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' Amy Eschberger Reference No. 20378105-1-TM-0 <br /> Colorado Division of Reclamation, Mining and Safety February 19,2021 <br /> ' 2.0 MONITORING WELL INSTALLATION <br /> The borehole total drilled depth reached 235 ft bgs to confirm the Niobrara—Codell contact at 230 ft bgs. <br /> ' Therefore, per the work plan a screen interval of 206 ft bgs to 226 ft bgs was selected. The borehole was reamed <br /> to 229 ft bgs,just above the Niobrara —Codell contact. Two feet of coated bentonite tablets were used to backfill <br /> the borehole from 227 ft bgs to 229 ft bgs to create a seal at the bottom of the borehole, and prior to proceeding <br /> ' with well construction the bentonite was allowed to hydrate for approximately an hour. Above the bentonite seal, <br /> from 226 ft bgs to 227 ft bgs, sand (10/20 fraction)was placed (Attachment C). <br /> ' The well was constructed with 4-inch diameter, flush-threaded, Schedule 80 PVC screen and riser pipe. The <br /> 20-feet long screen was perforated with 0.010-inch slots. PVC casing was added to the top of the screen as it <br /> was lowered into the borehole. The screen interval spans 205.6 ft bgs to 225.6 ft bgs. A centralizer was placed <br /> ' in the center of the screen, and then centralizers were placed approximately every 50 feet above that point. The <br /> filter pack extends from 202.1 ft bgs to 227 ft bgs with a bentonite seal above the filter pack from 199.3 ft bgs to <br /> 202.1 ft bgs followed by grout to approximately 1 ft bgs. Additional bentonite was added on top of the grout to <br /> ' bring the annular space material up to grade. The PVC riser extends 3 feet above the ground surface and is <br /> protected with a locked protective steel casing. A 3 x 3 concrete pad was constructed around the protective <br /> casing. <br /> 2.1 Monitoring Well Development <br /> ' MW-8 was developed on November 24, 2020, six days after grout was poured. The water level was drawn down <br /> using a stainless steel bailer to just above the top of the screen prior to surging the screen by rapidly lowering and <br /> raising the full bailer. After surging, the well was purged dry using the bailer. In total, approximately <br /> ' 125 gallons of water were purged from the well. Per TR-11, the purge water was discharged on the ground <br /> surface. Water quality parameters were collected approximately every half casing volume, and parameters <br /> appeared stable with pH fluctuating around 8.5 standard unit (SU) and specific conductivity ranging from <br /> t approximately 4,200—4,900 microSiemens/cm (Attachment D). Turbidity was initially low and became moderate <br /> as development progressed. It is likely the water from the shallow saturated groundwater zone encountered at <br /> approximately 115 ft bgs flowed into the open borehole and a localized area surrounding the borehole. <br /> ' Groundwater recharge was monitored for an hour after the well was bailed dry and only a few inches of recharge <br /> was observed. <br /> A second development was completed on December 7, 2020, detailed in Attachment D. Approximately 13 gallons <br /> of water were purged from the well using a disposable bailer until the well was bailed dry, and water quality <br /> parameters were recorded throughout development. Generally, water quality parameters showed pH stabilizing at <br /> ' 8.34 SU, specific conductivity stabilizing at 13,136 microSiemens/cm, and turbidity increasing throughout <br /> development. The purged groundwater was gray in color with a slight sulfur odor. The increase in conductivity <br /> from the initial development indicates the initial development was effective at removing a portion of the water from <br /> ' the shallow groundwater zone that entered the borehole and a localized area surrounding the borehole. <br /> The depth to groundwater recorded before the initial development did not reflect the screened interval due to <br /> groundwater from the shallow saturated groundwater zone present in the borehole and well prior to development. <br /> ' Depth to groundwater as recorded before the second development and subsequent groundwater sampling, which <br /> will be discussed briefly in Section 3.0, are presented in Table 1. The December 7, 2020 groundwater <br /> ' measurement was recorded 13 days after the initial development, while the December 14, 2020 measurement <br /> ' ' GOLDER 3 <br />