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-. <br />-,- <br />•` Brown <br />Page 2 <br />July 26, 2000 <br />there has been a significant increase in TDS concentration from the upstream monitoring point <br />on Trout Creek (TR-A) to the downstream monitoring point (TR-D) in conjunction with the <br />mining and reclamation activities. <br />It also appeazs [hat the predicted post-mining mean annual concentration of TDS in Trout Creek <br />has been exceeded for the past several years at the downstream monitoring point TR-D. The <br />PHC predictions presented in the PAP indicate that after mining the West Ridge and Moffat <br />Areas, the mean TDS concentration in Trout Creek would be expected to increase to 330 mg/l. <br />Monitoring data reported in 1999 show that the mean annual TDS concentration for TR-D was <br />420 mg/1. Please clarify the statement on page 9 that all values for TDS are consistent with the <br />PHC projections. Exceedances of PHC predictions should be addressed in future AHRs so that <br />any significant trends can be identified and conclusions regarding PHC predictions can be <br />verified. <br />3. On page 31 of the 1999 AHR, P&M indicates that the elevated levels of TDS in Well TR- <br />1.5 may be from an old abandoned underground mine up the Little Trout Creek drainage or <br />possibly from the inundation of the area in late spring of 1995 and the laying of telephone cable <br />upstream of the area during the summer of 1995. To aid in identifying the source of the elevated <br />TDS values, the Division is requesting additional information regarding the on-site alluvial <br />monitoring wells. Please provide survey information (including ground surface elevation and top <br />of well casing/measuring point elevation) and depth to water measurements for 1995 through <br />1999 for Wells TR-1.5 and WR-1. Also, the Division cannot locate the well log for Well TR-3. <br />Please provide this monitor well log, if available. <br />The completion log of well TR-1.5 indicates that this well was only drilled to 6.0 below ground <br />surface and water level was initially 3.0 feet below ground surface. Well TR-1.5 is located <br />below the reclaimed West Ridge Area and does not appear to be entirely upgradient of [he <br />disturbance area. Further review of these data may determine the source of the elevated levels of <br />TDS a[ well TR-1.5. Please provide any information that P&M may have conceming [he <br />location and operation of the referenced old abandoned underground mine up the Little Trout <br />Creek drainage. <br />If you have any questions conceming my review of the 1999 AHR, please let me know. <br />m:\coal\mpb\edna 1999 <br />