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h <br />C~ <br />• <br />should provide, for insertion into the permit text, a more comprehensive public protection <br />program than currently described. <br />Such a program could include the existing proposal for dislodging, or scaling, rocks from the <br />source zone prior to undermining, and the existing proposal to close the county road during this <br />scaling. If TCC wishes to proceed with the proposal for temporary road closure, however, TCC <br />must provide proof that Routt County has approved such temporary closure before the Division <br />may approve the road closure. Though the Division asked for this proof, it is apparent that it <br />has not been provided. <br />While scaling the source zone may provide some measure of limiting rockfall, the Division is <br />uncertain whether this activity is sufficient [o completely prevent a rock from [he source zone <br />reaching the county road once longwall mining in Panel 12R begins. As such, public protection <br />measures in addition to scaling may be necessary. Such short-term measures could include the <br />temporary installation of "Jersey barriers" (portable concrete barriers) along the north shoulder <br />of County Road 33 before and for a period following undermining, as well as short-term <br />installation of chain link fencing draped over the source zone in an extent sufficient to reduce <br />rock fall bounce. An additional protective measure that could serve both in the short-term as <br />well as the long-term is an earthern berm built between the source zone and the county road of <br />a design sufficient to prevent any dislodged rock from falling onto County Road 33. <br />Should TCC prefer to not provide a guarantee that a rock from the source zone will not reach <br />County Road 33, and should TCC additionally prefer to not commit to providing for additional <br />short and long-term public protection measures, the Division may decide to place a condition <br />on the approval of PR-OS that limits the undermining of the Twentymile Sandstone outcrop that <br />overlies Northern Mining District Panel 12R and is situated above County Road 33 to room and <br />pillaz methods. <br />20. This item has not been adequately addressed. <br />TCC, in its April 10, 2000 response, committed to following the recommendations of Exhibit <br />7F-1 with regard to scaling of the source zone prior to longwall mining. Such a commitment <br />must be inserted as a text sentence into TCC's DMG permit. <br />21. This item has not been adequately addressed. <br />The Division is concerned that once [he "source zone" sandstone outcrop is undermined by <br />Panel 12R longwall operations, [he outcrop could be more susceptible to toppling, or raveling, <br />effects from freeze/thaw cycles. The Division believes [hat longwall-related subsidence has the <br />potential to open joints and other similar weakness features in the source zone sandstone, create <br />new infiltration pathways for snowmelt that could later freeze, which in turn could lead to <br />toppling or raveling of stone from the outcrop face. <br />Please discuss whether this possibility exists. If it does, the Division believes long-term (rather <br />than short-term) public protection measures, such as an earthern berm between the source zone <br />