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Mountain Coal Comparry 1998 Annual Hydrology Report West Elk Mine • Adequacy of Monitoring Program MCC continued to monitor the same resowces as in WY97, however, additional sites were incorporated into the baseline monitoring program for the Box Canyon permit azea (Permit Revision No. 8). Many of the sites in the monitoring program have been monitored since the early 1980s, so there is extensive data for many of the sites. In addition, with the approval of Minor Revision No. 208 on January 21, 1998, MCC began to report water quality samples from mine water inflows. During WY98, surface water continuous flow data were recorded on dataloggers in addition to the Sevens Type F recorders at the flume stations. The dataloggers helps to eliminate errors in transcribing the data. The strip charts remained in place as a backup system. The Upper and Lower Deep Creek stations did not have flumes installed in order to minimize impacts. Control sections were constructed from natwal materials and a presswe transducer with a datalogger was installed at both locations. Considerable difficulties were encountered at these stations, including equipment malfunction and channel geometry changing under high flows. Consequently, flow data for Deep Creek was limited to instantaneous flow measwements. MCC is working to improve the data collection reliability at the Deep Creek stations for WY99. During WY97, MCC closely evaluated their monitoring program. The first evaluation reviewed the groundwater monitoring wells in the program, and determined which of the wells continued to provide reliable data and those that, for various reasons, were no longer providing reliable • data. Technical Revision No. 85 proposed to delete seven wells from the monitoring program, and was approved by the Division on July 21, 1998. Therefore, GP-5, SOM 23-H-1, SOM-23- H-2, LP-1, B-32, SOM 38-H-1, and JMB-12 were not monitored after this date. Technical Revision No. 85 fully explains the basis for these wells being deleted from the monitoring program. The second evaluation involved closely reviewing all springs and remaining groundwater wells in the monitoring program. This investigation performed a comprehensive hydrogeologic chazacterization of the West Elk Mine permit and adjacent azeas. The chazacterization is based on a syntheses of existing hydrogeologic information, isotopic data, and the results of an in- mine, fault related, groundwater inflow investigation. This report, Characterization of Groundwater Systems in the vicinity of the West Elk Mine, Somerset, Colorado (January 1999) by Mayo and Associates was submitted as support for revising MCC's monitoring program in Technical Revision No. 88. Although, this revision application was not submitted in WY98, the isotopic data was collected during the water year. MCC anticipates approval of this revision during WY99. In 1996, MCC installed two groundwater wells to collect baseline data in the area where the Refuse Pile Expansion (RPE) would be constructed. These wells were known as LRP-1 and LRP-4. With the construction of the RPE, LRP-4 was destroyed, but LRP-1 (now identified as RPE-1 }has continued to be monitored. The data for RPE-I is included in this report. MCC will install a replacement well for LRP-4 during WY99. • 8 1-03 .500 Page 8 Wrig t ater Engineers