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Western Engineers was retained to do further evaluation of stability including installation of <br />piezometers isolated to narrow water bearing zones within the pile. Thirty piezometers (PZ 100- <br />107, 200-206, 300-307, & 400-406) were installed at four locations on the pile. Multiple 2" <br />diameter piezometers were installed in each bore hole. The bottom of each piezometer was <br />perforated and sand packed through a wet zone identified while drilling. The multiple zones <br />within the hole were separated by bentonite plugs. Stability was verified in the pile at the <br />measured water levels but the study recommended quarterly monitoring of the piezometers for <br />continued evaluation. A listing of these piezometers is given on Table 18-4. The water levels <br />were measured quarterly on these piezometers. The study established "critical target depths", <br />Table 18-4, at which stability of the pile could again be in question. Results of quarterly <br />monitoring was evaluated against the critical target depths and the Division was to be notified <br />within 2 days if measured levels were above the critical target depths. If that occurred the <br />stability of the pile would have been reevaluated and corrective action taken if necessary. <br />Piezometers CRDA-01 through 06 & 01 a were monitored quarterly for water level. The sixteen <br />temporary piezometers were eliminated during the pile cover project in 1994. Monitoring of the <br />CRDA-1 & CRDA-2 piezometers was discontinued with the approval of SL -8 & TR -67 in 2015. <br />These piezometers will be abandoned and plugged in early 2016. <br />Four piezometers were installed around the Unit Train Loadout to monitor water levels in the <br />alluvial material. Monitoring of these piezometers (UTL-01, 02, 03, & 04) was generally done <br />monthly from March 1984 through September 1987. Monitoring of water levels was <br />discontinued in 1987. Quarterly water level monitoring was resumed on the 4 piezometers in <br />1994 and annual quality monitoring was started on UTL-02 & 04 for the parameters listed in <br />Table 18-3 for ground water. Monitoring of the UTL piezometers was discontinued with the <br />approval of SL -7 in April 2011. UTL 01, 02, 03 & 04 wells were abandoned and reclaimed in <br />May 2011. <br />A former mine dewatering pipe is being used to monitor the water level in the north end of the <br />Roadside South Portals mine. This piezometer, N-1, which is located in the old North Decline <br />area is monitored quarterly. <br />TR -67 18-5 Rev 11/15 <br />