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Home My WebLink AboutDRC-2025-002095 195 North 1950 West • Salt Lake City, UT Mailing Address: P.O. Box 144830 • Salt Lake City, UT 84114-4830 Telephone (801) 536-4200 • Fax (801) 536-4211 • T.D.D. (801) 536-4284 www.deq.utah.gov Printed on 100% recycled paper State of Utah Department of Environmental Quality Kimberly D. Shelley Executive Director DIVISION OF DRINKING WATER Tim Davis Director SPENCER J. COX Governor DEIDRE HENDERSON Lieutenant Governor MEMORANDUM TO: Tim Davis, DDW Director FROM: Mark Berger, Monitoring and Standards Section Manager DATE: August 28, 2023 SUBJECT: White Mesa Ute Mountain Ute Water System Monitoring Data Summary Report Background The Utah Division of Drinking Water (DDW) was provided a data set of drinking water quality standards regulated by the Federal Safe Drinking Water Act for the White Mesa Ute Mountain Ute water system. DDW was asked to provide a summary report of that data. Due to the age of the initial data set DDW received, DDW reached out to the Environmental Protection Agency (EPA) Region 8 to request all current compliance data for these standards. This report is based on the initial data set provided and additional data received by EPA Region 8. The EPA is the regulatory entity responsible for determining the system’s compliance with the Federal Safe Drinking Water Act and may have more up-to-date monitoring data and a better understanding of the system’s physical infrastructure and compliance with the Safe Drinking Water Act. Results summary ● Groundwater Source Sampling ○ There are no exceedances of primary or secondary standards in the treated water from the North and South Wells. ■ Pre-treatment sample results indicate that the North Well had levels of Arsenic above primary drinking water standards. ■ Post-treatment sample results indicate that treatment has been effective in reducing Arsenic levels in the North Well. Average arsenic levels have increased in the South Well since treatment was installed; however, levels are still below primary MCL. Page 2 ● Lead and Copper ○ The first-draw samples collected in 2016 did not result in a system-wide action level exceedance. ○ Home # 3- EC sample result had high initial results, with follow-up samples at the home and source, demonstrating results below the standard. ○ Groundwater source samples collected in 2007-2008 exhibited high lead and copper results. Lead and copper samples are not routinely taken at the source, as the most common source of lead and copper in drinking water is the leaching of metals from plumbing materials due to corrosive water. ‘ ○ Routine lead and copper samples are usually taken on six-month, annual, or once-every-three-year compliance cycles. Utah Division of Drinking Water Data Review Groundwater Source Data Chemical data collected from the North Well and South Well (pre- and post-treatment) was provided by EPA. The data set spans from 1999 to 2021 and includes four different classes of drinking water chemical contaminants: inorganics and metals, synthetic organic chemicals (pesticides), volatile organic compounds (VOCs), and radiological contaminants. Drinking water contaminants present in the groundwater can originate from many different sources, including agriculture, industry, waste disposal, and natural mineral deposits. Detection of such contaminants does not always indicate a public health risk, instead, it quantifies the degree of contamination or presence of chemical constituents in the groundwater. The conclusions drawn by DDW from the provided data set were made by comparing observed levels with EPA’s primary drinking water standards, or maximum contaminant levels (MCLs). MCLs represent the levels at which a particular contaminant begins to pose a public health risk and were established using national averages of body mass in relation to water consumption. Manganese concentrations were compared to the established EPA Health Advisory Level (HAL) of 0.3mg/L. Volatile Organic Compounds (VOCs) Of the samples collected from the North and South wells, there have been no VOC detections in the raw groundwater. Additionally, as of 2021, there have been no VOC detections in the South Well as it undergoes treatment. In September of 2020, Dichloromethane and O-Dichlorobenzene were detected in the treated water originating from the North Well at 4.53 ug/L and 0.85 ug/L respectively. Although the levels observed were below their MCLs, (Dichloromethane MCL=600 ug/L, O-Dichlorobenzene MCL=2 ug/L) it appears that follow-up sampling was conducted in November 2020. Dichloromethane and O-Dichlorobenzene were not present in the follow-up sampling; however, Vinyl Chloride was found at levels of 0.55 ug/L (MCL= 2ug/L). Vinyl Chloride was not present in subsequent samples. No VOC results have exceeded drinking water standards. Page 3 Synthetic Organic Chemicals (Pesticides) There was only one detection of a pesticide present in the data set. In 2001 Di(2-ethylhexyl) phthalate was detected at 0.0014mg/L in the North Well. The MCL for this contaminant is 0.006mg/L. This result does not indicate pesticides are an issue for either the North Well or South Well. Inorganics and Metals By comparing the raw groundwater and treated water from both the North Well and South Well, it is apparent that treatment has been effective at removing Arsenic from the North Well. A summary of the available Iron and Manganese data is given below. North Well (pre-treatment) Pre-treatment groundwater samples demonstrated metals in the North Well, including Arsenic, Barium, Chromium, Nickel, Selenium, and Manganese. Of these metals, only Arsenic was present at levels that presented a health risk. The remainder yielded trace detections consistently below 50% of their respective MCLs. Manganese samples collected in 2022 indicate that the average Manganese levels in North Well were 0.1195mg/L. North Well (post-treatment) Treatment has been effective at reducing Arsenic levels in the North Well. Sample collection in 2020 demonstrated that average Arsenic