2012-07-10_GENERAL DOCUMENTS - C1981041

Home Browse Search

In conjunction with Permit Renewal No. 3, the Division found that the past subsidence monument survey monitoring had been sufficient to establish subsidence trends in the Roadside South Portals mining area. Because the geology, overburden thickness and coal seam extraction height remain the same as in previous mining areas that were monitored, similar effects are predicted to occur, should mining resume. Visual monitoring conducted twice yearly by the operator through 1998, had confirmed this projection. For mining under Coal Creek and Jerry Creek in the North Portal mining area, two subsidence monitoring monuments were installed adjacent to Coal Creek and three monuments were installed adjacent to Jerry Creek, in 1997 (see Exhibit 56, Tab 18). The approved subsidence monitoring plan for the entire permit area is described beginning on page 20 -8 of the permit application. Because there has been no coal extraction in the pelluiit area since 1999, and no future coal extraction is proposed or approved, regular annual subsidence monitoring and reporting is no longer required. Subsidence inspection, documentation, and evaluation will be triggered only if possible subsidence damage is reported by a surface owner or otherwise indicated. The regular monitoring program that was conducted through 2001 consisted of a visual surface inspection in spring and fall, to include areas to be mined within the next year, and areas mined during the previous two years. Coal Creek and Jerry Creek monuments were surveyed immediately prior to undermining and twice a year for two years subsequent to undermining All monitoring results, including documentation and photographs of subsidence features and structures, were submitted to the Division in an annual subsidence report by December 31, of each year. Any new structures within the affected area not previously documented will be included in the inspection schedule if new mining is projected beneath the structure. Follow -up inspection of structures will be undertaken if possible subsidence damage has been reported by the owner or otherwise indicated. The the Water Conservancy installed a waterline along the south and west perimeter of the Roadside Refuse Disposal Area in the winter of 1991/1992. Although this pile has remained stable since it was constructed in 1984, care was taken to protect the pipeline should any subsidence or settling occur. The waterline consists of a six -inch PVC pipe braced inside a ten -inch P.I.P. encasement pipe where it crosses the refuse pile. Should a rupture of the PVC pipe occur it would be contained in the P.I.P. pipe and directed off the pile. In 1998/99, TransColorado Gas Transmission Company (TGTC) installed a gas transmission line across a portion of the permit area, within a portion of the South Portals mine area which had at one time been approved for future undermining. The operator committed within the permit application to develop a subsidence survey or control and mitigation plan, upon resumption of mining via the South Portal. The plan will be approved by TGTC, and will be in place prior to mining within the subsidence angle of draw of the gas line. An agreement between PCC and TGTC is included as Appendix 20 -9, in Volume 6 of the permit application. The agreement includes the provision that the operator would notify TGTC six months prior to undermining of the gas transmission line. Because no further mining is proposed or approved, this provision is no longer applicable. Subsidence issues identified in association with PR -02, included updates to the "Man-made Features Map" to include the 345KV Rifle -San Juan transmission line, a house and shop building, and an area of "occasionally irrigated pastureland ", all within the South Portal mining area. The house and Permit Revision No. 5 50 July 10, 2012