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'MINE ID # OR PROSPECTI~ID#: M-1984-041 • PAGE: 2 <br />INSPECTION DATE: 1-26-00 INSPECTOR'S INITIALS: ACS <br />OBSERVATIONS <br />This inspection was conducted in association with the review of reclamation permit amendment <br />application AM-03. In response to adequacy issues raised by the Division of Minerals and <br />Geology, Centex Eagle Gypsum Company listed a number of factors contributing the inherent <br />stability of the waste rock fill that will be installed in the new gypsum mining area <br />described in the amendment AM-03 application. The following factors are among those listed <br />by Centex: <br />• The existing open cut mine has utilized valley fill waste rock dumping for the last ten <br />years with no incidence or indication of slope instability. <br />• The haul road fills are constructed of waste rock and have proven to be stable. <br />• The waste rock is typically granular and well drained. <br />• The valley fill waste rock dump in the amendment AM-03 mining area will be constructed <br />near the head of a drainage so the watershed above the dump will be small. <br />• The gulch where the waste dump will be located is dry and there is no evidence of ground <br />water seepage. <br />• End dumping of mine waste results in some particle size segregation so that coarse-grained <br />materials collect at the toe of the slope effectively providing underdrainage. <br />During this inspection, these factors and others were investigated, primarily through <br />observations made at the location of the existing rock dump. <br />The waste rock at the Eagle-Gypsum Mine consists of siltstone that is interbedded with the <br />gypsum. The siltstone is locally referred to as "elastic sediment." There are indications <br />of diapiric structural configuration in the gypsum siltstone contacts; gypsum easily <br />undergoes ductile deformation under a load. Some very hard and durable small boulder and <br />cobble size rocks are present within the waste dump; these rocks exhibit a ringing sound when <br />struck with a hammer. However, most of the waste rock is soft siltstone grading in size from <br />cobbles to silt. <br />It was observed in the existing waste rock dump that the particles have segregated according <br />to size as a result of end dumping. This observation demonstrates that one of the stability <br />factors listed by Centex is in effect. Observations of the exiting dump further demonstrate <br />that the material is well drained and that the gulch where the dump is located is typically <br />dry. Thus demonstrating two more of the listed stability factors. <br />The existing waste rock dump and the haul roads constructed of mine waste showed no <br />indications of cracking, slumping, bulging, saturation, or other indications of instability. <br />Reclamation of road fill side slopes, consisting of grading to 3:1, topsoil application, and <br />seeding, has been very successful in further stabilizing the fill material. The vegetation <br />is coming in very well considering the semiarid climate at the mine. <br />Additional relevant considerations indicating that the proposed waste dump in the amendment <br />AM-03 mining area will be stable and will be reclaimed to a beneficial use are: <br />• The Operator will clear the gulch within the footprint of the proposed dump and will strip <br />topsoil and any soft or other deleterious materials. <br />• The dump will be constructed from the top of the gulch and proceed downhill. If problems <br />with dump stability are observed during construction, Coe drainage or other stabilizing <br />