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both an underflow trash rack and a stilling plate, as <br />indicated in our revision request. Installation of the <br />pipeline from the treatment plant to the 020 pond has <br />been largely completed. <br />- The 001 pond(s) would be used for overflow on an <br />emergency basis when, due to some unforseen circumstance, <br />the 016 ponds provided insufficient back -up or there is <br />some problem with the 020 pond. The duration of use of <br />the 001 ponds for overflow would be temporary, until the <br />016 and 020 ponds could be restored to proper <br />functioning. <br />The 001 pond(s) would be used for underflow would be <br />during periods when storage for the underflow is <br />required, such as those times in which the water <br />treatment plant is operating but the coal preparation <br />plant is not operating. As indicated in the revision <br />request, Attachment E, the ponds have capacity for up to <br />277 days of additional flow, assuming the maximum <br />undeflow of 50 gpm @545.5 lb. /hr solids 24 hours a day. <br />The addition of the underflows to the 001 pond(s) might <br />increase the frequency of pond cleaning, depending on <br />run -off from the plant yard area. As indicated, Mid - <br />Continent intends to carry out pond - cleaning for the 001 <br />pond(s) on an as- necessary basis. <br />Attached is a revised permit page 33, to be inserted at <br />Chapter II of Vol. 1, indicating that pond cleaning will <br />be done for the 001 and 020 ponds, as well as the 016 <br />ponds, on an as necessary basis throughout the year. <br />- Sediment levels to trigger cleaning of the 020 pond have <br />been calculated, and included in Attachment D. A <br />sediment level of 60% triggers pond cleaning. <br />- Maps II -B -7 Att.4 -1 has been re- titled the "Rock Tunnel <br />Area Mine Water Distribution System" and should also be <br />placed in Vol. 3(A). Map IV -C -2 has been prepared to <br />show the components of the mine drainage water treatment <br />system and should be placed in Vol. 7. <br />- Replacement pages 25(a) and 25(b), Chapter 4, Vol. 7, are <br />enclosed. Replacement Page 33, Chapter II, Vol. 1, is <br />enclosed. Revised Table of Contents Pages are included <br />for Chapter IV and App. II -B -7. <br />- Please delete Appendix II -B -7 Att. 7, which had been <br />created for the materials relating to the mine treatment <br />system which was not delivered. We have determined to <br />include the relevant materials as an Appendix to the <br />Mitigation Chapter. <br />