levels had been reduced by 24% when compared to the historical average Arsenic concentration of the raw water. Iron and Manganese levels were below their detection limits in samples collected in 2019. South Well (pre-treatment) Pre-treatment groundwater samples demonstrated metals in the South Well, including Arsenic, Barium, Nickel, and Selenium. The South Well has considerably less Arsenic than the North Well. None of these parameters come close to their respective MCLs. No pre-treatment data for Iron or Manganese was provided for the South Well; however, detections in post-treatment samples collected in 2022 indicate Manganese in South Well water was present. South Well (post-treatment) Post-treatment results from the South Well indicate an 18% increase in Arsenic (Average=0.0083mg/L). These results are still below the MCL but possibly warrant increased monitoring to assess for increasingly high results. Nickel concentrations were reduced significantly post-treatment. No Iron or Manganese was found in the post-treatment samples collected in 2019. However, in 2022 Manganese was found at average levels of 0.132mg/L, which is below the Health Advisory Level of 0.3 mg/L. Radiological Contaminants The average of the observed levels of radionuclides in both the treated and untreated water in both the North and South Wells are well below National Primary Drinking Water Standards. Average radionuclide concentrations in the treated water as well as a summary table comparing untreated water to treated water is given below. Page 4 In both the North and South Wells, Combined Radium concentrations have increased, while Gross Alpha Particle Activity has decreased slightly since treatment was installed. Combined Uranium data for the untreated North Well water is not present in the data set. Combined Uranium concentrations have decreased since treatment was installed on the South Well. There have been no significant increases in radionuclide levels from 2006 to 2021. These results qualify for reduced monitoring under the Safe Drinking Water Act. Page 5 Lead and Copper Data Lead and copper samples were taken from the North Well and South Well from 2007 to 2008. These results showed elevated concentrations above or near the action levels. Lead and copper samples are not routinely taken at the source, as the most common source of lead and copper in drinking water is the leaching of metals from plumbing materials due to corrosive water. These metals can be naturally occurring in groundwater but are not normally seen at such high levels. Page 6 The sampling procedure and analysis were not provided with these results, therefore errors in the process may have occurred. Lead and Copper Results 2007-2008 Source Date Lead (mg/L) Copper (mg/L) South Well 9/11/2007 -- -- 12/11/2007 0.42 3.8 3/11/2008 0.08 E.65 11/12/2008 0.19 <4.0 North Well 9/11/2007 -- -- 12/11/2007 0.14 <1.2 3/11/2008 0.19 <1.2 11/12/2008 0.43 E3.0 Action Level (mg/L) 0.015 1.3 In 2016, five lead and copper samples were taken in homes throughout the distribution system. One home (Home # 3 - EC) resulted in elevated lead and copper samples above the action levels (0.015 and 1.3 mg/L, respectively). However, the 90th percentile resulted in 0.00055 and 0.0301 mg/L, lead and copper concentrations, so no system-wide action level exceedance was reported. Lead and Copper Results 2016 Sampling Point Lead (mg/L) Copper (mg/L) Home #1 - LD <0.005 0.0456 Home #2 -JCS <0.005 0.0035 Home # 3 - EC 0.0457 4.18 Home # 4 - TW 0.0006 0.0074 Home # 5 - BL 0.0005 0.0146 Sample Summary 90th Percentile 0.00055 0.0301 Action Level (mg/L) 0.015 1.3 Page 7 Follow-up samples were taken at Home # 3 - EC and the South Well source, demonstrating results below the action level. Parameters for calculating the Langelier Saturation Index were also sampled. The Langelier Saturation Index is used to assess corrosivity when an action level is triggered by the exceedance of a lead or copper MCL to figure out if the water itself is corroding the pipes or solder in the plumbing in a home or water supply system. In the case of this exceedance, the home and wellhead were sampled with very similar results, paired with more lead and copper samples. The lead and copper samples from both locations were below the MCL and the corrosivity index (-0.36) indicated that the water is slightly corrosive, but non-scale forming. While the exceedance appears to be an anomaly, it is recommended that the homeowner refrain from drinking the first-draw flush from their tap if it has been set for some time. Instead, it is advised to allow some of the water to run for a few minutes before drinking it under those circumstances. (Field data from USGS SIR 2011-5231 used for pH, EC, and temperature at South Wellhead for calculation) Corrective Action Samples at Home #3- EC 2016 Sampling Point Lead (mg/L) Copper (mg/L) Alkalinity, Bicarbonate (mg CaCO3/L) Alkalinity, Carbonate (mg CaCO3/L) Alkalinity, Hydroxide (mg CaCO3/L) Alkalinity, Total (mg CaCO3/ L) Calcium (mg/L) LSI Home # 3 - EC <0.0005 0.0048 183 <10 <10 183 23.4 -0.36 South Well Wellhead <0.0005 0.0009 186 <10 <10 186 23.4 -0.36 White Mesa Uranium Mill USGS Study Results and Discussion Review The Ute Mountain Ute Tribe at White Mesa is located approximately five miles southeast of the White Mesa Uranium Mill. The Mill is currently active and processes uranium, vanadium, rare earth minerals, and other products. Several studies have been conducted looking at the potential contamination of groundwater near the Ute Mountain Ute Tribe at White Mesa. Currently, the groundwater supply for the Ute Mountain Ute Tribe appears to contain no contamination from the Mill, and due to the geochemistry of the White Mesa, there is a low probability of released Uranium dissolving into the groundwater. (Naftz, D., Et all, (2012) USGS Assessment of Potential Migration of Radionuclides and Trace Elements of the White Mesa Uranium Mill to the Ute Mountain Ute Reservation and Surrounding Areas, Southeastern Utah) https://pubs.usgs.gov/sir/2011/5231/pdf/sir20115231.pdf.