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lUl MIIV[ JV OJIU [IV L.C "fhe state's subsidence regulations were intended to present ~~ straightforward permitting process. If an inventory of the area potentially affected by subsidence delineates structures or renewable resource lz:nds, the applicant is required to project t:he worst-possible subsidence consequences for tha::e inventoried structures and lands:. The operator may not materially damage them or reduce their reasonably foreseeable use or value. The applicant: may choose to demonstrate, through state-of-the-art predictive techniques, that material damage or diminution will not result from projected subsidence, or to prepare a subsidence control plan. In either case, the operator must monitor the inventoried structures and renewable resource lands, in order to verify the accuracy of subsidence predictions included within the permit application. 'fhe hydrologic por•tians of the state regulations apply to every coal mine permit application. Applieelnts are required to minimize imp+;cts upon the hydrologic balance. All applicants are required to collect sufficient baseline hydrologic data to characterize the pre•-mining ground waiver and surface water hydrologic systems within the permit and adjacent are+as. Having described the pre-mining hydrologic pars;meters of the permit area, the applicant is required to project the probable hydrologic consequences of the proposed mining plan, including comprehensive projections of effects upon the ground water and surface hydrologic systems. Coal mine operators throughout the country can attest to the difficulty of this tas~'t. The task of projecting probable hydrologic con:;equences is made significantly more challenging by the requirement to project the hydrologic consequences of subsidence for the ground water and surface water hydrologic systems of Che permit and adjacent areas. Rule 4.20.1 of the Colorado Regulations presents the general performance standards with which any underground coal mine must comply. That rule states, "Underground mining activity shall 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 reasonably foreseeable use of surface lands". Based upon the general responsibility conferred by this regulation, three applicants have been required to respond to the subsidence permitting requirements even though no structures or renewable resource lands were inventoried within their permit and adjacent areas. In each of these three cases, the Division feared that subsidence of steep slope terrain might generate landslide activity, causing material damage to surface lands Subsidence Inventories An application for an underground coal mine permit must include an inventory of all structures and renewable resource lands which exist within the proposed permit and adjacent area (Rule 2.06.6(61(a)]. "Structures" is interpreted by the Division to include all man-made objects, such as buildings, bridges, roadways, soil embankments, spoil piles, water holding and transportation facilities, pipelines, powerlines, etc. "Renewable resource lands" include aquifers, aquifer recharge areas, areas for agricultural r^ silvicultura7 production of food and fiber, any pasture lands. As of May 1, 1986, thirty Underground Coal Mine Permits had been issued within the State of Colorado. Four additional underground coal mine permit applications were currently under review. Three approved surface coal mine permits had also been the subject of subsidence regulation compliance, because they included angering operations. Each of these applicants has completed a subsidence inventory of their proposed permit and adjacent area. The applicant submits the subsidence inventory, delineating existing structures and renewable resource lands, as a portion of the permit application. Ten of the thirty-seven permit inventories determined that no structures or renewable resource lands existed within the permit and adjacent area. For these permits, no additional subsidence information was required. As Table 2 indicates, nineteen of the mines have renewable resource lands within their potentially subsided areas. Twenty-two of the mines have structures within their potentially affected areas. These inventoried structures include buildings, state highways, county roads, bridges, railroads, electrical powerlines, petroleum and shale-oil pipelines, oil and gas - wells, water pipelines, reservofrs, water stor~_ tanks, water purification plants, water wells, stock ponds, sediment ponds, irrigation ditches, spoil piles, coal refuse piles, and topsoil stock piles. Projection of ~Aorst Possible Subsidence Consequences If structures or renewable resource lands are determined to exist within the proposed permit or adjacent area, the permit application must include a description of the worst-possible consequences which subsidence, if it were to occur, could have for such structures or renewable resource lands [Rule 2.06.6(6)(b)]. The purpose of this worst-possible consequence projection is to determine whether subsidence could cause material damage or diminution of reasonably foreseeable use or value of the existing structures and renewable resource lands. This analysis is not intended to entail a sophisticated prediction of subsidence phenomena. Rather, it requires only that an acceptable estimate of worst-possible subsidence consequences be prepared. The OSM regulations intentionally avoid defining "material damage" in reference to subsidence. The Office of Surface Mining left the discretion to each state's regulatory authority to define am use the term in a manner appropriate for subsidence problems within their own jurisdiction. (Federal Register, Volume 44, No. 5, Page 15075, Tuesday, March 13, 1979).