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Home My WebLink AboutDRC-2019-006423 - 0901a06880aa1d47INTERA Incorporated 6000 Uptown Boulevard NE, Suite 220 Albuquerque, New Mexico 87110 USA 505.246.1600 NTERA GEOSCtENCE S. ENJSINEERING SOLUTIONS 1 D RC- 201, -00 G4-23 TECHNICAL MEMORANDUM To: Kathy Weinel, EFRI From: Angela Persico, INTERA Date: June 28, 2019 Re: Reanalysis of uranium data for the calculation of a groundwater compliance limit in MW-30 1.0 INTRODUCTION A Source Assessment Report ("SAR") for uranium in MW-30 was submitted to the Division of Waste Management and Radiation Control ("DWMRC") on January 15, 2019. The SAR concludes that (1) increasing concentrations of uranium are likely the result of site-wide decreases in pH; (2) with the exception of chloride, concentrations of indicator parameters in MW-30 have not changed significantly since the time of the New Wells Background Report; and (3) MW-30 is not being impacted by potential tailings system seepage. Therefore, a revised groundwater compliance limit ("GWCL") for uranium was proposed. A GWCL of 11 micrograms per liter ("p.g/L"), which is the highest historical value of the data set, was proposed in accordance with the DWMRC-approved Flowsheet. The 11 p.g/L value was measured and reported by Energy Laboratories in 2008 and is an outlier relative to the complete data set. Most uranium concentrations from that time were approximately 7 1.1g/L (Figure 1). The Flowsheet directs the analyst to only remove extreme outliers, while outliers are to remain in the dataset1. Since 11 i.tg/L is not an extreme outlier, the value was retained for analysis and, in accordance with the Flowsheet, selected as the GWCL for a dataset that is not normally distributed and contains 100 percent detected values. 2005 2010 2015 Sample Date Figure 1: Time series plot of uranium concentrations in MW-30 using all data 1 Extreme outliers are values greater than the third quartile plus three times the interquartile range or values less than the first quartile minus three times the interquartile range. Outliers are values greater than the third quartile plus 1.5 times the interquartile range or values less than the first quartile minus 1.5 times the interquartile range. California I Colorado I Florida I Hawai'i I Indiana I New Mexico I Texas I Washington I France I Switzerland Kathy Weinel June 28,2019 Page 2 During a preliminary discussion with DWMRC regarding their concern over using this historical data point generated by the previous laboratory as a GWCL, EFRI proposed reanalyzing the uranium data in MW-30 to identify a more representative GWCL. In the fourth quarter of 2012, EFRI switched laboratories from Energy Laboratories to American West Analytical Laboratory ("AWAL"). This analytical change resulted in more variability in uranium concentrations due to increased sensitivity of the measurement methods. The analytical change provides a temporal point of inflection that may be used to create a subset of more recent and more reliable data. Therefore, although outliers are appropriate to retain in the dataset in accordance with the Flowsheet, the 11 I.J.g/L data point, and all data collected prior to the fourth quarter of 2012, have been excluded from this reanalysis. 