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Title: Sampling and Analysis Plan for Environmental Control Number: Revision Date: <br /> Groundwater Monitoring PUE.EN.D.026.03 1 10/18/2019 Page 6 of 23 <br /> composed of dense shales, which provides an effective hydraulic barrier from the underlying <br /> Dakota Sandstone aquifer. <br /> 2.1 Sampling Locations <br /> Groundwater monitoring currently occurs at three monitoring wells (Figure 1). Well MW-5 <br /> was installed between the plant site and the Edson Arroyo in July of 2008. The well is <br /> completed in claystone (weathered shale) beneath a surficial clayey soil and screened from 9 <br /> to 25 feet. The borehole extended to 29 feet, but was terminated in the same claystone. Well <br /> MW-5 has been dry since it was installed. <br /> The other two site environmental monitoring wells are MW-6 and MW-7,which were installed <br /> in the Fort Hayes Limestone during December 2017 (Close Consulting Group, 2018). These <br /> wells were drilled in the area of a suspected fault downgradient of the second mine panel. Prior <br /> to drilling these wells, no free water had been encountered in the Fort Hayes or Codell <br /> Sandstone during other site drilling and well installations. The fault/fracture system that results <br /> in water occurring in these wells transects both the Fort Hayes and Codell. <br /> As mining progresses or compliance matters arise, additional monitoring wells will be <br /> installed. This SAP will also apply to those wells, unless specific modifications are approved <br /> by DRMS as part of future Technical Revisions. <br /> 2.2 Monitoring Frequency <br /> Groundwater monitoring currently is performed semi-annually for dry wells (MW-5) and <br /> quarterly for wells that typically produce water (MW-6 and MW-7). Quarterly monitoring is <br /> typically scheduled for April, June, September and December. Semi-annual monitoring is <br /> typically performed in June and December. Unexpected circumstances or adverse weather/site <br /> conditions may require that a sampling date be rescheduled or modified, but GCC will strive <br /> for overall consistency in the sampling schedule. <br /> 3.0 SAMPLING METHODS <br /> This section of the SAP presents a summary of groundwater documentation requirements, <br /> water level measurement procedures, field water quality measurement procedures, <br /> groundwater sample collection procedures, decontamination procedures, sample handling and <br /> custody requirements, and field QA/QC samples. <br />