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<br />Mr. Vern Pfannenstiel <br />-3- <br /> <br />April 24, 1986 <br />The concentration of total dissolved solids determined by <br />dates indicates that the lab determinations are accurate <br />0.6 times the EC values, as is usually the case. Because <br />reported for NPDES self-monitoring, and because accurate <br />PCC should identify the problem with field measurements, <br />soon as possible. <br />the lab on these <br />because TDS is about <br />EC is a variable <br />data is desirable, <br />and correct it as <br />8. Data from the 1985 AHR indicates that sulfate concentrations have <br />increased at station SW-S2-5 since 1983. Additionally the data indicate that <br />sulfate concentrations at site SW-S2-6 have doubled yearly since 1983. <br />The 1985 AHR asserts that sulfate levels will stabilize over the next two <br />years. It is the Division's position that as more land is disturbed in a <br />drainage, there is a greater volume of material available to be leached by <br />percolating waters. Asa greater volume of material is leached, increased <br />concentrations of dissolved constituents in receiving streams will be observed. <br />Considering continuing mining in the "Cow Camp Creek" drainage, Peabody should <br />further qualify their statement that sulfate concentrations will stabilize <br />during the next two years. <br />9. The sediment-level survey of NPDES ponds as described in the report <br />should be a regular inclusion in future AHR's. Amore frequent interval than <br />every three (3) years could provide valuable information on erosion rates. <br />The Division requests that Peabody include a brief section in future AHRs on <br />sediment control in the surface water discussion. This should include general <br />comments on maintenance of ditches, culverts, ponds, channels and rills and <br />gullies that were required during the previous year. This additional <br />information would be valuable for assessing the suspended-sediment aspect of <br />surface water quality. <br />The Division would like to resolve the above concerns in a timely manner. <br />Therefore, please submit to the Division the information requested above prior <br />to June 15, 1986. <br />If you have any questions or comments, please contact me. <br />Sincerely, <br />Steven Renner <br />Hydrologist <br />SR/tmb <br />cc: Mike Savage <br />John Doerfer <br />9528E <br />