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south of the downgradient 9MN portal and Empire P Seam Workings. <br /> Although minor increases to sulfate, sodium, chloride,and calcium have <br /> been observed,none of the increases are the result of adverse impacts from <br /> the adjacent mining as the mine workings are either downgradient or <br /> vertically disconnected. Therefore the increasing concentration of these <br /> parameters are most likely associated with either ambient conditions or <br /> unassociated activities located to the east-southeast. Review of historic water <br /> quality data for 9MN indicates that only a single sulfate sample has exceeded <br /> the drinking water supply standard. The chloride concentration(-50 mg/L) <br /> remains well below the current drinking water standard. Drinking water <br /> standards should not be applied to deep bedrock wells where there are no <br /> known users and limited potential for future use due to high economic cost <br /> for drilling to the depth of the Twentymile Sandstone (-600 ft bgs)and close <br /> proximity to historic mining. Boron was also noted as exhibiting the highest <br /> concentration on record,however review of the historic dataset suggests <br /> boron has remained below 0.1 mg/L since 2009. This is significantly lower <br /> than the agricultural groundwater standard of 0.75 mg/L,which is only <br /> applicable when specific crops are being irrigated with groundwater(see <br /> note g for Table 3 Agricultural Standards in Regulation 41).None of the <br /> other parameters noted above have groundwater standards or exhibit <br /> concentrations at levels that are of concern. <br /> Rule 4.05.8(1)-(3):Acid and Toxic-Forming Materials <br /> 25. Based on the Division's files the last refuse pile inspection report was submitted for the fourth <br /> quarter of 2017. In accordance with Rule 4.10.2(2)inspection of coal mine waste banks shall be <br /> performed in accordance with Rule 4.09.1(11)and other requirements listed in Rule 4.10.2(2). <br /> Please provide copies of the requisite refuse pile inspection reports from 2018, 2019, and 2020 <br /> within 30 days, on or before 1 Apri12021. <br /> a) MCM submitted copies of the refuse pile reports to DRMS via Laserfiche in December <br /> 2021. <br /> Rule 4.05.9(17) —Impoundment inspection reports <br /> 26. The last pond inspection reports the Division has on file are for the fourth quarter of 2017. In <br /> accordance with Rule 4.05.9(17), MCM must inspect all impoundments at least quarterly and <br /> submit a copy of the inspection report to the Division on a quarterly basis. Please provide copies <br /> of the requisite impoundment inspection reports from 2018, 2019, and 2020 within 30 days, on <br /> or before 1 Apri12021. <br /> a) MCM submitted copies of the missing quarterly pond inspection reports to DMRS via <br /> Laserfiche in December 2021. <br /> Please review the provided information and let me now if you have any further questions. <br /> Sincerely, �i <br /> /l a,6 � <br /> Miranda Kawcak <br /> Environmental Manager, Colorado Operations <br /> Peabody <br /> 5 1 P a g e <br />