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GROUND WATER <br />The piezometers on the mine bench were monitored quarterly for <br />water level. Graphs are included with this report which show <br />historical water levels of the piezometers. The water level in P-1 <br />peaked in March which is typical and then due to the dry summer the <br />water level dropped 12.9 feet to 17.9 feet. <br />Piezometer P-2 showed a peak water level in March then by June it <br />dropped 5.0 feet to a level consistent with prior years records for <br />this piezometer. <br />Piezometer P-3 showed water at 22.2 feet during March and then by <br />June the water level dropped to the typical 40 feet plus level for <br />the remainder of the year. <br />The piezometer at the top of the bench, P-4, showed little varia- <br />tion during the year. <br />On October 12, 1989, piezometers P-5 and P-6 were installed on the <br />face of the bench in the area of the 1989 cover material slump. P- <br />5 is 28.2 feet deep with a bentonite seal at 8 feet. It is <br />designed to measure the water level in the coal waste material. P- <br />6 is 12.2 feet deep with a bentonite seal at 2 feet on up to the <br />surface. It is designed to measure the water level in the cover <br />material. The piezometers are close enough together so it can be <br />determined if the water level in the cover material and the coal <br />waste material are independent of each other. <br />The water level in P-5 increased from 25.8 to 24.3 during the year. <br />At the end of the year the water level in P-5 was 3.9 feet deep <br />measured from the bottom of the hole, (26.2-24.3). <br />The water level in P-6 decreased from 7.5 to 10.2 feet during the <br />year. At the end of the year the water level in P-6 was 2 feet <br />deep measured from the bottom of the hole, (12.2-10.2). <br />The respective water levels in P-5 and P-6 indicate there is no <br />relationship between the water level in the cover material and the <br />water level in the waste material. <br />Both the north and south underdrains had slightly more flow during <br />1991 than 1990. The north underdrain's flow increased from 0.015 <br />to 0.0018 acre-feet. The south underdrain's total flow increased <br />from 0.01 to 0.02 acre-feet. The mass average conductivity for the <br />north and south underdrains increased compared to last year. The <br />averages for 1991 were 3034 and 4913 compared to 2300 and 4778 <br />during 1990 for the north and south underdrain respectively. The <br />conductivity is measured in umhos/cm. <br />-2- <br />