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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> Vent Shaft ID October 2019 Findings <br /> WS-2 Measured water level: dry <br /> T-1 Underground fan, did not access <br /> T-2 Measured water level: dry <br /> The October 2019 measurements from the vent shafts allowed for a recalculation of the <br /> potentiometric surface for these locations and the projection of this surface into the mine <br /> workings. <br /> 10.3 General Sampling Procedures <br /> After measuring water levels in the monitoring wells, contemporaneous groundwater chemistry <br /> sampling was conducted at wells MW-SUN1, MW-SUN2, and MW-SUN3 a total of 7 times from <br /> September 2013 to February 2020. The first five samples were collected in consecutive <br /> quarters; the last two samples were collected in the last quarter of 2019 and the first quarter of <br /> 2020. Wells MW-SUN1 and MW-SUN2 were also sampled in December 2012 and January <br /> 2013, respectively. <br /> Groundwater sampling was conducted consistent with protocols and procedures practiced in the <br /> professional environmental industry and as recommended by regulatory agencies, with minor <br /> modifications. Typically, low-flow sampling is conducted in such a way to minimize (less than a <br /> few tenths of a foot) drawdown in the well. Low-flow methods do not typically involve well <br /> purging prior to sampling. Because of the low recharge rate and extensive amount of time <br /> involved to collect samples from the MW-SUN1 and MW-SUN2 monitoring wells, EFR proposed <br /> a sampling method that reflected the initial method used at MW-SUN1. This method involved <br /> the initial evacuation of the BESST tubing water above the well screen followed by low-flow <br /> sampling of the well water within the screened interval. Following this purge, the pumping rate is <br /> regulated to keep drawdown controlled. Drawdown is measured with a water level indicator <br /> tape. This method was accepted by both the BLM (Blair, 2013) and DRMS (EFR, 2013 and <br /> DRMS, 2013). At well MW-SUN3, the Bennett pump was used for all sampling events. <br /> The samples collected on September 24, 2013, at well MW--SUN1 used low-flow methods with the <br /> newly installed BESST well apparatus. Because of the extremely low recharge rate at the wells,the <br /> low-flow sampling method initially used at MW-SUN1 involved some experimental sampling <br /> methods. Sample SMW1 Pre involved sampling of the BESST tubing water in the well above the <br /> pump intake and did not involve any purging of water in the screened interval. A duplicate sample, <br /> Western Water& Land, Inc. 33 <br />