Laserfiche WebLink
page 3 <br />(2) Observations regarding those areas of subsidence from past and existing <br />mining indicated on Map IV-l, including an analysis of coal and overburden <br />behavior, possibly applicable to prediction of future subsidE~nce. <br />(3) Detailed treatment of outcrop panel and barrier design t:o preclude the <br />occurrence of compressive failure analogous to that observed is the Geneva area. <br />While the application doesn't specifically treat this subject:, the included maps <br />appear to indicate panel extraction in several locations in relatively close <br />proximity to seam outcrops. <br />(4) A detailed analysis of anticipated shrinkage stoping to justify its <br />assumption. <br />(5) Preparation of a "Subsidence Control Plan Map(s)" designed to clarify the <br />proposed partial extraction parameters in various locations, depth of workings, <br />proximity to outcrop, pillar size and passage dimensions and the proposed <br />subsidence monitoring network. <br />(6) A detailed treatment of the implications of the mining configuration <br />proposed for Seam F upon the eventual extraction of the lower coal seams. <br />Protection Of The Hydrologic Balance <br />The Empire Energy Corporation permit application, as submitted, appears to <br />inadequately consider the potential impacts of subsurface extraction within <br />the mine plan area upon the surficial and ground water resources. The <br />application defines three types of local ground water aquifers: (1) Sandstones <br />within the stratigraphic section, (2) the alluvium of the Yampa and Williams <br />Fork Rivers, and (3) the fractured coal seams. The Sandstones are characterised <br />as being limited in primary permeability. Vertical permeability within the <br />section is believed precluded by the proportion of aquiclude shales in the <br />Local stratigraphic section. The application suggests no effect will be had <br />upon the alluvial aquifer because of the plans to preclude subsidence within <br />the renewable resource areas. <br />If, as the application suggests with little, if any quantitative verification , <br />the coals are significant fractured aquifers, dewatering of the coal seams <br />within the mine workings could significantly impact both the .groundwater and <br />surface hydrology of the mine plan area. The dewatering of t:~e mine workings <br />will establish drawdown cones of influence,as schematically indicated on <br />Drawing IV?51. This will reverse the existing piezometric gr:sdient, which <br />the application asserts, without quantitative verification, r~asults in all <br />bedrock aquifers being effluent to the rivers at their subcrops. During the <br />dewatering the sandstones and coals could recharge from the surficial alluvium <br />of the river valleys. The alluvial surficial aquifer will in.Eluently draw <br />water from the Yampa and Williams Fork Rivers. Thus the resu.Lt of mine <br />working dewatering could be the depletion of surface water rights. This <br />scenario could also eepresent a significant water invasion potential for <br />the coal seams, particularly as extraction approached the subc:rop areas <br />beneath and adjacent to the Yampa and Williams Fork Rivers. <br />The hydrological sections of the permit application should be amended to <br />include an analysis of the potential affects of dewatering upon the <br />groundwater and surface hydrology of the mine plan area. Particular attention <br />should be given to verifying the various assumptions regarding; groundwater <br />movement embodied within the presentation. Data concerning ttie permeability <br />of the coal seams appears particularly important to assessing the impact and <br />analyzing potential mine workings water invasion problems. <br />Proposed Mine Waste Pile Stability <br />The stability analysis appears to be relatively thorough considering the <br />limited height and low (4:1) slope angles proposed. The application permit <br />