_GENERAL DOCUMENTS - C1981017 (259)

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were dug out and filled with rock and now act as a series of "french drains" under the toe of the pile. They are active most of the year and always remain clear with no sign of sediment. The piezometers in the pile show no indication of changes either in quantity (water level) or quality. B. New Coal Refuse Pile The new pile was designed with an extensive rock underdrain covering the entire area of springs and seeps. This drain is functioning well and no other springs or seeps have been noted. C. Development Rock Pile - Tunnel This pile also had springs and seeps associated with the ground surface before construction. These areas were also backhoed out and filled with rock (see geo-hydro plans) . These small drains were connected to the large natural under- drain (pre-existing drainage under pile) . The sediment ponds were constructed on top of this underdrain which in turn sits on top of 40 ' to 50' of river bed alluvium. The seep in the alluvium below the last sediment pond is believed to come from this natural underdrain. This flow occurs every spring and has always remained clear. IV. Chemical parameters that should be addressed especially as they relate to the low flow regime are: 1. TDS and/or conductivity The graphs do not show any trends or relationship between high flow and TDS, but there is some indication of elevated TDS at low flows possibly attributed to the mine discharges. 2. Sulfates The sulfates appear to be elevated during low flow again probably due to the mine discharge (pyrite oxidation) or just to generally less dilution of the Basin waters. 3. Sodium Absorption Ratios (SAR) Some data from 4/82 on SAR also seems to be elevated during low flow, but all of the ranges seem quite low. (Station #20 Coal Creek low . 72; high 4 . 8) 4 . Flow - as increased by mine discharges and depleted from water uses for the mine complex. See Attachment #5.