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•~ 2a XXII. Subsidence - Rules 2.05.b(61 and 4.20 The Division cannot presently complete findings for the subsidence section. The applicant must submit plans for another set of subsidence monitoring monuments before the Division can consider this section adequate (see comment 1 below). The following are the Division's comments: In response to comments included within the Division's original adequacy review, the applicant's consultant, Subsidence Engineering, Inc., has completed numerous amendments to the original application's Appendix 4.5-]. Nonetheless, a few deficiencies still remain, as discussed here below. (1) The application's proposed survey subsidence monitoring program has not been amended in response to our earlier adequacy comments. The application proposes the installation of one linear set of widely-spaced subsidence monitoring monuments, oriented perpendicular to the spine of Coal Ridge. Considering the importance of verifying subsidence projections contained within the application (Appendix 4.5-1), reliance upon only one limited set of monuments is considered imprudent. The permit application must include the installation of a second analogous set of subsidence monitoring monuments at another agreed location on Coal Ridge. (2) In response to our earlier comments requesting elaboration of the subsidence mechanism discussion, the consultant has amended Appendix 4.5-1 to discuss the mechanisms controlling the character of roof strata failure. Further, the text now contains a specific discussion of anticipated gob movements in relation to bedrock dip. The consultant observes that a slight possibility exists for sinkhole collapse to occur near the outcrop crown pillar. The amended application proposes a specific visual monitoring program to concentrate in areas over and adjacent to the crown pillar, in order to specifically detect potential sinkhole collapse (page 41.4). The amended application also presents a proposed mitigative program for sinkhole collapse, were it to occur. On page 43.3 of amended Appendix 4.5-1 the consultant proposes that Storm King restrict access to any areas of sinkhole collapse and that appropriate amendments be made to the mine plan. In preparing our eventual findings, we should stipulate that, if a hazard to the public or environment is determined to exist, Storm King Mining will be required to implement appropriate sealing and backfilling of sinkhole collapse features. (3) In response to our original adequacy comments, the consultant amended pages 39.3 through 39.7 of Appendix 4.5-1 to present a more comprehensive discussion of slope stability and subsidence relationships on Coal Ridge. The amended application observes that moderate slumping and landsliding is limited to areas "outside and below the anticipated areas of surface subsidence effects." (page 39.5) With the exception of one questionable portion of the northeastern face of Horse Mountain, the Division concurs with that opinion. There appears, however, to be extensive geomorphic evidence of ancient slope movements throughout large portions of the slopes on the northeast face of Coal Ridge.