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REDE~VED GRAND MESA COAL COMPANY DEC Q ~ 1986 1986 HYDROLOGIC REPORT MIMkD LAND f~ECLAMATION DIVISION HYDROLOGIC YEAR 10/85 - 9/86 • During this hydrologic year the Red Canyon N1 Mine continued to be in temporary cessation. The Red Canyon #2 Mine has not been started. To reduce the expense of the Red Canyon #1 Mine, pumping was discontinued and the portals and shaft were temporarily sealed. A reduction in hydrologic monitoring was also analyzed as a means of cost savings. On February 25, 1986, Grand Mesa Coal Company submitted a Technical Revision Request requesting a reduction in monitoring on the basis of having already established adegyyate baseline information. Technical Revision 86-01 was approved June 6, 1985)with a reduced schedule. Due to monitoring reductions during the hydrologic yea tables are not necessarily representative of the year. l~`~P Surface Mater The information shown on Table 5-86 for Ward Creek and Williams Creek did not take into account flows and field information for June through August. the inclusion of the summer information may have resulted in a lower average flow, total flow and pH according to information from previous years. The interpretation of data for SP-A through SP-D on Table 5-86 is complicated by the change in monitoring schedule and the change in discharging mine water. The introduction of mine discharge into the sediment pond had the affect of stirring up excess suspended solids and increasing the pH. The mine discharge met NPDES discharge requirements therefore our CDPS permit NCO-0036935 was modified to allow direct discharge through outfall 002. The first discharge was made through outfall 002 on April 21, 1986. The higher conductivity and pH for SP-A is typical of low flows where springs influence the quality more. SP-B as usual was primarily influenced by mine discharge. No discharges have been made from this point since mine discharge was diverted around it. The flow on SP-C was largely influenced by infrequent high flows during mine discharge. SP-D did not show the influence of maximum water rights flows in June through August. The flow and field information for Nelson Ditch shown on Table 5-86 was calculated fora fu1T year from weekly flow and quarterly field information. As noted on the table the year did not correspond to the 1986 water year. Spring N's 1, 2, 3, and 5 were similar to 1985's readings inspite of the reduced monitoring schedule. Spring 4 showed a lower average flow due to the lack of irrigation run-off formerly present in the summer measurements. Ground Hater The average water levels shown on Table G-86 for the coal seam piezometers • were similar to previous averages except on E-3. In April 1986 the water level jumped 31' in E-3 and has continued to raise since. This piezometer has shown major variation in the past for no known reason.