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There are three alluvial aquifer systems present within the Seneca II <br />permit area: the Grassy Creek alluvial aquifer, the Cow Camp Creek <br />alluvial aquifer system (drainage from below 004 pond to Fish Creek), and <br />the Bond Creek alluvial aquifer (drainage from below 008 pond to Fish <br />Creek). The Fish Creek alluvial aquifer is not within the Seneca II <br />permit area, but may be affected by water discharging from the permit <br />area. <br />Currently, the Grassy Creek alluvial aquifer and the Cow Camp, Creek <br />alluvium are monitored by 6 wells which are used to monitor <br />depth-to-water and water quality. <br />The re saturation of portions of the backfilled pits has been expressed as <br />spoils aquifers. Water percolates through the replaced spoils materials <br />and flows down-gradient (topographic) until it reaches the lower-most <br />highwall. When the elevation head of the spoils aquifer exceeds the <br />ground surface elevation, the spoils water discharges in the form of <br />springs, at the topographically lowest point along the reclaimed <br />highwall. Nine spoil springs have been identified, eight of which are <br />monitored by Peabody Coal Company. In addition, Peabody Coal Company <br />monitors thirteen spoils wells as part of the approved monitoring plan. <br />The quality of the spoils water usually exhibits elevated concentrations <br />of sulfate, manganese, and magnesium. TDS concentrations are variable, <br />but average values upwards of 3,000 mg/1 are not uncommon from spoil well <br />samples, while spoils springs exhibit TDS concentrations which are much <br />lower, usually averaging about 2000 mg/1. The 2000 mg/1 average is the <br />concentration level at which the spoils spring discharges are thought to <br />be most representative of conditions at the Seneca II Mine site. <br />In about 1977, the Water Resources Division of the United States <br />Geological Survey (USGS) began a lysimeter study at the Seneca II Mine to <br />determine spoil aquifer discharge quality, and how that quality changes <br />over time. As mining becomes more concentrated in Twentymile Park, the <br />long-term quality impacts to the hydrologic balance will become <br />increasingly more important. A stipulation in the original permit <br />requires Peabody Coal Company to submit the USGS report to the Division <br />upon its completion. This stipulation, which follows, will be carried <br />over into the third permit term as it has not yet been resolved. <br />STIPULATION N0. 23: <br />WITHIN 90 DAYS OF ITS PUBLICATION, A COPY OF THE UNITED STATES <br />GEOLOGICAL SURVEY'S LYSIMETER STUDY MUST BE SENT TO THE DIVISION AND <br />OSM TO PROVIDE ADDITIONAL QUANTITATIVE DATA ON FLOW RATES AND WATER <br />QUALITY OF THE SPOIL LEACHATE. <br />With the continued acceptance of the above stipulation, the operation is <br />in compliance with the requirements of this section. <br />B. Surface and Ground Water Monitoring <br />1. The operator will conduct monitoring of surface water in a manner <br />approved by the Division. The monitoring plan was submitted under <br />2.05.6(3)(b)(iv) and includes the following: (4.05.13(2)). <br />-16- <br />