road, and vanadium was elevated in one of the other surface samples. The subsurface samples did not contain any substances at extraordinary levels; although, arsenic was present above ATSDR's comparison level for incidental ingestion.
Surface Water: Upstream and Downstream
Seven samples of water taken from Silver Creek upstream of Area B were analyzed; some also were reported from the creek immediately downstream of the site, near US 189, and many more analyses were for creek samples taken at Atkinson, approximately 4 miles downstream. Because water quality varies under different flow rates, the sampling data may not represent conditions over time. Maximum concentrations are shown in Table 10 (Appendix B). For most of the substances, ATSDR's review of the data suggests that maximum concentrations are not substantially greater downstream than upstream.
Upstream, substances that exceeded ATSDR's comparison values for drinking water are antimony, arsenic, beryllium, cadmium, lead, and zinc. Downstream, comparison values were exceeded by antimony, arsenic, beryllium, cadmium, lead, manganese, and zinc.
Sediments: Upstream and Downstream
Upstream of Area B, one sediment sample was taken in Pace Homer Ditch and two from Silver Creek. Downstream, a sample of sediment was taken from the creek several hundred feet from the site. Maximum concentrations of substances are shown in Table 11 (Appendix B).
The arsenic and beryllium in the upstream and downstream sediments exceed ATSDR's comparison values for incidental ingestion; antimony, lead, and zinc levels are also elevated for upstream sediments.
Ambient Air
In 1985, an EPA contractor obtained information that showed wind-driven fugitive dust moving off site. In 1986, ambient air was monitored at one station about 3,000 feet south-southeast of Area A. Because of the short sampling interval, the monitoring data may not be representative of conditions over time. Prevailing wind during the monitoring period was from the west-northwest and south east. Thus, the monitoring location was not in the prevailing downwind direction from the site at any time during the sampling program. Maximum concentrations of substances are shown in Table 12 (Appendix B). Several samples were analyzed for arsenic, cadmium, lead, and zinc. Constituent levels were much less than had been recorded at on-site locations during that study (Table 6). Arsenic was not detected. The concentration of cadmium, although quite low, exceeds ATSDR's comparison value for ambient air. Cadmium levels and the low concentrations of lead and zinc detected appear consistent with values for rural settings. However, had the monitoring station been in the direction of prevailing wind, ATSDR believes that the concentrations 3,000 feet from the site might have been greater. Review of the on-site air monitoring data shows that one of the stations that recorded substantial concentrations was only a few hundred feet inside Area A, thus the concentrations shown in Table 6 may be indicative of the levels in immediate off-site areas at that time.
In 1992, when an estimated 80% of the tailings deposit at Area A was covered with soil or salt grass, ambient air quality monitoring was conducted for two days at five locations along the fence, shown in Figure 2. Because of the short sampling interval, the monitoring data may not be representative of conditions over time. The monitor locations were about 150 to 800 feet from Area A. Those analyses detected only zinc at low concentrations (0.1 µg/m3) at three of the monitors. This is less than a tenth of the maximum zinc that had been found in on-site monitors in 1986. However, none of the monitors were situated downwind for any extended length of time (USEPA 1992c).
C. Quality Assurance and Quality Control
Only some of the reference documents contain quality assurance information for investigations, sampling, and laboratory analyses. In preparing this assessment, ATSDR presumed that protocols and results from other agencies are valid. The completeness and reliability of the information could affect the validity of ATSDR's conclusions.
ATSDR did not observe any physical or other hazards at the site.
ATSDR identifies human exposure pathways by examining environmental and human components that might lead to contact with contaminants. 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 and indicate that exposure to a contaminant has occurred in the past, is currently occurring, or will occur in the future. Potential exposure pathways are those for which one or more of the elements is not clearly defined, but could be present. Potential pathways indicate that exposure to a contaminant could have occurred in the past, could be occurring now, or could occur in the future.
