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• Bob Liddle -3- June 30, 1981 differential surface movements. For this reason the applicant should include a high-resolution system of subsidence monumentation across the fault zone adjoining an early-extracted panel, in order to determine what potential affects the adjoining fault zone might have upon ground subsidence. (See attached figure excerpted from map No. 6). Thirdly, the applicant proposes to install a wide-spread grid system of subsidence monuments above the mine plan area to verify its subsidence prediction. While these monuments are acceptable and encouraged, they are not sufficient to satisfy the purposes of a subsidence monitoring program. The purpose of such a program, as envisioned by the Division, is to determine, as quickly as passible, whether the mine plan proposed will succeed in pre- venting any material damage to the renewable resource lands overlying the workings. The applicant proposes to protect "Area A" by limiting extraction to 50% within that portion of the mine plan. The application should present a detailed typical panel configuration within "Area A", in order to clarify their exact proposal. Furthermore, the subsidence monitoring program should be designed to verify the magnitude of subsidence which occurs and the angle of draw surround- ing the boundary of mine extraction. In order to accomplish this task, high- resolution linear sets of monuments are commonly utilized. Interval spacings between monuments of .1 to .2 times the overburden thickness are commonly used • in such programs. Because of the specific configuration of the applicant's underground mine plan, I foresee additional problems. Several panels are pro- jected for extraction beneath "Area A", all of which are projected to be ex- tracted during the second and third years of the permit period. It would be highly preferable if the applicant were able to develop and monitor a test panel within "Area B" prior to production mining within "Area A". Unfortunately, this may not be practable. If reordering of the mining scheme is not practable,. the applicant should reconfigure the mine plan beneath Foidel and the Middle Creeks to specifically avoid undermining the two stream channels and their immediate surrounding areas. (See attached excerpt from map No. 6). Following completion of subsidence monitoring above the test panel, the mine plan could be modified to avoid material damage, if the results show it to be appropriate. rf appropriate, additional coal could be extracted beneath "Area A". Extraction within additional portions of "AreaA"should be limited to partial mining on ad- vance until the results from subsidence monitoring and the test panel have been reviewed by the Division and further extraction specifically approved. Fourthly, the applicant states that no structures exist within the affected areas. Structures is used within Rule 2.05.6(6)(a) in its generic sense to include all manmade structures, such as roads, overburden waste piles, irrigation works, etc. The applicant should discuss items such as the road paralleling Foidel Creek. Zn addition, appropriate additional monitoring monuments and operational observation plans should be provided for these structures. The applicant should amend the mine plan appropriately. The applicant should also include monitoring wells above the test panel to simultaneously:'monitor the • response of the alluvial aquifer to subsidence. Subsidence monuments should be subs tantiaZ and capable of resisting damage by normal traffic, wildlife and meterological occurrences. AlIuvia2 wells could be utilized for both hydrologic and topographic monitoring, if properly designed. The applicant should include