REP30907 - Laserfiche WebLink

Home Browse Search

III IIIIIIIIIIII I II I; Memo to Janet Binns Twenty Mile Coal Company 1998 Subsidence Reports page 2 You will recall that TMC's 1997 Second-Half subsidence report lacked the visual monitoring report sheets for Routt County Road #33, the Union Pacific track, and the two power lines. I recommended that TMC be required to provide the reports for file completeness. No visual inspection forms were submitted with the First-Half brief report. Some visual inspection forms have been included within the 1998 Second-Half subsidence report by TMC: "Wooden Line Visual Inspection Forms" for the power lines covering the period from November 20, 1998 to December 26, 1998, and "County Road 33 & Powerline Subsidence Survey" forms covering the period from August 24, 1998 to December 17, 1998. No explanation is provided by TMC within the report regarding why these particular period reports were chosen for submittal. The submitted example remedial actions recommended by the observers. As such, they depict appropriate observations and responses by TMC. In my opinion, as long as these reports, including any generated by Union Pacific relating to subsidence impact observations and repairs conducted upon the railroad spur, are maintained on file and available to the Division upon request, it is not necessary for TMC to/ submit the forms with the subsidence reports. My examination of the hard copy subsidence data reports has discerned several obvious computation busts within the "Cum" data fields on Table 1. Stations 111, 112 and 113 have incorrect entries within the "Cum" fields. The raw survey data is logical, considering that Station 111 overlies the 6th Right Gateroad and Station 113 overlies the 7th Right Gateroad. These stations respectively appear to have experienced -0.26' and -0.05' of cumulative vertical movement. Station 112, which overlies the center of Panel 6 Right has experienced -4.08' of cumulative vertical settlement. These magnitudes are i~ keeping with observations above previously subsidence panels, and fall within the predictions within the permit documents. Table 1 should be corrected. ~ Figure #1 within the 1998 Second-Half report presents the map and profile of Foidel Creek above Panels 6 Right, 7 Right, and 8 Right. The profile section presents profile lines representing pre-mining and post mining profiles observed from September, 1996 through November, 1998. Four subsidence created "sag-ponds" are depicted on Figure #1. These four ponds appear to total approximately 5 acres in surface area as of November, 1998. Assuming an