RICHARDSON FLAT TAILINGS SITE
PARK CITY, SUMMIT COUNTY, UTAH
EPA FACILITY ID: UTD980952840
July 24, 1990
The Richardson Flat Tailings, an Update 7 site proposed for theNational Priorities List, is located 3.5 miles northeast of ParkCity, Summit County, Utah. From 1975 to 1981, the 160-acre sitewas used for disposing mine tailing wastes from the KeetlyOntario Mine and other mines owned by United Park City Mines. Currently no tailings are dumped at the site; however, soil fromthe 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 throughsurface water, groundwater, and airborne-associated pathways. Human exposure to site contaminants may occur through theingestion of contaminated groundwater, food-chain entities, andsoil; through dermal contact with contaminants; and through theinhalation of airborne dusts. The site is considered to be ofpotential public health concern because of the high levels ofon-site contaminants.
A. Site Description and History
The Richardson Flat Tailings site (RFT), consisting of 160 acreslocated in a topographic depression approximately 3.5 milesnortheast of Park City, in Summit County, Utah, is an Update 7site proposed for the National Priorities List (NPL) (see Figures1 and 2). From 1975 until 1981, mine tailings from the KeetlyOntario Mine and other mining operations in the area weredisposed of at the site and currently range up to 10 feet indepth. Until 1987, mine tailings were removed from the site andused as backfill for sewer construction projects.
Currently, mine tailings at the site are being covered by soilexcavated from on-site areas. The thickness of the soil covervaries over the surface of the site, and, as noted during theApril 1989 site visit, the soil layer covering the mine tailingswas less than 1-inch thick in certain areas. Site featuresinclude a pond that covers the northeastern corner of the siteand is contained by a dam at the northwestern corner, and a ditchin 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 tothe RFT site on April 19, 1989. During the site visit,conditions on-site and off-site were observed, including landuses in areas adjacent to the site, the proximity of residentialareas to the site, the ease of site access, the presence ofon-site physical hazards, and the general physicalcharacteristics of the site. Specific observations made duringthe site visit will be discussed in appropriate sections of thisPreliminary Health Assessment.
C. Community Health Concerns
Staff from the Utah Department of Health indicated that they werenot aware of any community health concerns related to the RFTsite.
The site lies in a rural area with very widely scatteredresidences. It is within 1.5 miles of Prospector Square, whichis an extension of Park City, a popular recreational and ski areaof Utah. The area within a 1-mile radius of the site consists ofopen, undeveloped rangeland and agricultural fields. Only threeresidences are within a 1-mile radius of the site; however,because the site is close to a popular resort, which has expandedin recent years, future development of the area may increaseresidential, commercial, and recreational land uses (1).
Recreational land uses in the site vicinity include fishing inSilver Creek, a popular stream for trout fishing, and downhillskiing at nearby ski slopes. Piles of mine tailings on-site arecommonly used for unauthorized recreational motorcycling.
Other land uses in the site vicinity include pastureland forcattle and sheep and land parcels used for cultivating hay andgrain. No industrial or commercial land uses are within 1-mileof the site.
A. On-Site and Off-Site Contamination
Monitoring results were analyzed for groundwater, surface water,soil, and air samples collected during initial siteinvestigations conducted in 1985. These results are only ofpreliminary and are not sufficient to characterize the fullnature and extent of site contamination.
Groundwater samples were collected from monitoring wells locatedupgradient and downgradient from the site. Groundwater sampleswere analyzed for total metals, cyanide, sulfate, and dissolvedmetals. The highest concentrations of contaminants were detectedin unfiltered groundwater samples collected from monitoring wellslocated downgradient from the site (see Table 1).
|Maximum Concentration [ppb]||Drinking Water Criteria+|
+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 SilverCreek and from an intermittent stream that flows through thetailings. Surface water samples were analyzed for total metalsand sulfate. The highest contaminant levels in Silver Creek werefound immediately downstream from the site and at the dischargepoint for the intermittent, on-site stream (see Table 2). Approximately 2 miles upstream from the RFT site, the ProspectorSquare tailings may also serve as an important source of surfacewater contaminants.
|Maximum Concentration [ppb]|
|Contaminant||Upstream Silver Creek||Downstream Silver Creek|
Samples of surface and subsurface soil were collected fromon-site and off-site areas (see Table 3 and 4). Soil sampleswere analyzed for total metals. Samples of subsurface, on-sitesoil samples (tailings) were analyzed for total metals andcyanide. 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 concentrationsfor the western United States.