ATSDR's preliminary health assessment of 1990 addressed several exposure pathways associated with soil and tailings, groundwater, food-chain, ambient air, and surface water. This addendum evaluates exposure pathways using all available sampling and site-related information.
Pathway analyses conducted for the site area indicate that there are several completed exposure pathways associated with tailings, soil, surface water, and air. Affected populations include tailings workers, and site trespassers. A completed pathway also is noted for users of the public water systems because of metals (at low concentrations), but it is unlikely that the site is the source. The completed pathway elements are summarized in Table 13 (Appendix B).
Several potential exposure pathways--associated with tailings, soil, surface water, air, groundwater, sediment, and possibly foods--could also exist. Potentially exposed populations include site and area workers and residents, trespassers, road workers, ranchers, consumers, and possibly fishermen. The potential pathway elements are summarized in Table 14 (Appendix B).
Tables 15 and 16 (Appendix B) further characterize exposed and potentially exposed populations and associated media and contaminants.
A. Completed Exposure Pathways
Tailings and Surface Soil Pathways On Site: Area A
Metals are present in tailings, and, at low concentrations, in the tailing cover soils. Tailings also are likely to have been mixed with surface soil on the perimeter of Area A. During the years tailings were deposited, the workforce is considered to have been exposed to contaminants in tailings and some soils principally through incidental ingestion and inhalation. Trespassers are considered to have been exposed in a similar manner.
Surface Water Pathways On Site: Area A
Water used to transport tailings and surface water runon that ponded in Area A are likely to have contained elevated levels of metals. When tailings were being deposited, workers were likely to have been exposed to contaminants in those waters through incidental ingestion. Trespassers are likely to have been exposed less extensively to water-born contaminants through incidental ingestion.
Ambient Air Pathways On Site: Area A
Air sample data from 1986 confirm that metals have been entrained in ambient air in the past in Area A as a result of wind eroding and suspending particles from the tailings surface. At the time of that sampling activity, most of the tailings area was not covered or vegetated. ATSDR considers the on-site workforce to have been exposed to airborne contaminants through inhalation during the years the tailings were being deposited. Trespassers who entered the site before the property was fenced were likely to have been exposed through inhalation.
Public Water Systems Off Site: Downstream Silver Creek Watershed
Three public water systems obtain at least a part of their supply from wells that are within the Silver Creek watershed. Sampling data show some metals are present at low concentrations in those water supplies--arsenic, however, is potentially of concern at even low levels. Information reviewed indicates there is little likelihood that site-related contaminants do, or will, migrate to those wells. The wells are a considerable distance from the site, are located up on basin slopes--not by the stream, and withdraw from bedrock--not the valley alluvium. Also, well logs reviewed showed two of the three wells were under "artesian" pressure at the time of construction. That pressure, where it exists, results in a net upward flow of groundwater from the rock zone into the alluvium, thereby preventing downward flow of water from the valley alluvium. Furthermore, dilution and/or contaminant adsorption within the alluvium should substantially reduce metals concentrations in groundwater away from the site.
Water system customers are exposed to low levels of some contaminants--past, present, and future--principally through ingestion and, to a small degree, through aerosol inhalation (showering).
B. Potential Exposure Pathways
Tailings and Surface Soils Pathways On Site: Area A, Area B
Remediation and maintenance workers on site in Area A after tailings disposal stopped are potentially exposed--past, present, and in the future--through ingestion and inhalation to contaminants contained in tailings and possibly to those in the layer of cover soils or in adjacent natural surface soils. Should the area ever be developed for homes or businesses, residents and workers potentially would be exposed, principally through ingestion and inhalation, to contaminants in tailings and soils.
Trespassers might enter the flood plain in Area B infrequently. They potentially are exposed--past, present, and future--through ingestion and inhalation to contaminants in tailings and possibly to contaminants in adjacent surface soils.
