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evaluate stability as a result of higher than expected water levels in the pile. Their <br />• evaluation was inconclusive due to the piezometers being open the full length of the <br />hole. Western Engineers was retained to do further evaluation of stability including <br />installation of piezometers isolated to narrow water bearing zones within the pile. <br />Thirty piezometers (PZ 100.107, 200.206, 300.307, and 400.406) were installed at <br />four locations on the pile. Multiple'/2"diameter piezometers were installed in each <br />bore hole. The bottom of each piezometer was perforated and sand packed through <br />a wet zone identified while drilling. The multiple zones within the hole were <br />separated by bentonite plugs. Stability was verified in the pile at the measured water <br />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 <br />water levels will be measured quarterly on these new piezometers. The study <br />established °critical target depths", Table 18.4, at which stability of the pile could <br />again be in question. Results of quarterly monitoring will be evaluated against the <br />critical target depths and the Division will be notified within 2 days if measured levels <br />• are above the critical target depths. If that occurs the stability of the pile will be <br />reevaluated and corrective action taken if necessary. Piezometers CRDA•O1 through <br />06 and Ola will be monitored quarterly for water level. The sixteen temporary <br />piezometers were eliminated during the pile cover project in 1994. <br />Four piezometers were installed around the Unit Train Loadout to monitor <br />water levels in the alluvial material. Monitoring of these piezometers (UTL-O1, 02, <br />03, and 04) was generally done monthly from March 1984 through September 1987. <br />Monitoring of water levels was discontinued in 1987. Quarterly water level <br />monitoring was resumed on the four piezometers in 1994 and annual quality <br />monitoring was started on UTL-OZ and 04 for the parameters listed in Table 18.3 for <br />ground water. <br />A former mine dewatering pipe is being used to monitor the water level in the <br />north end of the Roadside South Portals mine. This piezometer, N•1, which is <br />located in the old North Decline area will be monitored quarterly. <br />J <br />vOL 5 Tab 18 18-5 7 . 7 - 99 <br />