Results of sample analyses of subsurface mine tailings indicatedelevated levels of heavy metals and arsenic (see Table 4). Off-site, subsurface samples did not have contaminant levelsabove mean concentrations for the western United States,indicating the likelihood that off-site soil contamination isgenerally limited to the upper portions of the soil profile (2).
|Maximum Concentration [ppb]|
|Background*||On-Site||Mean for Western U.S.|
*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.
|Maximum Concentration [ppb]|
|Background*||On-Site||Mean for Western U.S.|
*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.
Preliminary air monitoring was conducted using five high-volumeair samplers at four sampling locations over a 5-day period. Airsamples were analyzed for arsenic, cadmium, lead, and zinc. During air monitoring, weather conditions were dry with windsvarying up to 20 miles per hour, although winds gusted up to 40miles per hour during the first day of sample collection. Thehighest levels of airborne contaminants were detected during thefirst day of sampling at the air monitoring station downwind fromthe site (see Table 5). Air monitoring results verify thatreleases of airborne contaminants have occurred at the RFT site.
|Maximum Concentration [micrograms per cubic meter]|
*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 toensure the accuracy of the monitoring programs conducted duringsite investigations at the RFT site. Sample collection andanalyses were determined to have been performed according toapproved procedures; therefore, monitoring results weredetermined to be acceptable. The conclusions contained in thisreport are based on the data package supplied to ATSDR. Theaccuracy of these conclusions depends on the reliability andcomprehensiveness of the data contained in the materialsreviewed.
C. Physical and Other Hazards
No on-site physical hazards were noted during the site visit.
A. Environmental Pathways (Fate and Transport)
Groundwater was encountered within 12 feet of the site's surfaceduring the collection of on-site soil samples. In the sitevicinity, the uppermost aquifer, with an average depth of 60feet, lies within alluvial deposits overlying consolidated rocksof tertiary origin. It is not clear whether this alluvialaquifer is hydrologically connected to the deeper aquifer foundin the consolidated rock formation. Groundwater flow beneath thesite and in the site vicinity is to the north-northwest.
No private or monitoring wells are on-site. Two private domesticwells are located about 4,000 feet southwest of the site. Bothof these wells are completed to a depth of about 210 feet belowthe ground's surface. A single municipal well used as a backupsource for the Park City municipal water system is located 2.5miles southwest of the RFT site (1). Groundwater samples werenot collected from the above-mentioned private and municipalwells; however, because these wells are located upgradient fromthe site, they are not expected to be impacted by sitecontaminants.
2. Surface Water
Surface water and leachate from the site may transport sitecontaminants into nearby streams and creeks. The largest surfacewater feature in the site vicinity is Silver Creek, located about200 feet west of the site. Approximately 1,000 feet downstreamfrom the site, surface water from Silver Creek is diverted forthe irrigation of pastureland and hay fields. Silver Creek doesnot serve as a source of drinking water source for humans.
Several leachate (mine tailing drainage) seeps were noted on thenorthwest side of the on-site earth dam; however, surface watersamples were not collected in this area. These seeps flow fromthe site to the northwest into a swampy area that drains intoSilver Creek. Leachate from the mine tailings pile may serve asan important source of surface water contamination.
Mine tailings consist of finely crushed rock that are easilyeroded by surface water runoff and wind. Erosion of the minetailings is likely because portions of the mine tailing piles areuncovered and lack a vegetative cover. Although a soil cover isbeing placed over the surface of the mine tailings, the thicknessof the cover varies considerably and may be less than 1 inch. Soil used to cover the tailings may also be contaminated becauseit is being excavated from on-site areas in which mine tailingswere dumped. The soil covering the tailings is expected to havea minimal impact on the migration of tailing contaminants intogroundwater.
As precipitation percolates through the mine tailings, sulfatesin the tailings dissolve, increasing the acidity of water as itseeps downward. As infiltrating water becomes more acidic, itdissolves the arsenic and heavy metal compounds in the tailingsand carries these contaminants downward. Monitoring resultsindicate that contaminants have already migrated to lower levelsof the tailing piles and impacted local groundwater and nearbysurface waters. Contaminants will continue to impact groundwaterand surface water if no remediation is performed.
The small particle size of the tailings increases the likelihoodthat wind may be an important mechanism for dust transport tooff-site areas. Site documents indicate that releases ofwindblown contaminants to off-site areas have been observed,especially in the summer months when winds from the southwestblow dust from the site across Interstate 40.