Surface Water Pathways On Site: Area A
Surface water that ponds in Area A or flows through the diversion ditch to the marsh and into Silver Creek contains contaminants to which remediation and maintenance workers potentially are exposed--past, present, and future--principally through incidental ingestion.
Ambient Air Pathways On Site: Area A
On-site remediation and maintenance workers are potentially exposed through inhalation--past, present, and future--to contaminants entrained by wind or by vehicle and heavy equipment activity.
Groundwater Pathways Off Site
Residential-Type Wells
The formerly occupied residences and the vehicle repair business operating at another former residence are within a mile southwest of the site and close to Silver Creek. ATSDR assumes the now-vacant residences could be reoccupied in the future. The private wells that service those locations appear to be hydraulically upgradient from the RFT site and are not likely to be affected by site releases to groundwater. Groundwater at those wells is more likely to be affected by contaminants released from tailings deposits at Prospector Square or Silver Maple Claims. Data are not available to confirm water quality at those private wells. Therefore, ATSDR conservatively presumes that those well users potentially are exposed--past, present, and future--principally through ingestion and possibly through aerosol inhalation (showering) to contaminants that might originate from tailings near Park City.
Business/Industrial Wells
Three businesses northwest of the site get their industrial water supply from wells that are hydraulically downgradient from the site. The wells are not used for potable purposes. Arsenic and lead were present in one or more of the wells at low levels. Concentrations might increase if contaminated groundwater enters the water supply aquifer in substantive quantity in the future. However, dilution and adsorption in the groundwater regime are likely to prevent substantive contaminant increases in those wells. Workers using the industrial water potentially are exposed to contaminants in groundwater--past, present, and future--through incidental ingestion and aerosol inhalation.
Surface Soils Pathways Off Site
Wind has likely deposited tailings contaminants on surface soils in the vicinity of the site. Some surface soils on the creek flood plain also might contain elevated levels of contaminants as a result of tailings deposition. Workers who constructed US-40 possibly were exposed through incidental ingestion and inhalation to contaminants in surface soils in the vicinity. Also, nearby residents, employees, and road maintenance persons potentially are exposed--past, present, and future--through similar routes.
Creek Surface Water Pathways Off Site
Dissolved and particulate contaminants are present in creek water. The specific source(s) and amount(s) of contribution are not clear. County flood control maintenance workers and ranchers who draw water from the creek potentially are exposed--past, present, and future--through incidental ingestion to contaminants in creek water.
Creek Sediments Pathways Off Site
Creek sediments in the site vicinity contain contaminated sediment particles, including tailings particles, that have been transported from the site or from locations upstream of the site. County flood control maintenance workers and possibly ranchers who draw water from the creek potentially are exposed--past, present, and future--through incidental ingestion to contaminated creek sediments.
Ambient Air Pathways Off Site
In the past, wind was observed to suspend and transport dust (e.g., tailings and possibly contaminated surface soils) from on-site areas. Strong winds also are likely to suspend and transport flood plain tailings during dry weather. Winds also are likely to resuspend contaminated particles from areas off site where they had been deposited previously by wind. Results of air sampling at the fence in 1992 suggest that levels of site-related wind-borne contamination may be inconsequential when cover soils are in place, providing the cover and salt grass are maintained. However, data may not be representative of conditions over time.
The lateral extent of contaminant transport by wind or contaminant deposition is not known. The general prevailing wind direction is reported to be northwest; a several-day air quality study recorded winds toward the northwest and southeast (E&E 1985). For these dominant wind directions, the populations that would most likely be exposed through inhalation--past, present, and future--are the employees of three companies located a short distance northwest of the site. Other potential exposed populations include any residents of the homes and the business southwest of the site. Motorists, bikers, and maintenance workers on the roads adjacent to the site are potentially exposed for short periods. Workers who recently constructed the new segment of US-40 adjacent to the site may have been exposed as well.