1.1 Modified Approach to Calculating a GWO. for Uranium in MW-30 Since uranium is exhibiting a significantly increasing trend, a modified approach should be considered for determining a GWCL. Data collected after the laboratory change in October 2012 were used as a subset of data for reanalysis and revision of the proposed GWCL for uranium in MW-30. Figure 2 is a time series plot of uranium data in MW-30 from October 2012 to the present. 15) D 9 - icu 8 • a 7 — er RN. JO 6 — 2013 2014 2015 2016 2017 2018 2019 Sample Date Figure 2: Time series plot of uranium concentrations in MW-30 using data from October 2012 to the present The October 2012 dataset is representative of current conditions in MW-30. These data have been collected and analyzed in accordance with the Mill's Quality Assurance Plan ("QAP") and are considered more reliable than data collected prior to the laboratory change in 2012. Therefore, a revised GWCL has been calculated using data collected from October 2012 to the present. Table 1 is a summary of statistical results and a revised GWCL using the subset of data collected from October 2012 to the present. r. —11"- 7743C- l/ Pe" GE OSCE NCE St EN T IONS Highest historical value of dataset from Oct. 2012 to present Uranium (µg/L) 8.32 9.82 Kathy Weinel June 28,2019 Page 3 Table 1. Proposed revised GWCL for uranium in MW-30 The proposed revised GWCL for uranium in MW-30 is 9.82 p.g/L, which is the highest historical value from the data analyzed after the analytical change in October 2012. This GWCL was determined using a modified approach for trending constituents in accordance with the DWMRC-approved Flowsheet. -INIT xCIENCE ENGINEEMNIC3 SOLU tC NS APPENDIX A Statistical Summary of Uranium in MW-30 from October 2012 to the Present 11Nlie.'S 6 F'GINE RING SO.CaS APPENDIX A-1 MW-30 Data Used for Statistical Analysis I , NA a U W P z - s .• P-. 2012-present pg/L 80 0% 7.9 0.64 0.96 7.54E-03 Not normal 1457 7.25E-10 Increasing 9.82 8.32 9. 82 Highest Histoncal Value Notes: %ND = percent of non-detected values mg/L = milligrams per liter pg/L = micrograms per liter s.u. = standard units N = number of valid data points p = probability W = Shapiro Wilk test value S = Mann-Kendall statistic Distribution = Distribution as determined by the Shapiro-Wilk distribution test for constituents with % Detect > 50% and N>8 Mean = The arithmetic mean as determined for normally or log-normally distributed constituents with % Detect > 50% Standard Deviation = The standard deviation as determined for normally or log-normally distributed constituents with % Detect > 85% Highest Historical Value = The highest observed value for constituents with % Detect < 50% T 1-1 Reanalysis of Uranium in MW-30 White Mesa Uranium Mill Page 1 of 1 APPENDIX A-2 MW-30 Data Used for Statistical Analysis MW-30 10/23/2012 Uranium 7.86 ug/L MW-30 11/13/2012 Uranium 7.03 ug/L MW-30 12/26/2012 Uranium 5.80 ug/L MW-30 1/23/2013 Uranium 8.36 ug/L MW-30 2/26/2013 Uranium 7.40 ug/L MW-30 3/20/2013 Uranium 6.85 ug/L MW-30 4/17/2013 Uranium 7.08 ug/L MW-30 5/15/2013 Uranium 6.31 ug/L MW-30 7/10/2013 Uranium 7.48 ug/L MW-30 8/20/2013 Uranium 7.07 ug/L MW-30 9/18/2013 Uranium 7.00 ug/L MW-30 10/22/2013 Uranium 6.91 ug/L MW-30 11/20/2013 Uranium 8.57 ug/L MW-30 2/25/2014 Uranium 6.83 