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1.2 Sunday Low-Grade Stockpile <br /> The Sunday Low-Grade Stockpile covers about 2.7 acres (see note below) and is <br /> located <br /> on the east end of the Sunday Mine disturbed area. Based on a composite sample from <br /> this stockpile, the "Environmental Geochemistry Investigation of Rock and Soil Material, <br /> Sunday Group Mines", that was included as Attachment B to the EPP, reported that the <br /> stockpile had an average uranium concentration of 276 mg/kg. The investigation also <br /> conducted an environmental and health-based risk evaluation of the various materials <br /> on site and concluded that the mine sites were, in all cases, below the U.S. <br /> Environmental Protection Agency's (EPA's) industrial screening criteria for uranium of <br /> 3,100 mg/kg (see Table 4.1 of the investigation). <br /> The Colorado Division of Reclamation, Mining and Safety (DRMS) has established a <br /> guideline for uranium mines that limits the onsite storage of uranium ores containing <br /> 500 ppm or more uranium to 180 days. During a 2018 site inspection of the Sunday <br /> Mines Group, the DRMS requested that Pinon Ridge Mining LLC (PRM) conduct a more <br /> detailed survey of the surficial uranium content of the Sunday Mine Low-Grade <br /> Stockpile. The survey was conducted over forty-two 40-foot by 40-foot grids using an <br /> Olympus M Series Vanta X-Ray Fluorescence (XRF) Analyzer. The grids covered the <br /> entire surface area of the stockpile plus portions of undisturbed areas along the east <br /> perimeter of the stockpile. <br /> The grids were established using a tape measure and spray paint. Five random <br /> locations were surveyed within each grid and the results were averaged to obtain a <br /> uranium concentration for each grid. These in situ XRF measurements were performed <br /> by clearing away larger rocks and then holding the nose of the probe flush with the <br /> ground. After each measurement, the window of the probe was cleaned before another <br /> measurement was made. PRM submitted the results of the XRF survey to the DRMS on <br /> October 17, 2018. <br /> The survey found that all the grids on the south portion of the stockpile had uranium <br /> concentrations of less than 500 ppm. The 21 southern grids that had measurable levels <br /> of uranium averaged 252 ppm, which is consistent with the previous composite sample <br /> result of 276 mg/kg. However, 8 grids located on the north end of the stockpile had <br /> uranium concentrations higher than 500 ppm. These elevated concentrations were <br /> located on both the top and sides of the stockpile. <br /> On January 23, 2019, the DRMS requested that PRM prepare a TR to the EPP to <br /> address those areas of the Low-Grade Stockpile that had surficial uranium <br /> concentrations of 500 ppm or greater, as the agency was concerned that these areas <br /> were "vulnerable to windblown erosion" and had the "potential for adverse impact" to <br /> human health and the environment. In its request, the DRMS stated that the TR should <br /> describe "how the Operator will prevent adverse off-site impacts during periods of active <br /> mine site operations and periods of Temporary Cessation"and "clarify how the elevated <br /> materials will either be relocated to an appropriate underground location; OR removed <br /> to an appropriate offsite disposal or processing facility. OR otherwise stabilized and <br /> 4 <br />