Food Chain Pathways Off Site
Food Products--Cattle, Sheep, Milk, Grain
ATSDR is not aware of any sampling data for edible products grown in the site vicinity. Results of research and sampling elsewhere suggest that bioaccumulation of some metals may occur in agricultural products. This may include meat or milk from stock that drink contaminated water, from stock that graze on vegetation on which wind-blown contaminants have deposited or on vegetation grown in contaminated soil or irrigated with contaminated water from Silver Creek, or from stock that drink contaminated surface water. Some contaminants might also concentrate in grain. Therefore, persons who consume food products associated with cattle, sheep, or grain raised in the site vicinity potentially are exposed--past, present, and future--to contaminants taken up from environmental media. Appreciable exposure from this potential source is unlikely for people who obtain that food through mass distribution channels, but is plausible for repeat users of that food, such as the local ranchers and their families.
Fish in Silver Creek
A few fishery studies conducted by state wildlife personnel since 1954 either have shown that fish are present in small numbers in Silver Creek or they are absent. Additional information indicates that cutthroat trout have been noted in the creek, and EPA reported seeing pan-sized trout at the site in 1992. ATSDR's observations of the stream suggest that trout populations, if present, probably would not be viable year-around except possibly far downstream toward Wanship, which is about 10 miles from the site. The available information suggests that a fishery, if it exists, would not be an important exposure medium. Trout may concentrate some metals from surface water and from its foodchain. Therefore, if persons do consume trout or other game fish from Silver Creek, they potentially are exposed--past, present, and future--to site-related contaminants. No sampling data are available to confirm whether fish contain contaminants.
ATSDR staff evaluated all completed and potential exposure pathways in the following sections for toxicologic effects related to exposure.
Completed Exposure Pathways
To determine whether adverse health effects could result from exposure, ATSDR staff used contamination level data from each completed pathway to estimate exposure doses for each contaminant of concern. Doses were then compared to a Minimal Risk Level (MRL) or a Reference Dose (RfD). The MRL is developed by ATSDR; the RfD is developed by EPA. Both represent an estimate of daily exposure to a contaminant below which non-cancer adverse health effects are unlikely to occur. If an exposure dose has exceeded an MRL or RfD, the estimated exposure dose can then be compared to experimental data from human or animal studies to determine which effects may be of concern. When a contaminant is capable of causing cancer (carcinogenic), staff also considered the estimated exposure dose to calculate whether an increase in the cancer rate is expected.
Tailings and Surface Soil Pathways On Site; Area A
ATSDR staff assumed workers were in the most heavily contaminated areas at most 60 days per year, and incidently consumed 100 mg tailings (or soil) per day. ATSDR staff then compared the estimated ingestion exposure doses with doses received by people in epidemiologic studies or received by animals in laboratory studies and evaluated whether adverse health effects are possible. Estimated exposure doses were below levels of health concern for all contaminants in soil and tailings; therefore, adverse health effects are unlikely to have occurred in workers. Given the relative infrequency of people wandering on the site before construction of the fence, adverse health effects are unlikely for trespassers.
Surface Water Pathways On Site; Area A
People who worked when tailings were being deposited may have been exposed to contaminants principally via incidental ingestion of surface water. ATSDR staff estimated exposure doses to contaminants in surface water on the site; those doses are all significantly below levels of public health concern. ATSDR staff expect no adverse health effects in workers as a result of exposure to contaminated surface water. Given the relative infrequency of people wandering onto the site before the fence was constructed, adverse health effects are unlikely for trespassers.
Ambient Air Pathways on Site; Area A
People who worked on site without respirators before the site was substantially covered with soil and vegetation were exposed to contaminants in the air. Ambient on-site air concentrations were evaluated for adverse health effects of inhalation. Concentrations measured in air presented no public health hazard.
Public Water Systems Off Site; Downstream in Silver Creek Watershed
Long-term users of the High Valley Water Company and Summit County Service Area #3 public water supplies may have been exposed via ingestion to arsenic, but that exposure probably did not last a sufficient time to pose a public health hazard. Arsenic in the public water supply may not be site related.
