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quality data are presented in Appendix 7-2B. Also provided are statistical summaries, plots of TDS (total dissolved solids) over • time, and a table of percent milliequivalents per liter for major ions. The water quality of each aquifer is discussed below. The prefix "GW-S" will be dropped from each well label in the discussions below for the sake of brevity. For example, well "GW-55-TC" would be referred to as "5-TC". The locations of each well can be found on Exhibit 7-2, "Hydrology Monitoring Site Location Map". Grassy Creek Alluvial System. Four wells are used 'to monitor alluvial water cuality in the Grassy Creek drainage: wells 6-A, 32-A, and 31-A2, which are completed in the alluvium of Little Grassy Creek, a tributary to Grassy Creek, and well 33-A, which is completed in the Grassy Creek alluvium. All of these wells monitor the Grassy Creek alluvial system downgradient of mining and were constructed after the onset of mining in the Grassy Creek drainage, so premining or background water quality is • unavailable. Although the majority of the mine area that drains into the Grassy Creek basin has been reclaimed, active mining and/or reclamation is still taking place in the northeast portion of the permit area (i.e., the Wolf Creek pit area). Well 32-A is located the furthest upstream along Little Grassy Creek and has a NaMgCa-5O4HCO3 water type. As with all of the Seneca II alluvial wells, water quality (as indicated by TDS levels) at this site varies seasonally, with TDS values at their highest during the fall. TDS values at this well have been gradually increasing since it was first sampled in 1980, Progressing downstream from well 32-A, the Little Grassy Creek alluvial aquifer becomes increasingly affected by spoils water discharge; typically, calcium and magnesium replace sodium as the 7-313 Revised 02/05/97