Laserfiche WebLink
On completion of each MDW, a methane exhauster would be installed to draw the <br />methane to the surface where the methane would be used to power the exhauster blower <br />unit, with any excess vented to the atmosphere. Bottled propane would be used as a <br />back-up fuel source for starting the exhausters if methane concentrations are too low to <br />power the exhauster units. The MDWs would be used in combination with the existing <br />mine ventilation system and horizontal methane drains within the underground mine <br />workings to effectively reduce and control methane levels in active underground mining <br />azeas. <br />Exhauster units aze self-contained skid- and tire-mounted units. These units would be <br />MSHA approved for safety, would be inspected on a regular basis, and would be enclosed <br />within a security fence. Methane exhausters would remain in-place and continue to <br />operate so long as they continue to be effective in draining methane from the underground <br />mine workings. Based on recent MDW experience, it is anticipated that each MDW <br />would remain active and continue to be effective during the period when the coal <br />extraction face approaches it, passes underneath it, and for a period of time after it passes <br />beyond it. Experience with existing MDWs indicates that some wells continue to vent <br />methane for several months after the extraction face has passed by. It is currently <br />anticipated that the effective life of MDWs would range from six months to two yeazs. <br />MDWs in one panel may prove effective in venting methane for adjacent mining panels. <br />MCC would monitor and inspect active MDW installations daily following initial <br />installation to assure that they aze functioning properly. It is anticipated that the <br />frequency of monitoring would decrease to weekly monitoring, as required by MSHA. <br />Inspections, to assure proper operation, would be more frequent and vary seasonally. <br />MCC is testing remote sensing equipment that reduce required inspection frequency, if <br />proven consistently reliable. Access by ATV and/or pick-up,and snowcat or snowmobile <br />in the winter, for at least weekly monitoring would be needed for the life of the MDWs, <br />estimated at this time to be six months to two years. It is anticipated that all active <br />MDWs would be inspected and monitored in one weekly trip. <br />PROPOSED DRILL HOLE PLUGGING METHODS <br />The hole plugging methods described in 43 CFR II 3484.1(a) or Colorado Division of <br />Minerals and Geology (CDMG) Rules and Regulations at 4.07.3, will be used for all <br />holes. It is anticipated that each open hole will be plugged with cement from bottom to <br />50 feet above the uppermost thick coal seam and from 50 feet below to 50 feet above any <br />aquifers encountered in the hole. The remainder of the hole will be filled with an <br />approved completion mud, gel, cuttings, or cement to within 5 feet of the surface. A 5- <br />foot cement surface plug will be set, and an appropriately labeled monument marker will <br />be cemented into the surface plug. Surface casing will be cut off at or below the level of <br />the soil surface. However, most, if not all of the proposed MDW will be steel-cased and <br />cemented in-place effectively sealing the space between the outside annulus of the well <br />and the rock strata. Where the entire depth of the well is steel-cased alternative plugging <br />techniques maybe employed, after review with the regulatory agencies. <br />