Although other metals are present in the public drinking water supplies, none are at levels that may be considered harmful to the general public. Sodium is at a level that people on a sodium-restricted diet should avoid.
Potential Exposure Pathways
To determine whether adverse health effects could result from exposure, ATSDR staff used contamination level data when available from each potential pathway to estimate exposure doses for each contaminant of concern. These doses were then compared to MRLs or RfDs, as discussed above. When data were not available, staff made assumptions to enable analysis of pathways. These assumptions, when used, are stated below.
Tailings and Surface Soils Pathways On Site; Area A, Area B
ATSDR staff estimated ingestion exposure doses for workers and evaluated whether adverse health effects are possible. Estimated exposure doses were below levels of health concern for all contaminants in tailings in area B; therefore, adverse health effects are unlikely for workers. ATSDR staff do not have data regarding levels of contaminants in soils because tailings disposal ended; we also do not have information on contaminants in cover soil or adjacent natural surface soils. However, levels are not expected to be significantly higher, and could be considerably lower, than those measured in tailings on the site. Estimated exposure doses, therefore, would be lower than those estimated above in the COMPLETED EXPOSURE PATHWAYS section. Adverse health effects to workers are not expected from exposure via these potential pathways.
Should the property be developed, at a future time, for residential purposes, people would receive an exposure dose corresponding to typical residential exposures (365 days a year). ATSDR staff estimated potential ingestion exposure doses for individuals who would live on the site at a future time. In that case, people would receive exposure doses of arsenic, beryllium, cadmium and lead at levels of health concern.
Elevated levels of contaminants make the site unsuitable for residential or gardening purposes.
Surface Water Pathways On Site; Area A
It is not known whether people who have worked on the site since tailings disposal ceased have come in contact with surface water. Because the completed surface water pathway previously discussed was evaluated to be of no public health concern, adverse health effects are not expected from exposure via this potential pathway.
Ambient Air Pathways On Site; Area A
The completed ambient air pathway previously discussed was evaluated to be of no public health concern. Therefore, adverse health effects are not expected from exposure via this potential pathway.
Groundwater Pathways Off Site
Residential-Type Wells
ATSDR staff have no information about contaminant levels in residential-type wells southwest of the site. Formerly, those wells served four residences. More recently, ATSDR learned one residence has been converted to a small business. Only two other residences now exist; both are vacant, but ATSDR expects they could be occupied anytime in the future. Since those wells serving those locations are hydraulically upgradient from the site, it is unlikely that people have been exposed to site-related contaminants at levels of public health concern. This document does not consider contributions from Prospector Square.
Business/Industrial Wells
Workers are potentially exposed to contaminants through incidental ingestion and possibly aerosol inhalation. Exposures associated with those potential pathways are low enough to be considered of no public health concern.
Surface Soil Pathways Off Site
Nearby residents, employees, and road maintenance people are potentially exposed to contaminants through incidental ingestion. ATSDR staff estimated exposure doses associated with off-site surface soil. Those doses are low enough to be considered of no public health concern, primarily due to the infrequency of exposure.
Should that area be developed, at some future time, for residential purposes, those residents would receive a larger incidental ingestion exposure dose than would the occasional visitor or worker. ATSDR staff estimated potential ingestion exposure doses for individuals who would live near the site at some future time. In that case, individuals would receive exposure doses of arsenic and lead at levels of health concern.
Elevated levels of contaminants make the area near the site unsuitable for residential or gardening purposes.
Creek Surface Water Pathways Off Site
County maintenance workers and ranchers are potentially exposed to contaminants through incidental ingestion of creek water. Exposures associated with that potential pathway are low enough to be considered of no public health concern.
Creek Sediments Pathway Off Site
County maintenance workers and ranchers are potentially exposed to contaminants through incidental ingestion of creek sediments. Exposures associated with that potential pathway are significantly low enough to be considered of no public health concern.