5. Contaminated Food-Chain Entities
Site contaminants may bioaccumulate in food-chain entities. Inthe site vicinity, approximately 315 acres of agricultural landare irrigated with surface water diverted from Silver Creek. Irrigated lands are used for pastureland and the production ofgrains and hay. Crops irrigated with contaminated surface watermay bioaccumulate contaminants.
Animals may also become contaminated if they graze in areasimpacted by the site, feed on crops irrigated with contaminatedwater, or ingest contaminated surface water, soil, or sediments. Cattle and sheep are known to graze in shrub land adjacent to thesite.
Fish from Silver Creek may also bioaccumulate contaminants fromsurface water and sediment. Silver Creek is known to supportrecreational trout fishing.
B. Human Exposure Pathways
Several potential routes exist by which humans may be exposed tocontaminants from the RFT site. Ingestion of contaminatedgroundwater, soil, and food-chain entities and inhalation of dustare all potential routes of human contaminant exposure.
1. Soil - and Tailings-Associated Pathways
Ingestion, inhalation, and dermal exposures to soil and tailingsmay adversely impact human health. The highest contaminantlevels were found in on-site subsurface soil and tailings;however, on-site and off-site surface soil and tailings were alsocontaminated. The site is located in a rural area and becauseaccess to it is not restricted, trespassers may come in contactwith these contaminated media during cycling or other activitieson or near the site.
2. Groundwater-Associated Pathways
Human exposure to groundwater contaminants may result from theuse of contaminated groundwater for domestic, industrial, andagricultural purposes. Local residents are known to rely ongroundwater as a potable water supply; however, monitoring datafor off-site groundwater are limited to results from a singleupgradient well and two downgradient wells. The likelihood ofhuman exposure to groundwater contaminants is minimized by therural nature of the site and the lack of supply wells for potablewater downgradient from the site; however, without monitoringresults from nearby private wells, this pathway of human exposurecan not be ignored. The potential exists for completing thispathway of human exposure in the future if groundwater wells areinstalled on-site or downgradient from the site.
3. Food-Chain-Associated Pathways
Another potential pathway for human exposure to contaminants isthrough the consumption of food-chain entities that maybioaccumulate contaminants. Cultivated grains and vegetables andother edible plants may bioaccumulate soil contaminants andresult in food-chain contamination. Cattle, sheep, and wildlifethat consume contaminated plant material or surface water mayalso bioaccumulate contaminants.
Aquatic animals, such as trout in Silver Creek, that inhabitcontaminated surface water or aquatic systems with contaminatedsediments may also bioaccumulate contaminants. Analyticalresults of surface water samples collected from Silver Creekindicate contaminants at levels significantly in excess ofFederal Ambient Water Quality Criteria. These contaminants areknown to bioaccumulate in fish and may reach levels that makeSilver 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, orexcavation of tailings for use as fill may result in thegeneration of dust and the exposure of motorcyclists, on-siteworkers, and area residents to site contaminants. The relativeremoteness of the site may help reduce the impact of this pathwayof human exposure.
5. Surface-Water-Associated Pathways
Surface water obtained from local sources is not a source ofdrinking water within the site vicinity; however, surface wateris used to irrigate pastureland and hay and grain fields. As aresult, human exposure to site-related contaminants may resultfrom the ingestion of contaminated grains, animal products, orfish.
Results of preliminary groundwater and soil sampling indicatethat the RFT site is of potential public health concern becauseof contaminants in on-site air, soil, mine tailings, andgroundwater and on-site and off-site surface water and sediments.
A brief discussion of the identified site contaminants of publichealth concern follows.
Human exposure to arsenic is possible through three majorpathways: ingestion, inhalation, and dermal contact. Commoneffects from ingestion of arsenic include irritation of thedigestive tract leading to pain, nausea, vomiting, and diarrhea. Ingestion of inorganic arsenic, the form most likely found at theRFT site, also causes a pattern of skin abnormalities, such asdark 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 increasedrisk of liver, bladder, kidney, and lung cancer. Long-termexposure (greater than 14 days) to inorganic arsenic at levels aslow as 20 micrograms per kilogram of body weight per day mayresult in mild health effects. The severity of symptoms tends toincrease as exposure duration increases. The EnvironmentalProtection Agency (EPA) estimates that a dose of 1 microgram perkilogram of body weight per day corresponds to a cancer risk of1.5 in 1,000 (3). Arsenic levels are sufficiently high insurface soil to be of public health concern for ingestion,inhalation, or dermal exposures.
