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<br />' 4.2.4 Combustible Materials (675 Subpart El <br />Coal fines can be subject to spontaneous combustion under certain <br />' circumstances. In general, if coal fines are slightly moist and <br />exposed to a source of oxygen (generally air), then spontaneous <br />combustion may occur. However, coal fines will not spontaneously <br />' ignite under the following circumstances: <br />' 1. If the coal is too wet to support combustion. If the coal has <br />more than about l0~ by weight of water, then it is unlikely <br />' that spontaneous combustion will occur, or if it does occur <br />locally, it will not propagate. At the end of the spectrum of <br />' moisture content, if the coal is saturated, then it will not <br />ignite. <br />' 2. If the ash content of the coal is to hicxh to allow combustion <br />propagation. If the ash content is above about 50$, then it <br />' is difficult to get the coal material to burn, and it in <br />general will not initiate combustions. <br />It is proposed that, to avoid spontaneous combustion, the non- <br />combustible portion of the total disposal material, when gravity <br />' dewatered but not dried, shall be not less than an average of 65~ <br />by weight (as per §75.403). The non-combustible portion of the <br />' material shall include non-combustible solids and water combined <br />(as per §75.403-1). Averaging will be based on weekly sampling, <br />' <br /> SThe exa ct conditions upon which spontaneous combustion will <br />' and will <br />does not not <br />yet occur is a function of the coal being mined. NCEC <br />have a large enough coal sample, nor does it have a <br /> sample of the fines that it may wish to dispose of, to conduct the <br /> testing to establish the appropriate spontaneous combustion <br /> parameter s. This testing will be performed when the coal is <br />accessed, which will occur shortly after mining re-commences. <br />Based on the results of this testing NCEC will re-evaluate disposal <br />' limits for combustible materials in consultation with MSHA; if the <br />limits differ from the presently proposed values, then the limits <br />will be modified appropriately. <br />' Adrian Brown Consultants -21- 1145/900820 <br /> <br />