PERMFILE46933 - Laserfiche WebLink

Home Browse Search

Permit Revision Adequacy Comment Response November 30, 2004 Page 13 of 24 add information on groundwater quality effects of mining at the West Elk Mine from data gathered in the program. MCC Response: MCC has updated the text. 2.05.6 (~ Subsidence Survey, Monitoring, and Control Plan 70. On page 2.05-92, the first pazagraph under "subsidence survey," a prediction is made for azeas where only E-seam coal will be extracted. MCC should provide analysis and discussion for those areas where both B-seam and E-seam mining aze indicated by Maps 51 and 52 in the area directly north of the Minnesota Reservoir. MCC Response: Discussion was added to clarify that the area alluded to is outside the SOD Permit area. 71. Item 6 on page 2.05-96 discusses a subsidence survey but fails to note the year. Please add the yeaz of the survey. MCC Response: Text was revised to show 2003. 72. Page 2.05-101 contains a discussion of the mitigating effects provided by shale and claystone . units on subsidence-induced surface cracks (and consequent water loss from the surface). Can MCC provide any estimate of the proportion of these soft lithologies in the sequence overlying the E-seam, particulazly in areas of thinner cover above the mined seam? Are there any specific thick or persistent units identified? MCC Response: MCC quantified and discusses the soft layers above the E Seam. 73. Related to the comment above, the third paragraph of page 2.05-188 states that the fractured zone in the SOD azea will be less extensive than in the Box Canyon and Apache Rocks areas. The implication is that there is a greater proportion of shale and claystone above the mined seam in the SOD azea, but that is never stated directly. Please complete the discussion by directly addressing the reasons MCC predicts that fracture zone height above the mined panels will be less in the SOD area and provide reference to lithological variations or whatever other reason is attributed to this prediction. MCC Response: Text revised. 74. On page 2.05-109, in the first pazagraph, the statement is made that "areas of colluvium and alluvium 5 to 10 feet thick were observed to cover cracks as much as 10-14 inches wide" in earlier subsidence monitoring. Please add an explanation of how and where that was observed. Were bedrock cracks observed to disappear beneath a cover of unconsolidated material? MCC Response: Text was added and data are shown in the Alluvial Well completion >~ reports.