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Red Creek Quarry Baseline Water Investigation Section 3 <br /> <br /> <br />3-6 <br />DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this docu ment. <br />A stilling well was installed along the north side of Red Creek to measure water levels within the <br />saturated alluvium of the creek bed as a proxy measurement of the creek water elevation. The <br />stilling well was drilled using an auger to advance a hole to approximately 5 feet below ground <br />surface. A 5-foot PVC slotted screen with an end capped was placed into the hole then sand was <br />backfilled in the wellbore up to the surface. <br />3.3 Groundwater Elevations <br />Transducers were installed after development operations in Well 1, Well 2N, Well 2S, Well 3, Well 4, <br />and the Stilling Well to continuously monitor the groundwater levels. Immediately prior to transducer <br />installation, a depth-to water measurement was collected to establish a value between transducer <br />measurement and elevation. Coordinate and elevation data were collected by Holcim for each well <br />casing and adjacent ground surface using survey equipment. <br />Transducers were set to collect a measurement ever six hours beginning in December 2021. Data <br />from the transducers were routinely downloaded by BC or Holcim personnel. Gaps in the transducer <br />datasets are due to the transducers being paused during the groundwater monitoring events or due <br />to equipment technical issues. <br />3.4 Slug Test <br />The hydrologic properties of the Codell Sandstone were evaluated to assess the groundwater system <br />at the Site. Slug tests were conducted during the May 2023 sampling event using the existing <br />monitoring wells. Single-well slug tests provide a means to estimate hydraulic conductivity of the rock <br />mass near the piezometer. Slug tests generally involve the rapid removal or displacement of a <br />volume of water in a well, causing the water level to rise or fall from the original static water level <br />(Butler 2019). Well water levels are monitored until the water levels return to roughly static <br />conditions. The effects of changing the water level within the well is transmitted through the well <br />screen and filter pack to the formation in a manner that indicates the hydraulic properties of the <br />formation. The hydraulic conductivity of the aquifer material is calculated from the rate that the <br />water level recovers to static conditions. <br />The monitoring wells are bailed to purge as much of the stagnant water as possible prior to collecting <br />groundwater samples for analysis. The transducer data collection interval was changed to 1 minute <br />during the May 2023 sampling event to collect water level data as the wells recovered, resulting in a <br />slug-out test for each well. <br />3.4.1 Data Usability and Corrections <br />Prior to analyzing the slug testing data using AQTESOLV (HydroSOLV 2019), a commercial aquifer <br />testing analysis software, the usability of the data was evaluated. Water level data from select <br />portions during slug test recovery were not used for analysis due to insufficient data points during <br />water level response times or the lack of static water level conditions at the onset of secondary slug <br />withdrawals. Each well had one usable rising head test with the exception of Well 1 which had two <br />usable rising head tests. <br />To account for barometric effects, data from the weather station at the Fremont County airport <br />(K1V6, latitude: 38.42856, longitude: -105.10685, elevation 5442 ft above mean sea level [amsl]) <br />on the MesoWest website developed by the University of Utah (www.mesowest.utah.edu) was used <br />for barometric readings and a correction was applied.