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Foidel Creek Mine C-82-056 2021 Annual Hydrology Report <br /> 10 feet but will not be mined once its thickness is greater than 3 feet. The WC3 Seam ranges <br /> from 2.5 to 4 feet. The interburden between WC3 and WC4 ranges from 0.5 feet to 4.5 feet but <br /> will not be mined once its thickness is greater than 3 feet. The WC4 Seam ranges from 2 to 5 feet. <br /> Table 3-1 presents a summary of bedrock well monitoring frequencies. Water level and field <br /> parameters, which include pH, temperature, and conductivity, are measured semiannually at the <br /> Wadge and Wolf Creek Overburden wells, the Twentymile Sandstone wells, and Fish Creek <br /> Sandstone wells and annually at the Trout Creek Sandstone wells. Note that water level only is <br /> measured at two of the three Fish Creek Sandstone wells. Water quality is sampled annually at all <br /> Wadge and Wolf Creek Overburden wells, at two of the Twentymile Sandstone wells, and one of <br /> the Fish Creek Sandstone wells and biannually at four of the Trout Creek Sandstone Wells. Water <br /> quality parameters include total dissolved solids (TDS), dissolved calcium, dissolved magnesium, <br /> dissolved sodium, bicarbonate, carbonate, sulfate, dissolved cadmium, dissolved lead, dissolved <br /> mercury, dissolved selenium, dissolved iron, dissolved manganese, dissolved molybdenum, <br /> nitrate and nitrite, and orthophosphorus. A discussion of the 2021 monitoring results by bedrock <br /> unit is provided below. <br /> Wadge And Wolf Creek Overburden: <br /> Seven Overburden wells (009-79-4, 006-82-74C, 91M006, 008-77-58, 93M001, WC008A, and <br /> WC013A) are currently monitored. Water quality samples are collected at least annually. <br /> Attachment 1 shows the bedrock well monitoring data for the Water Year, including water levels, <br /> hydrographs, water quality, water quality statistics, and graphs of TDS and field conductivity. <br /> The potentiometric surface in the Wadge Overburden generally slopes from south to north in the <br /> vicinity of the TC facilities, as shown by water levels in wells 009-79-4, 006-82-74C, and 08-77-58. <br /> The water level in wells 009-79-4, 006-82-74C, and 008-77-58 remain within their historic range <br /> and have been stable for over a decade. A decline in water level, associated with dewatering <br /> impacts from the underground mining operation, has occurred at wells 91 M006 and 93M001. The <br /> water level at 93M001 began stabilizing in the 2010's and levels measured in 2020 remains within <br /> the historic range observed at the well. Well 91 M006 is currently damaged. TDS measured at the <br /> Wadge Overburden Wells in 2021 remain within historic ranges. TDS has been stable at wells <br /> 009-79-4 (-500 mg/L), 008-77-58 (-1100 mg/L), and 93M001 (-1100 mg/L) over the last couple <br /> 8 <br />