Laserfiche WebLink
<br />-2- <br />Rules 2.05.6(6) and 4.20: Subsidence <br /> <br />The application includes the results of the required survey of structures and <br />renewable resource lands within the potentially affected areas. The following <br />inadequacies were determined to exist within that survey discussion: <br />(I) The applicant observes that a dwelling exists within the potentially <br />affected area, but that this dwelling is owned by Colorado Yampa Coal Company. <br />The location of that dwelling should be clearly delineated on Map No, 4. Further, <br />on page 2.05-62, reference is made to an "unoccupied structure". If these <br />references regard one-in-the-same structure, the applicant should clarify the <br />point, If the structure is inhabitable, then the applicant must discuss "worst <br />case" projected effects of subsidence. In the case of inhabitable dwellings, <br />it has been common to require appropriate precautions be taken, such as special <br />utility connection modifications, in order to eliminate potential hazards to <br />occupants. <br />(2) County Road No. 27 is exposed to potential effects from subsidence and should <br />be monitored to safeguard the public. In connection with the proposed survey <br />mnnumentation, visual inspection techniques should suffice. <br />(3) The Denver, Rio Grande and Western Railroad spur is also within the <br />potentially affected area. As in the case of County Road No. 27, periodic visual <br />monitoring of this facility should suffice. <br />(4) The applicant projects localized impacts upon both bedrock and surficial <br />aquifers, based upon a specific concept of overburden response which has been <br />insufficiently justified within the application. Recent literature regarding <br />subsidence effects upon overburden above underground coal workings has documented <br />roof caving to heights in excess of IO times seam height and bed separation to <br />heights in excess of 50 times seam height. On page 2.05.61, among other instances, <br />the applicant refers to overburden caving limitations of 5 times the seam thick- <br />ness. The mechanical and hydrological implications of such variance in projected <br />overburden response could be significant. The applicant will have to more <br />thoroughly justify the assumptions being made in its projection of subsidence <br />impacts. In addition, the applicant will have to specifically discuss how the <br />proposed mechanical and hydrological monitoring programs will serve to verify <br />their assumptions made in completing the projections of impact. <br />The subsidence ronitoring program presented within the application proposes two <br />survey monitoring subsidence grid networks. These installations are acceptable <br />as proposed. The applicant also proposes to survey the one identified dwelling <br />within the potential area of subsidence effect. In addition, however, the <br />applicant will be required to conduct periodic visual monitoring of features such <br />as County Road No. 27 and the D and RGW Railroad spur. <br />The applicant observes that severe winter weather conditions make quarterly <br />monitoring undesirable and a proposal to monitor semi-annually is included within <br />the application. The justification is inadequate to allow approval of this <br />variance request. In particular, the monument sets installed above the main <br />entries in the vicinity of Foidel Creek could be locatable during winter conditions <br />if appropriate markers were installed. Admittedly, access to the ridge top <br /> <br />