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Page 9 Carol Russell April 8, 1981 The applicant observes that because the structures of Emp_re Village are owned by Empire Energy Corporation, damage which might re::ult from subsidence is not considered a significant issue. However, damage which might possibly affect critical items such as natural gas services, or electrical supplies could involve significant hazards to the residents. The applicant is required to develop a monitoring plan under Rule 2.05.6(6)(c) for the possibly affected structures and to prepare a statement of "measure's to be taken on the surface to prevent material damage" as a portion of t1~e subsidence control plan, in accordance with Rule 2.05.6(6)(f)(i)(C). The discussion of "Anticipated Overburden Affects" presented on page IV-1 5 through page N-I 37 is a generally acceptable qualitative discussion of overburden adjustment resulting from subsidence of longwai.l extracted seams. However, quantification of zone thicknesses is extremely approximate, at best. If the Middle Sandstone aquifer exists within 50 to 60 feet above the F seam, a significant probability exists that extraction of the F seam will affect that aquifer. Extensive aquifer monitoring ar.:d in-mine observations of roof caving phenomena would be required to reduce that probability sufficiently to justify the applicant's statement that; "No diminution of groundwater flows or material damage will result to the Middle Sandstone aquifer from planned subsidence." (Page N-140) The applicant's contention that there are no known users cf the Middle Sandstone aquifer should be supported by a listing of all reported wells within the permit and adjacent areas. That listing should include well location, total depth, production rates and aquifers encountered. 4.6.5 Subsidence Monitoring Program The configuration of the subsidence monitoring net proposed for installation above the 3E-1R and 3E-2R panels south of the third east entry of the q5 mine should allow the collection of valuable subsidence data. This data will allow verification of the applicant's subsidence projection.above the F seam. If the results indicate that modification of the plan is appropriate,it could be accomplished prior to the issuance of subsequent permits for mining in the Eagle Complex. The monument spacing and monitoring frequency proposed in the application are acceptable. In fact, the proposed monitoring frequency exceeds the regulatory requirements of Rule 2.05.6(6)(c). In accord with Rule 2.05.6(6)(c) monitoring should commence prior to commencement of mining within the monitored panel. Monitoring should continue until results indicate .subsidence has ceased, and concurrence with that opinion is received from the Division. The applicant's proposal to construct monuments; "By driving 3/4" diameter 4 ft. long rebar into the ground" (Page IV-L50), is not acceptab.e to the Division. Survey monuments should be capable of resisting normal traffic and.climatic extremes. Experience with monuments similar to those proposed by the applicant has determined that they are susceptible to frost problems. Monuments should (cont'd)