Inhalation of inorganic arsenic dusts may also result in mildirritation of the digestive tract. The inhalation route of humanexposure is more likely to increase the risk of lung cancer thanis the ingestion route. Air concentrations of about 200micrograms per cubic meter are associated with irritation of thenose, throat, and exposed skin. The National Institute forOccupational Safety and Health (NIOSH) has set a recommendedexposure limit (REL) for occupational exposure to arsenic in airat 2 micrograms per cubic meter not to be exceeded for more than15-minutes. EPA has estimated that a lifetime inhalationexposure to 1 microgram per cubic meter causes a lifetime cancerrisk of 4 in 1,000 (3). The maximum level of airborne arsenicdetected at the RFT site (0.093 micrograms per cubic meter) is ata level of public health concern. Soil-disturbing activities,such as excavation of soils or motorcycling, are likely to causean increase in airborne arsenic levels.
Dermal exposure to arsenic-containing compounds may result inmild-to-severe irritation of the skin, eyes, or throat. Noreliable dose estimates are available on the exposure levels atwhich these effects begin to appear.
Human exposure to cadmium at the RFT site can occur eitherthrough the ingestion of contaminated soil, mine tailings, andfood-chain entities or through the inhalation of contaminateddusts. Very small amounts of ingested cadmium are absorbed intothe blood (1%-5%) while 30%-50% of that which is inhaled is takeninto the blood (4). Once cadmium enters the body, it is retainedvery strongly. A proposed reference dose (a daily dose that isestimated to be without appreciable human health risk) of 0.5micrograms per kilogram of body weight per day for oral exposureis 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 nothigh enough to be of public health concern. If the site isdeveloped for residential or recreational uses, the levels maybecome a public health concern.
Human exposure to lead at the RFT site may occur through twomajor pathways: the ingestion of contaminated soil, minetailings, and food-chain entities or the inhalation of airbornecontaminated dusts. Levels of lead in surface soil and tailings,subsurface soil and tailings, and air are sufficiently high to beof public health concern.
Children are especially susceptible to the health effects of leadexposure. Low levels of lead exposure may cause decreased growthand may result in lower intelligence quotient (IQ) scores. Lowlevels of lead exposure may also cause hypertension inmiddle-aged men. Pregnant women exposed to lead transfer lead tothe fetus, and this may cause preterm birth, reduced birthweight, and decreased neurological development in the infant. Results of studies have shown that lead causes cancer inlaboratory animals; however, it is not known whether lead causescancer in humans.
Human inhalation of lead-contaminated dust or lead fumes mayresult in the same health effects that ingestion exposure causes. Air monitoring results at the RFT site indicated lead (1.65micrograms per cubic meter) at levels above EPA's NationalPrimary and Secondary Ambient Air Quality Standards for lead (1.5micrograms per cubic meter) (5). Airborne lead levels areexpected to be even higher if soil is disturbed by on-siteactivities such as soil excavating or cycling.
The Centers for Disease Control (CDC) has cautioned thatconcentrations of lead greater than 500-1,000 parts per million(ppm) in residential soil could lead to elevated blood leadlevels in children who inhale or ingest soil. Lead levels inexcess of these values were found in on-site surface soil andmine tailings and in subsurface soil and tailings. Sitetrespassers, site workers, and recreational cyclists mayexperience short-term exposures to lead-contaminated media.
Human exposure to selenium at the RFT site may occur through theingestion of contaminated groundwater or soil and through theinhalation of airborne dust. Once ingested, selenium in both theorganic and inorganic forms is readily absorbed. Althoughselenium is an essential nutrient, it may have toxic effects atlevels moderately above the daily nutritional requirement. TheFood and Nutrition Board of the National Academy of Sciences(NAS) suggests that 0.05 to 0.20 mg of selenium per person perday 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 ofthe skin and eyes (7). Air samples collected from the RFT sitewere not analyzed for selenium; however, the levels found insurface soil and tailings and the air monitoring results forother site contaminants indicate that airborne selenium levelsmay be of public health concern under normal site conditions. Soil disruption by such activities as soil excavation or cyclingcould increase airborne selenium levels.
Selenium may also bioaccumulate in plants and animals. Thehealth effects from long-term exposure to selenium via ingestionof contaminated food or water include loss of hair, loss anddeformities of nails, problems with walking, diminished reflexes,and some paralysis. These health effects were reported from astudy of populations in China that lived in areas with extremelyhigh selenium levels in the soil and in the rice and vegetablesthey consumed. Selenium levels in the food were 1.6 parts permillion or higher, and the period of exposure was months or evenyears (8).