Ambient Air Pathways Off Site
People who work or live near the site are potentially exposed to contaminants in the air. Off-site ambient air concentrations were evaluated for adverse health effects of inhalation. Concentrations measured in air do not represent a public health hazard.
Food Chain Pathways Off Site
ATSDR staff have no information about contaminant levels in cattle, sheep, milk, grains, or fish on or near the site. It is not likely that those sources of food are contaminated with site-related contaminants at a level of public health concern.
B. Health Outcome Data Evaluation
The lead at this site is bound up in tailings similar to the tailings found at Prospector Square. ATSDR studies at Prospector Square indicate that exposure to these tailings did not result in any increase in blood lead, arsenic, or cadmium at clinically meaningful levels, as compared to local controls (ATSDR 1988). No further health studies were recommended. The study showed a significant increase in blood lead levels in children aged 9 to 71 months, but considered that increase clinically insignificant. At that time, the Centers for Disease Control and Prevention (CDC) considered 25 micrograms lead per deciliter blood (ug/dl) a clinically significant blood level; the CDC has since revised that level down to 10 ug/dl (CDC 1991).
Nevertheless, 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 Flat, it is likely that exposure to lead at Richardson Flat will not result in an increase in blood lead levels. This conclusion is based on the margin of safety provided by the significant differences in frequency and duration of exposure to tailings at Richardson Flat, an uninhabited area, and at Prospector Square, one where people live. Furthermore, because of potential differences in populations (e.g., behavioral patterns, nutritional status, health status), and in type of construction (e.g., basement vs. slab) and landscaping, conclusions regarding exposure to people living at Prospector Square may not apply to a future population living at Richardson Flat.
Although it is not known exactly how many people have been exposed to contaminants at the site, ATSDR staff estimate that only a few people were exposed. Furthermore, the exposure level is not of public health concern. Finally, the exposure has ended. For those reasons, ATSDR staff consider it unlikely that anyone who was exposed will develop any adverse health effects from that exposure. In addition, ATSDR staff are unaware of any recent community health concerns of the residents. Therefore, ATSDR staff did not examine health outcome data. If new information becomes available, or if nearby residents have health concerns about contaminants associated with the site, ATSDR will reconsider evaluating health outcome data.
C. Community Health Concerns Evaluation
Because there is no information about levels of contaminants in blowing dust, ATSDR staff cannot evaluate the health hazard posed by inhalation of the dust. ATSDR staff evaluated available ambient air data (see Toxicologic Evaluation section). Levels of contaminants in blowing dust generated from topsoil should not pose a public health hazard. When the tailings are completely covered by topsoil or when vegetation has adequately anchored the soil, there should not be any contaminated dust or other contaminated particulates blowing off site in concentrations above comparison values. ATSDR staff are not aware of any other community health concerns.
Cease/Reduce Exposure Recommendations
Site/Area Characterization Recommendations
Health Activities Recommendation Panel (HARP) Recommendations
In accordance with the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended, data and information developed in the Amendment to the Public Health Assessment for the Richardson Flat Tailings site in Summit County, Utah, have been evaluated for appropriate followup with respect to health activities. Available information indicates that no human exposure to contaminants at levels of public health concern is occurring or has occurred. In addition, the community has not expressed health concerns. For these reasons, ATSDR has concluded that no follow-up actions should be pursued at this time. If more information becomes available indicating that human exposure to hazardous substances is occurring or has occurred in the past at levels of public health concern, ATSDR will reevaluate this site for any additional indicated followup.
Public Health Actions
The purpose of the Public Health Action Plan (PHAP) is to ensure that this public health addendum not only identifies public health hazards but also provides a plan of action designed to mitigate and prevent adverse human health effects resulting from exposure to hazardous substances in the environment.
