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Mr. Richard Mills - 3 - June 5, 1986 Detection limits for four elements were not low enough to ascertain whether the water was meeting stream standards. Comparison of Detection Limits and Receiving Steam Standards Receiving Stream Element Detection Limit Standard Mercury < 0.0005 0.00005 Cadmium <0.005 0.001 Molybdenum < 0.05 0.01 Copper* <0.02 0.01 *Copper detection levels for sites covered by the basic Hydrologic Monitoring Plan were inadequate. However detection levels for the Area 2 Pit/Pond D study are acceptable. Interpretation Bedrock Aquifer Well Monitoring The wells in the Wadge overburden and Twentymile sandstone did not appear to show any potentiometric changes attributable to mining. The hydrographs for 006-82-48 and 006-82-48A were helpful. It would be appreciated if hydrographs of all wells could be included in future reports. The hydrograph of well 006-82-48A did not show a consistent seasonal pattern, contrary to TCC'c analysis, but rather a series of fluctuations between 1982 and 1984 that have no correspondence with annual cycles. Are you aware of any pumping that went on in the vicinity during that period? Well 006-81-31 has much higher salt levels than other Wadge overburden sites. Has this well been examined to ascertain that it was completed properly? Do you have any other explanations for the high salt concentrations? Is well 006-81-30 an artesian well? The remarks column annotates the failure to provide depth data with the comment "flowing". Please elaborate. Foidel Creek Alluvial Aquifer Well Monitoring The Foidel Creek alluvial wells do not show any definite effects from mining from the hydrographs presented. However, future hydrographs should have an expanded abscissa of 20 feet rather than 35 feet. It is expected that water levels should rise in late summer with Foidel Creek's transition from an ephemeral to a perennial stream. Salt concentrations in the aquifer declined during the last two years at the downstream site, but increased at the two upstream sites, It there a comparable dilution effect in adjacent surface water sites as one proceeds downstream through the permit area? Fish Creek Alluvial Aquifer Well Monitoring Twentymile Coal Company submitted a graph of the potentiometric surface of a series of wells at the Fish Creek Tipple. This graph showed quarterly water levels from 1985 and fall quarter data from 1980. A comparison of 1980 and 1985 fall quarter data showed an increase in water level on the disturbed