ug/L MW-30 3/11/2014 Uranium 7.84 ug/L MW-30 4/23/2014 Uranium 6.84 ug/L MW-30 5/14/2014 Uranium 9.82 ug/L MW-30 6/3/2014 Uranium 7.35 ug/L MW-30 7/29/2014 Uranium 7.40 ug/L MW-30 8/20/2014 Uranium 7.60 ug/L MW-30 9/9/2014 Uranium 7.70 ug/L MW-30 10/7/2014 Uranium 7.76 ug/L MW-30 11/10/2014 Uranium 7.65 ug/L MW-30 12/10/2014 Uranium 7.67 ug/L MW-30 1/21/2015 Uranium 8.06 ug/L MW-30 2/4/2015 Uranium 8.23 ug/L MW-30 3/3/2015 Uranium 8.35 ug/L MW-30 4/8/2015 Uranium 7.45 ug/L MW-30 5/12/2015 Uranium 8.38 ug/L MW-30 6/24/2015 Uranium 7.46 ug/L MW-30 7/7/2015 Uranium 7.98 ug/L MW-30 8/11/2015 Uranium 8.16 ug/L MW-30 9/15/2015 Uranium 7.72 ug/L MW-30 10/7/2015 Uranium 8.10 ug/L MW-30 11/11/2015 Uranium 7.99 ug/L MW-30 12/9/2015 Uranium 8.22 ug/L MW-30 1/20/2016 Uranium 8.02 ug/L MW-30 1/20/2016 Uranium 8.34 ug/L MW-30 2/10/2016 Uranium 7.76 ug/L MW-30 3/2/2016 Uranium 7.82 ug/L MW-30 4/13/2016 Uranium 7.55 ug/L MW-30 5/4/2016 Uranium 8.18 ug/L MW-30 6/14/2016 Uranium 7.66 ug/L Reanalysis for Uranium in MW-30 White Mesa Uranium Mill Page 1 of 2 APPENDIX A-2 MW-30 Data Used for Statistical Analysis MW-30 7/13/2016 Uranium 8.10 ug/L MW-30 8/18/2016 Uranium 8.23 ug/L MW-30 9/14/2016 Uranium 8.22 ug/L MW-30 10/5/2016 Uranium 7.64 ug/L MW-30 11/3/2016 Uranium 7.92 ug/L MW-30 12/6/2016 Uranium 8.63 ug/L MW-30 1/18/2017 Uranium 8.01 ug/L MW-30 2/2/2017 Uranium 7.62 ug/L MW-30 3/7/2017 Uranium 7.89 ug/L MW-30 4/5/2017 Uranium 7.63 ug/L MW-30 5/2/2017 Uranium 8.11 ug/L MW-30 6/5/2017 Uranium 7.98 ug/L MW-30 7/11/2017 Uranium 8.33 ug/L MW-30 8/14/2017 Uranium 8.05 ug/L MW-30 9/12/2017 Uranium 7.80 ug/L MW-30 10/5/2017 Uranium 8.35 ug/L MW-30 11/1/2017 Uranium 7.19 ug/L MW-30 12/6/2017 Uranium 8.18 ug/L MW-30 12/6/2017 Uranium 8.29 ug/L MW-30 1/23/2018 Uranium 8.53 ug/L MW-30 2/22/2018 Uranium 8.23 ug/L MW-30 3/8/2018 Uranium 8.66 ug/L MW-30 4/12/2018 Uranium 7.98 ug/L MW-30 5/15/2018 Uranium 8.44 ug/L MW-30 6/19/2018 Uranium 8.80 ug/L MW-30 7/24/2018 Uranium 8.69 ug/L MW-30 8/10/2018 Uranium 7.69 ug/L MW-30 9/11/2018 Uranium 8.34 ug/L MW-30 10/22/2018 Uranium 8.08 ug/L MW-30 11/14/2018 Uranium 8.81 ug/L MW-30 12/11/2018 Uranium 8.20 ug/L MW-30 1/16/2019 Uranium 9.07 ug/L MW-30 2/13/2019 Uranium 9.09 ug/L MW-30 3/6/2019 Uranium 8.39 ug/L MW-30 4/9/2019 Uranium 8.62 ug/L MW-30 5/7/2019 Uranium 8.15 ug/L MW-30 6/3/2019 Uranium 8.88 ug/L Notes: U = Not detected above method detection limit pg/L = micrograms per liter 11ILEU Reanalysis for Uranium in MW-30 White Mesa Uranium Mill Page 2 of 2 APPENDIX A-3 Box Plot of Uranium in MW-30 Uranium in MW-30 Percent nondetect: 0% Min: 5.8, Mean: 7.93, Max: 9.82, Std Dew 0.64 Upper extreme threshold (Q75 + 3xH): 10.4475 Lower extreme threshold (025 - 3xH): 5.5125 =1NTERA Reanalysis for Uranium in MW-30 White Mesa Uranium Mill Page 1 of 1 0.75 0.80 0.85 0.90 0.95 _ 0 — 1 1 APPENDIX A-4 Histogram of Uranium in MW-30 Uranium (ug/L) in MW-30 SW-W = 0.9558, p = 0.0075 Log Result NTERA Reanalysis for Uranium in MW-30 White Mesa Uranium Mill Page 1 of 1 Ur a n iu m ( ug /L) APPENDIX A-5 Time Series Plot of Uranium in MW-30 Uranium in MW-30 2013 2014 2015 2016 2017 2018 2019 Sample Date • Indicates a detected result o Indicates a non-detect result ENTER Reanalysis for Uranium in MW-30 White Mesa Uranium Mill Page 1 of 1