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Permit C-81-071 1996 Annual Hydrology Report • bedrock wells monitored in the area. New maximum values for well 006-82-74C (Table 4 ' include total dissolved solids, recorded in April, and dissolved lead and ortho-dissolved phosphorus values recorded in September. At wells 94M001 (Table 6) and 94M002 (Table 7), several parameters returned values outside of previously established ranges for these sites as the database for these sites is limited and typical ranges are still being established. No significant deviations were noted however. ALLUVIUM Alluvial sediments are monitored in the Foidel Creek valley upstream and downstream of Mine 1 and Eckman Park and in the Fish Creek valley upstream and downstream of Mine 2. Three wells completed in the Foidel Creek alluvium are monitored (001-S-5, 009-S-10, and 008-AV-2). Three wells completed in the Fish Creek alluvium are also monitored (006-AY-1, 006-AZ-3, and 006-AW-2). Foidel Creek Alluvial Groundwater: During 1996, three Foidel Creek alluvial wells (009-S-10, 001-S-5, and 008-AV-2) required monitoring for water levels and field parameters on a monthly basis, and water quality sampling on a quarterly basis. All monitoring requirements were met at these sites. Tables 8 through 10 provide summaries of the 1996 Water Year data collected at each site. Tables 8a through 10a provide period of record statistical summaries of collected data at each site. Figures 12 through 17 provide graphical representations of water levels and TDS concentrations recorded at each site. Water levels during 1996 remained generally consistent with established ranges and patterns and showed the typical seasonal variability of elevated water levels in the spring. Well 009-S- • 10 provides data for the alluvial aquifer downgradient from the Eckman Park mine (Figure 14). This well exhibited noticeably higher water levels in the spring due to the significant snowpack causing high runoff levels. Well 001-S-5 is located downgradient from Mine 1 and below the Twentymile Coal Company mine portals and is monitored in conjunction with surface water monitoring site 8. Figure 12 is indicative of the general relationship between the alluvial groundwater elevations and surface water elevations at these two sites. Wells 008-AV-1 and 008-AV-2 are monitored in conjunction with surface water site 304 at a point on Foidel Creek approximately 1000 feet upstream of the confluence of Foidel and Middle Creeks. Water levels in these wells and the stream show the typical seasonal interrelationship of relatively rapid increases and declines associated with spring runoff (Figure 16). The longer term trends in water levels at these sites generally parallel the fluctuations observed in annual streamflows. Field conductivity measurements in general at well 001-S-5 (see Figure 13; 1996 average approximately 2000) were again noted to be higher than the upgradient site 009-S-10 (see Figure 15; 1996 average approximately 1250). Moving downgradient, field conductivities at well 008-AV-2 are averaging approximately 1750. Conductivity values at well 009-S-10 fluctuated within previously established ranges during 1996 with the exception of an unusually high value recorded in November 1995. The generally increasing field conductivity trend noted in 1994 and 1995 for well 001-S-5 appears evident again in the 1996 data although a marked decline was recorded during the latter half of the year. Field conductivity measurements at well 008- AV-2 are comparable to measurements at well 001-S-5 and occurred within previously established ranges for these sites. Previously noted increasing TDS concentrations at well 008-AV-2 appear to have stabilized somewhat during 1996. CYCC will continue to monitor the direction of this trend. • I \DOCUMENTWHR\ECKMAN\EP96TE%T DOC 03/28/97 Page 3