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Thoroughly documented subusidence case histories in the <br />western U.S. are rare and have been published only during <br />the last five to ten years; among them, the work by Dunrud <br />(1976) provides most data relevant to subsidence engineering <br />for coal of the Mesaverde Formation. Abel and Lee (1980) <br />evaluated the influence of lithology on subsidence. Geo- <br />Hydro Consulting, Inc. (1983) studied the influence of <br />outcrop barrier pillars on the stability of mountain slopes <br />containing coal outcrops; results of their study have been <br />used to deal with the potential subsidence or stability <br />problems within the south area of the lease, close to the <br />coal outcrop. <br />Brooks (1983) studied the geologic and hydrologic <br />conditions of the proposed long-term lease area and <br />evaluated the subsidence potential. Flis ~oork provided <br />valuable data for the study. <br />Very valuable experience has been obtained from field <br />inspections and documentation of the existing subsidence <br />cracks above the present Orchard Valley P9ine and from recent <br />landslides present close to the entry of the abandoned <br />Farmers Mine. <br />Finally, a study of several pertinent parts of mine <br />• permits for other proposed or operating coal mines in the <br />area, our general experience in subsidence engineering, and <br />our thorough knowledge of geologic and hydrologic conditions <br />of the area obtained from our work during the last decade <br />contributed to this study. <br />5.2 MINING SCHEDULE AND RATE OF SUBSIDENCE <br />Mining within the proposed lease area will proceed for <br />a number of. years; subsidence will be different at different <br />times depending on the immediate phase of mine development. <br />It is not possible to deal completely with the subsidence as <br />it will occur at various intervals during the lifetime of <br />the mine within this study. <br />As the scope of this study is to evaluate the <br />subsidence impacts on various resources, facilities and <br />structures within the lease area, it is more important to <br />specify the critical subsidence conditions; such conditions <br />can be defined as causing the maximum possible damage to <br />existing resources, facilities and structures. Rather than <br />dealing ~~~i*_h initial values of subsidence *_hat :night be <br />caused by developing of entries and!or ini*_ial room-and- <br />pillar development., the study is aimed at predicitions of <br /> <br />- ?3 <br />