PUBLIC HEALTH ASSESSMENT
KENNECOTT (SOUTH ZONE)
COPPERTON, SALT LAKE COUNTY, UTAH
This portion of the Kennecott South Public Health Assessment presents an evaluation of thepossible health impacts of the Southwest Salt Lake County exposure situation involvinggroundwater contaminants. Groundwater contaminants have also been reported in private wellsdowngrade of Pine Canyon in Tooele County. However, the Agency for Toxic Substances andDisease Registry (ATSDR) does not have any analytical data to confirm or dismiss reports ofprivate well contamination. Recent (1995) groundwater sampling data are still being evaluated by the Utah Department of Environmental Quality (UDEQ), the Environmental Protection Agency(EPA), and the U.S. Geological Survey (USGS) before release to ATSDR and others. When theyare available, ATSDR will evaluate the data and make a public health determination.
SOUTHWEST SALT LAKE COUNTY GROUNDWATER EXPOSURE SITUATION
There is extensive sulfate contamination of the drinking water aquifer in southwest Salt LakeCounty (29). Though there may be several sources of sulfate in the 150 square mile groundwaterstudy area, three major sources of sulfate contaminants have been identified: Bingham reservoirarea (immediately east of Copperton, Utah); Lark area (south of Copperton); and South JordanEvaporation Ponds (area near the center of the groundwater study area, about halfway betweenOquirrh Mountains to the west and the Jordan River to the east) (29). Source control measureshave been enacted at all three sources. However, plumes of sulfate with elevated total dissolvedsolids have spread eastward from these sources toward the Jordan River, contaminating manyprivate wells in the plume path.
The groundwater contamination problem has been throughly investigated and characterized by theby Kennecott scientists, with technical oversight from UDEQ, EPA, and USGS. ATSDRreviewed Kennecott reports covering more than 10 years of water quality analyses in SouthwestSalt Lake County. In addition to sulfate, ATSDR studied the reported concentrations of otherinorganic chemicals with special focus on lead, arsenic, selenium, and cadmium in private andpublic water supply wells. Metal contaminants do not exceed safe levels in any of the publicwater supply systems and only occasionally exceeded safe levels in private wells. The occasionalhigh metal contaminant concentrations reported in private wells appear to be a rare occurrencewith no evidence of contaminant levels exceeding safe levels for more than 6 months.
As a result of review and evaluation of groundwater contaminations, ATSDR determined thatsulfate was the key groundwater contaminant requiring further evaluation. Sulfate levels in thedrinking water aquifer range from below the secondary Maximum Contaminant Level of 250mg/L to 60,000 mg/L in a monitoring well. The highest concentration reported in a private wellwas 2,270 mg/L (Well #W337 in 1985, abandoned in 1986) (30). Some wells have had persistenthigh levels of sulfate for more than 1 year.
In 1995, Kennecott completed a detailed water well inventory in the study area. Table 9summarizes the inventory.
|Drinking water wells||347|
|Non-drinking water wells||219|
|Kennecott Utah Copper (KUC)monitoring wells||427|
|Non-KUC monitoring wells||90|
|Not in use water wells||601|
- Source: March 7, 1996, letter from Elaine Dorward-King, Kennecott Utah CopperCorporation, to Max Howie, ATSDR
The well inventory covered approximately 150 square miles and included water wells on theeastern side of the Jordan River. The majority of the 347 drinking water wells lie outside theknown boundaries of the sulfate plumes. ATSDR estimates that 35 existing private drinkingwater wells lie within or adjacent to a sulfate groundwater plume. Of those 35, 6 have sulfatemeasurements above 500 but below 1,000. Some of the wells currently listed as not in use mayhave been used as drinking water supplies before contaminants were measured. Of those 601nonuse wells, 8 had measurements of sulfate above 500 mg/L.
ATSDR noted that at least 1 residential well was contaminated with sulfate above EPA RegionVIII recommended level of 1500 mg/L. Assuming that 4 people live at the residence, 4 peopleare estimated to have ingested sulfates above 1500 mg/L in this completed exposure pathwaybefore the well was abandoned in 1986. Table 10 summarizes the pathway information.
As indicated earlier, only 1 drinking water well had a level above 1500 ppm (2270) and this wellwas closed in 1986. Typically, the toxicological evaluation in a public health assessment is acomparison of the exposure dose (i.e., the amount of a substance individuals in an exposurepathway are exposed to daily) with appropriate health guidelines for carcinogenic and non-carcinogenic effects. For sulfates, EPA Region VIII recommends a risk-based concentration of1500 ppm for sulfate in drinking water at the Kennecott South Proposed NPL site (31). ATSDRaccepts the EPA Region VIII recommended sulfate level of 1500 ppm and used it in thisevaluation. The recommendation is the result of recent information on sulfate in drinking waterreviewed and accepted by the Risk Assessment Task Force (RATF) for the Kennecott ProposedNPL site. The task force is composed of scientists representing Kennecott Corporation, UDEQ,and EPA.
ATSDR concludes that EPA Region VIII recommended level of 1500 ppm as a level to takeactions such as having water users switch to alternate water supplies.
ATSDR considers the Southwest Salt Lake County Groundwater exposure situation to be a pastpublic health hazard because at least 1 drinking water well was contaminated above the EPARegion VIII 1500 ppm action level for sulfate in drinking water.
This public health hazard has been mitigated by provision of alternative water supplies and sourcecontrol measures. In addition to providing alternative water supplies, Kennecott's comprehensivewell inventory, groundwater monitoring, and private well testing programs have greatly reducedthe potential for human exposure to concentrations of sulfate above 1500 ppm. ATSDRrecommends the continuation of the current practice of offering a connection to a public drinkingwater supply to anyone discovered to have a well with sulfate levels above 1500 ppm.
During the September and October site visits, two public availability sessions, and throughtelephone calls and letters, Agency for Toxic Substances and Disease Registry (ATSDR) staffmembers solicited community health concerns from the south Salt Lake County AreaNeighborhood Groups, Salt Lake City/County Health Department, Utah Department ofEnvironmental Quality, Utah Department of Health, Kennecott Corporation, and individualcitizens. The community health concerns identified and ATSDR's response to them follow:
|CONCERN:||A resident of the Bingham Creek delta expressed concern about four cancer deathsin four homes in his neighborhood. Three resulted from Hodgkin's lymphoma andone from melanoma.|
|Response:||ATSDR is following up on this concern.|
|CONCERN:||This same resident also expressed concern about the effects on his children fromlong-term exposure to lead in his yard. He shared copies of the soil sampling donein his yard with ATSDR, along with results of blood lead testing of his family.|
|Response:||The soil lead levels identified in 1990 sampling of this resident's yard may havebeen high enough to result in health effects if there were frequent exposure to thecontaminated soil. However, the results of the blood lead testing, also done in1990, indicate that significant exposures were not occurring at that time becauseblood lead concentrations were below the concern level of 10 micrograms perdeciliter (µg/dL). It is not possible to determine whether significant exposures(i.e., above 10 µg/dL) could have occurred at another time.|
Surface soil samples taken in 1990 from this residence were 11,100 and 14,200parts per million. A review of the literature on lead indicates these levels could behigh enough to cause significant health effects in children if there were regularingestion of those contaminated soils.
However, results of blood lead tests taken in 1990 from the members of the familyliving at this residence were 6 µg/dL, 5 µg/dL, and two >5 µg/dL. This indicatesthat the members of this family were not being exposed to the contaminated soil intheir yard at least for the period immediately before the tests were taken. It is notpossible to determine whether these blood results reflect typical exposureconditions.