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GRAND MESA COAL COMPANY • 1987 ANNUAL HYDROLOGIC REPORT HYDROLOGIC YEAR 10/86 - 9/87 During the 1987 hydrologic year, Grand Mesa Coal Company's operations continued to be in temporary cessation. The Delta loadout site was removed from the permit area and the majority of minesite equipment and facilities were removed during the year. This year's report was formatted to compare this year's monitoring results with an average of previous results for the same month. The averages generally included monitoring results from 1981 thru 1986. SURFACE PATER According to the local irrigation office, the run-off in 1987 was lower than during the previous four years. The run-off was still above the long-term average for the area. Williams Creek, Ward Creek and SP-D monitoring bear out this assessment. Spot flow readings in May are not very meaningful due to variations in timing and intensity of snowmelt but the September readings are a good indication how the irrigation season went. The late season flows on the creeks are augmented by reservoir discharges. Low flows in the fall indicate that reservoir water is near depletion. The conductivity in the • creeks is generally related to the flow: the lower the flow, the higher the conductivity. At high flow the conductivity is sometimes high due to the extra erosion from high velocities. On lower Ward Creek, the low flow conductivity is sometime low because the water has taken a direct flow path down the creeks rather than through irrigated fields. Examples of all three factors can be seen this year's in monitoring results as shown on Table 5-87. The flow in springs this year was generally lower than the average, see Table 5-87. All of these springs are somewhat related to the amount of water being used for irrigation. The sediment pond did not discharge during the year. Previous discharges were related to mine discharge. Prior to sealing the mine, a direct discharge of mine water was permitted to reduce discharge from the pond. 6ROUNDiWTER The coal seam piezometer water levels were generally higher than the average water levels, see Table G-87. This may show a delayed response to higher than normal run-off for the past several years. The May 87 measurement on D-3 may be a recording error according to adjacent data. The high water levels in E-3 appear to be related to near surface ground water indicating that the piezometer may have broken somewhere in the surface alluvium. The water level in the mine should not be affecting these water levels. The water level in the recently active portion of the mine is projected to be at approximately 6272' and in the old mine at approximately 6317'. The E-N piezometers are in the same seam as the Red Canyon fll Mine. II 17,1 I ~h1