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-z- The applicant projects-that subsidence will not significantly affect the proposed permit area's ground surface. However, portions of the previously mined areas above the longwall panels constitute steep slope areas, exceeding 20 degrees (36.4%) in slope gradient. Rule 4.20.(1) requires that underground activities be planned and conducted so as to prevent subsidence from causing material damage to the surface, to the extent technologically and economically feasible, so as to maintain the value and a reasonably forseeable use of surface lands. The Division is concerned that undermining of the previously mined areas may affect the stability of the backfilled and reclaimed spoils, as discussed under the following heading "Subsidence Monitoring". - Subsidence Monitoring Having predicted that no material damage will occur within the proposed affected area due to the projected 5.5 to 8 feet of subsidence, the applicant is required by Rule 2.05.0(6)(b)(ii) to conduct an appropriate subsidence monitoring program. The applicant has proposed a monitoring plan to which the Division requires amendment. Empire Energy Company proposes to install a monitoring net consisting of two parallel lines of subsidence monitoring monuments. Each line is proposed to extend 400 feet beyond each ribside of panels No. 1 and No. 2, utilizing 80 foot intervals spacing, as depicted on the map sheet entitled "East Addition, Topo Overlay, Map IV-7". These subsidence monitoring monument lines are depicted perpendicular to the long access of both panels. This depiction disagrees with the monument depiction on the overlapping portion of the map sheet entitled, "South Addition, Topol Overlay, Map IV-7". this discrepancy must be resolved. The proposed amended permit narrative also states that supplemental monuments may be installed at each panel ribside, along the ends of the: panels, above each chain pillar, and along the panel center lines. In addition, the narrative states that supplemental panel center line monuments will be positioned on a perpendicular monitor line, however, these monuments are not depicted on the amended application maps. These maps should be amended to depict the perpendicular panel center line monument lines, central in both panels No. 1 and No. 2, parallel to the pane]'s long axis. These monuments should be installed in equivalent manner and spacing intervals, as those in the two lines installed perpendicular to the long axis of thE~ panels. As stated in the amended map narrative, these monuments should tie extended past the limits of the proposed angle of draw surrounding these panels. The applicant should also install additional monuments for tf~e purpose of monitoring subsidence movements and slope stability of the representative portions of the previously mined and reclaimed portions of the affected area. The results of this monitoring could be instrumental in determining the potential relationship of planned subsidence and stability of these previously mined and reclaimed slopes. The applicant should propose appropriate monitoring installations for Division review and approval wil;hin these areas.