Based on discussions with EPA Region VIII, EPA will consider the Cease/Reduce Exposure and Site/Area Characterization recommendations listed above when they develop the work plan for this site. Based on the HARP determination that no health follow-up activities are required by ATSDR, no PHAP for health follow-up activities has been developed for this release.
ATSDR. 1988. Silver Creek mine tailings exposure study. Agency for Toxic Substances and Disease Registry.
ATSDR. 1990. Preliminary health assessment for Richardson Flat tailings. Agency for Toxic Substances and Disease Registry.
ATSDR. 1991a. Draft Toxicological profile for arsenic. Agency for Toxic Substances and Disease Registry.
ATSDR. 1991b. Draft Toxicological profile for lead. Agency for Toxic Substances and Disease Registry.
CDC. 1991. Preventing lead poisoning in young children. Centers for Disease Control.
E&E. 1985. Analytical results report, Richardson Flat tailings. Ecology and Environment.
E&E. 1987a. Analytical results report of air sampling at Richardson Flat. Ecology and Environment.
E&E. 1987b. Record of communication with Silver Creek Irrigation Company. Ecology & Environment.
E&E. 1989. Supplemental site inspection report. Ecology and Environment.
E&E. 1991a. Record of communication with Utah Division of Wildlife Resources. Ecology & Environment.
E&E. 1991b. Record of communication with farmer. Ecology and Environment.
E&E. 1991c. Memorandum regarding air data. Ecology and Environment.
E&E. 1991d. Trip report and analytical results of the ground water sampling of 3 wells at Richardson Flat tailings. Ecology and Environment.
E&E. 1992. Draft final report, Richardson Flat Tailings. Ecology and Environment.
E&E. 1993. Final report, Richardson Flat Tailings. Ecology and Environment.
IRIS. 1992. Integrated Risk Information System. National Library of Medicine, National Toxicology Information Program, Bethesda, MD. December 28.
PC. 1992. Letter to ATSDR dated November 9, 1992. Park City Municipal Corporation.
UDEQ. 1992a. Letter, with map, to ATSDR. Utah Department of Environmental Quality.
UDEQ. 1992b. Computer printouts of public water system data. Utah Department of Environmental Quality.
UDEQ. 1992c. Analytical results for surface water for Silver Creek. Utah Division of Water Quality, Department of Environmental Quality.
UTD. 1989. Memorandum and attached laboratory data sheets for landfill samples analyzed in 1988. Utah Department of Transportation.
UDNR. 1986. Water resources of the Park City area, Utah with emphasis on ground water. Utah Department of Natural Resources.
UDNR. 1992. Diversion records database, station data printout. Utah Division of Water Rights, Department of Natural Resources.
USBC. 1991. Census of population and housing, 1990: summary tape file 1 (Utah) [machine-readable data files]. Washington, D.C. U.S. Bureau of the Census.
USEPA. Undated. A summary description of tailings area and USEPA's listing actions. US Environmental Protection Agency.
USEPA. 1991a. Aerial photographic Analysis of the Richardson Flat tailings. US Environmental Protection Agency.
USEPA. 1991b. HRS documentation record. U.S. Environmental Protection Agency.
USEPA. 1992a. Sampling qa/qc work plan, Richardson Flat tailings. US Environmental Protection Agency.
USEPA. 1992b. National Priorities List fact sheet for Richardson Flat tailings. U.S. Environmental Protection Agency.
USEPA. 1992c. Final Air Sampling & Analysis Report, Richardson Flat. U.S. Environmental Protection Agency.
USEPA. 1993. Memorandum to ATSDR concerning EPA review of Initial Release Public Health Assessment. March 9, 1993.
Don Gibeaut
Environmental Health Engineer
Remedial Programs Branch
Division of Health Assessment and Consultation
Stephanie Prausnitz
Environmental Health Scientist
Remedial Programs Branch
Division of Health Assessment and Consultation
ATSDR Regional Representative
Glenn Tucker
Public Health Advisor
Region VIII
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