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Permit Revision Adequacy <br />July 6, 2004 <br />Page 9 of 18 <br />66. In the discussion of "time to fill" (pages 2.05-193 to 197), please carry out the calculations in <br />the text. It's not clear how the final results were obtained and calculations done by DMG <br />reviewers did not achieve the same results quoted in the text. <br />67. On page 2.05-197, the fourth line has a minor typographical error. Please correct. <br />68. On pages 2.05-190 and 220, it is relevant in a discussion of downgradient mine workings that <br />the Sanborn Creek Mine is downgradient of the B-seam and probably of the proposed Box <br />Canyon sump. Please add the Sanborn Creek Mine to the discussion. <br />69. On page 2.05-222 MCC discusses the potential for mining-related impact on groundwater from <br />acid leachate concluding that there is no potential. After years of mining and monitoring, MCC <br />should be able to discuss groundwater quality from existing data that would add greatly to the <br />discussion. This is an important issue relating to Rule 4.05.13 (1) and bears on decisions <br />regarding selection of appropriate "points of compliance" for groundwater monitoring. Please <br />add information on groundwater quality effects of mining at the West Elk Mine from data <br />gathered in the program. <br />2.05.6 (6) Subsidence Survey, Monitoring, and Control Plan <br />70. On page 2.05-92, the first paragraph under "subsidence survey," a prediction is made for areas <br />where only E-seam coal will be extracted. MCC should provide analysis and discussion for <br />those azeas where both B-seam and E-seam mining are indicated by Maps 51 and 52 in the azea <br />directly north of the Minnesota Reservoir. <br />71. Item 6 on page 2.05-96 discusses a subsidence survey but fails to note the year. Please add the <br />year of the survey. <br />72. Page 2.05-101 contains a discussion of the mitigating effects provided by shale and claystone <br />units on subsidence-induced surface cracks (and consequent water loss from the surface). Can <br />MCC provide any estimate of the proportion of these soft lithologies in the sequence overlying <br />the E-seam, particularly in azeas of thinner cover above the mined seam? Are there any <br />specific thick or persistent units identified? <br />73. Related to the comment above, the third paragraph of page 2.05-188 states that the fractured <br />zone in the SOD area will be less extensive than in the Box Canyon and Apache Rocks areas. <br />The implication is that there is a greater proportion of shale and claystone above the mined <br />seam in the SOD area, but that is never stated directly. Please complete the discussion by <br />directly addressing the reasons MCC predicts that fracture zone height above the mined panels <br />will be less in the SOD azea and provide reference to lithological variations or whatever other <br />reason is attributed to this prediction. <br />74. On page 2.05-109, in the first paragraph, the statement is made that "azeas of colluvium and <br />alluvium 5 to 10 feet thick were observed to cover cracks as much as 10-14 inches wide" in <br />