Human exposure to zinc at the RFT site may occur through twomajor pathways: the ingestion of contaminated soil, tailings, andgroundwater or the inhalation of airborne contaminated dust. Which health effects result from exposure to excess levels ofzinc depends on the pathway of exposure.
Ingestion of excess zinc may cause stomach or digestive problems. NAS has estimated the recommended dietary allowance (RDA) forzinc to be 15 milligrams per day (6). Long-term exposure toexcessive levels of zinc (2.1 milligrams per kilogram of bodyweight per day) may result in copper deficiency (8); however,exposures of this magnitude are not expected to occur at the RFTsite.
Inhalation of zinc dust may lead to breathing difficulties andnonspecific neurological effects such as headaches and malaise(9). Air monitoring results at the RFT site did not show zinc tobe at levels of public health concern; however, duringsoil-disturbing activities, such as soil excavation or cycling,airborne zinc levels may become a public health concern.
Using the available information, ATSDR has concluded that thissite is of potential public health concern because humans may beexposed to hazardous substances by ingestion of contaminatedsoil, groundwater, and food-chain entities; dermal contact withcontaminated soil; and inhalation of contaminated dust. ThisPreliminary Health Assessment is based on incomplete monitoringdata for groundwater and surface water. A full assessment of thepublic health implications of this site is not possible with theinformation presently available.
In accordance with the Comprehensive Environmental Response,Compensation, and Liability Act of 1980, as amended, theRichardson Flat Tailings site has been evaluated for possiblefollow-up with health effects studies. However, because nodocumentation or indication exists that human exposure tosite-related contaminants is occurring or has occurred in thepast, this site is not being considered for follow-up healthstudies at this time.
As ATSDR receives additional information, such information mayindicate that further assessment is warranted by site-specificpublic health issues.
ATSDR recommends the following:
1. Restrict public access to the site to reduce unauthorizedsite entry and use of the site for recreational purposes.
2. Monitor private wells within 1 mile of the site to determinewhether these wells are being impacted by site contaminants andwhether water from these wells can continue to be used forpotable purposes.
3. Conduct additional surface water monitoring, both upgradientand downgradient from the site, to determine the site's impact onSilver Creek and other nearby bodies of surface water.
4. Sample leachate seeps from along the north side of theon-site earthen dam, and analyze these samples forsite-associated contaminants.
5. Collect additional off-site soil samples from areas adjacentto the site, especially downwind of the site, to characterizeoff-site contamination.
6. Collect and analyze edible portions of trout from SilverCreek to determine whether they are suitable for continued humanconsumption.
7. Include the following in the remediation workplan ifadditional site remediation occurs:
Provide adequate personal protective equipment that meetsthe standards of the Occupational Safety and HealthAdministration (OSHA) for workers conducting remedialactivities in and around the site.
Follow appropriate precautionary guidelines, regulations,and advisories from the National Institute for OccupationalSafety and Health (NIOSH) and OSHA.
Employ optimal dust control measures if remedial activitieswill involve ground-disturbing activities. In addition toon-site air monitoring, appropriate real-time air monitoringat the worksite periphery should be conducted during workinghours in addition to on-site air monitoring. Levels ofcontaminants in the ambient air at the periphery of the siteshould not exceed National Ambient Air Quality Standards(NAAQS) or NIOSH recommendations.
8. When indicated by public health needs, and as resourcespermit, the evaluation of additional relevant health outcome dataand community health concerns, if available, is recommended.
Environmental and Health Effects Assessor:
Richard Earl Gillig, M.C.P.
Environmental Health Scientist
Remedial Programs Branch
ATSDR Regional Representative
Office of the Assistant
1. Hazardous Ranking Score Package, Richardson Flat TailingsSite, Park City, Utah.
2. Shacklette, J.T., and Boerngen, J.G., 1984, ElementalConcentrations in Soil and Other Surficial Materials of theConterminous United States. U.S. Geological Survey ProfessionalPaper 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. NationalResource 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 seleniumintoxication of humans in China. Am J Clin Nutr 37:872-881.
9. Porter K.G., McMaster D., Elmes M.E., et al. 1977. Anemiaand low serum-copper during zinc therapy. Lancet:744.
10. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Zinc. Atlanta: ATSDR, December 1989.