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Chapter IV <br /> 13.2 feet. The analysis also concludes that a 15 degree worst case angle of draw could <br /> result in horizontal subsidence occurring on the surface from 600 to 750 feet from the <br /> vertical extension of the edge of the mined coal. (See Appendix IV-F-3 for further <br /> • discussion on the angle of draw). <br /> NOTE ON SUBSIDENCE IN REPLY TO STIPULATION 32 <br /> Mid-Continent agrees that the extraction of coal shall be limited to those areas defined <br /> by the projection of the lease perimeters to the depth of the coal seam being extracted, <br /> along an angle of draw of 20.5 degrees from vertical. This limitation shall remain in <br /> effect until the company has verified, to the Division's satisfaction ,that the actual <br /> site-specific angle of draw varies from 20.5 degrees, through implementation of the <br /> proposed subsidence monitoring program. <br /> Alternatively, coal may be extracted to within 50 feet from the lease boundaries <br /> provided written consent and approval is obtained and filed with the Division from <br /> surface landowners of the area adjacent to the leases located within a 20.5 degree <br /> angle of draw from vertical. (See consent letter at the conclusion of the chapter). <br /> c. Description of Damage or Diminution of <br /> Reasonably Foreseeable Use of Structures <br /> and Renewable Resource Lands Which <br /> Could Result From Subsidence. <br /> • As there are no structures in that portion of the permit area where possible subsidence <br /> could occur other than those related to the mining operations, subsidence in a worst <br /> case condition could affect only grazing lands and aquifer recharge areas. <br /> The rate of mining will progress beneath about seven and a half acres per month, and <br /> this will be divided between three and four working panels. Since no more than 25 <br /> percent of the grazing area is forageable due to the lack of growth or naturally <br /> unfavorable terrain, the potential for dimunution of that renewable resource is further <br /> reduced. Also, worst case conditions only apply to very small plots of land. Since the <br /> probability that surface deformation would be "plastic" rather than widespread random <br /> fractures and hummocked profiles, the disruption of the plant growth and forage on the <br /> ground surface for grazing animals during the brief grazing period each year would be <br /> negligible. <br /> Assessment of recharge areas is simplified by the lack of perennial streams within that <br /> portion of the permit area where possible subsidence could occur, and by the existence <br /> of thick beds of shale which do not contain extensive fracture systems. <br /> Recharge areas for aquifers affecting regional hydrology outcrop or suboutcrop on <br /> steep easterly facing slopes east of the permit area. The surface recharge area for <br /> Mesaverde "aquifers" is small in the permit area because of the geology and <br /> • <br /> 31 <br />